Q1. vYVªklksfud VsfLVax dk D;k fl)kar gS\ ,d ckWDlu ,Dly dh vYVªklksfud VsfLVax djus dh

fof/k dk foLrr̀ o.kZu dhft,\

What is principle of ultrasonic testing? Describe ultrasonic testing method of

BOXN Axle in details.

Answer :-

A: Ultrasonic is done to avoid on line failure of axles due to various defects inherent

in the axles or while developing in-services.

The defects in axles can be broadly classified as

1. Inherent defects i.e. the defects associated with the faults in making of steels and

During manufacturing of axles, unsatisfactory chemical composition and

unsatisfactory micro structure.

2. Defect at the time of heat treatment, Coarse Grain, Banded structure, overheating

1. Harmful inclusions

2. Flakes & hairline cracks.

3. Pipes

4. Manufacturing defects.

5. Forging defects.

Principle:- Principle of ultrasonic testing is based on pizeo electric effect. Ultrasonic

waves can be generated and detected in a number of ways. The one which is most

commonly used in NDT is described here. Quartz and some other crystals have a lattice

structure such that if a plate is cut out of the crystal with a certain orientation with respect

to the crystallographic axes and subjected to an electric field in the right direction, it will

change its dimensions: it will contract or expand according to the polarity of the field.

Conversely, when a similar deformation of the plate is brought about by an external

mechanical force, electric charges appear on its opposite surfaces. This phenomenon is

known as piezoelectric effect. The materials which exhibit this property are known as

piezoelectric materials.

B: There are three basic techniques applied for ultrasonic testing of axles.

i. ‘FAR END SCAN’ – through scanning of the whole a length of the

axle.

ii. ‘NEAR END LOW ANGLE SCAN’ – scanning from axle and into

the nearer wheel seat.

iii. ‘HIGH ANGLE SCAN’ – scanning across the diameter.

METHOD/PROCEDURE

To start with take a full scale drawing of axle showing press fit

components & workout theoretical prediction for direct back reflection & delay

reflections. The probable reflections of an axle may be from

1. End of the axle

2. End of the journal.

3. Journal radii.

4. Wheel seat radii.

5. Stress relief grooves.

2. Cleaning the end face of axle, apply the coup lent and place the probe after

calibrating the ultrasonic flaw detector for the particular range.

Show that the reflected ray from the end of the axle & change of section can be

covered.

The Observations on the screen can be compared with the theoretical predicted

oscillograph pattern. The standard procedure is given by RDSO.

Scan the full axle from both the end faces.

‘FAR END SCAN’ – through scanning of the whole a length of the axle.

PROCEDURE:-

This type of scanning technique is used in longitudinal normal double crystal probes

of 2.5 MHZ with perplex wedge of 150

Calibrate the equipment for 500mm of range scan, for the first 500mm of the axle,

Keep the probe on the 100mm long bar, turning the delay control clockwise,

Count the 100mm signals as they pass the ‘0’.

Adjust the 5th

echo to ‘0’ & check the signals at 2,4,6,8 & 10 scale division.

Any error in the position of the signals may be corrected with the range control fine.

Again scan the 500mm length of the axle, follow the same sequence for remaining

length of the axle. Probing the complete axle to detect any unusual crack or defect in

the axle.

The probe is kept on the end face of axle with applying couplet / grease to avoid any

air bubble between probe & axle. For every 500mm of the axle, this is done & trace

delay pattern is observed on the oscillograph . Any difference in pattern indicates

unusual/ crack at particular position of axle .This crack can be verified from other

end of the axle.

‘NEAR END LOW ANGLE SCAN’ – scanning from axle and into the nearer wheel

seat.

PURPOSE:-This scanning is found to be useful in checking the cracks in raised wheel

seat & gear seat etc.

It is also a confirmation test for the cracks detected in far end scanning.

PROCEDURE:-

This type of scanning technique is used in longitudinal wave probes having

angle of reflection in steel 05 to 200

Take full scale half-length axle drawing having dimension of press fit

components & mark valuable location & choose a low angle suitable probe

on the axle end

Keeping the following points in view

Join the center of probe with points under consideration & measure the

distance.

Measure the angle between this line & normal drawn from the probe index

to know the suitable angle of the probe.

PRECAUTION

The probing surface should be free from indentation holes, loose scales,

foreign matter etc.

The couplent should be of effective transmission of ultrasonic energy such

as heavy oil or greases & good adherence & easy applicability.

The ultrasonic beam should be directed toward diametrically opposite end

from the probing position.

Ultrasonic beam should not strike the lathe centre or any drilled hole of the

axle.

The probe should always be positioned 02 to 05mm away from the outer

periphery.

The probes & the wires used should be of high quality.

Check the ultrasonic testing machine before utilizing them such that the

transmission & receiving of ultrasonic waves are easily traceable on time

scale.

Ensure the calibration and drawing available for the type of axle to be

tested.

Always use the probe of angle calculated for the full scale drawing of the

axle.

Place the probes in proper position.

Always apply rotation of probe for proper acoustic coupling.

Ensure that there is no air bubble between probe & perspex shoe.

EQUIPMENTS REQUIRED

Ultrasonic flaw detection machine mainly of model UFD model 301 M of

M/S VIBRONICS make having following main parts

1. time base

2. pulse generator

3. display unit

4. pulse transmitter

5. receiver

6. amplifier.

Probe & Perspex wedge - normal probes ,longitudinal normal double crystal probes of

2.5 MHZ with perplex wedge of 15 0 Probes having angle of reflection in steel 05 to

200Cables of proper quality Piezo electric crystals Calibration block recommended by

I.I.W as per IS 4904.

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D;k&D;k mik; fd;s tkrs gSa] foLr`r o.kZu dhft,\

What is corrosion? What are its causes? Describe the measures to be taken to

reduce/minimize the corrosion

Ans-

Definition Of Corrosion: -

Corrosion may be defined in several ways:

(1) Destruction or deterioration of a material and consequent loss of solid material,

through a chemical or electrochemical reaction by its environment, starting at its surface.

(2) Destruction of materials by means other than straight mechanical.

(3) Extractive metallurgy in reverse.

Definition (1) and (2) are preferred because they cover ceramics, plastics, rubber, and

other nonmetallic materials. For example, deterioration of paints and rubber by sunlight

or chemicals, fluxing of the lining of a steel-making furnace is all considered to be

corrosion.

2. Classification Of Corrosion

Corrosion has been classified in many ways. One method divides corrosion into (a) low

temperature and (b) high- temperature corrosion. Separates corrosion into (a) Direct

Chemical Corrosion or Dry Corrosion. (b) Electrochemical corrosion or Wet

Corrosion.

Dry or direct chemical corrosion

This type of corrosion occurs through the direct chemical action of

environment/atmospheric gases as oxygen, halogen, hydrogen, and hydrogen sulphide,

sulphur dioxide, and nitrogen with metal surface in immediate proximity. There are two

main types of direct chemical corrosion.

i) Oxidation corrosion. ii) Corrosion by other gases.

i) Oxidation corrosion: It is brought about by the direct action of oxygen at low or high

temperature on metals, usually in the absence of moisture. At ordinary temperatures,

metals, in general, are very slightly attacked. However, alkali metals (Li, NA, K, Rb, etc.)

are rapidly oxidized at low temperatures. At high temperature all metal (except Ag, Au,

Pt,) are oxidized.

The reactions in the oxidation are:

2M→2Mn+

+2ne- (Loss of electron)

Metal ion

nO2 + 2ne- → 2nO

2- (Gain of electron)

Oxide ion

or 2M+ nO2 → 2Mn+

+ 2nO2-

Metal ion Oxide ion

|__________|

Metal oxide

Absorption of oxygen: Rusting of iron in neutral aqueous solution of electrolytes (like

NaCI solution) in the presence of atmospheric oxygen is a common example of this type

of corrosion. The surface of iron is coated with a thin film of iron oxide. However, if this

iron oxide film develops some cracks, anodic areas are created on the surface; while the

well-metal parts acts as cathodes. It follows that the anodic areas are small surface parts;

while nearly the rest of the surface of the metal forms large cathodes.

At the anodic areas of the metal (iron) dissolve as ferrous ions with liberation of

electrons.

Fe→ Fe2+

+ 2e- (Oxidation)

The liberated electrons flow from anodic to cathode areas, through iron metal, where

electrons are intercepted by the dissolved oxygen as:

O2 + H2 O +2 e--→2OH

- (Reduction)

The Fe+ ions (at anode) and OH

- ions (at cathode) diffuse and when they meet, ferrous

hydroxide is precipitated.

Fe+ +2OH

-→Fe (OH) 2 ↓

If enough oxygen is present, ferrous hydroxide is easily oxidized to ferric hydroxide.

4Fe (OH) 2 + O2 +2H2O→4Fe (OH) 3

Measure to be taken for Corrosion Prevention: - Since corrosion is essentially due to attack by environment, the basic approach to prevent

corrosion involves control of the metal or control of the environment or providing a

suitable barrier between the metal and the environment. Also control on the

electrochemical nature of corrosion and finally the design consideration plays a major

role to reduce corrosion.

The corrosion can be prevented & controlled by the following methods.

1) Material Selection by using anti corrosive material.

2) Protection by design & Fabrication procedure.

3) Alteration / modifying corrosive environment.

4) Cathodic protection.

5) Sacrificial anode Method.

6) Application of protective coatings.

7) Purification & alloying of elements.

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dh fof/k dk o.kZu dhft,A

What are the different types of welding defects? Write down the reason and

remedial action of each defect?

Ans-

Welding Defect, Causes and remedy :-

These are a number of welding defects which are observed when

checking the quality of weld joints. These welding defects result in poor wild appearance

and reduction in strength of weld joint. These defects very be divided in to two type. I)

External defects ii) internal defects.

Welding procedure is the important for fabrication/manufacturing of rolling stock.

Due to improper welding. There are many reasons of poor performance of rolling

stock.

Following are important welding defects, reason/cause of defect and there remedial

actions are:-

Defect Causes Remedies

1. Lack of Fusion (It is the

failure of the adjacent layers

of the weld metal.)

i) Dirty Surface

ii) Improper cleaning of

weld bead.

iii) Current too low.

iv) Excessive welding

speed.

v) . Long Are length

vi) Indigent removal of slag

i) Cleaning the edges to be

welded.

ii) Proper cleaning of each

bead.

iii) Maintaining proper

current & welding

speed.

2. Lack of penetration (It is

caused when the weld metal

does not completely fill the

weld cavity. )

i) Inadequate joint

preparation.

ii) Wrong size of electrode.

iii) Low heat input.

iv) High welding speed.

v) Long are length

vi) wrong polarity of D.C

Supply

vii) Too large dia of

electrode

i) Proper joint preparation.

ii) Suitable size of

electrode as per root

gap.

iii) Proper heat input &

welding speed.

3. Overlap (It is the

overlapping of weld metal

beyond the toe or root of

weld.)

i) Wrong angle of

electrode.

ii) Too large deposition in a

single run.

i) Keep correct angle of

electrode.

ii) Use proper size of

electrode.

iii) Faulty electrode

manipulation.

iv) Insufficient current

4. Undercut (It. is cutting of

a groove into the base metal

parallel to the of weld)

i) Too fast welding

speed

ii) Long arc length.

iii) High current.

iv) Higher diameter of

electrode used.

v) Wrong electrode angle

.

i) Use proper current &

polarity in case of DC.

ii) Use proper diameter

electrode.

iii) Proper angle of

electrode.

5. Slag Inclusion Faulty electrode.

Wrong current.

Rapid rate of welding.

Defective weld design.

Improper technique.

Improper manipulation of

flux

Bad tack weld

Improper removal of slag.

i) Proper current & heat

input

ii) Proper design &

technique

iii) Proper cleaning of weld.

6. Porosity (It is a

development of a group

small gas pocket in the

weld.)

i) Wrong arc length.

ii) Inadequate gas shielding

due to clogging,

jamming or hose leaking

iii) Too high current

iv) Excessive moisture in

the electrode.

v) High rate of weld

freezing

vi) Dirty joint

i) Maintain proper arc

length & correct polarity

when welding with DC.

ii) Clean the surface

properly

iii) Check for proper gas

supply & leakage

7. Blow holes. (Porosity or

cavities are called blow

boles.)

a) Improper electrode

Less current

c) Excessive moisture in

electrode

d) Improper grove formation

in butt weld.

-do-

8. Cracks.

i) Rapid cooling

ii) Improper composition

parent metal.

iii) High welding speed.

iv) Electrode with high H2.

v) Excusive localized stress.

vi) High rigidity of the joint

vii) Concave, wide or

i) Avoid rapid cooling by

preheating.

ii) Maintain proper welding

parameter

iii) Use low hydrogen

electrodes.

shallow bead.

viii) High carbon sulphur

and silicon content in

metal.

9 CRATER (It is a

depression caused at the

termination of a weld bead.)

i) high current

ii) Wrong size of electrode

iii)Wrong electrode angle

iv)Rapid withdraw of

electrode.

i)Set proper current

ii) Select proper size of

electrode as per thickness of

plate & proper angle

10 SPETTER (It consists of

metal particles expelled from

welding.)

i) high current

ii) moisture in electrode

iii) Long arc length

9 Proper Current

Baking of electrode set

proper arc length

11 Warping (To twist from

true direction )

i)Improper sequence of

welding and presetting.

per sequence of welding

ii)Incorrect edge preparation.

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ls iSjkehVj ds }kjk tk¡p dh tkrh gS\

Write down the testing procedure of paint. What parameters are checked for quality

of paint.

Ans- Method of Testing of Paints: - Consistency: - Insert a clean metal rod into the original container and examine the nature

of setting. The material shall not cake hard inside the container and shall be in such a

condition that stirring easily produces a smooth uniform paint suitable for application by

the method specified.

1. Place the flow cup on the stand level by the use of a spirit level placed on the rim.

2. Strain the sample into a container and sieve through a 150 sieve.

3. With the orifice closed by the finger, fill up the cup with the sample unit it just

begins to overflow into the gallery.

4. Check that the temp. of the material in the cup is within 0.50C of test temp.

5. Place the scrapper on the rim of the cup and draw it firmly across until the excess

of the sample has flowed into the gallery. Place the receiver under the cup.

Remove the finger and simultaneously start the stopwatch. At the first evidence of

a break of stream into droplets stop the stopwatch. The time taken is recorded in

seconds as time of flow in flow cup.

Finish: - The material when applied on a mild steel panel by brushing or spraying, to

give a dry film and allowed to dry in a vertical position, a hard, firmly adherent, flexible

and smooth film free from sagging and wrinkling, with a matt, semi glossy or glossy

surface. When examined earlier than 48 hrs and not later than 100 hrs. After application

the film show inferior to a film prepared in the same manner that of approved sample.

Spreading Capacity: - Weigh an appropriate quantity of the material together with a

suitable brush. The material shall then be applied by brushing to a flat smooth and non-

absorbent surface. The balance of material with the brush shall than be weighed.

The spreading capacity is calculated as the number of square meters that can be

calculated as the number of sq .m that can be covered by 10 lt. of the paint.

Spreading Time: -Time taken to cover 100 sq. m. When tested as above.

Water Content: - Weigh 100 gm. of the material in a flask, add 100ml. of dry petroleum

hydrocarbon solvent and 1 ml. of ethyl acetate and thoroughly mix the content of the

flask. Pour petroleum hydrocarbon solvent into the receiver up to the level of the side

tube. Attach the flask to the dean and stark condensing and collecting system and heat the

flask at such a rate that the condense falls from the end of the condenser at a rate of 2 to 5

drops per second. Continue the distillation until the condensed water is no longer visible

in any part of the apparatus except at the bottom of the graduated tube and until the

volume of the water collected remains constant. Note the number of ml. of water in

receiver at the temp. At which the sample was measured. Assuming the density of

1.000gm/ml for the water collected in receiver, calculate the % of water by eight.

Hardness (Scratch Hardness): - Apply a coat of material by either brushing or spraying

to a 150X50 mmX0.315 mm toned plate to give a dry film weight. Allow the panel to air-

dry in a horizontal position for 48 hrs. Under specified drying condition or stove as stove

as specified in the material specification. Test the panel under a load of 1000 gm. unless

otherwise specified in the material specification. Fix the needle at the end of the counter

poise, which is kept horizontal by adjusting the length of the needle and draw the panel

under the needle at a rate of 30 to 40 mm per second. A scratch showing the bear metal

shall not be produced.

Pressure Test: - Apply a coat of the material to give a dry film. Allow it to air dry under

laboratory conditions in a horizontal position for a period as specified in the material

specification. At the end of the period, cut two test pieces approx. 20mm2 superimpose

them so that the paint films are in close contact and place on the metal table. Lower the

steel ball and plunger to the centre of the metal test pieces and place a 1.8 kg wt. on the

top of the plunger. Maintain the pressure on the paint film for 5 minutes. At the end of

this period, separate and examine the test pieces. The metal surface shall not be rendered

visible when two test pieces are separated.

Flexibility &Adhesion : - Apply a coat of the material by either brushing or spraying to

a 150X50X0.315 mm tinned plate to give dry film. Allow the panel to air dry or stove in

a horizontal position for the period as specified in spec. After drying bend panel double

44.5 mm from the upper edge over a 6.25mm dia. rod in the apparatus with the paint film

outside. Close the hinge in as regular manner without jerking in less than one second.

And not more than 1 ½ seconds. Remove the panel carefully from the hinge. The paint

film shall not show damage, detachment or cracking when examined under X-10

magnification.

Stripping Test: - Drying for 48 hrs as above test the dried film in the apparatus under

such a load that scratch is produced showing the bare metal surface. The scratch so

produced shall be free from jagged edges.

Protection against Corrosion : - The metal panel is cleaned and prepared applied one

coat of the paint on both sides of the mild steel panel to give a dry film keep the painted

panel in a vertical position at room temperature for 24 hrs to air dry and then at a

temperature of 60-650C for one hour. Cool the panel at room temperature and protect the

edges to a depth of 5 mm with a suitable protective composition (3 parts by weight of

paraffin wax+ one part by wt. of carnauba wax) having melting point 500C and then

suspend vertically in the corrosion cabinet. After exposure under these conditions for

seven days, remove the panel and examine for signs of deterioration of the paint film.

Remove 25mm strip of the film from canter of the panel carefully with a noncorrosive

paint remover neglecting 25 mm portion of the exposed surface from each end and

examine the exposed metal for signs of corrosion the metal surface shall show no signs of

corrosion, changes in appearance and condition of the paint film shall not be taken into

consideration in deciding about acceptability.

Resistance to Lubricating Oil: - Prepare a painted paint film panel. Dry horizontally for

8 hrs. in air. Immerse the paint panel for 2 hrs. at room temperature of 500C in mineral

lubricant oil having a viscosity of 18cs or having a time of flow of approximately 80

seconds for 50 ml at 600C in a no. 1 redwood viscometer.

Remove the panel from the oil after 2 hrs. and wipe the excess oil with a pad of

cotton wool. When examined after cooling for 30 minutes at room temperature. The paint

film shall show no permanent injury signs.

Resistance to Heat: - Prepare a painted panel as described above air dry for 48 hours

keeping horizontally at room temperature heat panel gradually to the temperature.

Specified in the material specification for testing resistance to heat and maintain there for

2 hours. Keep it at room temperature for one hour and then examine film. Test the

approved sample in the same manner and at the same time. The film shall remain firmly

adherent and shall not show any signs of cracking, blistering or change of color more

than those shown by the approved sample.

Resistance to Water: - After preparing the paint panel as stated above, immersed in

distilled water at room temperature for 48 hours remove it from water and examine after

4 hours. The film shall show no signs of deterioration and shall remain at least 60% of the

original gloss.

Flash Paint: - This is applicable for liquids flashing between 190-32

0C inclusive. Fill the

water bath to over flow with warm water, insert the bath thermometer and adjust the bath

temperature to 540C at the beginning of the test. Do not apply heat to water bath at any

time during the test.

Adjust the temperature of the sample between 00C and 10

0C place the cup on a level

surface and fill it with sample until the liquid just reaches the point of gauge fixed to the

wall of the cup. Place the cover with slide closed, on the cup and press it down so that its

edges rest on the rim of the rim of the cup. Place the cup in the water bath. Insert the oil

cup thermometer seating the collar firmly in the cover. When the temperature of the oil

reaches 180C apply the test flame by slowly opening the side in the cover.

Apply the test flame in this manner after every 0.50C rise in temperature until a

distinct flash occurs in the interior of the cup. Record the temperature of the sample when

the flash occurs.

Weight per 10 Liters: - Weigh the cylinder or cup when empty and then fill in the brim

with the material. Assuming that volume of content 650 ml. or 100 ml. calculate and

express as kg per 10 liters.

Volatile Matter: - Weigh accurately about 2 Gms. Of the well mixed material in a flat

bottomed circular metal dish about 75 mm in dia heat the dish and content for three hours

in a suitable oven maintained at 100±20C allow the dish and its contents to cool to room

temperature and weigh again. Calculate and express the result the result as percentage of

the weight of the material taken for the test.

Pigment and Non-Volatile Matter Content: - Pigment Content: - Weigh accurately 150 to 20 gm of the well mixed material into a

weighed centrifuge tube. Add 20-30 ml. of approx. extraction mixture and mix

thoroughly using a gloss rod.

Extraction Mixture: -

Benzene - 5 Parts

Methyl Alcohol - 4 Parts

Acetone - 1 Part

After mixing the gloss rod thoroughly with the extraction mixture in centrifuge tube

fill the tube and place in the container of the centrifuge, counter balance the container of

the opposite arm and whirl at a minimum speed of 3000 rpm until maximum separation is

affected. Decant the liquid and repeat the process twice or more required keep all

extracted liquid in a weighed ml. conical flask. Place the tube containing the pigment on

the top of the air oven for half an hour for the solvents to escape and then inside an oven

maintained at 100±20C and weigh after drying to constant weight. For pigment analysis,

grind the contents of the tube in a mortar to a fine homogeneous powder and keep in a

well stopper bottle.

Non-Volatile Vehicle Content: - Distill of the solvent from the conical flask and heat the

flask to constant weight in a vacuum oven or in a non-oxidizing atmosphere at a

temperature of 100±20C. Allow it to cool to room temperature and weigh. The difference

in weight gives the non-volatile vehicle content. Calculate the non-volatile vehicle

content and express as percentage on the wt. of the material taken for test. Add % to the

non-volatile vehicle content as allowance for in extractable material.

Total Insoluble Material: - Boil 1 gm of dry pigment in a 250 ml beaker with ml. of

conc. HCl for about 30 minutes add from time to time a drop of alcohol. Then add 50 cc

of water and boil again for 15 minutes. Filter on a filter paper, which has been dried and

weighed in a weighing tube. Wash the residue with hot water, dry in the weighing bottle,

cool in a desicator and weigh.

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dks laKku esa yk;k tkrk gS\

How failure analysis is done. What are the important Parameters considered during

failure analysis?

Answer:-

A part or assembly is said to have failed under one of the three conditions:-

When it becomes completely in operative-occurs when the components breaks into

two or more pieces.

When it is still inoperable but is no longer able to perform its intended function

satisfactorily-due to wearing and minor damages.

When serious deterioration has made it unreliable or unsafe for continuous use,

thus necessitating its complete removal from service for repair or replacement-due

to presence of cracks such as thermal cracks, fatigue crack, hydrogen flaking

General procedure for Failure Investigation

The Objective of failure investigations and subsequent analysis is to determine the

primary cause of failure, and based on this determination; decide on corrective measures,

which should be initiated to prevent similar failures. The principal stages of investigation

are:-

1. Collection of background data of sample –

All available information regarding the manufacturing, processing and service

history should be collected.

2. Visual examination of failed components-

The fracture face is cleaned with K oil, and soft metallic brush. Location of the

fracture must be done in relation to some fixed corner or side depending upon the

specimen. Examine the fracture face with a magnifying glass to determine the type

of fracture. Nature of stress raiser can also be determined

3. To determine the nature of fracture and stress-

Ductile fractures

Brittle fractures

Fatigue Fractures

4. Non-destructive testing-

These tests include magnetic particle inspection, ultrasonic testing, liquid

penetrate inspections, and radiography. These tests are done to find out surface

and sub-surface defects.

5. Mechanical Testing-

Mechanical test include hardness test, UTS. Nick break test is done on non-ferrous

materials to see segregation and oxidation.

6. Chemical Testing-

Drillings of the component are taken to determine its chemical composition.

7. Macro examination-

Deep etch test

Sulphur print

8. Micro-examination-

This determines the microstructure, inclusion, and mode of heat treatment given to

the component. This also tells about the presence of micro-cracks, welding,

structural changes due to working etc.

9. Analysis of all the evidence, formulation of conclusion on the basis of all the

previous steps.

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viuk;s tkus okys lHkh ekinaMksa dk o.kZu djsa

Write down the complete manufacturing process of spring from spring steel bar.

Explain all parameters to be considered during this process?

Ans.The springs are made of round bars of fine grained special quality spring steel ( The

material may be consist of chrome vanadium, chrome molybdenum or silico- mangnaese

spring steel. Bar is converted in a coil shape by various operations.

Generally the steel bar manufacturer supply the spring steel round to the specified length

and composition ordered by the spring manufacturer. After receiving of material at site

the bar is to be checked or examined by the chemical and metallurgical lab. The

procedure of manufacturing of spring step by step as below.

1) End cutting of bars :-Generally the spring bars are supplied by the supplier.

During transportation bar gets cracks on its edges. It is necessary that bars end must

be crack less. At this stage bars may be cut to length by shearing carefully so as to

prevent cracking at the ends. cutting by gas is not Permissible.

2) Straightening :-Straight bar is required for spring manufacturing . So each bar is

straightened at bar straightening machine. Permissible straightness 1.5 per meter.

3) Peeling:-The bar is peeled off at peeling machine for a good, regular and defect

free surface. peeled bar 3% of bar dia. or 1mm whichever is more to remove surface

defects.

4) Centre less Grinding:- Peeled bar again grinded by a centre less grinding machine

before this bar takes a shape of coil at coiling machine. Before coiling it is

mandatory that surface finish of the grinded bar is 5 microns.

5) Bar crack deduction:- After peeled and grinded the bar is send for the crack

detection at crack detection machine . This is done in magna flux machine. The bar

passed through magnetized portion. If there is any type of surface crack present in

bar is deducted in this machine.

6)End Tapering:- Both the end of the ground bar shall be tapered by taper rolling

machine to give the finish of spring about 75% firm bearing. The taper face should be

smooth and should not have step pits or cracks.

The tip thickness of taper end bar end grinding should not less than one fourth of

nominal bar dia. up to 33mm and 1/5th

beyond of 33mm. it is to ensure that the tip

thickness of the finish spring does not in any way affect the load test requirement.

6) Stamping:- It is a process of coding on spring which is applied at in-effecting coil.

The serial order in which the particulars are stamped as below

XXXXXXXXXXXXX. in 13 digit

From left 02 digit for internal name (CV,SM), 03 digit for manufacturing code like

X01, X02 ,X03 etc. Next 04 digit for month and year i.e. 0112(for jan 2012) and

last 04 digit referred to Drg. no.

7) Bar heating:-Tapered ends bar is heated in bar heating furnace up to specified

heating temperature 8300 C to 860

0 C. walking beam furnace is used for making

temperature of bar uniform and required soaking time.

8) Coiling:-A red hot heated bar comes out from bar heating furnace and rest on a

preheated mandrel which is the part of high speed automatic coiling machine. Bar is

guided by a guide roller in automatic coil operation. Bar takes a shape of specified

uniform pitched coil.

9) Quenching:- A red hot heated coil is a very mild condition so it need to be hard .

The spring is quenched in oil bath or suitable medium conforming to standard

specification. The temperature of quenching bath should not be more than 800C.It

should be necessary to achieve minimum 90% martensite structure

10) Tempering:- During the coiling process the grain structure of bar is deformed due

to twisting and internal stresses developed .hardness of spring increased and

toughness is less. Due to more hardness breakage of spring will increase To achieve

a homogeneous fine grain structure in the spring. And to reduce hardness and to

increase toughness, It need to temper in tempering furnace below lower critical

temperature of steel. The tempering temperature is 3500C to 450

0C.

11) Hardness testing:- Tempered springs are dipped in a water tank for a carburizing

process. After heat treatment, the hardness of the spring is tested by lab staff by

using Brinel hardness tester(BHN). The hardness of the spring should be in the

range 380 BHN to 440 BHN for silico manganese steel and 415 BHN to 460 BHN

for chrome vanadium/chrome molybdenum spring steel.

12) End Grinding:-After hardness testing , both the end faces of the spring are

grinded the actual grinded surface is kept at least 75% of mean coil circumference

of the spring.

13) Shot Penning:- Now springs takes into continuous type shot penning machine

where it shot penned by high intensity shot to improve fatigue strength of spring.

14) Magna Flux Testing of spring :- Springs are tested by magna flux testing

machine to detect the surface and sub surface crack in the springs.

15) Scragging :- Each and every spring is scragged at home. In this operation spring is

compressed 03 times holding it at the home load. All the coils of spring is contact

with another. Excluding the inactive coils.

16) Pre load testing :- The spring placed on a flat rigid metal support is subjected to

incremental increasing load up to the specified bearing load so each spring is tested

on its load , and loaded height of the individual spring is measured.

17) Black paint :- After the above operation springs are painted by black paint in the

painting plant.

18) Grouping of colour :- The spring is painted with a suitable colour code for

identification as per specified in the document.

19) Dispatch :- In the last stage, springs are packed in suitable box with its RDSO

code . Now springs are ready to dispatch.

Q.7) vYVhesV LVªsl] czsfdax LVªsl] IykLVhd fyfeV] bykLVhd fyfeV dks n'kkZrs gq, LVªSl rFkk LVªsu

dk vkys[k cukb, rFkk LVhy dh VsalkbZM LVªsaFk Kkr djus dh fof/k dk o.kZu dhft,\

Plot stress and strain graph( Chart) indicating ultimate, breaking, Yield,

stress, Plastic limit, Elastic limit and explain tensile testing method of steel?

Answer :-

As per hooks Law under a constant load stress is directly proportional to strain.

The stress is defined as the internal resistance set up by the molecules of a material

to resist deformation, due to the application of external forces. Mathematically,

stress is expressed as the force or load per unit area of cross-section.

Stress= force/area

The stress is represented in N/mm2

Strain: The strain is defined as the deformation of change in length under the

action of external forces. Mathematically it is represented by

Strain ‘e’= change in length/original length .There is no unit of strain

D

STRESS A E

Plastic limit

Fig: stress strain diagram for mild steel

OA - Proportionate limit

A B = Upper Yield Point

BC= Lower Yield Point

AC = Elastic Limit

CD = Plastic Limit

D = Ultimate Stress

B = Breaking Point

Elastic Limit:

B

STRAIN

O

C

The proportional limit of stress and strain is known as elastic limit. Line OB is

denoted elastic limit. If the load is removed this will gain the original shape and

size. This means the material has the elastic property up to point B.

Plastic Limit: If the load is increase/ continue from point B The permanent deformation will

takes place from the point B and will not come in original shape and size. From

the point B the strain increases faster than stress. This is goes up to point E. from

point B to E known as plastic limit.

Ultimate Strength: At D, the specimen re gain some strength and higher values

of stress are required for higher strain and those between A& D. The load goes on

increasing till the point E is reached At the point E the stress will maximum this

stress is known as ultimate tensile strength.

Breaking Strength:

The stress is reduced from the point B and fractured at F. the strength at

point F is known as breaking strength.

Q.8) ,Dly dh vYVªklksfud VsfLVax djuk D;ksa t:jh gS\ chlh,u ,Dly dh vYVªklksfud VsfLVax

djus dh fof/k dk foLrkj ls o.kZu dhft,\

Why ultrasonic testing of an axle is necessary ?Discribe method of ultrasonic

testing of BCN wagon in details?

Ans: Ultrasonic is done to avoid on line failure of axles due to various defects

inherent in the axles or while developing in-services.

The defects in axles can be broadly classified as

2. Inherent defects i.e. the defects associated with the faults in making of steels and

During manufacturing of axles, unsatisfactory chemical composition and

unsatisfactory micro structure.

What Is Ultrasonic – Sound waves having frequency above 20000 cycle/ second called

ultrasonic. It is inaudible to human ear.

Sonic – Sound waves having frequency 20 to 20000 cycle/ second called sonic or audible

sound.

Sub sonic – Sound waves having frequency below 20 cycle/ second called sub sonic. It is

inaudible to human ear.

Ultrasonic is a Non – Destructive Testing of material.

NDT – When a structure or metal part is not to be spoiled while testing certain test called

non – distractive testing.

TYPE OF NDT

1. Dye Penetrate Test

2. Radio Graphic Test

3. UST

4. Magnetic Particle Test etc.

NEED FOR UST

Ultrasonic method for testing is mainly employed for detection of internal flaw,

where the service failure of axle is mainly due to fatigue cracks originating from

the surface. The surface crack can be detected by magnaflux, Dye penetrate

methods. But axle in axle with press fitted wheels gears and bearings etc., so

ultrasonic method of testing is most suited.

PARAMETERS OF WAVES

Frequency – Cycle/ Sec. (Hz)

Wave Length – meter

Velocity of sound – meter/ sec

Amplitude – Meter

Intensity – Power/ meter2

A few of application of ultrasonic waves based on frequency are as under.

25 KHz – Ultrasonic drilling

40 KHz – For under water signaling

400 KHz - For emulsion & agitation work.

1 to 1.5 MHz – For coarse grained structure

2 to 4 MHz – For material with fine grain structure (Axle)

High frequency sound waves which are commonly employed in UST

Longitudinal wave

Transverse of Shear wave

1. The velocity of longitudinal waves is constant in a given material –

Steel – 5.9 x 103

mtr. per sec.

Perpex – 2.73 x 103 m. per. sec.

Air – 0.33 x 103 m. per. sec.

2. Velocity of shear wave is constant in a given material.

Steel – 3.23 x 103 m. per. sec.

Perpex – 1.43 x 103 m. per. sec.

The lower velocity, the wave length of the shear wave is much shorter than that of

longitudinal wave & hence flaw of smaller dimension can be detected.

Piezo electrical crystal used in probe

a. Natural crystal—

1-Quartz 2-Sodium Potassium Tartarate

b. Artificial Crystals

1—Barium Titanate 2 Lithium Sulphate 3 Lead Zirconate Titanate(PZT)

Location of cracks developed in Axle in Service

1. Wheel Seat.

2. Gear seat

3. Grooves and change in section

4. Journal

5. Body

Principle- UST-Pulse-Eco-Reflection Method:-

A series of Ultrasonic waves are introduced in the material under test through coupling

medium from probe. The probe in the reflection wave, which comes either from the

opposite faces of the material under test or from flaw in the path of the wave, so that they

cause Reflection.

The receiving Probe converts the Ultrasonic waves to the Electrical Energy which is

amplified and displayed on a Cathode rays oscillograph. The Cathode rays screen is

divided in to ten equal divisions along the X- axis and, five equal divisions along Y- axis.

The location of the Flaw in the material under test can therefore be established by the

position of the flaw peak on the screen indicating the distance at which the flaw is

situated from the probing face.

Technique of testing: - Contact between the Probe and test specimen

1 Surface Condition- The probing surface should be free from indentation holes,

machining or grounding particles, foreign matters etc.

2 Selection of couplent - selection of suitable couplent between the probe and the

probing surface serves as a medium which is important for an effective transmission of

Ultrasonic Energy from the probe in to the material. For this usually various grades of

oil, greases etc are used.

3 Selection of frequency range and Sensitivity- the choice of the frequency is obtained

in the first place by the permeability of the material. The ultrasonic beam must not be

very divergent at the location of flaw so that energy remains concentrated.

4 Pulse strength and amplification - These should not be selected to high in order to

avoid stray echoes and multiple reflections. After it is sufficient to keep the back echo

height approximately 3/4th

of the initial echo.

Different Techniques used in Ultrasonic Testing of Axle –

1. FAR END SCANNING

2. NEAR AND LOW ANGLE SCANNING

3. TRACE DELAY TECHNIQUES

4. HIGH ANGLE SCANNING

1. FAR END SCANNING :

The main purpose of Far end Scanning is the test the whole length of axle by probing

from each end face.

Probes to be use = 2.5 MHz crystal

Diameter – 10, 15, 20 mm normally used.

Procedure - clean the end face of the axle, apply the couplent and placed the prop after

calibrating the Ultrasonic Flaw detector. Waves travel through the whole length of the

axle and the reflected from the end change of section.

The Probable reflection in axle may be follows –

a. End of the axle.

b. End of the Journal.

c. Wheel seat radii.

d. Stress relief grooves.

e. Gear seat radii.

Plot the observation and compare with theoretical predicted oscillograph pattern. The

slandered procedure should be made out for each type of axle. Scan the full axle from

both the end faces.

2. NEAR AND LOW ANGLE SCANNING :

Near end low angle scan is used to search the half of an axle nearest to the end to

which prob. is applied.

This scanning has been found useful in checking cracks in raised wheel seat and

gear seat etc. of an axle and also for confirming the finding of far end scanning

techniques.

In this type of scanning probe having an angle of refraction in steel between – 50

to 100.

3. TRACE DELAY TECHNIQUE :

In far end scanning long testing range about (2500 mm) is required and as such the

slandered Echoes from various reflectors from the axle appear closer. Operator may

face difficulties in evaluating the oscillograph pattern. Therefore these techniques

shall be applied to examine the axle in parts of 500 mm or less as desired.

This is an additional test, where due to short range echoes will appear not closer

and as such. It may be useful for confirmation of flaw signal obtained during far end

scanning.

0 500mm : 1st Range

500 00mm : 2nd

Range

1000 500mm: 3rd

Range

1500 00mm: 4th

Range

2000 00mm: 5th

Range

Prob to be used same as given in for end scan.

4. High Angle Scanning :

To find out cracks which are not accessible by low angle scanning and to confirm the

finding obtained during far end low angle scan.

High angle scanning is carried out with a shear wave probe with angle 330 to 65

0

refraction in steel.

This technique is employed from the body of the axle and meant for detection of

cracks in wheel seat (Gear seat).

The most important feature of this test is detection of a shallow crack. Flaw size

nearly half that detected by using for far end and near end low scan can be detected by

high angle scan.

Q.9fLizax cukus ds fy, eVsfj;y dk p;u dSls fd;k tkrk gS\ vkbZ-lh-,Q cksxh dh

cksysLVj fLizax cukus ds fy, dkSu lh lkexzh dk iz;ksx gksxkA fLizax cukus dh fof/k

dk foLrr̀ o.kZu dhft,\

How material is selected for manufacturing of spring? What material is used for

manufacturing of ICF bolster spring? Explain the spring manufacturing process in

details.

Ans- Material IS:3195 is used for making springs .For manufacturing railway rolling

stock springs material mentioned in WD-01-HLS-94(Rev -III) is used. For making

springs having dia less than 30 mm 60Si 7 as per IS 3195-92 is used and for springs

having more than 30 mm and less than 57, 52 Cr4Mo2V is used in which sulphur and

phosphorus content is maximum 0.025%.

Following step should be taken for Manufacturing of Helical Spring

Selection of Spring steel bar to IS-3195 grade crome vanadium spring steel

Cut the bar as per specified length

Straitening the bar as per specified value 1.5 mm/met.

1) Peeling of bar – peeled bar 3% of bar dia. or 1mm which ever is more

2) Centre less Grinding – Grind the peeled bar for smooth surface roughness should

be less then 5 micron.

3) Magnetic Particle testing:-The peeled and ground bar shall be subjected to

magnetic particle testing by florescent wet method. The test procedure for detecting

surface and sub surface defect should be as per IS 3703.

4) End Tapering: - Both the end of the ground bar shall be tapered by taper rolling

machine to give the finish of spring about 75% firm bearing. The taper face should

be smooth and should not have step pits or cracks.

The tip thickness of taper end bar end grinding should not less than one fourth of

nominal bar dia. up to 33mm and 1/5th

beyond of 33mm. it is to ensure that the tip

thickness of the finish spring does not in any way affect the load test requirement.

5) Stamping :- The following material code shall be followed for Stamping:

CM – for chrome molybdenum

SM - for silico manganese

The serial no, drawing no, drawing code, month and year of production and

manufacture code is also stand.

6) Heating and Coiling: The spring steel bar with taper end should be heated in oil

fired walking beam furnace with variable speed and soaked sufficiently at

temperature in a controlled atmosphere so that excessive scaling and decarburization

do not take place. The furnace in which the bar heated for coiling and heat treatment

should be equipped with automatic temperature indicator, controller and recorder.

Temperature of Quenching media should not exceed more than 800C

7) Tempering the spring: After Quenching shall be conveyed immediately through a

continuous conversed tempering furnace. During the tempering spring shall be

treated to desire predetermine temperature and for a sufficient length of time to

produce the require spring hardness throughout the section. The furnace should be

oil fired with automatic temperature indicator, controller and recorder. In order to

ensure proper heat treatment of spring as specified.

The total depth of decarburization partial plus completed on the finish spring in

the quench and tempered condition shall not exceed 0.5% of bar dia.

The hardness of the steel 415 to 460 BHN for chrome molybdenum.

8) End Grinding: Both the end faces of spring should be ground to ensure square

seating of the spring. The actual ground and surface shall be at least 75% of the

mean coil circumference coil spring.

9) Scragging :

Each and every spring should be scrag 3 times in quick succession. The scragging

load should not exceed 1.5 times the theoretical axial load. For long during

scragging the spring shall be compressed 3 times holding it at home load for 2 min

for first 2 stroke and 48 hours at the last stroke. The scragged spring should not so

further permanent set on subsequent loading.

10) Crack Detection:

100% springs shall be tested for crack detection by the megna flux test

11) Shot peening:

All the spring shall be shot peened in a continuous type shot peening machine in

accordance with IS-7001 to fatigue life of spring.

12) Load Testing, Grouping and Colour coding:

100% of spring shall be compressed with specified working load and the loaded

height of the individual spring shall be measured. The spring shall be grouped and

painted with suitable colour code for identification. Any spring which is found to be

defective or which does not confirmed the test should be rejected.

Q.10fMLVkWjlu D;k gS\ ;g fdl dkj.k ls gksrk gS\ bldks nwj djus ds mik; fy[ksaA

What is distortion? Write down the reason of distortion. Write down the

methods to eliminate distortion?

Ans- Distortion

Distortion in the vicinity of welded joints is a natural and inevitable consequence of the

non-uniform heating and cooling that occurs during the welding thermal cycle. This note

identifies the factors affecting distortion and provides some brief guidance to Fabricators

on practical approaches to controlling and correcting distortion during the fabrication of

metal structures.

Thermal distortion occurs when a process generates thermal gradients resulting in

strains, due to non-uniform expansion or contraction that exceed the local yield point of

the material. During the rapid heating cycle of a fusion welding process, material in the

vicinity of the weld heats, expands in all directions and is compressed by the constraints

of the much larger and cooler surrounding structure. The heated volume has a lower yield

point than the cooler surrounding structure and is more readily upset to a smaller

dimension, i.e. the heated volume yields in compression. On cooling, the weld deposit &

the heated volume of the adjacent parent material contracts in all directions, creating

tensile strains that are constrained by the attached cool structures that did not reach a

yield point strain during the entire heating and cooling process. This localized contraction

results in buckling, localized tensile yielding, or development of residual stress. On

thinner members localized buckling will occur. On thicker members less localized

distortion is evident, however residual stresses tend to be higher.

For a structural steel with a yield point of 250 MPa, a thermal differential of just

100°C will result in a thermal strain that approaches tensile yield point under fully

constrained conditions. For a structural steel with a yield point of 400 MPa, a thermal

differential of 160°C will result in a thermal strain that approaches yield point under fully

constrained conditions.

The volume change of a structural steel weld during a fusion welding cycle occurs

in two parts. Firstly the molten weld volume reduces by approximately 3% on

solidification. We see this solidification shrinkage as craters at weld run terminations.

Secondly the volume of the of the solidified weld metal reduces by a further 7% as its

temperature falls from the melting point to room temperature. These, two volume

changes always occur and distortion control depends on developing an understanding of

how to manage the process to minimize any detrimental effects.

Distortion in a weld results from the expansion and contraction of the weld metal and

adjacent base metal during the heating and cooling cycle of the welding

All welders have faced the problem of weld distortion at one time or another. The parts

start off straight and square, and after welding, the finished part is warped. Thinner

material is more susceptible, as it has less stiffness. Also stainless steels are more

susceptible, as it has greater thermal expansion and lower thermal conductivity than

carbon steels.

First, let's discuss why distortion occurs. Weld metal is deposited at a high temperature,

above the melting point of material. For steel, this is around 2,500°F (1,370°C). As the

weld cools to room temperature, it shrinks, but is restrained from doing so by the adjacent

cold base metal, resulting in high-residual tensile stress. The weld is now like a stretched

rubber band, with the work piece holding the ends. This is the reason that the base metal

moves, or springs back, when the clamps holding the work piece are removed, distorting

the part.

When the weld shrinks across its width, it causes groove welds to “wing-up” or fillet

welds to close up. When the weld shrinks along its length, it causes base metal to twist

around the weld.

To minimize weld distortion, design and welding should be addressed. Weld shrinkage

cannot be prevented, but it can be controlled. These are recommended steps for

minimizing weld distortion:

Avoid over welding — The bigger the weld, the greater the shrinkage. Correctly

sizing a weld not only minimizes distortion, but also saves weld metal and time.

Intermittent welding — To minimize the amount of weld metal, use intermittent

welds instead of continuous welds where possible.

Fewer weld passes — A fewer number of big passes results in less distortion than a

greater number of small passes with small electrodes. Shrinkage accumulates from

each weld pass.

Place welds near the neutral axis or the center of the part— Distortion is

reduced by providing less leverage for the shrinkage forces to pull the plates out of

alignment.

Balance welds around the neutral axis — Welding on both sides of the plate

offsets one shrinkage force with another, to minimize distortion.

Use the back step welding technique — In the back step technique, the general

progression of welding may be left to right, but each bead segment is deposited from

right to left. As each bead segment is placed, the heated edges expand, with

successive beads; the plates expand less and less because of the restraint from the

prior welds.

Presetting the parts — presetting parts before welding can make shrinkage work

for you. The required amount of preset can be determined from a few trial welds.

Alternate the welding sequence — A well-planned welding sequence involves

placing weld metal at different points of the assembly so that, as the structure

shrinks in one place, it counteracts the shrinkage forces of welds already made. An

example of this is welding alternately on both sides of the neutral axis in making a

complete joint penetration groove weld in a butt joint.

Clamping — Clamps, jigs, and fixtures that lock parts into a desired position and

hold them until welding is finished are probably the most widely used means for

controlling distortion in small assemblies or components. While there is some

movement or distortion after the welded part is removed from the jig or clamps, it

will be lower compared to the amount of movement that would occur if no restraint

were used during welding.

Peening — Peening the weld bead stretches it and relieves the residual stresses.

However, peening must be used with care. For example, a root bead should never be

peened, because of the increased risk of concealing or causing crack. Also, peening

is not permitted on the final pass, because it can cover a crack and interfere with

visual inspection. Before peening is used on a job, engineering approval should be

obtained.

Thermal stress relieving — Another method for removing shrinkage forces is

thermal stress relieving, i.e., controlled heating of the weldment to an elevated

temperature, followed by controlled cooling.

Q.11 vkbZ-lh-,Q-cksxh fLizax ds fy, eSxuht LVhy D;ksa mi;qDr ugha ekuk tkrk gS]

tcfd ;g dSluc cksxh fLizax ds fy, mi;qDr ekuk tkrk gSA

Why manganese steel is not considered suitable for manufacturing of ICF

Bogie spring? However it is considered suitable for Casnub Bogie.

:-Why manganese steel is not considered adequate for ICF bogie spring.

Mn Steel is not considered adequate for manufacturing of ICF spring because

hardness of Manganese steel bar untreated condition is 255 BHN Max. and Annelid

condition is 245 BHN max. Whereas the chrome Vanadium steel having hardness

310 BHN Max .and 255 BHN Max. Respectively. The material use for Casnub

Bogie is 60Si-7 which is not considered high value of hardness and toughness as

compare to chrome Vanadium Spring Steel. Material is use for ICF Bogie is 52 Cr4

Mo2V where chemical composition of the material is different in which Chromium,

Molybdenum and Vanadium is used other than this as per RDSO specification WD-

01-HLS-94 (rev. 3) material use for less than 30 mm bar dia. is silco-manganese

steel and above 30 mm chrome Vanadium Spring steel is to be used.

Due to high hardness and toughness after heat treatment the chrome Vanadium steel

is suitable for ICF bogies. The wire dia. of all ICF springs is more than 30 mm.

Therefore manganese steel is not considered suitable for ICF springs.

In addition to this the hardness of casnub bogie springs is 380-420 BHN where as

the hardness of ICF bogie springs (Bolster and Axle Box Spring) is 415-460 BHN.

This hardness can be achieved only due to presence of chromium, molybdenum and

vanadium in spring steel alloy material.

Q.12,uMhVh D;k gS\ fLizax ckj dks VsLV djus dh ukWu MsLVsªDVho VsfLVax D;k&D;k gSa

DokW;y fLizax dh esXusfVd ikVhZdy VsLV djus dh fof/k dk o.kZu djsaA

What is NDT? What is the non destructive testing for testing of spring bar?

Explain the Magnetic particle test method of coil spring.

Ans :-NN..DD..TT.. iiss aa ppoowweerrffuull ttooooll ffoorr rreedduucciinngg ccoossttss.. IImmpprroovveedd pprroodduucctt qquuaalliittyy aanndd

mmaaiinnttaaiinniinngg qquuaalliittyy lleevveell.. IItt iiss aann aacccceepptteedd ddeecciissiioonn mmaakkiinngg ttooooll ooff sscciieennttiiffiicc

mmaannaaggeemmeenntt.. ““QQuuaalliittyy”” iiss tthhee ttoottaalliittyy ooff ffeeaattuurreess aanndd cchhaarraacctteerriissttiiccss ooff aa pprroodduucctt oorr

sseerrvviiccee tthhaatt bbeeaarrss oonn iittss aabbiilliittyy ttoo ssaattiissffyy aa ggiivveenn nneeeedd.. TThhiiss ddeeffiinniittiioonn iiss bbaasseedd oonn

““FFiittnneessss ffoorr uussee ccoonncceepptt ooff pprroodduucctt qquuaalliittyy””..

IInn sspprriinngg mmaannuuffaaccttuurriinngg pprroocceessss tthhee NNDDTT uusseedd iinn ttwwoo ssttaaggeess.. BBeeffoorree

mmaannuuffaaccttuurriinngg ooff sspprriinngg tthhee rraaww mmaatteerriiaall ((sstteeeell bbaarr)) iiss tteesstteedd bbyy eeddddyy ccuurrrreenntt

tteessttiinngg,, tthhee pprroocceessss ooff EEddddyy CCuurrrreenntt TTeessttiinngg iiss ffoolllloowwss::--

EEddddyy ccuurrrreenntt tteessttss ccaann bbee ccaarrrriieedd oouutt oonn aallll mmaatteerriiaallss wwhhiicchh ccoonndduucctt eelleeccttrriicciittyy..

TThheeyy hhaavvee bbeeeenn uusseedd ffoorr ccrraacckk ddeetteeccttiioonn ..TThhee ppaarrtt ttoo bbee iinnssppeecctteedd iiss ppllaacceedd oorr

aaddjjaacceenntt ttoo aann eelleeccttrriicc ccooiill iinn wwhhiicchh aann aalltteerrnnaattiinngg ccuurrrreenntt iiss fflloowwiinngg.. TThhiiss

aalltteerrnnaattiinngg ccuurrrreenntt,, ccaalllleedd tthhee eexxcciittiinngg ccuurrrreenntt,, ccaauusseess eeddddyy ccuurrrreennttss ttoo ffllooww iinn tthhee

ppaarrtt aass aa rreessuulltt ooff eelleeccttrroommaaggnneettiicc iinndduuccttiioonn..

The change in flow of Eddy current is caused by the presence of a crack in a bar.

When the bar travels along the length of the inspection coil and if no crack is

present, the flow of eddy currents is symmetrical, where a crack is present in the bar

the eddy current changes significantly changes in the impedance of the primary

coils. The defective bar is automatically discarded by automatic plant .

After manufacturing of coil spring the quality of spring is checked by magnetic

particle inspection method. In this method the surface and sub surface cracks are

present, is to be detected.

Magnetic particle inspection (magna flux) principle:-

Magnetic particle inspection is a technique used for testing ferromagnetic materials.

The technique is basically simple and easy to operate. The spring is suitably

magnetized and magnetic lines of force or magnetic flux of enough density is made

available. Discontinuities in the path of the magnetic flux create a disturbance in the

uniform magnetic field causing flux leakage. The flux leakage set up of magnetic

poles attracts iron oxide powder when dusted over the testing zone and form a line

on discontinuity.

Testing Method:-

(i)Head shot method – In this method, current is passed through the spring and this

induced directly a circular field. In this position the iron oxide powder suspended in

kerosene or in other carrier liquid is spread on the spring. If the crack is present

perpendicular to the magnetic field, is detected in this examination.

(ii)Central conductor method– This is used for hollow components like coil springs.

A circular field is generated and induced indirectly in to the components and can be

used for detecting discontinuities that are parallel to the central axis of the springs.

Testing is done always on two directions to ensure that the discontinuities in

different directions are suitable covered. The defective springs are rejected.

Demagnetization:- Springs tested by this method retain some residual magnetism. It is

necessary that springs should be demagnetized. For this purpose reversing

magnetizing force sufficient to overcome the original field. It is done by reversing

current direction.

Advantages-

(i) It is simple, cheap and fast method to detect surface cracks.

(ii) This test can be carried out in finished condition.

(iii) It is the best method to detect cracks of all directions.

Limitations-

There are certain limitations for using MPT methods. It can detect only surface

opening and sub surface in ferromagnetic materials .For best results, the magnetic

field must be in a direction that will intercept the discontinuity at 900.

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blesa viuk;s tkus okys lHkh ekinaMksa dk o.kZu djsa

Write down the complete manufacturing process of LHB spring from spring

steel bar. Explain all parameters to be considered during this process?

Ans- Indian Railways has decided to manufacture LHB coaches at RCF Kapurthala by

transfer of technology from M/s Gruber Germany. Railway Board nominated RSK

Sithouli Gwalior to manufacture fiat bogie various type of springs.

Spring Classification.

Depending upon their loading condition, springs have been grouped into classes denoted

by the following letters:

A - Springs used mainly in axial compression

B - Springs used in axial compression and lateral bending and fitted

according to CHASSE value and direction (Flexicoil).

Raw Material

RSK is using spring material “52CrMoV4” for 25 to 65mm Bar diameter springs as per

ISO 683 part-14 or EN10089

Chemical composition

C Mn Si Cr Mo V S&P

0.48-0.56 0.72-1.0 0.15-0.40 0.90-1.20 0.15-0.25 0.07-0.20 0.015 max

Manufacturing process

Steel shall be manufacture by electric process through secondary refining furnace. The

routing of the steel through vacuum de-gassing plant is essential and purging is

mandatory.

Bar Quality

Bars should be smooth and free from distortion, twist kinks and harmful defects namely

seem folds, laps, cracks. Depth of rim decarburization should not be more than 0.4mm.

Peeled Bar

Average grain size of the bar shall as per ASTM no.6 or finer. Non-metallic inclusion

rating shall not be worse than 2.0 A,B,C,D(IS 4163-1982).

End Formation

Both the ends of the rod shall be tapered by Taper rolling to a length which shall be

equivalent to an arc angle of 270 degree (minimum)formed by end coils of the spring.

This meant to ensure a firm bearing of about 75% of the mean coil circumference at

support surfaces of the finishes Springs.

Tapered portion elongated as per x d x w x 1.5mm for each en, where d-bar dia and w-

spring index i.e. D/d (mean dia. divided by wire dia.)

Stamping

After the ends of attained desired temperature (8500 C ± 10

0 C),

Following particulars shall be legibly hot stamped on both papered ends (outer side)

in serial order.

Material Code CV

Manufacturer’s Code ABC

Month & Year of Production 0101

Drawing number (code) A101

1. Heating of Bars

Spring steel bars up to the temp, as per iron carbon diagram to attain homogeneous

austenite structure through the section. Cr-Mo steel heated

Up to 9100-930

0C.

Soaking- In furnace for the period 0.83 minute to one minute per mm of bar dia. Over

soaking avoided as furnace gases like O2 and CO2 oxidized which result loses of metals,

deterioration in condition of ordinary most high stressed layer of metal. It reduces

hardness in the quenched condition as well as wear resistance and fatigue strength.

2. Hardening

Bars should be coiled after heating bar above the phase transformation temperature, the

bars are rapidly coil and then quenched in oil in between temperature 8300-860

0C to form

martensite structure. Super saturated solution of carbon in iron is formed, called

martensite, the crystal lattice is tetragonal.

Retained Austenite:- The presence of retained austenite in hardened steel has a

detrimental effect on its mechanical properties. The formation of austenite due to blanket

of bubbles of oxides always surrounded at the time of in initialization of quenching

(cooling which impede the cooling rate).

3. Quenching Oil

To obtain more complete transformation of austenite into martensite better result. It needs

to be proper agitated to faster and uniform heat removal. Oil should be checked regularly

for flash point, viscosity, Acid number, sludge, moisture etc. quenching cracks may occur

quenching or any time before tempering. Quenching oil temperature should be kept

minimum and should not exceed 700C.

4. Tempering

Spring require reheating to a temperature below transformation range to separation of

carbon from martensite lattice and corresponding reduction is stressed state at

temperature below 200-2500C at higher temperature, i.e. 350-450

0 C, elastic stresses are

released. Tempering near about 3500C for 1 hr, the retained austenite is decompose e-

carbide is replaced by cementite and martensite losses its tetragonality cause failure by

brittle in nature.

Metallurgical Examination

Micro structure revealed by cutting, grinding and polishing then etched by 2% natal

solution and observe in optical microscope. It should be minimum 90% martensite at

surface and 70% minimum at core.

The hardness value determined at three stage:

1. On as quenched condition at surface, it should be between 550-650

BHN.

2. On surface after tempering condition as tempered hardness, it should

be between 420-510 BHN.

3. Hardness from case to core, the difference in between should not be

More than 30 BHN.

Micrograph of tempered spring should show tempered martensite structure, the grains

should be evenly distributed through section.

End Grinding

To ensure squire seating of spring. The actual ground end surface shall be at least 75% of

the metal coil circumference of the spring. Checked for any blue mark or buns short

peening.

A cold work process in which shots are impinged on to the surface of spring thereby

reducing residual stresses in outside fiber of the material, which improve fatigue life of

spring. The shot peen intensity should be checked by ALMEN strip test. For a size of

strip, it should be minimum 0.4 mm. The coverage area should be minimum 90% floater

and inner surface

Magna flux Testing – All spring have to test for magnetic particle inspection

for any surface cracks.

Scragging – The object of this is to reduce relaxation of spring under

working condition.

Load Testing – A test on a spring to determine either preload at a given

length or length under a given load. The stiffness for vertical

compression and lateral compression determined from load

defection m/c.

Phosphating – To prevent surface of spring from corrosion atmospheric

decay. The coating of zinc phosphate should be 5-10m fine

crystalline.

Painting – Priming uses synthetic metal primer of alkydresin base storing

quality as per IS:2932

Dry layer thickness should be min 30 microns. Coating lacquering the dry

layer thickness should be 40 microns.

Packing – Spring packed in multilayer vinyl acetate cover bag under

corrugated box.

Labeled by

1. Supplier/manufacturer identification

2. Contract No or PO No.

3. Quantity

4. Designation of spring

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nks mnkgj.k lfgr o.kZu djs

What is radiographic welding quality? Where this welding is used. Explain one or

two with the help of example.

Ans :- The quality of weld joint which is inspected by radiography is called Radiographic

welding quality. Radiography is one of the most useful NDT which can be applied by

assigning the quality of the weld joint. it is use to impact all type and thickness ranging

from minute weld to weld up to 0.5m thick. This quality of weld can be detected flaws

and discontinuities in joint such as cracks, porosity and blow holes slag flux or oxide

inclusion, lack of fusion between the weld metal and the parent metal, incomplete

penetration.

Radio-graphic technique is based upon exposing the component to sort wave length in the

form of X rays & Gama rays. From a suitable source. Both rays are electromagnetic wave

which penetrates opaque materials and obtain a permanent record on the result on

sensitized film. The contrast on the developed film between the images of an area of the

specimen permits the observer to distinguish the flows. He X rays & Y rays passing

through less denser parts of the objects observed to the smaller extent the ray passing

through the adjacent sound material. The light sensitive film is called radiograph.

X-rays are generated when high energy electron strike a metal target in X ray tube the

cathode emits electrons by thermo ionic emission these electrons are accelerated by the

tube voltage and strike against the anode in the process X-rays are generated Gama rays

are emitted from radioactive isotopes that are used for industrial radiography are cobalt

60, iridium 192, Cesium 137 etc.

Use of Radio graphic quality of weld

If a crack occurs in an area where the plate is wasted and of inadequate strength, the

defective portion should be cut out and replaced with a let in patch. It must be ensured

that the let in patch is of the same material and thickness as the parent metal. Corners of

patches should be rounded to a minimum radius of 25mm and edges must be carefully

prepared to obtain a V butt weld. Weld deposits should be smoothened flush with the

parent metal. Perform DP test and radiography of barrel plate.

The radio graphic quality weldments are used in boilers pressure vessels pressure piping

gas pipe-line and component which are used in dynamic loading. The lowest permissible

ambient temperature which making welds in carbon steel material with less 0.24% carbon

and in low alloy manganese and silicon manganese steels for example the boiler

component should be tested by radio graphic inspection as percentage of the weld length

for prelatic or martens tic steel

The film by exposure to X- rays, Gama rays is made visible and permanent; processing is

called out under subdued light of color to which the film is relatively sensitive. The film

first immersed in a developer solution after developing a film is rinsed in a sell filled with

water. Interpretation of radio graph shows on film and size of each flaw in measured in

mm by applying a rule to its image on the radio graph.

Examples: Heat Exchanger, Boilers, Pressure Vessels, Boilers Components, Bridges,

Aircrafts, Railway Rolling Stock(chemical & fuel tanks, motive engines, wagons &

coaches etc)

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dkj.k ,oa fuokj.k dk o.kZu djsa \

What is corrosion? In ICF coaches what are the various locations of corrosion.

Explain the reason there of and remedial action.

CORROSION AND ITS PREVENTION

Introduction: When metals are put into use in various forms they are exposed to

environment containing liquids, gases etc. As a result of this the surface of metal starts

deteriorating. This type of deterioration or destruction may be direct chemical attack

or electrochemical attack.

Definition: corrosion is a chemical process of oxidation with metal to its

surroundings, covering it into metal oxide, carbonates, hydroxide and sulphides.

Oxidation takes place only when steel surface exposed to atmosphere or moisture.

Chemical reaction is as follows:

4Fe + 3O2 --------2Fe2O3

Example: rusting of iron. When iron is exposed to atmospheric conditions rusting of

iron takes place. During this exposure a layer of reddish scale and powder of oxide is

formed and iron becomes week.

Corrosion in ICF coaches: Corrosion in ICF coaches is very common phenomena.

Corrosion repair to coaches are mainly carried out during POH in workshops.

Corrosion repairs are also carried out during midlife rehabilitation of coaches those

are 12 to 13 years old especially at CRWS, Bhopal.

During POH all the under frame members are thoroughly inspected to locate corroded

members. Corrosion is indicated by flaking of paint, flaking of metal, pitting and scale

formation. Components that is not visible from both sides such as sole bar and trough

floor should be examined by tapping with a spiked hammer.

Particular attention should be paid to the more vulnerable members and locations

given below.

1. Sole bars, body pillars, turn under and trough floor below lavatories in all types

of coaches and luggage compartments of SLRS.

2. Sole bars, body pillars, turn under and pillars above lifting pads.

3. Sole bars, body pillars behind the sliding doors of SLRS

4. Sole bars, body pillars, turn under at the door corners & near coach body

bolster.

5. Headstock Inspection of under frame member for corrosion attention should be

done as per technical pamphlet no 7602(rev: 1)

Reason of corrosion in ICF Coach:

Accumulation of water, dust and salty discharge under luggage compartment in

coaches.

1) Incorrect fitness of side panels.

2) Galvanic cell formation between steel and aluminium near window area.

3) Seepage of water at corners and ends due to water accumulation on floor.

4) In sufficient surface preparation before welding.

5) Frequent use of concentrated acids for the cleaning of toilets.

6) Leaky push cocks, flusher valves.

7) Missing/defective commode chutes resulting in splashing of toilet discharge

leads to corrosion of under frame members.

8) Carrying of perishables items like fish in SLRS and Parcel vans and

insufficient cleaning after unloading.

9) Entry of water through gaps in window sills.

10) Cracks in body panels and roof left unattended.

11) Painting defects left unattended.

12) Damage to under frame and trough floor due to flying ballast in dynamic

condition.

13) Acid spillage from batteries.

ATTENTION TO MINIMIZE CORROSION

Corrosion in rolling stock cannot be altogether. Hot and humid conditions in our

country is responsible for corrosion. A change in climate also has an adverse effect.

However timely action during repairs and maintenance will minimize corrosion.

A) DURING POH

1) Thorough inspection giving extra attention to areas prone to corrosion.

2) Turn under repairs to be carried out with 5mm thick plates.

3) Only 8mm thick SS sheets to be used for head stock repairs.

4) Use stainless steel trough floor and inlays for toilets.

5) Use of 13mm compreg floor board instead of plywood.

6) Use PVC sheets for toilets and compartment floor.

7) Use stainless steel plates with drain holes in doorways.

8) Provision of tubular structure below lavatory area.

9) Corten steel is used for panel repairs.

10) Apply two coats of primer and three coats bituminous solution on all

under gear members.

B) IN OPEN LINE

1) During pit line examination check thoroughly all under gear and under

frame components, trough floor and headstock etc. for corrosion. If

corrosion is noticed take proper anticorrosive measures.

2) Drain holes and drain pipes should be clear so that water stagnation is

eliminated.

3) All water leakage to be arrested at the earliest.

4) Proper repairs to damaged PVC floor.

5) Gaps in window sills to be filled up.

6) Deficient/defective commode chutes to be made good.

7) Hosing of coach interior is to be avoided.

8) Avoid strong acids for toilet cleaning.

9) Body patches to be painted, carry out paint touch-up where paint is

peeled off.

During IOH all vulnerable areas are to be properly inspected after Cleaning of

turn under holes.

How to apply anti corrosive paint in coaching stock.

I. 1st coat ------- Zinc chromate

II. 2nd

coat ------ Zinc chromate, red oxide

III. 3rd

coat ------- Bituminous thin black solution

IV. 4th

coat ------- Bituminous red brown solution

V. 5th

coat ------- Bituminous primer thick black

VI. 6th

coat ------- Bituminous primer silver gray

Suggestions To Prevent Corrosion:

1) Supervisors involved in maintenance of rolling should be familiar with areas

prone to corrosion.

2) Supervisors should educate their technicians about areas prone to corrosion.

3) Identify corrosion prone areas and inspect them thoroughly during pit line

examination, sick line attention, ROH/IOH.

4) Suitable preventive measures to be adopted to save the affected component. In

case of heavy corrosion replace the component.

5) Ensure painting of wagons during ROH. Painting/ paint touch-up during IOH

and sick line attention.

6) Supervisors should educate their cleaning staff so that they follow proper

cleaning technique.

7) Ensure water tightness of covered wagons.

8) Educate Shunting staff so that they perform smooth shunting without damaging

the rolling stock.

9) Ensure proper cleaning of wagons by the contract staff after Unloading.

10) Electrical staff to be counselled about the corrosive effect of acids from batteries

Q.16.fo;fjax ds QsY;ksj gksus ds eq[; dkj.k D;k&D;k gS] budks de djus ds mik;ksa dk o.kZu

dhft,A

What is the main reason of bearing failure? Explain the measure to reduce the

bearing failure.

Component wise defects of bearing are as under:-

Defects in CTRB:

a) Double cup:

Stain discoloration, corrosion, pitting and rust.

Flaking/spilling.

Pitting.

Electric burns.

Cracks & fractures.

Decrease in outer diameter.

Increase in counter bore.

b) Cone assembly:

Stain discoloration, corrosion, pitting and rust.

Flaking/spilling.

Smearing & peeling.

Pitting marks on roller surface.

The clearance between cage pocket & roller is more than 1.5mm.

The clearance between cage flange & inner ring is more than 2.3mm.

c) Wear ring:

Breakage in contact route of lip.

Scratches or cracks on out face.

d) Grease seal:

Hardened, cracked or cut seal lip.

e) Backing ring:

Pitting marks

Cracked fractured or heavy corrosion.

Loose wear ring in counter bore of locking ring.

Increase internal diameter i.e. more than 178.56mm.

Defects, their cause & remedial action are as under:

Sr. No. Defect Possible reason Remedial action

1. Flaking Entry of foreign particles,

water & poor lubrication

Improve the sealing

mechanism, use the lubricant

with proper viscosity

2. Peeling Rough surface due to poor

lubrication, entry of debris

into lubricant

Use proper lubricant, Improve

the sealing mechanism

3. Scoring Excessive load, shaft

bending

Check the size of load, check

the precision of shaft

4. Smearing High speed & light load,

sudden

acceleration/deceleration

Improved the preload, check

bearing clearances

5. Fracture Impact during mounting,

poor handling

Improved mounting methods,

provide enough back up &

support for bearing rib

6. Cracks Heat generation due to creep,

excessive interference

Correct the interference, use

& appropriate shaft shape

7. Cage damage Poor mounting, excessive

rotation speed, shock & large

vibration

Check mounting method,

check the rotation & load

condition, reduce the vibration

8. Denting Debris caught in the surface,

shock during transport or

mounting

Wash the housing, improve

the mounting & handling

methods

9. Pitting Exposure to moisture in the

atmosphere, poor lubrication

improve sealing method

10. Wear Progression from rust &

electrical corrosion, sliding

due to irregular motion of

rolling elements

Improve the sealing methods,

prevent misalignment

11. Fretting Vibration with small

amplitude, in sufficient

interference

Check the interference fit,

apply a film of lubricant to the

fitting surface

12. False

brinelling

Oscillation & vibration of a

stationary bearing during

transporting, oscillation

motion with the small

amplitude

Secured the shaft & housing

during transporting, reduce

vibration while preloading

13. Creep Insufficient interference or

loose fit, insufficient sleeve

tightening

Check the interference &

prevent rotation, correct

sleeve tightening, tighten the

raceway ring side race, apply

adhesive to the fitting surface

14. Seizure Excessive small internal

clearance, poor precision of

shaft & housing

Check precision of shaft &

housing. Study preload,

bearing clearances & fittings

15. Electric Burn Electric potential difference

between inner & outer rings

Earthing during welding on

wagon should not be taken

through track.

16. Rust &

corrosion

Entry of corrosive gas &

water, poor rust prevention

Improve the sealing methods,

anti--rust treatment for periods

treatment of long running

17. Mounting

flaws

Inclination of inner & outer

rings during mounting or

dismounting, shock load

during mounting or

dismounting

Use appropriate jig & tool,

avoid a shock load by use of a

press machine, centre the

relative matting parts during

mountings

18. Discoloration Poor lubrication, oil stain due

to reaction with lubricant

Improve lubrication methods.

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fo'oluh;rk dks dkSu lh dkjd izHkkfor djrs gSa] LisDVksxzkQ fo'ys’k.k dk uewuk ysus ds fy,

D;k rjhdk gSA ,Ydks yksdkseksVho esa fdruk fo;j esVy da'kuVªs'ku fjde.MsM gS\

What is the necessity of Spectrograph in a diesel shed ? On which principle does it work? What are the factors affecting its reliability? What is the procedure for taking lube oil samples for spectrograph analysis? What are the recommended wear metal concentrations in an ALCO locomotive? What inference would you draw from the elements wear? The usual physical-chemical analysis of used diesel engines crankcase oil provides adequate information regarding :

Dilution with fuel

Contamination with cooling water. .

Extent of insoluble matter.

Additive depletion.

Acidity.

It does not however give indication in respect of wear pattern of the engine components, which may be resulting due to the above or from other cause. With the help of spec-trograph, it is possible to determine the various metal concentrations quickly, accurately and at a reasonable cost. The spectrographic analysis of used crankcase oil helps in :

Predicting the required maintenance.

Scheduling the overhauls thus avoiding unexpected down and thereby increasing

the locomotive availability Eliminating the premature engine removal. Preventing costly engine failures resulting from the incipient wear of engine

components. Controlling the quality of lube oil supplies. The spectrograph makes use of two phenomena in physics i.e., the emission of light from an excited atom or molecule and dispersion of this light by 3' prism/grating to produce a spectrum, which is characteristic of that atom or molecule. When the atoms of an element are excited, they emit electromagnetic radiations, which are uniquely characteristic of that element. The light emitted is passed through a lens and dispersed by a prism on to a focal plane. The intensities of various light bands are fed on to a photo-multiplier. the current output of which are proportional to the individual instantaneous light intensities. This is the principle of spectrograph and the method of producing the familiar line spectrum of the elements. This procedure

is adopted as an accurate method for quantitative evaluation of elements by mea-suring the intensity of the radiation of the various elements at the particular wavelengths.

Following factors are important in obtaining reliable and accurate information from the spectrograph

Environmental conditions - Room should be air-conditioned and dust free. The temperature and relative humidity should be maintained as per manufacturer’s recommendation

Stability of electronic circuits. Constant input voltage to the power unit - Fluctuation in input voltage varies the

sparking characteristics of the source unit resulting in uneven sparking. Proper calibration of the equipment. Homogeneity of standard samples for calibration. Follow proper procedure for drawing the test samples.

Procedure for taking lube oil samples

The lube oil samples for spectrograph analysis should be preferably be taken from the engine sump/crankcase immediately after the locomotive comes to the shed after performing its trip, with engine running at idle rpm.

Sample must be drawn before topping up oil. Samples should be taken with a syringe with the nozzle extended by a transparent

tube. The tube shall be inserted through the dip-stick hole in the diesel engine crankcase so as to reach midway between the bottom of the sump and surface of the oil.

The syringe shall be purged by filling and discharging at least twice back into the crankcase.

The sample contained shall be pre cleaned and shall be flushed with the crankcase oil at least twice.

The syringe shall be filled, sample taken out and transferred to the container which shall be filled to 2/3,rd of its capacity to facilitate thorough mixing prior to analysis.

. The syringe for drawing out the sample shal1 be made from aluminum or brass and shall have a capacity of about 1/4litre.

. . The lube oil sample should be taken during trip schedule. . . The following data must be recorded - homing shed, loco no, Schedule, Kms, last

oil changed, last filter changed, last major schedule, date of sampling, abnormality in last testing.

. . Before the analysis of lube oil sample is carried out, the sample of used oil shall be heated to 60+-10 C1: t O"C and vigorously agitated for 5 minutes in the original container until all the sediments are homogeneously suspended in the oil. After complete suspension of all sediments, strain the sample through a 100 mesh screen for the removal of large contaminant particles. The strained oil shal1 be heated and thoroughly mixed before carrying out the analysis. The strainer for straining oil, the aluminum boats for carrying out the analysis and the containers into which the oil is strained shal1 be thoroughly cleaned with chemical solvents like paraffin

. . The graphite rotating disc electrode shall be used only for one test and the tip of the counter graphite electrode shall be ground after each test.

Following are the recommended wear metal concentrations:

Element Abnormal PPM Critical PPM Comments

Copper 10 20 Bushing wear. If leads is abnormal,

main/connecting rod bearing wear

Lead 5 10 Main/connecting rod wear

Tin 5 10 Main/connecting rod wear

Iron 20 50 Wear of ring, piston ,liner, crankshaft

journal, gear train ,cams etc

Chromium 5 10 If sodium is normal, liner wear is

indicated. Otherwise water leakage

Sodium 30 50 Water leakage

Aluminium 5 10 Piston wear

Silicon 15 20 Inefficient air filteration

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Lakjpuk Kkr djus dh fof/k dk o.kZu djsaA

What do you understand by chemical composition of material? Explain the

Methods to find out the chemical compositions of cone assembly of CTRB.

Ans-

Constituent found in the material is the form of element is called Chemical

Composition of the material. The physical, chemical and metallurgical properties of the

material depend upon the composition of the element present in the material.

For testing of chemical composition of cone of the CTRB which is to be checked

is picked up and one inch width of the cone is cut on the abrasive cutter. The sample

piece is polished and ground by 60 No. abrasive paper to make the surface fine and

finished. Spectrometer on which sample is to be checked should be calibrated by standard

having equivalent composition to the sample as SAE 4320-H. the chemical composition

is as under:-

Carbon - 0.17-0.23

Manganese - 0.40-0.70

Silicon - 0.15-0.35

Nickel - 1.55-2.00

Chromium - 0.35-0.65

Molybdenum - 0.20-0.30

Sulphur - 0.025-max

Phosphorus - 0.025-max

The sample is kept in the spectrometer on the orifice for burning. On the basis of wave

length of each element the chemical composition of each element is displayed on the

screen of the spectrometer. In this way the chemical composition of cone of CTRB is

obtained. Permissible percentage of variation of each element as per specification is also

considered for final analysis of the cone.

Q.19 Dok;fyax ds fy, ckj dks xeZ djus ds fy, okfdax che QusZ'k dh D;ksa vko';drk gS\

Why walking beam furnace is necessary for heating the bar for Coiling?

Answer :-

Walking Beam Furnace is necessary for uniform heating of bar for coiling.

Sufficient soaking time at the rate of 0.83 to 1 minute per mm of bar dia. is

required for uniform heating of bar from case to core. In walking beam furnace is

designed with conveyer to move the bars at a designed and programmable speed.

Bars are moved and heated from started loading point to end of the furnace

with desirable speed. The speed of bar is so designed that soaking time of bar is

adequate as per the requirement of time mentioned above. Bar can also rotate in

furnace for heating at controlled temperature. As per RDSO specification.

Deference of hardness of core and surface should not be more than 20BHN. To

make uniform hardness of bar from surface and core walking beam furnace is

necessary.

To distribute Austenite structure throughout the section of the material

walking beam is required and for complete change in Martensite structure. Heating

at under controlled temperature and proper soaking time is required for

manufacturing of spring. Therefore walking beam furnace is necessary

Q.20LVhy dh vfufyax djus dh fofHkUu izfØ;kvkssa dk foLrkj ls o.kZu dhft,\

Describe the different processes of Annealing of steel in detail.

The main objects of annealing in heat treatment are:

1. To soften the steel, so that it may be more easily machined or cold worked

2. To refine the grain size and structure to improve mechanical properties like

strength and ductility

3. To relieve internal stresses which may have been caused by hot and cold working

or by unequal contraction in casting

4. To alter electrical, magnetic or other physical properties.

5. To remove the gases, trapped in the metal, during initial casting.

The process of annealing is of the following two types:

1. Full Annealing:-The main object of full annealing is to soften the metal, to refine

its gain structure, to relieve the stresses and to remove gases trapped in the metal.

This process consists of heating the steel 300C to 50

0C above the upper critical

temperature for hypo eutectoid steel and by the same temperature above the lower

critical temperature hypereutectoid steels. The steel then held at this temperature

for some time to enable the internal changes to take place. The time allowed is

approximately 3 to 4 minutes for each millimeter of thickness of the largest

section and then slowly cooled in the furnace.

The rate of cooling varies from 300C to 200

0C per hour, depending upon the

composition of steel. The cooling, usually, carried out in the furnace. The objects

may also be taken out of the furnace and cooled in ashes so as to prolong the

cooling time.

In order the avoid decarburization of the steel, during full annealing, the steel is

packed in a cast iron box containing a mixture of cast iron borings, charcoal, lime,

sand or ground mica. The box, along with its contents, is generally allowed to cool

slowly in the furnace after the proper heating has been completed.

2. Process Annealing:- The main object of process annealing is to relieve the

internal stresses set up in the metal and for increasing the machinability of the

steel. In this process, the steel is heated to a temperature below or close to the

lower critical temperature, held at this temperature for some time and then cooled

slowly. This causes complete re crystallization in steels, which have been severely

cold worked and a new grain structure is formed. The process of annealing is

commonly used in the sheet and wire industries.

The approximate temperatures for annealing depending upon the carbon

content steel, are given below:

Sr.

No.

Carbon Content (in percent) Annealing temperature in 0C

1. Less than 0.12 (Dead mild steel) 875-925

2. 0.12 to 0.25 (Mild Steel) 840-970

3. 0.25 to 0.55 (Medium carbon steel) 815-840

4. 0.55 to 0.80 (High carbon steel) 780-810

5. 0.80 to 1.40 (High carbon or tool steel) 760-780

Q.21fLizax LVhy ds dPpk lkexzh ¼jkW eVsfj;y½ dSluc cksxh fLizax cukus esa iz;ksx gksus okys jkm.M

ckj ds HkSfrd jlk;fud rFkk /kkrqdehZ; xq.kksa dk Hkkjrh; ekud la[;k 3195 ds vuqlkj o.kZu

dhft, \

Describe the Physical , Chemical & Metallurgical properties of Raw material of

spring steel (round bar)as per IS 3195 used for manufacturing casnub bogie spring.

Manufacture: - Steel shall be manufactured by any process of steel making except

Bessemer process. It shall be followed by secondary refining or vacuum melting.

The size of ingots, billets or continuous cast billets for any given size of finished

steel product shall be such that a minimum reduction ratio of 16:1 from the minimum

cross sectional area of the ingot billet or continuous cast billets to the maximum cross

sectional area of the product is ensured.

Chemical Composition: -

Designation Carbon Silicon Manganese Sulphur Phosphorus

60Si7 0.55 to 0.65 1.50 to 2.00 0.80 to 1.00 0.030 0.030

Constituent Permissible Variation over Specified Limit Percent

Carbon ± 0.03

Manganese ± 0.03

Silicon

(upto and including 0.40)

(above 0.40)

± 0.04

± 0.05

Sulphur ± 0.005

Phosphorus ± 0.005

Chromium ± 0.03

Vanadium ± 0.02

Molybdenum ± 0.03

Note: Variation shall not be applicable both over and under the specified limits in several

determinations in a heat.

Hardness: - The hardness of the material when tested accordance with IS 1500:1983

shall be as given:-

Grade Hardness in BHN

Untreated Condition

(For Guidance only)

Annealed Condition Max

60Si7 ~270 ~245

Decarburization: -

Complete Decarburization Depth: - Complete decarburization depth is the depth

measured at right angles to the surface of the zone which contains at least 80% ferrite.

Partial Decarburization Depth: - Partial decarburization depth is the depth measured at

right angles to the surface, of the zone, which contains less carbon content of the core.

The limit of this zone is the point where a micro structural change between the surface

and core is apparent.

Depth of Decarburization: - The average total depth of decarburization (partial plus

complete) of five deepest uniformly decarburized zones for plain carbon and Silicon-

Manganese spring steels shall be limited to 0.15 mm + 1.0 percent of the bar diameter.

Inclusion Rating: - The inclusion rating when determined as per IS 4163:1982 shall not

be worse than 2.0 A, B, C, D both for thick and thin series.

Grain Size: - As per ASTM E112 the grain size should be 6 or finer.

Freedom from Defects: - The surface of the hot rolled material shall be reasonably

smooth and free from distortion twist and kinks and shall be substantially straight.

The precision ground and peeled bars shall be free from surface defects, such as

folds, laps, cracks, pits and grooves. The surface shall be bright, straight, smooth and

free from scales distortion, twist and kinks.

The hot rolled bars shall be free from harmful defects namely seams, folds, lapses,

cracks deep pits, grooves, excessive scaling etc. which may lead to cracking during

hardening or impair the serviceability. The material (hot-rolled, as well as, peeled and

centre less ground bars) shall be free from harmful internal defects such as piping and

segregation, which may impair serviceability.

Q.22dksYM jksfyax D;k gS\ dksYM jksfyax djus dh izfØ;k dk o.kZu dhft,\ dksYM jksfyax ds D;k

ykHk gSa\

What is Cold Rolling? Described the process for Cold Rolling. What are the

advantages of cold rolling?

Hot rolling of sheets less than 0.05 inch in thickness is not economical, thin sheets

are produced by cold rolling. Hot-rolled strip is pickled by passing it through a bath

of dilute acid, and is washed successively in cold water, hot water, and steam, to

remove the surface scale of oxide formed during hot rolling. It then is given a light

coat of oil to prevent reformation of oxide, and is cold rolled to the desired

thickness, usually in three-high tandem mills. The result is a thin sheet of steel with

smooth surfaces. Cold rolling increases the tensile strength and yield strength of

steel, but hardens it excessively. To restore ductility and to make it suitable for

deep drawing, cold-rolled sheet is softened by annealing; this is done in a non

oxidizing atmosphere to prevent surface oxidation.

Tinplate used for making cans for food is sheet steel of light gauge, coated with pure

tin. Proper adhesion of the tin requires particularly careful preparation of the sheet steel.

In addition to the cold-rolling operations ordinarily performed on sheet steel, that

intended for tin- plating is etched to assist adhesion and is given additional treatment in

pickling baths to provide a surface which can be wetted by molten tin. The sheet is

passed through molten tin, which is spread evenly by rolls.

The tin forms on the steel sheet a thin layer of iron-tin alloy that is covered by a

thick layer of pure tin; the result is a firmly bonded surface of pure tin.

Wire and Tubular Products

Wire drawing consists of drawing a rod through a series of successively smaller

dies until it conforms to a predetermined shape. During the drawing operation, plastic

deformation takes place.

Lubricants must be used during metal drawing to permit easy passage of the metal

through the dies; to permit the dies to resist the high temperatures reached; to prevent the

dies from welding to the metal; and to permit rapid production of smooth-finished work.

The lubricants must remain stable under the high pressures and high temperatures

encountered during drawing; they should be slippery enough to reduce the coefficient of

friction, thereby minimizing the heat generated; they must adhere to the moving surfaces

and spread evenly over them; they must be corrosion-resistant. Drawing compounds are

applied by brushing, swabbing, or spraying. Lubricants used include mineral oils

containing special additives, lubricating greases, soaps, water-soluble pastes, and pastes

compounded from water-soluble and oil-soluble compounds.

Advantages: -

1. It improves the mechanical properties like hardness, tensile and fatigue strength.

2. It prevents the loss of metal due to oxidation.

3. The cold worked metals have good surface finish.

4. It maintains a closer tolerance on dimension of a metal.

Disadvantages: -

1. It decreases ductility and creep resistance of a metal.

2. It requires greater energy to deform a metal physically.

3. It produces internal stresses in a metal.

4. It produces distortion in the grain structure of a metal.

Q.23dkWVZu LVhy D;k gS\ blds xq.kksa dk foLrkj ls o.kZu dhft,\

What is carton steel? Write down the properties in detail.

Definition

Weathering means that due to their chemical compositions COR-TEN A and COR-TEN

B steels, when utilized unprotected, exhibits increased resistance to atmospheric

corrosion compared to unalloyed steels. This is because it forms a protective layer on its

surface under the influence of the weather.

The corrosion retarding effect of the protective layer is produced by the nature of its

structure components and the particular distribution and concentration of alloying

elements in it. The layer protecting the surface develops and regenerates continuously

when subjected to the influence of the weather.

Formation, duration of development and protective effect of the covering layer on

weathering steels depend largely upon the corrosive character of the atmosphere. Its

influence varies and depends mainly upon the general weather conditions (e.g.

continental) macroclimate (e.g. industrial, urban, maritime, or country-side climate) and

the orientation of the structure components (e.g. exposed to or shaded from the weather,

vertical or horizontal position). The amount of aggressive agents in the air has to be taken

into account. In general the covering layer offers protection against atmospheric

corrosion in industrial, urban and countryside climate.

When utilizing this steel in unprotected condition it is up to the designer to take into

account the expected loss of thickness due to corrosion and as far as necessary,

compensate for it by increasing the thickness of the material.

In cases of particular air pollution by aggressive agents conventional surface

protection is recommended. Coating is absolutely necessary in cases of contact with

water for long periods, when permanently exposed to moisture, or if it is to be used in the

vicinity of the sea. The susceptibility of paint coats to under creep by rust is less in the

case of weathering steel than in the case of comparable non-weathering steel.

Chemical Composition (heat analysis, %)

Grade C Si Mn P S Cr Cu V Ni

COR-

TEN A

≤0.12 0.25-

0.75

0.20-

0.50

0.07-

0.15

≤0.030 0.50-

1.25

0.25-

0.55

≤0.65

COR-

TEN B

≤0.16 0.30-

0.50

0.80-

1.25

≤0.030 0.030 0.40-

0.65

0.25-

0.40

0.02-

0.10

≤0.40

In order to obtain fine grain structure a sufficient amount of nitrogen absorbing elements

is added (e.g. ≥0.02% Al).

Mechanical Properties, in the state of delivery condition at room temperature for plates

≥3mm in thickness (transverse test specimens, according to ISO 6892-1, method B).

Requirements to hot rolled plates ≤3mm in thickness according to EN 10025-5.

Grade Minimum

yield point

ReH

Mpa *)

Tensile strength

Rm MPa

Minimum elongation A

(Lo=5.65 √So)

%

COR-

TEN A 355 470 – 630 20

Grade Material

thickness

mm

Minimum yield

point

ReH

Mpa *)

Tensile

strength

Rm MPa

Minimum elongation

A (Lo=5.65 √So)

%

COR-

TEN B ≤16 355 470-630 20

> 16 ≤50 345

Applications

Corrosion resistant steel - Weathering Steel grade

The steel is used for various types of welded, bolted and riveted constructions e.g. steel

frame structures, bridges, tanks and containers, exhaust systems, vehicles and equipment

constructions.

The entire application technology is of fundamental importance for the performance of

the products made from this steel. It must be taken into account that not only general

climate conditions but also specific unfavorable local climate conditions in the broadcast

sense as well as details of a construction may affect the corrosion behavior of unprotected

weathering steel. The dependency on these facts makes it understandable that no

warranty can be given. It is recommended to control the corrosion progress of protected

parts out of weathering steel exposed to the influence of weather in reasonable time

intervals. A minimum thickness of 5mm is recommended when exposed to the weather in

the unprotected condition.

To use the benefits of the higher atmospheric corrosion resistance of COR-TEN in

comparison to unalloyed steel it is necessary that design and execution of structures as

well as the performance of maintenance works allow an impeded formation and

regeneration of the protective rust layer. The methods must meet the latest requirements

of technical progress and must be suited for the proposed application. Due consideration

must be given to relevant construction specifications.

Disadvantages

Using weathering steel in construction presents several challenges. Ensuring that weld-

points weather at the same rate as the other materials may require special welding

techniques or material. Weathering steel is not rustproof in itself. If water is allowed to

accumulate in pockets, those areas will experience higher corrosion rates, so provision for

drainage must be made. Weathering steel is sensitive to salt-laden air environments. In

such environments, it is possible that the protective patina may not stabilize but instead

continue to corrode

Q.24 QfVx D;k gS\ fdlh ikVZ@daiksusaV ds QfVx QsY;ksj gksus ds dkj.kksa dk foLrkj ls o.kZu djsaA

What is fatigue? Give the reasons of fatigue failure of a component, in detail.

Failure of steels or other metals from fatigue occurs at ordinary temperature; it usually is

caused by repeated application of load and consequent concentration of stress on what is

originally a minor flaw, until the flaw progresses so far that the section is weakened and

fails; corrosion accelerates failure by fatigue but does not initiate it.

Fatigue failure:-

Fatigue failure is a progressive, localized and permanent damage, which appears in

those parts under fluctuation stresses and strains. Above certain stress levels, fatigue

gives rise to cracks or fractures after a sufficient number of cycles have elapsed. It can

be considered as a combination of cyclic stress, tensile stress and stains and, if any of

those factors is absent, fatigue failure will not initiate or propagate.

Fatigue Life

Fatigue life can be defined as the number of stress cycles required to cause failure.

Fatigue life is a function of many variables like stress level, cyclic wave form,

metallurgical condition of the material etc.

Fatigue Failure Types: Several different variables are involved in the failure

process, resulting in different types of fatigue failure. Three main types of fatigue can

be found:

Fatigue Cracking: Results from cyclic stresses that are below the static yield

strength of the material. It is the most important fatigue failure process.

Thermal Fatigue: It is the result of temperature cycling; thermal expansion and

contractions cause thermal stress.

Contact Fatigue: Parts under pressure contact with each other, usually rolling or

sliding, suffer metal fatigue.

Corrosion Fatigue: It occurs in metal parts under cycling stress in a corrosive

environment. The corrosive environment accelerated formation and propagation of

cracks, even where individual variables can produce stress.

To meet the problems arising from the use of metals at high temperatures, it became

necessary to develop heat-resistant irons and steels for use at temperatures between 1100

F and 2200 F. These alloys have varying degrees of resistance to heat and to oxidation

within that temperature range. In selecting iron or steel for high-temperature service,

several factors must be considered:

1. Temperature range in which they are to be used.

2. Maximum temperature that will be encountered in use.

3. Range and frequency of temperature cycling.

4. Thermal shock that will be encountered.

5. Type and size of load.

6. Corrosive conditions that will be encountered.

7. Wear conditions.

8. Ease of fabricating and replacing.

The strength and load-carrying abilities of ferrous alloys decrease with increase of

temperature above 600 F. When ferrous alloys are stressed, they first suffer elastic

deformation; when the stress becomes sufficiently high, they deform in a plastic manner.

An increase in temperature lowers the stress point at which plastic deformation begins, so

that it is important to determine the stress that produces the maximum allowable plastic

deformation at a specified temperature, for long periods of time

Q.25fczusy gkMZusl VsfLVax djus dh fof/k dk foLrkj ls o.kZu dhft,\

Describe Brenell hardness testing method in details.

The Brinell Hardness Test is mostly used for determining the hardness of metallic

materials. It is the oldest method for finding of metals by penetration. The test is related

to applying a test load normally to the surface of specimen of metals through a steel ball

or known diameter for a given time. The steel wall being of hardness greater than that of

the specimen shall give an impression on the specimen which forms part of solid

spherical ball.

Test Specimen

The brinell Hardness No. (B.H.N.) is defined as the ratio of the applied load in

new tons to the surface area of impression expressed in sq.mm. Thus, BHN is also

measure indentation stress which can be expressed in units of N/mm2.

BHN = _________Load in New tons_______

Surface Area of impression in mm2

= P_

лDH

Now H= EC=OC-OE= D/2 - √ {( D/2 )2 - ( d/2 )

2}

B.H.N = __________P________________

лD[ D/2 - √ {( D/2 )2 - ( d/2 )

2} ]

= __________P________________

лD/2 [ D- √( D2 – d

2 ) ]

P= Applied load in New tons,

D= Diameter of steel wall in mm

d = Diameter of impression in mm

From the above, we see that following are the main requirements of the BHN test

1 STEEL BALL :- The diameter of the steel ball is generally 10 mm ± . 01mm. For

testing harder steels, tungsten, carbide wall are widely used.

2) TEST SPECIMEN :- The thickness of the test specimen should always be more than

8 times the depth of indentation. The test surface should be free from any oxide flame.

3) LOAD :- For ferrous metals, the load should be applied for a period of 15 sec.

For soft metals the load should be applied for a minimum period of 30 sec.

(Moreover The load should be applied gradually and smoothly)

Testing Procedure – The specimen sample for which Hardness to be test , Grinding of

surface to be done by the help of grinder / Portable grinder ,sample is placed at on proper

alignment under the machine alignment is made that indentation of the ball should be

ground surface of the project .

Specified load is applied for specific time & after load is released .

The indentation dia on the object is measured at two opposite side & average of the dia

is noted .

The hardness of the material is calculated with help of chart .The hardness values in

BHN is directly available in the chart as per of indentation dia .thus the hardness of the

material is Tested complete procedure is done as per IS 1500.

Q.26 ukWu MsLVªDVho VsfLVax D;k gS\ buesa ls fdUgha nks dk o.kZu dhft,\

What is Non destructive testing? Explain any two methods of NDT.

Human perception is based primarily on sight, sound & touch & this assessment process

applied to materials is the subject of Non-Destructive Testing all about. The connotation

e.g. NDT, NDI, NDE etc have been used to designate Non-Destructive Testing and can

be defined as the “Discipline of science which deals with the detection of flaw & its

characterization without impairing the serviceability of the component.”

Principle

NDT involves subjecting the material to specific physical characteristic, processing the

response obtained to a useful form and interpreting the same for flaw detection and

characterization. In effect, it is the differential behavior of the material under test at sound

and unsound zone, which manifests itself in the form of a response. The physical

characteristics employed may be acoustics, electrical conductivity, thermal conductivity,

radiation absorption, magnetic permeability etc.

The modification in the applied energy may be attenuation, reflection, diffraction,

velocity change, amplitude variation and such other positive and observable changes in

the energy applied. These observations provide valuable information to assess the

structural integrity of the part under the test.

Non-Destructive test of Materials.

Testing of materials without destroying them.

Testing of components without affecting their serviceability.

NDT As Manufacturing Control

To detect defects which had occurred in connection with or as a consequence of

manufacturing processes.

To ensure product quality and consistency by making it possible to check 100 %

components.

Control of manufacturing process.

It ensures product reliability.

NDT AS CONDITION MONITORING/PREVENTIVE MAINTENANCE

To test the component during service at a regular interval of time so that it can be

withdrawn from service before it’s failure.

Advantages

To ensure trouble-free transportation, avoid accidents.

To anticipate the serviceability of the component.

To predict residual life of a component.

To prevent loss of property and human life.

To obtain maximum economic life of the component.

DIFFERENT NDT METHODS

There are large numbers of NDT methods for testing of materials. The five ‘Big-

Methods’ used all-over Indian Railways are: -

Dye penetrate examination (DPE or DPI)

Magnetic particle examination (MPE or MPI)

Radiography

Eddy Current Testing

Ultrasonic

DYE PENETRATE EXAMINATION

PRINCIPLE: This method is used to reveal defects, which reach the surface of non-

porous materials. The penetrating liquid, which is dyed or fluorescent, is applies to the

cleaned surface of the component. The penetrant is allowed to act for a period of time.

Excess penetrant is carefully removed from the surface of the component, after which a

developing liquid is applied and dried off. The developer acts like a blotter, drawing the

penetrant out of the defect. After a short time indications appear in the developer, which

are wider than the defect and which, therefore can be seen directly or under ultraviolet

light due to the enhancement of the contrast between the penetrant and the developer.

PROCEDURE

1. Pre-clean, remove grease and dry the component.

2. Penetrant is applied to the component and acts for a brief period.

3. Excess penetrant is completely removed from the surface.

4. A developer is applied and dried off.

5. Inspect for indication of defects.

PENETRANT TYPES

Dye Penetrant: The liquids are colored so that they provide good contrast against

the developer. The liquids are as a rule red with white developer.

Fluorescent Penetrants: The liquid contains fluorescent material, which glows

under ultraviolet light.

Water Washable Penetrants: The liquid contains an emulsifier, which allows

surface penetrant to be removed using water.

Post-Emulsifiable Penetrant: after the liquid has been applied, an emulsifier must

be applied to the excess surface penetrant to make it water-soluble.

Soluble Removable Penetrant: The penetrant can only be removed fully from the

surface by means of an appropriate organic solvent.

DEVELOPER TYPES

Dry powder developers

Water based wet developers

Non-water based water developers

LIMITATIONS

Components with porous surface cannot be tested.

The crack must be opened to the surface.

MAGNETIC PARTICLE EXAMINATION

PRINCIPLE: This technique is well suited to the detection of surface defects such

as cracks, lack of fusion and laminations etc. in ferromagnetic materials.

A surface defect in a magnetized ferromagnetic item will disturb the magnetic field in

the object of the test. The defect will cause some of the lines of magnetic force to

depart from the surface and thus to form a magnetic leak field. This leak field can be

found by placing fine iron particles on the surface. The leakage field will hold the

magnetic particles in a ridge on top of the crack.

PROCEDURE:

1. Clean the surface.

2. Magnetize the object using either permanent magnet or electromagnet.

3. Spray magnetic liquid over the object.

4. Inspect for indication of defects.

5. Repeat the above test in perpendicular direction.

ADVANTAGES:

The method is most dependable and sensitive for finding surface defects.

It is fast, simple and inexpensive.

The indications are directly visible on the surface of the object.

Simple and durable equipment.

LIMITATIONS:

The method can only be applied to ferromagnetic materials.

Defects below the surface will not always be indicated.

The direction of the magnetic field has an important bearing upon the result of the

examination.

Certain objects must be demagnetized before and after the examination.

Q.27 dkWij fc;fjax LVhy D;k gS\ D;k ;g ekbZYM LVhy vkbZ-,l-2062 ls fHkUu gSaA o.kZu djsaA

What is copper bearing steel. Does it differ from mild steel to IS: 2062 Explain in

detail.

Copper bearing steel is a type of steel in which small amount of Copper is added to

protect atmospheric corrosion. In IS 2062 mild steel specification is available .In copper

bearing steel Cu is present . Copper may be present between 0.20 to 0.35 % The copper

bearing quality shall be designated with a suffix Cu, for example, E 250 Cu. In case of

product analysis the copper content shall be between 0.17 and 0.38 %.

The properties of this type of steel according to IS :2062 is following.

WELD-ABILITY:

A metallic substance is considered to be weld able by a given process and for the given

purpose, when metallic continuity to a stated degree can be obtained by welding using a

suitable procedure, so that the joints comply with the requirements specified in regard to

both their local properties and their influence on the construction of which they form a

part.

CHEMICAL COMPOSITION

Grade designation Quality

Ladle Analysis, percent, Max Carbon

Equivalent

(CE), Max

Method of

Deoxidation C Mn S P Si

(1) (2) (3) (4) (5) (6) (7) (8) (9)

E 165

(Fe 290) - 0.25 1.25 0.045 0.045 - -

Semi-killed or

killed

E 250

(Fe 410 W) A 0.23 1.50 0.045 0.045 0.40 0.42

Semi-killed or

killed

E 250

(Fe 410 W) B 0.22 1.50 0.045 0.045 0.40 0.41 killed

E 250

(Fe 410 W) C 0.20 1.50 0.040 0.040 0.40 0.39 killed

E 300

(Fe 440) - 0.20 1.30 0.045 0.045 0.45 0.40

Semi-killed or

killed

E 350

(Fe 490) - 0.20 1.50 0.045 0.045 0.45 0.42

Semi-killed or

killed

E 410

(Fe 540) - 0.20 1.60 0.045 0.045 0.45 0.44

Semi-killed or

killed

E 450

(Fe 570) D 0.22 1.60 0.045 0.045 0.45 0.46

Semi-killed or

killed

E 450

(Fe 590) E 0.22 1.80 0.045 0.045 0.45 0.48

Semi-killed or

killed

Carbon equivalent (CE) based on ladle analysis = C +Min/6+(Cr+mo+V)/5+(Ni+Cu)/15

MECHANICAL PROPERTIES

Grade

designation Quality

Tensile

Strength

min mpa

Yield Stress R min

Mpa

%

elogation A

at gauge

length

5.65S min

Internal

Bend

diameter

min

Charpi V-

Notch Impact

Energy min J

<20 20-40 >40 ≤25 >25 Room

Temp.

-

200C

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

E 165

(Fe 290) -

290 165 23 2t - - -

E 250

(Fe 410 W) A

410 250 240 230 23 3t - - -

E 250

(Fe 410 W) B

410 250 240 230 23 2t 3t 27

21

E 250

(Fe 410 W) C

410 250 240 230 23 2t 3t 27

21

E 300

(Fe 440) -

440 300 290 280 22 2t 3t 50 30

E 350

(Fe 490) -

490 350 330 320 22 2t 3t 50 25

E 410

(Fe 540) -

540 410 390 380 20 2t 3t 50 25

E 450

(Fe 570) D

570 450 430 420 20 2t 3t 45 20

E 450

(Fe 590) E

590 450 430 420 20 2t 3t 45 20

BEND TEST

Number of bend test shall be 2 %/heat

Class of steel product Direction of Bend Test

Plates strips, Crosswise

Sections lengthwise for each

Flats and bars (round hexagonal, etc) type lengthwise

For bend test, the test piece at room temperature shall withstand bending through 180

degree to an internal diameter not greater than that given in table 2 without cracking.

IMPACT TEST

Impact test shall normally be carried out on products having thickness/diameter greater

than or equal to 12 mm or subject to mutual agreement between the purchaser and the

manufacturer/supplier. The test specimen is parallel to the direction of rolling and the

base closer to the rolled surface is more than 1 mm from it. The natch axis shall be

perpendicular to the rolled surface.

OTHER TESTS: - The material may be subjected to non-destructing testing to

determine soundness of material.

Metallurgical tests for grain size, directionally, inclusion content to be carried out.

Q.28 Mh&feujykbTM IykaV esa okVj VªhVesaV fof/k dk o.kZu dhft,A

Explain water treatment methods used in De mineralized plant

Procedure of DM Water Preparation: -

Why Treatment is required: - since impurities present in raw water which are classified as

under:-

1. Suspended or non-ionic

2. Dissolve or ionic

3. Colloidal

4. Organic dissolve or insoluble

5. Dissolve gas such as CO2+O2

Dissolve and suspended impurities cause major problem like scaling/deposition and

the presence of dissolve gas i.e. O2 and CO2 cause electrochemical corrosion in system.

The dissolve impurities are removed by ion exchange proem where as suspended

impurities are removed through physical filtration. Dissolve impurities in water soluble

salt gets ionized as cat-ion & anion the main impurities.

Cation: - Hardness Ca++

Mg++

Sodium Na++

Iron Fe++ Fe+++

Anion: - Alkaline - HCO-3 CO3

-- OH

-

Minimal acidity Cl- SO4

- NO3

-

SiO2

Sodium increase TDS

Iron – Accelerate corrosion and deposition

Alkinila – To P&M

Cl- and SO4

-- ion’s promote corrosiveness of water. It also cause stress corrosion,

Cracking.

Silica high silica level to deposite silicate Ca++ and Mg++ as very hard Silica scale.

In an open evaporative recirculating cooling system. The concern of impurities increase

as water vapor do not carry when evaporate.

Hencde treated water free from impurities are required for locomotive for this purpose

several methods are adopted i.e. D.M. water by ion exchange method by reverse osmosis

process.

In Indian Rly mostly ion exchange method is used.

Procedure of preparing Dim water: -

It is prepared by ion exchange method. The following process is adopt to prepare D.M.

water.

Physical Filtration by Charcoal Process: - it is first step to pass from this Colum in which

charcoal fine particle present if filtration the water for insoluble impurities are removed.

D.M. water used in cooling system is very vital to the successful operation of life of

diesel engine component. Raw water contains many impurities since undesirable effect of

using raw water formation of sludge scale and corrosion. Therefore water used for

coolant required treatment before it can be used in diesel engine.

Cation Exchange Resin (RH+): - Mainly styrene divinely benzene CO polymer resin are

used which on sulphonation carboxylation become capable to exchange their H+ with

cation in water.

Anion Exchanging Resin (ROH-): - Mainly styrene divinylo benzene or amine

formaldehyde CO polymer which contain Amino, Phosphonium, Sulphonium gp as an

integral part of resin matrix. There after treatment with dil. NaOH become capable to

exchange their OH- ion with anion in water.

Mix bed Resin Column: - the conlum have anion exchange resin and cation exchange

resin, which react on residual anion’s or cation particles.

Process: - Raw water passed through filtration conlum after this water is passed through

cation exchange which remove all the cation from it and equal amount of H ion are

released from this column to water.

2RH++Ca++ = R2 Ca+2+2H+

After cation exchange column, the hazel water is passed anion exchange column which

remain all the anion present in water

R+OH-+Cl- = R+Cl-+OH-

H ion and hydroxid ion get combined to produce water molecule.

H++OH- = H2O

The water coming out from the exchanger Is free from cation and anion iron free water is

known as Dim Water.

Cation and anion column and mix set column regenerated by acid and causte to produce

pure water free from impurities.

Q.29 ]fifyax rFkk ls.VjySl xzkbZafMax D;k gS]budk fLizax dh n{krk c<+kus esa D;k egRo

gS\

What is the significance of bar peeling for manufacturing of coil spring?

Bar Peeling of spring

The straightened Bar are peeled before manufacturing of spring. The peeling of

bar is done as per RDSO specification i.e. 3% of bar dia or 1 mm which ever is

more. Peeling is important before manufacturing of the spring because all surface

defects such as Seams, Cracks, Folds are removed by the peeling. Which improve

the performance of the spring. If Peeling will not be done the surface crack will

propagate during service and spring will be crack i.e. why peeling is important. Centre less Grinding:- Peeled bar again grinded by a centre less grinding machine

before this bar takes a shape of coil at coiling machine. Before coiling it is

mandatory that surface finish of the grinded bar is 5 microns. Grinding shall be 3%

of nominal bar dia. or 1.0 mm whichever is higher

Q.30 yksdkseksVho ds Lusgd rsy dks VsLV djus dh fof/k dk o.kZu dhft,\

Write the method of Lube Oil testing of locomotive?

Method of testing of lubricating oil in Diesel sheds

Water Contamination:-The lube oil in crankcase oil should be free from water. The

presence of water is undesirable in many cases.

Shake thoroughly the sample

Draw a small quantity of sample on the hot plate

If the cracking noise is heard, then it indicates the presence of water

Specific Gravity: - The specific gravity is determined by using Hydrometer. The

hydrometer is allowed to flow freely in the oil in the glass cylinder and the observed

reading on the stem indicates the specific gravity of the oil at the room temperature. The

observed reading is then converted to Special gravity at 150C.

Flash Point: - The flash point of a petroleum product is the temperature at which

it gives off sufficient vapor to form a mixture with air which will ignite under standard

test condition.

The procedure involves slow heating of a specified quantity of product in a

standard Cleveland open cup apparatus. When the temperature reaches above 1000C, a

pilot flame is passed over the oil surface at the interval of every 20C rise of temp. the

temperature at which the first flash occurs is the temperature, which indicates the flash

point of the sample.

Viscosity: - It is the most important single property of lube oil. It may be defined

as the measure of the internal resistance to motion of a fluid by reason of forces of

cohesion between the molecules.

Viscosity is determined by noting the time required for a specified and measured

quantity of oil to flow in a standard apparatus at a constant temperature.

To measure the viscosity types of apparatus, which are in used, are Redwood

viscometer, Saybolt viscometer and kinemetic viscometer. The kinemtic viscometer is

now used extensively throughout the world.

To determine kinetic viscosity of lube oil, the Cannon-Fensky Marten reverse flow

viscometer tube size no.6 is used.

Clean the viscometer tube using suitable solvent, dry by passing dry air through

the tube to remove the traces of solvent.

To charge the sample into the viscometer tube, invert the tube and apply suction

by means of suction bulb to wider limb and draw oil up to the mark. Wipe and turn

the tube to its normal position.

Place the viscometer tube into the holder and suspend it into the constant

temperature bath, close the open mouth of the wider limb with a stopper.

Allow approx. 10 minutes to the sample to attain the temperature of the bath i.e.

400C and 15 minutes in case of 100

0C.

Remove the stopper and allow the oil to move in upward bulb using a stopwatch to

measure the efflux time for the oil meniscus to pass from initial mark to the final

mark.

Calculate the viscosity of the oil sample by multiplying the efflux time by

viscometer tube constant.

Report the value in centistokes

Efflux time X Viscometer tube constant = Kinetic viscosity in cSt.

pH Value: - pH value is determined by pH meter provided with calomel and glass

electrodes.

TBN (Total Base No.): - Total Base No. of the oil is a measure of the potential of the

lube oil to the neutralize strong acid, which may get formed in service.

Solution Required for Estimation of TBNE: -

(b) Titration solvent:- 495 ml. isopropyl alcohol+500 ml. Toluene+ 5 ml.

(c) N/10 Alcoholic HCl: - 5 ml. HCL in 500 ml. isopropyl alcohol.

(d) pH-4& pH-7 tablets: - Dissolve one tablet in required quantity of water.

(e) N/10 Alcoholic KOH: - 2 gm. of KOH in 200 ml. of isopropyl alcohol.

Leave it for overnight. Filter through goacn funnel.

(f) N/10 Pot. Hydrogen Phthalate: - Dissolve 2.0423 gm. In 100 c.c. of distt. Water.

Testing of sample for TBNE: -

o Weigh accurately 20gm. of used lube oil sample in a beaker (5 gm. in case of

new oil).

o Add 125 ml. of titrating solvent.

o Stirrer it with the help of magnetic stirrer till the pH meter indicates a constant

reading.

o Titrate against alcoholic HCL solution with stirring continued.

o Record the vol. of HCL consumed to bring the pH to 4.

Calculation: -

56.1XVol. of alcoholic HCL consumed

TBNE = X F

Weight of sample

Insoluble (Coagulant Method)

Coagulant Preparation: - 100ml. Hexane+500ml. N-Butyl-Di-Ethanolamine+50ml. of

isopropyl alcohol

Weigh empty centrifuge tube.

Weigh accurately 10 gm. of oil sample in it.

Add coagulant solution up to 100ml. mark.

Counter poise the tubes and shake well the content.

Centrifuge for 30 minutes at 1200 to 1500 RPM.

Decant the clear liquid without disturbing the settled sediments.

Add 50 ml. of Hexane, shake well and centrifuge for 20 minutes at the same RPM.

Repeat the cleaning process with Hexane at least twice and dry the tube at the hot

air oven at 1000C to 120

0C for one hour. Cool and weight the tube and calculate

Hexane insoluble as %.

Calculation: -

Weight of the sediment

% of insoluble = X F

Weight of oil taken

Blotter Test: -

Translucent Area

Drop Core

Dark Halo

Zone of diffulation

It Reveals: -

Contamination with insoluble

Poor dispercency

Fuel dilution

Water contamination

Q.31fcyV@baxV esa fjMD'ku vuqikr D;k gS\ D;k ;g esVsfj;y dh baVjuy izksiVhZ ij

izHkko Mkyrk gS\ fcyV rFkk baxV dk f'kjs dks jksfyax djus ls iwoZ D;ksa dkVk tkrk

gS\

What is reduction Ratio in bullet/Ingot? Does it affect the internal properties of

material. Why End portion of bullets/Ingot are discarded before rolling.

ANS- Ratio of cross section area of billet /ingot and final product is known as reduction

ratio .steel flats, rounds, plates are rolled from billets by means of rolling in rolling mills.

Reduction ratio i.e. reduction of cross section area of final production from billet have

vital role on internal quality of product .As reduction ratio will be more/ higher ,quality

of product will be better.

After steel has tapped into a ladle it still contains dissolved free oxygen and combined

oxygen in the form of iron oxide. Unless some deoxidant is added, free oxygen comes out

of solution and iron oxide reacts with carbon to form carbon monoxide during the period

of solidification of an ingot, with resulting evolution of gas. Steels of highest quality,

particularly tool steels, forging steels, and nearly all alloy steels, must be as free as

possible from the blowholes caused by the bubbles of evolved gas. By use of suitable

slags in the furnace and addition of proper deoxidants in the furnace or in the ladle or

both, it is possible to produce steel which is almost completely deoxidized. Because such

steel solidifies in the ingot mold with little or no evolution of gas bubbles, it is called

killed steel.

The reason of this is that nonmetallic inclusion breaks in each pass of reduction .presence

of nonmetallic inclusion in steel is considered impurities of the material .as reduction

ratio is less ,nonmetallic inclusion will be more it means impurities more. And as reverse

of this reduction ratio is more, nonmetallic inclusion is less it means impurities less.

Therefore it is confirm that reduction ratio effect on internal quality of steel material.

End portion of ingot/billet are discarded because during pouring of ingot, pouring from

bottom to top is done . all slag, blow holes, impurities comes up during pouring and sat at

end portion of ingot/billet. If this end portion is not discarded these defect will come in

final rolled product. Therefore this is the reason why end portion of billet/ingot is

discarded.

Q.32jcj dh gkMZusl psd djus dh fof/k dk o.kZu dhft,\

Describe the method for testing of hardness of rubber.

Hardness Test of Rubber:-The measurement of hardness in a simple method to assess

the elastic modulus of rubber. It is determine by measurement its resistance to penetrate

to rigid indenter an application of force on indenter.

The International Hardness Test is based on the measurement of the penetration of

a rigid ball into the specimen under specified condition. The measured penetration is

converted to International hardness degree IHRD.

Test specimen is 8 to 10 mm thick and has lateral dimension not less than 20 mm.

Standard Test temperatures is 230C or room temperature sample is conditioned at this

temperature at least 3 hours at 50.5% relative humidity.

Durometer Test: - Hardness of rubber is tested by Durometer it is small hardness tester.

In this type of hardness tester a spring is used to produce the indenting force and not dead

load and hence there are less precise and inconsistent hardness reading are often obtained.

These hardness tests are still popular because of handling.

There are two scales used in this type of hardness test:

Shore A (for soft rubber)

Shore D (for hard rubber)

Shore A scale matches approximately with 1 HRD Scale.

Shore D scale is used for rubber having hardness of 901 HRD or above.

Q.33ckWDluvkj esa iz;ksx gksus okys LVsuysl LVhy vkbZ-vkj-,l-,e-44 dh D;k fo'ks’krk,¡ gSaA

Write the Properties of Stainless steel IRSM 44 used in manufacturing of BOXNR.

The Properties of Stainless steel according to IRS: M44 as follows

Steel shall be manufactured by the electric furnace process. In case, any other process

is employed by the manufacturer, prior approval of RDSO shall be obtained.

CHEMICAL COMPOSITION CHEMICAL COMPOSITION

ELEMENT PERCENTAGE

Carbon - 0.03 max

Silicon - 1.00 max

Manganese - 0.8-1.5

Chromium - 10.8-12.5

Nickel - 1.50 max

Phosphorous - 0.03 max

Sulphur - 0.03 max

Titanium - 0.75 max

FREEDOM FROM DEFECTS

All finished material shall be well and cleanly rolled to the dimensions and weights

specified. The finished material shall be free from cracks, surface flaws, laminations,

rough jagged and imperfect edges and all other harmful defects. The sheets shall be

reasonably flat and cleanly sheared and truly squared to the specified dimensions. The

inspecting officer or the purchaser’s representative shall be free to decide the method of

detecting these defects.

SURFACE FINISH

Plates, sheets and sections

The plates, sheets and sections shall be well and cleanly rolled. Minor surface defects

may be removed by the manufacturer by grinding, provided the thickness is not reduced

locally by more than 4% and the final thickness remains within the tolerance. However,

the manufacturer shall indicate the areas of defect and grinding location to the inspecting

officer.

The surface finish of the plates /sheets/sections shall be 1.6 or better.

WELDABILITY

The plates, sheets and sections shall be suitable for metal arc welding using RDSO

approved medium basic coated electrode under class M1 to IRS: M-28 (Gr E-19.9L of

IS: 5206) using DC power source.

Where plates or sections of more than one thickness are rolled from the same cast, one

additional tensile test shall be made from the material representing each class of product.

MECHANICAL PROPERTIES :

When tested according to method specified in IS-1608 the ultimate tensile strength, 0.2%

proof stress and elongation percentage shall be as follows:

0.2% proof stress – between 35Kg / mm2

and 45 Kg /mm

2

Percentage elongation – 25% minimum on a gauge Length of 50 mm

U.T.S - 50 kg/mm 2

min.

If the fracture of the tensile test piece is outside the gauge length, the test shall be

discarded and retest conducted. To facilitate this sufficient no. of test pieces shall be

prepared in advance.

BEND TEST

The bend test specimen shall withstand being bend at ambient, temperature in any

direction through 180 degree around a former of diameter equivalent to the thickness of

the material without cracking on the outside of the bent portion.

Q.34fouk”kh rFkk vfouk”kh VSLV esa D;k vUrj gS\ fLizax LVhy ckj dk VSUlkby VSLV djus dh fof/k

dk o.kZu djsaA

What is the difference between destructive &Non destructive method? Write down

the method of tensile testing of spring steel bar.

Comparison of Destructive and Non-Destructive Tests

Destructive tests Non-destructive tests

1. Measurements are direct and reliable. Measurements are indirect reliability is to

be verified.

2. Usually quantitative measurements. Usually qualitative measurements.

3. Correlation between test measurements

and material properties are direct.

Measurements can also be done

quantitatively. Skilled judgment and

experience are required to interpret

indications.

4. Tests are not made on the objects directly.

Hence correlation between the sample

specimen used and object needs to be

Proved.

Tests are made directly on the object.

100% testing on actual components is

possible.

5. A single test may measure only one or a

few of the properties.

Many NDT methods can be applied on the

same part and hence many or all properties

of interest can be measured.

6. In-service testing is not possible. In-service testing is possible.

7. Measurement of properties over a

cumulative period of time cannot

Readily be possible.

Repeated checks over a period of time are

possible.

8. Preparation of the test specimen is costly. Very little preparation is sufficient.

9. Time requirements are generally high. Most test methods are rapid.

NDT involves subjecting the material to specific physical characteristic, processing the

response obtained to a useful form and interpreting the same for flaw detection and

characterization. In effect, it is the differential behavior of the material under test at sound

and unsound zone, which manifests itself in the form of a response. The physical

characteristics employed may be acoustics, electrical conductivity, thermal conductivity,

radiation absorption, magnetic permeability etc.

Tensile Test): - The tensile test of a metal is generally performed to determine:

1. Proportional and Elastic Limit

2. Yield Point

3. Ultimate Tensile Strength

4. Percentage Elongation and Reduction of Area

The results obtained by the tensile test are widely used in the design of materials for

structures and other purposes. In this test, the test piece is pulled out at a constant rate by

gradually increasing the axial pull, till the rupture takes place.

The tensile test for a ductile material is, generally, carried out with the help of a

universal testing machine on the specimen made from the material to be tested.

The schematic working arrangement of a universal testing machine, the specimen is

held in the jaws of the machine. And the load is applied gradually by a hydraulic press,

which is measured from the pressure developed inside the cylinder. The function of the

oil pump is to supply oil under pressure to the hydraulic cylinder. The load reading is

noted directly from the load scale.

The dimension and form of the specimen varies according to the size and shape of the

material to be tested and the main objective in view. The test is carried out on a specimen

having uniform cross-section throughout the gauge length.

The Bureau of Indian Standards recommended several sizes of the specimen. But the

standard practice is to use a specimen whose gauge length in mm.

l0 =5.65√A0

=5.0 d0

where, A0= Area of cross-section in mm2, and

d0 = Diameter of the specimen in mm

It means for a gauge length of 50 mm, the specimen diameter should be 10 mm.

Yield point, ultimate strength and breaking strength are directly noted on UTM and

elongation percentage are calculated by measuring length after breaking

Percentage elongation = L2-LO X 100

LO

Q.35 ghV VªhVesaV D;k gS\ gkMZfuax] VSEifjax rFkk vuhfyax djus dh fof/k dk o.kZu djsaA

What is heat treatment. Explain the method of hardening, tempering & annealing

Heat Treatment: - The term Heat Treatment may be defined as an operation or a

combination of operations, in the manufacturing process of machine parts and tools. As a

matter of fact, the heat treatment of a metal or an alloy is carried out first by heating it in

solid state and then cooling it. It is possible to impart the required or desirable mechanical

properties to steel or alloys for normal operations by heat treatment.

Objectives of Heat Treatment: - Though there are innumerable objectives, which are

achieved by heat treatment, yet the following are important from the subject point of

view:

1. To relieve internal stresses which are set up in the metal due to cold or hot

working

2. To soften the metal.

3. To improve hardness of the metal surface.

4. To improve machineability.

5. To refine gain structure.

6. To improve mechanical properties like tensile strength, ductility and shock

resistance etc.

7. To improve electrical and magnetic properties.

8. To increase the resistance to wear, tear, heat and corrosion.

Types of Heat Treatment: - 1. Hardening: - The main object of hadening are:

i. To increase the hardness of the metal, so that it can resist wear.

ii. To enable it to cut other metals i.e.to make it suitable for cutting tools.

The process of hardening consists of heating the metal upto a temperature of 300C

to 500C above the upper critical temperature for the hypoeutectoid steels and by the

same temperature above the lower critical temperature point for hypoeutectoid steels.

The metal is held at this temperature for a considerable time, depending upon its

thickness and then quenched in a suitable cooling medium.

The hardness obtained from a given treatment depends upon the rate of cooling,

the carbon content and the work size. A very rapid cooling is necessary to harden low

and medium plain carbon steels. The quenching in a water or brine solution in a

method of rapid cooling, which is commonly used. For high carbon and alloy steels,

mineral oil is generally used as the quenching medium, because its action is not so

severe as that of water. Certain alloy steels can be hardened by air cooling. But for

ordinary steel, such a cooling rate is too slow to give an appreciable hardening effect.

Large parts are, usually, quenched in an oil bath. The temperature of the quenching

medium must be kept uniform to achieve uniform results. Any quenching bath, used

in production work, should be provided with some means for cooling.

2. TEMPERING: - The main objects of tempering in heat treatment are:

1. To reduce brittleness of the hardened steels and thus to increase its ductility.

2. To remove the internal stresses caused by rapid cooling of steel.

3. To make steel sufficiently tough to resist shock and fatigue.

The process of tempering consists of reheating the hardened steel to some temperature

below the lower critical temperature, followed by any desired rate of cooling. The exact

tempering temperature depends up on the purpose for which the article or tool is to be

used.

When steel is heated to low tempering temperature (2000C to 250

0C), the internal

stresses are removed and ductility increases without changing the structure of steel from

martensite or reducing its hardness. On heating it to about 3000C, troostite-martensite

mixture is obtained which imparts some ductility to the metal. On heating it to 4000C,

martensite begins to change into fine pearlite or sorbite and the transformation of sorbite

and the transformation of sorbite is completed on reaching a temperature of 6000C. The

sorbitic steel is employed for making highly stressed parts, because it has a remarkable

mechanical property like ductility, strength and shock resistance.

The tempering temperatures may be judged by the colour formed on the surface of the

steel being tempered. The colours are caused by oxidation of the steel with the formation

of thin films of iron oxide.

The baths using tempering oils may be employed for temperatures upto approximately

2300C. The tempering oils are, usually, mineral oils having flash points of the order of

3000C. An adequate quantity of oil should be employed and the baths should be provided

with wire baskets which when loaded with work may be lowered into the tempering

baths. For temperatures above about 2300C, liquid salt baths are preferred. These salt

baths, usually, consist of mixtures of nitrates and nitrites. The chlorides and fluorides are,

usually, employed for higher temperatures.

3. ANNEALING

The main objects of annealing in heat treatment are:

1. To soften the steel, so that it may be more easily machined or cold worked

2. To refine the grain size and structure to improve mechanical properties like

strength and ductility

3. To relieve internal stresses which may have been caused by hot and cold working

or by unequal contraction in casting

4. To alter electrical, magnetic or other physical properties.

5. To remove the gases, trapped in the metal, during initial casting.

The process of annealing is of the following two types:

A. Full Annealing:-The main object of full annealing is to soften the metal, to refine

its gain structure, to relieve the stresses and to remove gases trapped in the metal.

This process consists of heating the steel 300C to 50

0C above the upper critical

temperature for hypo eutectoid steel and by the same temperature above the lower

critical temperature hypereutectoid steels. The steel then held at this temperature

for some time to enable the internal changes to take place. The time allowed is

approximately 3 to 4 minutes for each milimeter of thickness of the largest section

and then slowly cooled in the furnace.

The rate of cooling varies from 300C to 200

0C per hour, depending upon the

composition of steel. The cooling, usually, carried out in the furnace. The objects

may also be taken out of the furnace and cooled in ashes so as to prolong the

cooling time.

In order the avoid decarburization of the steel, during full annealing, the steel is

packed in a cast iron box containing a mixture of cast iron borings, charcoal, lime,

sand or ground mica. The box, along with its contents, is generally allowed to cool

slowly in the furnace after the proper heating has been completed.

B. Process Annealing:- The main object of process annealing is to relieve the

internal stresses set up in the metal and for increasing the machineability of the

steel. In this process, the steel is heated to a temperature below or close to the

lower critical temperature, held at this temperature for some time and then cooled

slowly. This causes complete re-crystallization in steels, which have been severely

cold worked and a new grain structure is formed. The process of annealing is

commonly used in the sheet and wire industries.

Q.36 xzs dkLV vk;ju ds D;k xq.k gSa\ ;g OgkbV dkLV vk;ju ls fdl izdkj fHkUu gS\

What are the properties grey cast iron? How does it differ from white cast iron?

Gray Cast Iron

Gray cast iron is the form of iron most widely used for castings. Its matrix is

composed of pearlite with minor amounts of ferrite. If the iron contains an appreciable

amount of phosphorous, the structure also includes steadite, a hard and a brittle substance

containing about 10 % phosphorous, and consisting of a mixture of iron and iron

phosphide. Steadite usually is present in the grain boundaries of gray cast iron, and

appears under microscopic examination as a fine structure less area.

The characteristic gray fracture from which gray cast iron derives its name is

attributable to the presence in its structure of flakes of graphite, a practically pure form of

free carbon; graphite is formed by decomposition of cementite into iron and free carbon.

It is evident that the amount of graphite that can be formed is largely dependent upon the

carbon content of the cast iron, but for any stated amount of carbon the degree of

graphitization is determined primarily by the rate of cooling and the content of silicon.

The slower the cooling, the greater is the tendency toward formation of graphite. Because

silicon is soluble in ferrite, its presence in the iron reduces the capacity of ferrite to

dissolve carbon, and thereby promotes graphitization and softens the iron. When either

the carbon or silicon content of an iron is too low for the section thickness involved, hard

iron carbide forms at the corners and in other rapidly cooled places. On the other hand,

excessively high content of carbon or silicon in heavier sections makes the iron soft and

weak, because the iron will be open grained. The graphitizing effect of silicon may be

assisted or impeded by the presence of other elements. Sulfur tends to form iron sulfide,

which impedes the formation of graphite by stabilizing cementite. If manganese is

present to about 0.35 % in excess of the theoretical amount required to combine with

sulfur, manganese sulfide is formed instead of iron sulfide, and the stabilizing effect of

iron sulfide is removed. A considerable excess of manganese, however, inhibits graphite

formation because it combines with carbon to form manganese carbide, leaving

correspondingly less free carbon to exist in the form of graphite. As an alloying element,

manganese imparts density and high strength. A manganese sulfur ratio of 6 to 1 is

suggested. Alloying elements such aluminium, nickel, and titanium are soluble in ferrite,

and therefore promote graphitization in the same manner as does silicon; other elements

such as chromium, tungsten, and vanadium form carbides and therefore inhibit

graphitizatiom by holding carbon in combination. A high phosphorous content weakens

cast iron and increases its fluidity in the molten state, but has little effect on

graphitization.

The properties of gray cast iron vary over a wide range depending upon the method

of making, heat treatment, and composition. Alloy cast irons are available for a wide

range of special purposes. In general, gray cast iron is characterized by its power to damp

vibrations and by the wear resistance imparted by the lubricating effect of graphite; both

properties make gray cast iron a useful material for the construction of machinery. Gray

cast iron of suitable composition is readily machinable and is an economical material of

which to make many metal parts used in various industries.

White cast iron

White cast iron normally is so low in silicon plus carbon that during and after

solidification no carbon is precipitated as graphite. All carbon therefore exists in

combination with iron as iron carbide, and the structure consists of pearlite and

cementite. A similar structure can be obtained on a section of gray cast iron by cooling it

rapidly; this is called chilled cast iron. White cast iron is hard, brittle, and almost

impossible to machine. It is used to a limited extent in applications, which require these

properties, such as plowshares, car wheels, chilled rolls, dies, and grinding balls.

Q.37LVhy esa dkcZu dUVsUV c<+kus ls D;k izHkko iM+rk gS\ Iysu dkcAu LVhy esa fuEu ,yhesaV dk

D;k izHkko iM+rk gS\

¼v½ lYQj ¼c½ eSaXuht ¼l½ flfydku

What are the effects on increasing carbon content of steel? What are the effects of

following elements on plain carbon steel:-

(a) Sulpher (b) Manganese (c) Silicon

Answer :-

Steels which have its properties mainly due to its carbon content and do not contain

more than 0.5% silicon and 1.5% manganese are called plain carbon steel. These

steels are strong, tough, ductile and used in expensive materials. They can be cast,

worked, machined and heat treated to a wide range of properties. Unfortunately, plain

carbon steel has poor atmospheric corrosion resistance. But it can be protected easily

by painting, enameling or galvanizing.

The properties of plain carbon steels depend upon the presence of carbon content.

The hardness and strength increases with an increase in carbon content. These

properties increase due to the presence of hard and brittle cementite. The ductility and

toughness decreases with an increase in the carbon content.

The following are important effects of silicon, sulphur,and the manganese on steel:

1. Silicon: - The amount of silicon in the in the finished steel usually ranges from

0.05% to 0.30% silicon is added in low carbon steels to prevent them from

becoming porous. It removes the gases and oxides, prevent blow holes and thereby

makes the steel tougher and harder.

2. Sulphur: - It occurs in steel either as iron or manganese sulphide. Iron sulphide,

because of its melting point produces red shortness, whereas manganese sulphide

does not affect so much. Therefore manganese sulphide is less objectionable in

steel than iron sulphide.

3. Manganese: - It serves as a valuable deoxidising and purifying agent in steel.

Manganese also combines with sulphur and thereby decreases the harmful effects

of this element in the steel. When decreases the harmful effects of this element in

the steel. When used in ordinary low carbon steels, manganese makes the metal

ductile and of good bending qualities. In high speed steels, it is used to toughen

the metal and to increase its critical temperature.

Q.38LoPN fp= dh lgk;rk ls vk;ju dkcZu Mk;xzke dk o.kZu djsa rFkk bldk rkieku ds lkis{k

QsTk+ psfUtax dk o.kZu djsaA

Describe Iron carbon diagram with help of neat sketch. Explain the phase change

with respect to temperature.

Answer:

In the iron-iron carbide diagram is not of any practical importance. Therefore, it is

possible to modify the iron-iron carbide phase diagram by omitting the low carbon region

above 14000C. Moreover, the various solubility curves, in the actual phase diagram, are

taken as straight lines. We shall use this diagram to study transformation of various alloys

from the liquid to the solid state. The transformation of various alloys may be discussed

under the following two heads:

1. Primary Solidification: - This corresponds to the transformation of alloys from its

liquid state to a temperature just below the eutectic temperature. It is also called

transformation from liquid to solid state.

2. Secondary Solidification: - This corresponds to the transformation of alloys from

the solid state below the eutectic temperature to the solid state below the eutectoid

temperature. It is also called transformation of alloy from solid-to-solid state or

secondary crystallisation.

1. Primary Solidification: - The transformations which occur on cooling iron-carbon

alloys from the liquid state below the eutectic temperature, i.e. 11480C are called

primary solidification. To study these transformations, consider the sequence of

events when liquid alloys of various carbon contents are cooled to a temperature just

below the eutectic temperature 11480C. If an alloy containing 0.8% carbon is cooled

from a point ‘m’ (in the liquid state) lying above the liquids line AE, it will remain in

its liquid state up to a temperature t1 (about14630C). At this temperature, the crystals

of austenite crystals (or ɣ-phase) begin to participate from the liquid alloy. The

composition of austenite crystals at t1 may be determined by drawing a horizontal line

(called tie-line) at t1. The intersection of the tie-line with solids line AC (point B)

gives the composition of austenite crystals at t1. As the alloy is further cooled below

the liquids line AE, the amount of austenite increases continuously. The composition

of austenite formed during cooling, varies along the solidus line AB and that of the

liquid phase along the liquids line AE.

When the temperature decreases to a temperature t2, the alloy will become

completely solid and will consist entirely of crystal austenite. The alloys with

carbon content varying from 0.2% will solidify exactly in the same manner as

discussed above. All these alloys, at the end of solidification, will consist of only

austenite.

Now consider an alloy containing 2.11% carbon. When this alloy is cooled

from point ‘n’ a process similar to the one discussed above will take place. The

austenite crystals will begin to from a temperature t3 lying on the liquids line AE.

As the crystals separate, the liquid gets richer in carbon and the last drop of liquid

containing 4.3% carbon will solidify when the eutectic temperature of 11480C is

reached. At this temperature, the alloy will consist entirely of austenite crystals

containing 2.11% carbon dissolved in ɣ-iron. Thus austenite of 2.11% carbon

composition is a solid solution of carbon in ɣ-iron. When a liquid alloy containing

3.0% carbon is cooled from point ‘O’, it begins to precipitate austenite crystals

from the liquid alloy at temperature t4 lying on the liquids line AE. In this case,

also the austenite crystals also increase continuously as the temperature falls.

When the temperature falls to 11480C, the remaining liquid of eutectic

composition decomposes into a mixture of saturated austenite and cementite. This

eutectic mixture is called ledeburite. The cast iron alloys of any composition

between 2.11% and 4.3% carbon will solidify in this manner only. It may be noted

that the microstructure of all these alloys is composed of a proeutectic austenite in

a matrix of eutectic mixture.

Now, suppose an alloy of exactly the eutectic composition i.e. 4.3% carbon

from a temperature corresponding to point ‘p’. This alloy will remain in the liquid

phase, until the eutectic temperature is reached. At this temperature, the alloy will

solidify completely to a eutectic mixture called ledeburite.

2. Secondary Solidification: - The transformations, which occur on cooling iron carbon

alloys below the eutectoid temperature i.e. 7230C, are called secondary solidification

or secondary crystallization.

To study these transformations consider the sequence of events, when the solid alloys

of various carbon contents are cooled below the eutectoid temperature. Now consider an

alloy with 0.3% carbon cooled from a temperature above the line KD, where the steel is

entirely austenite. A little consideration will show that nothing will happen to this until, a

temperature of about 800C, on the line KD, is reached. At this temperature ɣ-iron is

austenite. It will begin to transform into ɑ-iron. As the alloy is further cooled, the carbon

content in the austenite increases along the line KD. When the alloy is cooled to 7230C,

the remaining austenite containing 0.8% carbon decomposes into eutectoid, a mixture of

ferrite and cementite. This eutectoid mixture is called pearlite. The point ‘D’ is called the

eutectoid point and the line GDH as eutectoid line.

Now consider and alloy with 0.8% carbon being cooled from austenite state. When

this alloy is cooled, no change occurs until the eutectoid point ‘D’ is reached. At this

point, the entire austenite will decompose into pearlite.

When an austenite containing 1.3% carbon is cooled from the austenite state, no

change occurs until kit is cooled to 9600C. at this temperature, austenite begins to

decompose with the precipitation of excess carbon as cementite. Since cementite contains

6.7% carbon, its separation will cause a progressive decrease in carbon content of the

austenite with the fall in temperature along the line CD. When the eutectoid temperature

is reached, the remaining austenite will have eutectoid composition. This will transform

completely into pearlite at this constant temperature.

Q.39LVsuySl LVhy D;k gS\ fofHkUu izdkj ds LVsuySl LVhy dk o.kZu djsaA

What is stainless steel? Describe different type of stainless steel.

Corrosion of steel at ordinary temperature is in most cases a process of gradual oxidation.

This is produced by combined action of moisture and oxygen, by action of various

chemical substances such as acids, or by the action of corrosive atmospheres, which

result from some chemical process. At high temperatures, corrosion by formation of

oxides and sulfides is often so rapid that a scale forms on the surface of steel. The best

protection against corrosion is the formation of a closely adherent film of oxide on the

surface of the steel, but unfortunately the ferric oxide, which forms initially on iron or

steel is not sufficiently adherent to afford any useful protection; it is therefore necessary

to add an alloying element or elements capable of forming an efficient film of oxide.

Although copper and nickel have some beneficial effect in protecting steel from

corrosion, the most potent alloying element has been found to be chromium;

consequently all corrosion-resistant (stainless) steel have contents of chromium.

Oxidation of chromium starts more rapidly than does oxidation of iron, with the result

that a thin transparent film of chromium oxide forms on the surface of chromium alloy

steel, protecting it from further action of moisture and oxygen. Because tendency to

corrode increases with increasing temperature; steel, which is to be used in high

temperature service must have greater resistance to corrosion and therefore greater

content of chromium than is required in steel used at ordinary temperatures.

For a low carbon steel that contains about 0.15 % or less of carbon, approximately 11

% of chromium is required to provide adequate resistance to corrosion by moisture and

air, or by fruit juices. As the carbon content of steel is increased, some of the chromium

acts to form carbide and is therefore not available to form the protective oxide film; to

compensate, about 1.0% more chromium for each additional 0.05% of carbon is required

to maintain resistance to corrosion. Resistance to corrosion increases almost

proportionally to chromium content of steel; other alloying elements are added to

stainless steel chiefly for their effects upon the physical properties rather than for such

assistance as they may give in prevention of corrosion. Many varieties of stainless steel

have been developed to serve specific purposes.

MARTENSITIC STAINLESS STEELS

Steels of this type contain typically less than 18% chromium, together with small

amounts of aluminium, niobium, molybdenum, tungsten, nickel, or silicon. They are

magnetic and may be hardened and tempered by methods similar to those used for plain

carbon steels. These steels harden uniformly throughout even sections of large cross

section, with oil or air cooing. With minimum chromium content of about 11.5%, steel of

this variety is resistant to weather, water, steam, and mildly corrosive chemicals. Rustless

16-2 contains a maximum of 0.20% carbon, 15 to 17 % chromium, and 1.25 to 2.5 %

nickel; it can be hardened to about 400 to 440 Brinell. Rustless 17-C-100 is a high-carbon

steel containing 0.95 to 1.10% carbon, 16 to 18 % chromium, but no nickel; it can be

hardened to about 620 to 630 BHN.

FERRITIC STAINLESS STEEL

Ferritic stainless steels contains usually more than 18% of chromium, but with such

low carbon content that they do not form austenite at any temperature however high; they

therefore cannot be hardened by heat treatment, but can be given a hard surface by

nitriding. Because the iron content has the alpha structure, these steels are magnetic.

Some varieties contain small amounts of copper, molybdenum, nickel, nitrogen, silicon,

or tungsten. Their resistance to corrosion is considerably greater than that of martensitic

stainless steel, and they are suitable for use with nitric and other strongly oxidizing acids.

AUSTENITIC STAINLESS STEEL

These steels contains enough nickel in addition to the chromium to cause the steel to

retain the austenitic structure at all temperatures; because the iron content has the gamma

structures, such steels are non-magnetic. Steels of this group have the highest resistance

to corrosion of any of the stainless steels, particularly to organic acids. The chromium

content is usually approximately double the nickel content, or vice versa, and other

elements sometimes are added; addition of molybdenum increases resistance to corrosion

by brine and strong reducing agents such as sulfurous acids.

Q.40okVj dwfyax flLVe esa okVj dks VSLV djus dh fof/k dk o.kZu djsaA

Describe the testing procedure of cooling water.

Cooling water testing procedure.

The dematerialized water should b used in the cooling water system of Diesel engine. 36

liter H.P. Power Cool to be added initial full dose. The sample of cooling water should be

drawn from the cooling water circuit immediately after stopping the engine. The

following testing carried out.

1. Estimation of Carboxylate:-

(i) Accurately weigh 100 gm of test solution in a 250 ml open mouth beaker with

spout drop wise add HCL while stirring till the PH of the solution reaches a

value of less than 5.0 A white (PPt) precipitate will be formed. Although very

low PH does not affect the determination, effort should be made to maintain

the Ph between 3.0 to 4.5

(ii) In a separate petridish dry a whatman 42 filter paper and weigh filter paper

along with petridish (W1). Now carefully lift the filter paper not allowing any

foreign material to adhere either to the petridish or filter paper. Keep the

petridish in dessicator.

(iii) Filter the precipitate in beaker obtained in step (i) through pre dried and pre

weighed whatman filter paper obtained in step (ii) wash the beaker 4-5 times

with 20 ml aliquots of distilled water so as to remove any adhering precipitate

on filter paper. Allow all the liquid to drain.

(iv) Once all the liquid in step (iii) has drained, wash the precipitate with three 50

ml aliquots of distilled water allowing water to drain completely in between

each washing.

(v) Once all the water has drained, keep the filter paper along with ppt. In petridish

and dry the ppt. at 120 C for three hours along with filter paper.

(vi) Weigh the petridish along with filter paper and ppt. after cooling in dessicator

for half an hour (W2).

Calculation

Calculate the weight % of carboxylate by the expression.

Carboxylate % = W2 –W1

Estimation of Chloride.

(i). Pipette out 50 cc of coolant water collected from the engine.

(ii).Titrate slowly against N/58.5 Silver Nitrate solution till a permanent

Brick red colour is obtained.

(iii) If V is value in cc of standard AgNO3 solution consumed, then the

concentration of chloride as Sodium Chloride is 20 V PPM

Estimation of PH value

(i) PH value of the coolant solution is estimated with PH meter using coloured

and glass electrodes.

(ii) In case PH meter not available, Narrow Range Ph indicator paper (PH 8.5 to

10.0) manufactured by BDM (India) Pvt Ltd.

Estimation of Total Hardness (EDTA Method)

(i) Pipette out 50 ml of the coolant water sample into 250 ml conical flask.

(ii) Add 2 to 3 drops of indicator solution and mix well.

(iii) Add 0.5 of buffer solution and mix

(iv) Titrate immediately with EDTA solution with continuous shaking of the flask

until the color changes from red to blue

Calculation

Total hardness (as CaCO3 in ppm) = 1000(V1/V2)

Where V1 = Vol in ml of Std. EDTA Solution Consumed

V2= Vol in ml of the sample taken for test.

Q.41ihtks bySfDVªd bQSDV D;k gS\ ;g dgk¡ iz;ksx esa yk;k tkrk gS\ blds iz;ksx dk foLrr̀ o.kZu

djsaA

What is PIZEO electric effect? Where it is applicable? Explain its application in

detail.

Piezoelectric Effect: - Ultrasonic waves can be generated and detected in a number of

ways. The one which is most commonly used in NDT is described here. Quartz and some

other crystals have a lattice structure such that if a plate is cut out of the crystal with a

certain orientation with respect to the crystallographic axes and subjected to an electric

field in the right direction, it will change its dimensions: it will contract or expand

according to the polarity of the field. Conversely, when a similar deformation of the plate

is brought about by an external mechanical force, electric charges appear on its opposite

surfaces. This phenomenon is known as piezoelectric effect. The materials which exhibit

this property are known as piezoelectric materials.

Among the various naturally occurring piezoelectric materials, quartz is the most

important one, because it combines reasonably good piezoelectric properties with

excellent mechanical and dielectric strength and stability. X-cut quartz plate is used for

generating and receiving longitudinal waves. Y-cut plate is used for generating transverse

and surface waves in solids. Quartz transducers can be operated at high temperatures up

to 5000C. a multitude of materials exhibiting piezoelectric properties are now available,

each material having characteristics which suit to particular applications. Besides

naturally occurring crystals like quartz, chemical compounds, such as lithium sulphate,

lead niobate etc. and specially produced polycrystalline ceramics such as Barium titanite

and lead zicronate titanate are used for ultrasonic flaw detection. These transducer

materials are mechanically less resistant. Lithium sulphate is the most sensitive but

barium titanate is best transmitter. Because of its higher acoustic impedance.

The matching of barium titanate is always unsatisfactory and its sensitivity cannot be

fully exploited. Lead metaniobate and lithium sulphate are far superior in this respect.

Again because of their low acoustic impedance and high intrinsic internal damping, they

are most suited to produce short pulses as is required in pulse-echo technique.

The transducers (piezoelectric crystals) cannot be used on their own, but have to be

mounted as suitable probe. The role of the probe is to protect the operator from electric

shock, to protect the transducers from mechanical damage and to make the transducers

more suitable for the job. Various types of probes are made to different applications.

Normal beam transducers are used for testing by using waves at normal incidence. For

under-water testing, the probe, especially the cable, must be waterproof. For good

performance, the transducer impedance should be matched to that of the water. For very

short range operation a twin probe is needed with separate transmitter and receiver probes

built into one housing and acoustically isolated from each another. There is a n acoustic

delay rod, also called as stand-off, in front of both.

Q.42bySDVªks dSfedy lSy esa fdl izdkj ds ifjorZu gksrs gSa\ blds vUrj gksus okyh jlk;fud

izfrfØ;k dk xSyosfud lSy dk mnkgj.k nsrs gq;s o.kZu djsaA

What type of change occur in electro chemical cell? Describe the chemical reaction

with example of Galvanic cell.

Electrochemical cell or galvanic cell

Electrochemical cell is a device in which oxidation and reduction reactions take place in

two separate containers and electrical energy is produced during these reactions.

Electrochemical cell (or galvanic cell) is also called voltaic cell.

Working of an electrochemical cell

Let us explain the working of a galvanic cell by taking the example of a Daniell cell.

This cell consists of two beakers, one of which contains 1 M solution of ZnSO4 and the

other beaker contains 1 M solution of CuSO4. A Zn-rod is dipped into ZnSO4 solution,

while a Cu-rod is dipped into CuSO4 solution. These metallic rods are called electrodes.

The metallic rods are connected with ammeter, by means of an insulated wire. A key

is also inserted in the circuit. Ammeter is used to know the presence of electric current.

The solutions in two beakers are called electrolyte solutions .These solutions are

connected together by an inserted U-tube, containing saturated solution of an inert

electrolyte like KCL, KNO3, or NH4NO3. The U-tube is called salt bridge.

When the circuit is completed by inserting the key in the circuit, the needle of the

ammeter shows a deflection. The deflection of the needle indicates that electric current is

flowing in the external circuit.

Following observations are made:

(i) Zn (s) is oxidized to Zn2+

(aq) ions

Zn (s) Oxidation

> Zn2+

(aq) + 2e-

The above oxidation reaction results in the following: (a) Zn2+

ions, obtained by the

oxidation of Zn, go into the solution of ZnSO4 and hence the concentration of Zn2+

ions

in ZnSO4 solution increases (b) Due to the conversion of Zn into Zn2+

ions, Zn rod loses

its weight.

(ii) Electrons released at Zn-electrode move towards the Cu-electrode through the outer

circuit. These electrons are accepted by Cu2+

(aq) ions of CuSO4 solution, which are

reduced to Cu (s).

Cu2+

(aq) + 2e-

Reduction> Cu (s)

The above reduction reaction results in the following (a) Since Cu2+

(aq) ions of

CuSO4 solution are reduced to Cu (s) the concentration of Cu2+

ions in CuSO4 solution

decreases (b) Cu obtained by reduction of Cu2+

(aq) ions gets deposited on Cu-rod and

hence Cu-rod gains weight.

In the external circuit, electrons flow from Zn-rod to Cu-rod. Therefore, by

convention, electric current flows in the opposite direction, i.e. electric current flows

from Cu-rod to Zn-rod.

Zn-electrode, where oxidation of Zn (s) to Zn2+

(aq) ions takes place or electrons are

released, is called anode or oxidation electrode, while Cu-electrode, at which reduction

of Cu2+

(aq) ions to Cu (s) takes place or electrons are accepted, is called cathode or

reduction electrode.

Since electrons move from Zn-rod to Cu-rod, Zn-rod (i.e. anode or oxidation

electrode) is also called negative terminal and Cu-rod (i.e. cathode or reduction electrode)

is also called positive terminal. Sometimes, negative and positive signs are also put on the

electrodes, to show the release and loss of electrons taking place on them.

The two containers, in which oxidation and reduction takes place, are called half-

cells. The beaker containing Zn-rod dipped in ZnSO4 solution is called oxidation half-

cell, while the beaker having Cu-rod dipped in CuSO4, is called reduction half-cell.

Oxidation reaction taking place at Zn-electrode (anode) is called oxidation half-cell

reaction and the reduction reaction taking place at Cu-electrode (cathode) is called

reduction half-cell reaction. The sum of these half-cell reactions is called cell reaction.

Thus:

Oxidation half-cell reaction : Zn (s)—> Zn2+

(aq) + 2e-

Reduction half-cell reaction : Cu2+

(aq) + 2e- —* Cu (s)

.

Cell reaction : Zn (s) + Cu2+

(aq) —> Zn2+

(aq) + Cu (s)

Cell reaction is a redox reaction which takes place in the cell. We know that

oxidation of metal to metal ions takes place at anode and in this process of oxidation

electrons are generated. These electrons move towards the cathode through the external

circuit. When these electrons reach cathode, they reduce the metal ions into metal atoms.

Thus we saw, that in a galvanic cell, electrons flow through the external circuit from the

negative electrode (anode) to positive electrode (cathode). Since the oxidation potential

of anode is higher than that of cathode, we can say that the electrons, in the external

circuit flow from the electrode of higher oxidation potential to the electrode of lower

oxidation potential. For example, the flow of electrons in the Daniell cell, namely

Zn (s) I Zn2+

(aq) II Cu2+

(aq) I Cu (s)

Anode Cathode

takes place from Zn (s) / Zn2+

(aq) (anode) to Cu2+

(aq) / Cu (s) (cathode) in the external

circuit. This is due to the difference in the relative oxidation tendencies of Zn and Cu, to

give their corresponding cations (Zn2+

and Cu2+

ions respectively) or due to the difference

in the relative reduction tendencies of Zn2+

(aq) and Cu2+

(aq) ions to give Zn (s) and Cu

(s) atoms respectively.

Q.43dkWij] fufdy] dksckYV] flfydu] eSXuhf”k;e rRoksa ds D;k xq.k gSa\ LVhy esa bu rRoksa dks

tksM+us ij D;k izHkko iM+sxk\

What are the properties of copper, nickel, cobalt, silicon, magnesium elements?

What will be the effect in steel by adding these elements?

Alloy Steel: -

1. Nickel: It is one of the most important alloying elements. Steel sheets contain 2%

to 5% nickel and 0.1% to 0.5% carbon. In this range, nickel improves tensile

strength, raises elastic limit, imparts hardness, toughness and reduces rust

formation. It is largely used for boiler plates, automobile engine parts, large

forgings, crankshafts, connecting rods etc. When nickel is added to steel in

appreciable proportions (about 25%) it results in higher strength steels with

improved shocks and fatigue resistance. It makes the steel resistant to corrosion

and heat. It is used in the manufacture of boiler tubes, valves for gas engines,

pump barrels, sparking plugs for petrol engines, liners and pump parts etc. A

nickel steel alloy containing about 36% nickel and 0.5% carbon is known as invar.

It can be rolled, forged, turned and drawn. It has nearly zero coefficient of

expansion. So it is widely used for making pendulums of clocks, precision

measuring instruments etc.

2. Manganese: - It is added to steel in order to reduce the formation of iron sulphide

by combining with sulphur. It is usually, added in the form of ferro-manganese or

silico-manganese. It makes the steel hard, tough and wear resisting. The

manganese alloy steels, containing over 1.5% manganese with a carbon range of

0.40% to 0.55% are widely used for gears, axles, shafts and other parts where high

strength combined with fair ductility is required.

3. Silicon: - It increases the strength and hardness of steel without lowering its

ductility. Silicon steels containing from 1% to 2% silicon and 0.1% to 0.4%

carbon have good magnetic permeability and high electrical resistance. It can

withstand impact and fatigue even at elevated temperatures. These steels are

principally used for generator and transformers in the form of laminated cores.

4. Cobalt: - It is added to high speed from 1% to 12%, to give red hardness by

retention of hard carbides at high temperatures. It ends to decarburise steel during

heat treatment. It increases hardness and strength. But too much of cobalt it

decreases impact resistance of steel. It also increases residual magnetism and

coercive magnetic force in steel for magnets.

Q.44gkbZ LihM Mhty ¼,p,lMh½ rsy dks VSLV djus dh fof/k dk o.kZu djsaA

Describe the testing procedure of High Speed Diesel (HSD) oil. in detail.

In high speed diesel oil testing following parameter & tests is carried out in loco

sheds.

WATER CONTAMINATION

Petroleum products should be free from water. Products may pick up water during

storage, handling or through condensation. Traces of water can be detected by crackle

test. When a properly shacked sample is spread over a hot plate, crackling noise is heard.

SPECIFIC GRAVITY

It is the ratio of weight of a given volume of a substance to the weight of an equal

volume of water at the same temperature. In petroleum industry the standard temperature

is 15 C.

Pour the sample into the clear measuring cylinder without splashing to avoid the

formation of bubbles.

Remove any air bubbles formed by touching with glass rod.

Lower the hydrometer gently into the sample.

Depress the hydrometer into the sample and then release.

When the hydrometer has come to rest and floating freely away from the walls of

the cylinder, read the hydrometer reading.

Record the temperature of the oil at the time of testing.

Correct the reading of the hydrometer to 15 C by means of temperature correction

coefficient given as in IS 1448

Report the final value as Sp. Gr. At 15 C.

VISCOSITY

The viscosity of any oil is a measure of its resistance to flow. A liquid has low viscosity

if its flow is readily water. It has high viscosity if it flows sluggishly like molasses or

honey.

Viscosity is determined by noting the time required for a specified and measured

quantities of oil to flow in standard apparatus at constant temperature.

For determination of viscosity in HSD oil, the Cannon-Fensky direct flow

viscometer tube no. 100 is being used.

Take the sample in the tube up to the mark with the help of suction bulb by

immersing the wider limb in the sample.

Keep the tube in the constant temperature bath maintained at 40 C.

Allow the sample to attainted bath temperature by keeping it for 30 minutes.

Suck the oil above the mark.

Measure the time taken in seconds for the oil to travel from upper mark to the

lower one using stopwatch.

Calculation:-

K.V. in centistokes = Time taken in seconds X viscometer constant

FLASH POINT

The flash point of a petroleum product is the temperature at which it gives of sufficient

vapor to form a mixture with air, which will ignite under standard test condition.

Clean with solvent and dry all the parts of the cup and accessories.

Fill the cup with the sample to the level indicated by marks.

Place the lid on the cup and set the assembly in the heater.

Apply heat at such a rate that the temperature does not increase not more than 5 C

per minute.

Apply the test flame by operating the mechanism on the cover into the vapour

space in half a second and raise quickly.

Record as the flash point temperature read on the thermometer at the time when

the test flame application causes distinct flash in the interior of the cup.

COLOUR COMPARISON

Color comparison of fuel oil with 2% Potassium dichromate solution

Take two identical Nessler tubes.

Take 10 ml of HSD oil in one of the tube.

In another tube take 10 ml of 2% Potassium dichromate solution in bright light.

Report the observation as lighter or darker.

POUR POINT

Pour point of oil is the lowest temperature, at which it will remain still fluid or can be

poured under specific condition. The lowest temperature expressed as the multiple of 3 C.

Pour HSD oil to 50ml levels into tube of pour point apparatus.

Place the tube in the clamp provided at the center of the container vessel.

Fill the container with ice and common salt.

Close the vessel with lid.

Introduce a -10 C to + 10 C thermometer to the tube with the help of rubber cork

provided in the lid so that the mercury bulb, of the thermometer is inside the ice

and salt mixture.

At every 3 C decrease of the temperature in the sample take out the tube from the

container and tilt it to ascertain whether there is move of the oil.

Continue the cooling until a point at which the oil in the tube shows no movement

when the tube is tilted horizontally for 5 sec.

Add 3 C to the temperature recorded.

Report the value as the pour point

CARBON RESIDUE

HSD oil tends to form carbonaceous deposits when they are burnt. Carbon residue test

determine the amount of residue left behind by a petroleum product after heating under

specific test condition.

Take the weight of empty coking bulb.

Insert HSD oil in the coking bulb with the help of injection syringe.

Weigh accurately 3 gm of oil.

Heat the Rams bottom furnace up to 450 C and insert the bulb in it.

After inserting the bulb with sample, it is allowed to coke for 30 mins.

Remove the bulb and cool it in desiccators.

The bulb along with residue is weighed and the percentage of carbon residue is

collected.

DISTILLATION RECOVERY

Distillation is a process of separating of some constituents of a product with a view to

finalizing its composition and suitability for use.

Measure out 100 ml of HSD oil sample into a round bottom 125 ml distillation

flask.

Place the flask on the heater of the distillation apparatus after inserting a 0 C to

400 C thermometer into the flask through one hole cork.

Insert the side stem of the flask into the condenser tube and tighten the cork at the

side stem.

Place the 200 ml measuring cylinder at the further end of condenser tube.

Heat the sample and regulate temperature so that the time interval between the

first application of heat and the initial boiling point range between 5 to 10 mints.

Record the temperature of initial boiling point.

Record the temperatures at 10%, 20%, 50%, 85% and 95% of the distillate

collected.

Report 95% distillate temperature in C.

SULPHUR CONTENT

One of the most important test in HSD oil is its sulphur content because high sulphur oil

is injurious to fuel oil system.

Connect the inside terminal of the bomb lid with Nichrome or Platinum wire.

Tie a cotton thread at the center of the wire.

Weigh accurately 0.2 to 0.3 gm of HSD oil sample in the sample cup.

Place the sample cup in the steel wire loop attached to the end portion of one of

the terminals.

Suspend the cotton thread in such a way that it just touches oil surface in oil cup.

Pour approx. 5 ml of 15% sodium carbonate solution and rinse the bomb with the

solution.

Place the lid assembly in the bomb and tighten the cover securely.

Fill the bomb with oxygen in a slow stream to avoid spitting of the oil from the

sample cup.

Keep the pressure of the oxygen in the bomb to the level of maximum 40 kg/cm2

Disconnect the cylinder outlet.

Connect the terminal to the ignition circuit.

Ignite the sample by pushing the button of the ignition circuit.

When the bomb is sufficiently cooled, release the pressure very slowly.

Open the lid and wash the interior of the bomb and transfer the solution into a

beaker. Give washing twice or thrice with hot distilled water and transfer the

washings to the same beaker.

Place the oil cup in a small beaker and add some distilled water and a few c.c. of

conc. HCL and boil for a moment.

Transfer the solution to the original beaker. Wash the cup and the beaker with hot

water and transfer the washing to the original one.

To the original beaker add a few C.C of HCL followed by 5 cc of bromine water.

Boil till the bromine is off from the solution.

To the boiling solution add 10 c of 10% hot Barium Chloride solution and boil till

the volume is sufficiently reduced.

Since the ppt. is in the colloidal state hence sufficient time should be allotted for

proper settlement.

Filter through Whattman filter paper no. 42

Wash severally with boiling water to make it free from acid.

Dry in air oven for an hour, ignite by taking in a crucible, cool and weigh the

residue as BaSO4

Calculation % Sulphur = 13.73 x A/B

Where A = Wt. of BaSO4 in mg

B = Wt. of sample taken.

REACTION WITHIN THE BOMB CALORIMETER

Sodium Carbonate is a stable compound. It does not decomposed even at a very high

elevated temperature. But under high pressure and temperature it breaks into Sodium

Oxide and Carbon Dioxide. The gas makes inert medium inside the bomb thus preventing

the oxidation of the product. Sodium oxide reacts with water to Form Sodium Hydroxide.

Sulphur present in HSD oil cracks and forms Sulphur dioxide, which dissolves in Sodium

hydroxide solution forming soluble Sodium Sulphate.

Sodium Sulphate solution when reacts with Barium Chloride forms Barium sulphate.

Na2CO3 = Na2O + CO2

Na2O + H2O = 2NaOH

2NaOH + SO2 = Na2SO4 +H2

Na2SO4 + BaCl2 = BaSO4 + 2NaCl

CETANE NUMBER

Cetane number is s measure of the ignition quality of fuel oil as it indicates the

comparative ease with which a diesel fuel will ignite in a diesel engine cylinder.

Q.45VSEifjax izfdz;k D;k gS\ VSEifjax djus dk mnns”; D;k gS\ fofHkUu izdkj dh VSEifjax izfdz;k

dk o.kZu djsaA

What is tempering process? What is the aim of tempering? Describe different

types of temping process.

Answer :

The main objects of tempering in heat treatment are:

1. To reduce brittleness of the hardened steels and thus to increase its ductility.

2. To remove the internal stresses caused by rapid cooling of steel.

3. To make steel sufficiently tough to resist shock and fatigue.

The process of tempering consists of reheating the hardened steel to some temperature

below the lower critical temperature, followed by any desired rate of cooling. The exact

tempering temperature depends up on the purpose for which the article or tool is to be

used.

When steel is heated to low tempering temperature (2000C to 250

0C), the internal

stresses are removed and ductility increases without changing the structure of steel from

martensite or reducing its hardness. On heating it to about 3000C, troostite-martensite

mixture is obtained which imparts some ductility to the metal. On heating it to 4000C,

martensite begins to change into fine pearlite or sorbite and the transformation of sorbite

and the transformation of sorbite is completed on reaching a temperature of 6000C. The

sorbitic steel is employed for making highly stressed parts, because it has a remarkable

mechanical property like ductility, strength and shock resistance.

The tempering temperatures may be judged by the colour formed on the surface of the

steel being tempered. The colours are caused by oxidation of the steel with the formation

of thin films of iron oxide.

The baths using tempering oils may be employed for temperatures up to

approximately 2300C. The tempering oils are, usually, mineral oils having flash points of

the order of 3000C. An adequate quantity of oil should be employed and the baths should

be provided with wire baskets which when loaded with work may be lowered into the

tempering baths. For temperatures above about 2300C, liquid salt baths are preferred.

These salt baths, usually, consist of mixtures of nitrates and nitrites. The chlorides and

fluorides are, usually, employed for higher temperatures. The process of tempering is of

the following two types:

Austempering: - It is a process of tempering in which steel is heated, above the upper

critical temperature, at about 8750C, where the structure consists entirely of austenite. It

is then suddenly cooled by quenching it in a salt bath or lead bath maintained at a

temperature of about 2500C to 525

0C, so as to facilities the transformation of austenite

into bainite. After complete transformation, the steel is cooled air. In this process, a good

impact strength is obtained and the degree of cracking is also reduced.

Martempering: -It is a process of tempering in which the steel is heated above the upper

critical point and then quenched in a bath kept at a suitable temperature, so that it is in the

upper martensite range. After the temperature becomes uniform throughout the steel

structure, without the formation of bainite, it is further cooled in the air. The steel is then

tempered. The martempered steel is free from internal stresses. It avoids cracks and

warping etc., which is usually caused by ordinary hardening. The martempering is mostly

used in case of alloy steels.

Q.46QksftZax ds D;k fMQsDV gksrs gSa\muds dkj.k rFkk fuokj.k fyf[k;sA

What is forging defects? Write their reasons and remedial measures.

The defects occur during forging process are known as forging defect. Main forging

defects ,reason thereof and remedial action can be classified as under-

FORGING DEFECTS

Causes and Remedies

Nature of defects Causes Remedy

a. Cracks 1. Ingot Cracks.

i. Excessive high pouring

temperature.

ii. Proneness to crack near

peritectic compositions

(especially for killed steel)

iii.Surging of molten metal in the

mold from discontinuities.

2. Improper Heating

3. Forging at low temp.

4. Incorrect soacking of alloy steel

forging.

5. Incorrect forging methods.

1. i. Keep Low pouring temp.

ii. To avoid transverse cracking in

case of killed steel, 0.15-0.25 %

C steel composition is avoided.

iii. Use of mold coatings &

improved mold design.

2. Ensure minimum forging temp.

For a particular grade.

3. Rapid cooling to be avoided.

Furnace cooling or cooling in

insulating material is preferred.

4. Proper forging sequence to be

maintained.

5. Remove cracks by hot set.

b. Laps Due to folding of metal over itself

during die forging. Laps are usually

found where vertical & horizontal

section intersects, when fillet radius

is too small.

i. Proper selection of fillet radii.

ii. Ensure uniform metal flow in rib

& web forgings.

iii.Relocating the parting line.

c. Tears i. Low temperature forging.

ii. Ingot quality poor.

iii.Burnings

iv. Presence of segregation, seams or

low melting second phase.

v. Large, rapid reduction.

i. Maintain proper forging temp.

ii. Eliminate inter-dendritic zone of

weakness by avoiding

overheating.

iii.Avoid large reduction during

upsetting at a time.

iv. Heating time at high temp.

should be minimized

d. Fitting Incomplete cleaning of the dies. Ensure that the die are free from

scale while forging

e. Coarse grain

wrinkle

Billets containing coarse grain

whether as cast or wrought will

develop wrinkles during forging.

Wrinkles fold into Lap while

forging in closed-die and they are

not deep removed by grinding or

re-striking forging.

f. Flow through

Defects

i. When metal flows past die

recesses after they have filled.

ii. Die impression not completely

filled

iii.Forging metal to flow past an

impression

i. Sufficient number of blows to be

given.

ii. Avoid low temp. of forging

stock.

iii.Ensure that lubricant are not

being trapped

g. Distributed metal

Defects

No loose oxides which help

minimize metal to metal contact.

Avoid too much or inadequate

lubricant.

h. Dents i. Improper positioning of stock on

the die

ii. Hot forgings are thrown from

place to place

i. Before making final blow, check

stock are correctly inserted in

the die or not

ii. Check that the forging are

stacked in top die.

iii.Avoid throwing of hot forging.

i. Under filling i. Inadequate forging pressure

ii. Chilled die or forge metal

iii. Short supply of feed metal from

either web or blocker rib.

i. Adjust pressure.

ii. Ensure adequate metal supply.

j. Void at the base

of rib

i. Supply of metal from web is

inadequate.

i. By thickening the web or

placing an under bead.

ii. Provide, for a rib prior blocker

impression.

iii.Additional rib on the web

k. Push through of

web under rib

When a rib fills completely before

adjacent web area has been

reduced at the base of rib.

i. Reducing stock size.

ii. Reducing web thickness in

blocking operations before

finishing.

iii.Moving the parting line location

to the top of rib.

iv. Widening the rib to on.

Q.47dkfLVax esa fofHkUu izdkj ds D;k nks’k gksrs gSa\muds dkj.k rFkk fuokj.k fyf[k;sA

What are casting defects? Write their reasons and remedial measures.

The defects in casting may be due to pattern and moulding box equipment moulding sand

core gating system or molten metal. In another words the following factors are

responsible.

i. Design of casting & pattern equipment.

ii. Mould and core material and making equipment and technique.

iii. Gating & rise ring.

iv. Melting & pouring.

v. Metal composition.

Some of the defects and their reasons are as follow-

1. Below Holes – They appear as cavities in casting surface.

Causes :-

i. High moisture content in molding sand.

ii. Low permeability of sand.

iii. Defected gating system.

iv. Sand grains are too fine.

v. Sand is remained too hard.

Remedies : Selecting proper sand and required permeability, proper

venting moisture content must be adjusted, venting should be adequate.

2. Warage – It is undesirable deformation.

Causes:-

i. No directional solidification of casting

ii. Continuous large flat surface on casting or poor design.

Remedies :

i. Modified the casting design to break.

ii. Adequate care in setting of cores in the mould, proper directional

solidification.

3. Shrinkage – Cracks in casting on surface which results from unequal

contraction of metal during solidification.

Causes :-

i. Due to incorrect metal composition and pouring temperature, lack of

directional solidification

ii. Improper location and size of gate and reamer.

Remedies: Ensure proper directional solidification by moulding, gating,

Rise ring and chilling.

4. Porosity – It occurs in the form of pinhole or gas porosity.

Causes: - High pouring temperature gas dissolve in metal charge high

Moisture and low permeability, slow solidification of casting, not proper

Degassing.

Remedies: Regulate pouring temperature effective de gassing adequate moisture

And increase permeability of mould.

5. Inclusions – Nonmetallic foreign metal in cast metal in form of oxides

dirt, slag sand or gas.

Causes: Faulty gating, pouring, rough handling of mould or care, inferior

Molding sand in use.

Remedies: Modified gating system, improve pouring, use a superior sand

of more strength.

6. Hot Tear – Hot tear are cracks which appear in casting during

solidification from melting. It is an internal or external ragged

discontinuity in metal.

Causes: Improper pouring temp, poor collapsibility of mould.

Remedies: Abrupt change in see should be avoided pouring temp, should be

correct.

7. Rough Surface Finish – Lack of sufficient smoothness in casting.

Causes: Coarser sand, hard pouring, improper use of mould.

Remedies: By using proper mould and Ramming of sand.

8. Metal Penetration – Between sand and grain.

Causes: Soft sand, rammed sand, improper use of sand, excessive metal

temperature.

Defect can be eliminated by removing the above mentioned reason.

9. Fin – A thin projection not intended as a part of casting is called fins. Occurs at

pasting of the mould.

Causes: Incorrectly assembling of mould and core. Improper clamping of flask.

Remedies: Correct assembly of mould and core.

10. Swell – It is an enlargement of mould cavity by metal pressure.

Causes: By improper defective ramming of mould.

Remedies: To avoid swell sand should be rammed properly.

11. Honey Combing - External defect small cavity in close proximity.

Causes: By dirt scurf & due to imperfect skimming in ladle.

Remedies: Proper skimming, removal of slag.

12. Cold shut & mission – It is an external defect formed due to imperfect fashion of

two stream of metal in mold cavity defect appear crack.

Causes: Thin section & wall thickness improper gating system, poor fluidity of

metal.

Remedies: Use hotter metal frequent inspection & replacement of pattern.

13. Shot metal –

Cause: To low pouring temp, excessive sulphur content in metal, faulty gating,

high moisture content in molding sand.

Remedies: High pouring temperature, reduced sulphur content, modified gating

system, reduced moisture content.

Q.48HkVVh dk rkieku fdl izdkj ukik tkrk gS\ FkeksZ bySfDVªd ik;jksehVj rFkk vkWiVhdy

ik;jksehVj dk o.kZu dhft;sA

How temperature of furnace is measured? Explain thermo electric pyrometer and

optical pyrometer.

Answer : Temperature of furnace is measured with the help of thermocouple ,or

pyrometer .

Thermo electric pyrometer

A thermocouple consists of a pair of wires of dissimilar metals welded together at one

end. When this junction is heated to a temperature higher than that of a similar junction in

the same electric circuit, a difference of thermoelectric potential is set up between the two

junctions, and if the circuit is closed a current flows. This current can be measured by a

suitable electric measuring instrument inserted into the circuit. The potential difference,

and therefore the current, vary directly, but not necessarily proportionately, with the

difference in temperature between the hot and the cold junction. In industrial practice an

actual cold junction is not used, but is replaced by the measuring instrument, usually a

mill voltmeter, and the associated external wiring. The meter then measures the

difference between the temperature of the hot junction and the temperature of the meter.

If the meter is kept at a constant temperature its scale may be calibrated to read the high

temperature directly.

Optical Pyrometer

A pyrometer is an instrument for measuring elevated temperature above the range of

Thermometer.

Principle

Matters glow above 900o F (482

o C) and the color of visible radiation is proportional

to the temperature of the glowing matter.

- The amount of light radiated from the glowing matter (solid or liquid) is

measured and employed to determine its temperature.

- All this is accomplished with the help of instrument known as optical pyrometer.

Operation

i. The optical pyrometer is sighted at the hot body (which may be molten

metal, coke bed, hot crucible, etc.) and focused.

ii. In the beginning filament will appear dark as compared to the background

(say molten metal) which is bright (being hot).

iii. By varying the resistance in the filament circuit, more and more circuit is

fed into it, till filament becomes equally bright as the background and hence

disappears.

iv. The current flowing in the filament at this stage is measured with the help

of an ammeter which is calibrated directly in terms of temperature.

v. If filament current is further increased, the filament appears brighter as

compared to the background which then looks dark.

An optical pyrometer can measure temperature ranging from 700-4000o C.

-Optical pyrometers are of limited value for measuring temperature of molten

metal owing to,

(a) The absence of the black body condition and

(b) The partial dependence of results on the emissivity of the

metal surface.

- Pyrometers are calibrated (for use) with black body condition and a

correction needs to be applied for nonblack body condition which introduce errors.

The correction factor depends upon the ratio of absorbed radiant energy to the

radiant energy falling upon it. This ratio is called the emissivity of the material.

- An optical pyrometer is preferred for measuring temperature of high melting

point metals such as iron and steel.

-An optical pyrometer measures tem temperature between 700-4000oC

-An optical pyrometer is employed to measure temperature of the body where

because of its (i.e. body’s) position a thermocouple pyrometer cannot be used.

-Errors can be introduced by smoke or gases between the observer and the heat

source.

Q.49baMLVªh;y lsQVh ls vki D;k le>rs gSa\ blds D;k mnns”; gSa\ fdlh dkj[kkus esa dkexkjksa

dh ls¶Vh ds fy;s D;k&D;k mik; fd;s tkrs gSa\

What do you understand by Industrial Safety? What are its objective? What

measures is taken for safety of workshop employee?

Industrial safety means condition and environment for prevention of accidents and

protection of workers even from hazardous chemicals, radiation and pollution which

could affect physical and mental health of employees. To ensure zero disturbances in

industries, it is concerned with elimination of unsafe act and unsafe condition. Industrial

safety is the statutory duty of employer under factories act 1948 and other acts to protect

workers from accident, injury and ill health. The breach of law may result in prosecution,

fine ,punishment and adverse publicity. Heavy penalty and compulsory imprisonment are

provided for breach of safety provisions resulting in death, serious bodily injury or

occupational diseases (hazard). Thus legal reason for accident prevention is strictly set

out for the employee.

Objectives – Employee should observe safety rules maintain safety guards and

conditions ensure the proper use availability of safety equipment and tools to prevent

injuries provide proper safe and hazardous free working conditions/environment to

prevent occupational diseases to train employees in handling safety equipment’s and

important of safety.

The prime objective is make the working condition to zero accident/Disaster with no

injury to working employee and others, no pollution working environment. Employee

should protect their works from any kind of accident and ensure physical and mental

health. Employee should also protect their fallowness and surrounding by their safety

consciousness. Safety duty, precautions and safe practices.

Protection of self and other is primary duty of every employee and employer.

There are three agencies who sufferer economical and image losses due to

accidents/disasters.

(1) Management – who not only get set back of cost benefit but its market and society

image is affected adversely.

(2) Employer and their family- suffer economic losses due to loss of limb or life, loss

of earning capacity and other extra expenses as medical, nutrition, transport and

physical care including emotional and mental suffering.

(3) Society – suffer from help and development it was receiving from healthy works

including and other benefits now accidental employees becomes burden on society

there for at all cost accident must be prevented.

The safety measures taken by work shop in order to prevent injuries/accident and

occupational disease by adopting why and mean, which should be appropriate less

compensation and less costly. This is done by proper safety management. Dy CME

(safety) with safety officers who are trained on industrial safety and fire from labour

ministry at Kanpur, they ensure elimination of unsafe acts and unsafe conditions

through proper safety planning, direction, organizing controlling, motivation and

communication with workers/employers of workshop. They also provide training on

industrial safety and handing of safety tools. To reduce occupation health OHSAS and

ISo-14000 and ISO-18000 to provide better working condition and pollution free

environment.

The hand tools being used account for approx. 10% of all industrial loss time injuries

are analyze as:

(a) Use of wrong tool.

(b) Incorrect method of using tool.

(c) Defective tool.

(d) Ignorance and lack of knowledge.

Mainly drills, polishers, grinders, pivots, nut-bots chippers, circular saws, grinders are

tools which are usually subjected to considerable amount of abuse and improper

handling.

So proper training of their use and handing is given mainly the welding equipment,

tools,. To ensure proper use of cranes hoists the periodic maintenance is done. To

ensure that electric power points, transformer V-belts, moving machines the proper

safety guards and learning bells are provided. Helmets, hand gloves, goggles and

other less costly but highly essential safety devices are provided to concern persons

and places.

Portable power operated tools are given special consider to prevent addition hazardous

proper ventilation and lighting is provided at working places. Safety training, firefighting

and safety related work instruction and safety slogans are displayed at concerned places.

Q.50 fuEu ij laf{kIr fVIi.kh fy[ksaA

Write down short notes on following:-

(I)ukeZykbftax (Normalising)

: - Main objects of normalizing in heat treatment are:

1. To refine the grain structure of the steel and to improve machinability, tensile

strength and structure of the weld.

2. To remove stains caused by cold working processes like hammering, rolling,

bending etc. which makes the metal brittle and unreliable.

3. To remove dislocations caused in the internal structure of the steel due to hot

working.

4. To improve certain mechanical and electrical properties.

The process of normalizing consists of heating the steel 300C to 50

0C above its upper

critical temperature for hypoeutectic steel or line for hypereutectoid steels. It is held at

this temperature fro about fifteen minutes and then allowed to cool down in still air.

The process provides a homogeneous structure consisting of ferrite and pearlite for

hypoeutectic steels, and pearlite and cementite for hypereutectoid steels. The

homogeneous structure provides a higher yield point, ultimate tensile strength and impact

strength with lower ductility to steels. The process of normalizing is frequently applied to

castings and forgings etc. The alloy steels may also be normalized. But they should be

held for two hours, at a specified elevated temperature and then cooled in the furnace.

(II) vkWLVukbV (Austenite)

At temperature above the A3 point, the structure of steel is that of a solid solution with

gamma iron as the solvent. This solid solution, whether the solute consists of iron carbide

only, or of any number of other elements, is known as austenite. Austenite exists at room

temperature in plain carbon steels only if they contain more than 0.9% of carbon and

have been quenched rapidly from about 1630 F. Special alloy steels which contain 18%

of chromium and 8% of nickel show austenitic structures when less drastic quenches are

employed.

When hypo eutectoid steel is heated to 10600C the pearlite content changes to

austenite; as heating is continued the excess ferrite is absorbed in the austenite grains,

until at the temperature that corresponds to the line GOS, the entire mass is of austenitic

structure.

It is definitely established that the carbon atoms in austenite occupy interstitial

positions in the F.C.C lattice, causing the parameter of the lattice to increase

progressively with the carbon content. This leads one to infer that the carbon atoms make

room for themselves in the interstitial pockets among the iron atoms, which otherwise are

closely packed.

With a hypereutectoid steel the pearlite changes to austenite at 10600C just as it does

in hypo eutectoid steel, and the excess cementite goes into solution as the temperature is

raised further, until at the temperature, which corresponds to the line SE the entire

structure becomes austenitic.

(III) ekfVZulkbV (Martensite )

The effectiveness of heat treatment depends upon the fact that when austenite is cooled

below the critical point, transformation into pearlite does not start instantaneously, and

when once started requires a finite amount of time for completion. Because this

transformation takes place only between the Ac1 pint and about 800 F, formation of

pearlite can be prevented by cooling steel rapidly to about 800 F or below. If rapid

cooling is continued to about 400 F or to room temperature, the austenite is transformed

into a structure known as martensite. The lowest rate of cooling which results in

transformation of austenite into martensite without production of any pearlite is called the

critical cooling rate; it is largely dependent upon the carbon content of the steel, being

greater for low-carbon steels than for high-carbon steels. A cooling rate of at least 54,000

F degrees per hour is necessary to obtain fully martensitic microstructures; this is

therefore the critical cooling rate for full martensite, and it is usually obtained in practice

by quenching the steel in an agitated liquid medium. Martensite is considered to be a

supersaturated solid solution of carbon in ferrite; it is the hardest, strongest, and least

ductile form of steel.

(IV) FkeksZdiy (Thermocouples)

A thermocouple consists of a pair of wires of dissimilar metals welded together at

one end. When this junction is heated to a temperature higher than that of a similar

junction in the same electric circuit, a difference of thermoelectric potential is set up

between the two junctions, and if the circuit is closed a current flows. This current can be

measured by a suitable electric measuring instrument inserted into the circuit. The

potential difference, and therefore the current, varies directly, but not necessarily

proportionately, with the difference in temperature between the hot and the cold junction.

In industrial practice an actual cold junction is not used, but is replaced by the measuring

instrument, usually a millivolt meter, and the associated external wiring. The meter then

measures the difference between the temperature of the hot junction and the temperature

of the meter. If the meter is kept at a constant temperature its scale may be calibrated to

read the high temperature directly.

(V) dsl gkMZfuax (Case hardening )-

In many engineering applications, it is desirable that a steel to be used should have a

hardened surface to resist wear and tear. At the same time, it should have soft and tough

interior or core so that it is able to absorb any shocks etc. This is achieved by hardening

the surface layers of the article, while the rest of it is left as such. This type of treatment

is applied to gears, ball bearing, railway wheels etc.

Following are the various case hardening process by means of which the surface

layer is hardened:

1. Carburising: - As we already know that low carbon steel cannot be hardened

appreciably by any one of the hardening processes. Such steels are enriched in carbon

on their surface before hardening by quenching. The process of introducing carbon,

to low carbon steels, in order to give it a hard surface, is called carburizing.

The surface is made hard only upto a certain depth. Following two methods are

commonly used for carburizing:

a. Pack carburising

b. Gas carburising

2. Nitriding: - It is a process of case or surface hardening in which nitrogen gas is

employed in order to obtain hard surface of the steel. This process is commonly used

for those steels, which are alloyed with chromium, molybdenum, aluminium,

manganese etc. The steel article, usually, well machined and finished are placed in an

air tight container made of high nickel chromium, steel and provided with inlet and

outlet tubes through which the ammonia gas is circulated. The nitriding process is

generally carried out in the electric furnace, where the temperature in the range of

4500C to 550

0C is maintained. The container with the articles is placed in the furnace

and ammonia gas is passed through it. The ammonia gas, when comes in the contract

with steel articles, gets dissociated in the form of nascent nitrogen, which reacts with

the surface of the articles and form nitrides which is very hard. This process can give

surface hardness upto a depth of 0.8 mm.

The nitriding process is used in the production of machine parts, which require

high wear resistance at elevated temperatures such as automobile and air valves and

valve parts, piston pins, crank shafts and cylinder liners. It also finds some

application in the production of the ball and roller bearing parts or other parts to

withstand high pressure steam services die-casting dies, wire-drawing dies etc.

3. Cyaniding: - The cyaniding is a case of surface hardening process in which both

carbon and nitrogen are absorbed by the metal surface to get it hardened. In this

process, the piece of low carbon steel is immersed in a bath of cyanide salt, such as

sodium cyanide or potassium cyanide maintained at 8500C to 950

0C. The immersed

steel piece is left in the molten cyanide salt bath, at the above temperature, for about

15 to 20 minutes. It is then taken out of the bath and quenched in water or oil. The

cyanide yields carbon monoxide and nitrogen, which behaves as active carburising

agents in hardening the surface of steel. The process can give surface hardness upto a

depth of 0.8 mm.

(VI) VSUlkby VSLV (Tensile Test): -

The tensile test of a metal is generally performed to determine:

1. Proportional and Elastic Limit

2. Yield Point

3. Ultimate Tensile Strength

4. Percentage Elongation and Reduction of Area

The results obtained by the tensile test are widely used in the design of materials for

structures and other purposes. In this test, the test piece is pulled out at a constant rate by

gradually increasing the axial pull, till the rupture takes place.

The tensile test for a ductile material is, generally, carried out with the help of a

universal testing machine on the specimen made from the material to be tested, as per

specification.

The schematic working arrangement of a universal testing machine, the specimen is

held in the jaws of the machine. And the load is applied gradually by a hydraulic press,

which is measured from the pressure developed inside the cylinder. The function of the

oil pump is to supply oil under pressure to the hydraulic cylinder. The load reading is

noted directly from the load scale.

The dimension and form of the specimen varies according to the size and shape of the

material to be tested and the main objective in view. The test is carried out on a specimen

having uniform cross-section throughout the gauge length.

The Bureau of Indian Standards recommended several sizes of the specimen. But the

standard practice is to use a specimen whose gauge length in mm.

l0 =5.65√A0

=5.0 d0

where, A0= Area of cross-section in mm2, and

d0 = Diameter of the specimen in mm

It means for a gauge length of 50 mm, the specimen diameter should be 10 mm.

Yield point, ultimate strength and breaking strength are directly noted on UTM and

elongation percentage are calculated by measuring length after breaking

L2-LO X 100

LO

(VII) bEiSDV VSLV (Impact Test):

Many machine parts are subjected to suddenly applied load called impact blows. It has

been observed that a metal may be hard, strong or of high tensile strength. But it may be

unsuitable for uses where it is subjected to sharp blows. The capacity of a metal to

withstand such blows without fracture is known as an impact resistance or impact

strength. It is an indicative of the toughness of the metal i.e. the amount of energy

absorbed by the metal during plastic deformation. The S.I. unit for expressing impact

strength is mega newton per square meter, i.e. MN/m2.

There are many types of impact testing machines available in the market. But the

basic principle, on which all of them are based, is the same. The following two types of

impact testing machines are important from the subject point of view.

1. Charpy Test: - The Charpy test is carries out on a specimen, which is

55mmX10mmX10mm in size and has 2 mm deep notch at its centre making an

angle of 450. The specimen is placed horizontally as a simply supported beam

between two anvils 40 mm apart in such a way that the striking hammer strikes the

specimen on the face which is opposite to the notch.

2. Izod Test: - The Izod test is carried out on specimen, which is

75 mm X 10 mm X 10 mm in size and has a 2 mm deep notch making an angle of

450. The specimen is held vertically as a cantilever between two jaws, in such a

way that the striking hammer strikes the specimen on the same face as that of

notch.

(VIII) Mh&dkcqZjkbZts'ku (Decarburization): -

It is the loss of carbon on the surface layers of the metal or alloy. Decarburization

results in lower hardness and lower fatigue limit. It is caused by the oxidizing furnace

atmosphere. In order to prevent decarburization, the metal or alloy should be heated in

a neutral or reducing atmosphere or in boxes with cast iron or in molten salt baths.

Air & flue gases formed from the combustion of fuels will oxidize steel and form

scale on the surface. The flue gases contained CO2, H2O (from the air & from the

combustion of hydro carbons) and usually some free O2. All of these will

oxidize steel even if there is incomplete combustion so that there is no O2.and

considerable CO scale will be formed.

Besides oxidizing the surface of the steel, the furnace atmosphere may remove carbon,

leaving a decarburized layer. Presence of even a thin decarburized layer may

seriously reduce fatigue Strength. Material fails in fatigue by development of

cracks in the surface layer. Obviously, decarburization reduces the carbon

content and hence the strength of the surface. Heavy sealing will largely

protect the steel beneath from decarburizing.

(IX) ljQs”k gkMZfuax (Surface hardining )

In many engineering applications, it is desirable that a steel to be used should have a

hardened surface to resist wear and tear. At the same time, it should have soft and tough

interior or core so that it is able to absorb any shocks etc. This is achieved by hardening

the surface layers of the particle, while the rest of it is left as such. This type of treatment

is applied to gears, ball bearing, railway wheels etc.

Following are the various surfaces or case hardening process by means of which

The surface layer is hardened:

Carburizing: - As we already know that low carbon steel cannot be hardened

appreciably by any one of the hardening processes. Such steels are enriched in carbon

on their surface before hardening by quenching. The process of introducing carbon,

to low carbon steels, in order to give it a hard surface, is called carburising.

Nitriding: - It is a process of case or surface hardening in which nitrogen gas is

employed in order to obtain hard surface of the steel. This process is commonly used

for those steels, which are alloyed with chromium, molybdenum, aluminium,

manganese etc.

Cyaniding: - The cyaniding is a case of surface hardening process in which both

carbon and nitrogen are absorbed by the metal surface to get it hardened. In this

process, the piece of low carbon steel is immersed in a bath of cyanide salt, such as

sodium cyanide or potassium cyanide maintained at 8500C to 950

0C.

Induction Hardening: -It is a process of surface hardening in which the surface, to

be hardened, is surrounded by an inductor block which acts as a primary coil of a

transformer. The inductor block, should not touch the surface to be hardened. A high

frequency current is passed through this block. Heating effect is due to inducted eddy

current and hysteresis losses in the surface material.

Flame Hardening: - Sometimes, a particular portion of an article is required to be

hardened. This is generally done in case of a portion subject to wear, abrasion or

shocks. This type of local hardening is done by a process, known as flame hardening.

In this process, the portion to be hardened is heated with the help of a oxyacetylene

torch above its critical temperature. The heated portion is then immediately quenched

by means of spray of water, which is directed towards heated portion. Since the

heating is localised, therefore no stresses are developed. As a result of this, the

chances of distortion or cracking are reduced.

(X) ,e ih vkbZ (Magnetic Particle Inspection Test.)

Magnetic particle inspection, by the method known as Magnaflux, is a non-

destructive method for the detection of discontinuities at or near the surface of magnetic

materials. Such a test reveals all types of surface defects such as quenching and fatigue

cracks, grinding checks, and surface seams, and distinguishes between many of these

types of defects. It also detects such subsurface defects as slag pockets in welds, and

shrinkage cavities and pores in castings; such defects are usually detectable at a

maximum depth of about one quarter inch in highly finished machine parts, and from

three quarters inch to one inch in large castings and welds. The indication is a powder

pattern magnification of the defect.

The method depends upon the fact that a magnetic field is distorted by a crack, a

gas pocket, or an inclusion of slag or other nonmagnetic material. This distortion results

in leakage fields and formation of small local magnetic poles. When powder of finely

divided magnetic material is applied to the magnetized surface of a piece to be inspected,

the particles are attracted by the leakage field, and form patterns that indicate the

locations and shapes of any such discontinuities.

The work may be magnetized by passing an electric current through it or by

placing it within the magnetic field of a coil of wire in which current flows, the choice of

method depending upon the nature of the part to be inspected. For detection of subsurface

defects, magnetization usually is produced by use of direct current, which penetrates the

mass of the work. For surface defects, alternating current is used because of its skin

effect, which concentrates its effect in a relatively thin layer at the surface of the part.

Dry magnetic powder may be blown over the work, a light oil suspension of the

particles may be flowed over the work, or the work may be dipped in it. The dry method

is suited particularly for surface and subsurface inspection of un machined castings,

welds, forgings, heavy machinery, and the like; the wet method is used more often for

inspection of ground or polished parts with bright surfaces.

A variation of the wet method consists in coating the wet particles with material

that is highly fluorescent under near ultraviolet light. This modification, called zyglo,test

is especially useful for detection of defects on interior surfaces where illumination is poor; it is useful also for surface work because of the added visibility that it provides.

(XI) vkbZ lh Mk;xzke (IC Digram)

-In the iron-iron carbide diagram is not of any practical importance.

Therefore, it is possible to modify the iron-iron carbide phase diagram by omitting

The low carbon region above 14000C. Moreover, the various solubility curves, in the

actual phase diagram, are taken as straight lines. We shall use this diagram to study

Transformation of various alloys from the liquid to the solid state. The transformation

Of various alloys may be discussed under the following two heads:

1. Primary Solidification: - This corresponds to the transformation of alloys from its

liquid state to a temperature just below the eutectic temperature. It is also called

transformation from liquid to solid state.

2. Secondary Solidification: - This corresponds to the transformation of alloys from

the solid state below the eutectic temperature to the solid state below the eutectoid

temperature. It is also called transformation of alloy from solid-to-solid state or

secondary crystallization.

(XII) baMD”ku gkMªfauax (Induction Hardening)-

In many engineering applications, it is desirable that a steel to be used should have a

hardened surface to resist wear and tear. At the same time it should have soft and tough

interior or core so that it is able to absorb any shock etc. This is achieved by hardening

the surface layers of the article, while the rest of it is left as such. This type of treatment is applied to gears, ball bearings, railway wheels etc.

Induction hardening is one of the processes out of the various processes of surface

hardening as carburizing, Cyniding , nitriding, flame hardening etc.

In this process the surface to be hardened is surrounded by an inductor block which acts

as a primary coil of a transformer. The inductor block, should not touch the surface block

to be hardened. A high frequency is passed through this block. The heating effect is due

to induced Eddy current and Hysteresis losses in the surface material. The inductor block,

surrounding the heated surface, has water connection and numerous small holes on its

inside surface. As soon as the surface reaches to the proper temperature (750o C to 760

o C

for 0.5 percent carbon steel and 790o C to 800

o C for alloy steel), it is automatically spray

– quenched under pressure.

The induction hardening is widely used for wearing surfaces of crankshaft,

camshaft, gear teeth etc.

(XIII) dzzhi (Creep)

- Creep is the time-dependent permanent deformation that occurs under stress; for

most materials, it is important only at elevated temperatures..

- When subjected to creep, the material continuous to deform until its usefulness is

seriously impaired. Over the life time of the structure, creep may grow large and

even result in fracture without any increases in load.

Creep in metals occurs in three stages:

1) The Material elongates rapidly but at decreasing rate

2) The elongation is constant

3) The elongation increases rapidly until the material fails, the stress for a definite

rate of strength at a constant temperature is known as Creep strength.

(XIV)VsEifjax(TEMPERING ): -

The main objects of tempering in heat treatment are:

1. To reduce brittleness of the hardened steels and thus to increase its ductility.

2. To remove the internal stresses caused by rapid cooling of steel.

3. To make steel sufficiently tough to resist shock and fatigue.

The process of tempering consists of reheating the hardened steel to some temperature

below the lower critical temperature, followed by any desired rate of cooling. The exact

tempering temperature depends up on the purpose for which the article or tool is to be

used.

When steel is heated to low tempering temperature (2000C to 250

0C), the internal

stresses are removed and ductility increases without changing the structure of steel from

martensite or reducing its hardness. On heating it to about 3000C, troostite -martensite

mixture is obtained which imparts some ductility to the metal. On heating it to 4000C,

martensite begins to change into fine pearlite or sorbite and the transformation of sorbite

and the transformation of sorbite is completed on reaching a temperature of 6000C. The

sorbitic steel is employed for making highly stressed parts, because it has a remarkable

mechanical property like ductility, strength and shock resistance.

The tempering temperatures may be judged by the colour formed on the surface of the

steel being tempered. The colours are caused by oxidation of the steel with the formation

of thin films of iron oxide.

The baths using tempering oils may be employed for temperatures up to approximately

2300C. The tempering oils are, usually, mineral oils having flash points of the order of

3000C. An adequate quantity of oil should be employed and the baths should be provided

with wire baskets which when loaded with work may be lowered into the tempering

baths. For temperatures above about 2300C, liquid salt baths are preferred. These salt

baths, usually, consist of mixtures of nitrates and nitrites. The chlorides and fluorides are,

usually, employed for higher temperatures.

(XV)”kkV ihfuax(Shot Peening):-

This operation on Laminated Bearing spring/coil spring to be carried for minimizing the

stress and increasing the tensile strength & removing dust and dirt for preparation of

painting etc. During the service period there are few disturbances in grains. To prevent

the granular disturbance and keep the molecules intact, shot peening operation is

required. This operation is carry on shot peening machine for this spring plates/coil

spring to be feed inside the machine through conveyor, this machine equipped with

highly compressed spherical iron shots (balls) these balls collide with spring with high

velocity removing dust and dirt from the surface.

For this operation, matching group of spring plates to be set up and later on

started feeding the spring plate for shot peening. To assets the intensity as per I.S. 7377,

Elmin test to be done. This is standard plate for checking the top plate for unevenness

irregular surface.

During the shot peening of L.B.Top plate it is essential to ensure spherical iron piece to

be in good condition it should be changed after become flat shape or small size of Iron

peace otherwise result of shot peening will not be achieved.

(XVI) Mkb isuhVªsUV VsLV(DPT )

PRINCIPLE: This method is used to reveal defects, which reach the surface of non-

porous materials. The penetrating liquid, which is dyed or fluorescent, is applies to the

cleaned surface of the component. The penetrant is allowed to act for a period of time.

Excess penetrant is carefully removed from the surface of the component, after which a

developing liquid is applied and dried off. The developer acts like a blotter, drawing the

penetrant out of the defect. After a short time indications appear in the developer, which

are wider than the defect and which, therefore can be seen directly or under ultraviolet

light due to the enhancement of the contrast between the penetrant and the developer.

PROCEDURE

-Pre-clean, remove grease and dry the component.

-Penetrant is applied to the component and acts for a brief period.

-Excess penetrant is completely removed from the surface.

A developer is applied and dried off.

Inspect for indication of defects.

PENETRANT TYPES

DYE PENETRANT: The liquids are colored so that they provide good contrast

against the developer. The liquids are as a rule red with white developer.

FLUORESCENT PENETRANTS: The liquid contains fluorescent material, which

glows under ultraviolet light.

WATER WASHABLE PENETRANTS: The liquid contains an emulsifier, which

allows surface penetrant to be removed using water.

POST-EMULSIFIABLE PENETRANT: after the liquid has been applied, an

emulsifier must be applied to the excess surface penetrant to make it water-

soluble.

SOLUBLE REMOVABLE PENETRANT: The penetrant can only be removed

fully from the surface by means of an appropriate organic solvent.

DEVELOPER TYPES

Dry powder developers

Water based wet developers

Non-water based water developers

LIMITATIONS

Components with porous surface cannot be tested.

The crack must be opened to the surface.

(XVII)gkbZ LihM LVhy(High Speed Steel): -

These steels are used for cutting metals, at a much higher cutting speed than ordinary

carbon tool steel. The carbon steel cutting tools do not retain their sharp cutting edges

under heavier loads and higher speeds. This is due to the fact that at high speeds,

sufficient heat may be developed during the cutting operation and causes the temperature

of cutting edge of the tool to reach a red hot. This temperature would soften the carbon

tool steel and thus the tool will not work efficiently for a long period. The high speed

steels have the valuable property of retaining their hardness even when heated to red hot.

Most of the high speed steels contain tungsten as the chief alloying element. But other

alloying elements like cobalt, chromium, vanadium etc. may be present in some

proportions. Following are the different types of high speed steels:

1. 18-4-1 High Speed Steel: -This steel contains 18% tungsten, 4% chromium and

1% vanadium. It is considered to be one of the best of all purpose tool steels. It is

widely used for drills, lathes, planer and sharper tools, milling cutters, reamers,

threading dies, punches etc.

2. Molybdenum High Speed Steel: -This steel contains 6% tungsten, 6%

molybdenum, 4% chromium and 2% vanadium. It has an excellent toughness and

cutting ability. The molybdenum high speed steels are better and cheaper than

other types of steels. It is particularly used for drilling and tapping operations.

3. Super High Speed Steel: -This steel is also called cobalt high speed steel, because

cobalt is added from 2% to 4% in order to increase the cutting efficiency

especially at high temperatures. This steel contains 20% tungsten, 4% chromium,

2% vanadium and 12% cobalt. Since the cost of this steel is more, therefore it is

principally used for heavy cutting operations, which impose high pressures and

temperatures on the tool.

(XVIII) vkfIVdy ik;jksehVj (Optical Pyrometer):-

A pyrometer is an instrument for measuring elevated temperature above the range of thermometer.

Principle

Matters glow above 900o F (482

o C) and the color of visible radiation is proportional

To the temperature of the glowing matter.

- The amount of light radiated from the glowing matter (solid or liquid) is

measured and employed to determine its temperature.

- All this is accomplished with the help of instrument known as optical pyrometer.

Operation

vi. The optical pyrometer is sighted at the hot body (which may be molten

metal, coke bed, hot crucible, etc.) and focused.

vii. In the beginning filament will appear dark as compared to the background

(say molten metal) which is bright (being hot).

viii. By varying the resistance in the filament circuit, more and more circuit is

fed into it, till filament becomes equally bright as the background and hence

disappears.

ix. The current flowing in the filament at this stage is measured with the help

of an ammeter which is calibrated directly in terms of temperature.

x. If filament current is further increased, the filament appears brighter as

compared to the background which then looks dark. An optical pyrometer can measure temperature ranging from 700-4000

o C.

1. Optical pyrometers are of limited value for measuring temperature of

molten metal owing to,

The absence of the black body condition and

The partial dependence of results on the emissivity of the metal surface.

- Pyrometers are calibrated (for use) with black body condition and a

correction needs to be applied for nonblack body condition which introduce errors.

The correction factor depends upon the ratio of absorbed radiant energy to the

radiant energy falling upon it. This ratio is called the emissivity of the material.

2. An optical pyrometer is preferred for measuring temperature of high

melting point metals such as iron and steel.

3. An optical pyrometer measures tem temperature between 700-4000o C

4. An optical pyrometer is employed to measure temperature of the body

where because of its (i.e. body’s) position a thermocouple pyrometer cannot be

used.

5. Errors can be introduced by smoke or gases between the observer and the

heat source.

(XIX)uku esVkfyd bauDywtu(Non Metallic Inclusion)– Steel is made by melting pig iron & scrap in the presence of nonmetallic slag. During

the steel making process nonmetallic oxides are produced in the steel by oxidation of

such elements as silicon. These oxides being lighter than steel, tends to rise to the

surface and join the slag. Near the end of the process the molten steel is left quiet for

some time so that as much of the slag & non-metallic oxides as possible shall rise to

the surface. Then if the steel is carefully poured it will be free from all nonmetallic

particles. These are always present however many fine particles which rises too slowly

to be eliminated. These remains in the finished steel as solid nonmetallic inclusion.

The inclusions are principally sulphides of iron or manganese or oxide or

silicate of iron, manganese, silicon or aluminium. Inclusions which are large enough to

be visible to the naked eye are never found in properly made steel. They may cause

failure of steel & are sufficient course of rejection of steel. Steel with undue amount of

inclusion are called ‘dirty’ steel. The inclusions may cause notable decrease in

properties. Especially when they occur in bands, they frequently do. The examination

of steel for inclusion is difficult, since they are not uniformly distributed & vary

widely in shape and size. In general inclusions influence the quality of the steel.

Examination of inclusion of steel is done by cutting sample test piece and polished on

abrasives grinder with fine polishing .test piece is kept on microscope to see the

internal structure and compare with standard mentioned in I S.

(XX)lk;ukbfMax (Cyaniding): -

The cyaniding is a case of surface hardening process in which both carbon and nitrogen

are absorbed by the metal surface to get it hardened. In this process, the piece of low

carbon steel is immersed in a bath of cyanide salt, such as sodium cyanide or potassium

cyanide maintained at 8500C to 950

0C. The immersed steel piece is left in the molten

cyanide salt bath, at the above temperature, for about 15 to 20 minutes. It is then taken

out of the bath and quenched in water or oil. The cyanide yields carbon monoxide and

nitrogen, which behaves as active carburizing agents in hardening the surface of steel.

The process can give surface hardness up to a depth of 0.8 mm. This process is mainly

applied to the low carbon steel parts of automobiles, some parts of motor cycles and

agricultural machinery.