FLAME HARDENING TEST ON LOW CARBON STEELS

AT CASE AND CORE

A Project work submitted to

K L University

Under the partial fulfillment of

B.Tech (IIIYear) during 2015-16

TEAM MEMBERS:-

NAME ID.NO S.VENKATESH 13007015 D.JAGADESH 13007045 B.SAI SANDEEP 13007160 B.VISHNU VARDHAN REDDY 13007164 K.V.D.S.R.MANIDEEP KUMAR 13007176

Under the guidance of

Dr. S. MADUSUDHAN

K.L. UNIVERSITY

Green fields, Vaddeswaram, Guntur Dist.522502

DECLARATION

We hereby declare that the project work entitled “FLAME HARDENING TEST ON LOW

CARBON STEELS AT CORE AND CASE” was carried out by us during V Semester

October 2015, and this work is not the same as that of any other and has not been submitted

for award of any other degree/diploma .

Place: K.L.University

Date:

K.L. UNIVERSITY Green fields, Vaddeswaram, Guntur Dist.

CERTIFICATE

This is to certify that this project work entitled “FLAME HARDENING TEST ON LOW

CARBON STEEL AT CORE AND CASE" done by S.Venkatesh(13007015), D.

Jagadesh(13007045), B. Sai Sandeep(13007160), B.Vishnu Vardhan Reddy(13007164),

K.V.D.S.R. Manideep Kumar(13007176) is a bonified work carried out by them in the

Department of Mechanical.

Project supervisor Head of the Department

(MECHANICAL)

ACKNOWLEDGEMENT

We express our sincere gratitude to Mr. S. MADHUSUDHAN, T.Vijay kumar for

their outstanding support throughout the project and for the completion of the work.

We express our deep sense of gratitude to T. VIJAY KUMAR for his excellent

teaching during the class hours. We express our gratitude to Dr.Y.V.Hanumanth Rao ,Head

of the department for providing us the adequate facilities , ways and means by which we are

able to complete this project work.

Last but not least we thank all teaching and non-teaching staff of our department for

their support in the completion of the work

Place: K.L.University

Date:

CONTENTS

1. Introduction

a. Low carbon steels

b. Properties of mild steel

c. Applications of mild steel

d. Hardening

i. Flame hardening

2. Experimental setup

a. Flame hardening

b. Brinell’s hardness test

3. Results

4. Conclusion

5. Bibliography

ABSTRACT

Flame hardening is a rapid, economical method for selectively hardening specific

areas on the surface of a part. This process is applied to selected metal surfaces which

contains some percentage of carbon in it and alloy steels, cast and ductile irons and some

stainless steels, followed by an appropriate quenching method.

Flame hardening uses direct impingement of an oxy-acetylene gas flame onto a

defined surface area.

Here we took a mild steel rod of the required dimensions and heating it using the gas

or arc welding for a required time of 5 min and calculate the hardness by using charpy or

brinells hardness test.

INTRODUCTION:-

1.a. LOW CARBON STEELS :

As we know there is a little bit of steel in everybody life. Steel has many practical

applications in every aspects of life. Steel with favourable properties are the best among the

goods. The steel is being divided as low carbon steel, high carbon steel, medium carbon steel,

high carbon steel on the basis of carbon content.

Low carbon steel has carbon content of 0.15% to 0.45%. Low carbon steel is the

most common form of steel as it’s provides material properties that are acceptable for many

applications. It is neither externally brittle nor ductile due to its lower carbon content. It has

lower tensile strength and malleable. Steel with low carbon steel has properties similar to

iron. As the carbon content increases, the metal becomes harder and stronger but less ductile

and more difficult to weld.

1.b. MILD STEEL PROPERTIES :

1. It is weldable, very durable (although it rusts), it is relatively hard and is easily

annealed.

2. structural strength is not usually sufficient to be used in structural beams and girders.

3. Because of its poor resistance to corrosion it must be protected by painting or

otherwise sealed to prevent it from rusting. At worst a coat of oil or grease will help

seal it from exposure, and help prevent rusting.

4. Being a softer metal it is easily welded.

5. Its inherent properties allow electrical current to flow easily through it without

upsetting its structural integrity.

6. less brittle and can therefore give and flex in its application.

1.c. APPLICATIONS :

Mild steel composes many of the ordinary, everyday objects that are made from steel. This

includes motorcycle frames, automobile chassis, and most cookware.

1.d. HEAT TREATMENT :

It is a very broad term and indicates heating and cooling operations or any sequence of two or

more such operations-applied to any material in order ot modify its internal structure or to

alter its physical, mechanical or chemical properties. Usually it consists of heating the

material to specific temperature, holding at this temperature for a definite period and cooling

to room temperature or below room temperature with a definite rate. The process heat

treatment is carried out first by heating the metal and then cooling it in water, oil and brine

water.

The purpose of heat treatment is to soften the metal, to change the grain size,

to modify the structure of the material and relive the stress set up in the material. It also

improves hardness, wear and abrasion resistance and cutting ability of steels. It improves

mechanical, physical or chemical properties such as Tensile strength, Toughness, ductility,

hardness. To produce special microstructures to increase machinability or corrosion

resistance. To change the composition of the surface by diffusion of C, N, Si etc., so to

increase fatigue life.

The various heat treatment process are annealing, normalizing, hardening,

austempering , mar tempering, tempering and surface hardening, case hardening.

Surface hardening a process which includes a wide variety of techniques is used to

improve the wear resistance of parts without affecting the softer, tough interior of the part.

This combination of hard surface and resistance and breakage upon impact is useful in parts

such as a cam or ring gear that must have a very hard surface to resist wear, along with a

tough interior to resist the impact that occurs during operation. Further, the surface hardening

of steels has an advantage over through hardening because less expensive low-carbon and

medium-carbon steels can be surface hardened without the problems of distortion and

cracking associated with the through hardening of thick sections.

Surface hardening consists of two methods:-

1. Flame hardening

2. Induction hardening

1.d.i). FLAME HARDENING

It is a process of heating the surface layer of hardenable steel to above its upper critical

temperature by means of oxy acetylene or oxy hydrogen torch and immediately quenching

with water or water-based polymer. There is no change in composition, and therefore, the

flame-hardened steel must have adequate carbon content for the desired surface hardness. The

rate of heating and the conduction of heat into the interior appear to be more important in

establishing case depth than the use of a steel of high hardenability.

Flame-heating equipment may be a single torch with a specially designed head

or an elaborate apparatus that automatically indexes, heats, and quenches parts. Large parts

such as gears and machine toolways, with sizes or shapes that would make furnace heat

treatment impractical, are easily flame hardened. With improvements in gas-mixing

equipment, infrared temperature measurement and control, and burner design, flame

hardening has been accepted as a reliable heat treating process that is adaptable to general or

localized surface hardening for small and medium-to-high production requirements.

TYPES OF FLAME HARDENING:-

There are four types of flame hardening:

Stationary flame hardening –This requires that the specified area be heated

Progressive flame hardening - This involves the use of a flame head with integrated quench

capability

Spin flame hardening - This requires the specified area being treated to be spun in front of

the flame head(s)

Combination flame hardening – This couples the progressive and spinning methods

BENEFITS OF FLAME HARDENING:-

1) flame hardening imparts a hard, wear-resistant surface to the component whilst improving

its fatigue strength through the development of residual surface compressive stresses in

suitably deep cases. Because only the surface is heated and quenched, heat treatment

distortion can be minimised.

2) Faster localised cooling rates permit higher surface hardness values than might be

achieved by through hardening.

3) Deeper hardening can be obtained than with thermo-chemical treatments. Depending upon

process parameters, hardened depths can be in the range 0.5-10mm.

4) Localised hardening can be used to strengthen components at critical points while leaving

other areas soft, without the need for the stopping-off procedures required in thermochemical

case-hardening.

5)Induction and flame hardening offer options for the treatment of exceptionally large

components, where conventional furnace heating and cooling would be impractical and

where only localised surface hardening is necessary.

6) Both techniques can be automated for reproducible results once the processing parameters

have been set.

MATERIALS THAT CAN BE TREATED :

Induction and flame hardening can be applied to a wide range of steels and cast irons.

Normally, medium-carbon steels (0.35-0.5% carbon), with or without alloying additions, are

used to ensure a satisfactory hardening response, final choice depending on required surface

hardness and core properties. With higher carbon contents there is an increased risk of

cracking and careful control is necessary for successful treatment.

What are the limitations?

• Applications such as gears and shafts, which have readily-accessible and geometrically-

uniform surfaces, are easily treated. Components with irregular shapes and surfaces requiring

treatment can be difficult to induction harden in view of the restrictions imposed by coil

design or limited accessibility. Flame hardening offers a somewhat greater degree of

versatility.

• The treatments can be applied to materials in the hardened and tempered, normalised or

annealed condition. Because of its metallurgical structure, material in the hardened and

tempered condition promotes optimum response to these short-time processes.

• The size and shape of a component that can be induction or flame hardened depends on the

type of equipment operated by the heat treater. For large components, check the availability

of suitably-sized facilities at an early stage..

2.EXPERIMENTAL PROCEDURE

2.a FLAME HARDENING :

Fig 1 hardening of the lowcarbon steel material using oxy-acetylene flame

Fig 2 quenching of the flame hardened low carbon steel material

2.b BRINELL’S HARDNESS TEST

The objective of conducting this experiment is to determine the Brinell’s hardness

number for aluminium. So, the apparatus necessary to conduct the test are hardness

testing machine, brinell microscope, aluminium specimen, weights of 250 grams.

Fig 3. Brinell’s hardness testing machine

PROCEDURE:

1) First select an unhardened low carbon steel material of required dimensions

2) Now flame harden it using the oxyacetylene torch by the to and fro moment of torch

uniformly over the surface of the material for a specified time of 5 min

3) After heating for the required time quench it by using a water bath immediately after

heating

4) Now take the other work pieces and repeat the above steps for the material by heating it

for 10 and 15 min

5) After completion of the quenching we need to test the hardness for the flame hardened

work pieces by using a brinells hardness in the following method:

1. Select proper indenter based on the material to be tested and fix it in the holder.

2. Select proper load by turning the load selector disc on the right hand side according to the

Brinell scale.

3. Place the specimen on the testing machine and turn the wheel till thesmall pointer of the

inner dial reads 3. A red spot is marked against this reading on the inner dial. This is to apply

a minor load of 10kg in order to ascertain proper seating of the indenter on the specimen

avoiding slipping off of the indenter, when the major load is applied.

4. Turn the load lever to loading position in order to apply the major load (balance of the

selected load) under the influence of which the indenter

penetrates into the specimen.

5. Apply the load for about 30 seconds and bring back the load lever to normal position while

the pointer in outer dial reaches a constant

position.

6. Remove the specimen and measure the diameter of the impression by Brinell microscope.

7. Repeat the same for another trail at a place away from the previous

location on the same specimen and find the average value.

8. Repeat the above procedure for all the given specimens and tabulate the observations.

Fig 4:material with indentation and brinell's microscope

OBSERVATION:-

S.No. Specimen Load

(Kgf)

Diameter

of

Indenter

(mm)

Diameter

of

impression

(mm)

B.H.N.

Core

B.H.N

Case

1 Mild steel

Hardened for 5

min

3000 10 Core-4.33

Case-4.6

193.68 170

2 Mild steel

Hardened for 15

min

3000 10 Core-3.8

Case-4.43

254.6 184.56

BAR GRAPH:

From this bar graph we can observe as the hardening time increase the hardness value

also increases. Here we observed that the hardness value at the core is greater than the

hardness value at case. But according to the scientifical observation the hardness value at the

core should be less than the hardness value at case. The reasons are as follows:

The material may be hardened before we purchase.

The material composition may not be pure steel.

Irregular hardening of the material.

0

50

100

150

200

250

300

CORE CASE

5 MIN

10 MIN

CALUCULATIONS:

Where,

F = Total load applied on the specimen

D = Diameter of the indenter = 10 mm

d = Diameter of the impression

The value is rounded to the nearest integer.

RESULT:-

Brinell Hardness Number for Mild steel flame hardened for 5 min at core=193.68

Brinell Hardness Number for Mild steel flame hardened for 5 min at case=170

Brinell Hardness Number for Mild steel flame hardened for 15 min at core =254.6

Brinell Hardness Number for Mild steel flame hardened for 15 min at case =184.56

CONCLUSION:-

From the obtained results we concluded that the hardness of the material is increasing

by increasing the hardening time .

Also we observed that the hardness value is more at the core when compared to the

hardness value at case.

BIBLIOGRAPHY:-

1. http://www.laser-cutting-online.com/properties-of-mild-steel.html

2. http://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1

&cad=rja&uact=8&ved=0CCoQFjAAahUKEwjh_4TWyPnIAhUmUKY

KHc8HA2g&url=http%3A%2F%2Fethesis.nitrkl.ac.in%2F1138%2F1%2

FHeat_Treatment_of_Low_Carbon_Steel.pdf&usg=AFQjCNHo19ztYDl

1vuxnxsDEmgfOZ-s6Ng&sig2=c21pq7K6pHO2wys5YH759g