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SRI LANKA INSTITUTE of ADVANCED TECHNOLOGICAL EDUCATION

Training Unit

Soldering and BrazingTheory & Practice

No: WE 026

ELECTRICAL AND ELECTRONIC

ENGINEERING

Instructor Manual


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Training Unit

Soldering and Brazing

Theoretical and Practical Part

No.: WE 026

Edition: 2008Al l Rights Reserved

Editor: MCE Industrietechnik Linz GmbH & CoEducation and Training Systems, DM-1Lunzerstrasse 64 P.O.Box 36, A 4031 Linz / AustriaTel. (+ 43 / 732) 6987 3475Fax (+ 43 / 732) 6980 4271Website: www.mcelinz.com


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SOLDERING & BRAZING

CONTENTS Page

1

SOLDERING ................................................................................................................4

1.1 Hard soldering......................................................................................................4

1.1.1 Types of hard solder ........................................................................................5

1.1.2

Fluxes for hard soldering..................................................................................7

1.2 Soft soldering .......................................................................................................7

1.2.1 Sources of heat................................................................................................7

1.2.2

Soldering tools .................................................................................................8

1.2.3 Soft solders .................................................................................................... 12

1.2.4

Fluxes for soft soldering .................................................................................13

1.2.5 Finishing a soldered joint ...............................................................................14

1.2.6 Blowlamp or gas torch soldering (application for soft soldering)....................14

2 SOLDERING BRAZING ..........................................................................................17

2.1 Flame soldering (brazing) ..................................................................................17

2.2

Brazing solders ..................................................................................................18

2.3 Fluxes ................................................................................................................18

2.4

Work procedure when brazing ...........................................................................19

3 BRAZE WELDING......................................................................................................21

3.1 Braze welding of copper with steel ....................................................................22

4 FAULTY GAS WELDING ...........................................................................................22

4.1 Butt-welds .......................................................................................................... 23

4.1.1

Reinforced joint ..............................................................................................24

4.1.2 Sagged weld ..................................................................................................24

4.1.3 Porous final run..............................................................................................24

4.1.4

Lateral notches...............................................................................................25

4.1.5 End crater faults.............................................................................................25

4.1.6 Incomplete root penetration ...........................................................................26

4.1.7

Lateral root notches .......................................................................................26

4.1.8 One-sided root fusion fault.............................................................................26


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4.1.9

Sagged root....................................................................................................27

4.1.10 Slag on root (burnt root) .............................................................................27

4.1.11

Pipe misalignment......................................................................................28

4.1.12 Pores, slag and fusion faults between two runs.........................................28

4.2

Fillet welds .........................................................................................................29

4.2.1 Improper built-up of weld................................................................................29

4.2.2 Lateral notches...............................................................................................29

4.2.3 Fusion faults...................................................................................................30

5 PRACTICAL PART.....................................................................................................31

Instructions for practical exercise 1 - Soldering Exercise...............................................31

Instructions for practical exercise 2 - Bending Sample .................................................. 33

Bending Sample.............................................................................................................34

Braze weld copper to steel exercise:3 ...........................................................................35


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BRAZING AND BRAZING

1 SOLDERING

Soldering means the joining of metals using separate metals (solders) which have

melting points below those of the parent materials.

A distinction is made two types of soldering:

- Hard soldering working temperature above 450 C.

- Soft soldering working temperature below 450 C.

1.1 Hard soldering

Sources of heat:

Acetylene-oxygen flame, propane gas, town coal gas, hydrogen and natural gas.

Soldering:

- Alloy formation solder

- Diffusion

Scale 1:2000

material brass

diffusion layer

alloy layer

solder

alloy layer

diffusion layer

material steel


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Advantages:

- Components of different thickness and materials made of different alloys can be

joined.

- In this way, an even and clean soldered joint is made which generally requires no

mechanical treatment (milling etc.) afterwards.

Caution:

Solder gap width must be at least 0.05 mm and at most 0.2 mm.

1.1.1 Types of hard solder

Hard solders with high heat-resistant:

Palladium nickel chromium alloys; working temperature 1220 C.

Pure copper hard solders:

Addition of up to 1% silver or silicon assists fluidity; working temperature 1080 C.

good bad good bad


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Application:

Soldering carbide tips onto tools.

Brass hard solders (Cu-Zn):

Overheating can cause zinc to vaporise. The alloy component zinc melts at 420 C and

vaporises at 907 C; working temperature 900 950 C.

Application:

Mainly for soldering steel.

Nickel-silver hard solders:

Cu-Ni-Zn alloys containing up to 10% nickel; working temperature 900 950 C.

Application:

For welding steel (high strength).

Silver hard solders:

Silver (Ag), copper (Cu), zinc (Zn), cadmium (Cd), nickel (Ni), manganese (Mn) and

alloys; working temperature 550 850 C.

Application:

For almost all metals except aluminium (AI).

Good wettability, low thermal yield, high strength. The silver solder L-Ag 40 (40%

silver) has the lowest possible working temperature of 610 C. With a low silver content

the working temperature is higher.

Copper-phosphorus hard solders:

8% phosphorus, the remainder copper; copper combines with the oxygen of the copper-

oxygen layer. No flux is needed for soldering; working temperature approximately 710 C.

Application:

For hard soldering of copper where flux residue can no longer be removed. Hard solders

alloyed with phosphorus may not be used for steel soldering (brittle soldered joint).

Copper-phosphorus-silver hard solders:2.5 15% silver, 8% phosphorus, remainder copper; working temperature approximately

710 C.

Application:

Plumbing with copper pipes, electrical components, refrigerators; the silver filler increases

expansion. No flux is needed.


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Aluminium hard solders: (silicon)

11 13.5% silicon, remainder; silicon makes aluminium very fluid, which is important for

penetration of narrow solder gaps, working temperature approximately 610 C.

Application:

For hard soldering of pure aluminium.

1.1.2 Fluxes for hard soldering

1.1.2.1 Purpose

Flux prevents access of air at the place being soldered and thereby inhibits oxidation.

Caution:Use flux suited to the solder. Avoid overheating the material being soldered and avoid

overheating the flux.

Soldering times should be as short as possible, otherwise oxidation may occur.

Remove flux residue.

If the shape of the piece to be soldered makes it possible to remove the flux entirely,

neutral (non-corrosive) fluxes must be used.

1.2 Soft soldering

Working temperature is below 450 C.

1.2.1 Sources of heat

These include:

Electricity, gas flame, forge, petrol blowlamp.


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1.2.2 Soldering tools

The following distinction is made:

- indirectly heated soldering irons or bits

- directly heated soldering irons or bits.

1.2.2.1 Indirectly heated soldering irons

The most common forms are:

Pointed soldering irons:

Application:

Mainly for spot soldering and internal soldering.

soldering iron tip


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Heated soldering irons:

Application:

Mainly for soldered joints on sheet metal.

Both types of soldering iron are of simple design and can only be used for a short time,

because they cool off rapidly.

The heat needed for the soldering process is stored in the copper body of the soldering

iron. Copper absorbs heat well and releases it quickly to the place being soldered.

Care and maintenance of the soldering iron tip and face:

When minor damage occurs, the soldering face is resurfaced with a single-cut file applied

to the tip surface.

hatchet soldering iron face


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The surface must be metallically clean. Heat the soldering iron. As soon as the solder

runs tin the point of the soldering iron using flux and a rag.

Wipe away excess solder.

The soldering iron face may be tinned with sal ammoniac stone with the addition of

solder.

Cause of damage:

Too much heat causes the tinning to burn and damages the body of the soldering iron.

The soldering joint is rough and granular if the soldering iron is too cold, the solder cannot

run.

1.2.2.2 Directly heated soldering irons

These have a built-in heat source.

Advantages:

A constant heat supply renders this type suitable for continuous soldering processes.

solder

sal ammoniac stone


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Gas soldering iron;

Electric soldering iron (for batch soldering):

heating element handle

pointed copper bit


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1.2.3 Soft solders

The following types of soft solder can be obtained:

Solder sticks, rods, filaments, wired, ribbons and foils.

Distinctions are made between soft solders according to their alloy components:

Examples:

Lead-tin solders and Tin-lead solders

75 Pb + 25 Sn 60 Sn + 40 Pb

60 Pb + 40 Sn 90 Sn + 10 Pb

Tin-lead solder with added cooper or silver:

50 Sn + 48.8 Pb + 1.2 Cu63 Sn + 48.8 Pb + 1.5 Ag

Eutectic solder:

68 Sn + 32 Pb

This has the lowest melting point of 182 C. At this temperature the solder becomes fluid

immediately (no pasty stage).

All other solders have an incipient pasty stage.

Soft solders for heavy metals are mainly tin-lead alloys.

For soldering on electrical equipment, resin-cored solder is generally used.

There are standard symbols for pipe solder, e.g.,

LSn 50 Pb = 50% Sn + 50% Pb, melting point 210 C

LSn 60 Pb = 60% Sn + 40% Pb; melting point 190 C

Plumbers solder (cored solder) rod solder

tin shell (LSn60)

Plumbers solder has a core made of resin (distilled pine resin) which serves as flux.

tin component in %

d = 11.5 mm2 mm3 mm

resin core


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Melting phases:

The solder melts when heated. From a solid state it becomes first pasty and then fluid.

These solders may be called smearing solders, e.g., 33 Sn + 77 Pb = smearing solder for

wiped joints (e.g., joining lead pipes).

1.2.4 Fluxes for soft soldering

The purpose of fluxes:

They lower the surface tension of the liquid solder by approximately one third, thereby

increasing effective fluidity.

They dissolve light oxide layers on the metals.

They protect the joint against oxidation during solidification.

Different types flux:

Fluxes can be obtained in liquid, paste or powder form.

The choice of flux includes:

Acid fluxes:

Hydrochloric acid (dilute) for soldering zinc and galvanized sheet metal.

Killed spirits (natural flux):

For soldering steel, tinplate, copper and brass.

Soldering fluid is made by adding zinc fillings to hydrochloric acid.

Sal ammoniac:

For tinning the soldering iron.

Acid-free fluxes (basic fluxes):

These include resin, mixtures of tallow and sal ammoniac, soldering pastes.

They are suitable for soldering metals which must not be exposed to the subsequent

action residues.

Caution:

Acid flux residue must be removed from the soldered joint by washing.


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1.2.5 Finishing a soldered joint

- The joint must be meticulously clean. It can be cleaned mechanically by abrasion (file

and cloth etc.) or chemically with acids or solvents.

- Assemble component parts and fix temporarily.

- The solder gap should be kept as small as possible.

- Apply flux to the joint.

- Apply solder to the heated soldering iron, then draw the soldering iron carefully and

slowly over the place to be soldered.

- Do not loosen the fixed pieces until the solder has hardened.

- Clean the soldered joint.

1.2.6 Blowlamp or gas torch soldering (application for soft soldering)

Blowlamp soldering means soldering with a soldering blowlamp or a soldering torch.

Blowlamp soldering is used when the heat of a soldering iron is in sufficient; it is ideal for

large areas needing to be soldered and for places which cannot be easily reached with a

soldering iron.

Modern gas soldering torches are usually heated by either butane or propane.


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Preparation of surface to be soldered:

The preparatory work to be done for blowlamp soldering is similar to that for soldering with

a soldering iron (clean, assemble and apply flux).

Example:

Soldering of bearing brass or copper-tin zinc alloys (bronze bushes) or copper-lead alloys

(gun-metals).

nozzle

valve

liquid-gas cartridge

abraded (emery clothed)surfaces


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Procedure for soldering bearing brass:

- Cleaning paste (based on hydrochloric acid) is applied with a brush to the abraded

surfaces. Let the paste reach for a short time and then wash it off.

- Apply tinning paste (tin and lead dust mixed with tallow and sal ammoniac mixture)

evenly to the surface being cleaned.

- Both halves of the bush are heated evenly to the soldering temperature. Test the

temperature with a thermochrome stick.

- Spread the tinning paste evenly with a clamp cloth.

- Apply rod solder to the tinned surfaces of one half of the bush.

- Place the other half on it and adjust.

- For bushes of two-thirds aluminium and one-third zinc, the solder is brushed on with a

steel brush without flux.

Safety instruction for soldering:

There is always danger of accidents and fire where open flames are used.

Observe the following:

- Check that all equipment to be used is safe to operate.

Do not leave any inflammable objects or liquids near the flame

(if necessary, cover with a protective asbestos shield).

- Ensure that fire-fighting equipment is at hand (fire-extinguishers, water and sand).

- Protect hands, hair and clothes from flames.- Immediately after soldering, turn off the blowpipe or torch.

- Ventilate working areas.

- After work, wash hands (solder contains lead which is poisonous).

soldered bush

soldered joint


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2 SOLDERING BRAZING

Soldering and brazing are joining processes which form semi-permanent joints. In such

processes two metal pieces are bonded at the interface with an easily meltable solder i.e.,

a partially chemical, partially mechanical union.

The difference between soldering, brazing and welding is as follows:

- In soldering and brazing the surface the surfaces are heated only to the working

temperature of the bonding metal. In welding the edges and the welding wire are

heated (Melting point).

- One can differentiate between two methods:

Soldering up to 450 C (soft) working temperature.

Brazing over 450 C (hard) working temperature.

Soldering

up to 450 C

Brazing

over 450 C

Zn 419

Pb 327

Sn 232

Penetrating solders 182

S1 Cu F1 red 1083

S2 Ms F2 yellow 900

S3 Ns F3 green 900

Ag 550

S = welding rod

F = flux

2.1 Flame soldering (brazing)

This is effected with a welding torch and filler rod.

Application:It is used for closed joint, open joint and deposition brazing.

open joint brazing closed joint brazing deposition brazing


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2.2 Brazing solders

Heat resistant brazing solders are nickel, chromium and cobalt (Palladium alloys).

Cu pure copper

Ms60 copper-zinc (brass brazing solders)

SnBz12 copper-tin (bronze brazing solders)

Ns copper-nickel-zinc (nickel silver solders)

CuP8 copper-phosphorus brazing solders (phosphorus-bronze solder)

Ag40 silver-brazing solders

ALS 13 aluminium brazing solders

Generally available in wore or bar form in combination with a flux or pure metals. Power

forms and leaf forms may be used for specialised applications.

2.3 Fluxes

The oldest fluxing agent is dispersion borax (potash and common salt).

Because of the large variety and the different compositions of brazing solders a large

assortment of fluxes are available which are matched to the respective brazing solders.

Fluxes are used in powder form and paste form.

Note:

Fluxes must be mixed in paste form.

Aluminium flux should only be mixed with distilled water.

Function of the fluxes:

- Prevent oxidation.

- Exclusion of air from the brazing faces.

- Promote the fluidity of the brazing faces.

- Indicate the working temperature.


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2.4 Work procedure when brazing

- The joint space must be meticulously clean.

- Apply the flux and spread on the brazing solder.

- Heat until the flux becomes liquid.

- Guide the brazing solder along the joint with light pressure.

- The base material is wetted by the brazing solder.

The surface is alloyed partially.

The brazing solder penetrated into the material mechanically.

prepare workpiece

apply flux

brazing

solder

BRAZING


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a)

In accordance with the soldering method, distinctions are made between:

b)

c)

soldering -stone

bit soldering(soft soldering)

flame soldering andflame brazing

muffle furnace brazing induction brazing


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d)

3 BRAZE WELDING

With braze welding, preparation of the joint to be brazed is very important. Breaks in

pieces of cast iron or while malleable cast iron must be prepared so that they have a 90Vee.

Joint preparation brazing + welding =

braze welding

tooth gap prepared for welding braze steel.

resistance brazing

BRAZING WELDING

STEEL COPPER


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3.1 Braze welding of copper with steel

With a copper rod, the copper is welded and the steel brazed.

copper steel

4 FAULTY GAS WELDING

The strength of a weld depends on the tools and fillers used, their shapes, their

arrangement on the piece to be welded and the manner in which it is made by the welder.

Weld, root and fusion faults are recognisable.


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4.1 Butt-welds


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4.1.1 Reinforced joint

speed of travel is too low, too much filler material applied.

4.1.2 Sagged weld

4.1.3 Porous final run

Poses arise as a result of incorrect application of flame and filler or where the material

welded is very dirty.


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4.1.4 Lateral notches

Undercutting results from incorrect application of the flame and filler rod movement or

insufficient application of filler material.

4.1.5 End crater faults

When the joint is finished the flame is removed too quickly.


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4.1.6 Incomplete root penetration

Root faults occur when the pear-shaped aperture is not maintained during welding.

4.1.7 Lateral root notches

The root has been melted only on one side because the torch has been incorrectly held.

Root notches can also occur as a result of improper joint preparation, especially when

welding is performed without moving the item being welded.

4.1.8 One-sided root fusion fault

Flame held too far away, torch held improperly and pear-shaped aperture in the root

disregarded these are the main causes of root fusion faults.


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4.1.9 Sagged root

Occurs when the travel speed is too low and where torch is held at too steep an angle.

4.1.10 Slag on root (burnt root)

This occurs with leftward welding of sheet metal over 3 mm thick (weld flame has no

protective effect on the root side).


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4.1.11 Pipe misalignment

Improper joint preparation; misalignment must be corrected with heat treatment before

begins.

4.1.12 Pores, slag and fusion faults between two runs

The fault can arise as a result of the molten pool running ahead or as a result of jerky

torch movement. Slag and pores occur as a result of dirty filler rod or parent metal.


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4.2 Fillet welds

4.2.1 Improper built-up of weld

This occurs where the speed of travel is too high, insufficient filler material is applied and

the torch held at the wrong angle.

4.2.2 Lateral notches

These occur when an incorrect torch angle is used and the upper sheet metal is melted

too much.


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4.2.3 Fusion faults

These occur when the lower run is not melted properly, when the speed of travel is too

high and the torch is held at the wrong angle.Note:

These welding faults show that, in addition to good practical ability, extensive theoretical

knowledge is also needed in order to be able to check the suitability of materials for

welding.


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SOLDERING AND BRAZING

5 PRACTICAL PART

Instructions for practical exercise 1 - Soldering Exercise

1. PREVIOUS KNOWLEDGE

a) Correct flame adjustment.

b) Filling.

c) Safety precautions for gas welding.

1. INSTRUCTIONS

Working procedure:

- Cut the plate to size

- Deburr

- Clean surface with a file according to specifications

- Apply flux

- Heat

- Apply solder

- Remove flux residue

- Bend test (Sheet No.:1)

3. SUMMARY AND ADDITIONAL REMARKS

a) Safety precaution:

Make sure that the file handle is securely fixed.

b) Sources of error:

Overheating

Faulty seams due to oil or grease residues.


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SOLDERING EXERCISE

Exercise No.:1

Procedure:

1. Prepare to size

2. Deburr

3. File the parts according to instructions

4. Fit into the soldering jig

5. Apply fluxing agent (spread on solder)

6. Heat (fluxing agent must become liquid)

7. Solder along the soldering area

8. After cooling, remove flux film and clean

9. Bend test

Legend:

XXX ......... Welders ID Number

Material: M.S.

Plate dimension: 35 x 25 x 5 1Pc35 x 20 x 4 1Pc

Filler material: Brazing rods 1030xFC, Flux SILOX F2

Welding gases: C2 H2, O2

Repetition of the exercise if the result is not satisfactorily as per instructors advice.

BASIC SKILLS IN BRAZING

Part 2

LONGITUDINAL FILED Part 1

CROSS FILED


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Instructions for practical exercise 2 - Bending Sample

Test procedure:

As shown in drawing sheet 2. The bend test has to be done on an anvil, by using of a

hand hammer. Evaluation of the workpiece use evaluation sheet.

SUMMARY AND ADDITIONAL REMARKS

a) Safety precaution:

Make sure that the file handle is securely fixed.

b) Sources of error:

Overheating.Faulty seams due to oil or grease residues.


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Bending Sample

From exercise No.:1

EVALUATION OF THE BENDING SAMPLE

(5 POINTS)

Exercise No.:2

1 point is subtracted for:

a) tearing

b) overheating

c) excess of brazing solder

900 .. OPFRACTURE AT ~ 700 ... 1p

~ 450 ... 2p

~ 30

0

... 3p

~150 ... 4p

1

2

3

4

5p


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Braze weld copper to steel exercise: 3

Legend:

XXX .... Welders ID Number

1. Copper pipe: 60 x 4 x 100 1Pc. (Din 1754)

2. Steel pipe: 60 x 4 x 100 1Pc.

Filler material: Brass Welding Rods 2 mm (Bhler 18 x FC)

Remarks: - 90 bead angle

- Soften copper, heat steel to melting temperature of copper (1083)

welding

brazing

COPPER STEEL

XXX

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