mem05051a select welding processes - learner guide

8/10/2019 MEM05051A Select Welding Processes - Learner Guide

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MEM05 Metal and Engineering

Training Package

Learner guide

Version 1

Training and Education Support

Industry Skills Unit

Meadowbank

Product Code: 5721

MEM05051A

Select welding processes


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TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2012

MEM0 5 0 5 1 A S e le c t w e l d i n g p r o c e s s es

AcknowledgmentsThe TAFE NSW Training and Education Support Industry Skills Unit, Meadowbankwould like to acknowledge the support and assistance of the following organisationsand people in the production of this learner guide.

Capral AluminiumBlue Scope SteelCIGWLEDHardface TechnologyHarris Product group (Australia)Lincoln Electric Company (Australia)Silverwater Welding SuppliesWelding Industries of AustraliaWestern Safety Wear

Writer:

(Updated from existing TAFE Publications)

Reviewers:John Anderson (Hunter Institute)Ed Harkness (Illawarra Institute)

Project Manager:Stephen DaviesEducation Programs ManagerTAFE NSW

Enquiries

Enquiries about this and other publications can be made to:

Training and Education Support Industry Skills Unit, Meadowbank Meadowbank TAFE

Level 3, Building J, See Street,

MEADOWBANK NSW 2114

Tel: 02-9942 3200 Fax: 02-9942 3257

TAFE NSW (Training and Education Support, Industry Skills Unit

Meadowbank) 2012

Copyright of this material is reserved to TAFE NSW Training and EducationSupport, Industry Skills Unit Meadowbank. Reproduction or transmittal in wholeor in part, other than for the purposes of private study or research, and subject tothe provisions of the Copyright Act, is prohibited without the written authority ofTAFE NSW Training and Education Support, Industry Skills Unit Meadowbank.

ISBN 978-1-74236-431-5


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TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2012


Table of Contents

Introduction ................................................................................... 7

1. General introduction ............................................................................. 7

2. Using this learner guide ......................................................................... 7

3. Prior knowledge and experience ............................................................. 9

4. Unit of competency overview ................................................................. 9

Topic 1: Properties of metal ......................................................... 13

Review questions ................................................................................... 16

Topic 2: Carbon steels .................................................................. 17


Topic 3: Alloy steels ..................................................................... 23

Review questions .................................................................................. 31

Topic 4: Non ferrous metals ......................................................... 33


Topic 5: Fusion welding processes ............................................... 41


Topic 6: Pressure welding processes ............................................ 53


Topic 7: Low temperature welding processes ............................... 59


Topic 8: Welding safety ................................................................ 65


Topic 9: Fillet and butt joint terminology ...................................... 73


Topic 10: Fillet and butt weld defects ........................................... 87


Topic 11: Distortion control .......................................................... 93

Review questions ..................................................................................102

Resource Evaluation Form .......................................................... 105
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TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012 Page 13 of 108

Topic 1: Properties of metalAll metals exhibit different properties which make them unique in their own right.A metals properties are important as they inuence how they perform in a given

industrial environment. Metal properties can be classied as being either physicalor mechanical. For example, aluminium is soft, light and has a low melting pointwhereas carbon steels are harder, heavier and has a much higher melting point.These are typical examples of physical properties of a metal.

Due to these differences it is important that metal fabricators have a basicunderstanding of the properties of metals. A number of common physical andmechanical properties are briey outlined below.

P h y s i ca l p r o p e r t i e s

Density: Refers to a metals mass per unit volume. For example, steel isheavier than aluminium and therefore has a greater density.

Colour: Iron or steel exhibits are silvery colour, copper is red, brass isyellow. The colour of a metal can quickly provide the operatorwith an idea of the type of material they are dealing with.

Thermalexpansion:

Metals expand when heated. The amount of expansion perdegree (C) rise in temperature is an important measurementand is expressed as the metals co-efcient of thermalexpansion. For example, stainless steel will exhibit a greaterdegree of expansion than carbon steel for the same heat input.

Thermalconductivity:

Refers to the ease by which heat travels through a metaland how far heat will travel over a given time. Copper andaluminium are excellent thermal conductors whereas stainlesssteel is a poor conductor.

Electricalconductivity:

Relates to how easily electricity travels through the metal.Copper and aluminium are excellent conductors of electricity.Steel on the other hand has a much higher resistance andtherefore is a poor conductor.

Corrosion: Some metals corrode easily, others are more resistant. Forexample, stainless steels and aluminium are resistance to

corrosion whereas steel will rust.

Melting point: This is the temperature at which a metal melts. Some metalshave a high melting point such as carbon steel (approx1500C) while others such as aluminium (approx 660C) arelower.

Magnetism: Ferrous metals (iron based) are magnetic while, almost withoutexception non-ferrous metals are not. For example carbonsteels are attracted to a magnet whereas aluminium, copperand brass are not magnetic.


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Page 14 of 108 TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2012

MEM0 5 0 5 1 A S el e ct w e l d i n g p r o c e s s es

Me c h a n i c a l p r o p e r t i e s

Malleability: Refers to the ability of a material to be hammered into shapewithout cracking. Aluminium is extremely malleable whereby

cast iron is not.

Ductility: Is to the ability of a metal to withstand deformation bybending, rolling and/or folding without cracking. For example,low carbon steel is very ductile, cast irons are not.

Yield Strength: This property is the ability of a metal to resist permanentdeformation (bending) when a force is applied. When ametal is bent, rolled or pressed it has yielded and thereforebecomes permanently deformed.

Brittleness: Is a weakness in a metal and will crack or break when force isapplied. Brittle materials such as cast iron or high carbon,steels are not used for fabrication purposes for this reason.

Hardness: Refers to a metal's ability to resist indentation by a given forceor load. For example, it is easy to make a pop mark on lowcarbon steels but near impossible to make one on heat treatedhigh carbon steel.

Impactstrength:

This property refers to the amount of energy a metal willabsorb due to a sudden blow without cracking or breaking.High impact strength gives a measure of material toughness.

A low toughness measure shows the metal to be brittle. Forexample, low carbon steels resist impact whereas cast iron orhigh carbon steel are much less resistant.

Fatiguestrength:

This refers to a metals ability to resist breaking or crackingwhen subjected to stressful load cycles. A load cycle can bedescribed as forcing a metal in one direction and then in theopposite direction.

Weldability: Refers to the ease by which a metal can be welded. Forexample, low carbon steels are easily welded and thereforehave good weldability. A hardened material such as high

carbon steel has poor weldability and will crack unless specialprecautions are taken.


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W e l d b en d t e s t o f

d e t e r m i n e d u c t i l i t y


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Review questions

These questions have been included to help you revise what you have learnt in

Topic 1: Properties of metal.

1. List six(6) physical properties of a metal.

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2. Listsix(6) mechanical metal properties of a metal.

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3. What mechanical property is used to describe a metals ability to withstanddeformation by hammering, rolling or bending without fracturing?

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4. Name the property of a metal that resists stretching or pulling apart whensubjected to stress by two opposing forces.

______________________________________________________________

5. What is meant by the term "weldability.

______________________________________________________________

6. What property is used to determine a metals density or weight?

______________________________________________________________


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Topic 2: Carbon steels

I n t r o d u c t i o n

Metals are produced from mined materials called an ore. Some metals are used intheir pure form however; most have other elements added to them to form an alloy.Alloying elements are normally added to pure metals to improve their physical andmechanical properties and industrial applications. Steels are produced by extractingthe iron from the ore by a process called steelmaking which involves placing ironore into a heated blast furnace to separate the iron (Fe) content from the impuritiesin the ore.

Once the iron content is extracted it is further processed and rened in a basicoxygen steelmaking furnace (BOS). The BOS stage of steel production is a veryimportant one as it removes excess carbon and other impurities in the material.Once this stage is complete the steel is formed into the desired shape by rolling

which also improves the strength and toughness of the material. Steel is themost common metal used in fabrication and allied engineering industries and iscommercially available in sheet, coil, plate, tube, pipe and structural sections.

Small amounts of manganese, silicon and carbon remain in the processed steelto give it strength and toughness. Carbon in steel is very important as the metaldepends on its carbon content to give it specic properties. The effect of retainingmeasured amounts of carbon will have a direct effect on its properties. For example,the effects of increasing the carbon content in plain steel will:

Lower it's melting point Increase tensile strength of the steel (within limits) Lower ductility Increase hardness and brittleness Increase the capacity of the steel to harden through heat treatment Reduce weldability.

T y p e s o f c a r b o n s t e e l

Carbon steels can be divided into three (3) main groups. The groups are inuencedby the percentage (%) range of carbon they contain. The three groups are classiedas:

1. Low carbon steels.

2. Medium carbon steels3. High carbon steels.

L o w c a r b o n s t ee l

Low carbon steels have carbon content of ranging from 0.01% and 0.30%. Steelswith a carbon content of 0.15% or less, are soft and ductile. Steel containing 0.23%to 0.27% carbon is used where greater strength is needed.


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A p p l i c a t i o n s

Low carbon steels are ductile and readily welded materials. For these reasons theyare widely used for:

Deep drawing and deep pressing applications. Sheet, plate and rolled sections (angle, beam, columns). Car and truck bodies. Sheetmetal cabinets and assemblies. Ship building.

Me d i u m c ar b o n s t e e l

Medium carbon steels have a carbon content ranging from 0.3% to 0.5%. Thesesteels will harden if allowed to cool too quickly. Special precautions are neededif they need to be welded to slow the cooling rate and reduce hardening. Theincreased carbon content can cause hard and brittle areas to form in the weld joint.


Medium carbon steels contain higher carbon contents than low carbon steels. Asa result they are more susceptible to hardening and cracking due to rapid cooling.Medium carbon steels have higher strengths and are much stronger than low carbonsteels and therefore require careful attention when they need to be welded to avoidcracking or excessive hardness forming in the weld zone. Typical applications forthis group of steels include:

Steel rails - railways, tramways and overhead crane tracks Hand tools such as cold chisels Machine parts Agricultural equipment parts.

H i g h c a r b o n s t e e l

High carbon steels have a carbon content ranging from 0.5% to 1.2%. If they areheated special precautions need to be observed to prevent these steels becomingextremely hard and brittle. High carbon steels are not normally welded (exceptfor repair purposes) as they are often used for wear-resistant parts, and for themanufacture of some cutting tools.


Cutting tools Springs Carbon steel cutting edges Wire cables Dredging equipment Files.


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A d d i t i o n a l El e m e n t s i n Ca r b o n St e e l

Carbon steels contain additional elements other than iron and carbon. Someelements have been deliberately added to the steel to improve its properties while

others are considered impurities that cannot be completely removed during thesteelmaking process. The level of impurities must be strictly controlled otherwisethe required properties of the steel will be severely compromised. The effects ofvarious elements in steel are as follows:

Manganese - Produces a hardening effect - Helps produce a ne grain structure - Acts as a mild deoxidiser or scavenger against the harmful effects

of sulphur.

In most carbon steels the manganese content is kept within 0.3% to0.8%.

Silicon - Acts as a deoxidising agent or scavenging agent. Normally silicon in carbon steels is kept to within 0.1% to 0.35%.

Sulphur- - Considered an impurity in steels and kept to a maximum of 0.05%.Excessive amounts of sulphur combines with iron to form a harmfulcompound called iron sulphide which can cause a condition called"hot-short", cracking at elevated temperatures.

Phosphorus - Considered an impurity in steels and kept to a maximum of 0.05%.Excessive amounts of phosphorus combines with iron to form aharmful compound called iron phosphide which can cause anundesirable condition called "cold-short, cracking at normal

working temperatures.

Su r f a c e t r e a t m e n t s f o r s t e e l

Plain carbon steels readily oxidise (rust) when exposed to the atmosphere thereforeexposed surfaces must be protected from corrosion. Common methods used toprotect steel structures from corrosion include:

Painting Powder coating Galvanizing (zinc) Mill scale

Sheetmetal is supplied with factory painted Colorbond or with a sacricialmetal coating of zinc based galvanised or zincalume coating.

G a lv a n i s e d z i n c s u r f a c e Co i l o f z i n c a lum e


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M i n i n g i r o n o r e

H o t r o l l i n g s t e e l


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Review questions

These questions have been included to help you revise what you have learnt in

Topic 2: Carbon steels.

1. List four(4) properties affected by increasing the carbon content in steel.

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2. State the carbon range (%)for the following:

Low carbon steels: _______________________________________________

Medium carbon steels: ____________________________________________

High carbon steels: ______________________________________________

3. Give two (2) typical industrial applications for each of the following:

Low carbon steels:

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Medium carbon steels:

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High carbon steels:

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4. Briey explain the effect of having too much sulphur in steel.

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5. List three(3) methods used to protect steel surfaces from corrosion.

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True/False questions(circle the correct response)

6. An excessive amount of phosphorus in carbon steel can cause hot cracking atnormal operating temperatures.

True False

7. Small amounts of silicon is added to steel as a deoxidiser.

True False

8. Manganese is added to steel to improve and rene the grain structure.

True False

9. The sulphur content in most carbon steels is kept within 0.1% to 0.8%.

True False

10. Medium carbon steels are heat treatable and will harden if allowed to cool tooquickly.

True False

11. Increasing the carbon content in steel increases ductility.

True False

mem05051a select welding processes - learner guide

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