mem05018c - vetres · pdf filejob 4: fillet - vertical (pipe to plate) ... use power...

MEM05 Metal and Engineering Training Package

Learner guide

Version 2

Training and Education Support

Industry Skills Unit

Meadowbank

Product Code: 5755

MEM05018C Perform advanced welding

using gas metal arc welding process (steel edition)

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MEM05018C Perform advanced welding using gas metal arc welding process (Steel edition)

© TAFE NSW (Training & Education Support Industry Skills Unit, Meadowbank) 2013

Acknowledgments

The TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank would like to acknowledge the support and assistance of the following people in the production of this resource package:

Avesta PolaritBOC Gases AustraliaCIGWELDFroniusLincoln AustraliaOneSteel AustraliaSilverwater Welding SuppliesStandards Australia

Writer:Updated from existing TAFE resources.

Reviewer:John Anderson (Hunter Institute)TAFE NSW

Project Manager:Stephen DaviesEducation Programs ManagerTraining and Education Support, Industry Skills Unit, MeadowbankTAFE 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) 2013

Copyright of this material is reserved to TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank. Reproduction or transmittal in whole or in part, other than subject to the provisions of the Copyright Act, is prohibited without the written authority of TAFE NSW Training and Education Support, Industry Skills Unit Meadowbank.

ISBN 978 1 74236 465 0

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MEM05018C Perform advanced welding using gas metal arc process (Steel edition)


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ContentsIntroduction .................................................................................. 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: GMAW safety .................................................................. 13

Review questions .................................................................................. 18

Topic 2: GMAW consumables ....................................................... 21


Topic 3: Pulse GMAW ................................................................... 33


Topic 4: Welding carbon and low alloy steels ............................. 39


Topic 5: High alloy stainless steels .............................................. 57


Topic 6: Welding symbols ............................................................ 67


Topic 7: Destructive weld tests ................................................... 73


Topic 8: Structural welding standard .......................................... 79


Practical work ............................................................................. 83

JOB 1: T-Fillet - Horizontal/vertical (Plate) ................................................ 88

JOB 2: T-Fillet - Vertical (Plate) ............................................................... 90

JOB 3: T-Fillet - Overhead (Plate) ............................................................ 92

JOB 4: Fillet - Vertical (Pipe to plate) ....................................................... 94

JOB 5: Fillet - Overhead (Pipe to plate) .................................................... 96

JOB 6: Butt weld - Flat - Double Vee (Hex bar) ......................................... 98

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MEM05018C Perform advanced welding using gas metal arc process (Steel edition)


JOB 7: Butt weld - 1G (Pipe rotated) ...................................................... 100

JOB 8: Butt weld - Horizontal (Plate) ..................................................... 102

JOB 9: Butt weld - 2G (Pipe)................................................................. 104

JOB 10: Butt weld - Vertical (Plate) ....................................................... 106

Resource Evaluation Form ......................................................... 109

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of 112 © TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2013


Prerequisites

Before you commence this unit of competency you must have completed the following prerequisite units.

• MEM05007C - Perform manual heating and thermal cutting• MEM05050B - Perform routine gas metal arc welding• MEM05017D - Weld using gas metal arc welding process• MEM05051A - Select welding processes• MEM05052A - Apply safe welding practices• MEM09002B - Interpret technical drawing• MEM12023A - Perform engineering measurements• MEM18001C - Use hand tools• MEM18002B - Use power tools/hand held operations.

Unit pathway It can be seen from the pathway below that MEM05018C Perform advanced welding using gas metal arc welding process is an advanced trade level unit that leads towards welder Certification in accordance with AS 1796 Certification of welders and welding supervisors. For more information regarding certification refer to the standard or discuss with your teaching section.

It is important that all relevant prerequisite units are achieved before attempting MEM05018C.

MEM05043BPerform welds to code standards using GMAW

process

MEM05026CApply welding

principles

MEM05017DWeld using gas

metal arc welding process

MEM05050BPerform routinegas metal arc

welding

MEM05018CPerform advanced

welding using GMAW process

(steel edition)

MEM05018CPerform advanced

welding using GMAW process(aluminium edition)SAMPLE


© TAFE NSW (Training & Education Support, Industry Skills Unit Meadowbank) 2013 Page 11 of 112

Elements and performance criteria

ELEMENT PERFORMANCE CRITERIA1. Prepare welding

materials and equipment.

1.1 Welding equipment is prepared.

1.2 Welding equipment appropriate to task requirements is assembled and adjusted correctly and safely.

1.3 Materials are prepared to achieve the required weld specification.

2. Weld joints to code requirements using GMAW.

2.1 Weld requirements are interpreted correctly.

2.2 Welds are deposited correctly to specifications.

2.3 Appropriate distortion prevention measures are selected for the weld type and material and distortions are rectified as required.

3. Assess weld quality and rectify faults.

3.1. Weld joints are visually inspected against specifications.

3.2. Defects are removed using appropriate methods for the given task.

3.3. Weld records are correctly completed and maintained.

Required knowledge

Look for evidence that confirms knowledge of:

• In-depth knowledge of the properties and characteristics of a wide range of materials

• Requirements to conform to Australian Standard 1554 Structural Purpose, Bureau Det Norske Veritas or equivalent

• Weld procedures and requirements• Different welder identification systems such as numbering, bar coding, paint

coding, letter stamps• Safe welding practices• Use and application of personal protective equipment for GMAW.

Required skills

Look for evidence that confirms skills in:

• Welding to conform to Australian Standard 1554 Structural Purpose, Bureau DET Norse Vertas or equivalent

• Perform safe welding practices • Using and applying personal protective equipment for GMAW• Interpreting weld requirements and specifications• Using hand and power tools to prepare and weld material using GMAW• Entering information onto proformas and standard workplace forms• Interpreting technical drawings and weld specifications relating to advanced

GMAW • Using hand and power tools to prepare and weld material using GMAW• Using measurement and numeracy skills relating to advanced GMAW and

preparation

• Selecting equipment and consumables appropriate to the task.

For further details pertaining to this unit refer to the website http://training.gov.au

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Context of and specific resources for assessment

This unit may be assessed on the job, off the job or a combination of both on and off the job. Where assessment occurs off the job, that is the candidate is not in productive work, then an appropriate simulation must be used where the range of conditions reflects realistic workplace situations. The knowledge and skills covered by this unit would be demonstrated by an individual working alone or as part of a team. The assessment environment should not disadvantage the candidate.

Work health and safety

Your teacher will encourage you to assist in identifying and eliminating hazards and to devise control measures for potential risks to yourself and others that may arise during practical sessions. The Work, Health and Safety Act 2011 (WHS Act) and WHS Regulations 2011 are enforced throughout all Australian States and Territories to protect people in the workplace.

This legislation is aimed at providing consistency, certainty and clarity across Australia making it easy to understand workplace health and safety responsibilities. The WHS Act and its Regulations will require teachers and learners to take every possible step to control and monitor potential risks in the classroom, TAFE workshop and in the workplace. Detailed information relating to the WHS Act and regulations can be found on the following websites:

• WorkCover Authority of NSW www.workcover.nsw.gov.au• Safe Work Australia www.safeworkaustralia.gov.au

What you will need

• Pens, pencils and calculator • Welding helmet or face-shield (minimum SAA shade 10 filter lens)• Oxy-fuel gas cutting visor or goggles (minimum SAA shade 5 filter lens)• Leather gloves or gauntlets• Safety capped shoes/boots with leather upper and rubber soles• Close fitting overalls, or heavy drill cotton long sleeved shirt and trousers• Learner resource MEM05018C Perform advanced welding using gas metal arc

welding process (steel edition).

Objectives

At the end of this unit you will be able to:

• Revise key safety concepts associated with the GMAW process

• State a range of solid wire electrodes and gas mixtures used for GMAW carbon and low alloy steels

• Explain the principles associated with pulse GMAW and its applications

• List a range of ferrous metals used in fabrication industries

• Determine the weldability of alloy steels in relation to GMAW

• Identify and explain the application of welding symbols on engineering drawings• List and describe a range of common destructive workshop weld tests

• Determine the type and permissible level of weld defects permitted in SP and GP welds as specified in AS/NZS 1554.1

• State the purpose and application of structural steel welding codes• Deposit fillet and butt welds in all positions using solid wires to weld quality

requirements specified in AS/NZS 1554.1 Structural Purpose (SP)• Document and record welding procedures as required in AS/NZS 1554.1• Follow and apply safe welding and workshop procedures.

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Topic 2: GMAW consumablesConsumable selectionIt is important to select the correct type of wire electrode and shielding gas to suit a particular type of metal and job if parts are to be welded successfully. A wire electrode must be able to produce sound weld deposits that closely match the physical and mechanical properties of the parent metal.

When welding high strength low alloy (HSLA) steels it is vital that mechanical properties such as impact, yield and tensile strength of the weld metal match those of the parts being welded. Physical properties also need to be considered such asweather resistance and colour match.

In addition to mechanical and physical properties, other factors that influence the selection of a wire electrode include:

• Type of shielding gas used (see shielding gases)• Composition of the parent metal • Service conditions the weldment is to perform in • Standard or code requirements you are complying with • Cost, dependable supply and availability of consumables• Capacity of the power source used (current range, duty cycle, pulse facilities etc).• Type of joints and weld positions likely to be encountered.

Large diameter wires are capable of producing high deposition rates and are used for welding heavy plate sections whereas smaller diameter wires are better suited for positional welding and joining thinner sections.

Wire electrodes are classified in accordance with AS/NZS 14341:2012 which has been reproduced from an International Standard (ISO 14341:2010). The purpose of the Standard is to provide specific requirements for consumable manufacturers to produce wires to a specified composition and quality for GMAW applications. The classification system also provides fabricators, the user of the product, with details relating to a wires mechanical properties and other information needed to select a wire for a given application.

For further reference relating to the classification of GMAW wires refer to AS/NZS 14341:2012 Welding consumables–Wire electrodes for gas metal arc welding of non alloy and fined grain steels– Classification (ISO 14341:2010, MOD).

Special Note As manufacturers of GMAW consumables have not yet reclassified their wires to the new Standard, wires mentioned in this resource will remain referenced to the superseded Standard AS/NZS 2717.1.1996 Welding–Electrodes–Gas metal arc–Ferritic steel electrodes. When suppliers align their wires to the new classification system the notes in this learner resource will be updated.

Fabricators should be aware some wires may be supplied bearing American Welding Society (AWS) specifications to meet code requirements of AWS A5.18 and AWS A5.28.

For detailed information on classification of wires it is recommended to consult the appropriate standard, code or manufacturers’ guides. See learner resource MEM05017D for examples of details relating to the wire electrode classification system.

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Carbon and low alloy wiresSolid wire electrodes used for joining plain carbon and HSLA steels are normally manufactured with a thin “flashing” of copper to improve:

• Electrical conductivity as the wire passes through the contact tip• Resistance to rusting from moisture in the atmosphere• Wire feeding characteristics by reducing friction when high wire speed rates are

selected.

The copper flashing on the wire does not contribute to the finished mechanical properties of the weld joint. Precision wound wire spools for welding plain carbon and HSLA steels are supplied in hermetically sealed packaging. The most common being the standard 15 kg spools, others available include:

• 0.8 kg mini-spools• 5 kg handy-spools• 30 kg coils.Wire electrodes used for large volume production work are available in sealed 220 kg bulk containers. Solid wires are always used with direct current, electrode positive (d.c. +). Some examples of wires and their applications are indicated in the following table.

Parent metal Type of wire and application

Plain carbon steels (hot or cold rolled)

A double de-oxidised wire developed for welding low to medium strength structural steel plate, sheet and rolled sections. This type of wire is produced by most consumable manufacturers and marketed by trades names such as:

• CIGWELD - Autocraft LWI-S6• LINCOLN - Ultramag ® S6• WIA - Austmig ES6

These wires are suitable for depositing multiple run welds on light to medium thickness steels in all positions.

High in manganese and silicon these wires are designed to tolerate base metal surface contaminants such as mill scale. This type of wire is the most widely used for steel fabrication.

Triple deoxidised wires contain small amounts of manganese, aluminium and titanium to produce welds with improved toughness and where radiographic qualities are required of the finished structure.

Wire classification

Wire size (Ø mm)

Voltage range(volts)

Current range(amps)

ES6-GC/M-W503AH0.91.2

16-2420-28

70-200150-280

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Parent metal Type of wire and application

Plain carbon and HSLA steels.

This group of wires are designed to match the properties of HSLA steels such as:

• High tensile and yield strength of welded structures• High service temperatures of welded parts• Dynamic loading requirements• Where post weld heat treatments are required of weld

structures.

Types of structural, HSLA steel sections and castings weldable would include:

• Quench and tempered (Q and T) structural steels • Chromium-Molybdenum, creep-resistant steels• Carbon-Manganese steels.

Some examples of wires for such applications include:

• WIA Austmig ESD2; are low alloy wires used for welding medium and high strength steels, particularly where service temperatures up to 500°C are encountered. Applications include the welding of carbon manganese and HSLA steels used for pressure vessel and boiler construction.

• CIGWELD Autocraft Ni Cr Mo; are low alloy steel wires used for joining high strength steels depositing welds of a tensile strength up to 760 MPa. Applications include welding quenched and tempered steels such as Bisalloy 80, USS-T1 types and Welten 80C etc.

• Lincoln SuperArc LA-90; A low alloy wire manufactured to meet minimum tensile strength requirements ranging from 552 to 620 MPa. Additional alloying elements of 0.5% molybdenum provides improved strengths after post-weld stress relief.

• Applications include welding of pipe, fittings, flanges, valves and pressure vessel forgings subject to elevated working temperatures.

Wire classifications

Wire size(Ø mm)

Voltage range(volts)

Current range(amps)

ESB2-GM-W559AH 1.2 18-32 120-350

ESMG-GC/ M-W769AH

1.20.9

18-3216-28

120-35070-230

ES2D-GC/ M-W559AH

1.2 18-32 120-350

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Note: HSLA wires are covered by AS/NZS 21952:2012 Welding consumables - Wire electrodes, wires, rods and deposits for gas shielded arc welding of creep- resisting steels - Classification (ISO 21952:2012, MOD)

15 kg precision wound wire spools

Care and storage of wire electrodes

• Always store wire packages off the floor in a clean, dry and well ventilated area

• Do not unseal wire spools from their packaging until such times as they are to be used

• Never remove classification codes, identification labels or trade names from either the storage box or spool. This can lead to an improper type of wire being used on a job

• Always replace and store partially used wire spools in the packaging (box) they were originally supplied in

• Never use badly corroded wires as they will contaminate the weld and cause unnecessary wear and tear on conduit liners, drive rolls and contact tips

• Damaged spools should be discarded as they will cause irregular wire feed problems resulting in poor quality weld deposits

• Wire spools “loaded” on welding machines should be covered to avoid contamination from moisture and workshop dust.

For more information on wire electrodes go to:

http://www.bocworldofwelding.com.au/welding-consumables-and-supplies.htmlhttp://www.lincolnelectric.com.au/http://www.austwelding.com.au/Technical%20pages/CIGWELD%20Filler%20Metals%2 0PocketGuide%202008.pdfhttp://www.welding.com.au/

Shielding gasesAs shielding gases perform such a vital function, it is important for operators to have a sound understanding of the impact the atmosphere has on the weld metal and how shielding gases influence the characteristics of the arc during welding.

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Plain carbon steel, when in a molten state has a natural tendency to combine with the oxygen and nitrogen in the atmosphere to form harmful oxides and nitrides. Metallic oxides and nitrides are formed as well as oxygen combining with carbon to form carbon monoxide.

These reactive constituents are easily formed as a result of the atmospheric environment which is composed of approximately 80% nitrogen and 20% oxygen. Oxides and nitrides absorbed into a molten weld are unwanted because they can major cause weld defects such as:

• Porosity• Worm holes/piping• Weld metal embrittlement• Cracking (in some sensitive HSLA steels).

Porosity and wormholes in a fillet weld

In some instances the inclusion of oxides and nitrides can render the finished weld mechanically and physically unfit for service. For example, if high levels porosity were to form in a weld it can result in a loss of strength and dissolved oxides/nitrides can cause severe embrittlement. For these reasons it is vitally important for the arc and weld pool to be fully protected throughout the welding operation.

Selection of an appropriate shielding gas or gas mixture is important as they directly influence the welding arc and other operating characteristics. Some examples include:

• Shielding efficiency• Metal transfer characteristics• Welding arc stabilisation• Depth of penetration• Weld bead contour/toe wetting• Speed of welding• Surface cleaning action• Strength of completed weld.

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Gases such as argon (Ar) or helium (He) are widely used in the fabrication industry for the joining non-ferrous metals such as aluminium and aluminium alloys. These gases are chemically non-reactive or inert and as a standalone or as mixed gases they are not suitable for GMAW plain carbon or HSLA steels. Using argon or helium gas on steel promotes a tendency for the weld metal not to flow in to the toes of the weld properly resulting in undercutting and/or uneven shaped profiles.

Poor bead profile and unfavourable arc conditions render argon uneconomical to use on steels. The operating characteristics of argon are greatly improved by combining measured quantities of reactive gases such as carbon dioxide (CO

2) and oxygen.

Argon based gas mixtures containing CO2 and oxygen are extensively used for

welding plain carbon, low alloy and stainless steel structures.

Shielding gasesShielding gases for GMAW are classified in accordance with AS 4882-2003 Shielding gases for welding. This standard provides a designation system to identify welding gases. The table below reflects AS 4882 by providing a letter to indicate a type of gas.

Designator Gas A Argon

C Carbon Dioxide (CO2)

He Helium

H Hydrogen

N Nitrogen

O Oxygen

Note: The chemical symbol for Argon is Ar, although only the letter A is used as the designator in AS 4882.

Shielding gases comprise of the following designator and numbering arrangement:

SG – B X - % 2 component mix

SG – B XY - % % 3 component mix

SG – B XYZ - % % % 4 component gas mix

Where:

SG – identifies the product as a “shielding gas”;

SG – B - Indicates the singular, or the base or major gas in the shielding gas or gas mixture

SG – B XYZ - % % % - Indicates individual minor component gases for two or more component mixtures. A “backslash” is used to separate the quantities stated.

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Examples for a singular gas/gas mixtures

SG–A - Represents welding grade argon as the shielding gas

SG–C - Represents carbon dioxide as the shielding gas

SG–AC–25 - Represents an argon + carbon dioxide shielding gas mixture with 25% CO

2

SG–ACO–18/2 - Represents an argon + carbon dioxide + oxygen shielding gas mixture with 18% CO

2 and 2% O

2.

Gases for carbon and low alloy steels An argon based gas mixture is the most widely used for GMAW of low carbon and HSLA steels. Mixtures can contain varying quantities of CO

2 and oxygen or both.

Section of a shielding gas or mixture is dependent on such factors as:

• Composition/type of material to be welded• Mode of metal transfer required (spray, short arc, pulse)• Application - automated, robotic welding• Weld profile and penetration levels required.

Argon + CO2 mixturesIncreasing the CO

2 level in gas mixtures improves depth of penetration, heat of the

arc, weld width and welding speed but may also give an increase in spatter levels.

The following table shows typical compositions and applications for Ar/CO2 gas

mixtures.

Argon % CO2 % Application90

85

82

80

77

75

10

15

18

20

23

25

Welding sheetmetal sections using short arc (dip)

Light steel section using short arc (dip)

Fillet welds up to 12 mm – produces good penetration

Thick sections – fast travel speeds with good penetration

Thick steel sections using spray where deep penetration is required

Welding heavy steel sections.

Argon + CO2 + O2 mixturesOxygen added to an argon + CO

2 mixture has a tendency to flatten the weld bead,

improve spray transfer characteristics, weld bead profile and penetration. The following table shows typical compositions and applications for argon + CO

2 + O

2

mixtures.

Argon %

CO2 %

O2 % Application

92

91.5

81.5

5

7

16

3

1.5

2.5

Welding sheetmetal sections using short arc (dip)

Welding light steel sections - produces excellent appearances

Welding thicker sections, produces deep penetration and fast

travel speeds.

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• Low O2 and CO

2 levels are suitable for short arc welding of sheetmetal products

• High CO2 with low O

2 levels produce lower spatter levels than straight CO

2

shielding but comparable penetration and fusion levels

• The addition of O2 reduces the droplet diameter and improves the stability of

metal transfer.

Argon + O2 mixturesOxygen is added to argon in small percentages to stabilise the arc, improve bead profiles, edge wetting characteristics and to minimise the tendency to produce undercut in fillet welds. This range of gas mixtures are mainly used for the welding light gauge sheetmetal products. Spatter is virtually eliminated with this mixture.

The following table shows typical compositions and applications for argon/O2

mixtures.

Argon % O2 % Application95

93

5

7

Welding light steel sections using short arc (dip)

For steel up to 7 mm, good weld profile, reduced penetration, low spatter levels.

Advantages of argon-based mixtures• The range of mixtures available suit most applications• Improves weld bead profile and appearance• Spatter levels are reduced compared to using straight carbon dioxide• Depth of penetration can be controlled• Increased weld travel speeds improves production rates• reduces undercutting and lack of fusion.

Weld bead profilesAdding various quantities of reactive gases such as carbon dioxide and oxygen to argon will influence the characteristics of the welding arc, often improving bead profile, edge wetting and penetration levels. Some typical examples of weld profiles using gas mixtures are illustrated below.

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Topic 3: Pulse GMAWThis mode of metal transfer is a highly controlled form of spray transfer requiring specially designed power sources equipped with pulse welding capabilities. Pulse transfer involves using a welding current programmed to operate between two separate current levels, these being a high energy peak current and a low background current.

When the welding current is in the background cycle it will operate in the globular transfer mode and when it reaches its peak current level it will operate in the spray transfer range. This action results in the arc constantly alternating back and forth between the two current ranges.

During a single pulse cycle the arc will form a background current which keeps the arc “energised” and stable without actually depositing any filler wire. In other words, a droplet forms but is not transferred.

As the current reaches its high energy “peak”, the droplet is detached from the end of the wire and transferred across the arc into the weld pool. One metal droplet is transferred per each pulse; the frequency of pulses per second is controlled by settings on the machine. Pulsed transfer technology offers control over several key variables. These include:

• Peak current - spray mode • Peak current time• Background current - a reduced current value that keeps the arc energised

without depositing wire• Background current time• Period – the time the background and peak currents operate through one cycle • Frequency – refers to the number of times a pulse cycle occurs per second.

Most modern power sources have a range of factory set programs inbuilt to automatically adjust pulse parameters such as those mentioned above. This option removes a large degree of guesswork out of setting up equipment to produce optimum welding conditions. Selecting a given program can be as simple as entering the type and thickness of metal to be welded.

Pulse sequence A typical pulse sequence is explained in the diagram below.

1. The arc is established2. Heating the electrode and parent metal3. Droplet starts to form at the electrode tip4. Droplet is “nipped off” and transferred during the peak current (spray mode)5. Droplet joins parent metal to form the weld.

Pulse sequence

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A graphical description of pulsed arc metal transfer illustrated below shows the pulse transfer in relation to current input.

Pulsecurrent

Pulse time

tp

MeancurrentBack-

groundtime tb

Pulse sequence

Note: 0.9 to 1.2 mm diameter wires are most commonly used with pulsed arc transfer.

Advantages

Pulse arc metal transfer offers a number of advantages compared to other conventional GMAW transfer mode. Some of these include:

• Greater control of weld penetration levels• Improved control of weld metal deposits• Smooth regular weld profiles and crater control• More resistant to lack of fusion defects than other modes of transfer• Excellent arc stability with very low spatter levels• Less distortion when welding thinner sections due to more controlled heat inputs• Root pass quality is comparable with GTAW• Lower fume outputs• Able to cope with poor joint fit-ups better than conventional GMAW.

Limitations

• Equipment is more expensive than conventional systems• Can be more complex to set up for the operator• Higher arc energy requires the use of additional safety protection for operators

and those working nearby.

Applications

Typical applications for pulse GMAW include:

• Welding pipes and tubes• Welding high strength low alloy steels• Ship and boat building• Welding aluminium and stainless steels fabrications• Ideally suited for robotic, fully automated setups.

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Review questions

These questions have been included to assist you revise what you have learned in Topic 3: Pulse GMAW.

Q1. List four (4) advantages of pulse GMAW over conventional GMAW.

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Q2. Briefly explain how pulse GMAW differs from conventional GMAW.

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Q3. State one (1) limitation associated with pulse GMAW.

____________________________________________________________

Q4. Provide a brief explanation of the following.

Peak current: __________________________________________________

____________________________________________________________

Background current: ____________________________________________

____________________________________________________________

Period: _______________________________________________________

____________________________________________________________

Frequency: ____________________________________________________

____________________________________________________________

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Q5. Give two (2) typical applications for pulse GMAW.

____________________________________________________________

____________________________________________________________

True / False questions (circle the correct answer)

Q6. Pulse GMAW is less resistant to lack of fusion defects than conventional GMAW.

True False

Q7. Ø0.9 to 1.2 mm wires are commonly used for pulse GMAW.

True False

Q8. The purpose of peak current is to keep the arc energised without depositing any filler material.

True False

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