Perform Routine
Manual Metal Arc
Welding
(MEM5.12C)
LEARNING RESOURCE
MANUFACTURING, ENGINEERING, CONSTRUCTION
AND TRANSPORT CURRICULUM CENTRE
Metal Fabrication & Welding
Insert clipart
MEM5.12C/1
First Edition
MEM5.4C/1 Perform Routine Manual Metal Arc Welding
First Edition – February 2006
© MECAT Curriculum Centre, TAFE NSW
i
MEM5.12C
Perform routine MMAW
Publishing details:
This published in January 2006 by
Manufacturing, Engineering, Construction and Transport Curriculum Centre
NSW TAFE Commission
Corner Showground and Green (formerly Victoria) Roads, Castle Hill
First edition published in January 2006
Copyright details:
© Manufacturing, Engineering, Construction and Transport Curriculum Centre, TAFE
NSW, 2006
Copyright of this material is reserved to the Manufacturing, Engineering, Construction
and Transport Curriculum Centre, TAFE NSW. Reproduction or transmittal in whole or
part, other than for the purposes and subject to the provision of the Copyright Act, is
prohibited without the written authority of Manufacturing, Engineering, Construction and
Transport Curriculum Centre, TAFE NSW.
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TAFENSW
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MEM5.12C
MEM5.12C
Perform routine MMAW
Perform routine manual metal arc welding.
The scope of this unit incorporates all the theory & practical content for completion of
MEM5.12C Perform routine manual metal arc welding
Scope of competency unit & performance criteria
Scope of unit.
Addresses unit performance
criteria;
Apply safe welding practices;
 Hazards of MMAW
 personal protective equipment (PPE)
 welding helmets
 filter lens shades
 welding gauntlet gloves
 emergency stop switches/buttons
 welding screens
 electrical connections
 good housekeeping
4.1 Safe welding practices are
applied
Correctly set up welding equipment;
 welding machine power source
 polarity
 current selection
 electrode holder
 electrode lead
 return lead & clamp
 return lead position
3.1 Welding equipment is set up
properly
Select correct electrodes for metal
being welded;
 metals welded with the MMAW
process
 core wire
 flux coating
 flux type
 polarity selection
 electrode diameter
 current selection
 weld positions
 condition & care of electrodes
3.2 Correct electrodes are
selected to suit application &
settings
Identify the location of welds from
drawings & job specifications
 weld measurement
 engineering drawings
1.1 Weld requirements are
identified from job instructions
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1.2 Location of welds is identified
in accordance with standard
operating procedures & job
specifications
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Clean and prepare materials ready
for welding
 surface condition of metal
 cleaning methods
 grinding
 wire brush
2.1 Materials are cleaned &
prepared ready for welding
Weld materials to job requirements
 tack welds
 jigs/fixtures
 assembly & alignment of joint
 weld size
 weld quality
4.2 Materials are welded to job
requirements
Clean completed Welds in accordance.
with job requirements
 level of cleaning required
 slag removal
 spatter removal
 cleaning methods
 visual inspection of completed
welds
4.3 Welds are cleaned in
Accordance with standard
operating procedures
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1. Introduction
The learning resource MEM5.12C Perform routine manual metal arc welding contains theory
based learning material, work method statements, (WMS), practical exercises, projects* and
revision questions. It is designed to assist students achieve the outcomes described in the national
competency unit descriptor MEM5.12C Perform routine manual metal arc welding.
This learning resource is based on the concept of completing fabrication projects which
will allow for training delivery and assessment of a number of competencies at the same
time.
Teachers are encouraged to substitute other learning materials, activities and projects
which they consider to be more appropriate for their students under instruction.
Prerequisites
Before you commence this unit of competency you should have completed the following competency
units.
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•None required
Assessment
Assessment against competency standards relies on your teacher gathering enough evidence to
demonstrate that you can meet the requirements of each unit.
To pass MEM5.12C Perform routine manual metal arc welding, you must show competency in
relation to the underpinning knowledge (the theory notes in this unit) as well as demonstrate you
can safely carry out the practical tasks in this unit. (the practical exercises and projects)
The Student Assessment Guide which explains the details of how you will be assessed in this unit &
how assessment results are recorded is enclosed in these resource notes.
Unit Purpose
When you have achieved this unit of competency you will have developed the knowledge and skills
to safely carry out routine manual metal arc welding on metal sections using the manual metal arc
welding process. As a result you will be able to apply these skills to manual metal arc weld metal
structures as required by various manufacturing and servicing industries. MEM5.12C perform routine
manual metal arc welding is a fabrication stream unit of competency designed to support your
ongoing skill development when undertaking more specialised metal and engineering units.
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MEM5.12C
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Perform routine MMAW
Select equipment and accessories.
Clean and prepare metal ready for welding.
Assemble metal to be welded in accordance with job requirements.
Adjust welding current for selected electrode size.
Determine sequence of operations.
Complete weld in accordance with job requirements.
Follow all safety requirements and use safe operating procedures.
Record weld parameters.
Unit mapping.
MEM5.12C Perform routine manual metal arc welding is a unit in the Metal & Engineering Industry
Training Package MEM05.
It is a unit of study in Certificate III in Engineering, and may also be selected as a unit of study in
other Engineering courses, packaged to include a group of fabrication & specialist units.
In conjunction with further units of study, this qualification provides students with the skills
necessary to perform routine manual metal arc welding in an engineering workshop or site.
A pathway of training in the use of manual metal arc welding might include the following
competency units;
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Recognition of prior learning (RPL)
TAFE NSW allows students to have their current units of study assessed against previous studies,
workplace skills performed or life experience.
MEM5.12C Perform routine manual metal arc welding covers the competencies required to select,
set up and operate manual metal arc welding equipment; make appropriate material allowances,
manual metal arc weld, checking for compliance to specifications. This unit applies to a range of
manual metal arc welding operations conducted on plate, sections or sheet materials.
If you believe you can already meet the assessment criteria for a particular competency
standard(s), or have completed similar training, you may be eligible for Recognition of Current
Competency (RCC) or Recognition of Prior Learning (RPL). Eligibility for RCC or RPL will
reduce the learning time or remove the need for you to complete this unit. Contact your teacher
to discuss this further.
Your teacher can provide you with details of TAFE NSW requirements and policy for the
recognition of previous learning.
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ABOUT THE STUDENT NOTES FOR MEM5.12C PERFORM ROUTINE MANUAL
METAL ARC WELDING
MEM5.12C resource book theory content
These theory notes have been compiled to provide you with the underpinning knowledge (theory)
associated with the routine manual metal arc welding procedures used in metal fabrication
industries.
This information is a broad guide to the manual metal arc welding equipment and techniques used
by metal fabricators, namely boilermakers and sheetmetal workers, when routine manual metal arc
welding plate, sheet & rolled sections; information includes;
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manual metal arc welding equipment used to weld metal parts
typical applications for equipment
setting up equipment prior to operation
safe working procedures when operating manual metal arc welding equipment
tooling and ancillary equipment
materials manual metal arc welded and techniques used
material economy and efficient work practices
MEM5.12C resource book practical content
Practical content in MEM5.12C Perform routine manual metal arc welding
will require you to set up and safely operate the equipment. If this MMAW unit is used in
conjunction with other fabrication units, practical worksheets may need to be completed. These
may include;
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safe working procedures (SWP)
work method statements (WMS)
material planning lists
job instruction sheets
planning sheets
in-process checklists
project record sheets
Appropriate copies of these sheets are included in your notes although your teacher may use his/her
own practical lesson sheets
If you are to use the practical worksheets provided in these notes, the following information is
important:
 These sheets must be completed with each project.
 They are evidence which your teacher needs to gather to prove your competence and
assessment in the tasks.
 Further information about these forms is provided with any included project instructions.
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If projects are included in this unit of competency, it is intended that wherever possible, you will
work as part of a team in designing and discussing certain aspects of each project, as indicated in
the instruction sheets. Also, wherever possible you will be completing other competency units at
the same time as this MMAW unit, such as measurement, pattern development, fabrication and
thermal cutting.
All planning and design work should be submitted to your teacher for discussion, correction and
assessment prior to proceeding with each project. Each individual is required to complete all
project practical work.
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MEM5.12C
Perform routine MMAW
Perform routine manual metal arc welding.
Theory notes.
Objectives;
At the end of the unit you will be able to;
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List the hazards of the manual metal arc welding process
 burns
 electricity
 fumes
 arc radiation
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state the safety precautions when using the MMAW process
 personal protective equipment
 protective clothing
 welding screens
 electrical safety
 ventilation
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describe the MMAW process
 electric arc heat source
 weld metal
 weld pool protection
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List the MMAW equipment
 welding power source
 welding cables
 electrode holder & return clamp
 storage & care
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identify electrodes used in the MMAW process
 core wire
 flux coating
 commonly used sizes (diameters)
 electrode information sources
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Name the properties of low carbon steel relative to welding
 mechanical properties
 physical properties
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The manual metal arc welding process
MMAW safety
Manual metal arc welding is a safe welding process provided it is used in the correct manner and
strict safety guidelines are followed.
As well as the operator, manual metal arc welding can injure others in the area where welding is
taking place.
Safety hazards from the process include;
Burns
Burns occur when welding, the causes include;
 touching hot metal
 spatter, sparks or hot slag coming in contact with exposed skin or eyes
 heat of the arc, arc radiation
Burns from welding can cause extreme discomfort and will often require first aid attention.
Electrocution
Electric shock by;
 welding in damp or wet conditions
 contact with a non-insulated welding circuit
 damaged welding plant or equipment
 body parts completing the welding circuit
Electric shock from arc welding can cause serious injury or death.
Weld fume
Fumes are given off from;
 the electrode flux coating melting in the arc
 oxides or the surface coating on metal parts being welded
Certain fumes can cause discomfort after a short period of exposure, whereas some other weld
fumes can cause serious respiratory problems over a longer period of time.
In general, weld fumes can cause serious respiratory problems for welding operators and others
nearby.
Ultra-violet and infra-red rays/arc radiation
The welding arc emits especially strong ultra-violet and infra-red rays.
Ultra-violet (UV) rays are especially dangerous and can cause painful injuries to exposed skin and
eyes.
Skin injuries are similar to sun burn. UV rays will cause eye injury to welding operators and others
nearby, this painful condition known as “welders flash” or “arc eye”.
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Safety precautions
To protect yourself and others from injury it is essential that the following safety precautions are
observed:
Use protective clothing and equipment
This includes;
 overalls or heavy drill cotton long trousers & long-sleeve shirt made from non-flammable
material
 safety footwear
 welders leather gloves/gauntlets
 approved safety glasses or other eye protection when removing hot slag from a completed
weld
 Australian standards approved welding face-shield/helmet with correct filter lens shade (eg.
Shade 10-13; see table below)
 wearing standards approved safety glasses when working near welding operators
Note; clothing worn by the welding operator should be in good repair. Frayed clothing is a fire
hazard.
Never leave butane cigarette lighters in your pockets whilst welding as this can result in
an explosion causing serious injury or death.
Lightweight clothing is not suitable for the intense rays emitted from manual metal arc welding.
New clothing should be washed to remove starching agents which have been known to be
flammable.
Selection of filter lens.
Shade of filter lens
10
11
12
13
14
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Recommended welding current
(amps)
Up to 150 amps
150-250 amps
250-300 amps
300-400 amps
Over 400 amps
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Erect welding screens
 In an open workshop or on-site, erect a welding screen made from a nonreflective material. This will protect others nearby from the effects of
the arc.
 It is also important to warn others working nearby that you are about to
strike the arc. Safety glasses should be worn at all times by both the
welding operator and others working nearby.
A portable welding screen
Electrical safety;
Before turning on the welding machine;
 check all welding cables are in good condition
 make sure all electrical connections are tight and in good repair
 wear dry insulated safety footwear and work on a dry insulated floor
where possible
 wear dry leather gloves and do not change electrodes with bare hands or
wet gloves
 never hold the electrode and holder under your arm
 never use welding equipment in a confined space or hazardous area
without supervision by a competent person
 never place any part of your body in or across the welding circuit
 know were to turn the electrical power off on welding equipment in an emergency situation.
If there is an electrical accident, turn off the power to the circuit first. When this isn’t possible, clear
the victim from the electrical source using dry non-conducting material.
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Adequate ventilation
Methods of ensuring that the air is safe to breathe are;
 Natural ventilation. In a workshop that has large doors and windows,
the natural movement of air will help to dilute and remove weld fumes.
 Forced fume extraction. If welding in a confined space or where there
is little air movement a forced fume extraction system must be used.
 Respirators. Wear a standards-approved welding respirator when
natural or forced ventilation is not good enough.
Other methods of limiting exposure to fumes include;
 Keep your head out of the fumes rising from the arc
 Avoid breathing fumes from metals such as stainless steel and nickel/nickel alloys, and
coated metal surfaces like galvanised steel.
 Ventilation and respirators should be used when welding these materials.
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The manual metal arc welding process
A welding machine provides the electrical energy to make an arc between the flux coated electrode
and the workpiece. There has to be a strong enough electric current (amps) to melt the surface of
the workpiece and the end of the electrode. The machine has a control which changes the amount
of current to suit different welding conditions & electrode sizes.
When the arc is formed, the temperature at the point of contact rises to about 6000°C..This intense
heat is concentrated at the electrode end and the point of welding. It melts a small pool of metal in
the workpiece and also melts the end of the electrode into globules of molten metal which are forced
across the arc and into the weld pool on the work. The electrode flux coating melts, providing a
gaseous shield around the arc and producing a protective slag on the completed weld. The melting
rate of the electrode metal depends on the amount of electric current used.
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Uses.
Manual metal arc welding is a versatile process and has many uses in industry. The process can be
used to weld pressure vessels, steel bridges, structural steel work, mining and earthmoving
equipment.
As well as heavy engineering industries, MMAW can also be used in general fabrication to
successfully weld a range of metal thicknesses from 2.4mm upwards.
Metals welded by the MMAW process.
The MMAW process can be used to join a range of metals including;
 low carbon steels
 low alloy steels
 stainless steels
 cast irons
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Equipment
Welding power source
The power source for MMAW should be a welding machine capable of sustaining the welding current
required for a particular electrode diameter, without overheating.
Welding machines are capable of producing alternating current (a.c.), direct current (d.c.), or both,
and may be powered by 415 or 240 volts.
Inverter welding machines are a newer type of power source. They are lighter, portable and
multifunctional. Although they are designed to produce d.c polarity, more specialised and expensive
types also provide a.c.
It is important that the welding machine is placed as close as possible to the mains power isolating
switch. This allows power to be turned off quickly in an emergency. Primary power cables carry
dangerously high voltages, therefore they should be kept short to avoid damage.
Electrode and work cables.
Electrode and work cables should be fully insulated, in good repair, and have good connections.
Select cables that are rated high enough to carry the current you require without overheating.
Damaged or worn cable connections will overheat and may result in damage to the welding
equipment.
Electrode holder and work clamp.
Electrode holders should be relatively light, comfortable to hold, fully insulated and in good repair.
They need to be sturdy enough to withstand the wear and tear of constant use.
Work clamps are fastened to the work or workbench to complete the welding circuit.
Electrode holders and work clamps have maximum current ratings.
Note
Hang the electrode holder on a hook insulated from the workbench.
Check welding cables for damage.
Switch off welding machine when not in use.
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Electrodes
Manual metal arc welding uses flux coated electrodes to produce welds. The electrode is measured
by the diameter of the core wire, common sizes available are 2.5 mm; 3.15 mm; and 4 mm. Each
electrode size has the operating current range, recommended polarity, and flux type printed on the
electrode packet.
Electrodes should be stored in their original packaging in a weather proof area, clear of the floor.
They should be stored away from moisture, high humidity & possible damage.
Note;
There are different consumables and welding procedures for a range of metal types & properties.
The completed weld tensile strength should match, if not exceed that of the job being welded.
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Metal properties
Low carbon steel is the most commonly arc welded material in the metal fabrication industry.
It is a magnetic metal with a melting point of about 1450°C, has good ductility which is necessary
for fabrication & good weldability.
Other
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properties important to fabrication & welding may include;
tensile strength
yield strength
impact strength
toughness
thermal expansion
MMAW electrode parts
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Revision questions.
These questions will help you revise what you’ve learned in the theory notes of this unit.
1.
Arc radiation is a safety hazard associated with manual metal arc welding. List three (3)
other safety hazards associated with this welding process.
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2.
Name four (4) items of protective equipment/clothing a welding operator
should wear when using the manual metal arc welding process.
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3.
Complete the following table.
Shade of filter lens
Recommended welding current range
(amps
10
150-250 amps
4.
Name the two (2) harmful rays generated by the manual metal arc
welding process.
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5.
In the space provided, briefly describe one way in which to reduce the risk
of electric shock when arc welding.
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___________________________________________________________
___________________________________________________________
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6.
In the sketch below, label the seven (7) parts of the manual metal arc welding equipment.
7.
List three (3) industrial uses for the manual metal arc welding process.
8.
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In the sketch below, label the parts of the manual metal arc welding
electrode.
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Practical exercises and projects
For the teacher (omit these teacher instructions from student’s printed
notes)
Teachers are encouraged to substitute other learning materials, practical exercises, activities and
projects which they consider to be more appropriate for their students under instruction.
Practical exercises and projects may be customised to suit trade requirements.
If however the teacher relies solely on the practical exercises and projects in these resource notes,
as a minimum the student will need to complete manual metal arc welding-based exercises and
projects† such as:
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Flat stringer bead welds on plate or flat bar
Flat pad welds on plate or flat bar
Flat & horizontal/vertical fillet welds, single & multiple runs on plate, flat bar & rolled section
Multiple run flat corner welds on flat bar or plate
†Simple exercises could include metal parts used for future fabrication & welding projects.
Notes to teachers;
These practical exercises, projects† and assessments are a SUGGESTED sequence for
development of the knowledge and skills relating to this unit of competency. However,
individual teachers may prefer to develop and use practical exercises, projects and
assessments of their own.
Other competencies
This learning resource is based on the concept of completing fabrication and welding projects which
will allow for training delivery and assessment of a number of competencies (or elements within
competencies) at the same time.
For instance, it is considered that this unit of competence would be delivered concurrently with the
mandatory unit MEM12.23A Perform engineering measurements, or the marking off unit
MEM12.7C Mark off structural fabrications and shapes. Hence suggested exercises and
projects would require a student to be provided with instruction on measurement in order to
complete each task.
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Similarly, to complete projects in conjunction with MEM5.12C Perform routine manual metal arc
welding, the following units could be used:
Pattern development could be carried out in:
 MEM5.37B Perform geometric development
Other forms of cutting could be carried out in:
 MEM5.5B Carry out mechanical cutting
 MEM5.7C Perform manual heating and thermal cutting
Fabrication, forming and shaping could be carried out in;
 MEM5.10B Perform fabrication, forming and shaping
Assembly processes could be carried out in:
 MEM5.11C Assemble fabricated components
Recording results.
Progress record sheet
The progress record sheet in this resource book is provided to assist you to keep track of where
learners are in relation to each unit of competency. You may choose to copy and store the
progress record sheet separately, or with a group of other progress records to assist you in
monitoring the student’s progress through units of competency.
Work method statements (WMS)
Each practical exercise and project is detailed on a WORK METHOD STATEMENT sheet, and the
teacher should explain to students how they are to complete this worksheet.
Successful completion will be recorded by the teacher and used as a source of evidence regarding
the student’s competency.
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Practical exercises and projects
For the student
Instruction & demonstration.
Your teacher will provide you with instruction & demonstration for each practice task, project &
assessment exercise.
After a period of initial practice, exercises and projects may be customised by your teacher to suit
your trade requirements, so you may even undertake completely different projects more closely
aligned to tasks performed in your workplace.
If you are to undertake projects only contained in this resource, as a minimum you will be expected
to successfully complete manual metal arc welding-based exercises and projects† such as:
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Flat stringer bead welds on plate or flat bar
Flat pad welds on plate or flat bar
Flat & horizontal/vertical fillet welds, single & multiple runs on plate, flat bar & rolled section
Multiple run flat corner welds on flat bar or plate
†Simple exercises could include metal parts used for future fabrication & welding projects.
Practical assessment
Assessment against competency standards relies on your teacher gathering enough evidence to
demonstrate that you can meet the requirements of each unit.
As well as assessment of your underpinning knowledge (the theory notes in this unit) your
assessment will be based on successful completion of practical exercises, activities and projects.
Recording results.
Progress record sheet
The progress record sheet in this resource book is provided to assist you to keep track of your
progress through this unit of competency. You should make sure your teacher initials each
performance criteria you complete successfully, and keep this sheet as a record of the work you
have completed.
Work method statements (WMS)
Each practical exercise and project is detailed on a WORK METHOD STATEMENT sheet, & your
teacher will explain how you should complete this worksheet.
Successful completion will be recorded by your teacher. However, make sure your teacher signs
your worksheet as this will be your record of successful completion of the practical exercise and
project
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Practical exercises.
Practical Exercise
1
Bead welds
Practice exercise
2
Pad welds
Practice exercise
Assessment exercise
Fillet welds – flat – single run
Practice exercise
3
4
Fillet welds – horizontal/vertical – single run
Practice exercise
5
Fillet welds – horizontal/vertical – 3 run 2 layer
Practice exercise
6
Fillet welds – Plate to section horizontal/vertical –
3 run 2 layer
Practice exercise
Assessment exercise
Corner fillet welds – flat – multiple run
Practice exercise
7
8
Teacher signature
on successful
completion
Butt welds – flat – multiple run
Practice exercise
Assessment exercise
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