Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
ContentsTraining Record Introduction Topics Prerequisites
Instructions Competency 3 7 7 7 7 7 9 9 9 10 10
assessment
Section 1 - Introduction to Manual Metal Arc Wdding Aim Acti
vity MMAWelding video response Arc welding
Section 2 - Operating Principles for Manual Arc Welding 13 Aim
13 Activity 13 Electricity 14 Hazards 14 Protective clothing 17
Maintenance of welding equipment.. 2021 Welding machines 23 Power
source 26 Rating of power sources 29 Current range 29 Electrodes 30
Basic symbols 33 Welding symbols 33 \Velding procedures 35 Joint
preparation 37 Review questions - Operating principles for manual
arc welding38 Review questions - Weld symbols 42 Review questions -
Electrode identification - Current settings .. 44 Section 3 -
Manual Metal Arc Welding - Basic Welds Aim Acti vity Manual metal
arc welding - basic welds Material preparation HOViT strike an arc
to Laying down a weld bead Weld cleaning Review questions -
Material preparation and weld cleaning 45 45 45 .46 46 47 48 49
50
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Practical exercise 1 - Beads on plate - flat Procedure sheet 1 -
Beads on plate - flat Practical exercise 2 - Pad welds - flat..
Procedure sheet 2 - Pad weld - flat Section 4 - Fillet Weld Joint
Terms and Faults Aim Activity Fillet weld joint terminology and
faults Fillet weld terminology Weld Defects Workshop tests Review
questions - Fillet weld joint terminology and faults Practical
exercise 3 - Fillet weld, single run - horizontaL Procedure sheet 3
- Fillet weld, single run - horizontal Practical exercise 4 -
Fillet weld, 3 run 2 layer - horizontal.. Procedure sheet 4 -
Fillet weld, 3 run 2 layer - horizontal. Practical exercise 5 -
Outside corner fillet - horizontal Prooedure sheet 5 - Outside
corner fillet - horizontaL Practical exercise 6 - Fillet weld -
horizontal Prooedure sheet 6 - Fillet weld - horizontal Seotion 5 -
Butt Weld Terminology and Faults Aim Activity Butt weld terminology
and faults Weld preparation Preparation types Weld defects The
principle of expansion and contraction in a metal Angular
distortion Review questions - Butt weld terminology and faults
Practical exercise 7 - Butt weld, flat sheet steel Procedure sheet
7 - Butt weld, flat sheet steel
52 54 55 57 59 59 59 60 60 62 67 69 78 80 81 83 84 86 87 89 90
90 90 91 91 93 96 101 101 102 108 110
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Metals and Engineering S.12AB Perform
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Routine Manual Metal Arc Welding
IntroductionThis training guide is designed to support training
for the Metal and Engineering Training Package.
Topics Operating principles for manual arc welding Manual metal
arc welding - basic welds Fillet weld joint terms and faults Butt
weld terminology and faults
PrerequisitesNil
Instructions1. Study the information for each topic and complete
review questions Complete the practical exercises.
2.note
The pr~ctical exercises are suggested only and may be replaced
by any other suitable training activity. 3. The Training Record
must be signed by your trainer on completion of each activity.
Complete the theory test. (The test results may be recorded as part
evidence of competency.)
4.
Competency assessmentTo achieve competency other approved
activities must be entered in the Assessment and Evidence Record
section.
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Metals and Engineering S.12AB Perform
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Routine Manual Metal Arc Weldiug
Section 1 - Introduction to Manual Metal Arc WeldingAimTo
understand the operating principles, equipment, consumables and
safety requirements for general purpose welding using the manual
metal arc welding process.
Activity1. 2. View video No. 47 Arc Welding. Complete the video
response questions immediately after watching the video. during
or
3.
Ask your supervisor or teacher if the information is not clear
to you. Ask your trainer to check and sign your Training Record. On
completion of this section you must attempt the test on this topic
and reach the required level of competence before proceeding to the
next section.
4. S.
Safety Wear safety glasses at all times while in welding
workshops. Follow safe working practices to avoid electric shock.
Weld in well ventilated areas. Wear protective clothing.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Section 2 - Operating Principles for Manual Arc WeldingAimTo
practice manual metal arc welding exercises in order for you to
develop the manipulative skills for striking an arc and depositing
weld metal on low carbon steel plate.
Activity1. 2. 3. Read and study the resource material following.
Complete the review questions. Ask for assistance if the
information or instructions are not clear to you. 4. Ask a teacher
or your supervisor to check and sign your Training Record.
Safety Follow OHS workshop procedures. Protect your eyes from
the welding arc and wear the proper eye protection. Wear suitable
protective clothing including dry leather gloves.
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Metals and Engineering Industry S.12AB Perform Routine Manual
Metal Arc Welding
The welding process uses electricity and generates heat and
fumes. Safety precautions including wearing protective clothing are
important. Maintenance of equipment and supplies and a thorough
understanding of safety aspects of welding will minimise the risk
of accident and injury.
ElectricityElectricity is the flow of electrons through a
conductor at a certain pressure and speed. It's like water running
through a hose. Some of the terms associated with electricity are
explained here. Conductor In welding an electrical conductor is a
metal through which electricity will easily flow. Copper is the
most used conductor. Voltage This is the unit of electrical
pressure. The voltage at the terminals of an AC welding machine is
never more than 80 volts for safety reasons. This electrical
pressure (or force) is responsible for the current flow in a
welding circuit. Amperage This is the measurement of the electron
flow,or current, through an electrical conductor. Amperage is
measured in amps. An amp is a unit quantity of electricity passing
through a given point per second. This is similar to the rate water
flows through a pipeline. Electric arc welding process This is also
called manual metal arc welding or MMA In MMA a high output
amperage (low voltage) is passed W. W through a consumable flux
coated electrode and the work piece. This sets up an electrical
resistance between the tip of the electrode and the work which
causes the electrode to melt off and form a weld bead.
HazardsWorking with electrical equipment can be hazardous.
Youmust take proper precautions and follow the set safety
procedures. Hazards in the welding workshop include electric shock,
fumes, heat, glare and harmful rays.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Electric shocks - low voltage Electric shocks are possible on
the secondary welding circuit. They may be caused by: working on
wet floors - a shock may be felt when putting an electrode in the
holder. Always stand on insulated mats or wooden boards to reduce
the risk and wear dry leather gloves working in a very humid
climate or rainy weather - a shock may be felt when changing
electrodes. gloves dry. Electrical shocks high voltage High voltage
shocks shouldn't happen if precautions are taken such as Keep
electrodes and (low voltage) side of the
ensuring welding machines are maintained by licensed electrical
tradesmen and that you never interfere with the inside parts of the
welding machines. Symptoms of electrical shock Often electric shock
stuns but doesn't kill. However when electricity passes through the
body it causes muscles to contract from beating or cause breathing
to stop. Electricity can also cause serious burns. Fumes Fumes can
result from: the production combustion of oxides and nitrous gases
from incomplete and can stop the heart
or oxidation of nitrogen from the atmosphere cadmium
the surface coatings on steel such as galvanising,
parts/degreasing elements solvents
or chrome plating and paints and solvents such as red oxide
within the parent metal
electrode flux coatings.
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Metals and Engineering S.12AB Perform Routine
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Manual Metal Arc Welding
Safety
Welding should be carried out in well ventilated areas. When
welding high fuming materials such asga1vanised steel, use
extraction systems to carry away the fumes. If an extraction system
is not available, an approved respirator should be used to filter
out the fumes. Respirators should only be used as a secondary
protection.Dangerous fumes
Gases, dusts and vapours are given off during welding. They can
cause: gassing or asphyxiation because the oxygen has been used up
in the work area (common in confined spaces) build up of poisonous
metals in the body, such as lead, cadmium, zinc, beryllium or
mercury respiratory disorders. Heat Heat is a form of energy. When
a substance is heated the molecules vibrate or move more rapidly.
Heat may be generated by various means. In manual metal arc welding
it is generated by the passage of an electric current across an
arc;: ap. g The electric arc (about 6000C) generates the heat to
melt and fuse the metal surfaces. Heat is transferred in two ways,
by conduction and by radiation. Conduction Solid bodies must be in
physical contact for heat to travel through them. Some materials
conduct heat more rapidly than others. Metals are generally good
conductors but, because of their different properties, some have a
greater conductivity rate than others, for example copper and
aluminium are very good conductors while cast iron and stainless
steel are poorer conductors. ailments from wheeziness to serious
lung
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Radiation This is the transfer of heat through space by wave
motion. No
physical contact is needed. All bodies at a higher temperature
than their surroundings radiate heat, for example, the sun radiates
heat energy in the form of cosmic rays and an electric radiator
transfers heat through space across a room.
Protective clothingProtective clothing will help to protect you
from heat, hot metal and harmful rays.Helmet
Gauntlets
Leather apron
Gaiters,
'''-.
Spats ~--..~
Full protective clothingProtection against hot metal
Molten droplets have a way of getting into boots. You can avoid
this by wearing proper protective clothing and footwear. When
welding out of position wear spats over your boots and under
overall legs.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Protection from harmful rays
The harmful rays given off from an electrical welding process
are ultraviolet rays and infra-red rays. These rays can damage the
skin. Ray burn is like very severe sunburn; your skin reddens and
then peels. If the ray burn is very severe, there may be blisters
and sores. Rays will also harm the eyes causing a condition called
a flash or arc eye. The first symptom of a flash is an itchy
feeling in the eye. Afterwards a throbbing pain (much like sand in
the eye) may stop you sleeping. There are eye drops that relieve
the pain. Continuos flashes may cause blindness. The use of Safety
Glasses will help protect your eyes from these rays. Filter lenses
These are specially designed glass lenses to filter out harmful
rays and allow you to see what you're welding without causing any
changes in the pupil size or damage to your eyes. Filters come in
different shade numbers, according to the current range or type of
welding.Recommended minimum protective filters
Process MMAW
Approximate Welding (AMPS) Up to 100 100 - 200 200 - 300 300 -
400 Over 400
Filter Recommended
81011
12 13
Safety Wear safety glasses at all times. Wear appropriate
clothing to protect your eyes and skin, from welding rays.
Prevention, is the best policy, avoid exposing eyes to harmful
rays.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Are Welding
Wear a welding shield or helmet, fitted with the correct filter
to protect you from arc rays, heat and the spatter from molten
metal. The filter reduces the intensity of the radiation, but
allows sufficient light through for you to see the weld pool and
the end of the electrode.
Swivel filter
Clear glass
Head shield
hand held shield
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Metals and Engineering lndustry 5.12AB Perform Routine Manual
Metal Arc Welding
Maintenance of welding equipmentBefore carrying out any
maintenance on electrical equipment, it's important that you first
switch off the power and remove the plug. If there isn't a plug,
lock off the machine or danger tag the isolator
switch.Transformer
Never do maintenance work inside the case of the welding
machine. Operators can care for the machine by: keeping the case
clean and dust free maintaining the secondary circuit in good
condition sending the machine to a licensed electrician for any
maintenance on the internal parts, the primary lead and
plug.Machine terminals
Keep terminals clean and tight to ensure that the current will
flow freely. If you don't check nut tightness now and then, you may
get arcing and/or overheating of the terminal and lug connections.
This will also be detrimental to weld quality and machine
performance. This can lead to fire or cause burns.Joints
Loose joints or bad contacts cause cable, clamps and other parts
of the welding plant to overheat and may give you unstable arcing.
Use properly designed cable connectors when you make any joints in
cables. Make sure that good electrical contact is made when you
connect cables to the power source, electrode holder and the return
work clampSecondary leads (electrode/return lead)
Damaged leads may cause the operator discomfort from
overheating, and poor arcing characteristics. Maintain leads by:
rolling them up after use unroll prior to using
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Metals and Engineering 5.12AB Pedorm
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Routine Manual Metal Arc Welding
making electrode
sure that the ends are fixed correctly holder, work-clamp or
terminal lugs
into the
covering lug connections with insulation tape when necessary.
The size of the cable must suit the output of the welding power
source at the maximum duty cycle (refer to Australian Standard AS
1995 on welding cables for the cable size).Electrode holders
Electrode
holders should suit the minimum
output current
being used.
The holder should be relatively light, comfortable holder should
be rated to withstand the activity.Retumclamp
to hold, fully insulated current required for
and sturdy enough to withstand the wear and tear from constant
use. The the maximum
This is fastened to the work or to the workbench type clamps are
also available.Twist handle to grip electrode
to complete the welding
circuit. Spring pressure and screw type clamps are normally
used. Magnetic
Insert electrode
Heavy duty type
Spring-loaded jaws to grip electrode
Electrode holders
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Metals and Engineering Industry5.12AB Perform Routine Manual
Metal Arc Welding
Screw Clamp
Work cable attachments
~/-...,Cable attachments
.
-: /0'1
/-
a
/.
SafetyProtect yourself by wearing the following safety clothing:
overalls or work clothes leather apron and/or coat welding
gloves.
Machine locationWelding machines should always be in a dry
protected area as close to the
power outlet as possible.
Protection of othersWelding should be done in special welding
bays. When this is not possible, use portable screens to shield
others working in the area from the rays generated from the arc.
You should also put up signs to warn people that you are
welding.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Welding machinesWeldingmachines operate with either alternating
current or direct current.Alternating current (AC) welding
machines
Alternating current welding machines are transformers which step
down line voltage (240 or 415 volts) to provide a safe welding
voltage. The welding current supplied by the secondary circuit of
the transformer is set by the operator to suit the type and size of
electrode and its use. Transformer welding machines are less
complex and slightly less expensive than other types.Direct current
(DC) welding machines
The direct current output may be supplied by a
transformer/rectifier or generator power
source.Transformer/rectifiers
An efficient and reliable transformer/rectifier is a machine
designed to transform AC input current to DC output current
suitable for welding. Transformer/rectifiers have no moving parts
and like the transformer are quiet to operate, convenient and cost
less than motor generated units. If an AC current is needed from
this type of machine, all the operator has to do is to select the
AC output switch. Transformer/rectifiers are often designed to
provide either DC or AC outputs. DC is normally preferred because
of its greater arc stability but AC may be required at higher
currents to avoid arc blow.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Arc welding power source - AC transforrner
Arc welding power source - mobile engine driven DC generator
24
Metals and Engineering lndustl)' 5.12AB Perlorm Routine Manual
Metal Arc Welding
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Metals and Engineering 5.12AB Perform Routine
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Manual Metal Arc Welding
Power sourceA welding source provides enough current (heat
energy) to melt the electrode and the parent metal. Manual metal
arc welding machines have a variable (adjustable) current output
that can be set to suit the job and type of electrode.Power source
terminals and polarity
Electrical connections for a welding machine are illustrated
below. Output terminals on AC machines are marked electrode and
work. On a DC machine the terminals are marked positive (+) and
negative (-) except in the case where the polarity can be changed
by means of a polarity reversing switch. In such cases the
terminals are marked electrode and work with electrode terminal
polarity indicated at the polarity switch. Most electrodes designed
for DC operate on DC electrode terminal positive (+) while some
types of electrodes should be operated on DC electrode negative
(-). Refer to the manufacturer's instructions for polarity
selection.
Main voltage 415 or 240 volts
45-80V Weld M/C
Open circuit 'Voltage (no currentjlowing)
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Mctals and Enginccring Industry S.12AB Perform Routine Manual
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Main voltage 415 or 240 volts
Arc voltage (currentjlowing) Welding cables
A multiple-strand, insulated flexible copper or aluminium lead
conducts the welding current from the power source to the work. A
return cable is needed to complete the welding circuit between the
work and the power source.
Power source
Electrode holder
Cable connections (secondary circuit side)
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Open circuit voltage - arc voltage Power sources may supply
direct current (DC) or alternating current (AC) to the electrode.
AC transformers and DC generators supply only one type of current,
but many transformer/rectifiers can be switched between AC and DC
output. AC power supply is used more often because the cost is
lower and the welding machines are simpler in design. However, DC
current has some advantages. The DC arc is much more stable with
certain types of electrode. DC is better for working with sheet
metal because a stable arc is produced. Engine driven DC models
provide welding power where there are no electrical supply lines
available, for example on site work. The current should remain
nearly constant during welding where the operator's movements tend
to vary the arc length. These movements may be accidental, or
deliberate, to control the weld pool. An increase in arc length win
increase the voltage across the arc, however the machine is
designed to control the current close to the amperage set by the
operator. Melting of the electro 0 Amps
60
200 100 250 150 SO
20:l!!
60 40 0
Output curvefor constant current power source, adjustedfor
minimum current 'Variation
Rating of power sourcesAustralian Standard AS1966 rates the
output (duty cycle) of electric arc welding power sources. The
machines are classified according to the type of service for which
they are designed, for example: continuous duty, heavy duty, light
industrial or limited output cycles. The standard defines each of
the classes according to the output (load current, load voltage)
needed for a nominated duty cycle. The duty cycle allows for the
Jact that in any five minute period, current for welding may be
drawn for only part of that time. For example, if welding is for a
maximum of three minutes in any five minute period, the machine
only operates up to 60% duty cycle (3/5 of 5 minutes). A much lower
current must be selected for continuous (100%) operation. All power
sources must display a name plate stating the equipment class and
the rated output and duty cycle for its class (eg 300 amps, 32
volts, 60%duty cycle). The 100% duty cycle output current must also
be noted.
Current rangeThe manufacturer's recommendations on the range of
current for different types and sizes of electrodes will only give
you their lower and upper current range.
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Metals and Engineering 5.12AB Perform
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Typical current ranges for the electrode
classifications
4.0
130-160 75-125
130-190 90-140
140-200 95-150
130-170 100-130
140-200 105-150
185-235 130-170
3.25
You should use the recommended amperage and electrode type and
size as stated in the procedure sheets for the practical exercises.
This will help you gain the experience to select the electrode type
and size for future welding exercises.
4113~
The choice of current will depend on such factors as weld
position, thickness of the joint parts, root gap and access to the
structure.Packet of electrodes
ElectrodesElectrodes are available in different types.EXX12
Electrodes These have rutile coatings with other constituents
added to form a gaseous shield and slag modification. These
electrodes are easy to use in any positions (including vertical
do\'\rn).They operate with a quiet, medium penetrating arc able to
bridge gaps or misaligned sections. These electrodes are general
purpose electrodes used for structural and sheet steel
fabrication.EXX13 Electrodes These also have a rutile coating,
similar to the EXX12
type, but they produce a more fluid and easily removed slag (not
suitable for vertical down) with a very neat and flat profile. They
are generally
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Metals and Engineering 5. 12AB Pertonn
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Routine Manual Metal Arc Welding
more suited to overhead and vertical welding in an upwards
direction than EXX12. They have good X-ray and impact qualities.
(these qualities vary dependant on the impact grading number)The
effect of moisture on electrodes
Any electrode that absorbs excessive moisture into the coating
may cause one or more of the following problems: porosity excessive
spatter arc instability poor weld contour undercut difficulty in
slag removal cracking through hydrogen embrittlement.Storage
All types of electrode should be stored in their original
packaging in a weather proof area on racks clear of the floor. They
should be stored away from moistvre and high humidity and possible
damage. Storage in an unheated room is satisfactory for a period of
less than six months. If storing for more than six months, or if in
tropical or very wet climates, all electrodes except cellulose
types (EXXIO,EXXll) should be stored in a room or insulated
building heated to 15C to 20C room (or ambient) temperature, but at
no time more than 40C. Electrodes stored in hermetically sealed
(airtight) boxes need not be kept in such an environment.
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Metals and Engineering 5.12AB Perform Routine
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Manual Metal Arc Welding
Never tear electrode information data from the boxes. This can
lead to confusion and/or improper use of electrodes.Storing
electrodes
Welders are responsible for the care and handling of electrodes
on the shop floor or work site. Electrodes should be kept clean and
dry. Defective electrodes should not be used. Discard electrodes or
which are wet or seek manufacturer's advice. Don't use electrodes
showing signs of rust or of damaged coating. Only remove from the
packet the number of electrodes you need for the next few hours or
the immediate job in hand. This reduces the risk of contamination
and waste.
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Metals and Engineering 5.12AB Perform Routine
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Unseal packets of electrodes just before you use them and not
before.
Basic symbolsBasic symbols which are used to denote the type of
weld are illustrated in
FieldSurface weld roundor Weld Convex Backing strip site Flush
all shape
~
C\.symbols used
the table below. Also shown are a number of instructional to
impose certain requirements
on the actual welding operation.
Welding symbols
Number of stud, plug,slot, spot or projection welds Arrow
connecting reference line to joint
Basic weld symbol area
Spacing between intermittent welds
I L1J WUJ
S rS4eld
r--t~'-lf
I _ ~_ I I t I U'} Ot/) I
0 :I:o
r
/::!Fi'eld or site of weld all round
I b Ow I I m ~0:::0 I 0:::_ I I :r: ~lflJ I L __
F(N)
Tail of reference line (omitted when reference P is not
used)
The standard welding symbol used to represent welds on drawings
is shown below. The symbol can be used in many ways.
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Metals and Engineering 5.12AB Perform
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note Information relating to a particular weld, such as S, (N),
F, W, (M) must be placed on the same side of the reference line as
the symbol for that weld.
Symbol below reference line Symbol above reference line
Application of the standard welding symbol When applying the
standard welding symbol, thought must be given as to whether the
actual weld is situated on the same side of the joint as the arrow
or on the other side. Arrow 1 W is called the arrow side of joint X
is called the other side of joint Arrow 2 Z is called the arrow
side of joint 2 Y is called the other side of joint 2 Arrow
joints.
1 1
1 bears
no relation to arrow 2 as they refer to different
For weld A, the basic fillet symbol is placed underneath the
reference line indicating that the weld is on the arrow side of
joint 1. For weld B, however, the basic fillet symbol is placed
above the reference line indicating that the weld is on the other
side of joint 2. 34
Metals and Engineering Industry 5.12AB Perform Routine Manual
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Wherever possible, the arrow should be positioned adjacent to
the weld, as with joint 1, with the symbol underneath the reference
line.
Welding proceduresIt is sometimes necessary to specify certain
procedures or requirements about a weld. The standard symbol used
in such cases should be provided with a tail as shown on the
previous page and the information inserted where shown, for
example, at P. In order to control a welding process more fully, a
procedure sheet may be added to the drawing. The sheet should
contain the following general information. type of material being
welded; form of weld (to include plate preparation such as angle of
bevel, root penetration, root radius, etc.); set-up details such as
welding position, alignment, gap required; number and order of
runs; electrode size, type and make (consultAS1552, Classification
of Covered Electrodes); electrical supply data such as polarity,
current and voltage values; preheating requirements; pre- and
post-weld cleaning procedures; treatment of joint after welding;
preparation and/or procedures to apply in between runs. The arrow
is cranked as shown below and points towards the plate which has to
be prepared. The crank is omitted when the edge to be prepared is
abvious, for example, a tee but joint.
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Metals and Engineering 5.12AB Perform
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Routine Manual Metal Arc Welding
IOrll~""\.::'::::?
~
Symbol below the horizontal reference line. This indicates that
the weld is to be placed on the same side as the arrow.
Symbol above the horizontal reference line. This indicates that
the weld is to be placed on the opposite side to the arrow.
~;v;a the c joint the arrow the Weld Cross Explanationothera
side I 1"- bIbflush Section c side Symbol Ibead arrow on I I I
Drawing weld side Drawing Application the other I thethe jointside
ground of arrow side with a c) Single V butt weld sides of Filet
weld on both on c) Single bevel button a) Seal bead weld at the a)
Single V butt weld on
Symbol below and above the horizontal reference line. This
indicates that the weld is to be placed on both sides of the
arrow.
ed
I'...'f~~
Jkt1 I~~ ,bk;~~
Cs VI ~\}m LE 11a
a) Filet weld at the arrow side b
b) Filet weld on the other side b) Single V butt weld on b) Bead
weld at the arrow side
the other side
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Joint preparationThe arrow may also be used to indicate when one
plate only of a joint is to be prepared in welding single bevel and
single J butt joints. The arrow is cranked as shown below and
points towards the plate which has to be prepared. The crank is
omitted when the edge to be prepared is obvious, for example, a tee
but joint.
Cranked arrow
Plate to be bevelled
Actual weld
End view
Front view
~~:~~ooeclfue~o
~m~~~~u~d
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Metals and Engineering 5.12AB Perform Routine
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Manual Metal Arc WeWing
Section 3 Manual Metal Arc Welding Basic WeldsAimTopractice
manual metal arc welding exercises in order for you to develop the
manipulative skills for striking an arc and depositing weld metal
on low carbon steel plate.
Activity1. 2. 3. Read and study the resource material following.
Complete the practical exercises. Ask for assistance if the
information or instructions are not clear to you. 4. Ask a teacher
or your supervisor to check and sign your Training Record. These
are skill practice exercises which are assessed. You must reach the
required standards to enable progression to the section .
5.
Safety Follow OHS workshop procedures. Protect your eyes from
the welding arc and wear the proper eye protection. Wear suitable
protective clothing including dry leather gloves.
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Metals and Engineering Industry S.12AB Perform Routine Manual
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Manual metal arc welding - basic weldsThe following instructions
will provide you with basic information about material preparation,
striking an arc and laying down a weld bead. The cleaning
requirements for a finished weld will also be identified along with
the equipment used for this task. Read them carefully before
attempting the four practical exercises in this section.
Material preparationCleaning
A welded joint on low carbon steel (mild steel) requires the
material to be cleaned in such a way as to remove all matter that
may contaminate the weld runs (beadlbeads). This can be in the form
of Mechanical or Chemical cleaning. If chemical cleaning is to be
carried out it is critical that all safety factors are adhered to
as chemicals may produce dangerous substances when heated by the
arc. Consult the Material Safety Data Sheet (MSDS) or the
manufacturer/distributor if you are not sure about using any
cleaning agents.Mechanical cleaning
The weld area may be machined. This preparation will generally
require minimal cleaning. If the material is flame cut or hot
rolled it will have an oxide skin that will need to be removed.
This will usually require grinding as wire brushing may not be
aggressive enough to bring the material back to bare metal.
Aggregate blasting such as sand or other particles may be also used
to clean the weld area.Tools used for cleaning
The hand held power tools that are used for material removal may
include: Angle grinder Straight portable grinder Die grinder Belt
sander Grinding or sanding Grinding or wire brushing
46
Aleta!s and Engineering 5.12AB Perform
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These tools can be either pneumatic (air driven) or electric. A
floor mounted pedestal grinder may also be used for material
removal. The practical exercise in this module will require you to
use an electric angle grinder.
How to strike an arcPreparation
1.
Select a piece of steel and after material preparation place it
on the work bench. Select a 4.0 mm E4112 or E4113 Manual Metal Arc
electrode. Set amperage on power source to approximately amps.
165
2.
3.
4.
It is important that you get yourself into a comfortable and
relaxed position when welding to counter the effects of body sway,
movement restrictions and heat generated by the arc. To get
comfortable you can be seated, lean against the bcnch or lean
against a wall in the welding bay.
Striking the arc
1. 2.
Turn on the power source. Lightly touch the end of the electrode
on to the work and you will complete the circuit and current will
flow. The electrode end rapidly heats, melting sufficiently to
momentarily weld the electrode on to the work. Due to the low
voltage current we are using the arc will not jump an air gap (as
in a spark plug). We must therefore establish an arc by first
touching the end electrode onto the work and then immediately,
lengthen the distance between end of the electrode and work
allowing droplets of metal and flux to cross the ARC GAP(3 mm
approx.) to form a molten pool.
3.
4.
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Metals and Engineering Industry S.12AB Perform Routine Manual
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5.
If you fail to do this, droplets will bridge the arc gap,
causing a short circuit and a freezing of the electrode end onto
the work. If your action is incorrect and the electrode freezes
onto the work, that is becomes welded or stuck to it, a sharp
backward angling of the electrode should break it free. Keep your
head shield over your face, as an arc flash will occur as the
electrode breaks contact.
6.
7.
Laying down a weld bead1. Once the arc has been established,
reduce the arc length to about 3 mm and note that molten metal is
beginning to mount up under the end of the electrode. Start moving
the tip of the rod slowly away to the right, (if you are left-
handed, to the left) endeavouring to maintain a molten pool
approximately 8mm wide behind the arc. You will have to feed in the
electrode as it burns off, maintaining a steady rate across the
plate using the correct arc length. Continue to deposit a
beadlbeads across the plate. Remove the slag cover and wire brush
and inspect your weld. A little more practice and some of these
actions will begin to happen automatically. Remember, not all
people are born natural welders. Welding requires practice to gain
the necessary skills to lay down consistent welds. You only obtain
these skills by running lots of electrodes and concentrating on
what you are doing.
2.
3.
4. 5.
6.
7. 8.
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Metals and Engineering S.12AB Perform
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Weld cleaningIt is important specifications that the finished
weld is of an acceptable spatter. The finished appearance
additional work. and may require standard free of slag and adhering
may be given in job This may need to be
ca.rried out before the final finish is added to the completed
job/component. Cleaning may just require you to use a chipping
hammer and a wire brush. It could also require you to use the
following tools. Angle grinder Straight portable grinder Die
grinder Belt sander Chisel (hand, electric, air) File Peening gun
(electric, air) used to remove slag. By the removal of slag and
spatter many welds on fabrication work are left as cleaned.
Additional treatment such as machining, sand blasting, grinding and
sanding are after treatments in the manufacturing process. that may
be carried out by other personnel The practical exercises in this
module will Grinding or sanding Grinding or wire brushing
require you to use a chipping hammer, chisel and wire brush.
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Metals and Engineering IndustryS.12AB Perform Routine Manual
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Practical exercise 1 - Beads on plate -
flatAim To develop the skills to deposit uniform weld beads to
the standards below.Material
1 piece low carbon steel 75 x 10 x 225 mmConsumables
Mild steel electrodes 4.0 mm E4112 or E4113 at approx. 165
amps.Instructions
Check the following points: Amperage setting and heat input,
position of the plate on the bench, correct method of arc striking,
correct arc length, correct welding speed arid travel, electrode
angles. Your teacher will demonstrate if required. 1. Obtain your
MMA welding board, safety equipment (head shield, gloves),
material, and consumables (if necessary) from the store. Position
the plate on the bench so that a right handed operator would weld
across the body from left to right (left hand opposite direction).
Deposit a weld bead along the plate length, maintaining the angles
as shown, and an arc gap of approximately 2-3 mm. Deposit
additional runs parallel to the plate edge approximately 10mm
apart. When the top surface of the plate has been covered, turn the
material over and repeat the exercise.
2.
3.
4.
5.
Metals and Engineering Industry 5.12AB Perform Routine Manual
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6.
Evaluate the weld exercise and complete the procedure sheet.
Submit your completed weld and procedure sheet for assessment.
7.
Economy
Materials and consumables are expensive. Use electrodes to 50 mm
maximum stub length. Standards Your work should have: uniform beads
with consistent, even restarts, free from slag and spatter+2
bead height 3 -1 mm.
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Metals and Engineering 5.12AB Perform
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Procedure sheet 1 - Beads on plate - flat
Electrode
View A
~B
A~,.
11- Start
VlewB Weld current data Electrode dataSize Type Brand Name
Electrode Angles Lead Lateral Rutile
Run
1
2
3
60' 80
90
Material dataType Thickness Low carbon steel
10mmComplies
Assessment
Workshop safety
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Practical exercise 2 - Pad welds - flatAim
To deposit a pad weld on low carbon steel plate in the flat
position.Safety
Follow OHS workshop procedures. Use an approved shade 10 welding
glass filter. Wear suitable protective clothing to stop ray burn.
Always wear your safety glasses when removing slag.Material
1 piece low carbon steel 75 x 10 x 225 mmConsumables
Mild steel electrodes 4.0 mm E4112 or E4113 at approx. 165
ampsInstructions
Check the following points. Setting of amperage and heat input,
position of the plate on the bench,' correct method of arc striking
and arc length, correct welding speed and travel, electrode angles.
Your teacher will demonstrate if necessary. 1. Obtain your
MMAwelding board, safety equipment (head shield, gloves), material,
and consumables (if necessary) from the store. Outline, with chalk,
a rectangular shape 40 x 200 mm. Position the plate on the bench.
Deposit a weld bead along the plate length, maintaining the angles
shown.
2. 3. 4.
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Metals and Engineering 5.12AB Perform Routine
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Manual Metal Arc Welding
5.
Remove all slag from each individual weld bead before depositing
subsequent runs. Each run must have a staggered stop and restart.
Build up the pad to the required dimensions and on completion,
evaluate your weld with the given standards. Fill in all the
relevant information on the procedure sheet. If it meets the
standard, submit your work for assessment.
6.
7. 8.Economy
Use electrodes down to a stub length of SOmm maximum. Standards
Your work should have:+2
pad weld height 3 -1 rnm a maximum of four significant surface
defects on a unit area of 40 x 150 mm with the accumulative area
not exceeding the square of the plate thiclmess no adhering slag or
spatter.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Procedure sheet i-Pad
weld - flat
First run
Subsequent runs
View A
~B
View B
Weld current data
Run
1
Electrode data Size Type Brand Name Electrode Angles Lead
Lateral.. .
2
3
Material data Type Thickness Assessment Low carbon steel 10mm
Complies
Workshop safety
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Metals and Engineering Industry 5.12AB Perform Routine Manua!
Meta! Arc Welding
Section 4 - Fillet Weld Joint Terms and FaultsAimTo learn the
basic terminology (technical language) used to describe weld
positions, areas and locations of a welded joint, and common
defects and their causes.
Activity1. 2. 3. 4. 5. Read and study the resource material
following. Complete the review questions. Ask for assistance if the
information is not clear to you. Complete the practical exercises
at the end of the section. Ask a teacher or your supervisor to
check and sign your Training Record. On completion of this section
you must attempt the test on this topic and reach the required
level of competence before proceeding to the next section.
6.
Safety
Wear the right clothing to protect you against rays and hot
metal spatter.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Fillet weld joint terminology and faultsIt is important for you
to know the terms used to describe fillet weld joints and fillet
weld defects so that you are able to talk to other trades persons,
clients and inspection authorities in an informed way. An
understanding of the technical terminology will also assist you to
get the most out of your training.
Fillet weld terminologyPositions of welds//Vertical
Horizontal Single v .,~ butt weld Intermittent fillet welds
Overhead Lap weldFillet weld,/
/
'.... Plug weld -
'-.--- Slot weld
-'--- Corner weld
Weld names
[vertic.al
\I... ~-
.]1~1 . r "--...
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Metals and Engineering S.12AB Perform
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Definition of a fillet weldA fillet weld is a weld of
approximately triangular cross-section which is
formed in the corner between surfaces of two components.
Parts of a fillet weld
Fillet weld contours and
0--
Toe Root face Heat metal Penetration Weld metal Parent zone
Fusion 12. 7. Nominal thickness thickness9. fillet) Reinforcement
11. 10. 8. Leg lengththroatzone(concave fillet) Throataffected
(convex
measurements
13.
Parts of a welded structure
.
/penetration/fUSionWeld face
Parent metal
Fillet weld
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Fillet weld dimensions
The size of a fillet weld is determined by the following
dimensions. These can easily be checked with a fillet gauge. Note
that the strength of a welded structure is determined by the type
of metal, leg length and the effective throat thickness.
Fillet weld dimensions.
Fillet weld profiles
Weld DefectsWeld defects are either external or internal.
External defects can be detected by visually inspecting the
finished weld for plate misalignment, incomplete penetration, weld
craters, blowholes, weld spatter and correct weld size. Internal
defects can only be detected by destructive or non destructive
testing, which may reveal slag inclusions, porosity, cracks and
incomplete fusion or incomplete penetration.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Common weld defects The most common weld defects
are:Undercut
A sharp groove at the toe of a ron between the weld and the
parent metal or in previously deposited weld metal, due to welding.
It may be continuous or intermittent. This is caused by using the
wrong electrode current, incorrect operating technique angle,
excessive welding
or excessive arc length.
~
~Undercut
Over roll (overlap)
Weld metal at the toe of a weld which covers the parent metal
surface but is not fused to it. It is caused by overflowing molten
weld metal on the surface of unmelted parent metal which leaves an
unwelded area. This is or too slow welding speed, or by using
caused by using too Iowa current too large an e!ectrode.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Misalignment
Misalignment is any variation from line or dimension of a welded
joint. It is caused by faulty setting up of job, distortion or lack
of tack welds.
Misalignment
Incomplete
penetration
Incomplete penetration may be classified as an internal or
external weld fault. Incomplete penetration is the failure of the
weld metal to fill and fuse the root of the joint. It is caused by
faulty preparation of work, using too Iowa welding current or poor
operating technique.
Incomplete penetration
Slag inclusions
Slag inclusions are non-metallic particles trapped in the weld
metal. They may weaken the weld joint. Inclusions result from not
removing slag from previous runs, using too Iowa current or using
too long an arc length.
Inclusions
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Metals and EngIneering 5.12AB Perform
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Porosity
Gaseous substances such as oxygen or nitrogen trapped in the
weld metal leave a cluster of small holes in the weld. It is caused
using wet or damp electrodes, welding over coated surfaces, over
painted oily or greasy surfaces or by using the wrong type of
electrode.
Cracking
A variety of different types of cracks may occur in the welded
area of fabricated products. Identifying the type of crack helps to
isolate the possible causes. Causes are using wrong type of
electrode, not applying preheat to crack sensitive steel, using
damp or wet electrodes or welding over oil, grease or a plated
metal surface .
/I..
.....
Lack of fusion
Incomplete fusion between weld metal and weld metal or weld
metal and parent metal is caused by not enough amperage, incorrect
joint preparation and incorrect welding technique.
Lack of fusion
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Metals and Engineering Industry S.12AB Perform Routine Manual
Metal Arc Welding
Undersized and oversize welds
Welded joints are designed by structural
engineers
to carry loads safely. weld might
The size and type of weld depends on its use. An undersized not
be strong enough to carry the load it supports.
A weld that is reinforced
(over welded) too much can make other sections of the work too
rigid and cause them to crack or break. You will be asked to weld
to the designer's specification. For example
a 6 mm fillet weld requires a 6mm leg length and a 4.2 mm throat
thickness a butt weld requires an even or slightly curved surface.
You may not be given the weld size for all jobs. If no weld size is
specified, deposit the weld in proportion to the plate thickness.
For example:
a 10 mm plate requires a 10 mm weld thiclmess. Butt welds should
always be built up to the thickness of the parent metal.
Oversize
Correct size
"\
\
Undersize
Weld assembly (undersized welds)
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Metals and Engineering 5.12AB Perform
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Workshop testsThese are only some of the tests which call be
carried out to check the weld quality. Visual Youcan do a visual
check for external weld defects. Internal ones can't be seen.
Fillet break A fillet break shows satisfactory fusion,
penetration, and inclusions or porosity. Summary of weld defects
and how to fix them When preparing the plate, check that you have:
correct edge preparation clean/smooth surfaces correct plate
alignment. When welding, check that you have: correct electrode
correct current (amperage) correct speed of travel
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Metals and Engineering S.12AB Perform
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correct arc length correct operation (welder). When checking the
electrode for condition, check for damp or damaged electrodes. When
inter-run cleaning remove all slag, rust, undercut, and excess weld
spatter before depositing the next pass.
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Metals and Engineering 5. 12AB Perform Routine
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Practical exercise 3 - Fillet weld, single run -
horizontalAim
To deposit 6 mm fillet weld in the horizontal position on 10 mm
low carbon steel plate.Note
This is a skill practice exercise which is assessed. You must
reach the required standards to enable progression to the next
section. Safety Youmust wear eye protection . Make sure that the
centre of the press ram and the highest point of the exercise are
in line when breaking welds.Material
2 pieces low carbon steel 75 x 10 x 225.Consumables
4 mm 4112 or 4113 electrodes at 160 to17S amps
approximately.Instructions
Your teacher will demonstrate. 1. Wire brush the material to
remove surface rust and loose scale. Tack both ends of the plate to
ensure metal to metal contact. Complete approximately half the
weld, stop, remove slag, restart and finish the weld. Remove all
slag and spatter and submit the exercise for visual inspection.
2.
3.
4.
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Metals and Engineering 5.12AB Perform Routine
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Manual Metal Arc Welding
5.
Break the weld and resubmit the exercise for internal
inspection.
6.
Relocate the plates for further practice using all edges as
shown. Evaluate the weld exercise and complete the procedure sheet.
Submit your work for assessment.
7.
8.Economy
Consumables and materials are expensive. Relocate plates for
maximum use. See chart (on earlier page) for suggested plate
positioning sequence to obtain four or more fillet welds from one
material unit. Use all electrodes down to a maximum stub length of
50 mm and return unused material to the store. Standards Your work
should have: correct alignment and assembly smooth regular weld
contour angular distortion 0 to 5 a maximum of two significant weld
defects per 250 mm of weld length with an accumulative area of less
than twice the square of the plate thickness weld size 8 mm
complete fusion for the length of the weld joint.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Procedure sheet 3 - Fillet weld, single run horizontal
View A Weld current data
ViewB Electrode data Size Type Brand Name Electrode
classification Angles Lead Lateral
1 2
3
Material data Type Low carbon steel Thickness 10 mm Assessment
Alignment and assembly Angular distortion Surface finish Weld size
Surface defects Complete fusion Workshop Safety No. of units
completed to standard
Complies: Complies: Complies: Complies: Complies: Complies:
Complies: Complies:
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Practical exercise 4 - Fillet weld, 3 run 2 layer -
horizontalAim
To use the fillet welding technique necessary to deposit an 8 mm
three run, two layer fillet weld to the requirements
below.Material
2 pieces low carbon steel 75 x 10 x 225Consumables
Mild steel electrodes F4112 or E4113 at 160 to 175 amps
approx.Instructions
Your teacher will demonstrate. 1. Wire brush or grind the weld
fusion faces to remove the rust and mill scale. Tack both ends of
the plate ensuring metal to metal contact with no gap. Tack only on
the ends or side to be welded. Complete approximately half the
first run, stop, remove slag, and examine the weld profile. Finish
the run and subsequent runs using the sequence illustrated with at
least one staggered stop and start per run. Submit the exercise for
visual inspection then fracture the weld and resubmit it for
internal inspection. Relocate the plates for further practice using
all edges as shown. Evaluate the weld exercise and complete the
procedure sheet. Submit your work for assessment.
2.
3.
4.
5.
6.
7.
8.
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Metals and Engineering IndustryS.12AB Perform Routine Manual
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Economy
Consumables and materials are expensive. Relocate plates for
maximum use. See chart (on earlier page) for suggested plate
positioning sequence to obtain four or more fillet welds from one
material unit. Use all electrodes down to a maximum stub length of
50 mm and return unused material to the store. Standards Your work
should have: correct alignment and assembly smooth regular weld
contour angular distortion 0 to 5 a maximum of two significant weld
defects per 250 mm of weld length with an accumulative area of less
than twice the square of the plate thickness weld size 8 mm
complete fusion for the length of the weld joint.
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Metals and Engineering Industry 5.12AB Petform Routine Manual
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Procedure sheet 4 - Fillet weld, 3 run 2 layerhorizontal
Weld current data Amperage used
Run
1 2
Electrode data Size Type Brand Name Electrode classification
Angles Lead
Lateral
3
Material data Type Thickness Assessment
Low carbon steel 10 cm Complies
Workshop safety
Complies
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Practical exercise 5 - Outside corner fillet - horizontalAim
To deposit a multiple nm corner weld in the horizontal position
using fillet welding techniques to the requirements
below.Safety
Always wear safety glasses when chipping slag deposits away from
the weld.Materials
Material from the single or 3 run fillet (crucifixes) exercises
or 2 pieces 25 x lOx 225 111111 low carbon steel.Consumables
Mild steel electrodes E4112 or E4113 , 3.25 m at approx 120-130
amps. Mild steel electrodes E4112 or E4113 4.0 mm at approx 160-175
amps.Instructions
Your teacher will demonstrate if required. 1. A-ssemble and tack
plates using a suitable spacer to maintain root gap. Position the
plates and deposit approximately 50 mm of the root run. Examine the
bead shape and penetration continuing the weld. before
2.
3.
4.
Completely fill the remainder of the weld using 3.2 diameter
electrodes and a logical weld sequence. Seal the reverse side with
a 6 mm horizontal vertical fillet weld.
5.
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Metals and Engineering 5.12AB Perform
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6. 7.
Add additional plates as required and repeat the exercise.
Evaluate the weld exercise and complete the procedure sheet. Submit
your work for assessment.
8.Economy
Maximise the use of electrodes and return all unused material to
the store. Standards Your work should have: correct alignment and
assembly smooth regular weld contour angular distortion00
to 5
a maximum of two significant weld defects per 250 mm of weld
length with an accumulative area of less than twice the square of
the plate thickness weld size 8 ~6mm complete fusion for the length
of the weld joint full radius weld.
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Metals and Engineering 5.12AB Perform
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Routine Manual Metal Arc Welding
Procedure sheet 5 - Outside corner fillet horizontal
Weld current data Amperage used
Electrode data Size Type Brand Name Electrode classification
Angles Lead
Lateral
Material data Type Thickness Assessment Complies
Workshop safety
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Metals and Engineering 5.12AB Perform
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Practical exercise 6 - Fillet weld horizontalAim To fillet weld
3 mm low carbon steel sheet assembled in the horizontal position to
the requirements below. Safety Always use tongs to position tacked
and welded work. Never leave hot work unattended in the workshop.
Material 6 pieces low carbon steel 50 x 3 x 225 mm. Consumables
Mild steel electrodes E4112 or E4113 2.5 mm at approx 85-95 amps.
Mild steel electrodes E4112 or E4113 3.25 mm at approx 110-115
amps. Instructions Your teacher will demonstrate. Students must
attend this demonstration before beginning the exercise. 1. Clean,
assemble and tack weld at three locations for each joint. Use E4112
electrodes and stop each run at least once. Weld both sides of the
horizontal fillet. Repeat the exercise with E4113 electrodes.
2. 3. 4.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Economy
Materials and consumables are expensive. use electrodes down to
a maximum total length of 50 mm. Standards Your weld should have:
correct alignment and assembly smooth regular weld contour angular
distortion 00 to 50 a maximum of two significant weld defects per
250 mm of weld length with an accumulative area of less than twice
the square of the sheet thickness. weld size equal to the sheet
thickness ::.~ mill complete fusion for the length of the weld
joint.note
Watch for these points. Distortion tack at regular intervals,
assembly and 'fit up' of cornerjoint.
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Metals and Engineering 5.12AB Perform
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Routine Manual Metal Arc Welding
Procedure sheet 6 - Fillet weld - horizontal
Outside corner weld
Weld current data Amperage used
Electrode data Size Type Brand Name Electrode classification
Angles Lead
Lateral
Material data Type Thickness Assessment Complies
Workshop safety
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Metals and Engineering Indust/) 5.12AB Perform Routine Manual
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Section 5 - Butt Weld Terminology and FaultsAimTo learn the
technical terms used for butt welds and to be able to identify
typical weld defects.
ActivityL 2. 3. 4. Read and study the resource material
following. Complete the review questions. Ask for assistance if the
information is not clear to you. Ask a teacher or your supervisor
to check and sign your Training Record. On completion of this
section you must attempt the test on this topic and reach the
required level of competence before proceeding to the next
section.
5.
Safety Wear the proper clothing to protect your skin and eyes.
Do nottry to take short cuts or risks
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Butt weld terminology and faultsIn this section you will learn
about the different types of butt welds and how to identify some of
the faults which can occur in butt welds. Butt welds are used to
join metal products such as sheet, plate, rolled and pressed
sections. This type of joint has the advantage of giving high
strength without changing the profile of the structure. Industrial
uses for butt welds include: boiler and pressure ship building
earth moving equipment aircraft and submarines. Butt weld joints
can be designed for full penetration welding to give vessel
construction
maximum strength or for partial penetration strength of the
joint is not so important.
welding in places where the
Weld preparationReinforcement Toe Parent metal
Fusion zone
Root penetration
Weld components Joint edges have to be prepared before plates
are welded together. Joint or edge preparation is essential for
complete fusion and penetration.
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Metals and Engineering 5.12AB Perform
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\
~
;
Root face: fa supporf fhe fltst run of weld
-JLWeld preparations multi-run fillet welds Double butt welds
and U V preparations Single butt welds less difficult to
distortion. maximum =strength. moreheat less prepare. On thick
plate
~ _~_=========::~Roof gap: to allow complefe weld
penetration
use gouge and U preparations. Less for needweld metal
flametopreparations runweld less double V by than V cutting or
machining. = back to done or joint a backing but are usually
balance deposit minimise distortion.
{.~
'j(~L
)
Plate thickness
DCJ DCJ
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Metals and Engineering Industry 5.12AB Perform Routine Manual
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Preparation typesThere are several preparation types and details
are given below.
Closed butt jointThis is used when the edges do not need
preparing. suitable for sheet up to 3 mm thick. They are placed
close together and single or double welded. The closed butt
joint is
j~ -~-
Sr [Open butt joint
I~--~Sof material. An open butt
This is used when the edges do not need preparing. They are
separated slightly to allow fusion of the full thickness joint is
suitable for material up to 5 rom thick.
r~mm
~
JI -1L-'.S-2.S
s
Single V butt jointThis is commonly
used on material up to 12 rom thick.
1.5mmm~JL
?2\/,--~?1.5
o
mm
~12m~
f
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Metals and Engineering S.12AI3 Perform Routine
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Double V butt jointThis is used on plate 12 mm to 38 mm in
thickness are welded. when both sides
Single bevel butt jointUsed only when one member of the joint
can be prepared a T joint. as in the case of
~5 ~Minimum
",
15M~imu~JLSingle U butt jointThe single U butt is used as an
alternative to single V butt joint.
~inimum r-\1-'
\ \1I
~ __
r
Radius5mm Minimum
t
-~-UPto . II 3 mm Maximum--i+-- 3 mm
;'-1=V;r-
25mmtJ
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Metals and Engineering Indnstry 5.12AB Perform Routine Manual
Metal Arc Welding
Double U butt jointThis is used on material done from both
sides. over 2S mm thick where welding can be
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Minimum
Ll====---"~ 3 mm Maximum
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"/_1_r -===RadiUS 5 mmMitm3 mm Up to 25mm
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r
When you need to butt weld two sections of different thickness,
you should taper the thicker one to match the other. The length of
the tapered section should be at least three times the difference
in the thickness between the plates. This type of butt weld is used
to join dished ends to pressure vessels.
Uneven section" butt joint
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Metals and Engineering 5.12AB Periorm
Industry
Routine Manual Metal Arc Welding
Weld defectsCommon weld defects are detailed below.
Excesspenetration Definition Too much weld metal extending through
the root of the weld .
---
u
u'-etration
Causes are: incorrect preparation amperage too high incorrect
welding technique. Incomplete penetration Definition Failure of the
weld metal to extend into the root of a joint.
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Incomplete penetration
Causes are: incorrect preparation amperage too low arc length
too long.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Lack of fusion Definition Incomplete fusion between weld metal
and weld metal or weld
metal and parent metaL
)Lack of fusion
Causes are: not enough amperage incorrect joint preparation
incorrect welding technique.Inclusions Definition Slag or other
foreign matter trapped during welding.
Causes are: faulty joint preparation not enough amperage poor
cleaning of prior runs.
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Metals and Engineering 5.12AB Perform
Industry
Routine Manual Metal Arc Welding
Porosity Definition A group of gas holes in the weld metal.
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Causes are: damp or old electrodes composition of parent metal
incorrect electrode type.Cracking
Definition Discontinuity produced from tearing of the weld metal
while in a plastic condition when hot or a fracture when cold.
HAZ cracking
Causes are: insufficient weld deposit insufficient pre-heat
incorrect electrode.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
UndercutDefinition A groove or channel in the parent metal at
the toe of the weld.Undercut
Causes are: too much current welding too fast incorrect welding
technique. OverrallDefinition A section of unfused metal extending
past the toe of the weld.
~verrOI1~w/ove~OIlCauses are: electrode too large welding speed
too slow incorrect electrode angle.
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Metals and Engineering Industry 5.12AB Perform Routine Manual
Metal Arc Welding
Misalignment Definition Any variation from line or dimension of
a welded joint.
Misalignment
Causes are: incorrect weld procedure careless preparation too
few tack welds. Incompletely filled joint
~
~comPletelY filled joint
~~----( ~.=Causes are: not enough weld metal welding too fast
too few beads.
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Metals and Engineering 5.12AB Perform
Industry
Routine Manual Metal Arc Welding
The principle of expansion and contraction in a metalMetals
expand when heated and contract when cooled. For example, a piece
of low carbon steel, if not restrained in any way, will increase
its dimensions in all directions for every degree Celsius the
temperature rises. On cooling, the steel will return to its
original size.
Angular distortionThere is distortion when unequal contractional
forces cause angular change in the parent metal position.
j~ Outwardby expansion caused movement
i
Inward movement caused by contraction
Transverse distortion by butt weld
6
4
2
'3
5
7
Tack weld sequence
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Metals and Engineering lndustry S.12AB Perfonn Routine Manual
Metal Arc Welding
Practical exercise 7 - Butt weld, flat sheet steelAim
To deposit single run butt welds in the flat position on 3.0 mm
low carbon sheet steel.Materials
4 pieces 40 x 3.0 x 150 mm low carbon flat bar.Consumables
Mild steel electrodes E4112 or E4113 2.5 mm at approx 85-95
amps. Mild steel electrodes E4112 or E4113 3.25 mm at approx
110-115 amps.Instructions
Your teacher will demonstrate. 1. Assemble and tack weld sheets
using the sequence illustrated. Position the plates with a sligh t
slope and weld approximately 50 mm of the joint. Examine weld
profile and penetration before completing the weld. Complete the
weld and submit for inspection. Cut sheets and relocate for further
practice as illustrated. Evaluate the weld exercise and complete
the procedure sheet. Submit your work for assessment.
2.
3.
4. 5. 6.
7.
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Metals and Engineering Industry S.12AB Perform Routine Manual
Metal Arc Welding
Economy Cut and relocate sheets for maximum the store. use.
Return all unused material to
StandardsYour work should have: correct alignment and
assembly
smooth regular weld contour weld penetration angular distortion
for a minimum00 to 50
of 20% of the weld length
a maximum
of two significant
weld defects per 250 mm of area of less than twice the
weld length with an accumulative square of the plate
thickness.
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Metals and Engineering S.12AB Perlorm Routine
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Manual Metal Arc Welding
Procedure sheet 7 - Butt weld, flat sheet steel
Weld current data Amperage used 1.6mm 3.0mm
Electrode data Size Type Brand name Electrode classification
Angles Lead Lateral
Material data Type
Thickness
Assessment
Workshop safety
110