Download Mig Welding Booklet - Weldwell New Zealand

WELDWELL NEW ZEALAND
Private Bag 6025
NAPIER
Telephone (06) 834-1600
Fax (06) 835-4568
www.weldwell.co.nz
INTRODUCTION
Our business is welding and we offer this handbook to both the handyman
and industry in general, in an earnest endeavour to assist all those engaged
in MIG welding.
We have not covered all phases of welding, but present briefly, the basic
facts of the MIG welding process and techniques.
LIST OF CONTENTS
History of MIG
MIG Overview
Power Sources
Feeder
MIG Handpieces
Regulators
Shielding Gas
Stick Out
Travel
Wire Electrodes
Process Types
i)
Short Circuit / Dip
ii)
Globular
iii)
Spray
iv)
Pulse Spray
Amperages
MIG Welding Hazards
Personal Protection
Troubleshooting
Page No
2
3
5
7
12
14
15
16
17
18
19
22
25
26
27
Branches and Outlets throughout New Zealand
Check your Yellow pages
or www.weldwell.co.nz
1
HISTORY OF MIG / MAG (GMAW)
GMAW was developed during the early 1940’s and technology was taken
from the TIG welding process that was already around at the time. MIG
(MAG) welding has the advantage of a particular gas shield that TIG has,
and then adds the advantage of a continuous consumable wire electrode.
At the time the MIG process was able to increase the production of war
manufacturing. It has since become one of the main stages of manufacturing
from that time until the present day. Through the years MIG/MAG has
undergone changes in the types of wires, gases, and power sources, but
the principles remain the same. With the onset of the manufacturing in the
1960’s and 1970’s the types of wire electrodes have been upgraded to give
wire electrodes with higher deposition rates, better finishes and wires more
suitable for more modern steel types.
The welding gases have also evolved in the same way to make MIG welding
faster, more efficient and with a better finish.
One of the major changes has also been with power sources and feeders.
MIG welding power sources have, over the years, gone from basic transformer
types to the highly electronic power sources of the world today.
2
MIG OVERVIEW
A MIG welder uses a
DC voltage controlled
electric power source
(different from that of an
arc welder), connected to
a wire feeder which holds
a spool of the type of wire
needed to do the job. The
feeder will push the wire
down what is known as a
MIG handpiece. This is
done by feeding the wire
through a set of rollers.
A suitable gas mixture is
also fed down the MIG
handpiece.
Different
gases are used for
different types of wire.
A MIG welder at work
Basically, the MIG process uses a gas or gas mixture to displace the air
around the arc that is being formed between the wire being used and the base
metal. This is done by using an electric MIG power source. The electrode
is still being melted with an electric arc, but in the case of MIG it is a special
wire which is mechanically fed into the arc.
The feed rate is adjusted depending on the thickness of the material being
welded. The voltage of the electric power source is also adjusted depending
on the material thickness being welded.
Advantages of MIG Welding
1) Welds most metals.
2) Simple technique and very easy to learn and use.
3) Higher deposition, greater speed and a lot more efficient than most
other forms of welding.
4) Minimised weld defects.
5) Produces little or no slag.
6) With the correct wire and settings, can be welded out of position.
3
Application
1) Fabrication and Manufacturing
i)Due to increases in speed and efficiency, MIG welding is
well suited for Fabrication and Manufacturing.
ii) Clean up time is greatly reduced due to little or no slag.
2) Repair and Maintenance
i) Lightweight MIGs can be portable.
ii) Easy for the D-I-Yer to learn.
iii) Welds various types of material.
iv) Great for the farming industry with the use of gasless wire
which makes it possible to weld outdoors.
v) Single phase domestic power supply MIGs are available.
4
3) Professionals
i)
Panelbeaters, bodyshops, etc
ii)
Truck repairers.
POWER SOURCES
MIG welding power sources have come a long way from the basic transformer
type power source to the highly electronic and sophisticated types we see
around today.
Even though the technology of MIG welding has changed, the principles of
the MIG power source have, in most cases, not. The MIG power sources
use mains power and converts that mains power into CV (constant voltage),
DC (direct current) power suitable for the MIG welding process.
MIG welding power sources control voltage – this is done by either voltage
stepped switches, wind handles, or electronically. The amperage that the
power source produces is controlled by the cross sectional area of the wire
electrode and the wire speed, ie the higher the wire speed for each wire size,
the higher the amperage the power source will produce.
Because the output of the MIG power source is DC (direct current) the
terminals on the front will have + pos and – neg on the output side. The
principles of electric circuits states that 70% of the heat is always on the
positive side. This means that the lead that is connected to the positive side
of the welder, will carry 70% of the total energy (heat) output. The connections
(polarity) can be different for different electrode wires, so the operator must
check this when connecting up the leads for the MIG process.
5
Other things to check about the MIG power source :-
6
1) Amperage needed to do the job. Will it be sufficient?
2) Does it have a suitable voltage range (eg do the volts go low enough
for light material, or does the voltage go high enough for spray welding
if it is needed?)
3) Power supply three phase or single phase? Is there enough mains
power to allow the MIG welder to perform at its best?
4) Is weight a problem? If so, is the inverter type welder more useful?
5) Will a mobile MIG power source be better to do the job (as some
engine drive welders have a CV [constant voltage] range)?
6) Would a multi process type power source be a better choice, as most
multi process MIG welders have a CC (constant current) range, which
would allow the power source to be used for more than MIG alone?
WIRE FEEDER
The wire feeder is the part of the MIG welding set up that —
i) Controls the speed of the wire electrode and pushes this wire from the
feeder through the welding handpiece to the workpiece.
ii) Provides the path for welding current to be passed from the welding
power source through the interconnecting lead to the feeder and then
to the welding handpiece.
iii) Provides gas flow control through a solenoid valve. The gas is fed
down from the gas regulator to the weld area via the feeder and then
the MIG welding handpiece.
Wire feeders come in many different shapes and sizes, but they all do the
same basic job roles. Feeders can be separate from the power source or
built into the power source itself. Feeders are made up of different parts,
each having a different job role. (See Fig. 1, page 8.)
Wire spool holder. This is designed to hold the spool of the correct wire
size in place on the feeder to ensure the wire electrode is on the correct input
angle for the drive roller to be able to do its job properly.
The spool holder also has the job of being the spool brake, so that when the
rollers stop turning the wire spool will stop without over-running, this can also
be a cause for the wire electrode to tangle up on the spool or run down the
side of the spool – this would cause the wire electrode to jam. The brake
pressure must be set correctly, so as not to put too much pressure on the
spool and stop it turning freely when the rollers are turning; but it must have
enough tension to stop the wire spool from over-running.
To set up the brake please read the feeder manual as each feeder has a
different way of setting the spool holder brake.
7
Open Feeder
Built-in Feeder
(compact machine)
Closed in Feeder
Fig. 1
8
Drive Motor MIG welding relies on smooth and constant wire feed. Lower
quality machines usually have poor feed systems. The wire drive motor has
the job of turning the drive rollers (this can be one or more sets of rollers).
Undersize drive motors can result in poor feeding of the wire electrode down
the MIG welding handpiece. This will have the effect of making the overall
performance of the MIG machine sub-standard as compared to a machine
with a quality drive system.
Drive Rollers The drive rollers grasp the wire electrode and continuously
feed the wire down the MIG handpiece into the welding arc. The rollers need
to be selected by –
i) the wire size
ii) the type of wire to be fed. Each type of wire may need a different style
of roller groove – eg V rollers for steel and other hard wires
V-Knurled for Fluxcored wire
U-Grooved for aluminium and other soft wires
U-Cogged for soft shelled fluxcored wires
The idea of using the correct roller is to have a good wire drive without
crushing the wire. The pressure roller is also used to set the wire tension.
This must be set with enough pressure to feed the wire electrode, but not too
much tension as to crush the wire.
9
All the wire guides on the input and output side of the rollers must be
i) lined up to feed the wire straight into the rollers
ii) lined up in a way as to make sure the wire is lined up with the grooves
in the drive rollers
iii) all guides must be as close as possible to the drive roller to prevent
the possibility of the wire bunching up.
Wire Feed Controls
The wire feeder will have its own built-in control system. The number of
controls that will be built into the feeder will depend on the type of feeder
(some feeders come with more bells and whistles) but the most common
are
i)
Wire speed – this control is the adjustment for how fast the drive
rollers will turn and as stated earlier, the faster the wire speed for each
wire size the more amperage the power source will produce. The wire
speed controls can be labelled as wire speed, eg ipm or mpm, or as
a percentage from the slowest speed being zero to the highest speed
being 100%.
The amperage being set by the wire speed setting will also have
an effect on the speed of travel and the deposition rate of the wire
(how fast the weld metal is being put onto the weldpiece); with the
advantage of, the higher the amperage the thicker the material that
can be welded.
10
ii)
Purge switch. Some feeders have a purge switch. This is to allow
the gas flow setting to be set on the gas regulator without turning of
the wire feed roller or without any welding power being turned on.
iii)
Burnback.
Burnback is the setting of the degree that the wire
electrode will melt back towards the contact tip at the completion of
the weld. If there is too much burnback the wire electrode will melt
back onto the contact tip, possibly damaging it. If there is not enough
burnback set, the wire electrode will not melt away from the weldpool
and can be left stuck to the weld metal.
iii)
Spot timers or stitch modes are to be found on some feeders. These
controls normally control the time the drive roller will turn for after the
trigger contactor has been activated.
The Handpiece Connection
The handpiece connection is the system in which the MIG handpiece is
connected to the wire feeder. There are various types of MIG handpiece
connections. Different manufacturers can use any one of many systems to
connect their handpieces to the wire feeder.
When ordering a new handpiece tell the supplier
a) the type of handpiece you need, including amperage rating
b) the type of connection on the feeder so the handpiece can be supplied
to match the connection
The handpiece connection is also the area where the wire electrode, welding
current and welding gases are passed onto the welding handpiece. This
means these components should be checked for damage or leaky seals etc,
so the connection will do its job correctly.
11
MIG Handpieces
The MIG handpiece is connected to the
wire feeder, and its job is to deliver the wire
electrode, shielding gas and the electrical
welding current to the welding site. There
are a lot of different shapes and styles of
MIG handpieces out in the marketplace
(Fig. 3) but they all have things in common(Fig. 2).
1)
2)
3)
Gas Nozzle
Contact Tube
Electrode
Shielding Gas
Arc
Weld Pool
Weld Metal
Base Metal
Fig. 2
Aircooled or watercooled
Current rating. The operator must select the correct size handpiece.
Using a handpiece that is not sufficiently rated for the machine may
result in the handpiece overheating. This may result in a poor weld
and damage to the handpiece. A handpiece with an excessive rating
will be larger and heavier than the smaller handpiece, which could
result in discomfort for the operator.
They all have parts that will wear out (consumables eg liners, tips,
diffuser, nozzle, etc.)
Let’s take a look at each part
Liner The liner causes the most problems I have faced out in the
workshop. First, they have a life span that is approximately one to
four rolls of MIG wire depending on the quality of the liner and wire.
The life of the liner will also be increased if the operator removes and
cleans it by soaking in non-corrosive and a non-toxic solvent. Each
wire size needs to have the correct wire size liner. Be aware some
liners may fit more than one size of wire.
There are also different materials for different types of wire electrode, eg
steel or stainless liners for solid wires and Teflon liner for aluminium.
The liner length is most important. In the field it is very common to find
even newly fitted liners that have been cut too short. This results in
the wire being able to move around behind the welding tip and leading
to bad wire feeding. The liner has to be fitted correctly and different
MIG handpieces will often have a different way of ending up with a
liner that is the correct length.
Please don’t just take out the old liner and cut the new one to the same
length. It could end up with an incorrect result. Please refer to your
MIG handpiece manual.
All MIG handpieces should be laid out straight ont he floor before
trimming the liner, to prevent the new liner being cut too short. Do not
cut the liner if the handpiece lead is coiled up.
12
Gas Diffusers The gas diffuser’s job is to make sure that the shielding
gas is delivered to the shielding nozzle correctly. It is designed to
make the gas come out as straight as possible and equally supplied
around inside the gas shield nozzle. Diffusers can be made of different
materials, eg copper, brass or fibre. Some diffusers will also be the tip
holder.
Tip Holder This is the item which holds the welding tip in place. Again,
tip holders can be very different in design and are very often unique to
that brand of MIG handpiece.
MIG Tips The MIG tip is the key to good welding. First of all, it is the
way that welding amperage is delivered to the welding wire electrode,
often with a very high amperage.
Most tips are made of copper alloy, and as a rule you only get what you
pay for. The better the alloy the better the tip will pass current to the
wire electrode and the less wear the MIG tip will have; also the less
the tip will oxidize.
The size is important. The right size tip must be selected. If the
selected tip size is too large the wire electrode will not make a good
contact, leading to poor welding performance.
If a tip selected is too small, the wire electrode will feed poorly and may
even jam in the contact tip.
Fig. 3
13
REGULATORS
The job of the gas regulator is to reduce the bottle pressure gas down to a
lower pressure and deliver it at a constant flow. The constant flow of gas is
fed to the feeder then through the interconnection to the handpiece, down
the handpiece to the weld area.
Different gases don’t always use different fittings, so check with your supplier
what type you will need.
As well as different types of regulators for different gases there are also
different styles of regulator as well. The two main ones are regulators with
(Fig 4) and without (Fig. 5) flow tubes. Both regulators do the same job, but
have a different way of setting the gas flow.
The amount of gas flow needed to do the job will depend on the welding gas
and the job being done, but a common setting to start with is 10 L/min.
Fig. 4
14
Fig. 5
SHIELDING GAS
The shielding gases are necessary for MIG/MAG welding processes to
protect the welding site from gases that are in the surrounding air, eg nitrogen
and oxygen. If the weld pool is contaminated by these gases fusion defects
can be caused, also porosity and the embrittlement of the weld metal.
The choice of the shielding gas depends on the type of material being welded
and the type of electrode wire being used. CO2 (Fig. 9) was commonly used
but now argon-mixtures (Figs. 7 and 8) are becoming more common. Argon
mixtures are more user friendly and result in higher deposition rates.
Nozzle
Non-Ionized
Shielding
Gas
With the advent of different welding gas
suppliers, each with their own belief on
what gas mixture they make, it is difficult
to list which gases are needed for which
job. Please see your local gas supplier or
Weldwell agent.
The flux core open arc range of wires
produce the gas shield as the material in
Fig. 6 Shielding Gas Area at the Arc
the core burns off, protecting the welding
site.
The desirable rate of gas flow will depend on the type of electrode wire,
speed and current being used and the metal transfer mode.
As a rule
and
small weld pools
medium weld pools
large spray weld pools
10 L/min
15 L/min
20-25 L/min
Too much gas flow can be just as bad as not having enough. The reason
being that if the gas flow is too high it will come out of the MIG handpiece
This will cause
1)air to be sucked into the spinning gas
2) cause turbulence of the weld pool
Both resulting in a poor weld.
Fig. 7 - 75% Ar - 25% CO2
Fig. 8 - 50% Ar - 50% CO2
Fig. 9 - CO2
15
STICK OUT
Stick out is the distance of the contact tip to the workpiece. Changing the
stick out will change the resistance that is present between the contact tip
and the workpiece. (Fig. 10.)
Increasing the stickout will increase the resistance and both the voltage and
amperage will be lessened. This will lessen penetration and the weld will
achieve less heat. (Fig. 13.)
Once the stick out becomes too long a poor weld can result caused by a
shallow penetration and possible lack of fusion between the weld metal and
the base metal.
A short stick out can help give a good start but can make the weld profile
becoming concave, thus making a lower strength weld. (Fig. 11.)
Nozzle Shroud
Contact Tube
Nozzle-towork distance
Contact Tip
Contact Tubeto-work distance
Stick out
Arc
Length
Workpiece
Fig. 10
Fig. 11
Too short
Normal
Fig. 12
Fig. 13
Too long
16
DIRECTION OF TRAVEL AND ANGLE
When MIG/MAG welding the direction of travel is now coming down to
operator preference. Travel using the push method will result in a weld that
is wider, flatter and has less penetration and better appearance than the drag
method. (Fig. 14.)
The dragging method will result in a narrower, higher crown and a deeper
penetrating weld. (Fig. 14.)
The angle to the direction of travel
should be 10 - 15 degrees (Fig.
14.)
If a fillet joint is being welded the
handpiece should be a 45 degree to
each plate. (Fig. 15.)
In the downhand position (flat) the
handpiece should be 90 degrees to
the flat joint. (Fig. 16.)
a
Travel
Direction
b
Fig. 14
Fig. 15
Fig. 16 - Work Angle - Flat Position (front view)
17
WIRE ELECTRODES
The selection of the wire electrode to be used in the MIG/MAG process is a
decision that will depend on
1) the process being used (eg, solid wire or fluxcore wire)
2) the composition of the metal being welded
3) welding indoors or outdoors
4) joint design
5) cost
6) mechanical properties of the weld material and those that are a match
for the base material.
All wire electrodes contain deoxidising agents which can be silicon,
manganese or aluminium. The job of the deoxidising agent is to help prevent
porosity caused by oxygen and other contaminants.
15 kg spool of MIG/MAG Wire
18
PROCESS TYPES
Short Circuiting Transfer ( Dip) - Fig. 17
Short circuiting transfer is a method of metal transfer in which metal is
deposited only when the wire actually touches the workpiece. Metal is not
transferred across an open arc. The short circuiting transfer has a lower
current than other methods of metal transfer (spray and globular). This
means lower heat input and therefore more suitable for welding thinner
materials. It is also suitable for welding out-of-position.
The principle of dip
transfer can be further
explained as follows.
On
touching
the
workpiece a short circuit
is formed back through
to the power source (a).
Welding current will flow,
thus heating up the wire
a
b
c
d
e
f
molten
pool
pinch
separate
separate
Fig. 17
electrode, thiswill cause the wire electrode to pinch (b), the wire will separate
(c) and a little of the electrode wire is left in the weld puddle (d). The heat
of the arc then flattens out the molten pool (e), the wire feed will overcome
the heat of the welding arc and come down, touch the workpiece (f) and the
cycle starts all over again. The sound that is produced from short circuit
transfer should be smooth and consistent and have a sound very much like
frying bacon.
Globular Transfer - Fig. 18
The globular method of metal transfer is formed when the voltage is increased
over the short circuitry method. As the voltage is increased an arc length
is formed (a gap between the end of the wire
electrode and the workpiece). The voltage fits
into the area between short circuitry transfer
and spray transfer.
The globular method of metal transfer is very
rarely used as the metal droplets travelling
across the arc are unstable and can be
described as wobbly. The resulting weld has
a lot of spatter and the welding is not pretty, as
the weld pool is unstable because of the bad
metal transfer across the welding arc. Globular
transfer has poor weld appearance and cannot
be used out of position.
Fig. 18
19
Spray Transfer - Fig. 19
The spray method of metal transfer occurs when the voltage is increased
over both the short circuiting method and the globular method. As the voltage
is increased a good arc length should form and the metal droplets should
become uniform in shape as they cross the arc in a consistent manner.
Once the correct setting for the spray transfer mode is found the arc sound
will become smooth.
To obtain a good spray mode of welding shielding gases containing a blend
of argon is used. (Please see your gas supplier for their correct mixture.)
The spray method of metal transfer can be used with most of the common
welding wire electrodes (eg mild steel, aluminium, stainless steel).
The advantages of metal spray transfer are
i)
high deposition rates
ii)
good travel speeds
iii)
good looking weld appearance
iv)
little weld spatter
v)
good weld fusion
vi)
very good on heavy sections
The disadvantages of the spray mode are
i)
higher capacity power source needed
ii)
weld position is limited to flat and horizontal fillet
iii)
the cost of using a more expensive mixed gas
iv)
higher radiated heat is produced so extra protection is needed
Metal
droplets
Fig. 19
20
Pulsed Spray Transfer
Pulsed spray transfer has a steady stream of metal droplets crossing the
welding arc. The pulsed power source supplies the welding arc with two
types of welding current.
1)
2)
Peak current - this current allows the formation of metal droplets which
then cross the welding arc.
Background current - the background current will keep the arc alive,
but doesn’t allow for any weld metal transfer.
Pulsed spray transfer allows time for the weld puddle to freeze a little on the
background current cycle, which allows for
i) more control of the weld puddle
ii) more time for impurities to float to the top of the weld pool resulting in
cleaner and stronger welds
Advantages
i) able to spray thinner metals
ii) less heat input
iii) stronger welds
iv) more weld control
v) out-of-position welding
Disadvantages
i) higher set up costs
ii) needs operator training
iii) lower deposition rate
21
22
Volts
CO2
16-17
17-18
18-19
19-20
20-21
21-22
21-22
23-24
23-24
24-25
Thickness
mm
0.8
0.9
1.2
1.5
2.0
3.2
5.0
6.3
8.0
9.5
Steel
23-24
21-22
21-22
18-19
18-19
17-18
17-18
16-17
15-16
15-16
Volts
Ar75/
CO225
MIG Volts / Amps
220-250
200-210
180-190
160-170
140-150
120-130
90-110
70-80
50-60
40-55
Amps
Short
Circuit
300
220-250
200-210
180-190
160-170
140-150
120-130
90-110
70-80
50-60
Amps
Spray
—
—
—
—
—
—
—
6.3-8.6
5.6-6.4
3.8-4.5
3.1-3.4
Spray
0.8 mm
—
—
—
—
6.3-8.6
5.6-6.4
3.8-4.5
3.1-3.4
2.3-2.5
Short
Circuit
0.8 mm
10.7-13.2
10.2-10.7
9.1-9.7
8.1-8.6
7.1-7.6
6.1-6.6
4.6-5.6
3.6-4.1
2.7-2.9
—
Short
Circuit
0.9 mm
10.7-13.2
10.2-10.7
9.1-9.7
8.1-8.6
7.1-7.6
6.1-6.6
4.5-5.6
3.6-4.1
2.7-2.9
Spray
0.9 mm
5.6-6.9
5.3-5.6
4.7-5.0
4.1-4.5
3.6-3.8
3.0-3.3
2.3-2.8
1.8
—
—
Short
Circuit
1.2 mm
Wire Feed Speed (mm/min)
9.5
5.6-6.9
5.3-5.6
4.7-5.0
4.1-4.5
3.6-3.8
3.0-3.3
2.3-2.8
1.8
—
Spray
1.2 mm
Stainless
Thickness
mm
Volts
CO2 S/S
Amps
Short
Circuit
Amps
Spray
Volts
AR + 2%
O2 S/S
Short
Circuit
0.9 mm
Spray
0.9 mm
1.2
19-20
50-60
70-80
—
3.1-3.8
4.6-5.2
1.5
19-20
70-80
90-110
_
4.6-5.2
5.8-7.0
2.0
20-21
90-110
120-130
_
5.8-7.0
7.6-8.3
2.5
20-21
120-130
140-150
_
7.6-8.3
8.9-9.5
4.8
21-22
140-150
160-170
23-24
8.9-9.5
10.2-10.8
6.3
21-22
160-170
180-190
24-25
10.2-10.8
11.4-12.0
8.0
21-22
180-190
200-210
24-25
11.4-12.0
Use 1.2
9.5
200-210
220-250
25-26
Use 1.2
Use 1.6
11.0
220-250
300
26-27
Use 1.6
Use 1.6
23
Aluminium
24
Thickness
mm
Argon
Volts
3.2
21-22
5.0
23-24
6.3
24-25
8.0
Amps
Spray
Spray
0.9 mm
Spray
1.2 mm
Spray
1.6 mm
110-130
8.9-10.2
6.1-6.9
—
140-150
10.8-11.4
7.6-8.3
—
180-210
——
8.9-9.5
4.3-4.7
26-27
200-230
—
10.2-10.8
5.1-5.3
10.0
26-28
220-250
—
11.4-12.2
5.6-5.8
11.0
28-29
280
—
—
6.1-6.9
MIG WELDING HAZARDS
Fumes
Fumes from the MIG welding process are produced by the burning of
contaminants on the surface of the material being heated.
The MIG welding of galvanised metal is extremely dangerous to the operator
because of zinc poisoning unless suitable protection is used.
Heat
Welding in any form produces heat which can cause burns and the possibility
of fire.
Ultra Violet Light
During MIG welding Ultra Violet Light production is at the higher end of the
scale and suitable eye protection must be used. All the operator’s skin should
be covered to avoid burning, which could lead to skin cancer.
25
PERSONAL PROTECTION
Skull Cap
Helmet
Mask
Welding
Helmet
lens
Gloves
Jacket
Fire retardant pants/
overalls
boots
26
g
s
(Reproduced with permission from Miller
Electric, USA)
When troubleshooting gas metal-arc welding processes and equipment
problems it is well to isolate and classify them as soon as possible into one
of the following categories:
1)
Electrical
2)
Mechanical
3)
Process
TROUBLESHOOTING
This eliminates much needless lost time and effort. The data collected here
for your benefit discusses some of the common problems of gas metal-arc
welding processes. A little thought will probably enable you to solve your
particular problem through the information provided.
Problem 1: Electrode wire stops feeding while welding
Probable Causes
Suggested Remedy
1. Welding machine’s contactor open
2. Fuse blown in welding machine’s primary
3. Welding machine’s control circuit fuse blown
4. Primary power line fuse blown
5. Wire feeder’s control relay defective
6. Wire feeder’s protective fuse blown
7. Wire feeder’s drive rolls misaligned
8. Drive roll pressure too great or too little
9. Wire feeder’s spindle friction too great
10.Excess loading of drive motor
11. Drive rolls worn; slipping
12.Feeder drive motor burned out
13.Handpiece liner dirty, restricted
14.Broken or damaged handpiece casing or liner
Check for open circuit volts
Replace fuse
Replace fuse
Replace fuse
Replace control relay
Replace fuse. Find overload cause
Realign drive rolls
Loosen and readjust drive rolls
Loosen and readjust nut pressure
Clear resistance in drive assembly
Replace drive rolls
Test motor; replace if necessary
Remove liner, blow out with
compressed air
Replace faulty part
15.Handpiece trigger switch defective
16.Contact tube opening restricted;
burnback of electrode
17.Friction in handpiece liner
Replace switch; check connection
Replace contact tube
18.Sharp or excessive bend in handpiece cables
or liners
19.Liner too short
Check wire liner – clean, replace
parts as required
Straighten handpiece cables and/or
replace liners
Refit new liner that is the correct
length
27
Problem 2: Porosity in weld
Probable Causes
1.
2.
3.
4.
5.
6.
7.
8.
9.
Dirty base metal; heavy oxides, mill
scale
Gas cylinder valve off
Gas regulator’s diaphragm defective
Flowmeter cracked or broken
Gas hose connections loose
Gas hose leaks
Not enough gas flow
Moisture in shielding gas
Freezing of CO2 regulator/flowmeter
10.Wrong gas for type of wire or type of
transfer
11. Wire feeder’s gas solenoid defective
12.Too much wire feed speed (amperage)
13.Handpiece and/or cables leaking gas
14.Contact tube extended too far out from
nozzle for short circuit transfer
15.Nozzle-to-work distance too great
16.Improper handpiece angle
17.Welding travel speed too fast
18.Electrode not centred in nozzle
19.Voltage (arc length) too high
20.Short circuit current too high.
(Not enough slope)
Suggested Remedy
Clean metal before welding
Turn cylinder valve on
Replace diaphragm or regulator
Replace and repair
Tighten fittings
Repair or replace
Increase flow rate
Replace gas cylinder or supply
Thaw unit; install gas line heater or high
volume CO2 regulator
Install proper gas
Replace solenoid
Reduce wire feed speed
Test; repair or replace faulty parts
Move distance from nozzle end to max of
3.25mm
Should be recommended by wire
manufacturer
Use correct handpiece angle
Adjust conditions for slower speed
Adjust contact tube, nozzle and wire
Lower voltage
Adjust slope setting if adjustable
Problem 3: Electrode Wire stubs into workpiece
Probable Causes
Suggested Remedy
1. Too much slope. (Too much droop)
2. Arc voltage too low
3. Too much wire feed speed
4. Poor work connection
28
Reduce slope settings as required. (Find
flatter Volt-Amp curve)
Increase voltage
Reduce wire feed speed
Connect properly
Problem 4: Electrode wire feeds but is not energised. Little or no
welding arc
Probable Causes
1. Primary power line fuse blown
2. Machine’s contactor plug not tight in receptacle
3. Machine’s contactor control leads
broken
4. Machine’s Remote-Standard switch
defective or in wrong position
5. Machine’s primary contactor coil
defective
6. Machine’s contactor points defective
7. Welding cables loose on machine
terminals
8. Work connection loose (or incomplete
circuit due to rust or paint, etc.)
9. Wire feeder contactor plug not properly
connected
10.Contactor relay defective
Suggested Remedy
Replace line fuse
Tighten plug in receptacle
Repair or replace
Repair or replace; position correctly
Replace
Replace points or contactor
Tighten connections
Connect properly to work; clean and
tighten connections
Tighten plug
Repair or replace
Problem 5: Excessive spatter while welding
Probable Causes
1.
2.
3.
4.
5.
6.
Too much voltage
Not enought slope or inductance.
(Too flat of a slope)
Too high of a gas flow
Contact tube recessed too far inside
nozzle
Wrong electrode wire
Wrong welding technique
Suggested Remedy
Reduce voltage
Increase slope or inductance as needed.
(Add more droop)
Reduce flow rate as required
Use longer contact tube
Use correct electrode wire
Use proper technique
29
Problem 6: Weld bead appearance shows a need for more amperage
and/or larger bead
Probable Causes
1. Volt-amp (wire feed speed) condition
too low
2. Too much slope
3. Wire feed speed too slow
Suggested Remedy
Increase voltage and wire feed speed
slowly
Decrease slope (Find a flatter Volt/Amp
curve)
Increase wire feed speed
Problem 7: Weld bead appearance shows a need for less amperage
and/or smaller bead
Probable Causes
1. Volt-amp (wire feed speed) condition
too high
2. Not enought slope
30
Suggested Remedy
Reduce voltage and wire feed speed slowly
Increase slope. (Find a slope with more
droop)