Linde BOC RAPTOR 200 MIG User manual

200 MIG
Operating Manual
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Welcome to a better way of welding
Congratulations on puchasing the Raptor 200 MIG weldingmachine.
The products in BOC's manual MIG range perform with reliability and have the
backing of one of South Pacic's leading welding suppliers.
This operating manual provides the basic knowledge required for MP welding,
aswell as highlighting important areas of how to operate the Raptor machine.
With normal use, and by following these recommended steps, your
Raptor machine can provide you with years of trouble-free service.
Raptor equipment and technical support is available through the national
BOCCustomer Engagement Centre or contact your local Gas & Gear outlet.
Important Notice: This document has been prepared by BOC
Limited ABN 95 000 029 729 ('BOC'), as general information and
does not contain and is not to be taken as containing any specic
instructions. Thedocument has been prepared in good faith and is
professional opinion only. Information in this document has been
derived from third parties, and though BOC believes it to be reliable
as at the time of printing, BOC makes no representation or warranty
as to the accuracy, reliability or completeness of information in this
document and does not assume any responsibility for updating any
information or correcting any error or omission which may become
apparent after the document has been issued. Neither BOC nor
any of its agents has independently veried the accuracy of the
information contained in this document. The information in this
document is commercial in condence and is not to be reproduced.
The recipient acknowledges and agrees that it must make its own
independent investigation and should consider seeking appropriate
professional recommendation in reviewing and evaluating
the information. This document does not take into account the
particular circumstances of the recipient and the recipient should
not rely on this document in making any decisions, including but not
limited to business, safety or other operations decisions.
Except insofar as liability under any statute cannot be excluded,
BOC and its a󹟾liates, directors, employees, contractors and
consultants do not accept any liability (whether arising in contract,
tort or otherwise) for any error or omission in this document
or for any resulting loss or damage (whether direct, indirect,
consequential or otherwise) su󹟽ered by the recipient of this
document or any other person relying on the information contained
herein. The recipient agrees that it shall not seek to sue or hold
BOC or their respective agents liable in any such respect for the
provision of this document or any other information.

3
1.0 Recommended Safety Guidelines 4
2.0 Recommended Safety Precautions 5
2.1 Health Hazard Information 5
2.2 Personal Protection 5
2.3 Cylinder Safety 6
2.4 Electrical Shock 7
2.5 User Responsibility 7
Switch on to electrical safety 8
3.0 Package Contents 11
3.0 Control panel 12
4.0 Installation 13
4.1 Installation for MIG/MAG process 13
5.0 Machine Specifications 14
6.0 MIG/MAG Welding Process 15
6.1 Introduction to Metal Inert Gas(MIG)
& Metal Active Gas (MAG) 15
6.2 Introduction to Flux Cored Arc Welding
(FCAW) 16
6.3 Introduction to Metal Cored Arc
Welding(MCAW) 18
6.4 Modes of metal transfer 20
6.5 Fundamentals of MIG/MAG, FCAW
and MCAW 22
6.6 4T/2T Trigger Latch Selection 24
6.7 Recommended Welding Parameters
forMIG/MAG 25
6.8 Correct Application Techniques 26
7.0 Periodic Maintenance 28
7.1 Power Source 28
8.0 Troubleshooting and Fault Finding 29
9.0 Warranty Information 30
9.1 Terms of Warranty 30
9.2 Limitations on Warranty 30
9.3 Warranty Period 30
9.4 Warranty Replacement 30
Contents

4
• Repair or replace defective cables immediately.
• Never watch the arc except through
lenses of the correct shade.
• In conned spaces, adequate ventilation and
constant observation are essential.
• Leads and cables should be kept clear
of passageways.
• Keep re extinguishing equipment at a handy
location in the shop.
• Keep primary terminals and live parts e󹟽ectively
covered.
• Never strike an electrode on any gas cylinder.
• Never use oxygen for venting containers.
1.0 Recommended Safety Guidelines
Diagram and safety explanation
Electrical safety alert
Welding electrode causing
electric shock
Fumes and gases coming from
welding process
Welding arc rays
Read instruction manual
Become trained
Diagram and safety explanation
Wear dry, insulated gloves
Insulate yourself from
work and ground
Disconnect input power before
working on equipment
Keep head out of fumes
Use forced ventilation or local
exhaust to remove fumes
Use welding helmet with
correct shade of lter
Some safety precautions BOC recommends are as follows:

5
2.1 Health Hazard Information
The actual process of welding is one that
can cause a variety of hazards. All appropriate
safety equipment should be worn at all times, i.e.
headwear, respiratory, hand and body protection.
Electrical equipment should be used in accordance
with the manufacturer’s recommendations.
Eyes
The process produces ultra violet rays that can
injure and cause permanent damage. Fumes can
cause irritation.
Skin
Arc rays are dangerous to uncoveredskin.
Inhalation
Welding fumes and gases are dangerous to the
health of the operator and to those in close
proximity. The aggravation of pre-existing
respiratory or allergic conditions may occur in some
workers. Excessive exposure may cause conditions
such as nausea, dizziness, dryness and irritation of
eyes, nose andthroat.
2.2 Personal Protection
Respiratory
Conned space welding should be carried out
with the aid of a fume respirator or air supplied
respirator as per AS/NZS 1715 and AS/NZS 1716
Standards.
• You must always have enough ventilation in
conned spaces. Be alert to this at all times.
• Keep your head out of the fumes rising from
thearc.
• Fumes from the welding of some metals could
have an adverse e󹟽ect on your health. Don’t
breathe them in. If you are welding on material
such as stainless steel, nickel, nickel alloys
or galvanised steel, further precautions are
necessary.
• Wear a respirator when natural or forced
ventilation is not good enough.
Eye protection
A welding helmet with the appropriate welding
lter lens for the operation must be worn at all
times in the work environment. The welding arc
and the reecting arc ash gives out ultraviolet
and infrared rays. Protective welding screen and
goggles should be provided for others working in
the same area.
Recommended filter shades for arc welding
Less than 150 amps Shade 10*
150 to 250 amps Shade 11*
250 to 300 amps Shade 12
300 to 350 amps Shade 13
Over 350 amps Shade 14
*Use one shade darker for aluminium
Clothing
Suitable clothing must be worn to prevent
excessive exposure to UV radiation and sparks. An
adjustable helmet, ameproof loose tting cotton
clothing buttoned to the neck, protective leather
gloves, spats, apron and steel capped safety boots
are highly recommended.
2.0 Recommended Safety Precautions

6
2.3 Cylinder Safety
1Cylinder valve hand-wheel
2Back-plug
3Bursting disc
Back view of typical
cylinder valve
1
2
3
Operator wearing personal
protective equipment
(PPE) in safe position
Ten Points about Cylinder Safety
1Always read the labels and Safety Data Sheet
(SDS) before use.
2Store cylinders upright and use in
well-ventilated, secure areas away from
pedestrian or vehicle thoroughfares.
3Ensure cylinders are appropriately secured
and guarded against being knocked violently
or being allowed to fall.
4Wear safety shoes, glasses and gloves when
handling, connecting and using cylinders.
5Ensure cylinders are appropriately restrained
to mechanical lifting/handling devices prior
to movement.
6Keep in a cool, well-ventilated area, away
from heat sources, sources of ignition and
combustible materials, especially ammable
gases.
7Keep full and empty cylinders separate.
8Keep ammonia-based leak detection
solutions, oil and grease away from cylinders
and valves.
9Never use force when opening or closing
valves.
10 Never repaint or disguise markings and
damage on cylinders. If damaged, return
cylinders to BOC immediately.
Cylinder Valve Safety
When working with cylinders or operating
cylinder valves, ensure that you wear appropriate
protective clothing – gloves, boots and safety
glasses.
Ensure cylinder value is closed before moving or
disconnecting equipment.
Before operating a cylinder valve:
Ensure that the system you are connecting the
cylinder into is suitable for the gas and pressure
involved.
Cylinder valves should not be open unless a
pressure regulator has been tted.
Ensure that any accessories (such as hoses
attached to the cylinder valve, or the system being
connected to) are securely connected. Ahose, for
example, can potentially ail around dangerously
if it is accidentally pressurised when not restrained
at both ends.
Stand to the side of the cylinder so that neither
you nor anyone else is in line with the back of
the cylinder valve. This is in case a back-plug is
loose or a bursting disc vents. The correct stance is
shown in the diagram above.
When operating the cylindervalve
Open it by hand by turning the valve hand-wheel
anti-clockwise. Use only reasonable force.
Ensure that no gas is leaking from the cylinder
valve connection or the system to which the
cylinder is connected. DO NOT use ammonia-
based leak detection uid as this can damage
the valve. Approved leak detection uid, can be
obtained from a BOC Gas & Gear centre.
When nished with the cylinder, close the cylinder
valve by hand by turning the valve hand-wheel in
a clockwise direction. Use only reasonable force.
Remember NEVER tamper with thevalve. If
you suspect the valve is damaged, DONOT
use it. Report the issue to BOC and arrange
for the cylinderto be returned to BOC.

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2.4 Electrical Shock
• Never touch ‘live’ electrical parts.
• Always repair or replace worn or damagedparts.
• Disconnect power source before performingany
maintenance or service.
• Earth all work materials.
• Never work in moist or damp areas.
Avoid electric shock by
• Wearing dry insulated boots
• Wearing dry leather gloves
• Never changing electrodes with bare
handsorwet gloves
• Never cooling electrode holders in water
• Working on a dry insulated oor where possible
• Never hold the electrode and holder under
yourarm.
2.5 User Responsibility
• Read the Operating Manual prior to installation of
this machine.
• Unauthorised repairs to this equipment may
endanger the technician and operator and will
void your warranty. Only qualied personnel
approved by BOC should perform repairs.
• Always disconnect mains power before
investigating equipment malfunctions.
• Parts that are broken, damaged, missing or worn
should be replaced immediately.
• Equipment should be cleaned periodically.
BOC stocks a huge range of personal protective
equipment. This, combined with BOC’s extensive
Gas and Gear network, ensures fast, reliable
service throughout the South Pacic.
PLEASE NOTE that under no circumstances should
any equipment or parts be altered or changed in
any way from the standard specication without
written permission given by BOC. To do so, will void
the EquipmentWarranty.
Further information can be obtained from
Weld Australia (WTIA) Technical Note No.7
‘Health and Safety Welding’
Published by Weld Australia,
PO Box 6165 Silverwater NSW 2128
Phone [phone].
STOP

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BOC welding machines are designed and manufactured to conform
to IEC 60974 or AS 60974. This Standard not only covers themachine
but also the input cable and plug requirements including the size of
theplug that should be used.
X
Rated duty cycle
I0
Rated no-load
supply current
I1
Rated
supply current
AS 60974-1
Formula in clause 3.33
Maximum effective supply current
I1eff = √I12× X + I02(1-X)
The I1e󹟽 determines thecorrect plug, input cable
andinput current required for each machine.
10A
I1eff ≤
I1eff ≤
I1eff ≤
I1eff ≤
1. 5 – 2 . 5 m m 2
min –max cable size
size must be indicated
on the cable
15A 1. 5 – 4 m m 2
25A 2 . 5 – 6 m m 2
32A 4 – 10 m m 2
Before operating your welding machine, follow the instructions in the operating
manual. For more information refer to WTIA TN 22 – Welding Electrical Safety (Revised
2003) and WTIA TN 07 Health &Safety in Welding. If you have any queries please
contact BOC 131 262 (AU), 1800 111 333 (NZ).
Remember…
Switch on to
electrical safety
for single-phase equipment

9
DO
Example
How important is the correct input cable and
plug on a welding machine?
The size of the plug depends on a formula that
not only uses the maximum current draw but
also the duty cycle of the power source. Theuse
of any welding power source will not only cause
the machine itself to heat up, but the input cable,
plug and mains power circuit will increase in
temperature as well. That’s why it’s important
to understand input and output currents and to
make sure that the input circuit is correctly rated
to supply the required input draw. Thisallows the
machine to operate at or near maximum output
and protects the circuit board from tripping,
overheating and/or catchingre.
Foryour safety, BOC meets AS/NZS Standards
for safe electricalcompliance.
Regulatory Compliance Mark
(RCM) andnumber
All BOC welding machines undergo an independent
certication process to meet Australian and New
Zealand regulations regarding electrical safety.
The triangle-circle-tick (RCM) symbol signies
that BOC has taken the necessary steps to have
the product comply with the electrical safety
and/or electromagnetic compatibility (EMC)
legislative requirements as specied by the
Electrical Regulatory Authorities Council (ERAC).
Depending on the machine, BOC may be required
to have a 32A single phase plug to ensure that
when the machine runs at its maximum output, the
input supply plug and lead will not overheat. For
your safety, please check for this symbol before
buying any welding machine in Australia and
NewZealand.
✓ Use the correct input current, ✓ cable and
✓ plug in accordance with AS60974-1 for your
safety and to get the maximum performance
from your welding machine.
If the I1e󹠢 rating on your machine is 27A
then you must use a 32A plug as a 15A
is undersized for the welding current
being used and may cause the cable to
overheat.

10
Always
DON‘T
Example of BOC rating plate
Check the rating plate onyourmachine.
All welding machines that comply with IEC 60974
or AS 60974 must have a rating plate similar to the
one shown. Welding machines draw some current
when idle (not welding) and a higher current
when welding. E󹟽ective rated primary current
(I1e󹟽 ) combines the conductor heating due to
these two levels of current. I1e󹟽 is the maximum
rated e󹟽ective supply current that determines
the minimum plug and input cable rating as well
as the minimum capacity of the input circuit that
the machine gets plugged into to safely operate
the machine. Look for the I1e󹟽 on the welding
machine’s rating plate and ensure that you have
the correct input circuit to support this powerdraw.
What if I don’t have a 240volt 15amp or
32 ampoutlet?
If you don’t have a suitable power outlet, you
should contact a qualied electrician to advise
whether the wiring in your building will cater for
a 15 amp or 32 amp outlet. You mayalso need
to upgrade your circuit breakers and possibly
switchboard to suit. Failure to do this may cause
an electrical re in the building which may
voidinsurances.
✖ Don’t risk damage to your machine or cause
tripping and/or re by using the wrong
input current, cable orplug.
✖ Don’t tamper with plugs or ledown earth
pins. Doing so willvoidwarranty.
✓ Inspect cables and plugs regularly.
✓ Contact a qualied electrician for advice
and/or upgrade and, if needed, to replace
any damaged plugs orcables.
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11
3.0 Package Contents
Package consists ofthe following:
• Power source with input cable 2.5m and plug
• Binzel-style MB15KD MIG torch 3m
• Argon regulator
• Work return lead 1.8m
• Gas hose with quick release
• Wire feed rollers - V Groove 0.6-1.0
• Operating manual

12
3.0 Control panel
Function
1Voltage input (machine is on)
2Over temperature / fault
3Amperage output (Machine operating)
4Wire feed speed
5Voltage
6Spot timer
72T / 4T / Spot welding
1 2 3 7
4 65
Front panel of Raptor 200 MIG

13
4.1 Installation for MIG/MAG process
1. Connect the gas hose to the regulator and the
rear of the machine. Select correct shielding gas
for the application.
2. Insert the work return lead connection into the
front panel.
3. Select correct welding wire for application.
Fitthe wire spool to the machine.
4. Select the appropriate feed roller to suit the
wire being used.
5. Loosen the wire feed tension screws and insert
the wire. Re t and tension rollers ensuring the
wire is gripped su󹟾ciently so as not to slip but
avoid over tightening as this can a󹟽ect feed
quality and cause wire feed components to
wear rapidly.
6. Fit and tighten the torch on the output
connection. Ensure correct torch liner and
contact tip are selected.
7. Select the correct polarity for the type of
wire used as indicated on the consumable
packaging. This is achieved by swapping the
lead on the front of the machine (A). Formost
solid wires the terminal should be set as torch
positive (DCEP). Therefore the work return lead
should be connected to the negative terminal.
8. For torch negative (DCEN), the opposite to point
7 with the work return lead coupled to the
positive terminal.
4.0 Installation
DCEP DCEN
Installation for MIG/MAG process Polarity change for MIG/MAG process
IMPORTANT
Please ensure that all power to machine is
turned o󹠢 during installation process and
when changing torches/leads.

14
5.0 Machine Specifications
BOC RAPTOR200 MIG
Part No. RAPTOR200MIG
Input voltage Single phase AC 240V ±15%
Frequency 50 /60 Hz
Rated input plug 15 A
Maximum rated input current (I1max) 35 A
Maximum e󹠢ective supply current (I1e󹠢) 13.6 A
Output current adjustment range 200 A
Output voltage 15.5–24 V
Duty cycle @ 15% 200 A
Type of wirefeeder machine Internal
Welding-wire diameter 0.6-1.0 mm
Wire feed speed 2–10 m/min
Protection grade IP21S
Weight without wire (kg) 11 kg
Dimensions (L x W x H) 441x 195x 272 mm
Recommended generator rating 12 kVA
Standards AS/NZS 60974-1 IEC/EN60974-10

15
6.1 Introduction to Metal Inert Gas(MIG)
&MetalActive Gas (MAG)
MIG/MAG welding embraces a group of arc welding
processes in which a continuous electrode (the
wire) is fed by powered feed rolls (wire feeder)
into the weld pool. An electric arc is created
between the tip of the wire and the weld pool. The
wire is progressively melted at the same speed at
which it is being fed and forms part of the weld
pool. Both the arc and the weld pool are protected
from atmospheric contamination by a shield of
inert (non-reactive) gas, which is delivered through
a nozzle that is concentric with the welding wire
guide tube.
Operation
MIG/MAG welding is usually carried out with a
handheld torch as a semi-automatic process. The
MIG/MAG process can be suited to a variety of job
requirements by choosing the correct shielding
gas, electrode (wire) size and welding parameters.
Welding parameters include the voltage, travel
speed, arc (stick-out) length and wire feed rate.
The arc voltage and wire feed rate will determine
the ller metal transfer method.
This application combines the advantages of
continuity, speed, comparative freedom from
distortion and the reliability of automatic welding
with the versatility and control of manual welding.
The process is also suitable for mechanised set-
ups, and its use in this respect isincreasing.
MIG/MAG welding can be carried out using solid
wire, ux cored, or a copper-coated solid wire
electrode. The shielding gas or gas mixture may
consist of the following:
• Argon (MIG)
• Carbon dioxide (MAG)
• Argon and carbon dioxide mixtures (MAG)
• Argon with oxygen mixtures (MAG)
• Argon with helium mixtures (MIG)
Each gas or gas mixture has specic advantages
and limitations. Other forms of MIG/MAG welding
include using a ux-cored continuous electrode
and carbon dioxide shielding gas, or using self-
shielding ux-cored wire, requiring no shielding.
6.0 MIG/MAG Welding Process
Extended self shielded flux cored wire nozzle
Typical MIG/MAG set up
Torch trigger
Welding wire
Weld
Weld pool
Torch
Shroud
Gas di󹠢user
Contact tip
Shielding
Droplets

16
6.2 Introduction to Flux Cored Arc
Welding (FCAW)
How it Works
Flux-cored arc welding (FCAW) uses the heat
generated by a DC electric arc to fuse the metal
in the joint area, the arc being struck between a
continuously fed consumable ller wire and the
workpiece, melting both the ller wire and the
workpiece in the immediate vicinity. Theentire arc
area is covered by a shielding gas, which protects
the molten weld pool from the atmosphere.
FCAW is a variant of the MIG/MAG process and
while there are many common features between
the two processes, there are also several
fundamental di󹟽erences.
As with MIG/MAG, direct current power sources
with constant voltage output characteristics are
normally employed to supply the welding current.
With ux-cored wires the terminal that the ller
wire is connected to depends on the specic
product being used, some wires running electrode
positive, others running electrode negative. The
work return is then connected to the opposite
terminal. It has also been found that the output
characteristics of the power source can have an
e󹟽ect on the quality of the weldsproduced.
The wire feed unit takes the ller wire from a
spool, and feeds it through the welding torch,
to the arc at a predetermined and accurately
controlled speed. Normally, special knurled feed
rolls are used with ux-cored wires to assist
feeding and to prevent crushing theconsumable.
Unlike MIG/MAG, which uses a solid consumable
ller wire, the consumable used in FCAW is of
tubular construction, an outer metal sheath being
lled with uxing agents plus metal powder.
The ux ll is also used to provide alloying, arc
stability, slag cover, de-oxidation, and, with some
wires, gasshielding.
In terms of gas shielding, there are two di󹟽erent
ways in which this may be achieved with the FCAW
process.
• Additional gas-shielding supplied from an
external source, such as a gas cylinder
• Production of a shielding gas by decomposition
of uxing agents within the wire, self-shielding
Gas shielded wires are available with either a basic
or rutile ux ll, while self-shielded wires have a
broadly basic-type ux ll. The ux ll dictates the
way the wire performs, the properties obtainable,
and suitable applications.
Gas-shielded Operation
Many cored wire consumables require an auxiliary
gas shield in the same way that solid wire MIG/
MAG consumables do. These types of wire are
generally referred to as ‘gas-shielded’.
Using an auxiliary gas shield enables the wire
designer to concentrate on the performance
characteristics, process tolerance, positional
capabilities, and mechanical properties of
theproducts.
In a ux cored wire the metal sheath is generally
thinner than that of a self-shielded wire. The area
of this metal sheath surrounding the ux cored
wire is much smaller than that of a solid MIG/MAG
wire. This means that the electrical resistance
within the ux cored wire is higher than with solid
MIG/MAG wires and it is this higher electrical
resistance that gives this type of wire some of its
novel operatingproperties.
One often quoted property of uxed cored wires
are their higher deposition rates than solid MIG/
MAG wires. What is often not explained is how they
deliver these higher values and whether these
can be utilised. For example, if a solid MIG/MAG
wire is used at 250 amps, then exchanged for a
ux cored wire of the same diameter, and welding
power source controls are left unchanged, then
the current reading would be much less than 250
amps, perhaps as low as 220 amps. This is because

17
of Ohms Law that states that as the electrical
resistance increases if the voltage remains stable
then the current must fall.
To bring the welding current back to 250 amps
it is necessary to increase the wire feed speed,
e󹟽ectively increasing the amount of wire being
pushed into the weld pool to make the weld. It is
this a󹟽ect that produces the ‘higher deposition
rates’ that the ux cored wire manufacturers claim
for this type of product. Unfortunately in many
instances the welder has di󹟾culty in utilising this
higher wire feed speed and must either increase
the welding speed or increase the size of the weld.
Often in manual applications neither of these
changes can be implemented and the welder
simply reduces the wire feed speed back to where
it was and the advantages are lost. However, if the
process is automated in some way then the process
can show improvements inproductivity.
It is also common to use longer contact tip to
workplace distances with ux cored arc welding
than with solid wire MIG/MAG welding and this
also has the e󹟽ect of increasing the resistive
heating on the wire further accentuating the drop
in welding current. Research has also shown that
increasing this distance can lead to an increase in
the ingress of nitrogen and hydrogen into the weld
pool, which can a󹟽ect the quality of the weld.
Flux cored arc welding has a lower e󹟾ciency than
solid wire MIG/MAG welding because part of the
wire ll contains slag forming agents. Although
the e󹟾ciency varies di󹟽ers by wire type and
manufacturer it is typically between 75–85%.
Flux cored arc welding does, however, have the
same drawback as solid wire MIG/MAG in terms
of gas disruption by wind, and screening is always
necessary for site work. It also incurs the extra cost
of shielding gas, but this is often outweighed by
gains in productivity.
Self-shielded Operation
There are also self-shielded consumables designed
to operate without an additional gas shield. In this
type of product, arc shielding is provided by gases
generated by decomposition of some constituents
within the ux ll. These types of wire are referred
to as ‘self-shielded’.
If no external gas shield is required, then the
ux ll must provide su󹟾cient gas to protect the
molten pool and to provide de-oxidisers and nitride
formers to cope with atmospheric contamination.
This leaves less scope to address performance, arc
stabilisation, and process tolerance, so these tend
to su󹟽er when compared with gas shielded types.
Wire e󹟾ciencies are also lower, at about 65%, in
this mode of operation than with gas-shielded
wires. However, the wires do have a distinct
advantage when it comes to site work in terms of
wind tolerance, as there is no external gas shield
to be disrupted.
When using self-shielded wires, external gas
supply is not required and, therefore, the gas
shroud is not necessary. However, an extension
nozzle is often used to support and direct the long
electrode extensions that are needed to obtain
high deposition rates.

6.3 Introduction to Metal Cored Arc
Welding(MCAW)
How it Works
Metal-cored arc welding (MCAW) uses the heat
generated by a DC electric arc to fuse metal in
the joint area, the arc being struck between a
continuously fed consumable ller wire and the
workpiece, melting both the ller wire and the
workpiece in the immediate vicinity. The entire arc
area is covered by a shielding gas, which protects
the molten weld pool from the atmosphere.
As MCAW is a variant of the MIG/MAG welding
process there are many common features between
the two processes, but there are also several
fundamental di󹟽erences.
As with MIG/MAG, direct current power sources
with constant voltage output characteristics are
normally employed to supply the welding current.
With metal-cored wires the terminal the ller
wire is connected to depends on the specic
product being used, some wires designed to run
on electrode positive, others preferring electrode
negative, and some which will run on either. The
work return lead is then connected to the opposite
terminal. Electrode negative operation will usually
give better positional welding characteristics.
The output characteristics of the power source
can have an e󹟽ect on the quality of the welds
produced.
The wire feed unit takes the ller wire from a spool
or bulk pack, and feeds it through the welding
torch, to the arc at a predetermined and accurately
controlled speed. Normally, special knurled feed
rolls are used with metal-cored wires to assist
feeding and to prevent crushing the consumable.
Unlike MIG/MAG, which uses a solid consumable
ller wire, the consumable used in MCAW is
of tubular construction, an outer metal sheath
being lled entirely with metal powder except
for a small amount of non-metallic compounds.
These are added to provide some arc stability and
de-oxidation.
Gas hose
Gas cylinder
Power source
Return cable
Continuous wire
Wire feed unit
Power cable
Torch conduit
Welding torch
Workpiece
Arc
Earth clamp
Process Schematic Diagram for MIG/MAG, FCAW and MCAW

19
MCAW consumables always require an auxiliary
gas shield in the same way that solid MIG/MAG
wires do. Wires are normally designed to operate
in argon-carbon dioxide or argon-carbon dioxide-
oxygen mixtures or carbon dioxide. Argon rich
mixtures tend to produce lower fume levels than
carbon dioxide.
As with MIG/MAG, the consumable ller wire and
the shielding gas are directed into the arc area by
the welding torch. In the head of the torch, the
welding current is transferred to the wire by means
of a copper alloy contact tip, and a gas di󹟽user
distributes the shielding gas evenly around a
shroud which then allows the gas to ow over the
weld area. The position of the contact tip relative
to the gas shroud may be adjusted to limit the
minimum electrode extension.
Modes of metal transfer with MCAW are very
similar to those obtained in MIG/MAG welding,
the process being operable in both ‘dip transfer’
and ‘spray transfer’ modes. Metal-cored wires may
also be used in pulse transfer mode at low mean
currents, but this has not been widely exploited.
1 2 63 4 5
Time
Short circuit cycle Arcing cycle
Current (A)
Voltage (V)
1Short circuit
2Necking
3Arc re-ignition
4Arc established
5Arc gap shortens
6Short circuit
Schematic of Dip Transfer

20
6.4 Modes of metal transfer
The mode or type of metal transfer in MIG/MAG
and MCAW welding depends upon the current, arc
voltage, electrode diameter and type of shielding
gas used. In general, there are four modes of metal
transfer.
Modes of metal transfer with FCAW are similar to
those obtained in MIG/MAG welding, but here
the mode of transfer is heavily dependent on the
composition of the ux ll, as well as on current
and voltage.
The most common modes of transfer in FCAW are:
• Dip transfer
• Globular transfer
• Spray transfer
• Pulsed arc transfer operation has been applied
to ux-cored wires but, as yet, is not widely used
because the other transfer modes are giving
users what they require, in most cases.
Dip Transfer
Also known as short-circuiting arc or short-arc, this
is an all-positional process, using low heat input.
The use of relatively low current and arc voltage
settings cause the electrode to intermittently
short-circuit with the weld pool at a controlled
frequency. Metal is transferred by the wire tip
actually dipping into the weld pool and the short-
circuit current is su󹟾cient to allow the arc to be
re-established. This short-circuiting mode of metal
transfer e󹟽ectively extends the range of MIG/MAG
welding to lower currents so thin sheet material
can readily be welded. The low heat input makes
this technique well-suited to the positional welding
of root runs on thick plate, butt welds for bridging
over large gaps and for certain di󹟾cult materials
where heat input is critical. Each short-circuit
causes the current to rise and the metal fuses o󹟽
the end of the electrode. A high short-circuiting
frequency gives low heat input. Dip transfer occurs
between ±70-220A, 14–23 arc volts. It is achieved
using shielding gases based on carbon dioxide and
argon.
Large droplet Splatter
Workpiece
Gas shroud
Wire
Shielding gas
Droplets
Weld
Workpiece
Schematic of Globular Transfer Schematic of Spray Transfer