Rival multiprocess 175 Operating Manual
Multiprocess 175
Operating Manual
03
EN
Multiprocess 175. Operating manual.
Important Notice: This document has been prepared by Ryval, as general information and does not contain and is not to be taken as containing any specific 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 Ryval believes it to
be reliable as at the time of printing, Ryval 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 Ryval
nor any of its agents has independently verified the accuracy of the information contained in this document. The information in this document is commercial in confidence 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, Ryval and its affiliates, 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)
suffered 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 Ryval or
their respective agents liable in any such respect for the provision of this document or any other information.
Congratulations on purchasing the Ryval Multiprocess 175 welding
machine. The products in Ryval’s manual metal arc range perform
with reliability and have the backing of one of the world’s leading
suppliers of welding products.
This operating manual provides the basic knowledge required for the
Multiprocess 175 welding machine.
For more information or support please contact your local Ryval supplier.
Welcome to a better way of welding.
04 05
EN
Multiprocess 175. Operating manual.Multiprocess 175. Operating manual.
Contents.
Page
03 Welcome to a better way of welding
06 1. Recommended safety precautions
1.1 Health hazard information
1.2 Personal protection
1.3 Cylinder safety
1.4 Electrical shock
1.5 User responsibility
08 2. Metal Inert Gas & Metal Active Gas
arc welding (MIG/MAG)
2.1 Introduction to Metal Inert Gas (MIG)
& Metal Active Gas (MAG)
2.2 Introduction to Flux-Cored Arc Welding (FCAW)
2.3 Introduction to Metal-Cored Arc Welding (MCAW)
2.4 Modes of metal transfer
2.5 Fundamentals of MIG/MAG, FCAW and MCAW
15 3. Gas Tungsten Arc Welding (GTAW/TIG)
3.1 Introduction
3.2 Process
3.3 Process variables
3.4 Shielding gas selection
3.5 Consumable selection
3.6 Non-consumable tungstens –
tungsten electrode selector chart
Page
18 4. Manual Metal Arc Welding (MMAW)
4.1 Introduction
4.2 Process
4.3 Welding machine
4.4 Welding technique
4.5 Electrode selection
4.6 Types of joints
21 5. General welding information
5.1 Recommended welding parameters for MIG/MAG
22 6. Package contents
23 7. Multiprocess 175 installation
7.1 Installation for MIG/MAG process
7.2 Installation for TIG setup
7.3 Installation for MMA process
25 8. Control panel
26 9. Multiprocess 175 operation
9.1 Starting up
9.2 Operation for MMA mode
9.3 Operation instruction under LIFT TIG mode
9.4 Data selection
9.5 Polarity selection
9.6 Operation instruction under MIG mode
Page
30 10. Technical specifications
31 11. Troubleshooting guide
11.1 TIG/MMA functions
11.2 MIG/MAG functions
35 12. Periodic maintenance
12.1 Daily maintenance
12.2 Regular power source maintenance
36 13. Warranty information
13.1 Terms of warranty
13.2 Limitations on warranty
13.3 Warranty period
13.4 Warranty repairs
37 14. Recommended safety guidelines
06 07
EN
Multiprocess 175. Operating manual.Multiprocess 175. Operating manual.
1. Recommended safety precautions.
Clothing
Suitable clothing must be worn to prevent excessive exposure to UV
radiation and sparks. An adjustable helmet, flameproof loose fitting
cotton clothing buttoned to the neck, protective leather gloves, spats,
apron and steel capped safety boots are highly recommended.
Recommended filter shades for arc welding
Less than 150 amps
150 to 250 amps
250 tp 300 amps
300 to 350 amps
Over 350 amps
Shade 10*
Shade 11*
Shade 12
Shade 13
Shade 14
* Use one shade darker for aluminium
1.3 Cylinder safety
1
Cylinder valve hand-wheel, 2 Back-plug, 3 Bursting disc
Operator wearing personal
protective equipment (PPE)
in safe position
Backview of typical
cylinder valve
1
2
3
Ten points about cylinder safety
1. Read labels and Material Safety Data Sheet (MSDS) before use.
2. Store upright and use in well ventilated, secure areas away from
pedestrian or vehicle thoroughfare.
3. Guard cylinders against being knocked violently or being allowed to
fall.
4. Wear safety shoes, glasses and gloves when handling and connecting
cylinders.
5. Always move cylinders securely with an appropriate trolley. Take care
not to turn the valve on when moving a cylinder.
6. Keep in a cool, well-ventilated area, away from heat sources, sources
of ignition and combus tible materials, especially flammable gases.
7. Keep full and empty cylinders separate.
8. Keep ammonia-based leak detection solutions, oil and grease away
from cylinders and valves.
9. Never use force when opening or closing valves.
10. Don’t repaint or disguise markings and damage. If damaged, return
cylinders to Ryval immediately.
Cylinder valve safety
When working with cylinders or operating cylinder valves, ensure that
you wear appropriate protective clothing – gloves, boots and safety
glasses. When moving cylinders, ensure that the valve is not accidentally
opened in transit.
Before operating a cylinder valve:
→ Ensure that the system you are connecting the cylinder into is
suitable for the gas and pressure involved.
→ 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 flail 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 backplug is loose or a bursting disc vents. The correct stance is shown in
the diagram.
When operating the cylinder valve:
→ 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 fluid as this can damage the valve. Approved
leak detection fluid can be obtained from your Ryval supplier.
→ When finished 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 Ryval and arrange for the
cylinder to be returned to Ryval.
1.4 Electrical shock
→ Never touch ‘live’ electrical parts
→ Always repair or replace worn or damaged parts
→ Disconnect the 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 floor where possible
→ Never hold the electrode and holder under your arm.
1.5 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 qualified personnel
approved by Ryval 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.
PLEASE NOTE that under no circumstances should any equipment or
parts be altered or changed in any way from the standard specification
without written permission given by Ryval. To do so, will void the
Equipment Warranty.
1.1 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 ultraviolet 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.
1.2 Personal protection
Respiratory
Confined space welding should be carried out with the aid of a fume
respirator or air supplied respirator.
→ You must always have enough ventilation in confined 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 effect
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 filter lens for the
operation must be worn at all times in the work environment. The
welding arc and the reflecting arc flash gives out ultraviolet and infrared
rays. Protective welding screen and goggles should be provided for
others working in the same area.
08 09
EN
Multiprocess 175. Operating manual.Multiprocess 175. Operating manual.
2. Metal Inert Gas & Metal Active Gas arc
welding (MIG/MAG).
→ Argon with oxygen mixtures (MAG)
→ Argon with helium mixtures (MIG)
Each gas or gas mixture has specific advantages and limitations. Other
forms of MIG/MAG welding include using a flux-cored continuous
electrode and carbon dioxide shielding gas, or using self-shielding fluxcored wire, requiring no shielding.
2.2 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 filler wire and the workpiece, melting both
the filler 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 differences.
As with MIG/MAG, direct current power sources with constant voltage
output characteristics are normally employed to supply the welding
current. With flux-cored wires the terminal that the filler wire is
connected to depends on the specific 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 effect on
the quality of the welds produced.
2.1 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 semiautomatic 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 filler 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, flux-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)
The wire feed unit takes the filler 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 fluxcored wires to assist feeding and to prevent crushing the consumable.
Unlike MIG/MAG, which uses a solid consumable filler wire, the
consumable used in FCAW is of tubular construction, an outer metal
sheath being filled with fluxing agents plus metal powder. The flux fill
is also used to provide alloying, arc stability, slag cover, de-oxidisation,
and, with some wires, gas shielding.
In terms of gas shielding, there are two different 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 fluxing agents
within the wire, self-shielding
Gas shielded wires are available with either a basic or rutile flux fill,
while self-shielded wires have a broadly basic-type flux fill. The flux
fill 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 flux-cored wire the metal sheath is generally thinner than that of a
self-shielded wire. The area of this metal sheath surrounding the fluxcored wire is much smaller than that of a solid MIG/MAG wire. This
means that the electrical resistance within the flux-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 fluxed 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 flux-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 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, effectively increasing the amount of
wire being pushed into the weld pool to make the weld. It is this affect
that produces the ‘higher deposition rates’ that the flux-cored wire
manufacturers claim for this type of product. Unfortunately in many
instances the welder has difficulty 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
flux-cored arc welding than with solid wire MIG/MAG welding and this
Typical MIG/MAG set up
1
Torch, 2 Torch trigger, 3 Shroud, 4 Gas diffuser, 5 Contact tip, 6 Welding wire,
7
Shielding, 8 Weld, 9 Droplets, 10 Weld pool
1
2
3
4
5
6
7
9
10
8
Extended self shielded flux-cored wire nozzle
EN
Multiprocess 175. Operating manual.Multiprocess 175. Operating manual. 1110
also has the effect 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 affect the quality
of the weld.
Flux-cored arc welding has a lower efficiency than solid wire MIG/
MAG welding because part of the wire fill contains slag forming agents.
Although the efficiency varies 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
flux fill. These types of wire are referred to as ‘self-shielded’.
If no external gas shield is required, then the flux fill must provide
sufficient 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 suffer when compared with gas shielded types.
Wire efficiencies 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.
2.3 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 filler wire and the workpiece, melting
both the filler 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 differences.
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 filler wire is connected
to depends on the specific 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 effect on the quality of the welds
produced.
The wire feed unit takes the filler 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 filler wire, the
consumable used in MCAW is of tubular construction, an outer metal
sheath being filled entirely with metal powder except for a small amount
of non-metallic compounds. These are added to provide some arc
stability and de-oxidisation.
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 filler 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 diffuser distributes the shielding gas evenly
around a shroud which then allows the gas to flow 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.
2.4 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 flux fill, 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 flux-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
sufficient to allow the arc to be re-established. This short-circuiting mode
of metal transfer effectively 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 difficult materials where heat input is critical. Each shortcircuit causes the current to rise and the metal fuses off the end of the
Process schematic diagram for MIG/MAG, FCAW and MCAW
1
Gas cylinder, 2 Gas hose, 3 Continous wire, 4 Wire feed unit, 5 Power cable, 6 Torch conduit, 7 Welding torch, 8 Arc, 9 Workpiece, 10 Earth clamp, 11 Return cable,
12
Power source
2
1
12
11
5
6
4
3
10
9
8
7
Schematic of dip transfer
1
Short circuit, 2 Necking, 3 Arc re-ignition, 4 Arc established, 5 Arc gap shortens,
6
Short circuit
Time
Short circuit cycle Arcing cycle
Current (A)
Voltage (V)
1 2 3 4 5 6
EN
Multiprocess 175. Operating manual.Multiprocess 175. Operating manual. 1312
Schematic of globular transfer
1
Large droplet, 2 Splatter, 3 Workpiece
Schematic of spray transfer
1
Gas shroud, 2 Wire, 3 Shielding gas, 4 Droplets, 5 Weld, 6 Workpiece
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.
Metal-cored wires transfer metal in dip mode at low currents just like
solid MIG/MAG wires. This transfer mode is used for all positional work
with these types of wire.
Globular transfer
Metal transfer is controlled by slow ejection resulting in large,
irregularly-shaped ‘globs’ falling into the weld pool under the action
of gravity. Carbon dioxide gas drops are dispersed haphazardly. With
argon-based gases, the drops are not as large and are transferred in
a more axial direction. There is a lot of spatter, especially in carbon
dioxide, resulting in greater wire consumption, poor penetration and
poor appearance. Globular transfer occurs between the dip and spray
ranges. This mode of transfer is not recommended for normal welding
applications and may be corrected when encountered by either
decreasing the arc voltage or increasing the amperage. Globular transfer
can take place with any electrode diameter.
Basic flux-cored wires tend to operate in a globular mode or in a
globular-spray transfer mode where larger than normal spray droplets
are propelled across the arc, but they never achieve a true spray
transfer mode. This transfer mode is sometimes referred to as non-axial
globular transfer.
Self-shielded flux-cored wires operate in a predominantly globular
transfer mode although at high currents the wire often ‘explodes’ across
the arc.
Spray transfer
In spray transfer, metal is projected by an electromagnetic force from
the wire tip in the form of a continuous stream of discrete droplets
approximately the same size as the wire diameter. High deposition
rates are possible and weld appearance and reliability are good. Most
metals can be welded, but the technique is limited generally to plate
thicknesses greater than 6mm. Spray transfer, due to the tendency of
the large weld pool to spill over, cannot normally be used for positional
welding. The main exception is aluminium and its alloys where, primarily
because of its low density and high thermal conductivity, spray transfer
in position can be carried out.
The current flows continuously because of the high voltage maintaining
a long arc and short-circuiting cannot take place. It occurs best with
argon-based gases.
In solid wire MIG/MAG, as the current is increased, dip transfer passes
into spray transfer via a transitional globular transfer mode. With metalcored wires there is virtually a direct transition from dip transfer to spray
transfer as the current is increased.
For metal-cored wires, spray transfer occurs as the current density
increases and an arc is formed at the end of the filler wire, producing
a stream of small metal droplets. Often the outside sheath of the wire
will melt first and the powder in the centre flows as a stream of smaller
droplets into the weld pool. This effect seems to give much better
transfer of alloying elements into the weld.
In spray transfer, as the current density increases, an arc is formed at
the end of the filler wire, producing a stream of small metal droplets. In
solid wire MIG/MAG this transfer mode occurs at higher currents. Fluxcored wires do not achieve a completely true spray transfer mode but a
transfer mode that is almost true spray may occur at higher currents and
can occur at relatively low currents depending on the composition of the
flux.
Rutile flux-cored wires will operate in this almost-spray transfer mode, at
all practicable current levels. They are also able to operate in this mode
for positional welding too. Basic flux-cored and self-shielded flux-cored
wires do not operate in anything approaching true spray transfer mode.
Pulsed transfer
Pulsed arc welding is a controlled method of spray transfer, using
currents lower than those possible with the spray transfer technique,
thereby extending the applications of MIG/MAG welding into the range
of material thickness where dip transfer is not entirely suitable.The
pulsed arc equipment effectively combines two power sources into one
integrated unit. One side of the power source supplies a background
current which keeps the tip of the wire molten. The other side produces
pulses of a higher current that detach and accelerate the droplets of
metal into the weld pool. The transfer frequency of these droplets is
regulated primarily by the relationship between the two currents. Pulsed
arc welding occurs between ±50-220A, 23–35 arc volts and only with
argon and argon-based gases. It enables welding to be carried out in all
positions.
2.5 Fundamentals of MIG/MAG, FCAW and MCAW
Welding technique
Successful welding depends on the following factors:
1. Selection of correct consumables
2. Selection of the correct power source
3. Selection of the correct polarity on the power source
4. Selection of the correct shielding gas
5. Selection of the correct application techniques
a Correct angle of electrode to work
b Correct electrical stickout
c Correct travel speed
6. Selection of the welding preparation
Selection of correct consumable
Chemical composition
As a general rule the selection of a wire is straightforward, in that it
is only a matter of selecting an electrode of similar composition to
the parent material. It will be found, however, that there are certain
applications where electrodes will be selected on the basis of their
mechanical properties or level of residual hydrogen in the weldmetal.
Solid MIG/MAG wires are all considered to be of the ‘low Hydrogen type’
consumables.
Physical condition
Surface condition
The welding wire must be free from any surface contamination including
mechanical damage such as scratch marks.
A simple test for checking the surface condition is to run the wire
through a cloth that has been dampened with acetone for 20 secs. If a
black residue is found on the cloth the surface of the wire is not properly
cleaned.
1
2
3
1
2
3
4
5
6
Typical metal transfer mode
Process
Metal Inert Gas (MIG)
Metal Active Gas (MAG)
Flux-Cored (Gas Shielded)
Flux-Cored (Self Shielded)
Metal-Cored
Dip
transfer
Yes
Yes
Yes
Yes
Globular
transfer
No
Yes
Yes
No
Spray
transfer
Yes
Yes*
No
Yes
* Not true spray
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