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CSWIP 3.1 Welding Inspection
TWI Training & Examination Services
Course Reference WIS 5Course Reference WIS 5
Gas Metal Arc Welding Gas Metal Arc Welding
Metal Inert GasMetal Inert Gas
Metal Active GasMetal Active Gas
The MIG/MAG welding process was initially developed in the
USA in the late 1940s for the welding of aluminum alloys.
The latest EN Welding Standards now refer the process by the
American term GMAW (Gas Metal Arc Welding)
• The process uses a continuously fed wire electrode
• The weld pool is protected by a separately supplied shielding gas
• The process is classified as a semi-automatic welding process but may be fully automated
• The wire electrode can be either bare/solid wire or flux cored hollow wire
Gas Metal Arc Welding
MIG/MAG - Principle of operation
Gas Metal Arc Welding
PROCESS CHARACTERISTICSPROCESS CHARACTERISTICS
• Requires a constant voltage power source, gas supply, wire
feeder, welding torch/gun and ‘hose package’
• Wire is fed continuously through the conduit and is burnt-off
at a rate that maintains a constant arc length/arc voltage
• Wire feed speed is directly related to burn-off rate
• Wire burn-off rate is directly related to current
• When the welder holds the welding gun the process is said to be a semi-automatic process
• The process can be mechanised and also automated
• In Europe the process is usually called MIG or MAG
Power return Power return
cablecable
Transformer/ Transformer/
RectifierRectifier
Power cable & Power cable &
hose hose
assemblyassembly
Liner for wireLiner for wire
Welding gun Welding gun
assemblyassembly
External wire External wire
feed unitfeed unit
Power control Power control
panelpanel
Internal wire Internal wire
feed systemfeed system
15kg wire spool15kg wire spool
Equipment for MIG/MAG
Plain top rollerPlain top roller
Half grooved Half grooved
bottom rollerbottom roller
Wire guideWire guide
Internal wire Internal wire
drive systemdrive system
MIG/MAG wire drive system
MIG/MAG wire drive system
Types of wire drive systems:
4 roll wire drive4 roll wire drive2 roll wire drive2 roll wire drive
MIG/MAG wire drive system
Types of drive rolls
••recommended for steel recommended for steel
wireswires
••recommended for softer recommended for softer
wires (aluminium)wires (aluminium)
MIG/MAG wire drive system
Close wound stainless steel
spring wire liner
Teflon liner
MIG/MAG welding gun types
Goose neck type
Push-pull type
Welding gun bodyWelding gun body
Contact tipsContact tips
Spot welding Spot welding
spacerspacer
Gas diffuserGas diffuser
Nozzles or Nozzles or
shroudsshrouds
Welding gun assembly Welding gun assembly
(less nozzle)(less nozzle)
On/Off switchOn/Off switch
Hose Hose
portport
MIG/MAG welding gun assembly
Spatter Spatter
protectionprotection
MIG/MAG welding gun assembly
The Push-Pull gun
HandleHandle
Gas Gas
nozzlenozzle
Contact Contact
tiptip
Gas Gas
diffuserdiffuser
TriggerTrigger WFS remote WFS remote
control control
potentiometerpotentiometer
Union nutUnion nut
ARC CHARACTERISTICS
Volts
Amps
OCV
Constant Voltage Characteristic
Small change in voltage = large change in amperage
The self adjusting arc.
Large arc gap
Small arc gap
O.C.V. Arc Voltage O.C.V. Arc Voltage
Virtually no Change. Virtually no Change.
VoltageVoltage
Flat or Constant Voltage Characteristic Used With Flat or Constant Voltage Characteristic Used With
MIG/MAG, ESW & SAW < 1000 ampsMIG/MAG, ESW & SAW < 1000 amps
100100 200200 300300
3333
3232
3131
Large Current ChangeLarge Current Change
Small Voltage Small Voltage
Change. Change.
AmperageAmperage
Flat or Constant Voltage Characteristic
Wire feed speed:Wire feed speed:
Increasing the wire feed speed automatically increases the current in the wire
Voltage:
The voltage is the most important setting in the spray transfer mode, as it controls the arc length. In dip transfer it controlsthe rise in current
Current: Current:
The current is automatically increased as the wire feed is increased. Current mainly affects penetration
MAG Welding Variable Parameters
Inductance:
• Applicable to MIG/MAG process in dip transfer mode.
• The electrode is fed slowly through the arc until it touches the
weld pool, at this point the output from the power supply is
short circuited and a very high current flows through the
electrode. If this was allowed to continue, the wire would melt
and eject excessive amounts of spatter.
• The inclusion or the choke in the welding circuit controls the
rate at which the current rises so that the electrode tip is
melted uniformly without excessive spatter
MAG Welding Variable Parameters
Shielding Gases: Shielding Gases:
The gasses used in MIG/MAG welding can be either 100% CO2
or Argon + CO2 mixes.
• 100% CO2: Can not sustain true spray transfer, but gives very good penetration. The arc is unstable which produces
a lot of spatter and a coarse weld profile.
• Argon + CO2 mixes: Argon can sustain spray transfer above 24 volts, and gives a very stable arc with a reduction in spatter. Argon being a cooler gas produces less penetration than CO2. Argon in normally mixed with CO2 at a mixture of between 5-25%
MAG Welding Variable Parameters
Gas Metal Arc Welding
MODES OF METAL TRANSFERMODES OF METAL TRANSFER
The current and voltage settings determine the way molten The current and voltage settings determine the way molten
droplets of weld metal transfer from the tip of the wire to the droplets of weld metal transfer from the tip of the wire to the
weld poolweld pool
There are 3 principle modes of droplet transfer, namelyThere are 3 principle modes of droplet transfer, namely
••dip transfer (shortdip transfer (short--circuiting)circuiting)
••spray transferspray transfer
••pulsed transferpulsed transfer
Dip TransferDip Transfer: (Voltage < 22) / (Amperage < 200)
• Thin materials positional welding
Globular Transfer: Between Dip & Spray Transfer
• Limited commercial, Used only in some mechanised MAG process using CO2 shielding gas
Spray Transfer: (Voltage > 27) / (Amperage > 220)
• Thicker materials, limited to flat welding positions, high deposition
Pulse Transfer: Both spray and dip transfer in
• one mode of operation, frequency range 50-300 pulses/second
• Positional welding and root runs
Gas Metal Arc Welding
MIG/MAG - metal transfer modes
Current/voltage conditions
CurrentCurrent
VoltageVoltage
Dip transferDip transfer
Spray Spray
transfertransferGlobular Globular
transfertransfer
Electrode diameter = 1,2 mmElectrode diameter = 1,2 mm
WFS = 3,2 m/minWFS = 3,2 m/min
Current = 145 ACurrent = 145 A
Voltage = 18Voltage = 18--20V20V
Electrode diameter = 1,2 mmElectrode diameter = 1,2 mm
WFS = 8,3 m/minWFS = 8,3 m/min
Current = 295 ACurrent = 295 A
Voltage = 28VVoltage = 28V
Gas Metal Arc Welding
Dip TransferDip Transfer
• Dip transfer occurs when current & voltage settings are low
(typically < ~ 200amps & ~ 22volts)
• There is just enough energy to give an arc and cause fusion at the tip of the wire
• A droplet grows to a size larger than the wire diameter and eventually extinguishes the arc - causing a short-circuit
• The short circuit causes the current rises very quickly giving energy to violently ‘pinch-off’ the droplet
• This is akin to ‘blowing a fuse’ and causes spatter
• When the droplet detaches, the arc is re-established and the current
falls
• This cycle occurs at up to ~ 200 times per second
MIG/MAG-methods of metal transfer
Dip transferDip transfer
• Transfer occur due to short circuits between wire and weld pool, high level of spatter, need inductance control to limit current raise
• Can use pure CO2 or Ar- CO2
mixtures as shielding gas
• Metal transfer occur when arc is extinguished
• Requires low welding current/arc voltage, a low heat input process. Resulting in low residual stress and distortion
• Used for thin materials and all position welds
MIG/MAG - metal transfer modes
The pinch effect
CSA
CurrentPforcePinch
2
=
Gas Metal Arc Welding
Dip TransferDip Transfer
TransferTransfer--mode advantagesmode advantages
•• The low energy conditions allow welding in all positionsThe low energy conditions allow welding in all positions
•• It can be used for putting in the root run on singleIt can be used for putting in the root run on single--sided sided
weldswelds
•• It can be used for welding thin materialsIt can be used for welding thin materials
TransferTransfer--mode disadvantagesmode disadvantages
•• It frequently gives lack of fusion and may not be allowed in It frequently gives lack of fusion and may not be allowed in
semisemi--automatic mode for highautomatic mode for high--integrity applicationsintegrity applications
•• It tends to give spatterIt tends to give spatter
(this can be reduced/controlled by having an (this can be reduced/controlled by having an ‘‘inductanceinductance’’
control on the power source)control on the power source)
MIG/MAG-methods of metal transfer
Globular transfer Globular transfer
• Transfer occur due to gravity or short circuits between drops and weld pool
• Requires CO2 shielding gas
• Metal transfer occur in large drops (diameter larger than that of electrode) hence severe spatter
• Requires high welding current/arc voltage, a high heat input process. Resulting in high residual stress and distortion
• Non desired mode of transfer!
Gas Metal Arc Welding
Spray TransferSpray Transfer
When current & voltage are raised together higher energy is
available for fusion (typically > ~ 25 volts & ~ 250 amps)
This causes a fine droplets of weld metal to be ‘sprayed’ from the tip of the wire into the weld pool
Transfer-mode advantages
• High energy gives good fusion
• High rates of weld metal deposition are given
• These characteristics make it suitable for welding thicker
joints
• Transfer-mode disadvantages
• It cannot be used for positional welding
MIG/MAG-methods of metal transfer
Spray transfer Spray transfer
• Transfer occur due to pinch effect NO contact between wire and weld pool!
• Requires argon-rich shielding gas
• Metal transfer occur in small droplets, a large volume weld pool
• Requires high welding current/arc voltage, a high heat input process. Resulting in high residual stress and distortion
• Used for thick materials and flat/horizontal position welds
MIG/MAG-methods of metal transfer
Pulsed transferPulsed transfer
• Controlled metal transfer, one droplet per pulse,
• No transfer between droplet and weld pool!
• Requires special power sources
• Metal transfer occur in small droplets (diameter equal to
that of electrode)
• Requires moderate welding current/arc voltage, a reduced heat input . Resulting in smaller residual stress and distortion compared to spray transfer
• Pulse frequency controls the volume of weld pool, used for root runs and out of position welds
MIG/MAG - metal transfer modes
Pulsed transfer
• Controlled metal transfer � one droplet per pulse � NO transfer during
background current!
• Requires special power sources
• Metal transfer occur in small droplets
(diameter equal to that of electrode)
• Requires moderate welding current/arc voltage �reduced heat input � smaller residual stress and
distortions compared to spray transfer
• Pulse frequency controls the volume of weld pool � used
for root runs and out of position welds
MIG/MAG - metal transfer modes
Pulse current parameters
Time (sec)Time (sec)
Current (A)Current (A)
Peak Peak
currentcurrent
Background Background
currentcurrent
Transition Transition
currentcurrent
Average current Average current
(ammeter reading)(ammeter reading)
Gas Metal Arc Welding
Pulsed TransferPulsed Transfer
CurrentCurrent IIpp = peak current= peak current (spray transfer)(spray transfer)
IIbb = background current= background current (continuous arc but little or no fusion)(continuous arc but little or no fusion)
IIpp
IIbb
TTpp TTbb
TimeTimeTTpp = peak time= peak time
TTbb = background time= background time
MIG/MAG - metal transfer modes
Set-up for dip transfer Set-up for spray transfer
Electrode Electrode
extension extension
1919--25 mm25 mm
Contact tip Contact tip
recessed recessed
(3(3--5 mm)5 mm)
Contact tip Contact tip
extension extension
(0(0--3,2 mm)3,2 mm)
Electrode Electrode
extension extension
66--13 mm13 mm
MIG / MAG - self-regulating arc
Stable conditionStable condition
LL19 mm19 mm
Sudden change in gun positionSudden change in gun position
25 mm25 mmLL’’
Arc length L = 6,4 mmArc length L = 6,4 mm
Arc voltage = 24VArc voltage = 24V
Welding current = 250AWelding current = 250A
WFS = 6,4 m/minWFS = 6,4 m/min
Melt off rate = 6,4 m/minMelt off rate = 6,4 m/min
Arc length LArc length L’’ = 12,7 mm= 12,7 mm
Arc voltage = 29VArc voltage = 29V
Welding current = 220AWelding current = 220A
WFS = 6,4 m/minWFS = 6,4 m/min
Melt off rate = 5,6 m/minMelt off rate = 5,6 m/min
Current (A)Current (A)
Vo
lta
ge
(V
)V
olt
ag
e (
V)
MIG/MAG - self-regulating arc
Sudden change in gun positionSudden change in gun position
25 mm25 mmLL’’
Arc length LArc length L’’ = 12,7 mm= 12,7 mm
Arc voltage = 29VArc voltage = 29V
Welding current = 220AWelding current = 220A
WFS = 6,4 m/minWFS = 6,4 m/min
Melt off rate = 5,6 m/minMelt off rate = 5,6 m/min
Current (A)Current (A)
Vo
lta
ge
(V
)V
olt
ag
e (
V)
ReRe--established stable conditionestablished stable condition
25 mm25 mmLL
Arc length L = 6,4 mmArc length L = 6,4 mm
Arc voltage = 24VArc voltage = 24V
Welding current = 250AWelding current = 250A
WFS = 6,4 m/minWFS = 6,4 m/min
Melt off rate = 6,4 m/minMelt off rate = 6,4 m/min
The effect of inductance
Controls the rate of current rise
Time (sec)
Current (A)
Short circuit
current
No inductance
Inductance added
Excessive current, high
spatter
Desired current for
good stability, low
spatter
The effect of inductance
Maximum inductanceMaximum inductance Minimum inductanceMinimum inductance
••reduced spatterreduced spatter
••Hotter arc Hotter arc �������� more more
penetrationpenetration
••More fluid weld pool More fluid weld pool ��������
flatter and smoother weldflatter and smoother weld
••Recommended on thicker Recommended on thicker
materials and stainless materials and stainless
steelssteels
••Colder arc Colder arc �������� used only for used only for
arc stability when welding arc stability when welding
wide gapswide gaps
••ConvexConvex weld, more spatterweld, more spatter
••Improved weld pool controlImproved weld pool control
••Recommended on thin Recommended on thin
materialsmaterials
Terminating the arc
• Burnback time
– delayed current cut-off to prevent wire freeze in the
weld end crater
– depends on WFS (set as short as possible!)
Contact tipContact tip
WorkpieceWorkpiece
Burnback timeBurnback time 0,05 sec0,05 sec 0,10 sec0,10 sec 0,15 sec0,15 sec
14 mm 14 mm
8 mm 8 mm 3 mm 3 mm
Current Current -- 250A250A
Voltage Voltage -- 27V27V
WFS WFS -- 7,8 m/min7,8 m/min
Wire Wire diamdiam. . -- 1,2 mm1,2 mm
Shielding gas Shielding gas -- Ar+18%COAr+18%CO22
Insulating Insulating
slagslag
• Crater fill
MIG/MAG process variables
• Welding current
• Polarity
•Increasing welding current
•Increase in depth and width
•Increase in deposition rate
MIG/MAG process variables
• Arc voltage
• Travel speed
•Increasing travel speed
•Reduced penetration and width, undercut
•Increasing arc voltage
•Reduced penetration, increased width
•Excessive voltage can cause porosity,
spatter and undercut
Penetration Deep Moderate ShallowPenetration Deep Moderate Shallow
Excess weld metal Maximum Moderate MinimumExcess weld metal Maximum Moderate Minimum
Undercut Severe Moderate MinimumUndercut Severe Moderate Minimum
MIG/MAG process variables
Electrode orientation
• Electrode
extension
••Increased extensionIncreased extension
Gas Metal Arc Welding
Types of Shielding GasTypes of Shielding Gas
MIG (Metal Inert Gas)MIG (Metal Inert Gas)
•• Inert Gas is required for Inert Gas is required for all nonall non--ferrous alloysferrous alloys (Al, Cu, Ni)(Al, Cu, Ni)
•• Most common inert gas is ArgonMost common inert gas is Argon
•• Argon + Helium used to give a Argon + Helium used to give a ‘‘hotterhotter’’ arc arc -- better for thicker better for thicker
joints and alloys with higher thermal conductivityjoints and alloys with higher thermal conductivity
Gas Metal Arc Welding
Types of Shielding GasTypes of Shielding Gas
MAG (Metal Active Gas)
• Active gases used are Oxygen and Carbon Dioxide
• Argon with a small % of active gas is required for all steels (including stainless steels) to ensure a stable arc & good droplet
wetting into the weld pool
• Typical active gases areAr + 20% CO2 for C-Mn & low alloy steelsAr + 2% O2 for stainless steels100% CO2 can be used for C - steels
MIG/MAG – shielding gases
Type of materialType of material Shielding gasShielding gas
Carbon steelCarbon steel
Stainless steelStainless steel
AluminiumAluminium
COCO22 , Ar+(5, Ar+(5--20)%CO20)%CO22
Ar+2%OAr+2%O22
ArAr
Gas Metal Arc Welding
Pulsed TransferPulsed Transfer
TransferTransfer--mode advantagesmode advantages
•• Good fusionGood fusion
•• Small weld pool allows allSmall weld pool allows all--position weldingposition welding
TransferTransfer--mode disadvantagesmode disadvantages
•• More complex & expensive power sourceMore complex & expensive power source
•• Difficult to set parameters Difficult to set parameters -- requires power source requires power source
manufacturer to provide pulse programmes to suit wire type, manufacturer to provide pulse programmes to suit wire type,
dia. and type of gasdia. and type of gas
Gas Metal Arc Welding
Types of Filler WireTypes of Filler Wire
•• Filler wires have similar composition to the base materialFiller wires have similar composition to the base material
•• Wires can be solid, flux cored or metal coredWires can be solid, flux cored or metal cored
•• Flux cored wires are designed to run in spray mode and thereforeFlux cored wires are designed to run in spray mode and therefore they they
give good fusiongive good fusion
•• Flux cored wires cannot be used for root runs on unbacked jointsFlux cored wires cannot be used for root runs on unbacked joints
•• The slag formed from flux cored wire enables welding to be done The slag formed from flux cored wire enables welding to be done in allin all--
positionspositions
•• Most flux cored wires have a folded seam that can allow moistureMost flux cored wires have a folded seam that can allow moisture to get to get
into the fluxinto the flux
•• Controlled storage & handling is required for Controlled storage & handling is required for ‘‘seamedseamed’’ wireswires
•• Metal cored wires have the same general characteristics as solidMetal cored wires have the same general characteristics as solid wires wires --
they can be operated in dip or spray modethey can be operated in dip or spray mode
•• Some flux cored wires do not require a gas shield (Some flux cored wires do not require a gas shield (InnershieldInnershield))
The welding equipment
A visual check should be made on the equipment to ensure it is in good
working order
The electrodes
The diameter, specification and the quality of the wire are essential for
inspection. The level of deoxidisation in the wire, single, double or triple
de-oxidised. The quality of the wire winding and the copper coating
should also be inspected to minimize wire feed problems.
Checks when MAG Welding
Wire liner
Check that the liner is the correct type and size for the wire being used.
Steel liners for steel and Teflon liners for aluminium.
Contact tips
Check the tip is the correct size for the wire being used and check the
amount of wear. Excessive wear will affect wire speed and electrical
current pick-up
Gas and gas flow-rates
Type of gas and the flow rate need to be checked to ensure they comply
with the WPS
Other welding variables
Check WFS, amps, volts and travel speed
Checks when MAG Welding
Most welding imperfections in MIG/MAG are caused by lack of
welder skill, or incorrect settings of the equipment
•Worn contact tips will cause poor power pick up, or transfer
•Bad power connections will cause a loss of voltage in the arc
•Silica inclusions (in Fe steels) due to poor inter-run cleaning
•Lack of fusion (primarily with dip transfer)
•Porosity (from loss of gas shield on site etc)
•Solidification problems (cracking, centerline pipes, crater pipes) especially on deep narrow welds
MIG/MAG typical defects
AdvantagesAdvantages DisadvantagesDisadvantages
�� High productivity
� Easily automated
� All positional (dip & pulse)
� Material thickness
range
� Continuous electrode
�� Lack of fusion (dip)
� Small range of consumables
� Protection on site
� Complex equipment
� Not so portable
Gas Metal Arc Welding
QU 1. State the possible problems when using the dip
transfer mode in the MAG welding process
QU 2. State the application areas for the spray transfer mode when using the MAG welding process.
QU 3. What power source characteristic is required and
electrode polarity/current type for the MAG welding process
QU 4. State the main variables for the MAG welding process
QU 5. State the advantages and disadvantages of the MAG
welding process when compared to MMA
Questions
Metal Active Gas Welding
Flux Core Arc Welding
WELDING PROCESS
Flux cored arc welding
FCAW FCAW
methodsmethods
With gas With gas
shielding shielding --
““OutershieldOutershield””
Without gas Without gas
shielding shielding --
““InnershieldInnershield””
With metal With metal
powder powder --
““Metal coreMetal core””
“Outershield” - principle of operation
“Innershield” - principle of operation
Arc Characteristics
VoltsVolts
AmpsAmps
OCVOCV
Constant Voltage CharacteristicConstant Voltage Characteristic
Small change in voltage = Small change in voltage =
large change in amperagelarge change in amperage
The self The self
adjusting arc.adjusting arc.
Large arc gapLarge arc gap
Small arc gapSmall arc gap
Insulated extension nozzleInsulated extension nozzle
Current carrying guild tube Current carrying guild tube
Flux cored hollow wire Flux cored hollow wire
Flux powderFlux powder
Arc shield composed of Arc shield composed of vaporized and slag forming vaporized and slag forming compounds compounds
Metal droplets covered Metal droplets covered
with thin slag coating with thin slag coating
Molten Molten weld weld poolpoolSolidified weld Solidified weld
metal and slagmetal and slag
Flux coreFlux core
Wire jointWire joint
Flux core Flux core wireswires
Flux Core Arc Welding (FCAW)
Flux cored arc welding
FCAW FCAW
methodsmethods
With gas With gas
shielding shielding --
““OutershieldOutershield””
Without gas Without gas
shielding shielding --
““InnershieldInnershield””
(114)(114)
With metal With metal
powder powder --
““Metal coreMetal core””
With active With active
gas shielding gas shielding
(136)(136)
With inert gas With inert gas
shielding (137)shielding (137)
FCAW - differences from MIG/MAG
• usually operates in DCEP but some “Innershield”wires operates in DCEN
• power sources need to be more powerful due to the higher currents
• doesn't work in deep transfer mode
• require knurled feed rolls
• “Innershield” wires use a different type of
welding gun
FCAW - differences from MIG/MAG
350 Amps self shielded welding gun
Courtesy of Lincoln Electric
Contact tip
Thread protector
Conductor tube
Trigger
Handle
Hand shield
24V insulated
switch lead
Welding
gun cable
Close wound stainless steel spring wire liner
(inside welding gun cable)
FCAW - differences from MIG/MAG
Self shielded electrode
nozzle
Travel Angle
75° 75°90°
Backhand (“drag”) technique
Advantages
• preferred method for flat or horizontal position
• slower progression of the weld
• deeper penetration
• weld stays hot longer � easy to remove dissolved gasses
Disadvantages
• produce a higher weld profile
• difficult to follow the weld joint
• can lead to burn-through on thin sheet plates
Forehand (“push”) technique
Advantages
• preferred method for vertical up or overhead position
• arc is directed towards the unwelded joint �preheat effect
• easy to follow the weld joint and control the
penetration
Disadvantages• produce a low weld profile, with coarser ripples
• fast weld progression � shallower depth of
penetration
• the amount of spatter can increase
FCAW advantages
• less sensitive to lack of fusion
• requires smaller included angle compared to MMA
• high productivity
• all positional
• smooth bead surface, less danger of undercut
• basic types produce excellent toughness properties
• good control of the weld pool in positional welding
especially with rutile wires
• seamless wires have no torsional strain � twist free
• ease of varying the alloying constituents
• no need for shielding gas
FCAW advantages
Deposition rate for carbon steel welding
FCAW disadvantages
• limited to steels and Ni-base alloys
• slag covering must be removed
• FCAW wire is more expensive on a weight basis than solid wires (exception: some high alloy steels)
• for gas shielded process, the gaseous shield may be affected by winds and drafts
• more smoke and fumes are generated compared
with MIG/MAG
• in case of Innershield wires, it might be necessary to
break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)
Advantages:Advantages:
1) Field or shop use1) Field or shop use
2) High productivity2) High productivity
3) All positional3) All positional
4) Slag supports and 4) Slag supports and
shapes the weld Beadshapes the weld Bead
5) No need for shielding 5) No need for shielding
gasgas
Disadvantages:Disadvantages:
1) High skill factor1) High skill factor
2) Slag inclusions2) Slag inclusions
3) Cored wire is 3) Cored wire is
ExpensiveExpensive
4) High level of fume 4) High level of fume
((InnershieldInnershield))
5) Limited to steels and 5) Limited to steels and
nickel alloysnickel alloys
FCAW advantages/disadvantages
Recommended