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GMAW FCAW and MCAW
Gas Metal Arc Welding
Flux Core Arc Welding
Metal Core Arc Welding
Unit 6
What is GMAW?
Gas
Metal Arc Welding
GMAW
is produced by an electric arc
between the base metal and a solid
wire continuously fed electrode using
a shielding gas.
Also
called MIG welding (Metal Inert
Gas)
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What is FCAW?
Flux Core Arc Welding
Very similar to GMAW, except it uses a
tubular continuous electrode with a
flux core.
Generally, does not require the use a
separate shielding gas.
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What is MCAW?
Metal Core Arc Welding
Also, very similar to GMAW and FCAW, except it
uses a tubular continuous electrode with a metal
powder flux core.
Generally does require the use a separate shielding
gas.
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What are the benefits/disadvantages of
GMAW?
High
productivity, little waste
Most efficient, fast
Relatively easy to use.
Clean welds, little or no slag.
Equipment is specialized.
Equipment needs to be setup for specific
applications.
Actually less types of metals can be welded
when compared to SMAW and GTAW.
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What are the benefits/disadvantages of
FCAW?
Not
designed for high productivity.
Somewhat fast and efficient.
Relatively easy to use.
Some slag, not as clean as GMAW.
FCAW welding wire is very expensive
Equipment is specialized.
Equipment needs to be setup for specific
applications.
Only a few metals can be FCAW.
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What are the benefits/disadvantages of
MCAW?
Fast
metal deposit.
Fast and efficient.
Relatively easy to use.
Some slag, not as clean as GMAW.
MCAW welding wire is expensive
Equipment is specialized.
Equipment needs to be setup for specific
applications.
Only a few metals can be MCAW, generally
steels and stainless steels.
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What are some specific safety precautions for
GMAW, FCAW and MCAW?
Similar
to SMAW.
Produces intense ultra-violet rays.
Need to use number 10 shade lens.
U-V rays burn the outer layers of the
skin/eyes.
Electrical shock.
Harmful Fumes/smoke
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How do the GMAW, FCAW and MCAW
processes produce heat?
Basically
the same as SMAW

Resistance – produces heat.

Welder works at a lower voltage, pushes large
amounts of electricity, across a gap.

Voltage is a constant, amperage varies as the
feed rate of the electrode changes and arc length
varies.
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What are the key variables when
GMAW, FCAW and MCAW?
Size and type of electrode wire
Type of shielding gas
Set shielding gas flow rate.
Set voltage.
Set wire feed speed, inches per minutes
(ipm).
Welder characteristics, speed, skill, electrode
angles.
FCAW the same except no shielding gas.
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What are welders are used for GMAW,
FCAW and MCAW?
Only one type:
Constant
potential (voltage), set the
voltage, amperage varies.
Uses
either an inverter or a rectifier type
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What types of electrical current used
for GMAW, FCAW and MCAW?
DC – direct current, only
GMAW generally uses DCEP – reverse polarity,
electrode positive, heat is greater at the metal,
deeper penetration.
FCAW applications generally use DCEN – straight
polarity.
MCAW applications generally use DCEP – reverse
polarity.
As a general rule, use DCEP when using a supplied
shielding gas and DCEN when not using a supplied
shielding gas.
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What are the characteristics of the
shielding gases used for GMAW?
 Argon
– inert, all metals except steels.
 Helium – Inert, Al, Mg, and Cu alloys.
 Ar + He, Inert, better than He, same metals.
 Ar + 1-2% O2, oxidizing, stainless steel, some alloy
steels.
 Ar + 3-5% O2, oxidizing, carbon and some low alloy
steels.
 CO2, oxidizing, carbon and some low alloy steels
 Ar + 20 –50 % CO2, oxidizing, various steels, short
circuiting arc.
 90%He +7.5%Ar + 2.5% CO2, oxidizing, short
circuiting.
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What are the different types of metal
transfer for GMAW?
 Two
basic types:

Short circuiting,
 used with Argon +Co2 mixture gases, low
amperage, wires less than 0.045”, low heat input
to the base metal

Metal Transfer, 3 types
 Globular metal transfer, higher welding current,
high % of inert gas, larger diameter electrode wire.

Spray Arc, high current, voltage, usually 100%
Argon, current is above the transition current,
creating a fine spray of molten metal.

Pulsed spray, same as spray arc, except the welder
pulses the current, good for thinner metal, sheet
metal, auto body work
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How do we identify the different types
of GMAW electrodes?
Solid Wire Electrodes:
Example: ER70S-6
E – Electrode
R – Rod, carries the current
70 – tensile strength in 1,000#
S – solid wire
(last digit) – special characteristics, shielding
gas, composition. 6 is general purpose wire.
Common sizes: 0.030”, 0.035”, 0.045”
diameters
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How do we identify the different types
of FCAW and MCAW electrodes?
Tubular Wire Electrodes:
Example: ER71T-6
E – Electrode
R – Rod, carries the current
7 – tensile strength in 10,000#
1 = all positions, 0 = flat and horizontal only.
T - Tubular wire
(last digit) – special characteristics, indicates
if FCAW or MCAW electrode.
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References:
Metals and Welding: pages 188 – 197.
Modern Welding: chapter 15.
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