2. Gas Metal Arc Welding
Is a process where a continuously fed
metal electrode ( Wire ) contacts the base
metal and produces heat . The arc is
shielded by an inert gas
3. GMAW Components
DC or Direct Current power supply
Electrode or wire feed controller
Wire drive roller assembly
Shielding gas source (cylinder) & regulator
Manually held Gun & ground clamps
Wire reel
5. Gas Metal Arc Welding Principles
Gas metal arc welding is generally used
due to the high efficiency of filler metal
that can be deposited per hour.
GMAW is approximately 92% - 98% efficient
GMAW requires a shielding gas
6. Gas Metal Arc Welding Principles
The GMAW process is performed using
DCEP ( Direct Current Electrode Positive)
Alternating current is never used for
GMAW
DCEN is used only for a specialized
process using emissive electrodes
7. GMAW Advantages
• Welding can be done in all positions
• No slag removal required
• High efficiency
• Less work piece distortion
• Large gaps bridged easily , Good for poor
fitup
• High Weld Quality
8. Typical Setup for voltage
• The GMAW machine is a “Constant Voltage” power
supply. This is set using the voltage dial
• This setting can be monitored by the “Volt” meter
on the front panel of the welder
• Ideal voltage settings can be found in the wire
manufactures data book
9. Typical Setup for Wire speed
• The wire feed rate or speed is set using the dial on the
wire controller This setting increases or decreases
current or “Heat”. This setting is measured in AMPS or
IPM (inches per minute )
• Ideal settings can be monitored by the “Amp” meter on the
front panel of the welder. Note : Some machines display
“Current” (Same as AMPS) or IMP
• Ideal settings can be found in the wire manufactures data
book for both IPM and Current
10. Shielding Gas
• Air in the welding zone is displaced by inert gas to
“Shield” the molten weld pool and prevent it from
contamination from Oxygen, Nitrogen and Water
present in the atmosphere.
• Insufficient gas flow will not displace the
atmosphere resulting in “porosity” or voids in the
deposited weld.
• Flow is measured in CFH (Cubic Feet per Hour).
11. Insufficient Shielding Gas coverage
• Gas not turned on
• Flow rate not properly adjusted
• Leaks in the hose supplying the shielding
gas to the machine
• GMAW / MIG Gun loose at wire drive
connection
• Spatter buildup on gas cup
• Windy environment
12. Excessive Gas coverage
• Will cause porosity.
• The turbulence caused by the rapid flow of
shielding gas exiting from the gas cup will
draw the surrounding atmosphere into the
stream of gas.
• It will reduce weld pool temperatures
causing decreased penetration .
