Gas Metal Arc WeldingGas Metal Arc Welding
GMAW Modes of Metal TransferSpray Globular
Short Circuiting Pulsed Spray
Gas Metal Arc Welding
GMAW Filler Metal Designations
ER - 70S - 6
Electrode
Rod (can be used with GMAW) Minimum ultimate tensile
strength of the weld metal
Solid Electrode
Composition6 = high silicon
AWS Specifications for GMAW Wire
AWS A5.18 - Carbon Steel ElectrodesAWS A5.28 - Low Alloy Steel Electrodes
Shielding Gas
• Shielding gas can affect– Weld bead shape– Arc heat, stability,
and starting– Surface tension– Drop size– Puddle flow– Spatter
Ar Ar-He He CO2
Gas Metal Arc Welding
GMAW Advantages• Deposition rates
higher than SMAW
• Productivity higher than SMAW with no slag removal and continuous welding
• Easily automated
Gas Metal Arc Welding
Quality• Spatter
– Droplets of electrode material that land outside the weld fusion area and may or may not fuse to the base material
• Porosity – Small volumes of
entrapped gas in solidifying weld metal
Gas Metal Arc Welding
Limitations• Equipment is more
expensive and complex than SMAW
• Process variants/metal transfer mechanisms make the process more complex and the process window more difficult to control
• Restricted access– GMAW gun is larger than
SMAW holder
Gas Metal Arc Welding