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