Shielding Gases for GMAW

MIG Welding	Sheilding Gases for GMAW
Base metal	Thickness, in.	Shield gas	Advantages
GMAW-Short-circuit transfer
Carbon steel	Up to 14 gage	Argon-8 CO2	Good burnthrough and distortion control. Used also for spray-arc-welding.
	14 gage-1/8	Argon-25 CO2	High welding speeds without burnthrough. Minimum distortion and spatter. Best puddle control for out of position welding. Provides best mechanical properties for any given wire.
	Over 1/8	Argon-25 CO2	High welding speeds without burnthrough. Minimum distortion and spatter. Best puddle control for out of position welding. Provides best mechanical properties for any given wire.
	Over 1/8	50 Argon-50 CO2	Deep penetration; low spatter
	Over 1/8	CO2	Deep penetration. Faster welding speeds.
Carbon steel	Up to 14 gage	Ar-8 CO2	Good burnthrough and distortion control. Used also for spray arc welding.
	Over 14 gage	Ar-25 CO2	For use where corrosion resistance is not mandatory.
	Over 14 gage	Ar-CO2-He	No effect on corrosion resistance. Small heat-affected zone. No undercutting, minimum distortion. Good bead shape and mechanical properties.
High-yield- strength steels	Up to 14 gage	Argon-8 CO2	Good burnthrough and distortion control. Used also for spray arc welding.
	Over 14 gage	Ar-CO2-He	Excellent arc stability, welding characteristics, bead contour. Little spatter. High impacts.
GMAW-Spray transfer
Carbon steel	All	Argon-5 CO2	Improves droplet rate and arc stability.
		Argon-8 CO2	Produces a fluid, controllable weld puddle; good coalescence and bead contour. Minimizes undercutting; permits higher speeds.
		Argon-25 CO2	Suitable for high current welding.
Low-alloy steel	Up to 3/32	Argon-2 O2	Reduces undercutting. Improves coalescence and bead contour. Good mechanical properties.
	Over 3/32	Argon-8 CO2	Excellent arc and weld characteristics.
Stainless Steel	All	Argon-1 CO2	Good arc stability. Produces a fluid and controllable weld puddle; good coalescence and bead contour. Minimizes undercutting.
		Argon-2 O2	Can be used on the more sluggish alloys to improve puddle fluidity, coalescence and bead contour.