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Guide to MIG Shielding Gas

Metal Thickness in. (mm) Recommended Shielding Gas Advantages
MIG SHORT ARC
Carbon Steel Up to 14 gauge (0.1) 92% Argon / 8% CO2 Good burnthrough and distortion control. Used also for spray arc welding
14 gauge - 1/8 (3.2) 75% Argon / 25% CO2 88% Argon / 12% 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 (3.2) 75% Argon / 25% CO2 88% Argon / 12% 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
50% Argon / 50% CO2 Deep penetration; spatter
CO2 Deep penetration; faster welding speeds; high spatter
Stainless Steel Up to 14 gauge (0.1) 92% Argon / 8% CO2 Good burnthrough and distortion control. For use where corrosion resistance is not mandatory
Over 14 gauge (0.1) 92% Argon / 8% CO2 Good burnthrough and distortion control. For use where corrosion resistance is not mandatory
90% He 7.5% Ar 2.5% CO2 No effect of corrosion resistance. Small heat-affected zone. No undercutting, minimum distortion. Good bead shape and mechanical properties
High Yield Strength Steels Up to 14 gauge (0.1) 92% Argon / 8% CO2 Good burnthrough and distortion control. Used also for spray arc welding
Over 14 gauge (0.1) Argon - Hydrogen Excellent arc stability, welding characteristics bead contour, little spatter, high impacts
MIG SPRAY ARC
Carbon Steel All thicknesses 95% Argon / 5% O2 Improves droplet rate and arc stability
92% Argon / 8% CO2 Produces a more fluid and controllable weld puddle; good coalescence and bead contour. Minimizes undercutting; permits high speeds
Aluminum Up to 3/8 (12.7) Argon Best metal transfer, arc stability and plate cleaning. Little or no spatter.
Over 3/8 (12.7) Argon - Helium Higher heat input. Produces more fluid puddle and flatter bead. Minimizes porosity.
Helium Highest heat input. Good for mechanized welding.
Low Alloy Steel Up to 3/32 (2.4) 98% Argon / 2% O2 Reduces undercutting. Improves coalescence and bead contour. Good mechanical properties.
Over 3/32 (2.4) 92% Argon / 8% CO2 Excellent arc and weld characteristics.
Stainless Steel All thicknesses 99% Argon / 1% O2 Good arc stability. Produces a fluid and controllable weld puddle; good coalescence and bead contour. Minimizes undercutting.
98% Argon / 2% O2 Can be used on more sluggish alloys to improve puddle fluidity, coalescence and bead contour.
Copper, Nickel & Copper-Nickel alloys Up to 1/8 (3.2) Argon Good arc stability.
Over 1/8 (3.2) Argon - Helium Higher heat input of helium mixture offsets high heat conductivity of heavier gauges.
Helium Higher heat input and improved Penetration.
Magnesium Titanium -- Argon Excellent cleaning action. Provides more stable arc than helium-rich mixtures
MIG CORED WIRE
Carbon Steel All thicknesses CO2 Deep penetration.
75% Argon / 25% CO2 Low smoke and spatter. Good puddle control. Bridges gaps
Stainless Steel All thicknesses CO2 Deep penetration.
75% Argon / 25% CO2 Low smoke and spatter. Good puddle control. Bridges gaps