Welding / Shielding gases:

Argon

Argon has an inert atmosphere
Good for spray transfer
Necessary for non-ferrous metals ie: Aluminum, magnesium, copper

Helium

Helium has an inert atmosphere
Globular transfer
Usually used in a mixture with Argon for Non-ferrous metals
The thicker the metal, the greater the percentage of helium

Argon / CO2

90% Argon 10% CO2
Oxidizing atmosphere
Modified spray transfer for carbon steels , low alloy steels of all thicknesses.

85% Argon 15% CO2
Oxidizing atmosphere
Modified globular transfer for carbon steels and low alloy steels of all thicknesses

75% Argon 25% CO2
Oxidizing atmosphere
Modified globular / short circuit transfer for carbon steels and low alloy steels

Carbon Dioxide

Carbon Dioxide has a oxidizing atmosphere
Short circuit transfer or buried arc
Excellent for low carbon and mild steel

Argon/Helium

75 % argon 25% Helium
Modified spray, for Aluminum and magnesium ¼" to ½" thickness

50% Argon 50% Helium
Modified globular for aluminum and Magnesium ½" to ¾"

25% Argon 75% Helium
Modified globular / globular for Aluminum and Magnesium over 1" thick

Argon / Oxygen

98% argon 2% oxygen
Oxidizing atmosphere
Spray transfer for carbon steels, low alloy steels, and series 300 stainless

95% argon 5% oxygen
Oxidizing atmosphere
Spray transfer for carbon steels, low alloy steels, and 300 series stainless steels for electrode diameter 1/16" and larger.

Argon / Helium / CO2

90% Helium 7.5% Argon 2.5% CO2
Oxidizing atmosphere