Handbook - Shielding Gases

13 Ternary (3) Shielding Gas Mixtures Argon-Oxygen-Carbon Dioxide Mixtures containing these three components have been termed ”universal” mixtures due to their ability to operate using short circuiting, globular, spray, pulse and high density type transfer characteristics. Several triple-mixes are available and their application will depend on the desired metal transfer mechanism and optimization of the arc characteristics. Argon-5-10% CO₂ - 1-3% 0₂ – This ternary mixture range has gained popularity in the U.S. over the last several years. The chief advantage is its versatility to weld carbon steel, low alloy steel and stainless steel of all thicknesses utilizing whatever metal transfer type applicable. Stainless steel welding should be limited to spray arc only due to the stiffness of the puddle at low current levels. Carbon pick-up on stainless steel should also be considered in some instances. On carbon and low alloy steels, this mixtures produces good welding characteristics and mechanical properties. On thin gauge materials, the 0₂ constituent assists the arc stability at very low current levels (30 to 60 amps) permitting the arc to be kept short and controllable. This helps minimize burnthrough and distortion by lowering the total heat input into the weld zone. Argon - 10-20% CO₂ - 5% 0₂ – This mixture is not common in the U.S. but has found applications in Europe. The mix produces a hot short circuiting transfer and fluid puddle characteristics. Spray arc transfer is good and seems to have some benefit when welding with triple deoxidized wires since a sluggish puddle is characteristic of these wires. Argon-Carbon Dioxide-Hydrogen Small additions of hydrogen (1-2%) have been shown to improve bead wetting and arc stability when Pulse Mig welding stainless steel. The CO₂ is also kept low (1-3%) to minimize carbon pick-up and maintain good arc stability. This mixture is not recommended on low alloy steels in the excessive weld metal hydrogen levels could develop causing weld cracking and poor mechanical properties. Continued on next page...