Which of the following is a correct shielding gas option for short-circuit transfer on carbon steels and low-alloy steels?

• A. 100% Argon
• B. 100% CO2
• C. 75% Argon / 25% CO2
• D. 95% Argon / 5% Oxygen

Answer: (C)

Short-circuit transfer needs a shielding gas that keeps the arc stable at low current while producing a clean, well-wetted weld bead on carbon and low-alloy steels. A balance of Argon and CO2 does this well: Argon provides arc stability and a smooth bead, while CO2 adds enough reactivity to promote reliable short-circuit transfer and good puddle control without causing excessive spatter. About a quarter CO2 in the mix hits that sweet spot, giving better transfer and bead quality than either gas alone. Pure Argon tends to be too inert for optimal short-circuit transfer on these steels, and pure CO2 can cause more spatter and oxidation. Gas mixtures with small amounts of oxygen (like 95% Argon / 5% Oxygen) are more aligned with spray transfer and are not ideal for short-circuit on carbon/low-alloy steels. So the 75% Argon / 25% CO2 option best fits the short-circuit transfer needs.