A welder needs to achieve a very high deposition rate on a large, flat butt joint using GMAW on thick mild steel. They are currently using a 75% Argon / 25% CO2 mixture. To maximize deposition while maintaining a good bead profile, what modification to the shielding gas would be most beneficial?

Question: A welder needs to achieve a very high deposition rate on a large, flat butt joint using GMAW on thick mild steel. They are currently using a 75% Argon / 25% CO2 mixture. To maximize deposition while maintaining a good bead profile, what modification to the shielding gas would be most beneficial?

Answer options: ✅ Increasing the Argon content to 90% or higher.

• Switching to 100% CO2.
• Adding 5% Nitrogen to the current mixture.
• Decreasing the gas flow rate significantly.

Correct answer: Increasing the Argon content to 90% or higher.

Explanation: To achieve very high deposition rates with large diameter wires, especially in controlled positions on thick material, increasing the argon content to 90% or higher (to facilitate spray transfer) is most beneficial. High argon content promotes spray transfer, which offers the highest deposition rates among the conventional transfer modes. 100% CO2 would result in globular transfer which has high spatter and not very high deposition, and nitrogen is typically not added to mild steel GMAW for deposition reasons.