Question

what two shielding gases can be used on steel?
(select all that apply.)

75% argon / 25% carbon dioxide
100% helium
100% carbon dioxide
100% argon

Explanation:

Identify the requirements for shielding steel

Using the Steel Shielding Gases knowledge point

• Carbon steel welding requires active shielding components or specific mixtures to ensure proper penetration, arc stability, and to prevent porosity.
• Pure inert gases like 100% Argon or 100% Helium are not typically used alone for GMAW on carbon steel due to poor bead profile, lack of penetration, and arc instability.

Evaluate the given options

Using the Steel Shielding Gases knowledge point

• 75% Argon / 25% Carbon Dioxide (C25): This is the industry standard mixture for short-circuit gas metal arc welding (GMAW) on carbon steel, providing a stable arc and minimal spatter.
• 100% Helium: Typically reserved for non-ferrous metals like aluminum or specialized tri-mixes, not used alone on steel.
• 100% Carbon Dioxide (\(\text{CO}_2\)): This is a common, low-cost shielding gas used for welding steel, offering deep penetration but more spatter.
• 100% Argon: Causes undercutting and poor wetting when used alone on carbon steel.

Answer:

• 75% Argon / 25% Carbon Dioxide (Correct answer)
• 100% Helium
• 100% Carbon Dioxide (Correct answer)
• 100% Argon