Question

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Explanation:

Analyze the effect of carbon dioxide in MIG welding

Using the GMAW Shielding Gas Effects knowledge point
Carbon dioxide \(\text{CO}_2\) is a reactive shielding gas commonly used in MIG (GMAW) welding of carbon steel. It provides deep joint penetration due to its high thermal conductivity in the arc column, but its chemical reactivity increases arc instability, which significantly increases weld spatter compared to inert gas mixtures like argon.

Evaluate the given options

Using the GMAW Shielding Gas Effects knowledge point

• Penetration: \(\text{CO}_2\) increases penetration, making this a correct effect.
• Weld cost: Pure \(\text{CO}_2\) is inexpensive, so it decreases rather than increases overall weld cost.
• Spatter: \(\text{CO}_2\) increases spatter, which is also a correct physical effect.
• Porosity: Shielding gas prevents porosity; it does not increase it unless there is a loss of gas coverage.

In standard welding curricula (such as AWS-aligned courses), the primary metallurgical and physical benefit highlighted when using pure \(\text{CO}_2\) or high \(\text{CO}_2\) mixtures on steel is its ability to increase penetration (specifically deep, broad joint penetration).

Answer:

• (A) Penetration (Correct answer)
• (B) Weld cost
• (C) Spatter
• (D) Porosity