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Welder Red Seal · Question

When butt welding 3 mm thick 304 stainless steel pipe using GTAW, what is the primary purpose of introducing argon shielding gas to the back of the weld joint?

Purging the back side of the weld with argon prevents atmospheric oxygen from reacting with the hot metal, which would cause sugaring, porosity, and reduced cor

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Question: When butt welding 3 mm thick 304 stainless steel pipe using GTAW, what is the primary purpose of introducing argon shielding gas to the back of the weld joint?

Answer options:

  • To increase the cooling rate of the weld bead. ✅ To prevent oxidation of the back side of the weld.
  • To improve penetration into the root of the joint.
  • To reduce distortion in the weldment.

Correct answer: To prevent oxidation of the back side of the weld.

Explanation: Purging the back side of the weld with argon prevents atmospheric oxygen from reacting with the hot metal, which would cause sugaring, porosity, and reduced corrosion resistance. This maintains the metallurgical integrity of the root pass.

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