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Welder Red Seal · Question

When performing an open root GTAW on a stainless steel pipe, what is the primary purpose of maintaining an argon purge on the inside of the pipe?

Stainless steel is highly reactive with oxygen at welding temperatures. An internal inert gas purge displaces the oxygen inside the pipe, protecting the molten

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Question: When performing an open root GTAW on a stainless steel pipe, what is the primary purpose of maintaining an argon purge on the inside of the pipe?

Answer options:

  • To cool the inside of the pipe and reduce warpage
  • To prevent the formation of a concave root profile (suck-back) ✅ To prevent oxidation of the root face and ensure a clean, fused root bead
  • To create positive pressure to help push the weld through the root opening

Correct answer: To prevent oxidation of the root face and ensure a clean, fused root bead

Explanation: Stainless steel is highly reactive with oxygen at welding temperatures. An internal inert gas purge displaces the oxygen inside the pipe, protecting the molten root of the weld from oxidation. This prevents the formation of a heavily oxidized, non-fused root known as 'sugaring'.

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