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SESK: Stuff Everyone Should Know · sesk.info/weld-preheat-purpose

According to Miller, what does preheating the metal do for a weld?

It slows cooling and drives out moisture.

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  1. Speeds cooling so the weld sets faster
  2. Slows cooling and drives out moisture ✔
  3. Removes the need for shielding gas

Why: Warm metal cools more slowly after welding. Slower cooling and less moisture help stop hydrogen buildup that can crack the weld.

Huh, didn't know that: Miller says shops commonly preheat steel plate or pipe 1 inch thick or more, and the welding code typically dictates it.

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References

Answer: Slows cooling and drives out moisture. Warm metal cools more slowly after welding. Slower cooling and less moisture help stop hydrogen buildup that can crack the weld.

  1. Miller Electric, Preheat in Welding: What Is It and When Should You Use It? www.millerwelds.com/resources/article-library/preheat-in-welding-what-is-it-and-when-should-you-use-it
    This reduces the cooling rate of the weld and drives out moisture.
    Checked 2026-10-10.

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