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Plug for rolling of seamless steel pipe, method for manufacturing the same and method for manufacturing seamless steel pipe using the same

  • US 10,441,982 B2
  • Filed: 09/09/2013
  • Issued: 10/15/2019
  • Est. Priority Date: 09/11/2012
  • Status: Active Grant
First Claim
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1. A plug for rolling of a seamless steel pipe, the plug comprising:

  • a base metal;

    a coating layer formed on the base metal by coating a surface of the base metal with pure cobalt comprising 99 mass % or more of cobalt and a balance being inevitable impurities or a cobalt-nickel alloy, the cobalt-nickel alloy containing 0.3 mass % or more and 30 mass % or less of Ni; and

    an oxide layer including a cobalt-base oxide formed on a surface of the coating layer,wherein an average thickness of the oxide layer is in the range of 10 μ

    m to 40 μ

    m.

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