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HOT ROLLED STEEL PLATE FOR ELECTRIC RESISTANCE WELDED STEEL PIPE HAVING EXCELLENT WELDABILITY, AND MANUFACTURING METHOD THEREOF

  • US 20190323103A1
  • Filed: 11/29/2017
  • Published: 10/24/2019
  • Est. Priority Date: 12/19/2016
  • Status: Active Grant
First Claim
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1. A hot rolled steel plate for an electric resistance welded steel pipe having excellent weldability, comprising, by wt %:

  • carbon (C);

    0.05 to 0.14%, silicon (Si);

    0.1 to 1.0%, manganese (Mn);

    0.8 to 1.8%, phosphorus (P);

    0.001 to 0.02%, sulfur (S);

    0.001 to 0.01%, aluminum (Al);

    0.1 to 0.3%, chromium (Cr);

    0.3 to 1.0%, titanium (Ti);

    0.01 to 0.05%, niobium (Nb);

    0.025% or less, vanadium (V);

    0.035% or less, nitrogen (N);

    0.001 to 0.01%, and the balance of iron (Fe) and inevitable impurities,wherein Mn and Si satisfy the following Relational Expression 1, a microstructure comprises a mixture of martensite and bainite phases together with a ferrite phase as a matrix structure, and the following Relational Expression 2 is satisfied,
    4<

    Mn/Si<

    12 



    [Relational Expression 1]where, Mn and Si refers to a weight content of each element,
    SSGM+B/(M+B+SSGM+B)≥

    0.6 



    [Relational Expression 2]where, M refers to a martensite phase, B refers to a bainite phase, and SSGM+B refers to a hard phase in which the B and M phases exist together in a single grain, that is, a structure in which the M phase exists around a grain boundary, and the B phase exists in a central region, and each phase refers to an area fraction (%).

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