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HIGH-STRENGTH H-BEAM STEEL EXHIBITING EXCELLENT LOW-TEMPERATURE TOUGHNESS AND METHOD OF MANUFACTURING SAME

  • US 20140301888A1
  • Filed: 12/12/2012
  • Published: 10/09/2014
  • Est. Priority Date: 12/15/2011
  • Status: Active Grant
First Claim
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1. An H-beam steel with a composition comprising, in mass %:

  • C;

    0.011 to 0.040%;

    Si;

    0.06 to 0.50%;

    Mn;

    0.80 to 1.98%;

    Al;

    0.006 to 0.040%;

    Ti;

    0.006 to 0.025%;

    N;

    0.001 to 0.009%;

    O;

    0.0003 to 0.0035%;

    Nb;

    0.020 to 0.070%;

    B;

    0.0003 to 0.0010%;

    P;

    limited to not more than 0.010%; and

    S;

    limited to not more than 0.005%,with a balance including Fe and inevitable impurities, whereinan amount of Nb and an amount of B satisfy, in mass %, Equation 1 described below,the H-beam steel has a metal structure in which, in a microstructure, an area fraction of bainite is not less than 70%, a total of an area fraction of pearlite and an area fraction of cementite is not more than 15%, and the remainder consists of at least one of ferrite and island martensite,an effective crystalline-grain size of the bainite is not more than 40 μ

    m, anda thickness of a flange falls in a range of 12 to 40 mm.
    0.070≦

    Nb+125B≦

    0.155 



    Equation 1

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