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HOT-PRESSED MEMBER AND METHOD FOR MANUFACTURING SAME, AND COLD-ROLLED STEEL SHEET FOR HOT PRESSING AND METHOD FOR MANUFACTURING SAME

  • US 20200131596A1
  • Filed: 03/30/2018
  • Published: 04/30/2020
  • Est. Priority Date: 06/30/2017
  • Status: Active Grant
First Claim
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1. A hot-pressed member comprising:

  • a steel chemical composition containing, by mass %, C;

    0.28% or more and less than 0.42%, Si;

    1.5% or less, Mn;

    1.0% or more and 2.2% or less, P;

    0.05% or less, S;

    0.005% or less, Al;

    0.01% or more and 0.50% or less, N;

    0.005% or less, and Ti;

    0.005% or more and 0.15% or less, with the balance being Fe and inevitable impurities;

    a microstructure in whichat least 5 Ti-based precipitates having a grain size of 0.10 μ

    m or less are present on average per 100 μ

    m2 of a cross section parallel to a thickness direction of the member within a range of 100 μ

    m in a thickness direction from a surface of the member, a volume fraction of martensite is 95% to 100% within a depth range of 20 μ

    m to 100 μ

    m in the thickness direction from the surface of the member, and at least 10 cementite grains having a grain size of less than 0.20 μ

    m are present on average in a prior austenite grain; and

    a tensile strength of 1780 MPa or more.

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