HIGH STRENGTH STEEL SHEET
    1.
    发明申请

    公开(公告)号:US20220195554A1

    公开(公告)日:2022-06-23

    申请号:US17603726

    申请日:2020-07-08

    摘要: A high strength steel sheet according to the present invention contains a predetermined chemical composition, in a metallographic structure, the total area ratio of tempered martensite and bainite is 80% or more, at a sheet thickness ¼ position of a cross section parallel to a rolling direction and perpendicular to a rolled surface, the standard deviation of number densities of precipitates having a diameter of 10 nm or less and including one or both of Ti and Nb is less than 5×1010 numbers/mm3, and the tensile strength is 780 MPa or more.

    HIGH STRENGTH STEEL SHEET
    2.
    发明申请

    公开(公告)号:US20220177995A1

    公开(公告)日:2022-06-09

    申请号:US17601799

    申请日:2020-07-08

    摘要: A high strength steel sheet according to the present invention contains a predetermined chemical composition, a metallographic structure includes, by an area ratio, ferrite: 20% to 70%, residual austenite: 5% to 40%, fresh martensite: 0% to 30%, tempered martensite and bainite: 20% to 75% in total, and pearlite and cementite: 0% to 10% in total, in a range of a ⅛ thickness to a ⅜ thickness from a surface, a number proportion of residual austenite having an aspect ratio of 2.0 or more with respect to the number of all residual austenite is 50% or more, at a sheet thickness ¼ position of a cross section parallel to a rolling direction and perpendicular to the surface, a standard deviation of area ratios of ferrite measured at 10 points every 50 mm along a width direction is less than 10%, and a tensile strength is 780 MPa or more.

    HIGH STRENGTH STEEL SHEET
    4.
    发明申请

    公开(公告)号:US20200010919A1

    公开(公告)日:2020-01-09

    申请号:US16487043

    申请日:2018-02-20

    摘要: High strength steel sheet having a tensile strength of 800 MPa or more comprising a middle part in sheet thickness and a soft surface layer arranged at one side or both sides of the middle part in sheet thickness, wherein each soft surface layer has a thickness of more than 10 μM and 30% or less of the sheet thickness, the soft surface layer has an average Vickers hardness of more than 0.60 time and 0.90 time or less the average Vickers hardness of the sheet thickness 1/2 position, and the soft surface layer has a nano-hardness standard deviation of 0.8 or less is provided.

    STEEL SHEET AND METHOD FOR PRODUCING SAME
    8.
    发明申请

    公开(公告)号:US20200071799A1

    公开(公告)日:2020-03-05

    申请号:US16466610

    申请日:2018-02-20

    摘要: Steel sheet low in cost and improved in fatigue characteristics without causing a drop in the cold formability, characterized in that it comprises an inner layer and a hard layer on one or both surfaces of the inner layer, a thickness of the hard layer is 20 μm or more and 40% or less of the thickness of the steel sheet, an average micro-Vickers hardness of the hard layer is 240 HV or more and less than 400 HV, an amount of C of the hard layer is 0.4 mass % or less, an amount of N is 0.02 mass % or less, a variation of hardness measured by a nanoindenter at a depth of 10 from the surface of the hard layer is a standard deviation of 2.0 or less, an average micro-Vickers hardness of the inner layer is 80 HV or more and less than 400 HV, a volume rate of carbides contained in the inner layer is less than 2.00%, and the average micro-Vickers hardness of the hard layer is 1.05 times or more the average micro-Vickers hardness of the inner layer.