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公开(公告)号：EP4303328A1
公开(公告)日：2024-01-10
申请号：EP22784374.5
申请日：2022-03-02
摘要： Provided is a high-strength cold-rolled steel sheet having tensile strength of 1320 MPa or more and also excellent in fatigue strength of a spot welded portion. The high-strength cold-rolled steel sheet has a chemical composition containing C: 0.150 to 0.350 mass%, Si: 0.80 to 3.00 mass%, Mn: 1.50 to 3.50 mass%, P: 0.100 mass% or less, S: 0.0200 mass% or less, Al: 0.100 mass% or less, N: 0.0100 mass% or less, and O: 0.0100 mass% or less, with a remaining part consisting of Fe and inevitable impurities. The amount of diffusible hydrogen in-steel is 0.50 mass ppm or less, the total area ratio of tempered martensite and bainite is 55 to 95%, the area ratio of retained austenite is 5 to 30%, a prior austenite grain has an average circle equivalent diameter of 15.0 µm or less, and the ratio b/a is 0.80 or less, where a circumferential length of the prior austenite grain is a, and a circumferential length of a portion of the prior austenite grain having a carbon concentration of 0.6 mass% or more is b.
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公开(公告)号：EP4435128A1
公开(公告)日：2024-09-25
申请号：EP22920503.4
申请日：2022-12-06
发明人： MORIMOTO, Ryohei , YANG, Lingling , TOJI, Yuki
摘要： A high-strength steel sheet having a tensile strength of 1320 MPa or more and excellent in ductility, hole expandability, and delayed fracture resistance characteristics is provided. The above-described high-strength steel sheet includes a specific component composition including Ti and the like, wherein a diffusible hydrogen amount in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0 to 95.0%, fresh martensite is 15.0% or less, retained austenite is 5.0 to 15.0%, an average grain size of a precipitate A, which is a carbide, nitride, or carbonitride containing at least one selected from the group consisting of Ti, Nb, and V is 0.001 to 0.050 µm, a number density NS of the precipitate A having a major axis of 0.050 um or less is 10/µm2 or more, and a ratio of the number density NS and a number density NL of the precipitate A having a major axis of more than 0.050 um is 10.0 or more.
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公开(公告)号：EP4435127A1
公开(公告)日：2024-09-25
申请号：EP22920500.0
申请日：2022-12-06
发明人： MORIMOTO, Ryohei , YANG, Lingling , TOJI, Yuki
摘要： A high-strength steel sheet having a tensile strength of 1320 MPa or more and excellent in hole expandability and delayed fracture resistance characteristics is provided. The above-described high-strength steel sheet includes a specific component composition, wherein a diffusible hydrogen in steel is 0.50 ppm by mass or less, tempered martensite and bainite are 70.0% or more, fresh martensite is 15.0% or less, iron-based carbides existing in the tempered martensite and the bainite have an average equivalent circular radius of 0.10 um or less and an average aspect ratio of 4.5 or less, and a proportion p of tempered martensite and bainite including iron-based carbides, which have major axes facing the same direction within a range of 0 to 10°, at a number density of 7 to 35/µm2 among the tempered martensite and the bainite is 25 to 70%.
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