Invention Grant
- Patent Title: Hot-rolled steel sheet for tailored rolled blank and tailored rolled blank
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Application No.: US16398310Application Date: 2019-04-30
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Publication No.: US10590506B2Publication Date: 2020-03-17
- Inventor: Tatsuo Yokoi , Eisaku Sakurada , Natsuko Sugiura , Kiyoyuki Fukui
- Applicant: NIPPON STEEL & SUMITOMO METAL CORPORATION
- Applicant Address: JP Tokyo
- Assignee: NIPPON STEEL CORPORATION
- Current Assignee: NIPPON STEEL CORPORATION
- Current Assignee Address: JP Tokyo
- Agency: Clark & Brody
- Priority: JP2014-088778 20140423; JP2014-088779 20140423
- Main IPC: C21D9/46
- IPC: C21D9/46 ; C22C38/00 ; C22C38/58 ; C21D6/02 ; C21D8/02 ; C22C38/02 ; C22C38/04 ; C22C38/06 ; C22C38/08 ; C22C38/12 ; C22C38/14 ; C22C38/16 ; C22C38/28 ; C22C38/30 ; C23C2/06 ; C23C2/28 ; B21D22/20

Abstract:
A hot-rolled steel sheet for a tailored rolled blank is provided that has high tensile strength and is excellent in cold formability. The hot-rolled steel sheet has: a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, with the balance being Fe and impurities, and that satisfies Formula (1); and a microstructure containing, in terms of area ratio, 20% or more of bainite, wherein 50% or more in terms of area ratio of the balance is ferrite. In the interior of the hot-rolled steel sheet an average value of pole densities of an orientation group {100} to {223} is 4 or less, and a pole density of a {332} crystal orientation is 4.8 or less. In an outer layer of the hot-rolled steel sheet, a pole density of a {110} crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the hot-rolled steel sheet, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.0×1017 per cm3 or less, and a bake hardening amount is 15 MPa or more, [Ti]−48/14×[N]−48/32×[S]≥0 (1).
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