Invention Grant
- Patent Title: Hot-pressed member and method for manufacturing same, and cold-rolled steel sheet for hot pressing and method for manufacturing same
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Application No.: US16617133Application Date: 2018-03-30
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Publication No.: US11293074B2Publication Date: 2022-04-05
- Inventor: Katsutoshi Takashima , Chikaumi Sawanishi , Takashi Kobayashi , Yoshimasa Funakawa
- Applicant: JFE STEEL CORPORATION
- Applicant Address: JP Tokyo
- Assignee: JFE STEEL CORPORATION
- Current Assignee: JFE STEEL CORPORATION
- Current Assignee Address: JP Tokyo
- Agency: Kenja IP Law PC
- Priority: WOPCT/JP2017/024258 20170630
- International Application: PCT/JP2018/013718 WO 20180330
- International Announcement: WO2019/003540 WO 20190103
- Main IPC: C21D9/46
- IPC: C21D9/46 ; B21D22/02 ; B32B15/01 ; C21D1/18 ; C21D6/00 ; C21D8/02 ; C22C38/00 ; C22C38/02 ; C22C38/06 ; C22C38/08 ; C22C38/10 ; C22C38/16 ; C22C38/26 ; C22C38/28 ; C22C38/32 ; C22C38/38

Abstract:
Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing as high as TS: 1780 MPa or more, excellent resistance to resistance welding cracking, and excellent delayed fracture resistance after resistance welding by having a specific chemical composition, and a microstructure such that a prior austenite average grain size is 7 μm or less, a volume fraction of martensite is 90% or more, and at least 5 Nb-based precipitates having a grain size of less than 0.08 μm are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member within a range of 100 μm in the thickness direction from a surface of the member, and such that a Ni diffusion region having a thickness of 0.5 μm or more is present in a surface layer of the member.
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