Title:
HOT-PRESSED MEMBER AND METHOD FOR MANUFACTURING SAME, AND COLD-ROLLED STEEL SHEET FOR HOT PRESSING
Document Type and Number:
WIPO Patent Application WO/2019/003448
Kind Code:
A1
Abstract:
The hot-pressed member according to the present invention contains, as the component composition thereof in mass%, 0.28% to less than 0.42% C, 0.05% to 1.5% Si, 1.0% to 3.0% Mn, 0.05% or less of P, 0.005% or less of S, 0.01% to 0.50% Al, 0.005% or less of N, 0.001% to 0.10% Nb, 0.001% to 0.15% Ti, and 0.0002% to 0.0040% B, the remainder being Fe and unavoidable impurities, and the microstructure thereof is configured as a steel structure in which the average crystal grain size of prior austenite grains is 7 µm or less, the volume fraction of martensite is 90% or greater, there are an average of 5 or more Nb-based deposits having a grain size of less than 0.08 µm per 100 µm2 of steel sheet cross-sectional area in a range from the steel sheet surface to a depth of 100 µm or less in the sheet thickness direction, and an Ni diffusion region having a thickness of 0.5 µm or greater is furthermore present in a surface layer of the steel sheet, whereby it is possible to obtain not only an extremely high tensile strength of 1780 MPa or greater after hot pressing, but also to obtain excellent resistance to cracking in resistance welding as well as excellent delayed fracture resistance after resistance welding.
Inventors:
TAKASHIMA KATSUTOSHI (JP)
SAWANISHI CHIKAUMI (JP)
KOBAYASHI TAKASHI (JP)
FUNAKAWA YOSHIMASA (JP)
SAWANISHI CHIKAUMI (JP)
KOBAYASHI TAKASHI (JP)
FUNAKAWA YOSHIMASA (JP)
Application Number:
PCT/JP2017/024258
Publication Date:
January 03, 2019
Filing Date:
June 30, 2017
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; B21D22/20; C21D1/18; C21D9/00; C21D9/46; C22C38/14; C22C38/60
Domestic Patent References:
| WO2007129676A1 | 2007-11-15 | |||
| WO2015147216A1 | 2015-10-01 |
Foreign References:
| JP2015151615A | 2015-08-24 | |||
| JP2016089274A | 2016-05-23 | |||
| JP2011173135A | 2011-09-08 |
Attorney, Agent or Firm:
SUGIMURA Kenji (JP)
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