公开(公告)号：US20210355559A1

公开(公告)日：2021-11-18

申请号：US17286148

申请日：2019-10-16

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Junya TOBATA ,  Hiroyuki AKIMOTO ,  Yoichiro MATSUI ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C21D6/00 ,  C21D1/20 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/44 ,  C22C38/42 ,  C22C38/14 ,  C22C38/12 ,  C22C38/60 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100% by area percentage, and retained γ: 4% to 15% by volume percentage. Retained γUB has a specified area percentage SγUB, retained γLB has a specified distribution number NγLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

公开(公告)号：US20220010397A1

公开(公告)日：2022-01-13

申请号：US17285375

申请日：2019-10-16

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Junya TOBATA ,  Hiroyuki AKIMOTO ,  Yoichiro MATSUI ,  Shinjiro KANEKO

IPC: C21D9/46 ,  C21D8/02 ,  C21D1/22 ,  C21D6/00 ,  C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/42 ,  C22C38/44 ,  C22C38/14 ,  C22C38/12 ,  C22C38/04 ,  C22C38/02 ,  C22C38/06 ,  C22C38/00

Abstract: A steel sheet having a specified chemical composition and a method for producing the steel sheet. The steel sheet has a microstructure comprising ferrite: 5% or less, and at least one of upper bainite, fresh martensite, tempered martensite, lower bainite, and retained γ: 95% to 100%, and retained γ: 5% to 20%. Retained γUB has a specified area percentage SγUB, retained γLB has a specified distribution number NγLB, and at least one of (i) fresh martensite has a specified equivalent circular grain diameter and aspect ratio and (ii) retained γ grains has a specified equivalent circular grain diameter and aspect ratio.

公开(公告)号：US20180298503A1

公开(公告)日：2018-10-18

申请号：US15737904

申请日：2016-07-07

Applicant: JFE STEEL CORPORATION

Inventor： Yuta TERASAKI ,  Hiroyuki AKIMOTO ,  Hiroyuki MASUOKA

IPC: C23G1/08 ,  C21D9/56 ,  C23G3/02

Abstract: A method of producing a cold rolled steel strip includes: subjecting a steel strip that has been cold rolled and subsequently continuously annealed to pickling by continuously feeding the steel strip into a mixed acid solution containing a first acid that is oxidizing and a second acid that is non-oxidizing to immerse the steel strip; and subsequently subjecting the steel strip to repickling by continuously feeding the steel strip into an acid solution containing a third acid that is non-oxidizing to immerse the steel strip. The concentration of the first acid in the mixed acid solution is lowered and the concentration of the second acid in the mixed acid solution is raised as the iron ion concentration in the mixed acid solution rises.