公开(公告)号：US20180100212A1

公开(公告)日：2018-04-12

申请号：US15558201

申请日：2016-03-23

Applicant: JFE STEEL CORPORATION

Inventor： Yoshihiko ONO ,  Yoshimasa FUNAKAWA ,  Ryosuke YAMAGUCHI ,  Nobuyuki NAKAMURA

IPC: C21D9/46 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02

CPC classification number: C21D9/46 ,  C21D8/0236 ,  C21D2211/002 ,  C21D2211/008 ,  C22C38/00 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/60

Abstract: A cold-rolled steel sheet has: a predetermined chemical composition; and a microstructure in which tempered martensite and bainite are contained in a total area ratio of 95-100% with respect to a whole volume of the microstructure; a number of predetermined inclusion groups is at most 0.8/mm2, the inclusion groups being formed by one or more inclusion particles, the one or more inclusion particles having a major axis length of 0.3 μm or more and extending and/or distributed in a dot-sequence manner along a rolling direction; a number of carbides mainly composed of Fe having a predetermined size is at most 3,500/mm2; a number of carbides that are distributed in the tempered martensite and/or in the bainite and that have a diameter of 10 nm to 50 nm is at least 0.7×107/mm2; and prior γ grains have a mean grain size of 18 μm or less.

公开(公告)号：US20180044753A1

公开(公告)日：2018-02-15

申请号：US15559576

申请日：2016-03-22

Applicant: JFE STEEL CORPORATION

Inventor： Yuma HONDA ,  Yoshimasa FUNAKAWA ,  Kozo HARADA

IPC: C21D9/46 ,  C22C38/48 ,  C22C38/16 ,  C22C38/12 ,  C22C38/06 ,  B32B15/01 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00 ,  C23C2/40 ,  C23C2/28 ,  C22C38/54 ,  C22C38/04

CPC classification number: C21D9/46 ,  B32B15/013 ,  B32B15/04 ,  B32B15/043 ,  B32B15/18 ,  C21D6/004 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C21D8/0278 ,  C21D2211/005 ,  C21D2211/009 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/20 ,  C22C38/22 ,  C22C38/26 ,  C22C38/48 ,  C22C38/54 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23C28/025 ,  C23C30/00 ,  C23C30/005 ,  Y10T428/12792 ,  Y10T428/12958 ,  Y10T428/12972

Abstract: A high-strength steel sheet having a high yield ratio and a reduced difference in strength between the center and edges of the steel sheet in the width direction. The high-strength steel sheet includes a composition containing, by mass, C: 0.02% or more and less than 0.10%, Si: less than 0.10%, Mn: less than 1.0%, P: 0.10% or less, S: 0.020% or less, Al: 0.01% or more and 0.10% or less, N: 0.010% or less, Nb: 0.005% or more and less than 0.070%, and the balance being Fe and inevitable impurities. Additionally, the steel sheet has a microstructure including, by area, ferrite: 90% or more, pearlite: 0% to 10%, and the total of martensite, retained austenite, and cementite: 0% to 3%. The average crystal grain diameter dC of the ferrite at the center of the steel sheet in the width direction is 15.0 μm or less.

公开(公告)号：US20170218475A1

公开(公告)日：2017-08-03

申请号：US15500446

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Takeshi YOKOTA ,  Yoshimasa FUNAKAWA ,  Kazuhiro SETO ,  Yukihiro MATSUBARA

IPC: C21D9/46 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00 ,  C21D8/02 ,  C22C38/60 ,  C22C38/38 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  B32B15/01 ,  C23C2/06

CPC classification number: C21D9/46 ,  B32B15/013 ,  C21D1/26 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0247 ,  C21D8/0263 ,  C21D8/0278 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  C23G1/00

Abstract: Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; and subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, then cooling the steel sheet at a mean cooling rate of 5-50° C./s to a cooling stop temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet in a temperature range of higher than 350° C. to 550° C. for 10 s or more.

公开(公告)号：US20170204491A1

公开(公告)日：2017-07-20

申请号：US15326793

申请日：2015-08-05

Applicant: JFE STEEL CORPORATION

Inventor： Yoshiyasu KAWASAKI ,  Hiroshi MATSUDA ,  Takeshi YOKOTA ,  Yoshimasa FUNAKAWA ,  Kazuhiro SETO ,  Yukihiro MATSUBARA

IPC: C21D9/46 ,  C21D6/00 ,  C22C38/60 ,  C22C38/38 ,  C22C38/16 ,  C23C2/06 ,  C22C38/12 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00 ,  C23F17/00 ,  C21D8/02 ,  C22C38/14

CPC classification number: C21D9/46 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23C2/28 ,  C23F17/00

Abstract: Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, and the cooling the steel sheet at a mean cooling rate of 5-30° C./s to a cooling stop temperature of 150-350° C.; and subjecting the steel sheet to reheating treatment by reheating the steel sheet to a reheating temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet at the reheating temperature for 10 s or more.