公开(公告)号：US11827950B2

公开(公告)日：2023-11-28

申请号：US17992240

申请日：2022-11-22

Applicant: POSCO Co., Ltd

Inventor： Yeon-Sang Ahn ,  Chang-Hyo Seo ,  Kang-Hyun Choi ,  Eul-Yong Choi

IPC: C21D9/46 ,  C21D1/26 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/32 ,  C22C38/60 ,  C23C2/06 ,  C21D8/02

CPC classification number: C21D9/46 ,  C21D1/26 ,  C21D8/0226 ,  C21D8/0236 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/32 ,  C22C38/60 ,  C23C2/06 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: Provided is a method of manufacturing a high strength steel sheet having excellent workability, including: reheating a steel slab; hot-rolling the reheated steel slab at an Ar3 transformation point or higher; coiling in a temperature range of 400 to 700° C.; primary cooling at a cooling rate of 0.1° C./s or less to room temperature; producing a cold rolled steel sheet at a cold reduction ratio of 40 to 70%; continuously annealing the cold rolled steel sheet in a temperature range of Ac1+30° C. to Ac3−20° C.; secondary cooling at a cooling rate of 10° C./s or less to 630 to 670° C.; third cooling to 400 to 500° C. at a cooling rate of 5° C./s or more in a hydrogen; maintaining for 70 seconds or more; hot-dip galvanizing; and performing a final cooling to Ms or less at a cooling rate of 1° C./s or more.