US 12,215,397 B2
High-yield-ratio cold-rolled dual-phase steel and manufacturing method therefor
Wei Li, Shanghai (CN); Xiaodong Zhu, Shanghai (CN); and Peng Xue, Shanghai (CN)
Assigned to BAOSHAN IRON & STEEL CO., LTD., Shanghai (CN)
Appl. No. 17/295,942
Filed by BAOSHAN IRON & STEEL CO., LTD., Shanghai (CN)
PCT Filed Nov. 22, 2019, PCT No. PCT/CN2019/120247
§ 371(c)(1), (2) Date May 21, 2021,
PCT Pub. No. WO2020/103927, PCT Pub. Date May 28, 2020.
Claims priority of application No. 201811404464.3 (CN), filed on Nov. 23, 2018.
Prior Publication US 2022/0010394 A1, Jan. 13, 2022
Int. Cl. C21D 8/02 (2006.01); C21D 1/26 (2006.01); C21D 6/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01)
CPC C21D 8/0263 (2013.01) [C21D 1/26 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A cold-rolled dual-phase steel having a high yield ratio, comprising the following chemical elements in mass percentages:
C: 0.05-0.08%, Mn: 0.9-1.2%, Si: 0.1-0.6%, Nb: 0.030-0.060%, Ti: 0.030-0.060%, Al: 0.015-0.045%, and a balance of Fe and other unavoidable impurities,
wherein the steel has a microstructure which is a complex phase structure of martensite+ferrite+[NbxTiy(C,N)z] carbonitride,
wherein the martensite has a phase proportion of 20-30%, and the martensite is in the shape of long strip-islands,
wherein the [NbxTiy(C,N)z] carbonitride has an irregular spherical shape and is uniformly distributed in ferrite grains, and the [NbxTiy(C,N)z] carbonitride has a phase proportion of 5-10%, and
wherein the steel has a yield ratio of greater than 0.8.