US 12,473,620 B2
Cold rolled and annealed steel sheet and method of manufacturing the same
Astrid Perlade, Le Ban-Saint-Martin (FR); Kangying Zhu, Metz (FR); and Frédéric Kegel, Yutz (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Appl. No. 18/016,543
Filed by ArcelorMittal, Luxembourg (LU)
PCT Filed Jul. 12, 2021, PCT No. PCT/IB2021/056243
§ 371(c)(1), (2) Date Jan. 17, 2023,
PCT Pub. No. WO2022/018567, PCT Pub. Date Jan. 27, 2022.
Claims priority of application No. PCT/IB2020/057000 (WO), filed on Jul. 24, 2020.
Prior Publication US 2023/0279528 A1, Sep. 7, 2023
Int. Cl. C22C 38/14 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/12 (2006.01); F16B 5/08 (2006.01); B32B 7/05 (2019.01); B32B 15/01 (2006.01)
CPC C22C 38/14 (2013.01) [C21D 6/005 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/12 (2013.01); F16B 5/08 (2013.01); B32B 7/05 (2019.01); B32B 15/011 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 9 Claims
 
1. A cold rolled and annealed steel sheet, made of a steel having a composition comprising, by weight percent:
C: 0.03-0.18%
Mn: 6.0-11.0%
Al: 0.2-3%
Mo: 0.05-0.5%
B: 0.0005-0.005%
S≤0.010%
P≤0.020%
N≤0.008%
and optionally one or more of the following elements, in weight percentage:
Si≤1.20%
Ti≤0.050%
Nb≤0.050%
Cr≤0.5%
V≤0.2%
a remainder of the composition being iron and unavoidable impurities resulting from processing;
the steel sheet having a microstructure comprising, in surface fraction, from 25% to 55% of retained austenite, from 45% to 75% of ferrite, less than 5% of fresh martensite, a carbon [C]A and manganese [Mn]A content in austenite, expressed in weight percent, such that the ratio ([C]A×[Mn]A2)/(C %×Mn %) is from 19.0 to 41.0 wt %, C % and Mn % being the nominal values in carbon and manganese in weight %, a carbides density below 3×106/mm2 and an inhomogeneous repartition of manganese defined by a manganese distribution with a slope above or equal to −30.