US 12,247,273 B2
Cold rolled and heat treated steel sheet, method of production thereof and use of such steel to produce vehicle parts
Patrick Barges, Rozerieulles (FR); and Ian Alberto Zuazo Rodriguez, Saint Vallier (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Appl. No. 16/466,959
Filed by ArcelorMittal, Luxembourg (LU)
PCT Filed Dec. 22, 2016, PCT No. PCT/IB2016/057941
§ 371(c)(1), (2) Date Jun. 5, 2019,
PCT Pub. No. WO2018/115938, PCT Pub. Date Jun. 28, 2018.
Prior Publication US 2019/0345590 A1, Nov. 14, 2019
Int. Cl. C22C 38/04 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/08 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/16 (2006.01)
CPC C22C 38/04 (2013.01) [C21D 6/005 (2013.01); C21D 8/0236 (2013.01); C21D 8/0247 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/08 (2013.01); C22C 38/12 (2013.01); C22C 38/14 (2013.01); C22C 38/16 (2013.01); C21D 2211/001 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01)] 34 Claims
OG exemplary drawing
 
1. A cold rolled and heat treated steel sheet having a composition consisting of the following elements, expressed in percent by weight:
0.15%≤carbon≤0.6%,
5.05%≤manganese≤20%,
5%≤aluminum≤15%,
0≤silicon≤2%,
17%≥aluminum+silicon≥6.5%,
optionally one or more elements selected from the group consisting of niobium, titanium, vanadium, copper, nickel, cerium, boron, magnesium, zirconium, molybdenum, tantalum, tungsten, sulfur, and phosphorus,
a remainder being composed of iron and unavoidable impurities caused by processing,
wherein the manganese content is greater than the aluminum content and Mn/Al ratio is at least 8.2/7.8;
wherein a microstructure of said steel sheet consists in area fraction, 10 to 50% of austenite, a remainder of the microstructure being regular ferrite and ordered ferrite of D03 structure, and optionally intragranular kappa carbides, and
wherein an ultimate tensile strength of said steel sheet is higher than or equal to 900 MPa, and
the microstructure includes in area fraction at least 0.1% ordered ferrite of D03 structure.