US 12,247,274 B2
Method of production of a cold rolled and heat treated steel sheet to produce vehicle parts
Patrick Barges, Rozerieulles (FR); and Ian Alberto Zuazo Rodriguez, Saint Vallier (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Filed by ArcelorMittal, Luxembourg (LU)
Filed on Oct. 1, 2020, as Appl. No. 17/060,493.
Application 17/060,493 is a division of application No. 16/466,959, previously published as PCT/IB2016/057941, filed on Dec. 22, 2016.
Prior Publication US 2021/0025041 A1, Jan. 28, 2021
This patent is subject to a terminal disclaimer.
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)] 30 Claims
OG exemplary drawing
 
1. A method of production of a cold rolled and heat treated steel sheet comprising the following steps:
providing a cold rolled steel sheet with a composition consisting of the following elements, expressed in percent by weight:
0.15%≤carbon≤0.6%,
4%≤manganese≤20%,
5%≤aluminum≤15%,
0≤silicon≤2%,
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;
heating said cold rolled steel sheet up to a soaking temperature between 80° and 950° C. for a duration of less than 600 seconds, then cooling the sheet down to room temperature,
reheating the steel sheet at a heating rate of at least 10° C./h to a soaking temperature of 150° C. to 600° C. for a duration of 10 s to 250 h, then cooling the sheet to room temperature,
wherein after the reheating the steel sheet has an ultimate tensile strength higher than 900 MPa, and a microstructure of the steel sheet consisting of, in area fraction, 10 to 50% of austenite, at least 0.1% of ordered ferrite of D03 structure, a remainder of the microstructure being regular ferrite and optionally up to 2% of intragranular kappa carbides.