	US 12,392,008 B2
	Steel sheet for manufacturing press hardened parts, press hardened part having a combination of high strength and crash ductility, and manufacturing methods thereof
Martin Beauvais, Marange Silvange (FR); Alice Dumont, Metz (FR); Alexandre Gibot, Metz (FR); Astrid Perlade, Le Ban-Saint-Martin (FR); and Kangying Zhu, Metz (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Filed by ArcelorMittal, Luxembourg (LU)
Filed on Mar. 1, 2023, as Appl. No. 18/177,109.
Application 18/177,109 is a division of application No. 16/616,937, previously published as PCT/IB2018/053950, filed on Jun. 1, 2018.
Claims priority of application No. PCT/IB2017/053282 (WO), filed on Jun. 2, 2017.
Prior Publication US 2023/0203617 A1, Jun. 29, 2023
Int. Cl. C21D 9/50 (2006.01); B32B 15/01 (2006.01); C21D 6/00 (2006.01); C21D 8/04 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/22 (2006.01); C22C 38/26 (2006.01); C22C 38/28 (2006.01); C22C 38/32 (2006.01); C22C 38/38 (2006.01); C23C 2/02 (2006.01)

CPC C21D 9/50 (2013.01) [B32B 15/013 (2013.01); C21D 6/002 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0405 (2013.01); C21D 8/0426 (2013.01); C21D 8/0436 (2013.01); C21D 8/0463 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/22 (2013.01); C22C 38/26 (2013.01); C22C 38/28 (2013.01); C22C 38/32 (2013.01); C22C 38/38 (2013.01); C23C 2/02 (2013.01); C23C 2/022 (2022.08); C23C 2/0224 (2022.08); C23C 2/024 (2022.08); B32B 2605/00 (2013.01); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/003 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)]

13 Claims

1. A method for producing an uncoated steel sheet for manufacturing a press hardened steel part, said method comprising the following successive steps:

providing a steel semi-product having a composition comprising, by weight:

0.15%<C<0.22%

3.5%<Mn<4.2%

0.001%<Si<1.5%

0.3%<Al<0.9%

0.001%≤Cr<1%

0.001%<Mo<0.3%

0.001%<Ti<0.040%

0.0003%<B<0.004%

0.001%<Nb<0.060%

0.001%<N<0.009%

0.0005%<S<0.003%

0.001%<P<0.020%

a remainder being iron and unavoidable impurities;

hot-rolling said steel semi-product to obtain a hot-rolled steel sheet;

coiling said hot-rolled steel sheet at a coiling temperature T_collower than 550° C. to obtain a coiled steel sheet; and

cold-rolling the coiled steel sheet to obtain the uncoated steel sheet,

wherein no annealing is carried out after cold rolling

the uncoated steel sheet has a microstructure consisting of

less than 50% ferrite,

1% to 20% retained austenite,

cementite, such that the surface density of cementite particle larger than 60 nm is lower than 10⁷/mm²,

the complement consisting of bainite and/or martensite.