	US 12,404,571 B2
	Steel sheet and high strength press hardened steel part having excellent bending anisotropy and method of manufacturing the same
Sebastian Cobo, Montigny les Metz (FR); Emmanuel Lucas, Metz (FR); Matthieu Salib, Maizieres-les-Metz (FR); and Guillaume Stechmann, Marly (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Filed by ArcelorMittal, Luxembourg (LU)
Filed on Dec. 19, 2024, as Appl. No. 18/988,468.
Application 18/988,468 is a division of application No. 18/811,384, filed on Aug. 21, 2024.
Application 18/811,384 is a continuation of application No. PCT/IB2024/054085, filed on Apr. 26, 2024.
Claims priority of application No. PCT/IB2023/056848 (WO), filed on Jun. 30, 2023.
Prior Publication US 2025/0129459 A1, Apr. 24, 2025
This patent is subject to a terminal disclaimer.
Int. Cl. C22C 38/04 (2006.01); C21D 8/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/14 (2006.01)

CPC C22C 38/04 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0242 (2013.01); C21D 8/0278 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/14 (2013.01); C21D 2211/002 (2013.01); C21D 2211/004 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)]

16 Claims

1. A process for manufacturing a steel sheet, comprising the following successive steps:

providing a liquid steel having a chemical composition comprising, by weight percent:

C: 0.2-0.3%;

Mn: 0.8-2.0%;

Si: 0.1-0.5%;

Al: 0.01-0.1%;

Ti: 0.01-0.1%;

B: 0.0005-0.005%;

P≤0.040%;

Ca≤0.01%;

S≤0.006%;

N≤0.01%;

and comprising optionally:

Cr≤0.4%;

Mo≤0.3%;

Nb≤0.1%;

V≤0.3%;

wherein Cr+Mo+Nb+V≤0.5%,

the remainder of the composition being iron and unavoidable impurities,

casting said liquid steel to obtain a semi-product able to be hot-rolled;

hot rolling the semi-product at a finish hot rolling temperature comprised from 800° C. to 950° C.; and

coiling the hot rolled steel sheet at a coiling temperature T_coillower than 670° C. to obtain a coiled steel sheet,

the obtained steel sheet having a microstructure in surface fraction comprising from 75% to 90% of ferrite, a rest being comprised of Fe₃C and hard phases made of martensite and/or bainite,

said steel sheet comprising from a bulk to the surface of the steel sheet:

the bulk representing 80% of a thickness of the steel sheet; and

the bulk being topped by a top skin layer and a bottom skin layer occupying an outermost 10% of the thickness on either sides of the bulk, said bulk comprising an inclusion population wherein a sum of clustering indexes of MnS and TiN/Ti(C,N) inclusions is less than or equal to 300 μm/mm².