	US 12,151,297 B2
	Production method for a spot welded joint using high strength and high forming steel
Astrid Perlade, Le Ban-Saint-Martin (FR); Samuel Vignier, Pont Astier (FR); Frederic Kegel, Maizieres-les-Mets (FR); and Artem Arlazarov, Maizieres-les-Mets (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Filed by ArcelorMittal, Luxembourg (LU)
Filed on Oct. 7, 2022, as Appl. No. 17/961,877.
Application 17/961,877 is a division of application No. 16/293,264, filed on Mar. 5, 2019, granted, now 11,504,795.
Application 16/293,264 is a continuation of application No. 14/907,429, granted, now 10,272,514, previously published as PCT/IB2014/001366, filed on Jul. 22, 2014.
Prior Publication US 2023/0050317 A1, Feb. 16, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. B23K 11/11 (2006.01); B22D 11/00 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C21D 8/04 (2006.01); C21D 9/46 (2006.01); C21D 9/50 (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); C23C 2/06 (2006.01); C23C 2/12 (2006.01); B23K 11/16 (2006.01); B23K 101/18 (2006.01); B23K 101/34 (2006.01); B23K 103/04 (2006.01); C22C 38/14 (2006.01)

CPC B23K 11/11 (2013.01) [B22D 11/001 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0263 (2013.01); C21D 8/0278 (2013.01); C21D 8/0436 (2013.01); C21D 9/46 (2013.01); C21D 9/50 (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); C23C 2/06 (2013.01); C23C 2/12 (2013.01); B23K 11/166 (2013.01); B23K 2101/18 (2018.08); B23K 2101/34 (2018.08); B23K 2103/04 (2018.08); C21D 9/505 (2013.01); C21D 2211/001 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01); C22C 38/14 (2013.01)]

18 Claims

1. A method to permit production of a spot welded joint of at least two steel sheets, comprising the following steps:

casting an aluminum alloyed steel so as to obtain a slab, a composition of the aluminum alloyed steel comprising, by weight percent:

0.05≤C≤0.21%;

4.0≤Mn≤7.0%;

0.5≤Al≤3.5%;

P≤0.025%; and

B≤0.0035%;

reheating the slab at a temperature T_reheatbetween 1150° C. and 1300° C.;

hot rolling the reheated slab with a temperature between 800° C. and 1250° C. to obtain a hot rolled steel, a last hot rolling pass taking place at a temperature T_lpgreater than or equal to 800° C.;

cooling the hot rolled steel between 1 and 150° C./s until a coiling temperature T_coilingless than or equal to 650° C. is reached; then coiling the hot rolled steel cooled at T_coiling;

de-scaling;

cold rolling with a cold rolling ratio between 30% and 70% so as to obtain a cold rolled steel sheet;

heating at a heating rate H_rateat least equal to 1° C./s up to an annealing temperature T_anneal;

annealing at the annealing temperature T_annealbetween T_minand T_maxdefined by:

T_min=721−36*C−20*Mn+37*Al+2*Si, in ° C.

T_max=690+145*C−6.7*Mn+46*Al+9*Si, in ° C.,

during a time between 30 and 700 seconds;

cooling down to a targeted temperature at a cooling rate between 5° C./s and 70° C./s; and

cutting the cold rolled steel into sheets to obtain cold rolled steel sheets;

providing at least one of the cold rolled steel sheets to be welded in a welding process, the welding process including welding to another metal with an effective intensity between 3 kA and 15 kA and a force applied on the electrodes between 150 and 850 daN, an electrode active face diameter being between 4 and 10 mm.