US 12,110,572 B2
Manufacturing process of press hardened parts with high productivity
Alexandre Blaise, Chantilly (FR); Pascal Drillet, Rozerieulles (FR); and Thierry Sturel, Le Ban Saint Martin (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Appl. No. 16/968,880
Filed by ARCELORMITTAL, Luxembourg (LU)
PCT Filed Mar. 5, 2019, PCT No. PCT/IB2019/051764
§ 371(c)(1), (2) Date Aug. 11, 2020,
PCT Pub. No. WO2019/193434, PCT Pub. Date Oct. 10, 2019.
Claims priority of application No. PCT/IB2018/051546 (WO), filed on Mar. 9, 2018.
Prior Publication US 2020/0399734 A1, Dec. 24, 2020
Int. Cl. C21D 9/48 (2006.01); C21D 1/673 (2006.01); C21D 8/04 (2006.01); C23C 2/12 (2006.01); C23C 2/26 (2006.01); C23C 2/28 (2006.01); C23C 2/40 (2006.01)
CPC C21D 9/48 (2013.01) [C21D 1/673 (2013.01); C21D 8/0484 (2013.01); C23C 2/12 (2013.01); C23C 2/261 (2022.08); C23C 2/28 (2013.01); C23C 2/29 (2022.08); C23C 2/40 (2013.01); C21D 2211/005 (2013.01); C21D 2211/009 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A method for manufacturing a non-stamped prealloyed steel coil, sheet or blank, comprising the following successive steps:
providing a non-stamped precoated steel coil, sheet or blank composed of a heat treatable steel substrate covered by a precoating of aluminum or an aluminum-based alloy, the aluminum-based alloy being defined as an alloy wherein aluminum is a largest element in weight percentage of the aluminium-based alloy, the precoating resulting directly from a hot-dip aluminizing process without additional heat treatment, wherein a thickness of the precoating thickness is between 10 and 35 micrometers on each side of the steel coil, sheet or blank, then
heating the non-stamped precoated steel coil, sheet or blank in a furnace under an atmosphere containing at least 5% oxygen, up to a temperature θ1 between 750 and 1000° C., for a duration t1 comprised between t1min and t1max, wherein:
t1min=23500/(θ1−729.5) and
t1max=4.946×1041×θ1−13.08,
t1 designating a total duration in the furnace,
θ1 being expressed in ° C. and t1min and t1max being expressed in seconds, then cooling the non-stamped steel coil, sheet or blank at a cooling rate Vr1 down to a temperature θi, wherein the cooling rate Vr1 is selected so that a sum of the area fractions of bainite and martensite is less than 30% in the steel substrate, after the cooling and before subsequent heating, then
maintaining the non-stamped steel coil, sheet or blank at a temperature θ2 comprised between 100 and 500° C., for a duration t2 between 3 and 45 minutes, so as to obtain a diffusible hydrogen content less than 0.35 ppm.