US 12,416,061 B2
Method for manufacturing a thermally treated steel sheet
Frédéric Bonnet, Avril (FR); and Yannick Doh, Montigny-les-Metz (FR)
Assigned to ArcelorMittal, Luxembourg (LU)
Filed by ArcelorMittal, Luxembourg (LU)
Filed on Feb. 15, 2023, as Appl. No. 18/110,036.
Application 18/110,036 is a continuation of application No. 16/469,231, abandoned, previously published as PCT/IB2017/058190, filed on Dec. 20, 2017.
Claims priority of application No. PCT/IB2016/001787 (WO), filed on Dec. 20, 2016.
Prior Publication US 2024/0026491 A1, Jan. 25, 2024
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 11/00 (2006.01); B32B 15/01 (2006.01); C21D 1/667 (2006.01); C21D 6/00 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C23C 2/06 (2006.01); C23C 2/12 (2006.01); C23C 2/28 (2006.01)
CPC C21D 11/005 (2013.01) [B32B 15/012 (2013.01); B32B 15/013 (2013.01); C21D 1/667 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/0205 (2013.01); C21D 8/0236 (2013.01); C21D 9/46 (2013.01); C23C 2/06 (2013.01); C23C 2/12 (2013.01); C23C 2/29 (2022.08); C21D 2211/001 (2013.01); C21D 2211/002 (2013.01); C21D 2211/005 (2013.01); C21D 2211/008 (2013.01)] 35 Claims
OG exemplary drawing
 
1. A method for manufacturing a thermally treated steel sheet having a microstructure mtarget comprising from 0 to 100% of at least one phase chosen among: ferrite, martensite, bainite, pearlite, cementite and austenite, in a heat treatment line comprising a heating section, a soaking section and a cooling section including a cooling system, wherein a thermal path TPtarget is performed, such method comprising:
A. preparation step comprising:
1) A selection substep, wherein:
a. mtarget and a chemical composition are compared to a list of predefined products, whose microstructure comprises predefined phases and predefined proportion of phases, and a product having a microstructure mstandard closest to mtarget and TPstandard is selected, comprising at least a heating, a soaking and a cooling steps, to obtain mstandard,
b. a heating path, a soaking path including a soaking temperature Tsoaking, a power cooling of the cooling system and a cooling temperature Tcooling are selected based on TPstandard and
2) A calculation substep, wherein through variation of a cooling power, new cooling paths CPx are calculated based on the product selected in step A. 1) a and TPstandard, an initial microstructure mi of the steel sheet to reach mtarget, the heating path, the soaking path comprising Tsoaking and Tcooling, the cooling step of TPstandard is recalculated using said CPx in order to obtain new thermal paths TPx, each TPx corresponding to a microstructure mx,
3) A selection substep wherein one TPtarget to reach mtarget is selected, TPtarget being chosen among the calculated thermal paths TPx and being selected such that mx is the closest to mtarget, and
B. a thermal treatment step wherein TPtarget is performed on the steel sheet, wherein in step A.2), a thermal enthalpy H released between mi and mtarget is calculated such that:
Hreleased=(Xferrite*Hferrite)+ (Xmartensite*Hmartensite)+(Xbainite*Hbainite)+(Xpearlite*Hpearlite)+(Hcementite*Xcementite)+(Haustenite*Xaustenite), X being a phase fraction.