ArcelorMittal S.A.
A METHOD FOR MANUFACTURING A THERMALLY TREATED STEEL SHEET

Abstract:

A method for manufacturing a thermally treated steel sheet is described. The method includes: A. preparation step containing: 1) a selection substep, wherein: a. m.sub.target and a chemical composition are compared to a list of predefined products, whose microstructure contains predefined phases and predefined proportion of phases, and a product having a microstructure m.sub.standard closest to m.sub.target and TP.sub.standard is selected, including at least a heating, a soaking and a cooling steps, to obtain m.sub.standard, b. a heating path, a soaking path including a soaking temperature T.sub.soaking, a power cooling of the cooling system and a cooling temperature T.sub.cooling are selected based on TP.sub.standard and 2) a calculation substep, wherein through variation of the cooling power, new cooling paths CP.sub.x are calculated based on the product selected in step A.1) a and TP.sub.standard, the initial microstructure m.sub.i of the steel sheet to reach m.sub.target, the heating path, the soaking path comprising T.sub.soaking and T.sub.cooling, the cooling step of TP.sub.standard is recalculated using said CP.sub.x in order to obtain new thermal paths TP.sub.x, each TP.sub.x corresponding to a microstructure m.sub.x, 3) a selection substep wherein one TP.sub.target to reach m.sub.target is selected, TP.sub.target being chosen among the calculated thermal paths TP.sub.x and being selected such that m.sub.x is the closest to m.sub.target, and B. a thermal treatment step wherein TP.sub.target is performed on the steel sheet.