ArcelorMittal S.A.
Method for the manufacture of TWIP steel sheet having an austenitic matrix

Abstract:

A method for the manufacture of a TWIP steel is provided including: (A) feeding of a slab comprising by weight: 0.5<C<1.2%, 13.0.ltoreq.Mn<25.0%, S.ltoreq.0.030%, P.ltoreq.0.080%, N.ltoreq.0.1%, Si.ltoreq.3.0%, 0.051%.ltoreq.Al.ltoreq.4.0%, 0.1.ltoreq.V.ltoreq.2.5%, and on a purely optional basis, one or more of Nb.ltoreq.0.5%, B.ltoreq.0.005%, Cr.ltoreq.1.0%, Mo.ltoreq.0.40%, Ni.ltoreq.1.0%, Cu.ltoreq.5.0%, Ti.ltoreq.0.5%, 0.06.ltoreq.Sn.ltoreq.0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from the elaboration, (B) reheating the slab and hot rolling the slab to provide a hot rolled slab, (C) coiling the hot rolled slab to provide a coiled slab, (D) first cold-rolling the coiled slab to provide a first cold rolled slab, (E) recrystallization annealing the first cold rolled slab such that an annealed steel sheet having an UTS.sub.annealed is obtained and (F) second cold-rolling the annealed steel sheet with a reduction rate CR % that satisfies the following equation A: 1216.472-0.98795*UTS.sub.annealed.ltoreq.(-0.0008*UTS.sub.annealed+1.0124- )*CR %.sup.2+(0.0371*UTS.sub.annealed-29.583)*CR %.