Manufacturing method of the multi-phase structure chromium stainless steel strip of small high ductility and high strength in-plane anisotropy

摘要

PURPOSE:To obtain a stainless steel strip of double phase structure having small intra-surface anisotropy and having high ductility and high strength by hot rolling a steel slab having a specific compsn. essentially consisting of Cr, then subjecting the slab to cold rolling including intermediate annealing and holding the rolled sheet in a specific temp. region in a continuous heat treatment furnace then subjecting the sheet to controlled cooling. CONSTITUTION:The slab of the steel consisting of =0.08wt.% C, =2.0% Si, =3.0% Mn, =0.040% P, =0.030% S, =3.0% Ni, 10.0-14.0% Cr, =0.08% N, =0.02% O, =3.0% Cu and the balance Fe and unavoidable impurities and satisfying the relations expressed by the formulas I, II is produced. Said slab is then subjected to hot rolling and =2 passes of cold rolling including intermediate annealing under heating to the single phase region temp. of ferrite to the product sheet thickness. The rolled sheet is passed through the continuous heat treatment furnace where the sheet is held at the two-phase region temp. of ferrite + austenite of Ac1 point or above and =1,100 deg.C within 10min and is then cooled at 1-500 deg.C/sec average cooling rate from the max. heating temp. down to 100 deg.C. The chromium stainless steel strip of double phase structure having =200HV hardness, the small intra-surface anisotroy and the high ductility and high strength is obtd. by the above-mentioned finishing heat treat ment.