Ferritic stainless steel strip excellent in freeze of shape formed by working

摘要

A ferritic stainless steel sheet, which is press-formed to a product shape without such dimensional defects as spring-back or torsion, has an alloying composition consisting of C up to 0.10%, Si up to 1.0%, Mn up to 1.0%, P up to 0.050%, S up to 0.020%, Ni up to 2.0%, 8.0-22.0% of Cr, N up to 0.05%, optionally one or more of Al up to 0.10%, Mo up to 1.0%, Cu up to 1.0%, 0.010-0.50% of Ti, 0.010-0.50% of Nb, 0.010-0.30% of V, 0.010-0.30% of Zr and 0.0010-0.0100% of B, and the balance being essentially Fe with the provision that a value-FM defined by the formula (1) is adjusted to 0 or less. Its mechanical properties are controlled to a plane anisotropic degree (rmax-rmin) of Lankford value (r) <=0.80 and an anisotropic degree (sigmamax-sigmamin) of 0.2%-yield strength <=20 N/MM<2>. The stainless steel sheet is manufactured by hot-rolling a stainless steel having the specified composition and then batch-annealing the hot-rolled steel sheet 1-24 hours at 700-800° C. 1 $\begin{array}{cc}\mathrm{FM}=420C-11.5\mathrm{Si}+7\mathrm{Mn}+23\mathrm{Ni}-3.5\mathrm{Cr}-12\mathrm{Mo}+9\mathrm{Cu}-49\mathrm{Ti}-50\mathrm{Nb}-23V-52\mathrm{Al}+470N+20& \left(1\right)\end{array}$