PRODUCTION OF HIGH CHROMIUM/FERRITIC STAINLESS STEEL EXCELLENT IN MOLDABILITY AND CORROSION RESISTANCE

摘要

PURPOSE:To obtain the title stainless steel excellent in moldability and corrosion resistance by subjecting ferritic stainless steel having composition consisting of prescribed components to bright annealing in the nonoxidative atmosphere in a range within the specified dew points and thereafter electrolytically treating it in a nitric acid soln. CONSTITUTION:Ferritic stainless steel which consists of 0.015-0.03 (hereinafter shown by wt.%) C, 0.1-1.0 Si, =1 Mn, =0.01 S, 20-25 Cr, 0.3-1.0 Mo, 0.1-1.5 Ni, 0.04-0.5 Cu, 0.015-0.03 N, 8(C+N)-20(C+N) (weight ratio) Nb and furthermore incorporates Ti and/or Zr at 0.02-0.1 as total amounts of (Ti+Zr/2) is heat-treated by the following method. In other words, this stainless steel is subjected to bright annealing at 925-975 deg.C in the nonoxidative atmosphere in a range within -60--45 deg.C dew point e.g. in the NH3 decomposition gas. Then the above-mentioned stainless steel subjected to bright annealing is electrolytically treated at 2-30 coulomb/dm2 quantity of electricity in an electrolytic bath of 5-30wt.% nitric acid aq. soln. to obtain the aimed high chromium/ ferritic stainless steel.