Ferritic stainless steel and production method therefor (as amended)

Abstract

Provided is a ferritic stainless steel that has excellent corrosion resistance and displays good brazing properties when brazing is carried out at high temperature using a Ni-containing brazing metal. These effects are obtained as a result of the steel having a chemical composition containing, in mass %: 0.003% to 0.020% of C; 0.05% to 1.00% of Si; 0.10% to 0.50% of Mn, 0.05% or less of P; 0.01% or less of S; 16.0% to 25.0% of Cr; 0.05% to 0.35% of Ti; 0.005% to 0.05% of Al; and 0.005% to 0.025% of N, the balance being Fe and incidental impurities, and as a result of a nitrogen-enriched layer being created that has a nitrogen concentration peak value of 0.05 mass % to 0.30 mass % at a depth of within 0.05 μm of a surface of the steel.

1 . A ferritic stainless steel comprising a chemical composition containing, in mass %:
 0.003% to 0.020% of C;   0.05% to 1.00% of Si;   0.10% to 0.50% of Mn;   0.05% or less of P;   0.01% or less of S;   16.0% to 25.0% of Cr;   0.05% to 0.35% of Ti;   0.005% to 0.05% of Al; and   0.005% to 0.025% of N,   the balance being Fe and incidental impurities, wherein   a nitrogen-enriched layer is present that has a nitrogen concentration peak value of 0.05 mass % to 0.30 mass % at a depth of within 0.05 μm of a surface of the steel.   
     
     
         2 . The ferritic stainless steel of  claim 1 , wherein
 the chemical composition further contains, in mass %, one or more of:   0.05% to 0.50% of Ni;   0.10% to 3.00% of Mo;   0.10% to 0.60% of Cu;   0.01% to 0.50% of V;   0.01% to 0.15% of Nb;   0.0003% to 0.0040% of Ca; and   0.0003% to 0.0100% of B.   
     
     
         3 . A production method for the ferritic stainless steel of  claim 1 , comprising
 subjecting a slab having the chemical composition of  claim 1  to hot rolling, subsequent hot band annealing as required, and a subsequent combination of cold rolling and annealing to produce the ferritic stainless steel, wherein   in final annealing of the annealing, treatment for creating a nitrogen-enriched layer is performed at a temperature of 800° C. or higher in an atmosphere having a dew point of −20° C. or lower and a nitrogen concentration of 5 vol % or greater.   
     
     
         4 . A production method for the ferritic stainless steel of  claim 2 , comprising
 subjecting a slab having the chemical composition of  claim 2  to hot rolling, subsequent hot band annealing as required, and a subsequent combination of cold rolling and annealing to produce the ferritic stainless steel, wherein   in final annealing of the annealing, treatment for creating a nitrogen-enriched layer is performed at a temperature of 800° C. or higher in an atmosphere having a dew point of −20° C. or lower and a nitrogen concentration of 5 vol % or greater.