Ferritic stainless steel and ferritic stainless steel for automobile exhaust gas passage member

Abstract

The present invention relates to a ferritic stainless steel containing 0.03% by mass or less of C; from 0.1 to 0.8% by mass of Si; 1.0% by mass or less of Mn; 0.04% by mass or less of P; 0.01% by mass or less of S; 0.5% by mass or less of Ni; from 12.0 to 15.0% by mass of Cr; 0.03% by mass or less of N; from 0.1 to 0.5% by mass of Nb; from 0.8 to 1.5% by mass of Cu; and 0.1% by mass or less of Al, the balance being Fe and unavoidable impurities, the ferritic stainless steel having a γ max of 55 or less, as represented by the following equation (1): γ max=420C−11.5Si+7Mn+23Ni−11.5Cr+470N+9Cu−52Al+189  (1), in which C, Si, Mn, Ni, Cr, N, Cu and Al mean % by mass of the corresponding elements.

1 . A ferritic stainless steel, containing:
 0.03% by mass or less of C;   from 0.1 to 0.8% by mass of Si;   1.0% by mass or less of Mn;   0.04% by mass or less of P;   0.01% by mass or less of S;   0.5% by mass or less of Ni;   from 12.0 to 15.0% by mass of Cr;   0.03% by mass or less of N;   from 0.1 to 0.5% by mass of Nb;   from 0.8 to 1.5% by mass of Cu; and   0.1% by mass or less of Al, the balance being Fe and unavoidable impurities, the ferritic stainless steel having a γ max of 55 or less, as represented by the following equation (1):
   γ max=420C−11.5Si+7Mn+23Ni−11.5Cr+470N+9Cu−52Al+189  (1),
 
   
       in which C, Si, Mn, Ni, Cr, N, Cu and Al mean % by mass of the corresponding elements. 
     
     
         2 . The ferritic stainless steel according to  claim 1 , further containing one or more selected from the group consisting of Ti: 0.20% by mass or less; Mo: 0.5% by mass or less; V: 0.1% by mass or less; Zr: 0.5% by mass or less; W: 0.5% by mass or less; Co: 0.5% by mass or less; and B: 0.01% by mass or less, wherein the ferritic stainless steel has a γ max of 55 or less, as represented by the following formula (2):
   γ max=420C−11.5Si+7Mn+23Ni−11.5Cr+470N+9Cu−12Mo−49Ti−52Al+189   (2),
 
 in which C, Si, Mn, Ni, Cr, N, Cu, Mo, Ti and Al mean % by mass of the corresponding elements. 
 
     
     
         3 . The ferritic stainless steel according to  claim 1 , wherein the ferritic stainless steel is for heat resistance. 
     
     
         4 . A ferritic stainless steel for automobile exhaust gas passage members, the ferritic stainless steel containing:
 0.03% by mass or less of C;   from 0.1 to 0.8% by mass of Si;   1.0% by mass or less of Mn;   0.04% by mass or less of P;   0.01% by mass or less of S;   0.5% by mass or less of Ni;   from 12.0 to 15.0% by mass of Cr;   0.03% by mass or less of N;   from 0.1 to 0.5% by mass of Nb;   from 0.8 to 1.5% by mass of Cu; and   0.1% by mass or less of Al, the balance being Fe and unavoidable impurities, the ferritic stainless steel having a γ max of 55 or less, as represented by the following equation (1):
   γ max=420C−11.5Si+7Mn+23Ni−11.5Cr+470N+9Cu−52Al+189  (1),
 
   
       in which C, Si, Mn, Ni, Cr, N, Cu and Al mean % by mass of the corresponding elements. 
     
     
         5 . The ferritic stainless steel for automobile exhaust gas passage members according to  claim 4 , further containing one or more selected from the group consisting of Ti: 0.20% by mass or less; Mo: 0.5% by mass or less; V: 0.1% by mass or less; Zr: 0.5% by mass or less; W: 0.5% by mass or less; Co: 0.5% by mass or less; and B: 0.01% by mass or less, wherein the ferritic stainless steel has a γ max of 55 or less, as represented by the following formula (2):
   γ max=420C−11.5Si+7Mn+23Ni−11.5Cr+470N+9Cu−12Mo−49Ti−52Al+189   (2),
 
 in which C, Si, Mn, Ni, Cr, N, Cu, Mo, Ti and Al mean % by mass of the corresponding elements.