Ferritic stainless steel plate

Abstract

The present invention provides a ferritic stainless steel sheet having excellent formability and excellent surface quality after forming. In specific means, the steel sheet contains, by mass %, 0.02 to 0.06% of C, 1.0% or less of Si, 1.0% or less of Mn, 0.05% or less of P, 0.01% or less of S, 0.005% or less of Al, 0.005% or less of Ti, 11 to 30% of Cr, 0.7% or less of Ni, the balance composed of Fe, and inevitable impurities, wherein N is contained to satisfy the relation to the C content represented by 0.06≦(C+N)≦0.12, and 1≦N/C, and V is contained to satisfy the relation to the N content represented by 1.5×10 −3 ≦(V×N)≦1.5×10 −2 (wherein C, N and V: the contents (mass %) of the elements).

1. A ferritic stainless steel sheet having excellent formability, comprising, by mass %:
 C: 0.02 to 0.06%;    Si: 1.0% or less;    Mn: 1.0% or less;    P: 0.05% or less;    S: 0.01% or less;    Al: 0.005% or less;    Ti: 0.005% or less;    Cr: 11 to 30%;    Ni: 0.7% or less; and    
       the balance composed of Fe, and N and V as inevitable impurities, wherein N is contained to satisfy the relation to the C content represented by the following equations (1) and (2), and V is contained to satisfy the relation to the N content represented by the following equation (3):
   0.06≦(C+N)≦0.12  (1)  
   1≦N/C  (2)  
   1.5×10 −3 ≦(V×N)≦1.5×10 −2   (3)  
 Wherein C, N and V equal the contents (mass %) of the elements;  
 wherein said sheet is made by continuous casting, reheating at 1050 to 1250° C., hot rolling with finish delivery temperature at 800 to 900° C. and cold rolling with 50-95% reduction.  
 
     
     
       2. A ferritic stainless steel sheet having excellent formability according to  claim 1 , wherein Si is present, by mass %, from 0.03 to 0.5%. 
     
     
       3. A ferritic stainless steel sheet having excellent formability according to  claim 1  or  2 , wherein Mn is present, by mass %, from 0.3 to 0.8%. 
     
     
       4. A ferritic stainless steel sheet having excellent formability, comprising, by mass %, of:
 C: 0.02 to 0.06%;    Si: 1.0% or less;    Mn: 1.0% or less;    P: 0.05% or less;    S: 0.01% or less;    Al: 0.005% or less;    Ti: 0.005% or less;    Cr: 11 to 30%;    Ni: 0.7% or less; and    
       the balance composed of Fe, and N and V as inevitable impurities, wherein N is contained to satisfy the relation to the C content represented by the following equations (1) and (2), and V is contained to satisfy the relation to the N content represented by the following equation (3):
   0.06≦(C+N)≦0.12  (1)  
   1≦N/C  (2)  
   1.5×10 −3 ≦(V×N)≦1.5×10 −2   (3)  
 wherein C, N and V: equal the contents (mass %) of the elements, further consisting, by mass %, of one or two of Nb and B to satisfy the following equation (4): 
   0.0030≦(Nb+10B)  (4)  
 
 wherein Nb and B equal the contents (mass %) of the elements;  
 wherein said sheet is made by continuous casting, reheating at 1050 to 1250° C., hot rolling with finish delivery temperature at 800 to 900° C. and cold rolling with 50-95% reduction.  
 
     
     
       5. A ferritic cold rolled stainless steel sheet according to claim  4    8  wherein Si is present between 0.03 and 0.5% by mass. 
     
     
       6. A ferritic cold rolled stainless steel according to claim  4    8  or  5  wherein Mn is present between 0.3 to 0.8% by mass. 
     
     
       7. A ferritic cold rolled stainless steel sheet according to  claim 8 , wherein N is present in an amount of ≦ 0 . 08 %  by mass.   
     
     
       8. A ferritic cold rolled stainless steel sheet having excellent formability, consisting of, by mass % , of:      C:  0 . 02  to  0 . 06   %;      Si:  1 . 0   %  or less;        Mn:  1 . 0   %  or less;        P:  0 . 05   %  or less;        S:  0 . 01   %  or less;        Al:  0 . 005   %  or less;        Ti:  0 . 005   %  or less;        Cr:  16 . 1  to  18 . 0   %;      Nb:  0 . 029   %  or less;        B:  0 . 003   %  or less;        Ni:  0 . 7   %  or less; and        the balance composed of Fe, and inevitable impurities, in a single - phase ferrite microstructure, wherein N is contained to satisfy the relation to the C content represented by the following equations  (   1   )  and  (   2   ) , and V is contained to satisfy the relation to the N content represented by the following equation  (   3   ): 
       0 . 06   ≦( C+N ) ≦ 0 . 12     (   1   )          1 ≦N/C   (   2   )      
           1 . 5 × 10     −3 ≦( V×N ) ≦ 1 . 5 × 10     −2   (   3   )
   wherein C, N and V: equal the contents  ( mass  %)  of the elements, further consisting, by mass  % , of one or two of Nb and B to satisfy the following equation  (   4   ): 
       0 . 0030   ≦( Nb+ 10 B )  (   4   )    
   wherein Nb and B equal the contents  ( mass  %)  of the elements;    
   wherein said sheet is made by continuous casting, reheating at  1050  to  1250 ° C., hot rolling, and followed by cold rolling with  50 - 95   %  reduction.