Ferritic stainless steel sheet having superior punching workability and method for manufacturing the same

Abstract

A ferritic stainless steel sheet and a method for manufacturing the ferritic stainless steel sheet include a composition which contains 0.0030 to 0.012 mass percent of C, 0.13 mass percent or less of Si, 0.25 mass percent or less of Mn, 0.04 mass percent or less of P, 0.005 mass percent or less of S, 0.06 mass percent or less of Al, 0.0030 to 0.012 mass percent of N, 20.5 to 23.5 mass percent of Cr, 0.3 to 0.6 mass percent of Cu, 0.5 mass percent or less of Ni, 0.3 to 0.5 mass percent of Nb, 0.05 to 0.15 mass percent of Ti, and the balance being Fe and inevitable impurities is hot-rolled at a finishing temperature of 900° C. or more and at a coiling temperature of 400 to 550° C., softening annealing is performed on an obtained hot-rolled steel sheet, picking is further performed, and cold rolling is subsequently performed.

1 . A ferritic stainless steel sheet comprising: a composition which contains 0.0030 to 0.012 mass percent of C, 0.13 mass percent or less of Si, 0.25 mass percent or less of Mn, 0.04 mass percent or less of P, 0.005 mass percent or less of S, 0.06 mass percent or less of Al, 0.0030 to 0.012 mass percent of N, 20.5 to 23.5 mass percent of Cr, 0.3 to 0.6 mass percent of Cu, 0.5 mass percent or less of Ni, 0.3 to 0.5 mass percent of Nb, 0.05 to 0.15 mass percent of Ti, and the balance being Fe and inevitable impurities; and a structure in which a ferrite crystal grain size is 20 μm or less, and a ratio [Nb]/[Ti] of a Nb content to a Ti content contained in a NbTi complex carbonitride present in ferrite crystal grain boundaries is in the range of 1 to 10. 
     
     
         2 . The ferritic stainless steel sheet according to  claim 1 , wherein the Nb content is 0.3 to 0.45 mass percent, and the Ti content is 0.05 to 0.12 mass percent. 
     
     
         3 . The ferritic stainless steel sheet according to  claim 1 , further comprising 0.001 mass percent or less of B, 0.1 mass percent or less of Mo, 0.05 mass percent or less of V, and 0.01 mass percent or less of Ca. 
     
     
         4 . A method for manufacturing a ferritic stainless steel sheet comprising:
 performing hot-rolling of a slab having a composition which contains 0.0030 to 0.012 mass percent of C, 0.13 mass percent or less of Si, 0.25 mass percent or less of Mn, 0.04 mass percent or less of P, 0.005 mass percent or less of S, 0.06 mass percent or less of Al, 0.0030 to 0.012 mass percent of N, 20.5 to 23.5 mass percent of Cr, 0.3 to 0.6 mass percent of Cu, 0.5 mass percent or less of Ni, 0.3 to 0.5 mass percent of Nb, 0.05 to 0.15 mass percent of Ti, and the balance being Fe and inevitable impurities at a finishing temperature of 900° C. or more and at a coiling temperature of 400 to 550° C.;   performing softening annealing of an obtained hot-rolled steel sheet;   performing pickling;   performing cold rolling; and   performing recrystallization annealing of an obtained cold-rolled steel sheet.   
     
     
         5 . The method for manufacturing the ferritic stainless steel sheet according to  claim 4 , wherein the Nb content is 0.3 to 0.45 mass percent, and the Ti content is 0.05 to 0.12 mass percent. 
     
     
         6 . The method for manufacturing the ferritic stainless steel sheet according to  claim 4 , further comprising 0.001 mass percent or less of B, 0.1 mass percent or less of Mo, 0.05 mass percent or less of V, and 0.01 mass percent or less of Ca. 
     
     
         7 . The method for manufacturing a ferritic stainless steel sheet according to one of  claim 4 , wherein a slab heating temperature is 1,000° C. or more. 
     
     
         8 . The ferritic stainless steel sheet according to  claim 2 , further comprising 0.001 mass percent or less of B, 0.1 mass percent or less of Mo, 0.05 mass percent or less of V, and 0.01 mass percent or less of Ca. 
     
     
         9 . The method for manufacturing the ferritic stainless steel sheet according to  claim 5 , further comprising 0.001 mass percent or less of B, 0.1 mass percent or less of Mo, 0.05 mass percent or less of V, and 0.01 mass percent or less of Ca. 
     
     
         10 . The method for manufacturing a ferritic stainless steel sheet according to one of  claim 5 , wherein a slab heating temperature is 1,000° C. or more. 
     
     
         11 . The method for manufacturing a ferritic stainless steel sheet according to one of  claim 6 , wherein a slab heating temperature is 1,000° C. or more. 
     
     
         12 . The method for manufacturing a ferritic stainless steel sheet according to one of  claim 9 , wherein a slab heating temperature is 1,000° C. or more.