Hot-rolled and annealed ferritic stainless steel sheet and method for manufacturing the same

Abstract

The present invention provides a hot-rolled and annealed ferritic stainless steel sheet which has sufficient corrosion resistance and in which cracks can be prevented during blanking into a thick flange, and a method for manufacturing the same. A hot-rolled and annealed ferritic stainless steel sheet has a chemical composition containing, in percent by mass, C: 0.001% to 0.020%, Si: 0.05% to 1.00%, Mn: 0.05% to 1.00%, P: 0.04% or less, S: 0.01% or less, Al: 0.001% to 0.100%, Cr: 10.0% to 19.0%, Ni: 0.65% to 1.50%, Ti: 0.10% to 0.40%, and N: 0.001% to 0.020%, with the balance being Fe and unavoidable impurities, and has a threshold stress intensity factor KIC of 35 MPa·m1/2 or more.

1 . A hot-rolled and annealed ferritic stainless steel sheet having a chemical composition containing, in percent by mass,
 C: 0.001% to 0.020%,   Si: 0.05% to 1.00%,   Mn: 0.05% to 1.00%,   P: 0.04% or less,   S: 0.01% or less,   Al: 0.001% to 0.100%,   Cr: 10.0% to 19.0%,   Ni: 0.65% to 1.50%,   Ti: 0.10% to 0.40%, and   N: 0.001% to 0.020%, with the balance being Fe and unavoidable impurities; and   having a threshold stress intensity factor K IC  of 35 MPa·m 1/2  or more.   
     
     
         2 . The hot-rolled and annealed ferritic stainless steel sheet according to  claim 1 , wherein the chemical composition further contains, in percent by mass, one or two or more selected from Cu: 0.01% to 1.00%,
 Mo: 0.01% to 2.00%,   W: 0.01% to 0.20%, and   Co: 0.01% to 0.20%.   
     
     
         3 . The hot-rolled and annealed ferritic stainless steel sheet according to  claim 1 , wherein the chemical composition further contains, in percent by mass, one or two or more selected from V: 0.01% to 0.20%,
 Nb: 0.01% to 0.10%,   Zr: 0.01% to 0.20%,   REM: 0.001% to 0.100%,   B: 0.0002% to 0.0025%,   Mg: 0.0005% to 0.0030%, and   Ca: 0.0003% to 0.0030%.   
     
     
         4 . The hot-rolled and annealed ferritic stainless steel sheet according to  claim 2 , wherein the chemical composition further contains, in percent by mass, one or two or more selected from V: 0.01% to 0.20%,
 Nb: 0.01% to 0.10%,   Zr: 0.01% to 0.20%,   REM: 0.001% to 0.100%,   B: 0.0002% to 0.0025%,   Mg: 0.0005% to 0.0030%, and   Ca: 0.0003% to 0.0030%.   
     
     
         5 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 1 , comprising:
 a hot rolling step of performing finish rolling with three or more passes; and   a hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 600° C. to 1,100° C. on a hot-rolled steel sheet obtained in the hot rolling step,   wherein, in the hot rolling step, the temperature of final three passes of finish rolling is set at 800° C. to 1,100° C., and the cumulative rolling reduction of the final three passes is set at 25% or more.   
     
     
         6 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 2 , comprising:
 a hot rolling step of performing finish rolling with three or more passes; and   a hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 600° C. to 1,100° C. on a hot-rolled steel sheet obtained in the hot rolling step,   wherein, in the hot rolling step, the temperature of final three passes of finish rolling is set at 800° C. to 1,100° C., and the cumulative rolling reduction of the final three passes is set at 25% or more.   
     
     
         7 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 3 , comprising:
 a hot rolling step of performing finish rolling with three or more passes; and   a hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 600° C. to 1,100° C. on a hot-rolled steel sheet obtained in the hot rolling step,   wherein, in the hot rolling step, the temperature of final three passes of finish rolling is set at 800° C. to 1,100° C., and the cumulative rolling reduction of the final three passes is set at 25% or more.   
     
     
         8 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 4 , comprising:
 a hot rolling step of performing finish rolling with three or more passes; and   a hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 600° C. to 1,100° C. on a hot-rolled steel sheet obtained in the hot rolling step,   wherein, in the hot rolling step, the temperature of final three passes of finish rolling is set at 800° C. to 1,100° C., and the cumulative rolling reduction of the final three passes is set at 25% or more.