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

Abstract

A hot-rolled and annealed ferritic stainless steel sheet which has sufficient corrosion resistance and with which it is possible to inhibit a crack from occurring when punching work is performed to form a thick-walled flange and a method for manufacturing the steel sheet. The hot-rolled and annealed ferritic stainless steel sheet has a chemical composition comprising, 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 24.0%, Ni: 0.01% to 0.60%, Ti: 0.10% to 0.40%, N: 0.001% to 0.020%, and the balance being Fe and inevitable impurities, and a threshold stress intensity factor KIC of 20 MPa·m1/2 or more.

1 . A hot-rolled and annealed ferritic stainless steel sheet having a chemical composition comprising, 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 24.0%,   Ni: 0.01% to 0.60%,   Ti: 0.10% to 0.40%,   N: 0.001% to 0.020%, and   the balance being Fe and inevitable impurities,   wherein the steel sheet has a threshold stress intensity factor K IC  of 20 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 comprises, by mass %, at least one selected from the group consisting of 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 comprises, by mass %, at least one selected from the group consisting of 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 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 1 , the method comprising:
 performing a hot-rolling process including finish rolling composed of three passes or more, in which rolling in a final three passes of the finish rolling is performed at a temperature in a range of 800° C. to 1100° C. with an accumulated rolling reduction ratio of 25% or more to obtain a hot-rolled steel sheet; and   performing hot-rolled-sheet annealing on the hot-rolled steel sheet at a temperature in a range of 800° C. to 1100° C.   
     
     
         5 . The hot-rolled and annealed ferritic stainless steel sheet according to  claim 2 , wherein the chemical composition further comprises, by mass %, at least one selected from the group consisting of 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%. 
     
     
         6 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 2 , the method comprising:
 performing a hot-rolling process including finish rolling composed of three passes or more, in which rolling in a final three passes of the finish rolling is performed at a temperature in a range of 800° C. to 1100° C. with an accumulated rolling reduction ratio of 25% or more to obtain a hot-rolled steel sheet; and   performing hot-rolled-sheet annealing on the hot-rolled steel sheet at a temperature in a range of 800° C. to 1100° C.   
     
     
         7 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 3 , the method comprising:
 performing a hot-rolling process including finish rolling composed of three passes or more, in which rolling in a final three passes of the finish rolling is performed at a temperature in a range of 800° C. to 1100° C. with an accumulated rolling reduction ratio of 25% or more to obtain a hot-rolled steel sheet; and   performing hot-rolled-sheet annealing on the hot-rolled steel sheet at a temperature in a range of 800° C. to 1100° C.   
     
     
         8 . A method for manufacturing the hot-rolled and annealed ferritic stainless steel sheet according to  claim 5 , the method comprising:
 performing a hot-rolling process including finish rolling composed of three passes or more, in which rolling in a final three passes of the finish rolling is performed at a temperature in a range of 800° C. to 1100° C. with an accumulated rolling reduction ratio of 25% or more to obtain a hot-rolled steel sheet; and   performing hot-rolled-sheet annealing on the hot-rolled steel sheet at a temperature in a range of 800° C. to 1100° C.