Method for manufacturing steel sheet

Abstract

A method for manufacturing a steel sheet, including annealing a steel raw material having an Si content of 1.0 mass % or more and a Cr content of 1 mass % or less, under a condition satisfying:a following formula 1A if the Cr content of the steel raw material is 0.2 mass % or more and 0.6 mass % or less:0.19≤exp⁡(-10770T+273)*t≤0.75Cr[%]+0.48Formula⁢1⁢Aa following formula 1B if the Cr content of the steel raw material is less than 0.2 mass %:0.19≤exp⁡(-10770T+273)*t≤0.63Formula⁢1⁢Bor a following formula 1C if the Cr content of the steel raw material is more than 0.6 mass % and 1.0 mass % or less:0.19≤exp⁡(-10770T+273)*t≤0.93Formula⁢1⁢Cwhere in the formulas 1A, 1B, and 1C, T is 500° C. or higher and a soaking temperature (° C.) during annealing, t is a soaking time (seconds) during annealing, and Cr [%] is the Cr content (mass %) of the steel raw material.

1 . A method for manufacturing a steel sheet comprising:
 annealing a steel raw material having an Si content of 1.0 mass % or more and a Cr content of 1 mass % or less, under a condition satisfying:   a following formula  1 A if the Cr content of the steel raw material is 0.2 mass % or more and 0.6 mass % or less:   
       
         
           
             
               
                 
                   
                     0.19 
                     ≤ 
                     
                       
                         exp 
                         ⁡ 
                         ( 
                         
                           - 
                           
                             
                               1 
                               ⁢ 
                               0 
                               ⁢ 
                               7 
                               ⁢ 
                               7 
                               ⁢ 
                               0 
                             
                             
                               T 
                               + 
                               273 
                             
                           
                         
                         ) 
                       
                       * 
                       t 
                     
                     ≤ 
                     
                       
                         0.7 
                         
                           Cr 
                           [ 
                           % 
                           ] 
                         
                       
                       + 
                       0.48 
                     
                   
                 
                 
                   
                     Formula 
                     ⁢ 
                         
                     1 
                     ⁢ 
                     A 
                   
                 
               
             
           
         
         a following formula 1B if the Cr content of the steel raw material is less than 0.2 mass %: 
       
       
         
           
             
               
                 
                   
                     0.19 
                     ≤ 
                     
                       
                         exp 
                         ⁡ 
                         ( 
                         
                           - 
                           
                             10770 
                             
                               T 
                               + 
                               
                                 2 
                                 ⁢ 
                                 7 
                                 ⁢ 
                                 3 
                               
                             
                           
                         
                         ) 
                       
                       * 
                       t 
                     
                     ≤ 
                     
                       0 
                       .63 
                     
                   
                 
                 
                   
                        
                     
                       Formula 
                       ⁢ 
                           
                       1 
                       ⁢ 
                       B 
                     
                   
                 
               
             
           
         
         or a following formula 1C if the Cr content of the steel raw material is more than 0.6 mass % and 1.0 mass % or less: 
       
       
         
           
             
               
                 
                   
                     0.19 
                     ≤ 
                     
                       
                         exp 
                         ⁡ 
                         ( 
                         
                           - 
                           
                             
                               1 
                               ⁢ 
                               0 
                               ⁢ 
                               7 
                               ⁢ 
                               7 
                               ⁢ 
                               0 
                             
                             
                               T 
                               + 
                               
                                 2 
                                 ⁢ 
                                 7 
                                 ⁢ 
                                 3 
                               
                             
                           
                         
                         ) 
                       
                       * 
                       t 
                     
                     ≤ 
                     0.93 
                   
                 
                 
                   
                     Formula 
                     ⁢ 
                         
                     1 
                     ⁢ 
                     C 
                   
                 
               
             
           
         
         wherein in the formulas 1A, 1B, and 1C, T is 500° C. or higher and a soaking temperature (° C.) during annealing, t is a soaking time (seconds) during annealing, and Cr is the Cr content (mass %) of the steel raw material. 
       
     
     
         2 . The method for manufacturing a steel sheet according to  claim 1 , further comprising hot rolling the steel raw material before the annealing and coiling a steel sheet at 500° C. to 700° C. 
     
     
         3 . The method for manufacturing a steel sheet according to  claim 1 , further comprising pickling the steel sheet after the annealing and then cold rolling the steel sheet.