Method of manufacturing a stainless steel sheet

Abstract

A method of manufacturing a stainless steel is provided. The stainless steel contains C, Si, Mn, P, S, Cr, Ni, and N in predetermined amounts. A total volume fraction of Cr-based carbides with a grain size of 2.0 μm or more is ≤10%. A steel slab is held at 1200° C.-1350° C. for at least 30 minutes and then hot rolled to obtain a hot-rolled steel sheet. The hot-rolled steel sheet is coiled, where at least three rolling passes with a finish temperature of ≥1050° C. and a rolling reduction of ≥20% are performed, and a coiling temperature of the hot-rolled steel sheet is ≥600° C. The hot-rolled steel sheet is subjected to hot-rolled sheet annealing to obtain a hot-rolled and annealed steel sheet, where a holding temperature is 750° C.-900° C. and a holding time is ≥10 minutes.

1 . A method of manufacturing a stainless steel, the stainless steel comprising:
 a chemical composition containing, in mass %,   C: 0.45% or more and 0.60% or less,   Si: 0.05% or more and 1.00% or less,   Mn: 0.05% or more and 1.00% or less,   P: 0.05% or less,   S: 0.020% or less,   Cr: 13.0% or more and less than 16.0%,   Ni: 0.10% or more and 1.00% or less, and   N: 0.010% or more and 0.200% or less with the balance being Fe and inevitable impurities,   wherein a total volume fraction of Cr-based carbides with a grain size of 2.0 μm or more is 10% or less,   the method comprising:   a first step in which a steel slab having the chemical composition is held at 1200° C. or higher and 1350° C. or lower for at least 30 minutes,   a second step in which the steel slab is hot rolled to obtain a hot-rolled steel sheet and the hot-rolled steel sheet is coiled, and   a third step in which the hot-rolled steel sheet is subjected to hot-rolled sheet annealing to obtain a hot-rolled and annealed steel sheet   wherein in hot rolling of the second step, at least three rolling passes with a finish temperature of 1050° C. or higher and a rolling reduction of 20% or more are performed, and a coiling temperature of the hot-rolled steel sheet is 600° C. or higher, and   in the hot-rolled sheet annealing of the third step, a holding temperature is 750° C. or higher and 900° C. or lower and a holding time is 10 minutes or more.   
     
     
         2 . The method according to  claim 1 , wherein the chemical composition further contains, in mass %, at least one selected from the group consisting of
 Mo: 0.05% or more and 1.00% or less,   Cu: 0.05% or more and 1.00% or less,   Co: 0.05% or more and 0.50% or less,   Al: 0.001% or more and 0.100% or less,   Ti: 0.01% or more and 0.10% or less,   Nb: 0.01% or more and 0.10% or less,   V: 0.05% or more and 0.50% or less,   Zr: 0.01% or more and 0.10% or less,   Mg: 0.0002% or more and 0.0050% or less,   B: 0.0002% or more and 0.0050% or less,   Ca: 0.0003% or more and 0.0030% or less, and   REM: 0.01% or more and 0.10% or less.   
     
     
         3 . The method according to  claim 1 , comprising the fourth step in which the hot-rolled and annealed steel sheet is cold rolled to obtain a cold-rolled steel sheet. 
     
     
         4 . The method according to  claim 3 , comprising the fifth step in which the cold-rolled steel sheet is subjected to cold-rolled sheet annealing to obtain a cold-rolled and annealed steel sheet
 wherein in the cold-rolled sheet annealing, a holding temperature is 700° C. or higher and 850° C. or lower and a holding time is 5 seconds or more.   
     
     
         5 . The method according to  claim 1 , comprising the sixth step in which the hot-rolled and annealed steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         6 . The method according to  claim 3 , comprising the sixth step in which the cold-rolled steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         7 . The method according to  claim 4 , comprising the sixth step in which the cold-rolled and annealed steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         8 . The method according to  claim 5 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.   
     
     
         9 . The method according to  claim 6 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.   
     
     
         10 . The method according to  claim 7 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.   
     
     
         11 . The method according to  claim 2 , comprising the fourth step in which the hot-rolled and annealed steel sheet is cold rolled to obtain a cold-rolled steel sheet. 
     
     
         12 . The method according to  claim 11 , comprising the fifth step in which the cold-rolled steel sheet is subjected to cold-rolled sheet annealing to obtain a cold-rolled and annealed steel sheet
 wherein in the cold-rolled sheet annealing, a holding temperature is 700° C. or higher and 850° C. or lower and a holding time is 5 seconds or more.   
     
     
         13 . The method according to  claim 2 , comprising the sixth step in which the hot-rolled and annealed steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         14 . The method according to  claim 11 , comprising the sixth step in which the cold-rolled steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         15 . The method according to  claim 12 , comprising the sixth step in which the cold-rolled and annealed steel sheet is subjected to quenching treatment
 wherein in the quenching treatment, a holding temperature is 950° C. or higher and 1200° C. or lower, a holding time is 5 seconds or more and 30 minutes or less, and an average cooling rate after holding is 1° C./s or more.   
     
     
         16 . The method according to  claim 13 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.   
     
     
         17 . The method according to  claim 14 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.   
     
     
         18 . The method according to  claim 15 , comprising the seventh step in which the steel sheet subjected to quenching treatment is subjected to a tempering treatment
 wherein in the tempering treatment, a holding temperature is 100° C. or higher and 800° C. or lower and a holding time is 5 minutes or more.