Martensite-based stainless steel material and method for producing same

Abstract

A martensite-based stainless steel material has a composition containing: 0.30 to 0.60% by mass of C; 0.05 to 1.00% by mass of Si; 0.05 to 1.50% by mass of Mn; 0.040% by mass or less of P; 0.030% by mass or less of S; 13.0 to 18.0% by mass of Cr; 0.01 to 0.30% by mass of Ni; 0.01 to 1.00% by mass of Mo; 0.030% by mass or less of Al; 0.010 to 0.350% by mass of N; 0.0001 to 0.0030% by mass of Ca; and 0.001 to 0.010% by mass of O; 2.5 C+N being 1.10% or more, and the balance being Fe and impurities. The martensite-based stainless steel material has an average grain diameter of carbides of 0.50 μm or less. Also, the number of the carbides having a size of 10 μm or more is 0.20/cm 2 or less.

1 . A martensite-based stainless steel material having a composition comprising: 0.30 to 0.60% by mass of C; 0.05 to 1.00% by mass of Si; 0.05 to 1.50% by mass of Mn; 0.040% by mass or less of P; 0.030% by mass or less of S; 13.0 to 18.0% by mass of Cr; 0.01 to 0.30% by mass of Ni; 0.01 to 1.00% by mass of Mo; 0.030% by mass or less of Al; 0.010 to 0.350% by mass of N; 0.0001 to 0.0030% by mass of Ca; and 0.001 to 0.010% by mass of O; 2.5 C+N being 1.10% or more, and the balance being Fe and impurities,
 wherein the martensite-based stainless steel material has an average grain diameter of carbides of 0.50 μm or less, and   wherein the number of the carbides having a size of 10 μm or more is 0.20/cm 2  or less.   
     
     
         2 . The martensite-based stainless steel material according to  claim 1 , further comprising at least one of: 0.50% by mass or less of V; 0.30% by mass or less of Nb; 0.3% by mass or less of Ti; 4.0% by mass or less of Cu; 0.100% by mass or less of Sn; 0.0050% by mass or less of B; and 0.30% by mass or less of Co. 
     
     
         3 . The martensite-based stainless steel material according to  claim 1 , wherein the martensite-based stainless steel material has a hardness of 500 HV or more after quenching or quenching and tempering. 
     
     
         4 . (canceled) 
     
     
         5 . A method for producing a martensite-based stainless steel material, wherein the method comprises a hot rolling step of subjecting a slab to a heat treatment at a temperature equal to or higher than T represented by the following equation (1) for 1 to 5 hours, and then subjecting the slab to hot rolling:
   T[° C.]=6500/(4−log C[%])−273  (1),
   wherein the slab has a composition comprising: 0.30 to 0.60% by mass of C; 0.05 to 1.00% by mass of Si; 0.05 to 1.50% by mass of Mn; 0.040% by mass or less of P; 0.030% by mass or less of S; 13.0 to 18.0% by mass of Cr; 0.01 to 0.30% by mass of Ni; 0.01 to 1.00% by mass of Mo; 0.030% by mass or less of Al; 0.010 to 0.350% by mass of N; 0.0001 to 0.0030% by mass of Ca; and 0.001 to 0.010% by mass of O; 2.5 C+N being 1.10% or more, and the balance being Fe and impurities.   
     
     
         6 . The method for producing a martensite-based stainless steel material according to  claim 5 , wherein the slab further comprises at least one of: 0.50% by mass or less of V; 0.30% by mass or less of Nb; 0.3% by mass or less of Ti; 4.0% by mass or less of Cu; 0.100% by mass or less of Sn; 0.0050% by mass or less of B; and 0.30% by mass or less of Co. 
     
     
         7 . The method for producing a martensite-based stainless steel material according to  claim 5 , wherein the method further comprises a softening step of performing annealing at a temperature of Ac1 point to (Ac1 point—50° C.) for 1 to 5 hours, after winding a hot-rolled sheet at a coiling temperature of 800° C. to 900° C. in the hot rolling step. 
     
     
         8 . The method for producing a martensite-based stainless steel material according to  claim 7 , further comprising:
 a cold rolling step of subjecting a hot-rolled annealed sheet obtained in the softening step to cold rolling; and   an annealing step of heating a cold-rolled sheet obtained in the cold rolling step in a temperature range from 100° C. to Ac1 point to (Ac1 point—50° C.) at a heating rate of 50° C./second or more.   
     
     
         9 . The martensite-based stainless steel material according to  claim 2 , wherein the martensite-based stainless steel material has a hardness of 500 HV or more after quenching or quenching and tempering. 
     
     
         10 . The method for producing a martensite-based stainless steel material according to  claim 6 , wherein the method further comprises a softening step of performing annealing at a temperature of Ac1 point to (Ac1 point—50° C.) for 1 to 5 hours, after winding a hot-rolled sheet at a coiling temperature of 800° C. to 900° C. in the hot rolling step. 
     
     
         11 . The method for producing a martensite-based stainless steel material according to  claim 10 , further comprising:
 a cold rolling step of subjecting a hot-rolled annealed sheet obtained in the softening step to cold rolling; and   an annealing step of heating a cold-rolled sheet obtained in the cold rolling step in a temperature range from 100° C. to Ac1 point to (Ac1 point—50° C.) at a heating rate of 50° C./second or more.