Heat-resistant cold rolled ferritic stainless steel sheet, hot rolled ferritic stainless steel sheet for cold rolling raw material, and methods for producing same

Abstract

Provided is a heat-resistant cold rolled ferritic stainless steel sheet containing, in terms of mass %, 0.02% or less of C, 0.1% to 1.0% of Si, greater than 0.6% to 1.5% of Mn, 0.01% to 0.05% of P, 0.0001% to 0.0100% of S, 13.0% to 20.0% of Cr, 0.1% to 3.0% of Mo, 0.005% to 0.20% of Ti, 0.3% to 1.0% of Nb, 0.0002% to 0.0050% of B, 0.005% to 0.50% of Al, and 0.02% or less of N, with the balance being Fe and inevitable impurities, in which {111}-oriented grains are present at an area ratio of 20% or greater in a region from a surface layer to t/4 (t is a sheet thickness), {111}-oriented grains are present at an area ratio of 40% or greater in a region from t/4 to t/2, and {011}-oriented grains are present at an area ratio of 15% or less in the entire region in a thickness direction.

1 . A heat-resistant cold rolled ferritic stainless steel sheet comprising, in terms of mass %, 0.02% or less of C, 0.1% to 1.0% of Si, greater than 0.6% to 1.5% of Mn, 0.01% to 0.05% of P, 0.0001% to 0.0100% of S, 13.0% to 20.0% of Cr, 0.1% to 3.0% of Mo, 0.005% to 0.20% of Ti, 0.30% to 1.0% of Nb, 0.0002% to 0.0050% of B, 0.005% to 0.50% of Al, and 0.02% or less of N, with the balance being Fe and inevitable impurities,
 wherein when a sheet thickness is represented by t, {111}-oriented grains are present at an area ratio of 20% or greater in a region from a surface layer to t/4, {111}-oriented grains are present at an area ratio of 40% or greater in a region from t/4 to t/2, and {011}-oriented grains are present at an area ratio of 15% or less in the entire region in a thickness direction.   
     
     
         2 . The heat-resistant cold rolled ferritic stainless steel sheet according to  claim 1 , further comprising, in terms of mass %, one or more selected from 0.4% to 2.0% of Cu, 0.1% to 2.0% of Ni, 0.1% to 3.0% of W, 0.05% to 0.30% of Zr, 0.05% to 0.50% of Sn, 0.05% to 0.50% of Co, and 0.0002% to 0.0100% of Mg. 
     
     
         3 . A hot rolled ferritic stainless steel sheet for a material for cold rolling for manufacturing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 1 ,
 wherein when a sheet thickness is represented by t′, a microstructure in a region from t′/2 to t′/4 is a non-recrystallized microstructure.   
     
     
         4 . A method for producing the hot rolled ferritic steel sheet for a material for cold rolling according to  claim 3 , the method comprising:
 performing hot rolling under conditions where a heating temperature of a slab is set to be in a range of 1200° C. to 1300° C. and a finishing temperature is set to be in a range of 800° C. to 950° C. so as to form a hot rolled sheet;   coiling the hot rolled sheet at a coiling temperature of 500° C. or lower; and   then, annealing the hot rolled sheet at a temperature of 925° C. to 1000° C.   
     
     
         5 . A method for producing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 1 , the method comprising:
 subjecting a hot rolled ferritic steel sheet for a material for cold rolling in which when a sheet thickness is represented by t′, a microstructure in a region from t′/2 to t′/4 is a non-recrystallized microstructure to cold rolling at a rolling reduction ratio of 60% or greater so as to form a cold rolled sheet; and   annealing the cold rolled sheet at a temperature of 1000° C. to 1100° C.   
     
     
         6 . The method for producing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 5 , the method further comprising:
 performing hot rolling under conditions where a heating temperature of a slab is set to be in a range of 1200° C. to 1300° C. and a finishing temperature is set to be in a range of 800° C. to 950° C. so as to form a hot rolled sheet;   coiling the hot rolled sheet at a coiling temperature of 500° C. or lower; and   annealing the hot rolled sheet at a temperature of 925° C. to 1000° C. so as to produce the hot rolled ferritic steel sheet for a material for cold rolling.   
     
     
         7 . A hot rolled ferritic stainless steel sheet for a material for cold rolling for manufacturing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 2 ,
 wherein when a sheet thickness is represented by t′, a microstructure in a region from t′/2 to t′/4 is a non-recrystallized microstructure.   
     
     
         8 . A method for producing the hot rolled ferritic steel sheet for a material for cold rolling according to  claim 7 , the method comprising:
 performing hot rolling under conditions where a heating temperature of a slab is set to be in a range of 1200° C. to 1300° C. and a finishing temperature is set to be in a range of 800° C. to 950° C. so as to form a hot rolled sheet;   coiling the hot rolled sheet at a coiling temperature of 500° C. or lower; and   then, annealing the hot rolled sheet at a temperature of 925° C. to 1000° C.   
     
     
         9 . A method for producing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 2 , the method comprising:
 subjecting a hot rolled ferritic steel sheet for a material for cold rolling in which when a sheet thickness is represented by t′, a microstructure in a region from t′/2 to t′/4 is a non-recrystallized microstructure to cold rolling at a rolling reduction ratio of 60% or greater so as to form a cold rolled sheet; and   annealing the cold rolled sheet at a temperature of 1000° C. to 1100° C.   
     
     
         10 . The method for producing the heat-resistant cold rolled ferritic stainless steel sheet according to  claim 9 , the method further comprising:
 performing hot rolling under conditions where a heating temperature of a slab is set to be in a range of 1200° C. to 1300° C. and a finishing temperature is set to be in a range of 800° C. to 950° C. so as to form a hot rolled sheet;   coiling the hot rolled sheet at a coiling temperature of 500° C. or lower; and   annealing the hot rolled sheet at a temperature of 925° C. to 1000° C. so as to produce the hot rolled ferritic steel sheet for a material for cold rolling.