Method of manufacturing grain-oriented electrical steel sheet

Abstract

Hot rolling is performed on a steel with a predetermined composition containing Ti: 0.0020 mass % to 0.010 mass % and/or Cu: 0.010 mass % to 0.50 mass % to obtain a hot-rolled steel sheet. Annealing is performed on the hot-rolled steel sheet to obtain an annealed steel sheet. Cold rolling is performed on the annealed steel sheet to obtain a cold-rolled steel sheet. Decarburization annealing is performed on the cold-rolled steel sheet at a temperature of 800° C. to 950° C. to obtain a decarburization annealed steel sheet. Then, nitridation treatment is performed on the decarburization annealed steel sheet at 700° C. to 850° C. to obtain a nitrided steel sheet. Finish annealing is performed on the nitrided steel sheet.

1 . A method of manufacturing a grain-oriented electrical steel sheet, comprising:
 performing hot rolling of a steel containing Si: 2.5 mass % to 4.0 mass %, C, 0.01 mass % to 0.060 mass %, Mn: 0.05 mass % to 0.20 mass %, acid-soluble Al: 0.020 mass % to 0.040 mass %, N: 0.002 mass % to 0.012 mass %, S: 0.001 mass % to 0.010 mass %, and P: 0.01 mass % to 0.08 mass %, further containing at least one kind selected from a group consisting of Ti: 0.0020 mass % to 0.010 mass % and Cu: 0.010 mass % to 0.50 mass %, and a balance composed of Fe and inevitable impurities, to obtain a hot-rolled steel sheet;   performing annealing on the hot-rolled steel sheet to obtain an annealed steel sheet;   performing cold rolling on the annealed steel sheet to obtain a cold-rolled steel sheet;   performing decarburization annealing on the cold-rolled steel sheet at a temperature of 800° C. to 950° C. to obtain a decarburization annealed steel sheet;   then, performing nitridation treatment on the decarburization annealed steel sheet at 700° C. to 850° C. to obtain a nitrided steel sheet; and   performing finish annealing on the nitrided steel sheet.   
     
     
         2 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 1 , wherein the hot rolling on the steel is performed after heating the steel to a temperature of 1250° C. or lower. 
     
     
         3 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 1 , wherein the steel further contains at least one kind selected from a group consisting of Cr: 0.010 mass % to 0.20 mass %, Sn: 0.010 mass % to 0.20 mass %, Sb: 0.010 mass % to 0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se: 0.005 mass % to 0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb: 0.005 mass % to 0.02 mass %, B: 0.005 mass % to 0.02 mass %, V: 0.005 mass % to 0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and As: 0.005 mass % to 0.02 mass %. 
     
     
         4 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 2 , wherein the steel further contains at least one kind selected from a group consisting of Cr: 0.010 mass % to 0.20 mass %, Sn: 0.010 mass % to 0.20 mass %, Sb: 0.010 mass % to 0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se: 0.005 mass % to 0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb: 0.005 mass % to 0.02 mass %, B: 0.005 mass % to 0.02 mass %, V: 0.005 mass % to 0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and As: 0.005 mass % to 0.02 mass %. 
     
     
         5 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 1 , wherein
 a Ti content in the steel is 0.0020 mass % to 0.0080 mass %,   a Cu content in the steel is 0.01 mass % to 0.10 mass %, and   a relation of “20×[Ti]+[Cu]≦0.18” is established where the Ti content (mass %) in the steel is expressed as [Ti] and the Cu content (mass %) is expressed as [Cu].   
     
     
         6 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 2 , wherein
 a Ti content in the steel is 0.0020 mass % to 0.0080 mass %,   a Cu content in the steel is 0.01 mass % to 0.10 mass %, and   a relation of “20×[Ti]+[Cu]≦0.18” is established where the Ti content (mass %) in the steel is expressed as [Ti] and the Cu content (mass %) is expressed as [Cu].   
     
     
         7 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 3 , wherein
 a Ti content in the steel is 0.0020 mass % to 0.0080 mass %,   a Cu content in the steel is 0.01 mass % to 0.10 mass %, and   a relation of “20×[Ti]+[Cu]≦0.18” is established where the Ti content (mass %) in the steel is expressed as [Ti] and the Cu content (mass %) is expressed as [Cu].   
     
     
         8 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 4 , wherein
 a Ti content in the steel is 0.0020 mass % to 0.0080 mass %,   a Cu content in the steel is 0.01 mass % to 0.10 mass %, and   a relation of “20×[Ti]+[Cu]≦0.18” is established where the Ti content (mass %) in the steel is expressed as [Ti] and the Cu content (mass %) is expressed as [Cu].   
     
     
         9 . The method of manufacturing a grain-oriented electrical steel sheet according wherein a relation of “10×[Ti]+[Cu]≦0.07” is established to  claim 5 . 
     
     
         10 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 6 , wherein a relation of “10×[Ti]+[Cu]≦0.07” is established. 
     
     
         11 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 7 , wherein a relation of “10×[Ti]+[Cu]≦0.07” is established. 
     
     
         12 . The method of manufacturing a grain-oriented electrical steel sheet according to  claim 8 , wherein a relation of “10×[Ti]+[Cu]≦0.07” is established.