Grain-oriented electrical steel sheet and method for producing same

Abstract

A grain-oriented electrical steel sheet having a composition containing, in mass %, C: 0.005% or less, Si: 2.0% to 4.5%, and Mn: 0.5% or less, and also containing Sb and P in respective ranges satisfying 0.01%≦[% Sb]≦0.20% and 0.02%≦[% P]≦2.0×[% Sb], with a balance being Fe and incidental impurities, wherein when the steel sheet is excited to 1.0 T at 50 Hz in a rolling transverse direction, a magnetizing force (TD-H 10 ) and an iron loss (TD-W 10 ) are respectively (TD-H 10 )≧200 A/m and (TD-W 10 )≧1.60 W/kg. Thus, a grain-oriented electrical steel sheet having excellent transformer core loss can be obtained industrially stably at low cost.

1 . A grain-oriented electrical steel sheet having a composition containing, in mass %, C: 0.005% or less, Si: 2.0% to 4.5%, and Mn: 0.5% or less, and also containing Sb and P in respective ranges satisfying 0.01%≦[% Sb]≦0.20% and 0.02%≦[% P]≦2.0×[% Sb], with a balance being Fe and incidental impurities,
 wherein when the steel sheet is excited to 1.0 T at 50 Hz in a rolling transverse direction, a magnetizing force (TD-H 10 ) and an iron loss (TD-W 10 ) are respectively (TD-H 10 )≧200 A/m and (TD-W 10 )≧1.60 W/kg. 
 
     
     
         2 . The grain-oriented electrical steel sheet according to  claim 1 ,
 wherein the composition further contains, in mass %, one or more selected from Ni: 0.005% to 1.50%, Sn: 0.03% to 0.20%, Cu: 0.02% to 0.50%, Cr: 0.02% to 0.50%, Mo: 0.01% to 0.50%, and Nb: 0.002% to 0.01%.   
     
     
         3 . A method for producing a grain-oriented electrical steel sheet, comprising:
 providing a steel slab having a composition containing, in mass %, C: 0.08% or less, Si: 2.0% to 4.5%, and Mn: 0.5% or less, containing each of S, Se, and O: less than 50 ppm, N: less than 60 ppm, and sol.Al: less than 100 ppm, and also containing Sb and P in respective ranges satisfying 0.01%≦[% Sb]≦0.20% and 0.02%≦[% P]≦2.0×[% Sb], with a balance being Fe and incidental impurities;   optionally reheating the steel slab;   thereafter hot rolling the steel slab to obtain a hot rolled sheet;   optionally hot band annealing the hot rolled sheet;   thereafter cold rolling the hot rolled sheet either once, or twice or more with intermediate annealing performed therebetween, to obtain a cold rolled sheet having a final sheet thickness;   thereafter performing decarburization and primary recrystallization annealing on the cold rolled sheet, to obtain a decarburization and primary recrystallization annealed sheet;   thereafter applying an annealing separator mainly composed of MgO to the decarburization and primary recrystallization annealed sheet;   thereafter performing secondary recrystallization annealing on the decarburization and primary recrystallization annealed sheet, to obtain a secondary recrystallization annealed sheet; and   further performing flattening annealing on the secondary recrystallization annealed sheet,   wherein 2.0 mass % to 15.0 mass % magnesium sulfate is contained in the annealing separator,   the flattening annealing is performed at a temperature of 830° C. or more in an atmosphere having a H 2  partial pressure of 0.3% or more, and   when the steel sheet is excited to 1.0 T at 50 Hz in a rolling transverse direction, a magnetizing force (TD-H 10 ) and an iron loss (TD-W 10 ) are respectively (TD-H 10 )≧200 A/m and (TD-W 10 )≧1.60 W/kg.