Nonoriented electromagnetic steel sheet

Abstract

The present invention provides a non-oriented electrical steel sheet containing: 0-0.010% of C; at least one of Si and Al in a total amount of 0.03% to 0.5%, or more than 0.5% to 2.5%; 0.5% or less of Mn; 0.10% or more to 0.26% or less of P; 0.015% or less of S; and 0.010% or less of N, on a mass percentage basis, wherein the non-oriented electrical steel sheet has excellent dimensional accuracy during a punching step. When the Si content is low, the non-oriented electrical steel sheet has the excellent balance between high magnetic flux density and low core loss. When the Si content is medium or high, the non-oriented electrical steel sheet has the excellent balance between high magnetic flux density and high strength.

1 . A non-oriented electrical steel sheet containing: 
 0-0.010% of C;    at least one of Si and Al in a total amount of 0.03% to 0.5%;    0.5% or less of Mn;    0.10% or more to 0.26% or less of P;    0.015% or less of S; and    0.010% or less of N, on a mass percentage basis, the remainder being fe and unavoidable impurities, and having:    an average grain size of 30 μm or more to 80 μm or less.    
     
     
         2 . The non-oriented electrical steel sheet according to  claim 1  further containing: 
 at least one of Sb and Sn in a total amount of 0.40% or less on a mass percentage basis.  
 
     
     
         3 . The non-oriented electrical steel sheet according to  claim 1  or  2  further containing: 
 2.3% or less of Ni on a mass percentage basis.  
 
     
     
         4 . The non-oriented electrical steel sheet according to any one of  claims 1  to  3  further containing at least any one. of: 
 0.01% or less of Ca;  
 0.005% or less of B;  
 0.1% or less of Cr;  
 0.1% or less of Cu; and  
 0.1% or less of Mo,  
 on a mass percentage basis.  
 
     
     
         5 . The non-oriented electrical steel sheet according to any one of claims  1  to 4 further having a thickness of 0.35 mm or less.  
     
     
         6 . A non-oriented electrical steel sheet containing: 
 0-0.010% of C;    at least one of Si and Al in a total amount of more than 0.5% to 2.5%;    0.5% or less of Mn;    0.10% or more to 0.26% or less of P;    0.015% or less of S;    0.010% or less of N; and    2.3% or less of Ni according to needs,    on a mass percentage basis, the remainder being Fe and unavoidable impurities, and satisfying:    at least one of the formula P≦P A  and the formula P F ≦0.26,    wherein    P A =−0.2Si+0.12Mn−0.32Al+0.05Ni 2 +0.10Ni+0.36   (1); and P F =−0.34Si+0.20Mn−0.54Al+0.24Ni 2 +0.28Ni+0.76   (2),    where the unit of each element content is mass %.    
     
     
         7 . The non-oriented electrical steel sheet according to  claim 6  further containing: 
 at least one of Sb and Sn in a total amount of 0.40% or less on a mass percentage basis.  
 
     
     
         8 . The non-oriented electrical steel sheet according to  claim 6  or  7  further containing at least any one of: 
 0.01% or less of Ca;  
 0.005% or less of B;  
 0.1% or less of Cr;  
 0.1% or less of Cu; and  
 0.1% or less of Mo,  
 on a mass percentage basis.  
 
     
     
         9 . A method for manufacturing a non-oriented electrical steel sheet comprising the steps of: 
 hot-rolling a steel slab having the composition according to any one of  claims 1  to  4  under the conditions of a heating temperature in the single-phase austenite region and a coiling temperature of 650° C. or less; and then descaling the hot-rolled sheet to cold-roll the descaled sheet once or twice or more with an intermediate annealing sub-step therebetween, and then finish-annealing the cold-rolled sheet at a temperature of 700° C. or more in the single-phase ferrite region.    
     
     
         10 . A method for manufacturing a non-oriented electrical steel sheet comprising the steps of: 
 hot-rolling a steel slab having composition according to any one of  claims 1  to  4  under the conditions of a heating temperature in the single-phase austenite region and a coiling temperature of 650° C. or less;    annealing the hot-rolled sheet at a temperature of 900° C. or more in the single-phase ferrite region or at a temperature of more than the Ac3 transformation point in the single-phase austenite region if Ni is not contained or the Ni content is 1.0% by mass or less;    annealing the hot-rolled sheet at a temperature of more than the Ac3 transformation point in the single-phase austenite region if the Ni content is more than 1.0% to 2.3% by mass or less;    descaling the annealed sheet to cold-roll the descaled sheet once or twice or more with an intermediate annealing sub-step therebetween; and then    finish-annealing the cold-rolled sheet at a temperature of 700° C. or more in the single-phase ferrite region.    
     
     
         11 . A method for manufacturing a non-oriented electrical steel sheet comprising the steps of: 
 hot-rolling a steel slab having composition according to any one of claims  6  to 8 under the conditions of a heating temperature of 1000-1200° C. and a coiling temperature of 650° C. or less;    annealing the hot-rolled sheet according to needs;    descaling the hot-rolled or annealed sheet to cold-roll the descaled sheet once or twice or more with an intermediate annealing sub-step therebetween; and then    finish-annealing the cold-rolled sheet.