Non-oriented electrical steel sheet and method of manufacturing the same

Abstract

A non-oriented electrical steel sheet includes chemical compositions including, in terms of mass %: C: 0.0001% to 0.01%; Si: 0.05% to 7.0%; Mn: 0.01% to 3.0%; Al: 0.0020% to 3.0%; S: 0.0001% to 0.1%; P: 0.0010% to 0.15%; N: 0.0010% to 0.01%; Cu: 0.01% to 5.0%; and a remainder including Fe and impurities, in which I 2θ=46.4 which is a diffraction intensity of Cu sulfide having a hexagonal structure shown at 2θ=46.4° and I 2θ=32.3 which is a diffraction intensity of Cu sulfide having a cubic structure shown at 2θ=32.3°, which are obtained through a X-ray diffraction of an electrolytic extraction residue, satisfy I 2θ=46.4 /I 2θ=32.3 ≦0.5.

1 - 8 . (canceled) 
     
     
         9 . A non-oriented electrical steel sheet comprising chemical compositions including, in terms of mass %:
 C: 0.0001% to 0.01%;   Si: 0.05% to 7.0%;   Mn: 0.01% to 3.0%;   Al: 0.0020% to 3.0%;   S: 0.0001% to 0.1%;   P: 0.0010% to 0.15%;   N: 0.0010% to 0.01%;   Cu: 0.01% to 5.0%; and   a remainder including Fe and impurities,   wherein I 2θ=46.4  which is a diffraction intensity of Cu sulfide having a hexagonal structure shown at 2θ=46.4° and I 2θ=32.3  which is a diffraction intensity of Cu sulfide having a cubic structure shown at 2θ=32.3°, which are obtained through a X-ray diffraction of an electrolytic extraction residue, satisfy the following Expression 1.
     I   2θ=46.4   /I   2θ=32.3 ≦0.5  Expression 1
 
   
     
     
         10 . The non-oriented electrical steel sheet according to  claim 9 ,
 wherein, when a Cu content, in terms of mass %, is denoted as [% Cu] and an S content, in terms of mass %, is denoted as [% S], the [% Cu] and the [% S] satisfy [% Cu]/[% S]≧2.5.   
     
     
         11 . The non-oriented electrical steel sheet according to  claim 9 ,
 wherein 0.5 pieces/μm 3  to 50 pieces/μm 3  of sulfide containing Cu and having a diameter of 5 nm to 500 nm are contained.   
     
     
         12 . The non-oriented electrical steel sheet according to  claim 10 ,
 wherein 0.5 pieces/μm 3  to 50 pieces/μm 3  of sulfide containing Cu and having a diameter of 5 nm to 500 nm are contained.   
     
     
         13 . A method of manufacturing the non-oriented electrical steel sheet according to any one of  claims 9  to  12 , the method comprising:
 performing a hot rolling on a slab to obtain a hot-rolled steel sheet; 
 annealing the hot-rolled steel sheet; 
 pickling the hot-rolled steel sheet; 
 performing a cold rolling on the hot-rolled steel sheet to obtain a cold-rolled steel sheet; and 
 annealing the cold-rolled steel sheet, 
 wherein, in the annealing of the cold-rolled steel sheet, after the cold-rolled steel sheet is held at T1° C., which is represented in the following Expression 2, to 1530° C. for 30 seconds to 3600 seconds, when an average cooling rate from the T1° C. to T2° C., which is shown in Expression 3, is denoted as CR1 in the unit of ° C./sec and an average cooling rate from the T2° C. to T3° C., which is shown in Expression 4, is denoted as CR2 in the unit of ° C./sec, the cold-rolled steel sheet is cooled to a temperature range of the T3° C. or lower so that the CR1 and the CR2 satisfy Expressions 5, 6 and 7:
     T 1=17000/(14−log 10 ([% Cu] 2 ×[% S]))−273  Expression 2
 
     T 2=17000/(14−log 10 ([% Cu] 2 ×[% S]))−323  Expression 3
 
     T 3=17000/(14−log 10 ([% Cu] 2 ×[% S]))−473  Expression 4
 
   CR1>CR2  Expression 5
 
   5≦CR1≦500  Expression 6
 
   0.5≦CR2≦50  Expression 7
 
 
 where [% Cu] is a Cu content in terms of mass % and [% S] is an S content in terms of mass %. 
 
     
     
         14 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 13 ,
 wherein the CR1 further satisfies the following Expression 8.
   CR1>20  Expression 8
 
   
     
     
         15 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 13 ,
 wherein the CR2 further satisfies the following Expression 9.
   CR2≦20  Expression 9
 
   
     
     
         16 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 14 ,
 wherein the CR2 further satisfies the following Expression 9.
   CR2≦20  Expression 9
 
   
     
     
         17 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 13 , further comprising:
 subsequent to the annealing of the cold-rolled steel sheet, holding the cold-rolled steel sheet in a temperature range of the T2° C. or lower to the T3° C. or higher for 30 seconds or longer as an additional annealing.   
     
     
         18 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 14 , further comprising:
 subsequent to the annealing of the cold-rolled steel sheet, holding the cold-rolled steel sheet in a temperature range of the T2° C. or lower to the T3° C. or higher for 30 seconds or longer as an additional annealing.   
     
     
         19 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 15 , further comprising:
 subsequent to the annealing of the cold-rolled steel sheet, holding the cold-rolled steel sheet in a temperature range of the T2° C. or lower to the T3° C. or higher for 30 seconds or longer as an additional annealing.   
     
     
         20 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 16 , further comprising:
 subsequent to the annealing of the cold-rolled steel sheet, holding the cold-rolled steel sheet in a temperature range of the T2° C. or lower to the T3° C. or higher for 30 seconds or longer as an additional annealing.   
     
     
         21 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 13 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         22 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 14 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         23 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 15 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         24 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 16 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         25 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 17 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         26 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 18 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         27 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 19 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.   
     
     
         28 . The method of manufacturing a non-oriented electrical steel sheet according to  claim 20 ,
 wherein, in the annealing of the hot-rolled steel sheet, the hot-rolled steel sheet is cooled so that CR3 which is an average cooling rate from the T1° C. to a room temperature is 15° C./sec or higher.