Composition for forming insulation film of oriented electrical steel sheet, method for forming insulation film by using same, and oriented electrical steel sheet having insulation film formed therein

1. A composition for forming an insulation coating film of an oriented electrical steel sheet, comprising:

a composite metal phosphate, a derivative thereof, or a mixture thereof, and

at least two colloidal silicas having different average particle diameters,

wherein a weight ratio of the colloidal silicas to the composite metal phosphate, the derivative thereof, or the mixture thereof (colloidal silicas/composite metal phosphate, a derivative thereof, or a mixture thereof) is 1.3 to 1.8.

2. The composition of claim 1 , wherein:

the at least two colloidal silicas include

a first colloidal silica having an average particle diameter of 12 nm, and

a second colloidal silica having an average particle diameter of 5 nm.

3. The composition of claim 2 , wherein:

a weight ratio of the second colloidal silica to the first colloidal silica is 1:9 to 9:1.

4. The composition of claim 1 , wherein:

the at least two colloidal silicas include

a sodium content inevitably included as impurities of less than 0.60 wt % (provided that except for 0 wt %).

5. The composition of claim 1 , wherein:

the composite metal phosphate, the derivative thereof, or the mixture thereof includes

one kind of composite metal phosphate selected from magnesium phosphate (Mg(H 2 PO 4 ) 2 ) and aluminum phosphate (Al(H 2 PO 4 ) 3 ), a derivative thereof, or a mixture thereof.

6. The composition of claim 5 , wherein:

the composite metal phosphate is

a mixture of the magnesium phosphate (Mg(H 2 PO 4 ) 2 ) and the aluminum phosphate (Al(H 2 PO 4 ) 3 ), and a content of the aluminum phosphate (Al(H 2 PO 4 ) 3 ) is less than 70 wt % (provided that except for 0 wt %) based on 100 wt % of the mixture.

7. The composition of claim 6 , wherein:

the composite metal phosphate has

a total solid content of more than 58 wt % to less than 63 wt %.

8. The composition of claim 5 , wherein:

the derivative of the composite metal phosphate is represented by

the following Chemical Formula 1 or 2:

9. The composition of claim 1 , further comprising:

chromium oxide, solid silica, or a mixture thereof.

10. An oriented electrical steel sheet having an insulation coating film formed thereon, comprising:

an oriented electrical steel sheet, and

an insulation coating film disposed on one surface or both surfaces of the oriented electrical steel sheet,

wherein the insulation coating film includes a composite metal phosphate, a derivative thereof, or a mixture thereof, and at least two colloidal silicas having different average particle diameters,

wherein a weight ratio of the colloidal silicas to the composite metal phosphate, a derivative thereof, or a mixture thereof (colloidal silicas/composite metal phosphate, a derivative thereof, or a mixture thereof) is 1.3 to 1.8.

11. The oriented electrical steel sheet of claim 10 , wherein:

in the oriented electrical steel sheet having the insulation coating film formed thereon,

Ps/P b is 3.0 or less (provided that except for 0) at the time of stress relief annealing (SRA) at 800° C.,

provided that Ps/P b is a result value obtained by measuring a crystallinity of the insulation coating film by synchrotron X-ray after the stress relief annealing at each temperature above, and means a ratio of a silica crystallization peak Ps to a baseline peak P b .

12. The oriented electrical steel sheet of claim 10 , wherein:

in the oriented electrical steel sheet having the insulation coating film formed thereon,

Ps/P b is 6.0 or less (provided that except for 0) at the time of stress relief annealing (SRA) at 840° C.,

provided that Ps/P b is a result value obtained by measuring a crystallinity of the insulation coating film by synchrotron X-ray after the stress relief annealing at the temperature above, and means a ratio of a silica crystallization peak Ps to a baseline peak P b .