A grain oriented electrical steel sheet according to an embodiment of the present invention comprises: an electrical steel sheet base comprising 2.0 to 7.0 weight % of Si and 0.01 to 0.07 weight % of Sb, and the remainder being Fe and other unavoidable impurities; a fine-grained interfacial layer positioned in a direction toward the inside of the electrical steel sheet base from the surface of the electrical steel sheet base; a base coating layer positioned on the fine-grained interfacial layer; and an insulating coating layer positioned on the base coating layer.

The grain oriented electrical steel sheet according to an embodiment of the present invention satisfies Formula 1 below.

([P][PS]+[F][FS]+[C][CS])/([S]/2)13.0 MPa [Formula 1]

(wherein [P] is thickness (m) of the insulating coating layer, [PS] is residual stress (MPa) of the insulating coating layer, [F] is thickness (m) of the base coating layer, [FS] is residual stress (MPa) of the base coating layer, [C] is thickness(m) of the fine-grained interfacial layer, [CS] is residual stress (MPa) of the fine-grained interfacial layer, and [S] is thickness (m) of the electrical steel sheet base)

The grain-oriented electrical steel sheet according to the present invention is a grain-oriented electrical steel sheet having a base steel sheet (1), an intermediate layer (4) disposed to be in contact with the base steel sheet (1), and an insulation coating (3) disposed to be in contact with the intermediate layer (4), and the grain-oriented electrical steel sheet includes a surface of the base steel sheet (1) having a groove (G) which extends in a direction intersecting a rolling direction of the base steel sheet (1), in which in a cross-sectional view of a plane parallel to the rolling direction and a sheet thickness direction of the base steel sheet (1), when a region between end portions of the groove (G) is defined as a groove part (R.sub.G), an average thickness of the intermediate layer (4) of the groove part (R.sub.G) is 0.5 times or more and 3.0 times or less an average thickness of the intermediate layer (4) other than the groove part (R.sub.G), and an area ratio of voids in the insulation coating (3) of the groove part (R.sub.G) is 15% or less.

The method for forming a coating of the present invention includes: a first step of applying a first solution containing a polysilazane to a surface 2a of a metal substrate 2, heating the first solution to make the first solution undergo conversion into silica and form a first coating 1 having open defects 3, on the surface 2a of the metal substrate 2, and a second step of applying a second solution containing a polysilazane to a surface 1a of the first coating 1 to fill the open defects 3, and heating the second solution at a temperature lower than a heating temperature in the first step to make the second solution undergo conversion into silica and form a second coating 5 on a surface 1a of the first coating 1.

The method for forming a coating of the present invention includes: a first step of applying a first solution containing a polysilazane to a surface 2a of a metal substrate 2, heating the first solution to make the first solution undergo conversion into silica and form a first coating 1 having open defects 3, on the surface 2a of the metal substrate 2, and a second step of applying a second solution containing a polysilazane to a surface 1a of the first coating 1 to fill the open defects 3, and heating the second solution at a temperature lower than a heating temperature in the first step to make the second solution undergo conversion into silica and form a second coating 5 on a surface 1a of the first coating 1.

A grain-oriented electrical steel sheet having an insulating film disposed on a surface thereon. The insulating film having a chemical composition comprising Si, P, O, and at least one selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, Mn, and Co. The insulating film has a crystallinity in a range of 20% or more, and a minimum tension provided to the steel sheet by the insulating film at a temperature in a range of 100 C. to 200 C. is 10 MPa or more.

The present disclosure provides an aqueous binder composition for forming a sacrificial corrosion-protective coating, said composition being free of chromates and also preferably free of borates and molybdates. Said binder composition advantageously has a pH of less than 6 and comprises a binder, particles of at least one metal oxide and at least one metallic phosphate, said binder comprising a hydrolyzed organosilane oligomer. In addition, the proportion by weight of said particles of at least one metal oxide relative to the total dry weight of said binder composition is greater than or equal to 75%.

The present disclosure provides an aqueous binder composition for forming a sacrificial corrosion-protective coating, said composition being free of chromates and also preferably free of borates and molybdates. Said binder composition advantageously has a pH of less than 6 and comprises a binder, particles of at least one metal oxide and at least one metallic phosphate, said binder comprising a hydrolyzed organosilane oligomer. In addition, the proportion by weight of said particles of at least one metal oxide relative to the total dry weight of said binder composition is greater than or equal to 75%.

Provided is a grain-oriented electrical steel sheet including a base steel sheet, an intermediate layer which is disposed in contact with the base steel sheet and mainly includes silicon oxide, and an insulation coating which is disposed in contact with the intermediate layer and mainly includes phosphate and colloidal silica, in which the base steel sheet contains predetermined chemical composition, BN having an average particle size of 50 to 300 nm is present, when an emission intensity of B is measured using glow discharge emission analysis, predetermined conditions are satisfied, and a ratio of a major axis to a minor axis of BN is 1.5 or less.

A grain-oriented electrical steel sheet having an insulating film disposed on a surface thereon. The insulating film having a chemical composition comprising Si, P, O, and at least one selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, Mn, and Co. The insulating film has a crystallinity in a range of 20% or more, and a minimum tension provided to the steel sheet by the insulating film at a temperature in a range of 100 C. to 200 C. is 10 MPa or more.

The present invention provides a chromium-free coating composition having high blackening resistance and corrosion resistance, the composition comprising: 20 to 70 wt % of waterborne silane modified polyurethane; 0.5 to 5 wt % of a hardener; 0.5 to 5 wt % of a blackening inhibitor; 0.5 to 5 wt % of a corrosion inhibitor; and 0.5 to 5 wt % of a lubricant, with the balance being a solvent. The chromium-free coating composition has the effect of improving blackening resistance, corrosion resistance, alkali resistance, solvent resistance and fingerprint resistance of a steel sheet on which a coating layer comprising the composition is formed.