Electrical steel sheet having insulating coating, method for producing the same, transformer core and transformer using the electrical steel sheet, and method for reducing dielectric loss in transformer

1 . An electrical steel sheet having an insulating coating, the insulating coating being disposed on at least one of surfaces of the electrical steel sheet, the insulating coating having a relative dielectric constant at 1000 Hz of less than or equal to 15.0 and a dielectric loss tangent at 1000 Hz of less than or equal to 20.0,

wherein the insulating coating includes an insulating coating layer that includes a low-dielectric-loss material dispersed in the insulating coating layer, the low-dielectric-loss material having a dielectric loss coefficient at 1 MHz of less than or equal to 0.10, wherein the low-dielectric-loss material is present as a solid crystalline phase, and

wherein the low-dielectric-loss material is selected from the group consisting of barium magnesium niobate (Ba(Mg 1/3 Nb 2/3 )O 3 ), barium neodymium titanate (Ba 4 Nd 9.3 Tl 18 O 54 ), diopside (CaMgSi 2 O 6 ), Mg 2 TiO 4 , and Nd 2 Ti 2 O 7 .

2 . A method for producing the electrical steel sheet having the insulating coating according to claim 1 , the method comprising:

using a treatment liquid for forming the insulating coating layer, the treatment liquid including the low-dielectric-loss material;

applying the treatment liquid to a surface of the electrical steel sheet or a surface of the electrical steel sheet having a forsterite coating layer; and

performing a baking process.

3 . A method for producing the electrical steel sheet having the insulating coating according to claim 1 , the method comprising:

using a treatment liquid for forming the insulating coating layer, the treatment liquid being a liquid from which the low-dielectric-loss material precipitates;

applying the treatment liquid to a surface of the electrical steel sheet or a surface of the electrical steel sheet having a forsterite coating layer;

performing a baking process; and

thereafter, performing a crystallization process to cause the low-dielectric-loss material to precipitate in the insulating coating layer, the crystallization process including performing heating at a temperature higher than or equal to 1050° C. for at least 30 seconds.

4 . A transformer core in which the electrical steel sheet having the insulating coating according to claim 1 is used.

5 . A transformer comprising the transformer core according to claim 4 .

6 . A method for reducing dielectric loss in a transformer, the method comprising constructing a core of the transformer by laminating pieces of the electrical steel sheet having the insulating coating according to claim 1 .

7 . The electrical steel sheet according to claim 1 , wherein the low-dielectric-loss material includes at least one selected from Mg 2 TiO 4 , Nd 2 Ti 2 O 7 , and CaMgSi 2 O 6 .