METHOD FOR PRODUCING ORIENTED ELECTRICAL STEEL SHEET WITH ULTRA-LOW IRON LOSS

1 . A method of manufacturing an oriented electrical steel sheet, the method comprising:

preparing an oriented electrical steel sheet; and

forming a ceramic coating layer by allowing a gas-phase ceramic precursor to contact-react with a portion or an entirety of one surface or both surfaces of the oriented electrical steel sheet in a plasma state using an atmospheric pressure plasma CVD process (APP-CVD).

2 . The method of claim 1 , wherein the ceramic coating layer is formed by, while plasma is generated by forming an electrical field on a surface of the steel sheet using a high-density radio frequency under atmospheric pressure, mixing a primary gas comprised of one or more of Ar, He, and N 2 with a gas-phase ceramic precursor, and allowing the mixture to contact-react with a surface of the electrical steel sheet.

3 . The method of claim 2 , wherein the ceramic coating layer is formed by adding a second gas comprised of one of H 2 , O 2 , and H 2 O to the primary gas and the ceramic precursor and allowing the mixture to contact-react with the surface of the electrical steel sheet.

4 . The method of claim 3 , wherein the primary gas and the secondary gas are heated to a temperature equal to or higher than a vaporizing point of the ceramic precursor.

5 . The method of claim 1 , wherein, when the ceramic coating layer is TiO 2 , titanium isopropoxide (TTIP), Ti{OCH(CH 3 ) 2 } 4 , or TiCl 4 is used as the ceramic precursor.

6 . The method of claim 1 , wherein a thickness of the ceramic coating layer is 0.1-0.6 μm, and an iron loss improvement rate depending on the thickness of the coating layer is 7-14%.

7 . The method of claim 1 , wherein the preparing the oriented electrical steel sheet includes:

preparing a steel slab including, by weight %, 2.6-4.5% of silicon (Si), 0.020-0.040% of aluminum (Al), 0.01-0.20% of manganese (Mn), and a balance of Fe and inevitable impurities;

manufacturing a hot-rolled sheet by heating and hot-rolling the steel slab;

manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;

obtaining a decarburized and annealed steel sheet by decarburizing and annealing the cold-rolled sheet; and

coating the decarburized and annealed steel sheet with an annealing separator and performing final-annealing.

8 . The method of claim 7 , wherein the obtaining the decarburized and annealed steel sheet by decarburizing and annealing the cold-rolled sheet includes decarburizing and nitriding the cold-rolled sheet at the same time or nitriding the cold-rolled sheet after decarburizing, and annealing the cold-rolled sheet, thereby obtaining the decarburized and annealed steel sheet.

9 . The method of claim 1 , wherein pre-heating and/or post-heating is performed on the electrical steel sheet at a temperature range of 200-1250° C. before and after the APP-CVD process.

10 . A method of manufacturing an oriented electrical steel sheet, the method comprising:

preparing an electrical steel sheet on a surface of which a forsterite film is formed; and

forming a ceramic coating layer by allowing a gas-phase ceramic precursor to contact-react with a portion or an entirety of one surface or both surfaces of the electrical steel sheet on a surface of which a forsterite film is formed in a plasma state using an atmospheric pressure plasma CVD process (APP-CVD).

11 . The method of claim 10 , wherein the ceramic coating layer is formed by, while plasma is generated by forming an electrical field on a surface of the electrical steel sheet using a high-density radio frequency under atmospheric pressure, mixing a primary gas comprised of one or more of Ar, He, and N 2 with a gas-phase ceramic precursor, and allowing the mixture to contact-react with a surface of the electrical steel sheet.

12 . The method of claim 11 , wherein the ceramic coating layer is formed by adding a second gas comprised of one of H 2 , O 2 , and H 2 O to the primary gas and the ceramic precursor and allowing the mixture to contact-react with the surface of the electrical steel sheet.

13 . The method of claim 12 , wherein the primary gas and the secondary gas are heated to a temperature equal to or higher than a vaporizing point of the ceramic precursor.

14 . The method of claim 10 , wherein, when the ceramic coating layer is TiO 2 , titanium isopropoxide (TTIP), Ti{OCH(CH 3 ) 2 } 4 , or TiCl 4 is used as the ceramic precursor.

15 . The method of claim 10 , wherein a thickness of the ceramic coating layer is 0.1-0.6 μm, and an iron loss improvement rate for each different thickness of the coating layer is 7-14%.

16 . The method of claim 10 , wherein the preparing the oriented electrical steel sheet includes:

preparing a steel slab including, by weight %, 2.6-4.5% of silicon (Si), 0.020-0.040% of aluminum (Al), 0.01-0.20% of manganese (Mn), and a balance of Fe and inevitable impurities;

manufacturing a hot-rolled sheet by heating and hot-rolling the steel slab;

manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;

obtaining a decarburized and annealed steel sheet by decarburizing and annealing the cold-rolled sheet; and

coating the decarburized and annealed steel sheet with an annealing separator and performing final-annealing.

17 . The method of claim 16 , wherein the obtaining the decarburized and annealed steel sheet by decarburizing and annealing the cold-rolled sheet includes decarburizing and nitriding the cold-rolled sheet at the same time or nitriding the cold-rolled sheet after decarburizing, and annealing the cold-rolled sheet, thereby obtaining the decarburized and annealed steel sheet.

18 . The method of claim 10 , wherein pre-heating and/or post-heating is performed on the electrical steel sheet at a temperature range of 200-1250° C. before and after the APP-CVD process.