Grain-oriented electrical steel sheet and method for manufacturing same

Abstract

Disclosed are a grain-oriented electrical steel sheet and a method of manufacturing the same. The method for manufacturing a grain-orientated electrical steel sheet according to an exemplary embodiment of the present invention includes: providing an electrical steel sheet before forming primary recrystallization or after forming the primary recrystallization; and forming a groove in a surface of the electrical steel sheet by radiating laser and simultaneously spraying gas onto the electrical steel sheet, in which energy density E.sub.d and a laser scanning speed V.sub.s of the radiated laser satisfy the following conditions,
1.0 J/mm.sup.2E.sub.d5.0 J/mm.sup.2,
0.0518 mm/secV.sub.s0.2 mm/sec.

Claims

1. A grain-oriented electrical steel sheet, which has a surface which is formed with grooves for a magnetic domain refinement treatment, wherein a scattering alloy layer in the groove is eroded in a Goss texture during a recrystallization annealing process, wherein when a thickness of the scattering alloy layer on a bottom surface of the groove is defined as T.sub.B, and a thickness of the scattering alloy layer at a point that is one-half the distance between any one end of the groove and the bottom surface of the groove is defined as T.sub.L, T.sub.B/T.sub.L is 0.2 to 0.8, and wherein the groove is formed at an angle greater than 0 and equal to or smaller than 5 with respect to the width direction of the electrical steel sheet.

2. The grain-oriented electrical steel sheet of claim 1, wherein: a thickness of the scattering alloy layer is 4% to 12% of a depth of the groove.

3. The grain-oriented electrical steel sheet of claim 2, wherein: the depth of the groove is 4% to 11% of a thickness of the electrical steel sheet.

4. The grain-oriented electrical steel sheet of claim 3, wherein: the groove is formed diagonally with respect to a width direction of the electrical steel sheet.

5. The grain-oriented electrical steel sheet of claim 1, wherein: three to six grooves are intermittently formed in the width direction of the electrical steel sheet.

6. A method of manufacturing a grain-oriented electrical steel sheet, the method comprising: providing an electrical steel sheet before forming primary recrystallization or after forming the primary recrystallization; and forming a groove in a surface of the electrical steel sheet by radiating laser and simultaneously spraying gas onto the electrical steel sheet, wherein energy density E.sub.d and a laser scanning speed V.sub.s of the radiated laser satisfy the following conditions,
1.0 J/mm.sup.2E.sub.d5.0 J/mm.sup.2,
0.0518 mm/secV.sub.s0.2 mm/sec, wherein a scattering alloy layer in the groove is eroded in a Goss texture during a recrystallization annealing process, and wherein when a thickness of the scattering alloy layer on a bottom surface of the groove is defined as T.sub.B, and a thickness of the scattering alloy layer at a point that is one-half the distance between any one end of the groove and the bottom surface of the groove is defined as T.sub.L, T.sub.B/T.sub.L is 0.2 to 0.8, and wherein the groove is formed at an angel greater than 0 and equal to or smaller than 5 with respect to the width direction of the electrical steel sheet.

7. The method of claim 6, wherein: pressure of the sprayed gas is 0.2 kg/cm.sup.2 to 5.0 kg/cm.sup.2.

8. The method of claim 7, wherein: an angle formed between the spray direction of the gas and the laser radiation direction is 0 to 50 (here, a state in which the angle formed between the spray direction of the gas and the laser radiation direction is 0 means that the spray direction of the gas and the laser radiation direction are parallel to each other).

9. The method of claim 8, wherein: in the radiating of the laser, a laser beam is radiated on the surface of the electrical steel sheet at an angle greater than 0 and equal to or smaller than 5 with respect to a width direction of the electrical steel sheet.

10. The method of claim 9, wherein: in the radiating of the laser, a movement speed V.sub.L of the electrical steel sheet is at least 0.9 m/s.

11. The method of claim 10, wherein: in the radiating of the laser, when a beam length in the width direction of the electrical steel sheet is d.sub.t, and a beam length in a rolling direction of the electrical steel sheet is L, a light collecting shape of the laser satisfies the following condition,
0.20L/d.sub.t1.0.

12. The method of claim 11, wherein: d.sub.t is 50 m or smaller.

13. The method of claim 12, wherein: in the radiating of the laser, a scattering alloy layer in which a melted portion of the electrical steel sheet by the radiation of the laser scatters and is resolidified is generated.

14. The method of claim 13, wherein: a thickness of the scattering alloy layer is 4% to 12% of a depth of the groove.

15. The method of claim 14, wherein: in the radiating of the laser, the laser is radiated diagonally with respect to a width direction of the electrical steel sheet.

16. The method of claim 15, wherein: in the radiating of the laser, the laser is radiated at an angle greater than 0 and equal to or smaller than 5 with respect to the width direction of the electrical steel sheet.

17. The method of claim 16, wherein: in the radiating of the laser, three to six grooves are intermittently formed in the width direction of the electrical steel sheet.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view illustrating a groove formed in a surface of a steel sheet by a magnetic domain refinement method according to the related art.

(2) FIG. 2 is a view illustrating shapes of grooves on an XY plane which are formed in a surface of a steel sheet when laser is radiated on the surface of the steel sheet.

(3) FIG. 3 is a view illustrating a cross section (YZ plane) of a part 30 of the continuous groove illustrated in FIG. 2.

MODE FOR INVENTION

(4) Advantages and features of the present invention and methods of achieving the advantages and features will be clear with reference to exemplary embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the exemplary embodiments set forth below, and may be embodied in various other forms. The present exemplary embodiments are for rendering the disclosure of the present invention complete and are set forth to provide a complete understanding of the scope of the invention to a person with ordinary skill in the technical field to which the present invention pertains, and the present invention will only be defined by the scope of the claims. Like reference numerals indicate like elements throughout the specification.

(5) Therefore, in some exemplary embodiments, well-known technologies will not be specifically described in order to avoid obscuring the present invention. Unless there are other definitions, all terms used in the present specification (including technical and scientific terms) have the meanings that those having ordinary skill in the technical field to which the present invention pertains typically understand. Unless explicitly described to the contrary, the word comprise and variations such as comprises or comprising, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, singular expressions used herein may include plural expressions unless they have definitely opposite meanings.

(6) A scattering alloy layer in which a melted portion, which has been melted from an electrical steel sheet by the laser, is resolidified on the steel sheet exists in a groove formed by magnetic domain refinement by radiation of laser.

(7) The scattering alloy layer is a texture having high energy, and in a case in which the scattering alloy layer is non-uniformly distributed, the scattering alloy layer may act as an obstruction factor to a growth a Goss texture at the time of recrystallization annealing. In addition, in a case in which the scattering alloy layer is non-uniformly distributed, the scattering alloy layer is not eroded in the Goss texture at the time of recrystallization annealing, and remains as random texturing instead of the Goss texture, thereby adversely affecting magnetism of the electrical steel sheet.

(8) According to a method of manufacturing a grain-oriented electrical steel sheet according to an exemplary embodiment of the present invention, the scattering alloy layer, which is a layer formed when a melted portion melted from the electrical steel sheet by the radiation of the laser is resolidified on the steel sheet, is uniformly distributed in the groove, and as a result, the scattering alloy layer is eroded in the Goss texture at the time of recrystallization annealing, such that a fraction of the Goss texture is improved, thereby providing a grain-oriented electrical steel sheet having excellent magnetism.

(9) In general, a manufacturing process of the grain-oriented electrical steel sheet is performed by allowing a slab to be subjected to hot rolling, hot rolled plate annealing, cold rolling, decarburizing annealing (primary recrystallization annealing), high temperature annealing (secondary recrystallization annealing), planarization annealing, insulation coating in sequence.

(10) The magnetic domain refinement treatment in the related art is performed after the insulation coating, but according to the method of manufacturing the grain-oriented electrical steel sheet according to the exemplary embodiment of the present invention, after cold rolling, before primary recrystallization or after the primary recrystallization, the magnetic domain refinement may be performed by radiating the laser to the electrical steel sheet.

(11) In addition, even though the magnetic domain refinement is performed by radiating the laser to the electrical steel sheet before the primary recrystallization, an effect of improving a core loss is maintained even after a subsequent heat treatment process.

(12) To provide the aforementioned method of manufacturing the grain-oriented electrical steel sheet, the following method of manufacturing the grain-oriented electrical steel sheet may be provided.

(13) The method of manufacturing the grain-oriented electrical steel sheet according to the exemplary embodiment of the present invention includes: providing an electrical steel sheet before forming primary recrystallization or after forming the primary recrystallization; and forming a groove in a surface of the electrical steel sheet by radiating laser and simultaneously spraying gas onto the electrical steel sheet.

(14) Energy density E.sub.d of the radiated laser may be 1.0 J/mm.sup.2 to 5.0 J/mm.sup.2. In a case in which the laser energy density exceeds 5.0 J/mm.sup.2, the melted portion is excessively formed, and as a result, in a final product, the scattering alloy layer is not eroded in the Goss texture, and forms random texturing. In the case of a value of the laser energy density which is less than 1.0 J/mm.sup.2, a sufficient groove depth cannot be ensured, and as a result, an effect of improving a core loss cannot be ensured after the heat treatment.

(15) A scanning speed V.sub.s of the radiated laser may be 0.0518 mm/sec to 0.2 mm/sec. In a case in which a value of the scanning speed of the laser exceeds 0.2 mm/sec, the scattering alloy layer is not formed, and as a result, an effect of improving a core loss cannot be ensured. In addition, in a case in which the scanning speed of the laser is lower than 0.0518 mm/sec, the melted portion is excessively formed, and as a result, in a final product, the scattering alloy layer is not eroded in the Goss texture, and forms random texturing.

(16) The sprayed gas may be air, inert gas, or any type of gas which does not cause oxidation of the electrical steel sheet.

(17) Pressure P.sub.a of the sprayed gas may be 0.2 kg/cm.sup.2 to 5.0 kg/cm.sup.2. In a case in which the pressure of the sprayed gas is lower than 0.20 kg/cm.sup.2, the scattering alloy layer is not formed, and as a result, an effect of improving a core loss cannot be ensured. In addition, in a case in which the pressure of the sprayed gas exceeds 5.0 kg/cm.sup.2, the melted portion is excessively formed, and as a result, in a final product, the scattering alloy layer is not eroded in the Goss texture, and forms random texturing.

(18) An angle formed between the spray direction of the gas and the laser radiation direction may be 0 to 50 (in this case, a state in which the angle formed between the spray direction of the gas and the laser radiation direction is 0 means that the spray direction of the gas and the laser radiation direction are parallel to each other). The angle formed between the spray direction of the gas and the laser radiation direction affects a shape of the scattering alloy layer formed. The smaller the angle formed between the spray direction of the gas and the laser radiation direction, the smaller the thickness of the scattering alloy layer on the bottom surface of the groove, and the greater the thickness of the scattering alloy layer at an end of the groove.

(19) Here, the bottom surface of the groove means the deepest portion in the groove formed in the electrical steel sheet.

(20) In addition, a light collecting shape of the laser may be 0.20L/d.sub.t1.0, in which d.sub.t is a beam length in a width direction (x-axis) of the electrical steel sheet, and L is a beam length in a rolling direction (y-axis). In addition, the d.sub.t may be 50 m or smaller.

(21) In a case in which the L/d.sub.t value exceeds 1.0, a heat-affected zone in the rolling direction is increased, thereby adversely affecting a growth of the Goss texture, and in a case in which the L/d.sub.t is below 0.20, a width of the groove in the rolling direction is narrow, and the melted portion does not scatter, such that it is impossible to ensure a sufficient groove depth.

(22) Under the above condition, a movement speed V.sub.L of the electrical steel sheet 10 may be 0.9 m/s or higher.

(23) In addition, the groove may be intermittently formed by being divided into three to six grooves.

(24) In addition, the laser may be radiated diagonally with respect to the width direction (x-axis) of the electrical steel sheet. In addition, an angle with respect to the width direction (x-axis) may be greater than 0 and equal to or smaller than 5. Since the laser is diagonally radiated, it is possible to improve magnetism by decreasing a demagnetizing field.

(25) The depth of the groove formed as described above may be equal to or greater than 4% of the thickness of the electrical steel sheet in order to ensure a core loss improvement rate. Alternatively, the depth of the groove may be 4% to 11% of the thickness of the electrical steel sheet.

(26) In addition, an average thickness of the scattering alloy layer may be 4% to 12% of the depth of the groove. In a case in which the average thickness of the scattering alloy layer is below 4% of the depth of the groove, an appropriate groove for improving a core loss is not formed, and in a case in which the average thickness of the scattering alloy layer exceeds 12% of the depth of the groove, the heat-affected zone is increased, which may have an adverse effect on a growth of the Goss texture.

(27) In addition, when a thickness of the scattering alloy layer on the bottom surface of the groove is defined as T.sub.B, and a thickness of the scattering alloy layer at a point that is one-half the distance between any one end of the groove and the bottom surface of the groove is defined as T.sub.L, T.sub.B/T.sub.L may be 0.2 to 1.5. Alternatively, the T.sub.B/T.sub.L may be 0.2 to 0.8, or 1.0 to 1.5. In a case in which a value of the T.sub.B/T.sub.L is below 0.2, or exceeds 1.5, non-uniformity of the scattering alloy layer is increased, which has an adverse effect on magnetism.

(28) In the case of the electrical steel sheet on which the recrystallization annealing has been performed under the aforementioned magnetic domain refinement condition, the scattering alloy layer may be eroded in the Goss texture during the recrystallization annealing process. In general, at the time of the magnetic domain refinement treatment of the grain-oriented electrical steel sheet, a heat-affected zone is included in the groove, and the heat-affected zone is not eroded in the Goss texture when the Goss texture grows during a high temperature annealing process, and remains in a shape recrystallized along the groove. The texture has an adverse effect on magnetism.

(29) However, the grain-oriented electrical steel sheet according to the exemplary embodiment of the present invention allows the scattering alloy layer to be uniformly distributed, such that a thermal effect is minimized, and as a result, the recrystallized texture does not remain in the groove.

(30) Hereinafter, the present invention will be described in detail with reference to Examples. However, the following Examples are intended for the purpose of illustration of the present invention, and the contents of the present invention are not limited by the following Examples.

Example 1

(31) The magnetism was measured by radiating continuous wave laser on the grain-oriented electrical steel sheet having a thickness of 0.23 mm under the condition as disclosed in Table 1. A radiation line is illustrated as a line divided into three to six sections in the width direction as illustrated in FIG. 2. A laser radiation interval was 2.50 mm, and the beam length d.sub.t in the width direction of the electrical steel sheet at the time of radiating the laser was 50 m and had a spherical shape. In this case, the movement speed of the electrical steel sheet was 0.9 m/s.

(32) TABLE-US-00001 TABLE 1 Average thickness of Before Before Before scattering radiating heat heat E.sub.d D.sub.H alloy layer Pa Vs laser treatment treatment J/mm.sup.2 m T.sub.L/T.sub.B m Kgf/cm.sup.2 m/s W.sub.17/50 W.sub.17/50 W.sub.17/50 Comparison 1.0 10.0 0.3 1.2 0.2 51.8 0.82 0.78 0.78 Example 11.0 0.4 1.1 5.0 51.8 0.82 0.75 0.74 Example 6.4 0.2 0.768 5.0 200 0.82 0.79 0.79 Example 5.0 21.0 0.7 1.26 0.2 51.8 0.82 0.70 0.69 Example 22.2 0.8 0.9 5.0 51.8 0.82 0.71 0.71 Example 15.3 0.5 1.224 5.0 200 0.82 0.69 0.69 Example 1.2 15 0.5 0.6 61.0 51.8 0.83 0.68 0.68 Example 20 0.6 1.6 51.8 0.82 0.67 0.67 Example 25 0.7 3 200 0.83 0.68 0.67 Example 5.3 25.5 0.85 1.5 5.0 51.8 0.82 0.86 0.82 Comparative Example 1.8 5.0 51.8 0.82 0.87 0.83 Comparative Example 0.5 5.0 200 0.82 0.85 0.83 Comparative Example

(33) In the laser radiation condition range according to the present invention, it is possible to provide the grain-oriented electrical steel sheet, which may obtain stable core loss characteristics even at a high movement speed of the steel sheet.

Example 2

(34) The magnetism was measured by setting the energy density to 1.2 J/mm.sup.2 and the depth of the groove to 15 m, and by radiating continuous wave laser on the grain-oriented electrical steel sheet having a thickness of 0.23 mm while changing the angle with respect to the width direction of the electrical steel sheet. A laser radiation interval was 2.50 mm, and the beam length d.sub.t in the width direction of the electrical steel sheet at the time of radiating the laser was 50 m and had a spherical shape. In this case, the movement speed of the electrical steel sheet was 0.9 m/s. In addition, pressure of the sprayed gas was 4.5 kg/cm.sup.2, and the scanning speed was 53 m/s.

(35) TABLE-US-00002 TABLE 2 Not treated by laser Before heat After heat core loss treatment treatment (W17/50)/ core loss core loss magnetic (W17/50)/ (W17/50)/ Radiation flux magnetic flux magnetic flux Angle density B8 density B8 density B8 Comparison 0 0.82/1.92 0.67/1.89 0.67/1.90 Example 3 0.83/1.92 0.68/1.905 0.68/1.910 Example 5 0.82/1.92 0.67/1.907 0.67/1.915 Example 7 1.07/1.34 0.88/1.330 0.88/1.330 Comparative Example 9 1.16/1.34 0.92/1.320 0.92/1.320 Comparative Example

(36) As can be seen from Table 2, magnetism is excellent when the laser is radiated at an angle greater than 0 and equal to or smaller than 5 with respect to the width direction of the electrical steel sheet.

(37) The exemplary embodiment of the present invention has been described with reference to the accompanying drawings, but those skilled in the art will understand that the present invention may be implemented in any other specific form without changing the technical spirit or an essential feature thereof.

(38) Thus, it should be appreciated that the exemplary embodiments described above are intended to be illustrative in every sense, and not restrictive. The scope of the present invention is represented by the claims to be described below rather than the detailed description, and it should be interpreted that all the changes or modified forms, which are derived from the meaning and the scope of the claims, and the equivalents thereto, are included in the scope of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

(39) 10: Electrical steel sheet 20: Groove 30: Part of continuous groove 40: Scattering alloy layer