KR20160019919A - Grain-oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

Disclosed is a manufacturing method of an oriented electrical steel sheet. According to the present invention, the manufacturing method of an oriented electrical steel sheet comprises: a step of providing an electrical steel sheet before a first recrystallization or after the first recrystallization; a step of rolling the electrical steel sheet; and a step of emitting a laser beam onto a surface of the electrical steel sheet at an angle of 82-98° with respect to a rolling direction when rolling the electrical steel sheet.

Description

TECHNICAL FIELD The present invention relates to a grain-oriented electrical steel sheet and a method of manufacturing the same. BACKGROUND ART [0002]

The present invention relates to an electric steel sheet, and more particularly, to a grain-oriented electric steel sheet having a groove formed by laser irradiation on the surface of a steel sheet to miniaturize the magnetic plate, thereby improving iron loss before and after stress relaxation annealing.

In general, the magnetic microfabrication method can be roughly divided into minute and minute blanking according to whether or not the effect of improving the micro-finishing after the stress relieving annealing is maintained. In the method of microminiaturizing the temporary blanking metal, a local compressive stress is applied to the surface by heat energy or mechanical energy Is a domain refinement technique in which a magnetic domain is miniaturized by forming a 90 占 domain to minimize the generated self elastic energy.

The permanent magnetic microfabrication method capable of maintaining the iron loss improving effect even after the heat treatment for removing stress can be divided into an etching method, a roll method and a laser method. Among the above laser methods, To form a groove on the surface of the steel sheet by vaporization of the steel sheet to secure the iron loss improvement ratio after the heat treatment of the grain-oriented electrical steel sheet. However, since the grooves are formed by evaporation by the pulse laser, it is difficult to secure the improvement rate of the iron loss before the heat treatment (stress relaxation heat treatment, SRA) because the melted portion is not formed, s or more), it is difficult to form deep grooves, and the iron loss improving effect required is not exhibited.

6A, the recrystallization 100 occurs in the groove 20 due to the thermal influence of the laser when the groove is formed by the laser according to the prior art. Alternatively, the recrystallization 100 occurs in the groove 20 along the groove 20 as shown in FIG. There arises a problem that the magnetic flux density is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a directional electrical steel sheet having uniform grooves formed on the surface of an electric steel sheet even under high-speed laser beam irradiation conditions, and a method of manufacturing the same.

To achieve the above object, a grain-oriented electrical steel sheet according to an embodiment of the present invention is a grain-oriented electrical steel sheet having wedge-shaped grooves formed on the surface of a steel sheet before or after primary recrystallization.

The groove may be characterized in that no recrystallization is formed in the groove.

The groove may be characterized in that no recrystallization is formed in the groove.

The groove may have an angle of 82 ° to 98 ° with respect to the rolling direction of the steel strip.

Further, the groove may be formed in a slanting line with respect to the rolling direction of the electric steel plate.

Further, the slanting line may be characterized by being in a range of 82 DEG to 98 DEG with respect to the rolling direction of the steel sheet.

The groove may have a depth of 5% to 12% of the thickness of the steel sheet.

A method of manufacturing a directional electrical steel sheet according to an embodiment of the present invention includes: providing a rolled electrical steel sheet; And a step of irradiating a laser on the surface of the rolled electrical steel sheet before or after the first recrystallization to form a groove; .

The grooves formed in the step of forming the grooves may be characterized in that no recrystallization is formed.

The groove formed in the step of forming the groove may be characterized in that no grain boundaries are formed along the groove.

The energy density of the laser irradiation (E _d), the laser power (P) and the scanning line speed (S) ratio (P ^/ S ^1/2) can be satisfied with the following conditions.

0.5 J / mm < ² > E _d ? 5.0 J / mm ² ,

^{5.0 W · mm 1/2 /} s 1/2 ≤P / S 1/2 ≤13.0W · mm 1/2 / s 1/2

The beam length dt in the irradiation direction of the laser and the beam width L in the rolling direction irradiated in the step of forming the groove may satisfy the following condition.

0.20? L / dt? 1.0

And the laser irradiated in the step of forming the grooves is irradiated with an oblique line with respect to the rolling direction of the electrical steel sheet.

And the traveling speed of the electric steel sheet is at least 0.5 m / s.

The grooves formed in the groove may have a wedge shape.

The depth of the groove formed in the step of forming the groove may be 5% to 12% of the thickness of the steel sheet.

The grooves may be intermittently formed three to eight in the width direction of the electrical steel sheet.

The angle of the laser beam irradiated with a slanting line with respect to the rolling direction of the electrical steel sheet is 82 to 98 °.

The laser may be a continuous wave laser.

Generally, the production of a directional electrical steel sheet is performed by a continuous casting process in which a slab is subjected to hot rolling, preliminary annealing, cold rolling, decarburization annealing, high temperature annealing, planarization annealing, insulation coating, However, in the present invention, the laser processing step can be applied at any stage before or after decarburization annealing after cold rolling. In particular, grooves can be formed by a laser before the first recrystallization, that is, a cold-rolled steel sheet.

The directional electric steel sheet according to the present invention minimizes the heat effect by the laser when forming the grooves 20, so that recrystallization is not formed in the grooves, and therefore the weak magnetic field of the groove portion is weakened, thereby suppressing the magnetic flux density deterioration as much as possible.

In addition, grooves can be formed in an electric steel plate which is running at a high speed of 0.5 m / s or more because a groove is formed by irradiating a high speed laser beam.

In the present invention, since the heat effect by the laser is minimized, recrystallization is not formed in the groove 20, and deterioration of the magnetic flux density can be suppressed as much as possible.

In the present invention, thermal influence of the laser is minimized during the formation of the grooves 20, and grain boundaries are not formed along the grooves 20, so that the occurrence of deterioration of the magnetic flux density can be minimized.

Further, by forming the groove in a slanting line with respect to the rolling direction of the steel sheet, it is possible to minimize the magnetic flux density degradation by weakening the half-field of the groove portion. The oblique line may be 82 to 98 ^° with respect to the rolling direction of the steel sheet.

1 is a view showing the shape of a groove formed on the surface of a steel sheet when a laser beam is irradiated on the surface of the steel sheet.
Fig. 2 is an enlarged view of a part 3 of the continuous groove shown in Fig. 1. Fig.
3 is a process diagram of a method for manufacturing a directional electrical steel sheet according to the present invention.
4 is a diagram showing the beam length d _{t in} the laser scanning line direction and the beam width L in the rolling direction of the laser according to the present invention.
5 is a view showing the shape of a groove formed by a laser.
FIG. 6 is a view showing the recrystallization and grain boundaries produced when the grooves are formed according to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, an electric steel plate in which grooves are formed on the surface of a steel sheet for miniaturization of a magnetic domain according to a preferred embodiment of the present invention will be described.

Fig. 1 is a view showing grooves formed by laser beams irradiated at regular intervals in a direction perpendicular to the rolling direction of the steel strip 10.

In the electric steel sheet 10 according to the preferred embodiment of the present invention, a wedge-shaped groove is formed on the surface of the steel sheet before the primary recrystallization or after the primary recrystallization.

As shown in Fig. 5, the grooves may have a wedge shape (Fig. 5A), a square shape (Fig. 5B), a trapezoid shape (Fig. 5C), a U shape, a semicircular shape, The middle wedge type is preferred.

Further, it is preferable that the groove is not formed with recrystallization in the groove. According to the present invention, since the recrystallization is not formed in the groove 20 when the groove is formed, deterioration of the magnetic flux density can be suppressed as much as possible.

In addition, it is preferable that no grain boundaries are formed along the grooves of the grooves. According to the present invention, since the grain boundaries are not formed along the grooves 20 when the grooves are formed, the occurrence of deterioration of the magnetic flux density can be minimized.

Further, by forming the groove in a slanting line with respect to the rolling direction of the steel sheet, it is possible to minimize the magnetic flux density degradation by weakening the half-field of the groove portion. The oblique line may be 82 to 98 ^° with respect to the rolling direction of the steel sheet.

Further, the groove 20 may be 5% to 12% of the thickness of the steel sheet.

Referring to FIG. 3, a method of manufacturing an electrical steel sheet according to a preferred embodiment of the present invention includes:

Providing a rolled electrical steel sheet; And a step of irradiating a laser on the surface of the rolled electrical steel sheet before or after the first recrystallization to form a groove; .

Generally, the production of a directional electrical steel sheet is performed by a continuous casting process in which a slab is subjected to hot rolling, preliminary annealing, cold rolling, decarburization annealing, high temperature annealing, planarization annealing, insulation coating, However, in the present invention, the laser processing step can be applied at any stage before or after decarburization annealing after cold rolling. Preferably, grooves are formed by a laser on a cold-rolled steel sheet before primary recrystallization.

A directional electrical steel sheet may be used as the electrical steel sheet 10, and the directional electrical steel sheet may have a GOSS texture in which the steel sheet has a texture of {110} < 001 > Magnetic material excellent in magnetic properties in the direction of magnetization.

The base portion is melted by laser irradiation, and a part thereof is resolidified to form a groove (20).

According to the present invention, even if the fusing part is melted and partially re-solidified by the laser irradiation, since the oxide layer is formed in the subsequent decarburization annealing step, the re-adhered part does not affect the formation of the secondary recrystallization. That is, the re-adhering layer is formed to be equal to or less than the thickness of the oxide layer. In addition, it is possible to melt the known portion by irradiating a laser, and blowing it to prevent the molten layer from remaining in the central portion of the groove.

The shape of the groove to be formed may be wedge-shaped.

5 (a), 4 (b), 5 (b), and 5 (c) of FIG. 5, the groove may have a wedge shape The loss rate is the highest.

The shape of the groove can be controlled by adjusting the intensity profile of the laser beam in the cross-sectional direction and the shape of the laser beam formed on the surface of the electrical steel sheet.

Alternatively, the shape of the groove can be controlled by adjusting the time (? T = D / V, D: scan width, V: scan speed) in which the laser beam formed on the surface of the steel sheet stays on the surface of the steel sheet.

That is, when the shape of the beam formed on the surface of the steel sheet is spherical, the spatial intensity of the beam cross-section is set to a sharp gaussian mode, and the side beam is cut by a beam damper to form a wedge- .

The shape of the laser beam formed on the surface of the steel sheet during the formation of the grooves 20 by laser irradiation need not be limited to a spherical or oval shape.

It is also preferable that the laser uses a continuous wave laser.

Further, FIG beam length ratio (L / d _t) value of the beam width (L) of _(t d) and the rolling direction of the laser scan line direction, such as 4, 0.20 ≤ L / d _t &Lt; / = 1.0, and the maximum value of d _t needs to be kept at 50 μm or less.

In this case, L / d _t when the value is greater than 1.0, the groove 20 is formed during the heat treatment does not represent the entire iron loss improvement effect by increase of the heat affected portion in the rolling direction, L / d _t If the value is less than 0.20, it is difficult to form grooves 20 having a depth corresponding to 5 to 12% of the thickness of the steel sheet on the surface of the steel sheet due to the narrow width of the grooves 20 in the rolling direction.

The laser energy density (E _d ) required for melting is 0.5 J / mm ² ≤ E _{d (} ² ) to form grooves with a depth of 5-12% of the thickness of the steel sheet during laser irradiation under steel sheet feeding conditions of 0.5 m / &Lt; / = 5.0 J / mm &lt; ² &gt;.

When the laser energy density is more than 5.0 J / mm ² , the iron loss before heat treatment can not be secured due to the excessive melting portion formation, and the laser energy density is 0.5 J / mm ² , The depth of the groove for ensuring the iron loss improvement ratio of the heat-treated steel sheet can not be ensured, so that the iron loss improving effect after the heat treatment can not be secured.

In addition, 0.5 m / in s or more of high-speed electrical steel sheet moving at the speed before heat treatment - the laser power (P) and the scanning line speed in order to improve the post-iron loss (S) ratio (P ^/ S ^1/2) of [Expression 1] Conditions Is satisfied.

[Formula 1]

^{5.0 W · mm 1/2 /} s 1/2 ≤P / S 1/2 ≤13.0W · mm 1/2 / s 1/2

P in Equation 1 means the laser average power, and S means the scanning line speed. The output of the laser, P is proportional to the S ^1/2 ΔT (the maximum attained temperature at the time of laser irradiation surface), and as shown in [Expression 2].

[Formula 2]

^{Pα (A · ΔT · S 1} /2 · d 3/2) / (α · κ 1/2)

A is a constant, d is the diameter of the beam,? Is the absorptance, and? Is the thermal diffusivity (W / cm ² ).

P ^/ S ^1/2 value of ^{13.0 W · mm 1/2 /} s 1/2 than the larger the excessive molten portions forming the non-uniformity of the thickness of the retake high rise of the groove is maximized to obtain the iron loss improvement effect more than 5% after the heat treatment And a recrystallization can be formed in the groove due to the thermal influence by the laser, and grain boundaries can be formed along the groove. P ^/ S ^1/2 value of ^{5.0W · mm 1/2 / s} 1/2 is less than when the depth of the groove exert a failure to sufficiently ensure the (5 to 12% of the sheet thickness) after the heat treatment improved 5% or more of iron loss effect I can not.

Further, in the step of forming the groove, it is preferable that the groove is not formed with recrystallization in the groove. According to the present invention, since the scan line speed of the laser is faster than the laser output, thermal influence by the laser is minimized and recrystallization is not formed in the groove 20, so that deterioration of the magnetic flux density can be suppressed as much as possible. In addition, grooves can be formed in a high-speed electric steel sheet moving at a speed of 0.5 m / s or more.

Further, in the step of forming the grooves, it is preferable that no grain boundaries are formed along the grooves of the grooves. According to the present invention, since the scan line speed of the laser is faster than the laser output, the thermal influence by the laser is minimized, and the grain boundary is not formed along the groove 20 to minimize the occurrence of deterioration of the magnetic flux density have.

Hereinafter, a method for manufacturing a directional electrical steel sheet by laser irradiation of a directional electrical steel sheet and injection of compressed air according to the present invention will be described in detail with reference to examples. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

< Example >

0.001% of C, 0.008% of P, 0.001% of S, 0.001% of S, 0.5% of Al, 0.0013% of N, 0.2% of Mn and 0.0015% of Ti and the balance Fe and other inevitable The slab composed of the impurities is reheated to 1150 DEG C and then hot rolled to produce a hot-rolled steel sheet. The hot-rolled steel sheet is wound, cooled, pickled, and then cold-rolled to produce a steel sheet.

The thickness of the cold-rolled steel sheet was 0.27 mm, and the surface of the cold-rolled steel sheet was irradiated with a laser in the rolling width direction by a continuous wave laser. The scanning lines were divided into 3 to 8 sections It appears as a line.

Figure 2 is one of the laser energy density to be illustrating, on an enlarged scale, a portion of the continuous groove (E _d) to ^{1.5 J / mm 2, P /} S 1/2 value of ^{10.2 W · mm 1/2 /} s 1 / ² , and a groove was formed at 85 ^o with respect to the rolling direction.

In Fig. 2, Ds was 3.1 mm in terms of the laser irradiation interval, and Bw was the width of the groove opening in the rolling direction when irradiated with laser, which was 45 [mu] m to 55 [mu] m.

division P ^/ S ^1/2 B _w D _H D _S Laser cooking dictionary Before heat treatment After heat treatment Iron loss improvement ratio (%) Magnetic flux density degradation rate (%) μm mm W _{17/50 /} B ₈ Before heat treatment After heat treatment Before heat treatment After heat treatment Example 1
(CW / Ova
l)
10.2 50 18 3.1 0.95 / 1.92 0.81 / 1.90 0.81 / 1.90 14.7 14.7 1.04 1.04 0.96 / 1.92 0.82 / 1.90 0.82 / 1.90 14.6 14.6 1.04 1.04 0.95 / 1.92 0.81 / 1.90 0.82 / 1.90 14.7 14.7 1.04 1.04 Example 2
(CW / Circ
le)
9.5 50 15 3.1 0.95 / 1.91 0.84 / 1.89 0.83 / 1.89 11.6 12.6 1.04 1.04 0.95 / 1.92 0.84 / 1.90 0.84 / 1.90 11.6 11.6 1.04 1.04 0.95 / 1.91 0.83 / 1.89 0.83 / 1.89 12.6 12.6 1.04 1.04 Comparative Example 1
(CW / Circ
le)
15 50 18 3.1 0.95 / 1.92 0.89 / 1.85 0.97 / 1.85 -2.1 6.3 3.64 3.64 0.96 / 1.92 0.88 / 1.86 0.99 / 1.86 -3.1 8.3 3.12 3.12 0.95 / 1.92 0.89 / 1.85 0.98 / 1.84 -3.2 6.3 3.12 4.16 Comparative Example 2
(Pulse
Laser /
Discontinuous home
) 10.2 48 20 3.2 0.96 / 1.92 0.91 / 1.86 0.99 / 1.83 -3.1 5.2 3.12 4.68 0.95 / 1.92 0.92 / 1.85 0.97 / 1.82 -One 3.2 3.64 5.2 0.96 / 1.92 0.91 / 1.86 0.96 / 1.82 -1.1 5.2 3.12 5.2

Table 1 shows changes in the iron loss improvement ratio of the grain-oriented electrical steel sheet according to the present invention.

As can be seen from Table 1, the directional electric steel sheet according to the embodiment of the present invention shows a remarkable improvement in the iron loss improvement ratio before and after the heat treatment as compared with the comparative example of the prior art.

1) _Iron loss (W _17/50 ) means the average loss (W / Kg) in the rolling direction and in the direction perpendicular to the rolling direction when magnetic flux density of 1.7 Tesla is maintained at a frequency of 50 Hz.

2) The magnetic flux density (B ₈ ) means the magnitude of the magnetic flux density (Tesla) induced when a magnetic field of 800 A / m is added.

3) The iron loss improvement rate means [iron loss of groove-formed electrical steel sheet - iron loss of grooved electrical steel sheet] / iron loss of groove-formed electrical steel sheet] x 100.

4) Magnetic flux density deterioration rate [Magnetic flux density of grooved electrical steel sheet - Magnetic flux density of grooved electrical steel sheet] / Magnetic flux density of grooved electrical steel sheet x100.

5) Heat treatment was maintained at 840 ^° C for 2 hours.

As can be seen from Table 1, the directional electric steel sheet according to the embodiment of the present invention shows a remarkable improvement in the iron loss improvement ratio before and after the heat treatment as compared with the comparative example of the prior art.

^{5.0 W · mm 1/2 /} s 1/2 ≤P / S 1/2 ≤13.0 W · mm 1/2 / s 1/2 and satisfy the depth of 5% to 12% of the thickness of the steel sheet is formed, which groove In the electrical steel sheets of Examples 1 and 2, the iron loss reduction ratio before the heat treatment (before the first recrystallization) was 14% or more, and the magnetic flux density deterioration rate was as low as 1.04. Also, the grooves were formed at 85 ^° with respect to the rolling direction to weaken the semi-magnetic field at the groove portion, thereby minimizing deterioration of the magnetic flux density.

It is also seen that the iron loss improvement ratio is maintained after the heat treatment of the electrical steel sheet (after the first recrystallization).

In contrast, as Comparative Example 1, the value of P ^/ S ^1/2 15 For a, lower than the scan speed embodiments. Therefore, it can be seen that the thermal influence by the laser received on the electric steel sheet is higher than that of the embodiment, so that the iron loss reduction ratio is low and the magnetic flux density degradation rate is high.

In the case of Comparative Example 2, since grooves are formed by the pulse laser, intermittent grooves appear instead of continuous grooves. Therefore, the value of P ^/ S ^1/2 The depth of grooves is deeper than that of Comparative Example 1 and the influence of heat around the grooves is large even though it is the same as in Embodiment 1, so that the iron loss improvement rate is low and the magnetic flux density degradation rate is high.

According to the method for producing a grain-oriented electrical steel sheet according to the present invention, a groove can be formed in an electric steel sheet which proceeds at a high speed of 0.5 m / s or higher because a groove is formed by irradiating a high speed laser beam. Of 5% or more, and at the same time, the magnetic flux density degradation rate can be secured to 1.3% or less.

In addition, the grain-oriented electric steel sheet according to the present invention does not have recrystallization in the grooves 20 and grain boundaries are not formed along the grooves, so that deterioration of the magnetic flux density is suppressed as much as possible.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

10: Electric steel plate,
20: groove
30: part of continuous groove
B _W : Rolling direction width of the groove
D _S : Spacing of successive grooves
D _H : Depth of groove
100: Recrystallization formed in the groove
101: grain boundary formed along the groove

Claims (10)

Providing a rolled electrical steel sheet; And
Irradiating the rolled electrical steel sheet with a laser before the first recrystallization or after the first recrystallization to form a groove by irradiating the laser on the surface of the rolled electrical steel sheet;
/ RTI &gt;
The energy density of the laser is irradiated (Ed), the laser power (P) and the scanning line speed (S) ratio (P ^/ S ^1/2) and the beam length (dt) and the beam width in the rolling direction of the laser irradiation direction (L ) Satisfying the following conditions:
0.5 J / mm ² ? Ed? 5.0 J / mm ² ,
^{5.0 W · mm 1/2 /} s 1/2 ≤P / S 1/2 ≤13.0W · mm 1/2 / s 1/2
0.20? L / dt? 1.0 The method according to claim 1,
Wherein the grooves formed in the step of forming the grooves have no grain boundaries formed along the grooves. 3. The method of claim 2,
Wherein the grooves formed in the step of forming the grooves are not formed with recrystallization. The method of manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the laser irradiated in the step of forming the grooves is irradiated obliquely with respect to the rolling direction of the steel strip. 4. The method according to any one of claims 1 to 3,
Wherein the running speed of the electric steel sheet is at least 0.5 m / s. 4. The method according to any one of claims 1 to 3,
Wherein the grooves formed in the step of forming the grooves are wedge-shaped. 4. The method according to any one of claims 1 to 3,
Wherein the depth of the groove formed in the step of forming the groove is 5% to 12% of the thickness of the steel sheet. 8. The method of claim 7,
Wherein the grooves are intermittently formed three to eight in the width direction of the electrical steel sheet. The method of claim 4, wherein the laser is irradiated in an oblique angle to the rolling direction of the electrical steel sheet is 82 ~ 98 ^o method for producing a grain-oriented electrical steel sheet, characterized in that. 4. The method according to any one of claims 1 to 3,
Wherein the laser is a continuous wave laser.

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