KR101657466B1 - Oriented electrical steel sheet and method for manufacturing the same - Google Patents

Abstract

A method of making a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: 1.0% to 4.0% of Si and 0.1% to 0.4% of C, by weight, and the balance includes Fe and other inevitably incorporated impurities Providing a slab; Reheating the slab; Hot-rolling the slab to produce a hot-rolled steel sheet; Annealing the hot-rolled steel sheet by hot-rolling; Cold-rolling the hot-rolled steel sheet annealed; Decarbonizing and annealing the cold-rolled steel sheet; Cold-rolling the steel sheet after completion of the decarburization annealing; And a final annealing step of annealing the cold-rolled steel sheet, wherein the final annealing step includes a heating step, a first cracking step, and a second cracking step, wherein a heating rate from the heating step to 700 ° C is 100 ° C / s or higher and 400 ° C / s or lower.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a directional electric steel sheet,

To a directional electric steel sheet and a manufacturing method thereof.

The grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction, consisting of crystal grains having a Goss orientation in which the crystal orientation of the steel sheet is {110} < 001 >.

The directional electrical steel sheet is rolled to a final thickness of usually 0.15 to 0.35 mm through hot rolling, hot-rolled sheet annealing, and cold rolling after the slab is heated, followed by high-temperature annealing for primary recrystallization annealing and secondary recrystallization.

At this time, it is known that, at a high temperature annealing, the degree of integration of the Goss orientation to be secondary recrystallized becomes higher as the temperature increase rate is slower, and the magnetism is excellent. In general, the rate of increase in temperature during high temperature annealing of a directional electric steel sheet is not more than 15 ° C per hour, and not only takes 2 to 3 days to raise the temperature, but also requires energy annealing more than 40 hours. In addition, since the current high-temperature annealing process is performed in a batch-type annealing in a coil state, the following difficulties arise in the process. First, a temperature deviation of the outer and inner windings of the coil occurs due to the heat treatment in the coil state, so that the same heat treatment pattern can not be applied to each part, resulting in magnetism deviation between the outer and inner windings. Second, since the MgO is coated on the surface after decarburization annealing and various surface defects are formed in the process of forming the base coating during the high temperature annealing, the rate of water drop is decreased. Third, since the decarburized annealed annealed decarburized plate is wound in a coil form, then annealed at high temperature, and then subjected to planarization annealing, the insulating coating is performed. Thus, the production process is divided into three stages, thereby causing a problem of a low yield rate.

In one embodiment of the present invention, a method for producing a directional electrical steel sheet and a directional electrical steel sheet produced by the method are provided.

A method for producing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises 1.0 to 4.0% of Si and 0.1 to 0.4% of C, based on 100% by weight of the whole slab composition, Providing a slab comprising impurities that are inevitably incorporated; Reheating the slab; Hot-rolling the slab to produce a hot-rolled steel sheet; Annealing the hot-rolled steel sheet by hot-rolling; Cold-rolling the hot-rolled steel sheet annealed; Decarbonizing and annealing the cold-rolled steel sheet; Cold-rolling the steel sheet after completion of the decarburization annealing; And finally annealing the cold-rolled steel sheet.

The final annealing step may include a heating step, a first cracking step, and a second cracking step.

During the final annealing step, the temperature raising rate up to 700 占 폚 in the heating step may be 100 占 폚 / s or more and 400 占 폚 / s or less.

The decarburization annealing step includes a temperature elevating step and a cracking step, and the heating rate in the temperature increasing step of the decarburization annealing step may be 100 ° C / s or more and 400 ° C / s or less.

In the final annealing step, the first cracking step may be performed at a cracking temperature of 850 ° C to 1000 ° C, and the second cracking step may be performed at a cracking temperature of 1000 ° C to 1200 ° C.

The cracking step in the decarburization annealing step may be performed at a cracking temperature of 850 to 1000 캜.

The step of final annealing after the cold rolling step may be continuous.

The step of decarburizing and annealing the cold-rolled steel sheet and the step of cold-rolling the decarburized annealed steel sheet may be repeated twice or more.

The reduction ratio in the cold rolling may be 50% to 70%.

The reheating temperature of the slab may be between 1100 ° C and 1350 ° C.

In the grain-oriented electrical steel sheet according to an embodiment of the present invention, the ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) of the inscribed circle in the gossy grain may be 95% or more of the entire goss grain.

The grain-oriented electrical steel sheet may contain 1.0% to 4.0% of Si and less than 0.002% of C (not including 0%) based on 100% by weight of the whole steel sheet composition.

Also, the ratio of the goss grain parallel to the steel plate with an error range of 15 DEG or less may be 90% or more of the total grains.

According to one embodiment of the present invention, it is possible to provide a method of manufacturing a grain-oriented electrical steel sheet in which continuous annealing can be performed without annealing in a batch form in a coil state at the final annealing.

Further, it is possible to produce a grain-oriented electrical steel sheet with only a short time of annealing.

Unlike the conventional method for producing a grain-oriented electrical steel sheet, a step of winding a cold-rolled steel sheet is not required.

In addition, a method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention can provide a grain-oriented electrical steel sheet that does not use a grain growth inhibitor.

In addition, steep annealing can be omitted.

FIG. 1 is a photograph showing changes in texture through EBSD analysis of a directional electrical steel sheet during a final annealing process in a method of manufacturing a grain-oriented electrical steel sheet according to an embodiment.
FIG. 2 is a photograph showing crystal grain distribution of a grain oriented electrical steel sheet according to one embodiment of the present invention through EBSD analysis.
3 is a photograph showing the texture of a directional electric steel sheet produced by a final batch annealing process.
4 (a) is a photograph showing the grain distribution of the grain-oriented electrical steel sheet produced by Example 3 through EBSD analysis. 4 (b) is a photograph showing the grain distribution of the grain-oriented electrical steel sheet produced by the comparative example through EBSD analysis.

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.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

In addition, unless otherwise stated,% means weight%.

The method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention comprises: first, 1.0 to 4.0% of Si and 0.1 to 0.4% of C, based on 100% by weight of the entire composition of the slab; And other inevitably incorporated impurities, the remainder comprising Fe and other inevitably incorporated impurities.

The reason for limiting the composition is as follows.

Si improves the iron loss by lowering the magnetic anisotropy of the electrical steel sheet and increasing the resistivity. When the Si content is less than 1.0%, the iron loss is inferior, and when the Si content is more than 4.0%, the brittleness is increased. Therefore, the content of Si in the grain-oriented electrical steel sheet after the slab and the final annealing step may be 1.0% to 4.0%.

C is required for the process of C to escape to the surface layer during the middle decarburization annealing and the final decarburization annealing so that the Goss crystal grains in the surface layer diffuse to the center portion, so the content of C in the slab may be 0.1 to 0.4%. Further, the amount of carbon in the grain-oriented electrical steel sheet after the final annealing step in which decarburization is completed may be 0.0020 wt% or less.

The steel slab having the above composition is reheated. The slab reheating temperature may be 1100 ° C to 1350 ° C higher than the normal reheat temperature.

If the temperature is high during reheating of the slab, there is a problem that the hot-rolled structure is coarsened and adversely affects magnetism. However, according to one embodiment of the present invention, since the content of carbon is higher than that in the related art, the hot rolled steel sheet is not coarsened even when the slab reheating temperature is high, and reheated at a higher temperature than usual, It is advantageous.

The hot-rolled steel sheet is manufactured by hot-rolling the slab after reheating.

The hot-rolled steel sheet is subjected to hot-rolled sheet annealing. At this time, the hot-rolled sheet annealing can be carried out at an annealing temperature of 850 to 1000 占 폚. The dew point temperature may be 50 캜 to 70 캜.

Hot rolled steel sheet decarburization annealing is performed, pickling is carried out, and first cold rolling is performed to produce a cold rolled steel sheet. The cold-rolled steel sheet is decarburized and annealed. Further, the steel sheet after the decarburization annealing is subjected to second cold rolling.

The step of decarburizing and annealing the cold-rolled steel sheet and the step of cold-rolling the steel sheet after decarburization annealing may be repeated two or more times.

The decarburization annealing process of the method for producing a grain-oriented electrical steel sheet according to one embodiment of the present invention will be described.

The step of decarburization annealing in one embodiment of the present invention includes a temperature elevating step and a cracking step.

In the decarburization annealing step, the heating rate may be 100 ° C / s or more and 400 ° C / s or less in the heating step. It is possible to improve the magnetic property by raising the rate of the initially formed goss grain by carrying out the heating rate at 100 DEG C / s or more and 400 DEG C / s or less.

The cracking temperature during the decarbonization annealing step may be from 850 캜 to 1000 캜. Cracking temperature in the decarburization annealing step is performed at 850 to 1000 占 폚 to produce recrystallized grains having an appropriate grain size to improve the magnetic properties.

Further, in the decarburization annealing step, the gas atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. The decarbonization amount in the decarburization annealing may be 0.0300 wt% to 0.0600 wt%.

In this decarburization annealing process, the grain size on the surface of the electric steel sheet grows to a great extent, but the crystal grains inside the electric steel sheet remain as a fine structure. After the decarburization annealing, the size of the surface ferrite grains may be 150 μm to 250 μm.

The cold rolling step of the method for producing a grain-oriented electrical steel sheet according to one embodiment of the present invention will be described.

It is known that it is effective to carry out cold rolling at a high pressure lowering rate which is close to 90% once in the manufacturing process of a conventional high magnetic flux density directional electric steel sheet. This is because only Goss crystal grains in the primary recrystallized grains create an environment favorable for grain growth.

However, according to one embodiment of the present invention, since the method for producing a grain-oriented electrical steel sheet internally diffuses Goss grain in the surface layer caused by decarburization annealing and cold rolling without using abnormal grain growth of Goss orientation grain, It is advantageous to form them so as to have a large distribution.

Therefore, when cold rolling is carried out at a reduction ratio of 50% to 70% in the cold rolling, many goss texture can be formed in the surface layer portion. Or 55% to 65%. Here, the reduction rate is (thickness of steel sheet before rolling-thickness of steel sheet after rolling) / (thickness of steel sheet before rolling).

In addition, a plurality of surface Goss texture structures can be formed in the surface layer at least twice in the decarburization annealing and cold rolling processes.

After the decarburization annealing and cold rolling have been completed, the steel sheet is subjected to final annealing.

In the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, unlike the conventional batch method, final annealing can be performed successively after cold rolling.

The final annealing step in the method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes a heating step, a first cracking step, and a second cracking step.

The rate of temperature rise up to 700 占 폚 in the heating step may be 100 占 폚 / s or more and 400 占 폚 / s or less. It is possible to improve the magnetic property by raising the rate of the initially formed goss grain by carrying out the heating rate at 100 DEG C / s or more and 400 DEG C / s or less.

Further, in the final annealing step, the first cracking step may be carried out at a cracking temperature of 850 to 1000 캜.

If the cracking temperature is less than 850 ° C, the crystal grains may not sufficiently grow and the magnetic properties may deteriorate. If the cracking temperature is more than 1000 ° C, the crystal grains may grow to a great extent and the magnetic properties may deteriorate.

In addition, the first cracking step may be performed at a dew point temperature of 70 DEG C or lower.

In the final annealing step, the second cracking step may be performed at a cracking temperature of 1000 ° C to 1200 ° C. If the cracking temperature is less than 1000 ° C, the crystal grains may not sufficiently grow and the magnetic properties may deteriorate. If the cracking temperature is higher than 1200 ° C, the crystal grains may have poor coercive force.

Further, the second cracking step may be performed in an atmosphere of 50 vol% or more of H ₂ . More specifically, it may be 90 vol% or more of H ₂ .

FIG. 1 is a photograph showing changes in texture through EBSD analysis of a directional electrical steel sheet during a final annealing process in a method of manufacturing a grain-oriented electrical steel sheet according to an embodiment. In FIG. 1, the red portion indicates a structure having a Goss orientation, and the texture changes progressively in (a) to (i).

The cold-rolled sheet before final annealing is in a state in which decarburization annealing proceeds so that the amount of carbon black remaining in the slab is 40 wt% to 60 wt% of the minimum amount of carbon in the slab. Therefore, at the first stage of the final annealing, the carbon grains are removed and the crystal grains formed in the surface layer are diffused inside. In the first step, decarburization can be performed so that the amount of carbon in the steel sheet is 0.01 wt% or less.

Thereafter, in the second step, a texture having a Goss orientation diffused in the first step is grown. In the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, unlike the case where the grains are grown by the conventional abnormal grain growth, the goss texture structure has a plurality of goss grain grains having a small grain size have.

The directional electrical steel sheet after completion of the final annealing can be dried after applying the insulating coating liquid as necessary.

According to one embodiment of the present invention, a directional electrical steel sheet as described below can be provided by the method for manufacturing a directional electrical steel sheet.

FIG. 2 is a photograph showing crystal grain distribution of a grain oriented electrical steel sheet according to one embodiment of the present invention through EBSD analysis.

2, the grain oriented electrical steel sheet according to an embodiment of the present invention is characterized in that the ratio (D2 / D1) of the diameter (D1) of the circumscribed circle and the diameter (D2) Of which 95% or more.

Here, the circumscribed circle means the smallest circle among the virtual circles surrounding the outside of the crystal grains, and the inscribed circle means the largest circle of the virtual circles included in the crystal grains.

Table 1 is a table showing the ratio (D2 / D1) of the relative size of the inscribed circle and the circumscribed circle of the grain-oriented electrical steel sheet according to one embodiment of the present invention shown in FIG.

Circumscribed circle D1 Inscribed circle (D2) The ratio (D2 / D1) 2.22 1.6 0.720720721 2.6 1.5 0.576923077 2.8 2 0.714285714 1.7 1.1 0.647058824 1.9 1.3 0.684210526 2.5 1.3 0.52 2.2 1.2 0.545454545 2.9 1.7 0.586206897 2.2 1.39 0.631818182 1.89 1.1 0.582010582 1.28 0.9 0.703125 1.8 1.17 0.65 1.2 0.7 0.583333333 1.7 1.1 0.647058824 1.8 One 0.555555556 1.7 0.9 0.529411765 1.2 0.8 0.666666667 1.3 One 0.769230769 2 One 0.5 1.5 0.9 0.6 1.2 0.7 0.583333333

Referring to Table 1, the grain-oriented electrical steel sheet according to an embodiment of the present invention has a ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) 95% or more.

This is because the texture of the grain-oriented electrical steel sheet according to an embodiment of the present invention is such that the goth crystal grains on the surface grow into the steel sheet, and therefore, a round grain is produced.

Fig. 3 shows the texture of a directional electrical steel sheet produced by a final batch annealing process. It can be seen that the grain-oriented electrical steel sheet produced by the prior art produces grain ellipsoidal in shape longer than that of the grain oriented electrical steel sheet according to an embodiment of the present invention.

Table 2 shows the ratio (D2 / D1) of the relative size of the inscribed circle and the circumscribed circle of the grain-oriented electrical steel sheet shown in Fig.

Circumscribed circle D1 Inscribed circle (D2) The ratio (D2 / D1) 1.6 0.8 0.5 2.2 1.2 0.55 2.6 0.9 0.35 3.3 1.6 0.48 4.7 1.7 0.36 1.1 0.5 0.45 2.5 0.9 0.36 One 0.5 0.5 2.3 1.4 0.61 1.2 0.9 0.75 5.1 2.3 0.45 1.9 0.7 0.37 3.6 2.1 0.58 2.7 1.7 0.63 1.4 0.6 0.43 0.8 0.4 0.5 1.3 0.5 0.38 0.7 0.3 0.43 1.8 1.1 0.61 1.1 0.5 0.45 0.9 0.35 0.39

The directional electrical steel sheet produced by the prior art is a long elliptical type of grain, so that the value of D2 / D1 is smaller than that of the directional electrical steel sheet according to the embodiment of the present invention.

In addition, the ratio of the goss grain parallel to the <001> direction with an error range of 15 degrees or less with respect to the rolling direction of the steel sheet may be 90% or more of the total grains. Here, the plate surface of the steel sheet means the rolling direction of the steel sheet, and the x-axis direction when the x-axis width direction is the y-axis.

Further, the grain-oriented electrical steel sheet may further contain 1.0% to 4.0% of Si and less than 0.002% of C (not including 0%) based on 100% by weight of the total composition of the electrical steel sheet. The reason for limiting the components in the electric steel sheet has already been described for the reason of the limitation of the slab component, and further explanation is omitted.

Hereinafter, the embodiment will be described in detail. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

[Example 1]

A slab containing 2.0% of Si and 0.20% of C and containing the remainder Fe and unavoidable impurities was prepared. The slab was heated at a temperature of 1150 占 폚 and hot-rolled to a thickness of 3 mm. Thereafter, the hot-rolled sheet was annealed at a crack temperature of 900 ° C and a dew point temperature of 60 ° C for 150 seconds, cooled, and pickled. And then cold rolled at a reduction ratio of 60%.

The cold-rolled plate was heated from room temperature to a crack temperature of 900 DEG C, and then subjected to decarburization annealing at a dew point temperature of 60 DEG C in a mixed gas atmosphere of hydrogen and nitrogen.

Thereafter, the cold rolling was repeated three times. Here, the cold rolling is repeated three times, meaning that the hot-rolled sheet annealed is first cold-rolled, then subjected to primary decarburization annealing, and then subjected to second cold-rolling, secondarily decarburization annealing, and third cold- do. During the secondary decarburization annealing, the annealing time was 100 seconds under the same temperature and atmosphere as the first order annealing. At the time of the third decarburization annealing, decarburization annealing was performed for 45 seconds.

Thereafter, at the time of the final annealing, the substrate was heated from the room temperature to the first cracking temperature: 950 占 폚, and then subjected to a 45 second cracking treatment at a dew point temperature of 60 占 폚 in a mixed gas atmosphere of hydrogen and nitrogen. Thereafter, the steel sheet was heated to a second cracking temperature of 1080 DEG C in a hydrogen atmosphere and cracked for 2 minutes. Table 3 shows the rate of temperature rise up to 700 占 폚 in the final annealing.

Heating rate (℃ / s) Goss fraction (%) B10 (T) W17 / 50 (W / Kg) Remarks 30 86 1.87 1.45 Comparative material 100 90 1.9 1.27 Invention material 150 91 1.92 1.25 Invention material 200 92 1.91 1.25 Invention material 300 92 1.9 1.23 Invention material 400 91 1.9 1.24 Invention material 500 83 1.85 1.51 Comparative material

 Here, the goss fraction (%) refers to the ratio of the goss grain in which the < 001 > direction is parallel to an error range of 15 DEG or less with respect to the rolling direction of the steel sheet.

As shown in Table 3, when the heating rate at the final annealing is 100 ° C or more and 400 ° C or less per second, the Goss fraction of the final product plate increases and the magnetic flux density and iron loss are excellent. This seems to be due to the fact that the fraction of gossy crystal grains generated at the early stage is high due to a high temperature rise rate.

In addition, the specimen subjected to a temperature increase rate of 150 ° C. per second in the final annealing is shown in FIG. 4 (b) through EBSD analysis. The specimens subjected to the final annealing at a heating rate of 30 ° C. per second were shown in FIG. 4 (a) through EBSD analysis. Referring to FIG. 4, it can be seen that the goss fraction of the specimen subjected to a heating rate of 150 ° C. per second is high.

[Example 2]

A slab containing 2.0% of Si and 0.20% of C and containing the remainder Fe and unavoidable impurities was prepared. The slab was heated to a temperature of 1150 DEG C and hot-rolled to a thickness of 3 mm. Thereafter, hot-rolled sheet annealing was performed at a crack temperature of 900 占 폚 and a dew point temperature of 60 占 폚 for 150 seconds. Thereafter, the steel sheet was cooled, pickled, and then cold-rolled at a reduction ratio of 60%.

The cold-rolled plate was heated at a room temperature to a crack temperature of 900 DEG C, and then subjected to a primary decarburization annealing by cracking at a dew point temperature of 60 DEG C for 100 seconds in a mixed gas atmosphere of hydrogen and nitrogen. At this time, the rate of temperature increase up to 700 占 폚 during the process of raising to 900 占 폚 was carried out as shown in Table 2. After the first decarburization annealing was completed, the steel sheet was cold-rolled at a reduction ratio of 60% and subjected to secondary decarburization annealing. In the second decarburization annealing, the cracking temperature, the gas atmosphere, and the dew point temperature were the same as those of the first decarburization annealing, and the cracking time was 45 seconds. The rate of temperature rise up to 700 ° C in the second decarburization annealing was carried out as shown in Table 4. After the second decarburization annealing, cold rolling was performed at a reduction ratio of 60%, and final decarburization annealing was performed. Thereafter, at the time of the final annealing, the substrate was heated from the room temperature to the first cracking temperature: 950 占 폚, and then subjected to a 45 second cracking treatment at a dew point temperature of 60 占 폚 in a mixed gas atmosphere of hydrogen and nitrogen. Thereafter, the steel sheet was heated to a second cracking temperature of 1080 DEG C in a hydrogen atmosphere and cracked for 2 minutes.

Primary decarburization annealing rate (℃ / s) Second decarburization annealing rate (℃ / s) Goss fraction (%) B10 (T) W17 / 50 (W / Kg) Remarks 30 30 86 1.87 1.45 Comparative material 100 30 87 1.87 1.41 Comparative material 200 30 87 1.86 1.45 Comparative material 100 100 92 1.92 1.25 Invention material 200 200 94 1.93 1.18 Invention material 300 300 91 1.91 1.21 Invention material 400 400 91 1.92 1.22 Invention material 500 200 85 1.85 1.5 Comparative material

 Here, the goss fraction (%) refers to the ratio of the goss grain in which the < 001 > direction is parallel to an error range of 15 DEG or less with respect to the rolling direction of the steel sheet.

As shown in Table 4, when the heating rate up to 700 ° C during the first to second decarburization annealing is performed at 100 ° C or more and 400 ° C or less per second, the Goss fraction of the final product plate is increased and the magnetic flux density and iron loss are excellent Able to know.

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 .

Claims (10)

Providing a slab comprising 1.0% to 4.0% of Si and 0.1% to 0.4% of Si based on 100% by weight of the total composition of the slab, the balance comprising Fe and other inevitably incorporated impurities;
Heating the slab;
Hot-rolling the slab to produce a hot-rolled steel sheet;
Annealing the hot-rolled steel sheet by hot-rolling;
A first cold rolling step of annealing the hot rolled steel sheet;
Decarburizing and annealing the first cold-rolled steel sheet;
Second cold rolling the steel sheet after the decarburization annealing has been completed; And
And finally annealing the second cold-rolled steel sheet;
Wherein the final annealing step includes a heating step, a first cracking step, and a second cracking step,
Wherein the rate of temperature rise up to 700 占 폚 in the temperature-raising step in the final annealing step is 100 占 폚 / s or more and 400 占 폚 / sec or less.
The method according to claim 1,
The decarburization annealing step includes a temperature raising step and a cracking step,
Wherein the rate of temperature rise in the temperature increasing step of the decarburization annealing step is 100 DEG C / s or more and 400 DEG C / s or less.
3. The method of claim 2,
In the final annealing step,
The first cracking step is carried out at a cracking temperature of 850 캜 to 1000 캜,
And the second cracking step is carried out at a cracking temperature of 1000 ° C to 1200 ° C.
The method of claim 3,
Wherein the cracking step of the decarburization annealing step is performed at a cracking temperature of 850 to 1000 占 폚.
5. The method according to any one of claims 1 to 4,
And the final annealing step after the first cold rolling step is performed continuously.
6. The method of claim 5,
Wherein the step of decarburizing and annealing the first cold-rolled steel sheet and the second cold-rolling of the steel sheet after the decarburization annealing are repeated twice or more.
The method of claim 3,
Wherein the first and second cold rolling reduction rates are 50% to 70%.
The method according to claim 6,
And the reheating temperature of the slab is 1100 ° C to 1350 ° C.
The steel sheet comprises 1.0 to 4.0% of Si and less than 0.002% of C (not including 0%), based on 100% by weight of the total composition of the electrical steel sheet, the balance including Fe and other inevitably incorporated impurities,
The crystal grains in which the ratio (D2 / D1) of the diameter (D1) of the circumscribed circle to the diameter (D2) of the inscribed circle in the goss crystal grains is 0.5 or more is 95%
Wherein the ratio of the goss grain parallel to the <001> direction in the rolling direction of the steel sheet is 15% or less in the error range is 90% or more of the total grains. delete

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