JP6622919B2 - Oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a grain-oriented electrical steel sheet and a manufacturing method thereof.

A grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction, which is made of crystal grains having a so-called Goss orientation in which the crystal orientation of the steel sheet is {110} <001>.
Such a grain-oriented electrical steel sheet is usually finally rolled to a thickness of 0.15 to 0.35 mm by hot rolling after slab heating, hot-rolled sheet annealing, and cold rolling, followed by primary recrystallization. Manufactured through high temperature annealing for annealing and secondary recrystallization formation.

  At this time, it is known that the higher the rate of temperature increase during high-temperature annealing, the higher the degree of integration of Goss orientation recrystallized and the better the magnetism. Usually, the temperature rise rate during high-temperature annealing of grain-oriented electrical steel sheets is 15 ° C. or less per hour, and it takes 2-3 days not only for temperature rising but also requires 40 hours or more purification annealing. It can be said that it is a process with high consumption. In addition, since the current final high-temperature annealing process performs batch-type annealing in a coil state, the following difficulties occur in the process. First, the temperature deviation between the outer and inner winding portions of the coil due to the heat treatment in the coil state occurs, and the same heat treatment pattern cannot be applied to each portion, and the magnetic deviation between the outer and inner winding portions is different. appear. Secondly, since various surface defects are generated in the process of forming the base coating during high temperature annealing by coating MgO on the surface after decarburization annealing, the actual yield decreases. Thirdly, the decarburized plate that has been decarburized and annealed is wound into a coil form, and after the high-temperature annealing, the insulating coating is performed again through flattening annealing. .

  An object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet and a grain-oriented electrical steel sheet produced thereby.

  The production method of the grain-oriented electrical steel sheet according to the present invention is, in wt%, Si: 4.0% or less (excluding 0 wt%), C: 0.001% to 0.4%, and Mn: 0.001. Providing a slab containing 2.0%, the balance including Fe and other impurities inevitably mixed, a step of reheating the slab, and hot rolling the slab to produce a hot-rolled steel sheet A stage, a stage of hot-rolled sheet annealing of the hot-rolled steel sheet, a stage of primary cold-rolling the hot-rolled steel sheet that has been hot-rolled sheet annealed, a stage of decarburizing and annealing the cold-rolled steel sheet, and decarburization The steel plate that has been subjected to the final cold annealing of the steel sheet that has been annealed and that has been subjected to secondary cold rolling and the final annealing of the steel sheet that has been cold-rolled is the size of the magnetic domain existing in the crystal grains. (2L) is smaller than the thickness (D) of the steel plate (2L <D).

The slab preferably contains 1 wt% or less (excluding 0 wt%) of Si.
It is preferable that the slab further contains 0.01% by weight or less (excluding 0% by weight) of Al.
The reheating temperature of the slab can be from 1050 ° C to 1350 ° C.
The rolling reduction in the primary cold rolling stage and the secondary cold rolling stage may be 50% to 70%, respectively.

It is preferable that the step of decarburizing and annealing the cold-rolled steel plate and the step of secondary cold-rolling the steel plate after the decarburization annealing are repeated twice or more.
The stage of decarburization annealing is preferably performed in an atmosphere containing hydrogen at a temperature of 800 ° C. to 1150 ° C. and a dew point temperature of 0 ° C. or higher.
The final annealing step is a first step performed in an atmosphere having a dew point temperature of 10 ° C. to 70 ° C. at a temperature of 850 ° C. to 1150 ° C., and a mixture containing hydrogen and nitrogen having a dew point temperature of 10 ° C. or less at a temperature of 900 ° C. to 1200 ° C. It is preferable to include a second stage performed in a gas atmosphere.
The first stage is preferably performed for 300 seconds or less, and the second stage is preferably performed for 60 seconds to 300 seconds.

The final annealing step after the cold rolling step can be performed continuously.
The amount of carbon in the electrical steel sheet after the final annealing stage is preferably 0.003% by weight or less (excluding 0% by weight).
The steel sheet that has undergone the final annealing may have a volume fraction of crystal grains having an orientation within 15 degrees from the {110} <001> orientation that is 50% or more.
The steel sheet after the final annealing preferably has a volume fraction of crystal grains having a grain size of 20 μm to 1000 μm of 50% or more.

  The grain-oriented electrical steel sheet of the present invention is, by weight, Si: 4.0% or less (excluding 0% by weight), C: 0.003% or less (excluding 0% by weight), and Mn: 0.001-2. 0.0%, the balance contains Fe and other impurities inevitably mixed, and the size (2L) of the magnetic domains existing in the crystal grains is smaller than the thickness (D) of the steel sheet. .

Si is preferably contained in an amount of 1.0% by weight or less (excluding 0% by weight).
It is preferable to further contain 0.01% by weight or less (excluding 0% by weight) of Al.
The size (2L) of the magnetic domains present in the crystal grains can be 10 to 500 μm.
The volume fraction of crystal grains having an orientation within 15 degrees from the {110} <001> orientation is preferably 50% or more.
The volume fraction of crystal grains having a particle diameter of 20 μm to 1000 μm is preferably 50% or more.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the grain-oriented electrical steel sheet which can perform continuous annealing, without performing batch-type annealing in the coil state at the time of final annealing can be provided.
Moreover, according to this invention, a grain-oriented electrical steel sheet can be produced only by short-time annealing.
Furthermore, according to one embodiment of the present invention, a grain-oriented electrical steel sheet that does not use a crystal grain growth inhibitor can be provided.
Furthermore, according to one embodiment of the present invention, nitrous annealing can be omitted.

It is a photograph which shows the fine structure and magnetic domain of the grain-oriented electrical steel sheet manufactured in Example 1. FIG.

Terms such as first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, the first part, component, region, layer or section described below can be referred to as the second part, component, region, layer or section within the scope of the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms used herein include the plural unless the word has a clearly opposite meaning. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, operation, element and / or component and other property, region, integer, step, operation, element and / or component. It does not exclude the presence or addition of.

When one part is “on top” of another part, it is directly above or above the other part, or another part may be interposed therebetween. In contrast, when one part is “directly above” another part, no other part is interposed between them.
Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries are further interpreted as having a meaning consistent with relevant technical literature and the presently disclosed content, and are not interpreted as ideal or overly formal meaning unless defined .
Moreover, unless otherwise stated,% means% by weight, and 1 ppm is 0.0001% by weight.
Hereinafter, embodiments of the present invention will be described in detail so as to be easily performed by those having ordinary knowledge in the technical field to which the present invention belongs. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In general, the characteristics required for grain-oriented electrical steel sheets used for power conversion as a core material of a transformer are high magnetic flux density and low iron loss characteristics. The characteristics of high magnetic flux density not only increase the power conversion efficiency, but also increase the design magnetic flux density, and have the advantage that the size of the transformer can be reduced by using less core material. Furthermore, in the case of iron loss, which is a loss generated in the grain-oriented electrical steel sheet itself during the power change process, there is an advantage that the no-load loss of the transformer can be reduced.
Until now, most research and technology development on grain-oriented electrical steel sheets has been carried out in order to reduce iron loss. Iron loss of grain-oriented electrical steel sheets is roughly classified into hysteresis loss, traditional eddy current loss, and abnormal eddy current loss as follows.
In the case of the hysteresis loss, the loss of the magnetic steel sheet itself caused by the degree of magnetization of the grain-oriented electrical steel sheet is low, and the loss is small when the grain-oriented electrical steel sheet has no impurities or defects and the Goth orientation is highly integrated.

  Traditional eddy current loss is loss caused by eddy current generated in a steel sheet itself during the process of magnetization of a grain-oriented electrical steel sheet. By increasing the Si content and reducing the thickness of the steel sheet, the eddy current of the steel sheet is reduced. Efforts have been made to minimize and reduce losses. The other abnormal eddy current loss is a loss related to the movement and rotation of the magnetic domain magnetic domain (magnetic domain) under the alternating current in which the transformer is operated, and the magnetic domain size (Magnetic domain size, 2L) is fine. There is a characteristic that the loss is reduced. Research to improve abnormal eddy current loss is a relatively recent study compared to studies on hysteresis loss and traditional eddy current loss. There have been developed a method for temporarily refining magnetic domains by applying a specific stress and a method for refining permanent magnetic domains by changing a structural magnetic domain by imparting a certain pattern of bending to the surface of a steel sheet. As another magnetic domain refining method, a method of applying a coating material having a different expansion coefficient to the steel sheet surface to apply a tension due to the difference in expansion coefficient to the steel sheet surface to refine the magnetic domain has been developed.

As a result of repeated studies to reduce the abnormal eddy current loss of the grain-oriented electrical steel sheet, the inventors can reduce the size of the magnetic domain by reducing the grain size of the grain-oriented electrical steel sheet. , Discovered the fact that it is possible to dramatically reduce the iron loss of the entire grain-oriented electrical steel sheet manufactured by this.
Usually, the size of the magnetic domain is in the relationship of the size of the crystal grains and the following formula (1).
Magnetic domain size (2L) ∝ (crystal grain size) 1/2 (1)
That is, the smaller the size of the crystal grains, the smaller the size of the magnetic domain, thereby reducing the abnormal eddy current loss.

The abnormal eddy current loss is related to the traditional eddy current loss by the following equation (2).
Wea = [1.63 * (2L / d) -1] * Wec (2)
In Equation (2), Wea is an abnormal eddy current loss, Wec is a traditional eddy current loss, 2L is the size of the magnetic domain, and d is the thickness of the steel sheet.
Assuming that the thickness of the steel sheet is constant in Equation (2), the abnormal eddy current loss decreases as the magnetic domain size decreases.
If the size of the Goss-oriented crystal grains is reduced, it is possible to dramatically reduce the size of the magnetic domain based on the relational expression (1) between the crystal grain size and the magnetic domain size. The iron loss of the grain-oriented electrical steel sheet can be dramatically reduced.

  In summary, in order to reduce the iron loss of grain-oriented electrical steel sheets, the hysteresis loss is reduced according to the excellent magnetization characteristics by the formation of recrystallized grains in the goth orientation, the Si content is increased, and the steel sheet thickness is reduced. It is necessary to reduce the size of the magnetic domain and reduce the abnormal eddy current loss by reducing the traditional eddy current loss by reducing the thickness and finally refining the size of the goth-oriented grains . In order to reduce the overall loss of grain-oriented electrical steel sheets, it is preferable to reduce all hysteresis loss, traditional eddy current loss and abnormal eddy current loss, but in some cases hysteresis loss and traditional eddy current loss Even if there is no breakthrough improvement, the grain-oriented electrical steel sheet that is easy to produce and has excellent magnetic properties is manufactured by minimizing the size of goth-oriented grains and greatly improving only the abnormal eddy current loss. be able to.

  The method of manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention is, in wt%, Si: 4.0% or less (excluding 0 wt%), C: 0.001% to 0.4%, and Mn: A slab containing 0.001 to 2.0%, the balance including Fe and other impurities inevitably mixed, a step of reheating the slab, and hot rolling the slab by hot rolling A step of producing a steel plate, a step of hot-rolling the hot-rolled steel plate, a primary cold-rolling of the hot-rolled steel plate that has been hot-rolled, and a step of decarburizing and annealing the cold-rolled steel plate. And a step of secondary cold rolling the steel plate that has been decarburized annealed, and a step of final annealing the steel plate that has been cold rolled. In addition to this, the method for manufacturing the grain-oriented electrical steel sheet may further include other stages as necessary.

Below, it explains in detail according to each stage.
First, by weight, Si: 4.0% or less (excluding 0% by weight), C: 0.001% to 0.4% and Mn: 0.001 to 2.0%, the balance being A slab containing Fe and other impurities inevitably mixed is prepared.
The reason for limiting the composition is as follows.
Silicon (Si) improves the iron loss by lowering the magnetic anisotropy of the grain-oriented electrical steel sheet and increasing the specific resistance. One embodiment of the present invention is characterized in that the size of the final product crystal grains is reduced to greatly reduce the abnormal eddy current loss, but the iron loss can be further improved as Si is added. It is effective to add a certain amount or more. Therefore, the Si content can be added up to a range of 4% by weight, which is a content that allows cold rolling. However, when there is too much Si content, there exists a possibility that the brittleness at the time of cold rolling may increase, and cold rolling may become impossible. More specifically, Si is preferably 1% by weight or less (excluding 0% by weight).

Carbon (C) is an element that promotes the austenite phase transformation, and makes the hot-rolled structure of the grain-oriented electrical steel sheet uniform, promotes the formation of goss-oriented crystal grains during cold rolling, and is excellent in magnetism. It is an important element necessary for producing steel sheets. However, if C is present in the final product, a magnetic aging phenomenon occurs and magnetic properties are deteriorated. Therefore, C must be 0.003% by weight or less in the finally manufactured electrical steel sheet. In order to promote the phase transformation due to the addition of C and the recrystallization of goth-oriented grains, the effect is not obtained unless C is added in an amount of 0.001% by weight or more in the slab. Secondary recrystallization is unstablely formed by the hot rolled structure. However, if C is added to the slab in an amount exceeding 0.4% by weight, the primary recrystallized grains become fine due to the formation of a fine hot-rolled structure due to the austenite phase transformation during hot rolling, and winding after the hot rolling is completed. There is a possibility that coarse carbides may be formed in the cooling process after the process or hot-rolled sheet annealing, and Fe ₃ C (cementite) is formed at room temperature, and the structure tends to be unevenly guided. Furthermore, there is a problem that the annealing time becomes long to decarburize to 0.003% by weight or less in the decarburization step and the final annealing step. Therefore, the C content in the slab is preferably limited to 0.001 to 0.4% by weight.

Manganese (Mn), like Si, has the effect of increasing the specific resistance and reducing iron loss. Like C, it promotes austenite phase transformation and refines the grain size in the hot rolling and annealing processes. It is an important element to be converted. When the amount of Mn added is less than 0.001% by weight, the phase transformation is not sufficiently performed similarly to the effect of C, the slab and the hot rolled structure are coarsened, and the grain size of the crystal grains of the final product is fine. The effect of iron loss improvement due to an increase in specific resistance is also insignificant. Furthermore, when Mn is added in excess of 2.0% by weight, manganese oxide (Mn Oxide) is formed on the steel sheet surface in addition to Fe ₂ SiO ₄ , and decarburization is not smoothly performed in the final annealing step. Therefore, the preferable amount of Mn added may be 0.001 to 2.0% by weight. More specifically, the amount of Mn added is more preferably 0.01 to 1.0% by weight.

In one embodiment of the present invention, aluminum (Al) is treated as an inevitable impurity. That is, the content of Al is preferably minimized in the slab and the steel plate. Specifically, when Al is further contained, the range is preferably limited to 0.01% by weight or less.
The above-described components are the basic structure of the present invention, and other fine elements of the Goss-oriented crystal grains that are the characteristics of the present invention are included unavoidably or other alloying elements that improve magnetic properties are added. Does not weaken the effect of iron loss improvement by aging.
As a method for producing the slab from the molten steel having the above-described composition, a lump method, a continuous casting method, a thin slab casting or a strip casting can be used.
Next, the slab is reheated. The reheating temperature of the slab can be from 1050 ° C to 1350 ° C. If the temperature at the time of reheating the slab is low, the rolling load increases, and if the temperature is high, the slab washing phenomenon occurs due to the formation of a high melting point oxide with a low melting point, the actual yield decreases, and the hot rolled structure Becomes coarse and causes problems that adversely affect magnetism. Therefore, it is preferable to adjust the reheating temperature of the slab within the above-described temperature range.

Next, the slab that has been reheated is hot-rolled to produce a hot-rolled steel sheet. At the time of hot rolling, it is preferable to produce a hot-rolled steel sheet by hot rolling within a temperature range in which an austenite phase exists. At a low temperature at which no austenite phase exists, not only the rolling load increases, but also the effect of grain refinement due to phase transformation cannot be obtained.
Next, the hot rolled steel sheet is subjected to hot rolled sheet annealing. The hot-rolled sheet is preferably annealed at a temperature higher than the temperature at which recrystallization and phase transformation are possible. Specifically, in order to prevent the formation of a low melting point oxide layer due to high-temperature heating, hot-rolled sheet firing can be performed at a temperature of 850 to 1150 ° C. The atmosphere during the hot-rolled sheet annealing is preferably an atmosphere containing a dew point temperature of 0 ° C. or higher and hydrogen gas that can cause a decarburization reaction of the hot-rolled sheet.
Next, the hot rolled steel sheet annealed by hot rolling is subjected to primary cold rolling. After hot-rolled sheet annealing, the steel sheet may be pickled and cold rolled. The rolling reduction during cold rolling is preferably 50% to 70%.

Next, the cold-rolled steel sheet is decarburized and annealed. The cold-rolled steel sheet is annealed for recrystallization, and at this time, annealed in an atmosphere containing a dew point temperature of 0 ° C. or more and hydrogen gas at a temperature of 800 ° C. to 1150 ° C. so that a decarburization reaction occurs. Do. If the temperature is too low, decarburization is difficult, and if the temperature is too high, a thick oxide layer is formed, and rather the decarburization reaction is inhibited. If the dew point temperature is too low, the decarburization reaction is inhibited. More specifically, the dew point temperature is more preferably 10 to 70 ° C.
Next, secondary cold rolling is performed on the steel sheet that has been decarburized and annealed. At the time of cold rolling, the rolling reduction can be 50% to 70%. The stage of decarburizing and annealing the cold-rolled steel sheet and the stage of secondary cold rolling of the steel sheet that has been decarburized and annealed are repeated twice or more. As an example, in the case of repeating twice, in the order of primary cold rolling, decarburizing annealing, secondary cold rolling, decarburizing annealing, third cold rolling, and final annealing. Do. At this time, cold rolling is performed to the final product thickness at the final cold rolling stage, and each decarburization step is performed at a temperature of 800 ° C. to 1150 ° C. so that a decarburization reaction occurs, and a dew point of 0 ° C. or more. Annealing is performed in an atmosphere containing temperature and hydrogen gas.

Next, the steel sheet that has been cold-rolled is finally annealed.
In the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, unlike the existing batch system, the final annealing can be performed continuously after the secondary cold rolling.
The final annealing step is a first step performed in an atmosphere having a dew point temperature of 10 ° C. to 70 ° C. at a temperature of 850 ° C. to 1150 ° C., and a mixed gas containing hydrogen and nitrogen having a dew point temperature of 10 ° C. or less at a temperature of 900 ° C. to 1200 ° C. It is good to carry out at the 2nd step performed in atmosphere. The first stage is performed for 300 seconds or less, and the second stage is performed for 60 seconds to 300 seconds.
The cold-rolled sheet before final annealing is in a state in which decarburization annealing is progressed and the carbon content of the steel remains 40 wt% to 60 wt% with respect to the carbon content of the minimum slab. Therefore, in the first stage at the time of the final annealing, crystal grains formed in the surface layer portion diffuse into the inside while carbon escapes. In the first stage, decarburization is preferably performed so that the amount of carbon in the steel sheet is 0.01% by weight or less.

Thereafter, in the second stage, a texture having Goth orientation diffused in one stage grows. In the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, the Goss texture is different from the case where crystal grains are grown by conventional abnormal grain growth, and the grain size of the crystal grains is within 1 mm. Can do. Therefore, it is possible to obtain a fine structure composed of goth-oriented crystal grains in which the grain size of the crystal grains is much smaller than that of the conventional grain-oriented electrical steel sheet.
The amount of carbon in the electrical steel sheet after the final annealing is preferably 0.003% by weight or less.
The grain-oriented electrical steel sheet that has been subjected to final annealing may be dried after applying an insulating coating liquid as necessary.

On the other hand, in order to apply an annealing separator mainly composed of MgO to the conventional batch (Batch) form, there is an MgO coating layer, but the grain-oriented electrical steel sheet according to an embodiment of the present invention is a batch. Since the final annealing can be performed in a continuous manner that is not a form, the MgO coating layer may not exist.
The crystal grains of the Goss orientation (an orientation within 15 degrees from the {110} <001> orientation) generated according to an embodiment of the present invention tend to further increase as cold rolling and decarburization annealing are repeated. Shown, when performing at least two cold rolling and decarburization annealing, the volume fraction of crystal grains having goth orientation in the steel sheet increases to at least 50% or more.
The crystal grains produced according to one embodiment of the present invention have a grain size of less than 5 mm, and the volume fraction of crystal grains of 20 μm to 1000 μm is 50% or more. Eventually, the size of the magnetic domains present in the crystal grains becomes very small. The magnetic domain size found in conventional grain-oriented electrical steel sheets is usually larger than the thickness of the steel sheet, but the steel sheet manufactured according to one embodiment of the present invention has a magnetic domain size (2L) present in the crystal grains. It is formed smaller than the thickness (D) of the steel plate.

The grain-oriented electrical steel sheet according to one embodiment of the present invention is, by weight, Si: 4.0% or less (excluding 0% by weight), C: 0.003% or less (excluding 0% by weight), and Mn: 0.001 to 2.0% is contained, the balance contains Fe and other impurities inevitably mixed, and the size (2L) of the magnetic domain existing in the crystal grains is smaller than the thickness (D) of the steel plate. .
About the composition of a grain-oriented electrical steel sheet, since it is the same as the composition of the slab mentioned above and the composition range does not change substantially in the manufacturing process of a grain-oriented electrical steel sheet, the overlapping description is abbreviate | omitted. However, as described above, since the decarburization is performed in the decarburization annealing and the final annealing process, the carbon content is 0.003% by weight or less.

In the grain-oriented electrical steel sheet according to an embodiment of the present invention, the volume fraction of crystal grains having the Goth orientation in the steel sheet is increased by at least 50%, and the iron loss and magnetic flux density are excellent. In addition, the grain size of the grain in the grain-oriented electrical steel sheet is 50% or more of 20 to 1000 μm, and the size does not exceed 5 mm at the maximum. At this time, the size of the magnetic domain existing in the grain is The size is smaller than the thickness of the steel plate. Due to such a fine magnetic domain structure, the abnormal eddy current loss of the steel sheet manufactured according to the present invention is dramatically reduced from the abnormal eddy current loss of the grain-oriented electrical steel sheet manufactured by the conventional method, and the entire iron The loss can be greatly improved.
More specifically, the size (2L) of the magnetic domains present in the crystal grains is preferably 10 to 500 μm.

Hereinafter, the present invention will be described in more detail with reference to examples. However, this example is merely to illustrate the present invention, and the present invention is not limited thereto.
Example 1
The slab containing Si: 2.0%, C: 0.15%, Mn: 0.05% by weight, the balance being Fe and unavoidable impurities was heated at a temperature of 1100 ° C., and the thickness was 3 mm. Then, hot rolling was performed, and then hot-rolled sheet annealing was performed at an annealing temperature of 1000 ° C. After cooling, pickling was performed, and cold rolling was performed to a final thickness of 0.27 mm. In performing cold rolling to the final thickness, the method of cold rolling directly to the final thickness without decarburization annealing between cold rolling and cold rolling, and cold rolling and cold rolling A method of cold rolling through a plurality of stages was performed, including decarburization annealing at least once. The decarburization annealing was performed at a temperature of 1000 ° C. in a wet mixed gas atmosphere of hydrogen and nitrogen (dew point temperature 60 ° C.).
After the final annealing, annealing was performed at a temperature of 1000 ° C. in a wet mixed gas atmosphere of hydrogen and nitrogen (dew point temperature 60 ° C.) for 2 minutes, followed by drying at 1100 ° C. (dew point temperature 0 ° C.) in a hydrogen and nitrogen mixed gas atmosphere. Annealing was performed for 3 minutes.

表１に示したとおり、熱延板焼鈍を行った後に、最終の厚さまで冷間圧延過程で少なくとも１回以上の脱炭が起こる中間焼鈍を含む場合に最終製品にゴス方位の結晶粒の分率は少なくとも５０％以上確保し得、微細な磁区の大きさが得られた。このような高いゴス方位分率及び微細な磁区の大きさによって最終製品において優れた磁束密度及び低鉄損の特性が得られた。 Table 1 below shows a comparison of the relationship between the fraction of goth-oriented crystal grains and the magnetic properties of the steel sheets after the final annealing treatment.
Here, evaluation of the crystal grain fraction of Goss orientation is performed by measuring the volume fraction of crystal grains having an orientation in which an error within 15 degrees can be seen from the ideal {110} <001> orientation by using a normal crystal orientation measurement method. did.
Further, the magnetic domain average size was measured by magnetic domain observation in a state where the magnetic steel sheet was demagnetized using Kerr microscopy.

As shown in Table 1, the content of goth-oriented grains in the final product includes intermediate annealing in which at least one decarburization occurs in the cold rolling process to the final thickness after hot-rolled sheet annealing. The rate could be secured at least 50% or more, and a fine magnetic domain size was obtained. Due to such high Goss orientation fraction and fine magnetic domain size, excellent magnetic flux density and low iron loss characteristics were obtained in the final product.

Example 2
C: 0.2% by weight and Mn: 0.05% were contained, and the balance was produced by changing the Si content of the slab composed of Fe and inevitable impurities as shown in Table 2 below. The slab was heated at a temperature of 1150 ° C., hot-rolled to a thickness of 3 mm, and then hot-rolled sheet annealed at an annealing temperature of 950 ° C. After cooling, pickling was performed, and cold rolling was performed at a reduction rate of 60%. The cold-rolled plate was again recrystallized and decarburized and annealed in a mixed gas atmosphere of hydrogen and nitrogen having a dew point of 60 ° C. and a temperature of 900 ° C. Thereafter, the same cold rolling and decarburization annealing were further repeated twice. After the steel sheet was finally cold-rolled to 0.23 mm, decarburization annealing (one stage) was performed for 180 seconds in a mixed gas atmosphere of hydrogen and nitrogen at a temperature of 950 ° C. and a dew point of 60 ° C., then 1000 Heat treatment (two steps) was performed for 100 seconds in a hydrogen atmosphere dried at 0 ° C. (dew point 0 ° C.). Table 2 shows the magnetic properties of the final annealed steel sheet according to the Si content change.

表２に示したとおり、Ｓｉ含有量が４重量％以下は、複数の冷間圧延及び脱炭焼鈍により最終結晶粒の粒径１０００μｍ以下の微細組織を確保し、この時磁区の大きさは、鋼板の厚さより小さい磁区の大きさを確保した結果、優れた鉄損を確保することができた。Ｓｉ含有量が４重量％を超えた場合は脆性が増加して冷間圧延時の板破断により最終の厚さまで冷間圧延することが難しく、脱炭焼鈍時間のあいだ脱炭が行われず、非常に小さい結晶粒の粒径と劣位である磁気特性を示した。

As shown in Table 2, when the Si content is 4% by weight or less, a fine structure having a grain size of 1000 μm or less of the final crystal grains is ensured by a plurality of cold rolling and decarburization annealing. As a result of securing a magnetic domain size smaller than the thickness of the steel plate, excellent iron loss could be secured. When the Si content exceeds 4% by weight, brittleness increases and it is difficult to cold-roll to the final thickness due to sheet breakage during cold rolling, and decarburization is not performed during the decarburization annealing time. The magnetic properties of small crystal grains and inferiority were shown.

Example 3
The slab containing Si: 3.0%, C: 0.25%, Mn: 0.5% by weight, the balance being Fe and unavoidable impurities is heated at a temperature of 1200 ° C., and then 2.5 mm. And then hot-rolled sheet annealing in a mixed gas atmosphere of hydrogen and nitrogen having an annealing temperature of 1100 ° C. and a dew point temperature of 40 ° C., and after cooling and pickling, at a rolling reduction of 65% Primary cold rolling was performed. Next, the cold-rolled plate was decarburized and annealed again in a wet mixed gas atmosphere of hydrogen and nitrogen having a dew point temperature of 60 ° C. at a temperature of 1050 ° C. Thereafter, the primary decarburized annealed plate was subjected to secondary cold rolling to a final thickness of 0.30 mm, and then final annealed. The final annealing is a decarburization annealing by changing the annealing temperature as shown in Table 3 below in a wet mixed gas atmosphere of hydrogen and nitrogen with a dew point temperature of 65 ° C. so that the carbon content is 0.003% by weight or less (one step) ) Finally, after decarburization annealing, the temperature was additionally increased, and finish heat treatment (two steps) was performed in a dry hydrogen atmosphere with a dew point of 0 ° C. at 1150 ° C. The grain size of the crystal grains of the steel sheet after the final annealing and the size of the magnetic domain using Kerr microscopy were measured and shown in Table 3 below in comparison with the magnetic properties.

表３に示したとおり、最終焼鈍温度（１段階）が８５０〜１１５０℃である場合は、最終製品で結晶粒の粒径が２０〜１０００μｍの比率が５０％以上となりれ、そのために磁区の大きさも鋼板の厚さより小さい大きさとなって優れた鉄損特性示した。脱炭焼鈍温度が８５０℃より低い場合、磁区の大きさが非常に小さいにもかかわらず、全体的な磁気特性劣位である理由は、結晶粒の中にゴス方位分率が５０％以下であるためと判断された。逆に、１１５０℃より高い場合は、結晶粒の粒径が粗大になることによって、磁区の大きさが鋼板の厚さより大きくなるため、鉄損が改善されなかった。

As shown in Table 3, when the final annealing temperature (one stage) is 850 to 1150 ° C., the ratio of the crystal grain size of 20 to 1000 μm in the final product can be 50% or more. In addition, the iron loss characteristic was excellent because it was smaller than the thickness of the steel sheet. When the decarburization annealing temperature is lower than 850 ° C., the reason for the overall magnetic property inferiority despite the fact that the size of the magnetic domain is very small is that the Goth orientation fraction in the crystal grains is 50% or less. It was judged because. On the other hand, when the temperature is higher than 1150 ° C., the grain size of the crystal grains becomes coarse so that the size of the magnetic domain becomes larger than the thickness of the steel sheet, and thus the iron loss is not improved.

  The present invention is not limited to the embodiments and can be manufactured in various forms different from each other. Those skilled in the art to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing the technical idea and essential features of the present invention. Accordingly, it should be understood that the embodiments described above are illustrative in all aspects and not limiting.

Claims (15)

In weight percent, Si: 4.0% or less (excluding 0%), C: 0.001% to 0.4% , Mn : 0.001 to 2.0% , and Al: 0.01% or less ( containing excluding 0%), the balance comprising: providing a slab consisting of Fe and other inevitable impurities to be mixed,
Reheating the slab;
Hot rolling the slab to produce a hot rolled steel sheet,
Annealing the hot-rolled steel sheet,
Primary cold rolling the hot-rolled steel sheet annealed by the hot-rolled sheet;
Decarburizing and annealing the primary cold-rolled steel sheet;
Secondary cold rolling the steel plate after the decarburization annealing is completed;
Including a step of continuous final annealing of the steel sheet on which the secondary cold rolling has been completed,
Steel sheet wherein the final annealing is completed, the size of the magnetic domains present in the crystal grains (2L) is rather smaller than the thickness of the steel sheet (D), a steel sheet wherein the final annealing is completed, the particle size of 20μm~1000μm A method for producing a grain- oriented electrical steel sheet, wherein the volume fraction of crystal grains is 50% or more .   2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the slab contains 1% by weight or less (excluding 0% by weight) of Si. The method for manufacturing a grain-oriented electrical steel sheet according to claim 1 or 2 , wherein the reheating temperature of the slab is 1050C to 1350C. The directionality according to any one of claims 1 to 3 , wherein the rolling reduction in the primary cold rolling and the secondary cold rolling is 50% to 70%, respectively. A method for producing electrical steel sheets. The step of rolling said cold rolled stages steel sheet decarburization annealing and the steel sheet secondary cold decarburization annealing is completed, any one of claims 1 to 4, characterized in that repeated more than once The manufacturing method of the grain-oriented electrical steel sheet according to one item. The grain-oriented electrical steel sheet according to any one of claims 1 to 5 , wherein the decarburization annealing is performed in an atmosphere containing hydrogen at a temperature of 800 ° C to 1150 ° C and a dew point temperature of 0 ° C or higher. Manufacturing method. The final annealing step includes a first step performed in an atmosphere having a dew point temperature of 10 ° C. to 70 ° C. at a temperature of 850 ° C. to 1150 ° C., and hydrogen and nitrogen having a dew point temperature of 10 ° C. or less at a temperature of 900 ° C. to 1200 ° C. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 6 , comprising a second stage performed in a mixed gas atmosphere. The method for producing a grain-oriented electrical steel sheet according to claim 7 , wherein the first stage is performed for 300 seconds or less, and the second stage is performed for 60 seconds to 300 seconds. The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 8 , wherein the step of final annealing after the step of cold rolling is performed continuously. The directional electromagnetic according to any one of claims 1 to 9 , wherein the carbon content in the electrical steel sheet after the final annealing stage is 0.003% by weight or less (excluding 0% by weight). A method of manufacturing a steel sheet. Steel sheet wherein the final annealing is completed, {110} <001> any one of claims 1 to 10 grain volume fraction having an orientation within 15 degrees from the orientation is equal to or 50% or more The manufacturing method of the grain-oriented electrical steel sheet as described in a term. By weight, Si: 4.0% or less (excluding 0%), C: 0.003% or less (excluding 0%), Mn: 0.001 to 2.0%, and Al: 0.01% contained the following (excluding 0%), the balance consisting of Fe and other inevitable impurities to be mixed,
The size of the magnetic domains present in the crystal grains (2L) is rather smaller than the thickness of the steel sheet (D), particle size of 20μm~1000μm grain volume fraction is characterized in that 50% or more Oriented electrical steel sheet. The grain-oriented electrical steel sheet according to claim 12 , comprising Si in an amount of 1.0% by weight or less (excluding 0% by weight). The grain-oriented electrical steel sheet according to claim 12 or 13 , wherein the size (2L) of the magnetic domains existing in the crystal grains is 10 to 500 µm. The grain oriented electrical steel sheet according to any one of claims 12 to 14 , wherein the volume fraction of crystal grains having an orientation within 15 degrees from the {110} <001> orientation is 50% or more.

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