KR102325750B1 - Annealing separating agent composition for grain oriented electrical steel sheet, grain oriented electrical steel sheet, and method for manufacturing grain oriented electrical steel sheet - Google Patents

Abstract

The present embodiments relate to an annealing separator composition for grain-oriented electrical steel sheet, grain-oriented electrical steel sheet, flux-cored wire, and a method for manufacturing the same. According to an embodiment, 100 parts by weight of a magnesium compound including at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive, wherein the antimony sulfide-based additive is included. The average particle diameter of can provide an annealing separator composition for grain-oriented electrical steel sheet in the range of 0.5㎛ to 15㎛.

Description

Annealing separator composition for grain-oriented electrical steel sheet, grain-oriented electrical steel sheet and manufacturing method of grain-oriented electrical steel sheet

This embodiment relates to an annealing separator composition for a grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet, and a method for manufacturing a grain-oriented electrical steel sheet. More specifically, it relates to an annealing separator composition for grain-oriented electrical steel sheet capable of suppressing bare spots, which are oxidative defects mainly appearing in the outermost part of a large coil, and a method for manufacturing a grain-oriented electrical steel sheet.

Grain-oriented electrical steel sheet is an electrical steel sheet containing Si component in the steel sheet, has a grain orientation aligned in the {110} <001> direction, and has extremely excellent magnetic properties in the rolling direction.

Recently, as grain-oriented electrical steel sheets of high magnetic flux density have been commercialized, materials with low iron loss are required. Improvement of iron loss in electrical steel sheet can be approached by four technical methods. First, the {110} <001> grain orientation including the easy magnetization axis of grain-oriented electrical steel sheet is accurately oriented in the rolling direction, and second, the thinness of the material. Third, there is a magnetic domain refinement method that refines the magnetic domain through chemical and physical methods, and finally, there are surface properties improvement or surface tension application by chemical methods such as surface treatment and coating.

In particular, for improving surface properties or imparting surface tension, a method of forming a primary film and an insulating film has been proposed. _{As a primary film, forsterite (2MgO·SiO 2} ) layer _{made of a reaction between silicon oxide (SiO 2} ) generated on the material surface during the primary recrystallization annealing process of electrical steel sheet material and magnesium oxide (MgO) used as an annealing separator This is known The primary film formed during high-temperature annealing should have a uniform color without defects in appearance, and functionally prevent fusion between the plate and the plate in the coil state, and tension on the material due to the difference in the coefficient of thermal expansion between the material and the primary film. Because stress is applied, it can bring about the effect of improving the iron loss of the material.

This primary film should basically have a uniform color without defects on the surface of the material. However, since commercialized products are manufactured in the form of large coils, it is very difficult to maintain uniform film properties over the entire length of the coil. The biggest cause of this is the annealing separator containing water.

That is, the amount of heat transferred from the annealing furnace to the coil is different in the process of the magnesium oxide slurry being applied to the steel sheet, wound in a coil state, and subjected to the final finishing high-temperature annealing process. Oxidation defects, which are one of the defects that occur mainly due to the discharge of hydration moisture in the coil called bare spots, occur too quickly in the windings.

Therefore, in the mass production process, it is very urgent to secure the technology to suppress these defects as much as possible and produce a uniform product without defects on the surface of the material.

In this embodiment, the annealing separator composition for grain-oriented electrical steel sheet that can improve the surface quality characteristics of the primary film by including an antimony sulfide-based additive having a particle size in a specific range in the annealing separator composition, grain-oriented electrical steel sheet and grain-oriented electrical steel sheet To provide a manufacturing method.

Annealing separator composition for grain-oriented electrical steel sheet according to an embodiment, 100 parts by weight of a magnesium compound comprising at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive Including, the average particle diameter of the antimony sulfide-based additive may be in the range of 0.5㎛ to 15㎛.

In the grain-oriented electrical steel sheet according to another embodiment, a film including a Mg-Si composite and an antimony sulfide-based additive is formed on one or both surfaces of a grain-oriented electrical steel sheet substrate, and the average particle diameter of the antimony sulfide-based additive is in the range of 0.5 μm to 15 μm. can be

A method of manufacturing a grain-oriented electrical steel sheet according to another embodiment includes the steps of heating a steel slab and then hot rolling to manufacture a hot-rolled sheet, cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet, the cold-rolled sheet Comprising the steps of primary recrystallization annealing, applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing, and performing secondary recrystallization annealing of the steel sheet coated with the annealing separator, the annealing separator Silver contains 100 parts by weight of a magnesium compound containing at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive, and the average particle diameter of the antimony sulfide-based additive is It may range from 0.5 μm to 15 μm.

According to one embodiment, by including the antimony sulfide-based additive having a particle size in a specific range, it is possible to suppress a bare spot, which is an outermost oxidative defect that may occur in a large coil unit. Accordingly, a grain-oriented electrical steel sheet having excellent surface quality can be manufactured.

1A shows a cross-section of a sample with a good primary coating formed thereon.
1B is a photograph showing a cross-section of a sample on which a coating having a bare spot defect is formed.
Figure 2 schematically shows the shape change of the coil inner and outer winding in the high temperature annealing process.
Figure 3a shows a transmission electron microscope (TEM) and crystal observation photograph of the sample 11, which is an example extracted at 1000 °C.
Figure 3b shows a transmission electron microscope (TEM) and a crystal observation photograph of the specimen 33, which is a normal material extracted at 1000 °C.

Terms such as first, second and third are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part refers to being "directly above" another part, the other part is not interposed therebetween.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, they are not interpreted in an ideal or very formal meaning.

In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

In an embodiment of the present invention, the meaning of further including the additional element means that the remaining iron (Fe) is included by replacing the additional amount of the additional element.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Annealing separator composition for grain-oriented electrical steel sheet according to an embodiment, 100 parts by weight of a magnesium compound comprising at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive may include

In this embodiment, the average particle diameter of the antimony sulfide-based additive may be in the range of 0.5㎛ to 15㎛.

In general, in the manufacturing process of grain-oriented electrical steel sheet, when the cold-rolled sheet passes through a heating furnace controlled in a wet atmosphere for decarburization and quenching, Si, which has the highest oxygen affinity in the steel, reacts with oxygen supplied from the steam in the furnace and cold-rolled first. _{SiO 2} is formed on the surface of the plate, and thereafter, the Fe-based oxide is produced by the penetration of oxygen into the steel. _{SiO 2} thus formed _{forms a forsterite (Mg 2} SiO ₄ ) layer, which is a primary film, through a chemical reaction such as Scheme 1 below.

[Scheme 1]

2Mg(OH) ₂ + SiO ₂ → Mg ₂ SiO ₄ + 2H- ₂ O

In the grain-oriented electrical steel sheet process for commercial production, the finish annealing process is performed in a coil state. At this time, the coil is erected in a state perpendicular to the width direction of the coil and the ground and charged into the finishing annealing furnace. In general, the upper plate is placed on the upper part of the coil to prevent direct contact of the reducing gas in the furnace with the upper part of the coil. The coil charged in the finishing annealing furnace takes time to achieve thermal equilibrium with the coil according to the high-temperature annealing temperature pattern, and temperature deviations for each coil location occur until the high-temperature annealing furnace set temperature and the temperature equilibrium between the coils are achieved. Therefore, heat transfer and mass transfer occur at the same time to naturally achieve temperature equilibrium in the coil.

In the high-temperature annealing process, at a relatively low temperature below 900°C, magnesium oxide is applied in a slurry state, and the substituted magnesium hydroxide (Mg(OH) ₂ ) reacts with hydroxyl groups (-OH) in the molecule to generate water. This occurs as shown in Reaction Equation 2 below, and the generated water induces a mass transfer phenomenon in the coil to achieve a thermal equilibrium state in the coil.

[Scheme 2]

2Mg(OH) ₂ + Heat → 2MgO + 2H ₂ O

In the section above 900 °C, the same reaction as in Scheme 1 occurs, and water is produced from magnesium hydroxide as in the low-temperature section. Therefore, in the process of forming the primary film, magnesium hydroxide and water are always present in the coil and affect the film properties.

However, in the case of electrical steel sheets produced on a commercial scale, the high-temperature annealing process is performed in units of coils, and as described above, it takes time to achieve thermal equilibrium with the coils according to the finish annealing temperature pattern. In addition, a temperature deviation occurs for each coil position until the high-temperature annealing furnace achieves temperature equilibrium between the set temperature and the coil. As a result, the outer winding of the coil discharges hydration moisture quickly at the beginning of the high-temperature annealing process, but is exposed to an environment in which the hydration moisture generated from the inner winding rides the upper part of the coil and continuously supplies moisture to the outer winding.

In general, it can be interpreted that the hydrated moisture discharge pattern like normal materials discharges a small amount in the low-temperature region of 900°C or less in the high-temperature annealing section, and discharges a large amount in the high-temperature region of 900°C or more. Therefore, in the case of ordinary materials, the amount of hydration moisture generated from the coil is relatively small at the beginning of high-temperature annealing, and an environment is created in which the hydration moisture suddenly increases in the high-temperature annealing furnace at the end of relatively high-temperature annealing.

On the other hand, magnesium oxide, which is an annealing separator, is a solid present in powder form, and intrinsic properties such as viscosity of a slurry prepared by mixing with water are greatly affected by the intrinsic properties of magnesium oxide. A physical property value to be noted here is the degree of hydration. Generally, the degree of hydration is defined as the weight increased by hydration with _{Mg(OH) 2 under certain conditions after dispersing magnesium oxide in a mixture with water.} In general, the hydrated moisture in the magnesium oxide application process releases moisture during high-temperature annealing and oxidizes the material surface unevenly. this is becoming Therefore, in order to form a uniform surface in the coil unit, it is important to understand and respond to the influence of hydration moisture by coil position during high-temperature annealing.

As described above, the magnesium oxide slurry applied on the steel sheet after decarburization quenching annealing passes through a drying furnace at about 500° C. During the final finishing high-temperature annealing process, poor bare spot defects occur in the primary film formed on the outer winding of the coil, and the difference can be clearly seen from the photograph of the cross-section ( FIGS. 1A and 1B ).

This bare spot defect is considered to be a defect caused by FeO-based oxides that occur mainly at the edge of the coil where the coil and the outermost reducing atmosphere are in contact. Bare spot defects occur in the electric field and do not occur at the edge of the lower coil that is in close contact with the lower surface by finishing annealing. From the above empirical facts, the cause of the bare spot defect is that the wet gas generated from the inner coil part during finish annealing rides between the coil upper part and the coil upper plate toward the outer coil part and then stagnates and concentrates on the edge of the coil outer coil part. can be assumed to occur.

In addition, for the reason that it occurs intensively at the top of the outer winding part, a shape change as shown in Fig. 2 occurs in the outer winding part during high-temperature annealing. It is thought to be caused by gas intrusion.

According to this embodiment, in the case of the outer coil part, when the primary film is formed, oxidative defects are likely to occur due to hydration moisture continuously supplied from the inner coil part, and also in the reducing atmosphere due to the winding pressure loosened in the coil outer part part. It can be presumed that this is a defect in which the metal film is partially exposed due to the extremely thin film.

The present invention suggests that such a bare spot defect can be prevented by controlling the temperature for forming the primary film. That is, Sb ₂ S ₃ , Sb(SO ₄ ) ₃ Antimony sulfide-based additives such as 3 are introduced to form the primary film of the outer volume at a lower temperature than that of ordinary materials. In this way, when the primary film is formed earlier than the normal material on the outer winding, oxidative defects such as bare spots can be prevented even when a large amount of moisture flows from the inner winding of the coil toward the outer winding.

In order to confirm the effect of these reactive additives, the shape of the primary film according to the presence or absence of additives in the annealing separator was observed from 900 to 1200°C. In the case of a conventional grain-oriented electrical steel sheet, in general, the primary film during high-temperature annealing is _{formed through a substitution reaction between phyllite (Fe 2} SiO ₄ ) and magnesium ions (Mg+) introduced as an annealing separator, which are present on the surface of the material at 1000°C or higher. _{Mg 2} SiO _{4 as a} primary film begins to form, and at 1050 or 1100° C. or higher, SiO ₂ and Mg, _{which form a large number of oxide layers on the material surface, react in earnest to form Mg 2} SiO4. Therefore, in order to confirm the effect of the additive introduced in the present invention, it can be known through structural analysis whether _{the (Mg-Fe) SiO 4} complex _{formed near 1000° C. is close to the Fe 2} SiO ₄ form or _{close to the Mg 2} SiO _{4 form.} have.

Figure 3a shows a transmission electron microscope (TEM) and crystal observation photograph of the sample 11, which is an example extracted at 1000 ° C., Figure 3b is a transmission electron microscope (TEM) and crystal observation photograph of the specimen 33, which is a normal material extracted at 1000 ° C. is shown. Figure 3a is a photograph of the cross-sectional shape and structure of a specimen having a film formed with an antimony sulfide-based additive extracted at 1000 ° C. as in this Example, and Figure 3b is a cross-sectional shape and structure of a normal material extracted at 1000 ° C. It's a photo.

Referring to FIGS. 3A and 3B , the (Mg-Fe)SiO ₄ composite _{formed on the surface has a crystal structure of Mg 2} SiO ₄ , and in the case of a normal material, Fe ₂ SiO _{4 has a} crystal structure. From these results, it can be directly confirmed that in the case of the annealing separator to which the reaction promoting additive is introduced, the primary film formation temperature is lower than that of the normal annealing separator.

The additive, which has been proven effective as described above, is introduced into the annealing separator composition based on a magnesium compound including at least one of magnesium oxide and magnesium hydroxide.

Specifically, the annealing separator composition for grain-oriented electrical steel sheet of this embodiment is 100 parts by weight of a magnesium compound containing at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive include

The antimony sulfide additive _{may be at least one of Sb 2} S ₃ and Sb(SO ₄ ) ₃ , and the average particle diameter of the antimony sulfide additive is in the range of 0.5 μm to 15 μm, more specifically in the range of 1 μm to 10 μm. can If the average particle diameter of the antimony sulfide additive is less than 0.5 μm, the particles are fine and the reaction area is increased, so that the primary film may be formed at too low a temperature. In this case, a defect in which the film thickness is thinned may occur. In addition, when the average particle diameter of the antimony sulfide-based additive exceeds 20 μm, the reactivity of the additive is low, so that a downward effect of the film formation temperature cannot be seen.

The content of the antimony sulfide-based additive may be 0.5 to 15 parts by weight, more specifically 1 to 10 parts by weight, or 0.5 to 5 parts by weight, based on 100 parts by weight of the magnesium compound. When the content of the antimony sulfide-based additive satisfies the above range, the surface quality characteristics of the film formed by applying the annealing separator of this embodiment may be further improved.

The ceramic powder may be at least one selected from the group consisting _{of Al 2} O ₃ , SiO ₂ , TiO ₂ and ZrO _{2 .}

In addition, the composition may further include 0.1 to 5 parts by weight of a boron compound based on 100 parts by weight of the magnesium compound.

The boron compound may be, for example, one or more of _{boric acid trioxide (B 2} O ₃ ), boric acid (H ₃ BO ₃ ), and sodium borate (Na ₂ B ₄ O _{7 ).}

The composition may further include 50 to 500 parts by weight of a solvent. The solvent may include, for example, water.

This embodiment can provide a grain-oriented regular steel sheet having a uniform and excellent surface quality after secondary recrystallization annealing by applying the annealing separator composition for grain-oriented electrical steel sheet as described above.

In the case of high-hydrated magnesium used as an annealing separator for general electrical steel sheet, magnesium hydroxide is obtained through the reaction of magnesium chloride and calcium hydroxide purified from seawater and calcined at 800 ~ 1200 ℃ to obtain a product. In the case of products produced by such primary firing, the degree of activation and particle size distribution are very limited, so it is difficult to change the physical properties.

Therefore, in the present invention, when magnesium hydroxide is produced through the reaction of magnesium chloride and calcium hydroxide, 'low hydrated magnesium oxide', which significantly lowered the activation degree by calcination at 1500 ° C or higher, is added to the existing high hydrated magnesium oxide to increase the activation degree of the overall annealing separator. adjusted. In particular, in the case of low-hydrated magnesium oxide, since it is fired at a high temperature, the particles have excellent cohesive force and thus take on a granular form even after firing and pulverization.

The particle size D50 value of magnesium oxide used as the main raw material of the annealing separator is limited to 2.75 or more and 3.25 or less. If the D50 value is 2.75 or less, the discharge of hydration water is not smooth at low temperatures because the particle fraction is high, and if it is 3.25 or more, the discharge of hydration water is too fast at low temperatures, which may cause oxidative defects in the outer sphere.

The degree of activation (CAA 40) can be between 40 and 500 seconds. When the activation degree of magnesium oxide is too small, it may not react with the oxide layer, and thus a primary film may not be formed. On the other hand, if the degree of activation is too large, there may be a problem of leaving an _{unwanted spinel-based oxide (MgO·Al 2} O _{3 ) on the surface after the secondary recrystallization annealing in the present invention.} Therefore, the degree of activation of magnesium oxide can be controlled within the above-described range.

According to another embodiment, a film including a Mg-Si composite and an antimony sulfide-based additive is formed on one or both surfaces of the grain-oriented electrical steel sheet substrate, and the film contains 5 to 50% by weight of Mg, 1 to 25% by weight of Si, 5 to 35 wt% O, 0.1 to 5 wt% Ti, 0.1 to 5 wt% Sb, 0.1 to 5 wt% S, and Fe may be included in the balance.

In this embodiment, since the antimony sulfide-based material having an average particle diameter in an appropriate range to be added during the production of the grain-oriented electrical steel sheet is added, Sb may be included in the range of 0.1 to 5 wt% in the film of the grain-oriented electrical steel sheet, S may be included in the range of 0.1 to 5% by weight.

The average particle diameter of the antimony sulfide-based additive added when manufacturing the grain-oriented electrical steel sheet of this embodiment may be in the range of 0.5 μm to 15 μm. That is, when the average particle diameter range of the antimony sulfide-based material included in the annealing separator applied to form a film when manufacturing the grain-oriented electrical steel sheet satisfies 0.5㎛ to 15㎛, in the film located on at least one surface of the grain-oriented electrical steel sheet The content of Sb and S may satisfy the above range. A detailed description of the antimony sulfide-based additive will be omitted here in the same room as described in one embodiment.

In addition, the average thickness of the film formed on one or both surfaces of the grain-oriented electrical steel sheet manufactured according to this embodiment may be 0.1 μm to 5 μm. In this embodiment, it is possible to implement a grain-oriented electrical steel sheet having a film that satisfies the thickness range and has excellent surface quality.

On the other hand, the material of the grain-oriented electrical steel sheet of this embodiment, for example, silicon (Si): 2.0 to 7.0 wt%, aluminum (Al): 0.020 to 0.040 wt%, manganese (Mn): 0.01 to 0.20 wt%, phosphorus (P) 0.01 to 0.15 wt%, carbon (C) 0.01 wt% or less (excluding 0%), N: 0.005 to 0.05 wt% and antimony (Sb), tin (Sn), or a combination thereof from 0.01 to 0.15% by weight, and the balance may include Fe and other unavoidable impurities. Since the description of each component of the grain-oriented electrical steel sheet material is the same as the generally known content, a detailed description will be omitted.

A method of manufacturing a grain-oriented electrical steel sheet according to another embodiment includes the steps of heating a steel slab and then hot rolling, manufacturing a hot-rolled sheet, cold rolling the hot-rolled sheet, manufacturing a cold-rolled sheet, the cold-rolled sheet Comprising the steps of primary recrystallization annealing, applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing, and performing secondary recrystallization annealing of the steel sheet coated with the annealing separator, the annealing separator Silver contains 100 parts by weight of a magnesium compound containing at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, and 0.5 to 15 parts by weight of an antimony sulfide-based additive, and the average particle diameter of the antimony sulfide-based additive is It may range from 0.5 μm to 15 μm.

First, prepare a steel slab.

Next, the steel slab is heated. At this time, the slab heating can be heated by a low-temperature slab method at 1,200 ° C or less.

Next, by hot-rolling the heated steel slab, a hot-rolled sheet is manufactured. Thereafter, the manufactured hot-rolled sheet may be hot-rolled and annealed.

Next, a hot-rolled sheet is cold-rolled, and a cold-rolled sheet is manufactured. In the step of manufacturing the cold-rolled sheet, cold rolling may be performed once, or cold rolling including intermediate annealing may be performed two or more times.

Next, the cold-rolled sheet is subjected to primary recrystallization annealing. In the primary recrystallization annealing process, the cold-rolled sheet may be simultaneously subjected to decarburization annealing and nitridation annealing, or may include a step of nitriding annealing after decarburization annealing.

Next, on the surface of the steel sheet subjected to the primary recrystallization annealing, an annealing separator is applied. Since the annealing separator has been specifically described above, a repeated description will be omitted.

The application amount of the annealing separator may be 6 to 20 g/m ² based on the weight after drying. If the application amount of the annealing separator is too small, the base coating may not be formed smoothly. If the application amount of the annealing separator is too large, secondary recrystallization may be affected. Therefore, the application amount of the annealing separator can be adjusted within the above-described range.

After applying the annealing separator, drying may be further included.

The temperature for drying the annealing separator may be 300 to 700 °C. If the temperature is too low, the annealing separator may not be easily dried. If the temperature is too high, it may affect secondary recrystallization. Therefore, the drying temperature of the annealing separator can be adjusted in the above-described range.

Next, the steel sheet coated with the annealing separator is subjected to secondary recrystallization annealing. During the secondary recrystallization annealing, a film including the Mg-Si composite and the antimony sulfide additive is formed on the outermost surface by the annealing separator component and the silica reaction.

The secondary recrystallization annealing may be performed at a temperature increase rate of 18 to 75 °C/hr in a temperature range of 700 to 950 °C, and a temperature increase rate of 10 to 15 °C/hr in a temperature range of 950 to 1200 °C. By controlling the temperature increase rate in the above range, the Mg-Si-based forsterite film and the aluminum borate-based composite film can be smoothly formed.

In addition, the process of increasing the temperature of 700 to 1200 ℃ is carried out in an atmosphere containing 20 to 30 vol% of nitrogen and 70 to 80 vol% of hydrogen, and after reaching 1200 ℃, it can be carried out in an atmosphere containing 100 vol% of hydrogen. have. By controlling the atmosphere in the above-mentioned range, the forsterite film can be smoothly formed.

As described above, since the grain-oriented electrical steel sheet process for commercial production passes through the unit process in a coil state, after the decarburization annealing process, a slurry of magnesium oxide and water, an annealing separator, is applied on the steel sheet, dried, and wound in a coil shape. It is then charged into the high-temperature annealing furnace.

In the manufacturing process of grain-oriented electrical steel sheet, the grain-oriented electrical steel sheet that has undergone the decarburization annealing process is subjected to a final finishing high-temperature annealing process after an annealing separator containing water, that is, magnesium oxide slurry is applied to the steel sheet and wound in a coil state. At this time, since the amount of heat transferred from the annealing furnace to the coil is different, and accordingly, the amount of hydration moisture is different for each coil location and part, an oxidative defect called a bare spot occurs mainly in the outermost part.

Bare spot defects are classified as surface defects, and eventually they are judged as defective during quality inspection, which is a major factor in reducing the productivity of the mass production process.

In this embodiment, by applying an annealing separator composition comprising an antimony sulfide additive having an average particle diameter in the range of 0.5 μm to 15 μm together with a magnesium compound, a grain-oriented electrical steel sheet with remarkably improved surface quality of the primary film can be produced and , can improve productivity.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Examples and Comparative Examples

A steel slab containing Si: 3.2%, C: 0.055%, Mn: 0.12%, Al: 0.026%, N: 0.0042%, S: 0.0045% by weight percent and additionally added Sn, Sb, and P was prepared. .

After heating the slab, hot rolling was performed to prepare a 2.8 mm hot-rolled sheet. Thereafter, the hot-rolled sheet was annealed and pickled to perform cold rolling to a final thickness of 0.23 mm.

The cold-rolled steel sheet is subjected to primary recrystallization annealing. Specifically, the cold-rolled steel sheet is put into a furnace maintained at 875° C., and then maintained in a mixed atmosphere of 74 vol% hydrogen, 25 vol % nitrogen, and 1 vol % dry ammonia gas for 180 seconds. It was decarburized and nitridized.

As the annealing separator composition, magnesium oxide, additives, TiO- ₂ , Na2B4O7 and pure water were mixed in the weights shown in Table 1 below to prepare an annealing separator composition.

10 g/m ² of an annealing separator was applied, and secondary recrystallization annealing was performed in a coil shape.

During the secondary recrystallization annealing, the first cracking temperature was 700 ℃, the secondary cracking temperature was 1200 ℃, and the temperature increase condition of the temperature increase section was 45 ℃/hr in the temperature section of 700 to 950 ℃, and in the temperature section of 950 to 1200 ℃ It was set as 15 degreeC/hr. On the other hand, the soaking time at 1200°C was 15 hours. The atmosphere at the time of final annealing was a mixed atmosphere of 25 vol% nitrogen and 75 vol% hydrogen until 1200 °C, and after reaching 1200 °C, it was maintained in a 100 vol% hydrogen atmosphere and then furnace cooled.

Table 2 below shows the results of measuring the presence or absence of oxidative defects, primary film tension, and adhesion after applying the annealing separator prepared with the same components as in Table 1 to the specimen.

Psalm number Oxidation
magnesium
(g) additive Oxidation
titanium
(g) Na ₂ B ₄ O ₇
(g) pure
(g) note Sb ₂ S ₃
(g) Sb(SO ₄ ) ₃
(g) particle size
(μm) One 100 0.1 - 0.1 5 0.3 1000 comparative goods 2 100 0.5 - 0.1 5 0.3 1000 comparative goods 3 100 5 - 0.1 5 0.3 1000 comparative goods 4 100 20 - 0.1 5 0.3 1000 comparative goods 5 100 0.1 - One 5 0.3 1000 comparative goods 6 100 0.5 - One 5 0.3 1000 Example 7 100 5 - One 5 0.3 1000 Example 8 100 20 - One 5 0.3 1000 comparative goods 9 100 0.1 - 10 5 0.3 1000 comparative goods 10 100 0.5 - 10 5 0.3 1000 Example 11 100 5 - 10 5 0.3 1000 Example 12 100 20 - 10 5 0.3 1000 comparative goods 13 100 - 0.1 0.1 5 0.3 1000 comparative goods 14 100 - 0.5 0.1 5 0.3 1000 comparative goods 15 100 - 5 0.1 5 0.3 1000 comparative goods 16 100 - 20 0.1 5 0.3 1000 comparative goods 17 100 - 0.1 One 5 0.3 1000 comparative goods 18 100 - 0.5 One 5 0.3 1000 Example 19 100 - 5 One 5 0.3 1000 Example 20 100 - 20 One 5 0.3 1000 comparative goods 21 100 - 0.1 10 5 0.3 1000 comparative goods 22 100 - 0.5 10 5 0.3 1000 Example 23 100 - 5 10 5 0.3 1000 Example 24 100 - 20 10 5 0.3 1000 comparative goods 25 100 - 0.1 20 5 0.3 1000 comparative goods 26 100 - 0.5 20 5 0.3 1000 comparative goods 27 100 - 5 20 5 0.3 1000 comparative goods 28 100 - 20 20 5 0.3 1000 comparative goods 29 100 0.1 0.1 10 5 0.3 1000 comparative goods 30 100 0.25 0.25 10 5 0.3 1000 Example 31 100 2.5 2.5 10 5 0.3 1000 Example 32 100 10 10 10 5 0.3 1000 comparative goods 33 100 - - - 5 0.3 1000 ordinary goods

Psalm number bare spot
Non-occurrence (○)/
Defect occurrence (×) film tension
(kgf/mm ² ) adhesion
(mmf) note One X 0.26 40 comparative goods 2 X 0.28 35 comparative goods 3 X 0.23 40 comparative goods 4 X 0.25 40 comparative goods 5 X 0.3 30 comparative goods 6 O 0.49 15 Example 7 O 0.52 15 Example 8 X 0.37 30 comparative goods 9 X 0.3 30 comparative goods 10 O 0.53 15 Example 11 O 0.55 15 Example 12 X 0.36 30 comparative goods 13 X 0.2 40 comparative goods 14 X 0.24 35 comparative goods 15 X 0.24 35 comparative goods 16 X 0.21 40 comparative goods 17 X 0.33 30 comparative goods 18 O 0.47 20 Example 19 O 0.5 15 Example 20 X 0.33 30 comparative goods 21 X 0.39 30 comparative goods 22 O 0.49 15 Example 23 O 0.53 15 Example 24 X 0.39 30 comparative goods 25 X 0.31 30 comparative goods 26 X 0.22 40 comparative goods 27 X 0.24 35 comparative goods 28 X 0.23 35 comparative goods 29 X 0.37 25 comparative goods 30 O 0.58 15 Example 31 O 0.56 15 Example 32 X 0.38 25 comparative goods 33 X 0.35 30 ordinary goods

Referring to Table 2, the specimens of Example Nos. 6 to 7, 10 to 11, 18 to 19, 22 to 23, and 30 to 31, which are comparative specimens, Specimen Nos. 1 to 5, 8 to 9, 12 to 17, 20 to 21, 24 to 29 and 32, and compared with the specimens of specimen number 33, which is a common material, it can be seen that the film tension and adhesion are very excellent. In particular, the specimens of the Examples were able to reduce the occurrence of bare spot defects in principle. Specifically, in the specimens of Specimen Nos. 6 to 7 and 10 to 11, Sb ₂ S ₃ having an appropriate average particle diameter was appropriately introduced, Specimen Nos. 18 to 19, 22 to 23, Sb(SO ₄ ) ₃ having an appropriate average particle diameter is appropriately introduced. In addition, the specimens of specimen Nos. 30 to 31 were introduced by mixing _{the Sb 2} S ₃ and Sb(SO ₄ ) _{3 .}

As described above, when an appropriate amount of antimony sulfide having an average particle diameter in the range of 0.5 μm to 15 μm is introduced into the annealing separator composition in this embodiment, the formation temperature of the primary film can be controlled, and thus bare spot defects can be prevented

That is, in the component system in which the additive is introduced as in the example, the primary film of the outer winding portion is formed at a lower temperature than that of the normal material. Oxidative defects such as bare spots can be prevented even when a large amount of moisture flows from the winding to the outer winding.

In addition, as can be seen in Table 2, in the case of a specimen that does not have such a bare spot defect, the bond between the primary film and the base material is also good, which is expected to improve adhesion as well as the film tension, which will help improve iron loss.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (14)

100 parts by weight of a magnesium compound including at least one of magnesium oxide and magnesium hydroxide;
1 to 10 parts by weight of ceramic powder;
0.5 to 15 parts by weight of an antimony sulfide-based additive; and
0.1 to 5 parts by weight of boron compound
including,
The average particle diameter of the antimony sulfide-based additive is in the range of 0.5 μm to 15 μm,
The antimony sulfide-based additive is at least one _{of Sb 2} S ₃ and Sb(SO ₄ ) _{3 ,}
The ceramic powder includes at least one selected from the group consisting _{of Al 2} O ₃ , SiO ₂ , TiO ₂ and ZrO _{2 ,}
The boron compound is boric trioxide (B ₂ O ₃ ), boric acid (H ₃ BO ₃ ), and sodium borate (Na ₂ B ₄ O ₇ ) Annealing separator composition for grain-oriented electrical steel sheet comprising at least one of. delete delete delete delete According to claim 1,
The composition is an annealing separator composition for grain-oriented electrical steel sheet further comprising 50 to 500 parts by weight of a solvent. A film containing a Mg-Si composite and an antimony sulfide-based additive is formed on one or both surfaces of the grain-oriented electrical steel sheet substrate,
The film contains 5 to 50% by weight of Mg, 1 to 25% by weight of Si, 5 to 35% by weight of O, 0.1 to 5% by weight of Ti, 0.1 to 5% by weight of Sb, and 0.1 to 5% by weight of S And Fe, Na, B grain-oriented electrical steel sheet containing the balance. 8. The method of claim 7,
The average thickness of the film is in the range of 0.1 μm to 5 μm grain-oriented electrical steel sheet. 8. The method of claim 7,
The average particle diameter of the antimony sulfide-based additive is in the range of 0.5㎛ to 15㎛ grain-oriented electrical steel sheet. After heating the steel slab, hot rolling to prepare a hot-rolled sheet;
manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet;
primary recrystallization annealing the cold-rolled sheet;
applying an annealing separator on the surface of the steel sheet subjected to the primary recrystallization annealing; and
Comprising the step of secondary recrystallization annealing of the steel sheet coated with the annealing separator,
The annealing separator,
100 parts by weight of a magnesium compound comprising at least one of magnesium oxide and magnesium hydroxide, 1 to 10 parts by weight of ceramic powder, 0.5 to 15 parts by weight of an antimony sulfide-based additive, and 0.1 to 5 parts by weight of a boron compound,
The average particle diameter of the antimony sulfide-based additive is in the range of 0.5 μm to 15 μm,
The antimony sulfide-based additive is at least one _{of Sb 2} S ₃ and Sb(SO ₄ ) _{3 ,}
The ceramic powder includes at least one selected from the group consisting _{of Al 2} O ₃ , SiO ₂ , TiO ₂ and ZrO _{2 ,}
The boron compound is boric trioxide (B ₂ O ₃ ), boric acid (H ₃ BO ₃ ), and sodium borate (Na ₂ B ₄ O ₇ ) Method of manufacturing a grain-oriented electrical steel sheet comprising at least one of. 11. The method of claim 10,
After applying the annealing separator, the method of manufacturing a grain-oriented electrical steel sheet further comprising the step of drying at 300 to 700 ℃. 11. The method of claim 10,
The coating amount of the annealing separator is 6 to 20 g/m ² based on the weight after drying The method of manufacturing a grain-oriented electrical steel sheet to be applied in the range. 11. The method of claim 10,
The secondary recrystallization annealing step,
In the temperature range of 700 to 950 ℃, the first step of raising the temperature at a temperature increase rate of 18 to 75 ℃ / hr; and
In a temperature range of 950 to 1200 ℃, a method of manufacturing a grain-oriented electrical steel sheet comprising the step of raising the secondary temperature at a temperature increase rate of 10 to 15 ℃ / hr. 14. The method of claim 13,
The step of raising the first temperature and the step of raising the second temperature,
carried out in an atmosphere containing 20 to 30% by volume of nitrogen and 70 to 80% by volume of hydrogen,
A method of manufacturing a grain-oriented electrical steel sheet performed in an oxygen atmosphere of 100% by volume after reaching 1200°C.

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