JP7465380B2 - Electrical steel sheet, insulating coating composition for electrical steel sheet, and method for producing electrical steel sheet - Google Patents

Description

The present invention relates to an electromagnetic steel sheet, an insulating coating composition for an electromagnetic steel sheet, and a method for manufacturing an electromagnetic steel sheet, and more specifically, to an electromagnetic steel sheet, an insulating coating composition for an electromagnetic steel sheet, and a method for manufacturing an electromagnetic steel sheet, which use a silane compound containing a specific chemical structure and have excellent heat resistance and thermal conductivity during stress relief annealing.

The insulating coating of electromagnetic steel sheets used in motors, transformers, etc. is required to have various properties in addition to interlaminar resistance. For example, convenience during processing and shaping, and stability during storage and use are required. In addition, because electromagnetic steel sheets are used for a variety of purposes, various insulating coatings are being developed according to the purpose. For example, when electromagnetic steel sheets are subjected to punching, shearing, bending, etc., the magnetic properties deteriorate due to residual deformation. Therefore, stress relief annealing (SRA) may be performed at high temperatures to restore the deteriorated magnetic properties. Therefore, the insulating coating needs to have heat resistance properties that do not peel off during stress relief annealing and maintain its inherent electrical insulation.

Insulation coating compositions that are already known are made by mixing chromic anhydride, magnesium oxide, and acrylic resin or acrylic-styrene copolymer resin to improve corrosion resistance and insulation. However, these insulation coating compositions have limitations in terms of the heat resistance required during stress relief annealing, which is a recent requirement. A method has also been proposed in which metal phosphate is used as the main component of the insulation coating composition to improve adhesion during stress relief annealing. However, this method has the problem that due to the characteristics of phosphate, which has strong absorption resistance, whitening defects occur on the surface, generating dust during product processing, and there is also the problem that the heat resistance is actually inferior in the areas where whitening defects occur.

The object of the present invention is to provide an insulating coating composition for electrical steel sheets and electrical steel sheets including the insulating coating. More specifically, the object is to provide an insulating coating composition for electrical steel sheets and electrical steel sheets including the insulating coating that use a silane compound having a specific chemical structure and have excellent heat resistance and thermal conductivity during stress relief annealing.

（化学式１において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） An electrical steel sheet according to an embodiment of the present invention includes an electrical steel sheet substrate and an insulating coating located on one or both sides of the electrical steel sheet substrate, and the insulating coating includes a silane compound represented by the following Chemical Formula 1 and a metal hydroxide.
[Chemical Formula 1]

(In Chemical Formula 1, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

（化学式２において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌ^１は直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） The silane compound is characterized by being represented by the following chemical formula 2.
[Chemical Formula 2]

(In Chemical Formula 2, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L ¹ is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

The silane compound is characterized by containing one or more of triacetoxymethylsilane (Triacetoxy(methyl)silane), triacetoxyvinylsilane (Triacetoxy(vinyl)silane), dimethyldi(methacryloyloxy-1-ethoxy)silane, and 3-(trimethoxysilyl)propylmethacrylate.

The metal hydroxides are characterized as comprising one or more of Ni(OH) ₂ , Co(OH) ₂ , Cu(OH) ₂ , Sr(OH) ₂ , Ba(OH) ₂ , Pd( _OH ) ₂ , In(OH) ₃ , ( _{CH3CO2 ) 7Cr3} (OH) ₂ , Bi(OH) ₃ and Sn(OH) ₂ .

The insulating coating further contains a metal nitride, and is characterized by containing 0.1 to 40% by weight of metal nitride, 25 to 75% by weight of a silane compound, and 0.5 to 60% by weight of a metal hydroxide.

The metal nitrides are characterized by including one or more of BN, _AlN , _{Si3N4 , Mg3N2} , _{Ca3N2 , Sr3N2 , Ba3N2 ,} and _{Ge3N4 .}

The electrical steel sheet is characterized in that it satisfies the following general formula 1.
[General Formula 1]
20≦TC≦200W/mK
(In the above formula 1, TC represents the thermal conductivity value measured by induction heating a 600×400 mm test piece at 230° C. using a PPMS (Physical Property Measurement System).)

The electromagnetic steel sheet substrate contains C: 0.01% by weight or less, Si: 6.0% by weight or less, P: 0.5% by weight or less, S: 0.005% by weight or less, Mn: 0.1-1.0% by weight, Al: 0.40-2.0% by weight, N: 0.005% by weight or less, Ti: 0.005% by weight or less, and Sb, Sn, Ni or a combination thereof: 0.01-0.15% by weight, with the balance being Fe and unavoidable impurities.

（化学式１において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） The insulating coating composition for electrical steel sheets according to one embodiment of the present invention includes a silane compound represented by the following Chemical Formula 1 and a metal hydroxide.
[Chemical Formula 1]

(In Chemical Formula 1, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

It further contains metal nitride, and is characterized by containing 0.1 to 40 wt % of metal nitride, 25 to 75 wt % of silane compound, and 0.5 to 60 wt % of metal hydroxide based on the solid content.

The metal nitrides are characterized by including one or more of BN, _AlN , _{Si3N4 , Mg3N2} , _{Ca3N2 , Sr3N2 , Ba3N2 ,} and _{Ge3N4 .}

（化学式１において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） A method for manufacturing an electrical steel sheet according to an embodiment of the present invention includes the steps of: preparing a steel sheet by hot rolling a slab to produce a hot-rolled sheet, cold rolling the steel sheet, and then completing final annealing; and applying an insulating coating composition to the steel sheet to form an insulating coating, the insulating coating composition including a silane compound represented by Chemical Formula 1 below and a metal hydroxide.
[Chemical Formula 1]

(In Chemical Formula 1, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

The electrical steel sheet having an insulating coating formed thereon is characterized in that it satisfies the following general formula 1.
[General Formula 1]
20≦TC≦200W/mK
(In the above formula 1, TC represents the thermal conductivity value measured by induction heating a 600 x 400 mm test piece at 230°C using a PPMS (Physical Property Measurement System).)

（化学式１において、Ｒ^１は水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） An insulating coating composition for electrical steel sheet according to an embodiment of the present invention includes a silane compound represented by the following Chemical Formula 1, and one or more chromate compounds selected from chromic anhydride, chromate salts, and dichromate salts.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.)

It is characterized by containing 10 to 80 parts by weight of a silane compound and 20 to 90 parts by weight of a chromate compound per 100 parts by weight of the combined total of the silane compound and the chromate compound.

In Chemical Formula 1, R ¹ is a hydrogen atom, a halogen atom, a linear or branched alkyl group, or an alkoxy group.

In Chemical Formula 1, L is at least one of a direct bond, an alkylene group, and --CF ₂ --.

（化学式２において、Ｒ^１～Ｒ^３はそれぞれ独立して水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌ_１は直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） The silane compound is characterized by being represented by the following chemical formula 2.
[Chemical Formula 2]

(In Chemical Formula 2, R ¹ to R ³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L ₁ is a direct bond or a divalent linking group; m is an integer of 1 to 3; and n is 4-m.)

In Chemical Formula 2, ^R2 and ^R3 are each independently a hydrogen or halogen element.

The silane compound is characterized by containing one or more of triethyl(trifluoromethyl)silane, trimethoxy(trifluoropropyl)silane, dimethoxy-methyl(trifluoropropyl)silane, and perfluorooctyl-triethoxysilane.

It is characterized by further containing 0.5 to 65 parts by weight of ceramic powder per 100 parts by weight of the combined amount of the silane compound and the chromate compound.

The ceramic powder is _{characterized} by comprising _{one or more of MgO} , _MnO , _Al2O3 , _SiO2 , _TiO2 , _ZrO2 , _Al6Si2O13 , _Al2O3.TiO2 , _{Y2O3 , 9Al2O3.B2O3} , _BN , CrN, _BaTiO3 , SiC and _TiC .

The ceramic powder is characterized by an average particle size of 0.05 to 20 μm.

It is characterized by further containing 0.5 to 30 parts by weight of one or more polymeric resins selected from acrylic resin, styrene resin, vinyl acetate resin, polyester resin, urethane resin, polyethylene resin, polypropylene resin, polyamide resin, polycarbonate resin, phenolic resin, alkyd resin and epoxy resin, per 100 parts by weight of the combined total of the silane compound and the chromate compound.

It is characterized by further containing 1 to 15 parts by weight of one or more of ethylene glycol, propylene glycol, glycerine, and butyl carbitol per 100 parts by weight of the combined weight of the silane compound and the chromate compound.

（化学式１において、Ｒ^１は水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） An electrical steel sheet according to an embodiment of the present invention includes an electrical steel sheet substrate and an insulating coating located on one or both sides of the electrical steel sheet substrate, and the insulating coating includes a silane compound represented by the following Chemical Formula 1, and one or more chromate compounds selected from chromic anhydride, chromate salts, and dichromate salts.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.)

The insulating coating is characterized by containing 0.1 to 50% by weight of Si and 0.01 to 25% by weight of F.

The thickness of the insulating coating is characterized by being 0.1 to 10 μm.

（化学式１において、Ｒ^１は水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） A method for manufacturing an electrical steel sheet according to an embodiment of the present invention includes the steps of manufacturing an electrical steel sheet substrate, and applying an insulating coating composition to one or both sides of the electrical steel sheet substrate to form an insulating coating, the insulating coating composition including a silane compound represented by Chemical Formula 1 below, and one or more chromate compounds selected from chromic anhydride, chromate salts, and dichromate salts:
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.)

The step of manufacturing the electrical steel sheet substrate is characterized by including a step of hot rolling a slab to produce a hot-rolled sheet, a step of cold rolling the hot-rolled sheet to produce a cold-rolled sheet, and a step of final annealing the cold-rolled sheet.

The step of forming the insulating coating is characterized by including a step of heat treating the steel sheet coated with the insulating coating composition at a temperature of 100 to 680°C.

The method further includes a step of performing stress relief annealing at a temperature of 700 to 1000°C after the step of forming the insulating coating.

According to one embodiment of the present invention, an electrical steel sheet having excellent core loss characteristics after the formation of an insulating coating can be obtained. According to one embodiment of the present invention, an electrical steel sheet having excellent space factor can be obtained. According to one embodiment of the present invention, an insulating coating having excellent adhesion and peel resistance even after stress relief annealing (SRA) can be obtained. According to one embodiment of the present invention, an electrical steel sheet having excellent thermal conductivity can be manufactured, and products such as motors manufactured using this electrical steel sheet have excellent efficiency.

1 is a schematic diagram of a cross section of an electromagnetic steel sheet according to an embodiment of the present invention. 1 is a flowchart of a method for manufacturing an electrical steel sheet according to an embodiment of the present invention. 1 is a scanning electron microscope (SEM) photograph of a single surface of the electrical steel sheet produced in Example 1-2. 1 is a scanning electron microscope (SEM) photograph of a single surface of the electrical steel sheet produced in Comparative Example 1-2. 1 shows the results of FT-IR-RAS analysis of the electrical steel sheet coating produced in Example 1-2. 1 is a scanning electron microscope (SEM) photograph of a single surface of the electrical steel sheet produced in Example 2-2. 1 is a scanning electron microscope (SEM) photograph of the surface of the electrical steel sheet produced in Comparative Example 2-3.

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 used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Thus, 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 merely for the purpose of referring to particular embodiments and is not intended to limit the invention. As used herein, the singular forms include the plural forms unless the context clearly indicates otherwise. As used in the specification, the term "comprising" means to embody certain features, regions, integers, steps, operations, elements and/or components and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and/or components.

When we say that a part is "on" or "above" another part, it means that it is immediately on or above the other part, or that there are other parts between them. In contrast, when we say that a part is "directly on" another part, there are no other parts between them.

Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the relevant technical literature and the currently disclosed content, and should not be interpreted as being overly ideal or formal unless otherwise defined. In this specification, when describing groups (atomic groups), a notation that does not indicate whether they are substituted or unsubstituted includes those that have a substituent as well as those that do not have a substituent. For example, "alkyl group" includes not only alkyl groups that have no substituents (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups).

Unless otherwise defined, in this specification, "substituted" means that at least one hydrogen of a compound is substituted with a C1 to C30 alkyl group; a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C1 to C10 alkylsilyl group; a C3 to C30 cycloalkyl group; a C6 to C30 aryl group; a C1 to C30 heteroaryl group; a C1 to C10 alkoxy group; a silane group; an alkylsilane group; an alkoxysilane group; an amine group; an alkylamine group; an arylamine group; an ethyleneoxyl group, or a halogen group.

In this specification, unless otherwise defined, "hetero" refers to an atom selected from the group consisting of N, O, S, and P. In this specification, unless otherwise defined, "alkyl group" refers to all of "saturated alkyl groups" that do not contain an alkenyl group or an alkynyl group; or "unsaturated alkyl groups" that contain at least one alkenyl group or alkynyl group. The "alkenyl group" refers to a substituent in which at least two carbon atoms form at least one carbon-carbon double bond, and the "alkyne group" refers to a substituent in which at least two carbon atoms form at least one carbon-carbon triple bond. The alkyl group may be branched, linear, or cyclic.

The alkyl group can be a C1-C20 alkyl group, specifically a lower alkyl group of C1-C6, a medium alkyl group of C7-C10, or a higher alkyl group of C11-C20. For example, a C1-C4 alkyl group means that there are 1-4 carbon atoms in the alkyl chain, which is selected from the group consisting of methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, and t-butyl.

Typical alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. An "aromatic group" refers to a cyclic substituent in which all elements have p-orbitals, and these p-orbitals form conjugation. Specific examples include aryl and heteroaryl groups.

An "aryl group" includes single or fused rings, i.e., multiple ring substituents sharing adjacent pairs of carbon atoms. A "heteroaryl group" means an aryl group that includes a heteroatom selected from the group consisting of N, O, S, and P within the aryl group. When the heteroaryl group is a fused ring, it contains from 1 to 3 of said heteroatoms in each ring.

Unless otherwise defined in this specification, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group means a substituted or unsubstituted alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group. Unless otherwise defined in this specification, a divalent linking group means one or more divalent linking groups selected from an alkylene group, an alkenylene group, an arylene group, -NR'-, -O-, -SO ₂ -, -CO-, and -CF ₂ -. R' is an alkyl group.

The following describes in detail an embodiment of the present invention so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, the present invention can be realized in various different forms and is not limited to the embodiment described here.

（化学式１において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） Insulating Coating Composition for Electrical Steel Sheet An insulating coating composition for electrical steel sheet according to an embodiment of the present invention includes a silane compound represented by the following Chemical Formula 1 and a metal hydroxide.
[Chemical Formula 1]

(In Chemical Formula 1, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

The insulating coating composition according to one embodiment of the present invention contains a silane compound with a unique chemical structure to dramatically improve heat resistance and corrosion resistance during stress relief annealing. Furthermore, when a silane compound is used alone, there are problems with the coating peeling off during the stress relief annealing process and difficulties in applying it uniformly to the surface of the electrical steel sheet. To improve this, a metal hydroxide is also included.

Below, the insulating coating composition for electrical steel sheets according to one embodiment of the present invention will be described in detail for each component.

As mentioned above, the insulating coating composition for electrical steel sheets according to one embodiment of the present invention contains a silane compound represented by Chemical Formula 1 based on the solid content. Specifically, it contains 30 to 75 parts by weight per 100 parts by weight of the total amount of the silane compound and metal hydroxide. The silane compound represented by Chemical Formula 1 contains a silicon element and a carbonyl group within the compound, and has excellent heat resistance. Furthermore, the carbonyl group has excellent reactivity with metal hydroxide, and plays an important role in forming a silane compound-metal hydroxide complex to dramatically improve surface quality.

（化学式２において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌ^１は直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） Specifically, the silane compound is represented by the following chemical formula 2.
[Chemical Formula 2]

(In Chemical Formula 2, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L ¹ is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

Specifically, in Chemical Formula 1 and Chemical Formula 2, R ¹ and R ² are hydrogen or an alkyl group. More specifically, R ¹ and R ² are a methyl group or an ethyl group. Specifically, in Chemical Formula 1, L is one or more divalent linking groups selected from an alkylene group, -O-, and -CO-. More specifically, in Chemical Formula 1, L is represented by -L ¹ -O-, and L ¹ is a direct bond or one or more divalent linking groups selected from an alkylene group, -O-, and -CO-.

The silane compound includes one or more of triacetoxymethylsilane (Triacetoxy(methyl)silane), triacetoxyvinylsilane (Triacetoxy(vinyl)silane), dimethyldi(methacryloyloxy-1-ethoxy)silane, and 3-(trimethoxysilyl)propylmethacrylate.

If the amount of silane compound is too small, the heat resistance decreases and the iron loss after stress relief annealing becomes poor. If the amount of silane compound is too large, the amount of metal hydroxide becomes relatively small and the coating peels off. Therefore, the amount of silane compound may be within the above-mentioned range. More specifically, the amount of silane compound is 40 to 55 parts by weight per 100 parts by weight of the total amount of silane compound and metal hydroxide.

An insulating coating composition for electrical steel sheets according to one embodiment of the present invention contains metal hydroxide. Specifically, the composition contains 25 to 70 parts by weight of metal hydroxide for every 100 parts by weight of the total of the silane compound and metal hydroxide. Metal hydroxide is characterized by its good dispersibility in solvents, and helps change the surface properties from hydrophobic to hydrophilic so that it disperses well in solvents through a chemical reaction with the functional groups of the silane compound. Such metal hydroxide is uniformly applied to the surface of the electrical steel sheet, which is of great help in dramatically improving the heat resistance and corrosion resistance of the insulating coating during stress relief annealing.

The metal hydroxide can be any metal containing a hydroxyl group (-OH) without any restrictions. Specifically, the metal hydroxide may include one or more of Ni(OH) ₂ , Co(OH) ₂ , Cu(OH) ₂ , Sr(OH) ₂ , Ba(OH) ₂ , Pd(OH) _{2 ,} In(OH) ₃ , ( _{CH3CO2 ) 7Cr3 (} OH) ₂ , Bi(OH) ₃ , and _Sn (OH) ₂ . More specifically, the metal hydroxide includes one or more of Co(OH) ₂ and ( _CH3CO2 ) _7Cr3 (OH) ₂ .

If the metal hydroxide content is too low, problems occur with dispersing the silane compound, making it difficult to apply uniformly. If the metal hydroxide content is too high, the amount of silane compound becomes relatively small, and the improvement in heat resistance and corrosion resistance during stress relief annealing is insufficient. More specifically, the metal hydroxide content is 45 to 60 parts by weight per 100 parts by weight of the combined amount of silane compound and metal hydroxide.

The insulating coating composition for electrical steel sheets according to one embodiment of the present invention may further contain a metal nitride in addition to a silane compound and a metal hydroxide. When an appropriate amount of metal nitride is further contained, the insulating properties and thermal conductivity properties of the insulating coating formed can be further improved. When a metal nitride is further contained, the composition contains 0.1 to 40 wt % of metal nitride, 25 to 75 wt % of silane compound, and 0.5 to 60 wt % of metal hydroxide, based on the solid content. The solid content means the solid portion of the insulating coating composition excluding volatile components such as solvents, based on 100 wt %.

If the amount of metal nitride is too small, the effect of improving the insulating properties and the thermal conductivity properties is insufficient. If the amount of metal nitride is too large, the amount of silane compound and metal hydroxide is relatively small, and the improvement of heat resistance and corrosion resistance during stress relief annealing is insufficient. More specifically, based on the solid content, the composition contains 1 to 25 wt% of metal nitride, 35 to 65 wt% of silane compound, and 15 to 50 wt% of metal hydroxide. The metal nitride includes one or more of BN, AlN, Si ₃ N ₄ , Mg ₃ N ₂ , Ca ₃ N ₂ , Sr ₃ N ₂ , Ba ₃ N ₂ and Ge ₃ N _4. The average particle size of the metal nitride is 0.05 to 20 μm. Only when the particle size of the metal nitride is appropriate, dispersibility and coating property are easy.

The insulating coating composition for electrical steel sheets according to one embodiment of the present invention further contains at least one of ethylene glycol, propylene glycol, glycerine, and butyl carbitol in addition to the silane compound and metal nitride. By further containing the above-mentioned additives, an insulating coating having excellent surface gloss and very beautiful roughness can be formed. The above-mentioned additives can be further contained in an amount of 1 to 15 parts by weight per 100 parts by weight of the silane compound and metal hydroxide. If the additive is contained in an excessively small amount, the above-mentioned improving effect is insufficient. Even if the additive is further contained, there is no additional improving effect and the dispersibility is rather deteriorated. More specifically, the additive is contained in an amount of 3 to 10 parts by weight per 100 parts by weight of the silane compound and metal hydroxide.

The insulating coating composition further contains a solvent for uniform dispersion of solids and easy application. The solvent may be water, alcohol, etc., and contains 300 to 1000 parts by weight per 100 parts by weight of the silane compound and metal hydroxide combined. Thus, the insulating coating composition is in the form of a slurry.

（化学式１において、Ｒ^１は水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） An insulating coating composition for electrical steel sheet according to an embodiment of the present invention includes a silane compound represented by the following Chemical Formula 1; and one or more chromate compounds selected from chromic anhydride, chromate salts, and dichromate salts.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.)

The insulating coating composition according to one embodiment of the present invention contains a silane compound with a unique chemical structure to dramatically improve heat resistance and corrosion resistance during stress relief annealing. Furthermore, when a silane compound is used alone, there are problems with the coating peeling off during the stress relief annealing process and difficulties in applying it uniformly to the surface of the electrical steel sheet. To improve this, a chromate compound is also included.

Below, the insulating coating composition for electrical steel sheets according to one embodiment of the present invention will be described in detail for each component.

First, the insulating coating composition for electrical steel sheets according to one embodiment of the present invention contains a silane compound represented by Chemical Formula 1. The silane compound represented by Chemical Formula 1 contains Si and F elements in the compound, and has excellent heat resistance. In particular, the F element has the effect of suppressing the chemical reaction in which moisture in the air penetrates into the insulating coating, and plays an important role in dramatically improving the surface quality of electrical steel sheets by providing excellent chemical resistance, insulation, and corrosion resistance. The silane compound is contained in an amount of 10 to 80 parts by weight per 100 parts by weight of the total amount of the silane compound and the chromate compound. If the silane compound is contained in an excessively small amount, the content of Si and F elements in the insulating coating formed will be low, the heat resistance will decrease, and the iron loss after stress relief annealing will be inferior. The miscibility with the solvent will decrease, making it difficult to form a uniform insulating coating. Therefore, the silane compound may be contained in the above-mentioned range. More specifically, the silane compound is contained in an amount of 40 to 70 parts by weight.

In Chemical Formula 1, R ¹ is hydrogen, a halogen atom, a linear or branched alkyl group, or an alkoxy group. When m is 2 or more, the multiple R ^1s may be the same or different from each other. In Chemical Formula 1, L is one or more of a direct bond, an alkylene group, and -CF ₂ -. When n is 2 or more, the multiple Ls may be the same or different from each other.

（化学式２において、Ｒ^１～Ｒ^３はそれぞれ独立して水素、ハロゲン元素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌ_１は直接結合または２価の連結基である。ｍは１～３の整数であり、ｎは４－ｍである。） Specifically, the silane compound is represented by the following chemical formula 2.
[Chemical Formula 2]

(In Chemical Formula 2, R ¹ to R ³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L ₁ is a direct bond or a divalent linking group; m is an integer of 1 to 3; and n is 4-m.)

Specifically, in Chemical Formula 2, R ¹ , m, and n are the same as those in Chemical Formula 1. L ₁ is a direct bond or a divalent linking group. More specifically, L ₁ is one or more of a direct bond, an alkylene group, and -CF ₂ -. R ² and R ³ are each independently a hydrogen or a halogen element. The silane compound includes one or more of Triethyl(trifluoromethyl)silane, Trimethoxy(trifluoropropyl)silane, Dimethoxy-methyl(trifluoropropyl)silane, and Perfluorooctyl-triethoxysilane.

More specifically, the silane compound includes one or more of triethyl(trifluoromethyl)silane, trimethoxy(3,3,3-trifluoropropyl)silane, dimethoxy-methyl(3,3,3-trifluoropropyl)silane, and 1H,1H,2H,2H-perfluorooctyl-triethoxysilane.

An insulating coating composition for electrical steel sheets according to an embodiment of the present invention includes at least one chromic acid compound selected from chromic anhydride, chromates, and dichromates. The chromic acid compound chemically reacts with the silane compound to improve dispersion stability and form a uniform coating. In addition, the chromate compound has the effect of reducing costs during mass production and is advantageous in that it allows stable operation in the insulating coating process.
As the chromate and dichromate, for example, salts of Na, K, Mg, Ca, Mn, Mo, Zn, Al, etc. can be used.

The chromate compound is contained in an amount of 20 to 90 parts by weight per 100 parts by weight of the combined total of the silane compound and chromate compound. If the chromate compound is contained in an excessively small amount, problems may occur in dispersing the silane compound, making it difficult to apply the compound uniformly. If the chromate compound is contained in an excessively large amount, the amount of the silane compound will be relatively small, and the improvement in heat resistance and corrosion resistance during stress relief annealing will be insufficient. More specifically, the chromate compound is contained in an amount of 30 to 60 parts by weight.

The insulating coating composition for electrical steel sheets according to one embodiment of the present invention further contains ceramic powder in addition to the silane compound and chromate compound. When the composition further contains an appropriate amount of ceramic powder, the insulating properties of the insulating coating formed can be further improved. The ceramic powder is contained in an amount of 0.5 to 65 parts by weight per 100 parts by weight of the total amount of the silane compound and chromate compound. If the amount of ceramic powder is too small, the effect of improving the insulating properties is insufficient. If the amount of ceramic powder is too large, the amount of the silane compound and chromate compound is relatively small, and the improvement of heat resistance and corrosion resistance during stress relief annealing is insufficient. More specifically, the ceramic powder is contained in an amount of 5 to 30 parts by weight per 100 parts by weight of the total amount of the silane compound and chromate compound.

_The ceramic powder includes _{one or more of MgO, MnO, Al2O3, SiO2, TiO2, ZrO2, Al6Si2O13, Al2O3.TiO2, Y2O3 , 9Al2O3.B2O3 , BN , CrN , BaTiO3 ,} SiC, and _TiC . More specifically, the ceramic powder includes one or _more of MgO, _{CaO , Al2O3 , SiO2 , TiO2 , ZrO2 , Al2O3.TiO2 , Y2O3} , _{9Al2O3.B2O3 , BN} , _CrN , _BaTiO3 , SiC, and TiC. The average particle size of the ceramic powder can be 0.05-20 μm. Only when the particle size of the ceramic powder is appropriate, it can be easily dispersed and applied.

The insulating coating composition for electrical steel sheets according to one embodiment of the present invention further contains 0.5 to 30 parts by weight of one or more polymer resins selected from acrylic resin, styrene resin, vinyl acetate resin, polyester resin, urethane resin, polyethylene resin, polypropylene resin, polyamide resin, polycarbonate resin, phenol resin, alkyd resin and epoxy resin, per 100 parts by weight of the total amount of the silane compound and the chromate compound. By further adding an appropriate amount of the aforementioned polymer resin, it is possible to manufacture an electrical steel sheet with excellent surface gloss and very beautiful roughness.

The insulating coating composition for electrical steel sheets according to one embodiment of the present invention further contains 1 to 15 parts by weight of one or more of ethylene glycol, propylene glycol, glycerine, and butyl carbitol per 100 parts by weight of the silane compound and the chromate compound. By further containing the above-mentioned additives, an insulating coating having excellent surface gloss and very beautiful roughness can be formed. If the additive is contained in an excessively small amount, the above-mentioned improving effect is insufficient. Even if an additive is further contained, there is no additional improving effect and dispersibility is rather deteriorated. More specifically, the additive is contained in an amount of 3 to 10 parts by weight per 100 parts by weight of the silane compound and the chromate compound.

The insulating coating composition may further contain a solvent for uniform dispersion of solids and easy application. The solvent may be water, alcohol, etc., and contains 300 to 1000 parts by weight per 100 parts by weight of the silane compound and chromate compound combined. In this way, the insulating coating composition is in the form of a slurry.

An electromagnetic steel sheet 100 according to an embodiment of the present invention includes an electromagnetic steel sheet substrate 10 and an insulating coating 20 located on one or both sides of the electromagnetic steel sheet substrate 10. Figure 1 shows a schematic side cross-sectional view of an electromagnetic steel sheet according to an embodiment of the present invention. Figure 1 shows a case where an insulating coating 20 is formed on the upper surface of the electromagnetic steel sheet substrate 10.

（化学式１において、Ｒ^１およびＲ^２はそれぞれ独立して、水素、直鎖状または分枝状アルキル基、シクロアルキル基、アルケニル基、アルキニル基、アリール基、ヘテロアリール基、アルコキシ基またはアミノアルキル基であり、Ｌは直接結合または２価の連結基である。ｍは１～４の整数であり、ｎは４－ｍである。） The insulating coating 20 contains a silane compound represented by the following chemical formula 1 and a metal hydroxide.
[Chemical Formula 1]

(In Chemical Formula 1, R ¹ and R ² are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L is a direct bond or a divalent linking group; m is an integer of 1 to 4; and n is 4-m.)

The insulating coating 20 of the electrical steel sheet 100 according to one embodiment of the present invention contains a silane compound with a unique chemical structure to dramatically improve heat resistance and corrosion resistance during stress relief annealing and also to improve thermal conductivity. Furthermore, when a silane compound is used alone, there are problems with the coating peeling off during the stress relief annealing process and difficulties in applying it uniformly to the surface of the electrical steel sheet. To improve this, a metal hydroxide is also included.

The components of the insulating coating 20 have been described in detail in relation to the insulating coating composition described above, so a duplicated description will be omitted. During the process of forming the insulating coating 20, the chemical structure of some silane compounds is changed, but many silane compounds maintain their chemical structure. In addition, during the process of forming the insulating coating 20, a silane compound and a metal hydroxide may react to form a compound. In this case, the ratio of the silane compound and the content ratio of the metal hydroxide in the compound are calculated, and calculated by the weight of the silane compound and the metal hydroxide, respectively. During the process of forming the insulating coating 20, volatile components such as the solvent are removed, so the components in the insulating coating 20 are substantially similar to the solid components in the insulating coating composition.

The insulating coating 20 contains _0.1 to 50 wt % Si. In this case, the Si is Si in the silane compound, Si in the metal nitride when _Si3N4 is used as the metal nitride, and Si diffused from the electrical steel sheet substrate 10. The appropriate amount of Si is contained, so that the insulating properties of the insulating coating 20 can be ensured.

In addition to Si, the insulating coating 20 contains elements such as Fe, C, and O derived from the insulating coating composition and the electromagnetic steel sheet substrate 10. The thickness of the insulating coating 20 is 0.1 to 10 μm. If the insulating coating 20 is too thin, the heat resistance decreases, resulting in poor core loss after stress relief annealing. If the insulating coating 20 is too thick, the space factor decreases, resulting in poor motor characteristics. Therefore, the thickness of the insulating coating 20 can be adjusted to the above-mentioned range. More specifically, the thickness of the insulating coating 20 is 0.2 to 5 μm.

For the electromagnetic steel sheet substrate 10, non-oriented electromagnetic steel sheet or oriented electromagnetic steel sheet can be used without restrictions. Specifically, non-oriented electromagnetic steel sheet can be used. In one embodiment of the present invention, the insulating properties are generated by the components of the insulating coating 20 and are unrelated to the alloy components of the electromagnetic steel sheet. The alloy components of the electromagnetic steel sheet will be described below as an example.

The electrical steel sheet contains C: 0.01% by weight or less, Si: 6.0% by weight or less, P: 0.5% by weight or less, S: 0.005% by weight or less, Mn: 0.1 to 1.0% by weight, Al: 0.40 to 2.0% by weight, N: 0.005% by weight or less, Ti: 0.005% by weight or less, and Sb, Sn, Ni, or a combination thereof: 0.01 to 0.15% by weight, with the balance being Fe and unavoidable impurities.
Each alloy component will be described in detail below.

The reasons for limiting the components of the non-oriented electrical steel sheet substrate 10 are explained below.

C: 0.01 wt% or less Carbon (C) is an ingredient that does not contribute much to improving the magnetic properties of the electrical steel sheet in the embodiment of the present invention, so it is preferable to remove it as much as possible. Since C causes magnetic aging in the final product and reduces the magnetic properties during use, it is contained at 0.01 wt% or less, and since the lower the C content, the better the magnetic properties, it is more preferable to limit it to 0.005 wt% or less in the final product.

Si: 6.0 wt% or less Silicon (Si) is a component that increases the resistivity of steel and reduces eddy current loss among core losses. If the Si content is too high, it can cause problems such as increased brittleness and difficulty in cold rolling. Therefore, it is preferable to limit the Si content to 6.0 wt% or less. More specifically, the Si content is 0.1 to 4.0 wt%.

P: 0.5% by weight or less Phosphorus (P) is added to increase resistivity, improve texture, and enhance magnetic properties. If added in excess, cold rolling properties deteriorate, so it is preferable to limit the content to 0.5% by weight or less.

S: 0.005% by weight or less Sulfur (S) forms fine precipitates of MnS and CuS, which inhibit crystal grain growth and deteriorate magnetic properties, so it is preferable to control the S content as low as possible. Therefore, the S content is limited to 0.005% by weight or less.

Mn: 0.1 to 1.0% by weight
When manganese (Mn) is present at less than 0.1 wt%, fine MnS precipitates are formed, which inhibits grain growth and deteriorates magnetic properties. Therefore, when present at 0.1 wt% or more, coarse MnS is formed, and the S component can be prevented from precipitating as finer precipitates, CuS. However, when Mn is increased, magnetic properties deteriorate, so it is added to 1.0 wt% or less.

Al: 0.40 to 2.0% by weight
Al is an effective component for increasing resistivity and reducing eddy current loss. If the content is less than 0.40% by weight, AlN precipitates finely, resulting in inferior magnetic properties, and if the content exceeds 2.0% by weight, workability deteriorates, so it is preferable to limit the content to 2.0% by weight or less.

N: 0.005% by weight or less N forms fine, long AlN precipitates inside the base material and inhibits grain growth, so its content should be small, preferably limited to 0.005% by weight or less.

Ti: 0.005% by weight or less Ti forms fine precipitates of TiN and TiC to inhibit grain growth, and if added in an amount exceeding 0.005% by weight, many fine precipitates are generated, which deteriorates the texture and deteriorates the magnetic properties.

Sb, Sn, Ni or a combination thereof: 0.01 to 0.15% by weight
Sb, Sn, or Ni is a surface-precipitating element that is concentrated in the surface layer of the steel sheet to suppress the adsorption of nitrogen, and as a result, it plays a role in lowering iron loss without hindering the growth of crystal grains. If the content of Sb, Sn, or Ni added alone or in combination is too small, the effect is inferior. If the content of Sb, Sn, or Ni added alone or in combination is too high, grain boundary segregation becomes severe, the brittleness of the steel sheet increases, and sheet breakage occurs during rolling. When two or more types of Sb, Sn, and Ni are added in combination, the total amount is 0.01 to 0.15 wt%. More specifically, Sb is 0.01 to 0.05 wt%, Sn is 0.01 to 0.12 wt%, and Ni is 0.01 to 0.06 wt%.

As described above, the electrical steel sheet according to the embodiment of the present invention has excellent thermal conductivity due to the formation of the insulating coating. Specifically, the following general formula 1 is satisfied.
[General Formula 1]
20≦TC≦200W/mK
(In the above formula 1, TC represents the thermal conductivity value measured by induction heating a 600 x 400 mm test piece at 230°C using a PPMS (Physical Property Measurement System).)

The insulating coating 20 of the electrical steel sheet 100 according to one embodiment of the present invention contains a silane compound having a unique chemical structure to dramatically improve heat resistance and corrosion resistance during stress relief annealing. Furthermore, when a silane compound is used alone, there are problems with the coating peeling off during the stress relief annealing process and difficulties in applying it uniformly to the surface of the electrical steel sheet. To improve this, a chromate compound is also included.

The components of the insulating coating 20 have been specifically described in relation to the insulating coating composition described above, so a duplicated description will be omitted. During the process of forming the insulating coating 20, the chemical structure of some silane compounds is changed, but most silane compounds maintain their chemical structure. In addition, during the process of forming the insulating coating 20, a silane compound and a chromate compound may react to form a compound. In this case, the ratio of the silane compound and the content ratio of the chromate compound in the compound are calculated and calculated by the weight of the silane compound and the chromate compound, respectively. During the process of forming the insulating coating 20, volatile components such as the solvent are removed, so the components in the insulating coating 20 are substantially the same as the solid components in the insulating coating composition. The solid content refers to the solid portion of the insulating coating composition excluding volatile components such as the solvent, based on 100% by weight.

The insulating coating 20 contains 0.1 to 50 wt % Si and 0.01 to 25 wt % F. In this case, the Si is Si in the silane compound, Si in the ceramic powder when _SiO2 is used as the ceramic powder, and Si diffused from the electrical steel sheet substrate 10. The appropriate amount of Si is contained, so that the insulating properties of the insulating coating 20 can be ensured.
Furthermore, F originates from F in the silane compound. The appropriate amount of F is contained, which can improve the chemical resistance, insulating properties, and corrosion resistance of the insulating coating 20. In addition to Si and F, the insulating coating 20 also contains elements such as Cr, Fe, C, and O that originate from the insulating coating composition and the electrical steel sheet substrate 10.

The thickness of the insulating coating 20 is 0.1 to 10 μm. If the thickness of the insulating coating 20 is too thin, the heat resistance decreases, resulting in poor core loss after stress relief annealing. If the thickness of the insulating coating 20 is too thick, the space factor decreases, resulting in poor motor characteristics. Therefore, the thickness of the insulating coating 20 can be adjusted to the above-mentioned range. More specifically, the thickness of the insulating coating 20 is 0.2 to 5 μm.

2 is a schematic flow chart of a method for manufacturing an electrical steel sheet according to an embodiment of the present invention. The flow chart of the method for manufacturing an electrical steel sheet in FIG. 2 is merely for the purpose of illustrating the present invention, and the present invention is not limited thereto. Therefore, the method for manufacturing an electrical steel sheet can be modified in various ways.

As shown in FIG. 2, the method for manufacturing an electromagnetic steel sheet includes a step of manufacturing an electromagnetic steel sheet substrate (S10), and a step of forming an insulating coating by applying an insulating coating composition to one or both sides of the electromagnetic steel sheet substrate (S20). In addition, the method for manufacturing an electromagnetic steel sheet further includes other steps. In the previous step (S10), an electromagnetic steel sheet substrate is manufactured. The alloy components of the electromagnetic steel sheet substrate have been specifically described, so a repeated description will be omitted.

The steps of manufacturing the electrical steel sheet substrate include hot rolling a slab to manufacture a hot-rolled sheet; cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet; and final annealing of the cold-rolled sheet. First, the slab is heated to a temperature of 1,200°C or less. Next, the heated slab is hot rolled to manufacture a hot-rolled sheet. The manufactured hot-rolled sheet is then hot-rolled annealed.

Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. Cold rolling can be performed once or two or more cold rolling steps including intermediate annealing can be performed. Next, the cold-rolled sheet is final annealed. In this step, the cold-rolled sheet is degreased to remove the rolling oil present in the cold-rolled sheet, and the cold-rolled sheet is subjected to a primary annealing, and then a secondary annealing in an atmosphere composed of hydrogen and nitrogen. In addition, the dew point temperature is controlled to -5°C or less during the final annealing to prevent oxides from forming on the surface, which would cause deterioration of the magnetic property.

Returning to the explanation of the method for manufacturing the electromagnetic steel sheet, the next step (S20) is to apply an insulating coating composition to one or both sides of the electromagnetic steel sheet substrate to form an insulating coating. The insulating coating composition is the same as described above, so a duplicated explanation will be omitted.

The step of forming the insulating coating includes heat treating the steel sheet coated with the insulating coating composition at a temperature of 100 to 680°C. If the heat treatment temperature is too low, the solvent is not easily removed and it is difficult to form a beautiful insulating coating. If the heat treatment temperature is too high, problems with poor adhesion occur. More specifically, the heat treatment is performed at a temperature of 350 to 650°C. The heat treatment time is 5 to 200 seconds.

After the step of forming the insulating coating, the method further includes a step of performing stress relief annealing at a temperature of 700 to 1000°C. In one embodiment of the present invention, the silane compound and metal hydroxide in the insulating coating composition allow the insulating coating to maintain excellent adhesion and surface properties even after stress relief annealing. If the stress relief annealing temperature is too low, the desired stress relief is not achieved smoothly. If the stress relief annealing temperature is too high, the magnetic properties of the electrical steel sheet are deteriorated. The stress relief annealing step is performed in a nitrogen atmosphere for 1 to 5 hours.

The present invention will be described in more detail below with reference to examples. However, these examples are merely for the purpose of illustrating the present invention and are not intended to be limiting.

Experimental Example 1-1: Characteristics of different silane compounds Example 1-1
A slab containing 3.4% by weight of silicon (Si), 0.80% by weight of aluminum (Al), 0.17% by weight of manganese (Mn), 0.0015% by weight of titanium (Ti), 0.03% by weight of tin (Sn), 0.01% by weight of nickel (Ni), 0.003% by weight of carbon (C), 0.0013% by weight of nitrogen (N), 0.012% by weight of phosphorus (P), 0.001% by weight of sulfur (S), and the balance being Fe and other unavoidable impurities was prepared. The slab was heated at 1130°C and then hot-rolled to a thickness of 2.3 mm to produce a hot-rolled sheet.

The hot-rolled sheet was coiled at 650°C and cooled in air, and then hot-rolled at 1040°C for 2 minutes, quenched in water, pickled, and cold-rolled to a thickness of 0.35 mm to produce a cold-rolled sheet. The cold-rolled sheet was final-annealed at 1040°C for 50 seconds in a 20% hydrogen, 80% nitrogen atmosphere with the dew point temperature adjusted to produce an annealed steel sheet.

The insulating coating composition was prepared by mixing 60 parts by weight of triacetoxymethylsilane, 20 parts by weight of nickel hydroxide (Ni(OH) ₂ ), 10 parts by weight of strontium hydroxide (Sr(OH) ₂ ), 5 parts by weight of boron nitride, and 5 parts by weight of ethylene glycol with distilled water to prepare a slurry. The slurry was applied to the steel sheet that had been final annealed using a roll, and then heat-treated at 650°C for 30 seconds and cooled in air. The electrical steel sheet was subjected to stress relief annealing (SRA) at 750°C for 2 hours in a 100% nitrogen atmosphere and cooled in air. The thickness of the insulating coating was about 0.8 μm.

Examples 1-2 to 1-12
The same procedure as in Example 1-1 was carried out, but the contents and types of the silane compound, metal hydroxide, and metal nitride in the insulating coating composition were changed as shown in Table 1 below to form an insulating coating.

Comparative Example 1-1
The same procedure as in Example 1-1 was carried out, except that no metal hydroxide was present and an insulating coating composition containing 100 parts by weight of triacetoxymethylsilane was used.

Comparative Example 1-2
The same procedure as in Example 1-1 was carried out, except that the silane compound was omitted and an insulating coating composition containing 100 parts by weight of chromium hydroxide was used.

Comparative Example 1-3
The same procedure as in Example 1-1 was carried out, except that no silane compound was used and an insulating coating composition containing 60 parts by weight of chromium hydroxide and 40 parts by weight of boron nitride was used.

The properties of the electrical steel sheets manufactured in the examples and comparative examples were measured and summarized in Table 2 below. Core loss (W _15/50 ) refers to the power loss that occurs when a magnetic field of 50 Hz frequency is magnetized with an alternating current up to 1.5 Tesla. Insulation properties were measured on the upper part of the insulating coating using a Franklin measuring device according to the ASTM A717 international standard. Adhesion was expressed as the minimum arc diameter at which the coating did not peel off when the test piece was bent 180° in contact with a 10 to 100 mm arc. Surface characteristics were evaluated with the naked eye to see how uniform the coating was formed and the color was uniform. Thermal conductivity was measured by induction heating the electrical steel sheet at 230°C and measuring the thermal conductivity of the test piece using a PPMS (Physical property measurement system, manufactured by Quantum Design).

As shown in Tables 1 and 2, it can be confirmed that the insulating coating properties of the Examples are superior to those of the Comparative Examples. It can also be confirmed that when the silane compound or metal hydroxide is contained alone, severe peeling of the coating occurs, resulting in inferior magnetic properties.

Figures 3 and 4 show scanning electron microscope (SEM) photographs of a single surface of the electrical steel sheet produced in Example 1-2 and Comparative Example 1-2, respectively. As shown in Figure 3, in the case of Example 1-2, it can be seen that a beautiful insulating coating is maintained even after SRA. In contrast, as shown in Figure 4, in the case of Comparative Example 1-2, it can be seen that numerous cracks appear on the surface of the insulating coating after SRA. Figure 5 shows the results of FT-IR-RAS analysis of the electrical steel sheet coating produced in Example 1-2. As can be seen in Figure 5, it can be seen that triacetoxyvinylsilane is present in the coating.

Experimental Example 1-2: Space factor evaluation Example 1-13
A slab containing 4.2 wt% silicon (Si), 0.80 wt% aluminum (Al), 0.15 wt% manganese (Mn), 0.001 wt% titanium (Ti), 0.08 wt% tin (Sn), 0.004 wt% carbon (C), 0.0015 wt% nitrogen (N), 0.015 wt% phosphorus (P), 0.001 wt% sulfur (S), and the balance being Fe and other unavoidable impurities was prepared. The slab was heated at 1150°C and then hot-rolled to a thickness of 2.3 mm to produce a hot-rolled sheet.

The hot-rolled sheet was coiled at 650°C and cooled in air, and then hot-rolled at 1040°C for 3 minutes, quenched in water, pickled, and cold-rolled to a thickness of 0.35 mm to produce a cold-rolled sheet. The cold-rolled sheet was final-annealed at 1050°C for 60 seconds in a 30% hydrogen, 70% nitrogen atmosphere with a dew point temperature adjusted to -40°C to produce an annealed steel sheet. Then, 25 parts by weight of triacetoxymethylsilane, 25 parts by weight of triacetoxyvinylsilane, 15 parts by weight of chromium _hydroxide (( _CH3CO2 ) _7Cr3 (OH) ₂ ), 15 parts by weight of cobalt hydroxide (Co(OH) ₂ ), 3 parts by weight of strontium hydroxide (Sr(OH) ₂ ), 15 parts by weight of boron nitride, and 2 parts by weight of propylene glycol were mixed with distilled water to prepare an _insulating coating composition in the form of a slurry, and the slurry was applied to a thickness using a roll, and then heat-treated at 650°C for 30 seconds and cooled in air. The magnetic steel sheet was subjected to stress relief annealing (SRA) heat treatment in a 100% nitrogen atmosphere at 820°C for 2 hours and cooled in air. The stress-relief annealed steel sheets were treated at 60° C. and 95% humidity for 24 hours, and the degree of rust on the surface was evaluated. The results are shown in Table 3 below.

Comparative Examples 1-5
About 7 parts by weight of MgO and CaO were slowly added to the ionized water, and then about 20 parts by weight of _CrO3 , which generates an exothermic reaction, was gradually added to the solution (MgO, CaO + ionized water) and stirred until it became a transparent brown liquid.

Then, about 30 parts by weight of either an acrylic resin or an acrylic-styrene copolymer resin and 6.7 parts by weight of butyl carbitol as a reducing agent were added to the solution to prepare an insulating coating composition. The same procedure was carried out as in Example 1-13, but the insulating coating composition prepared above was used to form an insulating coating.

Comparative Examples 1-6
An insulating coating composition was used that contained 50 parts by weight of aluminum phosphate dibasic (Al(H ₂ PO ₄ ) ₃ ), 50 parts by weight of zinc phosphate dibasic (Zn(H ₂ PO ₄ ) ₂ ), 210 parts by weight of epoxy resin, 1 part by weight of cobalt hydroxide, 1 part by weight of strontium hydroxide, and 0.05 parts by weight of a Ti chelating agent. The same procedure as in Example 1-13 was repeated, but an insulating coating was formed using the insulating coating composition.

As shown in Table 3, it can be seen that the properties of Example 1-13 are far superior to those of Comparative Examples 1-5 and 1-6.

Experimental Example 2-1: Characteristics of different silane compounds Example 2-1
A slab containing 3.4% by weight of silicon (Si), 0.80% by weight of aluminum (Al), 0.17% by weight of manganese (Mn), 0.0015% by weight of titanium (Ti), 0.03% by weight of tin (Sn), 0.01% by weight of bismuth (Bi), 0.003% by weight of carbon (C), 0.0013% by weight of nitrogen (N), 0.012% by weight of phosphorus (P), 0.001% by weight of sulfur (S), and the balance being Fe and other inevitable impurities, was prepared. The slab was heated at 1130°C and then hot-rolled to a thickness of 2.3 mm to produce a hot-rolled sheet. The hot-rolled sheet was coiled at 650°C, cooled in air, and hot-rolled sheet annealed at 1040°C for 2 minutes, then quenched in water and pickled, and cold-rolled to a thickness of 0.35 mm to produce a cold-rolled sheet. The cold-rolled steel sheet was subjected to final annealing at 1040° C. for 50 seconds in an atmosphere of 20% hydrogen and 80% nitrogen while controlling the dew point temperature, to produce an annealed steel sheet.

As an insulating coating composition, 60 parts by weight of triethyl(trifluoromethyl)silane, 20 parts by weight of chromic anhydride ( _CrO3 ), 10 parts by weight of magnesium oxide (MgO), and 5 parts by weight of ethylene glycol were mixed with distilled water to prepare a slurry, and the slurry was applied to the steel sheet that had been final annealed using a roll, and then heat-treated at 650°C for 25 seconds and cooled in air. The electrical steel sheet was subjected to stress relief annealing (SRA) at 820°C for 2 hours in a 100% nitrogen atmosphere and cooled in air. The thickness of the insulating coating was about 0.8 μm.

Examples 2-2 to 2-12
The same procedure as in Example 2-1 was carried out, but the contents and types of the silane compound, chromate compound and ceramic powder in the insulating coating composition were changed as shown in Table 4 below to form an insulating coating.

Comparative Example 2-1
The same procedure as in Example 2-1 was carried out, except that the chromate compound was omitted and an insulating coating composition containing 100 parts by weight of triethyl(trifluoromethyl)silane was used.

Comparative Example 2-2
Example 2-1 was carried out in the same manner as Example 2-1, except that the silane compound was omitted and an insulating coating composition containing 100 parts by weight of chromic anhydride was used.

Comparative Example 2-3
The same procedure as in Example 2-1 was carried out, but an insulating coating composition containing 60 parts by weight of chromic anhydride and 40 parts by weight of magnesium oxide was used without the silane compound. The properties of the electrical steel sheets manufactured in the examples and comparative examples were measured and summarized in Table 5 below. Core loss (W _15/50 ) means the power loss that occurs when a magnetic field of 50 Hz frequency is magnetized with an alternating current up to 1.5 Tesla. The insulating properties were measured on the upper part of the insulating coating using a Franklin measuring device in accordance with the ASTM A717 international standard. The adhesion was expressed as the minimum arc diameter at which the coating did not peel off when the test piece was bent 180° in contact with a 10 to 100 mm arc. The surface characteristics were evaluated with the naked eye to see how uniform the color of the uniform coating was formed.

As shown in Tables 4 and 5, it can be confirmed that the insulating coating properties of the Examples are superior to those of the Comparative Examples. It can also be confirmed that when a silane compound or a chromate compound is contained alone, severe peeling of the coating occurs, resulting in inferior magnetic properties.

Figure 6 is a scanning electron microscope (SEM) photograph of a single surface of the electrical steel sheet manufactured in Example 2-2. Figure 7 shows a scanning electron microscope (SEM) photograph of the surface of the electrical steel sheet manufactured in Comparative Example 2-3. As shown in Figure 6, in the case of Example 2-2, it can be seen that a beautiful insulating coating is maintained even after SRA. In contrast, as shown in Figure 7, in the case of Comparative Example 2-3, it can be seen that numerous cracks occur on the surface of the insulating coating after SRA.

Experimental Example 2-2: Evaluation of the effect of adding polymer resin Example 2-11
A slab was prepared containing 4.5 wt% silicon (Si), 0.80 wt% aluminum (Al), 0.15 wt% manganese (Mn), 0.001 wt% titanium (Ti), 0.05 wt% tin (Sn), 0.004 wt% carbon (C), 0.0015 wt% nitrogen (N), 0.015 wt% phosphorus (P), 0.001 wt% sulfur (S), with the remainder being Fe and other unavoidable impurities.

The slab was heated to 1150°C and hot-rolled to a thickness of 2.3 mm to produce a hot-rolled sheet. The hot-rolled sheet was coiled at 650°C, cooled in air, and hot-rolled at 1040°C for 3 minutes, then quenched in water, pickled, and cold-rolled to a thickness of 0.35 mm to produce a cold-rolled sheet. The cold-rolled sheet was final-annealed at 1050°C for 60 seconds in a 30% hydrogen, 70% nitrogen atmosphere with a dew point temperature of -40°C to produce an annealed steel sheet. Then, the insulating coating composition described in Example 2-2 was mixed with a polymer resin as shown in Table 6 below to produce a slurry, which was heat-treated at 650°C for 30 seconds and cooled in air. The electrical steel sheet was subjected to stress relief annealing (SRA) heat treatment in a 100% nitrogen atmosphere at 820°C for 2 hours and cooled in air. The insulating coating was formed to a thickness of approximately 0.4 μm.

The stress-relief annealed steel sheets were then treated for 24 hours at 60°C and 95% humidity, after which the degree of rust on the surface was evaluated. The results are shown in Table 6 below.

As shown in Table 6, changes in iron loss, surface roughness, space factor, and rust occurrence area were confirmed by changing the type and amount of polymer resin added.

The present invention is not limited to the above examples and can be manufactured in a variety of different forms. The above examples are illustrative and not limiting.

100 Electromagnetic steel sheet 10 Electromagnetic steel sheet substrate 20 Insulating coating

Claims (18)

A silane compound represented by the following chemical formula 1; and one or more chromate compounds selected from chromic anhydride, chromate salts, and dichromate salts,
An insulating coating composition for electrical steel sheets, comprising 10 to 80 parts by weight of the silane compound and 20 to 90 parts by weight of the chromate compound per 100 parts by weight of the total amount of the silane compound and the chromate compound.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.) 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein in Formula 1, R ¹ is hydrogen, a halogen element, a linear or branched alkyl group, or an alkoxy group. 3. The insulating coating composition for electrical steel sheet according to claim 1, wherein in Chemical Formula 1, L is at least one of a direct bond, an alkylene group, and -CF ₂ -. The insulating coating composition for electrical steel sheets according to claim 1 , wherein the silane compound is represented by the following chemical formula 2:
[Chemical Formula 2]

(In Chemical Formula 2, R ¹ to R ³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group; L ₁ is a direct bond or a divalent linking group; m is an integer of 1 to 3; and n is 4-m.) 5. The insulating coating composition for electrical steel sheets according to claim 4, wherein in Chemical Formula 2, ^R2 and ^R3 are each independently hydrogen or a halogen element. The insulating coating composition for electrical steel sheets according to any one of claims 1 to 5, characterized in that the silane compound contains one or more of triethyl(trifluoromethyl)silane, trimethoxy(trifluoropropyl)silane, dimethoxy-methyl(trifluoropropyl)silane, and perfluorooctyl-triethoxysilane. The insulating coating composition for electrical steel sheets according to any one of claims 1 to 6, further comprising 0.5 to 65 parts by weight of ceramic powder per 100 parts by weight of the combined amount of the silane compound and the chromate compound. 8. _The insulating coating composition for electrical _{steel sheet according to} claim ₇ , _{characterized} in that the ceramic powder contains one _or more of MgO, _MnO , _Al2O3 , _SiO2 , _TiO2 , _ZrO2 , Al6Si2O13, _Al2O3.TiO2 , _{Y2O3 , 9Al2O3.B2O3} , BN, CrN, _BaTiO3 , SiC and TiC. The insulating coating composition for electrical steel sheets according to claim 7 or 8, characterized in that the average particle size of the ceramic powder is 0.05 to 20 μm. The insulating coating composition for electrical steel sheets according to any one of claims 7 to 9, further comprising 0.5 to 30 parts by weight of one or more polymeric resins selected from acrylic resin, styrene resin, vinyl acetate resin, polyester resin, urethane resin, polyethylene resin, polypropylene resin, polyamide resin, polycarbonate resin, phenolic resin, alkyd resin and epoxy resin, per 100 parts by weight of the total amount of the silane compound and the chromate compound. The insulating coating composition for electrical steel sheets according to any one of claims 1 to 10, further comprising 1 to 15 parts by weight of one or more of ethylene glycol, propylene glycol, glycerine, and butyl carbitol per 100 parts by weight of the combined total of the silane compound and the chromate compound. The magnetic steel sheet includes an insulating coating disposed on one or both sides of the magnetic steel sheet.
The insulating coating includes a silane compound represented by the following chemical formula 1; and one or more chromate compounds selected from chromic anhydride, chromate, and dichromate,
The electrical steel sheet comprises 10 to 80 parts by weight of the silane compound and 20 to 90 parts by weight of the chromate compound relative to 100 parts by weight in total of the silane compound and the chromate compound.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.) The electrical steel sheet according to claim 12, characterized in that the insulating coating contains 0.1 to 50% by weight of Si and 0.01 to 25% by weight of F. The electrical steel sheet according to claim 12 or 13, characterized in that the thickness of the insulating coating is 0.1 to 10 μm. The method includes the steps of: preparing an electrical steel sheet substrate; and applying an insulating coating composition to one or both sides of the electrical steel sheet substrate to form an insulating coating,
The insulating coating composition includes a silane compound represented by the following chemical formula 1, and one or more chromate compounds selected from chromic anhydride, chromate, and dichromate,
A method for producing an electrical steel sheet, comprising the steps of: mixing the silane compound with the chromate compound in an amount of 10 to 80 parts by weight; and mixing the chromate compound in an amount of 20 to 90 parts by weight, based on a total of 100 parts by weight of the silane compound and the chromate compound.
[Chemical Formula 1]

(In Chemical Formula 1, ^R1 is hydrogen, a halogen element, a linear or branched alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, or an aminoalkyl group, L is a direct bond or a divalent linking group, m is an integer of 1 to 3, and n is 4-m.) The step of manufacturing the electrical steel sheet substrate comprises:
hot rolling the slab to produce a hot rolled sheet;
The method for producing an electrical steel sheet according to claim 15, comprising: cold rolling the hot-rolled sheet to produce a cold-rolled sheet; and final annealing the cold-rolled sheet. The method for manufacturing an electrical steel sheet according to claim 15 or 16, characterized in that the step of forming the insulating coating includes a step of heat treating the steel sheet coated with the insulating coating composition at a temperature of 100 to 680°C. After the step of forming the insulating coating,
The method for producing an electrical steel sheet according to any one of claims 15 to 17, further comprising the step of performing stress relief annealing at a temperature of 700 to 1000°C.

Images