Method for producing electromagnetic steel sheet with insulating film

Abstract

An electromagnetic steel sheet having a forsterite film is coated with a pretreatment film-forming agent, baked in an atmosphere having a hydrogen concentration of 0.01-10.0 vol% at 130-600 DEG C to form a pretreatment film, then cooled to 100 DEG C or less, coated with an insulating film-forming agent on the pretreatment film, and baked at 600-1000 DEG C to form an insulating film. The content of the chromium compound is 1.00 parts by mass or less with respect to 100 parts by mass of the phosphate in the pretreatment film-forming agent. The insulating film-forming agent contains a cationic surfactant, and the content of a chromium compound is 1.00 parts by mass or less and the content of colloidal silica is 50-250 parts by mass per 100 parts by mass of a phosphate. The total weight per unit area of the pretreatment film and the insulating film is 7.5 g / m2 or less. As a result, an electromagnetic steel sheet with an insulating film, which has excellent appearance, rust resistance, heat resistance, and duty factor, is obtained.

Description

Technical Field

[0001] The present invention relates to a method for producing an electromagnetic steel sheet with an insulating coating. Background Art

[0002] Generally, an electromagnetic steel sheet has a coating on its surface that imparts properties such as insulation, baking resistance, and rust resistance. For example, a grain-oriented electromagnetic steel sheet has a coating containing forsterite (forsterite coating) formed on the steel sheet surface during final annealing and an insulating coating formed thereon.

[0003] The insulating film is formed by applying an insulating film forming agent containing phosphate on the forsterite film and baking it at high temperature. For example, Patent Documents 1 and 2 describe the formation of an insulating film using an insulating film forming agent containing phosphate, colloidal silica and a chromium compound (anhydrous chromic acid).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 50-79442

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 48-39338

[0008] Patent Document 3: International Publication No. 2020 / 026627

[0009] Patent Document 4: Japanese Patent Application Laid-Open No. 9-272982

[0010] Patent Document 5: Japanese Patent Application No. 2013-542323 Summary of the invention

[0011] Problems to be solved by the invention

[0012] If the wettability between the insulating film forming agent and the forsterite film is insufficient, the insulating film forming agent may sink (liquid sink), streak defects may occur, and insufficient leveling may occur, and the thickness of the formed insulating film may become uneven. In this case, the appearance cannot be said to be good.

[0013] Since electromagnetic steel sheets are stacked in large numbers and used as an iron core, a uniform, beautiful and good appearance is strongly required to avoid deterioration of the space factor.

[0014] However, in recent years, there has been an increasing demand for products that do not contain chromium from the viewpoint of environmental protection, and a coating that does not contain chromium compounds has also been desired for electrical steel sheets.

[0015] However, the so-called chromium-free insulating film forming agent containing no chromium compound has insufficient wettability with the forsterite film, and thus a uniform, beautiful and good appearance cannot be obtained.

[0016] Patent Documents 3 to 5 disclose technologies for obtaining an insulating film with good appearance by using a chromium-free insulating film-forming agent.

[0017] However, the present inventors have conducted studies and found that the electrical steel sheets with insulation coatings obtained using the techniques described in Patent Documents 3 to 5 may be insufficient in at least one of heat resistance, rust resistance, and space factor.

[0018] The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain an electrical steel sheet with an insulation coating that is excellent in appearance, rust resistance, heat resistance, and space factor.

[0019] Methods used to solve problems

[0020] The present inventors have conducted intensive studies and, as a result, have found that the above-mentioned object can be achieved by adopting the following configuration, thereby completing the present invention.

[0021] That is, the present invention provides the following [1] to [5].

[0022] [1] A method for manufacturing an electromagnetic steel sheet with an insulating film, wherein a pretreatment film forming agent is applied to an electromagnetic steel sheet having a forsterite film, and the pretreatment film is baked at a baking temperature of 130 to 600° C. in a baking atmosphere having a hydrogen concentration of 0.01 to 10.0% by volume to form a pretreatment film, and then the electromagnetic steel sheet is cooled to a steel sheet temperature of 100° C. or less, an insulating film forming agent is applied to the pretreatment film, and the pretreatment film is baked at a baking temperature of 600 to 1000° C. to form an insulating film, wherein the pretreatment film forming agent contains a phosphate , the content of the chromium compound in the pretreatment film-forming agent is 1.00 mass part or less in terms of chromium element relative to 100 mass parts of the solid content of the phosphate, the insulating film-forming agent contains phosphate, colloidal silica and a cationic surfactant, the content of the chromium compound in the insulating film-forming agent is 1.00 mass part or less in terms of chromium element relative to 100 mass parts of the solid content of the phosphate, the content of the colloidal silica in the insulating film-forming agent is 1.00 mass part or less in terms of SiO2 relative to 100 mass parts of the solid content of the phosphate 2 The solid content is 50 to 250 parts by mass, and the total weight per unit area of ​​the pretreatment film and the insulation film on one side is 7.5 g / m 2 the following.

[0023] [2] The method for producing an insulating steel sheet according to [1] above, wherein the content of the cationic surfactant in the insulating film forming agent is 0.2 to 7.0 parts by mass based on 100 parts by mass of the solid content of the phosphate.

[0024] [3] A method for manufacturing an electromagnetic steel sheet with an insulating coating according to [1] or [2] above, wherein the insulating coating forming agent contains a metal compound, and the content of the metal compound in the insulating coating forming agent is 5 to 60 parts by mass in terms of metal element relative to 100 parts by mass of the solid content of the phosphate.

[0025] [4] The method for producing an electrical steel sheet with an insulation coating according to any one of [1] to [3] above, wherein the pretreatment coating-forming agent contains colloidal silica.

[0026] [5] The method for producing an electrical steel sheet with an insulating coating according to [4], wherein the content of the colloidal silica in the pretreatment coating forming agent is 100 parts by mass of SiO2 relative to 100 parts by mass of the solid content of the phosphate. 2 The solid content is 30 to 230 parts by mass.

[0027] Effects of the Invention

[0028] According to the present invention, an electrical steel sheet with an insulation coating having excellent appearance, rust resistance, heat resistance and space factor can be obtained. DETAILED DESCRIPTION

[0029] [Method for manufacturing electrical steel sheet with insulating coating]

[0030] In the method for manufacturing an electromagnetic steel sheet with an insulating coating according to the present embodiment (hereinafter also referred to as "the present manufacturing method"), in brief, first, a pretreatment coating forming agent is applied to an electromagnetic steel sheet having a forsterite coating and baked to form a pretreatment coating. Then, the electromagnetic steel sheet having the pretreatment coating formed thereon is cooled, and an insulating coating forming agent is applied to the pretreatment coating and baked to form an insulating coating.

[0031] The electrical steel sheet with an insulation coating produced by the present production method is excellent in appearance, rust resistance, heat resistance, and space factor.

[0032] Hereinafter, the present production method will be described in detail.

[0033] <Electromagnetic steel sheet with forsterite coating>

[0034] The electromagnetic steel sheet having a forsterite coating is not particularly limited as long as it has a steel sheet and a forsterite coating (a coating containing forsterite) disposed on the surface of the steel sheet, and one example is a grain-oriented electromagnetic steel sheet.

[0035] 《Composition of steel plates》

[0036] A preferred component composition of the steel sheet will be described. Hereinafter, unless otherwise specified, the unit "%" of the content of each element means "mass %".

[0037] (C: 0.001~0.100%)

[0038] C is useful for the generation of Goss-oriented grains. In order to effectively exert this function, the C content is preferably 0.001% or more.

[0039] On the other hand, when the C content is too high, decarburization may be insufficient even by decarburization annealing. Therefore, the C content is preferably 0.100% or less.

[0040] (Si: 1.0~5.0%)

[0041] Si increases electrical resistance to reduce iron loss, and stabilizes the BCC structure of iron to enable high-temperature heat treatment. Therefore, the Si content is preferably 1.0% or more, and more preferably 2.0% or more.

[0042] On the other hand, when the Si content is too high, cold rolling becomes difficult. Therefore, the Si content is preferably 5.0% or less.

[0043] (Mn: 0.01~1.00%)

[0044] Mn effectively contributes to the improvement of hot brittleness. In addition, when S and Se are mixed, Mn forms precipitates such as MnS and MnSe, and functions as an inhibitor of grain growth. Therefore, the Mn content is preferably 0.01% or more.

[0045] On the other hand, when the Mn content is too high, the particle size of precipitates such as MnSe becomes coarse, and the function as an inhibitor may be lost. Therefore, the Mn content is preferably 1.00% or less.

[0046] (sol.Al: 0.003~0.050%)

[0047] Al forms AlN to become a dispersed second phase and functions as an inhibitor. Therefore, the Al content is preferably 0.003% or more as sol.Al.

[0048] On the other hand, when the Al content is too high, AlN is coarsely precipitated and the function as an inhibitor may be lost. Therefore, the Al content is preferably 0.050% or less in terms of sol.Al.

[0049] (N: 0.001~0.020%)

[0050] N forms AlN similarly to Al. Therefore, the N content is preferably 0.001% or more.

[0051] On the other hand, when the N content is too high, expansion may occur when the steel slab is heated. Therefore, the N content is preferably 0.020% or less.

[0052] (at least one of S and Se: 0.001~0.050%)

[0053] S and Se combine with Mn and Cu to form MnSe, MnS, Cu 2 -xSe、Cu 2 -xS becomes a dispersed second phase and functions as an inhibitor. Therefore, the total content of at least one of S and Se is preferably 0.001% or more.

[0054] On the other hand, if the content of S and Se is too high, solid solution becomes incomplete when the steel slab is heated, and defects may occur on the surface of the steel plate. Therefore, the total content of at least one of S and Se is preferably 0.050% or less.

[0055] (Other elements)

[0056] The above-mentioned component composition may further contain at least one element (for convenience, referred to as "element A") selected from the group consisting of Cu: 0.01-0.20%, Ni: 0.01-0.50%, Cr: 0.01-0.50%, Sb: 0.01-0.10%, Sn: 0.01-0.50%, Mo: 0.01-0.50% and Bi: 0.001-0.100%.

[0057] By containing an element that functions as an auxiliary inhibitor, magnetic properties can be further improved. Examples of such an element include element A that is easy to segregate on the crystal grain size and surface.

[0058] A useful effect can be obtained by making the content of element A equal to or more than the lower limit of the above range. In addition, when the content of element A is too large, secondary recrystallization defects may occur easily, so the content of element A is preferably equal to or less than the upper limit of the above range.

[0059] The above-mentioned component composition may further contain at least one element selected from the group consisting of B: 0.001-0.010%, Ge: 0.001-0.100%, As: 0.005-0.100%, P: 0.005-0.100%, Te: 0.005-0.100%, Nb: 0.005-0.100%, Ti: 0.005-0.100% and V: 0.005-0.100%.

[0060] This further strengthens the suppression force of grain growth, and enables a higher magnetic flux density to be stably obtained.

[0061] (margin)

[0062] The balance of the above composition is composed of Fe and inevitable impurities.

[0063] 《Method for producing electromagnetic steel sheet having forsterite coating》

[0064] The cold rolled sheet of the electromagnetic steel sheet is subjected to electrolytic degreasing using, for example, an alkaline degreasing bath. Then, primary recrystallization annealing and decarburization annealing are performed, and then, after applying an annealing separator containing MgO, final annealing is performed. In this way, an electromagnetic steel sheet is obtained, which is a final annealed sheet having a coating containing forsterite (forsterite coating) formed on the surface as a final annealing coating.

[0065] <Pretreatment film forming agent>

[0066] Next, the pretreatment film-forming agent applied to the forsterite film of the electromagnetic steel sheet will be described.

[0067] Phosphate

[0068] The pretreatment film-forming agent contains phosphate.

[0069] The phosphate preferably contains at least one metal element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al and Mn. As the phosphate, one kind can be used alone or two or more kinds can be used in combination. By using two or more phosphates in combination, the physical property values ​​of the pretreatment film can be finely controlled. As the phosphate, dihydrogen phosphate (heavy phosphate) is preferred because it is easy to obtain.

[0070] Chromium compounds

[0071] The pretreatment film-forming agent is a so-called chromium-free agent.

[0072] Specifically, the content of chromium compounds (chromic acid compounds) such as anhydrous chromic acid (chromium trioxide), chromates, and dichromates is 1.00 part by mass or less, preferably 0.10 part by mass or less, and more preferably 0.01 part by mass or less, calculated as chromium element (Cr) per 100 parts by mass of the solid content of the phosphate.

[0073] 《Colloidal Silica》

[0074] The pretreatment film-forming agent may contain colloidal silica.

[0075] The content of colloidal silica was SiO2 / 100 parts by mass of the solid content of the phosphate. 2 The solid content is, for example, 15 parts by mass or more, preferably 30 parts by mass or more, more preferably 45 parts by mass or more, and further preferably 60 parts by mass or more from the viewpoint of improving wettability between the pretreatment film and the insulating film forming agent.

[0076] For the same reason, the content of colloidal silica is 100 parts by mass of SiO2 relative to 100 parts by mass of the solid content of the phosphate. 2 The solid content is, for example, 260 parts by mass or less, preferably 230 parts by mass or less, more preferably 200 parts by mass or less, and further preferably 170 parts by mass or less.

[0077] Metal Compounds

[0078] The pretreatment film-forming agent may contain a compound containing a metal element (metal compound).

[0079] The metal compound is a substance different from the above-mentioned phosphate, chromium compound and colloidal silica.

[0080] Examples of the metal element contained in the metal compound include at least one selected from the group consisting of Ti, Zr, Hf, V, Mg, Zn, and Nb.

[0081] The metal compound is, for example, an oxide or a nitride containing these metal elements, and its form is, for example, particles.

[0082] The metal element contained in the metal compound may be at least one selected from the group consisting of Mg, Al, Ca, Ba, Sr, Zn, and Mn.

[0083] The metal compound is, for example, a nitrate, sulfate, chloride, iodide or organic acid salt containing these metal elements, and its form is, for example, a water-soluble compound.

[0084] The content of the metal compound is, for example, 3 parts by mass or more, preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and further preferably 10 parts by mass or more, in terms of metal element, relative to 100 parts by mass of the solid content of the phosphate.

[0085] On the other hand, the content of the metal compound is, for example, 75 parts by mass or less, preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less, in terms of metal element relative to 100 parts by mass of the solid content of the phosphate.

[0086] When the content of the metal compound is within the above range, the contact angle of the insulating film forming agent with respect to the pretreatment film becomes low, and the insulating film has a better appearance and better rust resistance.

[0087] As a solvent for the pretreatment film, water is preferred.

[0088] The pretreatment film forming agent may have the same composition as the insulating film forming agent described later.

[0089] <Insulation film forming agent>

[0090] Next, the insulating film forming agent applied on the pretreatment film will be described.

[0091] Phosphate

[0092] The insulating film forming agent contains phosphate.

[0093] The phosphate preferably contains at least one metal element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al and Mn. As the phosphate, one type may be used alone or two or more types may be used in combination. By using two or more types of phosphates in combination, the physical property values ​​of the insulating coating can be finely controlled. As the phosphate, dihydrogen phosphate (heavy phosphate) is preferred because it is easy to obtain.

[0094] 《Colloidal Silica》

[0095] The insulating film forming agent contains colloidal silica.

[0096] From the viewpoint of obtaining good appearance and rust resistance, the content of colloidal silica is 100 parts by mass of SiO2 with respect to 100 parts by mass of the solid content of the phosphate. 2 The amount is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 70 parts by mass or more in terms of solid content.

[0097] For the same reason, the content of colloidal silica is 100 parts by mass of SiO2 relative to 100 parts by mass of the solid content of the phosphate. 2The solid content is preferably 250 parts by mass or less, more preferably 235 parts by mass or less, and even more preferably 220 parts by mass or less.

[0098] Cationic surfactants

[0099] The insulating film forming agent contains a cationic surfactant. As a result, the speed of wetting and spreading of the insulating film forming agent applied on the pretreatment film increases, and leveling is easily promoted. In addition, rust resistance is further improved.

[0100] The reason is not clear, but is speculated as follows.

[0101] Among the substances (compounds) contained in the insulating film forming agent, the surface of the particulate compound is negatively charged, and the cationic surfactant is adsorbed on the particulate compound. When the insulating film forming agent is applied on the pretreatment film, the cationic surfactant is distributed to the interface between the pretreatment film and the insulating film forming agent together with the particulate compound, and the interfacial free energy is reduced. As a result, the insulating film forming agent containing the particulate compound is easy to wet and spread.

[0102] In addition, during baking, carbides derived from the cationic surfactant accumulate on the surface of the insulating coating, forming a surface with reduced wettability with water. This makes it easier to suppress condensation during storage of the electromagnetic steel sheet with the insulating coating, and improves rust resistance.

[0103] From the viewpoint of obtaining the effect of adding the cationic surfactant, the content of the cationic surfactant is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and more preferably 0.4 parts by mass or more, based on 100 parts by mass of the solid content of the phosphate.

[0104] However, when the content of the cationic surfactant is too high, the viscosity of the insulating film forming agent increases, and streak defects are likely to occur, and the appearance of the insulating film may become insufficient.

[0105] Therefore, the content of the cationic surfactant is, for example, 8.0 parts by mass or less, preferably 7.0 parts by mass or less, and more preferably 5.0 parts by mass or less, relative to 100 parts by mass of the solid content of the phosphate.

[0106] Chromium compounds

[0107] The insulating film forming agent is a so-called chromium-free agent.

[0108] Specifically, the content of chromium compounds (chromic acid compounds) such as anhydrous chromic acid (chromium trioxide), chromates, and dichromates is 1.00 part by mass or less, preferably 0.10 part by mass or less, and more preferably 0.01 part by mass or less, in terms of Cr, per 100 parts by mass of the solid content of the phosphate.

[0109] Although the reason is not known, when the content of the chromium compound is within the above range, the wettability of the insulating film forming agent to the pretreatment film is good.

[0110] Metal Compounds

[0111] The insulating film forming agent may contain a compound containing a metal element (metal compound).

[0112] The metal compound is a substance different from the above-mentioned phosphate, chromium compound, colloidal silica and cationic surfactant.

[0113] Examples of the metal element contained in the metal compound include at least one selected from the group consisting of Ti, Zr, Hf, V, Mg, Zn, and Nb.

[0114] The metal compound is, for example, an oxide or a nitride containing these metal elements, and its form is, for example, particles.

[0115] The metal element contained in the metal compound may be at least one selected from the group consisting of Mg, Al, Ca, Ba, Sr, Zn, and Mn.

[0116] The metal compound is, for example, a nitrate, sulfate, chloride, iodide or organic acid salt containing these metal elements, and its form is, for example, a water-soluble compound.

[0117] Regarding the content of the metal compound, it is, for example, 3 parts by mass or more in terms of metal element conversion relative to 100 parts by mass of the solid content of the phosphate, preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and further preferably 10 parts by mass or more, because the heat resistance of the resulting insulating coating is better.

[0118] On the other hand, regarding the content of the metal compound, it is, for example, 75 parts by mass or less in terms of metal element conversion relative to 100 parts by mass of the solid content of the phosphate. From the perspective of lowering the contact angle of the insulating coating forming agent with respect to the pretreatment coating and improving the appearance of the insulating coating, it is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0119] As a solvent for the insulating film forming agent, water is preferred.

[0120] <Formation of Pretreatment Film>

[0121] A pretreatment film forming agent is applied on the forsterite film of the electromagnetic steel sheet, and baking is performed under the conditions (baking temperature and hydrogen concentration in the baking atmosphere) described below. Thus, pretreatment films are formed on both surfaces of the electromagnetic steel sheet.

[0122] Baking temperature

[0123] When the baking temperature of the pretreatment film is too low (or too high), the wettability between the pretreatment film and the insulating film forming agent becomes insufficient, and a good insulating film appearance cannot be obtained.

[0124] Therefore, the baking temperature of the pretreatment film is 130°C or higher, preferably 190°C or higher, and more preferably 250°C or higher. On the other hand, the baking temperature of the pretreatment film is 600°C or lower, preferably 530°C or lower, and more preferably 450°C or lower.

[0125] 《Hydrogen concentration in baking atmosphere》

[0126] The baking atmosphere contains hydrogen, which is considered to promote the drying and dehydration reaction of the pre-treatment film.

[0127] When the hydrogen concentration in the baking atmosphere is too low, gaps are generated between the pretreatment film and the forsterite film or between the pretreatment film and the insulating film, and the pretreatment film and / or the insulating film expand, thereby causing an insufficient space factor.

[0128] Therefore, the hydrogen concentration in the baking atmosphere is 0.01 volume % or more, preferably 0.50 volume % or more, and more preferably 1.00 volume % or more.

[0129] On the other hand, when the hydrogen concentration in the baking atmosphere is too high, the surface properties of the pretreatment film deteriorate due to drying, and the wettability between the pretreatment film and the insulating film forming agent becomes insufficient, and an insulating film having good appearance and rust resistance cannot be obtained.

[0130] Therefore, the hydrogen concentration in the baking atmosphere is 10.0 volume % or less, preferably 8.0 volume % or less, and more preferably 5.0 volume % or less.

[0131] Regarding the baking atmosphere of the pretreatment film, as a component (gas) other than hydrogen, an inert gas such as nitrogen is preferable.

[0132] The baking time of the pretreatment film is not particularly limited, but is preferably 3 to 120 seconds, more preferably 5 to 100 seconds.

[0133] Weight per unit area

[0134] The pretreatment film preferably has a weight per surface area of ​​3.8 g / m2 for the reason of better heat resistance and rust resistance. 2 Below, more preferably 3.2g / m 2 Below, more preferably 2.5g / m 2 the following.

[0135] The weight per unit area of ​​the pretreatment film can be controlled, for example, by adjusting the amount of the pretreatment film-forming agent applied. The method for applying the pretreatment film-forming agent is not particularly limited. For example, a roll coater can be used for application.

[0136] <Cooling>

[0137] After the pretreatment film is formed and before the insulating film forming agent is applied, the electromagnetic steel sheet having the pretreatment film formed thereon is cooled.

[0138] Steel plate temperature

[0139] If the temperature of the electromagnetic steel sheet after cooling is too high, the insulating film forming agent applied later deteriorates before baking, and the wettability deteriorates, resulting in insufficient appearance and rust resistance.

[0140] Therefore, the temperature of the electromagnetic steel sheet after cooling (steel sheet temperature) is 100° C. or lower, preferably 80° C. or lower, and more preferably 60° C. or lower.

[0141] <Formation of Insulation Film>

[0142] Next, a pretreatment film forming agent is applied to the pretreatment film of the electromagnetic steel sheet after cooling, and then dried and baked as needed under the conditions (baking temperature) described below. Instead of baking, flattening annealing combined with baking may be performed. Thus, an insulating film is formed on both sides of the electromagnetic steel sheet. That is, an electromagnetic steel sheet with an insulating film is obtained.

[0143] The formed insulating film has an excellent appearance and low wettability with moisture in the air, exhibits good rust resistance, and is also excellent in heat resistance.

[0144] The reason is not clear, but is speculated as follows.

[0145] When the insulating film is baked, the pre-treated film is baked for the second time, and the dehydration reaction of the pre-treated film is reduced, so the insulating film formation reaction by drying and baking is accelerated. As a result, the number of hydrophilic groups on the surface of the insulating film is reduced, the wettability with water is reduced, and a surface shape with excellent rust resistance can be formed. Furthermore, by accelerating baking, heat resistance is also improved.

[0146] Baking temperature

[0147] If the baking temperature of the insulation coating is too low, the insulation coating is not baked sufficiently, and the rust resistance and heat resistance become insufficient. Therefore, the baking temperature of the insulation coating is 600°C or higher, preferably 700°C or higher, and more preferably 800°C or higher.

[0148] On the other hand, if the baking temperature of the insulation coating is too high, the wettability of the insulation coating with moisture in the air increases, and sufficient rust resistance cannot be obtained. Therefore, the baking temperature of the insulation coating is 1000°C or less, preferably 930°C or less, and more preferably 860°C or less.

[0149] The baking atmosphere of the insulating film is preferably an inert gas atmosphere such as a nitrogen atmosphere.

[0150] The baking time of the pretreatment film is not particularly limited, but is preferably 5 to 120 seconds, more preferably 10 to 100 seconds.

[0151] <Total weight per unit area>

[0152] When the weight per unit area of ​​the pretreatment film and the insulation film is too large, the baking behavior deviates from the appropriate conditions, resulting in cracks in the film and insufficient rust resistance.

[0153] Therefore, the total weight per unit area of ​​the pretreatment film and the insulation film (per single side) is 7.5 g / m 2 Below, preferably 7.0g / m 2 Below, more preferably 6.5g / m 2 the following.

[0154] The weight per unit area of ​​the insulating film can be controlled, for example, by adjusting the amount of the insulating film forming agent applied. The method for applying the insulating film forming agent is not particularly limited. For example, the insulating film forming agent can be applied using a roll coater.

[0155] Example

[0156] The present invention will be described in detail below with reference to the following examples, but the present invention is not limited to the following examples.

[0157] [Test 1]

[0158] <Manufacturing of Magnetic Steel Sheet with Insulation Coating>

[0159] 《Preparation of electromagnetic steel sheet with forsterite coating》

[0160] A grain-oriented electrical steel sheet (electrical steel sheet) having a thickness of 0.2 mm and having been subjected to final annealing was prepared. Since the final annealing was completed, a forsterite film was formed on the surface (the same also applies to Tests 2 to 3 described later).

[0161] 《Preparation of pretreatment coating forming agent and insulating coating forming agent》

[0162] Next, a pretreatment film-forming agent and an insulating film-forming agent were prepared having the component compositions shown in the following Table 1. Pure water was used as a solvent (the same also applies to Tests 2 to 3 described later).

[0163] As the phosphate, dihydrogen phosphate was used. In Table 1 below, magnesium phosphate is expressed as "Mg phosphate". The same applies to other phosphates (also in Tests 2 to 3 described later).

[0164] As colloidal silica, SNOWTEX C manufactured by Nissan Chemical Industries, Ltd. was used (the same applies to Tests 2 to 3 described below).

[0165] In Table 1 below, "parts by mass" of phosphate refers to parts by mass based on solid content. "Parts by mass" of colloidal silica refers to parts by mass of SiO 2 Parts by mass in terms of solid content (the same applies to Tests 2 to 3 described later).

[0166] As the cationic surfactant, SANISOL C manufactured by Kao Corporation was used.

[0167] 《Forming a pretreatment film》

[0168] The prepared pretreatment film-forming agent was applied to the forsterite film of the electrical steel sheet. The coating amount was adjusted so that the basis weight (per surface) of the pretreatment film formed would be the value shown in Table 1 below (the same applies to Tests 2 and 3 described below).

[0169] Next, baking was performed to form a pretreatment film under the conditions (baking temperature and hydrogen concentration in the baking atmosphere) shown in Table 1. The baking atmosphere contained nitrogen gas other than hydrogen, and the baking time was 30 seconds (the same applies to Tests 2 and 3 described below).

[0170] When no pretreatment film was formed, "-" is written in the corresponding column in the following Table 1.

[0171] "cool down"

[0172] Then, the electromagnetic steel sheet having the pretreatment film formed thereon was cooled so as to reach the steel sheet temperature shown in Table 1 below.

[0173] 《Formation of insulation coating》

[0174] After cooling, the prepared insulating film forming agent was applied on the pretreatment film. The coating amount was adjusted so that the total weight per unit area (per single side) of the pretreatment film and the insulating film formed was the value shown in Table 1 below (the same applies to Tests 2 to 3 described below).

[0175] Next, baking was performed for 30 seconds in a nitrogen atmosphere under the conditions (baking temperature) shown in Table 1 below to form an insulating film. In this way, an electrical steel sheet with an insulating film was obtained.

[0176] <Evaluation>

[0177] The following tests were performed on the obtained electrical steel sheets with insulation coatings to evaluate various properties.

[0178] Regarding the contact angle, a test was performed when the pretreatment film was formed.

[0179] Contact Angle

[0180] The contact angle between the insulating film-forming agent and the pretreatment film (forsterite film when no pretreatment film is formed) was measured using a contact angle meter (DMo-501, manufactured by Kyowa Interface Chemical Co., Ltd.).

[0181] The measurement was performed 1 second and 5 seconds after the insulating film forming agent was dropped onto the pretreatment film (or forsterite film), and the average value was taken as the contact angle. The results are shown in the following Table 1. When the contact angle was 60° or less, it was evaluated that the wettability of the insulating film forming agent and the pretreatment film (or forsterite film) was good.

[0182] Appearance

[0183] The surface condition of the insulating coating was visually observed, and the occurrence rate (ratio to the surface area of ​​the insulating coating) of coating unevenness such as streak defects, moire patterns, and Bernard vortices was determined.

[0184] In the following Table 1, the case where the occurrence rate of uneven coating is greater than 15% is recorded as "×", the case where the occurrence rate of uneven coating is 15% or less and greater than 10% is recorded as "△", the case where the occurrence rate of uneven coating is 10% or less and greater than 5% is recorded as "○", and the case where the occurrence rate of uneven coating is 5% or less is recorded as "◎".

[0185] In the case of "◎", "○" or "△", it was evaluated that the appearance of the insulation coating was good.

[0186] 《Rust resistance》

[0187] The electrical steel sheet with the insulation coating was cut to obtain three test pieces (50 mm×50 mm).

[0188] The three test pieces thus obtained were kept for 50 hours in an air atmosphere having a relative humidity of 98% or more and a temperature of 50° C. Then, the surface of each test piece was observed to determine the ratio of the rusted area (rust area ratio).

[0189] The case where the rust area ratio was 5.0% or more was marked as ×, the case where the rust area ratio was 2.5% or more and less than 5.0% was marked as △, the case where the rust area ratio was greater than 0% and less than 2.5% was marked as ○, and the case where there was no rust (the case where the rust area ratio was 0%) was marked as ◎.

[0190] In the following Table 1, the case where all three test pieces were ◎ was recorded as "A", the case where the three test pieces were a combination of ◎ and ○ was recorded as "B", the case where all three test pieces were ○ was recorded as "C", the case where the three test pieces were a combination of ○ and △ was recorded as "D", the case where all three test pieces were △ was recorded as "E", and the case where all three test pieces were × was recorded as "×".

[0191] The case of "A", "B", "C", "D" or "E" was evaluated as having good rust resistance.

[0192] Heat resistance

[0193] The heat resistance was evaluated by a drop weight test assuming the heat resistance during stress relief annealing.

[0194] Specifically, the electrical steel sheet with the insulation coating was cut to obtain 10 test pieces (50 mm×50 mm). The 10 test pieces were stacked and subjected to a 2 kg / cm 2 The test pieces were annealed at 830°C for 3 hours under a compressive load. Then, a 500g weight was dropped from a height of 20cm to confirm the separation of the 10 test pieces. The height from which the weight was dropped was increased by 10cm each time until all 10 test pieces were separated. The height of the weight (height of the drop weight) when all 10 test pieces were separated is recorded in Table 1 below.

[0195] When all 10 test pieces were separated after annealing, the drop height was set to 0 cm. When the drop height was 40 cm or less, it was evaluated that the heat resistance of the insulation film was good.

[0196] 《Duty factor》

[0197] The space factor was evaluated by a method in accordance with JIS C 2550.

[0198] In the following Table 1, the case where the duty factor is less than 97.0% is recorded as "×", the case where the duty factor is 97.0% or more and 97.4% or less is recorded as "○", and the case where the duty factor is greater than 97.4% and 97.8% or less is recorded as "◎". The case of "◎" or "○" is evaluated as a good duty factor.

[0199] In the following Table 1, underlines indicate outside the scope of the present invention (or outside the preferred scope). This also applies to Tables 2 and 3 described below.

[0200]

[0201]

[0202] <Summary of evaluation results>

[0203] As shown in Table 1, the electromagnetic steel sheets with insulation coatings of Examples are good in appearance, rust resistance, heat resistance, and space factor, even though the pretreatment coating and the insulation coating are chromium-free.

[0204] On the other hand, the electrical steel sheet with insulation coating of the comparative example was insufficient in at least one of appearance, rust resistance, heat resistance, and space factor.

[0205] When No. 1-13 and No. 1-14 are compared, No. 1-14, in which the insulating coating is baked at 800° C., has better rust resistance and heat resistance than No. 1-13, in which the insulating coating is baked at 600° C.

[0206] In addition, when No. 1-15 and No. 1-16 are compared, No. 1-15, in which the insulation coating is baked at 930° C., has better rust resistance and heat resistance than No. 1-16, in which the insulation coating is baked at 1000° C.

[0207] Comparing No. 1-19 with No. 1-20, No. 1-20 having an insulating film forming agent containing 60 parts by mass of colloidal silica had better appearance and rust resistance than No. 1-19 having an insulating film forming agent containing 50 parts by mass of colloidal silica.

[0208] Comparing No. 1-21 with No. 1-22, No. 1-21 having an insulating film forming agent content of 220 parts by mass had better appearance and rust resistance than No. 1-22 having an insulating film forming agent content of 250 parts by mass.

[0209] If No.1-26 to No.1-28 are compared, the unit area weight (per side) of the pre-treated film is 4.0 g / m 2 Compared with No.1-28, the unit area weight (per single side) of the pre-treated film is 3.8g / m 2 The rust resistance of No.1-27 is better.

[0210] In addition, the unit area weight (per single side) of the pre-treatment film is 3.8g / m 2 Compared with No.1-27, the unit area weight of the pre-treated film (per single side) is 1.0g / m 2 The heat resistance of No.1-26 is better.

[0211] Comparing No. 1-30 to 1-32, No. 1-30 and No. 1-31, in which the content of the cationic surfactant in the insulating film forming agent is 5.0 parts by mass or less, have better appearance than No. 1-32, in which the content of the cationic surfactant in the insulating film forming agent is 7.0 parts by mass.

[0212] Comparing No. 1-35 to 1-37, the contact angle increases as the hydrogen concentration in the baking atmosphere during the formation of the pretreatment film increases to 8.0 volume %, 10.0 volume %, and 10.5 volume %. In particular, No. 1-37 (comparative example) in which the hydrogen concentration in the baking atmosphere is 10.5 volume % has insufficient appearance and rust resistance.

[0213] [Test 2]

[0214] <Manufacturing of Magnetic Steel Sheet with Insulation Coating>

[0215] A pretreatment film-forming agent and an insulating film-forming agent having the component compositions shown in Table 2 below were prepared.

[0216] As the metal compound, water-soluble Mg(NO 3 ) 2 and Ca gluconate, and TiO 2 and ZnO.

[0217] In the following Table 2, "parts by mass" of the metal compound means parts by mass converted into metal elements (the same also applies to Test 3 described later).

[0218] As the cationic surfactant, ACETAMIN 86 manufactured by Kao Corporation was used.

[0219] The prepared pretreatment film forming agent was applied to the forsterite film of the electromagnetic steel sheet, and baked under the conditions (baking temperature and hydrogen concentration in the baking atmosphere) shown in Table 2 below to form a pretreatment film. Then, the electromagnetic steel sheet with the pretreatment film formed was cooled so as to reach the steel sheet temperature shown in Table 2 below. Next, an insulating film forming agent was applied to the pretreatment film, and baked under the conditions (baking temperature) shown in Table 2 below in a nitrogen atmosphere for 30 seconds to form an insulating film.

[0220] In this way, an electrical steel sheet with an insulation coating is obtained.

[0221] <Evaluation>

[0222] The obtained electrical steel sheet with insulation coating was evaluated for various properties in the same manner as in Test 1. The results are shown in Table 2 below.

[0223]

[0224] <Summary of evaluation results>

[0225] As shown in Table 2, the electrical steel sheets with insulation coatings of Examples (No. 2-1 to No. 2-6) were good in appearance, rust resistance, heat resistance, and space factor.

[0226] If No.2-1 is compared with No.2-6, No.2-1 having a content (total) of metal compounds of the insulating coating forming agent of 10 parts by weight has a lower contact angle and better appearance and heat resistance than No.2-6 having a content (total) of metal compounds of the insulating coating forming agent of 5 parts by weight.

[0227] If No.2-3 to No.2-5 are compared, No.2-5 having a content (total) of metal compounds of the insulating coating forming agent of 63 parts by weight has a lower contact angle and better appearance and heat resistance than No.2-4 having a content (total) of metal compounds of the insulating coating forming agent of 63 parts by weight.

[0228] In addition, compared with No. 2-5 in which the content (total) of the metal compound of the insulating film forming agent is 60 parts by mass, No. 2-3 in which the content (total) of the metal compound of the insulating film forming agent is 30 parts by mass has a lower contact angle and better appearance and heat resistance.

[0229] [Test 3]

[0230] <Manufacturing of Magnetic Steel Sheet with Insulation Coating>

[0231] A pretreatment film-forming agent and an insulating film-forming agent having the component compositions shown in Table 3 below were prepared.

[0232] As the metal compound, Mg(NO 3 ) 2 and ZrO 2 .

[0233] As the cationic surfactant, ACETAMIN 86 manufactured by Kao Corporation was used.

[0234] The prepared pretreatment film forming agent was applied to the forsterite film of the electromagnetic steel sheet, and baked under the conditions (baking temperature and hydrogen concentration in the baking atmosphere) shown in Table 3 below to form a pretreatment film. Then, the electromagnetic steel sheet with the pretreatment film formed was cooled so that the steel sheet temperature shown in Table 3 below was reached. Next, an insulating film forming agent was applied to the pretreatment film, and baked under the conditions (baking temperature) shown in Table 3 below in a nitrogen atmosphere for 30 seconds to form an insulating film.

[0235] In this way, an electrical steel sheet with an insulation coating is obtained.

[0236] <Evaluation>

[0237] The obtained electrical steel sheet with insulation coating was evaluated for various properties in the same manner as in Test 1. The results are shown in Table 3 below.

[0238]

[0239] <Summary of evaluation results>

[0240] As shown in Table 3, the electrical steel sheets with insulation coating according to Examples (No. 3-1 to No. 3-7) were good in appearance, rust resistance, heat resistance, and space factor.

[0241] Comparing No. 3-1 and No. 3-2, No. 3-2 having a colloidal silica content of 30 parts by mass in the pretreatment film-forming agent has a lower contact angle and better rust resistance than No. 3-1 having a colloidal silica content of 25 parts by mass in the pretreatment film-forming agent.

[0242] Comparing No. 3-4 with No. 3-5, No. 3-4 having a colloidal silica content of 230 parts by mass in the pretreatment film-forming agent has a lower contact angle and better rust resistance than No. 3-5 having a colloidal silica content of 235 parts by mass in the pretreatment film-forming agent.

[0243] Compared with No. 3-1 to No. 3-4 in which the pretreatment film-forming agent does not contain a metal compound, No. 3-6 to No. 3-7 in which the pretreatment film-forming agent contains a metal compound have better rust resistance.

Claims

1. A method for manufacturing an electromagnetic steel sheet with an insulating coating, in, A pretreatment film-forming agent is applied to an electromagnetic steel sheet having a forsterite film, and the pretreatment film is formed by baking the pretreatment film at a baking temperature of 130 to 600° C. in a baking atmosphere having a hydrogen concentration of 0.01 to 10.0% by volume. Then, the electromagnetic steel sheet is cooled to a steel sheet temperature below 100° C. An insulating film forming agent is applied on the pre-treatment film, and the film is baked at a baking temperature of 600 to 1000° C., thereby forming an insulating film. The pretreatment film-forming agent contains phosphate, The content of the chromium compound in the pretreatment film-forming agent is 1.00 parts by mass or less in terms of chromium element relative to 100 parts by mass of the solid content of the phosphate. The insulating film forming agent contains phosphate, colloidal silica and a cationic surfactant. In the insulating film forming agent, the content of the chromium compound is 1.00 parts by mass or less in terms of chromium element relative to 100 parts by mass of the solid content of the phosphate. In the insulating film forming agent, the content of the colloidal silica is 100 parts by mass of SiO2 relative to 100 parts by mass of the solid content of the phosphate. 2 The solid content is 50 to 250 parts by mass. The total weight per unit area of ​​the pretreatment film and the insulation film on each side is 7.5 g / m 2 the following.

2. The method for producing an electrical steel sheet with an insulation coating according to claim 1, in, In the insulating film forming agent, the content of the cationic surfactant is 0.2 to 7.0 parts by mass based on 100 parts by mass of the solid content of the phosphate.

3. The method for producing an electrical steel sheet with an insulation coating according to claim 1 or 2, in, The insulating film forming agent contains a metal compound, In the insulating film forming agent, the content of the metal compound is 5 to 60 parts by mass in terms of metal element relative to 100 parts by mass of the solid content of the phosphate.

4. The method for producing an electrical steel sheet with an insulation coating according to any one of claims 1 to 3, in, The pretreatment film-forming agent contains colloidal silica.

5. The method for producing an electrical steel sheet with an insulation coating according to claim 4, in, In the pretreatment film-forming agent, the content of the colloidal silica is 100 parts by mass of SiO2 relative to 100 parts by mass of the solid content of the phosphate. 2 The solid content is 30 to 230 parts by mass.

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