JP5974636B2 - Electrical steel sheet with insulation coating - Google Patents

Description

  The present invention relates to an electromagnetic steel sheet with an insulating coating. In particular, the present invention does not deteriorate the corrosion resistance even if the insulating coating does not contain a chromium compound, achieves both high interlayer resistance and good TIG weldability, and also provides good water resistance and coating appearance. The present invention relates to a magnetic steel sheet with an insulating coating that can be used.

  Insulating coatings on electrical steel sheets used for motors and transformers are required not only for interlayer resistance but also for various characteristics such as convenience during processing and storage, and stability during use. Since electrical steel sheets are used for various applications, various insulating coatings have been developed according to the applications. Further, when punching, shearing, bending or the like is performed on the magnetic steel sheet, the magnetic properties are deteriorated due to residual strain. In order to solve this problem, strain relief smelting is often performed at a temperature of about 700 to 800 ° C. . Therefore, in this case, the insulating coating must be able to withstand strain relief annealing.

Insulating coatings for electrical steel sheets can be broadly classified as follows: (1) Emphasis on weldability and heat resistance, and an inorganic coating that can withstand strain relief annealing.
(2) Resin-containing inorganic coating (ie, semi-organic coating) that can withstand strain relief annealing to achieve both punchability and weldability;
(3) Although it is classified into three types of organic coatings that cannot be strain-relieved and annealed for special applications, the general-purpose products that can withstand strain-relieving annealing are coatings containing inorganic components shown in (1) and (2) above. In general, both of them contain a chromium compound. In particular, the chromate-based insulating coating of type (2) is widely used because punchability can be remarkably improved as compared with inorganic insulating coatings in the production of one coat and one bake.

  However, in recent years, environmental awareness has increased, and in the field of electrical steel sheets, a chromate-free product having an insulating coating that does not contain a chromium compound is desired by customers and the like. Techniques for forming an insulating coating corresponding to the above (2) by applying a surface treatment agent containing both an organic component and an inorganic component to the surface of an electromagnetic steel sheet without including a chromium compound include the following. .

  Patent Document 1 adds an organic substance composed of one or more water-soluble or emulsion type resins to an inorganic colloidal substance composed of one or more of colloidal silica, alumina sol, and zirconia sol. A technique for forming an insulating film having excellent corrosion resistance before strain relief annealing using an aqueous solution as a surface treatment agent is described.

  In Patent Document 2, a surface treatment agent includes a treatment liquid mainly composed of 100 parts by weight of an Al primary phosphate solution and 1 to 300 parts by weight of an organic resin emulsion having a particle size of 0.2 to 3.0 μm. Describes a technique for forming an insulating film having excellent weldability, adhesion and slipperiness after strain relief annealing.

  Patent Document 3 discloses a corrosion resistance, adhesion, solvent resistance, and sticking resistance having an insulating coating composed of a polysiloxane polymer obtained by copolymerizing polysiloxane and various organic resins, and an inorganic compound such as silica and silicate. An electrical steel sheet having excellent properties is described.

Japanese Patent Laid-Open No. 10-46350 JP-A-6-330338 JP 2007-197820 A

  Here, when an insulating coating is formed using a conventional surface treatment agent including Patent Documents 1 to 3 and an electromagnetic steel sheet with an insulating coating having a high interlayer resistance is manufactured, it is necessary to increase the adhesion amount of the insulating coating. was there. However, when the adhesion amount of the insulating coating is increased, the TIG weldability is deteriorated, so that it is difficult to achieve both high interlayer resistance and good TIG weldability. In Patent Documents 1 to 3, water resistance and coating appearance are not considered.

  Therefore, in view of the above problems, the present invention does not deteriorate the corrosion resistance even when the insulating coating does not contain a chromium compound, and achieves both high interlayer resistance and good TIG weldability, and has good water resistance and coating. An object of the present invention is to provide an electrical steel sheet with an insulating coating that can also have an appearance.

  As a result of intensive studies by the present inventors to achieve this object, at least one (A) selected from trialkoxysilane, dialkoxysilane, and tetraalkoxysilane as a surface treatment agent to be applied to the surface of the electrical steel sheet. And using an epoxy silane coupling agent (B) in combination, it is found that by adjusting the pH to a predetermined range, an electrical steel sheet with an insulating coating that can achieve the above-mentioned purpose can be obtained. The present invention has been completed.

This invention is made | formed based on such knowledge, The summary structure is as follows.
(1) Trialkoxysilane and dialkoxysilane, in which the substituent other than the alkoxy group bonded to Si is composed of at least one non-reactive substituent selected from hydrogen, an alkyl group, and a phenyl group, and tetra A surface treatment agent containing at least one selected from alkoxysilane (A), an epoxy silane coupling agent (B), and water and adjusted to pH 4.3 to 5.3 is applied to at least one surface of the electrical steel sheet. An electrical steel sheet with an insulating coating, comprising an insulating coating formed by coating and drying.

  (2) The electrical steel sheet with an insulating coating according to (1), wherein the surface treatment agent includes at least one of formic acid, glycolic acid, acetic acid, and lactic acid in order to adjust the pH to the above range.

  (3) The said surface treating agent contains 5-30 mass% of water dispersible silica (C) whose average particle diameter is 5-100 nm with respect to the total solid of the said surface treating agent, (1) or (2 The electrical steel sheet with an insulating coating as described in).

  (4) The surface treatment agent comprises 2 to 15 plate silica (D) having an average particle diameter of 0.08 to 0.5 μm and an aspect ratio of 10 to 100 with respect to the total solid content of the surface treatment agent. The electrical steel sheet with an insulating coating according to any one of (1) to (3), which is contained by mass%.

  (5) The electrical steel sheet with an insulating coating according to any one of (1) to (4), wherein a drying temperature after applying the surface treatment agent is 200 ° C. or lower.

  According to the present invention, the corrosion resistance is not deteriorated even if the insulating coating does not contain a chromium compound, and both high interlayer resistance and good TIG weldability are achieved, and good water resistance and coating appearance are obtained. It is possible to provide a magnetic steel sheet with an insulating coating that can be applied.

  Hereinafter, the present invention will be specifically described.

<Electromagnetic steel sheet>
In the present invention, the electromagnetic steel sheet as a material is not particularly limited, and any conventionally known steel sheet is suitable. That is, a so-called soft iron plate (electric iron plate) having a high magnetic flux density, a general cold-rolled steel plate such as SPCC, and a non-oriented electrical steel plate containing Si or Al for increasing the specific resistance are advantageously suitable.

<Surface treatment agent>
The surface treating agent used in the present invention includes a trialkoxysilane and a dialkoxysilane in which the substituent bonded to Si is composed of at least one non-reactive substituent selected from hydrogen, an alkyl group, and a phenyl group, and And at least one selected from tetraalkoxysilane (A), an epoxy-based silane coupling agent (B), and water. Furthermore, you may contain the acid for adjusting pH.

The kind of trialkoxysilane is not particularly limited, and is represented by the general formula R1Si (OR ′) ₃ , and one or more of them can be used. R1 is a non-reactive substituent selected from hydrogen, an alkyl group, and a phenyl group. When R1 is an alkyl group, it is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 3 carbon atoms. R ′ is an alkyl group, preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 2 carbon atoms. For example, methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, and their hydrolysates can be used. Especially, the trialkoxysilane which has an alkyl group from a viewpoint that the corrosion resistance of an electromagnetic steel plate is more excellent is preferable.

The kind of dialkoxysilane is not particularly limited, and is represented by the general formula R2R3Si (OR ″) ₂ , and one or more of them can be used. Here, R2 and R3 are non-reactive substituents selected from hydrogen, an alkyl group, and a phenyl group, preferably a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably 1 carbon atom. -3 linear or branched alkyl groups. R ″ is an alkyl group, preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 2 carbon atoms. For example, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, and their hydrolysates can be used. Especially, the dialkoxysilane which has an alkyl group from a viewpoint that the corrosion resistance of an electrical steel sheet is more excellent is preferable.

The kind of tetraalkoxysilane is not particularly limited, and is represented by the general formula Si (OR ′ ″) ₄ , and one or more of them can be used. R ′ ″ is an alkyl group, preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 2 carbon atoms. For example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and their hydrolysates can be used. Of these, tetraethoxysilane and tetramethoxysilane are preferred from the viewpoint that the corrosion resistance of the electrical steel sheet is more excellent.

The silane coupling agent (B) is an epoxy silane coupling agent that is stable at pH 4.3 to 5.3. It is represented by the general formula XSi (R4) _n (OR) _3-n (where n is in the range of 0 to 2), X is an active hydrogen-containing epoxy group, and one or more of them can be used simultaneously. . R4 is an alkyl group, preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 2 carbon atoms. OR is any hydrolyzable group, R is, for example, an alkyl group, preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a linear or branched group having 1 to 2 carbon atoms. It is an alkyl group. R is, for example, an acyl group (—COR5), and R5 is preferably a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably a linear or branched alkyl group having 1 to 2 carbon atoms. It is. Examples of the silane coupling agent (B) include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltriethoxysilane, and hydrolysates thereof. Etc. can be used.

  In the surface treating agent used in the present invention, a combination of at least one (A) selected from trialkoxysilane, dialkoxysilane, and tetraalkoxysilane and a silane coupling agent (B) was used as the organic component. . By using the surface treatment agent containing both of them, an insulating coating that does not deteriorate the corrosion resistance can be obtained even if it does not contain a chromium compound.

  In the surface treatment agent used in the present invention, the mass ratio (A / B) of at least one (A) selected from trialkoxysilane, dialkoxysilane and tetraalkoxysilane and the silane coupling agent (B) is preferably used. Is in the range of 0.05 to 1.0, more preferably in the range of 0.1 to 0.5. By setting the mass ratio (A / B) to 1.0 or less, sufficient water resistance can be obtained. Moreover, the tendency for the TIG weldability of an electromagnetic steel plate to improve is acquired by making mass ratio (A / B) 0.05 or more.

  However, in the case of the surface treatment agent containing the above components (A) and (B), although the corrosion resistance is good, when a high interlayer resistance is required, it is necessary to increase the adhesion amount of the insulating coating. Increasing the amount of adhesion not only increases the cost for the insulating coating, but also vaporizes organic components derived from the silane compound of component (A) and the epoxy silane coupling agent of component (B) in welding. There was a problem that blowholes occurred and the strength of TIG welding was weakened as well as the appearance of the coating.

As a result of intensive studies by the present inventors, by adjusting the pH of the surface treatment agent using the silane compound (A) and the epoxy silane coupling agent (B) as main components, for example, 0.5 g / m ^2. It has been found that a sufficiently high interlayer resistance can be obtained even with a small coating amount such as the following. As a result, it was possible to achieve both high interlayer resistance and good TIG weldability.

  In the present invention, the pH of the surface treatment agent is adjusted to 4.3 to 5.3. When the pH exceeds 5.3, the surface of the steel sheet is less etched, and the applied surface treatment agent accumulates in the concave portions of the steel plate, resulting in less adhesion to the convex portions. However, if the coating amount is increased in order to increase the interlayer resistance, the TIG weldability is impaired. Furthermore, when the pH is lower than 4.3, the interlayer resistance increases, but there is a risk that the surface of the steel sheet rusts before baking after coating, the appearance of the coating is impaired, and the water resistance after baking due to the remaining acid component. Inferior. When the pH is adjusted to 4.3 to 5.3, the insulating film becomes a uniform film following the unevenness of the steel sheet by appropriate etching of the steel sheet surface without rusting the steel sheet surface. As a result, both high interlayer resistance and good TIG weldability can be achieved, and good water resistance and coating appearance can be obtained.

  As the acid for adjusting the pH to the above range, at least one of formic acid, glycolic acid, acetic acid, and lactic acid can be used. On the other hand, other acids, for example, acids such as sulfuric acid, hydrochloric acid, and nitric acid, have a strong etching power on the surface of the steel sheet and may rust. In addition, when formic acid, glycolic acid, acetic acid, and lactic acid are used, the pH of the surface treatment agent can be stably adjusted within the above range as compared with acids such as carbonic acid.

  The surface treating agent used in the present invention can contain water-dispersible silica (C) having an average particle diameter of 5 to 100 nm. Water-dispersible silica (C) is effective in that the interlayer resistance can be further increased and TIG weldability can be further improved. The reason is not clear, but the water-dispersible fine particle silica (C) is at least one selected from trialkoxysilane, dialkoxysilane, and tetraalkoxysilane (A) and an epoxy-based silane coupling agent (B). It is presumed that the form of the film formed by is changed to a uniform insulating film following the unevenness of the steel sheet. In the present specification, the “average particle diameter” of the water-dispersible fine particle silica is a particle diameter at which the cumulative frequency of the particle size distribution measured by a laser diffraction particle size distribution measuring device is 50% by volume.

  The content (solid content) of the water-dispersible silica (C) is in the range of 5 to 30% by mass with respect to the total solid content of the surface treatment agent. If it is 5 mass% or more, the effect of improving interlayer resistance and TIG weldability can be obtained reliably. On the other hand, in the case of 30% or less, since the polysiloxane bond by the silane (A) and the silane coupling agent (B) is not broken, the corrosion resistance is not lowered.

  The kind of water-dispersible silica (C) is not particularly limited, and colloidal silica or dry silica can be used. Examples of colloidal silica include Snowtex C, N, 20, OS, OXS, OL (all are trade names) manufactured by Nissan Chemical Co., Ltd., and Nippon Silica Aerosil Co., Ltd. as dry silica. AEROSIL50, 130, 200, 300, and 380 (all are brand names) manufactured by the company etc. are mentioned, These 1 or more types can be used.

  The surface treating agent used in the present invention can contain plate-like silica (D) having an average particle diameter of 0.08 to 0.5 μm and an aspect ratio of 10 to 100. Plate-like silica (D) is also effective in that the interlayer resistance can be further increased and TIG weldability can be further improved. The reason is not clear, but the plate-like silica (D) is formed of at least one (A) selected from trialkoxysilane, dialkoxysilane, and tetraalkoxysilane and an epoxy-based silane coupling agent (B). It is presumed that the form of the coating film changes to a layered structure.

  In the present specification, the “average particle diameter” of the plate-like silica is the length averaged among a plurality of particles in the visual field with respect to the long diameter in a plane perpendicular to the thickness of the plate-like silica when observed by SEM. Means. In the present specification, the “aspect ratio” of the plate-like silica means the value of the ratio of the major axis / maximum thickness in the plane perpendicular to the thickness of the plate-like silica for each particle when observed by SEM. It shall mean the averaged value for the 10 particles.

  The content (solid content) of the plate-like silica (D) is in the range of 2 to 15% by mass with respect to the solid content of the surface treatment agent. If it is 2 mass% or more, the effect of improving interlayer resistance and TIG weldability can be obtained reliably. On the other hand, in the case of 15 mass% or less, since the polysiloxane bond by a silane (A) and a silane coupling agent (B) is not divided, corrosion resistance does not fall.

  The surface treatment agent can be obtained by mixing the above-described components in water such as deionized water or distilled water. What is necessary is just to select the solid content ratio of a surface treating agent suitably. In addition, alcohol, ketone, cellosolve-based water-soluble solvent, surfactant, antifoaming agent, leveling agent, pH adjuster, antibacterial and antifungal agent and the like may be added to the surface treatment agent as necessary. . By adding these, the drying property, coating appearance, workability, and designability of the surface treatment agent are improved. However, it is important to add them to such an extent that the quality obtained in the present invention is not impaired, and the addition amount is less than 5% by mass based on the total solid content of the surface treatment agent.

  As described above, in the present invention, a coating is formed by applying a surface treatment agent to the surface of the electrical steel sheet and drying, preferably drying by heating. Examples of the method for applying the surface treatment agent to the electrical steel sheet include a roll coating method, a bar coating method, a dipping method, a spray coating method, and the like, and an optimal method is appropriately selected depending on the shape of the electrical steel sheet to be processed. More specifically, for example, a roll coating method, a bar coating method, or a spray coating method can be selected if the magnetic steel sheet is a sheet. The spray coating method is a method of adjusting the coating amount by spraying a surface treatment agent on a magnetic steel sheet and blowing a roll squeeze or gas at a high pressure. If the electromagnetic steel sheet is a molded product, a method of adjusting the coating amount by immersing it in the surface treatment agent and pulling it up, and blowing off the excess surface treatment agent with compressed air is selected.

  The drying temperature (maximum reached plate temperature) when drying the surface treatment agent applied to the surface of the electrical steel sheet is usually 80 to 350 ° C., but the silane compound (A) and the silane coupling agent (B) are mainly used. In the case of the surface treating agent used in the present invention as a component, it is more preferably 200 ° C. or lower. If it is 200 degrees C or less, it is because the substituent of a silane compound (A) or a silane coupling agent (B) does not decompose | disassemble and performances, such as water resistance, are not deteriorated. The heating time is appropriately selected according to the type of electromagnetic steel sheet used. In addition, from the viewpoint of productivity and the like, 0.1 to 60 seconds are preferable, and 1 to 30 seconds are more preferable.

  In addition, the pretreatment of the electromagnetic steel sheet is not particularly limited, and before applying the surface treatment agent, pretreatment for removing the oil, dirt, and oxide film of the electromagnetic steel sheet is performed as necessary before applying the surface treatment agent. You may give to a steel plate. Electrical steel sheets are often coated with rust-preventing oil for the purpose of rust prevention, and even when not coated with rust-preventing oil, there are dirt and oxide films attached during the work. In addition, these oil coatings, dirt, and oxide films inhibit the wettability of the surface of the electrical steel sheet and hinder the formation of a uniform film. However, by applying the above pretreatment, The surface is cleaned, and it becomes easy to wet uniformly. When there is no oil, dirt, oxide film or the like on the surface of the electrical steel sheet and the surface treatment agent is uniformly wetted, the pretreatment process is not particularly necessary. The pretreatment method is not particularly limited, and examples thereof include hot water washing, solvent washing, degreasing treatment with alkali, and pickling treatment with hydrochloric acid, sulfuric acid, phosphoric acid, and the like.

The coating amount of the electromagnetic steel sheet is not particularly limited, but is preferably about 0.05 to 3.0 g / m ² per side. The adhesion amount, that is, the total solid mass of the insulating coating of the present invention can be measured from the weight reduction after removing the coating by alkali peeling. Moreover, when there is little adhesion amount, it can measure from the calibration curve obtained by measuring the standard sample with known adhesion amount measured by the alkali peeling method by fluorescent X-ray analysis. If the adhesion amount is 0.05 g / m ² or more, it is possible to satisfy the insulation with corrosion, whereas if 3.0 g / m ² or less, not only improves coating adhesion, during heating and drying No blistering occurs and paintability is not reduced. More preferably 0.1 to 2.0 g / ^{m 2,} still more preferably 1.0 g / ^{m 2} or less. The insulating coating is preferably formed on both sides of the steel sheet, but depending on the purpose, only one side may be formed, and the other side may be another insulating coating.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to a following example at all.

(1) Material Plate thickness: 0.5 mm electromagnetic steel plate [A230 (JIS C 2552 (2000))] was used as a test material.

(2) Pretreatment (cleaning)
As a method for preparing the test plate, first, oil and dirt on the surface of the test material are removed, and after confirming that the surface of the test material is 100% wet with water, pure water (deionized water) is further poured. The test plate was dried and dried in a 100 ° C. oven.

(3) Surface treatment agent Each component was mixed in water by the composition (mass ratio) shown in Table 1, and the surface treatment agent was obtained. Below, the compound used in Table 1 is demonstrated. As the acid for adjusting the pH, any of formic acid, glycolic acid, acetic acid, and lactic acid was used, and the pH of the surface treatment agent is shown in Table 1.

<Trialkoxysilane / dialkoxysilane / tetraalkoxysilane>
A1: Methyltrimethoxysilane A2: Dimethyldimethoxysilane A3: Tetramethoxysilane

<Epoxy silane coupling agent>
B1: 3-glycidoxypropyltrimethoxysilane B2: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane

<Water-dispersible fine particle silica>
C1: Average particle size: 15 nm, colloidal silica C2: Average particle size: 50 nm, colloidal silica C3: Average particle size: 100 nm, colloidal silica

<Plate silica>
D1: Average particle size: 0.1 μm, aspect ratio 10
D2: Average particle diameter: 0.2 μm, aspect ratio 30

(4) Treatment method Using the above-mentioned surface treatment agent, the surface treatment agent is coated on the surface of the test plate by bar coating, and then put into an oven as it is without being washed with water. As shown in Table 1, an insulating coating having an adhesion amount per one side shown in Table 1 was formed on both sides of the test plate. The drying temperature was adjusted by the atmospheric temperature in the oven and the time in the oven. The drying temperature indicates the highest temperature reached on the test plate surface. The specific method of bar coating is as follows.

  Bar coat coating: A surface treatment agent was dropped onto a test plate and painted with a # 3-10 bar coater. It adjusted so that it might become a predetermined adhesion amount with the count of the bar coater used and the density | concentration of a surface treating agent.

  (Evaluation method)

(1) Corrosion resistance A wet test (50 ° C., relative humidity ≧ 98%) was performed on the test plate, the red rust generation rate after 48 hours was visually observed, and the area ratio was evaluated.
(Criteria)
◎: Red rust area ratio of less than 15% ◯: Red rust area ratio of 15% or more and less than 50% △: Red rust area ratio of 50% or more and less than 70% ×: Red rust area ratio of 70% or more

(2) Interlaminar resistance The test plate was measured at 10 points with a voltage of 0.5 V and a pressure of 2 N / mm ^{2 using} the surface insulation resistance measurement method specified in JIS C2550-4: 2000, and the average value was obtained. It was.
◎: 10Ω · cm ² / sheet or more ○: 5-10Ω · cm ² / sheet △: 2-5Ω · cm ² / sheet ×: 2Ω · cm ² / sheet or less

(3) TIG weldability The test plate was laminated at a pressure of 9.8 MPa (100 kgf / cm ² ) so as to have a thickness of 30 mm, and TIG welding was performed on the end face portion (length 30 mm) under the following conditions. Carried out.
・ Welding current: 120A
Ar gas flow rate: 6 liters / min
-Welding speed: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 cm / min
(Criteria)
The superiority or inferiority was determined by the maximum value of the welding speed at which the number of blow holes satisfied 5 or less per bead.
◎: 60 cm / min or more ○: 40 cm / min or more, less than 60 cm / min Δ: 20 cm / min or more, less than 40 cm / min ×: less than 20 cm / min

(4) Water resistance The test plate was exposed to boiling water vapor for 30 minutes, and the appearance change was observed.
(Criteria)
◎: No change ○: Slightly discolored visually △: Discolored clearly visible ×: Film dissolution

(5) Coating appearance The appearance immediately after the formation of the insulating coating was visually observed.
(Criteria)
○: Neither rust nor discoloration Rust: Rust is observed

  Tables 1-1 and 1-2 show the results of the above evaluations on the electrical steel sheets with insulating coatings obtained using the surface treating agents described in Examples and Comparative Examples.

  As a result of the examples, as shown in Table 1-1 and Table 1-2, the electrical steel sheet of the present invention has sufficient corrosion resistance, and has both high interlayer resistance and good TIG weldability, and Good water resistance and coating appearance could also be obtained. On the other hand, the comparative example whose pH deviated from the appropriate range of the present invention resulted in incompatibility between interlayer resistance and TIG weldability, or inferior in water resistance and coating appearance.

  According to the present invention, the corrosion resistance is not deteriorated even if the insulating coating does not contain a chromium compound, and both high interlayer resistance and good TIG weldability are achieved, and good water resistance and coating appearance are obtained. It is possible to provide a magnetic steel sheet with an insulating coating that can be applied.

Claims (3)

Substituents other than alkoxy groups bonded to Si are trialkoxysilanes and dialkoxysilanes consisting of at least one non-reactive substituent selected from hydrogen, alkyl groups, and phenyl groups, and tetraalkoxysilanes. At least one selected from (A), an epoxy silane coupling agent (B), and water, and further water-dispersible silica (C) having an average particle diameter of 5 to 100 nm with respect to the total solid content 5 to 30% by mass and / or 2 to 15% by mass of plate-like silica (D) having an average particle size of 0.08 to 0.5 μm and an aspect ratio of 10 to 100 based on the total solid content, pH 4 A magnetic steel sheet with an insulating coating, comprising an insulating coating formed by applying and drying a surface treatment agent adjusted to 3 to 5.3 on at least one surface of the magnetic steel plate.   The electrical steel sheet with an insulating coating according to claim 1, wherein the surface treatment agent includes at least one of formic acid, glycolic acid, acetic acid, and lactic acid in order to adjust the pH to the range. The electrical steel sheet with an insulating coating according to claim 1 or 2 , wherein a drying temperature after applying the surface treatment agent is 200 ° C or lower.