JP6805762B2 - Non-oriented electrical steel sheet - Google Patents

Description

The present invention relates to non-oriented electrical steel sheets.

In recent years, there has been an increasing demand for higher efficiency and smaller size of electrical equipment in order to prevent global warming and from the viewpoint of global energy saving. Various measures are required to improve the efficiency and size of electrical equipment, but even for electrical steel sheets used as motor iron cores or small transformer iron cores, improvements in magnetic characteristics and workability can be achieved. It has been demanded.

Generally, an insulating film is formed on the surface of these electrical steel sheets. In addition to insulating properties, such insulating coatings are required to have coating properties such as corrosion resistance, weldability, adhesion, and heat resistance. In order to improve the efficiency and miniaturization of electrical equipment, it is important to suppress the heat generation (Joule heat) of the motor, and as measures for that, increase the efficiency of the iron core and windings, heat dissipation plate, etc. Measures have been taken to improve heat removal by installing a coil.

Even if the performance and efficiency of the electrical steel sheet itself is improved, processing strain is introduced into the electrical steel sheet by processing the electrical steel sheet into a predetermined shape when manufacturing a motor or a transformer. Since the introduced processing strain deteriorates the magnetic characteristics, it is possible to further improve the efficiency of electronic devices by performing so-called strain removal annealing at the consumer after processing.

On the other hand, the insulating coating applied to the surface of the electromagnetic steel sheet is roughly classified into the following three types.
(1) Inorganic film that can be annealed and annealed at 750 ° C with an emphasis on heat resistance (2) Organic-inorganic mixed film that can be annealed and annealed with the aim of achieving both punching properties and weldability (3) Emphasis on punching properties Strain-removing and non-annealable organic film

Among the above three types of insulating coatings, the one that is widely used is an insulating coating containing the inorganic components of the above (1) and (2) that can be strain-removed and annealed. In particular, the organic-inorganic mixed coating of the above (2) has become the mainstream because the punching property is remarkably superior to that of the inorganic coating.

As a technique relating to an organic-inorganic mixed insulating film of an electromagnetic steel sheet as shown in (2) above, for example, there is a technique disclosed in Patent Document 1 and Patent Document 2 below. Patent Document 1 below discloses a method of forming an insulating film using a treatment liquid containing a dichromate and an organic resin emulsion such as vinyl acetate, a butadiene-styrene copolymer, and an acrylic resin as main components. Has been done. In Patent Document 2 below is obtained by mixing an aqueous chromic acid solution and emulsion-type resin and an organic reducing agent, an aqueous solution such chromic acid, easily soluble aluminum compound, divalent oxides and H ₃ of metal It contains BO ₃ , and the molar ratio of Me ²⁺ / Al ^{3+ in} the chromic acid aqueous solution is 0 to 7.0, and the molar ratio of ((Al ³⁺ ) + (Me ²⁺ )) / CrO ₃ is 0.2. A method for forming an insulating film is disclosed using a treatment liquid having a molar ratio of H ₃ BO ₃ / CrO ₃ in the range of 0.1 to 1.5.

On the other hand, in recent years, due to growing awareness of environmental issues, the development of an insulating coating that does not use an aqueous solution of chromic acid containing hexavalent chromium has been promoted. As such a technique, for example, in Patent Document 3 below, a phosphate having a specific composition, boric acid and / or colloidal silica, and an organic resin emulsion having a specific particle size are blended in a specific ratio and baked onto a steel sheet. Therefore, a treatment method in which a treatment liquid containing no chromium compound has the same coating characteristics as a conventional insulating coating containing a chromium compound and maintains excellent slipperiness after strain removal annealing is described. There is.

Further, in Patent Document 4 below, an electromagnetic steel plate having an insulating coating having excellent coating characteristics is manufactured by blending a metal phosphate salt and a resin emulsion having a hydroxyl value and a particle size in a specific range in a specific ratio. The technology to be used is disclosed.

More recently, in Patent Document 5 below, an electromagnetic steel plate having an insulating film formed from a treatment liquid in which a metal phosphate salt and an organic resin emulsion having an absolute value of zeta potential of 30 mV or more are mixed in a specific ratio. The technology related to is disclosed.

Further, as the technique related to the inorganic coating of the above (1), for example, there is a technique as disclosed in Patent Documents 6 and 7 below. The following Patent Document 6 relates to an electromagnetic steel plate having an insulating coating having excellent insulating properties, containing a specific amount of a metal phosphate and a silica or a silicate filler having a specific particle size and a specific surface area. The technology is disclosed. Further, Patent Document 7 below describes a technique relating to an electromagnetic steel sheet with an inorganic insulating film, which contains Zr compound, B compound, and Si compound in a specific ratio to prevent deterioration of water resistance and corrosion resistance and has excellent punching property. It is disclosed.

Special Publication No. 50-1501 Japanese Unexamined Patent Publication No. 03-36284 Japanese Unexamined Patent Publication No. 06-330338 Japanese Unexamined Patent Publication No. 2000-129455 JP-A-2002-69657 International Publication No. 2010/146821 Japanese Unexamined Patent Publication No. 2011-246683

With the increase in efficiency and miniaturization of motors and transformers as described above, magnetic deterioration due to machining strain introduced during machining has become an issue. Therefore, strain relief annealing to remove machining strain is important. Is taking on. Recently, there has been an increasing demand for more efficient strain relief annealing. That is, conventionally, the strain removing annealing is generally performed at an annealing temperature of about 750 ° C. and a soaking time of about 2 hours, but in recent years, in order to further improve productivity, 800 ° C. or 850 ° C. There is an increasing demand for shortening the annealing temperature by raising the annealing temperature to ° C. However, the electromagnetic steel sheet having an organic-inorganic mixed type insulating film, which has been the mainstream until now, has a problem that the strain removing annealing temperature cannot be raised because the heat resistance is not sufficient.

In addition, conventional inorganic insulating coatings contain various properties such as chromate, punching resistance, corrosion resistance, appearance, adhesion after strain removal annealing, corrosion resistance, and heat resistance required for insulating coatings of electromagnetic steel sheets. There was a problem that it could not be used as an insulating film because it could not be obtained.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to have better heat resistance, corrosion resistance and appearance, and to perform strain relief annealing at a higher temperature than before. An object of the present invention is to provide a non-oriented electrical steel sheet that exhibits excellent insulating properties even after the implementation.

As a result of diligent studies by the present inventors in order to solve the above problems, a specific composition of a metal phosphate metal salt, a specific fine particle of an inorganic compound, and a low molecular weight organic compound are contained in a specific ratio. Based on the finding that it is possible to improve the heat resistance of the insulating coating of the non-directional electromagnetic steel plate by forming the insulating coating on the surface, the present invention described in detail below has been completed.
The gist of the present invention completed based on such findings is as follows.

(1) The surface contains a metal phosphate, inorganic compound fine particles having an average particle size of 2 μm or less, and a low molecular weight organic compound having a hydroxyl group and a molecular weight of 50 to 2000. The content of the low molecular weight organic compound is 0.5 to 20 parts by mass with respect to 100 parts by mass of the metal phosphate salt, and the content of the low molecular weight organic compound is 0.05 with respect to 100 parts by mass of the metal phosphate salt. A non-directional electromagnetic steel plate having 10 parts by mass and having an inorganic insulating film containing no chromium.
(2) The phosphoric acid metal salt is a salt of one or more metal elements selected from the group consisting of Al, Ba, Co, Fe, Mg, Mn, Ni, and Zn, and phosphoric acid. The non-directional electromagnetic steel plate according to (1).
(3) The non-oriented electrical steel sheet according to (1) or (2), wherein the average particle size of the inorganic compound fine particles is 0.05 μm to 2.0 μm.
(4) The non-directional electromagnetic steel plate according to any one of (1) to (3), wherein the inorganic compound is at least one of an oxide, a hydroxide, a carbonate, and a sulfate.
(5) The inorganic compound is at least one of alumina, gibsite, magnesium oxide, magnesium hydroxide, magnesium carbonate, titanium oxide, talc, kaolin, silica, bentonite, and barium sulfate, (1) to (4). ) Is described in any one of the non-directional electromagnetic steel sheets.
(6) The non-directionality according to any one of (1) to (5), wherein the low molecular weight organic compound is a linear or heterocyclic organic compound having two or more hydroxyl groups in the molecule. Electromagnetic steel plate.
(7) The low molecular weight organic compound includes ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,6-hexanediol, glycerin, polyoxyalkylene glycol, polyoxyalkylene alkyl ether, and polyoxy. The non-directional electromagnetic steel sheet according to any one of (1) to (6), which is at least one of alkylene esters.

As described above, according to the present invention, by forming an insulating film containing a specific composition of a metal phosphate, a specific inorganic compound fine particle, and a low molecular weight organic compound in a specific ratio on the surface. It is possible to improve the heat resistance, corrosion resistance and appearance of the insulating coating of the non-directional electromagnetic steel plate, and maintain excellent insulation even after strain removal annealing at a higher temperature than before. It becomes possible to obtain a directional electromagnetic steel plate.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The embodiment of the present invention described in detail below describes an electromagnetic steel sheet (non-oriented electrical steel sheet) used as an iron core material of an electric device, and in particular, has good heat resistance and is organic. A non-oriented electrical steel sheet having a chromic acid-free insulating coating, which retains properties equal to or higher than those of a resin-containing insulating coating, will be described in detail.

<About electrical steel sheets on which an insulating film is formed>
First, an electromagnetic steel sheet on which an insulating film according to an embodiment of the present invention is formed will be described.

The electromagnetic steel sheet used in the present embodiment is not particularly limited, but contains Si: 0.1% or more and Al: 0.05% or more in mass%, and the balance is Fe and impurities. It is preferable to use a grain-oriented electrical steel sheet. Si is an element that increases the electrical resistance as the content increases to improve the magnetic properties, but the brittleness increases at the same time as the electrical resistance increases. Therefore, the Si content is preferably less than 4.0% by mass. Similarly, Al is also an element that improves the magnetic properties by containing it, but the rollability decreases as the magnetic properties improve. Therefore, the Al content is preferably less than 3.0% by mass.

Further, in the electromagnetic steel sheet used in the present embodiment, in addition to the above Si and Al, Mn is contained in the range of 0.01% by mass to 3.0% by mass in place of a part of the remaining Fe. It is possible. Further, in the electromagnetic steel sheet used in the present embodiment, the content of other typical elements such as S, N, and C is preferably less than 100 ppm in total, and more preferably less than 30 ppm.

In the present embodiment, a steel ingot having the above steel components (for example, a slab) is wound into a coil as a hot-rolled plate by hot rolling, and in some cases, annealed in the state of a hot-rolled plate in the range of 800 ° C to 1050 ° C. After that, it is preferable to use a steel sheet that has been cold-rolled to a thickness of 0.15 mm to 0.5 mm and then annealed. Further, in the electromagnetic steel sheet used in the present embodiment, it is preferable that the surface roughness is relatively small because the magnetic characteristics are good. Specifically, the average roughness (Ra) of the center line in the rolling direction (L direction) and the direction perpendicular to the rolling direction (C direction) is preferably 1.0 μm or less, and is 0.1 μm or more. It is more preferably 0.5 μm or less. This is because when the average roughness Ra of the center line exceeds 1.0 μm, the magnetic characteristics tend to deteriorate.

<Insulation coating>
On the surface of the above-mentioned electromagnetic steel sheet (non-oriented electrical steel sheet), a chromium-free insulating film as described in detail below is formed as an insulating film. The insulating film formed on the surface of the non-directional electromagnetic steel plate according to the present embodiment is an inorganic insulating film containing a metal phosphate and fine particles of an inorganic compound as main components and does not contain chromium, and is such an inorganic film. A predetermined amount of a low molecular weight organic compound is further contained in the insulating film. Hereinafter, such an insulating coating will be described in detail.

[Metal phosphate]
The metal phosphate salt contained in the inorganic insulating coating according to the present embodiment becomes a solid content when a solution containing phosphoric acid and metal ions as main components (for example, an aqueous solution) is dried. The type of the phosphoric acid is not particularly limited, and various known phosphoric acids can be used, but for example, orthophosphoric acid, metaphosphoric acid, polyphosphoric acid and the like are preferably used.

The type of the metal ion is not particularly limited, but one or more selected from the group consisting of Al, Ba, Co, Fe, Mg, Mn, Ni and Zn should be used. Is preferable, and it is more preferable to use at least one of Al and Zn.

Here, when preparing a metal phosphate salt solution, it is preferable to mix at least one of an oxide of a metal ion, a carbonate, and a hydroxide with various phosphoric acids such as orthophosphoric acid. ..

[Inorganic compound fine particles]
The inorganic insulating coating according to the present embodiment contains fine particles of an inorganic compound as one of the main components. The inorganic compound fine particles according to the present embodiment have an average particle size of 2 μm or less, preferably an average particle size of 0.05 μm to 2 μm or less. Further, as the inorganic compound fine particles according to the present embodiment, it is preferable to use relatively poorly soluble ones (for example, those having a solubility in water at 20 ° C. of less than 1 g).

The average particle size of the inorganic compound fine particles as described above can be measured by a known method, but in the present embodiment, the integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method is used. Means the particle size of.

In the inorganic insulating coating according to the present embodiment, the content of the inorganic compound fine particles is 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the metal phosphate. When the content of the inorganic compound fine particles is less than 0.5 parts by mass, it becomes difficult to improve the heat resistance of the insulating film, which is not preferable. On the other hand, when the content of the inorganic compound fine particles exceeds 20 parts by mass, the appearance is inferior, which is not preferable. The content of the inorganic compound fine particles is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the metal phosphate salt.

As the component of the inorganic compound fine particles, for example, at least one of oxides, hydroxides, carbonates, and sulfates is preferable, and chlorides, nitrates, nitrides, bromides, and the like are not preferable. Specific examples of such an inorganic compound include alumina, silica, bentonite, talc, kaolin, magnesium oxide, titanium oxide and the like as the oxide, and hydroxide, for example, as the hydroxide. Magnesium, gibsite and the like can be mentioned, examples of the sulfate include barium sulfate and the like, and examples of the carbonate include magnesium carbonate and the like.

[Low molecular weight organic compounds]
The inorganic insulating coating according to the present embodiment contains a low molecular weight organic compound. Such a low molecular weight organic compound is a relatively low molecular weight organic compound having a hydroxyl group and having a molecular weight in the range of 50 to 2000. Such a low molecular weight organic compound preferably has two or more hydroxyl groups. Further, it is more preferable that the low molecular weight organic compound has the above-mentioned hydroxyl group and molecular weight, is more water-soluble, and has a solubility in 100 g of water of 10 g or more. By containing such a low molecular weight organic compound in the inorganic insulating film, corrosion resistance and appearance can be improved.

More specifically, the low molecular weight organic compound according to the present embodiment is preferably a linear or complex cyclic organic compound having two or more hydroxyl groups in the molecule. Specific examples of such low molecular weight organic compounds include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,6-hexanediol, glycerin and the like, and further, polyethylene glycol and polypropylene. Examples thereof include polyoxyalkylene glycols such as glycols, polyoxyethylene monoalkyl ethers, polyoxyalkylene alkyl ethers such as polyoxyethylene methyl glucoside, and polyoxyalkylene esters such as polyoxyethylene monoesters. In the insulating coating according to the present embodiment, at least one of various low molecular weight organic compounds as described above can be used. Here, when the low molecular weight organic compound of interest in the present embodiment is a part of the high molecular weight compounds as described above, the number average molecular weight measured by gel permeation chromatography is used as the above molecular weight. ..

When the molecular weight of the low-molecular-weight organic compound having a hydroxyl group is less than 50, it is liable to volatilize during preparation of the treatment liquid, and it may be difficult to maintain a predetermined composition, which is not preferable. On the other hand, when the molecular weight of the low molecular weight organic compound having a hydroxyl group exceeds 2000, the organic compound is likely to remain in the film even after baking for film formation, and the remaining organic compound is oxidatively burned during strain removal and annealing. It is not preferable because it may deteriorate the film characteristics. The molecular weight of the low molecular weight organic compound is preferably 80 or more and 1500 or less, and more preferably 100 or more and 1200 or less.

In the inorganic insulating coating according to the present embodiment, the content of the low molecular weight organic compound having a hydroxyl group as described above is 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of phosphate. When the content of the low molecular weight organic compound is less than 0.05 parts by mass, the effect of containing the low molecular weight organic compound is not observed, which is not preferable. On the other hand, when the content of the low molecular weight organic compound exceeds 10 parts by mass, the optimum temperature range at the time of coating and drying becomes narrow, which is not preferable. The content of the low molecular weight organic compound is preferably 0.1 parts by mass or more and 8.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 5.0 parts by mass with respect to 100 parts by mass of the metal phosphate. It is less than a part by mass.

In the non-directional electromagnetic steel plate according to the present embodiment, the inorganic insulating coating containing a specific composition of a metal phosphate, specific inorganic compound fine particles, and a low molecular weight organic compound in a specific ratio as described above. By forming the above on the surface, it is possible to improve the heat resistance of the insulating coating of the non-directional electromagnetic steel plate. The reason why the heat resistance is improved by forming the insulating film having the above-mentioned components is unknown, but the heat resistance is caused by the combination of a specific metal phosphate metal salt around the inorganic compound fine particles. Is presumed to improve. By forming such an inorganic insulating film on the surface of the non-oriented electrical steel sheet, it is possible to realize excellent insulating characteristics even after performing strain removing annealing at a higher temperature than before.

[Adhesion amount of insulating film]
In the non-oriented electrical steel sheet according to the present embodiment, the amount of the insulating coating (inorganic insulating coating) adhered as described above is not particularly limited, but for example, 0.5 g / m ² or more and 2.5 g / m ² It is preferably within the following range. When the amount of the insulating film adhered is less than 0.5 g / m ² , the interlayer resistance and the like are likely to deteriorate, and it may be difficult to maintain the insulating property. On the other hand, when the amount of the insulating film adhered exceeds 2.5 g / m ² , the adhesiveness tends to deteriorate significantly. The amount of the insulating film adhered is more preferably 0.5 g / m ² or more and 1.0 g / m ² or less.

Here, the solid content content in the treatment liquid used for forming the insulating film is substantially equal to the amount of adhesion of the insulating film as described above. When the amount of the insulating film adhered is measured after the fact, various known measuring methods can be used. For example, a method of measuring the weight difference before and after immersion in the sodium hydroxide aqueous solution, or a calibration curve. The fluorescent X-ray method or the like using the method may be appropriately used.

[Method of forming an insulating film]
In the present embodiment, a treatment liquid containing the above components is prepared, and the treatment liquid is applied to and dried on the surface of an electromagnetic steel sheet (non-oriented electrical steel sheet) to form an insulating film as described above. It is possible to do.

When the above-mentioned treatment liquid is applied to the surface of the electromagnetic steel sheet, the coating method is not particularly limited, and a known coating method can be appropriately used. When applying the treatment liquid, for example, a roll coater method may be used, or a coating method such as a spray method or a dip method may be used.

Further, the heating method for heating and drying the applied treatment liquid is not particularly limited, and a known heating method can be appropriately used. As the heating method, for example, a method using a normal radiant furnace may be used, or a heating method using electricity such as an induction heating method may be used, but from the viewpoint of control accuracy of the heating rate, the induction heating method is used. It is more preferable to use it. By utilizing these heating methods and maintaining a temperature equal to or higher than the boiling point of the solvent of the treatment liquid for a predetermined time, an insulating film can be formed.

In addition, an additive such as a surfactant may be further contained in the above-mentioned treatment liquid. As such a surfactant, for example, it is preferable to use a nonionic surfactant. In addition, other brighteners and the like may be contained in the above-mentioned treatment liquid.

The insulating coating on the non-oriented electrical steel sheet according to the present embodiment has been described in detail above.

Subsequently, the non-oriented electrical steel sheet according to the present invention will be specifically described with reference to Examples. Of the examples shown below, those corresponding to the examples of the present invention are merely examples of the non-oriented electrical steel sheets according to the present invention, and the non-oriented electrical steel sheets according to the present invention are limited to the following examples. It's not something.

By mass%, it contains Si: 3.1%, Al: 0.6%, Mn: 0.1%, the balance is composed of Fe and impurities, the plate thickness is 0.30 mm, and it is in the L direction and the C direction. The treatment liquid shown in Table 1 below is applied to the surface of non-oriented electrical steel sheets having a surface roughness of Ra (center line average roughness) of 0.28 μm with a roll coater, and then 50 at a furnace temperature of 500 ° C. It was heated for seconds to form an insulating coating.

The treatment liquids shown in Table 1 below were adjusted as follows.
That is, as the metal phosphate, orthophosphoric acid and each metal hydroxide, oxide, carbonate such as Al (OH) ₃ and Mg (OH) ₂ are mixed and stirred, and each of them shown in Table 1 below is mixed and stirred. A metal phosphate salt treatment solution was prepared and used as a 40 mass% aqueous solution. Then, using such an aqueous solution, the treatment liquid was adjusted so that the ratio of each metal element in the metal phosphate was as shown in Table 1 below. The low molecular weight organic compounds shown in Table 3 below were added and stirred in the treatment liquid. Further, as the inorganic compound fine particles, powdery ones are used, and those prepared in advance by using an organic dispersant or the like to disperse 20 parts by mass with respect to 100 parts by mass of water are prepared with respect to 100 parts by mass of the metal phosphate. Then, the solid content in the coating film was added to the above-mentioned treatment liquid so as to have a mass portion shown in Table 1. Stirred and mixed. When adjusting the concentration, pure water was added as appropriate. When the dispersion of the inorganic compound fine particles was poor, those previously dispersed in water with a homogenizer were contained so as to have the ratio shown in Table 1 in terms of dry mass.

Here, in the metal phosphate salt treatment liquid shown in Table 1 below, the following commercially available compounds were used as each metal source. As for Mg chromate, a commercially available product was used.

Al: Al (OH) ₃
Ba: Ba (OH) ₂
Co: CoCO ₃
Fe: Fe ₃ O ₄
Mg: Mg (OH) ₂
Mn: MnO
Ni: Ni (OH) ₂
Zn: ZnO
Ca: CaO
K: KOH

In addition, commercially available compounds were also used for each of the inorganic compound fine particles shown in Table 2 below and the low molecular weight organic compounds shown in Table 3 below. The average particle size (D50) of each compound shown in Table 2 and the molecular weight of each compound shown in Table 3 are catalog values.

Each of the obtained treatment liquids is applied to the surface of the above-mentioned non-oriented electrical steel sheet using a roll coater, and baked in a heating furnace at 500 ° C. for 50 seconds so that the plate temperature becomes 350 ° C. The coating characteristics of the insulating coating were evaluated as described above. The results obtained are shown in Table 4 below.

<Insulation>
Insulation is based on the interlayer resistance measured according to the JIS method (JIS C2550).
4:30 Ω ・ cm ² / sheet or more 3: 10Ω ・ cm ² / sheet or more 30Ω ・ cm ² / sheet less than 2: 3Ω ・ cm ² / sheet or more 10Ω ・ cm ² / sheet less than 1: 3Ω ・ cm ² / sheet Evaluated as.

<Corrosion resistance>
The corrosion resistance was evaluated according to the salt spray test (JIS Z2371) of the JIS method, and a 10-point evaluation was performed on the sample after 4 hours. The evaluation criteria are as follows.

10: No rust was generated 9: Very small amount of rust was generated (area ratio 0.1% or less)
8: Rusted area ratio = 0.1% excess 0.25% or less 7: Rusted area ratio = 0.25% excess 0.50% or less 6: Rusted area ratio = 0.50 % Exceeding 1% or less 5: Rusted area ratio = 1% Exceeding 2.5% or less 4: Rusted area ratio = 2.5% Exceeding 5% or less 3: Rusted area ratio = 5% Excess 10% or less 2: Rusted area ratio = 10% Exceeded 25% or less 1: Rusted area ratio = 25% Exceeded 50% or less

<Appearance>
For the appearance of the insulating coating, the appearance inspection of the obtained non-oriented electrical steel sheet with the insulating coating was carried out by a skilled inspector.
5: Glossy, smooth and uniform 4: Glossy but slightly inferior in uniformity 3: Slightly glossy and smooth but inferior in uniformity 2: Low gloss and slightly inferior in smoothness Inferior in uniformity 1: Evaluated as inferior in gloss, uniformity, and smoothness.

<Heat resistance>
The heat resistance was evaluated by the corrosion resistance after strain removal and annealing. Heat treatment was performed for 1 hour in a 100% nitrogen atmosphere at each temperature of 750 ° C., 800 ° C., and 850 ° C., and then after 48 hours in a constant temperature and humidity chamber at a temperature of 50 ° C. and a humidity of 90%, rust resistance was obtained. A similar rust generation area ratio was evaluated. The evaluation criteria are as follows.

10: No rust was generated 9: Very small amount of rust was generated (area ratio 0.1% or less)
8: Rusted area ratio = 0.1% excess 0.25% or less 7: Rusted area ratio = 0.25% excess 0.50% or less 6: Rusted area ratio = 0.50 % Exceeding 1% or less 5: Rusted area ratio = 1% Exceeding 2.5% or less 4: Rusted area ratio = 2.5% Exceeding 5% or less 3: Rusted area ratio = 5% Excess 10% or less 2: Rusted area ratio = 10% Exceeded 25% or less 1: Rusted area ratio = 25% Exceeded 50% or less

As is clear from Table 4 above, as a result of the test, the surface of the steel plate is mainly composed of a metal phosphate and inorganic compound fine particles having an average particle size of 2 μm or less, having a molecular weight of 50 to 2000 and retaining a hydroxyl group. It contains a low molecular weight organic compound, the content of the inorganic compound fine particles is 0.5 to 20 parts by mass with respect to 100 parts by mass of the metal phosphate, and the content of the low molecular weight organic compound is 0.05 to 10 parts by mass. The electromagnetic steel sheet of the present invention, which is a mass part and has an insulating film containing no chromium, has excellent insulation, corrosion resistance, and appearance as compared with Comparative Examples, and further withstands strain removal and quenching at high temperatures. The effect of improving heat resistance was remarkable.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

Claims (7)

On the surface
Phosphate metal salt and
Inorganic compound fine particles with an average particle size of 2 μm or less,
Low molecular weight organic compounds that retain hydroxyl groups and have a molecular weight of 50 to 2000,
Contains,
The content of the inorganic compound fine particles is 0.5 to 20 parts by mass with respect to 100 parts by mass of the metal phosphate salt.
The content of the low molecular weight organic compound is 0.05 to 10 parts by mass with respect to 100 parts by mass of the metal phosphate salt, and
A non-oriented electrical steel sheet having a chromium-free inorganic insulating coating. The metal phosphate salt is a salt of one or more metal elements selected from the group consisting of Al, Ba, Co, Fe, Mg, Mn, Ni, and Zn, and phosphoric acid. Item 2. The non-directional electromagnetic steel plate according to Item 1. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the average particle size of the inorganic compound fine particles is 0.05 μm to 2.0 μm. The non-directional electromagnetic steel sheet according to any one of claims 1 to 3, wherein the inorganic compound is at least one of an oxide, a hydroxide, a carbonate, and a sulfate. Any one of claims 1 to 4, wherein the inorganic compound is at least one of alumina, gibsite, magnesium oxide, magnesium hydroxide, magnesium carbonate, titanium oxide, talc, kaolin, silica, bentonite, and barium sulfate. The non-directional electromagnetic steel plate described in the section. The non-directional electromagnetic steel sheet according to any one of claims 1 to 5, wherein the low molecular weight organic compound is a linear or heterocyclic organic compound having two or more hydroxyl groups in the molecule. The low molecular weight organic compounds include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, 1,6-hexanediol, glycerin, polyoxyalkylene glycol, polyoxyalkylene alkyl ether, and polyoxyalkylene ester. The non-directional electromagnetic steel sheet according to any one of claims 1 to 6, which is at least one of them.