JPH1112756A - Nonoriented silicon steel sheet with insulating film excellent in seizure resistance and sliding characteristic after stress relief annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet having a film excellent in seizure resistance at stress relief annealing and sliding characteristic at iron core working by incorporating specific amounts of silicone resin in the form of spherical monodisperse fine grains having an average grain size specific times the film thickness after drying into an inorganic-organic mixture film. SOLUTION: The basic composition of the inorganic-organic mixture film consists of one or more kinds selected from chromic acid compounds and phosphoric acid compounds and an organic composition. A silicone resin in the form of spherical monodisperse fine grains having an average grain size 0.5 to 3.0 times the film thickness after drying is incorporated into the mixture film by 1 to 20 wt.%. The basic composition of the inorganic-organic mixture film consists of an inorganic colloidal composition and an organic composition. The film thickness of the insulating film after drying is regulated to 0.1 to 3 μm. The silicone resin has a three-dimensional reticular structure having a siloxane bond of ≡Si-O-Si≡ being a skeleton and has excellent lubricity, heat resistance, chemical resistance, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an inorganic material which exhibits no slippage between steel sheets in strain-relieving annealing of a non-oriented electrical steel sheet cut or punched into a predetermined shape, and exhibits excellent slip properties even after strain-relieving annealing. The present invention relates to a non-oriented electrical steel sheet having an insulating coating of an organic mixed composition.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets used for iron cores of motors and electric equipment are formed by forming an electrical insulating coating on the surface of a steel sheet, slitting the sheet to a predetermined width, and then punching it into an iron core shape, and then laminating. The end face is fixed and assembled by TIG welding or caulking. Further, in order to remove iron loss deterioration due to processing strain and improve magnetic flux density by improving crystal structure, strain relief annealing may be performed at a temperature of 700 to 800 ° C. Therefore, the properties required for the insulating coating of the non-oriented electrical steel sheet are not only excellent in electrical insulation properties but also many properties such as adhesion, corrosion resistance, punching properties, weldability and heat resistance. In addition, when lamination is performed after performing stress relief annealing as in the case of an EI iron core, it is important that the steel sheets do not fuse with each other even after annealing and that they have excellent slip properties.

Conventionally, insulating coatings of various compositions have been developed and improved in order to satisfy these required characteristics. Among them, the punching property has been found to be significantly improved by the use of an organic resin. Recently, a water-soluble resin and an emulsion have been added to a main agent such as chromate, phosphate or an inorganic colloidal composition which can be formed at a low temperature. Insulating coatings of an inorganic-organic mixed composition mixed with a resin are most often used.

[0004] However, the insulating film having the above-mentioned mixed composition has a heat-resistant temperature of about 400 ° C. for an organic substance.
When annealing is performed at a high temperature of 0 ° C., the organic matter in the coating is burned off, resulting in a porous coating structure. Therefore, after annealing, important film properties as an insulating film of the electromagnetic steel sheet, such as electrical insulation, corrosion resistance, and slip property of the steel sheet, are lost.

[0005] As described above, the inorganic-organic mixed coating obtained by adding a water-soluble resin or an emulsion resin to a chromate, phosphate or inorganic colloidal solution has excellent punching properties of a steel sheet, but is subjected to strain relief annealing. In such a case, there is a fundamental problem that the film properties are extremely deteriorated, and improvement of the film has been strongly desired.

[0006]

As means for improving the annealing resistance of the mixed coating, Japanese Patent Publication No. 55-1348 discloses phosphoric acid, chromic acid, boric acid, a water-soluble organic compound having a thio bond, and alum. A method is disclosed in which a treatment liquid mixed with is applied to an electromagnetic steel sheet. In addition, Japanese Unexamined Patent Publication
No. 656663 discloses that a treatment liquid containing chromate and an emulsion resin as main components contains Si having a particle diameter of 1 to 30 μm.
There is disclosed an insulating coating treatment method in which a colloidal inorganic substance such as O ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ is added.
These prior arts utilize heat resistance to the annealing temperature of the inorganic composition, and can prevent deterioration of seizure resistance and electrical insulation due to strain relief annealing, but have poor punching properties. or,
Slip properties after strain relief annealing could not be expected.
Therefore, a method has been proposed in which a powder resin is added with the aim of improving the punchability, weldability, and slipperiness.

For example, Japanese Patent Application Laid-Open No. 3-240970 discloses a chromate / phosphate aqueous solution containing a fine grain emulsion resin having a particle diameter of 0.2 to 0.5 μm and a coarse resin having a particle diameter of 1 to 50 μm. How to apply. JP-A-4-218
No. 677 discloses that a spherical resin powder having a particle diameter of 2 to 20 μm is added to an emulsion resin compounding treatment liquid containing chromate as a main component, and that the surface of the magnetic steel sheet has a surface roughness of Ra = 0.3 to 0.5 μm. It is a method of treating an insulating film having the above. In these methods, by adding a coarse-grained resin, the coarse-grained resin on the coating surface remains as carbon fiber-like projections after annealing by annealing.
Although an attempt is made to prevent seizure of the steel sheet and to improve the slipperiness, the carbon fiber-like projections on the coating surface have weak adhesion and easily peel off during the lamination work of the EI iron core. For this reason, the EI piece after lamination has a problem in that many scratches are generated on the surface of the coating, and electrical insulation and corrosion resistance are impaired.

As described above, in the prior art, a method of blending a new inorganic composition or a coarse-grained resin into an inorganic-organic mixed coating containing an organic composition has been proposed. The electrical insulation and the corrosion resistance deteriorated due to the deterioration of the steel and the occurrence of scratches after annealing, and did not satisfy the requirements of the electrical steel sheet processing manufacturer. Therefore, the present invention has an inorganic-organic mixed coating, which does not impair the conventional coating performance, has a coating that prevents the above-mentioned coating defects and has excellent seizure resistance during strain relief annealing and slipperiness during iron core processing. An object is to provide a non-oriented electrical steel sheet.

[0009]

In order to prevent a new coating defect from being generated by adding a coarse-grained resin, the present inventors fixed the coating surface after annealing without deteriorating the punching property. Various studies were conducted on the composition, form, and amount of the additive because it was considered effective to develop an additive that does not easily peel off. As a result, by blending a small amount of fine powder having the properties of inorganic substance and organic substance as described later in detail, it has lubricity peculiar to organic resin at the punching stage before annealing, and peculiar to inorganic substance after strain relief annealing. In addition, the additive adheres to the film during the strain relief annealing process, and does not lead to the occurrence of new film defects of electric insulation and corrosion resistance, which were disadvantages of the prior art, and has seizure resistance. The present inventors have found that slipperiness is improved, and have completed the present invention.

That is, the gist of the present invention resides in that an inorganic-organic mixed film containing at least one selected from chromic acid compounds and phosphoric acid compounds and an organic composition as a basic component has a thickness of 0% after drying. 1 to 20% by weight of silicone resin of spherical monodisperse fine particles having an average particle diameter of 0.5 to 3.0 times
It is a non-oriented electrical steel sheet having an insulating coating contained therein.

Another gist of the present invention is to provide an inorganic-organic mixed coating containing an inorganic colloid composition and an organic composition as a basic component without using a chromic acid or phosphoric acid-based compound as a main component. A non-oriented electrical steel sheet having an insulating coating containing 1 to 20% by weight of a silicone resin of spherical monodispersed fine particles having an average particle diameter of 0.5 to 3.0 times. In any of the above cases, the dried film thickness of the insulating film is 0.1 to 3.0 μm.
It is preferably within the range of m.

[0012]

[Action]

(Silicone resin used in the present invention) A feature of the present invention is that a non-oriented electrical steel sheet having an inorganic-organic mixed coating is punched into a predetermined shape, and then a steel sheet produced in the process of performing strain relief annealing at a temperature of 700 to 800 ° C. In order to prevent slippage deterioration due to mutual fusion and thermal decomposition of the resin, the coating contains spherical silicone resin fine particles having excellent heat resistance.

The silicone resin is {Si-O-Si}
It has the advantages of organic substances and inorganic substances, such as a three-dimensional network structure having a siloxane bond as a skeleton and excellent lubricity, heat resistance and chemical resistance. Therefore, the lubricating property of the coating is improved, and the punching property of the steel sheet works advantageously. In addition, even when the treatment liquid is prepared, it does not deteriorate or decompose even when mixed with a strong acid such as chromate or phosphate, and has a relatively small specific gravity (SG1.3) as compared with inorganic fine powder. Precipitation hardly occurs in the liquid, and liquid management is easy. The biggest feature is the heat resistance characteristic of siloxane, and the strain relief annealing temperature is 700 ~
At a temperature of 800 ° C., there is no melting and only a weight loss of about 10%. As a result, the silicone resin powder remains in the coating as a sintered body of silica without being burned out even when subjected to strain relief annealing, and is firmly bonded to the silicone resin powder. The disadvantages of the prior art addition of inorganic powders, such as a decrease in corrosion resistance and deterioration of corrosion resistance, and new coating defects caused by the addition of coarse resin can be alleviated at once.

The silicone resin particles used in the present invention are spherical monodispersed fine particles, have relatively smooth surfaces without angular surfaces, and form uniform single particles rather than aggregates. It is. Particularly, a spherical shape is desirable in terms of punching properties and slip properties after annealing. The film containing such fine particles of silicone resin has a surface shape with fine irregularities, and the shape is maintained after annealing, so that fusion of steel sheets can be prevented during the annealing process, and slipperiness after annealing Can be improved.

FIG. 1 shows a sheet thickness of 0.1 mm processed by a known method.
A 5 mm non-oriented electrical steel sheet, which has been subjected to finish annealing, is applied with a rubber roll to the following treatment liquid obtained by adding a spherical silicone resin powder having a different particle diameter in the range of 0.3 to 45 μm to a final roll. It was baked at a temperature of 300 ° C. After the obtained coating film was subjected to strain relief annealing at 750 ° C. in dry (Dry) N ₂ , the slip property and the dusting resistance were investigated by the method described below.
The values are shown with respect to the particle diameter / film thickness of the silicone resin. After coating and drying, the film thickness was 0.7 to 1.3 μm in terms of an average film thickness at a portion where the silicone resin did not protrude on the surface as a cross-sectional film thickness observed with an optical microscope, with respect to the target film thickness of 1.0 μm.

Treatment liquid (numerical value is weight% as coating solid content) Magnesium dichromate 45 wt% vinyl acetate / veova emulsion resin 25 wt% ethylene glycol 8 wt% boric acid 12 wt% silicone resin powder 10 wt%

The preferred range of the particle size of the silicone resin is 0.5 to 3.0, preferably 1.0 to 2.0 times the film thickness.
When the particle diameter is smaller than 0.5 times, it is difficult to obtain a fine uneven film, and the effect of improving the slip property after annealing is small. However, when the particle diameter is increased to more than three times the film thickness, the surface roughness increases and the space factor is reduced, and the adhesion of the particles is weakened. It is not preferable because powdering easily occurs in the core lamination process. This phenomenon was similarly observed in a resin mixed film formed of a phosphate compound other than the above or an inorganic colloid composition.

FIG. 2 is based on the following inorganic colloidal composition and organic composition using the same cut and annealed plate as above and changing the addition amount of a spherical silicone resin powder having a particle diameter of 0.5 μm. a component, chromic acid, coated with a rubber roll processing liquid without using phosphoric acid compound as a main component in the film thickness 0.4μ goal was baked at peak metal temperature of 200 ℃, DryN ₂
The results are obtained by conducting a strain relief annealing at 750 ° C. in the inside and examining the slipperiness and the adhesion of the coating by the method described later. If the amount of silicone resin in the coating is less than 1% by weight, a coating excellent in slipperiness of the present invention cannot be obtained. However, if the addition amount exceeds 20%, the adhesion of the coating film is inferior, and no further improvement effect on the slipperiness is not observed.
20, preferably in the range of 5 to 20% by weight.

Treatment liquid (numerical value is a value as solid content of coating) Colloidal silica: 100 parts by weight Water-soluble acryl: 100 parts by weight Silicone resin: particle diameter 0.5 μm, content in coating 0-30% by weight

It is important that the spherical fine particles of the silicone resin are added in a monodispersed state in the coating. In the state where the agglomerated particles are formed, spot-like poor adhesion occurs locally, Corrosion resistance is deteriorated due to cracks in the film. In order to uniformly disperse in the coating, it is advisable to mix and stir with a water-soluble resin or an emulsion resin in advance, uniformly disperse the mixture, and then add it to a chromate, phosphate or inorganic colloid solution of the inorganic composition. If the dispersion is still insufficient, it can be added after an aqueous dispersion treatment with an ultrasonic wave using an anionic surfactant or a nonionic surfactant before mixing with the aqueous resin or emulsion resin. As the spherical silicone resin, for example, “TOSpearl” (trade name) of Toshiba Silicone Co., Ltd. can be used.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

(Inorganic composition used in the present invention) Chromic acid-based compounds and phosphoric acid-based compounds as inorganic compositions which are the main components of the film constituents are oxides and hydroxides of Mg, Ca, Al, Zn, K and the like. And an aqueous solution in which at least one kind of carbonate is dissolved in chromic acid or phosphoric acid, and a chromic acid compound or a phosphoric acid compound can be used alone or as a mixture of both. In the case of a treatment liquid mainly composed of a chromic acid compound, a polyhydric alcohol such as glycerin, ethylene glycol or sucrose may be added as a reducing agent for chromic acid in order to insolubilize the film. On the other hand, when a treatment solution mainly containing a phosphate compound is used, a small amount of a nitrate or a nonionic surfactant (described in Japanese Patent Publication No. 6-99813) is used in order to lower the film formation reaction of the phosphate film. It may be added.

The inorganic colloidal composition is composed of Si, Al, T
It is a commercially available colloidal solution of an oxide of i, Zr. The colloidal solution is classified into an acidic type and an alkaline type depending on the type of the stabilizer of the colloid composition, but any type can be used as long as there is no problem in compatibility with the water-soluble resin or the emulsion resin. The particle size of the oxide is not particularly limited, and is 5 to 100
μm can be used advantageously. If the particle size is larger than this, the content of the alkali metal, sulfate, etc. increases due to the increase in the amount of the stabilizer, and the corrosion resistance of the coating film is deteriorated.

(Organic composition used in the present invention) The organic composition, which is the second component of the film, is a mixture of at least one of an aqueous resin, a dispersion resin, and an emulsion resin with the inorganic composition. The type of resin is not particularly limited, and is widely used in the prior art. For example, use thermoplastic resin such as vinyl acetate resin, veova (abbreviation of Versatech Acid Vinyl Ester), acrylic resin, polystyrene resin, polyester resin, polyethylene resin, etc., and thermosetting resin such as phenol resin, epoxy resin and amino resin. it can. Although the content is not particularly limited, the punching property is poor when the content is small, and the corrosion resistance and adhesion after annealing are deteriorated when the content is excessive, and the content is preferable. The organic composition is in the range of 10 to 150 parts by weight based on 100 parts by weight (solid content) of the inorganic composition.

(Coating Amount) The dried film thickness of the insulating film formed on the surface of the steel sheet is limited to the range of 0.1 to 3 μm. If the film thickness is less than 0.1 μm, sufficient punching properties cannot be obtained, and as described above, the coating improvement effect of the present invention can be obtained by controlling the particle diameter and the film thickness of the silicone resin to obtain a fine projection surface shape. Is formed, and the seizure resistance and the slip property after annealing are improved. If the film thickness is too thin, an appropriate surface shape cannot be produced, and the effect is reduced. On the other hand, if the thickness exceeds 3.0 μm, the adhesion of the coating film is deteriorated, which is not preferable. The film thickness is a cross-sectional film thickness observed with a light microscope, and is an average film thickness of a flat portion where the silicone resin does not protrude on the surface.

(Treatment method) The treatment liquid is applied and baked by applying a predetermined amount of the treatment liquid using a roll coater or the like. The silicone resin in the treatment liquid has a true specific gravity of about 1.3, which is not much different from the specific gravity of the treatment liquid, so that no special stirring is required. The baking may be performed only by short-time baking in an electric furnace, a hot blast furnace or the like within a temperature range of 150 to 400 ° C. in the reached plate temperature. In the case of a treatment liquid having an inorganic colloid composition capable of low-temperature baking, if the baking temperature is lower than 150 ° C., baking is insufficient, and rust may be generated by water remaining in the coating. On the other hand, in the case of a chromic acid-based composition or a phosphoric acid-based composition, stickiness is easily generated. Therefore, when baking this composition at a low temperature, the amount of the reaction accelerator may be increased. When the sheet temperature is 400 ° C. or higher, the thermal decomposition of the organic composition proceeds, and there is a possibility that the punching property is deteriorated. As described above, the reasons for limiting the constituent elements, the effects, and the like in the present invention have been described. However, boric acid may be added to the treatment liquid of the present invention as an adhesion improver of the film after annealing.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. (Example 1) For a non-oriented electrical steel sheet having a thickness of 0.5 mm treated in a known manner and having been subjected to finish annealing, a spherical silicone resin having a different particle diameter shown in Table 1 was used. Varying amounts were added to the treatment liquid and applied with a rubber roll.
Subsequently, baking was performed at an ultimate plate temperature of 290 ° C. The thickness of the film is adjusted by adjusting the rolling amount of the rubber roll and the specific gravity of the processing solution to obtain a film thickness of 0.
The range was 2 to 4.0 µ. A sample was cut out from the steel plate after baking, and subjected to strain relief annealing at 750 ° C. × ₂ hours in DryN ₂ to examine the film properties. Table 1 shows the results. The details of each performance evaluation method are as follows. Slip properties are evaluated as ○ or better, and others are evaluated as △ or more.

Treatment liquid composition Magnesium dichromate 50 g Acrylic-styrene-epoxy resin 20 g Ethylene glycol 17 g Boric acid 13 g As is clear from Table 1, the examples of the present invention are all different from the comparative examples in terms of interlayer resistance after strain relief annealing. , Adhesion, seizure resistance,
This is an electrical steel sheet having an insulating coating with excellent slip properties and corrosion resistance.

Interlayer resistance The interlayer resistance was measured according to JIS method 2. ◎: more than 20Ω-cm / sheet ○: 5 to 20Ω-cm / sheet △: less than 2 to 5Ω-cm / sheet ×: less than 2Ω-cm / sheet

Evaluation was made based on the peeling rate of the film after the 180 ° bending-back test at an adhesion of 20 mmφ. ：: No peeling ：: ~ Peeling less than 20% 剥離: Peeling 20% ~ Peeling less than 40% ×: Peeling 40% ~ Peeling

Seizure resistance Ten steel sheets of 50 mm square are stacked and loaded (200 kgf /
After annealing at 750 ° C. for 2 hours in a nitrogen atmosphere while applying a pressure of ² cm ^2, 500 g of a weight was dropped on a steel plate, and the drop height at the time of dividing into five was investigated. ◎: less than 10 cm ○: less than 10 to 15 cm △: 15 to 30 cm ×: more than 30 cm

3 cm × 3 c in which shear burrs have been removed from the surface of the steel sheet after the slip annealing.
200g vertical load to the same steel plate of m
Evaluation was made based on the coefficient of kinetic friction when moving at a speed of min. ◎: dynamic friction coefficient is less than 0.4 ０．４: 0.4 to less than 0.5 Δ: 0.5 to less than 0.6 ×: more than 0.6

The steel sheet after the corrosion resistance annealing was cut into 50 × 100 mm, and evaluated by the area ratio of red rust after 14 days of constant temperature and humidity test (50 ° C., relative humidity 80%). ◎: 0 to less than 20% ：: less than 20 to 40% Δ: less than 40 to 60% ×: 60 to 100%

The same steel plate of 5 cm square, from which shear burrs were removed on the surface of the steel plate after the powdering annealing, was subjected to a vertical load of 500 g, and evaluated by the weight change rate before and after 10 reciprocations. ◎: less than 0.005% ：: 0.005 to less than 0.05% Δ: 0.05 to less than 0.1% ×: 0.1% or more

(Example 2) In the same manner as in Example 1, a base treating solution having an inorganic-organic mixed composition shown in Table 2 was coated with a treating agent having a different addition amount of the spherical silicone resin fine particles of the present invention. It was applied with a roll and baked in a hot air oven. A sample was cut from this steel sheet and dried in DryN ₂ for 7 hours.
The film was subjected to strain relief annealing at 50 ° C. for 2 hours, and the film properties were examined.
Investigation of the film properties was conducted in the same manner as in Example 1. The results are shown in Table 3. The coating film to which the silicone resin fine particles of the present invention were added was superior in seizure resistance, slipping property, and interlayer resistance after annealing to the comparative example containing no silicone resin as in Example 1, and also had good adhesion and corrosion resistance. No problem was obtained.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[0038]

The present invention is constructed as described above, and has a coating having the necessary performance as an insulating coating of an electromagnetic steel sheet. It can be widely used as an electromagnetic steel sheet, including its intended use.

[Brief description of the drawings]

FIG. 1 is a diagram showing the slipperiness and dusting resistance of a film after strain relief annealing with respect to the particle diameter / film thickness ratio of a silicone resin.

FIG. 2 is a diagram showing the relationship between the content of silicone resin particles and the slipperiness and adhesion of an annealed coating.

Claims (3)

[Claims] 1. An inorganic composition comprising, as a basic component, at least one selected from a chromic acid compound and a phosphoric acid compound and an organic composition.
After the strain relief annealing, the organic mixed film contains 1 to 20% by weight of a spherical monodisperse fine particle silicone resin having an average particle size of 0.5 to 3.0 times the film thickness after drying. Non-oriented electrical steel sheet with an insulating coating with excellent seizure resistance and sliding properties. 2. An inorganic-organic mixed coating film comprising an inorganic colloidal composition and an organic composition as basic components, and having a film thickness of 0.
An insulating coating having excellent seizure resistance and slip resistance after strain relief annealing characterized by containing 1 to 20% by weight of a silicone resin of spherical monodisperse fine particles having an average particle diameter of 5 to 3.0 times. Non-oriented electrical steel sheet. 3. The method according to claim 1, wherein the thickness of the dried insulating film is 0.1%.
The non-oriented electrical steel sheet according to claim 1, wherein the thickness is within a range of from 3 μm to 3 μm.