JP2000345360A - Silicon steel sheet with chromium-free insulation coating film, excellent in property after stress relief annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silicon steel sheet having an insulation coating film free from toxic compounds such as hexavalent chromium and has excellent corrosion resistance and sticking resistance even after stress relief annealing for recovering magnetic properties, and its manufacturing method. SOLUTION: The silicon steel sheet has an insulation coating film formed by applying a film composition containing inorganic colloid in an amount of 50-150 pts.wt. (as solid content) based on 100 pts.wt. (as solid content) of aqueous resin. The inorganic colloid contains a component (A) having a glass transition temperature not lower than stress relief annealing temperature and a component (B) having a glass transition temperature lower than stress relief annealing temperature, and the weight ratio of component (A)/component (B) is regulated to 2/8 to 8/2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical steel sheet having an insulating coating, and more particularly to an electrical steel sheet having an insulating coating containing no harmful compounds such as hexavalent chromium and having been subjected to strain relief annealing for recovery of magnetic properties. The present invention relates to an electrical steel sheet with an insulating coating having excellent corrosion resistance and sticking resistance.

[0002]

2. Description of the Related Art Insulating coatings on magnetic steel sheets used for motors, transformers, and the like are required to have various characteristics from the viewpoint of not only interlayer resistance but also convenience during working and storage.
Further, in order to improve the magnetic properties after the punching, 700 to
In many cases, the strain relief annealing is performed at about 850 ° C., and it may be necessary to withstand the strain relief annealing and exhibit required performance. In this way, electrical steel sheets are subjected to various processes or treatments, are placed in various storage environments, and are used for various applications. Is being done.

[0003] The insulating coating of this magnetic steel sheet emphasizes the weldability and heat resistance according to its role, aims at inorganic coating exhibiting the required characteristics withstanding strain relief annealing, and aiming at both punchability and weldability. It can be roughly classified into three types: semi-organic coatings containing resin and inorganic material that exhibit the required properties while resisting strain relief annealing, and organic coatings that cannot be strain relief annealed and are used for special applications. Among these, the coatings containing inorganic materials that can withstand the strain relief annealing and exhibit the required characteristics as general-purpose products. In particular, a chromate-based insulating film containing an organic resin is widely used because punching properties can be remarkably improved as compared with an inorganic-based insulating film by one-time application baking.

[0004] For example, Japanese Patent Publication No. 36476/1985 discloses that a dichromate aqueous solution containing at least one divalent metal is mixed with 100 parts by weight of CrO ₃ in the aqueous solution and vinyl acetate / vinyl acetate as an organic resin. The veova ratio is 90/10 to 40
/ 60 resin emulsion in the ratio of resin solids
To 120 parts by weight and a treatment solution containing an organic reducing agent in a proportion of 10 to 60 parts by weight is applied to the surface of the iron plate, and the insulating film is formed through a baking process by a conventional method. Is disclosed.

However, hexavalent chromium is highly toxic, so that there is a problem in that waste liquid treatment for detoxification is costly. On the other hand, an insulating coating containing no resin and an inorganic colloid as an insulating coating having good piercing properties without containing chromium has been proposed in JP-A-10-34812 and the like. There is a problem that the corrosion resistance after strain relief annealing is slightly inferior to the semi-organic coating.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electromagnetically-coated electromagnetic coating comprising chromium-free resin and inorganic colloid and having excellent corrosion resistance without impairing sticking resistance after strain relief annealing. It is to provide a steel plate.

[0007]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that an inorganic colloid containing a resin component and two or more components having different glass transition temperatures in a specific ratio. The present inventors have found that a magnetic steel sheet with an insulating coating having improved corrosion resistance can be obtained without impairing the sticking resistance after strain relief annealing by using an insulating coating containing.

That is, generally, the strain relief annealing is performed at 70
It is often performed at a temperature of about 0 to 850 ° C. At this time, if the glass transition temperature is equal to or higher than the annealing temperature for annealing, a part of the film is fused, but a complete film cannot be formed. On the other hand, those having a glass transition temperature lower than the strain relief annealing temperature are fused to form a denser film, but are easily fused to other steel sheets, so-called sticking is likely to occur. Therefore, inorganic colloids with different glass transition temperatures,
In particular, by using a mixture of colloidal silica,
It has been found that both properties of sticking resistance and corrosion resistance after strain relief annealing can be improved. Moreover,
It has been found that it is effective to include those having a glass transition temperature equal to or higher than the strain relief annealing temperature and those having a glass transition temperature lower than the strain relief annealing temperature at a specific ratio.

The present invention is based on this finding,
Component (A) having a glass transition temperature equal to or higher than the strain relief annealing temperature and component (B) having a temperature lower than the strain relief annealing temperature with respect to 00 parts by weight (solid content), and the weight ratio of component (A) / component (B) A magnetic steel sheet provided with an insulating coating, characterized by having an insulating coating formed by applying a coating composition containing 50 to 150 parts by weight (solid content) of an inorganic colloid having a ratio of 2/8 to 8/2. Is what you do.

Further, the present invention provides a method for obtaining the above-mentioned electrical steel sheet with an insulating coating, which comprises as a component (A) having a glass transition temperature equal to or higher than a strain relief annealing temperature with respect to 100 parts by weight (solid content) of an aqueous resin. Component (B) having a temperature lower than the strain relief annealing temperature, and the weight ratio of component (A) / component (B) is 2
An object of the present invention is to provide a method comprising a step of applying a coating composition containing 50 to 150 parts by weight (solid content) of an inorganic colloid of / 8 to 8/2 to the surface of an electromagnetic steel sheet to form an insulating coating. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electromagnetic steel sheet with an insulating coating according to the present invention (hereinafter referred to as "the steel sheet")
The “steel plate of the present invention” will be described in detail. The steel sheet of the present invention is an electromagnetic steel sheet having an insulating coating formed by applying a coating composition containing an aqueous resin and an inorganic colloid as essential components on the surface. The electromagnetic steel sheet as the material of the steel sheet of the present invention is not particularly limited. For example, a non-oriented electrical steel sheet, a grain-oriented electrical steel sheet, an amorphous foil, etc., which are used in the field utilizing electromagnetism, are particularly preferably applied to a non-oriented electrical steel sheet.

In the steel sheet of the present invention, the aqueous resin, which is a component of the coating composition applied to the electromagnetic steel sheet to form an insulating coating, is made of water in a water-soluble state, an emulsion state, a dispersion state, or the like. Any form may be used as long as it is dispersed. The resin component constituting the water-based resin is not particularly limited as long as it is used as a resin component of an insulating film of this type of electromagnetic steel sheet. For example, one or more resins selected from acrylic resin, alkyd resin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin, melamine resin, and the like can be suitably applied. These resin components play a large role as a coating component before the strain relief annealing, but disappear by thermal decomposition during the strain relief annealing.

When the aqueous resin is in an emulsion state, the particle size of the emulsion particles is 0.01 to 100 μm.
And preferably in the range of 0.1 to 10 μm.

The inorganic colloid, which is an essential component of the coating composition, is a colloid in which an inorganic substance is dispersed in water. The inorganic substance constituting the inorganic colloid is not particularly limited as long as the coating composition can be applied to a steel sheet to form an insulating coating, and the coating can be formed after annealing. Specific examples of the inorganic colloid include colloidal silica (silica gel), alumina sol,
Titanium oxide sol and the like can be mentioned. Among these, colloidal silica is desirable from the viewpoints of versatility, economy, and film properties (film forming properties during strain relief annealing, insulating properties, etc.).

In the present invention, the inorganic colloid comprises:
Component whose glass transition temperature is higher than the strain relief annealing temperature (A)
And a component (B) having a temperature lower than the strain relief annealing temperature. The inorganic colloid may contain one or more of each of the component (A) and the component (B). In the present invention, the strain relief annealing temperature refers to a strain relief annealing performed by a user after the steel sheet of the present invention having an insulating film formed on the surface is transferred to a user such as a motor or a transformer as a product, or transferred to a user. This refers to the temperature at the time of annealing applied to the steel sheet of the present invention in the strain relief annealing performed in advance before performing the annealing. Usually, the strain relief annealing temperature of the magnetic steel sheet is in the range of 750 to 850 ° C. Therefore, depending on the use of the steel sheet of the present invention, the strain relief annealing treatment to be performed, etc., by appropriately selected strain relief annealing temperature,
Components (A) and (B) may be selected. Further, the glass transition temperature of the colloidal silica can be adjusted by decreasing the alkali metal such as Na, Li, K or the like or by increasing the content.

In the inorganic colloid, the weight ratio of component (A) / component (B) is 2/8 to 8/2, preferably 3/7 to 7/3. When the weight ratio of the component (A) / the component (B) is less than 2/8, the steel sheets tend to stick to each other, and when it exceeds 8/2, the corrosion resistance deteriorates.

In the present invention, the content ratio of the aqueous resin and the inorganic colloid in the coating composition used for forming the insulating coating is such that the inorganic colloid is 50 to 150 parts by weight (solids) based on 100 parts by weight (solid content) of the aqueous resin. Min), preferably 75 to 125 parts by weight. If the amount of the inorganic colloid is less than 50 parts by weight with respect to 100 parts by weight of the aqueous resin, the amount of the inorganic component is reduced and the properties (corrosion resistance and anti-sticking) after annealing are deteriorated. There is a possibility that the amount of the components is reduced and the corrosion resistance of the product electromagnetic steel sheet and the adhesion of the coating film are deteriorated.

In the present invention, in order to further improve the performance of the insulating film, a rust preventive, a film forming aid,
Various additives such as a surfactant may be blended. In this case, in order to secure the performance after the strain relief annealing, the total amount of the inorganic substance with respect to 100 parts of the organic substance in the coating composition is 3 to
It is preferable to make the range of 300 parts.

[0019] In the steel sheet of the present invention, the adhesion amount of the insulating coating is preferably from 0.05-4 g / m ^2, it is particularly preferably 0.2 to 2 g / m ^2. If the adhesion amount is less than 0.05 g / m ² , the insulating coating becomes non-uniform and the base iron is exposed, so that the sticking resistance and the exposure to boiling steam are insufficient, and if the adhesion amount is more than 4 g / m ^2. ,
Coating properties are reduced, such as blistering during low-temperature drying.

In the steel sheet of the present invention, the insulating film is formed by mixing the aqueous resin, an inorganic colloid containing the components (A) and (B) at a specific ratio, and various additives to be added as required. The coating can be carried out by applying and baking the coating composition contained on the electromagnetic steel sheet. The method of applying the coating composition is not particularly limited, and various methods generally used industrially, such as a roll coater method, a flow coater, a spray coating, and a knife coater, can be applied. In addition, the method of baking is not particularly limited, and various methods such as a hot air method, an infrared method, an induction heating method and the like which are usually performed can be applied. The baking temperature is appropriately determined depending on the resin used, but is usually 100 to 3 times.
It is about 00 ° C.

The steel sheet of the present invention is preferably cleaned before coating and baking by a degreasing step, an acid step and the like.

[0022]

The present invention will be specifically described below based on examples and comparative examples.

(Examples 1 to 3 and Comparative Examples 1 and 2) In each example, an electric iron plate (electromagnetic steel plate) having a thickness of 0.5 mm was applied to Table 1.
A coating solution comprising the coating components shown in (1) was applied to form an insulating coating containing chromium-free aqueous resin and colloidal silica on both surfaces. The coating was performed by applying a coating solution with a roll coater, baking at a reaching plate temperature of 200 ° C., and then allowing to cool. The obtained electromagnetic steel sheet with an insulating coating was subjected to the following tests of sticking resistance and corrosion resistance after strain relief annealing. Table 1 shows the results.

Comparative Example 3 A magnetic steel sheet provided with a chromium-containing semi-organic coating mainly composed of a resin emulsion and magnesium dichromate was subjected to a test for sticking resistance and corrosion resistance after strain relief annealing. Table 1 shows the results.

[0025] Ten samples of 5 × 5 cm was cut out from the electromagnetic steel sheet with anti-sticking insulating film is laminated, under a load of 200g / cm _^2, N ²
Annealing was performed at 750 ° C. for 2 hours in an atmosphere. After cooling, a 500 g weight was dropped onto the upper surface of the laminated sample at different heights, and the falling height of the weight when the laminated sample was divided into five parts was defined as a sticking five division height. The lower the sticking five-part height, the better the sticking resistance.

Corrosion resistance after strain relief annealing A sample obtained by subjecting an electrical steel sheet with an insulating coating to strain relief annealing at 750 ° C. × 2 hours in an N ₂ atmosphere was heated at 50 ° C.
The corrosion test was performed by placing the sample in a constant temperature and humidity chamber of 80% RH. 7
After a day, the surface of the sample was visually inspected and the rust generation rate (7
Rust rate), and used as an index of corrosion resistance after strain removal.

[0027]

[Table 1]

As is evident from Table 1, all of the magnetic steel sheets provided with an insulating coating according to the present invention (Examples 1 to 3) have excellent sticking resistance in strain relief annealing and improved corrosion resistance after strain relief annealing. are doing.

[0029]

The electromagnetic steel sheet with the insulating coating of the present invention does not contain any harmful compounds such as hexavalent chromium, because the insulating coating contains a resin containing no chromium and colloidal silica, and has an anti-sticking property and distortion. It has excellent corrosion resistance after strip annealing.

Continued on the front page (72) Inventor Masaki Kono 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside Kawasaki Steel Research Institute (72) Inventor Atsuto Honda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel 4K026 AA03 BB05 CA39 CA41 DA02 EB11 4K033 PA04 TA03

Claims (4)

[Claims] (1) 100 parts by weight (solid content) of an aqueous resin,
Component (A) having a component (A) having a glass transition temperature equal to or higher than the strain relief annealing temperature and a component (B) having a glass transition temperature lower than the strain relief annealing temperature.
And having an insulating coating formed by applying a coating composition containing 50 to 150 parts by weight (solid content) of an inorganic colloid wherein the weight ratio of the component (B) is 2/8 to 8/2. Electrical steel sheet with insulating coating. 2. The strain relief annealing temperature is 700 to 850.
The electromagnetic steel sheet with an insulating coating according to claim 1, wherein the temperature is in the range of ° C. 3. The magnetic steel sheet with an insulating coating according to claim 1, wherein the inorganic colloid is colloidal silica. 4. An aqueous resin (100 parts by weight (solid content))
Component (A) having a component (A) having a glass transition temperature equal to or higher than the strain relief annealing temperature and a component (B) having a glass transition temperature lower than the strain relief annealing temperature.
A coating composition containing 50 to 150 parts by weight (solid content) of an inorganic colloid in which the weight ratio of / component (B) is 2/8 to 8/2 is applied to the surface of an electromagnetic steel sheet to form an insulating coating. A method for producing an electromagnetic steel sheet with an insulating coating having a process.