JPS60190572A - Formation of insulator covering film superior in punchability and weldability on electrical steel sheet - Google Patents

Abstract

PURPOSE:To form an insulation coating film superior in punchability and weldability by coating a treating liquid in which a polyethylene resin powder suspension is combined with a mixed liquid of dichromate and organic resin emulsion to an electrical steel sheet, and baking said body under a specified condition. CONSTITUTION:Polyethylene powder resins having 5-80mum particle diameter are dispersed into water by using a surfactant. The suspension is combined with the mixed liquid of aqueous dichromate solution, organic resin emulsion of acryl- vinyl acetate, etc. and a reducing agent. The treating liquid is coated on the surface of the electrical steel sheet. In performing the baking successively, the temp. rising rate is controlled under the condition of 2-10 deg.C/s between 110- 150 deg.C steel sheet temp. The temp. is rised successively to finish the baking in 250-350 deg.C temp. range. By this method, insulation coating film superior in sticking property and satisfying both punchability and weldability can be formed on the electrical steel sheet.

Description

[Detailed Description of the Invention] Technical Field The technical content described in this specification regarding a method for forming an insulating coating on an electrical steel sheet with excellent punchability and weldability is to apply a dichromate-organic coating on the surface of an electrical steel sheet. When forming a resin-based film, improving the dispersibility and adhesion of the polyethylene powder resin that is blended to maintain the surface roughness of the film in an appropriate state improves the punchability of the film as well as the bathing properties. It is related to improving communication skills.

Conventional technology and its problems The properties required for the insulation coating of electrical steel sheets include electrical insulation, adhesion, punchability, weldability, heat resistance, and chemical resistance. Numerous studies have been conducted to satisfy these characteristics. Among these, it has been found that the punchability is significantly improved by the use of organic resins, and in particular, recently, a mixed solution of weight tetramate and organic resin has been treated and applied as a processing solution to the surface of electrical steel sheets. It has been found that by baking, the punching performance is improved to the extent that the number of punches is 80 to 50 times that of conventional inorganic coatings, and it is now widely put into practical use.

However, when an insulating film containing such an organic resin is laminated with iron core plates after punching and the end faces are TIG welded, the organic matter decomposes due to welding heat and generates gas, and this generated gas causes a speed increase. The problem was that blowholes formed in the parts, significantly deteriorating weldability.

Therefore, as a result of repeated research in order to simultaneously satisfy both punchability and weldability, which were considered to be contradictory properties in insulating coatings containing organic resins, we have developed a material that satisfies these requirements. As 1, Special Public Service 1977-1907
In Publication No. 8, blowing at the bead portion is prevented by imparting a surface roughness of 2 μH or more to the insulating coating and forming a gas passage gap through which gas generated by welding during stacking is easily dissipated from the periphery of the welded portion. An electromagnetic drawing board that avoids the occurrence of holes has been proposed.

By the way, the above-mentioned publication discloses a method of blending organic particles with a particle size of approximately 2 μm or more into the treatment liquid as a method for imparting surface roughness to the insulating plate film, but simply adding organic particles does not work. However, there were problems in that the dispersibility in the treatment liquid and the adhesion to mJfj- were not sufficient.

In order to further solve this problem, an attempt was made to improve the dispersibility of the emulsion resin solution by adding organic resin particles to the emulsion resin solution in advance.

A method for forming an edge coating was proposed in Japanese Patent Publication No. 55-21111.

However, in the above method, stirring is necessary in order to add organic resin particles into the emulsion resin solution, but if stirring is too strong, the emulsion resin will be destroyed and the resin will aggregate, resulting in a poor dispersion. On the other hand, weak stirring can produce a good dispersion without destroying the emulsion fat (t4), but it takes a long time to achieve uniform dispersion, which is uneconomical, and the handling of the resin powder is complicated. , leaving problems in the rough spots.

In addition, in the above method, after applying a treatment solution made from 214 to the surface of an electrical steel sheet, a treatment solution made from 400 to 70
Baking at a temperature in the range of 0°C melts some of the organic resin particles and improves the adhesion to the steel plate.
In , a protrusion arises from the center of the particle, and the kujiku V-ko sometimes forms an outer rim like a volcanic crater, but the strength of such a protrusion (outer rim) is very weak.
There was also a problem in that part of the material was easily peeled off due to tightening with the tension buttner during slitting.

Furthermore, when punching a material that is prone to film peeling, the peeling powder may stick to the punching die and cause the metal to seize, and in severe cases, the die may be damaged. There was also the risk of inviting

Purpose of the Invention The present invention advantageously solves the above-mentioned problems.In forming an insulating coating of dichromate-organic resin yarn, G is added to adjust the surface roughness of the coating. By making it easier to uniformly disperse the organic resin particles in the processing solution and also improving the adhesion of the film,
The purpose of the present invention is to propose a method for forming an insulating coating on an electrical steel sheet that has excellent not only punchability but also weldability.

Components of the Invention In other words, this invention uses a dichromate aqueous solution, an organic resin emulsion, and a reducing agent as a treatment liquid when forming an insulating film of dichromate-organic resin threads on the surface of an electromagnetic board. A suspension is used in which polyethylene powder resin with a particle size of 5 to 80 μm is predispersed in water using a surfactant, and then mixed with a mixed solution of A4 electromagnetic plate. After coating the surface, when the temperature of the steel plate is from 110°C to 150°C, the heating rate is 2 to 1.
Raise the temperature under the condition of 0°C/S, then 250-850°C
This patent is characterized in that baking is completed within a heating range of

In this invention, the surface roughness of the insulating film obtained is as follows:
The centerline average roughness Ra is preferably about 0.4 to 1.5 μm.

This invention will be explained in detail below.

First, regarding the treatment solution for forming the insulating film,
;To clarify.

The particle size of the polyethylene powder resin used in this invention needs to be in the range of 5 to 80 μm. This is because if the particle size is less than 5 μm,
For coating and baking, it is difficult to maintain surface roughness Ra: m6 of 0.4 μm or more after treatment, making it difficult to obtain good weldability.On the other hand, when the particle size exceeds 80 μm, coating and baking become difficult to maintain surface roughness Ra: 0.4 μm or more. This is because not only does the space factor exceed 1.5 μm, resulting in a decrease in the space factor, but also the coating uniformity deteriorates.

Next, the polyethylene powder W resin having a particle size of 5 to 80 μm is made into an aqueous dispersion using a surfactant, and then added to the mixture of dichromate and organic resin emulsion. Toi.

The surface of the powdered resin is coated with an activator, allowing it to be easily incorporated into a mixture with dichromate and a resin emulsion. This is because the dispersibility of the powder resin is improved.

Next, as the dichromate aqueous solution, any one selected from divalent metals such as zn, ca, and Mg.
A glaze or an aqueous solution of chromic acid containing 2 or more chromic acid or anhydrous tetramic acid 1... is advantageously suitable, and such an aqueous solution is suitable for oxidation of divalent metals such as those mentioned above,
It can be obtained by dissolving the hydroxide or carbonate in an aqueous solution of chromic anhydride.

The organic resin emulsion is preferably a single or copolymer of two or more of acrylic, vinylstyrene acetate, beoba, and ethylene, which are stably compatible with dichromium 1 and the acidic side of an aqueous solution. be. Further, as reducing agents for chromium, polyhydric alcohols such as ethylene glycol, glycerin and sucrose are particularly advantageously suited.

Next, the preferred amounts of each of these components to be added are as follows.

First, the organic resin solid content including the 4af uJ fat emulsion and the polyethylene powder resin, and C is 5 parts by weight relative to 100 parts by weight of C1r08 in the dichromate aqueous solution.
It is preferable to set it to about 150 to 150 bt r'jls.

This is because if the resin solid content is less than 5 parts by weight, sufficient punchability cannot be obtained, whereas if it is more than 150 parts by weight, heat resistance deteriorates. The proportion of polyethylene powder resin in the total organic resin solid content is lθ~60
% is preferable. If it is less than 10%, good weldability cannot be obtained because it is difficult to secure an Ra of 0.4 μm or more because of the roughness of the surface of the film after the rupture, while if it exceeds 60%, the roughness of the film surface becomes rough. This is because the thickness exceeds 1.5 μm and the space factor deteriorates.

Next, regarding the amount of polyhydric alcohol added as a chromium reducing agent, cro, z o in the weight tetramate aqueous solution
It is preferably about 10 to 60 parts by weight based on parts of fflDt. If it is less than 10 parts by weight, the water resistance of the ruptured membrane will deteriorate, while if it is more than 60 parts by weight, a reduction reaction will proceed in the treatment liquid, resulting in the disadvantage that the treatment liquid will gel.

In the present invention, in addition to the above-mentioned components, boric acid may be added to further improve the heat resistance of the coating. In this case, (the composition of cholic acid 1'IF is 0r081
It is more effective to set the range of 20 to 45 weight jF<tsi5 for 00 weight parts.

Next, a treatment liquid having the above-mentioned mixing ratio is uniformly applied to the surface of the electrical steel sheet, and any conventionally known method such as a roll coater method or a dipping method can be used for this application method. be able to.

The electromagnetic steel sheet that has been uniformly coated with the treatment solution is then subjected to baking, which is done in the temperature range near the softening point of the polyethylene powder (approximately 120°C), that is, the temperature of the steel sheet. Board temperature from 110°C to 150°C
It is important to control the temperature increase rate to 2 to 10°C/S.

When the temperature increase rate exceeds 10°C/S, bumping occurs from the center of the polyethylene powder resin, and the adhered particles form an outer ring like a volcanic crater, which is then tightened with a tension butt during slitting. This is because there is a great possibility that the chicks will peel off, and on the other hand, if the temperature is less than 2°C/S, it will take a long time and is not economical.

Then, by raising the temperature and completing the baking at a temperature range of 250 to 850°C, the desired good insulation coating is formed. 8 Baking is completed at a temperature of 250°C. If the temperature is lower than 350°C, the corrosion resistance will deteriorate because the film remains hygroscopic, while if it exceeds 350°C, the adhesion will deteriorate, so the baking completion temperature needs to be in the range of 250 to 350°C.

In addition, the amount of film deposited on the baked glass is -0'4'/m''
If the length is shorter or shorter, it is difficult to obtain good punching properties, while 69/m
Since the adhesion of the film deteriorates if the amount is more than 1.0, the adhesion of the film is preferably about 0.4 to 6 l/m2.

Example [Example 1] After coating the surface of an O, A% Si-containing electrical steel sheet with a plate thickness of 0.5 mm and a plate width of 98 om with a rubber roll, a baking process was performed. , the board temperature was 110
The temperature was increased from 150°C to 150°C at a heating rate of 5°C/sec, and then baked until the plate temperature reached 800°C, and the amount of film deposited on the surface of the steel plate was 8.5°C. 89/m
2 coatings were formed.

[Processing liquid A]

Add the dispersion of (2) to the mixture of (2).

The cross-sectional shape of the obtained coating has convex portions as shown in Fig. 1, and its surface roughness Ha is 0.77μ.
It was m.

In the figure, number 1 is the base metal, 2 is the coating, and 8 is the Al foil for surface protection.

The obtained electrical steel sheet with an insulating coating was slit into a width of 1 mm using a slitter line. During the slitting process, there was no peeling of the coating due to the tension pad, and the adhesion was good.

Next, this material was continuously punched at a punching speed of aOO times/minute using a punching die of 5 kD-1 and a punching force J1 of light oil. The burr diameter after punching 1 million times was 42 μm.

Then, after laminating the punched materials, an electrode of 2.4 m
When TIG welding was carried out under the conditions of myl Th -W+IT flow of 120 A, argon flow rate of 61/min, and clamping pressure of 100 kg/ci, no blowholes were observed even at a welding speed of 120 cm/min. There wasn't.

Other film characteristics were as shown in Table 1.

, [Comparative Example 1] Treatment liquid A was applied in the same manner as in Example 1, and during the baking process, the plate temperature was 13° between 110°C and 150°C.
The temperature was raised at a temperature increase rate of C/sec, and the steel plate was baked until the temperature reached 300°C, and a film was attached to the surface of the steel plate.
A coating of 4 x 7 m was formed.

The cross-sectional shape of the obtained coating was as shown in FIG. 2, and had a outer ring shape similar to a volcanic crater. Moreover, the surface roughness Ra was 0.14 μm.

This material was slit 1□ to a 9i width on a slitter line, but peeling of the film was observed at the tension pad portion.

Then, the punching property was examined in the same manner as in Example 1, but when the die was punched 580,000 times, the die was cut, so the punching was stopped. The cause of the chipping is thought to be the peeling of the film and the seizure of the mold by □1 force.

Furthermore, when T'IG welding was performed in the same manner as in Example 1, no plowholes were observed even at high speed welding of 120 cm/min.

The results of investigating other film properties are also listed in Table 1.

[Comparative Example 2] Treatment liquid B consisting of the following components was applied and baked in the same manner as in Example 1 to form a broken insulation film on the surface of an electrical steel sheet.

Baking occurred after membrane rupture adhesion +i (was 3.79/m2, and surface roughness Ha was 0.16 μm. No peeling was observed.

Next, under the same conditions as in Example 1, punchability and weldability were examined. The burr height after punching 1 million times was 42 μm, and the punching performance was good. Regarding weldability, blowholes occurred even at a welding speed of 20 Crn/min, and it was found that the weldability was extremely poor.

Other coating properties are as shown in Table 1.

[Example 2] Plate thickness: Q, 5 M, plate width H94Qsm, 3. gq
After coating the surface of a y Si-containing 1 (L magnetic i plate with a treatment liquid C all-rubber roll consisting of the following components, the plate temperature was heated between 110' and 150°C at 8°C/8°C during the baking process.
The temperature was raised at a temperature increase rate of 2 seconds, and the steel plate was baked until the temperature reached 310°C.
2 coatings were formed.

[Processing liquid C]

Add the dispersion (2) to the mixture (H).

The surface roughness Ra of the rolled coating was 1.21 μm.

・This was 450 m with a slitter.
It was a good J゛.

Next, this material was punched with a continuous punching machine until a 50 μm force) burr was generated, resulting in approximately 600,000 Jl ("r). Then, after lamination, T welding was performed, and the result was 120C
Even during high-speed welding of rnZ, there was no blowhole G1-4 and the weldability was good. Furthermore, the insulation resistance was measured using JIS method 2.
Excellent insulation strength of 0Ω-cJ/sheet;

[Comparative Example 8] A treatment liquid consisting of the following components was applied to the surface of an electromagnetic steel sheet in four areas as in Examples 2 and 1, and baked to form an insulating coating on the surface of the sheet.

[Processing liquid D]

Add the dispersion of I to the mixture of (2).

The coating weight after baking was 5.117/m 2 and the surface roughness Ra was 1.62 μm. When this coating material was slit into 460 mm widths using a slitter line, some of the particles adhering to the tension pad part were peeled off.

Furthermore, the space factor was 95.8%, which was inferior to the examples of the present invention.

Effects of the Invention Thus, according to the present invention, when forming a romate-based resin coating on the surface of an electrical steel sheet, the uniform dispersion of the polyethylene powder resin in the treatment solution is improved. Therefore, it is possible to simultaneously satisfy both punchability and weldability, which have conventionally been considered contradictory properties in such an insulating coating.

[Brief explanation of drawings]

FIG. 1 is a sketch diagram of a cross-sectional structure of an electrical steel sheet with an insulating coating obtained according to the present invention, and FIG. 2 is a sketch diagram of a cross-sectional structure of an electrical steel sheet with an insulating coating obtained by a conventional method. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] t. When forming a dichromate-organic resin-based insulating film on the surface of an electrical steel sheet, a treatment solution consisting of an FR chromate aqueous solution, an organic resin emulsion, and a reducing agent is used. A suspension of polyethylene powder resin with a particle size of 5 to 80 μm is dispersed in water using a surfactant and then mixed into the mixed solution, and this treatment solution is applied to the surface of the electromagnetic drawing board. After coating, the temperature of the steel plate was increased from 110℃ to 15℃.
Temperature increase rate up to 0°C: 2-b Continuing Electrical Ri1 with excellent punchability and weldability, characterized by completing baking in the temperature range of 250-850°C
A method of forming an insulating coating on a steel plate.