JPS5985872A - Electrical sheet having electrically insulating film generating no malodor during welding - Google Patents

Abstract

PURPOSE:To obtain an electrical sheet having an electrically insulating film generating no malodor during welding by coating a sheet with a treating liq. prepared by blending an aqueous soln. of dichromate contg. a bivalent metal with specified amounts of a specified vinyl acetate-veova resin emulsion and an org. reducing agent and by baking the treating liq. CONSTITUTION:A treating liq. is prepared by adding a vinyl acetate-veova resin emulsion having 90/10-40/60 ratio of vinyl acetate/veova and an org. reducing agent such as glycerol to an aqueous soln. of dichromate contg. >=1 kind of bivalent metal such as Ca, Mg or Zn. The amount of the emulsion to be added is 5-120pts.wt. per 100pts.wt. CrO3 in the aqueous soln. when expressed in terms of solid resin, and the amount of the reducing agent is 10-60pts.wt. The surface of an electrical sheet is uniformly coated with the treating liq., and the liq. is baked at about 300-700 deg.C for a short time in a drying furnace to form an electrically insulating film by 0.4-6g/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical steel plate having an electrically insulating coating, particularly an electrically insulating coating containing an organic resin, and is particularly intended to specifically prevent the occurrence of bad odors that have been a concern during lamination welding of this type of electrical steel plates. That is.

Insulating coatings on electrical steel plates are required to have a number of properties, including excellent punchability, weldability, adhesion, corrosion resistance, heat resistance, chemical resistance, and space factor in addition to electrical insulation. That is required.

For this reason, many improvements have been made and insulating coatings of various compositions have been developed in order to satisfy these requirements regarding performance.

Among these insulating coatings, it has been found that punchability in particular can be significantly improved by using organic resins, and recently chromate or dichromate (hereinafter simply referred to as dichromate-based) and organic resins have been found to be significantly improved. By using a treatment solution mixed with resin and applying it to an electric iron plate and baking it to form a film containing organic resin, it is 30 to 50
Insulating coatings containing organic resins are now widely used, and some have been developed that can improve punching performance by twice as much.

However, in the case of such an insulating coating containing an organic resin, when the core plate is laminated after being punched and the end faces are TIG welded, the organic resin component in the coating may thermally decompose or burn, producing a foul or irritating odor. This has often caused a problem in that it significantly deteriorates the working environment and causes discomfort to workers.

For example, Japanese Patent Laid-Open No. 50-122580 and Japanese Patent Laid-open No. 5
There is a method disclosed in Japanese Patent No. 8-79296. The former is vinyl acetate resin: 10 to 50 parts by weight, and lyryl resin: 20 to 8 parts per 100 parts by weight of chromic anhydride in the treatment solution.
A method of forming an insulating film using a treatment liquid containing 3 to 150 parts by weight of an emulsion resin with a ratio of 3 to 80 parts by weight of styrene resin: 7% by weight,
The latter is based on 100 parts by weight of chromic anhydride in the treatment solution.
Resin emulsion consisting of acrylic resin = 50 to 80% by weight, remainder vinyl acetate resin, total resin solid content: 5 to 80% by weight
This method uses a mixture of 120 parts by weight.

However, although the insulating coating obtained by the method described above has some improvement in odor during welding compared to conventional coatings, it still has problems that cannot be said to be sufficient.

That is, as a resin for a chromate-organic resin coating,
This is because when acrylic resins or styrene resins are used, they thermally decompose or burn during laminated welding of electric iron plates, causing the generation of their own strong and irritating odors. When resin was used, substances such as methyl methacrylate and butene were produced during welding, which gave off a bad odor.

When vinyl acetate resin is used as the blended resin, there is almost no odor during welding, but it also improves coating workability, stability over time of the processing solution, and chemical resistance of the resulting insulating coating. The disadvantage was that it deteriorated.

This invention was developed as a result of extensive research to advantageously solve the above problems, and is a resin made by copolymerizing vinyl acetate resin with Beoba resin as the resin for the dichromate-organic resin coating. This work is based on the new finding that by using an emulsion, it is possible to obtain an insulating coating that does not generate bad odors during lamination welding of electric iron plates and has excellent other properties.

That is, this invention provides a dichromate-based aqueous solution containing at least one type of divalent metal, with 0rO8:10 in the aqueous solution.
0 parts by weight of an organic resin, a resin emulsion with a hinyl acetate/veova ratio of 90/10 to 40/60 is mixed with 5 to 120 parts by weight of resin solids and 1 part of an organic reducing agent.
A treatment liquid mixed in a proportion of 0 to 60 parts by weight is applied to the surface of the base iron plate, and an insulating film containing an organic resin is formed on the surface of the base iron plate through a baking process using a conventional method. This is a means to solve the above-mentioned electricity charge, and the amount of coating applied is 0.4 per 1 m2 of surface area of base steel plate.
~6g is suitable.

Beoja resin, which is a component of the resin emulsion, is a vinyl ester of 8th class carboxylic acid, and easily forms a copolymer with vinyl acetate.

Further, as the base iron plate in this invention, any material commonly used as an electromagnetic material such as a soft iron plate or a silicon steel plate is suitable.

This invention will be specifically explained below.

The dichromate-based aqueous solution used in this invention is
A dichromate containing one or more divalent metals such as OalMg and Zn, or an aqueous solution prepared by adding a small amount of chromic anhydride to this dichromate. It can be obtained by dissolving a valent metal oxide, hydroxide or carbonate in an aqueous solution of total chromic anhydride.

Furthermore, as the organic resin to be blended into the above dichromate-based aqueous solution, vinyl acetate-based resin is most preferable from the viewpoint of odor during welding, but as mentioned above, the resulting film has poor chemical resistance. It had some disadvantages. In order to solve this drawback, they discovered through trial and error that copolymerization of Beoba resin would be effective. Moreover, they completed this invention by confirming that there was no bad odor during welding.

In the above copolymer, the blending ratio of Beoba resin is 1
If it is less than 0%, the effect of improving chemical resistance will not be recognized, and if the blending ratio of Manbeova resin exceeds 60%, the stability of the treatment solution over time will deteriorate when it is blended with a dichromate-based aqueous solution. The mixing ratio of vinyl acetate/Beova resin should be 90/10 to 4.
°/60.

Next, the blending amount of the vinyl acetate Rubeova resin emulsion in the dichromate-based aqueous solution is 5 to 120 parts by weight as resin solid content based on 100 parts by weight of 0rb8 in the dichromate-based aqueous solution. This is because if the resin solid content is less than 5 parts by weight, sufficient punchability cannot be obtained;
This is because if the amount exceeds 20 parts by weight, heat resistance will deteriorate.

Furthermore, in order to make the film insoluble, polyhydric alcohols such as glycerin, ethylene glycol, and sucrose are added as a chromium reducing agent. At this time, the amount of the organic reducing agent added is 10 to 60 parts by weight relative to 100 parts by weight of the dichromate-based aqueous solution. This is because if the amount of the reducing agent is less than 10 parts by weight, the water resistance of the film will deteriorate, while if it is more than 60 parts by weight, the reduction reaction will proceed in the processing solution, causing the processing solution to gel. This is because it occurs.

In addition, in order to further improve the heat resistance of the coating, boric acid can also be blended, and in this case, the blending amount of boric acid is 0r081
It is effective if the amount is within the range of 20-45 parts by weight relative to 00 parts by weight.

Further, in order to improve the interlayer insulation after strain relief annealing, a colloidal substance such as colloidal silica may be added.

After continuously and uniformly applying the treatment liquid having the above-mentioned mixing ratio to the surface of the electric iron plate using a roll coater, etc.,
By baking for a short time in a drying oven of 0.00" (l), a desired electrically insulating film of good quality can be formed.

At this time, the amount of coating after baking is 0.4 to 69yfn2
It is preferable to set it as approximately. No, 4g/m2
This is because if the amount of the coating is smaller, the effect of improving punching properties is poor, while if the amount is more than 6 g "III", the adhesion of the coating deteriorates.

Generally, when emphasis is placed on punchability, it is desirable to increase the amount of film deposited, and on the other hand, when emphasis is placed on weldability, it is desirable to decrease the amount of film deposited.

The insulating coating thus obtained not only does not emit bad odors during lamination welding, but also has other properties required for the coating, such as electrical insulation, heat resistance, adhesion, corrosion resistance, and chemical resistance. It has also been confirmed that the results are fully satisfactory.

Next, examples of the present invention will be described together with comparative examples.

Example 1 After coating the surface of an electric iron plate with a plate thickness Q of 5 mm with a treatment solution A' consisting of the following components, it was heated to 80°C in a hot air oven at 450°C.
An insulating film was formed on the surface of the iron plate by baking for a second. The amount of film deposited was 5 g/mg.

Coating workability and stability of treatment liquid over time (8) The properties were extremely good, and a uniform film was obtained.

The resulting electrical steel plates with insulating coating were then cut out into a predetermined shape, laminated, and TIG welded to assemble into an actual machine.

No bad odor was generated during this welding, and other properties of the coating were as shown in Table 1.

[Processing liquid A]

080% magnesium dichromate solution 180 parts by weight 0r08 minutes 32.5 parts by weight O Vinyl acetate/Beova resin emulsion (resin solid content: 50%) <Vinyl acetate/Beova=70/ao> 20 parts by weight 1
゛Part O ethylene glycol ] 0 weight -: Part Example 2 After coating the surface of an electric iron plate with a thickness of 0.5 mm with treatment liquid B consisting of the following components, it was baked for 80 seconds in a hot air oven at 450''C. Then, a film was formed with a film adhesion amount: s, x, !;'/m9.

At this time, the coating workability and the stability over time of the treatment liquid were good, and a uniform film was obtained.

When the obtained electrical steel plate with an insulating coating was then assembled into an actual machine in the same manner as in Example, no bad odor was generated during welding. Other film characteristics were as shown in Table].

[Processing liquid B]

030% calcium dichromate solution 180 parts by weight 0r08 minutes 80.5 parts by weight O Vinyl acetate Rubeova resin emulsion (resin solid content =
50%) 20 parts by weight <Vinyl acetate/Beover 50150>O ethylene glycol
10 li parts by weight boric acid
] 0 parts by weight Comparative Example 1 After coating the surface of an electric iron plate with a thickness of 0.5 mm with a treatment liquid C consisting of the following components whose organic resin components are different from those of this invention, the solution was heated in a hot air oven at 450"0 for 80 seconds. By baking, a coating of 777 m2 was formed.

Thereafter, it was assembled into an actual machine in the same manner as in Examples 1 and 2.

The coating workability and the stability of the treatment solution over time were good, and a uniform film was obtained, but the odor during laminated TIG welding was a strong pungent odor. The other coating properties were also listed in Table 1.

[Processing liquid C]

030% magnesium dichromate solution 130 parts by weight 0r08 min: 82.5" O Acrylic resin emulsion (resin solid content: 50%) 20 parts by weight O Ethylene glycol 10 parts by weight Comparative example 2 Electric iron plate with plate thickness o, 5 mm After applying a treatment solution In consisting of the following components, which does not contain Beoba resin, which is an essential component of this invention, to the surface of A film of /lT12 was formed. Thereafter, it was assembled into an actual machine in the same manner as in Example 1.2.

During the coating operation, the resin emulsion formed a film on the surface of the coating roll after about 5 hours, and a uniform film could not be obtained. Note that no foul odor was generated during laminated TIG welding. Other coating properties were as shown in Table 1.

[Processing liquid D]

630% magnesium dichromate solution 130 parts cro 8 minutes: 82.5 parts by weight O Vinyl acetate resin emulsion 80 parts by weight (
Resin solid content = 50%) O ethylene glycol l O parts by weight O
Boric acid 10 parts by weight (1
2) (14) β W ・・ ・・ ・・ ・・ ・・
As described above, the electric steel plate having the insulating coating according to the present invention can completely prevent the occurrence of bad odors during lamination welding, and also meet the requirements of the coating. etc.) There is no deterioration in characteristics at all.

Patent applicant: Kawasaki Steel Corporation 315-355-

Claims (1)

[Scope of Claims] 1. An electric iron plate having an electrically insulating coating on its surface, the coating being applied to a dichromate-based water bath solution containing at least one divalent metal at 0rb8 in the aqueous solution. : Vinyl acetate/Beopa ratio as organic resin per 100 parts by weight is 90/i
A resin emulsion with a ratio of o~40/60 is made of 5~120 parts by weight of resin solids and a total of 10~120 parts by weight of an organic reducing agent.
An electric insulating coating that does not generate a bad odor during welding, characterized in that a treatment liquid mixed at a ratio of 60 parts by weight is applied to the surface of the base iron plate, and the baking process is carried out by a conventional method. Iron plate. The amount of electrical insulation film deposited is 1 m per unit area of base steel plate.
The electric iron plate according to claim 1, having a weight of 90.4 to 6 g.