JPH07230908A - Magnetic steel plate having insulating film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a magnetic steel plate having insulating films more excellent in adhesion, and its manufacturing method capable of making exfoliation more difficult to occur at the time of processing, compared to a former magnetic steel plate having insulating films composed of inorganic-organic substance mixed films (chromic acid organic substance mixed films). CONSTITUTION:A processing solution made by adding an organic reducing agent, organic reducing agent, organic resin emulsion, and wax having a softening point of 50 deg.C or higher to an inorganic aqueous solution containing a chromate and/or a bichromate, is applied to a magnetic steel plate having insulating films composed of chromic acid organic resin and wax mixed films containing 10-50wt.% of organic resin and 5-20wt.% of wax of a softening point of 50'C or higher; the total amount of both is less than 60wt.%. After that, baking is performed to form insulating films on the surfaces of the steel plate.

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 a method for producing the same, and more particularly, an electrical steel sheet having an insulating coating on the surface that is difficult to peel off during processing and has excellent adhesion, and a method for producing the same. Regarding

[0002]

2. Description of the Related Art Magnetic steel sheets used for iron cores of motors, transformers, etc. of household electric appliances are usually coated with an insulating film in order to reduce eddy current loss. That is, as these magnetic steel sheets for iron cores, magnetic steel sheets having an insulating coating on the surface are used.

This electromagnetic steel sheet is assembled into an iron core by the following steps. First, an electromagnetic steel sheet is slit to a predetermined width with a slit line, punched into a predetermined shape, then subjected to strain relief annealing, a plurality of sheets are laminated, and end faces thereof are TIG-welded to be assembled into an iron core. The strain relief annealing may not be performed in some cases.

In such an electrical steel sheet, the insulating coating on the surface thereof is excellent in electrical insulation, adhesion, corrosion resistance, punching resistance, heat resistance, refrigerant resistance (stability of insulating coating against refrigerant such as CFC), etc. Is required.

Conventionally, as a method for producing an electromagnetic steel sheet having an insulating film, an inorganic aqueous solution containing a chromate or / and a phosphate is applied to a steel plate and then baked to form an insulating film on the surface of the steel plate. A method of forming (hereinafter referred to as an inorganic film forming method) or an inorganic aqueous solution containing a chromate (chromate and / or dichromate) to which an organic reducing agent and an organic resin emulsion are added and contained. A method of forming an insulating film on the surface of the steel sheet by applying the treatment liquid to the steel sheet and then baking it (hereinafter referred to as an inorganic / organic mixed film forming method) is adopted. Here, the former inorganic film forming method yields a magnetic steel sheet having an insulating film made of an inorganic film, and the latter inorganic / organic mixed film forming method provides an inorganic / organic mixed film (that is, a chromic acid organic mixed film). An electrical steel sheet having an insulating coating of

Among these conventional magnetic steel sheets, the magnetic steel sheet having an insulating coating made of an inorganic coating has a drawback that it is inferior in punchability and corrosion resistance. An improved version of this is inorganic
This is a magnetic steel sheet having an insulating film made of an organic mixed film (chromic acid-based organic mixed film), and this electromagnetic steel plate is widely used.

[0007]

However, in electromagnetic steel sheets having an insulating coating composed of the conventional inorganic / organic mixed coating (chromic acid-based organic mixed coating), the adhesion of the insulating coating is often inferior to the iron core. The following problems often occur during the assembly process to

That is, when the electromagnetic steel sheet is slit to a predetermined width by a slit line, the surface of the insulating film is rubbed by the stabilizer and a part of the insulating film is easily peeled off. This peeling of the insulating coating deteriorates the quality of the electromagnetic steel sheet itself, and the peeled coating (powder) adheres to the tension roll, tension pad, etc. and accumulates,
As a result, it causes a trouble that the operation of the slit line is forced to be stopped.

Also, when punching a slit coil of an electromagnetic steel sheet into a motor core or the like with a continuous punching press, the surface of the insulating film is rubbed by a coil guide or the like and a part of the insulating film is peeled off, and the pinch roll and punching are performed. The release coating powder adheres to the mold, causing troubles such as operation stop, and further, the release coating powder adheres to the punched core, resulting in a decrease in space factor.

The present invention has been made in view of such circumstances, and its purpose is to solve the above problems.
Compared with the conventional electromagnetic steel sheet having an insulating coating composed of an inorganic / organic mixed coating (chromic acid-based organic mixed coating), a magnetic steel sheet having an insulating coating having excellent adhesion, which is less likely to be peeled off during processing, and a manufacturing method thereof are provided. It is the one we are trying to provide.

[0011]

In order to achieve the above object, the present invention provides an electromagnetic steel sheet having an insulating film having the following construction and a method for producing the same. That is, the electromagnetic steel sheet having the insulating film according to claim 1 is made of an organic resin and a softening point of 50.
A magnetic steel sheet having an insulating coating consisting of a chromic acid-based organic resin containing a wax of ℃ or more and a wax mixed coating, wherein the content of the organic resin in the coating is 10 to 50 wt.
%, The wax content is 5 to 20 wt%, and the total content of the organic resin and the wax is 60 wt% or less.

According to a second aspect of the present invention, there is provided a method for producing an electromagnetic steel sheet having an insulating film, wherein an organic reducing agent, an organic resin emulsion and a softening point of 50 ° C. or higher are added to an inorganic aqueous solution containing chromate and / or dichromate. A method of manufacturing an electromagnetic steel sheet, wherein a treatment liquid containing a wax is applied to a steel sheet and then baked to form an insulating film on the surface of the steel sheet, wherein the amount of the organic reducing agent added to the inorganic aqueous solution. Is 10 per 100 parts by weight of CrO ₃ equivalent of chromium in the inorganic aqueous solution.
-40 parts by weight, the amount of organic resin emulsion added is adjusted to 10 to 50 wt% in terms of the amount of organic resin in the insulating film, and the amount of wax is adjusted to 5 to 20 wt% in terms of the amount of wax in the insulating film. In addition, the present invention is a method for producing an electromagnetic steel sheet having an insulating film, wherein the sum of the amount of organic resin and the amount of wax in the insulating film is adjusted to 60 wt% or less.

An electrical steel sheet having an insulating coating according to a third aspect is an electrical steel sheet having an insulating coating according to the first aspect, wherein the amount of the insulating coating is 0.5 to 5 g / m ² per side.

[0014]

The present invention aims to solve the problems (defective adhesion of the coating) in the electrical steel sheet having the insulating coating composed of the inorganic / organic mixed coating obtained by the conventional method for forming the mixed inorganic / organic coating. As a result, by adding a wax having a softening point of 50 ° C or higher to the conventional inorganic / organic mixed film,
It was completed based on the knowledge that the adhesion of the coating is improved.

That is, a conventional inorganic / organic mixed coating (chromic acid-based organic mixed coating) is coated with 10 wt.
%, The adhesiveness of the film is improved. At this time, the content of the wax is 50 wt% or less and the content of the organic resin is 10 to 50 wt%, and at the same time, the content of the organic resin and the wax is It was found that when the total amount is 60 wt% or less, the adhesiveness of the coating can be improved without impairing the excellent properties (punching property, etc.) originally possessed by the conventional inorganic / organic mixed coating.

The chromic acid-based organic mixed film containing the wax (chromic acid-based organic resin and wax mixed film) is prepared by adding an organic reducing agent to an inorganic aqueous solution containing chromate or / and dichromate. It was found that the organic resin emulsion and the wax having a softening point of 50 ° C. or higher were added to the coating composition in an amount adjusted to the above film composition, and the coating solution was applied to a steel sheet and then baked. .

Therefore, the electrical steel sheet having an insulating coating according to the present invention is an electrical steel sheet having an insulating coating composed of a chromic acid type organic resin containing an organic resin and a wax having a softening point of 50 ° C. or higher and a wax mixed coating. An electromagnetic coating having an organic resin content of 10 to 50 wt% and a wax content of 5 to 20 wt% and a total content of the organic resin and wax of 60 wt% or less. It is a steel plate. Therefore, the adhesion of the film is improved without impairing the excellent characteristics (punching property, etc.) originally possessed by the conventional inorganic / organic mixed film (chromic acid-based organic mixed film). Compared to magnetic steel sheets that have an insulating coating made of coating, the coating has excellent adhesion and does not easily peel during processing.

The wax contained in the coating has a softening point of 50 ° C. or higher because a wax having a softening point of less than 50 ° C. cannot improve the adhesion of the coating. For example, as shown in FIG. 1 (a diagram showing the relationship between the softening point of wax and the adhesiveness of the film), when the softening point of the wax is less than 50 ° C., the adhesiveness of the film is poor, but when it is 50 ° C. or more, The film has excellent adhesion, and this figure also shows a softening point of 50.
It indicates that the wax must be at or above ℃.
Also, the content in the coating is 5 to 20 wt% is 5
This is because if it is less than wt%, the adhesion of the coating cannot be improved, and if it exceeds 20 wt%, the corrosion resistance of the coating deteriorates. The softening point of the wax is preferably 60 to 145 ° C. in order to further improve the adhesion of the film, and the wax content in the film is 5 to 18 to maintain good corrosion resistance.
It is desirable to set wt%.

The content of the organic resin in the film is 10 to 50 wt%
If it is less than 10 wt%, continuous punching property deteriorates, and if it exceeds 50 wt%, strain relief annealing (process after punching).
This is because the adhesion of the film afterwards deteriorates. Further, in order to further maintain good adhesion and weldability of the coating, it is desirable that the content be 10 to 40 wt%.

The total content of organic resin and wax is 60
The reason why the content is less than wt% is that if the content exceeds 60 wt%, the adhesion of the film after strain relief annealing deteriorates. Incidentally, in order to maintain a further good weldability, it is desirable to set it to less than 50 wt%.

The reason why the adhesion of the coating is improved by including the wax having a softening point of 50 ° C. or higher as described above is not clear, but the insulating coating on the surface of the electromagnetic steel sheet was rubbed against the slit line stabilizer. It is considered that the peeling of the film is sometimes reduced by the lubricating action of the wax.

On the other hand, the method for producing an electromagnetic steel sheet having an insulating film according to the present invention is a method in which an inorganic aqueous solution containing chromate or / and dichromate is added to an organic reducing agent, an organic resin emulsion and a softening point of 50 ° C. or higher. A method for producing an electromagnetic steel sheet, comprising applying a treatment liquid containing the wax of claim 1 to a steel sheet and then baking it to form an insulating coating on the surface of the steel sheet, which comprises adding an organic reducing agent to the inorganic aqueous solution. The amount of chromium is 100 parts by weight of CrO ₃ equivalent of chromium in the inorganic aqueous solution.
10 to 40 parts by weight, the amount of organic resin emulsion added is adjusted to 10 to 50 wt% in terms of the amount of organic resin in the insulating film, and the amount of wax added is adjusted to 5 to 20 wt% in terms of the amount of wax in the insulating film. In addition, the total amount of the organic resin equivalent and the wax equivalent in the insulating film is adjusted to 60 wt% or less.

This method has a softening point of 50.degree.
In addition to adding and containing the above wax, the addition amount thereof is set to the above wax amount conversion amount: 5 to 20 wt% and the total of the organic resin amount conversion amount and the wax amount conversion amount: 60 wt% or less. Different from the conventional inorganic / organic mixed film forming method. Due to this, the conventional inorganic
In the case of the organic mixed film forming method, a chromic acid-based organic mixed film is formed, whereas in the method for producing an electromagnetic steel sheet having an insulating film according to the present invention, an organic resin and a wax having a softening point of 50 ° C. or higher are contained. A chromic acid organic resin and wax mixed film is formed, and the wax content in the film is 5 to 5.
20 wt%, the content of the organic resin is 10 to 50 wt%, and the total content of the organic resin and the wax is 60 wt% or less. Therefore,
It is possible to obtain an electromagnetic steel sheet having an insulating film according to the present invention, that is, an electromagnetic steel sheet having an insulating film that is hard to peel off during processing and has excellent adhesion.

Here, the wax to be contained in the treatment liquid is a wax having a softening point of 50 ° C. or higher, and the content thereof is adjusted to 5 to 20 wt% in terms of the amount of wax in the insulating film. , 5 to 20 wt% wax with a softening point of 50 ° C or higher is added to the formed chromic acid organic resin and wax mixed film
This is because it is included.

The amount of the organic resin emulsion added is 10 to 50 wt% in terms of the amount of the organic resin in the insulating film.
This is because the content of the organic resin in the film is 10 to 50 wt%. The total amount of the organic resin equivalent amount and the wax equivalent amount in the coating is set to 60 wt% or less because the total content of the organic resin and the wax in the coating is 60 wt% or less.

The amount of the organic reducing agent added to the inorganic aqueous solution is 10 to 40 parts by weight with respect to 100 parts by weight of CrO ₃ equivalent of the amount of chromium in the inorganic aqueous solution. The reduction of hexavalent chromium in the treatment liquid becomes insufficient, and the water resistance of the resulting insulation film deteriorates. If it exceeds 40 parts by weight, the reduction of hexavalent chromium in the treatment liquid proceeds too much and the treatment liquid Is unstable, part of the treatment liquid is separated, and the performance of the film is deteriorated, so that the treatment liquid is frequently renewed and the productivity is lowered.

The dichromate is sodium,
Salts of potassium, calcium, magnesium, zinc and the like can be used. As the chromate, salts such as sodium, potassium, calcium, magnesium and zinc can be used. Further, a mixture of chromic anhydride and an oxide or hydroxide of magnesium, calcium, zinc or the like can be used as a chromate source.

In addition to dichromate and chromate, the above-mentioned inorganic aqueous solution may contain oxides such as boric acid, silicic acid, and aluminum oxide, if necessary, in order to improve the insulation properties of the insulating film. Can be included.

As the organic reducing agent, glycerin, polyethylene glycol and the like can be preferably used. Examples of the organic resin include acrylic resin, acrylic-styrene copolymer resin, epoxy resin, phenol resin, vinyl acetate resin, polyurethane resin, polyester resin and the like.

The wax having a softening point of 50 ° C. or higher includes
Among natural waxes, petroleum waxes, and synthetic waxes, waxes having a softening point of 50 ° C. or higher can be mentioned. Of these, petroleum wax and synthetic wax are preferable from the viewpoint of stability of the treatment liquid.

The treatment liquid can be applied to the steel sheet using a roll coater or the like. When baking after application,
When the temperature of the steel sheet exceeds 350 ° C, the wax tends to undergo thermal decomposition and the adhesion of the coating tends to decrease. Therefore, it is desirable to keep the temperature of the steel sheet at 350 ° C or less, and to maintain good adhesion of the coating. Therefore, it is preferable to set the temperature to 250 to 330 ° C.

The thickness (adhesion amount) of the insulating film is 0.5 to
It is desirable to set it to 5 g / m ² . If it is less than 0.5 g / m ² , the punching property and corrosion resistance tend to decrease, and if it exceeds 5 g / m ² , the space factor and weldability tend to decrease. From this point of view, it is more desirable that the amount is 0.7 to 4 g / m ² . In order to maintain good film adhesion, 0.5 to
It is desirable to set it to 3 g / m ² .

[0033]

EXAMPLE First, an organic reducing agent, an organic resin emulsion and a wax were added to an inorganic aqueous solution containing magnesium dichromate (a kind of dichromate): 150 g / l and boric acid: 30 g / l. A treatment liquid was prepared (prepared). here,
Glycerin was used as the organic reducing agent. As the organic resin emulsion, a mixed emulsion of polyester resin: 20 parts and acrylic-styrene resin: 80 parts was used. Paraffin wax (softening point 37
C., wax a) in Table 1, microwax (softening point 77.degree. C., wax b in Table 1), polyethylene wax (softening point 128.degree. C., wax c in Table 1) were used. Further, the addition amounts of these were changed as shown in Table 1. That is, the addition amount of the organic reducing agent is 15 to 25 parts by weight with respect to 100 parts by weight of the CrO ₃ equivalent amount of chromium in the inorganic aqueous solution, and the addition amount of the organic resin emulsion is the amount of the organic resin in the insulating film. The converted amount was 2 to 45 wt%, and the wax addition amount was changed to be 2 to 30 wt% in terms of the wax amount in the insulating film. In addition, the total amount of organic resin equivalent and wax equivalent in this insulating film is a part (No. 5 of Comparative Example)
Except for, the content was set to 60 wt% or less.

Next, the above treatment liquid was applied to a magnetic steel sheet (corresponding to JIS 50A1000) having a plate thickness of 0.5 mm by using a grooved roll so that the coating amount after drying was 1.3 to 1.5 g / m ² . rear,
Furnace temperature: An insulating film was formed on the surface of the electrical steel sheet by baking at 330 ° C for 60 seconds. The maximum plate temperature during baking is
It was 290 ° C.

With respect to the electrical steel sheet having an insulating film produced in this manner, test pieces were sampled therefrom, and a film adhesion test, a punching test, a corrosion resistance test, and a film adhesion test after stress relief annealing were carried out as follows. I went to. That is, the film adhesion test is performed by pulling out the test piece 1 while pressing the wood piece 2 of 20 mm × 20 mm with a load of 120 kg from both sides of the test piece 1 as shown in FIG. The peeling condition of the insulating film on the surface was investigated. The punching test was carried out by punching a 10 mm square blank using an SKD-11 mold, and evaluation was made by the number of blanks until the blank burrow height reached 50 μm. The corrosion resistance test was carried out by a salt spray test in which salt water was sprayed continuously for 8 hours, and the rust generation area was investigated after spraying for 8 hours. Film adhesion test after stress relief annealing, after performing stress relief annealing of 750 ° C. × 2 hours in N ₂ to the test piece,
It is done by pressing the white paper strongly and rubbing the surface of the film.
The state of film peeling was investigated.

[0036]

[Table 1]

[0037]

[Table 2]

The test results are shown in Table 2. In Table 2, each mark indicates the following level. That is, in the column of film adhesion, ⊚ indicates that peeling was not observed, ◯ indicates that the amount of peeling was very small, Δ indicates that peeling was observed, and x indicates that significant peeling was observed. In the column of adhesion after strain relief annealing, ◯ indicates that almost no peeling was observed, Δ indicates that slight peeling was observed, and x indicates that significant peeling was observed. As can be seen from Table 2, in the samples according to the comparative examples, any one of the film adhesion, punching property, corrosion resistance, and film adhesion after strain relief annealing is not good and insufficient. The film according to the example has good film adhesion, punching property, corrosion resistance, and film adhesion after stress relief annealing, and is superior to the film according to the comparative example.

[0039]

The electrical steel sheet having an insulating coating according to the present invention has excellent characteristics (punching property, etc.) originally possessed by an electrical steel sheet having an insulating coating of a conventional inorganic / organic mixed coating (chromic acid-based organic mixed coating). ), The problem of poor adhesion of the insulating film can be solved.
Compared to this conventional electrical steel sheet, the adhesion of the insulating film is superior, so it is possible to assemble to the iron core without causing troubles due to peeling of the insulating film during processing. This has the effect of eliminating troubles in the process.

According to the method of manufacturing an electrical steel sheet having an insulating coating according to the present invention, it is possible to obtain an electrical steel sheet having an insulating coating capable of eliminating troubles in the process of assembling the iron core as described above.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the softening temperature of wax and the adhesion of a film.

FIG. 2 is a side sectional view showing an outline of a film adhesion test method according to an example.

[Explanation of Codes] 1--Test piece, 2--Wood piece.

Claims (3)

[Claims] 1. A magnetic steel sheet having an insulating coating composed of a chromic acid-based organic resin containing an organic resin and a wax having a softening point of 50 ° C. or higher and a wax mixed coating, wherein the content of the organic resin in the coating is 10%. A magnetic steel sheet having an insulating coating, characterized in that the content of the wax is 5 to 20 wt% and the total content of the organic resin and the wax is 60 wt% or less. 2. A steel plate is coated with a treatment liquid containing an organic reducing agent, an organic resin emulsion and a wax having a softening point of 50 ° C. or higher added to an inorganic aqueous solution containing chromate and / or dichromate. After that, it is a method of manufacturing an electromagnetic steel sheet for forming an insulating film on the surface of a steel sheet by baking, wherein the amount of the organic reducing agent added to the inorganic aqueous solution is 100 in terms of CrO _{3 in the} amount of chromium in the inorganic aqueous solution. 10 parts by weight
-40 parts by weight, the amount of organic resin emulsion added is adjusted to 10 to 50 wt% in terms of the amount of organic resin in the insulating film, and the amount of wax is adjusted to 5 to 20 wt% in terms of the amount of wax in the insulating film. In addition, the method for producing an electromagnetic steel sheet having an insulating film, wherein the sum of the amount of organic resin and the amount of wax in the insulating film is adjusted to 60 wt% or less. 3. The amount of the insulating film is 0.5 to 5 g / side.
An electrical steel sheet having an insulating coating according to claim 1, wherein the electrical steel sheet is m ² .