JPH0346186B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a method for producing an insulating coating on an electrical steel sheet, and in particular to a method for producing an organic insulating coating made of a water-soluble resin on an electrical steel sheet with excellent adhesion. be.

``Prior Art'' Generally, electromagnetic steel sheets used for the iron cores of motors and transformers for home appliances are continuously punched, laminated, and welded at the edges. In this punching process, if the adhesion of the insulating film is poor, problems such as peeling of the insulating film, seizing of the powder, shortening of the life of the die, and hindrance to work due to powder generation occur.

The insulating coating is applied after continuous annealing, and as shown in FIG. 3, the electrical steel sheet 2 that has been annealed through an annealing furnace 1 and a cooling zone 3 is sent to a pre-coating steel sheet cooling device 4 where it is heated to a predetermined temperature. After the temperature is reached, an insulating paint is applied using a coating roll.

The manufacturing process for electrical steel sheets that produced the above-mentioned insulating coating generally requires a long time from continuous annealing to application. Contact with various types of rolls may cause foreign matter to adhere or become dirty, resulting in poor adhesion.

In addition, the insulation coating of electrical steel sheets is a very thin coating in order to lower the space factor.
In order to apply a thin and uniform insulating coating to the surface of a steel plate, it is necessary to make the viscosity of the paint as low as possible and improve its spreadability on the surface of the steel plate.

However, if it takes a long time to apply, the temperature of the steel plate will drop to room temperature, and some paints may lack leveling properties even when applied to the steel plate surface, resulting in uneven coating and poor adhesion in areas where the film is thick. It has the disadvantage of becoming worse.

The usual method of reducing the viscosity of paint to ensure leveling properties is to dilute it with an organic solvent, but this method is rarely used for coating insulation coatings on electrical steel sheets due to fire hazards and pollution concerns. Not put into practice.

The method currently employed is to dilute a water-soluble paint with water, apply it to a steel plate, and bake it to form an insulating coating.

Furthermore, as shown in JP-A No. 56-031477, a method of coating with a water-insoluble coating resin and a coating roll heated to 150 to 350°C has been proposed, but it is difficult to remove the coating roll. There are problems with workability such as changing the paint, cleaning the coating roll, and changing the paint.

"Problems to be Solved by the Invention" However, with regard to the means for diluting the water-soluble paint with water and applying it,
As described in Comparative Example No. 031477, it is necessary to hold the coating in a hot air oven for a predetermined period of time after coating, and at this time, there is a drawback that a large amount of energy is required to remove water and harden the film.

``Means for Solving Problems'' and ``Operations'' The present invention was made in view of the above circumstances, and its gist is that an organic coating made of a water-soluble resin is applied to an electrical steel sheet through a coating roll. In the method of producing an insulating film for electrical steel sheets, which is applied to the surface and baked by heating, the temperature of the steel sheet before application is controlled at 60 to 100°C to create an insulating film with excellent adhesion due to the residual heat baking effect. This is achieved by reducing the additional heat load of sintering.

In other words, the present inventor found that applying the coating to a high-temperature plate and baking it to dry it helps the drying process, not only from the surface of the coating but also from the boundary between the coating and the steel plate, and is effective in improving adhesion. From the perspective of reducing the subsequent heating load, we will shorten the time from continuous annealing to application in the continuous annealing line for electrical steel sheets, and use the residual heat of the steel sheet during the cooling process after continuous annealing as energy for paint baking. We explored the conditions under which this would be possible.

As a result, in the conventional manufacturing process, the steel plate temperature before coating was 40℃ or less, but after continuous annealing,
It has been found that by shortening the time until application, it is possible to easily maintain a steel plate temperature of 60°C or higher before coating, and when the steel plate temperature is 60°C or higher, the viscosity of the paint decreases before coating, resulting in poor leveling properties. It was also found that the coating was improved, uneven coating was eliminated, and the coating could be applied uniformly to the surface of the steel plate.

At this time, if the commonly used and inexpensive coating roll 8 is used at a temperature exceeding 100°C, its life will be shortened as it is used, so the upper limit of the steel sheet temperature before coating was set to 100°C.

Therefore, if the steel plate temperature exceeds 100℃, use the steel plate cooling device 4 before coating to reduce the optimum temperature to 60℃.
Control at ~100℃.

As mentioned above, the results of examining the correlation between the steel plate temperature and adhesion before coating, and the correlation between the steel plate temperature before coating and the surface roughness of the coating are shown in FIGS. 1 and 2.

From Figure 1, it is clear that when the steel plate temperature is 60°C or higher, the adhesion passes 100%.
It is clear from the figure that a good result of Ra < 0.4 μm is obtained when the steel plate temperature is 60°C or higher.

It should be noted that as a result of the residual heat of the steel plate acting on coating and baking, the baking heating load after coating was reduced.

Based on the above, the present invention has found that a water-soluble organic coating has excellent adhesion without any problems in workability, at a relatively low plate temperature, and without heating the paint or application roll. It is something.

"Example" An electrical steel sheet containing 3.2% Si was cold rolled to a thickness of 0.5 mm.
This cold-rolled electrical steel sheet is heated to 900°C in continuous annealing furnace 1.
After annealing in an atmosphere of 50secN ₂ (75) + H ₂ (25),
The temperature of the steel plate before coating was controlled at 60°C, and a coating with the following composition [A] was applied to the surface of the steel plate using a coating roll 8 so that the coating thickness after baking was 2.0 μm, and baking was performed after coating. Summer.

As a result, when the steel plate temperature before coating is 60℃, 10mm
It had excellent adhesion without peeling even when bent by 180°. When the coating thickness exceeded 5 μm, the peeling phenomenon became noticeable.

Composition [A]: Alkyd resin 45g :Melamine resin 55g :250g water A comparative example is shown below.

A 3.2% Si electrical steel sheet was cold rolled to a thickness of 0.5mm.
This cold-rolled electrical steel sheet is heated to 900°C in continuous annealing furnace 1.
After annealing in an atmosphere of 50secN ₂ (75) + H ₂ (25),
The temperature of the steel plate before application is controlled at 30°C, and the coating of composition [A] is applied to the surface of the steel plate using the coating roll 8 so that the coating thickness after baking is 2.0 μm, and baking is performed after application. Ta.

As a result, when the steel plate temperature before coating is 30℃, 10mm
When I bent it 180 degrees at φ, a part came out that peeled off.

``Effects of the Invention'' As described above, according to the present invention, by controlling the steel plate temperature before coating to 60 to 100°C, the surface roughness of the coating after coating and baking can be reduced to Ra0.4 μm compared to conventional coatings.
In contrast, Ra<0.4 μm, the leveling properties of the coating film were improved, the space factor was improved, adhesion defects were completely eliminated, and the baking heating load after coating was reduced.

[Brief explanation of drawings]

Figures 1 and 2 serve as condition setting materials for the present invention and show the study results; a correlation graph between the steel plate temperature before coating and adhesion; a correlation graph between the steel plate temperature before coating and the surface roughness of the coating; and Figure 3: is an explanatory diagram of a continuous annealing line for electrical steel sheets. 1...Annealing furnace, 2...Electromagnetic steel sheet, 3...Cooling zone, 4...Steel plate cooling device before coating, 5...Paint saucer, 6...Pick-up roll, 7...Metering roll, 8...Coating roll.

Claims (1)

[Claims] 1. A method for producing an insulating film on an electrical steel sheet in which an organic film made of a water-soluble resin is applied to the surface of an electrical steel sheet via a coating roll and then heated and baked, by controlling the temperature of the steel sheet before application to 60 to 100°C. A method for producing a water-soluble organic insulating coating on an electrical steel sheet, which is characterized by obtaining an insulating coating with excellent adhesion due to the residual heat seizure effect.