JP2004107796A - Coating solution for insulation film of grain-oriented silicon steel sheet having excellent sticking resistance and space factor, and method for forming insulation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an insulation film of a grain-oriented silicon steel sheet by which a space factor and resistance to sticking of steel sheets to each other during stress-relieving annealing can be improved. <P>SOLUTION: Inorganic mineral particles having >2 to 20μm average particle size and having no electric charge are incorporated into a coating solution for insulation film formation in an amount of 0.02 to 20 mass% at the ratio of solid content in the coating solution. The coating solution is applied to a finish-annealed grain-oriented silicon steel sheet. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method for forming a tension imparting insulating film on a finish-annealed unidirectional silicon steel sheet.

Unidirectional silicon steel sheet is used as electric core material for voltage conversion electrical equipment, mainly transformers. There are two main types of transformer core manufacturing methods. One is a stacked iron core method of manufacturing an iron core by laminating unidirectional silicon steel sheets of a predetermined shape and size. The other is a wound iron method in which a unidirectional silicon steel sheet adjusted to a predetermined shape and size is wound into a cylindrical shape and used as an iron core.

う ち The latter method involves the following steps. First, the unidirectional silicon steel sheet is sheared to a predetermined width, and then is wound into a cylindrical shape. Next, this cylindrically wound product (hereinafter, referred to as a core) is subjected to a bending process and formed into a predetermined form. At this time, a mechanical strain is introduced into the steel sheet with the bending. Since the introduced strain deteriorates the core properties, the core is annealed to remove the strain.

コ ア The annealed core is deployed once. The developed annealed steel sheet is inserted between copper wires and the like to form a transformer. A series of work of unfolding the core and winding it around the copper wire is called a racing work. Racing is an important step that affects the productivity of transformer manufacturing. In this operation, if it takes time to develop the core, the productivity is reduced. Therefore, it is desired that the annealed core be easily developed. However, sometimes the steel sheets in the annealed core cause a kind of adhesion phenomenon. When the steel sheets adhere to each other, a great deal of labor and time are required for core development, and the productivity is reduced. Therefore, the following technology is disclosed as a technology that does not induce such an adhesion phenomenon.

For example, as a technique for adding a powder to a coating liquid, there is the following technique. First, in Patent Document 1, an aqueous dispersion mainly composed of colloidal silica, a first phosphate, and chromic acid contains SiO ₂ and Al having a primary particle size of 70 to 500 ° (7 to 50 nm) and an apparent specific gravity of 100 g / liter or less. A technique for adding one or more of ₂ O ₃ and TiO ₂ particles has been proposed.

Next, Patent Literature 2 proposes a technique of adding one kind of alumina, silica, titania, and mica powders to a lithium silicate aqueous solution. Also, in Patent Document 3, ultrafine particles of SiO ₂ , Al ₂ O ₃ , and TiO ₂ having a primary particle diameter of 1000 ° (100 nm) or less are added to an aqueous dispersion mainly composed of colloidal silica, aluminum phosphate, boric acid, and sulfate. Techniques for adding one or more particles have been proposed.

Further, Patent Document 4 proposes a technique of adding a non-colloidal solid having a particle diameter of 5 to 2,000 nm to a coating solution mainly containing phosphate, chromic acid, and colloidal silica having a particle diameter of 50 nm or less. Was. Apart from the technique of adding powder to the coating solution described above, JP-A-3-39484 discloses a technique using colloidal silica having a relatively small particle size and a relatively large particle size. A technique of adding colloidal silica having a particle diameter of 20 nm or less and colloidal silica having a particle diameter of 80 to 2,000 m (80 nm to 2,000 nm) to an aqueous dispersion mainly composed of silica is also proposed.
JP-A-52-25296 JP-A-53-6338 JP-A-54-143737 JP-A-4-165082

(4) The inventor has applied these techniques and made repeated studies. As a result, it has been found that simply applying the above-described techniques as is cannot completely prevent the adhesion phenomenon that may occur during strain relief annealing. Generally, the adhesion of a two-phase interface depends on its contact area. Therefore, when the two phases are brought into contact with each other and kept at a high temperature, adhesion is less likely to occur if the contact area is reduced. As one of the methods for reducing the contact area, there is a method of providing irregularities on the surface. However, in the strain relief annealing of the wound iron core, a large surface pressure is applied between the plates, so that the unevenness formed on the surface must be considerably large. For that purpose, it is necessary to use particles having a large particle diameter. The particle size of the particles proposed in the conventional literature is 7 to 50 nm in Patent Literature 1 and 100 nm or less in Patent Literature 3, and has a particle diameter mainly in a submicron region. Further, although the particle size of the particles disclosed in Patent Document 4 is relatively large, it is still 2 μm at the maximum. With particles having such a particle size, the contact area of the insulating film cannot be controlled.

癒 Adhesion can be suppressed by the fine particles as described above because they aggregate to form coarse particles. Generally, aggregation of particles in an aqueous solution is affected by various factors, one of which is the particle size. Since particles having a small particle diameter have a large surface energy, many particles are aggregated and united to reduce the surface area. Once coalescence occurs, the individual particles grow into coarse particles having a particle size hundreds to thousands of times as large as the individual particles. The grain size of the coarse grains grown in this way reaches several hundred μm. If coarse particles having a particle diameter of several hundred μm are present in the coating, the space factor is remarkably deteriorated when the plates are laminated due to the projections.

The space factor is the ratio of iron to the entire thickness of the iron core when the iron core is manufactured by laminating unidirectional silicon steel sheets. If the insulating film on the surface of the steel sheet is too thick, or if a gap is formed due to the unevenness of the film or the steel sheet itself, this ratio decreases. If the space factor is low, when the iron core operates as a voltage conversion unit in the transformer according to the law of electromagnetic induction, it becomes difficult for magnetic flux to pass therethrough, and heat energy loss increases.

The present invention is to provide a tension-imparting insulating film of a grain-oriented electrical steel sheet that can suppress adhesion between steel sheets without reducing the space factor.

The present invention comprises the following requirements.
(1) Tensile application of a unidirectional silicon steel sheet characterized by containing uncharged inorganic mineral particles having an average particle size of more than 2 μm and not more than 20 μm in a solid content ratio of 0.02 to 20% by mass. Coating solution for conductive insulation film.

(2) A method for forming a tension-imparting insulating film on the steel sheet by applying, drying and baking a coating liquid on a finish-annealed unidirectional silicon steel sheet, wherein the coating liquid has an average particle diameter of more than 2 μm. The coating liquid contains 0.02% by mass or more and 20% by mass or less of inorganic mineral particles having no electric charge of 20 μm or less, and has excellent space factor and excellent adhesion for strain relief and annealing. A method for forming a directional silicon steel sheet insulating film.

(3) The formation of a unidirectional silicon steel sheet insulating film excellent in space factor and strain relief annealing adhesion according to (2), wherein the main component of the coating solution is phosphate, chromic acid and colloidal silica. Method.

The coating liquid for forming an insulating film contains inorganic mineral particles having an average particle diameter of not less than 2 μm and not more than 20 μm having no charge in a solid content ratio of 0.02% by mass or more and 20% by mass or less. By forming moderate irregularities on the surface, adhesion resistance during strain relief annealing can be significantly improved while maintaining a high space factor.

The inventors came to think that as a means for suppressing the adhesion phenomenon described above, particles having a relatively large particle size were added to the coating solution, and the surface of the film formed on the steel plate was roughened, and The inventors have studied particles having a large particle size that cannot be imagined from the prior art.

Based on the above-mentioned concept, the inventors added particles having a particle diameter of mainly μm region to the coating solution to prepare samples with an insulating film, and examined the adhesion and adhesiveness of these samples during strain relief annealing. The space factor was examined in the following manner. Sample preparation and evaluation were performed by the following methods. A number of steel sheets with a primary coating (a coating composed of a forsterite-based inorganic mineral substance) having been subjected to finish annealing and having undergone secondary recrystallization were prepared. 50 ml of an aqueous solution of aluminum phosphate containing chromic acid having a concentration of 50% by mass, 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by mass, and 11 types of alumina particles having an average particle size of 0.6 μm to 23.9 μm were respectively added to the steel plate. The mixture of 0.25 g was applied and dried. Next, these were annealed at 835 ° C. for 30 seconds in a nitrogen atmosphere to form an insulating film on the surface of the steel sheet. The samples prepared in this manner were evaluated for adhesion and space factor by the following methods.

The adhesion was evaluated by the following method. First, a large number of samples having a short side of 3 cm and a long side of 4 cm were cut out from a unidirectional silicon steel sheet on which an insulating film was formed. Next, these samples were stacked such that the short side and the long side were alternated. When laminated in this manner, the samples come into contact with each other at just 3 cm square. Therefore, the contact area is 9 cm ² . A load of 60 kg / cm ² was applied to this laminated product and fixed with bolts. Then, this was annealed at a temperature of 800 ° C. and a soaking time of 2 hours. After cooling to room temperature, the sheet was peeled off one by one, and the peeling force at that time was determined. Fifteen samples were prepared, and the average value of their peeling forces was determined. It is considered that the peel force obtained by such a test method reflects the ease of deployment in actual core deployment.

(4) The occupancy rate was evaluated by the following method. First, a large number of samples having a short side of 3 cm and a long side of 15 cm were cut out from a unidirectional silicon steel sheet on which an insulating film was formed in the same manner as the adhesion evaluation sample. After laminating these samples and applying a constant load, the thickness at that time is measured. Next, assuming that all of the thickness is made of iron, the mass is calculated (calculated mass). On the other hand, the substantial amount of this sample is also measured. The ratio of the real amount to the calculated mass expressed in% is the space factor. It is considered that the space factor obtained by such a test method reflects the actual space factor in the iron core. Table 1 shows the results of the evaluation as described above.

Table 1 shows the following. First, looking at the peeling force indicating the adhesiveness during strain relief annealing, the peeling force is 173 g under the conditions where the average particle size of the added particles is 0.6 μm to 1.9 μm (Experiment No. 1) 2) 3))). On the other hand, when the average particle diameter of the added particles is 2.1 μm to 23.9 μm (Experiment No. 4) to Experiment No. 11), the peeling force is as very small as 19 g or less.

Next, regarding the space factor, when the average particle size of the added particles is from 0.6 μm to 20.0 μm (Experiment No. 1 to Experiment No. 10)), the space factor is from 97.6% to 97.8. % Under the condition that the average particle size of the added particles is 23.9 μm (Experiment No. 11), the space factor is as very small as 95.9%. From the above results, the small peeling force, that is, the excellent adhesion at the time of strain relief annealing and the high space factor can be compatible with each other because the added particles have an average particle size of more than 2.0 μm and 20 μm or less. Turned out to be something.

者 Next, the inventors examined the effect of the amount added. First, similarly to the case where the dependence on the particle size was obtained, a number of steel sheets with a secondary coating which had been subjected to secondary recrystallization were prepared. An aluminum phosphate aqueous solution containing chromic acid at a concentration of 50% by mass, an aqueous dispersion of colloidal silica at a concentration of 20% by mass, and four types having an average particle diameter of 2.1 μm, 4.3 μm, 10.7 μm, and 20.0 μm were prepared. A mixture of alumina particles in a proportion of 0.01% by mass to 20% by mass in terms of the solid content of the alumina particles in the coating solution was applied and dried. Next, these were annealed at 835 ° C. for 30 seconds in a nitrogen atmosphere to form an insulating film on the surface of the steel sheet. The samples prepared in this manner were evaluated for adhesion and space factor by the methods described above. Table 2 shows the results.

Table 2 shows the following. First, looking at the peeling force, which indicates the adhesion during strain relief annealing, the condition that the addition rate of particles having any average particle size is 0.01% by mass (Experiment Nos. 1, 7, 13, and 19). In this case, the peeling force is as large as 102 g or more, while the peeling force is as extremely small as 18 g or less under the condition of the addition rate of 0.02 mass% or more.

Next, regarding the space factor, the space factor is as high as 97.6% or more under the condition that the addition amount is 0.01% by mass or more and 20.0% by mass or less for particles having any average particle size. On the other hand, when the addition ratio is 30.0% by mass, it is very low at 95.7% by mass or less. Therefore, the peeling force is small, that is, the excellent adhesion at the time of strain relief annealing and the high space factor can be compatible with each other because the addition rate is 0.02% by mass or more and 20.0% by mass or less. I understood.

From these two experiments, the conditions of good space factor and good adhesion resistance during strain relief annealing are based on the condition that the inorganic mineral particles having an average particle size of more than 2 μm and 20 μm or less in the coating solution are 0.02% by solid content in the coating solution. It has been found that the content is not less than 20% by mass and not more than 20% by mass. Hereinafter, the present invention will be described in detail. The grain-oriented silicon steel sheet used in the present invention is manufactured by an ordinary method. That is, a cast slab having Si: 2 to 4% and an inhibitor component is hot-rolled, and hot-rolled sheet annealing is performed, or cold rolling is performed once or twice or more with intermediate annealing, and decarburization annealing is performed. Finish annealing is performed, and then an insulating film is applied.

There are several types of insulating films, but typical ones are phosphate, chromic acid, and colloidal silica as main components, which are dissolved in water, applied, and dried and baked. There is a mold insulating film. The present invention is characterized in that inorganic mineral particles having a relatively large particle size are added to the coating solution. The insulating film to which the present invention can be applied is not particularly limited, and can be applied to the above-mentioned tension imparting type insulating film, an inorganic mineral film formed by a sol-gel method, an organic resin film, and the like.

種類 The type of particles is also not particularly limited, but those having no charge, that is, non-colloidal ones are important in preventing coarsening due to aggregation. Here, having no charge means not having enough charge to cause particles to be bonded to each other due to the charge, and does not deny the existence of a local charge when viewed microscopically. . The main types of particles include alumina, zirconia, titania, and titanium nitride. The average particle size and the amount of the particles were determined based on the test results described above. When the average particle size is 2 μm or less, the adhesion resistance is small, while when the average particle size is more than 20 μm, the space factor decreases.

On the other hand, if the added amount is less than 0.02% by mass in solid content ratio, the anti-adhesion effect cannot be obtained, while if the added amount is more than 20% by mass, the space factor decreases, and furthermore, the film itself such as film tension and adhesion decreases. Characteristics may be impaired. On the other hand, comparing the present invention with the conventional technology, the technology proposed in Patent Document 1 has a primary particle diameter of 70 ° to 500 ° (7 nm to 50 nm) as described in the claims. It is characterized in that particles having a fine primary particle size and an apparent specific gravity of 100 g / liter are added to a coating solution. The use of particles having such characteristics impairs the "smoothness" of the surface of the formed film, as described in page 19, the upper right column, line 19, to the lower left column, line 5, in the same gazette. I try not to. In particular, the powder having advanced agglomeration level in Example 6 of the above specification has a space factor of 96.0%, which is worse than that of the other examples (97.8%). Referring to the scanning electron micrograph of Example 6 in the figure, "a large number of aggregates of about 1 μ are observed as irregularities on the surface" (line 1 to line 8 in the upper right column on page 7 of the specification). ).

That is, in the technology disclosed in the above publication, the formation of irregularities on the film surface is avoided. However, it is difficult to effectively suppress adhesion between steel plates.
The feature of the technology disclosed in Patent Document 4 is that a non-colloidal solid having a particle size of 5 to 2,000 nm is added to the coating solution. The purpose is described in line 2 to line 5 in the upper left column of page 5 of the text of the gazette of the gazette, stating that "the solid material is to form fine irregularities on the film surface and to enhance slipperiness". As described above, it is considered that solids are intended to improve the slip property.

に お い て Also, in the same publication, page 4, lower left column, line 6 to line 10, states that "in the range of 5 to 100 nm, moderate aggregation occurs in the insulating coating solution". That is, in the technique disclosed in the above specification, it is recommended that the particles be positively coarsened in the coating solution. However, in this method, the secondary particle diameter cannot be controlled, and the secondary particle size becomes large, and it is difficult to suppress a decrease in the space factor.

A 50% by mass aqueous solution of chromic acid-containing aluminum / magnesium phosphate with a concentration of 50% by mass and a 20% by mass concentration of colloidal silica aqueous dispersion are applied to a 0.23mm-thick steel plate with a primary film that has been subjected to finish annealing and has been subjected to secondary recrystallization. 100 ml of the solution was applied and dried. At this time, a coating liquid was prepared in which alumina particles having an average particle size of 2.5 μm were added in an amount of 0.5% by mass in terms of a solid content ratio, and a coating liquid in which alumina particles were not added. Next, these samples were annealed at 835 ° C. for 30 seconds in a nitrogen atmosphere to form an insulating film on the surface of the steel sheet. The samples thus prepared were evaluated for adhesion and space factor by the methods described above. Table 3 shows the results.

か ら Table 3 shows that the space factor is as high as 97.7% in both Examples and Comparative Examples. However, when the peeling force was compared, Comparative Example 2) in which alumina particles were not added was a very large value of 452 g, whereas Example 1) in which alumina particles were added was as small as 17 g, which is excellent. .

On a 0.30 mm-thick steel sheet with a primary film that has been subjected to finish annealing and has been subjected to secondary recrystallization, 50 ml of a 50% by mass aqueous solution of aluminum phosphate containing chromic acid and 50 ml of a 20% by mass aqueous colloidal silica dispersion liquid 100 ml Was applied and dried. At this time, one prepared by adding 0.1% by mass of silica particles having an average particle size of 10.2 μm to the coating solution in a solid content mass ratio, and one prepared by adding no silica particles were prepared. Next, these samples were annealed at 835 ° C. for 30 seconds in a nitrogen atmosphere to form an insulating film on the surface of the steel sheet. The samples thus prepared were evaluated for adhesion and space factor by the methods described above. Table 4 shows the results.

か ら Table 4 shows that the space factor is as high as 97.6% in both Example 1) and Comparative Example 2). However, when the peeling force is compared, Comparative Example 2) in which the silica particles were not added was a very large value of 541 g, whereas Example 1) in which the silica particles were added was a small value of 15 g, which was excellent. .

A 50% by mass aqueous solution of chromic acid-containing aluminum / magnesium phosphate with a concentration of 50% by mass and a 20% by mass concentration of colloidal silica aqueous dispersion are applied to a 0.23mm-thick steel plate with a primary film that has been subjected to finish annealing and has been subjected to secondary recrystallization. 100 ml of the solution was applied and dried. At this time, there were prepared one in which aluminum borate particles having an average particle size of 5.2 μm were added to the coating liquid in an amount of 0.3% by mass in terms of a solid content mass ratio, and one in which aluminum borate particles were not added. Next, these samples were annealed at 835 ° C. for 30 seconds in a nitrogen atmosphere to form an insulating film on the surface of the steel sheet. The samples thus prepared were evaluated for adhesion and space factor by the methods described above. Table 5 shows the results.

か ら Table 5 shows that the space factor is as high as 97.7% in both Example 1) and Comparative Example 2), which is good. However, when the peeling force is compared, Comparative Example 2) in which aluminum borate particles were not added was a very large value of 635 g, whereas Example 1) in which aluminum borate particles were added was a small value of 16 g. It is excellent.

Claims (3)

One direction excellent in adhesion resistance and space factor, characterized by containing uncharged inorganic mineral particles having an average particle size of more than 2 μm and not more than 20 μm in a solid content ratio of not less than 0.02% by mass and not more than 20% by mass. Coating solution for tension-imparting insulating film on functional silicon steel sheet. In a method of forming a tension-imparting insulating film on the steel sheet by applying a coating liquid to a finish-annealed unidirectional silicon steel sheet, drying and baking, the coating liquid has an average particle size of more than 2 μm and not more than 20 μm. Unidirectional silicon steel sheet insulation excellent in adhesion resistance and space factor, characterized by containing non-charged inorganic mineral particles in a solid content ratio of 0.02% by mass to 20% by mass in the coating solution. Film formation method. 3. The method for forming a unidirectional silicon steel sheet insulating film having excellent adhesion resistance and space factor according to claim 2, wherein the coating liquid is mainly composed of phosphate, chromic acid and colloidal silica.