JP2002322566A - Unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a unidirectional silicon steel sheet having good film adhesion of a tension imparting insulating film and a method for producing the same. SOLUTION: After removing the inorganic mineral material film such as forsterite by means of pickling or the like and intentionally preventing its production, a one-way film having a tension imparting insulating film is formed. A silicon steel sheet having an average film thickness of 2n at the interface between the tension-imparting insulating film and the finish-annealed steel sheet.
A unidirectional silicon steel sheet having, in addition to an external oxidized oxide film mainly composed of silica having a diameter of m or more and 500 nm or less, preferably having a particulate external oxide mainly composed of silica having a sectional area ratio of 2% or more. In the manufacturing method, a minute strain or minute unevenness is imparted to the steel sheet surface before annealing in a low oxidizing atmosphere for ensuring film adhesion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates is or prepared intentionally prevent the formation of composed inorganic mineral coating with forsterite (Mg ₂ SiO ₄₎ or the like, and further, the surface to exhibit a specular gloss The present invention relates to a unidirectional silicon steel sheet in which a tension-imparting insulating film is formed on a finish-annealed unidirectional silicon steel sheet prepared by flattening, for example, and a method for producing the same.

[0002]

2. Description of the Related Art A grain-oriented silicon steel sheet is widely used as a magnetic iron core material. In particular, in order to reduce energy loss, a material having a small iron loss is required. It is effective to apply tension to the steel sheet to reduce iron loss, so by forming a film made of a material having a smaller coefficient of thermal expansion at a high temperature compared to the steel sheet, the tension is applied to the steel sheet to reduce iron loss. It has been planned. The forsterite-based film generated by the reaction between the oxide on the steel sheet surface and the annealing separator in the finish annealing process contributes to the improvement of the magnetic properties by applying tension to the steel sheet, and also has excellent film adhesion. .

Further, a method of forming an insulating film by applying a coating liquid mainly composed of colloidal silica and phosphate to the surface of a steel sheet and baking the coating solution disclosed in Japanese Patent Application Laid-Open No. 48-39338 is disclosed in Japanese Patent Application Laid-Open No. 48-39338. The effect of applying tension is great, and is effective in reducing iron loss. Therefore, forming a phosphate-based insulating film while leaving the forsterite-based film generated in the finish annealing step is a general method for producing a unidirectional silicon steel sheet.

In recent years, it has become clear that the disordered interface structure between the forsterite-based film and the ground iron has reduced the effect of improving iron loss due to the film tension to some extent. Therefore,
For example, as disclosed in Japanese Patent Application Laid-Open No. 49-96920, by removing a forsterite-based film generated in the final annealing step, and further performing mirror finishing, and then forming a tension film again, Techniques have been developed to further reduce iron loss.

[0005] However, in the above insulating film,
When formed on a film mainly composed of forsterite, considerable adhesion can be obtained, but forsterite-based films have been removed or forsterite formation has not been intentionally performed in the finish annealing process. On the other hand, the film adhesion is not sufficient. In particular, when the forsterite-based film is removed, it is necessary to secure the required film tension only with the tension-imparting insulating film formed by applying the coating liquid, and the film must be thickened inevitably. Further, further adhesion is required.

[0006] Therefore, it is difficult for the conventional film forming method to achieve a film tension sufficient to bring out the effect of mirror finishing and to secure film adhesion, and it is possible to reduce iron loss sufficiently. Had not been. Therefore, as a technique for securing the adhesion of the tension-imparting insulating film, prior to the formation of the tension-imparting insulating film, a method of forming an oxide film on the surface of a finish-annealed unidirectional silicon steel sheet, for example,
JP-A-60-131976, JP-A-6-1847
No. 62, JP-A-7-278833, JP-A-8
Japanese Patent Application Laid-open No. 191010 and Japanese Patent Application Laid-Open No. 9-078252.

[0007] The method described in Japanese Patent Application Laid-Open No. 60-131976 is a method in which a finish-annealed unidirectional silicon steel sheet is mirror-finished, and the vicinity of the steel sheet surface is internally oxidized. Internal oxidation,
In other words, the method is intended to compensate for iron loss deterioration caused by the decrease in specularity by increasing the applied tension brought about by the improvement in film adhesion.

[0008] The method described in Japanese Patent Application Laid-Open No. 6-184762 discloses a method of subjecting a finish-annealed unidirectional silicon steel sheet, which has been mirror-finished or adjusted to a mirror-like state, to annealing in a specific atmosphere for each temperature. In this method, an external oxidation type oxide film is formed on the substrate, and the oxide film is used to secure adhesion between the film of the tension imparting insulating film and the steel sheet. The method described in Japanese Patent Application Laid-Open No. Hei 7-278833 discloses a method in which, when a tension-imparting insulating film is crystalline, a surface of a finish-annealed unidirectional silicon steel sheet without an inorganic mineral substance film is previously subjected to amorphous oxidation. By forming a base coat on the object,
This is a method of preventing oxidation of a steel sheet which occurs when a crystalline tension-imparting insulating film is formed, that is, a decrease in specularity.

The method described in Japanese Patent Application Laid-Open No. Hei 8-191010 discloses a method in which a crystalline firelite is formed on the surface of a finish-annealed unidirectional silicon steel sheet from which a nonmetallic substance has been removed, thereby imparting tension by firelite crystals. This is a method for reducing iron loss by using the effect and the adhesion improving effect. JP-A-9-
In the method described in Japanese Patent No. 078252, the amount of the base silica layer formed on the surface of the finish-annealed grain-oriented silicon steel sheet having no inorganic mineral substance film is set to 100 mg / m 2 or less, so that only the adhesion of the tension film is secured. However, this method is intended to realize a good iron loss value.

[0010]

By applying the above method,
The effect of improving the coating adhesion and reducing the iron loss value by forming an oxide film on the surface of a grain-oriented silicon steel sheet free of inorganic minerals is recognized as such. However, the film adhesion of the tension imparting insulating film was not always perfect.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and to provide sufficient film adhesion to finish-annealed unidirectional silicon steel sheet having no inorganic mineral material film. The present invention is characterized in that a tension imparting type insulating film is formed. The gist of the present invention is as follows.

(1) An inorganic mineral substance film such as forsterite is removed by means of pickling or the like, or the production thereof is intentionally prevented, and then a tension-imparting insulating film is formed. A grain-oriented silicon steel sheet having an average film thickness of 2 nm or more and 500
In addition to a film-like external oxide film mainly composed of silica at nm or less,
A unidirectional silicon steel sheet having excellent film adhesion of a tension-imparting insulating film, characterized by having a granular external oxide mainly composed of silica.

[0013] (2) The one direction excellent in film adhesion of the tension imparting insulating film according to (1), wherein the sectional area ratio of the granular external oxide to the film external oxide film is 2% or more. Silicon steel sheet. (3) The tension according to (1) or (2), wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of phosphate and colloidal silica. Unidirectional silicon steel sheet with excellent adhesiveness of imparting insulating film.

(4) The tension-imparting insulating film according to the above (1) or (2), wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. Unidirectional silicon steel sheet with excellent film adhesion of conductive insulating film. (5) Tension imparting insulation is applied to the finish-annealed unidirectional silicon steel sheet manufactured by removing the inorganic mineral substance film such as forsterite by pickling or the like or intentionally preventing its formation. Prior to forming the tension-imparting insulating film, the steel sheet is annealed in a low-oxidizing atmosphere to form an oxide mainly composed of silica on the surface of the steel sheet, in order to secure the adhesion between the film and the steel sheet. After that, a coating solution for forming a tension-imparting insulating film is applied and baked to form a tension-imparting insulating film and produce a unidirectional silicon steel sheet. Prior to the middle annealing, the surface of the steel sheet is provided with micro-strain or fine irregularities so that the average film thickness is 2 nm or more and 500
In addition to a film-like external oxide film mainly composed of silica at nm or less,
A method for producing a unidirectional silicon steel sheet having excellent film adhesion to a tension-imparting insulating film, wherein a granular external oxide mainly composed of silica is formed.

(6) The tension-imparting insulating film according to (5), wherein the sectional area ratio of the granular external oxide to the film-shaped external oxide film is 2% or more. A method for producing a grain-oriented silicon steel sheet. (7) The unidirectional silicon steel sheet excellent in film adhesion of the tension imparting insulating film according to the above (5) or (6), wherein minute strain is imparted to the surface of the steel sheet by a brush with abrasive grains. Production method.

(8) A unidirectional silicon steel sheet excellent in film adhesion of the tension imparting insulating film according to (5) or (6), wherein the surface of the steel sheet is provided with fine irregularities by pickling. Manufacturing method. (9) The tension imparting insulating film is formed by baking a coating solution mainly composed of phosphate and colloidal silica, (5),
(6) A method for producing a unidirectional silicon steel sheet having excellent adhesion to the tension-imparting insulating film according to (7) or (8).

(10) The above (5), (6), and (7), wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. Or the method of forming an insulating film of a unidirectional silicon steel sheet having excellent film adhesion of the tension imparting insulating film according to (8).

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. Prior to the formation of the tension-imparting insulating film, the present inventors
Even with the method of forming an oxide film on the surface of a finish-annealed unidirectional silicon steel sheet, the reason why the film adhesion is not always perfect is not that there is a problem in the surface state of the steel sheet before forming the oxide film. I thought. In other words, it was presumed that the structure of the external oxidation type oxide film fluctuated due to the difference in the surface state, and as a result, a difference in the film adhesion of the tension imparting insulating film might have occurred.

Therefore, the steel sheet before the formation of the external oxidation type oxide film was subjected to a pretreatment, and the relationship between the presence or absence of the pretreatment on the adhesion of the tension imparting insulating film and the structure of the external oxidation type oxide film was examined. . As a test material, a decarburized annealed sheet of 0.225 mm unidirectional silicon steel sheet is coated with an annealing separator mainly composed of alumina, finish-annealed, and secondary recrystallized to obtain a mirror gloss. A unidirectional silicon steel sheet was prepared. Then, samples were prepared under the conditions of performing and not performing the pretreatment for introducing a minute strain on the surface of the steel sheet with a brush with silicon carbide abrasive grains.

Next, nitrogen 25%, hydrogen 75%, dew point -1
Heat treatment was performed at various temperatures at a soaking time of 10 seconds in an atmosphere of ° C. to form an external oxidation type oxide film mainly composed of silica. Finally, in order to form a tension-imparting insulating film, a coating liquid mainly composed of aluminum phosphate, chromic acid, and colloidal silica is applied, and 835 is applied in a nitrogen atmosphere.
Bake at 300C for 30 seconds. The steel sheet thus produced was examined for film adhesion.

The film adhesion is defined as an area ratio of a portion where the film does not peel off when the sample is wound around a cylinder having a diameter of 20 mm and the steel film and the film remain in close contact (hereinafter referred to as a film remaining area ratio). evaluated. When the adhesion was poor and the film was completely peeled, it was judged as 0%, and when the film adhesion was good and the film was not peeled at all, it was judged as 100%. The evaluation was x when the film residual area ratio was 90% or less, and x when 95% was 95%.
A sample having a value of 00% was evaluated as ◎.

Further, in order to examine the structure of the external oxidation type oxide film existing at the interface between the tension imparting insulating film and the steel sheet, a sample is prepared by a concentrated ion beam method (hereinafter, referred to as FIB method), The cross-sectional structure was observed with a microscope (hereinafter, referred to as a TEM). The FIB method is a method of producing and collecting a flaky sample having a thickness of several μm from a desired position of a coated steel sheet sample so that a coating having a thickness of several μm formed on a steel plate can be observed from a cross-sectional direction.

When a thin film sample was prepared by the FIB method, and the interface between the steel sheet and the tension-imparting insulating film was examined by TEM, an external oxidized oxide film mainly composed of silica was observed. Above all, for the sample in which micro-strain was introduced into the steel sheet surface with a brush containing abrasive grains before forming the oxide film as the intermediate layer, in addition to the film type oxide film of the external oxidation type, the film shape as shown in FIG. A silica-based granular oxide was observed, which penetrated the oxide film and fitted into the tension-imparting insulating film side.

A large number of such interface portions were observed, and in the cross section, the ratio of the granular oxide to the film oxide film (hereinafter, referred to as the granular oxide area ratio) was calculated. Further, the average thickness of the external oxidation type oxide film was also determined. Table 1 shows the results
Summarized in

[0025]

[Table 1]

From Table 1, conditions for securing the adhesion of the tension-imparting insulating film are obtained as follows. First, under the conditions of Sample No. 1 and Sample No. 2 in which the thickness of the external oxidized oxide film was 1 nm under the condition of the heat treatment temperature of 500 ° C., the film remaining area ratio was as low as 10% and 20%, respectively. Regardless of the presence or absence of pretreatment with a brush with a coating, film adhesion cannot be ensured.

On the other hand, the heat treatment temperature of Sample Nos. 3 to 16 in which the thickness of the external oxidation type oxide film is 2 nm or more is 600
Under the conditions of 1 ° C. to 1150 ° C., the film remaining area ratio becomes 90% or more, and the film adhesion can be generally secured. However, perform pre-processing with a brush with abrasive grains,
Under the condition that the sectional area ratio of the particulate oxide is 2% or more, the film adhesion is good, but the pretreatment with a brush with abrasive grains is not performed, and the particulate oxide is small, that is, 0% in terms of the sectional area ratio. Under the conditions of 1% or 1%, even if the thickness of the external oxidation type oxide film was large, the film adhesion was not always perfect, and the film remaining area ratio was 90%.

In particular, the sample Nos. 12, 14, and 16 have an outer oxide type oxide film having a thickness of 40 nm or more and a heat treatment temperature of 10
Under the condition of 00 ° C. or higher, the film adhesion is remarkably good. From Table 1, it can be seen that the thickness of the external oxidation type oxide film is 2 nm in order to completely secure the film adhesion of the tension imparting insulating film.
From the above, it is understood that it is essential that the sectional area ratio of the granular oxide is 2% or more. In order to form such a granular oxide together with the film oxide, a micro-strain is introduced into the steel sheet surface before the heat treatment for forming the external oxide type oxide film, and then the external oxide type oxide film is formed. It is understood that it is necessary to carry out the process at a temperature of 600 ° C. or higher, particularly preferably at 1000 ° C. or higher.

Next, as a pretreatment of the steel sheet before forming the external oxidation type oxide film, light pickling was performed in 1% nitric acid at room temperature for 10 seconds to form fine irregularities on the surface.
Experiments and evaluations were performed in the same procedure as described above. Table 2 shows the results.

[0030]

[Table 2]

From Table 2, conditions that can secure the adhesion of the tension-imparting insulating film are obtained as follows. First, under the conditions of Sample No. 1 and Sample No. 2 in which the thickness of the external oxidized oxide film is 1 nm under the condition of the heat treatment temperature of 500 ° C., the film remaining area ratios are as low as 20% and 30%, respectively. Regardless of the presence / absence of the surface roughness treatment by washing, the film adhesion cannot be ensured.

On the other hand, the heat treatment temperature of Sample No. 3 to Sample No. 16 in which the thickness of the external oxidation type oxide film is 2 nm or more is 600
Under the conditions of from 1 ° C. to 1150 ° C., film adhesion can be generally secured. However, under the condition that the pretreatment with a brush with abrasive grains is performed and the sectional area ratio of the particulate oxide is 2% or more, the film adhesion is good, but the nitric acid washing treatment is not performed, and the particulate oxide is small. That is, under the condition of 0% or 1% in terms of the sectional area ratio, even if the thickness of the external oxidation type oxide film is large, the film adhesion is not always perfect, and the film remaining area ratio is 90%. It became.

In particular, when the thickness of the external oxidation type oxide film of Sample Nos. 12, 14 and 16 is 40 nm or more, and the heat treatment temperature is 10
Under the condition of 00 ° C. or higher, the film adhesion is remarkably good. From the above, in order to completely secure the film adhesion of the tension-imparting insulating film, the thickness of the external oxidation type oxide film must be 2 nm.
From the above, it is understood that it is essential that the sectional area ratio of the granular oxide is 2% or more. In order to form such a granular oxide together with a film oxide, fine irregularities are introduced into the surface of the steel sheet prior to the heat treatment for forming the external oxide type oxide film, and then the external oxide type oxide film is formed. It is understood that it is necessary to carry out the process at a temperature of 600 ° C. or higher, particularly preferably at 1000 ° C. or higher.

The inventors of the present invention consider the mechanism of the film adhesion to be largely influenced by the film thickness of the external oxidation type oxide film and the sectional area ratio occupied by the particulate oxide as follows. I have. First, the relationship between the temperature and the film thickness of the external oxidation type oxide film will be described. The adhesion between the steel sheet and the tension-imparting insulating film is determined by the external oxidation type oxide film formed at the interface between the two. Generally, the external oxidation type oxide film is
It is said that metal atoms diffuse from steel into the surface and grow by reacting with oxidizing gas on the surface. Therefore, the growth rate of the oxide film is determined by the diffusion rate of atoms. Atomic diffusion is enhanced by thermal energy. Therefore, the higher the temperature is, the more the diffusion of atoms is promoted, and the external oxidation type oxide film grows more.

Due to such a mechanism, the heat treatment temperature is 500 ° C.
Under these conditions, the adhesion of the film is not sufficient because the growth of the external oxidation type oxide film is not sufficient. On the other hand, when the heat treatment temperature is 600 ° C. or more, the external oxidation type oxide film grows sufficiently. It is considered that the adhesion is good, and if the temperature is 1000 ° C. or higher, the oxide film is more likely to grow.

It is clear from the results of measuring the thickness of the external oxidation type oxide film using a transmission electron microscope that the above assumption is appropriate. That is, under the condition of a heat treatment temperature of 500 ° C. where the film thickness is 1 nm and the growth of the external oxidation type oxide film is not sufficient,
While the adhesion of the tension-imparting insulating film is poor, the film adhesion is good under the condition of a heat treatment temperature of 600 ° C. or more where the external oxidation type oxide film has grown to a film thickness of 2 nm or more.

Although the details of the mechanism of the formation of the particulate oxide in the external oxidation type oxide film are still unknown, it is necessary to wipe the surface of the steel sheet with a brush containing abrasive grains before forming the external oxidation type oxide film. By introducing micro-strain, or by forming micro-roughness by pickling, the oxide film grows especially from such micro-strain or micro-roughness,
The inventors believe that it may develop into a granular form.

Next, the relationship between the adhesion of the tension imparting insulating film to the steel sheet and the sectional area ratio of the particulate oxide will be described. Tension is applied to the steel sheet by the tension-imparting insulating film due to a difference in thermal expansion coefficient between the tension-imparting insulating film and the steel sheet. At this time, a great deal of stress is generated at the interface between the tension imparting insulating film and the steel sheet. It is the external oxidation type oxide film that withstands this stress and ensures the adhesion between the steel sheet and the tension-imparting insulating film.

The inventors presume that particulate oxides may affect such stress resistance.
In other words, the granular oxide is generated in a form penetrating through the thickness of the external oxidation type oxide film, so that when forming the tension-imparting insulating film, it is as if the granular oxide was inserted into the tension-imparting insulating film side. It is presumed that strong stress resistance is exhibited by fitting in a form, a so-called wedge shape.

When the ratio of the particulate oxide to the external oxide type oxide film is 2% or more, it can withstand the stress, but when the ratio of the particulate oxide is less than 2%, the external oxide type oxide film has a tension-imparting property. We believe that the insulating film cannot withstand the stress applied and that the tension-imparting insulating film may peel off. The upper limit of the thickness of the external oxidation type oxide film is not particularly limited from the viewpoint of film adhesion,
If the thickness is more than 500 nm, the space factor, which is an important index in the transformer, is deteriorated due to the increase in the nonmagnetic portion.

[0041]

(Example 1) A cold rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.225 mm and a Si concentration of 3.30% by mass was subjected to decarburizing annealing, and then a surface oxide layer was formed of ammonium fluoride. It was pickled in a mixed solution of sulfuric acid and sulfuric acid and dissolved and removed. Then, alumina powder was applied by an electrostatic coating method, and dried in an atmosphere of dry hydrogen at 12
Finish annealing was performed at 00 ° C. for 20 hours. The surface of the secondary recrystallized unidirectional silicon steel sheet thus prepared is free of inorganic minerals and has a mirror gloss.

With respect to this steel sheet, a steel sheet whose surface was wiped with a brush with alumina abrasive grains (Example) and a sheet not wiped (Comparative Example) were produced. Then, heat treatment was performed at a temperature of 900 ° C. in an atmosphere of 50% nitrogen, 50% hydrogen, and a dew point of −10 ° C., thereby forming an external oxidation type oxide film. Next, a mixed solution consisting of 50 ml of a 50% strength aqueous magnesium phosphate / aluminum solution, 66 ml of a 30% strength aqueous colloidal silica dispersion, and 5 g of chromic anhydride was applied to the prepared steel sheet, and baked at 850 ° C. for 30 seconds. And an insulating film having a tension imparting property was formed.

The cross section of the thus-prepared unidirectional silicon steel sheet with an insulating film was examined by FIB-TEM.
The average film thickness of the external oxidation type oxide film was calculated as the sectional area ratio of the granular oxide. Further, the film adhesion was evaluated based on the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm. Table 3 shows the results.

[0044]

[Table 3]

As can be seen from Table 3, without wiping with a brush with abrasive grains, the area ratio of the granular oxide was 1% and the area ratio of the remaining film was 90%.
As compared with the comparative example, it was found that the example in which wiping was performed with a brush with abrasive grains and the granular oxide area ratio was 10% and the film remaining area ratio was 95% had better and better film adhesion. Example 2 A cold rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.225 mm and a Si concentration of 3.35 mass% is subjected to decarburizing annealing, and an annealing separator mainly composed of magnesia and bismuth chloride is provided on the surface. Was applied and dried. Next, a finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere to obtain a unidirectional silicon steel sheet having a surface completely free of inorganic minerals and having undergone secondary recrystallization. Then, the product was pickled with 2% nitric acid at room temperature for 5 seconds to prepare a product having fine irregularities on the surface (Example) and a product not subjected to acid cleaning (Comparative Example).

Next, this steel sheet is subjected to a heat treatment at a temperature of 1150 ° C. in an atmosphere of 25% of nitrogen, 75% of hydrogen and a dew point of −15 ° C., thereby forming an external oxidation type oxide film mainly composed of silica. Was. Then, 50 ml of a 50% magnesium phosphate aqueous solution and a concentration of 20% were added to the prepared steel sheet.
% Of colloidal silica aqueous dispersion 100 ml and chromic anhydride 5 g was applied and baked at 850 ° C. for 30 seconds to form a tension imparting insulating film.

With respect to the thus-prepared unidirectional silicon steel sheet provided with an insulating film, the adhesion of the insulating film was evaluated by the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm.
Table 4 shows the results.

[0048]

[Table 4]

As shown in Table 4, the pretreatment by pickling was not performed.
Compared to the comparative example in which the area ratio of the granular oxide is 1% and the area ratio of the film remaining is 90%, the example in which the pickling is performed and the area ratio of the film oxide is 95% and the area ratio of the film oxide is 95% is better. Is good and excellent. (Example 3) A cold rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.225 mm and a Si concentration of 3.25% by mass is subjected to decarburizing annealing, and a water slurry of an annealing separating agent mainly composed of alumina is provided on the surface. Was applied and dried. Then, in a dry hydrogen atmosphere,
Finish annealing was performed at 200 ° C. for 20 hours to obtain a unidirectional silicon steel sheet which had almost no inorganic minerals on the surface and had been subjected to secondary recrystallization and had mirror gloss. With respect to this steel sheet, a steel sheet whose surface was wiped with a brush with silicon carbide abrasive grains (Example) and a steel sheet not wiped (Comparative Example) were produced.

Then, nitrogen 30%, hydrogen 70%, dew point
By performing heat treatment at a temperature of 800 ° C. in an atmosphere of 2 ° C., an external oxidation type oxide film was formed. Then, an aqueous solution of aluminum phosphate having a concentration of 50% was added to the prepared steel sheet.
0 ml, 20% aqueous colloidal silica dispersion 100
and a mixed solution consisting of 5 g of chromic anhydride,
Baking was performed at 0 ° C. for 30 seconds to form a tension-imparting insulating film.

With respect to the thus-prepared unidirectional silicon steel sheet provided with an insulating film, the film adhesion was evaluated by the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm. Table 5 shows the results.

[0052]

[Table 5]

As can be seen from Table 5, without wiping with a brush with abrasive grains, the area ratio of the granular oxide was 1% and the area ratio of the remaining film was 90%.
As compared with the comparative example, it can be seen that the example in which wiping was performed using a brush with abrasive grains and the granular oxide area ratio was 21% and the film remaining area ratio was 95% had better and better film adhesion. (Example 4) A cold-rolled sheet for producing a unidirectional silicon steel sheet having a thickness of 0.23 mm and a Si concentration of 3.30% by mass is subjected to decarburizing annealing, and a water slurry of an annealing separating agent mainly composed of magnesia is provided on the surface. Is applied and dried, and then dried in a dry hydrogen atmosphere.
Finish annealing was performed at 0 ° C. for 20 hours. A film mainly composed of forsterite is formed on the surface of the thus-prepared unidirectional silicon steel sheet after the secondary recrystallization.

Next, after pickling in a mixed solution of ammonium fluoride and sulfuric acid to dissolve and remove the surface film, the resultant was chemically polished in a mixed solution of hydrofluoric acid and hydrogen peroxide, and inorganic minerals were deposited on the steel sheet surface. A steel sheet having no mirror gloss was obtained. This steel sheet was prepared by projecting alumina powder onto the surface by projecting alumina powder (Example) and without (Comparative Example). Then, 50% of nitrogen, 50% of hydrogen
%, And an external oxidation type oxide film was formed by performing a heat treatment at a temperature of 1050 ° C. in an atmosphere having a dew point of −8 ° C.

Next, a mixed solution consisting of 100 ml of a 10% aqueous colloidal alumina dispersion, 10 g of amorphous alumina powder, 5 g of boric acid and 200 ml of water was applied.
For 30 seconds to form a tension imparting insulating film. With respect to the thus-prepared unidirectional silicon steel sheet with an insulating film, the film adhesion was evaluated based on the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm. Table 6 shows the results.

[0056]

[Table 6]

From Table 6, it can be seen that the alumina powder was projected and the surface was strained, as compared with the comparative example in which the alumina powder was not projected and the oxide film area ratio was 1% and the film remaining area ratio was 90%. It can be seen that the example in which the oxide area ratio is 30% and the film remaining area ratio is 95% has better and better film adhesion.

[0058]

According to the present invention, it is possible to obtain a unidirectional silicon steel sheet having no inorganic mineral substance film having good film adhesion.

[Brief description of the drawings]

FIG. 1 is a view (micrograph) showing an embodiment of a granular external oxide mainly composed of silica.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shuichi Nakamura 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Yoshiyuki Ushigami 20-1 Shintomi, Futtsu-shi, Chiba New Japan (72) Inventor Motoichi Shigesato 20-1 Shintomi, Futtsu-shi, Chiba F-term (reference) 4N026 AA03 AA22 BA03 BA08 BA11 BA12 BB05 BB10 CA18 CA18 CA21 CA24 CA41 DA02 DA16 EA02 EA03 EA07 EA17 EB11 5E041 AA02 BC01 BC08 CA01 HB11

Claims (10)

[Claims] 1. A one-way method in which an inorganic mineral material film such as forsterite is removed by means of pickling or the like, or after its production is intentionally prevented to form a tension-imparting insulating film. Silicon steel sheet having an average film thickness of 2 nm or more and 500 nm at the interface between the tension imparting insulating film and the steel sheet.
A unidirectional silicon steel sheet having excellent film adhesion of a tension-imparting insulating film, comprising a granular external oxide mainly composed of silica in addition to a film-shaped external oxide film mainly composed of silica. 2. The unidirectionality excellent in film adhesion of the tension-imparting insulating film according to claim 1, wherein a sectional area ratio of the granular external oxide to the film-shaped external oxide film is 2% or more. Silicon steel sheet. 3. The tension applying device according to claim 1, wherein the tension applying insulating film is formed by baking a coating solution mainly composed of phosphate and colloidal silica. Unidirectional silicon steel sheet with excellent film adhesion of conductive insulating film. 4. The tension-imparting insulating film according to claim 1, wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. Unidirectional silicon steel sheet with excellent film adhesion. 5. Applying tension to a finish-annealed unidirectional silicon steel sheet manufactured by removing an inorganic mineral substance film such as forsterite by pickling or the like or intentionally preventing its formation. Prior to the formation of the tension-imparting insulating film, the steel sheet is annealed in a low-oxidizing atmosphere to secure the adhesion between the conductive insulating film and the steel sheet, thereby forming an oxide mainly composed of silica on the surface of the steel sheet. After forming, a coating solution for forming a tension-imparting insulating film is applied and baked to form a tension-imparting insulating film and produce a unidirectional silicon steel sheet. Prior to annealing in a neutral atmosphere, the surface of the steel sheet is provided with micro-strain or fine irregularities, so that the silica is mainly added to the film-shaped external oxide film having an average film thickness of 2 nm or more and 500 nm or less and mainly composed of silica. A method for producing a unidirectional silicon steel sheet having excellent film adhesion of a tension-imparting insulating film, characterized by forming a granular external oxide as a body. 6. The unidirectionality excellent in film adhesion of the tension-imparting insulating film according to claim 5, wherein a sectional area ratio of the granular external oxide to the film-shaped external oxide film is 2% or more. Manufacturing method of silicon steel sheet. 7. The production of a unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film according to claim 5, wherein a minute strain is applied to the surface of the steel sheet by a brush with abrasive grains. Method. 8. The method for producing a unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film according to claim 5, wherein fine irregularities are imparted to the surface of the steel sheet by pickling. 9. The tension-imparting insulating film is formed by baking a coating solution mainly composed of phosphate and colloidal silica. A method for producing a unidirectional silicon steel sheet having excellent film adhesion of the tension imparting insulating film described in the above. 10. The tension-imparting insulating film is formed by baking an application liquid mainly composed of alumina sol and boric acid.
A method for producing a unidirectional silicon steel sheet having excellent film adhesion of the tension-imparting insulating film according to 6, 7, or 8.