JP3921199B2 - Method for producing unidirectional silicon steel sheet excellent in film adhesion of tension imparting insulating film - Google Patents

Description

The present invention intentionally prevents an inorganic film composed of forsterite: 2 (MgO) SiO ₂ or the like from being formed during finish annealing, or grinding or acidizing the inorganic film formed during finish annealing. A secondary recrystallized unidirectional silicon steel plate prepared by removing by means such as washing, or by flattening the steel plate surface until it exhibits a specular gloss by means such as chemical polishing or electrolytic polishing. On the other hand, the present invention relates to a method for producing a unidirectional silicon steel sheet in which a tension-providing insulating film is formed with good adhesion.

  Unidirectional silicon steel plates are frequently used as magnetic iron core materials, and in particular, materials with low iron loss are required to reduce energy loss. To reduce iron loss, it is effective to apply tension to the steel sheet. Therefore, by forming a film made of a material having a smaller thermal expansion coefficient than that of the steel sheet at a high temperature, tension is applied to the steel sheet and iron loss is reduced. Reduction has been attempted.

  The forsterite-based film produced by the reaction of the oxide on the surface of the steel sheet and the annealing separator in the final annealing step can give tension to the steel sheet and has excellent film adhesion.

  On the other hand, the 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 it disclosed in Patent Document 1 has the effect of imparting tension to the steel sheet. It is large and effective in reducing iron loss.

  Therefore, it is a general method for producing a unidirectional silicon steel sheet to leave the forsterite-based film generated in the finish annealing step and form an insulating film mainly composed of phosphate.

  In recent years, it has become clear that the disordered interface structure between the forsterite film and the ground iron has reduced the iron loss improvement effect due to the film tension to some extent. Therefore, for example, as disclosed in Patent Document 2, the forsterite-based film generated in the finish annealing process is removed, and further, by performing a mirror-finishing finish, a tension film is formed again. Technology has been developed to try to reduce iron loss.

  However, in the above insulating film, when the film is formed on a film mainly composed of forsterite, a considerable adhesion can be obtained, but the forsterite-based film can be removed or a final annealing step. In the case where the forsterite is not intentionally formed, the film adhesion is not sufficient.

  When the forsterite film is removed, it is necessary to secure the required film tension only with the tension-applying insulating film formed by applying a coating solution. However, further adhesion is required. Therefore, in the conventional film formation method, it is difficult to achieve a film tension enough to bring out the effect of mirroring and to ensure film adhesion, and sufficient iron loss reduction has not been achieved. It was.

  Therefore, as a technique for ensuring 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 the finished unidirectional silicon steel sheet, for example, It was disclosed in Patent Documents 3 to 7.

  Patent Document 3 is a method of mirror-finishing a unidirectional silicon steel sheet that has been subjected to finish annealing and then internally oxidizing the vicinity of the steel sheet surface. This internal oxide layer improves the adhesion of the tension film, and internal oxidation, In other words, this is a method for compensating for the iron loss deterioration caused by the decrease in the specularity by increasing the applied tension caused by the improvement of the film adhesion.

  Patent Document 4 discloses that an external oxide type oxide film is formed on the surface of a steel sheet by annealing the unidirectional silicon steel sheet that has been mirror-finished or close-finished and annealed in a specific atmosphere at each temperature. However, this oxide film is a method of ensuring the adhesion between the tension-imparting insulating film and the steel sheet.

  In Patent Document 5, an amorphous oxide base film is formed on the surface of a finish annealed unidirectional silicon steel sheet without an inorganic mineral film when the tension-imparting insulating film is crystalline. Thus, this is a technique for preventing steel plate oxidation, that is, reduction of specularity, which occurs when a crystalline tension-imparting insulating film is formed.

  Patent Document 6 discloses that by applying crystalline firelite on the surface of a finish annealed unidirectional silicon steel plate from which nonmetallic substances have been removed, the tension imparting effect by the firelite crystals and the adhesion between the tension imparting insulating film are disclosed. This is a method of reducing iron loss by improving the performance.

In Patent Document 7, not only ensuring the adhesion of the tension coating, by making the amount of the base silica layer formed on the surface of the unidirectional silicon steel plate that has been annealed without an inorganic mineral coating to 100 mg / m ² or less. It is a method that tries to realize a good iron loss value.

JP 48-39338 A JP-A 49-96920 JP 60-131976 A JP-A-6-184762 JP-A-7-278833 JP-A-8-191010 JP 9-078252 A

  In the above-described method, the steel plate is subjected to heat treatment to form a specific oxide film on the steel plate surface. By applying these methods, secondary recrystallized unidirectional silicon steel sheets without a forsterite film have the effect of improving the adhesion of the tension-imparting insulating film and the iron loss improving effect by stabilizing the film-imparting tension. It ’s acceptable.

  However, the method of forming an oxide film by heat treatment has a problem that the equipment process burden is large. This point will be described below.

The tension imparting insulating film is generally formed by applying a water-soluble coating solution to a steel sheet using a roll coater or the like and baking it at around 850 ° C. Therefore, in order to apply a water-based coating liquid to a steel sheet after forming a specific oxide film as in the prior art, the steel sheet must be cooled to room temperature or higher and lower than 100 ° C. If strain is introduced during the cooling, the magnetic properties of the unidirectional silicon steel plate will deteriorate immediately.

  Therefore, when cooling from a high temperature state that can form an oxide film, slow cooling or the like is required. Therefore, in the method of forming a specific oxide film on the surface of the steel plate, an appropriate equipment length and cooling time are required for the cooling process.

As described above, the method for forming an oxide film by heat treatment requires a certain amount of equipment, and therefore can be carried out at a temperature between room temperature and less than 100 ° C. In other words, development of a simple film adhesion securing measure is desired. It was rare.

The present invention solves the above-described problems, and can be carried out at room temperature or higher and lower than 100 ° C. on a unidirectional silicon steel sheet that has been subjected to secondary recrystallization without an inorganic film, and is sufficient for a tension-imparting insulating film. The present invention provides a method that can ensure adhesion.

  The gist of the present invention is as follows.

(1) After intentionally prevented or or generated its removal by forsterite film pickling means for generating during finish annealing, the method of manufacturing grain-oriented silicon steel sheet to form a tensioning insulating coating, Prior to the formation of the tension-imparting insulating film, phosphate hydrate is deposited on the surface of the steel sheet in a solution at a temperature of room temperature to less than 100 ° C. , in an amount of 0.1 g / m ² or more and 10 g / m ² or less per side of the steel sheet. A method for producing a unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film, characterized by comprising:

(2) Unidirectionality excellent in film adhesion of the tension-imparting insulating film according to (1), wherein the phosphate hydrate is one or more of the following phosphate hydrates: A method for producing a silicon steel sheet.
・ Zinc phosphate tetrahydrate (Hopite: Zn ₃ (PO ₄ ) ₂ · 4H ₂ O)
・ Zinc iron phosphate tetrahydrate (phosphophyllite: Zn ₂ Fe (PO ₄ ) ₂ · 4H ₂ O)
・ Calcium zinc phosphate dihydrate (Scholzite: CaZn ₂ (PO ₄ ) ₂ · 2H ₂ O)
・ Iron manganese phosphate tetrahydrate (Hurolite: (Mn, Fe) ₅ H ₂ (PO ₄ ) ₄ · 4
H ₂ O)
・ Iron phosphate octahydrate (Vivianite: Fe ₃ (PO ₄ ) ₂ · 8H ₂ O)
· Modified zinc phosphate tetrahydrate _{(Zn 3-XYZ (Ni X} , Mn Y, Co Z) (PO 4) 2 · 4H 2
O)

  (3) The method for producing a unidirectional silicon steel sheet excellent in film adhesion of the tension-imparting insulating film according to (1) or (2), wherein the precipitation method of the phosphate hydrate is an immersion method.

  (4) The method for producing a unidirectional silicon steel sheet excellent in film adhesion of the tension-imparting insulating film according to (1) or (2), wherein the method for depositing the phosphate hydrate is an electrolytic method.

  (5) The tension according to any one of (1) to (4), wherein the tension-imparting insulating film is generated by baking a coating liquid mainly composed of phosphate and colloidal silica. A method for producing a unidirectional silicon steel sheet excellent in film adhesion of an imparting insulating film.

  (6) The tension-imparting insulating film according to any one of (1) to (4), wherein the tension-imparting insulating film is formed by baking a coating solution mainly composed of alumina sol and boric acid. A method for producing a unidirectional silicon steel sheet having excellent film adhesion.

  According to the present invention, a tension-imparting insulating film can be formed with good adhesion to a secondary annealed finished annealed plate that does not have an inorganic film after finish annealing.

  Hereinafter, details of the invention will be described.

The inventors have searched for a number of elemental technologies that can be carried out at room temperature or higher and lower than 100 ° C. and can also be expected to have an effect of improving film adhesion. In the following experiment, it was found that a film mainly composed of phosphate hydrate has a desired effect.

  As an experimental material, a 0.225 mm thick decarburized annealed plate is coated with an annealing separator mainly composed of alumina and subjected to finish annealing, secondary recrystallization, and no forsterite film having a specular gloss. A unidirectional silicon steel sheet was prepared.

  This steel sheet is immersed in a saturated aqueous solution of primary zinc phosphate containing sodium nitrite at a temperature of 40 ° C. for different times, and is a film made of zinc phosphate tetrahydrate and iron zinc phosphate tetrahydrate. Formed. The coating amount was calculated by immersing the coated sample in a chromium trioxide aqueous solution at 75 ° C. for 15 minutes, peeling the coating, and calculating the sample weight difference before and after immersion.

  Next, in order to form a tension-providing insulating film, a coating solution mainly composed of aluminum phosphate, chromic acid, and colloidal silica was applied and baked at 835 ° C. for 30 seconds in a nitrogen atmosphere. The film adhesion of the steel sheet thus prepared was examined.

  The film adhesion was evaluated by the area ratio (hereinafter referred to as the film remaining area ratio) of the part where the steel sheet and the film remained in close contact with each other when the sample was wound around a cylinder having a diameter of 20 mm.

  When the adhesion was poor and the film was completely peeled off, it was judged as 0%, and when the film adhesion was good and the film was not peeled off at all, it was judged as 100%. In the evaluation, the case where the film remaining area ratio was less than 90% was evaluated as x, and the case where the film was 90% or more was evaluated as o. The results thus examined are summarized in Table 1.

Table 1 shows the following. If phosphoric acid hydrate of Sample No. 1 phosphate hydrate of 0.01 g / m ² and sample No. 2 of 0.05 g / m ^2, the film residual area ratio, respectively, 20% and 60% The film adhesion was not sufficient.

On the other hand, when Sample No. 3 to Sample No. 9 and the amount of phosphate hydrate is 0.1 g / m ² to 10.0 g / m ² , the film remaining area ratio is 90% to 100%, which is a very good film. Adhesion was shown.

In particular, under conditions where the phosphate hydrate amount of Sample Nos. 6, 7, 8 and 9 is 1.0 g / m ² or more, the film residual area ratio is 100%, that is, no film peeling occurs and the film adhesion is It was very good.

From this experiment, it was found that the film adhesion can be greatly improved by forming a phosphate hydrate amount of 0.1 g / m ² or more per side. However, in the method of simply immersing the steel sheet sample in the liquid, 10 seconds are required as the immersion time.

  The inventors aimed at further shortening the processing time and proceeded with studies. Then, it was found in the next experiment that precipitation of phosphate hydrate can be promoted by applying an electric field while the steel sheet sample is immersed in the liquid, and the immersion time can be shortened.

The sample produced by the same method as the experiment of Table 1 was used for the experimental material. The steel plate was immersed in a saturated aqueous solution of nitric acid-containing primary zinc phosphate at a temperature of 40 ° C., applying a current density of 0.1 A / cm ² , changing the time, and zinc phosphate tetrahydrate and A film mainly composed of zinc iron phosphate tetrahydrate was formed.

  Next, in order to form a tension-providing insulating film, a coating solution mainly composed of aluminum phosphate, chromic acid, and colloidal silica was applied and baked at 835 ° C. for 30 seconds in a nitrogen atmosphere.

  The film adhesion of the steel sheet thus prepared was examined. Evaluation of film adhesion was also performed by the same method and standard as the experiment of Table 1. The results thus examined are summarized in Table 2.

  Table 2 shows the following. First, compared with the experiment of Table 1 in which an electric field is not applied, the experiment of Table 2 in which an electric field is applied has a larger amount of phosphate hydrate even at the same immersion time.

For example, when the immersion time is 2 seconds, the amount of phosphate hydrate is 0.05 g / m ² in the experiment of Table 1 in which no electric field is applied, whereas in the experiment of Table 2 in which an electric field is applied, phosphoric acid is used. The amount of salt hydrate is 1.0 g / m ^2, and the amount of precipitation is large even at the same immersion time.

Under the condition of Sample No. 2 where the phosphate film amount is 1.0 g / m ² , the film remaining area ratio is 100%, and the adhesion of the insulating film is extremely good.

Even under the conditions of Sample No. 1 where the immersion time is 1 second and the immersion time is shorter, the phosphate hydrate amount is 0.1 g / m ² and the film remaining area ratio is 91%, which is favorable. In the experiment of Table 2, the adhesiveness of the insulating film was good under all conditions.

From the experiment of Table 2, it is confirmed that the film adhesion can be secured by forming a phosphate hydrate amount of 0.1 g / m ² or more per side, and at the same time, the electric field is applied while the sample is immersed in the liquid. It was also found that the precipitation of phosphate hydrate can be promoted by application, and a predetermined amount of phosphate hydrate can be formed in a short time.

  Next, the inventors conducted experiments by changing the type of phosphate hydrate to be precipitated.

The sample produced by the same method as the experiment of Table 1 was used for the experimental material. This steel sheet was immersed in various primary phosphoric acid saturated aqueous solutions containing sodium nitrite at a temperature of 40 ° C., applying a current density of 0.1 A / cm ² , changing the time, and various types of phosphate hydration. A film mainly composed of an object was formed.

  Next, in order to form a tension-providing insulating film, a coating solution mainly composed of aluminum phosphate, chromic acid, and colloidal silica was applied and baked at 835 ° C. for 30 seconds in a nitrogen atmosphere.

  The film adhesion of the steel sheet thus prepared was examined. Evaluation of film adhesion was also performed by the same method and standard as the experiment of Table 1. The results thus examined are summarized in Table 3.

Table 3 shows the following. First, the sample No. 1, 7, 13, 19 and 25, the amount of phosphoric acid salt hydrate, ^{respectively, 0.05g / m 2, 0.04g /} m 2, 0.06g / m 2, 0.03g / M ² and 0.07 g / m ^2, and under the condition of less than 0.1 g / m ² , the residual area ratio after the bending test of the tension-imparting insulating film was 20%, 10%, 40%, Adhesiveness is not good at 5% and 70% and less than 90%.

On the other hand, when the sample number was other than the above five samples, that is, when the precipitation amount of phosphate hydrate was 0.1 g / m ² to 10.0 g / m ² , the film remaining area ratio was 90%. As described above, the adhesion was good. In particular, the adhesiveness was particularly good at a film remaining area ratio of 100% under the condition where the phosphate precipitation amount was 1.0 g / m ² or more.

From the experiments whose results are shown in Table 3, it was found that 0.1 g / m ² or more of phosphate hydrate should be precipitated in order to ensure good film adhesion.

From the above experiment, in order to ensure good film adhesion of the tension-imparting insulating film, the amount of phosphate hydrate is important, and when the amount is 0.1 g / m ² or more per side , Film adhesion is improved.

The upper limit of the amount of phosphate hydrate, for example, the amount of phosphate hydrate that deteriorates the adhesion of the insulation film, is not known at present, but unidirectional silicon steel sheets are used as transformer materials. From the viewpoint of the space factor, which is important when the coating is performed, the amount of zinc phosphate coating is desirably 10 g / m ² or less.

  The reason why the adhesion of the tension-imparting insulating film is improved by the phosphate hydrate film has not been completely clarified yet, but when the phosphate hydrate precipitates on the steel sheet surface, it has a specific alignment with the steel sheet surface. By precipitating with a property, a strong adhesion between the phosphate hydrate and the steel sheet is expressed, and as a result, on the phosphate hydrate, the tension imparting property as in the present invention, that is, It is speculated that good adhesion can be secured even when a tensile stress can be applied to the steel sheet and a film where a large stress concentration is formed at the interface portion.

  After decarburization annealing was performed on 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%, the surface oxide layer was pickled in a mixed solution of ammonium fluoride and sulfuric acid. And dissolved and removed. Next, alumina powder was applied by an electrostatic coating method, and finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere.

  There is no inorganic coating on the surface of the secondary recrystallized unidirectional silicon steel sheet thus prepared, and the surface exhibits a specular gloss.

This steel sheet was immersed in a bath composed of PO ₄ ³⁻ concentration = 45 g / liter, Zn ²⁺ concentration = 40 g / liter, and NO ³⁻ concentration = 35 g / liter at a temperature of 45 ° C. for 150 seconds. A mixed film of zinc phosphate tetrahydrate and zinc iron phosphate tetrahydrate of 1.5 g / m ² per side was formed. As a comparative example, a sample that does not form phosphate hydrate was also prepared.

  Next, a mixed solution consisting of 50 ml of a 50% magnesium phosphate / aluminum aqueous solution, 66 ml of a 30% colloidal silica aqueous dispersion, and 5 g of chromic anhydride was applied and baked at 850 ° C. for 30 seconds. An insulating film was formed.

  With respect to the unidirectional silicon steel sheet with an insulating film thus prepared, 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. The results are shown in Table 4.

From Table 4, the comparative example in which the phosphate hydrate was not formed had a film remaining area ratio of 10%, and the film adhesion of the tension-imparting insulating film was not good, whereas 1.5 g / In the example in which the phosphate hydrate of m ² was formed, the film residual area ratio was 100%, and the film adhesion of the tension-imparting insulating film was good.

  Decarburized and annealed cold-rolled sheet for unidirectional silicon steel sheet with 0.225mm thickness and Si concentration of 3.35%, and water slurry of annealing separator mainly composed of magnesia and bismuth chloride is applied on the surface. And dried. Next, finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere to obtain a unidirectional silicon steel sheet having a secondary recrystallization without an inorganic coating on the surface.

This steel plate is composed of PO ₄ ³⁻ concentration = 40 g / liter, Zn ²⁺ concentration = 35 g / liter, Ca ²⁺ concentration = 1 g / liter, and NO ³⁻ concentration = 30 g / liter. Immerse in a bath for 50 seconds to form a mixed film consisting of 0.6 g / m ² calcium zinc phosphate dihydrate, iron zinc phosphate tetrahydrate, and zinc phosphate tetrahydrate per side. It was. As a comparative example, a sample that does not form phosphate hydrate was also prepared.

  Next, a mixed solution consisting of 50 ml of a 50% magnesium phosphate aqueous solution, 100 ml of a 20% colloidal silica aqueous dispersion, and 5 g of chromic anhydride was applied and baked at 850 ° C. for 30 seconds to form a tension-providing insulating film. I let you.

  With respect to the unidirectional silicon steel sheet with an insulating film thus prepared, the adhesiveness of the insulating film was evaluated based on the film remaining area ratio when the sample was wound around a cylinder having a diameter of 20 mm. The results are shown in Table 5.

From Table 5, the comparative example in which the phosphate film was not formed had a film remaining area ratio of 20% and the film adhesion was not good, whereas the phosphate hydrate was 0.7 g / m ² per side. In the example in which the film was formed, the film residual area ratio was 95%, and the film adhesion was good.

  A cold rolled sheet for producing a unidirectional silicon steel sheet with a sheet thickness of 0.225 mm and a Si concentration of 3.25% is decarburized and annealed, and a water slurry of an annealing separator mainly composed of alumina is applied to the surface and dried. did. Next, finish annealing was performed at 1200 ° C. for 20 hours in a dry hydrogen atmosphere, and a unidirectional silicon steel sheet having no surface mineral and having a secondary recrystallization having a specular gloss was obtained.

This steel plate is composed of PO ₄ ³⁻ concentration = 50 g / liter, Zn ²⁺ concentration = 50 g / liter, Mn ²⁺ concentration = 0.6 g / liter, and NO ³⁻ concentration = 40 g / liter, with a temperature of 35 Electrolysis was performed in a bath at 0 ° C. with an electric field applied at a current density of 0.2 A / cm ² for 2 seconds to form 0.7 g / m ² of manganese iron phosphate tetrahydrate per side. As a comparative example, a sample that does not form phosphate hydrate was also prepared.

  Next, a mixed liquid composed of 300 ml of alumina sol having a concentration of 10% and 15 g of metaboric acid was applied to the prepared steel sheet, and baked at 850 ° C. for 30 seconds to form a tension-imparting insulating film.

  About the unidirectional silicon steel plate with an insulating film prepared in this way, 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. The results are shown in Table 6.

From Table 6, the comparative example in which the phosphate hydrate was not formed had a film residual area ratio of 10% and the film adhesion was not good, whereas the phosphate hydration was 0.5 g / m ² per side. In the example in which the product was formed, the film remaining area ratio was 94%, and the film adhesion was good.

  According to the present invention, a tension-imparting insulating film can be formed with good adhesion to a secondary annealed finished annealed plate that does not have an inorganic film after finish annealing.

  Therefore, this invention accelerates | stimulates the utilization as a magnetic iron core material of a unidirectional silicon steel plate.

Claims (6)

After intentionally prevented or or generated its removal by pickling means forsterite film formed during finish annealing, the method of manufacturing grain-oriented silicon steel sheet to form a tensioning insulating coating, tensioning of Prior to the formation of the insulating film, it is possible to deposit phosphate hydrate on the steel sheet surface in an amount of 0.1 g / m ² or more and 10 g / m ² or less per one surface of the steel sheet in a solution at room temperature or higher and lower than 100 ° C. A method for producing a unidirectional silicon steel sheet having excellent film adhesion of a tension-providing insulating film. The unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film according to claim 1, wherein the phosphate hydrate is one or more of the following phosphate hydrates: Manufacturing method.
・ Zinc phosphate tetrahydrate (Hopite: Zn ₃ (PO ₄ ) ₂ · 4H ₂ O)
・ Zinc iron phosphate tetrahydrate (phosphophyllite: Zn ₂ Fe (PO ₄ ) ₂ · 4H ₂ O)
・ Calcium zinc phosphate dihydrate (Scholzite: CaZn ₂ (PO ₄ ) ₂ · 2H ₂ O)
・ Iron manganese phosphate tetrahydrate (Hurolite: (Mn, Fe) ₅ H ₂ (PO ₄ ) ₄ · 4
H ₂ O)
・ Iron phosphate octahydrate (Vivianite: Fe ₃ (PO ₄ ) ₂ · 8H ₂ O)
· Modified zinc phosphate tetrahydrate _{(Zn 3-XYZ (Ni X} , Mn Y, Co Z) (PO 4) 2 · 4H 2
O)   The method for producing a unidirectional silicon steel sheet having excellent film adhesion of a tension-imparting insulating film according to claim 1 or 2, wherein the phosphate hydrate is precipitated by an immersion method.   The method for producing a unidirectional silicon steel sheet excellent in film adhesion of a tension-imparting insulating film according to claim 1 or 2, wherein the method for depositing the phosphate hydrate is an electrolytic method.   The tension application according to any one of claims 1 to 4, wherein the tension-imparting insulating film is produced by baking a coating liquid mainly composed of phosphate and colloidal silica. For producing a unidirectional silicon steel sheet excellent in film adhesion of a conductive insulating film.   The tension-imparting insulating film according to any one of claims 1 to 4, wherein the tension-imparting insulating film is formed by baking a coating liquid mainly composed of alumina sol and boric acid. A method for producing a unidirectional silicon steel sheet having excellent film adhesion.