JP2010043293A - Coating liquid for insulation film to be used for grain-oriented electromagnetic steel sheet, and method for forming insulation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation film for a grain-oriented electromagnetic steel sheet, which has a larger tensile strength than a conventional insulation film. <P>SOLUTION: This method for forming the insulation film which imparts a great effect of reducing iron loss to the grain-oriented electromagnetic steel sheet includes applying the coating liquid, in which a primary phosphate in an amount of a fixed range is mixed with a fine powder of a hydrous silicate, to the surface of the grain-oriented electromagnetic steel sheet, drying the same, and then baking the dried film at 600°C or higher. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating solution for forming an insulating film having a high film tension on a grain-oriented electrical steel sheet, and a method for forming an insulating film using the same.

  A grain-oriented electrical steel sheet is a steel sheet having a crystal structure with the (110) [001] orientation as the main orientation and usually containing 2% or more of Si. Its main use is for iron core materials such as transformers, and there is a demand for materials with low energy loss, particularly low iron loss, during transformation.

A typical manufacturing process of the grain-oriented electrical steel sheet is as follows. After hot rolling a slab containing 2 to 4% Si and annealing the hot-rolled sheet, cold rolling is performed twice or more with one or more intermediate sandwiches to obtain the final thickness, and decarburization annealing is performed. Do. Then, by applying an annealing separator mainly composed of MgO and performing final finish annealing, a crystal structure having the (110) [001] orientation as a main orientation is developed, and Mg ₂ SiO ₄ is mainly formed on the steel sheet surface. A finish annealing film is formed. Finally, the coating liquid for forming the insulating film is applied and baked and shipped.

  The grain-oriented electrical steel sheet has a property that iron loss is improved by applying tension to the steel sheet. Therefore, by forming an insulating film made of a material having a smaller thermal expansion coefficient than that of the steel plate at a high temperature, tension is applied to the steel plate and iron loss can be improved.

  The insulating film obtained by baking a coating liquid composed of colloidal silica and phosphate disclosed in Patent Document 1 is an insulating film suitable for the above purpose, and has been used for many years.

  In recent years, due to the serious global warming problem, the energy conversion loss of transformers has attracted attention. For this reason, a further reduction in iron loss is required for the grain-oriented electrical steel sheet, and further development of an insulating film for the grain-oriented electrical steel sheet having a greater tension effect is desired.

JP 48-39338 A

  An object of the present invention is to provide an insulating film for a grain-oriented electrical steel sheet having a higher film tension than conventional ones.

The gist of the present invention is as follows.
(1) Forming an insulating film for grain-oriented electrical steel sheets characterized by blending 100 parts by weight of hydrous silicate fine powder and 1 to 2 parts by weight of one or more primary phosphate aqueous solutions in terms of solid content Coating liquid for
(2) Mixing 100 parts by weight of hydrous silicate fine powder, one or two or more of the first phosphate aqueous solution in terms of solid content, and mixing 0.01 to 10 parts by weight of the peptizer. A coating solution for forming a characteristic insulating film for grain-oriented electrical steel sheet.
(3) The coating solution for forming an insulating film for grain-oriented electrical steel sheets according to (2), wherein the peptizer is either an alkali metal polyphosphate or an alkali metal disilicate. .
(4) The directivity according to any one of (1) to (3), wherein the first phosphate is any one of phosphates of Al, Mg, Ca, Zn, and Ni. Coating solution for forming an insulating film for electrical steel sheets.
(5) The average particle diameter of the hydrated silicate fine powder is 5 μm or less, for forming the insulating film for grain-oriented electrical steel sheet according to any one of (1) to (4) Coating liquid.
(6) The directional electromagnetic wave according to any one of (1) to (5), wherein the hydrous silicate is one or more of kaolin, serpentine, talc, and pyrophyllite. A coating solution for forming an insulating film for steel sheets.
(7) For the grain-oriented electrical steel sheet after the final finish annealing, 2 to 30 parts by weight of one or more primary phosphate aqueous solutions in terms of solid content is blended with respect to 100 parts by weight of the hydrous silicate fine powder. A method for producing a grain-oriented electrical steel sheet, wherein the coating liquid is baked at 600 ° C. or more and 1000 ° C. or less.
(8) 100% by weight of hydrated silicate fine powder, 1 type or 2 or more types of primary phosphate aqueous solution, 2-30 parts by weight in terms of solid content, peptizer, for grain-oriented electrical steel sheet after final finish annealing A method for producing a grain-oriented electrical steel sheet, comprising baking a coating solution containing 0.01 to 10 parts by weight at 600 ° C. or more and 1000 ° C. or less.
(9) The method for producing a grain-oriented electrical steel sheet according to (8), wherein the peptizer is either an alkali metal polyphosphate or an alkali metal disilicate.
(10) The iron loss according to any one of (7) to (9), wherein the first phosphate is any one of Al, Mg, Ca, Zn, and Ni phosphates. Manufacturing method for low grain-oriented electrical steel sheets.
(11) The method for producing a grain-oriented electrical steel sheet according to any one of (7) to (10), wherein an average particle size of the hydrated silicate fine powder is 5 μm or less.
(12) The iron loss according to any one of (7) to (11), wherein the hydrous silicate is one or more of kaolin, serpentine, talc, and pyrophyllite. A method for producing low-oriented electrical steel sheets.

  According to the present invention, the above-mentioned object is achieved by applying and drying a coating solution in which a first silicate is mixed in a certain range to a hydrated silicate fine powder on the surface of a grain-oriented electrical steel sheet and then baking at 600 ° C. or higher. can do.

  According to the present invention, without using harmful chromic acid as a raw material, an insulating film excellent in film tension and seizure resistance after strain relief annealing can be formed on a grain-oriented electrical steel sheet.

Hydrous silicates are also called clay minerals and often have a layered structure. The layered structure consists of a 1: 1 silicate layer expressed by the composition formula X _2-3 Si ₂ O ₅ (OH) ₄ and a composition formula X _2-3 (Si, Al) ₄ O ₁₀ (OH) ₂ (where X is A 2: 1 silicate layer expressed by Al, Mg, Fe, etc.) has a laminated structure, alone or mixed, and may contain water molecules and ions between the layers.

  The present invention is based on the following examination results. The film tension was measured by changing the blending ratio of the type of phosphate and colloidal silica, and the following findings were obtained.

In the above mixed composition, the chemical composition after film baking can be regarded as a ternary system of SiO ₂ —P ₂ O ₅ —MOx. Here, MOx is a phosphate cation (in the case of aluminum phosphate, M = Al). As a result of systematic investigation, it was found that the most effective component for film tension in the above three-component system is SiO ₂ , followed by MOx, and P ₂ O ₅ is a component without tension effect. did.

Accordingly, if the coating solution is essentially composed only of colloidal silica, the film tension becomes the highest. However, in actuality, when the blending amount of the phosphate is less than 100 parts by weight with respect to 100 parts by weight of the colloidal silica solid content, the film after baking becomes rough, and the original film tension is reduced. It will not develop. Therefore, in the component system composed of colloidal silica and phosphate, P2O5 cancels out the high tensile properties of the SiO ₂ component.

The present inventors have decided to consider the hydrous silicate fine powder as SiO ₂ source to replace the colloidal silica. However, it is necessary to add a certain amount of phosphate since the hydrated silicate fine powder alone does not form a smooth film.

  FIG. 1 shows the results of evaluation after the post-straining annealing after the formation of the insulating film in the case of adding an insulating film coating solution Karion composed of phosphate and colloidal silica.

The circles in Fig. 1 are mixed with kaolinite (Al ₂ Si ₂ O ₅ (OH) ₄ ) powder with an average particle diameter of 1 µm and 50% aqueous solution of primary aluminum phosphate in various proportions. It is the result of measuring the film tension when baked at 850 ° C. after coating m ² . When the added amount of aluminum phosphate is 40% or less, the film tension increases as the added amount of phosphate decreases. However, when the addition amount is 30% or less, the film tension decreases again.

  As a result of investigating the coating solution used in the experiment, it was found that the dispersion state of the kaolinite powder in the coating solution was insufficient in the range where the phosphate addition amount was less than 30%. Therefore, when 1 part by weight of sodium pyrophosphate was added as a deflocculant to the kaolinite powder and another experiment was conducted, the result as shown by ● in FIG. 1 was obtained. Unlike the case where sodium pyrophosphate was not added, a film tension greater than that of the component system disclosed in Patent Document 1 was obtained when the amount of phosphate added was in the range of 2 to 30%.

Similar trends to kaolinite include serpentine (Mg ₃ Si ₂ O ₅ (OH) ₄ ), talc (Mg ₃ Si ₄ O ₁₀ (OH) ₂ ), and pyrophyllite (Al ₂ Si ₄ O ₁₀ (OH)). ₂ ) It was also possible to confirm. Therefore, after adding 100 parts by weight of hydrous silicate fine powder and 2 to 30 parts by weight of phosphate in terms of solid content, adding a small amount of peptizer, a high film that cannot be obtained with conventional components It was found that tension could be achieved.

  In this invention, the coating liquid which mix | blended 0.01-10 weight part of hydrous silicate fine powder 100 weight part and 2-30 weight part peptizer in conversion of solid content is used.

When the average particle diameter of the hydrous silicate fine powder exceeds 5 μm, the unevenness of the film after baking becomes severe, and the space factor when the steel sheets are laminated to form an iron core deteriorates. Although the influence when the particle diameter of the hydrous silicate becomes remarkably small is not certain, no special adverse effect has been confirmed up to 0.1 μm which is industrially available. Hydrous silicates include kaolin (Al ₂ Si ₂ O ₅ (OH) ₄ ), serpentine (Mg ₃ Si ₂ O ₅ (OH) ₄ ), talc (Mg ₃ Si ₄ O ₁₀ (OH) ₂ ), pyro Fillite (Al ₂ Si ₄ O ₁₀ (OH) ₂ ) is easily industrially available as a fine powder.

  If the added amount of the phosphate aqueous solution is less than 2 parts by weight in terms of solid content, it is difficult to form a uniform film, and if it exceeds 30 parts by weight, the film tension decreases. The primary phosphate is not particularly limited as long as it is water-soluble, but industrially, primary phosphate aqueous solutions of Al, Mg, Ca, Zn, and Ni are easily available.

  Examples of those that effectively act as a peptizer include alkali metal polyphosphates and alkali metal disilicates. Li, Na, K, Cs, etc. are easily available as alkali metals of both alkali metal salts. Examples of the polyphosphate include pyrophosphate and tripolyphosphate. If it is a chemical | medical agent which acts as a peptizer of a hydrous silicate fine powder, it is not necessary to limit to what was illustrated here. The addition amount of the peptizer is suitably 0.01 to 10 parts by weight per 100 parts by weight of the hydrous silicate fine powder. When the amount is less than 0.01 part by weight, the effect as a peptizer is small, and when it exceeds 10 parts by weight, the stability of the coating solution is deteriorated.

The coating solution adjusted as described above is applied and baked onto the grain-oriented electrical steel sheet that has been subjected to finish annealing. The coating amount is determined depending on the purpose of use of the grain-oriented electrical steel sheet, but a range of 1 to 10 g / m ² is appropriate in consideration of the iron loss reduction effect and the space factor.

  In order to obtain a large film tension, it is necessary to sufficiently raise the temperature during baking, and the baking temperature is set to 600 ° C. or higher. When a baking temperature exceeding 1000 ° C. is adopted, the steel sheet softens and distortion easily occurs, so the baking temperature is set to 1000 ° C. or less.

Example 1
The directional magnetic steel sheet having a thickness of 0.23 mm, which has been subjected to finish annealing, is applied and dried so that the coating amount after baking the coating liquid having the composition shown in Table 1 is 5 g / m ^2, and at 850 ° C. for 30 seconds. Was baked. With respect to the obtained grain-oriented electrical steel sheet with an insulating film, the film characteristics and the magnetic characteristics were evaluated, and the results shown in Table 2 were obtained.

  As shown in Table 2, the insulating film of the present invention not only has a large film tension and a large effect of reducing iron loss, but also has excellent film adhesion and corrosion resistance.

The figure which shows the result of having evaluated the seizure property at the time of strain relief annealing after insulating film formation at the time of adding kaolin to the insulating film coating liquid which consists of a phosphate and colloidal silica.

Claims (12)

  For forming an insulating film for grain-oriented electrical steel sheet, comprising 100 parts by weight of hydrous silicate fine powder and 1 to 2 parts by weight of one or more primary phosphate aqueous solutions in terms of solid content Coating liquid.   100 parts by weight of hydrous silicate fine powder, 1 to 2 parts by weight of one or more of the first phosphate aqueous solution, and 0.01 to 10 parts by weight of peptizer Coating solution for forming an insulating film for grain-oriented electrical steel sheets.   3. The coating solution for forming an insulating film for grain-oriented electrical steel sheets according to claim 2, wherein the peptizer is any one of alkali metal polyphosphate and alkali metal disilicate.   The insulating coating for grain-oriented electrical steel sheets according to any one of claims 1 to 3, wherein the first phosphate is any one of phosphates of Al, Mg, Ca, Zn, and Ni. Coating liquid for forming.   The coating liquid for forming an insulating film for grain-oriented electrical steel sheets according to any one of claims 1 to 4, wherein the hydrated silicate fine powder has an average particle size of 5 µm or less.   The insulating coating for grain-oriented electrical steel sheets according to any one of claims 1 to 5, wherein the hydrated silicate is one or more of kaolin, serpentine, talc, and pyrophyllite. Coating liquid for forming.   For the grain-oriented electrical steel sheet after final finish annealing, a coating liquid containing 2 to 30 parts by weight of one or more of the first phosphate aqueous solution in terms of solid content with respect to 100 parts by weight of the hydrous silicate fine powder. Baked at 600 ° C. or higher and 1000 ° C. or lower.   With respect to the grain-oriented electrical steel sheet after the final finish annealing, 100 parts by weight of hydrous silicate fine powder, one or more of the first phosphate aqueous solution is 2-30 parts by weight in terms of solid content, and the peptizer is 0. A method for producing a grain-oriented electrical steel sheet, wherein a coating liquid containing 01 to 10 parts by weight is baked at 600 ° C. or more and 1000 ° C. or less.   The method for producing a grain-oriented electrical steel sheet according to claim 8, wherein the peptizer is any one of alkali metal polyphosphate and alkali metal disilicate.   The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 9, wherein the first phosphate is any one of phosphates of Al, Mg, Ca, Zn, and Ni. .   The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 10, wherein an average particle diameter of the hydrated silicate fine powder is 5 µm or less.   The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 11, wherein the hydrous silicate is one or more of kaolin, serpentine, talc, and pyrophyllite.

Images