JP3447697B2 - Oriented silicon steel sheet with insulating film that excels in space factor and seizure resistance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called directional silicon steel sheet for wound core, which is obtained by forming a grain-oriented silicon steel sheet into a predetermined shape and then annealing it to remove a processing strain introduced during the forming. Is.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are mainly used as core materials for transformers. There are roughly two types of manufacturing methods for iron cores for transformers. One of them is a stacked core method in which grain-oriented silicon steel sheets prepared in a predetermined shape and size are laminated to manufacture an iron core. The other one is a winding core method in which a grain-oriented silicon steel sheet having a predetermined size is wound into a cylindrical shape to form an iron core.

Of these, the latter wound iron core method goes through the following steps. First, a grain-oriented silicon steel sheet is sheared to a predetermined width, then rolled up into a cylindrical shape, and the rolled up cylindrical shape (hereinafter referred to as a core) is subjected to bending processing to be formed into a predetermined shape. At this time, mechanical strain is introduced into the steel sheet with the bending work, but the introduced strain deteriorates the magnetic characteristics of the iron core. Therefore, the core is annealed to remove the strain. The annealed core is once expanded. The expanded annealed steel sheet is inserted between copper wires or the like to form a transformer. A series of work consisting of core unwinding and winding on a copper wire is called lacing work.

The lacing operation is an important process that affects productivity in the transformer manufacturing process. In this work, if it takes time to develop the core, the productivity will be reduced. Therefore, it is desired that the annealed core be easily developed. However, sometimes, in the annealed core, a kind of seizure phenomenon called “seizure” occurs between steel sheets. When steel sheets are seized, a great deal of labor and time are required to expand the core, which lowers productivity. Therefore, the following technology is disclosed as a technology that does not induce image sticking.

For example, the following proposals have been made as techniques for adding powder to a coating liquid. First, JP-A-52-252
In Japanese Patent Laid-Open No. 96-96, a primary particle diameter of 70 to 70 is added to an aqueous dispersion mainly containing colloidal silica, primary phosphate and chromic acid.
A technique has been proposed in which one or two or more kinds of SiO ₂ , Al ₂ O ₃ , and TiO ₂ particles having an average specific gravity of 100 g / liter or less and 500 Å (7 to 50 nm) are added.

Next, in Japanese Patent Laid-Open No. 53-6338, alumina, silica, and
A technique of adding one kind of powder of titania and mica has been proposed. Further, in JP-A No. 54-143737, an aqueous dispersion mainly containing colloidal silica, aluminum phosphate, boric acid and sulfate has a primary particle diameter of 1000.
Ultra-fine particles of Å (100 nm) or less SiO ₂ , Al ₂ O
A technique of adding one or more kinds of ₃ , ₃ TiO ₂ particles has been proposed. Furthermore, in JP-A-4-165082, a coating solution mainly composed of phosphate, chromic acid, and colloidal silica having a particle size of 50 nm or less has a particle size of 5 to 5.
A technique of adding a non-colloidal solid substance of 2000 nm has been proposed.

In addition to the technique of adding powder to the coating liquid, as a technique of using colloidal silica having a relatively small particle size and a relatively large particle size, Japanese Patent Laid-Open No. 3-39484 discloses a phosphate and a chromium. Aqueous dispersion mainly containing acid and colloidal silica having a particle size of 20 nm or less and a particle size of 80 to 2
A technique of adding colloidal silica of 000 mμm (80 nm to 2000 nm) has also been proposed.

On the other hand, in the unidirectional silicon steel sheet targeted by the present invention, in addition to the seizure property in the strain relief annealing, a product index called a space factor is also important. The space factor is, when a grain-oriented silicon steel plate is laminated and an iron core is manufactured,
It shows the proportion of iron in the total iron core thickness. If the insulating coating on the surface of the steel sheet is too thick, or if the coating or the unevenness of the steel sheet itself is too severe, this ratio will decrease. The low space factor means that the iron occupies a small portion when compared with the same iron core thickness. When the portion occupied by iron is small, the magnetic flux becomes difficult to pass through when the iron core operates as a voltage conversion unit according to the law of electromagnetic induction inside the transformer. Then, the heat energy loss increases during voltage conversion. Therefore, a higher space factor is desirable.

As an insulating film for grain-oriented silicon steel sheet which is excellent in seizure resistance and space factor, the inventors of the present invention have disclosed, in Japanese Patent Laid-Open No. 2000-26979, an inorganic mineral substance having an average particle size of more than 2 μm and 20 μm or less. A method has been proposed in which the particles are contained in the coating liquid in a solid content ratio of 0.02% by mass or more and 20% by mass or less.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have applied these techniques and have been studying for practical use.
There was a problem to further reduce the decrease in space factor due to the occurrence of irregularities on the surface of the insulating film.

[0011]

The present invention has been made to solve the above problems, and the gist thereof is as follows. (1) A grain-oriented silicon steel sheet obtained by forming an insulating coating on a grain-finished grain-oriented silicon steel sheet, the surface roughness of one surface of which is 0.3 μm in average roughness (Ra).
Below, the surface unevenness on the other surface is 0.3 μm or more and 0.6 μm or less, and a grain-oriented silicon steel sheet with an insulating film having an excellent space factor and seizure resistance.

(2) The space factor and the seizure resistance of (1) are characterized by having a film mainly containing either or both of forsterite and spinel between the insulating film and the base metal. Excellent grain-oriented silicon steel sheet with an insulating film. (3) Forsterite between the insulating film and the base metal,
(1) A grain-oriented silicon steel sheet with an insulating film having excellent space factor and seizure resistance, which is characterized by not having a film mainly containing one or both of spinels.

(4) An insulating coating having excellent space factor and seizure resistance of (3), characterized in that the interface roughness between the coating and the base metal is 0.2 μm or less in average roughness (Ra). Grain-oriented silicon steel sheet.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As a means for minimizing the reduction of the space factor of a grain-oriented silicon steel sheet, the present inventors provide unevenness on one surface of the insulating film and do not form unevenness on the other surface. I remembered that. Generally, the seizure property of a two-phase interface depends on the contact area. Therefore, when the two phases are brought into contact with each other and kept at a high temperature, seizure easily occurs when the contact area is large, and seizure hardly occurs when the contact area is small. As one of the methods for reducing the contact area to prevent seizure, there is a method of giving unevenness to the surface. JP 2000-
Japanese Patent No. 26979 is a method of adding inorganic mineral particles to a coating liquid based on this technical idea.

On the other hand, from the viewpoint of the space factor, it is preferable that the surface unevenness is as small as possible. As a method of solving these contradictory technical requirements, it was recalled that unevenness is provided on one insulating film surface and unevenness is not formed on the other insulating film surface. In other words, we thought that the problem could be solved by the following mechanism by having such an asymmetrical form.

First, even though the surface on one side is flat, since the other surface is made uneven, the contact between the surfaces is point contact. Therefore, seizure resistance is good. In addition, since the space factor is flat on one insulating film surface, the space occupied by the space other than the silicon steel plate can be reduced as compared with the case where unevenness is formed on both surfaces. Therefore, the space factor is also good.

Based on the above concept, the inventors applied a coating solution for forming an insulating film containing particles of an inorganic mineral substance and a coating solution containing no particles to a finish-annealed silicon steel sheet on each side. A sample was prepared by baking, and the seizure property and space factor at the time of strain relief annealing were examined by the following methods. A large number of steel plates with a primary film (a film composed of forsterite and an inorganic mineral mainly composed of spinel) that had been subjected to finish annealing and had been subjected to secondary recrystallization were prepared. 50 ml of an aqueous solution containing 50% by mass of chromic acid and aluminum phosphate in this steel plate
And 100% colloidal silica aqueous dispersion with a concentration of 20% by mass
A liquid containing, as a main component, ml and alumina particles having an average particle diameter of 3.5 μm mixed therein was applied and dried on one side of each sample, and dried. At this time, by changing the addition amount of the alumina particles, the surface roughness finally determined in the next baking step was changed. 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 surface roughness of the sample thus prepared was evaluated by the average roughness (Ra) using a two-dimensional roughness meter. Moreover, the seizure property and the space factor were evaluated by the following methods. The image sticking property was evaluated by the following method. First, a large number of samples each having a short side of 3 cm and a long side of 4 cm were cut out from an unidirectional silicon steel sheet on which an insulating film was formed. Next, these samples were laminated so that the short side and the long side were staggered. When laminated in this way, the samples come into contact with each other at a 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. for a soaking time of 2 hours. After cooling to room temperature, removing the load and bolts, pull the laminated steel plates with a spring scale with a suction cup in the normal direction of the steel plates and peel them one by one.Read the value of the spring balance when peeled and peel it off. I asked for power. Fifteen samples were prepared, and the average value of their peeling forces was determined. It is considered that the peeling force obtained by such a test method reflects the ease of deployment in actual core deployment.

The space factor was evaluated by the following method. First, the short side 3 cm, the long side 15 from the unidirectional silicon steel plate on which the insulating film was formed in the same manner as the seizure evaluation sample.
A large number of cm samples were cut out. After laminating these samples and applying a constant load, the thickness at that time was measured. Next, assuming that all this thickness is composed of iron,
The mass was calculated. (Calculated mass). At this time, the density is 7.6.
Calculated as 5 g / m ² . On the other hand, the real amount of this sample was also measured, and the space factor was defined as the ratio of the real amount to the calculated mass in%. The space factor obtained by such a test method is considered to reflect the space factor in the actual iron core.

Table 1 shows the results of the evaluations performed as described above.

[0021]

[Table 1]

The following can be seen from Table 1. First, looking at the peeling force, which represents the seizure resistance during strain relief annealing,
Surface roughness of insulating film formation surface with alumina particles added: R
a is 0.24 μm to 0.28 μm (Experiment No. 1),
Under the conditions of 2) and 3)), the peeling force is 2.05 kPa (18
8 g) or more, while the surface roughness: Ra is 0.3.
Under the conditions of 0 to 0.60 (Experiment No. 4) to Experiment No. 11)), the peeling force is as very small as 0.21 kPa (19 g) or less.

Next, looking at the space factor, when the surface roughness Ra is 0.24 μm to 0.60 μm (Experiment No. 1 to Experiment No. 10)), the space factor is 97.5% to 97. ．
8%, which is extremely high, whereas surface roughness: Ra is 0.81
Under the condition of μm (Experiment No. 11)), the space factor is 96.1%
And very small. From the above results, the reason why both the small peeling force and the excellent seizure resistance at the time of strain relief annealing and the high space factor are compatible are that surface roughness: Ra is 0.30.
It was found that the condition has a surface roughness of not less than μm and not more than 0.60 μm.

As described above, the grain-oriented silicon steel sheet in which unevenness is provided on one surface of the insulating film and unevenness is not formed on the other surface is subjected to finish annealing according to a known manufacturing method as in the above experiment. After that, when applying and drying the insulating film, it can be obtained by adding an inorganic mineral substance of a certain particle size to the coating solution used on one side and not adding it on the other side. it can. The type of the inorganic mineral substance is not limited, but it is important that the structure such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ or a composite thereof is stable against heat, solvent, load and the like. The roughness of the surface of the insulating film can be adjusted by appropriately selecting the particle size and the addition amount of the inorganic mineral substance.

The inventors have conducted studies to realize a grain-oriented silicon steel sheet product having a better space factor. As a result, the space factor is better without the primary film mainly composed of forsterite or spinel, and further, if the metal surface without the primary film is smoothed by a method such as chemical polishing, the space factor is further increased. We speculated that it could be improved, and verified it by the procedure described below.

A large number of steel sheets having a primary film (a film composed of forsterite and an inorganic mineral mainly composed of spinel) which had been subjected to finish annealing and which had been subjected to secondary recrystallization were prepared. By immersing this steel sheet in a mixed acid of ammonium fluoride and sulfuric acid,
A secondary recrystallized grain-oriented silicon steel sheet having no primary coating on the surface of the steel sheet was produced. Then, some of the samples were chemically polished using an aqueous solution mainly containing hydrogen fluoride and hydrogen peroxide, and finally the surface roughness of the metal surface: Ra was 0.25 μm.
m (without chemical polishing), 0.20 μm, 0.12 μm,
The thickness was adjusted to 0.05 μm. The steel sheet thus prepared was mainly composed of 50 ml of an aqueous solution containing 50% by mass of chromic acid and aluminum phosphate and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by mass, and an average particle diameter of 5.1 μm.
The liquid in which the silica particles of m were mixed and the liquid in which the silica particles were not mixed were applied to one side of each sample and dried. At this time, by changing the addition amount of silica particles, the surface unevenness finally determined in the next baking step was changed. 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 thus prepared were evaluated for average roughness (Ra), seizure resistance, and space factor by the same method as described above. The evaluation results are shown in Table 2.

[0027]

[Table 2]

The following can be seen from Table 2. First, looking at the space factor, it is as high as 97.6% or more even under the condition with the primary coating (Experiment No. 1) to 3)), but the condition after removing the primary coating by pickling (Experiment No. 4) to 6)). Is 98.0% or more, and is higher than 98.2% under the condition of chemical polishing (Experiment No. 7) to 15)).

Next, looking at the peeling force, which represents the seizure resistance during strain relief annealing, the surface roughness Ra of the insulating film forming surface to which silica particles were added was Ra from 0.25 μm to 0.29.
Under the conditions of μm (Experiment No. 1), 4), 7), 10), 13)), the peeling force is as large as 2.37 kPa (218 g) or more, while the surface roughness: Ra is 0.30 to 0. 46
(Experiment No. 2), 3), 5), 6), 8), 11), 1
Under the conditions of 2), 14) and 15)), the peeling force is 0.21k.
It is very small, Pa (19 g) or less.

From the above results, it is possible to eliminate the primary coating in the grain-oriented silicon steel sheet with an insulating coating having a higher space factor while maintaining the excellent seizure resistance during strain relief annealing.
Alternatively, it was found that the surface roughness of the metal surface was 0.20 μm or less when the surface roughness of the metal surface was Ra by removing the primary coating and then performing chemical polishing or the like. The grain-oriented silicon steel sheet having no secondary coating after the secondary recrystallization to which the present invention can be applied may be formed by removing the primary coating by a pickling method or the like, or chlorinated in magnesia which is an annealing separator. It may be produced by adding a primary film formation-inhibiting compound such as a material so that the primary film is not formed during finish annealing.

Further, the flattening of the metal surface of the base metal may be performed by a chemical polishing method or an electrolytic polishing method, or by utilizing the condition of 1200 ° C. for 20 hours in a dry hydrogen atmosphere in the final annealing purification process, thermal energy is used. A thermal flattening method with the driving force may be used. Furthermore, instead of magnesia, a compound that does not form a primary film, such as alumina, is used as an annealing separator, and a thermal flattening method is applied to prevent the formation of a primary film during finish annealing. It doesn't matter what you do.

[0032]

[Example] <Example 1> Chromic acid and aluminum / magnesium phosphate were applied to a 0.23 mm-thick steel sheet with an inorganic mineral film mainly composed of forsterite and spinel that had been subjected to finish annealing and secondary recrystallization. 50 ml of an aqueous solution containing 50% by weight in total, and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by weight as a main component, and a coating liquid in which silica particles having an average particle diameter of 4.5 μm are added in different amounts. Then, a coating solution which was not added at all was prepared, and each side was coated and dried. 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 average roughness (Ra), seizure resistance, and space factor by the methods described above. The results are shown in Table 3.

[0033]

[Table 3]

From Table 3, in the case of the examples where the surface roughness of the surface containing silica particles: Ra is 0.3 μm or more and 0.60 μm or less, the peeling force is small, the seizure resistance is good, and the space factor is small. The rate is also good. <Example 2> A total of 50% by mass of chromic acid and aluminum phosphate was added to a 0.30 mm thick steel plate with an inorganic mineral film mainly composed of forsterite and spinel that had been subjected to finish annealing and secondary recrystallization. A coating solution containing 50 ml of an aqueous solution and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by mass, with an average particle size of 6.8 μm and alumina particles added at different amounts, and a coating solution not added at all were prepared. Each one side was coated and dried. 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 average roughness (Ra), seizure resistance, and space factor by the methods described above. The results are shown in Table 4.

[0035]

[Table 4]

From Table 4, the surface roughness of the surface containing alumina particles: In the case of the example where Ra was 0.3 μm or more and 0.60 μm or less, the peeling force was small and the seizure resistance was good, and the space factor was Is also good. <Example 3> A sheet of 0.30 mm-thick steel sheet having an inorganic mineral film mainly composed of forsterite and spinel, which has been subjected to finish annealing and secondary recrystallization, is subjected to sulfuric acid pickling to remove the inorganic mineral film. After that, chemical polishing is performed using an aqueous solution mainly containing hydrogen fluoride and hydrogen peroxide, and the surface roughness of the metal surface is Ra.
Was adjusted to 0.17 μm. Steel plate chromic acid prepared in this way and aluminum / magnesium phosphate 50 in total
50 ml of an aqueous solution containing mass% and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20 mass% were applied and dried. At this time, a coating solution in which zirconia particles having an average particle diameter of 5.5 μm were added to the coating solution in different amounts and a coating solution in which no zirconia particles were added at all were prepared, and each side was coated and dried. 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 sample thus prepared was subjected to the average roughness (R
a), seizure property, and space factor were evaluated. The results are shown in Table 5.

[0037]

[Table 5]

From Table 5, the surface roughness of the surface containing zirconia particles: Ra is 0.3 μm or more and 0.6 μm or less. In Examples, the peeling force is small and the seizure resistance is good.
And the space factor is also good.

[0039]

EFFECTS OF THE INVENTION A grain-oriented silicon steel sheet having a surface roughness (Ra) of an insulating film forming surface of 0.3 μm or less on one surface and 0.3 μm to 0.6 μm on the other surface is high. It also has good seizure resistance during strain relief annealing while maintaining the space factor.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Okada 1-1 Tobata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture Nippon Steel Co., Ltd. Yawata Works (72) Inventor Tanaka Osamu Nakahara, Tobata-ku, Kitakyushu, Fukuoka 59 Nittetsu Plant Design Co., Ltd. at address 46 (56) Reference JP-A-3-207868 (JP, A) JP-A-6-158340 (JP, A) (58) Fields investigated (Int.Cl. ⁷⁾ , DB name) C23C 22/00 B32B 7/02 104 C21D 9/46 501 H01F 1/16

Claims (4)

(57) [Claims] 1. A grain-oriented silicon steel sheet obtained by forming an insulating coating on a grain-finished grain-oriented silicon steel sheet, wherein the surface roughness of one surface of the insulating coating is 0.3 μm or less in average roughness (Ra). , And the surface unevenness on the other surface is 0.
A grain-oriented silicon steel sheet with an insulating film having an excellent space factor and seizure resistance, characterized in that it is 3 μm or more and 0.6 μm or less. 2. A space factor and seizure resistance according to claim 1, characterized by having a primary coating mainly composed of either or both of forsterite and spinel between the insulating coating and the base metal. Excellent grain oriented silicon steel sheet with insulation film. 3. The space factor and seizure resistance according to claim 1, wherein the insulating film and the base metal have no primary film mainly composed of either or both of forsterite and spinel. A grain-oriented silicon steel sheet with an insulating film that excels in properties. 4. An insulating coating having excellent space factor and seizure resistance, wherein the interface roughness between the coating and the base metal is 0.2 μm or less in average roughness (Ra). Grain-oriented silicon steel sheet.