JP2002206172A - Grain-oriented silicon steel sheet with insulating film having excellent space factor and seizure resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a grain-oriented silicon steel sheet having an insulating film in which reduction in space factor is minimized from the standpoint of core characteristics while securing seizure resistance by providing ruggedness to the surface of an insulating film. SOLUTION: The grain-oriented silicon steel sheet with an insulating film having excellent space factor and seizure resistance can be obtained by forming an insulating film on a finish-annealed grain-oriented silicon steel sheet and the surface irregularity at one surface of the insulating film is controlled to <=0.3 μm by center line average height of surface roughness (Ra) and also the surface irregularity at the other surface is controlled to 0.3-0.6 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called grain-oriented silicon steel sheet for a wound iron core, which is formed by shaping a grain-oriented silicon steel sheet into a predetermined shape and then subjecting the sheet to annealing in order to remove working strain introduced during the forming. It is.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are mainly used as core materials for transformers. There are two main types of transformer core manufacturing methods. One of them is a stacked iron core method for manufacturing an iron core by laminating oriented silicon steel sheets of a predetermined shape and size. The other is a wound iron method in which a grain-oriented silicon steel sheet adjusted to a predetermined size is wound into a cylindrical shape and used as an iron core.

[0003] Among them, the latter wound iron core method involves the following steps. First, a grain-oriented silicon steel sheet is sheared to a predetermined width, then wound into a cylindrical shape, and further, the cylindrically wound product (hereinafter referred to as a core) is subjected to a bending process to be formed into a predetermined shape. At this time, mechanical strain is introduced into the steel sheet by the bending, but the introduced strain deteriorates the magnetic properties of the iron core. Therefore, the core is annealed to remove the strain. The annealed core is deployed once. The developed annealed steel sheet is inserted between copper wires and the like to become a transformer. A series of operations including the core unrolling and the winding around the copper wire is called a racing operation.

[0004] Racing work is an important step that affects productivity in the transformer manufacturing process. At this time, if it takes time to develop the core, the productivity is reduced. Therefore, it is desired that the annealed core be easily developed. However, sometimes, in the annealed core, a type of seizure phenomenon occurs between the steel sheets called seizure. If the steel sheets are seized, a great deal of labor and time are required for core development, which lowers productivity. Therefore, the following technology is disclosed as a technology that does not induce image sticking.

[0005] For example, there is the following proposal as a technique for adding a powder to a coating solution. First, JP-A-52-252
No. 96, an aqueous dispersion mainly composed of colloidal silica, a first phosphate and chromic acid has a primary particle diameter of 70 to
A technique has been proposed in which one or more of SiO ₂ , Al ₂ O ₃ , and TiO ₂ particles of 500 ° (7 to 50 nm) and an apparent specific gravity of 100 g / liter or less are added.

Next, in Japanese Patent Application Laid-Open No. 53-6338, alumina, silica,
A technique of adding one kind of titania and mica powders has been proposed. In Japanese Patent Application Laid-Open No. 54-143737, an aqueous dispersion mainly composed of colloidal silica, aluminum phosphate, boric acid and sulfate is used.
超 (100nm) or less ultrafine SiO ₂ , Al ₂ O
₃ , a technique of adding one or more TiO ₂ particles has been proposed. Further, in Japanese Patent Application Laid-Open No. 4-165082, a coating liquid mainly composed of phosphate, chromic acid, and colloidal silica having a particle diameter of 50 nm or less has a particle diameter of 5 to 5 nm.
A technique for adding a 2000 nm non-colloidal solid has been proposed.

[0007] Apart from the technique of adding powder to a coating solution, Japanese Unexamined Patent Publication No. 3-39484 discloses a technique using colloidal silica having a relatively small particle size and a relatively large particle size. Colloidal silica having a particle diameter of 20 nm or less and a particle diameter of 80 to 2 are added to an aqueous dispersion mainly containing an acid.
A technique for 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 in the present invention, in addition to the seizure in the strain relief annealing, a product index called a space factor is regarded as important. The space factor means that when directional silicon steel sheets are laminated and an iron core is manufactured,
It shows the ratio of iron to the entire core thickness. If the insulating film on the surface of the steel sheet is too thick, or if the film or the unevenness of the steel sheet itself is too severe, this ratio will decrease. The lower space factor means that the iron occupies less portion when compared with the same iron core thickness. If the portion occupied by the iron is small, the iron core inside the transformer obeys the law of electromagnetic induction, and when operating as a voltage conversion unit, magnetic flux is difficult to pass. In that case, thermal energy loss increases during voltage conversion. Therefore, a higher space factor is desirable.

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

[0010]

SUMMARY OF THE INVENTION The present inventors have been applying these technologies and have been studying for practical use.
There has been a problem of further reducing the decrease in the space factor due to the occurrence of irregularities on the surface of the insulating film.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its gist includes the following requirements. (1) A grain-oriented silicon steel sheet in which an insulating film is formed on a grain-oriented silicon steel sheet that has been finish-annealed, and the surface roughness of one surface of the insulating film is 0.3 μm in average roughness (Ra).
A directional silicon steel sheet provided with an insulating film having excellent space factor and seizure resistance, characterized in that surface irregularities on the other side are 0.3 μm or more and 0.6 μm or less.

(2) The space factor and the seizure resistance of (1), wherein a film mainly composed of one or both of forsterite and spinel is provided between the insulating film and the base metal. Directional silicon steel sheet with excellent insulation coating. (3) Forsterite between the insulating film and the ferrous metal,
(1) The grain-oriented silicon steel sheet with an insulating film excellent in space factor and seizure resistance, characterized by not having a film mainly composed of one or both of spinels.

(4) An insulating film with excellent space factor and seizure resistance according to (3), characterized in that the roughness of the interface between the film and the base metal is 0.2 μm or less in average roughness (Ra). Oriented silicon steel sheet.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As means for minimizing a decrease in the space factor of a grain-oriented silicon steel sheet, the present inventors provide irregularities on one surface of an insulating film and do not form irregularities on the other surface. I remembered the thing. Generally, the seizure of the two-phase interface depends on the contact area. Therefore, when the two phases are brought into contact and kept at a high temperature, seizure is likely to occur when the contact area is large, and seizure is unlikely to occur when the contact area is small. As a method of reducing the contact area to prevent image sticking, there is a method of providing irregularities on the surface. JP-A-2000-
Japanese Patent No. 26979 is a method of adding inorganic mineral particles to a coating solution based on this technical idea.

On the other hand, from the viewpoint of the space factor, it is preferable that the surface irregularities be as small as possible. As a method for solving this conflicting technical demand, it was recalled that irregularities were given to one insulating film surface and irregularities were not formed on the other insulating film surface. That is, it was thought that the problem could be solved by the following mechanism by providing such an asymmetrical form.

First, although the surface on one side is flat, irregularities are formed on the other surface, so that contact between the surfaces is point contact. Therefore, the seizure resistance is good. Further, since the space factor of one of the insulating films is flat, the ratio of the space occupied by the space other than the silicon steel plate can be reduced as compared with the case where the unevenness is formed on both surfaces. Therefore, the space factor is also good.

Based on the above-described concept, the inventors applied a coating liquid for forming an insulating film containing particles of an inorganic mineral substance and a coating liquid containing no particles to a silicon steel sheet which has been subjected to finish annealing. A sample was prepared by baking, and the seizure property and space factor during strain relief annealing were examined by the following method. A number of steel sheets with a primary film (a film composed of forsterite and an inorganic mineral mainly composed of spinel) which had been subjected to finish annealing and secondary recrystallized were prepared. 50 ml of an aqueous solution containing a total of 50% by mass of chromic acid and aluminum phosphate in this steel sheet
And aqueous colloidal silica dispersion 100 having a concentration of 20% by mass
Each of the samples was applied to one side of the sample, and the mixture was dried with a liquid containing alumina particles having a mean particle diameter of 3.5 μm and a liquid not containing the same. At this time, by changing the amount of the alumina particles added, 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 irregularities of the sample thus prepared were evaluated by means of a two-dimensional roughness meter using the average roughness (Ra). In addition, the burn-in property and the space factor were evaluated by the following methods. The evaluation of image sticking was performed by the following method. First, a large number of samples having a short side of 3 cm and a long side of 4 cm were cut out from a unidirectional silicon steel sheet having an insulating film formed thereon. Next, these samples were stacked such that the short side and the long side were alternated. When the layers are stacked in this manner, the samples come into contact with each other at exactly 3 cm square. Therefore, the contact area is 9 cm ² . A load of 60 kg / cm ² was applied to the laminated product and fixed with bolts. Then, this was annealed at a temperature of 800 ° C. and a soaking time of 2 hours. After cooling to room temperature, removing the load and bolts, pull the laminated steel plates with a spring balance with a suction cup in the normal direction of the steel plate, peel off one by one, read the value of the spring balance when peeled, and peel Seeking power. Fifteen samples were prepared, and the average value of their peeling forces was determined. It is considered that the peel force obtained by such a test method reflects the ease of deployment in actual core deployment.

The space factor was evaluated by the following method. First, a unidirectional silicon steel sheet on which an insulating film was formed in the same manner as the sample for evaluation of seizure property was obtained from a short side of 3 cm and a long side of 15 cm.
Many 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 of this thickness is made 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 substantial amount of this sample was also measured, and the ratio of the substantial amount to the calculated mass expressed in% was defined as the space factor. It is considered that the space factor obtained by such a test method reflects the actual space factor in the iron core.

Table 1 shows the results of the evaluation as described above.

[0021]

[Table 1]

The following can be seen from Table 1. First, looking at the peeling force, which indicates the seizure resistance during strain relief annealing,
Surface roughness of the insulating film forming surface to which alumina particles are 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, whereas the surface roughness: Ra is 0.3
Under the conditions of 0 to 0.60 (experiment number 4) to experiment number 11)), the peeling force is extremely small at 0.21 kPa (19 g) or less.

Looking at the space factor, when the surface roughness Ra is 0.24 μm to 0.60 μm (experiment number 1) to experiment number 10)), the space factor is 97.5% to 97%. .
8%, which is very high, whereas the surface roughness Ra is 0.81.
μm (experiment number 11)), the space factor is 96.1%.
And very small. From the above results, it is possible to achieve both low peel strength and excellent seizure resistance during strain relief annealing and high space factor because the surface roughness Ra is 0.30.
It was found that the conditions had a surface roughness of not less than μm and not more than 0.60 μm.

As described above, a grain-oriented silicon steel sheet having irregularities on one surface of the insulating film and having no irregularities on the other surface can be subjected to finish annealing according to a known manufacturing method as in the above-described experiment. After performing, when applying and drying the insulating film, it can be obtained by adding an inorganic mineral substance having a certain particle size to the coating liquid used on one side and using a coating liquid not added to the other side. it can. Although the type of the inorganic mineral substance is not limited, it is important that the structure such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ and 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 amount of the inorganic mineral substance.

The inventors have studied to realize a grain oriented silicon steel sheet product having a better space factor. As a result, the space factor is better when there is no primary film mainly composed of forsterite or spinel, and if the metal surface without the primary film is smoothed by a method such as chemical polishing, the space factor is further increased. It was speculated that it could be improved, and verified by the following procedure.

A number of steel sheets having a primary film (film made of forsterite and an inorganic mineral mainly composed of spinel) which had been subjected to finish annealing and secondary recrystallized were prepared. By immersing this steel sheet in a mixed acid of ammonium fluoride and sulfuric acid,
A secondary recrystallized directional silicon steel sheet having no primary coating on the steel sheet surface was produced. Then, some of the samples were chemically polished using an aqueous solution mainly composed of hydrogen fluoride and hydrogen peroxide, and finally, the surface roughness of the metal surface: Ra was 0.25 μm.
m (no chemical polishing), 0.20 μm, 0.12 μm,
It was adjusted to 0.05 μm. The steel sheet thus prepared was mainly composed of 50 ml of an aqueous solution containing a total of 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.
A liquid containing m silica particles and a liquid containing no silica particles were applied to one surface of each sample and dried. At this time, the surface irregularities finally determined in the next baking step were changed by changing the addition amount of the silica particles. 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), image sticking resistance, and space factor in the same manner as described above. Table 2 shows the evaluation results.

[0027]

[Table 2]

The following can be seen from Table 2. First, the space factor is as high as 97.6% or more in the conditions with the primary coating (Experiment No. 1) to 3)), but the conditions in which the primary coating is removed by pickling (Experiment No. 4) to 6)). Is 98.0% or more, and further higher, and 98.2% or more under the conditions of chemical polishing (Experiment Nos. 7 to 15)).

Next, looking at the peeling force indicating the seizure resistance during strain relief annealing, the surface roughness Ra of the insulating film formation surface to which the silica particles are added is from 0.25 μm to 0.29 μm.
Under the conditions of μm (experiment number 1), 4), 7), 10) and 13)), the peeling force was as large as 2.37 kPa (218 g) or more, while the surface roughness Ra was from 0.30 to 0.1 mm. 46
(Experiment number 2), 3), 5), 6), 8), 11), 1
Under the conditions of 2), 14) and 15)), the peeling force is 0.21 k
It is very small at Pa (19 g) or less.

From the above results, the oriented silicon steel sheet with the insulating film having a higher space factor while maintaining the excellent seizure resistance at the time of strain relief annealing can be obtained by eliminating the primary film,
Alternatively, it was found that the metal film had a surface roughness of 0.20 μm or less with the surface roughness of the metal surface being Ra by a technique such as chemical polishing after removing the primary film. For a grain-oriented silicon steel sheet without a secondary recrystallized primary film to which the present invention can be applied, the generated primary film may be temporarily removed by an acid washing method or the like, or chloride may be added to magnesia as an annealing separating agent. It may be prepared by adding a primary film-forming interfering compound such as a product so that the primary film is not formed during the finish annealing.

The metal surface of the base iron may be flattened by a chemical polishing method or an electrolytic polishing method, or in a dry hydrogen atmosphere in a final annealing and purifying process at 1200 ° C. for 20 hours to obtain a thermal energy. A thermal flattening method using the driving force as a driving force may be used. Furthermore, using a compound that does not form a primary film, such as alumina, instead of magnesia as an annealing separator, prevents the formation of a primary film during finish annealing, and superimposes a thermal flattening method to smooth the metal surface. It can be anything you do.

[0032]

<Example 1> Chromic acid, aluminum magnesium magnesium phosphate and 0.23 mm thick steel plate with inorganic mineral material mainly composed of forsterite and spinel which have been subjected to finish annealing and secondary recrystallized Of 50 ml of an aqueous solution containing a total of 50% by mass and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by mass, and a silica particle having an average particle size of 4.5 μm added to the coating solution in a different amount. And a coating solution to which no coating was added at all, was applied and dried on each side. 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 the average roughness (Ra), the seizure resistance, and the space factor by the methods described above. Table 3 shows the results.

[0033]

[Table 3]

From Table 3, it can be seen that, in the examples where the surface roughness of the surface containing the silica particles: Ra is not less than 0.3 μm and not more than 0.60 μm, the peeling force is small, the seizure resistance is good, and the space factor is large. 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 sheet having a mineral annealing film mainly composed of forsterite and spinel which 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 as main components, and adding a variation amount of alumina particles having an average particle size of 6.8 μm and a coating solution not adding at all were prepared. Was applied and dried on each side. 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 the average roughness (Ra), the seizure resistance, and the space factor by the methods described above. Table 4 shows the results.

[0035]

[Table 4]

From Table 4, it can be seen that the surface roughness of the surface containing the alumina particles: In the embodiment where Ra is not less than 0.3 μm and not more than 0.60 μm, the peeling force is small, the seizure resistance is good, and the space factor is large. Is also good. Example 3 A 0.30 mm-thick steel sheet with a mineral substance coating mainly composed of forsterite and spinel which has been subjected to finish annealing and subjected to secondary recrystallization has been subjected to sulfuric acid pickling to remove the inorganic coating. Thereafter, chemical polishing is performed using an aqueous solution mainly composed of hydrogen fluoride and hydrogen peroxide, and the surface roughness of the metal surface is Ra.
Was adjusted to 0.17 μm. A total of 50 chromic acid and aluminum magnesium phosphate prepared in this way were used.
50 ml of an aqueous solution containing 50% by mass and 100 ml of an aqueous dispersion of colloidal silica having a concentration of 20% by mass were applied and dried. At this time, a coating liquid in which zirconia particles having an average particle diameter of 5.5 μm were added in different amounts and a coating liquid not added at all were prepared in the coating liquid, and the coating liquid was applied to each side 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 an average roughness (R
a), image sticking property, and space factor were evaluated. Table 5 shows the results.

[0037]

[Table 5]

As shown in Table 5, the surface roughness of the surface containing the zirconia particles: Ra is 0.3 μm or more and 0.6 μm or less.
The space factor is also good.

[0039]

The grain-oriented silicon steel sheet having a surface roughness (Ra) of 0.3 μm or less on one surface and 0.3 μm or more and 0.6 μm or less on the other surface is high. The seizure resistance during strain relief annealing is also good while maintaining the space factor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kimihiko Sugiyama 1-1 Niwahata-machi, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor Shingo Okada Tobata-ku, Kitakyushu-shi, Fukuoka Town 1-1 New Nippon Steel Corporation Yawata Works (72) Inventor Osamu Tanaka 59-46 Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka F-term (reference) 4F100 AA00C AA20B AA20H AB03A BA02 BA03 BA07 BA10A BA10B DD01B DE01B DE01H EJ41A GB48 JG04B JL00 JM02B JM02C YY00B 4K026 AA03 BA03 BA06 BB05 CA16 CA18 CA22 CA23 DA02 DA11 EA02 EA10 EB11 4K033 RA04 SA03 TA02 BC01

Claims (4)

[Claims] 1. A grain-oriented silicon steel sheet in which an insulating film is formed on a grain-oriented silicon steel sheet that has been finish-annealed, wherein the surface roughness of one surface of the insulating film 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, wherein the grain size is 3 μm or more and 0.6 μm or less. 2. The space factor and seizure resistance according to claim 1, wherein a primary film mainly composed of one or both of forsterite and spinel is provided between the insulating film and the base metal. Grain-oriented silicon steel sheet with excellent insulation film. 3. The space factor and seizure resistance according to claim 1, wherein a primary film mainly composed of one or both of forsterite and spinel is not provided between the insulating film and the base metal. Oriented silicon steel sheet with insulating film that has excellent resistance. 4. An insulating film having an excellent space factor and seizure resistance according to claim 3, wherein the unevenness of the interface between the film and the base metal is 0.2 μm or less in average roughness (Ra). Oriented silicon steel sheet.