JPH11181576A - Rain oriented silicon steel sheet good in film adhesion and extremely low in core loss value - Google Patents

Abstract

PROBLEM TO BE SOLVED: To coat the surface of a steel sheet with tension application type insulated film with tight adhesion by allowing the surface of a grain oriented silicon steel sheet produced through final finish annealing to have a ceramics base electrodeposited layer contg. calcium. SOLUTION: As for the ceramics base electrodeposited layer contg. calcium, by utilizing electric force, a ceramics layer is adsorbed and precipitated onto the surface of the steel sheet, and as the method, a plating method, an absorbing method by the electrophoresis method of charged colloidal particles or the like are given. Since the obtd. film is small in surface hardness, relatively soft and having plasticity, the peeling of the film does not occur even by the punching, bending or the like of the steel sheet, and its tension applying effect and surface coating effect are not deteriorated even if stress relieving annealing is executed. The ceramics contg. calcium contains calcium in ceramics capable of forming film on the surface of a metal such as calcium phosphate by electrodeposition. The surface of this electrodeposited layer is applied with ordinarily used tension application type insulated coating at request.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet and a method for producing the same, and more particularly to a grain-oriented electrical steel sheet having a ceramic coating as a tension-adding coating on the surface of a grain-oriented electrical steel sheet produced through final finish annealing. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron core materials for transformers and other electric equipment, and it is particularly important that magnetic flux density is high and iron loss is low. To reduce iron loss, measures such as reducing the thickness of the sheet, increasing the Si content, and increasing the orientation of the crystal orientation are taken, and it is effective to further apply tension to the steel sheet. 2. Description of the Related Art A coating made of a substance having a smaller thermal expansion coefficient is formed on a steel plate. Specifically, a coating mainly composed of forsterite is formed at the finish annealing stage during the production process of a series of grain-oriented electrical steel sheets. This film itself has a large tension applied to the steel sheet and is effective in reducing iron loss, but is further coated with a low-thermal-expansion coating (so-called tension-applied insulating film) to form a product.
Further reduction of iron loss has been achieved.

[0003] The iron loss reducing means according to the above means is almost saturated in its effect, and it is difficult to further improve it. Means for reducing pinning sites that hinder domain wall movement and significantly reducing iron loss values have been proposed. For example, Japanese Patent Publication No. 52-24
No. 499 discloses a method in which after finishing annealing, surface products are removed by pickling and then mirror-finished by chemical polishing or electrolytic polishing.
No. 3943 discloses that after removing the forsterite film, 1
A method of performing thermal etching in an H ₂ atmosphere at 000 to 1200 ° C. is disclosed. In addition, 4-729
Japanese Patent Publication No. 20 proposes a method in which after removing surface products, electrolysis is performed in a halogenated aqueous solution, and a so-called crystal orientation enhancement treatment is performed.

[0004] The application of tension is also extremely effective for steel sheets which have been subjected to such a mirror surface treatment, crystal orientation enhancement treatment, etc. (hereinafter referred to as magnetic smoothing treatment). However, since the surface of these steel sheets does not normally have a ceramic coating containing forsterite as a main component, which is present in conventional magnetic steel sheets, it is difficult to form a tension-added insulating coating thereon. There is. In particular, a film having a large tension applying ability will peel off unless the adhesion to the metal surface as the base is strong. In order to solve this problem, Tokubyo Sho 5
Japanese Patent Application Laid-Open No. 244499/1992 discloses after metal plating,
No. 84762 discloses a method in which a SiO ₂ thin film is formed and a tension-applied coating is formed thereon. Also,
Japanese Patent Publication No. Sho 56-4150 discloses a method in which a ceramic thin film is formed by vapor deposition, sputtering, thermal spraying, and the like. A method of forming is disclosed. In addition, Japanese Patent Publication No. 2-243770 discloses a method of directly applying a high-tension-applied insulating film on a steel sheet surface, such as a technique of forming a ceramic film by a so-called sol-gel method.

[0005]

However, these methods have been proposed as methods for applying tension to a steel sheet having a magnetically smoothed surface, but still have many problems. It has not been put to practical use. That is, in the method of applying thin metal plating, the adhesion of the coating is not sufficient because the plating surface is smooth, and SiO ₂
In the method of forming a thin film, the effect of improving iron loss was not sufficiently obtained because the effect of imparting tension was inferior. In addition, the method of applying a ceramic film made of nitride or carbide or a combination thereof has a large effect of imparting tension because their thermal expansion coefficient is considerably smaller than that of base steel. There was a problem with sex. Furthermore, the formation of ceramic coatings by vapor deposition, sputtering, thermal spraying, ion plating, and ion plantation is expensive, and it is difficult to ensure uniformity when processing large areas in large quantities. Although it is possible to form a film by coating and baking, it is extremely difficult to form a sound film having a thickness of 0.5 μm or more. Was not obtained. For this reason, it has not been achieved at the industrial level so far that the technology for reducing the iron loss by magnetically smoothing the surface and the technology for reducing the iron loss by the tension-applying type insulating film have been made so far.

The present invention provides a new means for applying a tension-applied insulating film to a surface of a grain-oriented electrical steel sheet, particularly a grain-oriented electrical steel sheet having a magnetically smoothed surface, with good adhesion.
Accordingly, it is an object of the present invention to apply a strong tension to the magnetic steel sheet and to propose a magnetic steel sheet having an extremely low iron loss value and a method for manufacturing the same.

[0007]

Means for Solving the Problems The present inventors have found that metal plating has a specific strong adhesion based on electroadsorption.
In addition, intensive studies were carried out to achieve both the fact that ceramics have the advantageous qualities of a tension-applied coating with a low coefficient of thermal expansion. In particular, ceramics containing calcium were magnetically smoothed in grain-oriented electrical steel sheets. The present inventors have newly found that, when applied to the surface, it is possible to extremely suitably achieve both the effect of imparting tension and the insulating property, and completed the present invention.

Specifically, the present invention provides a grain-oriented electrical steel sheet having a ceramics electrodeposited layer containing calcium on the surface of a grain-oriented electrical steel sheet produced through final finish annealing to improve film adhesion. This is to reduce the iron loss value. At that time, it is preferable that the surface of the grain-oriented electrical steel sheet is subjected to a magnetic smoothing treatment to further reduce the iron loss value, and furthermore, the ceramic electrodeposited layer is mainly made of calcium phosphate. This is intended to improve the adhesion of the coating and further reduce the iron loss value.

The present invention also provides a method for depositing a calcium-containing ceramic layer in an electrolytic solution using a grain-oriented electrical steel sheet which has been subjected to final finish annealing as a cathode. Coating is performed to produce a grain-oriented electrical steel sheet having good adhesion to the coating and extremely low iron loss value. That is, if a ceramic electrodeposited layer containing calcium is applied to a grain-oriented electrical steel sheet that has been subjected to final finish annealing according to the present invention, a sufficient tension applying effect and insulation can be imparted by itself, and therefore, a new tension is applied. Although it is not necessary to apply the mold insulating coating, if the tension applying insulating coating is applied, the effect of further reducing the iron loss can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The steel sheet to which the present invention is applied is a grain-oriented electrical steel sheet manufactured through finish annealing. The production method is not particularly limited, and according to a conventional method, a silicon steel material containing an appropriate inhibitor is hot-rolled, and the hot-rolled sheet is subjected to annealing as necessary, while being cold-rolled having a final sheet thickness. Directivity obtained by subjecting the plate to a primary recrystallization annealing that also serves as decarburization, applying an annealing separator mainly composed of MgO, and performing a final finish annealing including a secondary recrystallization process and a purification process The material may be an electromagnetic steel sheet.

In the present invention, a ceramic electrodeposited layer containing calcium is applied on the grain-oriented electrical steel sheet obtained as described above. This method uses an electric force to adsorb and deposit a ceramic layer on the surface of a steel sheet, and includes not only the method of electroplating metal salt ions but also the adsorption of charged colloid particles by electrophoresis. This is a technique basically different from a coating method using a roll or the like. The film obtained by this electrolytic deposition (electrodeposition) is different from that obtained by applying, baking and firing a slurry containing ceramics.
Since the surface hardness is small and relatively soft and plastic, even if the coating is subjected to strain relief annealing without peeling off even when punching, shearing, and repeatedly bending the steel sheet, the effect of applying tension and the effect of surface coating will not deteriorate. Absent.

[0012] The calcium-containing ceramics mentioned here are ceramics such as calcium phosphate which can form a coating on a metal surface by electrodeposition and which contain calcium. Especially Ca ((H ₂ PO ₄ ))
_2. Add NaF and NaNO ₃ to the aqueous solution of H ₂ O to adjust pH
In the acidic aqueous solution prepared as above, the electrodeposited layer electrically deposited at a bath temperature of 80 ° C. using Pt as an anode and an electromagnetic steel sheet as a cathode is a hydroxyapatite (Ca ₁₀ (PO ₄ ) _6.
It is presumed that (OH) ₂ ) is the main component, but it has the strong adhesion characteristic of electroplating to steel sheets, and the deposited ceramics have a porous surface with a unique touch,
As such, it acts as a tension-applied insulating film. Further, when a tension-applied coating liquid is applied thereon and baked, the coating liquid has good permeability, and the adhesion of the insulating coating to be formed is very strong. It can be suitably used.

The above-mentioned electrodeposition treatment of ceramics containing calcium can be applied to a steel plate having a so-called forsterite film in a state manufactured through finish annealing. The effect is obtained. However, when the purpose of the present invention is to significantly reduce iron loss, the surface of the magnetic steel sheet is preferably subjected to a so-called smoothing treatment.

Such a smoothing treatment can be obtained by, for example, minimizing the surface roughness by thermal etching or chemical polishing and finishing it to a mirror surface, or by crystal orientation enhancement treatment by electrolysis in an aqueous halide solution. And a graining-like surface. In particular, when the terraces and steps of the Si-Fe (110) plane are alternately arranged by the latter method, the adhesion of the electrodeposited layer is improved because the roughness is high unlike a simple mirror surface, and the electrodeposition of the ceramic layer is also improved. Since the speed does not depend on the plane orientation of each secondary recrystallized grain, there is no variation in the bonding force that affects the thickness and adhesion of the electrodeposited layer, and thus there is an advantage that the film characteristics are stabilized.

The thickness of the electrodeposited ceramic layer containing calcium is preferably in the range of 0.1 to 5 μm. If it is too thin, the tension given by the coating will be insufficient, and the adhesion of the tension-applied insulating coating will be insufficient.On the other hand, if it is too thick, cracks will occur in the surface layer of the ceramic coating, or as electromagnetic steel sheets Is not preferred because the space factor of The electrodeposition conditions vary depending on the type of bath, and cannot be said unconditionally. However, the current density is about 0.1 in the case of a calcium phosphate-based electrolytic solution.
The target electrodeposited ceramics layer can be formed in the range of 01 to 10 A / dm ² . In addition, the obtained electrodeposited ceramics layer is annealed to convert the hydroxide easily generated by electrodeposition from an aqueous solution into a complete oxide.
In particular, it is effective for the stability during baking of the tension coating.

In the ceramic electrodeposited layer containing calcium,
If necessary, a tensioned insulating coating is applied. As a tension-added type sono coating, a phosphate-colloidal silica-chromic acid type coating which has been conventionally used for a grain oriented silicon steel sheet having a forsterite coating, and the like, its effect, cost, uniform processing property, etc. It is preferable from the point of view. The thickness of the coating layer is 0.3 to 1 in view of the effect of imparting tension, the space factor, and the adhesion of the film.
A range of about 0 μm is preferable. However, the type of the tension-adding type insulating coating is not limited to a phosphate-colloidal silica-chromic acid type coating, and is disclosed in JP-A-6-65754, JP-A-6-65755, and JP-A-6-2993.
It is also possible to apply an oxide-based coating such as boric acid-alumina proposed in, for example, JP-A-66.

The steel sheet thus obtained is irradiated with a laser or a plasma flame or the like for the purpose of further reducing iron loss, and even if the magnetic domains are subdivided, the adhesion of the insulating coating of the present invention is not affected. no problem. In addition, in order to refine magnetic domains at any stage of the production process of the grain-oriented silicon steel sheet of the present invention, forming grooves at regular intervals by etching or tooth-shaped rolls on the surface is also effective as a means for further reducing iron loss. It is.

[0018]

【Example】

Example 1 A cold rolled sheet containing 3% Si and rolled to a final sheet thickness of 0.23 mm was subjected to decarburization and primary recrystallization annealing, and then an annealing separator containing MgO as a main component was used. Coating, final annealing including the secondary recrystallization process and the purification process is performed, and the surface of the obtained steel sheet is electrodeposited or coated using the solution shown in Table 1.
A film having a thickness of 1.2 μm was formed by baking. After forming the film, the film was further subjected to strain relief annealing at 800 ° C. for 3 hours.

The adhesion of the coating thus formed was evaluated by wrapping a steel sheet sample around a round bar having various diameters and measuring the minimum diameter at which the coating began to peel off. In addition, the iron loss W17 / 50 values before forming the coating and after performing the strain relief annealing were compared. The test results are shown in Table 1. As is clear from Table 1, Samples 1 to 3 have coatings formed by an electrodeposition method suitable for the present invention, and exhibit extremely excellent coating adhesion. On the other hand, Samples 4 and 5 coated and baked with calcium phosphate had insufficient adhesion. Further, as a result of applying a tension-adding type insulating coating to the steel sheet having these ceramic layers, in the case of samples 1 to 3, the adhesion of the coating is sufficient, and a tension is applied to the steel sheet. A low electrical steel sheet was obtained.

[0020]

[Table 1]

[0021]

Example 2 Final plate thickness 0.23 mm containing 3% Si
The rolled cold-rolled sheet is formed with etching grooves at intervals of 5 mm for domain refining treatment, decarburized, and first-stage recrystallization-annealed, and then contains SiO ₂ or CaO containing Al ₂ O ₃ as a main component. An annealing separator was applied, and a final annealed plate including a secondary recrystallization process and a purification process was applied. HCl pickling of the obtained steel sheet,
After removing the forsterite on the surface, two types of pretreatments, a mirror finishing treatment by chemical polishing in an HF-H ₂ O ₂ bath and a crystal orientation enhancement treatment by electrolysis in an NaCl aqueous solution, are performed.
The surface was magnetically smoothed. A 2.0 μm-thick calcium phosphate-based ceramic film was formed on the obtained steel sheet in the same manner as in Example 1.

A coating solution containing aluminum phosphate, colloidal silica and magnesium chromate as main components is applied to the steel sheet having the calcium phosphate-based ceramic film, and baked at 800 ° C. to about 4.0 g on one side.
/ M ² of thickness with a tensioned insulating coating layer. The obtained grain-oriented electrical steel sheet was evaluated for coating adhesion in the same manner as in Example 1, and the magnetic properties were measured for magnetic flux density (B8) and iron loss (W17 / 50). Table 2 summarizes these results.

[0023]

[Table 2]

As is clear from Table 2, Sample No. in which no ceramic film was formed was used. 27 and 28
When the tension-added insulating coating was formed, the coating was peeled off, the adhesion was extremely poor, and no tension effect was given, so that the iron loss value was poor. Sample No. on which a ceramic film was formed by coating Samples Nos. 25 and 26 had sufficient iron loss values, but had insufficient adhesion of the film including the tension-applied coating. On the other hand, the sample Nos. Corresponding to the invention examples of the present invention. Nos. 21 to 24 exhibited excellent iron loss values and remarkably excellent coating adhesion.

[0025]

According to the present invention, as described above, a ceramic containing calcium is electrochemically precipitated to form a tension-added insulating film having extremely high adhesion to an electromagnetic steel sheet. It has become possible to provide a grain-oriented electrical steel sheet having good adhesion and an extremely low iron loss value.

Claims (5)

[Claims] 1. A grain-oriented electrical steel sheet having a calcium-containing ceramic electrodeposited layer on the surface of a grain-oriented electrical steel sheet produced through final finish annealing, and having a good coating adhesion and an extremely low iron loss value. 2. The grain-oriented electrical steel sheet according to claim 1, wherein the surface of the grain-oriented electrical steel sheet has been subjected to a magnetic smoothing treatment. 3. The directional electromagnetic layer according to claim 1, wherein said ceramic electrodeposited layer containing calcium is mainly composed of a phosphate. steel sheet. 4. A grain-oriented electrical steel sheet having good coating adhesion and an extremely low iron loss value, wherein a grain layer containing calcium is deposited in an electrolytic solution using a grain-oriented electrical steel sheet which has been subjected to final finish annealing as a cathode. Manufacturing method. 5. A ceramic layer containing calcium is deposited in an electrolytic solution using a grain-oriented electrical steel sheet that has undergone final finish annealing as a cathode, and a tension-adding insulating coating is further applied on the electrodeposited layer. Method for producing grain-oriented electrical steel sheet with good coating adhesion and extremely low iron loss value.