JPH1180909A - Low iron loss grain-oriented silicon steel sheet good in adhesion of tension-applied type coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the adhesion of coating, to impart strong tension to a steel sheet and to improve the effect of improving iron loss by applying metallic plating to the magnetically smoothened surface of a steel sheet, furthermore subjecting the plated face to electrolytic etching and thereafter forming tension- applied type coating. SOLUTION: As for the metallic plating, one or two kinds among the simple substances and alloys Ni, Co, Fe, Cu and Cr are used, an a plating layer having 0.1 to 5 μm thickness is formed. After that, it is subjected to electrolytic etching, and 1/10 to 2/3 of the plating layer thickness is eluted to make the plated face porous, and coating of phosphate-colloidal silica-chromic acid or the like is applied thereto. Furthermore, it is simple and rational that the electrolytic etching is executed in such a manner that, in succession to the metallic plating in an electrolytic plating bath, the polarity is reversed. Since the plated metal subjected to the etching is reduced into the plating bath as it is, it can again be reutilized for the plating of a steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss directional silicon steel sheet and a method for producing the same, and more particularly to a low-iron-loss directional silicon steel sheet having good adhesion of a tension-adding type insulating film and a method for producing the same.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are mainly used as iron core materials for transformers and other electric equipment, and it is basically important that they have excellent magnetic properties such as magnetic flux density and iron loss value. Therefore, a material with low iron loss is required. To reduce iron loss, besides reducing the sheet thickness, there are methods such as increasing the Si content and increasing the orientation of the crystal orientation. In addition, it is effective to apply tension to the steel sheet. As a method of applying tension to a steel sheet, it is generally adopted to provide a coating made of a material having a smaller thermal expansion coefficient than that of the steel sheet. In other words, in the finish annealing process of silicon steel sheet, an annealing separator is applied to the steel sheet surface to form a forsterite-based coating, and a low-thermal-expansion, tension-applied insulating coating is further applied thereon to form a product, It gives strong tension to the steel plate.

In recent years, a method of magnetically smoothing the surface of a steel sheet has been proposed, for example, by intentionally suppressing the formation of a forsterite film in a finish annealing step or removing the formed forsterite film, and then removing the surface. Techniques have been developed to provide a smooth finish, and it has become clear that significant reductions in iron loss are observed. For example, Tokiko Sho 52
Japanese Patent Publication No. 24499 discloses a method of removing a surface product by pickling after finish annealing and then polishing to a mirror surface by chemical polishing or electrolytic polishing. And a method of performing an electrolytic treatment in an aqueous halide solution. In addition, Japanese Patent Laid-Open No.
No. 3943 discloses that after removing the forsterite film, 1
A method for performing thermal etching in a hydrogen stream at 000 to 1200 ° C. is disclosed. The iron loss is reduced by such a surface treatment because pinning sites that hinder domain wall movement near the surface of the steel sheet in the magnetization process are reduced, and hysteresis loss is reduced.

[0004] A tension-added insulating coating applied to a grain-oriented silicon steel sheet having a forsterite coating is generally composed mainly of aluminum or alkaline earth metal phosphate, colloidal silica, and chromic anhydride or chromate. It is formed by applying and baking a treating solution. However, there is a problem that the above-mentioned tension-applied type film is liable to be peeled off unless the adhesion to the steel sheet as the base is strong. Therefore, when the forsterite finish annealing coating is present on the steel sheet surface, sufficient adhesion can be obtained, so there is no problem. However, the above-mentioned surface smoothing treatment such as mirror finishing is performed, and the forsterite finishing annealing coating is performed. In the case of lacking, the tension-added type coating cannot be sufficiently adhered, and therefore, the technology for reducing iron loss by magnetically smoothing the surface and the technology for reducing iron loss by using the tension-added type coating can be used in parallel. It has been an issue for many years.

[0005] In order to solve such problems, several methods have conventionally been proposed. For example, Japanese Patent Publication No. 52-2449
No. 9, JP-B-7-118409 and JP-A-8-222423, after metal plating,
JP-A-184762 discloses a method in which a silica (SiO ₂ ) thin film is formed, and then a coating liquid is applied and baked. Japanese Patent Publication No. Sho 56-4150 discloses a method of forming a ceramic thin film by vapor deposition, sputtering, thermal spraying or the like.
No. 1 discloses a method of forming a ceramic film of nitride or carbide by ion plating or ion implantation. Tokuhei 2-243770
Discloses a method for forming a ceramic film by a so-called sol-gel method.

[0006]

Although these methods have been invented as methods for applying tension to a steel sheet having a smoothed surface, they have some problems.
It has not yet been put to practical use. That is, the method of forming a thin metal plating as a base and performing a coating treatment on the base is not sufficient in adhesion of the coating, and the method of forming a silica (SiO ₂ ) thin film is inferior in the effect of applying tension, and the effect of improving iron loss is not sufficient. Was not. In addition, any ceramic coating made of nitride, carbide or a combination thereof has a significantly lower thermal expansion coefficient than that of ground iron, so the tensile coating due to the difference in thermal expansion coefficient is large. There was a problem in bending adhesion. Furthermore, ceramic coatings formed by vapor deposition, sputtering, thermal spraying, ion plating, ion implantation, or sol-gel methods are expensive and difficult to maintain uniformity when processing large areas in large quantities. No improvement effect is obtained,
The problem of industrial production was not solved.

The present invention advantageously solves these problems of the prior art, and forms a tension-applied insulating coating having sufficient adhesion on a grain-oriented silicon steel sheet having a magnetically smooth surface. It is another object of the present invention to further improve the magnetic characteristics. The “magnetic smoothness” is not limited to the so-called center line average roughness (Ra), but may be, for example, a terrace-like {110} surface obtained by electrolytic treatment in an aqueous halide solution. Is large, but the hysteresis loss is extremely low, and it can be said that the surface is magnetically smooth.

[0008]

Means for Solving the Problems The present invention provides a smooth grain oriented silicon steel sheet having no forsterite coating,
In the case of applying a tension-added type insulating coating, various studies were conducted on a base that could secure the adhesion between the two, and as a result, it was completed, and a directional silicon steel sheet having a magnetically smoothed surface The object is achieved by providing a tension-adding type coating on the surface via an electrolytically etched metal plating layer.

In the above, the metal plating layer is made of Ni, C
o, Fe, Cu, and Cr, one or more of them alone or an alloy thereof, and the thickness of the metal plating layer is set to 0.1 to 5 μm.
/ 3 is eluted by the electrolysis and has a porous surface.

[0010] As a method for producing a low-iron-loss oriented silicon steel sheet having good adhesion of a tension-adding type coating, a method of producing a low-loss oriented silicon steel sheet having a magnetically smooth surface by applying metal plating to the surface of the oriented silicon steel sheet, Electroplating is performed on the plating surface, and a tension-applied coating is further applied. At this time, the metal plating is performed by using one or more of Ni, Co, Fe, Cu, Cr, or an alloy thereof. With a thickness of 0.
The etching is performed in a range of 1 to 5 μm, and the electrolytic etching is performed in a range where 1/10 to 2/3 of the metal plating layer is eluted by electrolysis. Further, metal plating is performed in an electrolytic plating bath, and thereafter, in the electrolytic plating bath, electrolytic etching is performed with the polarity reversed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, first, a grain-oriented silicon steel sheet is manufactured by an ordinary method. That is, Si2
The directional silicon steel material containing 4.5% is subjected to hot rolling and, if necessary, cold annealing with intervening intermediate annealing to obtain a final sheet thickness (generally 0.2 to 0.3 mm). After obtaining a cold rolled sheet and subjecting the cold rolled sheet to decarburization and primary recrystallization annealing, an annealing separator containing magnesia (MgO) as a main component is applied to perform secondary recrystallization and purification of the steel sheet. By performing the final annealing that also serves as the directional silicon steel, the (110) [001] orientation is sufficiently developed. In the present invention, any method may be used for the method for producing a grain-oriented silicon steel, and there is no particular limitation. For example, a material other than MgO may be used as the annealing separator to prevent the formation of a forsterite film.

If necessary, the grain-oriented silicon steel sheet obtained above is subjected to pickling treatment with a solution such as sulfuric acid.
The surface film such as forsterite is removed, and electrolytic polishing is further performed to magnetically smooth the surface of the directional silicon steel. In general, electropolishing may be performed by a known means in a phosphoric acid-chromic acid bath, and any means may be used as long as the steel sheet surface is magnetically smoothed. In addition, when the steel sheet surface is sufficiently magnetically smooth in the final annealed state, for example, when the formation of a so-called forsterite film is suppressed, the electrolytic polishing can be omitted. The term “magnetically smooth” refers to a surface state in which the number of pinning sites for domain wall motion is reduced, and is not limited to the so-called center line average roughness (Ra). It also includes a terrace-like {110} surface obtained by processing and a graining-like surface composed of steps, and can be determined by measuring the hysteresis loss of the steel sheet.

The magnetic steel sheet having the magnetically smoothed surface obtained as described above is subjected to metal plating. Metal plating is performed by electroplating using a steel sheet as a cathode in a usual plating bath. 800 as plating metal
It does not need to be a low-melting metal or alloy that liquefies at the baking temperature of tension coating of about ℃ or the strain relief annealing temperature.
Ni, Co, Fe, Cu, Cr and the like are easily used industrially and can be used alone or as composite or alloy plating.

[0014] The thickness of the plating layer is preferably in the range of 0.1 to 5 µm. If the thickness is too small, the adhesion of the tension coating is not sufficient, and not only the plating layer but also the steel sheet itself is etched during the positive electrode electrolytic treatment. Also,
If the thickness is too large, the space factor of the silicon steel sheet is undesirably reduced. Since the plating conditions vary depending on the type of bath, it cannot be said unconditionally, but the current density is about 1 to 10
The range of 0 A / dm ² is suitable for forming a target plating layer.

[0015] The metal-plated grain-oriented silicon steel sheet is then subjected to electrolytic etching. Electrolytic etching is carried out by performing electrolysis using a plated steel plate as a positive electrode, but in a bath of a metal-plated bath, after inverting the polarity of a steel plate used as a cathode at the time of plating, by inverting the polarity to make a positive electrode. It is simple and rational. Since the etched metal to be plated is directly reduced as ions in the plating bath, it can be used again for the plating treatment of the steel sheet, which is industrially extremely advantageous.

The amount of the electrolytic treatment is not particularly limited as long as it does not exceed the total amount of the electrodeposited plating.
It is preferably about / 10 to 2/3. In this range, the plating layer has a strong adhesion characteristic of electroplating to the steel sheet, and presents a rough and porous surface by electrolytic etching, and a tensile coating formed on the plating layer penetrates,
This is because both come into contact with a large surface area, and the adhesion of the tension film becomes very large. If the electrolytic etching treatment is not performed, the plating surface becomes uniform or flat, and the adhesion of the tension coating cannot be secured.

A tension coating is formed on the etched metal plating layer. As a kind of the tension coating, a phosphate-colloidal silica-chromic acid-based coating, etc., which has been conventionally used for a grain oriented silicon steel sheet having a forsterite film, is preferable in view of its effect, cost, uniform processing property, and the like. It is. The thickness of the coating is preferably in the range of about 0.3 to 10 [mu] m from the viewpoint of the effect of imparting tension, the space factor, and the adhesion of the coating.
In addition, besides the above, as a tension coating,
No. 65754, JP-A-6-65755, JP-A-6-299366 and the like.
It is also possible to apply an oxide-based coating such as alumina, and there is no particular limitation as long as the purpose is achieved.

Irradiation of the steel sheet thus obtained with a laser or plasma flame for the purpose of further reducing iron loss does not hinder the adhesion of the insulating coating even if the magnetic domains are subdivided. Absent. 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.

[0019]

【Example】

Example 1 Final thickness 0.23 mm containing 3% Si
After rolling the cold-rolled sheet to decarburization and primary recrystallization annealing,
An annealing separator containing MgO as a main component was applied, and a final annealing including a secondary recrystallization process and a purification process was performed. The finished annealed plate was washed with sulfuric acid to remove forsterite on the surface, and then electropolished in a phosphoric acid-chromic acid bath to magnetically smooth the surface. The steel plate obtained in this way
Electrodeposition and electrolytic etching of the plating layer shown in Table 1 were continuously performed. The metal to be plated was nickel (Ni), and the plating layer was electrodeposited by subjecting the steel sheet to cathodic electrolysis. Then, the polarity of the steel sheet was reversed and anodic electrolysis was performed to etch the surface of the plating layer. The plating bath was nickel sulfate (NiSO ₄ ) 400 g / l, nickel chloride (Ni
A Watt bath consisting of 85 g / l Cl _{2 and} 50 g / l boric acid (H ₃ BO ₃ ) was used. Thereafter, an aqueous treatment liquid containing magnesium phosphate, colloidal silica and chromic anhydride as main components was applied as a tension coating, and 800 ° C.
Baking to form a film having a thickness of about 3.0 μm. Magnetic flux density (B8), iron loss (W17 / 50) of the obtained steel sheet
Was measured, and the film adhesion was further evaluated. The adhesion of the coating was evaluated by wrapping the sample around a round bar having various diameters and the minimum diameter (mm) at which the coating did not peel off. Table 1 summarizes these results. As is clear from Table 1, the sample No. of the comparative example in which plating was not performed. In No. 6, peeling of the coating was observed at the time of coating, and the adhesion was extremely poor. The iron loss value is also poor because there is no tension effect due to the coating. In addition, the sample No. of the comparative example in which the plating layer was not subjected to the etching treatment. 4 and 5, the adhesion of the tension coating is poor, and the iron loss level is not sufficient. In contrast,
No. of the conforming example conforming to the present invention. 1-3 are excellent iron loss,
The film shows adhesiveness.

[0020]

[Table 1]

[0021]

Example 2 Final plate thickness 0.23 mm containing 3% Si
After rolling the cold-rolled sheet to decarburization and primary recrystallization annealing,
Alumina (Al ₂ O ₃ ) as the main component, with CaSiO
An annealing separator containing ₃ and MgO was applied, and a final annealing including a secondary recrystallization process and a purification process was performed. Hydrochloric acid (H
Cl) After pickling to remove forsterite surface, hydrofluoric acid - hydrogen peroxide (HF-H ₂ O ₂₎ subjected to chemical polishing in the bath, was magnetically smooth surface. On the obtained steel sheet,
The chromium plating layer shown in Table 2 was electrodeposited and its surface was etched. Plating was performed with a sargent bath composition consisting of 250 g / l of chromic anhydride and 2.5 g / l of sulfuric acid, and an experiment example in which electrodeposition and etching were not performed as in Example 1 was also performed. Thereafter, as a tension coating, an aqueous treatment liquid containing boric acid and alumina sol as main components is applied, and 950 is applied.
It was baked at ℃ to form a coating having a thickness of about 5.0 μm. The obtained grain-oriented silicon steel sheet was evaluated for magnetic properties and coating adhesion in the same manner as in Example 1. Table 2 summarizes these results. As is clear from Table 2, the sample No. of the comparative example in which plating was not performed. 16
And the sample No. of the comparative example in which the plating layer was not etched. 14 and 15 are also poor in both the adhesion of the tension coating and the iron loss value. On the other hand, sample Nos. Of conforming examples conforming to the present invention. Nos. 11 to 13 show excellent iron loss values and remarkably excellent film adhesion.

[0022]

[Table 2]

[0023]

Example 3 Final plate thickness containing 3% Si 0.23 mm
The cold-rolled sheet rolled to a thickness of 5 mm is formed into etching grooves at intervals of 5 mm for magnetic domain refining treatment, and then subjected to decarburization and primary recrystallization annealing. Magnesia (MgO) as a main component and calcium chloride (CaCl ₂ ) An annealing separator containing magnesium fluoride (MgF ₂ ) was applied, and a final annealing including a secondary recrystallization process was performed. After washing with hydrochloric acid to remove forsterite on the surface, sodium chloride containing polyethylene glycol (N
The surface was magnetically smoothed by electropolishing in an aCl) aqueous solution. The obtained steel sheet was subjected to electrodeposition of a cobalt plating layer and surface etching under the conditions shown in Table 3. The plating was performed on 300 g / l of cobalt sulfate (CoSO ₄ ), 120 g / l of ammonium chloride (NH ₄ C), and boric acid (H ₃ BO).
₃ ) A bath composition of 65 g / l was used. Electrodeposition and etching were continuously performed in the same plating bath as in Example 1. An experimental example in which anodic electrolytic etching was not performed was also performed for comparison. Thereafter, as a tension coating, an aqueous treatment liquid containing aluminum phosphate, colloidal silica and magnesium chromate as main components is applied,
It was baked at 800 ° C. to form a coating having a thickness of about 4.0 μm. The obtained grain-oriented silicon steel sheet was evaluated for magnetic properties and coating adhesion in the same manner as in Example 1. Table 3 summarizes these results. As is clear from Table 3, the sample No. of the comparative example in which plating was not performed. 2
6 and the sample No. 6 of the comparative example in which the plating layer was not etched. Nos. 4 and 25 are poor in both the adhesion of the tension coating and the iron loss value. On the other hand, sample Nos. Of conforming examples conforming to the present invention. Nos. 21 to 23 show excellent iron loss values and remarkably excellent film adhesion.

[0024]

[Table 3]

[0025]

Since the present invention is constructed as described above, the effect of making the surface of the plating layer porous by electrolytic etching allows the steel sheet to be subjected to bending, shearing, punching, or strain-relieving annealing. The effect of applying tension and the effect of covering the surface are not deteriorated. As a result, the excellent electromagnetic properties of the grain-oriented silicon steel sheet having a magnetically smoothed surface, particularly the low iron loss property, are combined with the properties of the tension-adding type insulating coating, so that the grain-oriented silicon steel sheet with extremely low iron loss is obtained. Steel sheet can be manufactured.

Claims (7)

[Claims] 1. A tension-applied coating having a tension-applied coating via a metal plating layer electrolytically etched on a surface of a grain-oriented silicon steel sheet having a magnetically smoothed surface. Low iron loss oriented silicon steel sheet with good adhesion. 2. The metal plating layer is made of Ni, Co, Fe, C
2. The low iron loss directional silicon steel sheet having good adhesion of the tension-added type coating according to claim 1, wherein one or two or more of u and Cr are used alone or an alloy thereof. 3. The metal plating layer has a thickness of 0.1 to 5 μm, and 1/10 to 2/3 of the metal plating layer is eluted by electrolysis to exhibit a porous surface. 2. A low iron loss directionally oriented silicon steel sheet having good adhesion of the tension-added coating according to 2. 4. The method according to claim 1, wherein the surface of the grain-oriented silicon steel sheet having a magnetically smooth surface is subjected to metal plating, then the plated surface is subjected to electrolytic etching, and further a tension-applied coating is applied. For producing a low-loss-oriented silicon steel sheet having good adhesion to a tension-applied type coating. 5. The metal plating is made of Ni, Co, Fe, C
5. The adhesion of a tension-added type coating according to claim 4, wherein the coating is performed by using one or more of u and Cr alone or two or more of them or an alloy thereof in a thickness of 0.1 to 5 [mu] m. Good low iron loss oriented silicon steel sheet manufacturing method. 6. An electrolytic etching method comprising the steps of:
5. The method for producing a low-iron-loss silicon steel sheet with good adhesion of a tension-applied coating according to claim 4, wherein 10 to 2/3 is carried out in a range where the elution is caused by electrolysis. 7. The tension according to claim 4, wherein metal plating is performed in an electrolytic plating bath, and thereafter, in the electrolytic plating bath, electrolytic etching is performed by reversing the polarity. A method for producing a low iron loss oriented silicon steel sheet having good adhesion of an additional coating.