JP2003166069A - Method for producing silicon steel sheet with insulating coating excellent in coating adhesion - Google Patents

Abstract

(57) [Problem] To provide a method for producing a directionally oriented silicon steel sheet and a non-oriented silicon steel sheet having an extremely low iron loss, having a steel sheet surface close to a mirror surface and having a tension imparting type insulating film. A method for producing a silicon steel sheet with an insulating coating, comprising forming an insulating coating on a silicon steel sheet having no inorganic coating on the surface, comprising: forming a silicate coating on the surface of the silicon steel sheet having no inorganic coating on the surface. Baking at a temperature not higher than 200 ° C. higher than the glass softening temperature of the silicate coating,
A silica-containing insulating coating is formed on the surface of the silicate coating such that the coating amount per unit area is 1.5 times or less of the silicate coating to obtain a silicon steel sheet with the insulating coating. Manufacturing method of silicon steel sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface of a grain-oriented silicon steel sheet or a non-oriented silicon steel sheet having no inorganic coating such as forsterite on the surface thereof, which is insulating and has a tension imparting effect. The present invention relates to a method for producing a silicon steel sheet with an insulating coating, which is formed.

[0002]

2. Description of the Related Art Silicon steel sheets are roughly classified into non-oriented silicon steel sheets and grain-oriented silicon steel sheets. Non-oriented silicon steel sheets are mainly used as iron core materials for rotating machines, and oriented silicon steel sheets are mainly used as iron core materials for transformers and other electrical equipment. Is required. An insulating coating is applied to the surface.

In order to reduce the iron loss of grain-oriented silicon steel sheets, there are used methods such as a method of reducing the sheet thickness, a method of increasing the Si content, and a method of enhancing the orientation of crystal orientation. In addition to that, tension is applied to the steel sheet. It is effective to do. As a method for applying tension to a steel sheet, a coating film made of a material having a smaller thermal expansion coefficient than that of the steel sheet is currently provided. That is, in the final annealing step that also serves as secondary recrystallization having a crystal orientation and purification of the steel sheet, forsterite is contained as a main component by reacting the oxide on the steel sheet surface with the annealing separator applied to the steel sheet surface. To form a film. This forsterite coating exerts a large tension on the steel sheet and has a great effect on reducing iron loss. Then, in order to further increase the tension, a low thermal expansion coating (tension imparting type coating) is generally provided on the forsterite coating to obtain a product.

However, in recent years, a method for magnetically smoothing the surface of a steel sheet has been developed. As one of the methods, there is a method of intentionally suppressing the formation of a forsterite coating in the finish annealing step or removing the formed forsterite coating, and then finishing the surface of the coating. According to this method, it has become clear that a remarkable decrease in iron loss is recognized. For example, Japanese Examined Patent Publication No. 52-2449
No. 9 discloses a method of removing surface products by pickling after finish annealing, and then finishing by chemical polishing or electrolytic polishing to obtain a mirror surface state. In addition, JP-A-5-4
Japanese Patent No. 3943 describes a method of thermal etching in H ₂ at 1000 to 1200 ° C. after removing the forsterite coating film. The iron loss is reduced by such surface treatments because the pinning sites that obstruct the domain wall movement near the surface of the steel sheet are reduced in the magnetization process.

The magnetically smooth surface that reduces the hysteresis loss is not limited to the so-called surface roughness generally indicated by _Ra (center line average roughness). For example, as described in Japanese Examined Patent Publication No. 4-72920, a magnetically smooth surface can be obtained by removing crystallized surface products and then electrolyzing in a halogenated aqueous solution.

At present, as a tension imparting type insulating coating applied to a grain-oriented silicon steel sheet having a forsterite coating, a phosphate of Al or an alkaline earth metal, colloidal silica, chromic anhydride or chromate is used. In many cases, it is formed by applying a treatment liquid mainly containing and and baking it. Tension-giving type insulating coating is formed by forming an inorganic coating represented by colloidal silica, which has a smaller coefficient of thermal expansion than steel sheet, at high temperature, and using the difference in coefficient of thermal expansion between the base steel and the insulating coating to increase the tension at room temperature. It is applied to a steel plate. The insulating coating formed by this method has a large effect of applying tension to the steel sheet and is effective in reducing iron loss. For example, the forming method is described in Japanese Patent Publication No. 53-28375 and Japanese Patent Publication No. 56-52117.

However, in the method of providing the tension-imparting coating, the forsterite finish annealing coating is a steel sheet because the coating having a larger tension imparting to the steel sheet will peel off unless the adhesion to the substrate is stronger. When present on the surface, there is no problem, but the coating could not be adhered to the steel sheet that did not have a forsterite-based finish annealing coating, such as a surface smoothing treatment such as mirror finishing. That is, the technique of magnetically smoothing the surface to reduce the iron loss and the technique of reducing the iron loss by the tension-imparting coating could not be put side by side.

A surface without a forsterite coating,
In particular, several methods have heretofore been proposed as a method for forming a tension-imparting film on a surface that has been subjected to a smoothing treatment. For example, in Japanese Examined Patent Publication No. 52-24499,
After thin metal plating, Japanese Patent Laid-Open No. 6-184762 discloses that
It describes a method of forming a SiO ₂ thin film, then applying a tension-imparting coating solution and baking it. In addition, Japanese Patent Publication No. 56-4150 discloses vapor deposition of a ceramic film.
A method of forming by sputtering, thermal spraying or the like is described. Further, Japanese Patent Publication No. 63-54767 describes a method of forming a nitride or carbide ceramic coating by ion plating or ion plantation. Further, Japanese Patent Publication No. 2-243770 describes a method of directly forming a high-tension imparting type ceramic coating on a steel sheet surface by a so-called sol-gel method.

Although these methods have been proposed as methods for applying tension to a steel sheet having a smoothed surface, they have some problems and have not been put to practical use. . That is, in the method of providing the tension-imparting coating after thin metal plating, the adhesion of the coating is not sufficient due to the uniform smoothness of the plated surface. In the method of forming the tension-imparting type coating after forming the SiO ₂ thin film, the tension-imparting effect is small and the iron loss improving effect is not sufficient. In addition, the coefficient of thermal expansion of each of the ceramic coatings of nitrides and carbides is considerably lower than that of base iron, and the effect of providing tension due to the difference in the coefficient of thermal expansion is great, but therefore the bending adhesion between the base iron and the coating is high. I have a problem. In addition, the method of forming a ceramics coating by vapor deposition, sputtering, thermal spraying, etc., and the method of forming a ceramics coating by ion plating or ion plantation are not only costly, but also when processing large-area steel sheets in large quantities. It is difficult to secure the uniformity of the surface. In the method of forming a ceramic film by the sol-gel method, the film can be formed by coating and baking in the same manner as in the past, but O. Since it is extremely difficult to form a sound film having a thickness of 5 μm or more, a large tension application effect cannot be brought about, and the desired iron loss improvement effect cannot be obtained.

On the other hand, a non-oriented silicon steel sheet, especially a non-oriented silicon steel sheet having a large amount of components close to (100) [001] in the texture of the product sheet, has a tension-imparting type on the surface of the steel sheet having no inorganic coating. It is effective to form the insulating coating for reducing the iron loss, but like the grain-oriented silicon steel sheet described above, it has not been put to practical use.

[0011]

SUMMARY OF THE INVENTION The present invention improves the adhesion of an insulating coating to a steel plate and has a steel plate surface close to a mirror surface,
Moreover, it is an object of the present invention to provide a method for manufacturing a grain-oriented silicon steel sheet and a non-oriented silicon steel sheet having a tension-imparting insulating coating and having extremely low iron loss.

[0012]

Means for Solving the Problems As a result of earnest research, the present inventor has applied a silicate aqueous solution represented by water glass, which is a liquid at room temperature, to a steel sheet in advance and baked it to form a silicate film. It has been found that by forming an insulating coating containing silica having a low coefficient of thermal expansion having a tension imparting effect, the adhesion between the insulating coating and the mirror surface becomes extremely good. Here, the present inventor conducted the following experiment, the temperature at the time of forming the silicate film by firing, and the amount of the film per unit area at the time of forming the silica-containing insulating film (hereinafter, simply It has been found that the "coating amount") is an important factor for obtaining a silicon steel sheet with an insulating coating, which has excellent appearance and excellent coating adhesion.

The above experiment will be described below. The cold-rolled sheet rolled to a final sheet thickness of 0.23 mm containing 3% by mass of Si was decarburized, primary recrystallization was annealed, and then an annealing separating agent containing MgO as a main component was applied, followed by secondary recrystallization. A final annealing including a crystallization process and a purification process was performed. The obtained finish annealed plate is H
₂ SO ₄ pickling to remove the forsterite film on the surface,
Next, electrolytic polishing is performed in a H ₃ PO ₄ —CrO ₃ bath,
The surface was magnetically smoothed. The thus obtained surface-smoothed silicon steel sheet was coated with a No. 1 sodium silicate aqueous solution (55 mass% water glass) at various coating amounts and baked at various baking temperatures to obtain a sodium silicate coating ( A silicate coating). Then, a 30 mass% colloidal silica aqueous solution was baked with various coating amounts at a firing temperature of 800 ° C. to form a silica coating (silica-containing insulating coating) to obtain a silicon steel sheet with an insulating coating.

In Table 1, the coating amount per one side of the sodium silicate coating and the silica coating is 3.0 g / m ^2.
The relationship between the firing temperature when firing the sodium silicate coating and the appearance of the obtained silicon steel sheet with an insulating coating is shown.

[0015]

[Table 1]

As is clear from Table 1, when fired at 700 ° C. or higher, the silica coating thereon was not formed uniformly and beautifully, and the appearance was whitish as if powder was blown.
On the other hand, when fired at less than 700 ° C, a beautiful appearance with gloss was obtained. Based on these results, the present inventor calcinated the sodium silicate coating at a low temperature to form the next silica coating in the semi-solidified state, so that the silicic acid components of each other were compatible with each other, and a uniform and beautiful coating was obtained. I thought

The present inventor considered as described above, and further examined the relationship between the glass softening temperature of the silicate coating and the firing temperature. The glass softening temperature of the silicate coating was measured using a differential transformer type thermal expansion coefficient measuring device, which was obtained by drying and solidifying an aqueous silicate solution and pressing it into a pellet. As a result, the glass softening temperature of sodium silicate used in the experiment was around 450 ° C, and the glass softening temperature was 200 ° C higher than the glass softening temperature.
It was found that when the firing temperature is set to a high temperature or lower as the upper limit of the firing temperature, the appearance becomes good, and when the firing temperature is higher than that, the silica coating is not compatible with the sodium silicate coating and a beautiful appearance cannot be obtained.

Further, as a reference, the present inventor conducted an experiment of mixing and applying a coating solution of a silicate coating and a coating solution of a silica-containing insulating coating. In this case, it was expected that a film having a uniform composition would be formed after coating and firing.
Actually, since the alkali metal contained in the aqueous silicate solution has hygroscopicity, the alkali metal is present on the outermost surface, the water resistance of the coating film is low, and problems such as stickiness occur. On the other hand, as in the present invention, a silicate film and a silica-containing insulating film are divided into two layers to form a film, and,
It was found that when joining by utilizing the compatibility of both, alkali metal such as sodium does not diffuse to the outermost surface, and there is no problem in water resistance.

As described above, the present inventor has found that the silicate coating should be kept at a low temperature (200 ° C. higher than the glass softening temperature of the silicate coating).
Silica component contained in the silicate film and the silica-containing insulating film on the silica-containing insulating film formed by baking at a high temperature or less) and applying the silica-containing insulating film on the silicate film in a semi-solidified state. It was found that the two are compatible with each other and that they exhibit excellent adhesion.

FIG. 1 shows the relationship between the combination of the coating amounts of the sodium silicate coating and the silica coating and the magnetic characteristics of the silicon steel sheet with an insulating coating. The magnetic characteristics of the silicon steel sheet with an insulating coating are 1.7 T and iron loss value W17 under 50 Hz.
/ 50 was evaluated in comparison with the silicon steel sheet before forming the coating film. In FIG. 1, those with an improved iron loss value W17 / 50 are shown by ◯, those with almost no change by Δ, and those with deterioration by x.

As is clear from FIG. 1, when the coating amount of the silica coating exceeds 1.5 times the coating amount of the sodium silicate coating, the magnetic properties are deteriorated despite the adhesion of the silica coating. On the other hand, when the coating amount of the silica coating film was 1.5 times or less than the coating amount of the sodium silicate coating film, the magnetic characteristics were improved or hardly changed.

Since the sodium silicate coating has a larger coefficient of thermal expansion than that of a silicon steel sheet, it has no effect of imparting tension by utilizing the difference in coefficient of thermal expansion, and is formed by applying an aqueous solution containing silica having a low coefficient of thermal expansion and firing it. The silica coating produced has a tensioning effect and improves the magnetic properties. Therefore, it is expected that the magnetic properties will be improved as the coating amount of the silica coating increases, but in reality, the magnetic properties deteriorated if the coating amount exceeds 1.5 times that of the sodium silicate coating. Here, when microscopic observation using an optical microscope or the like was performed, in the case of a material with deteriorated magnetic properties,
A so-called phase separation was observed, in which a phase composed of only SiO ₂ was separated. The present inventor has found that when the amount of the underlying sodium silicate coating is too small, the silica coating cannot be sufficiently compatibilized, leading to phase separation, resulting in local unevenness due to the non-uniform composition. It is presumed that the mechanical tension caused the deterioration of magnetic properties.

As described above, the present inventor has improved the magnetic properties of the silicon steel sheet with an insulating coating by setting the coating amount of the silica-containing insulating coating to be 1.5 times or less the coating amount of the silicate coating. I found out that.

The present inventor has completed the present invention based on these findings. That is, the present invention is a method for producing a silicon steel sheet with an insulating coating, which comprises forming an insulating coating on a silicon steel sheet having no inorganic coating on the surface, wherein the silicate coating is a silicon steel sheet having no inorganic coating on the surface. A silicate coating is formed on the surface by baking at a temperature not higher than 200 ° C. higher than the glass softening temperature of the silicate coating, and then a silica-containing insulating coating is formed on the surface of the silicate coating with a coating amount per unit area of the silicate coating. Provided is a method for producing a silicon steel sheet with an insulating coating, which is formed to be 1.5 times or less of the coating to obtain a silicon steel sheet with an insulating coating.

The silicate coating is preferably formed by coating and baking an aqueous solution containing at least one selected from the group consisting of sodium silicate, lithium silicate, potassium silicate and ammonium silicate.

The present invention also provides a silicon steel sheet with an insulating coating obtained by the method for producing a silicon steel sheet with an insulating coating.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION A method for manufacturing a silicon steel sheet with an insulating coating according to the present invention will be described in detail below. The first step of the method for producing a silicon steel sheet with an insulating coating according to the present invention is to provide a silicate coating on the surface of a silicon steel sheet not having an inorganic coating on the surface at a temperature 200 ° C. higher than the glass softening temperature of the silicate coating. It is a step of forming by firing below.

Preferable examples of the silicate used in the silicate coating of the present invention include alkali metal silicates such as sodium silicate, lithium silicate and potassium silicate, and ammonium silicate. Among them, it is preferable to use at least one selected from the group consisting of sodium silicate, lithium silicate, potassium silicate and ammonium silicate.
These silicates can be used as an aqueous solution at room temperature. This aqueous solution is known as water glass. The concentration of the aqueous solution of silicate is preferably 5 to 40% by mass. If it is less than 5% by mass, sufficient adhesion to the silica-containing insulating coating of the second layer may not be obtained, and 4
If it exceeds 0% by mass, the viscosity may be large and the coatability may be poor.

In the present invention, the silicate is placed on the surface of a silicon steel sheet having no inorganic coating on the surface and fired to form a silicate coating. Preferably, an aqueous solution containing a silicate, particularly sodium silicate, lithium silicate,
An aqueous solution containing at least one selected from the group consisting of potassium silicate and ammonium silicate is applied and baked to form a silicate film. This firing is performed at a temperature not higher than 200 ° C. higher than the glass softening temperature of the silicate coating. If the firing is performed at a temperature higher than that, when the silica-containing insulating coating is provided in the second step, the silicate coating and the silica-containing insulating coating may not be compatible with each other, and a beautiful appearance may not be obtained.

On the other hand, the lower limit of the firing temperature of the silicate coating is not particularly limited, but since it is an aqueous coating, it is 100.
If it is not baked at a temperature of not lower than 0 ° C., it may be directly mixed with the silica-containing insulating film formed thereon. Therefore, the firing temperature of the silicate coating is preferably 100 ° C. or higher.

In the second step of the method for producing a silicon steel sheet with an insulating coating of the present invention, after the above-mentioned first step, a silica-containing insulating coating is provided on the surface of the silicate coating, and the amount of coating per unit area is Is a step of forming a silicon steel sheet with an insulating coating so as to be 1.5 times or less of the silicate coating. The silica-containing insulating coating in the present invention is not particularly limited as long as it is a silica-containing insulating coating, and an inorganic coating generally used for a grain-oriented silicon steel sheet as a tension-imparting coating can be used.

As the silica-containing insulating coating, for example, a phosphate-colloidal silica-chromic acid coating, which has been conventionally used for grain-oriented silicon steel sheets having a forsterite coating, can be used to reduce iron loss. It is preferable in terms of cost and uniform processability.

In the present invention, the reason why the silica-containing insulating coating is used as the tension imparting coating is to make it compatible with the silicate coating to obtain adhesion. Further, the silica-containing insulating coating has a small coefficient of thermal expansion because it contains silica, and has a high effect of reducing iron loss.

In the second step, the silica-containing insulating coating is formed so that the coating amount per unit area is 1.5 times or less that of the silicate coating. When the coating amount per unit area of the silica-containing insulating coating exceeds 1.5 times the coating amount per unit area of the silicate coating, the magnetic properties may deteriorate. The thickness of the silica-containing insulating coating is not particularly limited, but in terms of the effect of tension application, space factor, coating adhesion, etc.,
It is preferably in the range of about 0.3 to 10 μm.

The silica content in the silica-containing insulating coating is preferably 5 to 80% by mass in terms of solid content. 5
If it is less than mass%, the effect of reducing the thermal expansion coefficient is small,
In some cases, it may not be possible to obtain a sufficient iron loss reduction effect.
If it exceeds 80 mass%, the silica may be excessive and a good glass coating may not be formed, resulting in poor adhesion.

The silicon steel sheet used in the present invention is not particularly limited, but preferred component compositions will be described below. The silicon steel sheet used in the present invention has a Si content of 1.5 to
It is preferable to contain 7.0% by mass. Si is an effective component for increasing the electrical resistance of products and reducing iron loss. S
When the i content exceeds 7.0% by mass, the hardness becomes high and the manufacturing and processing are likely to be difficult. Further, the Si content is 1.
If it is less than 5% by mass, transformation may occur during the final finish annealing, and a stable secondary recrystallization structure may not be obtained.

It is preferable that the silicon steel sheet used in the present invention contains 0.006% by mass or more of Al as an inhibitor element in the initial steel because the crystal orientation is further improved. If the Al content exceeds 0.06 mass%, the crystal orientation may deteriorate again. Therefore, A
The l content is preferably 0.06 mass% or less.

N has the same effect as Al. The N content is about 100 p in order to prevent the occurrence of blistering defects.
It is preferably pm or less. In addition, the content of N is 20
It is economically difficult to industrially reduce it to below ppm. Further, a silicon steel sheet obtained by performing a nitrogen increasing treatment after the primary recrystallization annealing is also suitably used. When the nitriding treatment is not performed, the total of Se and S in the initial steel is 0.01
It is preferable to contain 0.06 mass%. Furthermore, Mn
In order to precipitate as a compound, it is preferable to contain about 0.02 to 0.2 mass% of Mn. In either case, if the content is too small, the precipitate for causing secondary recrystallization becomes too small, and if it is too large, it becomes difficult to form a solid solution before hot rolling. When the nitriding treatment is not carried out, a suitable silicon steel sheet can be obtained without containing Mn, but it may be appropriately added for the purpose of improving the ductility of the steel.

In addition to the above elements, the silicon steel sheet used in the present invention contains B, Bi, Sb, Mo, Te, and B, Bi, Sb, Mo, Te, which are conventionally known as inhibitor components suitable for the production of grain-oriented silicon steel sheet.
Sn, P, Ge, As, Nb, Cr, Ti, Cu, P
b, Zn, In, etc. may be contained alone or in combination of two or more. Further, all of the impurities such as C, S and N have a harmful effect on the magnetic properties and particularly deteriorate iron loss, so that C: 0.003 mass% or less and S:
It is preferably 0.002 mass% or less and N: 0.002 mass% or less.

The method for producing the silicon steel sheet of the present invention is not particularly limited, but examples thereof include the following methods.
The steel adjusted to have the above-described predetermined components is usually subjected to slab heating and then hot rolled into a hot rolled coil. The slab heating temperature may be a high temperature of 1300 ° C. or higher, or a low temperature of 1250 ° C. or lower. Also,
In recent years, a method of performing hot rolling directly after continuous casting without performing slab heating has been developed, but this method can also be used.

The steel sheet after hot rolling is subjected to hot-rolled sheet annealing as required, and is finally cold-rolled by a plurality of times of rolling with one cold rolling or intermediate annealing. These rolling are so-called warm rolling aiming at dynamic aging,
It may be one that has been subjected to inter-pass aging for the purpose of static aging.

The steel sheet after the final cold rolling also serves as decarburization annealing.
The secondary recrystallization annealing is performed, and the secondary recrystallization treatment is performed by the final finishing annealing to obtain the orientation. When performing the final finish annealing, usually, an annealing separator is applied after the primary recrystallization annealing,
This forms an oxide film, but the composition of this annealing separator can be adjusted to suppress the formation of an oxide film on the surface of the steel sheet.

Even if the silicon steel sheet thus obtained is irradiated with a laser, a plasma flame or the like to further subdivide the magnetic domains for the purpose of further reducing iron loss, the adhesion with the silicate coating and the insulating coating is improved. Does not cause any problems. Further, since the iron loss is further reduced by subdividing the magnetic domains, it is possible to form grooves at regular intervals on the surface by etching or tooth profile rolls at any stage of the manufacturing process of the silicon steel sheet.

The metal surface after the finish annealing may be a base metal surface only after removing the inorganic coating such as forsterite, but the surface subjected to the smoothing treatment further has a core loss value. Is more effective in reducing. The smoothed surface can be obtained, for example, by thermal etching, chemical polishing, etc. to reduce the surface roughness as much as possible to a mirror-finished surface, or by crystal orientation enhancement processing by electrolysis in a halide aqueous solution. The graining aspect is mentioned.

As for the silicon steel sheet, the workability such as punchability is emphasized, and the finish annealing film is formed by changing the main component of the annealing separator used for finish annealing or adding an additive. A grain-oriented silicon steel sheet that has been suppressed can also be suitably used. Furthermore, not only a grain-oriented silicon steel sheet but also a non-oriented silicon steel sheet can be used.

By the way, Japanese Patent Application Laid-Open No. 63-57781 discloses a method of forming an insulating film mainly containing chromic acid or phosphoric acid after forming a silicate film on the surface of an electromagnetic steel sheet. . However, although the adhesion is improved by the method of the above-mentioned publication, neither the silicate film nor the chromic acid / phosphoric acid film has the effect of imparting tension to the steel sheet, and iron due to the tension of the film, which is the main object of the present invention, No loss value reduction effect can be obtained. That is, in the method for producing a silicon steel sheet with an insulating coating of the present invention, in the first step, the silicate coating is fired at a temperature not higher than 200 ° C. higher than the glass softening temperature of the silicate coating, so that Is formed in a semi-solidified state, and in the next second step, a silica-containing insulating coating containing silica is formed on the silicate coating,
The silicic acid components of both coatings are compatible, and the adhesion of both coatings is excellent, the appearance is uniform and beautiful, and the low thermal expansion coefficient silica contained in the silica-containing insulating coating reduces the iron loss. The characteristic is that a silicon steel sheet with an insulating film is obtained.

As described above, the insulating coated silicon steel sheet of the present invention obtained by the method for producing an insulating coated silicon steel sheet of the present invention is excellent in coating adhesion, iron loss value and appearance.

[0048]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1) Final plate thickness 0.2 containing 3% by mass of Si
The cold rolled sheet rolled to 3 mm is 5
After forming etching grooves at mm intervals, decarburizing, performing primary recrystallization annealing, applying an annealing separator containing MgO as a main component and containing lead chloride, and finally finishing annealing having a smooth surface without forsterite film. I got a plate. Then, a 20 mass% lithium silicate aqueous solution (Li ₂ O: SiO ₂₎ was added to the obtained silicon steel sheet.
₂ = 2: 7) was applied at various coating amounts and then fired at various firing temperatures to form a silicate coating (lithium silicate coating). The glass softening temperature of the lithium silicate used in this example was about 590 ° C. when measured using a differential transformer type thermal expansion coefficient measuring device. Furthermore, 30 parts by mass of 30% by mass colloidal silica was mixed with an aqueous solution in which 15 parts by mass of potassium dichromate was added to 100 parts by mass of 40% by mass magnesium monophosphate to prepare a coating solution. This coating solution is applied on a silicate film formed on a silicon steel plate with a roll coater,
Baking was performed at 0 ° C. to form a silica-containing insulating coating, and a silicon steel sheet with an insulating coating was obtained.

With respect to each of the obtained silicon steel sheets with an insulating coating, coating adhesion, iron loss value W1 under 1.7 T, 50 Hz
7/50 and appearance were evaluated. The coating adhesion was evaluated by wrapping a sample around a round bar having various diameters and by measuring the minimum diameter at which the coating did not peel off.

The results are shown in Table 2. As is clear from Table 2, the insulating coated silicon steel sheets (Samples 4 to 6) obtained by the method for producing an insulating coated silicon steel sheet of the present invention (Samples 4 to 6) are excellent in coating adhesion, iron loss value and appearance. Excel. On the other hand, when the silicate coating is not provided (Sample 1),
The silica-containing insulating coating did not adhere at all. When the firing temperature of the silicate coating was too high (Sample 2), the adhesion between the silicate coating and the silica-containing insulating coating was poor. Furthermore, when the coating amount of the silica-containing insulating coating was too large with respect to the coating amount of the silicate coating (Sample 3), the magnetic properties were inferior.

[0051]

[Table 2]

(Example 2) A non-oriented silicon steel sheet rolled to a final thickness of 0.50 mm containing 1.5% by mass of Si and 0.3% by mass of Al was applied to a 15% by mass aqueous solution of sodium silicate ( Na ₂ O: SiO ₂ = 1: 2) was applied at various coating amounts and then baked at various baking temperatures to form a silicate film (sodium silicate film). The glass softening temperature of sodium silicate used in this example was about 490 ° C. when measured with a differential transformer type thermal expansion coefficient measuring device. Then, a coating liquid containing colloidal silica, aluminum phosphate and chromic acid as main components was prepared. This coating solution is applied on a silicate film formed on a silicon steel plate by a roll coater and baked at 300 ° C. to form a silica-containing insulating film, and then 7
Strain relief annealing was performed at 50 ° C. for 2 hours.

The obtained non-oriented silicon steel sheet after annealing (silicon steel sheet with an insulating coating) had a coating adhesion of 1.0.
The iron loss value W10 / 50 and appearance under T and 50 Hz were evaluated. The coating adhesion was evaluated by the same method as in Example 1.

The results are shown in Table 3. As is clear from Table 3, a silicon steel sheet with an insulating film obtained by the method for producing a silicon steel sheet with an insulating film of the present invention (Samples 10 to 12)
Is excellent in coating adhesion, iron loss value and appearance after strain relief annealing. On the other hand, when the silicate coating is not provided (Sample 7), the firing temperature of the silicate coating is too high (Sample 9), and the coating amount of the silica-containing insulating coating is higher than that of the silicate coating. If too much (Sample 8)
Had an inferior appearance, insufficient adhesion, and slightly inferior magnetic properties.

[0055]

[Table 3]

[0056]

EFFECT OF THE INVENTION According to the method for producing a silicon steel sheet with an insulating coating of the present invention, a silicon steel sheet with an insulating coating having excellent coating adhesion, iron loss value and appearance can be obtained, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a combination of coating amounts of a sodium silicate coating and a silica coating and magnetic properties of a silicon steel sheet with an insulating coating.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsumasa Kurosawa             1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama             Shi) Kawasaki Steel Co., Ltd. Mizushima Steel Works F-term (reference) 4K026 AA03 AA22 BA02 BA03 BA12                       BB10 CA22 CA23 CA27 CA41                       DA02 EA03 EA07 EB11

Claims (2)

[Claims] 1. A method for producing a silicon steel sheet with an insulating coating, comprising forming an insulating coating on a silicon steel sheet having no inorganic coating on the surface, the method comprising the steps of: forming a silicate coating on the surface of a silicon steel sheet having no inorganic coating on the surface. The glass softening temperature of the silicate coating to 200 ° C
It is formed by baking at a high temperature or lower, and then a silica-containing insulating coating is formed on the surface of the silicate coating so that the amount of coating per unit area is 1.5 times or less that of the silicate coating. A method for producing a silicon steel sheet with an insulating coating, which comprises obtaining a silicon steel sheet with an insulating coating. 2. The method according to claim 1, wherein the silicate coating is formed by applying an aqueous solution containing at least one selected from the group consisting of sodium silicate, lithium silicate, potassium silicate and ammonium silicate and baking it. A method for manufacturing a silicon steel sheet with an insulating coating.