JPH06248465A - Grain-oriented silicon steel sheet low in iron loss - Google Patents

Abstract

PURPOSE:To obtain a grain-oriented silicon steel sheet low in iron loss value without deteriorating the occupying volume rate by forming a specified film of a specified film thickness on the surface of the steel sheet. CONSTITUTION:On the surface of a grain-oriented silicon steel sheet contg. <=5% Si and low in iron loss, a film constituted of E(alphaFe-alpha)>0.024kg.mm<-2>.K<-1> by <=0.5% film thickness; where E denotes the Young's modulum (kg.mm<-2>) of the film, and alphaFe and alpha denote the liner expansion coefficient (K<-1>) of the steel sheet ad film respectively. The material of the film is constituted of one or more kinds among the oxides, carbides, borides, nitrides and silicides of Li, Be, B, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Sn, Y, Zr Nb, Mo, Hf, Ta and W. The film is formed by a sol-gel method. In this way, the film having high tension applied to the steel sheet can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unidirectional silicon steel sheet having reduced iron loss and high space factor by forming a film having a large tension on the steel sheet.

[0002]

2. Description of the Related Art One-directional electrical steel sheets are (110) [00
1) has a crystal structure with the main orientation being [1] and is often used as a magnetic iron core material. In particular, a material with a small iron loss is required to reduce energy loss. By the way, since an iron alloy containing iron and 5% or less of silicon has a large crystal magnetic anisotropy, application of external tension causes subdivision of magnetic domains, thereby reducing eddy current loss, which is a main factor of iron loss. You can Therefore, it is effective to apply tension to the steel sheet in order to reduce the core loss of the unidirectional silicon steel sheet containing 5% or less of silicon.

The tension applied to the steel sheet due to the film formation increases as the film thickness increases with respect to a certain steel plate thickness, but the thick film causes a decrease in space factor. Therefore, there is a demand for a film having a film thickness as thin as possible and having a large tension applied to the steel sheet.

The film mainly composed of forsterite formed by the reaction between the oxide on the surface of the steel sheet and the annealing separator in the finish annealing step gives a large tension to the steel sheet and is effective in reducing iron loss.

Further, a method of forming an insulating film by baking a coating liquid containing colloidal silica and a phosphate as disclosed in JP-A-48-39338 is an effect of applying tension to a steel sheet. Is large and is effective in reducing iron loss. Therefore, a general method for producing a grain-oriented electrical steel sheet is to apply a tensile insulating coating after leaving the film produced in the finish annealing step.

In an industrially produced unidirectional silicon steel sheet, a finish annealing film of about 1 μm or more and about 2
An insulating film of μm is applied. When the plate thickness is 0.23 mm, the space factor is about 97%, and the tension applied to the steel plate by these coatings is about 1 kg / mm ^-2 . According to the study by the inventors, the tension effect on the iron loss value of the unidirectional silicon steel sheet is saturated at about 1.5 kg · mm ⁻² . Although the tension can be increased by increasing the amount of insulating film, the space factor is deteriorated and the design magnetic flux density is increased.
Especially in high magnetic field, iron loss does not decrease so much.

In order to reduce the iron loss without lowering the space factor, it is necessary to develop a coating material capable of imparting high tension to the steel sheet with a small coating amount. For example, Japanese Patent Laid-Open No. 2-24
Japanese Patent No. 3770 discloses that a film formed by the sol-gel method is effective in reducing iron loss. However, in this publication, a material having a small linear expansion coefficient is recommended for forming a sol-gel film, but there is no description of a specific film material other than SiO ₂ , eucryptite, and spodumene. Further, there is no description about the film thickness.

On the other hand, in Japanese Unexamined Patent Publication No. 3-130376, SiO ₂ as a gel component, antimony oxide,
Zircon oxide, SiZrO ₄ , Al ₂ O ₃ , Fe ₂ O
₃ and TiO ₂ are mentioned, but they are not mentioned as a film component that gives tension to the steel sheet, but as a film material for ensuring the adhesion between the insulating film to be baked and the steel sheet. There is. Also, JP-A-61-24
No. 6321 gazette and others disclose a technique of forming a carbide, boride, oxide, or silicide film by dry coating, but there is no description about the film thickness and the characteristics.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a unidirectional silicon steel sheet having a coating having a large amount of applied tension to the steel sheet with a small amount of coating, and thus having a low iron loss and a high space factor. And

[0010]

Means for Solving the Problem The gist of the present invention is to determine the iron loss of a film having a film thickness of 1.5% or less of the steel plate thickness and having Young's modulus and linear expansion coefficient satisfying certain conditions. The essence is a unidirectional silicon steel sheet with a low space factor and a high space factor. The constant condition referred to here is E (α _Fe −α)> 0.024 kg · mm ⁻² · K ⁻¹ , 1 μ for a steel sheet without a finish annealing film.
For a steel sheet having a finish annealing film of about m, E (α _Fe
-Α)> 0.018 kg ・ mm ^-2・ K ^-1 (E is the Young's modulus of the film (kg ・ mm ^-2 ), α _Fe and α are the linear expansion coefficients (K ^-1 ) of the steel plate and film, respectively) is there.

[0011]

In general, it is said that the magnitude of the tension applied to the base metal due to the film formation at room temperature is determined by the difference in linear expansion coefficient between the film and the base metal and the film formation temperature. Therefore, it is considered that the material of the film should have a small linear expansion coefficient.
However, this idea is not strictly correct.

For example, a comparison will be made between a forsterite coating and a coating made of colloidal silica and aluminum phosphate. The measured linear expansion coefficient of 3% silicon steel is about 12
× 10 ^-6 K ^-1 , that of forsterite is about 11 × 10
^-6 K ^-1 is reported (Ceramics Association, Vol. 70, p8)
6, 1962). Although there is no measurement value for the coefficient of linear expansion of a film made of colloidal silica and aluminum phosphate, it is assumed that this is a SiO ₂ —Al ₂ O ₃ —P ₂ O ₃ type glass, and It is about 6 × 10 ^-6 K ^{-1 when} it is estimated using the method of calculating the thermal expansion coefficient (AA Appen, "Chemistry of Glass", Chapter X, Nisso News Agency, 1974).

The formation temperature of the forsterite film is set to 120.
When the film made from colloidal silica and aluminum phosphate at 0 ° C is taken to have an estimated softening point of 500 ° C, the tension of the latter film should be about three times that of the former film, but the measured film The tension is about the same. Therefore, it can be said that the magnitude of the tension applied to the substrate by the film is not determined only by the difference in linear expansion coefficient, the temperature difference, and the film thickness.

According to various studies, the inventors have found that the determinant of the tension applied to the substrate by the film is the Young's modulus of the film in addition to the above, and that the tension σ (kg · mm ⁻² ) is approximately We have experimentally found that σ = E (α _Fe −α) ΔT (2d / D) (1) where ΔT is the temperature difference (K) between the film formation and room temperature, d
Is the film thickness and D is the thickness of the base steel sheet.

The process of deriving the above conclusion is shown below. A commercially available 3% silicon steel plate (plate thickness: about 0.18 mm) was pickled to remove the surface film. The sol-gel method was applied to this steel sheet to obtain Al
_{A 2} O ₃ , TiO ₂ , Y ₂ O ₃ , ZrO ₂ , and SiO ₂ film was formed. Table 1 shows film forming conditions.

[0016]

[Table 1]

After forming the film, the film was protected on one side and immersed in nitric acid to remove the film on only one side. After removing the protective resin film with an organic solvent, the tension of the film was measured from the curvature of the steel sheet. . The sample thickness after removing the coating on one side was 0.16 mm. Figure 1 shows the measured values of tension,
It shows in comparison with the value calculated by the formula (1). The values in Table 2 were used for the linear expansion coefficient and Young's modulus (room temperature) of the coating material used for the calculation. It can be seen that the correspondence of the calculated value to the measured value is good, and the tension applied to the steel sheet by the coating is given by the equation (1).

From equation (1), in order to obtain a large tension without decreasing the space factor, that is, without increasing the film thickness,
It suffices to form a film made of a material having a large E (α _Fe −α) at a film forming temperature as high as possible. Since the upper limit of the film formation temperature is the melting point of silicon steel (about 1400 ° C), the space factor of 97% or more (d / D = 0.015 or less) is satisfied and the tension is 1.0 kg · mm ^-2 or more. In order to ensure that the Young's modulus and the coefficient of linear expansion of the film are E (α _Fe −α)>
Any material may be used as long as it satisfies 0.024.

More preferably, E (α _Fe −α)> 0.
If a film is formed from a material that satisfies 036, the space factor is 9
8% or more (d / D ≦ 0.010) and tension 1.0 kg · mm
^-2 or more can be secured.

Further, when a finish annealing film having a film thickness of about 0.5% of the steel plate thickness is provided, the tension applied by the finish annealing film is about 0.5 kg · mm ⁻² . Therefore, in order to apply a tension of 0.5 kg · mm ^-2 , E
An insulating film made of a material satisfying (α _Fe −α)> 0.018 may be applied. Also in this case, more desirably, E (α
If a film is formed from a material that satisfies _Fe- α)> 0.036, the space factor is 98% or more and the total tension is 1.0 kg ・ mm ^-2.
The above can be secured.

As shown in Table 2, such materials include Al ₂ O ₃ , BeO, SiO ₂ , SnO ₂ and TiO ₂ .
₂ , Y ₂ O ₃ , MgO · Al ₂ O ₃ (spinel), 3A
l ₂ O ₃・ 2SiO ₂ (mullite), 2MgO ・ 2Al
₂ O ₃ · 5 SiO ₂ (cordierite), CaO · A
l ₂ O ₃・ 2SiO ₂ (anorthite), 2CaO ・ A
l ₂ O ₃ · SiO ₂ (gerenite), CaO · MgO
・ 2SiO ₂ (diopsite) oxides and complex oxides.

[0022]

[Table 2]

Even with materials other than the oxides listed here, E
Any material satisfying (α _Fe −α)> 0.024 or 0.018 may be used. These oxide films can be formed by the sol-gel method. In addition, non-oxide ceramics such as metal carbides, borides, nitrides, silicides,
As shown in Table 3, since the Young's modulus is generally high and the linear expansion coefficient is not so large, it is suitable as a coating material for unidirectional silicon steel sheet.

[Table 3]

It is shown in the following examples that the unidirectional silicon steel sheet having a coating satisfying the conditions of the present invention exhibits a lower iron loss value than before while keeping the space factor at 97% or more. .

[0025]

EXAMPLES In the following examples, an example in which a sol-gel method is mainly used as a film forming means will be described, but the present invention is not limited to the film forming means.

Example 1 On a silicon steel rolled to a final plate thickness of 0.23 mm containing 3% Si, an oxide layer containing SiO ₂ was formed on the surface of the silicon steel for decarburization annealing, and then MgO was formed. Was applied, and a final finish annealing was performed. On the surface of the unidirectional silicon steel sheet thus annealed, there is a film of 1 μm or more mainly composed of forsterite. On the surface of this steel sheet, Al ₂ O ₃ , SiO ₂ , MgAl was formed by the sol-gel method.
Films of ₂ O ₄ (spinel) and 3Al ₂ O ₃ .2SiO ₂ (mullite) were formed at 900 ° C.

A coating liquid containing colloidal silica, aluminum phosphate and chromic anhydride was used for some samples.
It was baked at 50 ° C. to form a 2 μm insulating film, which was used as a comparative material. Table 4 shows the properties of the obtained steel sheet. The material of the present invention has a higher space factor and a lower iron loss value than the conventional material.

[0028]

[Table 4]

Example 2 For a silicon steel rolled to a final plate thickness of 0.23 mm containing 3% Si, an oxide layer containing SiO ₂ was formed on the surface of the silicon steel also for decarburization annealing, and then MgO was formed. Was applied, and a final finish annealing was performed. After removing the final annealed film by pickling, the surface was mirror-finished by the method disclosed in JP-A-4-131326, that is, high temperature annealing in a dry hydrogen atmosphere (sheet thickness 0.22 m.
m).

Al ₂ O was formed on the surface of the steel sheet by the sol-gel method.
₃ , SiO ₂ , MgAl ₂ O ₄ (spinel), 3Al ₂
A film of O ₃ .2SiO ₂ (mullite) was formed at 900 ° C. Table 5 shows the characteristics of the obtained steel sheet. It can be seen that the unidirectional silicon steel sheet according to the present invention exhibits an extremely low core loss value with a high space factor.

[0031]

[Table 5]

Example 3 On a silicon steel rolled to a final plate thickness of 0.23 mm containing 3% Si, an oxide layer containing SiO ₂ was formed on the surface of the silicon steel also for decarburization annealing, and then MgO was formed. Was applied, and a final finish annealing was performed. After removing the final annealed film by pickling, the surface was mirror-finished by chemical polishing (plate thickness 0.20 mm).

WC, TiC, SiC, ZrC, TaC, AlN, A was applied to this steel sheet by the CVD method or PVD method.
A film of 1 ₂ O ₃ , ZrB ₂ , TiB ₂ , and MoSi ₂ was formed at a substrate temperature of 500 ° C. to a thickness of 1 μm. Table 6 shows the properties of the obtained steel sheet. It can be seen that the unidirectional silicon steel sheet according to the present invention exhibits an extremely low core loss value with a high space factor.

[0034]

[Table 6]

[0035]

According to the present invention, it is possible to obtain a grain-oriented silicon steel sheet having a low iron loss value without lowering the space factor.

[Brief description of drawings]

FIG. 1 is a chart comparing measured values of tension applied to a steel sheet by a coating and calculated values by an equation (1).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Kanai 1618 Ida, Nakahara-ku, Kawasaki City Nippon Steel Co., Ltd. Advanced Technology Research Laboratories

Claims (6)

[Claims] 1. E (α _Fe −α)> 0.02 on the surface of the steel sheet.
A unidirectional silicon steel sheet with a low iron loss containing Si 5% or less by forming a film of 4 kg · mm ⁻² · K ^{−1 with} a film thickness of 1.5% or less of the steel sheet thickness. Where E is the Young's modulus of the film (kg
mm ^-2 ), α _Fe and α are the linear expansion coefficient (K ^-1 ) of the steel sheet and the coating, respectively. 2. E (α _Fe −α)> 0.03 on the surface of the steel sheet.
The unidirectional silicon steel sheet with low iron loss according to claim 1, wherein the coating film of 6 kg · mm ⁻² · K ⁻¹ is formed with a film thickness of 1.0% or less of the steel sheet thickness. 3. A film of E (α _Fe −α)> 0.018 kg · mm ⁻² · K ^{−1 with} a film thickness of 1% or less of the steel plate thickness on the film formed by finish annealing. Formed, Si 5%
A low-loss grain-oriented silicon steel sheet containing: here,
E is the Young's modulus of the coating (kg · mm ⁻² ), α _Fe and α are the linear expansion coefficient (K ⁻¹ ) of the steel sheet and coating, respectively. 4. E (α _Fe −α)> 0.036 on the surface of the steel sheet.
The unidirectional silicon steel sheet with low iron loss according to claim 3, wherein the film of kg · mm ⁻² · K ⁻¹ is formed with a film thickness of 0.5% or less of the steel plate thickness. 5. The coating material is Li, Be, B, Mg, A
l, Si, Ca, Ti, Cr, Mn, Fe, Co, N
i, Cu, Zn, Sr, Sn, Y, Zr, Nb, Mo,
The unidirectional silicon steel sheet with low iron loss according to any one of claims 1 to 4, which is made of one kind or two or more kinds of oxides, carbides, borides, nitrides, and silicides of Hf, Ta, W. 6. The unidirectional silicon steel sheet with low iron loss according to claim 1, wherein the film is formed by a sol-gel method.