JP2664323B2 - Unidirectional silicon steel sheet with low iron loss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is (110) [00
1) has a crystal structure with a main orientation of 1), and is widely used as a magnetic iron core material. In particular, a material with small iron loss is required to reduce energy loss. Incidentally, an iron alloy containing iron and 5% or less of silicon has a large magnetocrystalline anisotropy. Therefore, when an external tension is applied, the magnetic domain is subdivided, and eddy current loss, which is a main element of iron loss, is reduced. Can be. Therefore, it is effective to apply tension to the steel sheet to reduce the iron loss of the unidirectional silicon steel sheet containing 5% or less of silicon.

[0003] The tension applied to a steel sheet due to the formation of a film increases as the film thickness increases for a given steel sheet thickness, but increasing the film thickness causes a decrease in the space factor. Therefore, there is a demand for a film having as small a thickness as possible and having a large applied tension to a steel sheet.

[0004] A coating mainly composed of forsterite produced by the reaction between the oxide on the steel sheet surface and the annealing separator in the finish annealing step has a large tension applied to the steel sheet, and is effective in reducing iron loss.

Further, the method of forming an insulating film by baking a coating solution mainly composed of colloidal silica and phosphate disclosed in Japanese Patent Application Laid-Open No. 48-39338 discloses an effect of imparting tension to a steel sheet. And is effective in reducing iron loss. Therefore, it is a general method of manufacturing a grain-oriented electrical steel sheet to apply a tensile insulating coating while leaving a film generated in the finish annealing step.

[0006] In the case of a grain-oriented silicon steel sheet which is actually manufactured industrially, a finish annealing film having a strength of about 1 μm or more and a
A μm insulating film is provided. When the thickness is 0.23 mm, the space factor is about 97%, and the tension applied to the steel sheet by these films 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 . The tension can be increased by increasing the amount of insulating film, but the space factor deteriorates and the design magnetic flux density increases,
In particular, iron loss in a high magnetic field does not decrease so much.

[0007] In order to reduce iron loss without lowering the space factor, it is necessary to develop a coating material capable of imparting a high tension to a steel sheet with a small coating amount. For example, Japanese Patent Application Laid-Open No. 2-24
Japanese Patent No. 3770 discloses that a film formed by a sol-gel method is effective in reducing iron loss. However, this publication recommends a material having a small coefficient of linear expansion in forming a sol-gel film, but does not describe specific film materials other than SiO ₂ , eucryptite, and spodumene. There is no description about the film thickness.

On the other hand, in JP-A-3-130376, SiO ₂ , antimony oxide,
Zircon _{oxide, SiZrO 4, Al 2 O 3} , Fe 2 O
₃ , TiO ₂ is mentioned, but not as a coating component for imparting tension to the steel sheet, but as a coating material for ensuring the adhesion between the insulating film to be baked and the steel sheet. I have. Also, JP-A-61-24
No. 6321 and others disclose a technique of applying a carbide, boride, oxide, or silicide film by dry coating, but there is no description about film thickness and characteristics.

[0009]

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

[0010]

SUMMARY OF THE INVENTION The gist of the present invention is to provide an iron loss coating having a thickness of 1.5% or less of the thickness of a steel sheet and having a Young's modulus and a linear expansion coefficient that satisfy certain conditions. The present invention is directed to a unidirectional silicon steel sheet having a low space factor and a high space factor. The certain conditions referred to herein are as follows: E (α _Fe −α)> 0.024 kg · mm ^-2 · K ⁻¹ , 1 μ for a steel sheet without a finish annealing film
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 sheet and the film, respectively) is there.

[0011]

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

For example, a comparison is made between a forsterite coating and a coating made of colloidal silica and aluminum phosphate. The measured value of the linear expansion coefficient of 3% silicon steel is about 12
× 10 ^-6 K ^-1 , that of forsterite is about 11 × 10
^-6 K ^-1 (Journal of the Ceramic Society of Japan, Vol. 70, p. 8)
6, 1962). The value has no measurement example of the linear expansion coefficient of the produced film from colloidal silica and aluminum phosphate, which assumes that the glass of _{SiO 2 -Al 2 O 3 -P 2} O 3 system, a multi-component glass Estimation using a method of calculating the coefficient of thermal expansion (AA Appen, “Chemistry of Glass”, Chapter X, Nisso Tsushinsha, 1974) gives about 6 × 10 ⁻⁶ K ⁻¹ .

[0013] The formation temperature of the forsterite film is 120
When the temperature of the film made of colloidal silica and aluminum phosphate is set to 500 ° C. at 0 ° C. and the estimated softening point, the tension of the latter film should be about three times that of the former film. The tension is comparable. 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 It was experimentally found that the following expression was used. σ = E (α _Fe −α) ΔT (2d / D) (1) where ΔT is the temperature difference (K) between the time of 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 will be described below. A commercially available 3% silicon steel sheet (sheet thickness about 0.18 mm) was pickled to remove the surface film. This steel sheet is coated with Al by the sol-gel method.
₂ O ₃ , TiO ₂ , Y ₂ O ₃ , ZrO ₂ , and SiO ₂ films were formed. Table 1 shows the film forming conditions.

[0016]

[Table 1]

After forming the film, one surface was protected with resin and then immersed in nitric acid to remove only the film on one surface. After removing the protective resin film with an organic solvent, the tension due to 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.
The values are shown in comparison with the values calculated by equation (1). The values shown in Table 2 were used for the coefficient of linear expansion and the Young's modulus (room temperature) of the coating material used in the calculation. The calculated values correspond well to the actually measured values, and it can be seen that the tension applied to the steel sheet by the coating is given by equation (1).

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

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

In the case where a finish annealing film having a thickness of about 0.5% of the thickness of the steel sheet is provided, the tension applied by the finish annealing film is about 0.5 kg · mm ⁻² . Therefore, to apply a further 0.5 kg · mm ^-2 tension, E
An insulating film 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 satisfying _Fe- α)> 0.036, a space factor of 98% or more and a total tension of 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 .5SiO ₂ (cordierite), CaO.A
l ₂ O ₃ · 2SiO ₂ (anorthite), 2CaO · A
l ₂ O ₃ · SiO ₂ (Gehlenite), CaO · MgO
And 2SiO ₂ (diopsite) oxides and composite oxides.

[0022]

[Table 2]

Materials other than the above-mentioned oxides may also be used.
Any material that satisfies (α _Fe −α)> 0.024 or 0.018 may be used. These oxide films can be formed by a sol-gel method. In addition, non-oxide ceramics such as metal carbides, borides, nitrides, and 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 a unidirectional silicon steel sheet.

[Table 3]

The following examples show that a grain-oriented silicon steel sheet having a coating satisfying the conditions in the present invention exhibits a lower iron loss value than the conventional steel sheet while keeping the space factor at 97% or more. .

[0025]

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

Example 1 A silicon steel containing 3% Si and rolled to a final thickness of 0.23 mm was subjected to decarburizing annealing to form an oxide layer containing SiO ₂ on the surface of the silicon steel. And a final finish annealing was performed. On the surface of the grain-oriented silicon steel sheet annealed in this way, a film of slightly more than 1 μm mainly composed of forsterite exists. Al ₂ O ₃ , SiO ₂ , MgAl is applied to the surface of this steel sheet by the sol-gel method.
A film of ₂ O ₄ (spinel) and 3Al ₂ O ₃ .2SiO ₂ (mullite) was formed at 900 ° C.

Some samples were coated with a coating solution composed of colloidal silica, aluminum phosphate and chromic anhydride.
It was baked at 50 ° C. to give 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 An oxide layer containing SiO ₂ was formed on the surface of a silicon steel containing 3% Si and rolled to a final thickness of 0.23 mm to serve as decarburizing annealing. And a final finish annealing was performed. After the finish annealing film was removed by pickling, the surface was mirror-finished by a method disclosed in Japanese Patent Application Laid-Open No. 4-131326, ie, high-temperature annealing in a dry hydrogen atmosphere (sheet thickness 0.22 m).
m).

The surface of the steel sheet is made of Al ₂ O by a 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 properties of the obtained steel sheet. It can be seen that the grain-oriented silicon steel sheet according to the present invention exhibits an extremely low iron loss value at a high space factor.

[0031]

[Table 5]

Example 3 A silicon steel containing 3% Si and rolled to a final thickness of 0.23 mm was subjected to decarburizing annealing to form an oxide layer containing SiO ₂ on the silicon steel surface. And a final finish annealing was performed. After the finish annealing film was removed by pickling, the surface was mirror-finished by chemical polishing (plate thickness: 0.20 mm).

The steel sheet is subjected to CVD or PVD to form WC, TiC, SiC, ZrC, TaC, AlN, A
Films of l ₂ O ₃ , ZrB ₂ , TiB ₂ , and MoSi ₂ were formed to a thickness of 1 μm at a substrate temperature of 500 ° C. Table 6 shows the properties of the obtained steel sheet. It can be seen that the grain-oriented silicon steel sheet according to the present invention exhibits an extremely low iron loss value at a high space factor.

[0034]

[Table 6]

[0035]

According to the present invention, a grain-oriented silicon steel sheet having a low iron loss value can be obtained without lowering the space factor.

[Brief description of the drawings]

FIG. 1 is a table showing a comparison between a measured value of a tension applied to a steel sheet by a coating film and a calculated value according to equation (1).

Claims (6)

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