JP2000328226A - Silicon steel sheet for motor having excellent high- frequency characteristic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicon steel sheet for motors having an excellent blanking property and high-frequency characteristics. SOLUTION: This process consists of a first stage of subjecting a low-carbon steel sheet to a siliconizing treatment by heating the steel sheet in a non- oxidizing gaseous atmosphere of 900 to 1000 deg.C and blowing a non-oxidizing gas of high temperature containing SiCl1 to the steel sheet surface, a second stage of subjecting the inside of the steel sheet to a diffusion treatment by heating Si subjected to the siliconizing treatment on the surface of the steel sheet in the non-oxidizing gaseous atmosphere not contg. SiCl1 at 900 to 1000 deg.C and a third stage of cooling the steel sheet subjected to the diffusion treatment in the non-oxidizing gaseous atmosphere. The Si concentration of the surface layer part is regulated to 5 to 6.5 wt.% and the Si concentration in the central part of the sheet thickness to <3%. When the thickness of the steel sheet is defined as (t) and the thickness of the surface layer part until the Si concentration decrease to 5% from the surface as (d), the thickness ratio R of the thickness (d) in the surface layer part to the sheet thickness (t) is specified to 0.01 to 0.25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon steel sheet for a motor, and more particularly to a silicon steel sheet excellent in high frequency characteristics and punching workability, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Normally, silicon steel sheets are used as electromagnetic steel sheets for motors. It is known that this type of steel sheet exhibits the best magnetic properties in both the iron loss and the maximum magnetic permeability when the iron content is reduced to 6.5% as the Si content increases. Conventionally, as a method of manufacturing a high silicon steel sheet, there are a rolling method, a direct casting method, and a siliconizing method. Among them, the rolling method can produce a Si content of up to 4%, but the Si content is higher than that. In such a case, the workability is significantly deteriorated, so that cold working is difficult. Also, it is difficult to punch a core of a motor or the like after manufacturing. In addition, although the direct casting method does not cause a processing problem, it is still a technology under development, and is liable to cause a shape defect, and it is particularly difficult to produce a high silicon steel sheet. On the other hand, the siliconizing method is invented by Goumi and Abe as a method of manufacturing a high silicon steel sheet by melting a low silicon steel sheet and rolling it into a thin sheet, and then infiltrating Si from the surface to produce a high silicon steel sheet. Mitani and Onishi et al. (For example, Japanese Patent Application Laid-Open Nos. Hei 04-246157 and Hei 04-246157).
323360).

[0003]

However, in a silicon steel sheet obtained by the conventional siliconizing method, the surface layer and the central portion are not suitable for the Si concentration and the thickness thereof, so that the punching workability of the motor core is poor, There were problems such as a large loss. If the amount of Si permeated from the surface is too large, the punching of the motor core is hindered. Further, simply increasing the Si concentration gradient between the surface layer and the central portion in order to increase the magnetic flux density has a problem that the steel sheet surface may be cracked during manufacturing. On the other hand, due to environmental energy issues,
It is desired to improve the efficiency of the motor, but it is difficult to improve the efficiency only by improving the structure of the motor. For this reason, the development of a new magnetic material that leads to the miniaturization and high performance of the motor is being promoted. For example, the frequency of an inverter excitation compatible motor is increasing, and in this case, it is desired to select a silicon steel sheet most suitable for a skin effect. Therefore, an object of the present invention is to provide a silicon steel sheet for a motor having excellent punching workability and high-frequency characteristics and a method for manufacturing the same.

[0004]

In order to solve the above-mentioned problems, the present invention is to heat a strip-shaped steel sheet while continuously passing the same in a high-temperature non-oxidizing gas atmosphere to thereby obtain a high-temperature non-oxidizing gas containing SiCl _4. A first step of spraying an oxidizing gas onto the surface of the steel sheet to continuously perform a siliconizing treatment;
A second step of heating in a high-temperature non-oxidizing gas atmosphere not containing SiCl ₄ to perform a diffusion treatment inside the steel sheet, and a third step of cooling the diffusion-treated steel sheet in a non-oxidizing gas atmosphere. In the method for producing a steel sheet, low carbon steel is used as the steel sheet, and the silicon concentration in the first step and the diffusion treatment temperature in the second step are 900 to 1000 ° C., and the Si concentration in the surface layer is 5 to 6. 5wt%, S at center of thickness
The i concentration is adjusted to be less than 3%. The average silicon concentration of the silicon steel sheet produced by the siliconizing treatment is 0.5 to 4 wt%, the concentration of Si in the surface layer of the steel sheet is 5 to 6.5 wt%, and the concentration of Si in the central part of the sheet thickness is 3 wt%. % Of the steel sheet. Further, the thickness of the silicon steel sheet is t (m
m), when the thickness of the surface layer from the surface of the silicon steel sheet until the Si concentration is reduced to 5% is d (mm), the ratio R of the thickness d of the surface layer to the sheet thickness t is 0.01. ０．２0.25.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on tables. The silicon steel sheet for motors of the present invention having excellent high-frequency characteristics was manufactured in the following steps. The steel sheets subjected to the siliconizing treatment were two types of low carbon steel sheets having a thickness of 0.3 mm and 0.6 mm. First, as a first step, a low-carbon steel sheet is heated while being continuously passed in a high-temperature non-oxidizing gas atmosphere, and a high-temperature non-oxidizing gas containing SiCl ₄ is sprayed on the steel sheet surface to perform a siliconizing treatment. did. Next, as a second step,
The siliconized steel sheet having a high Si concentration was heated in a high-temperature non-oxidizing gas atmosphere containing no SiCl ₄ to diffuse the surface layer of Si into the inside of the steel sheet. In the third step, the steel sheet subjected to the diffusion treatment was rapidly cooled in a non-oxidizing gas atmosphere. The siliconizing temperature was varied in the range of 850 to 1050 ° C, and the diffusion temperature was varied in the range of 900 to 1000 ° C. In this manner, the Si concentration in the surface portion is 4 to 6.5 wt%, and the Si concentration in the central portion is 0.1% to 4 w%.
Various steel sheets of t% were produced. [Example 1] Among the prepared steel sheets, the Si concentration was 5
The effect of the siliconizing treatment temperature was examined for those having a weight percentage of 1 wt. Table 1 shows the results.

[0006]

[Table 1]

[0007] In the table, ○ indicates that the finished state is good, and X indicates that the steel sheet has peeled off. As can be seen from Table 1, when the siliconizing temperature was in the range of 900 to 1000 ° C, the finished state of the steel sheet was good. But,
At 850 ° C, sufficient siliconizing treatment is not performed.
At a temperature of 050 ° C., the surface layer peeled off and the finished state was poor. It is presumed that the reason for this is that at a temperature exceeding 1000 ° C., the γ phase (Fe—Si phase diagram) in the surface layer increases and a crack is generated at the boundary with the α phase in the center. From this result, it was found that the siliconizing treatment temperature was optimally in the range of 900 to 1000 ° C. where the influence of the γ phase was small. [Example 2] Next, the influence of the Si concentration in the surface layer portion and the central portion was examined by punching workability. The sample thickness is 0.3
mm steel plate at a siliconizing temperature of 950 ° C., the Si concentration in the surface layer portion and the Si concentration in the central portion are 4.0 to 6.5 wt%,
The Si concentration at the central portion was variously changed from 0.1% to 4% by weight. Table 2 shows the results.

[0008]

[Table 2]

The punching workability was evaluated by the bending radius as a substitute property. That is, when the bending radius was 2 mm or less, the bending property was good (indicated by a circle in the table), and when the bending radius was more than 2 mm, the bending property was poor (in the table). Surface Si
When the concentration was 4.5 wt% or less and the Si concentration in the central portion of the steel plate was 3 wt% or more, the bendability was poor, but the Si concentration in the surface layer portion was 5 to 6.5 wt% and the Si concentration in the central portion was 3 watts.
It was found that the bendability was good with less than t%. [Example 3] The influence of the thickness of the surface layer was examined by punching workability and iron loss. Here, the thickness of the surface layer is the thickness t
(Mm) is expressed by a thickness ratio R to a distance d (mm) at which the Si concentration becomes 5% from the surface toward the center. The sample used had a plate thickness t of 0.6 mm and a thickness-to-thickness ratio R of the surface layer in the range of 0.005 to 0.35. First, the results of the punching workability are shown in Table 3.

[0010]

[Table 3]

From this table, it was found that the bendability deteriorated when the thickness ratio R of the surface layer portion was 0.3 or more. In addition, looking at the Si concentration at the center, the Si concentration at the center deteriorates when the Si concentration is 3 wt% or more. That is, the punching workability is such that the thickness ratio R of the surface layer portion is 0.25 or less and the Si concentration in the central portion is 2 wt.
%, It was found that good characteristics were exhibited.
Next, Table 4 shows the results of examining the iron loss.

[0012]

[Table 4]

In the table, the symbol ○ indicates good iron loss of less than 100 W / kg, and the mark x indicates poor iron loss of 100 W / kg or more. According to this, the thickness ratio R of the surface layer portion was poor when the thickness ratio was 0.005, but was good when the thickness ratio was 0.01 or more. Further, when the thickness ratio R of the surface layer portion is 0.01 or more and the effect of the Si concentration in the central region is seen,
It was good in the entire range of 0.1 to 4 wt%. From the two results of punching workability and iron loss, the thickness ratio R of the surface layer
Has been found to be optimal in the range of 0.01 to 0.25. Example 4 The influence of the average concentration of Si was examined by bending workability and iron loss. The average concentration of Si is expressed by S
A steel sheet having an i concentration in the range of 5 to 6.5 wt% and a central Si concentration of less than 3 wt% was determined. Iron loss was performed by a servo motor with a rated output of 5 kW. Table 6 shows the results.

[0014]

[Table 5]

First, the bending workability is such that the average concentration of Si is 5 watts.
It was found that the sample was poor at t%, but good at 4 wt% or less. The iron loss is that the average concentration of Si is 0.1 wt.
% Was bad, but 0.5% by weight or more was good. That is, it was found from the two characteristics that the average concentration of Si was optimal in the range of 0.5 to 4 wt%. Example 5 The effect of frequency on iron loss was examined. The thickness ratio R of the thickness d of the surface layer portion to the plate thickness t was changed, and a servo motor with a rated output of 5 KW was used. The thickness ratio R is 0.0
05 to 0.50. Table 6 shows the results.

[0016]

[Table 6]

At a rotational speed of 2000 rpm, the thickness ratio R was small even at 0.005. However, when the rotation speed is 4
At 000 rpm, the iron loss increased to 110 (W / kg) when the thickness ratio R was 0.005. On the other hand, when the thickness ratio R is 0.01, it is 80 (W / kg), 0.2
5 was 70 (W / kg), which was good. When the thickness ratio R is 0.50, the Si concentration is high, which is as good as 71 (W / kg). Rotation speed is 5000rpm
m, 160 (W / k) when the thickness ratio R is 0.005.
g), it was 110 (W / kg) when the thickness ratio R was 0.01, and 103 (W / kg) when the thickness ratio R was 0.25.
kg). As described above, if the thickness ratio R is set to 0.01 to 0.25 at a high rotation speed, S
It turned out to be sufficiently comparable to a thick i-layer. That is, it was found that when the thickness ratio R was within this range, iron loss at high frequencies was small and punching workability was good.

[0018]

As described above, according to the present invention, the siliconizing treatment temperature is lowered to 900 to 1000 ° C., the average concentration of Si is 0.5 to 4 wt%, and the surface layer of the steel sheet is removed. S
Since the concentration of i was 5 to 6.5 wt%, the Si concentration at the center of the plate thickness was less than 3 wt%, and the thickness ratio of the surface layer portion having a Si concentration of 5% or more was limited to 0.01 to 0.25. Thus, a silicon steel sheet having excellent high-frequency characteristics can be obtained, which has an effect of obtaining a small motor with high efficiency.

Claims (3)

[Claims] 1. A silicon steel sheet produced by a siliconizing treatment, wherein the average concentration of Si is 0.5 to 4 wt%, the Si concentration in the surface layer of the steel sheet is 5 to 6.5 wt%, and the center of the sheet is A silicon steel sheet for motors having excellent high-frequency characteristics, wherein a Si concentration in a portion is less than 3 wt%. 2. When the thickness of the silicon steel sheet is t (mm) and the thickness of the surface layer portion from the surface of the silicon steel sheet until the Si concentration is reduced to 5% is d (mm), the plate thickness t The silicon steel sheet for a motor having excellent high-frequency characteristics according to claim 1, wherein a ratio R of a thickness d of the surface layer portion to the thickness is in a range of 0.01 to 0.25. 3. A strip-shaped steel sheet is heated while continuously passing in a high-temperature non-oxidizing gas atmosphere, and a high-temperature non-oxidizing gas containing SiCl ₄ is sprayed on the steel sheet surface to continuously perform a siliconizing treatment. A first step of performing
A second step of heating in a high-temperature non-oxidizing gas atmosphere not containing SiCl ₄ to perform a diffusion treatment inside the steel sheet, and a third step of cooling the diffusion-treated steel sheet in a non-oxidizing gas atmosphere. In the method for producing a steel sheet, low carbon steel is used for the steel sheet, and the siliconizing treatment temperature in the first step and the diffusion treatment temperature in the second step are 900 to 100.
A method for producing a silicon steel sheet for motors having excellent high-frequency characteristics, wherein the Si concentration in the surface layer portion is adjusted to 5 to 6.5 wt% and the Si concentration in the central portion of the plate thickness is adjusted to 0 ° C. and less than 3%.