JPH0897024A - Oriented magnetic steel plate for laminated core with excellent transformer noise characteristics - Google Patents

Abstract

PURPOSE: To reduce transformer noise by a method wherein the macroscopic unevenness on the surface of an oriented magnetic steel plate is reduced more than the specified deviation of plate thickness. CONSTITUTION: An oriented magnetic steel plate for a laminated core, having excellent transformer noise characteristics, satisfies the surface property of Pc2 (>=0.04×t)<=INT(0.04×L) [provided the Pc2 (>=0.04×t): on the basis of the center line of the roughness curved line prescribed in JIS-B-0601, the number of crests having plate thickness t (mm)×height of 0.04mm or more, INT(): integer part of the number in parentheses, L: measurement length (mm) obtained by measuring peak]. A stacked transformer, having excellent noise characteristics, can be obtained using the above-mentioned oriented magnetic steel plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet for a laminated iron core, which has excellent noise characteristics of a transformer.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for transformers to reduce noise from the viewpoint of placing importance on the living environment. For this reason, in large-sized transformers installed inside and outside the building, there is a problem that the cost of soundproofing measures to keep the large noise within the environmental standard is occupying a large proportion. Further, in the vehicle transformer, an increase in the weight of the transformer for noise reduction is one of the factors that hinder the weight reduction of the vehicle.

Although the factors governing the noise of the transformer have not yet been clarified, the noise of the grain-oriented electrical steel sheet (hereinafter abbreviated as GO), which is the material, increases when the magnetostriction of the single plate is large. It has been pointed out. From this point of view, a search has been made for a technique for reducing the magnetostriction of GO, but even if the magnetostriction of the material veneer is small, the transformer noise may not necessarily be reduced.

Although it is considered that the method of assembling the transformer affects the transformer noise, there is a possibility that factors other than magnetostriction affect the transformer noise as a material. However, studies on factors governing transformer noise other than magnetostriction have not been made so far.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is to provide a grain-oriented electrical steel sheet for a stacked iron core which is excellent in noise as a transformer.

[0006]

Means for Solving the Problems As a result of intensive experiments to solve the above problems, the present inventors have found that there is a close relationship between the macroscopic unevenness on the surface of the steel sheet and the transformer noise. Originally, it is desirable that the electromagnetic steel plate is flat regardless of whether it is used as a laminated iron core or a wound iron core. According to JIS-C2553, the deviation of the thickness of the grain-oriented silicon steel strip in the width direction is 0. It is set to 02 mm or less. This is specified because the electromagnetic steel sheets are laminated and used,
In particular, it is not stipulated to suppress noise as a transformer.

The present invention makes it clear for the first time that transformer noise is drastically reduced by making macroscopic unevenness on the surface of the steel plate extremely smaller than the conventionally specified plate thickness deviation. The gist of the present invention is a grain-oriented electrical steel sheet having a surface property satisfying the following expression, which is a grain-oriented electrical steel sheet for stacked iron cores having excellent transformer noise characteristics. Pc ₂ (≧ 0.04 × t) ≦ INT (0.04 × L) ... Pc ₂ (≧ 0.04 × t): Plate based on the center line of the roughness curve specified in JIS B0601 Thickness t (mm) x 0.04
Number of peaks with a height of mm or more INT (): Function that digitizes only the integer value part in () L: Measured length of peak (mm)

[0008]

[Function] When the plate thickness is 0.23 mm, 0.23 x 0.0
4 = 0.0092 mm convex portion becomes a problem. This is JIS
The unevenness amount is on the order of smaller than the plate thickness deviation defined by. The point of the present invention is to clarify the material conditions for reducing the transformer noise, including not only the size of the unevenness but also the existence ratio of the convex portion, as the constituent requirement of the material with low transformer noise. Especially.

The present invention will be described in detail below. From steel making to cold rolling, a cold rolled material of grain-oriented electrical steel sheet was manufactured by a known means. By mechanically polishing the surface of the cold-rolled sheet, a material having a surface smoothness of 3 levels is produced, and the usual decarburization annealing,
Finish annealing and flattening annealing were performed. Pc _{2 of} product plate (≧
Fig. 1 shows the relationship between 0.0092 mm) and noise. It can be seen that the transformer noise is dramatically reduced by decreasing the value of Pc ₂ . Here, the steel plate was smoothed by cold-rolled plate polishing, but it is desirable to combine a technique for reducing the plate thickness deviation from hot rolling to cold rolling.

Further, the surface may be smoothed by mechanically / chemically polishing the product plate instead of polishing the cold-rolled plate. The surface of the present invention may include an oxide containing forsterite as a main component, and known means such as JP-B-5 can be used.
It may be microscopically mirror-finished by the technique disclosed in JP-A-2-24499.

Since these prior arts aim to improve iron loss by removing the internal oxide layer, no macroscopic unevenness on the surface is specified, but in order to reduce transformer noise, the outermost surface of the steel sheet is It is necessary that the irregularities satisfy the above formula. An organic or inorganic coating or an organic + inorganic coating may be applied onto the oxide or the mirror surface by a known means. However, also in this case, it is effective for reducing the transformer noise that the unevenness of the outermost surface of the steel sheet including the coating satisfies the above formula.

The reason why the noise of the stacking transformer can be remarkably reduced by reducing the surface protrusion is considered as follows. That is, when the plates are stacked and bound together, the convex portions on the surface are flattened by receiving a pressing force. At this time, local strain is locally generated around the convex portion. It is considered that in the vicinity of the strain introduced, the magnetization becomes non-uniform, and vibrations that cause noise are likely to occur. Therefore, if the presence of convex portions is suppressed to a certain ratio or less, the vibration due to such local strain is reduced,
The noise of the entire transformer will also be greatly improved.

It was found that the transformer noise can be reduced by reducing the convex portion on the surface of the steel sheet. However, the concave portion on the surface, for example, the groove-shaped portion on the surface by the magnetic domain control technique disclosed in JP-A-62-67114. For example, we could not find a clear relationship between the depth and transformer noise. It is considered that the concave portion is because strain is not locally concentrated even if pressure is applied by stacking.

However, since the groove is formed wide and deep and the center line of the roughness curve shifts from the steel plate surface to the center of the plate thickness, the surface of the steel plate can be regarded as a convex portion, and the above equation is satisfied. In special cases, an increase in transformer noise was observed. Therefore, it has been found that it is effective to reduce the transformer noise by satisfying the equation for all GOs.

Next, a stacking transformer was prepared with GO having a plate thickness of 0.18 mm to 0.35 mm, and the noise was measured in detail. As a result, the height of the convex portion on the surface of the steel plate was determined by the thickness of each steel plate. If it is less than 4%, noise will be significantly reduced,
It was also found that even if there is a protrusion having a thickness of 4% or more, if the number of protrusions is less than INT (0.04 × L) with the measurement length being L (mm), noise can be suppressed to a low level. This means that the smaller the plate thickness, the smaller the size of the convex part will be according to the plate thickness, and the problematic large convex part can reduce the transformer noise by setting a certain ratio or less in the coil. Is quantitatively disclosed.

The present invention limits its application to stacked iron cores or wound iron cores without strain relief annealing. The reason is that, in the wound iron core that has been subjected to stress relief annealing, the noise level is substantially constant regardless of the surface irregularities. It is considered that this is because the noise is recovered by removing the strain by the strain relief annealing even if the convex portion on the surface is large and the strain is locally applied by the pressing force.

[0017]

【Example】

Example 1 A grain-oriented electrical steel cold-rolled sheet having a sheet thickness of 0.23 mm was produced by a known means. Change the surface smoothness by mechanical polishing,
Decarburization annealing, finish annealing, and flattening annealing were performed by known means. The surface roughness of the product plate was measured with a surface roughness meter.
20KVA model transformers were made from materials with various surface protrusions, and noise was measured with a microphone when excited at 50Hz and 1.7T. The results are shown in Table 1. It can be seen that the noise is remarkably reduced when the height of the convex portion is 10 μm or more and the number of measurement is 30 mm or less and the number of measurement is 50 mm or less.

[0018]

[Table 1]

Example 2 A grain-oriented electrical steel cold-rolled sheet having a sheet thickness of 0.18 to 0.35 mm was produced by a known means. The surface smoothness was changed by mechanical polishing, and decarburization annealing, finish annealing, and flattening annealing were performed by known means. 50 mm length measured with a surface roughness meter on the product plate
The surface irregularities were measured with. A 20KVA model transformer is made from materials with various surface protrusions, 50Hz, 1.7T
The noise when excited at was measured with a microphone. The results are shown in Table 2. It can be seen that the noise is reduced when the height of the convex portion is about 4% or less of the plate thickness.

[0020]

[Table 2]

[0021]

By using the grain-oriented electrical steel sheet according to the present invention, a stacking transformer having excellent noise characteristics can be obtained, so that its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between Pc ₂ of a grain-oriented electrical steel sheet having a thickness of 0.23 mm and the noise of a stacking transformer manufactured using this steel sheet for each excitation magnetic flux density.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Yabumoto 20-1 Shintomi, Futtsu-shi Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Tsuneo Uchino 1-1, Hibahata-cho, Tobata-ku, Kitakyushu Steelworks Yawata Works

Claims (1)

[Claims] 1. A grain-oriented electrical steel sheet for stacked iron cores having excellent transformer noise characteristics, the surface texture of which satisfies the following formula. Pc ₂ (≧ 0.04 × t) ≦ INT (0.04 × L) Pc ₂ (≧ 0.04 × t): With reference to the center line of the roughness curve specified in JIS B0601, the plate thickness t ( mm) x 0.04
Number of peaks with height of mm or more INT (): Symbol that digitizes only the integer value part in () L: Measured length of peak (mm)