KR940008459B1 - Method of manufacturing electro-magnetic steel plate - Google Patents

Abstract

The method manufactures anisotropic silicone steel plate (I) of low iron loss by subdividing a magnetic domain through introducing regular strain on surface of the plate (I). The method for introducing regular strain has A) a mechanical method introducing 20-50 % of strain by scribing, B) a laser method introducing 50-80 % of strain by irradiating laser after paint coating on the scribed surface.

Description

Manufacturing method of low iron loss oriented electrical steel sheet

1 is a graph showing the change in iron loss according to the strain applied amount

The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet having a low iron loss, and more particularly, to a method for producing a grain-oriented electrical steel sheet having a low iron loss by introducing a regular strain on the surface of the grain-oriented electrical steel sheet to subdivide the magnetic domains. will be. In general, oriented electrical steel sheet is used for the iron core material of the energy change medium such as transformer, etc., when used in such iron core material, energy loss will inevitably occur. The energy loss of the transformer is divided into iron loss and copper loss, and the iron loss, which is a loss caused by the core material, occupies about 20-30% of the total loss. Therefore, in order to improve the efficiency of the transformer, a low electrical loss oriented electrical steel sheet is required. come.

Iron loss of oriented electrical steel is composed of hysteresis loss and eddy current loss caused by magnetic hysteresis, and the hysteresis loss is the purity of steel plate, the magnitude of inclusions, and (110) [ 001] depends on the accuracy of the orientation, and the eddy current loss is determined by the classical eddy current loss and the domain wall and movement, which are determined by the thickness of the resistive steel sheet, which is determined by the silicon content of the steel sheet. It consists of an abnormal eddy current loss, which is an eddy current loss that occurs. In addition, since the abnormal eddy current loss accounts for 50-60% of the breakage of the high magnetic flux density oriented electrical steel sheet, it is most effective to reduce the abnormal eddy current element in order to obtain a low electrical loss oriented electrical steel sheet. Since the size of the earth related to the ideal eddy current is proportional to the size of the grains, metallurgical conditions for reducing the grain size have been required in order to reduce the size of the magnetic domain. However, in order to manufacture a grain-oriented electrical steel sheet having a high magnetic flux density, it is necessary for the (110) [001] crystal orientation to be parallel to the rolling direction, which means that the [001] side selects the nucleus in the rolling direction. Therefore, in order to obtain a steel sheet having a high magnetic flux density, the secondary recrystallization nuclei are inevitably small and the grain size is large.

In other words, the directionality, that is, magnetic flux density and iron loss are opposite in metallurgical manufacturing principle, and it is difficult to always make iron loss and magnetic flux density simultaneously by metallurgical manufacturing principle.

If it is possible to directly reduce the magnetic domain of the grain-oriented electrical steel sheet product, it is possible to manufacture a steel sheet having excellent directionality and low iron loss free from the constraints of the contrary manufacturing principle.

Methods for improving iron loss by directly reducing the magnetic domains of oriented electrical steel sheet products have been proposed, and one of the methods is to scratch the surface of the oriented electrical steel sheet at the end of a sharp edge in order to subdivide the magnetic domains. To reduce iron loss [1975, 山 本 (1)]. However, the method has not been industrially moved and no iron loss improving mechanism has been disclosed. Another method is to reduce the iron loss by subdividing the magnetic domain without scratching the surface of high magnetic flux oriented electrical steel sheet with a ballpoint pen (1978, black wood,, 口). From this, it is clear that the earth improvement mechanism divides and subdivides the 180 ° C domain with residual stress due to slight plastic deformation. As a result, the residual stress caused by the flawless deformation such as scratches becomes the main role of the domain improvement.

On the other hand, a method of reducing plastic loss by introducing plastic deformation on the surface of a steel sheet by an indirect method such as a laser and dividing and subdividing magnetic domains by the residual strain has been proposed. The method of dividing the magnetic domain by introducing a little strain on the surface of the steel sheet regularly by the same direct or indirect such as a laser to generate the residual strain has been employed industrially. However, each of these direct (mechanical) and indirect (laser) methods has a big problem. That is, in the direct method, since the strain is mechanically imparted to the steel sheet, for example, there is a drawback that the degree of strain application tends to vary depending on the variation in sheet thickness or the shape of the steel sheet.

If you install a device that gives enough strain to self-division by a point of constant thickness, the thick plate part and the shape that is bad, for example, convex surface, will give excessive strain. There is a drawback of exposing the iron and steel by peeling off both the insulating film and the glassy film on the steel sheet.

On the other hand, the method of introducing the strain by the laser in an indirect manner is to use the instantaneous heat generated by the laser is absorbed on the surface of the steel sheet.

The surface of the grain-oriented electrical steel sheet is composed of a glass coating and a double coating coated with a chemical insulating coating thereon. Therefore, if a large amount of heat is rapidly applied, there is a possibility that the base iron is exposed by evaporating or peeling the film. In addition, in the grain-oriented electrical steel sheet, the variation in the light absorption rate of the glassy film becomes 30% or more. Therefore, when energy is matched to the upper limit of the absorption rate, strain introduction is insufficient in the low absorption rate. In some places, there is a drawback that the insulating film is peeled off.

Insulation coating of oriented electrical steel sheet is extremely important, and especially, insulated current due to eddy current in large transformers, it is necessary to prevent accidents when a large current flows, such as opening and closing the transformer. For this reason, the chemical coating treatment is further performed on the glass coating, and further, the baking of the varnish is prevented to prevent accidents caused by pin holes. Therefore, when the insulation coating or the glass coating peels off due to mechanical or laser strain application, the transformer manufactured as described above may include a serious accident.

Applying strain to the steel sheet to perform sufficient magnetic domain control using the mechanical or laser method described above will result in peeling of the coating, and this phenomenon is not solved as long as the thickness, shape and color tone of the steel sheet are varied.

It is conceivable to apply a color of steel sheet, for example, a paint having a constant absorption rate to the entire surface, or to add an additive to an insulating coating to make the absorption rate the same.However, considering the cost and quality of the coating, There is considerable difficulty.

In practice, self-regulated oriented electrical steel sheets are often repainted on the surface where the traces of peeling on the glassy film and the insulating film remain clearly. Such peeled traces may also cause a serious accident in the large transformer due to a decrease in insulation resistance of the peeled portion even by repainting.

The present inventors have conducted research and experiments to solve the problems of the conventional methods described above, and based on the results, the present invention has been proposed. The present invention provides a suitable combination of the mechanical method and the laser method. It is an object of the present invention to provide a method for manufacturing a grain-oriented electrical steel sheet which can reduce iron loss by sufficiently subdividing magnetic domains without breaking. EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention is a method of manufacturing a unidirectional electrical steel sheet with low loss by introducing a strain into the grain-oriented electrical steel sheet to subdivide the magnetic domain, the conventional directional electrical steel to give a strain of 20-50% of the total strain by a mechanical method Scribing the surface of the steel sheet and applying a coating agent having a constant light absorption rate to the scribed portion (linear) as described above; As described above, the present invention relates to a method of manufacturing a grain-oriented electrical steel sheet having low iron loss by subdividing magnetic domains by irradiating a laser to give 50-80% of the total strain of the scribing portion coated with the paint as described above.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. As shown in Fig. 1, the improvement of the magnetic domain, whether mechanical or laser, is just before film peeling occurs, and the strain at this time has about 5% more than the necessary strain (100%), that is, 105%. It can be seen.

When working with a certain strain intensity (strength), the variation of strain in steel sheet is ± 10% for mechanical method and ± 15% for laser method, so that any method alone can perform magnetic domain control with sufficient strength of strain. In this case, the strength of the total strain exceeds 105% at which the peeling starts, causing the peeling.

In the present invention, when the strain is imparted by the mechanical method, the variation of the strain is ± 10% as in the conventional mechanical method. On the other hand, when the strain is imparted by using a laser, after applying a paint having a constant light absorption Since the laser is irradiated, the variation of the strain becomes ± 0. In the present invention, only the variation of the strain in the case of applying strain by the mechanical method is considered.

The present invention is a suitable combination of both mechanical and laser methods, where the strain imparted by the mechanical method is 20-50% of the total strain, and the strain imparted by the laser should be 50-80% of the total strain.

In the present invention, when the strength of the strain by the mechanical method is less than 20% of the total strain, the strain imparting effect cannot be sufficiently obtained, so that the effect of reducing iron loss is small, and the amount is more than 50% of the total strain. There is a possibility that the total strain is more than 5% more than the necessary strain, that is, 105% or more, resulting in peeling of the film, considering the strain variation, so that the strength of the strain given by the mechanical method is 20- It is desirable to limit to 50%.

For example, if the scribing is performed at 30% of the total strain by a mechanical method and at the same time a coating is applied to make the laser absorption constant, then the laser is irradiated to give 70% of the strain on the line, the total strain Even if the strain variation of the mechanical method is ± 10%, the strain variation of the laser method is zero, so the actual total strain is in the range of 97-103%. Therefore, since the film peeling starts from 105% of the strain, the breakdown of the insulating film does not occur.

Considering the above, it can be seen that theoretically, the combination ratio between the mechanical method and the laser method can be 50% to 50%.

As shown in FIG. 1, the relationship between the mechanical strength and the strain strength of each of the laser methods for iron loss improvement is very similar, but in the case of the laser, the strength is slightly different from the mechanical method. However, in the present invention which uses a mechanical method initially, there is no problem and it is possible to handle the strengths interchangeably.

In order to obtain sufficient strain strength for the best improvement of magnetic properties by mechanical method, 30kg-f / cm ² reduction should be applied, and in the case of laser method, 3J / cm ² energy should be applied. It is possible to mark 100% and treat each other as compatible. For example, in the present invention, when a 15 kg-f / cm ² reduction is applied in the mechanical method, a strain of 100 ± 5% is applied when irradiating energy of 1.5 J / cm ² by the laser method. Magnetic properties are improved to the maximum.

As the paint used in the present invention, it is preferable to add 5% of polyvinyl alchol (PVA) or 5% of PAV to an aqueous solution of 5% fine graphite to improve adhesion to aqueous ink. Therefore, the light absorption of these paints is about 0.8%. Usually, since the absorption rate of a steel plate is 50-80%, when apply | coating using these paints, an absorption rate will correspond with the highest value of a steel plate.

The range of the preferable light absorption rate of the paint which can be used in the present invention is about 0.75-0.80.

The method of irradiating a laser on the line which apply | coated paint is easy, and absorption by the steel plate of a laser always becomes stable. Therefore, the fluctuations in energy absorption during laser processing are extremely small, so the actual fluctuations do not have to be taken into account.

If it becomes stable like this, it may be thought that the magnetic domain control may be performed only with the laser. However, considering the coating of the coating, the shape of the plate, and the abnormality of the laser, there is a risk of fluctuations. There will be no.

In the case of controlling the magnetic domain only by the laser, it is much more effective to perform the combination of the mechanical method and the laser method according to the present invention in consideration of the possibility that a defect such as a pin hole may cause a very serious accident. You can see that.

On the other hand, the grain-oriented electrical steel sheet to which the present invention can be applied can be any conventional low iron loss grain-oriented electrical steel sheet, and the typical composition is by weight, C: 0.02-0.1%, Si: 2.5-4.0%, Mn: 0.03 -0.15%, S: 0.010-0.050%, acid soluble Al: 0.006-0.040%, N: 0.0040-0.0110%, balance Fe and other unavoidable impurities.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Weight%, C: 0.072%, Si: 3.17%, Mn: 0.067%, S: 0.025%, acid soluble Al: 0.027%, N: 0.008%, balance Fe and other unavoidable impurities, magnetic flux density (B10) Has a steel ball with a diameter of 1.0mm and a steel ball with a diameter of 1.94 (T), iron loss (W17 / 50) of 0.89 (W / kg), and 0.23mm high magnetic flux density oriented electrical steel plate coated with glass film and insulating film. Strain was applied by mechanical method as shown in Table 1 below, followed by coating a paint (light absorption rate: 0.8) added with 5% PVA to a conventional ink in a width of about 1 mm, and then applying a Q-Switch YAG laser on the application line. Using a circular irradiation of about 200μm diameter was carried out, and the mechanical method and the laser method was performed simultaneously for comparison with the present invention, the strain interval was 10mm.

Iron loss and film peeling phenomenon were measured for the specimens subjected to the earth refining treatment as described above, and the measurement results are shown in Table 1 below.

TABLE 1

* The resin in () represents the strain value for the total strain imparted by each method.

As shown in Table 1, when the combination of the mechanical method and the laser method according to the present invention is 20: 80, 30: 70, 50: 50, the iron loss is low and stable, but no peeling of the film occurs. It can be seen that there is no. However, the results of magnetic domain segmentation by the mechanical method and the laser method, which are comparative materials, indicate that the iron loss is worse and the variation between specimens is larger than that of the present invention method.

Example 2

By weight%, C: 0.72%, Si: 3.20%, Mn: 0.067, S: 0.025%, acid-soluble Al: 0.027% N: 0.008%, balance Fe and other unavoidable impurities, and the magnetic flux density (B10) 1.93 (T), iron loss (W17 / 50) is 0.91 (W / kg), and the teeth with 0.5mm thickness of the blade tip were made of 0.23mm thick high magnetic flux density oriented electrical steel plate coated with glass film and insulating film. After the mechanical mechanical strain was applied to the blade by supplying a paint with the addition of PVA 5% to the aqueous solution of fine graphite 5% to be transferred when the strain is applied. Thereafter, a circle having a diameter of about 200 μm was irradiated with a YAG laser on a line coated with paint.

In the method of the present invention, the combination of the mechanical method and the laser method, that is, the combination of the required strengths, was performed by three methods of 30: 70, 20: 80, 50: 50, and the required strength for obtaining iron loss was 80%, 90%, 100%, and 105%.

In order to compare with the present invention, a mechanical method and a laser method were also performed simultaneously.

Iron loss and film peeling phenomena were measured on the specimens subjected to magnetic domain micronization as described above, and the measurement results are shown in Table 2 below.

TABLE 2

* "-" Above the iron loss value of Table 2 indicates peeling of the film.

As shown in Table 2, it can be seen that the iron loss is low and stable according to the present invention in comparison with the conventional method at the strength of 90% and 100%. Although film peeling occurs in strength, it can be seen that there is no peeling at 100% strength in the case of the present invention method.

Example 3

Using the same method as in Example 2, an experiment was conducted to compare the stability of the mechanical method, the laser method, and the present invention method.

Specimens are weight percent, C: 0.072%, Si: 3.22%, Mn: 0.067%, S: 0.025%, acid-soluble Al: 0.027%, N: 0.008%, remainder Fe and other unavoidable impurities. A high magnetic flux density oriented electrical steel sheet with a density (B10) of 1.92 (T) and iron loss (W17 / 50) of 0.92 W / kg was used. The combination ratio was 30:70 and the strain provision space | interval was 10 mm.

After 10 times of the micronized treatment as described above, the iron loss and the peeling phenomenon of the specimens were measured, and the measurement results are shown in Table 3 below.

TABLE 3

* "-" Above the loss value of Table 3 indicates the peeling of the film

**% improvement = × 100

Where A: representative iron loss of the specimen before magnetic domain control (W17 / 50), B: maximum iron loss after improvement (W15 / 50), and X: average iron loss.

As shown in Table 3, when controlling the magnetic domain according to the present invention it can be seen that the iron loss is the lowest and stable as 0.80W / kg, 90.7% in the improvement rate, 80.7% in the mechanical method, 83.7 in the laser corporation It shows excellent improvement compared to%, and also, in the case of the present invention, it can be seen that the film peeling does not occur at all unlike the conventional method.

As described above, according to the present invention, the mechanical method and the laser method are appropriately combined, and the strain is applied by the laser in particular, so that the magnetic properties are stable and excellent, and there is no concern about pinholes or peeling of the film. It is effective to provide a method for producing a low iron loss oriented electrical steel sheet.

Claims (1)

By weight, C: 0.02-0.1%, Si: 2.5-4.0%, Mn: 0.03-0.15%, S: 0.010-0.050%, Acid Soluble Al: 0.0060-0.040%, N: 0.0040-0.0110%, Balance Fe And a method for producing a grain-oriented electrical steel sheet having low iron loss by introducing a strain into a grain-oriented electrical steel sheet composed of other unavoidable impurities, so that a strain of 20-50% of the total strain is usually given by a mechanical method. Scribing the surface of the grain-oriented electrical steel sheet, and coating a scribed portion (linear) with a light absorption of 0.75-0.80 as described above; The method of manufacturing a low iron loss oriented electrical steel sheet characterized in that the magnetic domain is subdivided by irradiating a laser so that 50-80% of the total strain is applied to the scribing portion coated with the paint as described above.