JP2647322B2 - Low iron loss grain-oriented electrical steel sheet and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used as an iron core material for transformers and other electrical equipment, and has a low-loss oriented grain-oriented electrical steel sheet which does not deteriorate in magnetic properties even when subjected to strain relief annealing. The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as iron cores in transformers and other electrical equipment, not only to increase the magnetic flux density, but also to reduce energy consumption due to recent resources and environmental issues. Further lower iron loss is required. To improve iron loss, as is well known,
Texture of (110) [001] orientation of secondary recrystallized grains,
That is, the degree of integration of the so-called Goss orientation may be increased,
The higher the degree of integration, the larger the crystal grains, and as a result,
The magnetic domain width also increases, resulting in inferior iron loss, and particularly increases eddy current loss. Therefore, it is not so much expected that the iron loss characteristics are relatively improved and improved by only this.

[0003] Therefore, a method of subdividing magnetic domains has been developed and many proposals have been made in order to improve iron loss of a high magnetic flux density unidirectional magnetic steel sheet. For example, Japanese Patent Publication No. 58-59
No. 68, Japanese Patent Publication No. 57-2252, etc., a method of introducing linear minute distortion into a steel plate surface by using a ballpoint pen-shaped small ball by a scribing method or a method of introducing linear distortion by irradiating a laser. Is disclosed. However, there is a problem that the introduced strain obtained by subdividing the magnetic domains by these methods loses its effect by the subsequent strain relief annealing treatment.

Recently, as a method for improving a thermally stable iron loss characteristic that withstands stress relief annealing, Japanese Patent Publication No. Sho 62-5 has been proposed.
In Japanese Patent No. 3579, there is a method in which a steel sheet is mechanically deformed with a toothed roll to form a groove depth of 5 μm or more, and fine grains are formed by a subsequent heat treatment to refine magnetic domains.
However, since grooves are formed on the surface of the steel sheet having a forsterite film, the tooth tips of the toothed rolls wear quickly, and iron loss improvement decreases with wear, so it is necessary to replace the rolls. is there.

In Japanese Patent Laid-Open No. 50918/1990, a finish-annealed steel sheet having a forsterite film is wound around a roll with projections while being subjected to bending stress, to locally remove the film on the surface of the steel sheet, and to perform electrolytic etching. There has been proposed a method of forming a linear groove by using such a method. However, this method also requires an etching step in addition to the above technical problem, and has a problem that the cost is further increased. Further, Japanese Patent Application Laid-Open No. 63-7 / 1988
No. 6819, the surface of a finish-annealed steel sheet having forsterite is linearly removed by a mechanical means such as a laser or a knife or the like, or a forsterite film is not formed locally in advance, and then the electrolytic or It discloses that chemical etching is performed to improve iron loss, but this technology also requires removal and local application processing steps and etching steps, so operation costs are naturally increased due to increased cost and additional steps. Is also complicated.

[0006]

The above-mentioned prior art techniques for improving thermally stable iron loss all involve a method of forming a groove by mechanical or chemical etching or the like. Therefore, the space factor is reduced, which adversely affects the performance of the transformer. In addition, there is an increase in manufacturing costs due to increased roll wear and processes. The present invention solves these problems, and provides a grain-oriented electrical steel sheet having a low iron loss even after strain relief annealing in which a decrease in space factor is suppressed, and a method for manufacturing the steel sheet at low cost. .

[0007]

Means for Solving the Problems The present inventors melted the surface layer of a steel sheet by irradiating a laser beam to the surface of a grain-oriented electrical steel sheet after finishing annealing or almost perpendicularly to the direction of the sheet. By forming a solidified portion, a grain-oriented electrical steel sheet having a low iron loss even in the subsequent strain relief annealing process and having a low space loss after strain relief annealing with a high space factor without dents on the steel sheet surface can be obtained. I found that. This bead portion has a different steel composition and structure, and exists at a certain interval in the threading direction, so that the magnetostatic energy affecting magnetic domain segmentation increases.To reduce this, a reversal magnetic domain is formed and iron loss is reduced. It is thought that the improvement was achieved. The formation of the melt-solidified portion is not limited to the laser irradiation method, but may be another method. However, a laser is preferable from the viewpoint of a bead width that affects iron loss improvement.

The gist of the present invention is as follows. 1) The width of 50 to 300 µm and the depth of 5 to 35% of the thickness of the steel sheet on the surface layer of the grain-oriented electrical steel sheet with the tension-adding insulating film of the final product, ± 15 ° from the right angle to the passing direction A low iron loss grain-oriented electrical steel sheet having a melt-solidified wire portion having an interval within 5 to 30 mm and an excellent space factor.

2) After the final annealing or after the final annealing, the surface of the grain-oriented electrical steel sheet coated with an insulating coating and dried is irradiated with a laser beam to be passed through at a width of 50 to 300 μm and a depth of 5 to 35% of the steel sheet thickness. A method for producing a low iron loss grain-oriented electrical steel sheet, comprising: forming a melt-solidified wire portion having an interval of 5 to 30 mm within ± 15 ° from a direction perpendicular to the sheet direction and applying a tension-adding insulating film treatment.

Hereinafter, the present invention will be described in detail. S
After the slab containing i4% or less is heated, it is hot-rolled to an intermediate sheet thickness and, if necessary, heat-treated at this stage.
Cold rolling is performed twice or twice with intermediate annealing to make the final sheet thickness, and the obtained cold sheet is decarburized and annealed, coated with an annealing separator, and then subjected to high-temperature and long-time finish annealing, 11
0) The present invention is also applicable to a steel sheet in which secondary recrystallized grains of [001] orientation are developed, or a steel sheet in which an insulating film coating solution such as a tension applying film is applied and baked. By irradiating the surface of the steel sheet with a high-density laser beam, a part of the steel sheet surface is melted and solidified by heat, and a state like a bead of welding is created. The depth and width of the melt-solidified part at this time,
The spacing in the passing direction affects the effect of iron loss improvement.

The type of laser device used in the embodiment of the present invention and the oscillation state of the laser are not limited at all. For example, a commercially available laser device such as YAG, Ar, CO ₂ or the like capable of narrowing the beam of laser irradiation. And either continuous oscillation or pulse oscillation may be used.
In the case of pulse oscillation, a laser output, a frequency and a laser scanning speed can be selected and combined in order to form a continuous melt-solidified portion like a weld bead. At the time of irradiation, argon is blown.

FIG. 1 shows an oscillation output of 400 with a CO ₂ laser.
W shows a schematic view of a cross-sectional photograph after irradiation at a scanning speed of 40 cm / s, and the width of the melt-solidified portion is 250 μm,
The depth is about 20% of the thickness of the steel plate. Clearly, a melt-solidified portion was observed in the surface layer of the steel sheet, and since there is no dent, it is clear that there is no decrease in the space factor than the steel sheet having a dent as in the prior art publications. It is superior to downsizing and characteristics of transformers. Another advantage is that there is no notch effect for bending with a small radius of curvature because there is no dent formation.

FIG. 2 shows the transition of iron loss in the processing step of the present invention. The iron loss is temporarily deteriorated by the influence of thermal distortion due to the molten solidified wire portion formed by laser irradiation. The strain is released by the treatment, and the presence of the melt-solidified portion having different steel components and structures makes it possible to improve iron loss over the material.

By the way, if the angle from the perpendicular to the passing direction of the laser irradiation is within the range of ± 15 °, it is preferable to greatly reduce the iron loss. Even at more angles,
Although there is an improvement effect, it tends to be small, which is disadvantageous. The reason for setting the interval between the melt solidification lines in the passing direction to 5 to 30 mm is that the improvement in iron loss is the largest, and excluding less than 5 mm means that there is an iron loss improvement cost but an extreme effect. This is because they cannot be obtained. If it exceeds 30 mm, the improvement effect tends to decrease.

The width of the molten solidification line is 50 to 300 μm.
Range is appropriate. The reason is that when the thickness exceeds 300 μm, the magnetic flux density largely decreases. If it is less than 50 μm, the effect is improved but the reduction effect tends to be smaller. Further, the appropriate depth of the melt-solidified portion is in the range of 5 to 35% with respect to the plate thickness. If it is less than 5%, the iron loss improvement is small. On the other hand, if it exceeds 35%, the occupation of the molten bead portion in the plate thickness direction increases, which affects the flow of the magnetic flux and greatly reduces the magnetic flux density.

[0016] Since the coating component is also involved in the melted portion by the laser irradiation and melts, the high-temperature finish-annealed steel sheet does not have any problem if it is subjected to the usual inorganic insulating film treatment for applying tension. Even with a coating, if a thin insulating coating for applying tension is again applied and dried, the melt-solidified portion is concealed, and the core loss is maintained without lowering any insulation properties and withstand voltage. As described above, the effect of the molten and solidified portion by the laser irradiation is such that the above-described tension-adding insulating film is baked at a plate temperature of 800 to 850 ° C., and is subjected to a flattening process at the same time. As shown, the distortion in the melt-solidified portion disappears and the iron loss is improved.

[0017]

【Example】

Example 1 A finish-annealed steel sheet having a thickness of 0.23 mm was irradiated with an Nd-YAG laser at an average output of 50 W and a frequency of 30 kHz at an interval of 5 mm from a right angle to the sheet passing direction at an interval of 5 mm. The width of the melt-solidified portion after irradiation was 100 μm, and the depth was 13% of the thickness of the steel sheet. For comparison, the same material that was not treated was prepared. These materials were coated with a tension-adding insulating film mainly composed of aluminum phosphate, chromic acid or the like, subjected to a baking heat treatment at 800 ° C. for 60 seconds, and then subjected to a strain relief annealing at 850 ° C. for 2 hours. The magnetic properties and space factor are shown in Table 1. The space factor of the conventional example manufactured under the same conditions is 97.3%.

[0018]

[Table 1]

From Table 1, it can be seen that the iron loss characteristics of the example in which the melt-solidified portion was formed by laser irradiation were clearly improved as compared with the comparative example. Further, the space factor is better than that of the conventional example and is not reduced at all, equivalent to that of the comparative example.

Example 2 An insulating film having a tension effect after finish annealing was coated with 4
g / m ² and dried to a thickness of 0.23 mm (material properties: W _13/50 (W / kg) 0.47, W
_17/50 (W / kg) 0.87, B ₈ (T) 1.940)
The CO ₂ laser was continuously oscillated at an output of 600 W, and the irradiation was performed at an interval of 7 mm at 0 ° from a direction perpendicular to the sheet passing direction.
The depth of the formed melt-solidified portion is 20% of the plate thickness, and the width is 2%.
It was 00 μm. Thereafter, the insulating coating for tension application is applied at 800 ° C. so that the coating becomes 1 g / m ² per side.
After baking for 60 seconds, strain relief annealing was performed at 850 ° C. for 2 hours. Further, for comparison, a material which had been subjected to the same processing steps without laser irradiation treatment was prepared from the same material.

The magnetic properties and space factor are shown in Table 2. The space factor of the conventional example manufactured under the same conditions is 97.1.
%.

[0022]

[Table 2]

As is clear from Table 2, the examples of the present invention in which the melt-solidified portion of the present invention is formed have clearly good iron loss characteristics, and the space factor is also better than the conventional example.

[0024]

According to the present invention, a grain-oriented electrical steel sheet which maintains a magnetic domain control effect and has a good core loss and a low core loss without lowering the space factor even when a strain relief annealing treatment is carried out. And can contribute to downsizing of the transformer. Further, since the step of only laser processing is added, the above steel sheet can be manufactured at high productivity and at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view of a photograph showing a melt-solidified structure of a cross section of a steel sheet by laser irradiation.

FIG. 2 is a graph showing transition of iron loss in a treatment step of the present invention.

Claims (2)

(57) [Claims] 1. A finished product having a width of 50 to 300 μm and a depth of 5 to 35% of the thickness of a steel sheet on a surface layer of a grain-oriented electrical steel sheet provided with a tension-adding insulating film of a final product, which is perpendicular to the sheet passing direction. ±
A low iron loss grain-oriented electrical steel sheet characterized by having a molten solidification line portion with an interval of 5 to 30 mm within 15 ° and an excellent space factor. 2. The surface of a grain-oriented electrical steel sheet coated with an insulating film after the final annealing or after the final annealing and then dried is irradiated with a laser beam to a width of 50 to 300 μm and a depth of 5 to 35% of the steel sheet thickness. A method for producing a low iron loss grain-oriented electrical steel sheet, comprising: forming a melt-solidified wire portion having an interval of 5 to 30 mm within ± 15 ° from a direction perpendicular to the sheet direction and applying a tension-adding insulating film treatment.