JPH06212275A - Low iron loss grain-oriented silicon steel sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a grain-oriented silicon steel sheet holding low iron loss value and good in a space factor after being subjected to stress relief annealing. CONSTITUTION:The low iron loss grain-oriented silicon steel sheet in which the surface layer part of ferrite in a grain-oriented silicon steel sheet coated with a tension-applied insulating film as final product is provided with molten and solidified line parts in which the width is regulated to 50 to 300mum, the depth is regulated to 5 to 35% to the sheet thickness of the steel sheet, the angle is regulated to <=+ or -15 deg. from the right angles to the sheet passing direction and the distance is regulated to 5 to 30mm and excellent in the space factor is produced. Furthermore, the surface of the grain-oriented silicon steel sheet after being subjected to finish annealing or coated with an insulating film and dried after being subjected to finish annealing is irradiated with laser beams to form molten and solidified line parts in which the width is regulated to 50 to 300mum, the depth is regulated to 5 to 35% to the sheet thickness of the steel sheet, the angle is regulated to <=+ or -15 deg. from the right angles to the sheet passing direction and the distance is regulated to 5 to 30mm, and after that, tension-applied insulating film treatment is executed.

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 electric equipment, and has a low iron loss and a magnetic iron sheet having a low iron loss which does not deteriorate the magnetic properties even when strain relief annealing is performed. The present invention relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are used as iron cores for transformers and other electric equipment to increase the magnetic flux density, but also due to the recent trend of energy saving resulting from resource and environmental problems. Further reduction of iron loss is required. To improve iron loss, as is well known,
Texture of (110) [001] orientation of secondary recrystallized grains,
In other words, it is only necessary to increase the so-called Goth orientation integration,
The higher the degree of integration, the larger the crystal grains, and as a result,
The magnetic domain width also increases and iron loss is inferior, and eddy current loss in particular increases. Therefore, this alone cannot be expected to improve the iron loss characteristics relatively.

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

Recently, as a method for improving the thermally stable iron loss characteristics that can withstand strain relief annealing, Japanese Patent Publication No. 62-5.
In Japanese Patent No. 3579, there is a method in which mechanical distortion is applied to a steel sheet with a tooth profile roll to form a groove depth of 5 μm or more, and fine crystal grains are formed by a subsequent heat treatment to subdivide magnetic domains.
However, since a groove is formed on the surface of the steel plate having a forsterite film, the tooth tip wear of the tooth profile roll is fast and the iron loss improvement decreases as the wear progresses, so it is necessary to replace the roll, which causes an increase in manufacturing cost. is there.

Further, in Japanese Patent Application Laid-Open No. 2-50918, a finish-annealed steel sheet having a forsterite coating is wound around a roll having protrusions while bending stress is applied to locally remove the coating on the surface of the steel sheet, and electrolytic etching is performed. A method of forming a linear groove has been proposed, but this also has a problem that an etching step is required in addition to the above-mentioned technical problem and the cost cost further increases. Also, JP-A-63-7
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 a forsterite film is not formed locally before electrolysis or Although it discloses that iron loss is improved by performing chemical etching, this technology also requires a removal and local coating treatment step and an etching step, which naturally increases the cost and operation management due to the increase in the number of steps. Also has the problem of becoming complicated.

[0006]

The above-mentioned prior arts for improving the thermally stable iron loss are all methods of forming grooves by mechanical or chemical etching treatment, and a part of the steel sheet is missing. As a result, the space factor is lowered, which affects the performance of the transformer, which is disadvantageous. Further, there is an increase in manufacturing cost due to roll wear and additional processes. The present invention solves these problems, and provides a grain-oriented electrical steel sheet having a low iron loss even after stress relief annealing that suppresses a reduction in space factor and a method for producing the steel sheet at low cost. .

[0007]

Means for Solving the Problems The inventors of the present invention melted a surface layer of a steel sheet by irradiating a surface of a grain-oriented electrical steel sheet after finish annealing or with an insulating film with a laser beam almost at right angles to the sheet direction. By forming a solidified portion, a grain-oriented electrical steel sheet that has low iron loss even in the subsequent stress relief annealing treatment and has no dents on the steel sheet surface and has a low iron loss after strain relief annealing with a high space factor is obtained. I found that. This bead part has different steel composition and structure and exists at a certain interval in the strip running direction, so that the magnetostatic energy that affects the subdivision of the magnetic domain increases, and in order to decrease this, the reversed magnetic domain is formed and the iron loss I think that it has been improved. The formation of the melt-solidified portion is not limited to the laser irradiation method, and other methods may be used, but a laser is preferable from the viewpoint of the bead width that affects the improvement of iron loss.

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

2) After finishing annealing or after finishing annealing, the surface of the grain-oriented electrical steel sheet on which an insulating film has been applied and dried is irradiated with a laser beam to have a width of 50 to 300 μm and a depth of 5 to 35% of the thickness of the steel sheet. A method for producing a low iron loss grain-oriented electrical steel sheet, which comprises applying a tension-adding insulating film treatment after forming a melt-solidified wire portion having an interval of 5 to 30 mm within ± 15 ° from a right angle to the sheet direction.

The details of the present invention will be described below. S
After heating the slab containing i4% or less, it is hot-rolled to an intermediate plate thickness and heat-treated at this stage if necessary.
Times or two times of intermediate rolling, including cold rolling, to obtain the final plate thickness, the obtained cold plate is decarburized and annealed, after which an annealing separator is applied and finish annealing is performed for a long time at high temperature. 11
0) It is also applicable to a steel sheet having secondary recrystallized grains in the [001] orientation developed, or a steel sheet obtained by applying and baking an insulating coating solution such as a tension-imparting coating on the steel sheet. By irradiating the surface of the steel sheet with a high-density laser beam, a part of the surface of the steel sheet is melted and solidified by heat, and a state like a bead of welding can be formed. At this time, the depth and width of the molten and solidified part,
The spacing in the sheet passing direction affects the effect of improving iron loss.

The type of laser device used in the practice of the present invention and the lasing state of the laser are not limited in any way. For example, commercially available laser devices such as YAG, Ar, and CO ₂ capable of narrowing the luminous flux of laser irradiation. Can be used, and either continuous oscillation or pulse oscillation can be used.
In the case of pulse oscillation, in order to form a continuous melt-solidified portion like a weld bead, it is possible to selectively combine the laser output, frequency and laser scanning speed. Argon is sprayed during irradiation.

FIG. 1 shows an oscillation output 400 of a CO ₂ laser.
A schematic view of a cross-sectional photograph after irradiation with W at a scanning speed of 40 cm / s is shown. The width of the melt-solidified portion is 250 μm,
The depth is about 20% of the steel plate thickness. A melt-solidified portion is clearly observed in the steel sheet surface layer, and of course, there is no dent, so it is clear that the space factor does not decrease as compared with the steel sheet having a dent as in the prior art publication. It is superior to miniaturization and characteristics of transformers. In addition, since there is no depression, there is no notch effect even for bending work with a small radius of curvature, which is an advantage.

FIG. 2 shows the transition of iron loss in the treatment process of the present invention. Although it is remarkably deteriorated once by the influence of thermal strain due to the melt solidification line portion formed by laser irradiation, the tension-added insulating film thereafter. The strain is released by the treatment, and it becomes possible to improve the iron loss more than the material by the presence of different steel components and the melt-solidified portion of the structure.

By the way, if the angle of the laser irradiation from the right angle with respect to the plate passing direction is within a range of ± 15 °, it is preferable because the iron loss improvement margin is large. Even if the angle is larger than this,
There is an improvement effect, but it tends to become smaller, which is disadvantageous. The reason why the interval between the melted and solidified line portions in the sheet passing direction is 5 to 30 mm is that the improvement in iron loss is the largest, and the reason for excluding less than 5 mm is that there is a margin for improving iron loss, but there is an extreme effect. This is because it cannot be obtained. If it exceeds 30 mm, the improvement effect tends to decrease.

Further, the width of the melted and solidified line portion is 50 to 300 μm.
The range is appropriate. The reason is that if it exceeds 300 μm, the decrease in magnetic flux density is large. On the other hand, when it is less than 50 μm, there is an improvement effect but the reduction effect tends to be small. 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 improvement in iron loss is small. On the other hand, if it exceeds 35%, the occupancy of the molten bead portion in the plate thickness direction becomes high, which affects the flow of the magnetic flux and causes a large decrease in the magnetic flux density.

Since the film components are also entrained and melted in the melted portion due to the laser irradiation, naturally there is no problem in the case of a high-temperature finish-annealed steel sheet, if the usual inorganic insulating film treatment for tension application is performed. Even in the case of coating, if the insulating coating for tension application is thinly applied and dried again, the melted and solidified portion is hidden and the iron loss is maintained without lowering the insulating property and the withstand voltage. As described above, the effect of the melting and solidifying portion by laser irradiation is that the above-mentioned tension applying insulating film is baked and heated at a plate temperature of 800 to 850 ° C., and a flattening process is also performed at the same time. As shown, the strain in the melt-solidified portion disappears and the iron loss is improved.

[0017]

【Example】

Example 1 A 0.23 mm-thick finish-annealed steel sheet was irradiated with an Nd-YAG laser at an average output of 50 W and a frequency of 30 kHz at a distance of 5 mm from a right angle of 5 ° with respect to the sheet passing direction. The width of the melt-solidified portion after irradiation was 100 μm, and the depth was 13% of the steel plate thickness. For comparison, the same material without treatment was prepared. An insulating film for tension application containing aluminum phosphate, chromic acid or the like as a main component was applied to these materials, heat treatment was performed at 800 ° C. for 60 seconds, and then strain relief annealing was performed at 850 ° C. for 2 hours. Its 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 is apparent that the iron loss characteristics of the examples in which the melt-solidified portion was formed by laser irradiation were improved as compared with the comparative examples. Moreover, the space factor is better than that of the conventional example and is equal to that of the comparative example without any decrease.

Example 2 After finishing annealing, an insulating film having a tension effect was applied to each side by 4
Material with a plate thickness of 0.23 mm, coated and dried to achieve g / m ² (material characteristics: W _13/50 (W / kg) 0.47, W
_17/50 (W / kg) 0.87, B ₈ (T) 1.940)
A CO ₂ laser was continuously oscillated with an output of 600 W, and the irradiation was performed at an angle of 0 ° from a right angle to the sheet passing direction at 7 mm intervals.
The depth of the formed melt-solidified portion is 20% of the plate thickness, and the width is 2
It was 00 μm. After that, apply an insulating film coating for tensioning at 800 ° C. so that 1 g / m ² is applied to one side.
After baking for 60 seconds, strain relief annealing was performed at 850 ° C. for 2 hours. For comparison, the same material was prepared without going through the laser irradiation process and passing through the same processing steps.

Table 2 shows the magnetic characteristics and the space factor. 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 clearly have good iron loss characteristics, and the space factor is also better than that of the conventional example.

[0024]

According to the present invention, a grain-oriented electrical steel sheet having a low iron loss, which maintains a magnetic domain control effect, has a good iron loss, and has a low space factor even when a stress relief annealing treatment is performed, is obtained. It can be provided and can contribute to the miniaturization of the transformer. Further, since the step of only laser processing is added, the above steel sheet can be manufactured with high productivity and low cost.

[Brief description of drawings]

FIG. 1 is a schematic view of a photograph showing a melting and solidifying structure of a steel plate cross section by laser irradiation.

FIG. 2 is a graph showing changes in iron loss in the treatment process of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunobu Miyazaki 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technical Development Division

Claims (2)

[Claims] Claims: 1. The width of 50 to 300 μm, the depth of 5 to 35% of the steel plate thickness, and the right angle to the sheet passing direction, on the surface layer of the base iron of the grain-oriented electrical steel sheet with the tension-added insulating film of the final product. ±
A low iron loss grain-oriented electrical steel sheet having a melt solidification line portion with an interval of 15 ° or less and a space of 5 to 30 mm and having an excellent space factor. 2. The surface of a grain-oriented electrical steel sheet, to which an insulating film has been applied and dried after finish annealing or after finish annealing, is irradiated with a laser beam to have 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, which comprises applying a tension-adding insulating film treatment after forming a melt-solidified wire portion having an interval of 5 to 30 mm within ± 15 ° from a right angle to the sheet direction.