JP2000328139A - Production of thick low iron loss grain oriented silicon steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To irradiate the surface of a thick grain oriented silicon steel plate of >=0.30 mm plate thickness with a laser beam and to improve the iron loss characteristics therein. SOLUTION: In the method for producing a grain oriented silicon steel plate in which a grain oriented silicon steel plate having >=0.3 mm plate thickness is irradiated with a laser beam and magnetic domain fractionization is executed, the cumulative irradiating energy density at the optional point on a scan line in the laser beam irradiation is controlled to the range from (69t+44) to (104t+66)(mJ/mm2) to the plate thickness (mm), and moreover, the power density of the laser beam is controlled to <=(168t+106) kW/mm2. The irradiating diameter of the laser beam is preferably controlled to 6 to 10 mm major axis and 0.25 to 0.35 mm minor axis in the case of an oval and to 0.4 to 0.5 mm in the case of a circle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thick, low-iron-loss unidirectional magnetic steel sheet which is used for an iron core of a transformer, is magnetically controlled by laser beam irradiation, and has good iron loss characteristics. It is.

[0002]

2. Description of the Related Art Currently, unidirectional electromagnetic steel sheets that have been put to practical use have an axis of easy magnetization in the rolling direction of the steel sheet and are mainly used for electrical equipment such as transformers. There is an increasing demand for steel sheets to reduce iron loss to reduce energy loss and to improve magnetostriction to reduce noise during use.

When a magnetic domain is refined by introducing local strain or forming a groove in the steel sheet, an eddy current flowing in the cross section of the steel sheet is reduced, and generation of heat energy is suppressed, so that iron loss is reduced. Thereby, the energy loss of the electric device can be reduced. For example, JP-A-53-137016
As disclosed in Japanese Unexamined Patent Publication, by forming a linear minute strain on the surface of a grain-oriented electrical steel sheet and optimizing the strain introduction interval, an effect of reducing iron loss compared to before strain introduction is obtained. ing.

In particular, as disclosed in Japanese Patent Application Laid-Open No. 55-18566, a pulsed YAG laser beam is condensed and irradiated on the surface of a steel sheet to introduce a strain due to the evaporation reaction force of the film at the irradiated portion. The method is a method for producing a highly unidirectional magnetic steel sheet which has a great effect of reducing iron loss and has high reliability and controllability due to non-contact processing. On the other hand, as the unidirectional magnetic steel sheet, there is a type (thick material) in which the thickness is increased in order to reduce the load of the steel sheet laminating operation in the core manufacturing process of the electrical equipment. Thick materials have a large iron loss compared to thin materials, and the merit of the iron loss reduction effect by laser beam irradiation is low. Therefore, laser beam irradiation was not usually performed.

However, in recent years, even for thick materials,
There has been a demand for good workability and low iron loss, and research has been conducted accordingly.However, there are many unknowns about the iron loss reduction mechanism after laser irradiation on thick materials. Manufacturing conditions for low iron loss thick materials have not been established.

[0006]

SUMMARY OF THE INVENTION In a unidirectional magnetic steel sheet for controlling magnetic domains by introducing micro-strain by laser beam irradiation or the like, the steel sheet to be irradiated with the laser beam has a small thickness (0.27 mm or less). From many empirical findings, it was thought that there was a limit in reducing iron loss in a thick steel plate. That is, it is known that, when a small steel plate having a small thickness is subjected to an optimally small strain under a laser beam irradiation condition for obtaining an optimum iron loss determined in operation, the iron loss becomes a minimum value. Irradiation of a laser beam to a thick steel plate under the conditions does not show any improvement in iron loss characteristics.

Therefore, the present invention clarifies a method for reducing iron loss in a grain-oriented electrical steel sheet having a thickness of 0.3 mm or more,
It is an object of the present invention to provide a thick grain-oriented electrical steel sheet having excellent iron loss characteristics.

[0008]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a unidirectional electrical steel sheet having excellent iron loss characteristics by optimizing a laser beam irradiation condition for a steel sheet having a large thickness. . Specific means of the present invention are as follows. (1) In a method of manufacturing a unidirectional magnetic steel sheet in which a magnetic domain is subdivided by irradiating a laser beam onto a surface of a unidirectional magnetic steel sheet having a thickness of 0.3 mm or more, an arbitrary point on a scan line of laser beam irradiation. From (69t + 44) to (104t) with respect to the plate thickness t (mm).
+66) Adjust to the range of mJ / mm ² .

(2) In the manufacturing method of (1), the power density of the laser beam is set to (168t + 106) kW /
adjusted to mm ² or less. (3) In the method of the above (1) or (2),
When the irradiation diameter of the laser beam is elliptical, the major axis is 6 to 10.
mm, short axis: 0.25 to 0.35 mm, and in the case of a circular shape, the diameter: 0.4 to 0.5 mm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various studies on iron loss after applying elastic strain to a steel sheet by irradiating a laser beam, and as a result, by changing the strength of the elastic strain in the cross section of the steel sheet, Has been found to be able to change even with a thicker material. The details will be described below based on experimental results.

The present inventors examined the relationship between the energy density, the sheet thickness, and the iron loss after the magnetic domain refinement. The surface was subjected to magnetic domain refining treatment by changing the irradiation diameter and irradiation interval of the laser beam, and the iron loss was measured. Iron loss (W17 / 5) with respect to sheet thickness (mm) and integrated irradiation energy density (energy amount per unit area of steel sheet) (mJ / mm ² )
0 (W / kg)), and iron loss (W / mm ² ) with respect to sheet thickness (mm) and power density (energy given per unit area / unit time of steel sheet) (kW / mm ² ).
17/50 (W / kg)) is shown in FIG.

[0012] The principle of iron loss improvement by laser beam irradiation is as follows. A return domain perpendicular to the direction of easy magnetization is generated by a strain using the irradiation point as a heat source, and a 180 ° domain wall is used to minimize the magnetostatic energy here. The formed main magnetic domain is subdivided, and as a result, iron loss in proportion to the domain wall interval is reduced. The integrated irradiation energy density (mJ / mm ² ) that gives the best iron loss value is almost proportional to the plate thickness (mm), as is apparent from FIG. This is because the energy of domain wall formation is proportional to the domain wall area. From this, it is possible to strongly introduce local distortion,
It is considered that the magnetoelastic energy for increasing the domain wall for domain refining is increased.

In FIG. 1, the point of the integrated irradiation energy density at which the value of the iron loss at each sheet thickness becomes the best value plus 10% is taken, and the integrated irradiation energy density (E) is obtained.
Is obtained by the least squares method, the relationship between
= 104t + 66 and E = 69t + 44. That is, the integrated irradiation energy density (E) is (10)
If it is 4t + 66) mJ / mm ² or more, the 180 ° domain wall is pinned by the strain generated in the steel sheet, and as a result, the iron loss increases. On the other hand, the integrated irradiation energy density is (6
If it is 9t + 44) mJ / mm ² or less, there is no effect of laser beam irradiation. Thus, the integrated irradiation energy density is (69t + 44) to (104t + 66) mJ
/ Mm ² , iron loss is low and good electromagnetic characteristics are obtained.

From the above, the integrated irradiation energy density is (6
9t + 44) to (104t + 66) mJ / mm ² . In addition, the power density of the laser beam (kW / m
As for m ² ), the value giving the optimum iron loss is almost proportional to the plate thickness (mm), as is clear from FIG. It is considered that the energy density (mJ / mm ² ) indicates the degree of influence on the steel sheet, whereas the power density (kW / mm ² ) indicates the degree of impact on the steel sheet. Therefore, if the power density becomes too large in the magnetic domain refining process, that is, if the degree of impact becomes too large, the 180 ° domain wall contributing to the magnetization reversal is pinned, which increases the iron loss. , The power density is limited to a predetermined range.

In FIG. 2, as in the case of the energy density, the point of the power density at which the value of the iron loss at each sheet thickness becomes the best value plus 10% is taken, and the power density (P) and the sheet thickness are taken. When the relationship with (t) is obtained by the least square method, the relationship of P = 168t + 106 is obtained. That is, if the power density is (168t + 106) kW / mm ² or more, the impact strength becomes too large and the iron loss increases. On the other hand, the lower limit does not need to be particularly limited in terms of the impact degree, and a condition that satisfies both the power density and the energy density may be adopted. However, if the power density is small, it is necessary to increase the irradiation time correspondingly. Therefore, the optimum power density value is industrially determined as appropriate. Note that the laser may use a continuous wave or a pulse wave, and the power density of the present invention defines its output in the case of a continuous wave and its maximum output in the case of a pulse.

From the above, the power density of the laser beam is
(168t + 106) kW / mm ² or less. Also,
The irradiation diameter of the laser beam is important in forming an appropriate magnetic domain width, and is preferably determined appropriately in combination with the energy density and the power density. The limited range of the irradiation diameter is such that when the irradiation diameter of the laser beam is elliptical, the major axis is 6 to 10 m.
m, the short axis is 0.25 to 0.35 mm, and in the case of a circle,
The diameter is set to 0.4 to 0.5 mm. The reason is that if the irradiation diameter of the laser beam is smaller than this irradiation diameter, the energy required for magnetic domain segmentation will not be reached, and if it is larger than this, the irradiated part will be a part that is hard to pass magnetism, This is because this becomes too large and the iron loss characteristics deteriorate.

Hereinafter, embodiments will be described.

[0018]

EXAMPLES Example 1 A sheet having a thickness of 0.degree.
23 and 0.35 mm unidirectional electrical steel sheet
The beam has a long axis perpendicular to the steel sheet rolling direction.
The energy density is approximately
40mJ / mm ^Two~ 130mJ / mm^TwoAnd change
Fired. Laser beam as circular laser spot
In the case of irradiation, the diameter was 0.45 mm. 50Hz
Fig. 3 shows the change in iron loss at B = 1.7T when excited in
Shown in Thin steel plate (▲: 0.23mm thick in the figure)
Thicker steel plate (-: 0.35 mm in the figure)
Thickness) is shifted to the higher energy density
You.

From the above results, when the laser energy condition is in the range specified in the present invention, a low iron loss unidirectional magnetic steel sheet having a large thickness can be obtained. Example 2 A sheet having a thickness of 0.degree.
The surface of a unidirectional electrical steel sheet (average magnetic flux density B8: 1.920T) of 30 and 0.35 mm was irradiated with a laser beam linearly in a direction substantially perpendicular to the rolling direction of the steel sheet. The laser spot was made approximately circular with a diameter of 0.45 mm, and the irradiation energy was variously changed. The irradiation interval is 6500 in the rolling direction.
μm, and 500 μm in a direction perpendicular to the rolling direction.

The total irradiation energy density, as the present invention example 90 mJ / mm ^2, was 60 mJ / mm ² as a comparative example. Table 1 shows the iron loss values at B = 1.7T of 0.30 mm in plate thickness and 0.35 mm when excited at 50 Hz. In the present invention, iron loss is reduced by 3%.

[0021]

[Table 1]

[0022]

As described above, the iron loss characteristics of a thick unidirectional magnetic steel sheet can be compared with the iron loss characteristics of a conventional product by using the effect of domain refining by the width of the return magnetic domain and the distribution of elastic strain. The energy loss and noise of the transformer can be further reduced. Therefore, the industrial significance of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between integrated irradiation energy density and iron loss in a thin steel plate and a thick steel plate.

FIG. 2 is a diagram illustrating a relationship between power density and iron loss in a thin steel plate and a thick steel plate.

FIG. 3 is a diagram showing iron loss when the energy density is changed in a thin steel plate and a thick steel plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Atsushi Tanaka, Inventor 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (72) Inventor, Norihiro Yamamoto Tobata-ku, Tobata-ku, Kitakyushu, Fukuoka Town 1-1 Shin Nippon Steel Corporation Yawata Works F-term (reference) 4E068 AH00 CA01 CA07 DA12 DA14 DB01 4K033 AA02 PA08 RA04 TA06 5E041 AA02 CA02 HB05 NN06 NN17

Claims (3)

[Claims] 1. A method of manufacturing a grain-oriented magnetic steel sheet in which a magnetic field is refined by irradiating a surface of a grain-oriented magnetic steel sheet with a thickness of 0.3 mm or more to an arbitrary direction on a scan line of laser beam irradiation. The integrated irradiation energy density at the point was calculated from (69t + 44) to (1) with respect to the plate thickness t (mm).
04t + 66) (mJ / mm ² ). 2. The power density of the laser beam is (168)
^{2. The method according} to claim 1, wherein the thickness is adjusted to t + 106) kW / mm ² or less. 3. When the irradiation diameter of the laser beam is an ellipse,
The thick plate according to claim 1 or 2, wherein the major axis is 6 to 10 mm, the minor axis is 0.25 to 0.35 mm, and in the case of a circular shape, the diameter is 0.4 to 0.5 mm. Manufacturing method of low iron loss unidirectional electrical steel sheet.