JPS5953684B2 - Method for improving iron loss in magnetic steel sheet coils - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron loss improvement method for reducing the overall iron loss of unidirectional electrical steel sheet coils having various iron loss distributions.

Unidirectional electrical steel sheets are made by rolling steel containing several percent silicon so that the [001) axes of the crystal grains are aligned in the length direction of the rolling direction and the (110) planes of the crystal grains are aligned parallel to the rolling surface. Then, it is annealed, an insulating coating is applied to the surface, and the product is made into a coil shape.

When measuring the iron loss of each part of this steel plate coil, there is usually a large variation, but on the other hand, there is a permissible range of iron loss value depending on the product grade. When manufacturing unidirectional electrical steel sheets (trademark) manufactured by Co., Ltd., parts with measured iron loss values exceeding the allowable value are cut off, and parts with poor iron loss that cannot be used are either recycled to lower grade products or scrapped. The reality is that methods such as A portion exceeding this allowable value naturally reduces manufacturing yield. Incidentally, iron loss can be improved by irradiating a unidirectional electrical steel sheet with laser light in a predetermined manner. The present invention applies this to improve the iron loss of the portion by irradiating the laser beam to the portion where the iron loss exceeds the allowable value, thereby improving the manufacturing yield of grain-oriented electrical steel sheets of desired grade. It is something. Next, this will be explained in detail with reference to the drawings. As mentioned above, the unidirectional electrical steel sheet is (110) [
000 structure and is easily magnetized in the rolling direction.

As shown in FIG. 1a, the rolling direction F is
When the laser beam is irradiated in a line, chain line, or dotted line at a substantially right angle to the laser beam (12 indicates the irradiated part in the case of linear irradiation), the iron loss is reduced. This can be explained as follows. That is, the unidirectional electrical steel sheet 10 has a relatively large magnetic domain 14 extending in the rolling direction, as shown in FIG. 2a. In unidirectional steel sheets, as the degree of integration of the (110)[001] orientation in the rolling direction increases, the crystal grains become larger, and since the domain wall penetrates the grain boundary, the magnetic domain becomes larger, and the size of the magnetic domain and the iron loss Since there is a proportional relationship with the value, there is a contradictory problem in that increasing the directionality or increasing the ratio does not reduce the iron loss. On the other hand, when the laser beam is irradiated in a direction substantially perpendicular to the rolling direction, specifically, when the laser beam irradiated portion 12 extends substantially perpendicular to the rolling direction F, small projection groups 16 are formed on both sides of the irradiated portion 12. Occur. This can be observed using a scanning electron microscope or the like. Note that in the figure, only a portion of the small protrusions are shown for simplicity. These small protrusions are buds of magnetic domains, and when magnetized, the magnetic domains 14 of the steel plate 10 are subdivided by magnetic domains 18 extending from these buds. Therefore, iron loss becomes small. It is thought that the small protrusions 16 are generated because dislocations occur when the steel plate 10 is irradiated with laser light, and the probability of occurrence of magnetic domain buds is proportional to the density of these dislocations. When laser light is irradiated in the rolling direction as shown in FIG. 1b, small protrusions 16, which are buds of magnetic domains, are generated as shown in FIG. 2b.

It is thought that when an external magnetic field H is applied, microdomains are generated from this bud 16, which lowers the iron loss. The reason may be different, but in any case, the iron loss will decrease in this case as well. To give a specific example, the iron loss WL in the rolling direction (magnetic flux density 1.7T, frequency 50
Hz) is 1.00 W/Kg, which is the iron loss W in the direction perpendicular to the rolling direction.

(Magnetic flux density: 1.3 T, frequency: 50 H) is almost the same as that without laser beam irradiation. The W before laser beam irradiation is 1.10W/Kg. WO is 2.84W/K
It is g. In other words, with the laser beam irradiation in Figure 1a, 10% W
, can be reduced. In the case of Fig. 1b, WL hardly changes, but WO becomes 2.04 W/Kg, which is a significant W of about 28%. It has become possible to reduce In order to obtain such an effect, there are conditions for laser light irradiation.

First, the width d and pitch l of the laser beam irradiated portion 12 are as follows.
In the case of Fig. 1a, d=0.01 to 1 mm, . 1=1~3
0 mm, and the time width of the laser pulse is preferably 1 nS to 100 mS. In the case of Fig. 1b, d=0.01 to 1 mm, . 1=
1-30mm, laser pulse width is 1nS or more 100m
S or less is preferable. Moreover, the energy density P is 0.
01 to 100 J/Crff is preferable. In the present invention, the laser beam may be irradiated in the form of a chain line or a dotted line. In this case, in FIG. 1a, the diameter in the L direction d=0.
01 to 1 mm, the distance a in the irradiation point C direction is 3 mm or less, preferably 1 mm or less, and in FIG. It is preferable to set it to 1 mm or less. Furthermore, since the purpose of the laser used is to give a shock, a pulsed laser is best. Continuous lasers are less efficient than pulsed lasers because part of the irradiation energy spreads within the plane due to thermal diffusion, causing some energy loss. The orientation of the laser irradiated portion 12 in FIGS. 1A and 1B is not aligned perpendicularly and parallel to the rolling direction, that is, the [001) direction, but may deviate within a range of ±30° from that direction. There is no particular difference in effectiveness. Therefore, in the present invention, the coil is wound into a coil through processes such as rolling and annealing, or the coil is unwound and trimmed for width adjustment.

The purpose is to irradiate a unidirectional electromagnetic steel sheet (which is then wound again into a coil) with a laser to improve the defective core loss areas, thereby creating a high-grade electromagnetic steel sheet with low core loss as a whole. Third
An example is shown in the figure. In FIG. 3, 10 is a unidirectional electrical steel sheet that has been subjected to rolling, annealing, surface treatment, etc. and wound into a coil 24, and 20 is a device that continuously measures the iron loss of the steel sheet 10 while it is running; is a laser beam irradiation device.

As the iron loss measuring device 20, a well-known device including a flat coil that penetrates the steel plate 10 and magnetizes it, a voltmeter, a wattmeter, etc. is used. As the laser beam irradiation device 22, Q-switchable ruby laser, YAG laser,
Alternatively, any laser such as a continuous wave laser such as a CO2 laser, an Ar laser, or a CO laser can be used. To form the laser irradiated portion 12 in the striped pattern shown in FIGS. 1A and 1B, the beam diameter or side length is
A laser beam having a width d of 2 is deflected by a mirror and moved in the length direction of the portion 12, that is, scanned, or the laser beam is shaped by an optical system so that the beam cross-sectional shape becomes one or more laser beams. It may be irradiated using a material having the same shape as the irradiated portion 12, or any other appropriate method may be used. When the iron loss distribution over the entire length of the unidirectional electrical steel sheet 10 is measured by the iron loss measuring device 20 while being wound around the coil 24, C1 in FIG.
A curve of the iron loss value W versus its appearance frequency f is obtained.

There is considerable variation in iron loss values even for steel plates of the same rod.
This is the cause of a decrease in yield. Therefore, if the unidirectional electrical steel sheet to be manufactured is of grade Zi, and the upper limit of iron loss required for it is Wi, the measuring device 20 continuously measures the iron loss of each part of the steel sheet 10. If there is a portion where the measured value is greater than Wi, that portion is irradiated with pulsed laser light by the laser device 22 in the manner shown in FIG. 1a. As a result, the iron loss value in the rolling direction can be improved, and the distribution curve C1 in FIG. 4 can be improved as shown in C2. Note that when irradiated with laser light, there is a tendency that the worse the core loss is, the better the improvement is, so the width of the curve C2 is narrower than that of the curve C1. Since the degree of iron loss improvement is about 10%, all parts of the steel plate can be reduced to iron loss value W by laser beam irradiation.
It is not necessarily possible to do so within i.

Therefore, it is advisable not to irradiate laser light on portions where the iron loss value is greater than or equal to the large iron loss value Wi, which cannot be reduced to less than Wi even if irradiated with laser light. In other words, in this case, the setting value is Wi. W
j are set so that the laser beam irradiation is performed with Wi<W<Wj. It is also good to irradiate the portions with iron loss values of Wj or more with laser light to lower the grade and use them. In addition, while winding the steel plate 10 into the coil 24, find the iron loss distribution curve C1 of the entire length, find the value Wil where most of the steel plate 10 becomes a certain value Wil by irradiation with the laser beam, and when the steel plate 10 is irradiated with the laser beam at a value higher than Wil, the steel plate coil Most of the material can be made of the highest possible electrical steel sheet. In this case, since it is necessary to obtain an iron loss distribution curve for the entire length of the coil, it is preferable to irradiate the coil with laser light while using a suitable tracking device in the step of winding it once into the coil 24, unwinding it, and trimming it. If the iron loss distribution of the steel plate 10 shows periodicity, the set value Wil can be determined by measuring the iron loss for one period, etc. Therefore, in the system shown in FIG. It is possible to carry out irradiation. As is clear from its characteristics, unidirectional electrical steel sheets are suitable for passing magnetic flux in one direction, that is, in the rolling direction or in the longitudinal direction, but are not suitable for passing magnetic flux in multiple directions.

However, even in the case of transformer cores, apart from wound cores, in EI type or CI type cores, the magnetic flux passes in two directions, that is, two orthogonal sides, that is, the rolling direction and a direction perpendicular thereto. Therefore, the steel plate 10 is irradiated with a laser beam as shown in FIG.
[110] It is also meaningful to improve the axial iron loss.
In this case, it is necessary to magnetize the steel plate in the width direction and measure its iron loss. Therefore, the iron loss measuring device 20 is not a flat coil that penetrates the steel plate, but a nearly closed magnetic field that incorporates the steel plate into a part of the magnetic path. Use known iron cores for roads. As explained above, according to the present invention, it is possible to improve the grade or yield of unidirectional electrical steel sheets by the relatively simple means of laser beam irradiation, which is extremely beneficial.

[Brief explanation of drawings]

Figures 1A and b are diagrams explaining the laser beam irradiation procedure, Figures 2A and b are diagrams explaining the reason for improving iron loss, Figure 3 is a diagram explaining the embodiment of the present invention, and Figure 4 is a diagram explaining the iron loss improvement method. It is a figure explaining a loss improvement state. In the drawing, 10 is a unidirectional electrical steel sheet, 12 is a laser beam irradiation part, 20 is an iron loss measuring device, and 22 is a laser beam irradiation device.

Claims (1)

[Claims] 1. Continuously measure the iron loss of the strip-shaped unidirectional electrical steel sheet while it is being transferred, and apply a laser beam to the portion of the steel sheet where the iron loss exceeds a set value. A method for improving iron loss in an electromagnetic steel sheet coil, characterized by irradiating the coil in a striped manner with a predetermined width and pitch extending in a direction substantially perpendicular to the rolling direction.