JPS60233804A - Improvement of magnetism in amorphous alloy thin film - Google Patents

Abstract

PURPOSE:To obtain an iron core which has less iron loss in low frequency band by locally and momentarily melting the surface of an Fe group amorphous alloy thin belt used for the iron core of a power transducer irradiating laser light of the limited beam diameter of 0.5mm. or less and then by rapidly cooling to be solidified in amorphous again. CONSTITUTION:The surface of an amorphous alloy thin belt is melted locally and momentarily, the melted part is rapidly cooled and solidified to be made amorphous again and the iron loss is greatly reduced. In this case, the shape and the distribution of the locally melted part are desirable to be parallel lines or dotted lines and the area and the depth of each melted part are made under the conditions that the melted part and the peripheral part are not made amorphous in the solidification process during heating or after melting. For this reason, when locally melting using laser light, the width of the line of the melted part is made 0.3mm. or less and in the case of dotted lines, the diameter of the spot is made 0.5mm. or less.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention improves the magnetic properties, particularly the iron loss, of Fe-based amorphous alloy ribbons used mainly as cores of power converters such as electrocadrans and high-frequency transformers. It's about how to do it.

(Prior Art) Amorphous alloy ribbons produced by rapid solidification from a molten state exhibit various excellent properties and are attracting attention for applications. Among these, Fe-based amorphous alloys are being used as materials for various iron cores because of their high magnetic flux density and low iron loss. The reason why amorphous alloys have low core loss is that they have no anisotropy in principle and have no defects such as grain boundaries, so hysteresis loss is small, and the plate thickness is thin and electrical resistance is low. It is said that because of its large size, eddy current loss is also small. However, the eddy current loss in a broad sense, which is obtained by subtracting the DC hysteresis loss from the iron loss value, is several tens to 10,0 times larger than the classical eddy current loss calculated assuming uniform magnetization. This indicates that because the magnetic domain width is large, the proportion of abnormal eddy current loss caused by non-uniform magnetization changes is large.

As a method for reducing abnormal eddy current loss, the application of the method conventionally used for grain-oriented silicon steel sheets was first considered and attempted. For example, the scratch method. This uses a sharp tip made of hard material to score the surface of a silicon steel plate, dividing the magnetic domains into smaller pieces and reducing iron loss. However, even when applied to amorphous alloy ribbons, good results were not necessarily obtained.
s of 4th InternationalCon
ference on RapidlyQuenche
d Metal+ (1982) P1001-1004 reported the effect on core loss of linear strain introduced by scribing the surface of the ribbon with a diamond needle after annealing the Fe-based amorphous alloy ribbon. ing. According to this, the effect of distortion appears in the high frequency range above 5] (Hz), but the iron loss actually increases in the low frequency range below 100 Hz, which is important for electric quadrants.The reason for this is that silicon steel sheets Since eddy current loss is originally small in the low frequency range for amorphous alloys, which have a thin plate thickness compared to It is presumed that this was for the purpose of

A method of local crystallization has been proposed as a method of reducing iron loss unique to amorphous materials. This is Japanese Patent Publication No. 57-97606
This is the method disclosed in the publication, in which crystallized regions are formed in the form of lines or dots in the width direction of the ribbon. Here, the method of crystallization employed is a method of heating with electricity while bringing either a metal needle or a metal edge close to or in contact with the surface of the ribbon. Although this method of introducing local crystallized regions is an effective means for subdividing magnetic domains, it has the drawback that it does not necessarily have a certain effect on reducing iron loss in the low frequency range.

For example, in the above-mentioned Japanese Patent Application Laid-Open No. 57-97606,
While the effect is expressed at commercial frequencies, Narit
The above-mentioned paper by et al. also describes the effect of providing a linear crystallized region, and according to it, compared to the scratch method, the region where the effect is effective extends to the lower frequency side,
At frequencies below 200Hz, it is ineffective or rather deteriorates.

As described above, all the methods conventionally attempted to improve the core loss of amorphous magnetic alloys, particularly Fe-based amorphous alloy ribbons, have often been ineffective in commercial frequency bands.

In contrast, the present invention has a stable effect on reducing iron loss in amorphous alloys even in low frequency bands, and
This project proposes a new method that is highly effective.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for significantly and stably reducing the core loss of an amorphous magnetic alloy.

(Means for Solving the Problems) The present invention melts the surface of an amorphous alloy ribbon locally and instantaneously, and then rapidly solidifies that part to make it amorphous again. This is to stably achieve a reduction in iron loss. A narrowly focused laser beam is used to locally melt the surface of the ribbon.

The shape/shape and distribution of the introduced local dissolution parts are preferably in the form of parallel lines or dots as illustrated in FIG. The area and depth of each melting zone are determined on the condition that the melting zone and the surrounding area do not crystallize during heating or during the re-solidification process after melting. When using laser light, parameters to be controlled include irradiation intensity, beam diameter, sweep speed, and frequency (in the case of Noyals mode).

In the case of local melting using laser light, the line width of the melted part is 0.3- or less, and in the case of a dot array, the diameter of one spot is 0.3- or less.
5 tries or less is preferable. If it exceeds these ranges, crystallization may occur and no improvement in magnetic properties will be observed.

The direction of the line or dot array of the locally dissolved portion to be introduced is preferably in the width direction of the ribbon as shown in FIG. 1, but it may be in an inclined direction up to about 30 degrees. Further, adjacent lines or dots do not necessarily need to be parallel, nor do they need to be straight lines. If the average inclination angle with respect to the ribbon width direction is less than a predetermined value and the average interval between adjacent lines or dots is within a predetermined range, it will be effective in reducing iron loss. Therefore, the sinusoidal melting section shown in FIG. 2 is also included within the scope of the present invention. The average spacing of lines or dots showing the effect on commercial frequencies is 1 to 20+w+.

The average angle with respect to the width direction is preferably 30° or less.

In the present invention, the local melting portion may be introduced at any time before, during, or after the step of heat treating the amorphous alloy ribbon. However, the optimum conditions differ depending on the time of introduction of the dissolving part. For example, when introducing a localized dissolution part in the width direction using the laser mode of a YAG laser, Figs.
As shown in the figure, the effective diameter of the melting zone differs depending on the time of introduction. That is, when introduced after heat treatment, the optimum spot diameter is 50 to 100 μm, but when introduced before heat treatment, it was most effective around 200 to 250 μm. The reason for this is thought to be that the effect of introducing the melted zone is alleviated by heat treatment. Differences in effectiveness depending on the time of introduction are also reflected in the time of excitation and sex. Those introduced after heat treatment showed a decrease in magnetic flux density of several percent to 10 degrees at a magnetic field of 1 oersted, whereas those introduced before heat treatment showed almost no decrease in magnetic flux density.

In order to locally melt the surface of the amorphous alloy ribbon, the best way to rapidly heat it is to irradiate it with narrowly focused 1/-day light for a short period of time, as described above. Other methods are either ineffective or have negative effects. Attempting to melt the material by electron beam irradiation, contact with a high-temperature object, or locally applying electricity is not preferable because the incident energy density is small and the thermal effect spreads, resulting in crystallization.

The iron loss improvement effect when applying the present invention depends on the plate thickness of the material, and as shown in Figure 5, the larger the plate thickness, the greater the improvement effect (○ in the figure is before irradiation, ・ is after irradiation) . Plate thickness 60
While it shows a 40-50% iron loss reduction effect in μm,
When the thickness is 30 μm or less, it is about 10 to 20%. The reason for this is that, in general, as the plate thickness of an amorphous alloy increases, the magnetic domain width increases, and the absolute value of the abnormal eddy current loss and its proportion in the total core loss increase. It was verified by observation using a scanning electron microscope that the magnetic domain width can be subdivided into ⅓ in the case of a plate thickness of 60 μm by introducing the local melting portion of the present invention.

In the present invention, it is possible to clearly distinguish whether or not the laser-irradiated area has once melted and then re-solidified by observing the irradiated area with an optical microscope or a scanning electron microscope. / When irradiated with IP Lux, the center of the melted part becomes dark, and the periphery becomes slightly raised. This is thought to be because the alloy melted by the rapid incidence of thermal energy overflows into the surrounding area. An example of a melted zone introduced by a pulsed laser is shown in FIG.

In the present invention, it was confirmed by X-ray diffraction, transmission electron microscopy, optical microscopy, etc. that the portion locally melted and resolidified by laser irradiation and the surrounding area were not crystallized.

Further, the method of the present invention showed similar effects even when applied before or after surface treatment for the purpose of insulation or rust prevention was applied to the surface of the ribbon.

(Example) Example 1 Composition Fe80.58'6.5B produced by single roll method
12C1 65μm thick amorphous alloy ribbon at 360℃
After magnetic field annealing in N2 gas for 0 minutes, a local melting zone was introduced into the free surface using a YAG laser, and an experiment was conducted to examine the effect on iron loss. Irradiation conditions are frequency 400H
Z's A Luss mode, sweep speed 10 loli ec.

The direction of the dot row is parallel to the width direction of the ribbon, and the interval between the dot rows is 5 m.
The size of the melted zone was controlled by the irradiation energy and beam diameter. Figure 3 shows the relationship between the diameter of the introduced spot-shaped melted part and iron loss. The effect of reducing iron loss is large when the diameter of the melted part is in the range of 30 to 150 μm. Here, a single plate tester was used to measure iron loss. It was confirmed from the diffraction image when X-rays were irradiated along a dot array through a 0.5 m wide slit that the area irradiated under irradiation conditions with a large iron loss reduction effect and its surroundings were not crystallized. Ta.

Example 2 The free surface of an as-cast amorphous alloy ribbon of the same lot as that used in Example 1 was irradiated with a pulsed laser under the same irradiation conditions as in Example 1. The relationship between the core loss and the diameter of the melted part after magnetic field annealing at 360'C for 60 minutes in N2 gas after irradiation was as shown in Figure 4. The effect of reducing iron loss is remarkable when the diameter of the melted part is around 200/Am. The melted portion of the ribbon after magnetic field annealing was subjected to X-ray diffraction using the method described in Example 1, but no crystals were found.

(Effects of the Invention) As explained above, according to the present invention, iron loss can be reduced even in a low frequency band, so the present invention is extremely useful.

[Brief explanation of the drawing]

Figures 1 (a), (b) and 2 are explanatory diagrams showing amorphous alloy ribbon to which the method of the present invention is applied, and Figures 3 and 4 are diagrams showing the melted part diameter and iron loss in the method of the present invention. Figure 5 is an explanatory diagram showing the relationship between plate thickness and iron loss in the method of the present invention, and Figure 6 is a microscopic photograph showing the state of the metal structure of the melted part by the method of the present invention. be.゛Patent applicant Nippon Steel Corporation 1st (α) (b) $ 2 Figure 3 Melting part thickness 0/M) No. 41ff1 7z solution 11 diameter (, l/town board thickness (mm)

Claims (2)

[Claims] (1) A method for improving the magnetism of an amorphous alloy ribbon, which is characterized by locally and instantaneously melting the surface of the amorphous alloy ribbon, and then rapidly solidifying it to make it amorphous again. (2) The method according to claim 1, characterized in that the method for locally melting the surface of the amorphous alloy ribbon includes irradiating laser light with a beam diameter of Q, 5 mmφ or less. .