JPH0332888B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention aims to improve the magnetic properties of Fe-based amorphous alloy ribbons, which are mainly used as iron cores of power converters such as power transformers, high-frequency transformers, pulse transformers, and reactors, and in particular to simultaneously improve iron loss and excitation properties. It's about how to improve. (Prior Art) Amorphous alloy ribbons produced by rapid solidification from a molten state exhibit various excellent properties and are attracting attention for their 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 100 times larger than the classical eddy current loss calculated assuming uniform magnetization.
It's twice as big. 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. Furthermore, research by the present inventors has revealed that the absolute value of abnormal eddy current loss and its proportion to total iron loss increase as the thickness of the material increases. Therefore, the thickness of the conventional material (20
In order to fully bring out the performance of an amorphous alloy having a thickness (40 to 80 μm) greater than 30 μm), it is desirable to take measures to reduce eddy current loss. 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 is a device that uses a sharp point 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 this method was applied to amorphous alloy ribbons, good results were not necessarily obtained. for example
Narita et al. Proceedings of 4th International
Conference on Rapidly Quenched Metals
(1982) p.1001-1004 reported the effect on core loss of linear strain introduced by scribing the surface of an Fe-based amorphous alloy ribbon with a diamond needle after annealing. ing. According to this, the effect of distortion is
Iron loss appears in the high frequency range above 5kHz, but it actually increases in the low frequency range below 100Hz, which is important for power transformers. The reason for this is that in amorphous alloys, which are thinner than silicon steel sheets, the eddy current loss is originally small in the low frequency range, so the effect of reducing iron loss by magnetic domain refinement is slight, and on the contrary, the hysteresis loss increases. This is presumed to be because the total iron loss increases due to A method of local crystallization has been proposed as a method of reducing iron loss unique to amorphous materials. This is JP-A-57
This is a method disclosed in Japanese Patent No. 97606, in which crystallized regions are formed in the form of lines or dots in the width direction of the ribbon. The crystallization method here is to irradiate laser light or electron beam, or use metal needles or
A method is adopted in which one of the metal edges is heated with electricity while being brought 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 a low frequency range. For example, in the above-mentioned Japanese Patent Application Laid-Open No. 57-97606, the effect is expressed at commercial frequencies, whereas the above-mentioned paper by Narita et al. also describes the effect of providing a linear crystallized region; Compared to the scratch method, the range in which it is effective extends to the low frequency side, but it is not effective or even deteriorates below 200Hz. Furthermore, methods for reducing core loss without crystallization by irradiating laser light include methods disclosed in Japanese Patent Laid-Open No. 56-44710 and Japanese Patent Laid-Open No. 56-44711. Although this method was effective in reducing iron loss,
The drawback was that the excitation characteristics deteriorated somewhat. As described above, the application of the prior art has little effect on reducing the iron loss of amorphous alloys, or even when it is effective, it has the drawback of deteriorating the excitation characteristics. Excitation characteristics are usually expressed by the magnitude of excitation power (excitation effective VA) required to obtain a predetermined magnetic flux density, but more simply, they are expressed by the magnitude of excitation power (excitation effective VA) required to obtain a predetermined magnetic flux density.
10e) can also be expressed by the magnitude B ₁ of the magnetic flux density induced under The cause of deterioration in excitation characteristics caused by normal laser irradiation and scratching methods is thought to be due to the formation of perpendicular anisotropy due to locally introduced strain. The effects of laser irradiation and scratch treatment applied to unidirectional silicon steel sheets are completely lost after strain relief annealing, so strain relief annealing is performed to remove the local strain that is the cause of vertical anisotropy after treatment. I can't. Therefore, the main focus was on improving iron loss, and the deterioration of excitation characteristics was accepted as unavoidable. Regarding amorphous materials, as described above, the situation is the same as far as conventional known literature is concerned, and deterioration of excitation characteristics was thought to be unavoidable. In contrast, the present invention proposes a new method for the purpose of reducing the iron loss of an amorphous alloy and improving the excitation characteristics at the same time. (Problems to be Solved by the Invention) An object of the present invention is to provide a method for simultaneously improving the iron loss and excitation characteristics of an Fe-based amorphous alloy. (Means/effects for solving the problem) The present invention locally and instantaneously melts the surface of an amorphous alloy ribbon, and then rapidly solidifies that part to make it amorphous. It is constituted by a combination of a step of introducing thermal strain and an annealing step after applying the thermal strain. Irradiation is usually carried out on the as-cast ribbon, but it may also be applied to a ribbon that has been surface-treated for the purpose of insulation or rust prevention. The local melting area is created by irradiation with a pulsed laser with a narrow beam diameter. The individual melting portions to be introduced have a circular or elliptical shape as shown in FIG. Since the irradiated area does not crystallize, the beam diameter is
It is necessary to use a pulsed laser with a diameter of 0.5 mmφ or less.
Magnetism generally deteriorated upon crystallization. The local melted portion formed by pulsed laser irradiation has a depressed central portion and a raised peripheral portion. The dissolving part here includes the peripheral part. The swelling at the periphery is thought to be the result of melted alloy overflowing to the periphery and solidifying due to the rapid incidence of thermal energy due to laser irradiation. In order to keep the average diameter of the melted part, which is one of the constituent elements of the present invention, within a predetermined range, parameters such as the irradiation intensity, beam diameter, frequency, and sweep speed of the pulsed laser are controlled. Specifically, with a beam diameter of 0.5 mmφ or less, the irradiation energy density is per unit area of the melted part.
Adjust the irradiation intensity (laser power), frequency, and sweep speed so that it becomes 0.02 to 1.0 J/ ^mm2 . 0.02J/
Below ^mm2 , the effect of irradiation disappears due to annealing.
If it exceeds 1.0J/ ^mm2 , the magnetic flux density will deteriorate even if the iron loss is improved. In addition, the direction of the dot array in the melting zone is set at an average angle of 30 degrees or less with respect to the width direction of the ribbon, and the line speed (travel speed of the ribbon) and irradiation are adjusted so that the average distance between adjacent dot arrays is 1 to 20 mm. Select the sweep speed. Adjacent points do not need to be parallel, nor do they need to be straight lines. For example, a sinusoidal point sequence shown in FIG. 2 is also included within the scope of the present invention. Furthermore, what is important in the present invention is the distribution density of the melted portion. When the distribution density is expressed as the ratio of the sum of the diameters of the melted parts (l = l ₁ + l ₂ +...) to the length L of the straight line or curve formed by the point sequence as shown in Figure 3, this is 10 Must be greater than or equal to %. This range was determined because if it is less than 10%, the local strain will be completely removed by the subsequent annealing and the effect of irradiation will be visible. As a component of the present invention, there are conditions regarding annealing after laser irradiation. Annealing conditions (temperature and time)
must be selected depending on the laser irradiation conditions, the properties and distribution density of the melted part to be formed, etc. The appropriate range of annealing conditions depends on the composition of the alloy, so it is difficult to express them in concrete numbers.
It can be determined experimentally by the following method. That is, the optimum annealing conditions for a ribbon having the same alloy composition without laser treatment are experimentally determined in advance. If this temperature is Ta, the laser treatment is performed at a higher temperature. The annealing temperature in this case is usually in the range of Ta + 10 to 40°C, and is set higher when the laser irradiation conditions are strong (within the range selected by the present invention), and set lower when the irradiation conditions are strong. Composition Fe _80.5
In the case of an amorphous ribbon with Si _6.5 B ₁₂ C ₁ (at%) and a thickness of 65 μm, the optimum annealing temperature for iron loss was 360°C x 60 minutes (in N ₂ ) without laser irradiation. but,
Dissolved area of approximately 200μmφ with linear density of 70% and dot row spacing of 5
The laser treated material with mm is as shown in Example 1.
After annealing at 380°C for 60 minutes (in _N2 ), improvements in not only iron loss but also excitation characteristics were observed. If the annealing conditions after irradiation are inappropriate, even if an improvement in iron loss is recognized, an improvement in excitation characteristics cannot be achieved. In the method of the present invention, the ribbon after laser irradiation may be coated for the purpose of interlayer insulation. (Example) Next, an example will be given and explained. Example 1 Composition Fe _80.5 Si _6.5 B ₁₂ C ₁ produced by single roll method,
A YAG laser was irradiated onto the free surface of an as-cast amorphous thin strip with a width of 50 mm and a thickness of 65 μm to introduce local melting zones. Irradiation conditions are frequency 400Hz, beam diameter 0.2mm
φ, output 5W, beam sweep speed 10cm/sec, and dot array spacing 5mm. The melted area observed with an optical microscope was approximately circular, with an area of approximately 0.04 mm ² and a linear density of approximately 70%. Therefore, the irradiation energy density is calculated to be approximately 0.3 J/mm ² . Furthermore, it was confirmed by X-ray diffraction and optical microscopy that the dissolved area and the surrounding area were not crystallized. The magnetic properties of the irradiated ribbon after magnetic field annealing at 380° C. for 60 minutes (in N ₂ ) were as shown in Table 1. Table 1 also shows the magnetic properties of an unirradiated material, which was used for comparison, after annealing at 360° C. for 60 minutes (in N ₂ ), which is the optimum condition. It can be seen that the magnetic properties of the ribbon processed by the method of the present invention are superior to those of the comparative example in both iron loss and magnetic flux density.

[Table] Here, W _13/50 is the iron loss measured at a frequency of 50Hz and magnetic flux density of 1.3T, and B ₁ is the magnetic flux density at a magnetic field of 10e. A single plate measuring device was used for measurement. Example 2 A YAG laser was irradiated onto the free surface of an as-cast amorphous ribbon having the same composition, width, and thickness as in Example 1 to introduce local melting zones. Irradiation conditions are frequency
It was 400Hz, beam diameter 0.2mm ² φ, output 5W, line speed 2cm/sec, and beam sweep speed 10cm/sec.
The irradiated area of the ribbon observed with an optical microscope had almost the same properties as in Example 1. This irradiated thin strip 1300
Wrap g onto a stainless steel reel with an outer diameter of 120 mmφ,
Annealed in a magnetic field at 380°C for 120 minutes. However, the temperature rise
After holding at 150°C for about 120 minutes, the temperature was raised at an average rate of about 3°C per minute. The temperature decreases by furnace cooling, with an average rate of about 2°C per minute up to 250°C.
It was hot. The magnetic properties of the core after annealing are shown in Table 2. A thin strip of the same composition and shape without laser treatment is formed into a wound core of the same weight and shape, and heated at 360℃
The magnetic properties after magnetic field annealing for 120 minutes are shown in Table 2 for comparison. It can be seen that the magnetic properties of the iron core treated by the method of the present invention are superior to those of the comparative example in both iron loss and excitation properties.

[Table] (Effects of the Invention) As explained above, according to the present invention, the core loss and excitation characteristics of an amorphous magnetic alloy ribbon can be simultaneously improved.

[Brief explanation of drawings]

Fig. 1 is a microscopic photograph showing the structure of the melted and rapidly solidified portion in the present invention, Fig. 2 is an explanatory diagram showing an example of melting and rapidly solidified in the present invention, and Fig. 3 is a photomicrograph showing the structure of the melted and rapidly solidified portion in the present invention. FIG. 3 is an explanatory diagram showing the size and spacing of parts.

Claims (1)

[Claims] 1. By irradiating the width direction of the amorphous alloy ribbon with a pulsed laser with a beam diameter of 0.5 mmφ or less and an energy density of 0.02 to 1.0 J/mm ² per single pulse,
The surface of the amorphous alloy ribbon was locally and instantaneously melted, then rapidly solidified to become amorphous again, and a circular or elliptical region was introduced as a dot array with a linear density of 10% or more. A method for improving magnetism of an amorphous alloy ribbon, the method comprising: thereafter annealing the amorphous alloy thin film.