JP2006077264A - METHOD FOR RECYCLING RARE-EARTH SINTERED MAGNET AND TRANSITION-METAL BASED SCRAP, AND METHOD FOR MANUFACTURING MAGNETIC-MATERIAL POWDER FOR GHz BAND WAVE ABSORBER AND METHOD FOR MANUFACTURING WAVE ABSORBER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, with respect to a method for recycling scrap (e.g. machining chips generated in the course of grinding for a rare-earth magnet) generated in a rare-earth magnet manufacturing process, a method for manufacturing a magnetic-material powder having electromagnetic wave absorption property in a GHz band, particularly, in a GHz band whose amount of use is recently increasing in the fields of cellular phone waves, automatic payment systems, digital broadcasting, indoor wireless LAN, etc., and also to provide a method for manufacturing a wave absorber using the same. <P>SOLUTION: Remarkable reduction in raw-material costs can be attained by using, as a part of raw materials, the scrap generated at the manufacture of the rare-earth magnet constituted of an intermetallic compound of rare-earth metal and transition metal. The conventional Fe-metal-based electromagnetic wave absorber produced by the conventional technology shows absorption with respect to electric waves of several GHz alone because of the low magnetic anisotropy of the Fe metal; while on the other hand, the production of the electromagnetic wave absorber having excellent absorption property with respect to the electric waves of several GHz or higher can be attained in this method by combining the Fe metal and Ti both separated and recovered from the above scrap by a simplified process and providing crystalline magnetic anisotropy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recycling method for scraps generated in the manufacturing process of rare earth magnets (cutting scraps generated in the polishing process of rare earth magnets), and in particular in portable radio waves, automatic fee payment systems, digital broadcasting, indoor wireless LAN, etc. The present invention relates to a method of manufacturing a magnetic powder having electromagnetic wave absorption characteristics in the GHz band of the GHz band where the amount of use is increasing, and a method of manufacturing a radio wave absorber using the same.

  In recent years, high-performance rare earth sintered magnets have been used for information communication equipment, control equipment, consumer light electrical equipment using small motors, medical diagnostic equipment, etc., and their production volume is increasing year by year. In particular, in the production of Nd-Fe-B sintered magnets, the final magnet product is completed through alloy dissolution and pulverization, molding, sintering, cutting / polishing, and surface treatment. The magnet scrap generated in the process reaches tens of percent of the magnet charge.

As a method of reusing the sintered magnet scrap, a method is described in which only a rare earth element is extracted with a solvent after being dissolved in an acid, separated and dried, and further oxidized to be used again as a raw material for a sintered magnet (Japanese Patent Laid-Open No. Hei 5-). No. 287405 and JP-A-9-217132) have been proposed. However, the above method still has a problem in that it requires a complicated and high energy input process for regeneration as a magnet raw material alloy.

On the other hand, Ti metal, which is lightweight and has excellent corrosion resistance, is used in a variety of products, including aerospace industry, chemical plants, watches for consumer goods, and glasses. ing. For abrasive scraps generated during Ti cutting, these scraps contain oxygen as well as impurity metals, so after removing the impurity metals, they are regenerated as Ti metal by a thermite reaction using metal Mg. ing. These methods are intended to be reused as Ti metal, and require high purity as the quality, so that the energy used for regeneration is enormous.
JP-A-5-287405 JP-A-9-217132

  Nd-Fe-B rare earth sintered magnets occupy most of the rare earth magnet market due to their high magnetic properties, but a large amount of abrasive debris (sludge) is generated when the size and shape are adjusted to the desired dimensions. To do. These sludges contain a large amount of impurities such as oxygen and carbon and cannot be used as they are. Therefore, only rare earth components, which are valuable resources, are separated and purified by a wet method based on acid dissolution and reused. However, there are problems such as the need for a large amount of acid and the disposal of iron because it does not meet the cost, and it cannot be easily regenerated.

  On the other hand, Si is the most important material that supports the electronics industry. Although 20% of Si used in the semiconductor manufacturing process is commercialized, the remaining 80% is contained in wastewater and disposed of as industrial waste. There is a problem that has been.

  Similarly, Ti is a material with excellent properties such as light weight, toughness, high corrosion resistance, and high heat resistance, and its application is rapidly expanding in various industrial fields. However, it is thought that the establishment of effective recycling technology for these resources will become more and more important in the future. .

  Also, today, as information communication devices such as mobile phones and wireless LANs increase in speed and frequency, electromagnetic wave environmental problems are becoming more and more important. Since electromagnetic interference ranges from malfunction of equipment to effects on the human body, measures to use them safely without compromising the convenience of these electromagnetic waves are indispensable.

  As a novel recycling method of rare earth sintered magnet grinding scraps (sludge), the present inventors have used a metal such as Si, Al, Ti and the like to melt the Fe sludge by arc melting or high frequency induction heating and subsequent liquid quenching. By using the slag of a compound and a by-product, the former was used as an electromagnetic wave absorbing material effective for electromagnetic waves in the GHz region, and the latter was effectively recovered as a rare earth oxide slag phase containing a large amount of rare earth.

  The present invention can significantly reduce the raw material cost by using, as part of the raw material, scrap generated during the production of a rare earth magnet composed of an intermetallic compound of a rare earth metal and a transition metal. In addition, in the present invention, the electromagnetic wave absorbing material based on Fe metal produced by the conventional technology exhibits absorption only in radio waves of several GHz due to the low magnetic anisotropy of Fe metal. Production of a radio wave absorber having good absorption characteristics for radio waves of several GHz or more by combining Fe metal and Ti separated and recovered by a simpler process than scrap, and having crystal magnetic anisotropy Is possible.

  By applying the technology of the present invention, rare earth components and Fe components can be efficiently separated from rare earth magnet sludge as oxide slag and transition metal alloys or intermetallic compounds, and the former as rare earth metals for rare earth magnets and the latter as It can be effectively used as a magnetic material for a radio wave absorber corresponding to the GHz band, and the eco-material of the magnet can be realized.

すなわち、上記詳述した本発明の方法により得られる電波吸収体用磁性体粉末に対しエポキシ樹脂等の樹脂バインダを、例えば重量比において１００：１０〜１００：２５で配合、混練し、例えば金属板等を基板として所定の厚さのシートあるいはボード状に成型し、これを電波吸収体として使用する。なお、電磁波が最も良好に吸収される共鳴周波数は、上述の通り電波吸収体の厚みに依存し、所望の電波の周波数に応じて厚みを調整することができる。また、図１に示した形態よりも更に薄板状としたシートまたはテープ形態、あるいは信号用ケーブル等のコードの被覆体形状に電波吸収体を加工することも可能である。
Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 is a sectional view of a radio wave absorber according to the present invention. The reflection loss (radio wave absorption performance) is calculated using an impedance matching model as shown in FIG. In this model, as shown in the right figure, a metal plate is placed behind the absorber of thickness d. When radio waves are incident on the absorber vertically, the impedance Z _in of the sample looking into the metal plate from the absorber surface is Using the wavelength λ of radio waves, the complex dielectric constant ε _r , the complex magnetic permeability μ _r , and the free space impedance Z ₀ , the following expression (1) is used. In this model, the condition for maximum absorption, that is, minimum reflection is when the reflection coefficient S shown in the following equation (2) is minimum. At this time, the impedance Z _in viewed from the incident surface is equal to the free space impedance Z ₀ . In addition, the reflection loss (RL) can be written as in the following formula (3), and S includes f (λ = c / f) and d, so the test is performed using the formulas (1) to (3). It is possible to calculate the reflection loss when the thickness d of the body is changed. When S <0.1, the reflected wave amplitude is 1/10, and the reflected power is 1/100 (99% absorption). At this time, RL = 20 (dB) from equation (3). Thus, the electromagnetic wave absorber can be designed and manufactured using this value as a guide.

That is, a resin binder such as an epoxy resin is blended and kneaded in a weight ratio of, for example, 100: 10 to 100: 25 with the magnetic powder for a radio wave absorber obtained by the above-described method of the present invention, for example, a metal plate Etc. are molded into a sheet or board having a predetermined thickness as a substrate and used as a radio wave absorber. Note that the resonance frequency at which electromagnetic waves are best absorbed depends on the thickness of the radio wave absorber as described above, and the thickness can be adjusted according to the frequency of the desired radio wave. Further, it is also possible to process the radio wave absorber into a sheet or tape form that is thinner than the form shown in FIG. 1 or a covering form of a cord such as a signal cable.

Hereinafter, an example in which Si is introduced in the present invention will be described in detail.

Example 1
As the R′—Fe—B sintered magnet scrap, Nd—Fe—B sintered magnet polishing scrap powder was prepared. Moreover, Si piece was prepared as Si raw material.

  In order to facilitate melting during arc melting, Fe powder is added to the sintered magnet polishing powder so as to have a composition ratio of Nd: Fe: B of 1: 14: 0.5, followed by pressure molding. A compact was obtained. A desired Fe-based intermetallic compound was obtained by mixing this compact and Si pieces so as to be 3 atomic% with respect to the Fe component contained in the compact and arc melting in a reduced pressure argon atmosphere. At this time, since the rare earth component contained in the sintered magnet polishing powder is more easily oxidized than Fe, the rare earth oxide slag is generated.

  The product obtained by arc melting was separated into an alloy phase mainly composed of an Fe-based intermetallic compound and a slag phase mainly composed of a rare earth oxide. The obtained alloy phase was loaded into a quartz nozzle, and a ribbon-like product was obtained using a liquid rapid solidification apparatus. The production conditions at this time are: high-frequency dissolution in a reduced-pressure argon atmosphere, and then introducing a pressurized argon gas into the quartz nozzle to remove the molten alloy from the pores with a diameter of 0.5 mm below the quartz nozzle and the rotational peripheral speed. It was jetted onto a 25 m / s copper roll and rapidly solidified. At this time, the rare earth component remaining in the alloy separated after the arc melting becomes rare earth oxide slag and is generated on the quartz nozzle wall surface.

The ribbon-like alloy obtained through the above process has a low Si content and cannot be pulverized as it is. Therefore, nitriding was performed at 500 ° C. for 2 hours and then at 400 ° C. for 2 hours, followed by ball milling. Thereafter, the obtained powder was subjected to hydrogen reduction at 450 ° C. for 2 hours to obtain a final magnetic material powder for radio wave absorber. The change in the XRD pattern of the sample during this series of processes is shown in FIG. From the figure, a diffraction peak very close to α-Fe was observed in the sample first quenched after arc melting. After that, by performing nitriding, the XRD pattern became a broad diffraction peak based on Fe ₃ N, and it was confirmed that nitriding was sufficient. After that, in the hydrogen-reduced sample, the observed diffraction peak was very close to α-Fe again, and it was confirmed that the hydrogen reduction was sufficient.

  Next, the sample powder was mixed with 25 wt% epoxy resin, and heated and cured at 130 ° C. for 30 minutes and then at 170 ° C. for 30 minutes to produce a disk-shaped sample having an outer diameter of about 10 mmφ. This sample was formed into a donut shape having an outer diameter of 7.00 mmφ and an inner diameter of 3.04 mmφ using an ultrasonic processing machine, and then a complex dielectric constant and a dielectric constant in a frequency range of 0 to 20 GHz using a commercially available network analyzer by the S-parameter method. The frequency dependence of the complex permeability was obtained. The frequency dependence of the reflection loss (dB) was calculated from the obtained value, and the radio wave absorption characteristics of the sample were evaluated.

The obtained radio wave absorption characteristics are shown in FIG. In addition, FIG. 4 shows, as a comparison, the radio wave absorption characteristics measured for the Nd—Fe—B sintered magnet polishing powder powder compact (a) not subjected to any treatment and the α-Fe powder (b) not subjected to any treatment. . In both samples shown in FIG. 3, good radio wave absorption characteristics exceeding 20 dB were not observed. On the other hand, from the results shown in FIG. 2, this sample can absorb good electromagnetic waves exceeding 20 dB over a frequency range of 1.5 to 3.9 GHz by changing the sample thickness from 3.0 to 6.0 mm. I can see that. The maximum absorption was 34.4 dB at 1.9 GHz when the thickness was 5.4 mm. The resonance frequency of normally spherical α-Fe is 1.5 GHz. Since this sample had some shape anisotropy due to the addition of Si, although absorption in a slightly high frequency range was obtained, as can be seen from the XRD pattern, as a component contributing to electromagnetic wave absorption, It is considered to be almost α-Fe. However, the reason why the amount of absorption is greatly increased compared to α-Fe is that the crystal grains become finer and further covered with a rare earth oxide mainly composed of insulating Nd ₂ O ₃ , making it more vortex. This is thought to be due to less current generation.

Example 2
Sintered magnet polishing powder and Fe powder are mixed so that the composition ratio of Nd: Fe: B is 1.5: 14: 0.75, and compacted by pressure molding in the same manner as in Example 1. It was. The reason why the rare earth component is increased more than in Example 1 is to facilitate the grinding of the alloy phase. A desired Fe-based intermetallic compound was obtained by mixing this compact and Si pieces so as to be 10 atomic% with respect to the Fe component contained in the compact, and arc melting in a reduced pressure argon atmosphere. At this time, the rare earth component contained in the sintered magnet polishing powder is produced as rare earth oxide slag as in the first embodiment.

  The product obtained by arc melting was separated into an alloy phase and a slag phase in the same manner as in Example 1, and the alloy phase was formed into a ribbon using a liquid rapid solidification apparatus. Also in this treatment, as in Example 1, the rare earth component remaining in the alloy phase after arc melting becomes rare earth oxide slag and is generated on the quartz nozzle wall surface.

The ribbon-like alloy obtained through the above process had a high Si content and could be easily pulverized. Therefore, the ribbon-like alloy was pulverized by a ball mill to obtain a magnetic material powder for radio wave absorber. The ball mill pulverization conditions were 400 rpm and 2 hours. A peak close to Fe ₃ Si was observed in the XRD pattern of the obtained powder.

  The sample powder was mixed with 25% by weight of an epoxy resin, a molded product sample for measuring radio wave absorption characteristics was prepared in the same manner as in Example 1, and the radio wave absorption characteristics of the samples were evaluated.

  The obtained radio wave absorption characteristics are shown in FIG. This sample was found to have good electromagnetic wave absorption exceeding 20 dB over the frequency range of 1.2 to 2.3 GHz by changing the sample thickness from 3.7 to 6.0 mm. The maximum absorption was 33.7 dB at 1.6 GHz when the thickness was 5.0 mm. Compared with Example 1, although the frequency range where absorption exceeding 20 dB was observed was narrow, the frequency and the amount of absorption at which maximum absorption was observed were almost unchanged, and the Si component was 10 atomic% with respect to the Fe component. It was confirmed that there was no significant effect on the radio wave absorption characteristics even if it was introduced. When the amount of Si introduced can be increased, the obtained alloy can be easily pulverized, so that it is not necessary to undergo treatments such as nitridation and hydrogenation performed in Example 1. This indicates that the sintered magnet polishing powder scrap can be regenerated as a magnetic material powder for a radio wave absorber with less energy.

Example 3
The sintered magnet polishing powder and the Fe powder are mixed so that the composition ratio of Nd: Fe: B is 1: 14: 0.5, and the compact is obtained by pressure molding in the same manner as in Examples 1 and 2. It was. This, and the Al thin plate and Si piece are made to have the ratio of each element in Sendust alloy (Fe: Si: Al = 84.9: 9.7: 5.4 weight ratio) which is a soft magnetic material with high magnetic permeability. Mixed. In this case, the amount of Si component is 18.5 atomic% with respect to the Fe component. These powder compacts, the Al thin plate, and the Si piece were arc-melted under a reduced pressure argon atmosphere to obtain a desired Fe-based intermetallic compound. At this time, the rare earth component contained in the sintered magnet polishing powder is produced as rare earth oxide slag as in Examples 1-2.

The product obtained by arc melting was separated into an alloy phase and a slag phase in the same manner as in Examples 1 and 2, and the alloy phase was formed into a ribbon using a liquid rapid solidification apparatus. Also in this process, as in Examples 1 and 2, the rare earth component remaining in the alloy phase becomes a rare earth oxide slag and is generated on the quartz nozzle wall surface. The obtained ribbon-like alloy was ball milled by the same method as in Example 2 to obtain a magnetic material powder for a radio wave absorber. In the XRD pattern of the obtained powder, a diffraction peak of Fe ₃ Al _0.7 Si _0.3 was observed.

  The above sample powder was mixed with 25% by weight of an epoxy resin, a molded product sample for measuring radio wave absorption characteristics was prepared in the same manner as in Examples 1 and 2, and the radio wave absorption characteristics of the samples were evaluated.

  The obtained radio wave absorption characteristics are shown in FIG. This sample was found to have good electromagnetic wave absorption exceeding 20 dB over the frequency range of 1.9 to 4.6 GHz by changing the sample thickness from 3.5 to 7.0 mm. The maximum absorption was 34.0 dB at 2.9 GHz when the thickness was 5.0 mm. Compared with Examples 1 and 2, although the maximum absorption amount hardly changes, the frequency at which the maximum absorption was seen has moved to the high frequency side, and as an efficient absorber in a higher frequency region It turned out to be promising.

Example 4
The sintered magnet polishing powder and the Fe powder are mixed so that the composition ratio of Nd: Fe: B is 1: 14: 0.5, and a compact is obtained by pressure molding in the same manner as in Examples 1 to 3. It was. This and the Si piece were mixed so that the ratio of Fe and Si in a Sendust alloy (Fe: Si: Al = 84.9: 9.7: 5.4 weight ratio), which is a soft magnetic material having high permeability, was mixed. . In this case, the amount of Si component is 18.5 atomic% with respect to the Fe component. These powder compacts and Si pieces were arc-melted under a reduced pressure argon atmosphere to obtain a desired Fe-based intermetallic compound. At this time, the rare earth component contained in the sintered magnet polishing powder is produced as rare earth oxide slag as in Examples 1-3.

The product obtained by arc melting was separated into an alloy phase and a slag phase in the same manner as in Examples 1 to 3, and the alloy phase was formed into a ribbon using a liquid rapid solidification apparatus. In this process, as in Examples 1 to 3, the rare earth component remaining in the alloy phase becomes rare earth oxide slag and is generated on the quartz nozzle wall surface. The obtained ribbon-like alloy was ball milled by the same method as in Examples 2 to 3 to obtain a magnetic material powder for a radio wave absorber. In the XRD pattern of the obtained powder, a diffraction peak of Fe ₃ Si was observed.

  The above sample powder was mixed with 25% by weight of an epoxy resin, a molded product sample for measuring radio wave absorption characteristics was prepared in the same manner as in Examples 1 to 3, and the radio wave absorption characteristics of the samples were evaluated.

  The obtained radio wave absorption characteristics are shown in FIG. This sample was found to exhibit good electromagnetic wave absorption exceeding 20 dB over the frequency range of 2.2 to 4.6 GHz by changing the sample thickness from 3.4 to 6.2 mm. The maximum absorption was 38.9 dB at 3.3 GHz when the thickness was 4.5 mm. Compared with Examples 1 to 3, the maximum absorption amount of this sample was the largest, and the frequency at which the maximum absorption was observed was the highest. Furthermore, the thickness of the sample exhibiting the maximum absorption is 4.5 mm, which is the thinnest among Examples 1 to 3, and it was found that this sample is promising as a radio wave absorber having high absorption characteristics.

Example 5
Hereinafter, an example in which Ti is introduced in the present invention will be described in detail.

As the R′—Fe—B based sintered magnet scrap, Nd—Fe—B based sintered magnet polishing scrap powder was prepared. Further, a Ti rod was prepared as a Ti raw material.

First, a compact was obtained by pressure molding sintered magnet polishing scrap powder. Ti was mixed so that this powder and the Fe component contained in the powder would be 60 atomic%, and arc melting was performed in a reduced pressure argon atmosphere to obtain a desired Fe-based intermetallic compound. At this time, since the rare earth component contained in the sintered magnet polishing powder is more easily oxidized than Fe, the rare earth oxide slag is generated.

The product obtained by arc melting was separated into an alloy phase mainly composed of an Fe-based intermetallic compound and a slag phase mainly composed of a rare earth oxide. The obtained alloy phase was Fe ₂ Ti of the alloy phase Laves phase from the XRD pattern described later, and could be easily crushed in a mortar. By pulverizing using a mortar, the particle size of the powder was reduced to 35 μm or less, and then heat treatment was performed at 250 ° C. for 3 hours and 12 hours in a muffle furnace to oxidize the powder surface. The oxygen concentration of the powder was 0.33% by weight before heat treatment and 1.42% and 1.88% by weight after heat treatment for 3 hours and 12 hours, respectively.

Next, the sample powder was mixed with 20% by weight of an epoxy resin, and heated and cured at 130 ° C. for 30 minutes and then at 170 ° C. for 30 minutes to produce a disk-shaped sample having an outer diameter of about 10 mmφ. This sample was formed into a donut shape having an outer diameter of 7.00 mmφ and an inner diameter of 3.04 mmφ using an ultrasonic machine, and then a complex dielectric constant and a dielectric constant in the frequency range of 0 to 20 GHz by a S-parameter method using a commercially available network analyzer. The frequency dependence of the complex permeability was obtained. The frequency dependence of the reflection loss (dB) was calculated from the obtained value, and the radio wave absorption characteristics of the sample were evaluated.

FIG. 8 shows changes in the XRD pattern of the sample in a series of processes. The observed diffraction peaks were all of Fe ₂ Ti, and it was found that the XRD pattern hardly changed before and after the treatment.

  Next, the radio wave absorption characteristics obtained for the powder after the heat treatment are shown in FIG. 9 together with the characteristics of the sample not subjected to the heat treatment. The sample after heat treatment for 3 hours shown in FIG. 9 (a) is a good electromagnetic wave exceeding 20 dB over a frequency range of 7.8 to 17.6 GHz by changing the sample thickness from 0.9 to 2.0 mm. Was found to be absorbed. The maximum absorption was 45.3 dB at 11.3 GHz when the thickness was 1.4 mm. In addition, the sample after the heat treatment for 12 hours shown in FIG. 9 (b) exceeds 20 dB over the frequency range of 15.6 to 18.8 GHz by changing the sample thickness from 0.9 to 1.1 mm. It was found that electromagnetic wave absorption was observed. The maximum absorption was 37.4 dB at 17.5 GHz when the thickness was 1.0 mm. Compared with the sample without the heat treatment shown in FIG. 9 (c), both the samples with the heat treatment showed good absorption characteristics greatly exceeding 20 dB. This is thought to be because the generation of eddy currents is reduced by covering the powder surface with an insulating oxide film by oxidation treatment. Comparing FIGS. 9 (a) and (b), the frequency range in which the absorption peak is observed in (b) is covered by (a), and the time required for the heat treatment is sufficient for 3 hours. I understood it. The results of this example show that sintered magnet polishing powder scrap can be effectively recycled as magnetic material powder for radio wave absorbers.

Example 6
In the same manner as in Example 5, the sintered magnet polishing dust powder compact and Ti were mixed and arc-melted to obtain the desired Fe-based intermetallic compound and by-product rare earth oxide slag.

The product obtained by arc melting was separated into an alloy phase and a slag phase in the same manner as in Example 5. The alloy phase was pulverized to several hundred μm using a mortar and then subjected to ball mill pulverization. Subsequently, heat treatment was performed in a muffle furnace to oxidize the powder surface. Table 1 below shows the ball milling treatment, heat treatment conditions, and the oxygen concentration (% by weight) of the powder after the heat treatment. The oxygen concentration of the powder before the heat treatment was 0.34% by weight. In addition, an Fe ₂ Ti diffraction peak was observed in all samples in the XRD pattern.

  The sample powder was mixed with 20% by weight of an epoxy resin, a molded product sample for measuring radio wave absorption characteristics was prepared in the same manner as in Example 5, and the radio wave absorption characteristics of the samples were evaluated.

  The obtained radio wave absorption characteristics are shown in FIG. Among these three samples, the sample 3 shown in FIG. 10 (c) showed the best radio wave absorption characteristics. Sample 3 was found to have good electromagnetic wave absorption exceeding 20 dB over the frequency range of 6.2 to 13.4 GHz by changing the sample thickness from 1.0 to 2.3 mm. The maximum absorption was 32.5 dB at 12 GHz when the thickness was 1.2 mm. Compared to sample 3, sample 1 in FIG. 10 (a) has a thick sample thickness of 2.0 to 6.0 mm necessary for absorption exceeding 20 dB, and the frequency of maximum absorption is slightly low at 10.2 GHz. Met. Moreover, the sample 2 of FIG.10 (b) had a sample thickness required for absorption exceeding 20 dB as thick as 3.7-6.0 mm, and the frequency range was also narrow. It seems that the deterioration of the characteristics observed in these samples 1 and 2 is that the decomposition of the compound has started by grinding with a ball mill. Although the characteristics seen in Sample 3 are inferior to the radio wave absorption characteristics of the sample in Example 5, the necessary heat treatment conditions are mild conditions of 150 ° C. and 1 hour. It seems to be very effective as a method of regenerating as a magnetic material powder for absorbers.

Example 7
Included in rare earth oxide slag phase generated during arc melting or liquid rapid solidification treatment in Examples 1-4 in which Si was introduced into sintered magnet polishing scrap powder and Examples 5-6 in which Ti was introduced The amount of rare earth component was estimated.

(a) In the case of Examples 1 to 4, the obtained slag was 12.3% by weight with respect to the total amount of sintered magnet polishing scrap powder and Si as raw materials. Moreover, in the case of (b) Examples 5-6, the obtained slag was 17.5 weight% with respect to the total amount of the sintered magnet grinding | polishing waste powder and Ti of a raw material. In both cases (a) and (b), as a result of component analysis by XRD measurement and EDX (energy dispersive X-ray fluorescence analysis) of the obtained slag, the slag is almost a rare earth oxide Nd ₂ O ₃ I understood. In addition, the oxygen concentration of the slag in each of the cases (a) and (b) was 10.72 and 10.53% by weight.

From the above results, when the rare earth component contained in the slag is estimated, it is 62% of the rare earth component contained in the raw sintered magnet polishing scrap powder in the case of (a) and 64% in the case of (b), which is valuable. It was found that the rare earth component as a resource could be effectively recovered.

1 is a basic structure of a radio wave absorber according to the present invention. 3 is an X-ray diffraction pattern of a sample after introducing 3 atomic% Si into sintered magnet polishing scrap powder, arc melting and quenching, then nitriding sample, and then hydrogen reduction sample. This is the frequency dependence of reflection loss of a sample prepared by introducing 3 atomic% Si into sintered magnet polishing scrap powder. It is the frequency dependence of the reflection loss measured for (a) Nd—Fe—B based sintered magnet abrasive scrap powder compact without any treatment, and (b) α-Fe powder with no treatment. This is the frequency dependence of reflection loss of a sample produced by introducing 10 atomic% Si into sintered magnet polishing scrap powder. Frequency dependence of reflection loss of a sample prepared by introducing Al and Si into a sintered magnet polishing scrap powder so that Fe: Si: Al = 84.9: 9.7: 5.4 (weight ratio) It is sex. This is the frequency dependence of reflection loss of a sample prepared by introducing Si into a sintered magnet polishing scrap powder so that Fe: Si = 84.9: 9.7 (weight ratio). It is an X-ray diffraction pattern of a sample after introducing 60 atomic% Ti into sintered magnet polishing scrap powder, arc melting and pulverizing, and then heat treatment at 250 ° C. for 3 hours and 12 hours. After introducing 60 atomic% Ti into sintered magnet polishing scrap powder, arc melting and pulverizing, (a) heat treatment at 250 ° C. for 3 hours, (b) heat treatment at 250 ° C. for 12 hours, ( c) The frequency dependence of the reflection loss of each sample without heat treatment. Using a ball mill pulverizer and a muffle furnace, a sample prepared by introducing 60 atomic% Ti into sintered magnet polishing scrap powder is (a) pulverized at 400 rpm for 1 hour, and heat treated at 150 ° C. for 1 hour. (B) It is the frequency dependence of the reflection loss of a sample that was pulverized at 400 rpm for 1 hour, heat treated at 250 ° C. for 1 hour, (c) crushed at 200 rpm for 2 hours, and heat treated at 150 ° C. for 1 hour.

Claims (7)

As an effective recycling method for Nd-Fe-B rare earth sintered magnet grinding scrap (sludge), Fe, Co and Ni metal (hereinafter referred to as sludge powder, magnetic component (mainly Fe) composition ratio adjustment in the magnetic material) M 'metal) and Al, Si, Ti, Zr, Nb, and Mo metal (hereinafter referred to as M ″ metal), which is a structure forming component of the magnetic substance, at least one or more of each in an atomic ratio (sludge is included in the sludge) The total amount of Fe and M ′ metal / M ″ metal amount) dissolved in 3 to 60%, and oxide slag mainly composed of rare earth components in the sludge, Fe and M ′ metal in the slag And an alloy composed of M ″ metal or a melt of intermetallic compound, the former is reused as a rare earth crude material, and the latter is alloy or intermetallic compound composed of M ′ metal and M ″ metal. Magnetic material consisting of Play technology, characterized in that the re-use this in. 2. The sludge powder, a mixture of M ′ metal and M ″ metal is subjected to high-frequency or arc melting, and then the slag portion on the surface layer and the magnetic material portion made of an alloy or intermetallic compound are separated by coarse pulverization. The magnet scrap recycling technology characterized by the above. 2. The sludge powder, a mixture of M ′ metal and M ″ metal is made into a melt by high frequency or arc melting, and a slag part and a magnetic material part made of an alloy or an intermetallic compound are formed by pouring molten metal. The magnet scrap recycling technique characterized by separating. In the above-mentioned claim, the magnet scrap recycling technique according to claim 1, wherein the alloy or intermetallic compound ingot or molten metal separated from the slag portion is rapidly melted in the most molten state or as it is, to form a thin ribbon having a uniform microcrystalline structure. In Claims 1 to 3, the alloy or intermetallic compound ingot separated from the slag portion is used as it is, or the rapidly cooled alloy or intermetallic compound ribbon is crushed and compounded with a resin. Recycling technology that reuses molded products such as sheets or bonds as radio wave absorbers based on alloys or intermetallic compounds compatible with the GHz band. The Fe-based intermetallic compound obtained in the above claims is heat-treated in air at a temperature range of 150 to 250 ° C. for 1 to 12 hours to form an oxide film on the surface of the alloy or intermetallic compound powder. Insulation between Fe-based intermetallic powders, lowering the complex dielectric constant and suppressing the generation of eddy currents in the powder particles, which has further higher electromagnetic wave absorption characteristics A method for producing a compound powder. The recycling technology as claimed in claim 1, wherein the M ′ and M ″ metals are scrap generated from a manufacturing process or used equipment.

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