JP2009200425A - Manufacturing method of rare-earth magnet, and rare-earth magnet manufactured by the manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a rare-earth magnet having high coercive field, wherein grain boundary modification processing is performed in short working hours even in mass production, and an amount of M metal compound spent in the grain boundary modification processing is reduced to suppress costs. <P>SOLUTION: In the manufacturing method of the rare-earth magnet formed by diffusing and penetrating an M metal element (provided that M is Pr, Dy, Tb or Ho) into a grain boundary phase of the rare-earth magnet; slurries containing one or more kinds of compounds selected from fluoride, oxide, and chloride of the M metal element and a reducing agent are stored in a predetermined container, and the rare-earth magnet is taken out from the predetermined container after immersing the rare-earth magnet in the slurries, and then heating treatment is applied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a rare earth magnet and a rare earth magnet produced by the method. More specifically, the present invention relates to a method for manufacturing a rare earth magnet in which an M metal element (where M is Pr, Dy, Tb, or Ho) is diffused and penetrated into the grain boundary phase of the rare earth magnet, and the rare earth magnet manufactured by the manufacturing method.

  Rare earth magnets such as Nd—Fe—B are applied to voice coil motors (VCM) for hard disk drives, magnetic circuits for magnetic tomography (MRI), drive motors for electric vehicles, and the like. In general, magnets tend to be reduced in magnetic force due to heat. Therefore, it is necessary to prevent lowering of magnetic force due to heat in automobile applications used at high temperatures of 150 to 200 ° C., and magnets having higher coercive force are required. It has been.

For example, an Nd—Fe—B based sintered magnet has a structure in which an Nd ₂ Fe ₁₄ B compound main phase is surrounded by an Nd-rich grain boundary phase. The Dy ₂ Fe ₁₄ B compound or the Tb ₂ Fe ₁₄ B compound uses a magnetic property that an anisotropic magnetic field is larger than that of the Nd ₂ Fe ₁₄ B compound. Increasing the coercive force by adding about ˜10% by mass has been conventionally performed. However, in this case, there is a problem that the maximum energy product (BH) _max and the residual magnetization (Br) represented by the product of the magnetic flux density B and the magnetic field H are significantly reduced.

  In order to improve the coercive force while suppressing the decrease in the residual magnetic flux density, the present inventors have proposed a method for solving this problem by using a Dy metal on the surface of a Nd—Fe—B based sintered magnet that does not contain Dy metal or the like. And the like, and a method of thermally diffusing Dy metal and the like from the surface of the magnet to the grain boundary phase, and a fluoride of Pr, Dy, Tb, and Ho (hereinafter also referred to as M metal element) Solid phase reduction method (method in which a rare earth magnet is embedded in a mixed powder of M metal compound such as fluoride, oxide or chloride and a reducing agent, and heat treatment), liquid phase reduction method (in a heat-resistant container) After embedding a rare earth magnet in a mixture of an M metal compound, LiF, a reducing agent, and Ca metal particles, a method of melting the mixture by heating) or a molten salt electrolysis method (a rare earth magnet placed in a SUS cage) , M metal compound, LiF A reducing diffusion method in which M metal element is diffused and permeated into the grain boundary phase by being charged into a molten salt containing Ba salt and reduced by an electrolysis using the SUS steel as a cathode and graphite or the like as an anode (Patent Document 2) ) And other so-called grain boundary modification methods have been developed.

In such a method, since Dy metal or the like is selectively diffused and penetrated into the grain boundary phase rather than the main phase of the Nd ₂ Fe ₁₄ B compound, a reduction in residual magnetization is suppressed and a significant improvement in coercive force is realized. . These grain boundary modified magnets have the same coercive force as commercially available sintered magnets even if the content of Dy metal etc. is halved, so that they have the effect of saving rare resources and expensive Dy metal etc. .

In the above-described method, the sputtering method requires expensive equipment, a lot of labor, and a long processing time. Therefore, the reduction diffusion method is preferable, and in particular, the reduction diffusion method by solid-phase reduction requires any treatment under high temperature conditions during heating. In addition, this is a preferable method in that no chemical other than the reducing agent is required.
JP 2004-304038 A WO 2006/064848 A1 publication

However, in the solid-phase reduction method, the rare earth magnet is heated in a state where the rare earth magnet is embedded in a mixed powder of an M metal element compound (hereinafter also referred to as an M metal compound) and a reducing agent. The process of embedding in the mixed powder requires a large amount of M metal compound and a lot of labor, leading to an increase in cost. In addition, after the heat treatment, many residues such as CaF ₂ , CaO generated by the reduction reaction, excess M metal compound, and NdO generated by substitution with M metal are hardened and firmly attached around the rare earth magnet. In addition, if acid cleaning is performed with a large amount of solid residue remaining on the surface, not only the cleaning time is increased, but also the acid contamination becomes significant and the cleaning effect is impaired. . For this reason, a lot of work is required in the process of removing the rare earth magnet from the solidified residue after the heat treatment and removing the adhered residue, and the process takes a long time. Furthermore, the expensive M metal compound contained in the removed residue cannot be easily reused because it has been heat-treated. Thus, the conventional method has many problems in mass production.

  As described above, the present invention can perform the grain boundary reforming process in a short time, for example, by reducing the working time even in the case of mass production, thereby reducing the amount of M metal compound consumed for the grain boundary reforming process and reducing the cost. It is an object of the present invention to provide a method for producing a rare earth magnet having a high coercive force.

As a result of diligent research, the present inventor has solved the above problems and has completed the present invention.
Hereinafter, the invention of each claim will be described.

The invention described in claim 1
A method of manufacturing a rare earth magnet in which an M metal element (where M is Pr, Dy, Tb, or Ho) is diffused and penetrated into a grain boundary phase of the rare earth magnet, the fluoride, oxide, and chloride of the M metal element A rare earth magnet characterized in that a slurry containing one or more compounds selected from a product and a reducing agent is contained in a predetermined container, the rare earth magnet is immersed in the slurry, taken out from the predetermined container, and then heat-treated. It is a manufacturing method.

  In the first aspect of the invention, the grain boundary modification treatment can be performed in a short time, and the amount of the M metal compound consumed for the grain boundary modification treatment, and hence the amount of the M metal itself can be reduced. A method for producing a rare earth magnet having magnetic force can be provided.

  That is, after being immersed in a slurry (hereinafter also referred to as M metal slurry) containing one or more compounds selected from fluoride, oxide and chloride of the M metal element and a reducing agent (hereinafter also referred to as M metal slurry), The M metal element compound and the reducing agent necessary for grain boundary modification can be attached to the surface of the rare earth magnet in a short time by an efficient method of taking out.

  Moreover, since it is not an embedding method but an immersion method, it is not necessary to use a large amount of expensive M metal slurry. Further, after the rare earth magnet is immersed in the M metal slurry, it is taken out from the predetermined container and then heat-treated, that is, the M metal slurry left behind is not heat-treated, so that it can be used repeatedly. Usually, it is difficult to use up all of the M metal slurry, and since production is stopped at night or on holidays at actual production sites, a surplus of M metal slurry is generated. Since such surplus can be reused, it does not need to be discarded. Thus, since the M metal compound is not wasted, the amount of the M metal compound used for the grain boundary modification process can be reduced. In consideration of the vaporization of the solvent, it is difficult to store in a slurry state, and considering that the solvent and the reducing agent react gradually and the reducing ability is lowered, the M metal mixed powder is once dried. It is preferable to store in a state.

  In addition, after the heat treatment is completed, the residue is hardened and hardly adheres to the periphery of the rare earth magnet, and can be subjected to acid cleaning as it is, so that acid cleaning can be performed immediately. Is less contaminated.

  As described above, the invention of claim 1 is a method capable of adhering in a short time of slurry immersion treatment and further reducing the amount of the expensive M metal slurry used, but a sufficient amount of M on the surface of the rare earth magnet. Since the metal compound and the reducing agent can be attached, sufficient reduction diffusion occurs in the subsequent treatment, and the occurrence frequency of defective products whose magnetic characteristics do not reach the reference value does not increase.

The solvent of the M metal slurry is not limited as long as it is inert to the M metal compound and the reducing agent and can disperse them, and volatilizes by drying. For example, alcohol (methanol, ethanol, isopropanol, n-butanol, etc.), ketones (acetone, metholethyl ketone, methyl isobutyl ketone, etc.), esters (ethyl acetate, n-butyl acetate, etc.) can be mentioned. However, in the slurry state, the carbonyl group constituting acetone, the methyl group constituting hexane, and the hydroxyl group constituting ethyl alcohol gradually react with CaH ₂ and the reducing ability becomes insufficient. Preference is given to n-butanol.

The M metal compound is one or more compounds selected from fluorides, oxides and chlorides of M metal elements (Pr, Dy, Tb, or Ho), preferably fluorides, particularly preferably. Dy or Tb fluoride. As the reducing agent, metal hydrides are preferable, and known ones such as CaH ₂ and MgH ₂ can be used.

The concentration of the M metal compound and the reducing agent in the solvent varies depending on the required performance, but the total weight of the M metal compound and the reducing agent is preferably 65 to 75% with respect to the total weight. The ratio of the M metal compound to the reducing agent is preferably 3: 1 to 3: 2.5 by weight.
The M metal slurry can be easily obtained by stirring using a conventionally known mixer and is not particularly limited. However, since CaH ₂ powder is very active and easily reacts with water, these antioxidants can be prevented. Therefore, it is preferable to produce the M metal slurry in an inert atmosphere.

  When the M metal slurry is attached to the magnet surface and then dried to vaporize the solvent component, the mixture of the M metal compound and the reducing agent is uniformly distributed on the magnet surface. Further, when handling the M metal compound and performing the reduction diffusion, it is preferable to carry out in an inert atmosphere such as Ar gas, not in the atmosphere, in order to eliminate the influence of oxidation.

The invention described in claim 2
A method for producing a rare earth magnet in which an M metal element (where M is Pr, Dy, Tb, or Ho) is diffused and penetrated into a grain boundary phase of the rare earth magnet, and after the rare earth magnet is accommodated in a sealed container, A mixed powder containing one or more compounds selected from fluorides, oxides and chlorides of the M metal element and a reducing agent is sprayed into the sealed container in a mist, and after a predetermined time, the rare earth magnet is sealed. It is a method for producing a rare earth magnet, which is taken out from a container and then heat-treated.

  Also in the invention according to claim 2, a rare earth magnet having a high coercive force, which can perform the grain boundary reforming process in a short time, reduce the amount of M metal compound consumed for the grain boundary reforming process. The manufacturing method of can be provided.

  That is, after containing a rare earth magnet in a sealed container, a mixed powder containing one or more compounds selected from fluorides, oxides and chlorides of the M metal element and a reducing agent (hereinafter also referred to as M metal mixed powder). Is sprayed in the airtight container in a mist form, and after a predetermined time, the rare earth magnet is taken out from the airtight container (hereinafter also referred to as a mist-spraying process) and is necessary for grain boundary reforming in a short time. The M metal element compound and the reducing agent can be attached to the surface of the rare earth magnet. In addition, after completion of the heat treatment, the mixed powder of the M metal compound and the reducing agent is hardened and hardly adheres to the periphery of the rare earth magnet, and can be used for acid cleaning as it is. And the cleaning liquid is less likely to be contaminated.

  In addition, when the M metal mixed powder is sprayed in a sealed container in the form of a mist, it is preferable not to spray the M metal mixed powder directly on the rare earth magnet. By doing so, the M metal mixed powder is not excessively adhered or deposited locally, and the M metal compound is gradually deposited on the surface of the rare earth magnet to stably and uniformly adhere. It is also possible to suppress the peeling of the deposits. In order to efficiently attach the M metal mixed powder to the surface of the rare earth magnet, it is preferable to wet the surface of the rare earth magnet in advance with a solvent such as butanol prior to spraying in a mist.

  Further, the M metal mixed powder deposited in the sealed container can be collected and reused in the same manner as the method using the slurry, and the amount of M metal compound spent on the grain boundary reforming process can be reduced.

  Moreover, although the amount of adhesion is smaller than the slurry immersion treatment, for example, the mist-like spraying treatment is performed in a state where, for example, the mist-like spraying is performed a plurality of times, the spraying concentration is adjusted, or the rare earth magnet is sprayed in the M metal mixed powder. By adjusting the exposure time, an appropriate amount of M metal mixed powder can be deposited.

The invention according to claim 3
After the rare earth magnet is immersed in the slurry contained in the predetermined container, the rare earth magnet is taken out from the predetermined container, and then stored in the sealed container, and then the mixed powder is sprayed in the sealed container in the form of a mist. 2. The method for producing a rare earth magnet according to claim 1, wherein the rare earth magnet is removed from the sealed container after a period of time, and then heat-treated.

  In invention of Claim 3, after carrying out the slurry immersion process of the rare earth magnet, the M metal compound and the reducing agent are further carried out by performing a mist spraying treatment in which the M metal mixed powder is exposed to an atmosphere sprayed in a mist form. Since it can be made to adhere evenly and thinly onto the adhered slurry without being peeled off, it is possible to provide a method for producing a rare earth magnet having an enhanced effect of grain boundary modification and higher coercive force.

  That is, in order to increase the adhesion amount of the M metal compound and the reducing agent, there is a method of increasing the concentration of the M metal slurry used for the slurry immersion treatment, but if the concentration is increased, the deposit may be peeled off during drying. is there. On the other hand, after performing the slurry immersion treatment without increasing the concentration of the M metal slurry more than necessary, when the rare earth magnet is exposed to an atmosphere in which the M metal mixed powder is sprayed, the surface of the M metal slurry is exposed. Since the M metal mixed powder is gradually deposited, it does not peel off, and the adhesion amount of the M metal compound and the reducing agent can be increased.

  In addition, if the mist spraying process is performed after the slurry immersion treatment without drying or in a semi-dry state, the slurry is wet with the solvent, and the M metal mixed powder can be efficiently attached to the surface of the slurry. preferable.

The invention according to claim 4
4. The unevenness is formed on the surface of the rare earth magnet before the rare earth magnet is immersed in the slurry accommodated in the predetermined container or before the rare earth magnet is accommodated in the sealed container. The method for producing a rare earth magnet according to any one of the above.

  When performing grain boundary modification, M metal compounds and reducing agents attached to the surface of rare earth magnets do not peel off from the surface of rare earth magnets, and M metal elements diffuse efficiently from the magnet surface to the internal grain boundary phase. It is important to penetrate, and for that purpose, it is preferable that the adhesion between the rare earth magnet and the M metal mixed powder is good and the surface area of the rare earth magnet is large.

  In the invention according to claim 4, since the surface of the rare earth magnet is provided with irregularities, the adhesion between the rare earth magnet and the M metal mixed powder is improved as compared with a smooth surface, and the rare earth magnet is peeled off from the surface. Can be suppressed. Further, since the surface area of the rare earth magnet is large, the M metal element can be efficiently diffused and penetrated into the internal grain boundary phase.

  Examples of the method for forming irregularities include immersion in an acid solution, electrolytic polishing, and sanding.

The invention described in claim 5
5. The method for producing a rare earth magnet according to claim 4, wherein irregularities are formed on the surface of the rare earth magnet by immersing the rare earth magnet in an acid solution.

  In the fifth aspect of the present invention, irregularities can be formed on the surface of the rare earth magnet in a short time by a simple operation of simply immersing the rare earth magnet in an acid. At the same time, the impurity residue firmly adhered to the surface of the magnet can be efficiently removed. As a result, the M metal element can be efficiently diffused and penetrated from the magnet surface to the internal crystal grain boundary.

  The acid solution used is a strong inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid or hydrofluoric acid diluted with water several tens to several hundred times, or oxalic acid, formic acid, acetic acid, benzoic acid, benzenesulfonic acid, etc. An organic acid aqueous solution or the like can be used. Preference is given to aqueous solutions of strong inorganic acids.

  The conditions for immersion in the acid solution vary depending on the type and form of the magnet and the type of acid, but are adjusted by appropriately adjusting the acid concentration, temperature, time, etc. in consideration of smoothness. The immersion in the acid solution is performed in order to provide fine irregularities on the magnet surface. However, if it is performed excessively, smoothing of the magnet surface after the modification treatment may be significantly impaired, and a smoothing treatment may be necessary. It is preferable to fully study the conditions for the acid solution treatment in advance.

  In addition, it is preferable to apply an ultrasonic wave to the acid solution because it can prevent a disadvantage that the magnetic properties are deteriorated compared with that before washing. That is, when a rare earth magnet is immersed in an acid solution, hydrogen bubbles generated on the surface of the magnet grow and become visible with the passage of time, and after that, it takes about 1 minute until each bubble separates from the surface of the magnet. During this period, hydrogen is absorbed by the magnet, so that the magnetic properties are deteriorated. On the other hand, when ultrasonic waves are applied to the acid solution in which the magnet is immersed, impact force and large acceleration due to cavitation are generated in the solution, and hydrogen gas is not generated on the magnet surface. Has a function of separating from the surface of the magnet, and compared with a case where ultrasonic waves are not used, hydrogen absorption into the magnet can be suppressed, and a remarkable effect of avoiding deterioration in magnetic properties is recognized. This method of applying ultrasonic waves to the acid solution is a method suitable for mass production, and can be applied to subsequent acid cleaning.

The invention described in claim 6
The method for producing a rare earth magnet according to any one of claims 1 to 5, wherein the rare earth magnet is an Nd-Fe-B rare earth magnet.

  In the invention of claim 6, among the rare earth magnets, the Nd—Fe—B type rare earth magnet, in which the grain boundary modification effect is particularly prominent, is targeted. Therefore, a rare earth magnet having particularly high holding power can be provided. .

The invention described in claim 7
A rare earth magnet manufactured by the method of manufacturing a rare earth magnet according to any one of claims 1 to 6.

  According to the seventh aspect of the present invention, it is possible to provide a rare earth magnet that can perform the grain boundary reforming process in a short working time and has a high holding force while suppressing an increase in cost.

  According to the present invention, it is possible to perform the grain boundary reforming process in a short working time even in the case of mass production, to reduce the amount of the M metal compound that is spent on the grain boundary reforming process, to suppress the cost, and to further increase the cost. A method for producing a rare earth magnet having magnetic force and a rare earth magnet produced by the above production method can be provided.

  Hereinafter, the present invention will be described based on the best mode. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

  The whole process of the grain boundary modification process of the rare earth magnet according to the present invention is shown in FIG. Then, a preferred method for manufacturing an Nd—Fe—B rare earth magnet having a size of several millimeters will be described as an example for each step.

I. Pretreatment First, the rare earth magnet is pretreated. The pretreatment is a step of forming irregularities on the surface of the rare earth magnet. Examples of the method for forming the irregularities include immersion in an acid solution, electrolytic polishing, and scratching. Among these methods, pretreatment by immersion in an acid solution is preferable.

  The immersion in the acid solution is performed under a condition where ultrasonic waves are applied to the acid solution in order to prevent the rare earth magnet from absorbing hydrogen. A commercially available apparatus can be widely used as the ultrasonic cleaner to be used. Although it is not greatly affected by the frequency and the effect is sufficient, it is possible to use general-purpose 25 to 80 kHz for general magnets and 100 to 950 kHz for fine magnet powder. It is preferable from the viewpoint of smoothness.

  Taking a Nd-Fe-B rare earth magnet with a size of several mm as an example, water is injected into a tank of a commercially available ultrasonic cleaner, and nitric acid with a concentration of 70% is increased 100 times with pure water. A glass container filled with diluted acid solution is charged. After oscillating ultrasonic waves, a Teflon (registered trademark) -covered SUS mesh basket containing a large number of magnets is immersed in an acid solution in a glass container. Moreover, you may put a magnet in a glass container as it is. During immersion, it is preferable that the magnet surface is uniformly contacted with the acid solution by rotating or swinging the cage or constantly changing the contact position between the magnets by stirring the acid solution. The time is preferably about 2 minutes, and it is preferable that the decrease in the weight of the magnet is limited to about 1% before the treatment.

  Washing after the pretreatment is performed repeatedly while changing running water or water to completely remove acid radicals that cause rust. Next, the water is removed by replacing with ethanol, and finally, it is naturally dried or dried by heating to several tens of degrees Celsius.

  Thereafter, as shown in FIG. 1, the route is divided into three routes: slurry immersion treatment, mist spraying treatment, slurry immersion treatment + mist spraying treatment. The subsequent steps are performed in a glove box with an Ar gas atmosphere. First, the case where the slurry immersion treatment route is selected from the three routes shown in FIG. 1 will be described.

B. Slurry immersion treatment The slurry immersion treatment is a step of attaching an M metal slurry to the surface of the pre-treated rare earth magnet. As a specific example, TbF ₃ , CaH ₂ , and n-butanol (C ₄ H ₉ OH) are mixed to prepare a slurry, which is put in a vat-like container having a depth enough to sufficiently immerse the magnet. The ratio of TbF ₃ and CaH ₂ is preferably about 3: 2 by weight, and the concentration is adjusted by changing the ratio of n-butanol depending on the shape and size of the magnet. The pre-treated magnets are lined up on a Teflon (registered trademark) -coated SUS net or molybdenum net so as not to overlap, and immersed in a container filled with the slurry. Gently lift and dry within a few seconds after the magnet is completely buried in the slurry.

C. Heat treatment The heat treatment is a step in which TbF ₃ adhered to the surface of the rare earth magnet reacts with CaH ₂ to produce Tb, and the produced Tb is diffused into the grain boundaries of the rare earth magnet (reduction diffusion). After dipping the slurry, after drying at room temperature for about 10 minutes, the whole net is gently put into an electric furnace. In general, the heat treatment is performed at 800 to 1000 ° C. for 1 minute to 24 hours, and then an aging treatment is performed at 600 ° C. for about 1 minute to 1 hour, followed by cooling to around room temperature. Note that the temperature and time of the heat treatment are appropriately determined in consideration of the size and shape of the magnet.

D. Acid cleaning Next, acid cleaning, in which acid cleaning is performed, is a step of removing residues adhering to the surface of the rare earth magnet, and the same method as the immersion in the acid solution in the pretreatment can be applied.

  Next, a method when the mist-like spraying process shown in FIG. 1 is selected will be described.

E. Mist-like spraying process The mist-like spreading process is a process of attaching the M metal mixed powder to the surface of the pre-treated rare earth magnet. The powder of TbF _{3 and} the powder of CaH ₂ are mixed at a predetermined weight ratio (the ratio of TbF ₃ and CaH ₂ is preferably about 3: 2 by weight as with the M metal slurry) to obtain a mixed powder. The surface of the rare earth magnet is wetted with n-butanol, placed on a SUS net and accommodated in a sealed container (bag), and the mixed powder is sprayed into a sealed space so as not to hit the rare earth magnet. The amount of spraying is preferably about 3 g per liter of the volume of the sealed space, and Ar gas is sprayed as necessary, or an air current is generated in the sealed container using a fan to maintain a mist-like sprayed state. Further, the rare earth magnet is kept floating from the bottom surface of the sealed container so that the mixed powder adheres to the bottom surface of the rare earth magnet.
Next, after the elapse of a predetermined time, the rare earth magnet is taken out from the sealed container, and then subjected to heat treatment and then acid cleaning.

F. Slurry soaking process + mist spraying process
The method of performing the mist spraying process subsequent to the slurry immersion process shown in FIG. 1 can be more uniformly and thinly deposited on the adhered slurry without peeling off the M metal oxide and the reducing agent. This method is suitable for obtaining a high coercive force. Since each process has already been described, the description is omitted here.

Hereinafter, based on an Example, this invention is demonstrated more concretely.
(Example 1)
B. Pretreatment Example 1 is an example showing the effect of the present invention using a slurry dipping treatment. Further, the effectiveness of the pretreatment by dipping in an acid solution before the slurry dipping treatment is also examined. This is an example.
Using a commercially available ultrasonic apparatus, an Nd—Fe—B sintered magnet having a size of 3 mm × 3 mm × 2.8 mm is diluted with an acid solution obtained by diluting 70% nitric acid 100 times with pure water for 2 minutes. Then, it was immersed and subjected to pretreatment while applying ultrasonic waves. FIG. 2 shows micrographs of the surface of the rare-earth magnet before and after the pretreatment using a stereomicroscope. 2A is a photomicrograph before pretreatment, and FIG. 2B is a photomicrograph after pretreatment. As shown in FIG. 2, it can be seen that the surface is roughened after the pretreatment as compared with that before the pretreatment, and fine irregularities are formed on the entire surface. Moreover, the weight of the magnet before pre-processing was 191 mg, and the weight after pre-processing was 189 mg.

B) Slurry soaking treatment A magnet having been pretreated and a magnet of the same type and size not being pretreated are put into a glove box in an Ar gas atmosphere, and TbF ₃ , CaH ₂ , n-butanol (C ₄ H ₉₎ are contained in the glove box. OH) was mixed at a weight ratio of 3: 2: 2 to prepare a slurry, and the two kinds of magnets were immersed for about 2 seconds and taken out.

  When the adhesion state of the slurry depending on the presence or absence of the pretreatment was observed during drying, the side portions of the magnet that had not been pretreated were often peeled off. Table 1 shows the result of measuring the amount of slurry adhered depending on the presence or absence of pretreatment. Before the peeling occurs, there is no difference in the amount of adhesion depending on the presence or absence of the pretreatment, but it can be seen that the amount of adhesion decreases because the peeling occurs without the pretreatment.

  Table 2 shows the results of evaluating the performance of the magnets shown in Table 1 which were subjected to grain boundary modification by heat treatment at 950 ° C. for 2 hours and further aging treatment at 600 ° C. for 1 hour. As shown in Table 2, the rare earth magnet in Example 1 has excellent magnetic properties both with and without pretreatment. In particular, it can be seen that the pretreated rare earth magnet shows a higher coercive force (Hcj).

(Example 2)
Example 2 is an example in which after the slurry immersion treatment was performed, the influence on the grain boundary reforming effect by performing the mist spraying treatment was examined.
The magnet was pulled up by dipping in a slurry in the same manner as in Example 1 except that no pretreatment was performed. This magnet is put into a bag of about 1 liter in a semi-dry state and placed on a SUS net, and the mixed powder mixed at a weight ratio of TbF ₃ : CaH ₂ = 3: 2 does not directly hit the magnet in the bag. Injected into the gap space, distributed in the form of a mist in the vicinity of the magnet, and taken out from the bag after about 1 minute. In addition, the spraying process was performed with the net on which the rare earth magnet was placed floating from the bottom surface of the bag so that the mixed powder adhered to the bottom surface of the magnet. The injection amount was about 3 g for a bag having a volume of about 1 liter, and most of the sprayed mixed powder was deposited in the bag, and the mixed powder deposited in the bag was recovered.

  Table 3 shows the results of measuring the amount of adhesion depending on the presence or absence of mist spraying treatment. The amount of adhesion shown in Table 3 does not include the amount peeled off after the slurry immersion treatment and before the mist-spreading treatment. In addition, the weight of the used magnet is 190 mg in an untreated state.

  As shown in Table 3, it can be seen that the amount of adhesion increased by about 50% as compared with the case of only slurry immersion by the mist-like spraying treatment. Thus, even if the adhesion amount increased, there was no peeling of the deposit. Table 4 shows the results of performance evaluation of the magnets after heat treatment similar to the above. The superiority in coercive force was observed when the atomized spray treatment was applied.

Example 3
Example 3 is an example of investigating whether or not the recovered slurry after the slurry immersion treatment can be reused after storage.
A slurry prepared by mixing TbF ₃ , CaH ₂ , and n-butanol (C ₄ H ₉ OH) used in the slurry immersion treatment at a weight ratio of 3: 2: 2 is dried at room temperature for 2 hours, and is a solvent n- After removing butanol to obtain a mixed powder of TbF ₃ and CaH ₂ , the powder was stored in an Ar gas atmosphere at room temperature in a sealed state for 1105 hours. N-butanol was added to the mixed powder after storage and mixed to prepare a slurry. Using the prepared slurry, grain boundary modification treatment of the rare earth magnet was performed, and the magnetic properties of the obtained rare earth magnet were evaluated. At the same time, a slurry was prepared using a new raw material, a grain boundary modification treatment of the rare earth magnet was performed, and the magnetic properties of the rare earth magnet subjected to the grain boundary modification treatment using the recycled slurry were compared.

  The results are shown in FIG. As shown in FIG. 3, the rare earth magnet that has undergone the grain boundary modification treatment using the slurry after 1105 hours has the same magnetic properties as the rare earth magnet that has undergone the grain boundary modification treatment using the new slurry. It turns out that it has. From this, it was confirmed that the excess M metal slurry was dried to obtain an M metal mixed powder, which is a mixture of an M metal compound and a reducing agent, so that it could be stored for a long time and used repeatedly.

It is a flowchart which shows the outline of one Embodiment of the manufacturing method of this invention. It is the microscope picture by the stereomicroscope of the surface of the rare earth magnet of this invention, (a) is the rare earth magnet which has not performed the pre-processing, (b) is the microscope picture of the rare earth magnet which performed the pre-processing. It is a graph which shows the magnetic characteristic of the rare earth magnet which carried out the grain boundary modification process using the slurry and the newly produced slurry.

Claims (7)

  A method of manufacturing a rare earth magnet in which an M metal element (where M is Pr, Dy, Tb, or Ho) is diffused and penetrated into a grain boundary phase of the rare earth magnet, the fluoride, oxide, and chloride of the M metal element A rare earth magnet characterized in that a slurry containing one or more compounds selected from a product and a reducing agent is contained in a predetermined container, the rare earth magnet is immersed in the slurry, taken out from the predetermined container, and then heat-treated. Manufacturing method.   A method for producing a rare earth magnet in which an M metal element (where M is Pr, Dy, Tb, or Ho) is diffused and penetrated into a grain boundary phase of the rare earth magnet, and after the rare earth magnet is accommodated in a sealed container, A mixed powder containing one or more compounds selected from fluorides, oxides and chlorides of the M metal element and a reducing agent is sprayed into the sealed container in a mist, and after a predetermined time, the rare earth magnet is sealed. A method for producing a rare earth magnet, which is taken out from a container and then heat-treated.   After the rare earth magnet is immersed in the slurry contained in the predetermined container, the rare earth magnet is taken out from the predetermined container, and then stored in the sealed container, and then the mixed powder is sprayed in the sealed container in the form of a mist. The method for producing a rare earth magnet according to claim 1, wherein the rare earth magnet is removed from the sealed container after a period of time, and then heat-treated.   4. The unevenness is formed on the surface of the rare earth magnet before the rare earth magnet is immersed in the slurry accommodated in the predetermined container or before the rare earth magnet is accommodated in the sealed container. The manufacturing method of the rare earth magnet of any one of these.   5. The method for producing a rare earth magnet according to claim 4, wherein irregularities are formed on the surface of the rare earth magnet by immersing the rare earth magnet in an acid solution.   The method for producing a rare earth magnet according to any one of claims 1 to 5, wherein the rare earth magnet is an Nd-Fe-B rare earth magnet.   A rare earth magnet manufactured by the method of manufacturing a rare earth magnet according to any one of claims 1 to 6.