JP2013145769A - Anisotropic rare earth bond magnet and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic bond magnet provided with high magnetic characteristics, temperature characteristics and corrosion resistance by recycling municipal scraps of rare earth sintered magnets at low cost.SOLUTION: A method for manufacturing an anisotropic rare earth bond magnet includes the steps of: mechanically pulverizing rare earth magnets in an inert atmosphere; performing annealing treatment for eliminating strains to the pulverized material at a temperature from 400°C to 600°C during a retention time of 12 hours or more in a high vacuum or inert atmosphere; and kneading a binder and the material having been subjected to the annealing treatment for eliminating strains to be subjected to magnetic field molding. The method eliminates separation/purification of Sm and Nd, peeling of a magnet surface processing coating such as Ni plating, and removal of an adhesive.

Description

  The present invention relates to an anisotropic rare earth bonded magnet manufactured from a recovered rare earth anisotropic sintered magnet and a method for manufacturing the same.

Rare earth sintered magnets are used for home appliances, personal computers, digital cameras, mobile phones, office equipment OA, motors, and other FA equipment, and recently hybrids due to CO ₂ warming issues, against the backdrop of energy saving, downsizing and weight reduction, and high performance With the addition of applications such as automobiles and electric cars, these demands are growing more and more and their consumption is increasing year by year.
Rare earths contained in rare earth sintered magnets are rare in Japan, relying on 100% imports from China, the United States and Australia, more than 95% of which are China. In recent years, there has been concern about the supply of long-term rare earth (hereinafter referred to as “RE” as appropriate) resources, and the rare earth resource problem is an extremely important issue for maintaining Japan's advanced technology.

As described above, it is predicted that the amount of rare earth sintered magnet scrap to be discarded in the future will increase, and since these rare resources, which are rare resources, are included in a considerable amount, there is a need for recovery and reuse technology.

Many proposals have been made to obtain a magnet alloy by remelting and alloying rare earth magnet scraps (for example, Patent Document 1). These require not only remelting and alloying in order to produce a magnet product again, but also a magnet process of crushing, molding, sintering, and heat treatment, and the purchase of RE raw materials is more cost-effective. Moreover, the process (patent document 2) which reduces | reduces after separating magnet scraps into each rare earth, the method (patent document 3) which takes a decarbonization process and a Ca reduction | restoration process, decarbonization, a reduction | restoration, and a washing | cleaning process are required (patent document 4) ). In addition, the cost of waste liquid from the factory is high, and there are significant problems in terms of environmental measures. Alternatively, a plating removal method (Patent Document 5) and an adhesive removal (Patent Document 6) which are impurities at the time of recycling these recovery processes are necessary and not yet put into practical use.

In view of the above background, an object of the present invention is to provide an anisotropic bonded magnet having high magnetic characteristics, temperature characteristics, and corrosion resistance, which is higher than before, by effectively utilizing rare earth magnets.

JP 2003-113429 A JP2002-60855 JP 2004-91811 A JP 2005-57191 A JP2001-40425 JP2003-176659

As described above, no method has been found to efficiently recycle the rare earth sintered magnet city scrap at low cost. The present invention proposes a novel anisotropic rare earth bonded magnet obtained by recycling a rare earth sintered magnet and a method for producing the same.

In view of the above background, an object of the present invention is to provide an anisotropic bonded magnet having high magnetic characteristics, temperature characteristics, and corrosion resistance, which is higher than before, by effectively utilizing rare earth sintered magnet scraps.

The present invention aims to provide a high performance anisotropic rare earth bonded magnet, does not use any conventional recycling process of rare earth magnet materials, has no problem of waste liquid treatment such as acid, and separates and refines Sm and Nd. No need for process, no need for peeling of surface treatment film such as Ni plating, no need to remove adhesive, but magnetic properties are inferior to those of commercially available Nd sintered magnets. The present invention provides a novel anisotropic rare earth bonded magnet superior to a bonded magnet and a method for producing the same, and has the following characteristics.

[1] An anisotropic rare earth bonded magnet manufactured from the recovered rare earth anisotropic sintered magnet,
As components other than iron (Fe), at least neodymium (Nd) is 3 to 35 wt%, boron (B) is 0.3 to 1.3 wt%, samarium (Sm) is 0 to 30 wt%, and cobalt (Co) is 0. -15 wt%, nickel (Ni) 0-5.5 wt%, aluminum (Al) 0-5.5 wt%, and nickel (Ni) and aluminum (Al) combined 0.3 wt% or more An anisotropic rare earth bonded magnet having a maximum energy product (BH) max of 96 to 270 kJ / m ³ .

[2] The anisotropic rare earth bonded magnet according to [1], wherein the rare earth anisotropic sintered magnet is a neodymium sintered magnet or a neodymium sintered magnet and a samarium cobalt sintered magnet.

[3] In the anisotropic rare earth bonded magnet, the pulverized raw material has an average particle size of 30 to 200 μm (micron), and an average crystal particle size of the main phase forming each particle is 1 to 15 μm (micron). The anisotropic rare earth bonded magnet according to [1] or [2], wherein the anisotropic rare earth bonded magnet has a texture structure.

[4] A method for producing an anisotropic rare earth bonded magnet using a rare earth anisotropic sintered magnet as a raw material, the step of mechanically grinding the rare earth anisotropic sintered magnet in an inert atmosphere, and the ground material From a step of strain relief annealing at a temperature of 400 to 600 ° C. at a temperature of 400 to 600 ° C. in a high vacuum or an inert atmosphere, and a step of kneading the material subjected to the strain relief annealing treatment with a binder to form a magnetic field. A method for producing an anisotropic rare earth bonded magnet, comprising:

[5] The method for producing an anisotropic rare earth bonded magnet according to [4], wherein a wet molding method is used in the compression molding step of the magnetic field molding.

[6] The method for producing an anisotropic rare earth bonded magnet according to [5], wherein in the compression molding step of the magnetic field molding, a two-stage press molding is performed in which a CIP step is added after the compression molding.

According to the present invention, it is possible to reuse rare earth sintered magnets without having to obtain a magnet alloy by remelting and alloying rare earth magnet scraps, which is one of the methods for recycling rare earth sintered magnets conventionally proposed. .

In addition, according to the present invention, an anisotropic rare earth bonded magnet can be manufactured without removing the adhesive adhering to the magnet and before the surface treatment peeling removal such as Ni plating, Al plating or epoxy resin. It can be simplified.

Furthermore, the present invention eliminates the need for a separation step during RE refining of SmCo and Nd magnet scraps, which was unavoidable in the past, even when the rare-earth sintered magnet waste magnet contains an SmCo magnet. Conventionally, the purpose is to use the recovered scrap for sintered magnet applications, but the present invention is applied to a bonded magnet. There is no high-temperature processing step in the process of manufacturing the bonded magnet of the present invention, and individual bonding magnet powders show independent magnetic characteristics, so that arbitrary mixing is possible.

That is, the feature of the present invention is that there is no problem of separation and recovery of the above-mentioned SmCo magnet and Nd magnet, there is no need to peel and remove the magnet surface treatment film, which is inevitable in the current magnet recycling process, With almost no removal and reusable magnet material composition, there is no limit to the amount of recovered materials such as Ni, AI, Cr as surface treatment materials and O and C as impurity elements. It is possible to recover.

In addition, regarding the molding process of this magnet, the advantage of being able to provide bonded magnet powder with excellent corrosion resistance reliability due to extremely few surface cracks and breakage that occur during molding is the reason that this material is made from a microcrystalline sintered material Enclose with.

A further feature of the present invention is that it is characterized by using an anisotropic rare earth sintered magnet raw material as a raw material, and thus has a much higher coercive force and higher heat resistance than conventional anisotropic rare earth bonded magnets. (That is, a normalized squareness ratio p value (p = Hk / HcJ) defined as described later) is obtained.

One of the greatest performance features of the rare earth anisotropic bonded magnet of the present invention is heat resistance, specifically, thermal demagnetization characteristics.

In addition, one of the further characteristics in the magnet performance of the rare earth anisotropic bonded magnet of the present invention is high corrosion resistance, and the magnet has long-term stability that can be sufficiently applied for long-term use. It is.

In the present invention, the raw materials used are limited to only anisotropic rare earth sintered magnets recovered from the city. There are also isotropic Nd bonded magnets and isotropic full dense Nd magnets in the city's collected waste, and there is an idea to mix and collect these recovered waste, but in the present invention this recycling method Do not take. After all, anisotropic rare earth sintered magnets are a very long process of alloy melting, crushing, magnetic field molding, sintering, heat treatment, processing, and surface treatment, that is, even if it is scrap, it is “recovered scrap with very high added value” This is because it is not desirable to reduce reuse and energy reuse efficiency by mixing them. The present invention is a high-value-added anisotropic rare-earth sintered magnet material and is characterized by considering the characteristics of various recovered scraps with a view to maximizing scrap recovery and reuse.

The recovered rare earth sintered magnet of the present invention is a so-called Nd-based sintered magnet, but is characterized in that SmCo-based sintered magnets that are used in some markets and are available as recovered scrap can also be used as raw materials.

That is, in order to produce an anisotropic rare earth bonded magnet having a magnetic characteristic with a maximum energy product (BH) max of 96 to 270 kJ / m ³ , the composition of the magnet is at least neodymium as a component other than iron (Fe). (Nd) 3 to 35 wt%, boron (B) 0.3 to 1.3 wt%, samarium (Sm) 0 to 30 wt%, cobalt (Co) 0 to 15 wt%, nickel (Ni) 0 to It is necessary to contain 5.5 wt%, 0 to 5.5 wt% of aluminum (Al), and 0.3 wt% or more in total of nickel (Ni) and aluminum (Al).

In the present invention, since the recovered rare earth sintered magnet is used as a raw material, AL coating and Ni-coating are usually performed, so that Al and Ni components are usually combined with nickel (Ni) and aluminum (Al). .3 wt% or more, and in some cases, 1 wt% or more. Even if the content of Al or Ni is up to 5.5 wt% at the maximum, sufficient magnetic properties can be exhibited.

The magnet of the present invention also contains components other than Fe, Nd, B, Sm, Co, Ni and Al, and usually the components have the following composition (wt%).
Nd; 3-35, Pr; 0-10, Dy; 0-12, Tb; 0-3, Sm; 0-30, Ce; 0-10, B; 0.3-1.3, Co; 0-15, Nb; 0-1.5, Cu; 0-10, Al; 0-5.5, Ga; 0-1.5, Ni0-5.5, Zr; 0-0.5, Hf; 0-0.5, Fe; bal.

A desirable composition for realizing higher magnetic properties is as follows.
Nd; 3-33, Pr; 0-6, Dy; 0-7, Tb; 0-1, Sm; 0-10, Ce; 0-4, B; 0.8-1.1, Co; 0-5, Nb; 0-0.5, Cu; 0-4, Al; 0-3.5, Ga; 0-0.2, Ni0-3.5, Zr; 0-0.2, Hf; 0-0.2, Fe; bal.

The magnet scrap of the present invention is most preferably composed only of Nd magnet scrap in order to exert higher magnetic performance, but high magnetic performance even if the Nd magnet scrap contains SmCo-based magnet scrap. It is possible to demonstrate. However, as the mixing ratio of SmCo sintered magnet scrap increases, the magnetic properties such as residual magnetic flux density Br and maximum energy product (BH) max that are obtained at that time monotonously decrease. It is limited to Sm content.

That is, one of the features of the present invention is that excellent magnetic properties can be realized with a high Sm content even in a composition region that cannot be realized with a normal Nd-based anisotropic bonded magnet. It is possible even with a Sm content of up to 30 wt%.

Here, the major difference between the normal Nd magnet composition and the raw material scrap is the Sm, Co, and Cu contents, which are outside the normal composition of the Nd magnet. This is characterized by the fact that the entire amount of municipal waste or most of the waste with SmCo-based composition can be newly recovered by this method, which can not be reused by conventional remelting and alloying methods. .

Similarly, an epoxy resin-coated product can be obtained with an anisotropic rare earth bonded magnet without any problem by the method of the present invention without removing the resin.

The anisotropic rare earth bonded magnet of the present invention uses the magnet collected as described above as it is without pretreatment, removal of impurities, etc., so that a relatively high ratio of O (oxygen) amount, C (carbon) amount Even in this case, it has a performance equal to or higher than that of conventional isotropic bonded magnets and anisotropic bonded magnets.

Conventional alloy alloys for anisotropic rare earth bonded magnets have limited amounts of impurities O (oxygen) and C (carbon) in order to obtain excellent magnetic properties. When there is much O and C, a magnetic characteristic falls remarkably. An anisotropic rare earth bonded magnet is a high purity rare earth metal, iron, boron and other essential elements are all made of high purity raw materials. Therefore, a magnet alloy dissolved and refined using these materials has an O content of at least 0.08 wt%, usually less Is 0.01 wt% or less, and the C content is at least 0.03 wt% or less, usually 0.05 wt%.

On the other hand, since the raw material alloy of the anisotropic rare earth bonded magnet of the present invention uses the recovered rare earth anisotropic sintered magnet, the amount of O and C increased due to oxidation and binder addition during the sintered magnet manufacturing process. The amount of O is at least 1 wt%, usually 4 wt% or more, and the amount of C is 0.4 wt% or more, usually 0.5 wt% or more.

However, depending on the state of the recovered material, the magnet may be significantly oxidized and corroded, or there may be recovered scraps that are markedly adhered with adhesive or coated when the magnet is recovered, and these have sufficient magnetic properties. Absent. Therefore, in order for the anisotropic rare earth bonded magnet of the present invention to maintain a magnetic property having a maximum energy product (BH) max of 96 kJ / m ³ or more, the upper limit of the O amount is 8 wt% or less, and preferably 5 wt% or less. , C content is required to be 7 wt% or less, preferably 4 wt% or less.

The anisotropic rare earth bonded magnet of the present invention is equivalent to or more than conventional isotropic bonded magnets and anisotropic bonded magnets even if a raw material having a high amount of O, C as impurities, which is normally unusable, is used. One of the features is that it has excellent magnet characteristics, heat resistance characteristics, and corrosion resistance.

The anisotropic rare earth bonded magnet of the present invention is characterized by its magnet structure in order to obtain excellent magnetic properties. Specifically, a fine structure in which the average particle size of the magnet powder constituting the magnet is 30 to 200 μm, more preferably 50 to 170 μm, and the average crystal particle size of the main phase forming each particle is 1 to 15 μm. An anisotropic rare earth bonded magnet having

The coercive force of the rare earth magnet is reduced because of a multi-domain structure when the crystal grain size is large, and the coercive force is decreased due to oxidation or processing strain, although it is a single domain structure when the crystal grain size is small. Therefore, there is an optimal crystal grain size that depends on the magnet process.

The average crystal grain size of the main phase forming each particle of the anisotropic rare earth bonded magnet of the present invention is characterized by having a texture structure of 1 to 15 μm (microns), and further obtaining an excellent high coercive force, In order to suppress the oxygen content, 1.5 to 10 μm, more preferably 2.0 to 7.0 μm is most desirable. Here, the main phase is the Nd ₂ Fe ₁₄ B intermetallic compound phase in the case of Nd-based recovered scrap, and the SmCo ₅ or Sm ₂ (Fe, Co, Cu) ₁₇ intermetallic compound phase is the main phase in the SmCo system. Is a phase. The volume ratio of the main phase is 90% or more of the entire magnet.

The average particle diameter of the magnet powder is a condition from the bond magnet manufacturing condition in consideration of high density and productivity. On the other hand, since this magnet is essentially a recovered scrap material, it is essentially different from conventional bonded magnets with an average crystal grain size of submicron or less in a rapid cooling process (so-called melt spinning) such as MQI powder. Also, because of the Nd-based material, the magnet composition is different from that of the SmFeN bond.

Here, the average particle size measurement is a value measured by a hole permeation method (Fischer, subseed sizer, etc.), and the crystal particle size is a crystal particle size derived by image analysis of a two-dimensional metal structure photograph.

Then, the manufacturing method of an anisotropic rare earth bond magnet is demonstrated.
The method for producing an anisotropic rare earth bonded magnet using the rare earth anisotropic sintered magnet of the present invention as a raw material includes a step of mechanically crushing the rare earth anisotropic sintered magnet in an inert atmosphere, It consists of a step of strain relief annealing at a temperature of 400 to 600 ° C. in a vacuum or an inert atmosphere and a holding time of 12 hours or more, and a step of kneading the strain relief annealed material and a binder to form a magnetic field. It is characterized by.

In order to obtain the desired maximum energy product (BH) max, component analysis and magnetic property measurement of magnet recovery scrap are indispensable.

That is, in order to produce an anisotropic rare earth bonded magnet having any desired magnetic property with a maximum energy product (BH) max ranging from 96 to 270 kJ / m ³ , the collected rare earth sintered magnet is sampled in advance. Then, it is necessary to perform a component analysis of the recovered magnet material and confirm the composition of neodymium (Nd) and samarium (Sm) as the composition of the magnet. Judging from the analysis value, in order to obtain a desired magnetic characteristic, a bonded magnet can be prepared by further blending and adjusting magnet scraps with other components already known. However, for that purpose, it is necessary to accumulate data of CR values, which will be described later, with various collected scraps.

In addition, when the collected rare earth anisotropic sintered magnet is a single magnet scrap, this component analysis can be omitted, but in particular, when the collected rare earth anisotropic sintered magnet is various. Is essential, and it is preferable to have a large number of samplings.

In addition, the magnetic characteristic of the sintered magnet before disposal can be made the representative magnetic characteristic when n = 3 to 10 samples are usually sampled when the collected scrap is mixed municipal waste. Similarly, the magnetic scrap component analysis is also performed by ICP etc. and n = 3 to 10 sampling analysis.

Depending on the obtained component analysis values and magnetic characteristics, it is possible to mix and use one or more kinds of scraps.
When samarium (Sm) is detected by 30% by weight or more by component analysis, production of excellent anisotropic rare earth bonded magnets with higher magnetic properties than those of Nd magnet base with high mixing ratio of samarium cobalt sintered magnet It is a raw material not suitable for.

That is, when 30% by weight or more of samarium is detected as a result of component analysis in the collected rare earth anisotropic sintered magnet and the samarium-cobalt sintered magnet is mixed in a lot, the corresponding recovered scrap is replaced with other Nd magnet-based recovered scrap. Used by diluting and mixing.
In this collection process, in order to make effective use of the recovered rare earth sintered magnet material and process it in the optimal manufacturing process to exhibit the maximum anisotropic rare earth bonded magnet magnetic properties, component analysis of the magnet material used is It is essential.

Component analysis is based on ICP or X-ray fluorescence analysis. For the same reason, it is essential to measure the magnetic properties of the recovered raw material. In order to exhibit the required magnetic properties, it is possible to use one or more kinds of magnet material scraps in combination, which is a feature of this manufacturing method. This is because it is necessary to evaluate the waste performance by component analysis and magnetic property measurement, and to optimize and obtain the maximum maximum energy product (BH) max by adjusting the selection and mixing of the waste to be used according to the application.

  The steps of the method for producing an anisotropic rare earth bonded magnet using the rare earth anisotropic sintered magnet as a raw material will be described in detail below.

First, the collected magnet is pulverized. The pulverization can be performed by mechanical pulverization such as a ball mill, an attritor, and a jaw crusher. A two-stage treatment such as grinding with a jaw crusher and then finely grinding with a ball mill is also effective, the particle size distribution can be made uniform, and the magnetic properties can be improved. In order to prevent oxidation, the grinding atmosphere is carried out in an inert atmosphere such as Ar or N or in a solvent such as alcohol or acetone.

The recovered scrap uses a pulverization process that does not require any hydrogen pulverization, which is essential in the conventional magnet manufacturing process. This is because when hydrogen pulverization is used, microcracks are generated during press molding, and magnetic properties are deteriorated due to significant oxidation of the powder.

For fine pulverization, general ball mill pulverization or the like is used. However, since the raw material used is a rare-earth sintered magnet, which is a microcrystalline and extremely hard alloy, it is not a conventional high speed ball mill of 2 to 6 hours, but a low speed ball of 12 to 24 hours Using the process has higher magnetic properties.

The average particle size of the pulverized powder needs to be 30 to 200 μm, more preferably 50 to 170 μm.

As will be described later, it is also effective to use two types of powders having different particle sizes in order to improve magnetic properties by increasing the packing density during press molding. In particular, it is important to improve molding conditions such as using two types of powders with poor moldability.

One of the features of this magnet manufacturing process is a process that does not use hydrogen crushing. Hydrogen crushing is a production method that is often used because Sm magnets and Nd magnets have inherently hydrogen storage and hydrogen embrittlement, but the rare earth scrap recovery industry can spread and process a large amount safely and safely as a social scheme. In order to make the proposal as versatile as possible, a process that does not use any hydrogen pulverization process is proposed. Of course, the pulverization method by hydrogen pulverization is not excluded.

The magnet powder must be heat-treated in a high vacuum or inert atmosphere after pulverization. Without heat treatment, as seen in the prior patent (Japanese Patent Application No. 4-303254), the coercive force value HCJ obtained is extremely low at 800 kA / m (10 kOe) or less, and the heat resistance of the magnet is low.
The heat treatment temperature is 400 to 600 ° C., but the heat treatment time is 12 hours or longer, and 48 hours or longer as desired. If the temperature exceeds 600 ° C., the powder is welded and further diffusion occurs. Therefore, if possible, the temperature is preferably 500 ° C. or lower. At a low temperature of 400 ° C., it takes a long time for heat treatment to remove strain, and it is preferably 24 hours or more, or 48 hours or more.

The purpose of this strain removal heat treatment is to inevit the inevitable mechanical strain such as micro cracks generated during mechanical crushing, but in order to prevent oxidation of the magnet powder during heat treatment, a getter powder such as Ti is inserted into a sample-specific container. It is desirable to do it.

The resulting powder is then kneaded with a binder. As the binder, an epoxy resin is used for compression molding, and a thermoplastic resin such as PA resin (nylon 12 or the like) or heat-resistant PPS is used for injection molding. In order to maintain high magnetic properties, it is necessary to keep the amount of the binder at the lower limit that does not impair the moldability, and it is 3-7 wt% for compression molding and 5-10 wt% for injection molding. In addition, an antioxidant, a stearic acid-based mold lubricant, or the like may be added in an amount of 0.8 wt% or less depending on the product shape.

The biggest problem of this powder is press formability. The raw material is magnet alloy scrap, and unlike ordinary molten alloys, the crystal grain size is very uniform and fine and mechanically hard. Therefore, the particle size distribution of the powder is very steep and the formability is extremely difficult. If the molding pressure of a normal rare earth sintered magnet is 0.5 to 1.2 Ton / cm ² , a sufficient compact density cannot be obtained. In compression press molding, a magnetic field press method can be adopted, and molding corresponding to a magnet shape such as right-angle molding, parallel molding, radial molding, or diameter dipole molding is possible. The molding pressure is 0.9 Ton / cm ² or more, preferably 6.5 Ton / cm ² or more, and more preferably 8.5 Ton / cm ² or more in order to realize high magnetic properties by increasing the molding density. Thus, it is a feature that a pressure extremely higher than the molding pressure used in the normal sintered magnet manufacturing process is required, and the long life of the mold is a problem in the future mass production.

In the magnet forming process, a magnetic field forming method using powders having two or more types of particle sizes is also effective. However, this method is extremely effective in this raw material alloy system, and the average particle size ratio Cp of the two types of powders to be mixed is Cp. When the powder having = 0.1 to 0.3 is used, the magnetic properties are excellent. Desirably, Cp = 0.15 to 0.25.

When the mixing ratio Kp of these two kinds of powders is kneaded to Kp = 1.5 to 4.0, the density is increased and high excellent magnetic properties are obtained. Kp is more preferably Kp = 2.0 to 3.5. Kp is (coarse particle weight) / (microparticle weight). The conditions for Cp and Kp are the same for the injection molding press.

Since the present powder is very difficult to mold, wet molding, which easily increases the density of the molded body, is also an extremely effective method. Although the wet molding method is already used in the production method of rare earth sintered magnets, it is usually used at a higher cost than the dry process and requires a solvent removal process during sintering. There is no patent reported as a molding method. The present powder has been found to be very effective in this wet molding.

Since the rare earth sintered waste powder is a powder having poor press moldability as described above, a two-stage press molding in which a cold isotropic press (hereinafter referred to as CIP) is performed after compression molding or wet molding is employed. This is because it is effective to increase the magnetic properties by increasing the density of the molded body by applying a high molding pressure by CIP. The pressure at which CIP is effective is 200 MPa or more, preferably 300 MPa or more. The CIP medium is a solvent such as glycerin, and the CIP pressure application time is 10 to 20 minutes.

Wet press molding mainly contributes to densification mainly by improving the friction coefficient of the mold surface, and CIP contributes differently to densification by hydrostatic pressure from all directions, so a combination of wet molding and CIP. A multi-stage press having a special effect is effective. These powder moldings are unique to the powder physical properties such as mechanical properties and particle size distribution of rare earth sintered dust powder, which are hardly manifested in the effects of conventional rare earth sintered magnets.

The solvent used for the wet molding can be an organic solvent such as alcohol or acetone, lubricating oil, gasoline or the like. By the magnetic field molding under these solvents, the press molding pressure can be reduced by 20-30% from the normal dry pressure, and peeling, cracking, chipping, etc. during molding are remarkably improved. Wet molding essentially requires an inevitable solvent removal step, but it is extremely effective molding because it is not necessary at all in the proposed anisotropic rare earth bonded magnet manufacturing method.

Further, in the press magnet manufacturing method, in order to increase the density, a powder filling tapping process such as air tapping and ultrasonic tapping in the magnetic field forming process obtains a high tap density and is extremely effective as a molding technique for the present powder. Tapping is performed by propagating the pressure vibration of the compressed air, such as by attaching a vibration transmission board to a magnetic mold. Alternatively, the density is increased by inserting a green molded body previously air-tapped in a temporary press package into a mold.

A magnet obtained by compression molding or injection molding can be used as a product as it is, but by applying Ni plating, epoxy coating, etc., it can be applied to applications requiring corrosiveness and corrosion resistance. By applying these surface treatments, the corrosion resistance is equal to or higher than that of commercially available anisotropic bonded magnets. Specifically, the corrosion resistance is evaluated under the condition of 80 ° C. × 90% RH.

The above anisotropic rare earth bonded magnet manufacturing method realizes an energy product with a maximum energy product (BH) max of 96 to 270 kJ / m ³ and a high standard squareness ratio p0.70, and further, based on the analysis value, By selecting magnetized scraps, excellent magnetic properties with a coercive force HcJ of 800 kA / m or more can be realized.

In the present invention, since the purpose is to reuse the rare earth sintered magnet to be discarded, it is not necessary to ensure the reproducibility of the magnetic properties originally possessed by the magnet material before the disposal, but the discarded magnet material. Depending on the form, impurities, and the presence or absence of coating, etc., the magnetic material with one or several steps (cascade) magnetic properties will be realized and used effectively, but the magnetic force is still the conventional isotropic bond. It has the same or better performance as a magnet and an anisotropic bonded magnet.

Here, the definition of the CR rate shown in the examples is shown below.
The maximum energy product of the sintered magnet before disposal is α, and the maximum energy product (β) of the manufactured anisotropic bonded magnet is used. CR ratio = β / α

In the present invention, the CR rate is usually 0.3 to 0.7. The upper limit of the CR rate is 0.7 because the recovered magnet is simply pulverized without pretreatment, and the upper limit is usually 0.75. The lower limit is usually 0.30 or more, preferably 0.45, more preferably 0.55 or more in terms of magnet cost / magnetic performance. When the CR ratio is 0.3 or less, the cost merit is small compared to a normal commercially available isotropic bonded magnet.

The maximum energy product (BH) max is 96 to 270 kJ / m ³ , and a high standard squareness ratio p0.70 is achieved. Furthermore, by selecting sintered magnet debris based on the analysis value, the coercive force HcJ is Excellent magnetic characteristics of 800 kA / m or more can be realized.
This indicates that the heat resistance, which is extremely important in practical use of the permanent magnet, specifically, the heat demagnetization property is sufficiently high.

In general, in order to improve the thermal demagnetization characteristics of a permanent magnet, it is necessary that the coercive force HcJ and the squareness Hk of the demagnetization curve are large. Here, Hk is defined as the value of the magnetic field H at which the value of the magnetization J is 90% of the residual magnetic flux density (Br) on the JH demagnetization curve. However, since the squareness Hk value differs depending on the material of the permanent magnet, it is necessary to standardize and evaluate the numerical value. In the present invention, the value normalized by the coercive force HcJ and the normalized squareness ratio p are set for convenience. It defines and uses by p = Hk / HcJ.

The main reasons why the thermal demagnetization characteristics of current anisotropic rare earth bonded magnets are still insufficient in practical use are that the value of coercive force HcJ is low and the normalized squareness ratio p value is low. Currently, there are two types of anisotropic bonded magnets: an HDDR type magnet using a process called HDDR or d-HDDR and an SmFeN type produced by nitriding a SmFe alloy. Neither of these HDDR type anisotropic rare earth bonded magnets nor SmFeN type anisotropic rare earth bonded magnets has a high coercive force HcJ and a high normalized squareness ratio p value comparable to sintered magnets.

In particular, the normalized squareness ratio p value that greatly affects the thermal demagnetization characteristics is largely attributable to the magnet manufacturing process and uniformity. With HDDR magnets, it is very difficult to make anisotropy technology in which crystal grains are oriented in the same direction during the resorption process (desorption), and even for SmFeN, nitrogen diffuses uniformly from the surface to the SmFe alloy. The reaction technique is very difficult, and a high normalized squareness ratio p has not been obtained.

On the other hand, since rare earth sintered magnets are magnetically molded from a powder that is mechanically pulverized into a micro single crystal of several microns, the degree of crystal grain orientation is extremely high, and the present invention has an average powder particle size of 30 to 200. Since micron and much larger than the original crystal grain, a high normalized squareness ratio p can be realized relatively easily without disturbing the degree of crystal grain orientation. The magnet of the present invention becomes an anisotropic rare earth bonded magnet having a normalized squareness ratio of 0.70 or more and a maximum of 0.90 or more even in a normal process and having an extremely high p value, that is, excellent temperature characteristics such as thermal demagnetization. In order to have excellent heat resistance, it is essential that the normalized squareness ratio p is high in addition to high coercivity.

Since the present invention is characterized by using an anisotropic rare earth sintered magnet raw material as a raw material in this way, the coercive force is substantially higher than that of a conventional anisotropic rare earth bonded magnet, and a high p value. Is obtained.

Current commercially available anisotropic bonded magnets have a coercivity HcJ of 1,100 to 1,500 kA / m,
The normalized squareness ratio p is 0.2 to 0.3, and at most 0.4. This isotropic bonded magnet heat resistance, specifically thermal demagnetization, is approximately 120-140 ° C.
On the other hand, the anisotropic bonded magnet of the present invention has a maximum coercive force HcJ of 2,000 kA / m, a normalized squareness ratio p of 0.70-0.85 even in the normal process, and a maximum of 0.90, which is the same as a sintered magnet. According to the magnet of the present invention having excellent characteristics such as coercive force of 2,000 kA / m and normalized squareness ratio p of 0.85, heat resistance of 200 ° C. can be realized. Since the anisotropic sintered magnet material having extremely high squareness is used as a raw material, the magnet of the present invention is essentially a highly heat-resistant anisotropic rare earth bond having a normalized squareness ratio p. It becomes a magnet.

As described above, one of the greatest performance characteristics of the rare earth anisotropic bonded magnet of the present invention is heat resistance, specifically, thermal demagnetization characteristics.

Thermal demagnetization characteristics are evaluated by the amount of decrease in magnetic flux after high temperature and long time (usually 1000 hr) at a certain Pc (permeance coefficient, usually Pc = 1 or 2). The heat resistance is evaluated at the highest temperature at which the standard for the amount of magnetic flux reduction is normally 5%. It is said that the heat resistance of anisotropic rare earth bonded magnets is usually about 120 ° C because the decrease in magnetic flux after 1000 hours is 5% at 120 ° C, so this 120 ° C temperature can be used in practice. It means that it is the upper limit temperature.

The heat resistance of currently available anisotropic rare earth bonded magnets is about 120-140 ° C. For example, anisotropic SmFeN bonded magnets are reported to be 130 ° C. at the maximum for mass production and 150 ° C. at the research level. (For example, Japan Bond Magnetic Materials Association BMNews, No43, 2010).

The present invention is basically a Nd-based material system because the Nd magnet recovered scrap contained in the recovered scrap is a large amount in the market, and its heat resistance is normally 140 ° C., more than 180 ° C. An anisotropic bonded magnet having temperature characteristics.

Specifically, the present invention is such that Pc = 2, heat demagnetization is 5% or less under the condition of 140 ° C. × 1000 hr, further exceeds 160 ° C. under the same conditions as above, and the recovered waste is sorted and used, and the magnetic powder such as the kind and addition amount of the binder By selecting the production conditions other than those, extremely excellent heat resistance exceeding 180 ° C. can be provided.

On the other hand, it is known that the thermal demagnetization characteristic of the anisotropic bonded magnet by the manufacturing method of α-HDDR currently on the market is as large as about 11% of thermal demagnetization at Pc = 2, 150 ° C. × 1000 hr.

Another feature of the magnet performance of the rare earth anisotropic bonded magnet of the present invention is high corrosion resistance, and the magnet has long-term reliability and stability that can be sufficiently applied for long-term use. is there.

This magnet obtained by compression molding and injection molding can be used as a product as it is, but by applying surface treatment such as Ni plating, epoxy coating, etc., it has higher corrosion resistance than that of commercially available anisotropic bonded magnets. Have sex. Corrosion resistance evaluation is performed under the conditions of 80 ° C. × 90% RH, which is usually performed, and it is known that an anisotropic rare earth bonded magnet material has a limit of corrosion resistance of 200 to 400 hours.

The rare earth anisotropic bonded magnet of the present invention has a corrosion resistance of about 300 hours or more under the condition of 80 ° C. × 90% RH. Furthermore, by performing sufficient surface treatment, it is possible to have excellent corrosion resistance with no change in appearance up to 500 hours.

When converted to a reference for the life prediction estimated from the accelerated corrosion test of temperature and humidity, 80 ° C x 90% RH x 500 hours is equivalent to, for example, 23.8 ° C x 78% RH, about 20 years, 16.2 ° C x 67% RH, about 115 years It can be seen that the rare earth anisotropic bonded magnet has practically sufficient long-term corrosion resistance and long-term reliability.

It is known that a commercially available anisotropic bonded magnet material has a limit of 200 to 400 hours in corrosion resistance. The anisotropic bonded magnet according to the present invention is a magnet having excellent long-term corrosion resistance and long-term reliability with no change in appearance for up to 500 hours by applying a sufficient surface treatment for about 300 hours equivalent to or longer than these. Is possible.

<Example 1>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analysis values (Table 1-1, Table 1-2). The analytical values of the amount of O and C of the recovered waste were 4.3 wt% and 0.8 wt%, respectively. The average crystal grain size was 6.2 μm as measured by n = 5. This alloy powder was ball milled in acetone to obtain a press-molded powder. The average particle size is 75 μm. The resulting powder was heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, then added with 4.5t% of epoxy binder and kneaded to obtain a compound, and 4.0Ton / cm in a magnetic field After compression molding at ² , CIP treatment is further performed at a pressure of 300 MPa for 10 minutes. The obtained anisotropic bond magnetic properties and the magnetic properties (n = 5) of the collected magnets are shown below together with the measured average magnetic properties.
The recovered scrap was a component of the Nd magnet alone, and the CR obtained was 0.64.

<Example 2>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analysis values (Tables 2-1 and 2-2). The analytical values of the O amount and the C amount of the recovered waste were 4.8 wt% and 0.9 wt%, respectively. The average crystal grain size was 8.2 μm as measured by n = 5. This alloy powder was ball milled in acetone to obtain a press-molded powder. The average particle size is 51 μm. The resulting powder was heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, and then compounded by adding 4.5% of epoxy binder to this molded powder to obtain a compound, and in a magnetic field at 4.0 Ton / cm ² After compression molding, CIP treatment is further performed at a pressure of 300 MPa for 10 minutes.
The recovered scrap was a component containing a part of Nd magnet and Sm, and CR obtained was 0.69.

<Example 3>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the market, and obtained the following properties and analysis values (Tables 3-1 and 3-2). The analytical values of the O amount and C amount of the recovered waste were 3.5 wt% and 2.4 wt%, respectively. The average crystal grain size was 9.5 μm as measured by n = 5. This alloy powder was ball milled in acetone to obtain a press-molded powder. The average particle size is 85 μm. The obtained powder was heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, then kneaded by adding 6.5 wt% of nylon 12 binder to this molded powder, and obtained a compound, which was injection molded in a magnetic field. . The CR derived from the magnetic properties of the recovered magnet of the obtained anisotropic bond magnetic properties was 0.47.
Although this collection | recovery waste is a component which contains a part of Nd magnet and Sm, content of SmCo magnet is more than Example 2, and obtained CR was 0.47.

<Example 4>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analytical values (Tables 4-1 and 4-2). The analytical values of the amount of O and the amount of C of the collected waste were 6.9 wt% and 3.2 wt%, respectively. The municipal waste used was almost entirely recovered from Ni-plated products. The average crystal grain size was 7.0 μm as measured by n = 5. This alloy powder was first roughly pulverized with a jaw crusher and then finely pulverized in acetone to obtain a press-molded powder. The average particle size is 63 μm. The resulting powder was heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, then added with 4.5t% of epoxy binder to this molded powder and kneaded to obtain a compound, and a magnetic field of 3.5Ton / cm ² After medium compression injection molding, CIP treatment is further performed at a pressure of 300 MPa for 10 minutes.
In addition, in order to verify the air tapping effect, air tapping using compressed air is performed at the time of magnetic field molding, the green density before molding is increased and then molded, and after further compression molding, CIP treatment is further performed at a pressure of 300 MPa for 10 minutes. An anisotropic bonded magnet was prepared.
This recovered scrap was a component of the total amount of Nd magnet scrap.
It was found that CR of the obtained anisotropic bond magnetic properties was 0.61, and CR improved to 0.68 when air tapping was performed. It was confirmed that good magnetic properties can be obtained for Ni plating scraps with or without air tapping.

<Example 5>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analytical values (Tables 5-1 and 5-2). The analytical values of the O amount and C amount of the recovered waste were 5.8 wt% and 1.8 wt%, respectively. The average crystal grain size was 8.7 μm as measured by n = 5. This alloy powder was ball milled in acetone to obtain a press-molded powder. The average particle size is 95 microns. The obtained powder was heat treated in a high vacuum containing a Ti getter material at 550 ° C. × 24 hr, and then kneaded by adding 6.5 t% of PPS binder to this molded powder, and injection molded in a magnetic field. Reliability was also confirmed by applying an epoxy spray coating after molding.
The recovered scrap was a component containing a part of Nd magnet and Sm, and CR obtained was 0.49.
Further, the corrosion resistance and reliability of the magnet of the present invention were evaluated together with a commercially available SmFeN anisotropic bonded magnet (Table 5-3). The commercially available SmFeN anisotropic bonded magnet of the comparative example was obtained and treated under the same epoxy spray coating conditions as the magnet of the present invention. When the corrosion resistance was tested under the conditions of 80 ° C. × 90% RH, the commercially available SmFeN red spot rust generating magnet already generated micro red spot rust in 300 hours, while the magnet of the present invention did not generate rust until 600 hours. It has been found that it has long-term corrosion resistance and long-term stability that are significantly better than isotropic bonded magnets. This is presumed to be because the raw material used is a sintered magnet having a fine and uniform structure, so that corrosion from the crystal grain boundaries and the internal progress thereof are very unlikely to occur.

得られた異方性ボンド磁石の熱減磁特性を比較の為市販の等方性ボンド磁石、異方性ボンド磁石と比較評価した（表６―３）。熱減磁評価条件はPc=2, 保持温度が140℃もしくは180℃で1,000hrである。本表にあるように、本発明磁石は１４０℃で1.8%、１８０℃においても3.6%という極めて低い熱減磁量を達成していることがわかる。一方、比較例の市販の等方性、異方性いずれの磁石においても熱減磁量が140℃、180℃いずれの温度においても極めて熱減磁量が大きく、本発明磁石が優れた耐熱使用温度を具備していることがわかる。この理由は、用いた回収焼結磁石屑が成分分析結果からわかるようにDyやTb等の多い高耐熱性を有する磁石成分であることに大きく起因していると推測する。

<Example 6>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analysis (Tables 6-1 and 6-2). The analytical values of the amount of O and the amount of C of the collected waste were 4.1 wt% and 2.6 wt%, respectively. Part of the Nd magnet was mostly recovered scrap from Al (aluminum) surface treatment. The average crystal grain size was 6.3 μm as measured by n = 5. This alloy powder was ball milled in acetone, and a press-molded powder was obtained by sampling during grinding. Each average particle size is 14,59 μm. (Cp = 0.24)
These obtained powders were heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, then these two kinds of powders were blended and mixed at Kp = 2.0, and epoxy binder was added to this molded powder at 4.5wt%. Kneading is performed to obtain a compound, compression molding in a magnetic field at 4.0 Ton / cm ² , and then CIP treatment for 10 minutes at a pressure of 300 MPa.
The CR of the obtained anisotropic bonded magnetic property was 0.43, and the recovered scrap was an Al surface-treated Nd magnet and partly SmCo magnet, but good anisotropic bonded magnet magnetic properties were obtained. .

For comparison, the thermal demagnetization characteristics of the obtained anisotropic bonded magnets were compared with those of commercially available isotropic bonded magnets and anisotropic bonded magnets (Table 6-3). Thermal demagnetization evaluation conditions are Pc = 2, holding temperature is 140 ° C or 180 ° C and 1,000 hours. As shown in this table, it can be seen that the magnet of the present invention achieves a very low thermal demagnetization amount of 1.8% at 140 ° C. and 3.6% at 180 ° C. On the other hand, the thermal demagnetization amount is 140 ° C and 180 ° C both in the commercially available isotropic and anisotropic magnets of the comparative example, and the heat demagnetization amount is extremely large at any temperature. It turns out that it has temperature. This reason is presumably due to the fact that the recovered sintered magnet scrap used is a magnet component having a high heat resistance such as Dy and Tb as can be seen from the component analysis results.

得られた異方性ボンド磁石の熱減磁特性を比較の為市販の等方性ボンド磁石、異方性ボンド磁石と比較評価した（表７―３）。熱減磁評価条件はPc=2, 保持温度が140℃もしくは180℃で1,000hrである。本表にあるように、本発明磁石は１４０℃で2.3%、１８０℃においても4.2%という極めて低い熱減磁量を達成していることがわかる。一方、比較例の異方性SmFeNボンド磁石は熱減磁量が140℃、180℃いずれの温度でも極めて大きく、本発明磁石が優れた耐熱使用温度を具備していることがわかる。この理由は、用いた回収焼結磁石屑が成分分析からわかるようにDyやTb等の多い高耐熱性を有する焼結磁石であることに大きく起因していると推測する。

<Example 7>
We measured the magnetic properties and ICP component analysis (n = 3) of the municipal waste recovered from the starting materials, and obtained the following properties and analytical values (Tables 7-1 and 6-2). The analytical values of the O amount and C amount of the recovered waste were 3.7 wt% and 2.1 wt%, respectively. The average crystal grain size was 7.2 μm as measured by n = 5. This alloy powder was ball milled in acetone to obtain a press-molded powder. The average particle size is 58 μm. The obtained powder was heat-treated in a high vacuum containing Ti getter material at 550 ° C x 24hr, then added with 4.5 wt% of epoxy binder to this molded powder and kneaded to obtain a compound, and further mixed with an inorganic solvent. After wet compression molding at 4.0 Ton / cm ² in a magnetic field, CIP treatment is further performed at a pressure of 300 MPa for 10 minutes. The obtained anisotropic bond magnetic property CR was 0.62.

For comparison, the thermal demagnetization characteristics of the obtained anisotropic bonded magnet were compared with those of commercially available isotropic bonded magnets and anisotropic bonded magnets (Table 7-3). Thermal demagnetization evaluation conditions are Pc = 2, holding temperature is 140 ° C or 180 ° C and 1,000 hours. As shown in this table, it can be seen that the magnet of the present invention achieves a very low thermal demagnetization amount of 2.3% at 140 ° C. and 4.2% at 180 ° C. On the other hand, the anisotropic SmFeN bonded magnet of the comparative example has a very large amount of thermal demagnetization at both 140 ° C. and 180 ° C., indicating that the magnet of the present invention has an excellent heat resistant use temperature. This reason is presumably due to the fact that the recovered sintered magnet scrap used is a sintered magnet having a high heat resistance with a large amount of Dy, Tb, etc. as can be seen from the component analysis.

According to JABM (Japan Bond Magnetic Materials Association), the market for rare earth bonded magnets is estimated to be about 10 billion for the domestic market and about 50 billion for the global market, according to 2008 statistics. The market growth rate is about 11% per year, and demand is expected to continue expanding.
Most of the commercially available rare earth bonded magnets are isotropic bonded magnets. There are currently no materials that can be used in large quantities for anisotropic bonded magnets because of their marketability, magnet material performance, mass production costs, etc. Has a very low market share of several percent.
If the magnet material of the present invention becomes available, the conversion from isotropic to the anisotropic bonded magnet of the present invention will proceed rapidly. In other words, by switching from isotropic to anisotropic, electronic components can be reduced in size, weight, resources, energy, and efficiency.
Also, it can be applied to new applications and fields that could not be realized with conventional isotropic bonded magnets.

Claims (6)

An anisotropic rare earth bonded magnet manufactured from the recovered rare earth anisotropic sintered magnet,
As components other than iron (Fe), at least neodymium (Nd) is 3 to 35 wt%, boron (B) is 0.3 to 1.3 wt%, samarium (Sm) is 0 to 30 wt%, and cobalt (Co) is 0. -15 wt%, nickel (Ni) 0-5.5 wt%, aluminum (Al) 0-5.5 wt%, and nickel (Ni) and aluminum (Al) combined 0.3 wt% or more An anisotropic rare earth bonded magnet having a maximum energy product (BH) max of 96 to 270 kJ / m ³ .   The anisotropic rare earth bonded magnet according to claim 1, wherein the rare earth anisotropic sintered magnet is a neodymium sintered magnet or a neodymium sintered magnet and a samarium cobalt sintered magnet.   In the anisotropic rare earth bonded magnet, the pulverized raw material has an average particle size of 30 to 200 μm (micron) and a main phase forming each particle has an average crystal particle size of 1 to 15 μm (micron). The anisotropic rare earth bonded magnet according to claim 1, wherein the anisotropic rare earth bonded magnet is provided.   A method for producing an anisotropic rare earth bonded magnet using a rare earth anisotropic sintered magnet as a raw material, wherein the rare earth anisotropic sintered magnet is mechanically pulverized in an inert atmosphere, and the pulverized material is subjected to high vacuum. Alternatively, the method comprises a step of strain relief annealing at a temperature of 400 to 600 ° C. in an inert atmosphere and a holding time of 12 hours or more, and a step of kneading the strain relief annealed material and a binder to form a magnetic field. A method for producing an anisotropic rare earth bonded magnet.   The method for producing an anisotropic rare earth bonded magnet according to claim 4, wherein a wet molding method is used in the compression molding step of the magnetic field molding. 6. The method for producing an anisotropic rare earth bonded magnet according to claim 5, wherein, in the compression molding step of the magnetic field molding, two-stage press molding is performed in which a CIP step is added after the compression molding.