JP5906876B2 - Manufacturing method of RTB-based permanent magnet - Google Patents

Description

  The present invention relates to an RTB system permanent magnet having a porous structure manufactured by the HDDR method, and an RTB system manufactured by hot compressing the RTB system permanent magnet. The present invention relates to a method for manufacturing a high-density magnet.

R-T-B system sintered magnets (R is a rare earth element containing 50 atomic% or more of Nd and / or Pr, T is Fe, or Fe and Co), which is a typical high performance permanent magnet, is a ternary tetragonal crystal. It has a structure containing a compound R ₂ T ₁₄ B phase as a main phase, and exhibits excellent magnetic properties. In R-T-B permanent magnets, it is known that the coercive force is improved by reducing the crystal grain size of the R ₂ T ₁₄ B phase, which is the main phase. As a method for obtaining an RTB-based permanent magnet having an average crystal grain size of 1 μm or less, an HDDR (Hydrogenation-Disposition-Desorption-Recombination) processing method is known.

  “HDDR” means a process of sequentially performing hydrogenation and disproportionation, dehydrogenation and recombination. The known HDDR treatment is performed, for example, by holding an R-T-B alloy ingot or powder at a temperature of 500 ° C. to 1000 ° C. in a hydrogen atmosphere or a mixed atmosphere of a hydrogen gas and an inert gas. Alternatively, after hydrogen is occluded in the powder (hydrogen occlusion treatment), dehydrogenation treatment is performed at a temperature of 500 ° C. to 1000 ° C. until, for example, a vacuum atmosphere with a hydrogen pressure of 13 Pa or less, or an inert atmosphere with a hydrogen partial pressure of 13 Pa or less. And then cooled.

In the above treatment, the following reaction typically proceeds. That is, by the hydrogen storage treatment, hydrogenation and disproportionation reaction (both are referred to as “HD reaction”. Example of reaction formula: Nd ₂ Fe ₁₄ B + 2H ₂ → 2NdH ₂ + 12Fe + Fe ₂ B) progresses and is fine. An organization is formed. Next, dehydrogenation treatment causes dehydrogenation and recombination reaction (both are referred to as “DR reaction”. Example of reaction formula: 2NdH ₂ + 12Fe + Fe ₂ B → Nd ₂ Fe ₁₄ B + 2H ₂ ) An alloy containing the R ₂ Fe ₁₄ B phase is obtained.

  An RTB-based alloy powder (hereinafter referred to as HDDR magnetic powder) produced by performing the HDDR process has a large coercive force and exhibits magnetic anisotropy. A method for producing an RTB-based alloy powder by HDDR processing is disclosed in, for example, Patent Document 1 and Patent Document 2. According to the HDDR treatment, a permanent magnet powder having a very fine crystal grain size of 0.1 μm to 1 μm can be obtained.

  Furthermore, in recent years, an R-T-B alloy powder finely pulverized to an average particle size of less than 10 μm is molded to produce a green compact, and a porous material produced by subjecting the green compact to HDDR treatment. A bulk magnet (hereinafter referred to as a porous magnet) has been developed and disclosed in Patent Document 3. Since this porous magnet is subjected to HDDR treatment on fine powder having an average particle size of less than 10 μm, the HDDR reaction can proceed in a short time, and as a result, the HDDR reaction can proceed uniformly. Therefore, the squareness of the demagnetization curve is excellent. In Patent Document 3, in the HDDR process, it is desirable to perform the temperature rising process for the HD reaction in a vacuum or an inert atmosphere in order to suppress a decrease in magnetic characteristics due to difficulty in controlling the reaction rate at the time of temperature rising. It is described.

  Patent Document 4 discloses that the permanent magnet powder obtained by the HDDR process can be bulked by a hot molding method such as hot pressing.

In Patent Document 5, when magnet powder is obtained by HDDR treatment, a hydrogen atmosphere of 30 kPa (0.3 atm) or more and 100 kPa (1.0 atm) or less is required before performing HD treatment on the RTB-based alloy powder. Below, it is disclosed to hold at temperatures below 600 ° C. According to this method, hydrogen is contained in the R ₂ T ₁₄ B phase at a temperature at which no HD reaction occurs to obtain R ₂ Fe ₁₄ BH _x (x represents the amount of hydrogen), and then 20 kPa (0.2 atm). ) The temperature is raised to the HD reaction temperature in a hydrogen atmosphere of 60 kPa (0.6 atm) or less and maintained in that state. At this time, by performing hydrogenation and disproportionation, a permanent magnet powder having a high degree of anisotropy after the subsequent DR reaction is obtained.

Further, for example, Non-Patent Document 1 shows that the HDDR magnetic powder can be further increased in coercive force by mixing and heat-treating the HDDR magnetic powder and the Nd—Cu alloy powder. According to Non-Patent Document 1, the improvement in the coercive force of the HDDR magnetic powder is that when the heat treatment temperature is higher than the melting point of the Nd—Cu alloy, the melted Nd—Cu alloy diffuses between the R ₂ T ₁₄ B phase grains. This is because the magnetic coupling between crystal grains of the R ₂ T ₁₄ B phase is broken.

JP-A-1-132106 JP-A-2-4901 International Publication No. 2007/135981 JP-A-4-253304 JP 2001-76917 A

H. Sephri-Amin, T .; Ohkubo, T .; Nishiuchi, S .; Hirosawa, K .; Hono, Scripta Materialia vol. 63 pp. 1124-1127 (2010)

As described in Non-Patent Document 1, by mixing and heat-treating HDDR magnetic powder and Nd—Cu alloy powder, the Nd—Cu alloy diffuses into the R ₂ T ₁₄ B phase grain boundary, and the coercive force is improves. However, this magnetic powder has a problem that the squareness of the demagnetization curve is poor.

  Therefore, based on the background art described above, the present inventors diffuse an Nd—Cu alloy into a porous magnet with excellent squareness manufactured according to Patent Document 3, and have excellent squareness and coercive force. An attempt was made to make a magnet with high height. However, since a porous magnet is a bulk body, it is difficult to diffuse a rare earth alloy such as an Nd-Cu alloy to the inside of a large magnet, resulting in variations in magnetic properties inside and outside the magnet. There was a problem.

Patent Document 3 describes that another alloy may be mixed with the green compact before the HDDR treatment for the purpose of improving magnetic characteristics. For this reason, the present inventors molded a mixed powder of R—T—B alloy powder and Nd—Cu alloy powder in a magnetic field, and aligned the c-axis direction of the R ₂ T ₁₄ B phase in a predetermined direction. An attempt was made to subject the body to the HDDR process disclosed in Patent Document 3. However, the obtained porous magnet was greatly inferior in orientation and squareness as compared with the porous magnet not mixed with the Nd—Cu alloy powder.

  The present invention has been made to solve the above-mentioned problems, and the main object of the present invention is to show better squareness as compared with magnetic powder obtained by diffusing an Nd-Cu alloy in conventional HDDR magnetic powder, And it is providing the RTB type permanent magnet which has a high coercive force compared with the conventional porous magnet.

The manufacturing method of the RTB-based permanent magnet of the present invention is an RTB-based alloy powder having a 50% volume center particle size of 1 μm or more and less than 10 μm and containing an R ₂ T ₁₄ B phase (R is Nd And / or a rare earth element containing 50 atomic% or more of Pr, T is Fe, or Fe and Co) and an R ′ metal having a particle size of less than 75 μm (R ′ is one or more selected from Nd, Pr, Dy, and Tb) Or a step of preparing a mixed powder with a powder of an R′-M-based alloy (M is one or more selected from Al, Ga, Cu, Co, Ni, Cr, Fe, Si, Ge), and the mixed powder A step of forming a green compact by molding, a first heat treatment step of heat-treating the green compact in a hydrogen atmosphere at a temperature of 200 ° C. to 600 ° C., and after the first heat treatment step, the green compact The second heat that heat-treats the body in a hydrogen atmosphere at 650 ° C or higher and 1000 ° C or lower A first heat treatment step, comprising: a treatment step; and a third heat treatment step in which heat treatment is performed on the green compact in a vacuum of 650 ° C. to 1000 ° C. or in an inert atmosphere after the second heat treatment step. The temperature is raised from time to the start of the second heat treatment step in a vacuum or an inert atmosphere.

  In a preferred embodiment, the hydrogen partial pressure in the hydrogen atmosphere in the first heat treatment step is 10 kPa or more and 500 kPa or less.

  In a preferred embodiment, the time from the end of the first heat treatment step to the start of the second heat treatment step is 60 minutes or less.

  In a preferred embodiment, the hydrogen partial pressure in the hydrogen atmosphere in the second heat treatment step is 20 kPa or more and 500 kPa or less.

  In a preferred embodiment, the R ′ content in the R′-M alloy is 25 atomic% or more and less than 100 atomic%.

  In a preferred embodiment, a mixing ratio of the RTB-based alloy powder and the R ′ metal or R′-M-based alloy powder in the mixed powder is a weight ratio (RTB-based alloy). Powder): (R ′ or R′-M alloy powder) = m: 1 (5 ≦ m ≦ 100).

  In a preferred embodiment, the step of preparing the mixed powder includes the step of preparing the RTB-based alloy powder, the step of preparing the R ′ metal or R′-M-based alloy powder, Mixing the RTB-based alloy powder and the R ′ metal or the R′-M-based alloy powder.

  In a preferred embodiment, the step of preparing the mixed powder includes the step of preparing an RTB-based alloy and an R ′ metal or an R′-M-based alloy with a 50% volume center particle size of 1 μm to 10 μm. Crushing to powder.

  In a preferred embodiment, the step of preparing the mixed powder includes the step of occluding hydrogen in the R ′ metal or R′-M alloy powder, and then occluding the RTB alloy and the hydrogen. A step of pulverizing the mixture of the R ′ metal or the R′-M based alloy.

  In a preferred embodiment, the temperature of the heat treatment in the second heat treatment step and the third heat treatment step is 950 ° C. or lower.

  In a preferred embodiment, the green compact is held in a molded container during the first heat treatment step, the second heat treatment step, and the third heat treatment step.

  The manufacturing method of the RTB system high-density magnet of the present invention includes the steps of preparing an RTB system permanent magnet manufactured by any of the manufacturing methods described above, and hot compression molding. And increasing the density of the R-T-B permanent magnet.

  According to the present invention, a green compact obtained by molding a mixed powder of an RTB-based alloy powder having a 50% volume center particle size of 1 μm or more and less than 10 μm and an R ′ metal or R′-M alloy powder having a particle size of less than 75 μm. The body is first heat-treated in a hydrogen atmosphere of 200 ° C. or more and 600 ° C. or less. At this time, hydrogen can be occluded in the rare earth-rich phase and the R ′ metal or R′-M alloy in the RTB-based rare earth alloy. As a result, it is possible to manufacture a magnet having excellent magnetic properties by suppressing a decrease in squareness and orientation degree due to non-uniformity of reaction in the subsequent HDDR treatment.

It is a figure which shows the hot press apparatus which can be used suitably by embodiment of this invention. It is a graph which shows the relationship between temperature T1 of a _1st heat treatment process, and residual magnetic flux density _Br . It is a graph which shows the relationship between temperature T1 of a _1st heat treatment process, and coercive force _HcJ . It is a graph which shows the relationship between temperature T1 of a _1st heat treatment process, and orientation degree ( _Br / _Jmax ). It is a graph showing the relationship between the temperatures T ₁ and squareness ratio of the first heat-treatment step (H _k / H _cJ). It is a graph which shows the relationship between temperature T1 of a _1st heat treatment process, and maximum energy product ((BH) _max ). In an embodiment of the present invention, it is a diagram showing an electron microscope image showing the fracture surface of the samples produced in T ₁ = 300 ℃. It is a graph which shows the demagnetization curve of an Example and a comparative example. It is a graph which shows the demagnetization curve of a porous magnet and a high-density magnet. It is a reflected-electron image (1000 time) by the scanning electron microscope of the grinding | polishing surface of M71. It is a backscattered electron image (1000 times) of the polished surface of M76 by a scanning electron microscope. It is a backscattered electron image (1000 times) of the polished surface of M81 by a scanning electron microscope. It is a backscattered electron image (10000 time) with the scanning electron microscope of the grinding | polishing surface of M71. It is a backscattered electron image (10000 time) with the scanning electron microscope of the grinding | polishing surface of M76. It is a reflected-electron image (10000 time) with the scanning electron microscope of the grinding | polishing surface of M81. It is a backscattered electron image (10000 time) by the scanning electron microscope of the grinding | polishing surface of the sample of M96 S1. It is a backscattered electron image (10000 time) of the grinding | polishing surface of the sample of M96 S3 by the scanning electron microscope. It is a figure which shows the example of the shaping | molding container and press jig which can be used for preparation of a green compact.

  The inventors of the present invention have a degree of orientation and squareness of a magnet obtained by performing HDDR processing described in Patent Document 3 on a molded body of a mixed powder of an R-T-B alloy powder and an R′-M alloy powder. A detailed discussion was made on the cause of inferiority.

The c-axis that is the easy axis of magnetization of the R ₂ T ₁₄ B phase in the R-T-B magnet having magnetic anisotropy obtained by the HDDR process is the same as the c axis of the R ₂ T ₁₄ B phase before the HDDR process. It is known that the directions are almost the same. Thus, various considerations have been made on the mechanism for storing the orientation of the R ₂ T ₁₄ B phase. In the structure obtained after the HD treatment, there are typically RH ₂ phase, α-Fe phase, Fe ₂ B phase and the like. This structure is hereinafter referred to as “disproportionated structure”. In this organization, it is considered that there is a region where the direction of the c-axis of the R ₂ T ₁₄ B phase before HDDR processing is passed. This is considered to be the same for the porous magnet of Patent Document 3.

As described above, in Patent Document 3, it is difficult to control the reaction rate at the time of temperature rise in the HDDR process in which an R-T-B alloy powder is molded to produce a green compact and applied to the green compact. It describes that it is desirable to perform the temperature raising step for the HD reaction in a vacuum or in an inert atmosphere in order to suppress the deterioration of the magnetic characteristics due to the property. However, when the RTB-based alloy powder and the R′-M-based alloy powder are mixed and the molded body is heated in a vacuum or an inert atmosphere, the temperature at which the liquid phase is generated during the temperature rise is low. It was found that part or all of the R′-M alloy was dissolved. When the rare earth content of the liquid phase generated at that time R ₂ T ₁₄ B phase and greater than rare earth content of the liquid phase in equilibrium, thus dissolving the R ₂ T ₁₄ B phase to the liquid phase becomes equilibrium composition there is a possibility.

Thereafter, in the ordinary HD reaction in the prior art, both the R ₂ T ₁₄ B phase and the liquid phase react with hydrogen and decompose into RH ₂ phase, α-Fe phase, Fe ₂ B phase, etc. Form a chemical structure. However, when the above-mentioned RTB-based alloy powder and R′-M-based alloy powder are mixed and the molded green compact is subjected to HDDR treatment, the R ₂ T during the temperature rise at least in the liquid phase. _The structure formed by the reaction between the component in which the ₁₄ B phase is dissolved and hydrogen is generated in a direction irrelevant to the direction in which the c-axis directions of the R ₂ T ₁₄ B phase are aligned by molding in a magnetic field. The c-axis direction of the R ₂ T ₁₄ B phase recombined by the reaction is directed in a direction irrelevant to the direction in which the c-axis directions of the R ₂ T ₁₄ B phase are aligned by magnetic field molding, and as a whole, before HDDR processing. There is a possibility that the degree of orientation will be lower than in this state.

In addition, when the RH ₂ phase, α-Fe phase, and Fe ₂ B phase are decomposed and produced from any of the R ₂ T ₁₄ B phase and the liquid phase, the structure formed by the HD reaction becomes uneven. As a result, it is considered that the variation in coercive force is increased, and the squareness is deteriorated as compared with the case where the R′-M alloy powder is not mixed. Further, the element M is R ₂ T ₁₄ when the solid solution in the B-phase, vacuum or M element by diffusion from the liquid phase generated from R'-M alloy in the course of raising the temperature in an inert atmosphere R ₂ The solid solution in the vicinity of the surface of the T ₁₄ B phase and, as a result, the HDDR reaction is not uniform inside and outside the R ₂ T ₁₄ B phase, which may contribute to the deterioration of the squareness. .

  Deterioration of the degree of orientation and squareness caused by HDDR treatment of a green compact of a mixed powder of RTB-based alloy powder and R′-M-based alloy powder is caused by the temperature rise before the HD reaction as described above. The liquid phase produced by the dissolution of the R′-M alloy in the process is the main cause, and if this production can be suppressed, it is considered that the deterioration of the orientation degree and the squareness can be prevented. In order to solve this problem, the present inventors introduced a first heat treatment step in which heat treatment is performed at a temperature of 600 ° C. or less in a hydrogen atmosphere before the HD reaction, and the R—T—B system alloy is introduced before the HDDR reaction. R- having excellent orientation and squareness by suppressing the formation of the liquid phase by hydrogenating the rare earth-rich phase and / or R 'metal or R'-M alloy in the powder and then subjecting it to HDDR reaction. The inventors have found that a TB porous magnet can be obtained, and have completed the present invention.

  Hereinafter, preferred embodiments of the method for producing an R-T-B permanent magnet according to the present invention will be described in detail.

<Raw material alloy>
First, an R—T—B system alloy (raw material alloy) including an R ₂ T ₁₄ B phase, which is a hard magnetic phase, and a rare earth-rich phase as a main phase is prepared. Here, “R” is a rare earth element and contains Nd and / or Pr by 50 atomic% or more. The rare earth element R in this specification may contain yttrium (Y). T is Fe or Fe and Co. This RTB-based alloy (raw material alloy) preferably contains 50% or more of the R ₂ T ₁₄ B phase by volume. Most of the rare earth element R contained in the raw material alloy constitutes the R ₂ T ₁₄ B phase and the rare earth rich phase, but a part constitutes R ₂ O ₃ and other phases.

The composition ratio of the rare earth element R is preferably 10 atomic percent or more and 30 atomic percent or less, and more preferably 12 atomic percent or more and 17 atomic percent or less of the entire raw material alloy. Further, when the content is 12 atomic% or more and 14 atomic% or less, the mass of the rare earth-rich phase (non-magnetic) of 1 μm or more can be reduced in the structure after the HDDR treatment. Moreover, the grain growth of the R ₂ T ₁₄ B phase during HDDR treatment can be suppressed, and at the same time, the constituent ratio of the R ₂ T ₁₄ B phase can be increased. As a result, improvement in the squareness of H _cJ and demagnetization curve can be expected. Furthermore, it is possible to improve the magnetization when hot compression molding is performed. Moreover, the coercive force can be improved by setting a part of R to Dy and / or Tb.

  The composition ratio of B is preferably 3 atomic percent or more and 15 atomic percent or less, more preferably 5 atomic percent or more and 8 atomic percent or less, and further preferably 5.5 atomic percent or more and 7.5 atomic percent or less. A part of B may be substituted with C, but the amount of substitution is preferably 10 atomic% or less with respect to the amount of B before substitution.

  “T” occupies the remainder and is Fe or Co substituted for Fe and part of Fe. The amount of substitution is desirably 50 atomic% or less with respect to the total amount of T. Further, the total amount of Co with respect to the entire raw material alloy is preferably 20 atomic% or less, and more preferably 5 atomic% or less from the viewpoint of cost and the like. High magnetic properties can be obtained even when Co is not contained at all, but more stable magnetic properties can be obtained when Co of 0.5 atomic% or more is contained.

  In order to obtain effects such as improvement of magnetic characteristics, elements such as Al, Ti, V, Cr, Ga, Nb, Mo, In, Sn, Hf, Ta, W, Cu, Si, Zr, and Ni may be added as appropriate. Good. However, since an increase in the amount of addition causes a decrease in saturation magnetization in particular, the total amount is preferably 10 atomic% or less. The raw material alloy may contain inevitable impurities.

  The raw material alloy is preferably produced by a strip casting method that can reduce the amount of α-Fe phase that adversely affects magnetic properties, but can also be produced by a book mold method, a centrifugal casting method, an atomizing method, or the like. it can. For the purpose of homogenizing the structure of the raw material alloy, heat treatment may be performed on the raw material alloy before pulverization. Such heat treatment can be performed in a vacuum or inert gas atmosphere, typically at a temperature of 1000 ° C. or higher.

<Diffusion material>
An R ′ metal or an R′-M alloy is prepared as a diffusion material. These diffusing materials may be referred to as “diffusing metals”, but are collectively referred to as “diffusing materials” in this specification. Here, “R ′” is a rare earth element, and is at least one rare earth element selected from the group consisting of Nd, Pr, Dy, and Tb. “M” is at least one element selected from the group consisting of Al, Ga, Cu, Co, Ni, Cr, Fe, Si, and Ge. The R′-M alloy is decomposed into R ′ hydride (R′H _x ) and R′-M compounds (R′M, R′M _2, etc.) in the first heat treatment step described later. It is desirable to select “M” so that the melting point of the R′-M compound produced at this time is higher than the heat treatment temperature of the second heat treatment step (HD step) described later. The diffusing material may contain inevitable impurities.

  The composition ratio of the rare earth element R ′ in the R′-M alloy is preferably 25 atomic% or more and less than 100 atomic%, more preferably 30 atomic% or more and 80 atomic% or less, and 40 atomic% or more and 70 atoms or less. It is further desirable that it is not more than%.

  Alternatively, an R′-M alloy that has been occluded with hydrogen at a temperature of 600 ° C. or lower in a hydrogen atmosphere of 10 kPa or higher may be used. The R′-M alloy after hydrogen storage may be decomposed into a hydride of R ′ and an R′-M compound. In particular, when the composition ratio of R ′ is 80 atomic% or more, in the first heat treatment step of HDDR processing, which will be described later, the R′-M alloy expands in volume due to hydrogen storage, and cracks occur in the green compact. Therefore, it is desirable to use an R′-M alloy that has been previously occluded with hydrogen.

  The diffusing material can be produced by a known method such as a book mold method, a centrifugal casting method, an atomizing method, a strip casting method, or a liquid ultra-quenching method.

<Mixed powder>
Next, a mixed powder in which the raw material alloy and the diffusion material are mixed is prepared. At that time, the raw material alloy and the diffusing material may be separately pulverized and mixed, or the raw material alloy and diffusing material mixture may be pulverized.

  When the raw material alloy and the diffusion material are pulverized separately, the raw material alloy is first coarsely pulverized using a mechanical pulverization method such as a jaw crusher or a hydrogen storage pulverization method, and coarsely pulverized powder having a size of about 50 μm to 1000 μm Make it. The coarsely pulverized powder is finely pulverized by a jet mill or the like to produce a raw material alloy powder typically having a 50% volume center particle size of 1 μm or more and less than 10 μm.

The 50% volume center particle size (D ₅₀ ) can be measured by a gas flow dispersion type laser diffraction method. When the 50% volume center particle size is at a level where it can be clearly confirmed that it is within the desired range, the particle size of the arbitrarily extracted powder may be easily confirmed by observation with an electron microscope.

  On the other hand, the diffusing material is coarsely pulverized using a mechanical pulverization method, a hydrogen occlusion pulverization method, or the like to produce a diffusing material powder having a size of less than 75 μm, for example. When the diffusing material is pulverized, a solid lubricant and / or a liquid lubricant may be added for the purpose of improving the pulverization property. The size of the diffusing material powder may be classified by the method described in JIS Z 2510 using a sieve specified in JIS Z 8801-1, and adjusted to a desired particle size range. The particle diameter is determined by measuring by an air current dispersion type laser diffraction method or confirmed by an electron microscope.

  The produced raw material alloy powder and diffusing material powder are mixed by a known powder mixing method to obtain a mixed powder.

  From the viewpoint of handling, it is desirable that the 50% volume center particle size of the raw material alloy powder and the diffusing material powder is 1 μm or more, respectively. This is because when the 50% volume center particle size is less than 1 μm, the mixed powder easily reacts with oxygen in the air atmosphere, increasing the risk of heat generation and ignition due to oxidation. In order to make the handling easier, it is desirable to set the 50% volume center particle size to 3 μm or more. The 50% volume center particle size of the diffusing material powder is preferably 10 μm or more from the viewpoint of suppressing oxidation. From the viewpoint of improving the mechanical strength of the molded body, the desirable upper limit of the 50% volume center particle size of the raw material alloy powder is 9 μm, and the more desirable upper limit is 8 μm. From the viewpoint of the uniformity of the HDDR reaction, the particle size of the diffusing material powder is less than 75 μm.

  By separately pulverizing the raw material alloy and the diffusion material, the 50% volume center particle size of the raw material alloy powder can be set to 1 μm or more and less than 10 μm, and the 50% volume center particle size of the diffusion material powder can be set to 10 μm or more. Oxidation of a diffusing material that easily reacts with can be suppressed.

  When the mixture of the raw material alloy and the diffusing material is pulverized, first, the mixture of the raw material alloy and the diffusing material is roughly pulverized using a mechanical pulverization method such as a jaw crusher or a hydrogen storage pulverization method, and the size is 50 μm to A roughly pulverized powder of about 1000 μm is prepared. The coarsely pulverized powder is finely pulverized by a jet mill or the like to produce a mixed powder having a 50% volume center particle size of 1 μm or more and less than 10 μm. The raw material alloy and the diffusion material may be mixed as coarsely pulverized powder having a size of about 50 μm to 1000 μm, respectively, and the mixed coarsely pulverized powder may be finely pulverized.

  When the 50% volume center particle size of the mixed powder is less than 1 μm, the mixed powder easily reacts with oxygen in the air atmosphere, increasing the risk of heat generation and ignition due to oxidation. In order to make the handling easier, it is desirable to set the 50% volume center particle size to 3 μm or more. From the viewpoint of improving the mechanical strength of the green compact, a desirable upper limit of 50% volume center particle size is 9 μm, and a more desirable upper limit is 8 μm.

  By pulverizing the mixture of the raw material alloy and the diffusion material, a mixed powder in which the raw material alloy and the diffusion material are uniformly mixed can be easily produced.

The mixing ratio of the raw material alloy and the diffusing material is preferably (raw material alloy) :( diffusing material) = m: 1 (5 ≦ m ≦ 100) in weight ratio. When m is less than 5, the proportion of the diffusing material is excessively increased, leading to a decrease in the volume ratio of the main phase R ₂ T ₁₄ B phase, which may result in a decrease in residual magnetic flux density. . On the other hand, if m exceeds 100, the effect of adding the diffusing material may be hardly obtained.

  The total amount of rare earth elements R and R ′ in the mixed powder is preferably 10 atomic percent or more and 30 atomic percent or less, and more preferably 12 atomic percent or more and 17 atomic percent or less of the entire mixed powder. In addition, the total amount of rare earth elements R and R ′ in the mixed powder is more preferably 15 atomic% or less of the entire mixed powder because it is easy to remove from the mold after hot pressing.

<Green compact>
Next, the mixed powder is molded to produce a green compact. The step of molding the green compact is desirably performed in a magnetic field (such as a static magnetic field or a pulsed magnetic field) of 0.4 MA / m to 16 MA / m by applying a pressure of 10 MPa to 200 MPa. Molding can be performed by a known powder press apparatus. Compact density (compact density) when removed from the powder press device is 3.5g / cm ³ ~5.2g / cm ³ order.

Further, the compacting may be performed by, for example, filling a mixed powder in a container as shown in FIG. 18 or JP-A-7-153612 and applying a pressure of 0.05 MPa to 10 MPa. . In this case, the subsequent HDDR process is performed with the green compact in the container. By forming in a container, handling becomes easy even when the green compact density is low. By reducing the density of the green compact, internal stress generated by volume expansion accompanying hydrogen occlusion can be relieved in the green compact in subsequent HDDR processing, so that the occurrence of cracks can be suppressed. Compact density in this case is about ^{3.0g / cm 3 ~4.0g / cm 3} .

  You may perform said shaping | molding process, without applying a magnetic field. When magnetic field orientation is not performed, an isotropic porous magnet is finally obtained. However, in order to obtain higher magnetic characteristics, it is desirable to execute a molding process while performing magnetic field orientation and finally obtain an anisotropic porous magnet.

  The pulverizing step of the raw material alloy and the diffusion material and the compacting step of the green compact are desirably performed while suppressing the oxidation of the raw material alloy and the diffusing material. In order to suppress the oxidation of the raw material alloy and the diffusion material, it is desirable to perform each process and the handling between the processes in an inert atmosphere in which the oxygen amount is suppressed as much as possible. The amount of oxygen in the green compact before the DR treatment is preferably suppressed to 1% by mass or less, and more preferably to 0.6% by mass or less.

  In the present invention, the HDDR process is performed on the green compact obtained by compressing and molding the mixed powder. Inside the green compact, a gap through which hydrogen gas can move and diffuse exists between the powder particles with a sufficient size. Moreover, in this invention, since the raw material powder whose 50% volume center particle size is 1 micrometer or more and less than 10 micrometers is used, it is easy for hydrogen to move the whole in a powder particle. These HD and DR reactions can proceed in a short time. Thus, since the structure after HDDR is homogenized, it is possible to obtain an advantage that high magnetic properties, particularly good squareness can be obtained, and the time required for the HDDR process can be shortened.

<HDDR processing>
Next, the HDDR process is performed on the green compact obtained by the molding step. In the present embodiment, the HDDR process includes three steps of a first heat treatment step, a second heat treatment step, and a third heat treatment step.

The first heat treatment step is a step of heat-treating the green compact molded using the mixed powder in a hydrogen atmosphere at a temperature of 200 ° C. or higher and 600 ° C. or lower. In the first heat treatment step, but does not occur HD reaction R ₂ T ₁₄ B phase, hydrogen is occluded between the crystal lattice of the R ₂ T ₁₄ B phase. Further, the rare earth-rich phase existing between the crystal grains of the R ₂ T ₁₄ B phase is hydrogenated and exists mainly as a hydride of R. Further, the diffusing material is decomposed into R 'hydride and R'-M compound. Since the melting points of the hydrides of R and R ′ are higher than the heat treatment temperature in the second heat treatment step, the amount of liquid phase generated before the second heat treatment step can be reduced. Therefore, by performing the first heat treatment step, the liquid phase is generated before the second heat treatment step, reacts with the R ₂ T ₁₄ B phase, and the magnetic properties, particularly the degree of orientation and the squareness deteriorate. Suppress.

In the first heat treatment step, hydrogen is occluded between the crystal lattice of the R ₂ T ₁₄ B phase, that the volume of the R ₂ T ₁₄ B phase expands approximately 2%, the lattice constant determined from X-ray powder diffraction measurement Confirmed from. Therefore, depending on the size and shape of the green compact, there is a possibility that the green compact may crack due to internal stress caused by volume expansion. In order to suppress this crack, for example, the HDDR process may be performed using a restraining jig that suppresses the volume expansion of the green compact, such as a container hermetically sealed to allow hydrogen to pass through.

As an example, a case where an Nd ₉₀ Al ₁₀ alloy (atomic%) is used as the diffusion material will be specifically described.

When the raw material alloy and the Nd ₉₀ Al ₁₀ alloy are mixed and the first heat treatment step is not performed, that is, when the temperature is raised to the heat treatment temperature of the second heat treatment step in a vacuum or an inert atmosphere, the Nd ₉₀ Al ₁₀ alloy has Nd and Nd _{2 A} liquid phase is generated at 630 ° C. or higher which is the eutectic temperature of Al. Since this temperature is lower than the heat treatment temperature in the second heat treatment step, the generated liquid phase reacts with the R ₂ T ₁₄ B phase before the second heat treatment step. Sex worsens.

On the other hand, when the first heat treatment step was performed, it was confirmed by X-ray diffraction measurement that the Nd ₉₀ Al ₁₀ alloy was decomposed into NdH _x and NdAl ₂ . Since these melting points are both higher than the heat treatment temperature of the subsequent second heat treatment step, no liquid phase is generated below the heat treatment temperature of the second heat treatment step unless a dehydrogenation reaction occurs from NdH _x . Therefore, the deterioration of the degree of orientation and the squareness due to the liquid phase generation can be suppressed.

The heat treatment temperature of the first heat treatment step, the thus occurred HD reaction R ₂ T ₁₄ B phase, because the degree of orientation deteriorates the difficulty of reaction rate control, the temperature at which HD reaction R ₂ T ₁₄ B phase will occur You need to do the following:

When the hydrogen absorption behavior was investigated while raising the green compact of the RTB-based alloy powder in a hydrogen atmosphere of 100 kPa, it was confirmed that hydrogen was rapidly absorbed at 610 ° C to 700 ° C. Therefore, when the constituent phase was investigated by X-ray diffraction measurement after hydrogenating the green compact of the RTB-based alloy powder at 700 ° C., the R ₂ T ₁₄ B phase was disproportionated and the RH _x phase It was confirmed that it was decomposed into an α-Fe phase and an Fe ₂ B phase. Therefore, this hydrogen absorption is considered to be due to the HD reaction of the R ₂ T ₁₄ B phase. Further, when the constituent phase was investigated by X-ray diffraction measurement after hydrogenating the green compact of the RTB-based alloy powder at 600 ° C. lower than the reaction temperature, the HD reaction of the R ₂ T ₁₄ B phase was It was confirmed that the rare earth-rich phase was mainly the RH _x phase. Therefore, the heat treatment temperature in the first heat treatment step for converting the rare earth-rich phase to the rare earth hydride RH _x that is a high melting point compound without disproportionating the R ₂ T ₁₄ B phase is 600 ° C. or less.

  In order to improve the reaction rate of hydrogenation, the heat treatment temperature is 200 ° C. or higher, and preferably 400 ° C. or higher. Moreover, in order to fully advance hydrogenation, you may hold | maintain for a predetermined time, after heating up to the predetermined temperature of 600 degrees C or less, and it is desirable that the holding time is 120 minutes or less. Even if the heat treatment is carried out for more than 120 minutes, no further effect is seen and the productivity is deteriorated.

  Moreover, the hydrogen partial pressure of the atmosphere in the first heat treatment step is preferably 10 kPa or more. Moreover, if it is 50 kPa or more, since hydrogenation of a rare earth rich phase and a diffusion material will fully advance, it is more preferable. In addition, when the hydrogen partial pressure exceeds 500 kPa, a special apparatus is required for the treatment, and therefore, it is preferably 500 kPa or less. A more preferable hydrogen partial pressure is 150 kPa or less. When the hydrogen partial pressure exceeds 150 kPa, hydrogen occlusion occurs abruptly, and the green compact may crack due to volume expansion accompanying hydrogen occlusion.

Next, the atmosphere is switched to a vacuum (1.3 Pa or less) or an inert atmosphere, and the temperature is raised to the heat treatment temperature of the second heat treatment step. If hydrogen gas is present in the temperature-raising atmosphere, the HD reaction of the R ₂ T ₁₄ B phase proceeds, so that it is difficult to control the reaction rate, and as a result, the magnetic properties may be deteriorated. In the production of conventional HDDR magnetic powders (the average particle diameter of the raw material alloy powder is 50 μm to 10 mm) as in Reference 5, there is only a small part of the region disproportionated by the HD reaction caused by the presence of hydrogen gas. Under a high temperature increase rate, even if a certain amount of hydrogen is present, only a very small area of the surface is hydrogenated and disproportionated during the temperature increase, and the influence on the degree of orientation after HDDR treatment is not so much. It does not appear. On the other hand, in the production method of the present invention, a fine powder having a 50% volume center particle size of less than 10 μm is targeted, the surface area is more than 100 times larger than that of the conventional HDDR magnetic powder, and hydrogen exists in the atmosphere during temperature rise. The progress of the HD reaction caused by this is remarkable as compared with the production of conventional HDDR magnetic powder, and as a result, a decrease in the degree of orientation after the HDDR treatment becomes obvious.

In the present specification, an inert gas means a gas that does not react with rare earth elements such as argon and / or helium. When the temperature raising step is performed in a nitrogen atmosphere, the rare earth element and the nitrogen gas may react to generate a rare earth nitride (NdN ₃ or the like).

On the other hand, if the temperature rising time is too long, a dehydrogenation reaction of the hydride of R and R ′ generated in the first heat treatment step occurs, and as a result, a new liquid phase is generated, and R ₂ T ₁₄ which is the main phase. The temperature rise time (time from the end of the first heat treatment step to the start of the second heat treatment step) is 60 because it may react with the B phase and deteriorate the degree of orientation and squareness of the resulting magnet. It is desirable that the time be less than or equal to 30 minutes, more desirably 30 minutes or less, and even more desirably 10 minutes or less. In consideration of the time required for replacement of the atmospheric gas, the temperature rising capability of the apparatus, and the like, the temperature rising time is usually 1 minute or longer.

Next, the second heat treatment step to be performed is a step of obtaining a disproportionated structure by HD reaction of the R ₂ T ₁₄ B phase in a hydrogen atmosphere. At this time, the magnetic anisotropy of the finally obtained magnet can be increased by appropriately controlling the temperature and the hydrogen partial pressure in the second heat treatment step. At this time, the form of the diffusion material hydrogenated in the first heat treatment step does not change.

The temperature of the second heat treatment step is 650 ° C. or higher and 1000 ° C. or lower. If it is less than 650 degreeC, it will take time for disproportionation to fully advance. Further, when the temperature exceeds 1000 ° C., the disproportionated structure becomes coarse, and the texture of the R ₂ T ₁₄ B phase obtained by the subsequent third heat treatment step becomes coarse, resulting in a decrease in magnetic properties, particularly coercive force. From the viewpoint of suppressing grain growth, the temperature of the second treatment step is preferably set to 950 ° C. or lower, and more preferably set to 900 ° C. or lower.

The hydrogen partial pressure in the second heat treatment step is desirably 20 kPa or more. When the hydrogen partial pressure is less than 20 kPa, it takes too much time for the disproportionation of the R ₂ T ₁₄ B phase to proceed sufficiently, which may lead to a decrease in productivity. In addition, when the hydrogen partial pressure exceeds 500 kPa, a special apparatus is required for the treatment, and therefore, it is preferably 500 kPa or less. A more preferable hydrogen partial pressure is 150 kPa or less. When the hydrogen partial pressure exceeds 150 kPa, hydrogen occlusion occurs abruptly, and the green compact may crack due to volume expansion accompanying hydrogen occlusion.

The time required for the second heat treatment step is desirably 10 minutes or more and 5 hours or less. If it is less than 10 minutes, disproportionation of the R ₂ T ₁₄ B phase may not proceed sufficiently. Further, when the time exceeds 5 hours, the disproportionated structure becomes coarse, and the recombination structure after the third heat treatment step becomes coarse, which may cause a decrease in magnetic properties, particularly coercive force. More desirably, it is 15 minutes or more and 2 hours or less.

Next, in the third heat treatment step to be performed, a hydride of R and R ′ is dehydrogenated by holding at 650 ° C. or more and 1000 ° C. or less in a vacuum (1.3 Pa or less) or an inert atmosphere, and R ₂ T ₁₄ Phase B is generated by a recombination reaction. In addition, the process of a dehydrogenation reaction can also be controlled by changing the atmosphere of a 3rd heat treatment process in steps. For example, after controlling the absolute pressure or the hydrogen partial pressure in an atmosphere of 1 kPa to 20 kPa for a time of 5 minutes or more and 300 minutes or less, the H _cJ is controlled by holding at 650 ° C. or more and 1000 ° C. or less in a vacuum or an inert atmosphere. be able to.

The R ₂ T ₁₄ B phase generated in the third heat treatment step typically forms a texture having an average crystal grain size of 0.1 μm or more and 1.0 μm or less. Further, the dehydrogenation reaction of hydride was used in recombination R and R 'occur, the liquid phase rich in R is generated, the grain boundary phase to the grain boundary of the R ₂ T ₁₄ B phase (rare earth rich Phase) is formed and coercive force is developed. In this case, to dissolve the R'-M compound in a liquid phase, by the M element is diffused into the grain boundaries of the R ₂ T ₁₄ B Aiuchi and / or R ₂ T ₁₄ B phase, improving the coercive force To do. Furthermore, a sintering reaction also occurs at the same time, resulting in a porous permanent magnet. From the viewpoint of suppressing grain growth, the temperature of the third treatment step is preferably set to 950 ° C. or lower, and may be set to 900 ° C. or lower.

The temperature of the third heat treatment step is 650 ° C. or higher and 1000 ° C. or lower. If it is less than 650 degreeC, dehydrogenation reaction does not occur substantially. Further, when the temperature exceeds 1000 ° C., the recombined R ₂ T ₁₄ B phase grows in crystal grains, leading to a decrease in magnetic characteristics, particularly coercive force. The time required for the third heat treatment step is preferably 5 minutes or more and 10 hours or less, and more preferably 10 minutes or more and 2 hours or less.

<Porous magnet>
By the HDDR treatment, a porous magnet having a density of 3.5 g / cm ³ or more and 7.0 g / cm ³ or less is obtained. In this porous magnet, the easy magnetization axis of the powder particles is oriented in a predetermined direction before the second heat treatment step, so that the fine Nd ₂ Fe ₁₄ B type crystal phase in the texture formed by the HDDR process is obtained. Can be oriented in a predetermined direction throughout the magnet.

In this porous magnet, there is a void having a major axis of about 10 μm communicating with the three-dimensional network between the powder particles bonded to each other in the HDDR processing step. The individual powder particles constituting the green compact are combined with the adjacent powder particles by the HDDR process to form a three-dimensional structure exhibiting rigidity, and fine Nd ₂ Fe ₁₄ B in each powder particle. A texture of the type crystal phase is formed.

The density of the R-T-B type porous magnet of the present invention is 3.5 g / cm ³ or more and 7.0 g / cm ³ or less, but the particles are bonded to each other even when there are gaps between the powder particles. Demonstrate sufficient mechanical strength and excellent magnetic properties.

  In this embodiment, since the HDDR process is performed on the green compact after the molding process, the powder molding is not performed after the HDDR process. For this reason, it does not occur after HDDR processing that the magnetic powder is pulverized by pressurization for molding, and high magnetic characteristics can be obtained as compared with a bonded magnet that compresses HDDR powder.

<Hot compression molding of porous magnet>
The porous magnet obtained by the above method can be used as a bulk permanent magnet as it is, but it is further densified by using hot compression molding such as a hot press method, and the average crystal A high-density magnet having a texture of R ₂ T ₁₄ B phase with a particle size of 0.1 μm or more and 1 μm or less can be obtained. An example of a specific embodiment will be shown below for densification by hot compression molding. Hot compression on the porous magnet can be performed using a known hot compression technique. For example, hot compression molding such as hot pressing, SPS (spark plasma sintering), HIP, and hot rolling can be performed. Especially, the hot press and SPS which are easy to obtain a desired shape can be used suitably. Hereinafter, a procedure for performing hot pressing will be described.

  In the present embodiment, a hot press apparatus having the configuration shown in FIG. 1 is used. This apparatus includes a die (die) 27 having an opening in the center, an upper punch 28a and a lower punch 28b for pressurizing a porous magnet, and drive units 30a and 30b for raising and lowering these punches 28a and 28b. I have.

  A porous magnet (indicated by reference numeral “10” in FIG. 1) produced by the method described above is loaded into the mold 27 shown in FIG. At this time, it is desirable to perform loading so that the orientation direction and the pressing direction coincide. The mold 27 and the punches 28a and 28b are formed of a material that can withstand the heating temperature and the applied pressure in the atmosphere gas to be used. As such a material, carbon or cemented carbide such as tungsten carbide is desirable. In addition, the anisotropy can be increased by setting the outer dimension of the porous magnet 10 to be smaller than the opening dimension of the mold 27. Next, the mold 27 loaded with the porous magnet 10 is set in a hot press apparatus. The hot press apparatus preferably includes a chamber 26 that can be controlled to a vacuum (1.3 Pa or less) or an inert atmosphere. In the chamber 26, for example, a heating device such as a carbon heater by resistance heating and a cylinder for pressurizing and compressing the porous magnet are provided.

  After filling the chamber 26 with a vacuum or an inert gas atmosphere, the mold 27 is heated by a heating device, and the temperature of the porous magnet 10 loaded in the mold 27 is increased to 600 ° C. to 900 ° C., 9.8 The porous magnet 10 is pressurized with a pressure P of ˜294 MPa. It is desirable that the pressurization to the porous magnet 10 is started after the temperature of the mold 27 reaches a set level. If the mold temperature is not sufficiently high, the porous magnet may be cracked during pressurization, or the degree of orientation of the resulting high-density magnet may deteriorate. While maintaining the pressure at 600 ° C. to 900 ° C. for 10 minutes or more while cooling, it is cooled. After the magnet, which has been densified by heat compression, is cooled to a low temperature (about 100 ° C. or less) that does not oxidize due to contact with the atmosphere, the magnet of this embodiment is taken out of the chamber. Thus, the RTB-based high density magnet of the present embodiment can be obtained from the porous magnet.

  The density of the magnet thus obtained reaches 90% or more of the true density. In addition, according to the present embodiment, in the final crystal phase texture, the crystal grains in which the ratio b / a of the shortest particle diameter a to the longest particle diameter b of each crystal grain is less than 2 are 50 of the total crystal grains. It exists by volume% or more. In this respect, the magnet of the present embodiment is greatly different from the conventional anisotropic bulk magnet by hot plastic working described in, for example, Japanese Patent Laid-Open No. 02-39503. In such a crystal structure of a magnet, flat crystal grains in which the ratio b / a between the shortest particle diameter a and the longest particle diameter b exceeds 2 are dominant.

  A raw material alloy having the composition shown in Table 1 below and a diffusion material having the composition shown in Table 2 were prepared, and a porous magnet was produced by the manufacturing method of the above-described embodiment. Hereinafter, a method for producing a porous magnet in this experimental example will be described.

(Experimental example 1)
First, a rapidly solidified alloy having the composition shown in Table 1 was produced by strip casting. The obtained rapidly solidified alloy was coarsely pulverized into a powder having a particle size of 425 μm or less by the hydrogen occlusion / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a 50% volume center particle size of 4.2 to 4.5 μm. A fine powder was obtained. The 50% volume center particle size was measured by a laser diffraction particle size distribution measuring device (manufactured by Sympatec, HEROS / RODOS, hereinafter all measured by the same device).

  Moreover, a rapidly solidified alloy having the composition shown in Table 2 was produced by a melt spinning method. Specifically, the alloy was melted in a quartz nozzle having an orifice diameter of 0.8 mmφ and sprayed onto a copper roll rotating at a roll peripheral speed of 20 m / s to obtain a ribbon-like alloy. This alloy was pulverized by mechanical pulverization and classified using a sieve having an opening of 25 μm to obtain a diffusing material powder having a size of 25 μm or less. In addition, it confirmed by observation with an electron microscope that the particle size of the obtained diffusing material powder was clearly 1 μm or more.

  The obtained raw material alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 3 using an agate mortar to obtain mixed powders M1 to M5.

Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 76 MPa in a direction parallel to the magnetic field in a magnetic field of 0.64 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

Next, HDDR processing was performed on the green compact. Specifically, the green compact is heated to a temperature T ₁ = 200, 250, 300, 400, 600, 700 (° C.) at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa for 30 minutes. The first heat treatment step was performed. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

When the density was calculated from the size and weight of the prepared sample, it was 5.8 to 6.6 g / cm ³ .

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). Figure 2 is temperatures T ₁ and remanence B _r of the first heat-treatment step, Figure 3 is T ₁ and the coercivity H _cJ, 4 T ₁ and the degree of orientation (B _r / J _max), 5 T ₁ And the squareness ratio (H _k / H _cJ ), FIG. 6 shows the relationship between T ₁ and the maximum energy product ((BH) _max ). Note that J _max is the maximum measured value of the magnetization of the sample when an external magnetic field is applied up to 1.6 MA / m in the magnetization direction of the magnetized sample. The larger the B _r / J _max is, the better the degree of orientation is. ing. H _k is the value of the external magnetic field when the magnetization is B _r × 0.9 on the demagnetization curve, and the _squareness of the demagnetization curve is more excellent as H _k / H _cJ is larger.

  2 to 6 also show the result without the first heat treatment step as a comparative example. The sample without the first heat treatment step was heated up to 840 ° C./min in a 100 kPa argon flow at 14 ° C./min, and then the atmosphere was switched to a 100 kPa hydrogen flow and held at 840 ° C. for 2 hours. A second heat treatment step was performed, and then the atmosphere was maintained at 840 ° C. for 1 hour in a 100 kPa argon flow to perform a third heat treatment step, and then cooled to room temperature in a 100 kPa argon flow.

4 and 5 As is apparent, the sample T ₁ is prepared in 200 ° C. or higher 600 ° C. or less, compared to the sample without first heat-treatment step, is excellent in orientation and squareness, T ₁ However, the sample produced at 400 ° C. or higher and 600 ° C. or lower is particularly excellent in the degree of orientation and squareness. In the sample prepared at T ₁ of 700 ° C., the HD reaction of the R ₂ T ₁₄ B phase proceeds in the process of raising the temperature to 700 ° C. in a hydrogen stream, so both the degree of orientation and the squareness are small. The value is shown.

FIG. 7 is an electron micrograph showing a fracture surface of the sample produced at T ₁ = 300 ° C. in the above production method for the mixed powder M2. The relatively large gaps A of about 25 μm scattered in FIG. 7 are considered to be places where the diffusing material was present before the HDDR process. That is, it is considered that the diffusing material diffused between the crystal grains of the fine R ₂ T ₁₄ B phase generated after the DR treatment, thereby obtaining a large coercive force.

As an example of the demagnetization curve of the prepared sample, FIG. 8 shows the demagnetization curve of the sample prepared at T ₁ = 600 ° C. in the above preparation method for the mixed powder M3. As a comparative example, a demagnetization curve of a sample without the first heat treatment step manufactured by the above manufacturing method is also shown. As is clear from FIG. 8, the demagnetization curve of the sample of the comparative example has very poor squareness, but a magnet having excellent squareness of the demagnetization curve is produced by performing the first heat treatment step of the present invention. can do.

(Experimental example 2)
Rapidly solidified alloys of the raw material alloys B1 and B2 were produced by strip casting. A coarsely pulverized powder having a particle size of 425 μm or less was obtained from the obtained rapidly solidified alloy by a hydrogen storage and collapse method. In addition, quenching alloys of diffusion materials D1 and D4 were produced by a melt spinning method. Specifically, the alloy was melted in a quartz nozzle having an orifice diameter of 0.8 mmφ and sprayed onto a copper roll rotating at a roll peripheral speed of 20 m / s to obtain a ribbon-like alloy. This alloy was pulverized by mechanical pulverization to obtain a coarsely pulverized powder having a particle size of 425 μm or less. Moreover, the alloy of the diffusing material D7 was melted by high frequency heating and then solidified to obtain an ingot. The obtained ingot was pulverized to 425 μm or less by mechanical pulverization to obtain a diffusing material coarse powder.

  After mixing the raw material alloy coarse powder and the diffusing material coarse powder at the mixing ratio shown in Table 4, the mixed powder M6 having a 50% volume center particle size of 4.5 to 6.8 μm is pulverized by the jet mill method. ~ M8 was obtained.

The obtained mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 76 MPa in a direction parallel to the magnetic field in a magnetic field of 0.64 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

  The green compact of the obtained mixed powder was subjected to HDDR treatment. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). Incidentally, J _max is the maximum measurement value of the magnetization of the sample when an external magnetic field is applied to the magnetizing direction of the sample magnetized to 1.6 MA / m, H _k is the magnetization at demagnetization curve B _r This is the value of the external magnetic field when × 0.9.

  Table 5 shows the measurement results. As can be seen from the table, even when the raw material alloy and the diffusing material coarse powder were mixed and then finely pulverized to produce a mixed powder, it was found that good magnetic properties could be obtained.

(Experimental example 3)
The HDDR process was performed on the green compact of the mixed powder M2 described in Experimental Example 1 and the green compact of the mixed powder M6-8 described in Experimental Example 2. Specifically, the heating rate is 14 ° C./min up to 600 ° C. in a flowing atmosphere of hydrogen / argon mixed gas in which the total pressure is 100 kPa and the hydrogen partial pressure is P ₁ = 0, 10, 20, 50, 100 kPa. The temperature was raised and maintained for 30 minutes, and the first heat treatment step was performed. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)).

  Table 6 shows the measurement results. As can be seen from Table 6, good magnetic properties can be obtained when the hydrogen partial pressure in the gas flowing in the first heat treatment step is 10 kPa or more.

(Experimental example 4)
The HDDR process was performed on the green compact of the mixed powder M2 described in Experimental Example 1 and the green compact of the mixed powder M6-8 described in Experimental Example 2. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to the atmospheric gas flow shown in Table 7 (Argon gas flow with a total pressure of 100 kPa, or a hydrogen / argon mixed gas flow with a total pressure of 100 kPa and a hydrogen partial pressure of 50 kPa), 840 The temperature was raised to 14 ° C. at a rate of 14 ° C./min. Next, after the atmosphere was switched to a hydrogen flow with a total pressure of 100 kPa, the second heat treatment step was performed while maintaining 840 ° C. for 2 hours. In addition, in the case where the atmosphere from the end of the first heat treatment step to the start of the second heat treatment step is performed with a hydrogen / argon mixed gas flow with a hydrogen partial pressure of 50 kPa, the sample in which the second heat treatment step is performed as it is Also made. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, the sample was cooled to room temperature in a 100 kPa argon stream to prepare a sample.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)).

Table 7 shows the measurement results. As can be seen from Table 7, good magnetic properties can be obtained when the hydrogen partial pressure P ₂ of the gas flowing from the end of the first heat treatment step to the start of the second heat treatment step is 0 kPa, but when P ₂ is 50 kPa, Degree of orientation and squareness deteriorate. This is presumably because part of the HD reaction occurred during the temperature increase from the end of the first heat treatment step to the start of the second heat treatment step.

  Here, P2 is the hydrogen partial pressure of gas flowing from the end of the first heat treatment step to the start of the second heat treatment step, and P3 is the hydrogen partial pressure in the second heat treatment step.

(Experimental example 5)
The HDDR process was performed on the green compact of the mixed powder M2 described in Experimental Example 1 and the green compact of the mixed powder M6-8 described in Experimental Example 2. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for t ₁ in Table 8 to perform the first heat treatment step. Thereafter, the atmosphere was switched to an argon flow of 100 kPa, and then the temperature was raised to 840 ° C. at a rate of temperature rise of r ₂ in Table 8. Next, after the atmosphere was switched to a hydrogen flow of 100 kPa, the second heat treatment step was performed while maintaining 840 ° C. for 2 hours. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)).

  Table 8 shows the measurement results. As can be seen from Table 8, good magnetic properties can be obtained under any conditions.

(Experimental example 6)
A rapidly solidified alloy of the raw material alloy B2 was produced by strip casting. The prepared rapidly solidified alloy was pulverized in the same manner as described in Experimental Example 1 to produce a fine powder having a 50% volume center particle size of 4.2 to 4.5 μm.

  Further, powders having compositions of the diffusing materials D2, D3, D4, D5, D6, D7, D8, D9, D10, and D11 were produced in the same manner as described in Experimental Example 1. It was confirmed by electron microscope observation that the particle size of the obtained diffusing material powder was clearly 1 μm or more.

Using the produced raw material alloy powder and the diffusing material powder, the mixed powders M9 to M31 shown in Table 9 were obtained by mixing in the same manner as described in Experimental Example 1. A green compact was produced by the same method as described in Experimental Example 1. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

  The HDDR process was performed with respect to the produced green compact by the method similar to the method demonstrated in Experimental example 1. FIG. Further, as a comparative example, a green compact made only of the raw material alloy B2 was produced, and the same HDDR treatment was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)).

Table 10 shows the measurement results. As can be seen from the table, it can be seen that any sample mixed with the diffusing material has a higher coercive force than the sample not mixed with the diffusing material. Further, the coercive force tends to increase as the mixing amount of the diffusing material increases. In particular, the coercive force diffusing material composition _{Nd 80 Al 20 ~Nd 50 Al 50} , also the degree of orientation and squareness ratio is diffusion material composition showed good results in _{Nd 50 Al 50 ~Nd 35 Al 65} .

(Experimental example 7)
A rapidly solidified alloy of the raw material alloy B2 was produced by strip casting. The obtained rapidly solidified alloy was coarsely pulverized into a powder having a particle size of 425 μm or less by the hydrogen occlusion / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a 50% volume center particle size of 4.2 to 4.5 μm. A fine powder was obtained.

  Further, a rapidly solidified alloy of the diffusion material D7 was produced by a melt spinning method. Specifically, the alloy was melted in a quartz nozzle having an orifice diameter of 0.8 mmφ and sprayed onto a copper roll rotating at a roll peripheral speed of 20 m / s to obtain a ribbon-like alloy. This alloy was pulverized by mechanical pulverization and classified into the diffusing material particle size shown in Table 11 using a sieve to obtain diffusing material powder. The particle size of the obtained diffusing material powder was clearly confirmed to be 1 μm or more by observation with an electron microscope.

  The obtained raw material alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 11 using an agate mortar to obtain a mixed powder.

Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 76 MPa in a direction parallel to the magnetic field in a magnetic field of 0.8 Tesla (T). The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

  The HDDR process was performed with respect to the produced green compact. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

  The produced sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Giken)). Table 12 shows the measurement results. As can be seen from the table, the magnetic properties of the various diffusion materials were all good.

(Experimental example 8)
A rapidly solidified alloy of the raw material alloy B2 was produced by strip casting. The prepared rapidly solidified alloy was pulverized in the same manner as described in Experimental Example 1 to produce a fine powder having a 50% volume center particle size of 4.2 to 4.5 μm.

  Further, the rapidly solidified alloy having the composition of the diffusing material D12, D13, D14, D15, D16, D17, D19, D20, D21, D22, D23, D24, D25, D26, D27 is the same as the method described in Experimental Example 1. It was produced by the method. It was confirmed by electron microscope observation that the particle size of the produced diffusion material powder was clearly 1 μm or more.

  Using the produced raw material alloy powder and the diffusing material powder, a green compact of the mixed powder shown in Table 13 was produced in the same manner as described in Experimental Example 1.

The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

  The obtained green compact was subjected to HDDR treatment. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). J _max is the maximum measured value of the magnetization of the sample when an external magnetic field is applied up to 1.6 MA / m in the magnetization direction of the magnetized sample, and H _k is the magnetization B _r × 0.9. Is the value of the external magnetic field.

  Table 13 shows the measurement results. As can be seen from the table, good magnetic properties were shown for various diffusion materials.

(Experimental example 9)
A rapidly solidified alloy of the raw material alloy B2 was produced by strip casting. The obtained rapidly solidified alloy was coarsely pulverized into a powder having a particle size of 425 μm or less by the hydrogen occlusion / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a 50% volume center particle size of 4.2 to 4.5 μm. A fine powder was obtained.

  In addition, rapidly solidified alloys having compositions of the diffusing materials D1, D2, D5, and D18 were produced by a melt spinning method. Specifically, the alloy was melted in a quartz nozzle having an orifice diameter of 0.8 mmφ and sprayed onto a copper roll rotating at a roll peripheral speed of 20 m / s to obtain a ribbon-like alloy. This alloy was heated to 400 ° C. in a hydrogen gas stream, occluded with hydrogen, pulverized by mechanical pulverization, and classified using a mesh having an opening of 25 μm to obtain a diffusing material powder having a size of 25 μm or less. It was. In addition, it confirmed by observation with an electron microscope that the particle size of the obtained diffusing material powder was clearly 1 μm or more.

  The obtained raw material alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 14 using an agate mortar to obtain a mixed powder.

Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 76 MPa in a direction parallel to the magnetic field in a magnetic field of 0.64 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

  The HDDR process was performed with respect to the produced green compact. Specifically, the green compact was heated to 600 ° C. at a heating rate of 14 ° C./min in a hydrogen gas of 100 kPa and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to 100 kPa argon flow, the temperature was raised to 840 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to 100 kPa hydrogen flow, and then maintained at 840 ° C. for 2 hours. The second heat treatment step was performed. Then, it hold | maintained for 1 hour in the argon air pressure-reduced to 5.3 kPa with 840 degreeC, and performed the 3rd heat treatment process. Next, it was cooled to room temperature in a 100 kPa argon stream to obtain a sample.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)).

  Table 14 shows the measurement results. As can be seen from the table, good magnetic properties were exhibited even when a diffusion material storing hydrogen was mixed.

(Experimental example 10)
A green compact of mixed powder M4 was produced by the same method as described in Experimental Example 1, and the green compact was subjected to HDDR treatment. Specifically, the green compact is heated up to 420 ° C. at a heating rate of 14 ° C./min in a 100 kPa hydrogen flow to perform a first heat treatment step, and the atmosphere is maintained at 420 ° C. with an argon atmosphere of 100 kPa. It switched to flowing air and heated up to 840 degreeC with the temperature increase rate of 14 degrees C / min. Thereafter, the atmosphere was switched to a hydrogen flow of 100 kPa, and then the second heat treatment step was performed while maintaining 840 ° C. for 2 hours. Then, it maintained at 840 degreeC in 100 kPa (atmospheric pressure) argon stream for 1 hour, and after performing the 3rd heat treatment process, it cooled to room temperature and obtained the porous magnet.

Further, the obtained porous magnet was heated to 750 ° C. in a cemented carbide mold and subjected to hot compression treatment (hot press) for 10 minutes at a pressure of 196 MPa, whereby a density of 7.21 g / A high density magnet of cm ³ was obtained.

  The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The obtained results are shown in FIG. As can be seen from the figure, good magnetic properties can be obtained for both the porous magnet and the high-density magnet. It was also confirmed that the squareness of the demagnetization curve was improved while the coercive force hardly changed by hot pressing.

(Experimental example 11)
First, a rapidly solidified alloy having the composition shown in Table 15 was produced by strip casting. The obtained rapidly solidified alloy was coarsely pulverized into a powder having a particle size of 425 μm or less by the hydrogen occlusion / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a 50% volume center particle size of 4.2 to 4.5 μm. A fine powder was prepared.

  Further, a rapidly solidified alloy having the composition of the diffusing material D4 was produced by a melt spinning method. Specifically, the alloy was melted in a quartz nozzle having an orifice diameter of 0.8 mmφ and sprayed onto a copper roll rotating at a roll peripheral speed of 20 m / s to produce a ribbon-like alloy. This alloy was heated to 400 ° C. in a hydrogen stream and occluded with hydrogen, then pulverized by mechanical pulverization, and classified using a mesh having a mesh size of 53 μm to produce a diffusing material powder having a size of 53 μm or less. . In addition, it confirmed by observation with an electron microscope that the particle diameter of the produced diffusing material powder was clearly 1 μm or more.

  The produced raw material alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 16 using an agate mortar to produce a mixed powder.

Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 32 MPa in a direction perpendicular to the magnetic field in a magnetic field of 1.2 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to a temperature T ₁ = 600 ° C. at a temperature increase rate of 14 ° C./min in a 100 kPa hydrogen stream and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to a 100 kPa argon flow, the temperature was increased to 860 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then maintained at 860 ° C. for 120 minutes. The second heat treatment step was performed. Then, it hold | maintained for 60 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and performed the 3rd heat treatment process. Next, the sample was cooled to room temperature in a 100 kPa argon stream to prepare a sample.

When the density was calculated from the size and weight of the prepared sample, it was 5.8 to 6.7 g / cm ³ .

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The results are shown in Table 17. As can be seen from Table 17, all the samples have good magnetic properties. In particular, a comparison of samples using the material alloy B6, B7, B8, as a rare earth content of the raw material alloy is less B _R7.6 (true density assuming 7.6 g / cm ³ was calculated from the B _r and density Value) and squareness are improved. 10 to 12 show reflected electron images (1000 times) of the polished surfaces of M71, M76, and M81 using a scanning electron microscope (manufactured by Hitachi High-Technologies: S-800). As the amount of rare earth of the raw material alloy decreases from M71 to M81, a rare earth-rich phase that shows a bright contrast (a rare earth-rich phase includes a metal phase that shows a relatively bright contrast and an oxide phase that shows a dark contrast) It can be seen that the lump of 1 μm or more is present. 13 to 15 are backscattered electron images (10000 times magnification) of the polished surfaces of M71, M76, and M81 whose magnifications are higher than those of FIGS. 10 to 12 by a scanning electron microscope (manufactured by Hitachi High-Technologies: S-4300). ). From M71 to M81, it can be seen that the crystal grain size of the R ₂ T ₁₄ B phase, which is shown in dark contrast, decreases as the amount of rare earth in the raw material alloy decreases.

(Experimental example 12)
First, the raw material alloy powders of the raw material alloys B6 to B10 prepared in Experimental Example 11 and the diffusing material powder of the diffusing material D4 were mixed at a mixing ratio shown in Table 18 using an agate mortar to prepare a mixed powder.

Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 32 MPa in a direction perpendicular to the magnetic field in a magnetic field of 1.2 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to a temperature T ₁ = 600 ° C. at a temperature increase rate of 14 ° C./min in a 100 kPa hydrogen stream and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to a 100 kPa argon flow, the temperature was increased to 860 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then maintained at 860 ° C. for 120 minutes. The second heat treatment step was performed. Thereafter, while maintaining the temperature at 860 ° C., as shown in Table 19, the hydrogen partial pressure in the furnace was maintained for 60 minutes while adjusting the pressure to 2.0 to 10.0 kPa, and then the argon flow reduced to 5.3 kPa while maintaining the temperature at 860 ° C. Holding in the air for 60 minutes, a third heat treatment step was performed. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced.

When the density was calculated from the size and weight of the prepared sample, it was 6.1 to 6.7 g / cm ³ .

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The results are shown in Table 20. As can be seen from Table 20, all the samples have good magnetic properties. In particular, it can be seen that high H _cJ is obtained when treatment is performed at a hydrogen partial pressure of 2 kPa to 6 kPa in the first stage of the third heat treatment step as in the conditions S2 to S5. FIGS. 16 and 17 show reflected electron images of the polished surfaces of the M96 S1 and S3 samples by a scanning electron microscope (manufactured by JEOL: JSM-7001FA). In the case of S3, it can be seen that the fine Fe phase present in the R ₂ T ₁₄ B phase is reduced compared to S1.

(Experimental example 13)
Mixed powders similar to the mixed powders M92 to M96 produced in Experimental Example 12 were produced. Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 32 MPa in a direction perpendicular to the magnetic field in a magnetic field of 1.2 MA / m. The density of the green compact was calculated to be 4.2 to 4.5 g / cm ³ based on the size and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to a temperature T ₁ = 600 ° C. at a temperature increase rate of 14 ° C./min in a 100 kPa hydrogen stream and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to a 100 kPa argon flow, the temperature was increased to 860 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then maintained at 860 ° C. for 120 minutes. The second heat treatment step was performed. Thereafter, while maintaining the temperature at 860 ° C., as shown in Table 21, the hydrogen partial pressure in the furnace was maintained at 15 to 180 minutes while adjusting the hydrogen partial pressure to 4.0 kPa, and then reduced to 5.3 kPa at 860 ° C. The mixture was held for 60 minutes, and a third heat treatment step was performed. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced.

When the density was calculated from the size and weight of the prepared sample, it was 6.0 to 6.4 g / cm ³ .

The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The results are shown in Table 22. As can be seen from Table 22, good magnetic properties were obtained for all the samples. In particular, it can be seen that high H _cJ is obtained when treatment is performed for 45 to 120 minutes in the first stage of the third heat treatment step as in conditions S8 to S10.

(Experimental example 14)
A mixed powder similar to the mixed powder M80 prepared in Experimental Example 11 was prepared. Next, this mixed powder was filled in a mold of a press machine, and a green compact was produced by applying a pressure of 32 MPa in a direction perpendicular to the magnetic field in a magnetic field of 1.2 MA / m. The density of the green compact was 4.3 g / cm ³ when calculated based on the dimensions and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to a temperature T ₁ = 600 ° C. at a temperature increase rate of 14 ° C./min in a 100 kPa hydrogen stream and held for 30 minutes to perform the first heat treatment step. Then, after switching the atmosphere to a 100 kPa argon flow, the temperature was increased to 860 ° C. at a rate of 14 ° C./min, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then maintained at 860 ° C. for 2 hours. The second heat treatment step was performed. Then, the hydrogen partial pressure in the furnace was maintained at 860 ° C. while maintaining the pressure at 4.0 kPa for 1 hour, and then maintained at 860 ° C. for 10 minutes in an argon flow reduced to 5.3 kPa. Went. Then, it cooled to room temperature in 100 kPa argon flow, and produced the porous magnet. When the density was calculated from the size and weight of the produced porous magnet, it was 5.49 g / cm ³ .

  After magnetizing the produced porous magnet with a pulse magnetic field of 3.2 MA / m, the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The results are shown in Table 23.

Further, the porous magnet is heated to 800 ° C. in a cemented carbide mold and subjected to hot compression treatment (hot pressing) at a pressure of 50 MPa for 20 minutes, thereby obtaining a high density of 7.48 g / cm ³ . A magnet was obtained. After magnetizing the produced high-density magnet with a pulse magnetic field of 3.2 MA / m, the magnetic properties were measured with a BH tracer (device name: MTR-1412 (Metron Giken Co., Ltd.)). The results are shown in Table 23. As can be seen from Table 23, it can be seen that good magnetic properties were obtained for all the samples, and that the magnetic properties were further improved by hot pressing as compared with the HDDR treatment.

(Experimental example 15)
A mixed powder 1 similar to the mixed powder M80 prepared in Experimental Example 11 was prepared. Next, a forming container 2 and a pressing jig 3 as shown in FIG. 18 were prepared. The molded container 2 in this experimental example is made of nonmagnetic stainless steel. The mixed powder 1 was filled into a rectangular shaped container 2 having an inner dimension of 12 mm × 20 mm and a height of 20 mm. Next, the release surface of the molded container 2 was covered with a square press jig 3 slightly smaller than the inner dimension of the molded container 2. The press jig 3 was pressed by hand while applying a magnetic field of 1.2 MA / m in the direction perpendicular to the press direction (20 mm direction). At this time, a pressure of about 0.1 MPa was applied to mold the powder 1 in the molding container 2 to produce a green compact. The density of the green compact was approximately 3.6 g / cm ³ .

Thereafter, the press jig 3 was removed from the molding container 2 and the entire molding container 2 was subjected to HDDR processing. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow. Then, the first heat treatment step was performed, the atmosphere was switched to an argon flow of 100 kPa without maintaining at 600 ° C., and the temperature was increased to 860 ° C. at a temperature increase rate of 14 ° C./min. Next, after the atmosphere was switched to a hydrogen flow of 100 kPa, the second heat treatment step was performed while maintaining 860 ° C. for 3 hours. Next, it kept at 860 degreeC in 100 kPa argon stream for 1 hour, and after performing the 3rd heat treatment process, it cooled to room temperature and produced the porous magnet. The density of the produced porous magnet was about 4.7 g / cm ³ .

  As described above, the “green compact” in the present specification includes a powder in a state where the mechanical strength is insufficient by itself due to low density due to low-pressure compression, and the powder cannot be self-supported. In addition, the shaping | molding container 2 is not limited to the container which has the shape shown in figure. The filling container disclosed in JP-A-7-153612 and a modified example thereof can also be used as a forming container in the green compact forming process and / or HDDR processing step.

Next, the density is 7.47 g / cm ³ by heating the porous magnet to 800 ° C. in a cemented carbide mold and performing hot compression (hot pressing) for 15 minutes at a pressure of 50 MPa. A high-density magnet was prepared. The prepared sample was magnetized with a pulse magnetic field of 3.2 MA / m, and then the magnetic properties were measured with a BH tracer (device name: MTR-1412 (manufactured by Metron Engineering Co., Ltd.)). The results obtained are shown in Table 24. As can be seen from Table 24, good magnetic properties can be obtained even when molding is performed using a molded container and the entire container is subjected to HDDR treatment.

  The magnet produced according to the present invention shows a better squareness than a magnet obtained by diffusing an Nd-Cu alloy in a conventional HDDR magnetic powder, and has a higher coercive force than a conventional porous magnet, It is suitably used for various applications that require these characteristics.

10 Porous magnet 27 Mold (die)
28a Upper punch 28b Lower punch 30a Driving unit 30b Driving unit 26 Chamber

Claims (12)

An RTB-based alloy powder having a 50% volume center particle size of 1 μm or more and less than 10 μm and containing an R ₂ T ₁₄ B phase (R is a rare earth element containing 50 atomic% or more of Nd and / or Pr, T is Fe Or Fe and Co) and an R ′ metal (R ′ is one or more selected from Nd, Pr, Dy, Tb) having a particle size of less than 75 μm or an R′-M alloy (M is Al, Ga, Cu, A step of preparing a mixed powder with one or more powders selected from Co, Ni, Cr, Fe, Si, and Ge;
Forming the green compact by molding the mixed powder;
A first heat treatment step of heat-treating the green compact in a hydrogen atmosphere at a temperature of 200 ° C. or higher and 600 ° C. or lower;
After the first heat treatment step, a second heat treatment step of performing heat treatment on the green compact in a hydrogen atmosphere at 650 ° C. or higher and 1000 ° C. or lower;
After the second heat treatment step, a third heat treatment step of performing heat treatment on the green compact in a vacuum of 650 ° C. or higher and 1000 ° C. or lower or an inert atmosphere;
Including
The manufacturing method of the RTB type | system | group permanent magnet which heats up from the time of completion | finish of said 1st heat processing process to the time of the start of said 2nd heat processing process in a vacuum or inert atmosphere.   The manufacturing method of the RTB system permanent magnet according to claim 1 whose hydrogen partial pressure of hydrogen atmosphere in said 1st heat treatment process is 10 kPa or more and 500 kPa or less.   The manufacturing method of the RTB type | system | group permanent magnet of Claim 1 which makes time from the completion | finish of said 1st heat treatment process to the start of said 2nd heat treatment process 60 minutes or less.   The manufacturing method of the RTB system permanent magnet according to claim 1 whose hydrogen partial pressure of hydrogen atmosphere in said 2nd heat treatment process is 20 kPa or more and 500 kPa or less.   2. The method for producing an RTB-based permanent magnet according to claim 1, wherein an R ′ content in the R′-M alloy is 25 atomic% or more and less than 100 atomic%.   The mixing ratio of the RTB-based alloy powder and the R ′ metal or R′-M-based alloy powder in the mixed powder is a weight ratio (RTB-based alloy powder): (R ′ Or the manufacturing method of the RTB type | system | group permanent magnet of Claim 1 which is R'-M type | system | group alloy powder) = m: 1 (5 <= m <= 100). The step of preparing the mixed powder includes
Preparing the RTB-based alloy powder;
Preparing a powder of the R ′ metal or R′-M alloy;
Mixing the RTB-based alloy powder and the R ′ metal or R′-M alloy powder;
The manufacturing method of the RTB type | system | group permanent magnet of Claim 1 containing this. The step of preparing the mixed powder includes
2. The R according to claim 1, comprising a step of pulverizing a mixture of an RTB alloy and an R ′ metal or an R′-M alloy into a powder having a 50% volume center particle size of 1 μm to 10 μm. -Manufacturing method of TB permanent magnet. The step of preparing the mixed powder includes
After the step of occluding hydrogen in the R ′ metal or R′-M alloy powder, the R—T—B alloy and the R ′ metal or R′-M alloy mixed with the hydrogen are mixed. The manufacturing method of the RTB type | system | group permanent magnet of Claim 1 including the process of finely pulverizing.   The manufacturing method of the RTB system permanent magnet in any one of Claim 1 to 9 whose temperature of the heat processing in said 2nd heat treatment process and said 3rd heat treatment process is 950 degrees C or less.   The RT according to any one of claims 1 to 9, wherein the green compact is held in a molded container during the first heat treatment step, the second heat treatment step, and the third heat treatment step. -Manufacturing method of B type permanent magnet. A step of preparing an R-T-B system permanent magnet manufactured by the manufacturing method according to claim 1;
Increasing the density of the R-T-B permanent magnet by hot compression molding;
The manufacturing method of the RTB type | system | group high density magnet containing this.