JP2014022596A - Manufacturing method of rare earth-iron-boron-based porous magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an R-T-B-based permanent magnet having good squareness and high coercive force.SOLUTION: The method comprises: the step of compacting a powder mixture of R-T-B-based alloy powder having a 50%-volume center grain diameter of no smaller than 1 μm and below 10 μm and including an RTB phase, and powder of R' metal(R' is at least one of Nd, Pr, Dy and Tb) or R'-M-based alloy (M is at least one of Al, Ga, Co and Fe) having a grain size below 150 μm into a green compact; the HD processing step of causing hydrogenation and a disproportionation reaction by performing a thermal treatment on the green compact at a temperature of no lower than 650°C and below 950°C with a pressure of over 10 kPa up to 500 kPa in a hydrogen atmosphere or a mixed atmosphere of hydrogen and inert gas; the DR processing step of performing a thermal treatment on the resultant compact at a temperature of no lower than 650°C and below 950°C with a pressure of 2-10 kPa in a hydrogen atmosphere; and the grain-boundary-phase-forming-thermal-treatment step of thereafter forming a grain boundary phase in the vicinity of an interface of crystal grain of the RTB phase by performing a thermal treatment on the compact at a temperature of no lower than 650°C and below 950°C in a vacuum or inactive atmosphere.

Description

  The present application relates to a method for producing an R—Fe—B porous magnet.

R-T-B permanent magnets typical as high-performance permanent magnets (R is a rare earth element containing Nd and / or Pr, T is Fe or a part of Fe substituted with Co and / or Ni, B is Boron) contains the R ₂ T ₁₄ B phase (Nd ₂ Fe ₁₄ B type compound phase), which is a ternary tetragonal compound, as a main phase and exhibits excellent magnetic properties, so it is used for various applications. Yes.

In particular, in recent years, the demand for RTB-based permanent magnets used at high temperatures, such as drive motors for hybrid vehicles and electric vehicles, has been increasing. R-T-B permanent magnets used in such products are required to have a high coercive force. As a method for increasing the coercive force of an R-T-B system permanent magnet, a part of R of the R-T-B system permanent magnet is made of a heavy rare earth element such as Dy or Tb, so that the R ₂ T ₁₄ B phase ( It is generally known to increase the magnetocrystalline anisotropy of the main phase. However, heavy rare earth elements such as Dy and Tb are rare elements with small crustal abundance, and there is concern that the risk of resource depletion may become apparent in the future. R- without using Dy or Tb There is a need for a technique for increasing the coercive force of a T-B permanent magnet.

Among RTB-based permanent magnets, RTB-based sintered magnets manufactured by the powder metallurgy method can be used without using Dy or Tb by reducing the pulverized particle size of the raw material powder. It is known from Non-Patent Document 1 that magnetic force is improved. Also, HDDR (Hydrogenation-Deposition-Recombination-Recombination) processing method known as a method for refining the crystal grain size of R ₂ T ₁₄ B phase to submicron size, which is difficult with powder metallurgy, is an R-T-B system. A permanent magnet is attracting attention as a technique that has a possibility of obtaining a higher coercive force without using Dy or Tb, and is disclosed in Non-Patent Document 2, for example.

The HDDR processing method means a process of sequentially performing hydrogenation and disproportionation, dehydrogenation and recombination, and is mainly different from R-T-B system. It has been adopted as a method for producing magnet powder for isotropic bonded magnets. According to the known HDDR process, first, an R-T-B alloy ingot or powder is maintained at a temperature of 700 ° C. to 1000 ° C. in an H ₂ gas atmosphere or a mixed atmosphere of an H ₂ gas and an inert gas. Then, hydrogen is occluded in the ingot or powder. Thereafter, such as H ₂ pressure is 13Pa or less of vacuum atmosphere, or H ₂ partial pressure is dehydrogenated at a temperature 700 ° C. to 1000 ° C. or less inert atmosphere 13Pa, then cooled.

  In the above treatment, the following reaction typically proceeds.

First, a hydrogenation and disproportionation reaction proceeds by a heat treatment that occludes hydrogen at a predetermined temperature to form a fine structure. Both hydrogenation and disproportionation reactions are collectively referred to as “HD reactions”. In a typical HD reaction, a reaction of Nd ₂ Fe ₁₄ B + 2H ₂ → 2NdH ₂ + 12Fe + Fe ₂ B proceeds.

Next, dehydrogenation and recombination reaction proceed by heat treatment for releasing hydrogen at a predetermined temperature. The dehydrogenation and recombination reactions are collectively referred to as “DR reactions”. In a typical DR reaction, for example, a reaction of 2NdH ₂ + 12Fe + Fe ₂ B → Nd ₂ Fe ₁₄ B + 2H ₂ proceeds. Thus, an alloy containing a fine R ₂ T ₁₄ B crystal phase is obtained.

  In this specification, the heat treatment for causing the HD reaction is referred to as “HD treatment”, and the heat treatment for causing the DR reaction is referred to as “DR treatment”. Further, performing both HD processing and DR processing is referred to as “HDDR processing”.

  The R-T-B type HDDR magnet powder (hereinafter referred to as “HDDR magnetic powder”) obtained by the HDDR treatment has a crystal grain size of 0.1 μm to 1 μm and has a large coercive force while being a powder, and is magnetic. Anisotropy is shown. However, it has been difficult to obtain magnetic powder having a coercive force that can withstand use in a drive motor for a hybrid vehicle or an electric vehicle only by the HDDR process. Moreover, the HDDR magnetic powder for bonded magnets had poor squareness of the demagnetization curve and poor heat resistance.

  On the other hand, several methods have been proposed so far in which the HDDR magnetic powder obtained is mixed or coated with another material and heat-treated to improve the coercive force.

  In Patent Document 1, Dy, Tb, Ho, Er, Tm, Gd, Nd, Sm, Pr, Ce, La, Y, Zr, Cr, Mo, V, Ga, Zn, Cu, Mg, Li, Al, Mn It is disclosed that magnetic properties, corrosion resistance, and weather resistance are improved by attaching at least one metal vapor selected from Nb, Ti to magnetic powder and performing heat treatment / diffusion. It is described that a magnet having excellent magnetic properties can be obtained by diffusing Dy, Tb, etc. to the grain boundaries of the magnetic powder.

  Patent Document 2 discloses that coercive force is improved without using a heavy rare earth element by mixing and heat-treating HDDR magnetic powder and an R′-Al alloy.

  Patent Document 3 discloses that the HDDR magnet powder is coated with an aluminum film and then heat-treated at 450 ° C. to 600 ° C.

  Further, as a method for obtaining a bulk magnet while improving the squareness of HDDR magnetic powder, Patent Document 4 discloses a method for HDDR treatment using an R—Fe—B rare earth alloy powder having an average particle size of less than 10 μm as a green compact. ing.

JP 2008-69415 A JP 2012-49492 A Japanese Patent Laid-Open No. 2005-15918 International Publication No. 2007/135981

K. Kobayashi, T. Takano, T. Sagawa, The Institute of Electrical Engineers of Japan, MAG-05-118 (2005) Satoshi Hirosawa, Takeshi Nishiuchi, Tadakatsu Okubo, Li Wanfang, Kazuhiro Hono, Jiro Yamazaki, Masaaki Takezawa, Kanetsu Sumiyama, Samasu Yamamuro, Journal of the Japan Institute of Metals vol. 73 p. 135 (2009)

  The above magnetic powder obtained by diffusing an R′-M alloy into HDDR magnetic powder is inferior in squareness. Moreover, the conventional porous magnet does not necessarily have a sufficiently high coercive force.

  According to the embodiment of the present invention, the present invention exhibits good squareness as compared with magnetic powder obtained by diffusing an R′-M alloy into conventional HDDR magnetic powder, and has a higher coercive force than that of a conventional porous magnet. An R-T-B permanent magnet can be provided.

In an embodiment of the present invention, an RTB-based porous magnet manufacturing method includes an RTB-based alloy having a 50% volume center particle size of 1 μm or more and less than 10 μm and including an R ₂ T ₁₄ B phase. Powder (R is a rare earth element containing Nd and / or Pr of 50 atomic% or more, T is Fe, or Fe and Co), and R ′ metal having a particle size of less than 150 μm (R ′ is selected from Nd, Pr, Dy, Tb) Powder of one or more) or R′-M alloy (M is one or more selected from Al, Ga, Co, Fe, R ′ is 20 atomic% or more and less than 100 atomic% of the entire R′-M alloy) A step of preparing a mixed powder, a step of forming a green compact by molding the mixed powder, a hydrogen atmosphere of 10 kPa to 500 kPa or a hydrogen partial pressure of 10 kPa to 500 kPa with respect to the green compact 65 in a mixed atmosphere of hydrogen and inert gas Heat treatment at a temperature of 950 ° C. or more and less than 950 ° C., thereby causing hydrogenation and disproportionation reactions, and heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of 2 kPa or more and 10 kPa or less, Thereby, a DR treatment step for causing dehydrogenation and recombination reaction, and heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a vacuum or an inert atmosphere, thereby forming grains near the interface of the R ₂ T ₁₄ B phase grains. And a grain boundary phase forming heat treatment step for forming a boundary phase.

  In one embodiment, the R ′ metal or the R′-M alloy preliminarily stores hydrogen.

  In one embodiment, the temperature is raised from 200 ° C. to 600 ° C. in a hydrogen atmosphere in the temperature raising step before the HD treatment step.

In one embodiment, the density of the green compact before the HD treatment step is in a range of 3.5 g / cm ³ or more and 5.2 g / cm ³ or less.

In one embodiment, the molded body after the grain boundary phase formation heat treatment step is porous having a density of 3.5 g / cm ³ or more and 6.5 g / cm ³ or less.

  In one embodiment, the porous green compact has voids communicating in a three-dimensional network, and individual powder particles constituting the green compact are combined with adjacent powder particles.

  In one 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 ′ metal or R′-M alloy powder) = m: 1 (5 ≦ m ≦ 100).

  In one 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, and the R And a step of mixing the TB alloy powder and the R ′ metal or R′-M alloy powder.

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

  In an embodiment of the present invention, a method for producing an RTB-based high-density magnet includes a step of preparing an RTB-based porous magnet manufactured by any of the above-described manufacturing methods, and hot compression molding. And increasing the density of the RTB-based porous magnet to form a high-density magnet.

In one embodiment, the density of the high-density magnet is in a range of 7.0 g / cm ³ or more and 7.6 g / cm ³ or less.

  According to the embodiment of the present invention, the dehydrogenation reaction of the RTB-based alloy powder while suppressing the diffusion of at least a part of the R ′ metal or the R′-M-based alloy into the RTB-based alloy. And the recombination reaction can proceed.

It is a flowchart which shows an example of the manufacturing method of the RTB type porous magnet by this invention. It is a figure which shows the hot press apparatus which can be used suitably by embodiment of this invention. 2 is a reflected electron image (1000 times) of the polished surface of Comparative Example 1 by a scanning electron microscope and an element mapping image (1000 times) of Nd, Al, and Fe by an energy dispersive X-ray analyzer (EDX). It is the reflected electron image (1000 times) of the grinding | polishing surface of Example 1, and the element mapping image (1000 times) of Nd, Al, and Fe by an energy dispersive X-ray analyzer (EDX). It is a reflected electron image (5000 times) of the polishing surface of the comparative example 1 by the scanning electron microscope. 2 is a reflection electron image (5000 times) of the polished surface of Example 1 by a scanning electron microscope. It is a reflection electron image (400 time) by the scanning electron microscope of the grinding | polishing surface of the comparative example 2. It is a reflection electron image (10000 time) of the grinding | polishing surface of the comparative example 2 by a scanning electron microscope. It is a reflection electron image (400 time) by the scanning electron microscope of the grinding | polishing surface of the comparative example 3. It is a reflected electron image (9500 times) by the scanning electron microscope of the grinding | polishing surface of the comparative example 3.

Since HDDR magnetic powder is used as a bond magnet, it is made from a raw material powder having a relatively coarse particle size of about 75 μm. For this reason, uniform HDDR processing is difficult and the structure becomes inhomogeneous. As a result, the squareness of the demagnetization curve is poor. Further, as described in Patent Document 2, when HDDR magnetic powder and R′-Al alloy powder are mixed and heat-treated, the R′-Al alloy diffuses into the R ₂ T ₁₄ B phase grain boundary and is retained. Although the magnetic force was improved, the squareness of the demagnetization curve was not improved even after the R′-Al-based alloy was diffused into the HDDR magnetic powder, and H _k / H _cJ was about 0.3. H _k is the value of the magnetic field H at which the magnetization is B _r × 0.9, and the higher the H _k / H _cJ , the better the squareness of the demagnetization curve. Hereinafter, the squareness of the demagnetization curve may be simply referred to as “squareness”.

  Based on the background art described above, the present inventor diffuses an R′-M-based alloy into a porous magnet excellent in squareness manufactured by the manufacturing method of Patent Document 4, has excellent squareness, and An attempt was made to make a magnet with high coercivity. However, since the porous magnet is a bulk body, it is difficult to diffuse the R′-M alloy to the inside of a large magnet, resulting in variations in magnetic properties inside and outside the magnet. .

Next, in order to uniformly diffuse the R′-M alloy in the porous magnet, the inventors previously mixed the R′-M alloy powder with the RTB alloy powder before HDDR treatment. I tried to process HDDR. The porous magnet obtained thereby was excellent in squareness, and the coercive force was improved compared to the porous magnet not mixed with the R′-M alloy. However, it cannot be said that the coercive force is sufficiently improved as compared with the porous magnet in which the R′-M alloy is diffused after the HDDR treatment. As a factor, it was found that the R′-M alloy that had been mixed in advance had almost diffused before the DR-treated R ₂ T ₁₄ B phase was formed. The grain boundary phase of the R ₂ T ₁₄ B phase is formed after the DR treatment. For this reason, it has also been found that the R′-M alloy does not diffuse preferentially to the grain boundaries of the R ₂ T ₁₄ B phase and the grain boundary structure becomes inhomogeneous.

The inventors changed the DR treatment atmosphere from a conventional vacuum or inert gas atmosphere to a hydrogen atmosphere of 2 kPa to 10 kPa. Then, only the DR treatment of the RTB-based alloy powder is allowed to proceed without proceeding the diffusion of the R′-M alloy, and after completion of the DR treatment of the RTB-based alloy powder, a vacuum or an inert gas atmosphere The R′-M alloy was preferentially diffused into the crystal grain boundaries of the R ₂ T ₁₄ B phase. As a result, the R-T-B permanent permanent material exhibits better squareness than the conventional magnetic powder obtained by diffusing the R'-M alloy into the HDDR magnetic powder and has a higher coercive force than the conventional porous magnet. It has been found that a magnet can be obtained.

  FIG. 1A is a flowchart showing an example of a method for producing an RTB-based porous magnet according to the present invention.

In the example shown in FIG. 1A, first, a mixed powder of an RTB-based alloy powder (first powder) and an R ′ metal or R′-M-based alloy powder (second powder) is prepared (steps). S1). The RTB-based alloy powder is an RTB-based alloy powder having a 50% volume center particle size of 1 μm or more and less than 10 μm and including an R ₂ T ₁₄ B phase. R is a rare earth element containing 50 atomic% or more of Nd and / or Pr, and T is Fe, or Fe and Co. The R ′ metal or R′-M alloy powder is an R ′ metal or R′-M alloy powder having a particle size of less than 150 μm. R ′ is one or more selected from Nd, Pr, Dy, and Tb, and M is one or more selected from Al, Ga, Co, and Fe. In the R′-M alloy powder, R ′ is 20 atomic% or more and less than 100 atomic% of the entire R′-M alloy.

  Next, a molded body (a green compact) is produced by molding such a mixed powder (step S2).

  The green compact thus prepared is subjected to heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of more than 10 kPa and 500 kPa or less, or in a mixed atmosphere of hydrogen and inert gas having a hydrogen partial pressure of more than 10 kPa and less than 500 kPa. Then, an HD treatment process for causing hydrogenation and disproportionation reactions is performed (step S3).

  Next, the green compact subjected to the HD treatment process is subjected to a heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of 2 kPa or more and 10 kPa or less, thereby causing a dehydrogenation and a recombination reaction. A process is performed (step S4).

Thereafter, the green compact after the DR treatment process is subjected to heat treatment at a temperature of 650 ° C. or higher and lower than 950 ° C. in a vacuum or an inert atmosphere, so that the grains near the interface of the R ₂ T ₁₄ B phase crystal grains. A grain boundary phase forming heat treatment step for forming a boundary phase is performed (step S5).

The porous body obtained by this method has a density of 3.5 g / cm ³ or more and 6.5 g / cm ³ or less and a level of 46% or more and 86% or less with respect to the true density (about 7.6 g / cm ³ ). Although there are gaps between the powder particles, the individual particles are bonded to each other and exhibit sufficient mechanical strength and excellent magnetic properties.

  Hereinafter, an embodiment is described in detail about a manufacturing method of a RTB system permanent magnet by the present invention.

<R-T-B alloy (raw material alloy)>
First, an R—T—B system alloy including a hard magnetic phase, R ₂ T ₁₄ B phase and a rare earth-rich phase, is prepared as a main phase. Here, “R” is a rare earth element and contains Nd and / or Pr by 50 atomic% or more. The rare earth element in this specification is at least one element selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoid. Here, the lanthanoid is a general term for 15 elements from lanthanum to lutetium. T is Fe or Fe and Co.

The RTB-based alloy in the present embodiment includes 50% or more of the R ₂ T ₁₄ B phase by volume ratio. Most of the rare earth element R contained in the R-T-B-based alloy constitutes the R ₂ T ₁₄ B phase and the rare earth-rich phase, but some constitutes R ₂ O ₃ and other phases. Also good.

The composition ratio of the rare earth element R can be 10 atomic% or more and 30 atomic% or less, and can be 12 atomic% or more and 17 atomic% or less of the entire R-T-B 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. Further, since it is a rare element, it should be avoided to use a large amount, but the coercive force can be improved by using a part of R as Dy and / or Tb.

  The composition ratio of B may be 3 atomic% or more and 15 atomic% or less of the entire RTB-based alloy. The composition ratio of B may be 5 atom% or more and 8 atom% or less, and may be 5.5 atom% or more and 7.5 atom% or less. A part of B may be substituted with C, but the amount of substitution may be 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 may be 50 atomic% or less with respect to the total amount of T. In addition, the total amount of Co with respect to the entire RTB-based alloy in the present embodiment may be 20 atomic% or less and may be 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 the increase in the amount of addition leads to a decrease in saturation magnetization in particular, the total amount can be 10 atomic% or less of the whole. The RTB-based alloy may contain inevitable impurities.

  The RTB-based alloy can be produced by a strip casting method that can reduce the amount of α-Fe phase that adversely affects magnetic properties. The RTB-based alloy can also be produced by a book mold method, a centrifugal casting method, an atomizing method, or the like. For the purpose of homogenizing the structure of the R-T-B alloy, the R-T-B alloy before pulverization may be subjected to heat treatment. 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. 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, Co, and Fe. R′-M alloys include R ′ hydrides (R′H _x ), R′-M compounds (R′M, R′M ₂ etc.), R′-M compounds in the hydrogen storage treatment described later. It decomposes into a compound in which hydrogen is dissolved in solid, an M single phase, a phase in which hydrogen is dissolved in M, and the like. “M” can be selected so that the melting point of the R′-M compound produced at this time is higher than the heat treatment temperature of HD treatment described later. For example, in the case of an Nd ₇₀ Al ₃₀ alloy, it decomposes into NdH _x and NdAl ₂ , but the melting point of NdAl ₂ is a binary phase diagram of the Nd—Al alloy (for example, “Binary Alloy Phase Diagrams, II Ed., Ed. T B. Massalski, 1990, 1, 181-182, Gschneidner K.A. Jr.)), it is 1460 ° C., which is higher than the heat treatment temperature of HD processing. Note that the diffusing material may contain inevitable impurities.

  The composition ratio of the rare earth element R ′ in the R′-M alloy used in the present embodiment is 20 atomic% or more and less than 100 atomic%. When the composition ratio of the rare earth element R ′ is less than 20 atomic%, the rare earth element R ′ is not sufficiently supplied to the crystal grain boundary, so that the effect of improving the coercive force is small or cannot be obtained. The composition ratio of the rare earth element R ′ in the R′-M alloy may be 30 atomic% or more and 98 atomic% or less, and may be 60 atomic% or more and 90 atomic% or less.

  The R ′ metal or the R′-M alloy 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 superquenching method.

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

  When the RTB-based alloy and the diffusing material are separately pulverized separately, the RTB-based alloy is first roughly pulverized using a mechanical pulverization method such as a jaw crusher or a hydrogen storage pulverization method. A coarsely pulverized powder having a thickness of about 50 μm to 1000 μm is prepared. The coarsely pulverized powder is finely pulverized by a jet mill or the like to produce an RTB-based alloy powder (raw material alloy powder) 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 150 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 RTB-based alloy powder and diffusing material powder are mixed by a known powder mixing method to obtain a mixed powder.

  From the viewpoint of handling, the 50% volume center particle diameters of the RTB-based alloy powder and the diffusing material powder in this embodiment are each 1 μm or more. 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 handling easier, the 50% volume center particle size can be set to 3 μm or more. The 50% volume center particle size of the diffusing material powder may be 10 μm or more from the viewpoint of suppressing oxidation. From the viewpoint of improving the mechanical strength of the molded body, the upper limit of the 50% volume center particle size of the RTB-based alloy powder can be set to 9 μm and may be set to 8 μm. Further, from the viewpoint of the uniformity of the HDDR reaction, the particle size of the diffusing material powder in this embodiment is less than 150 μm.

  By separately crushing the RTB-based alloy and the diffusing material, the 50% volume center particle size of the RTB-based alloy powder is 1 μm or more and less than 10 μm, and the 50% volume center particle size of the diffusing material powder is The thickness can be 10 μm or more, and in particular, oxidation of the diffusing material powder that easily reacts with oxygen can be suppressed.

  In the case of pulverizing a mixture of an R-T-B alloy and a diffusing material, the mixture of the R-T-B alloy and the diffusing material is first subjected to a mechanical pulverization method such as a jaw crusher or a hydrogen occlusion pulverization method. And coarsely pulverized to produce coarsely pulverized powder having a size of about 50 μm to 1000 μm. 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 RTB-based alloy and the diffusing 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, the 50% volume center particle size can be set to 3 μm or more. From the viewpoint of improving the mechanical strength of the green compact, the upper limit of the 50% volume center particle size may be 9 μm, and may further be 8 μm.

  By pulverizing the mixture of the RTB-based alloy and the diffusing material, it is possible to easily produce a mixed powder in which the RTB-based alloy and the diffusing material are uniformly mixed.

The mixing ratio of the RTB-based alloy and the diffusing material may be (RT-B-based 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 may be 10 atomic% or more and 30 atomic% or less of the entire mixed powder, and may be 12 atomic% or more and 17 atomic% or less. Further, if the total amount of rare earth elements R and R ′ in the mixed powder is 15 atomic% or less of the entire mixed powder, it is easy to take out 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 can be performed, for example, by applying a pressure of 10 MPa to 200 MPa and in a magnetic field of 0.4 MA / m to 16 MA / m (static magnetic field, pulse magnetic field, etc.). Molding can be performed by a known powder press apparatus. Compact density (compact density) when removed from the powder press apparatus, for example 3.5g / cm ³ ~5.2g / cm ³ order.

  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, a molding step is performed while performing magnetic field orientation, and an anisotropic porous magnet can be finally obtained.

  The step of crushing the RTB-based alloy and the diffusion material and the step of forming the green compact can be performed while suppressing oxidation of the RTB-based alloy powder and the diffusion material powder. In order to suppress the oxidation of the RTB-based alloy powder and the diffusing material powder, each process and handling between the processes can be performed in an inert atmosphere in which the amount of oxygen is suppressed as much as possible. The oxygen content of the green compact before the DR treatment can be suppressed to 1% by mass or less, and further to 0.6% by mass or less.

  In the embodiment of 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. In the embodiment of the present invention, since the raw material powder having a 50% volume center particle size of 1 μm or more and less than 10 μm is used, it is easy for hydrogen to move entirely within the powder particles. 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 four steps: a temperature raising step, an HD treatment step, a DR treatment step, and a grain boundary phase formation heat treatment step.

  The temperature raising step is a step of heating the green compact to the processing temperature of the HD processing step with respect to the green compact molded using the mixed powder. The temperature raising step is performed in one of a hydrogen gas atmosphere with a hydrogen partial pressure of more than 10 kPa and 500 kPa or less, a mixed atmosphere of hydrogen gas and an inert gas (Ar, He, etc.), an inert gas atmosphere, or a vacuum. In order to suppress diffusion of the diffusing material during the temperature rise, the diffusing material is stored in a hydrogen atmosphere at a temperature of 950 ° C. or less in a hydrogen atmosphere of 1 kPa or more in advance or a mixed atmosphere of hydrogen and an inert gas having a hydrogen partial pressure of 1 kPa or more. Can be made. Alternatively, in order to suppress diffusion of the diffusing material during temperature rise, the temperature is raised to 600 ° C. in an atmosphere containing hydrogen, and after 600 ° C., the degree of orientation due to the progress of the HD reaction at a low temperature of the RTB-based alloy powder. The temperature can be raised in an inert gas atmosphere or in a vacuum in order to suppress the decrease in the temperature. Such a temperature rising process may be performed on the hydrogen occluded before the temperature rising as described above. Note that the rare earth-rich phase present in the RTB-based alloy powder during hydrogen occlusion or when the temperature is raised in a hydrogen atmosphere is hydrogenated and exists mainly as an R hydride. Further, the diffusion material is decomposed into R 'hydride, R'-M compound, and the like. Since the melting points of the hydrides of R and R ′ are higher than the processing temperature in the HD processing step, the diffusion of the R′-M alloy can be suppressed.

The HD processing step to be performed next is a step of obtaining a disproportionated structure by performing an 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 HD processing step. The temperature of the HD processing step is 650 ° C. or higher and lower than 950 ° C. If it is less than 650 degreeC, it will take time for disproportionation to fully advance. Further, since the disproportionated structure becomes coarser at 950 ° C. or higher, the texture of the R ₂ T ₁₄ B phase obtained by the subsequent DR treatment step becomes coarse, resulting in a decrease in magnetic characteristics, particularly coercive force. In particular, from the viewpoint of suppressing grain growth, the temperature of the HD treatment process can be set to 900 ° C. or lower.

The hydrogen partial pressure in the HD treatment process can be 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, so that it can be 500 kPa or less, and 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 HD processing step can be 10 minutes to 5 hours. 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 thus the recombination structure after the DR treatment process 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, the DR treatment step is performed by performing heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of 2 kPa or more and 10 kPa or less, thereby suppressing the diffusion of the diffusing material powder and dehydrating the RTB-based alloy powder. Elementary and recombination reactions occur and an R ₂ T ₁₄ B phase is generated by the recombination reaction. If it is less than 2 kPa, diffusion of the diffusing material proceeds, and if it exceeds 10 kPa, the DR reaction of the RTB-based alloy hardly occurs. In order to obtain a higher coercive force, it can be set to 3 kPa or more and 8 kPa or less. A hydrogen atmosphere of 2 kPa or more and 10 kPa or less can be realized by, for example, evacuating the inside of the heat treatment apparatus while controlling the exhaust speed by a vacuum pump or the like and balancing with hydrogen generated by dehydrogenating the green compact after the HD treatment process. . The temperature of the DR treatment process is 650 ° C. or higher and lower than 950 ° C. If it is less than 650 degreeC, dehydrogenation reaction does not occur substantially. Further, when the temperature is higher than 950 ° C., the recombined R ₂ T ₁₄ B phase grows in crystal grains, leading to a decrease in magnetic properties, particularly coercive force. From the viewpoint of suppressing grain growth, the temperature of the DR treatment step can be set to 900 ° C. or lower. Further, the time required for the DR treatment process is about 15 minutes, and the recombination reaction of the R ₂ T ₁₄ B phase is completed, so it can be set to 15 minutes or more. By treating for 30 minutes or more, the coercive force can be further improved. Can be obtained. On the other hand, if the treatment is performed for a long time, the production cost is increased, so that it can be set to 10 hours or less and further set to 3 hours or less.

The R ₂ T ₁₄ B phase generated in the DR treatment step typically forms a texture having an average crystal grain size of 0.1 μm or more and 1.0 μm or less. When an element that easily diffuses into the R ₂ T ₁₄ B phase such as Al is used as the M element of the R′-M alloy, the M element diffuses into the RTB alloy powder during the DR treatment process. However, since the diffusion of R ′ can be sufficiently suppressed, the effect of improving the coercive force is sufficiently exhibited.

Further, the hydrogen in the heat treatment apparatus may be replaced by flowing an inert gas between the HD treatment process and the DR treatment process for about several minutes. As a result, a large amount of hydrogen does not flow into the pump when the heat treatment apparatus is evacuated by the vacuum pump in the DR treatment process, and the treatment can be performed safely. Next, the grain boundary phase forming heat treatment step is carried out by holding at 650 ° C. or more and less than 950 ° C. in a vacuum or an inert atmosphere, so that the R hydride and R′-M alloy contained in the RTB-based alloy powder A dehydrogenation reaction of the powder occurs, a liquid phase rich in R is generated, a grain boundary phase (rare earth rich phase) is formed at the crystal grain boundary of the R ₂ T ₁₄ B phase, and a coercive force is developed. Compared with the case where the diffusing material powder is not mixed, the grain boundary phase (rare earth rich phase) is formed more homogeneously, so that a high coercive force is obtained. Furthermore, a sintering reaction also occurs at the same time, resulting in a porous permanent magnet. The atmosphere in the grain boundary phase forming heat treatment step is a reduced pressure atmosphere that is evacuated while introducing an inert gas, so that oxidation during the treatment can be suppressed and a reduction in coercive force is prevented. The temperature in the grain boundary phase forming heat treatment step is 650 ° C. or higher and lower than 950 ° C. If it is less than 650 degreeC, dehydrogenation reaction does not occur substantially. On the other hand, if the temperature exceeds 950 ° C., the R ₂ T ₁₄ B phase grows and the magnetic properties, particularly the coercive force, are reduced. From the viewpoint of suppressing grain growth, the temperature of the grain boundary phase forming heat treatment step can be set to 900 ° C. or lower. Further, the time required for the grain boundary phase forming heat treatment step can be set to 5 minutes or more and 10 hours or less, and can be further set to 10 minutes or more and 1 hour or less.

<Porous magnet>
By the HDDR treatment, a porous magnet having a density of 3.5 g / cm ³ or more and 6.5 g / cm ³ or less is obtained. The “density” in this specification refers to the apparent density including voids inside the magnet calculated from the size and weight of the magnet measured at room temperature (about 20 ° C. to about 30 ° C.). For this reason, the value displayed as “density” regarding the molded body that has risen to a temperature higher than room temperature by each heat treatment step is not a density value at that temperature but a value when measured at room temperature.

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 RTB-based porous magnet in the embodiment of the present invention is 3.5 g / cm ³ or more and 6.5 g / cm ³ or less. Combine to exhibit sufficient mechanical strength and excellent magnetic properties.

<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 1.0 μm or less can be obtained. Here, the high density magnet means a magnet having a density of 7.0 g / cm ³ or more and 7.6 g / cm ³ or less.

  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 this embodiment, a hot press apparatus having the configuration shown in FIG. 1B 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. 1B) produced by the method described above is loaded into the mold 27 shown in FIG. 1B. At this time, loading can be performed 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 may be used. 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 in this embodiment 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. In the present embodiment, pressurization of 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.

  An RTB-based alloy having the composition shown in Table 1 below and an R ′ metal or R′-M-based alloy having the composition shown in Table 2 are prepared, and a porous magnet is produced by the manufacturing method of the above-described embodiment. Was made. Hereinafter, a method for producing a porous magnet in this experimental example will be described.

(Experimental example 1) DR atmosphere control (structure change with and without grain boundary formation heat treatment)
First, an RTB-based alloy having the composition of B5 and B7 in Table 1 was produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.6 μm. 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).

  Further, a diffusing material having the composition of D5 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. These alloys were heated up to 400 ° C. in a hydrogen gas stream, occluded with hydrogen, pulverized by mechanical pulverization, classified using a mesh having an opening of 53 μm, and diffusing material powder having a size of 53 μm or less was obtained. Obtained. 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 RTB-based 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 and M2.

Next, the mixed powder M2 was filled in a die 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 4.2 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Then, while maintaining at 860 ° C., the atmosphere was switched to Ar and maintained for 2 minutes to replace the atmosphere in the heat treatment apparatus. Next, the Ar gas is stopped and the inside of the heat treatment apparatus is evacuated with a vacuum pump, and the hydrogen pressure generated in the green compact is adjusted to maintain the hydrogen pressure in the heat treatment apparatus at 4.0 kPa and held for 60 minutes. Processing steps were performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process was performed. Then, it cooled to room temperature in 100 kPa argon flow, and Example 1 (condition S1 of Table 4) was produced. Moreover, after performing the DR treatment process as a comparative example, Comparative Example 1 (condition S2 in Table 4) was prepared by cooling to room temperature in a 100 kPa argon flow without performing the grain boundary phase formation heat treatment process. Furthermore, the comparative example which performed DR process on the conventional conditions without performing the atmosphere control of DR process was produced.

The mixed powder M1 was filled in a die 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 0.6 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 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and kept at 600 ° C. for 30 minutes in a 100 kPa hydrogen flow. Then, after switching the atmosphere to 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 100 kPa hydrogen flow, and then kept at 860 ° C. for 120 minutes. The HD processing step was performed. Thereafter, as shown in Table 4 while maintaining at 860 ° C., the atmosphere was switched to argon flow of 100 kPa and maintained for 30 minutes and 50 minutes, and a DR treatment step corresponding to the conventional treatment was performed. Then, it cooled to room temperature in 100 kPa argon stream, and produced the comparative example 2 (condition S3 of Table 4) and the comparative example 3 (condition S4 of Table 4).

When the density was calculated from the dimensions and weights of the prepared samples, Example 1 was 5.56 g / cm ³ , Comparative Example 1 was 5.25 g / cm ³ , Comparative Example 2 was 5.56 g / cm ³ , and Comparative Example 3 was It was 5.65 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 5. As can be seen from Table 5, Comparative Example 1 in which the grain boundary forming heat treatment step was not performed after the DR treatment step has a very low coercive force (H _cJ ), and Example 1 in which the grain boundary forming heat treatment step was performed has a high coercive force. A magnetic force (H _cJ ) was obtained. Further, Comparative Example 3 obtained by the conventional DR treatment process had a lower coercive force (H _cJ ) than that of Example 1. In Comparative Example 2, the conventional DR treatment process is performed. However, since the DR treatment time is short, the DR reaction is not completed and no grain boundary is formed. H _cJ ). In Table 5, J _max is the maximum measured value of the magnetization J (T) of the sample when the magnetic field H is applied up to 2 Tesla (T) in the magnetization direction of the magnetized sample, and B _r / J _max is The higher the value, the better the orientation. H _k is the value of the magnetic field H at which the magnetization B _r × 0.9, and the higher the H _k / H _cJ , the better the squareness of the demagnetization curve.

  FIG. 2 shows a 1000-fold backscattered electron image (BSE images: four images) of a polished surface of Comparative Example 1 (with DR atmosphere control and no grain boundary phase formation heat treatment) using a scanning electron microscope (JSM-7001FA). And an element mapping image of Nd, Fe, and Al by an energy dispersive X-ray analyzer (EDX) equipped in the same microscope. FIG. 3 shows a 1000-fold backscattered electron image (BSE image: four images) of the polished surface of Example 1 (both DR atmosphere control and grain boundary phase formation heat treatment) using a scanning electron microscope (JEOL: JSM-7001FA). And an element mapping image of Nd, Fe, and Al by an energy dispersive X-ray analyzer (EDX) equipped in the same microscope.

  In Comparative Example 1 (FIG. 2) in which the grain boundary phase formation heat treatment was not performed, a size of 10 μm or more was confirmed in the rare earth-rich phase indicated by the bright contrast in the reflected electron image, and Nd was large from elemental mapping. Since Al is also relatively concentrated around it, it can be seen that some diffusion material remains after the DR treatment step.

  On the other hand, in Example 1 (FIG. 3) in which the grain boundary phase formation heat treatment was performed, a rare earth-rich phase having a size of 10 μm or more was not confirmed.

  FIG. 4 and FIG. 5 show 5000-fold reflected electron images (BSE images) of the polished surfaces of Comparative Example 1 and Example 1 using a scanning electron microscope (JEOL: JSM-7001FA), respectively. In Comparative Example 1 (FIG. 4) in which the grain boundary phase formation heat treatment was not performed, the grain boundary phase (rare earth rich phase) indicated by a bright contrast was not observed at the crystal grain boundary, particularly at the two grain boundary, In Example 1 (FIG. 5) in which the formation heat treatment was performed, a homogeneous grain boundary phase (rare earth rich phase) was formed at the two grain boundaries.

  From these results, after completion of the DR treatment in which the DR atmosphere is controlled, the diffusion material remains to some extent without being diffused, but the grain boundary phase is not yet formed, and the diffusion material is formed by the grain boundary phase formation heat treatment. It is thought that diffusion occurred rapidly and contributed to the formation of the grain boundary phase.

  FIG. 6 and FIG. 7 show 400-fold and 10,000-fold backscattered electron images (BSE images) of the polished surface of Comparative Example 2 (conventional DR treatment, DR reaction incomplete) using a scanning electron microscope (JEOL: JSM-7001FA). 8 and 9 show 400 and 9500 times BSE images of Comparative Example 3 (conventional DR processing).

In Comparative Example 2, it can be seen from the BSE image 400 times that in FIG. 6 that no diffusing material powder remains as in Example 1 in FIG. Further, from the 10,000 times BSE image of FIG. 7, the α-Fe phase remains in the RTB-based alloy powder, the recombination reaction of the RTB-based alloy powder is not completed, and the grains It can be confirmed that no boundary phase is formed. From these, it can be seen that in the comparative example 2, since the DR atmosphere control is not performed, the diffusion of the diffusing material has occurred before the grain boundary phase is formed. On the other hand, in Comparative Example 3, it was confirmed from the 400 times BSE image of FIG. 8 that the diffusion of the diffusing material occurred because the DR atmosphere was not controlled as in Comparative Example 2, and no diffusing material powder remained. From the BSE image of 9500 times in FIG. 9, the recombination reaction of the R-T-B alloy powder is completed, and a grain boundary phase is formed although it is inhomogeneous at the crystal grain boundary of the R ₂ T ₁₄ B phase. You can see that From these results, it is considered that in the conventional DR process in which the DR atmosphere control is not performed, diffusion of the diffusing material occurs before the formation of the grain boundary phase, which does not contribute much to the formation of the grain boundary phase. For this reason, it is considered that a high coercive force was not finally obtained as in Comparative Example 3.

  In Comparative Examples 2 and 3, the composition of the RTB-based alloy used in Example 1 is different from that in Example 1, but this is because the R'-M alloy remains using an alloy having a higher rare earth composition. This is because the R′-M alloy diffused before the formation of the grain boundary phase, but the effects of the examples could be confirmed.

(Experiment 2) DR atmosphere control (hydrogen pressure change)
First, an RTB-based alloy B6 having the composition shown in Table 1 was produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.9 μm. 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, the diffusing material D5 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 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 53 μm to obtain a diffusing material powder having a size of 53 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 RTB-based alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 6 using an agate mortar to obtain mixed powder M3.

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 4.2 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas was stopped and the heat treatment apparatus was evacuated with a vacuum pump, and the hydrogen pressure generated from the green compact was adjusted as shown in Table 7 to adjust the hydrogen pressure in the heat treatment apparatus to 0.01 to 15.0 kPa. It was held for 60 minutes while adjusting to DR process.

  Subsequently, it hold | maintained for 60 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process was performed. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced. In addition, as a comparative example, a sample was also prepared which was not subjected to the DR treatment step after the HD treatment step, was held for 60 minutes in an argon flow reduced to 5.3 kPa at 860 ° C., and was cooled to room temperature in a 100 kPa argon flow. .

It was 6.09-6.47 g / cm < ³ > when density was computed from the dimension and weight of the produced 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.)). The results are shown in Table 8. As can be seen from Table 8, high H _cJ is obtained when the hydrogen pressure in the DR treatment step is 2 kPa to 10 kPa.

(Experimental example 3) DR atmosphere control (R-T-B alloy composition)
First, RTB-based alloys B1, B2, B3, B5, and B7 having the compositions shown in Table 1 were produced by strip casting. The obtained alloy was coarsely pulverized into a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 5.0 μm. 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, the diffusing material D5 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 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 53 μm to obtain a diffusing material powder having a size of 53 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 RTB-based alloy powder and diffusing material powder were mixed using an agate mortar at a mixing ratio shown in Table 9 to obtain mixed powders M4 to M8.

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 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S7 in Table 7. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 60 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process was performed. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced.

It was 6.19-6.39 g / cm < ³ > when the density was computed from the dimension and weight of the produced 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.)). The results are shown in Table 10. As can be seen from Table 10, high H _cJ is obtained in any composition.

(Experimental example 4) DR atmosphere control (mixing amount of diffusion material)
First, an RTB-based alloy B6 having the composition shown in Table 1 was produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.6 μm. 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, the diffusing material D5 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 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 53 μm to obtain a diffusing material powder having a size of 53 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 RTB-based alloy powder and diffusing material powder were mixed at a mixing ratio shown in Table 11 using an agate mortar to obtain mixed powders M9 to M18. As a comparative example, a powder of only an RTB-based alloy powder B6 not mixed with a diffusing material powder was also 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 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 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process 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 5.58 to 5.67 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 12. As can be seen from Table 12, a porous magnet having a higher coercive force than any of the conventional powders is obtained in any of the mixed powders, but in particular by weight ratio (RTB-based alloy powder): (diffusing material powder) = M: 1 (5 ≦ m ≦ 100), a porous magnet having good squareness and high coercive force is obtained.

(Experimental example 5) DR atmosphere control (diffuser material composition difference)
First, an RTB-based alloy B6 having the composition shown in Table 1 was produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.2 μm. 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, the diffusing materials D1 to D4 and D6 to D13 having the compositions shown in Table 2 were produced by the 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. These alloys were heated up to 400 ° C. in a hydrogen gas stream, occluded with hydrogen, pulverized by mechanical pulverization, classified using a mesh having an opening of 53 μm, and diffusing material powder having a size of 53 μm or less was obtained. Obtained. However, since D8 was poor in pulverizability, it was classified using a 150 μm mesh to obtain 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 size of the obtained diffusing material powder was clearly 1 μm or more. The obtained RTB-based alloy powder and diffusing material powder were mixed using an agate mortar at a mixing ratio shown in Table 13 to obtain mixed powders M19 to M30.

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 4.2 to 4.3 g / cm ³ when calculated based on dimensions and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa, and then the HD treatment step was performed while maintaining 860 ° C. for 120 minutes. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and performed the grain-boundary-phase heat processing process. 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 4.58 to 5.67 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 14. As can be seen from Table 14, when the composition ratio of the rare earth element R ′ in the diffusing material is 20 atomic% or more and 100 atomic% or less, a porous magnet having good squareness and high coercive force is obtained. Furthermore, a porous magnet having better squareness and high coercive force is obtained when the content is 30 atomic percent or more and 98 atomic percent or less, and when the content is 60 atomic percent or more and 90 atomic percent or less, an even better rectangular shape is obtained. Porous magnets having high properties and high coercive force have been obtained. Further, even when Ga, Fe, or Co is used as the M element, or when Pr is used as the R ′ element, a porous magnet having good squareness and high coercive force is obtained.

(Experimental example 6) DR atmosphere control (without diffusion material hydrogen storage)
First, an RTB-based alloy B8 having the composition shown in Table 1 was produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.2 μm. 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, the diffusing material D5 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. The ribbon-like alloy was pulverized by mechanical pulverization, and classified using a mesh having an opening of 150 μm to obtain a diffusing material powder having a size of 150 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 RTB-based alloy powder and diffusing material powder were mixed using an agate mortar at a mixing ratio shown in Table 15 to obtain mixed powder M31.

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 4.2 g / cm ³ when calculated based on dimensions and weight.

Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa, and then the HD treatment step was performed while maintaining 860 ° C. for 120 minutes. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process 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 5.79 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 16. As can be seen from Table 16, a porous magnet having a good squareness and a high coercive force is obtained even when a diffusion material not occluded by hydrogen is used.

(Experimental Example 7) Temperature rise in Ar First, an RTB-based alloy B8 having the composition shown in Table 1 was produced by a strip cast method. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.6 μm. 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, the diffusing material D5 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 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 53 μm to obtain a diffusing material powder having a size of 53 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 RTB-based alloy powder and diffusing material powder were mixed using an agate mortar at a mixing ratio shown in Table 17 to obtain mixed powder M32.

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 4.2 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 860 ° C. at a heating rate of 14 ° C./min in a 100 kPa argon flow, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then 860 ° C. was maintained for 120 minutes. The HD treatment process was performed while holding. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process 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 5.79 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 18. As can be seen from Table 18, even when the temperature is raised in an argon atmosphere, a porous magnet having good squareness and high coercive force is obtained.

(Experimental example 8) No hydrogen occlusion + temperature rise in Ar A mixed powder similar to the mixed powder M31 produced in Experimental Example 6 was 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 4.2 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 860 ° C. at a heating rate of 14 ° C./min in a 100 kPa argon flow, and then the atmosphere was switched to a 100 kPa hydrogen flow, and then 860 ° C. was maintained for 120 minutes. The HD treatment process was performed while holding. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process 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 6.11 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 19. As can be seen from Table 19, compared to the case where the temperature was raised to 600 ° C. in the hydrogen atmosphere when the HDDR treatment was heated, as in Experimental Example 6, or the case where a diffusing material with hydrogen storage was used as in Experimental Example 7. Although the magnetic force is low, a porous magnet having good squareness and high coercive force has been obtained.

(Experimental example 9) DR atmosphere control (control time change)
A mixed powder similar to the mixed powder M2 prepared in Experimental Example 1 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 4.2 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas was stopped and the heat treatment apparatus was evacuated with a vacuum pump. As shown in Table 20, while adjusting the exhaust speed of hydrogen generated from the green compact and adjusting the hydrogen pressure in the heat treatment apparatus to 4.0 kPa, Holding for 15 to 180 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 60 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process 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 6.03 to 6.25 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 21. As can be seen from Table 21, all the samples have good magnetic properties.

(Experimental example 10) DR atmosphere control (change in vacuum time)
A mixed powder similar to the mixed powder M2 prepared in Experimental Example 1 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 4.2 to 4.3 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas was stopped and the inside of the heat treatment apparatus was evacuated with a vacuum pump. As shown in Table 22, while adjusting the exhaust speed of hydrogen generated from the green compact to adjust the hydrogen pressure in the heat treatment apparatus to 4.0 kPa. The DR treatment process was performed for 60 minutes. Subsequently, the grain boundary phase forming heat treatment step was performed by maintaining the pressure at 860 ° C. in an argon flow reduced to 5.3 kPa for 5 to 60 minutes. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced.

It was 5.47-6.10 g / cm < ³ > when the density was computed from the dimension and weight of the produced 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.)). The results are shown in Table 23. As can be seen from Table 23, all the samples have good magnetic properties.

(Experimental Example 11) Hot Press of DR Atmosphere Control Sample First, RTB-based alloys B4 and B9 having the compositions shown in Table 1 were produced by strip casting. The obtained alloy was coarsely pulverized to a powder having a particle size of 425 μm or less by the hydrogen storage / disintegration method, and then the coarse powder was finely pulverized using a jet mill to obtain a fine powder having a 50% volume center particle size of 4.6 μm. 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, the diffusing material D5 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 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 53 μm to obtain a diffusing material powder having a size of 53 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 RTB-based alloy powder and diffusing material powder were mixed at the mixing ratio shown in Table 24 using an agate mortar to obtain mixed powders M33 and M34.

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 4.2 to 4.3 g / cm ³ when calculated based on dimensions and weight.

  Next, the above-mentioned HDDR process was performed on the green compact. Specifically, the green compact was heated to 600 ° C. at a rate of 14 ° C./min in a 100 kPa hydrogen flow, and then the atmosphere was switched to a 100 kPa argon flow, and then 14 ° C. to 860 ° C. The temperature was increased at a rate of temperature increase of / min, and then the atmosphere was switched to a hydrogen gas flow of 100 kPa, and then the HD treatment step was performed while maintaining 860 ° C. for 120 minutes. Thereafter, while maintaining the temperature at 860 ° C., the flow was switched to Ar flow and maintained for 2 minutes to replace the inside of the heat treatment apparatus. Next, the Ar gas is stopped and the heat treatment apparatus is evacuated by a vacuum pump, and the hydrogen pressure in the heat treatment apparatus is adjusted to 4.0 kPa by adjusting the exhaust speed of hydrogen generated from the green compact as in the condition S1 of Table 4. While maintaining for 60 minutes, the DR treatment step was performed. Subsequently, it hold | maintained for 10 minutes in the argon air pressure-reduced to 5.3 kPa with 860 degreeC, and the grain boundary phase formation heat treatment process was performed. Then, it cooled to room temperature in 100 kPa argon flow, and the sample was produced.

If the dimensions and weight of the M33 and M34 of the porous magnet manufactured calculating the density, respectively 5.55 g / cm ^3, it was 5.85 g / cm ^3.

  After magnetizing the produced M33 and M34 porous magnets 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 25.

Further, the porous magnet was 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, whereby a density of 7.46 g / cm ³ , 7. A high-density magnet of 47 g / cm ³ 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 25. As can be seen from Table 25, good magnetic properties can be obtained for all the samples, and it can be seen that the magnetic properties are further improved by the hot press as compared with the HDDR treatment.

  The present invention can be applied to various devices and apparatuses including permanent magnets. The present invention can also be used for use in a drive motor for a hybrid vehicle or an electric vehicle.

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

Claims (11)

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, and Tb) having a particle size of less than 150 μm or an R′-M alloy (M is Al, Ga, Co, Fe) A step of preparing a mixed powder with a powder of at least one selected from R, R ′ being 20 atomic percent or more and less than 100 atomic percent of the entire R′-M alloy;
Forming the green compact by forming the mixed powder;
The green compact is subjected to a heat treatment at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of more than 10 kPa and 500 kPa or less, or in a mixed atmosphere of hydrogen and inert gas having a hydrogen partial pressure of more than 10 kPa and less than 500 kPa, thereby An HD treatment process that causes hydrogenation and disproportionation reactions;
A DR treatment step in which heat treatment is performed at a temperature of 650 ° C. or more and less than 950 ° C. in a hydrogen atmosphere of 2 kPa or more and 10 kPa or less, thereby causing dehydrogenation and recombination reaction;
A grain boundary phase forming heat treatment step in which heat treatment is performed at a temperature of 650 ° C. or more and less than 950 ° C. in a vacuum or an inert atmosphere, thereby forming a grain boundary phase in the vicinity of the interface of the R ₂ T ₁₄ B phase crystal grains;
The manufacturing method of the RTB type | system | group porous magnet containing this.   2. The method for producing an RTB-based porous magnet according to claim 1, wherein the R ′ metal or the R′-M-based alloy occludes hydrogen in advance.   The manufacturing method of the RTB type | system | group porous magnet of Claim 1 or 2 which heats up the temperature of 200 to 600 degreeC in hydrogen atmosphere in the temperature rising process before the said HD process process. The RTB system according to any one of claims 1 to 3, wherein a density of the green compact before the HD treatment step is in a range of 3.5 g / cm ³ or more and 5.2 g / cm ³ or less. A method for producing a porous magnet. The RTB-based porous material according to claim 4, wherein the formed body after the grain boundary phase forming heat treatment step is porous having a density of 3.5 g / cm ³ or more and 6.5 g / cm ³ or less. A method for producing a quality magnet.   6. The R- of claim 5, wherein the porous green compact has voids communicating in a three-dimensional network, and individual powder particles constituting the green compact are bonded to adjacent powder particles. A method for producing a TB porous magnet.   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 ′ The manufacturing method of the RTB type | system | group porous magnet in any one of Claim 1 to 6 which is metal or R'-M type 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 alloy powder and the R ′ metal or R′-M alloy powder;
The manufacturing method of the RTB type | system | group porous magnet in any one of Claim 1 to 7 containing these. The step of preparing the mixed powder includes
The method according to any one of claims 1 to 8, 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 or more and less than 10 μm. A method for producing an RTB-based porous magnet according to claim 1. Preparing an RTB-based porous magnet produced by the production method according to claim 1;
Increasing the density of the RTB-based porous magnet by hot compression molding to form a high-density magnet;
The manufacturing method of the RTB type | system | group high density magnet containing this. Density of the high density magnets, in 7.0 g / cm ³ or more 7.6 g / cm ³ or less in the range, method for producing the R-T-B-based dense magnet according to claim 10.