JP2005281755A - Method and device for producing rare earth alloy powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the reduction of magnetic properties in a rare earth alloy powder caused by oxidation by shortening cooling time after hydrogen storage treatment. <P>SOLUTION: The rare earth alloy coarse powder after grinding by hydrogen storage is transferred to a coarse grinding stage or a fine grinding stage by high concentration powder transportation. In the high concentration powder transportation, compressed nonoxidizing gas is used as carrier gas, and its temperature is controlled to ≤25°C. In the grinding treatment by hydrogen storage, hydrogen is allowed to occlude into a raw material alloy lump within a vessel, thereafter, heat treatment is performed in a vacuum or in an inert gas atmosphere, and, next, movement is applied to the vessel. Cooling in the cooling part of the hydrogen storage device is defined as primary cooling, and cooling at transportation by the high concentration transportation is defined as secondary cooling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for rare earth alloy powder used when manufacturing a permanent magnet such as a rare earth sintered magnet, and in particular, to shorten the cooling time after hydrogen storage treatment and to prevent oxidation. For technology.

  For example, an RTB system such as an Nd-Fe-B magnet (R is one or more of rare earth elements including Y. M is essential for Fe and includes other metal elements). In recent years, the demand has tended to increase more and more because it has advantages such as excellent magnetic properties and Nd as a main component, which is abundant in resources and relatively inexpensive. Under these circumstances, research and development for improving the magnetic properties of RTB-based sintered magnets and improvement of manufacturing methods for manufacturing high-quality rare-earth sintered magnets have been promoted in various fields. ing.

  As a manufacturing method of rare earth sintered magnets, the sintering method is generally used, and a process consisting of melting, casting, alloy lump coarse pulverization, fine pulverization, press, and sintering is widely applied, and a certain degree of magnet characteristics is obtained. (See, for example, Patent Document 1). However, when a sintered magnet is manufactured by the process as described above, there is a problem that productivity is low because it takes time to grind the alloy lump.

  Therefore, hydrogen occlusion pulverization has been conventionally used in order to easily pulverize the alloy lump. In hydrogen occlusion and pulverization, cracks occur in the alloy that occludes hydrogen, and powdering proceeds in a self-destructive manner. Hydrogen storage is also effective in improving the oxidation resistance of the alloy. After the hydrogen occlusion and pulverization, the powder obtained there is further mechanically pulverized and coarsely pulverized to a particle size of about 50 to 1000 μm.

  As the conventional method of performing the hydrogen storage and pulverization, for example, a raw material alloy lump is put in a box-shaped container, hydrogen storage is performed in a batch furnace, and then transported to a heat treatment room to extract hydrogen and further transported to the next room. Then, a method of cooling is performed. However, in this conventional method, since the raw material is not stirred, a long time is required for sufficient cooling. In addition, even if sufficient cooling is performed, the temperature inside is high, so that there is a problem that oxidation proceeds when taken out into the atmosphere. Under such circumstances, the review of the process from the hydrogen occlusion pulverization to the subsequent coarse pulverization process is underway, and various improvement proposals have been proposed (see, for example, Patent Documents 1 to 3).

  For example, in the invention described in Patent Document 1, after storing hydrogen in a batch furnace, transporting it in an inert gas using a transport device, and further cooling in an inert gas with a rotary cooler or the like , Taken out and pulverized with a jet mill or the like. Patent Document 2 includes a hydrogen pulverization processing means, a coarse pulverization processing means (roll crusher), a fine pulverization processing means (jet mill), a forming means, and a rare earth magnet manufacturing apparatus having a sintering means. There is disclosed a manufacturing apparatus having handling means (conveying path by N2 gas) in an inert atmosphere between each means of pulverization processing means and forming means. However, in the manufacturing apparatus described in Patent Document 2, a handling robot is used as a transport unit from the hydrogen pulverization processing unit to the coarse pulverization processing unit.

There is also a method of storing hydrogen in a continuous furnace. Patent Document 3 discloses a manufacturing apparatus in which hydrogen pulverization processing, hydrogen release processing, and cooling processing are performed in a vertical annular furnace, and the hydrogen pulverized powder is dropped into a storage tank. Is disclosed. In the manufacturing apparatus described in Patent Document 3, conveyance to the next pulverization process (coarse pulverization process or fine pulverization process) is performed by a storage tank.
JP 2002-339005 A JP-A-6-108104 Japanese Patent No. 3120172

  By the way, for example, rare earth alloy powder used in Nd—Fe—B rare earth magnets has high activity and is easily oxidized even though it is coarse powder. In particular, during the hydrogen storage treatment, it takes a long time to be exposed to a high temperature, and it is important to prevent oxidation at this stage and improve the magnetic properties of the obtained rare earth magnet.

  Therefore, it is necessary to perform all of hydrogen storage, transport, cooling, transport to the next process, etc. in an inert gas. In the conventional methods described in the above patent documents, for example, a hydrogen pulverization process (handling cell) and The coarse pulverization step (jaw crusher) is arranged in a room so as to be covered with an inert atmosphere filled with Ar gas, and the crushed lump is conveyed using a robot or the like in the inert atmosphere room.

  However, when such a method is adopted, the entire apparatus becomes complicated and an increase in size is inevitable. Also, a long processing time is required. Alternatively, in order for an operator to enter the inert atmosphere chamber for reasons such as device maintenance or product type change, it is necessary to perform an atmosphere exchange operation or the like, and the work requires a long time. Furthermore, when using a means for transporting the crushed mass in a separate storage tank, for example, if a gas leak (air ≈ mixed with oxygen) occurs at the connection between the hydrogen pulverization furnace and the storage tank, the powder is rapidly oxidized. There is still a danger of fire and fire. Furthermore, in any of the above-described methods, little consideration is given to shortening the cooling time after hydrogen storage and pulverization, and the fact is that the shortening of the processing time is hardly achieved.

  The present invention has been proposed in view of such a conventional situation, can reduce the cooling time after the hydrogen storage treatment, and reduce the magnetic characteristics due to oxidation without causing an increase in the size of the apparatus. It is an object of the present invention to provide a method and apparatus for producing a rare earth alloy powder capable of suppressing the above.

  In order to achieve the above object, a method for producing a rare earth alloy powder of the present invention is a method for producing a rare earth alloy powder by pulverizing a raw material alloy block containing a rare earth element, a metal element and boron to obtain a rare earth alloy powder. The rare earth alloy coarse powder after pulverization treatment by hydrogen occlusion is transferred to a coarse pulverization process or a fine pulverization process by high-concentration powder transportation.

  The rare earth alloy powder production apparatus of the present invention includes a hydrogen storage treatment means for pulverizing a raw material alloy lump by hydrogen storage, and a coarse pulverization means or fine pulverization for pulverizing the rare earth alloy coarse powder pulverized by the hydrogen storage treatment means. The hydrogen storage treatment means and the coarse pulverization means or the fine pulverization means are connected by a high-concentration powder transport system.

  In the present invention, the rare earth alloy coarse powder after the hydrogen occlusion treatment (hydrogen pulverization treatment) is transferred to the coarse pulverization step or the fine pulverization step by high-concentration powder transportation. In this high-concentration powder transportation, rare earth alloy coarse powder is conveyed by a high-pressure non-oxidizing gas (inert gas such as Ar or nitrogen gas), and the rare earth alloy coarse powder is cooled during conveyance. Has an effect. Therefore, the cooling time is significantly shortened by performing the primary cooling in the final process of the hydrogen storage process and performing the secondary cooling during the conveyance in the high concentration powder transportation.

  Further, in the present invention, a series of processes such as transport of rare earth alloy coarse powder after hydrogen storage treatment is performed by a high-concentration powder transport system that is a closed circuit of non-oxidizing gas and does not touch the atmosphere. Degradation of magnetic properties due to oxidation is avoided. Moreover, the high-concentration powder transport system only requires, for example, a transfer path (pipe) between the hydrogen storage treatment means and the coarse pulverization means or the fine pulverization means, and does not require an inert atmosphere chamber or a handling robot. For this reason, the device configuration is extremely simplified and the size of the device is not increased.

  According to the present invention, the cooling time after the hydrogen storage treatment can be significantly shortened, and the productivity of the rare earth alloy powder can be greatly increased. In addition, according to the present invention, since the alloy powder is conveyed in a closed circuit in which the path is hermetically sealed, it is possible to suppress a decrease in magnetic characteristics due to oxidation. Furthermore, it is possible to realize simplification and miniaturization of the apparatus by using high concentration powder transportation.

  Hereinafter, the manufacturing method and manufacturing apparatus of the rare earth alloy powder to which the present invention is applied will be described in detail with reference to the drawings.

  In the production method and production apparatus of the present invention, the rare earth alloy powder to be produced is used for the production of rare earth sintered magnets, for example. First, the rare earth sintered magnet and the manufacturing method thereof will be outlined.

  The rare earth sintered magnet is mainly composed of rare earth elements, transition metal elements and boron. Here, the magnet composition (alloy composition) may be arbitrarily selected according to the purpose. For example, R-T-B (R is a concept including one or more rare earth elements, where the rare earth element includes Y. T is one or two of transition metal elements essential for Fe or Fe and Co. In order to obtain a rare earth sintered magnet having excellent magnetic properties, the rare earth element R is 20 to 20 in the magnet composition after sintering. It is preferable that the composition be such that 40% by weight, boron B is 0.5 to 4.5% by weight, and the balance is the transition metal element T. Here, R is one or more selected from rare earth elements, that is, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. Especially, since Nd is abundant in resources and relatively inexpensive, the main component is preferably Nd. Further, the inclusion of Dy is effective in improving the coercive force Hcj because it increases the anisotropic magnetic field.

  Alternatively, the additive element M can be added to form an R-T-B-M rare earth sintered magnet. In this case, examples of the additive element M include Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, and Ga. A seed | species or 2 or more types can be selected and added. The addition amount of these additional elements M is preferably 3% by weight or less in consideration of magnetic characteristics such as residual magnetic flux density. If the amount of additive element M added is too large, the magnetic properties may be deteriorated.

  Of course, it is needless to say that the present invention is not limited to these compositions, and can be applied to all known compositions as rare earth sintered magnets.

  Powder metallurgy is employed to produce the rare earth sintered magnet described above. Hereinafter, a method for producing a rare earth sintered magnet by powder metallurgy will be described.

  FIG. 1 shows an example of a process for producing a rare earth sintered magnet by powder metallurgy. This manufacturing process basically includes an alloying step 1, a coarse pulverizing step 2, a fine pulverizing step 3, a magnetic field forming step 4, a sintering step 5, an aging step 6, a processing step 7, and a surface treatment step 8. Consists of. In order to prevent oxidation, most of the steps until aging are performed in a vacuum or in a non-oxidizing gas atmosphere (in a nitrogen atmosphere, an Ar atmosphere, etc.).

  In the alloying step 1, a metal or alloy as a raw material is blended according to the magnet composition, melted in a vacuum or an inert gas, for example, Ar atmosphere, and cast into an alloy. As a casting method, a strip casting method (continuous casting method) in which molten high-temperature liquid metal is supplied onto a rotating roll and an alloy thin plate is continuously cast is preferable from the viewpoint of productivity and the like. It is not limited to that. As the raw material metal (alloy), pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof can be used. A solution treatment may be performed as necessary for the purpose of eliminating solidification segregation. As a condition for the solution treatment, for example, it is held in a 700 to 1500 ° C. region for 1 hour or more under vacuum or Ar atmosphere.

  As the alloy, a single alloy having almost the final magnet composition may be used, or a plurality of types of alloys having different compositions may be mixed so as to have the final magnet composition. Mixing may be performed in any process of alloy, raw material coarse powder, and raw material fine powder, but in consideration of mixing properties, mixing with an alloy is desirable.

  In the coarse pulverization step 2, first, the cast raw alloy sheet or ingot is pulverized to some extent to form an alloy lump and used for hydrogen storage. Although there is no restriction | limiting in particular in the dimension and shape of an alloy lump, It is preferable to set it as about 5-100 mm square. This pulverization may be performed by, for example, a jaw crusher.

  In the coarse pulverization step 2, the alloy lump is occluded with hydrogen and pulverized. When hydrogen is occluded in the raw material alloy lump, the hydrogen occlusion amount differs depending on the phase, and pulverization proceeds from the surface in a self-destructive manner. In the coarse pulverization step 2, after the hydrogen storage treatment, the alloy powder is dehydrogenated by heat treatment, and the dehydrogenated alloy powder is cooled and taken out.

  After the coarse pulverization step 2 is completed, a pulverization aid is usually added to the coarsely pulverized raw material alloy powder. As the grinding aid, for example, a fatty acid compound or the like can be used. In particular, by using a fatty acid amide as the grinding aid, a rare earth sintered magnet having good magnetic properties can be obtained. The addition amount of the grinding aid is preferably 0.03 to 0.4% by weight. When the grinding aid is added within this range, the amount of residual carbon after sintering can be reduced, which is effective in improving the magnetic properties of the rare earth sintered magnet.

  After the coarse pulverization step 2, a fine pulverization step 3 is performed. The fine pulverization step 3 is performed using, for example, a jet mill. The conditions at the time of fine pulverization may be appropriately set according to the airflow pulverizer to be used, and the raw material alloy powder is finely pulverized until the average particle size becomes about 1 to 10 μm, for example, 3 to 6 μm. The jet mill opens a high-pressure non-oxidizing gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, and this high-speed gas flow accelerates powder particles. This is a method of generating a collision and a collision with a collision plate or a container wall and crushing. Jet mills are generally classified into jet mills that use fluidized beds, jet mills that use vortex flow, jet mills that use impingement plates, and the like.

  After the pulverizing step 3, in the forming step 4 in the magnetic field, the raw material alloy fine powder is formed in the magnetic field. Specifically, the raw material alloy fine powder obtained in the fine pulverization step 3 is filled in a mold in which an electromagnet is arranged, and is molded in a magnetic field with a crystal axis oriented by applying a magnetic field. Forming in the magnetic field may be either longitudinal magnetic field shaping or transverse magnetic field shaping. The forming in the magnetic field may be performed at a pressure of about 130 to 160 MPa in a magnetic field of 800 to 1500 kA / m, for example.

  Next, in the sintering process 5 and the aging process 6, sintering and an aging treatment are performed. That is, in the sintering step 5, after the raw material alloy fine powder is formed in a magnetic field, the compact is sintered in a vacuum or a non-oxidizing gas atmosphere. The sintering temperature needs to be adjusted according to various conditions such as composition, pulverization method, difference in particle size and particle size distribution, etc. For example, sintering may be performed at 1000 to 1150 ° C. for about 5 hours, and rapid cooling after sintering. Is preferred. After sintering, the obtained sintered body is preferably subjected to aging treatment. This aging step 6 is an important step for controlling the coercive force Hcj of the obtained rare earth sintered magnet. For example, aging treatment is performed in a non-oxidizing gas atmosphere or in a vacuum. As the aging treatment, a two-stage aging treatment is preferable, and in the first aging treatment step, the temperature is maintained at a temperature of about 800 ° C. for 1 to 3 hours. Next, a first quenching step is provided for quenching to room temperature to 200 ° C. In the second stage aging treatment step, the temperature is maintained at about 550 ° C. for 1 to 3 hours. Next, a second quenching step for quenching to room temperature is provided. Since the coercive force Hcj is greatly increased by heat treatment at around 600 ° C., when aging treatment is performed in a single stage, it is preferable to perform aging treatment at around 600 ° C.

  After the sintering step 5 and the aging step 6, a processing step 7 and a surface treatment step 8 are performed. The processing step 7 is a step of mechanically forming into a desired shape. The surface treatment step 8 is a step performed to suppress oxidation of the obtained rare earth sintered magnet. For example, a plating film or a resin film is formed on the surface of the rare earth sintered magnet.

  In the manufacturing process of the rare earth sintered magnet described above, in the present invention, the following manufacturing method and manufacturing apparatus are used, and coarse pulverization (hydrogen storage pulverization) is performed. For example, it is conveyed to a mechanical coarse pulverization process or a fine pulverization process. Hereinafter, an example of a manufacturing method and a manufacturing apparatus to which the present invention is applied will be described.

  FIG. 2 shows an example of a manufacturing apparatus to which the present invention is applied. This manufacturing apparatus includes a hydrogen storage device 11 as a hydrogen storage means, a raw material receiving hopper 12, and a high concentration powder transport device 13 as a high concentration powder transport system, and an alloy discharged from the hydrogen storage device 11. Coarse powder is received by the raw material receiving hopper 12, and the alloy coarse powder in the raw material receiving hopper 12 is processed by the high-concentration powder transport device 13 in the next step (not shown), for example, a jaw crusher as coarse pulverizing means. To a coarse pulverization step by mechanical pulverization, or a fine pulverization step by airflow pulverization such as a jet mill as fine pulverization means.

  Here, the hydrogen storage device 11 performs hydrogenation in a raw material alloy lump in a container, then heat-treats in a vacuum or in an inert gas atmosphere, and then pulverizes by applying motion to the container. As shown in FIG. 3, the hydrogen storage part 21 which occludes hydrogen in an alloy lump and is crushed or pulverized to obtain an alloy powder, the heat treatment part 22 for heating and dehydrogenating the hydrogen-occluded alloy powder, and the dehydrogenated alloy powder And a cooling unit 23 for removing heat. And these hydrogen storage part 21, the heat processing part 22, and the cooling part 23 are arrange | positioned along the central axis of the same cylindrical container.

  The integrated container in which the hydrogen storage unit 21, the heat treatment unit 22, and the cooling unit 23 are integrated is supported on a gantry (not shown) so that the central axis thereof is substantially horizontal. And it is the structure which carries out the rotational motion centering on a central axis. Moreover, the mechanism which jacks up the hydrogen storage part 21 side is attached to the mount frame which supports a container. Thereby, the movement assistance of the alloy powder in each part (the hydrogen storage part 21 to the heat processing part 22 and the heat processing part 22 to the cooling part 23) can be supported.

  A gas introduction pipe 24 is connected to the inlet side of the integrated container in which the hydrogen storage part 21, the heat treatment part 22 and the cooling part 23 are integrated, and a hydrogen introduction pipe 25 as an hydrogen supply mechanism and an Ar introduction pipe as an inert gas supply mechanism. 26 is inserted. On the other hand, an exhaust pipe 27 is connected to the outlet side to exhaust air, hydrogen gas, inert gas (Ar gas), etc. in the container. Further, the container in which the hydrogen storage unit 21, the heat treatment unit 22, and the cooling unit 23 are integrated is rotatable in both forward and reverse directions by a motor 34 and a chain 35 as shown in FIG. The motor 34 has its rotation direction and rotation speed controlled by, for example, an inverter.

  The hydrogen storage portion 21 is a region for storing hydrogen in the alloy lump, and a groove-shaped or fin-shaped spiral portion 28 having the container central axis as an axis is formed on the inner peripheral surface thereof. Therefore, depending on the rotation direction, the alloy lump can be retained or dispensed by the action of the spiral portion 28. In addition, the hydrogen storage unit 21 may be provided with a shower 29 for spraying cooling water on the top thereof for the purpose of suppressing heat generation associated with hydrogen storage.

  The heat treatment part 22 is a region where the alloy powder is dehydrogenated by heating, and a plurality of electric heaters 31 are arranged on the outside, and the alloy powder is heated from the outside of the container. In this example, three sets of panel-like resistance heaters are disposed as the electric heating body 31 as means for heating both side surfaces and the upper surface of the heat treatment section 32, and the inside of the container is controlled to have a uniform temperature.

  Moreover, in the heat processing part 22, the some protrusion part 30 which protrudes toward the center axis | shaft of a container is formed in the container internal peripheral surface. The plurality of protrusions 30 may be in any arrangement relationship. For example, as shown in FIG. 5, four protrusions 30 that are shifted by 90 degrees are formed, as shown in FIG. A plurality of sets may be arranged in a zigzag pattern in the central axis direction. The shape of the protrusion 30 may be an arbitrary shape as long as the alloy powder is stirred, such as a shelf.

  The cooling part 23 is an area for cooling and discharging the alloy powder after dehydrogenation. Like the hydrogen storage part 21, the cooling part 23 has a groove shape or fin shape with the container central axis as an axis on the container inner peripheral surface. A spiral portion 32 is formed. However, the spiral direction of the spiral portion 32 is opposite to the spiral direction of the spiral portion 28 of the hydrogen storage portion 21.

  The cooling unit 23 of the container used this time is provided with six small cylinders that revolve (not rotate) the central axis arranged on the circumference of the central axis (not shown). A groove-shaped or fin-shaped spiral portion 32 is formed so that the alloy powder is dividedly supplied from the above. The alloy powder is cooled while being stirred and moved by the groove-like or fin-like spiral portion 32 provided in each small cylinder. Furthermore, a plurality of radiating fins are provided on the outer periphery of each small cylinder, and a shower 33 for spraying cooling water is installed on the cooling portion 23 in this portion.

  In the hydrogen storage device 11 having the above-described configuration, when coarsely pulverizing by hydrogen storage, first, as shown in FIG. 6, the alloy lump is sealed in the hydrogen storage unit 21 which is a cylindrical stainless steel container (raw material charging step: Step S1). After the raw materials are charged, after evacuating to a substantially vacuum (evacuation step: step S2), hydrogen gas is then introduced (hydrogen introduction step: step S3). At this time, the pressure in the hydrogen storage unit 21 is set slightly higher than the atmospheric pressure.

  Then, while maintaining this atmosphere, the container is rotated about the central axis (cylindrical axis) of the container, and crushing or pulverizing is performed while storing hydrogen in the alloy lump. A groove-shaped or fin-shaped spiral portion 28 with the central axis of the container as an axis is formed on the inner peripheral surface of the hydrogen storage portion 21, and an alloy lump or alloy powder stays in the hydrogen storage portion 21 during hydrogen introduction. Reverse rotation is performed to store (step S4).

  In addition, it is preferable that the retention temperature of the alloy lump in a hydrogen storage process shall be 0-200 degreeC. Therefore, when the temperature rises too much, cooling water is sprayed from the shower 19. Further, the treatment time of the hydrogen storage step is not particularly limited, but it is usually preferable to set it to about 0.5 to 5 hours.

  Thereafter, the hydrogen storage unit 21 is rotated forward to move the alloy powder M in the hydrogen storage unit 21 to the heat treatment unit 22 by the action of the groove-shaped or fin-shaped spiral unit 28 (step S5). At this time, it is preferable to assist the movement of the alloy powder M by tilting the gantry supporting the container (lowering the container on the heat treatment part 22 side).

  After the hydrogen occlusion, the heat treatment unit 22 introduces Ar (other inert gas may be used) so as to exhaust the hydrogen gas in the container (step S6), while the alloy powder M in the heat treatment unit 22 is heated. The heater 31 is heated so that the temperature becomes about 600 ° C., and hydrogen gas is released from the alloy powder while maintaining this temperature (step S7).

  The Ar gas is introduced by an Ar introduction pipe 26 which is an inert gas supply mechanism, and Ar gas is caused to flow into the heat treatment portion 22 at a pressure equal to or higher than atmospheric pressure. By setting the supplied Ar gas to atmospheric pressure or higher, it is possible to prevent ambient air from entering the heat treatment portion 22. Further, by flowing Ar gas and exhausting sequentially from the exhaust pipe 27, hydrogen released from the alloy powder is also sequentially discharged, and efficient dehydrogenation becomes possible.

  The heat treatment step is a step of releasing hydrogen from the alloy powder M, and it is preferable to perform a heat treatment that releases about 50% to 90% of the stored hydrogen. The heat treatment step is preferably performed continuously following the hydrogen storage step as in this embodiment. Although there is no restriction | limiting in particular in heat processing conditions, In order to perform the hydrogen removal from an alloy powder efficiently, it is preferable to perform the heat processing for 0.5 to 5 hours at 200-800 degreeC.

  During the heat treatment step, the container in which the hydrogen storage unit 21, the heat treatment unit 22, and the cooling unit 23 are integrated is rotated forward. Since the spiral directions of the spiral portion 28 of the hydrogen storage portion 21 and the spiral portion 32 of the cooling portion 23 are opposite to each other, when rotating forward, the spiral portion 28 of the hydrogen storage portion 21 causes the alloy powder to move in the left direction in FIG. On the other hand, the spiral portion 32 of the cooling portion 23 acts to retain the alloy powder in the right direction in FIG. Therefore, by these actions, the alloy powder stays in the heat treatment part 22 during the heat treatment process.

  Here, since the shelf-like protrusion 30 is formed in the heat treatment part 22, pulverization is promoted and hydrogen release is promoted. That is, while the alloy powder stays in the heat treatment section 22, the heat treatment section 22 that is a cylindrical container rotates, and the alloy powder in the heat treatment section 22 is dehydrated while being crushed or pulverized by the plurality of protrusions 30. Elementary is done. At this time, since the remaining alloy lump and the collapsed alloy powder are accelerated by the protrusions 30, they frequently move in the heat treatment part 22 and contact or collide with each other, and the inner wall of the heat treatment part 22 or The protrusion 30 also contacts or collides. As a result, even if the amount of the alloy powder input into the heat treatment part 22 is large and the proportion of the alloy powder in the heat treatment part 22 is high, the alloy powder is heated uniformly. For this reason, the processing capability can be greatly improved with respect to the size of the apparatus. In the heat treatment section 22, the alloy powder is further crushed or pulverized, and the alloy lump can be almost completely powdered. Then, it cools so that the temperature in the heat processing part 22 may be set to about 100 degreeC. At this time, the alloy powder M may be cooled to about 200 ° C.

  After the heat treatment in the heat treatment part 22, finally, the container in which the hydrogen storage part 21, the heat treatment part 22 and the cooling part 23 are integrated is reversely rotated, and the dehydrogenated alloy powder is moved from the heat treatment part 22 to the cooling part 23. (Step S8). In the cooling unit 23, the alloy powder is cooled by any one of air cooling, water cooling, oil cooling, cooling gas, or a combination thereof, and moved to the next process (fine pulverization process) (step S9). The alloy powder is preferably stabilized by cooling to 50 ° C. or lower as primary cooling.

  In the cooling part 23, a groove-like or fin-like spiral part 32 is formed in the direction opposite to the hydrogen storage part 21. Therefore, by rotating backward, the alloy powder passes through the cooling part 23 by the groove-like or fin-like spiral part 32 in the cooling part 23 and the temperature is lowered, and then is discharged from the discharge part on the exhaust pipe 27 side. It is. At this time, it is preferable to assist the movement of the alloy powder by inclining the gantry supporting the container (lowering the container to the exhaust pipe 27 side).

  The alloy coarse powder discharged from the cooling unit 23 of the hydrogen storage device 11 is dropped into the raw material receiving hopper 12 and conveyed to the coarse pulverization step or the fine pulverization step by the high concentration powder transport device 13. The hydrogen storage device 11 does not continuously discharge the alloy coarse powder that has been hydrogen occluded and pulverized by a certain amount, and so to speak, a predetermined amount of the alloy coarse powder is discharged at regular intervals as in a batch system. . Accordingly, the raw material receiving hopper 12 serves as a buffer, and adjusts the amount of powder supplied to the high-concentration powder transport device 13 here. Of course, the raw material receiving hopper 12 may not be provided, and the powder may be directly supplied from the hydrogen storage device 11 to the high-concentration powder transport device 13. In this example, a discharge amount adjusting valve 14 is provided on the outlet side of the hydrogen storage device 11, and the high concentration powder transporting device 13 is provided by the cooperation of the discharge amount adjusting valve 14 and the material receiving hopper 12. The alloy coarse powder is configured to be stably supplied.

  For example, as shown in FIG. 7, the high-concentration powder transport device 13 includes a blow tank 41 into which the alloy coarse powder from the raw material receiving hopper 12 is introduced, a compressed gas introduction pipe 42, and the alloy coarse powder to be conveyed. It is comprised from the piping 43 used as a conveyance path | route.

  In the high-concentration powder transport device 13 having such a configuration, the alloy coarse powder introduced from the raw material receiving hopper 12 is first dropped into the blow tank 41. In the blow tank 41, the raw material alloy powder, which is a transported material, is brought into a fluidized state, and is blown and transported together with the compressed gas introduced from the compressed gas introduction pipe 42, here the non-oxidizing gas, into the pipe 43 serving as the transport path. The transport state by the high-concentration powder transport device 13 includes a low-concentration floating flow type in which powder is dispersed and scattered, and a high-concentration sliding type in which the powder is slid to some extent. In transportation, the transportation state is a plug-like sliding (high concentration sliding type).

  The carrier gas introduced from the compressed gas introduction pipe 42 is preferably a non-oxidizing gas from the viewpoint of preventing oxidation of the alloy coarse powder. For example, the oxygen concentration is 3000 ppm or less, preferably 1000 ppm or less, more preferably 100 ppm or less. Nitrogen gas is used. Of course, an inert gas such as Ar gas can be used, but nitrogen gas is practical in terms of cost. The carrier gas is preferably supplied at a pressure of 0.25 to 0.7 MPa, and thereby, the conveyance by the sliding in the plug shape can be realized. If the pressure of the carrier gas to be supplied is lower than the above value, it is not desirable because smooth conveyance of the alloy coarse powder becomes difficult or the alloy coarse powder may be blocked in the pipe. Further, if the pressure of the carrier gas to be supplied exceeds the above value, the transportation speed of the alloy coarse powder is increased, and the wear of the alloy coarse powder may be promoted, which is not desirable.

  In the conveyance by the high-concentration powder conveyance device 13, the alloy coarse powder is conveyed together with the air flow, and thus is cooled to some extent in the conveyance process. Therefore, in the present invention, the cooling during the conveyance is used as the secondary cooling. If the cooling in the cooling unit 23 of the hydrogen storage device 11 is the primary cooling and the cooling at the time of transport is the secondary cooling, it is possible to cool the coarse alloy powder after pulverization by hydrogen storage in a short time. It is.

  However, in order to efficiently perform the cooling during the conveyance, it is preferable to cool the conveyance gas introduced from the compressed gas introduction pipe 42 or cool the conveyance path (pipe 43). When the carrier gas is cooled, the temperature of the carrier gas is preferably 25 ° C. or lower. In order to set the temperature of the carrier gas to 25 ° C. or lower, the carrier gas may be cooled in advance. For example, it is easy to use nitrogen gas obtained by vaporizing liquid nitrogen. When the conveyance path (pipe 43) is cooled, it may be cooled from the outside of the pipe 43 by means of air cooling, water cooling, oil cooling or the like.

  Since the conveyance by the high-concentration powder transport device 13 is performed in a closed circuit of a non-oxidizing gas that does not come into contact with the atmosphere, the oxidation of the alloy coarse powder can be reliably suppressed, The contained oxygen content can be reduced. In addition, the processing time required for hydrogen storage, cooling, and transportation to the next process can be greatly reduced. The reduction of the oxygen content also contributes to the improvement of the magnetic properties of the rare earth sintered magnet produced using this.

  The conveyance by the high-concentration powder transport device 13 does not require special means such as an inert atmosphere chamber, so that the entire device is not complicated and does not increase in size. In addition, the degree of freedom of equipment maintenance and product change increases, which contributes to shortening of work time. Furthermore, it is advantageous in terms of safety because processes that may cause ignition due to rapid oxidation can be reduced.

  Hereinafter, specific examples of the present invention will be described based on experimental results.

(Hydrogen storage pulverization)
An alloy ingot for Nd—Fe—B permanent magnet having a composition of Nd 31.5%, Dy 1.5%, B 1.1%, Al 0.3% and the balance Fe in weight percentage was prepared and put into a hydrogen storage device. . The alloy lump was sealed in a hydrogen storage part 21 of a hydrogen storage device (cylindrical stainless steel container) and evacuated to a substantially vacuum, and then hydrogen gas was introduced into the device to make the pressure in the container 1 atmosphere. And while maintaining this atmosphere, the central axis (cylindrical axis) of the container was used as a rotation axis for one hour of rotation, and hydrogen was occluded in the alloy lump. Next, the alloy lump in which hydrogen has been occluded is moved to the heat treatment section 22, and Ar is introduced into the container so as to exhaust the hydrogen gas, and a heater is used so that the temperature of the alloy lump in the container becomes 600 ° C. Heating was performed to release hydrogen gas from the alloy lump while maintaining this temperature.

(Comparative example)
The alloy coarse powder pulverized as described above was moved to the cooling unit 23 and cooled. In the cooling part 23, the alloy coarse powder was stirred with a fan while introducing an inert gas.

(Example)
The alloy coarse powder pulverized as described above was moved to the cooling unit 23 to perform primary cooling, and when the temperature dropped to some extent, it was conveyed by a high-concentration powder transport device and subjected to secondary cooling. As the carrier gas, nitrogen gas having a temperature of 25 ° C. or lower was used.

(Evaluation)
About the comparative example and the Example, the relationship between cooling time and raw material temperature (alloy coarse powder temperature) was investigated. The raw material temperature was measured on the outside of the cooling unit 23 and the inside of the cooling unit. The results are shown in Table 1.

  As is apparent from this table, in the conventional process (comparative example), it takes 10 hours or more to bring the temperature inside the cooling section to room temperature. On the other hand, it is sufficient that cooling by the cooling unit 23 is performed for about 2.5 to 5 hours by combining conveyance by a high-concentration powder transportation device, and after powder transportation, the room temperature is set to 20 ° C. I was able to. Therefore, according to this invention, it turns out that the processing time required for hydrogen occlusion, cooling, and the conveyance to the following process can be shortened significantly.

It is a flowchart which shows an example of the manufacturing process of a rare earth sintered magnet. It is a figure which shows typically the example of 1 structure of the manufacturing apparatus to which this invention is applied. It is a side view which shows typically an example of a hydrogen storage apparatus. It is sectional drawing which shows the internal structure of a hydrogen storage part. It is sectional drawing which shows the internal structure of a heat processing part. It is a flowchart which shows the rough crushing process in a hydrogen storage apparatus in order of a process. It is a side view which shows an example of a high concentration powder conveying apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Hydrogen occlusion apparatus, 12 Raw material receiving hopper, 13 High concentration powder transport apparatus, 21 Hydrogen occlusion part, 22 Heat treatment part, 23 Cooling part, 25 Hydrogen introduction pipe, 26 Ar introduction pipe, 28 Spiral part, 30 Protrusion part, 31 Electric heating element, 32 spiral part, 41 blow tank, 42 compressed gas introduction pipe, 43 pipe

Claims (12)

A method for producing a rare earth alloy powder by pulverizing a raw material alloy lump containing a rare earth element, a metal element, and boron to form a rare earth alloy powder,
A method for producing a rare earth alloy powder, characterized in that the rare earth alloy coarse powder after pulverization treatment by hydrogen occlusion is transferred to a coarse pulverization step or a fine pulverization step by high-concentration powder transportation.   2. The production of rare earth alloy powder according to claim 1, wherein in the high-concentration powder transportation, a compressed non-oxidizing gas is used as a carrier gas, and the rare earth alloy coarse powder after the pulverization treatment by hydrogen occlusion is transported. Method.   The method for producing a rare earth alloy powder according to claim 2, wherein the temperature of the non-oxidizing gas is 25 ° C or lower.   4. The method for producing rare earth alloy powder according to claim 3, wherein nitrogen gas obtained by vaporizing liquid nitrogen is used as the non-oxidizing gas.   4. The method for producing a rare earth alloy powder according to claim 3, wherein a conveying path by the high-concentration powder transportation is cooled.   In the pulverization treatment by the hydrogen storage, the raw material alloy lump is made to store hydrogen in the container, and then heat-treated in a vacuum or in an inert gas atmosphere, and then pulverized by applying motion to the container. The method for producing a rare earth alloy powder according to any one of claims 1 to 5.   After the hydrogen occlusion is performed while rotating the integral container in the direction in which the raw material alloy lump stays in the hydrogen occlusion part, it is rotated forward to move the alloy powder from the hydrogen occlusion part to the heat treatment part, and further, the heat treatment is performed while rotating forward. The method for producing a rare earth alloy powder according to claim 6, wherein after the heat treatment is performed in the part, the alloy powder is moved to the cooling part by reverse rotation again, and cooled and discharged.   8. The method for producing a rare earth alloy powder according to claim 7, wherein the cooling in the cooling unit is primary cooling, and secondary cooling is performed in a transport path for transporting the high-concentration powder. A hydrogen storage treatment means for pulverizing the raw material alloy lump by hydrogen storage, and a coarse pulverization means or a fine pulverization means for pulverizing the rare earth alloy coarse powder pulverized by the hydrogen storage treatment means,
An apparatus for producing rare earth alloy powder, characterized in that the hydrogen storage treatment means and the coarse pulverization means or the fine pulverization means are connected by a high-concentration powder transport system.   The high-concentration powder transport system includes a blow tank that stores a rare earth alloy after pulverization by hydrogen storage, and a compressed gas introduction pipe and a transport path are connected to the blow tank. 9. An apparatus for producing a rare earth alloy powder according to 9.   The apparatus for producing rare earth alloy powder according to claim 10, wherein cooling means is provided in the transport path.   The raw material receiving hopper for storing the rare earth alloy coarse powder discharged from the hydrogen storage treatment means is provided between the high concentration powder transport system and the hydrogen storage treatment means. 11. The apparatus for producing a rare earth alloy powder according to any one of 11 above.

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