JP2006274366A - Method for filling powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for filling a powder where, the powder can be smoothly filled into a die cavity by attaining good fluidity of the powder for improving the filling properties of a raw material powder of a rare earth magnet upon molding in the production of a rare earth sintered magnet. <P>SOLUTION: In the method for filling a powder, a gas is introduced into the powder (rare earth magnet raw material powder) fed inside a feeder 3, and the powder in the feeder is packed into each cavity 2 of a die 1, wherein regarding the amount of the gas to be introduced, the flow rate of the gas is set in such a manner that the volume of the feeder is denoted as V0(L) and the flow rate of the gas is denoted as V1(L/min), 1≤V1/V0≤30 is satisfied. Alternatively, the flow rate of the gas is set in such a manner that the volume of the powder in the feeder is denoted as V2(L) and the flow rate of the gas is denoted as (L/min), 1.5≤V1/V2≤95 is satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a powder filling method, and more particularly to a technique for improving the filling properties of rare earth magnet raw material powder during molding in the production of rare earth sintered magnets.

  For example, an R-T-B system such as an Nd-Fe-B magnet (R is one or more of Y or a rare earth element. T contains Fe as an essential element and, if necessary, includes other transition metal elements. ) Sintered magnets have advantages such as excellent magnetic properties, Nd, which is a main component, and abundant resources, and are 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 method for producing a rare earth sintered magnet, a sintering method is generally used, and a process including steps of melting → casting → coal alloy coarse pulverization → fine pulverization → press → sintering is widely applied. Specifically, the raw material alloy is coarsely pulverized and finely pulverized, then pressure-formed in a magnetic field, and sintered and heat-treated to obtain a magnet body.

  In the above-described manufacturing process, the alloy powder before molding is about several μm in size, and the fluidity is extremely poor. For example, alloy fine powders aggregate to form a bridge, which makes it difficult to fill the mold during molding. There's a problem. In particular, along with the recent miniaturization of high-performance magnets, the opening of the mold cavity has also become smaller, making it more difficult to fill the rare earth magnet raw material powder.

  Under such circumstances, various techniques for quickly filling rare earth magnet raw material powder into a mold cavity have been studied (for example, see Patent Documents 1 to 3).

  For example, Patent Document 1 discloses a so-called wet filling method, in which a raw material powder for rare earth sintered magnet and one or a mixture of mineral oil or synthetic oil are injected into a mold cavity under pressure and pressure. A method for producing a rare earth magnet is disclosed in which after filling, wet molding is performed, and the resulting compact is sintered.

  Patent Document 2 describes a technique related to air tapping, in which an object to be filled is supplied to a sealed space including a closed space having an opening, and the sealed space is alternately switched between a low pressure state and a high pressure state. The filling method of the filling material is disclosed in which the filling material is filled in the closed space with high density by performing the air tapping.

Further, in Patent Document 3, alloy fine powder is put in a container (so-called feeder) on a die front end, and the container itself is swung back and forth and left and right, or at the same time, something like a stirring bar is installed in the container, Attempts have been made to make it possible to fill a narrow gap mold by applying an external force to the mold. That is, in Patent Document 3, a rod-shaped member that pushes powder downward is provided in a container (powder box), and the powder is stirred in the powder box when the powder box is positioned on the cavity. A powder filling orientation method and a powder filling orientation apparatus that move downward are disclosed.
JP 7-57914 A JP-A-9-169301 JP 2002-292498 A

  However, in the wet filling method described in, for example, Patent Document 1, since it is necessary to handle the rare earth magnet raw material powder as a slurry dispersed in a liquid, the handling is complicated, and the liquid needs to be recovered. In some cases, the process is complicated, and the productivity may be impaired. Furthermore, mineral oil and synthetic oil used as a liquid may cause residual carbon after sintering, and may deteriorate the characteristics of the obtained rare earth sintered magnet.

  On the other hand, in the case of air tapping described in Patent Document 2, inconvenience due to the use of a liquid is eliminated, but the invention described in Patent Document 2 has a high pressure state and a low pressure state with respect to the entire space including powder. It is a method of forcibly filling powder into the cavity by repeating alternately, and is not intended to improve the fluidity of the powder, so that the filling density of the filled powder becomes large, etc. The problem is inherent. In the case of rare earth sintered magnets, a magnetic field is often applied and oriented during molding. During the orientation, the magnetic powder moves, but if the packing density is high, the movement becomes insufficient and the orientation deteriorates. Therefore, an appropriate packing density is required. In Patent Document 2, it is inevitable to increase the density of the powder after filling into the mold cavity, and it does not consider the filling property when filling into the mold cavity. When filling powder such as rare earth magnet raw material powder, the filling property is not sufficient, especially when filling into a mold cavity with a small opening diameter, the powder often forms a bridge and a predetermined amount cannot be filled. Causes poor filling. In the invention described in Patent Document 2, such a filling failure cannot be solved.

  The invention described in Patent Document 3 has been proposed for the purpose of eliminating the above-described filling failure, but in the technique described in Patent Document 3, the alloy fine powder is forcibly molded by a mechanical external force. Since the cavities are filled, the filling density tends to be too high, and a sufficient degree of orientation may not be obtained even when a magnetic field is applied during molding. Moreover, in the technique described in Patent Document 3, it is necessary to install a stirring rod (shaker) or the like in the feeder, which complicates the equipment and may cause an increase in cost and trouble.

  The present invention has been proposed in order to eliminate such disadvantages of the prior art, can improve the fluidity of the powder, and can smoothly fill the mold cavity. It is an object to provide a simple powder filling method. Further, the present invention does not require the use of a liquid for improving the fluidity of the powder, and does not require a special feed mechanism, a stirring bar, a shaker, etc., and can be filled smoothly with simple equipment. The purpose is to provide.

  In order to achieve the above-mentioned object, the powder filling method of the present invention firstly introduces gas into the powder supplied into the feeder and fills the mold cavity with the powder in the feeder. A method of filling powder, wherein when the volume of the feeder is V0 (L: liter) and the gas flow rate is V1 (L / min), the gas flow rate satisfies 1 ≦ V1 / V0 ≦ 30. Is set. Second, a powder filling method for introducing gas into the powder supplied into the feeder and filling the mold cavity with the powder in the feeder, the volume of the powder in the feeder being The gas flow rate is set so as to satisfy 1.5 ≦ V1 / V2 ≦ 95, where V2 (L) and the gas flow rate are V1 (L / min).

  As described above, by introducing the gas into the powder, each powder can be wrapped with the gas. In other words, by obtaining a state close to a fluid in which powder is dispersed in a gas, interaction due to surface energy between powders can be minimized, and aggregation and bridging can be suppressed. This is a feature of the present invention. In the present invention, since powder can be filled in the above state, bridge clogging can be prevented, uniformity can be improved, even a cavity with a small opening can be filled, and the packing density can be kept small, and the magnetic field orientation effect can be reduced. It can be increased.

  Further, normally, the feeder is reciprocated to fill the powder, but when the gas is introduced into the powder, the reciprocating motion is added to cause the boiling (if the gas amount is inappropriate) Phenomenon in which gas is blown out as bubbles), slagging (a phenomenon in which powder separates into upper and lower layers, the whole layer becomes solid, and repeats rising and falling) or channeling (a gas passage is created, and the whole powder flows) Phenomenon), and the tolerance for the amount of gas is drastically increased. In addition, the mixing and dispersibility of the gas and powder are improved, and the fluidization effect is dramatically increased.

  In the present invention, as described above, by introducing the gas into the powder supplied into the feeder, the fluidity is remarkably improved, and bridge clogging at the time of filling is eliminated. Therefore, it is not necessary to stop the process and remove the adhering powder and the bridge, thereby improving the productivity and reducing the cost. In addition, a space having a small opening shape or a space having a depth larger than that of the opening shape can be filled smoothly. However, when the gas is introduced, the introduction amount (gas flow rate) needs to be set appropriately.

  For example, when the volume of the powder supplied into the feeder is substantially constant or the fluctuation is small, the gas flow rate is set according to the volume of the feeder. That is, when the volume of the feeder is V0 (L) and the gas flow rate is V1 (L / min), the gas flow rate is set so as to satisfy 1 ≦ V1 / V0 ≦ 30. On the other hand, when the volume of the powder supplied into the feeder varies greatly with time, the gas flow rate is set according to the volume of the powder. That is, the gas flow rate is set so as to satisfy 1.5 ≦ V1 / V2 ≦ 60, where V2 (L) is the powder volume in the feeder and V1 (L / min) is the gas flow rate. By such a gas flow rate setting, the gas is evenly distributed in the powder, the fluidity of the powder in the entire feeder is reliably improved, and the bridge is also reliably removed.

  In the filling method of the present invention, since it is not necessary to use a liquid for improving the fluidity of the powder, there is no fear of complication of the process due to the recovery of the liquid or the deterioration of the characteristics due to the residual liquid. In addition, a mechanically complicated mechanism such as a stirring bar or a shaker is not required for improving fluidity and eliminating the bridge.

  According to the present invention, the fluidity of the powder can be improved efficiently, and smooth filling without bridge clogging is possible. In particular, uniform filling is possible even in a space having a small opening shape or a space having a depth larger than that of the opening shape. Further, according to the present invention, it is not necessary to use a liquid for improving the fluidity of the powder, and a special feed mechanism, a stirring bar, a shaker, etc. are unnecessary, and smooth filling is possible with simple equipment. In addition, since the packing density can be reduced, a magnet with superior orientation and improved characteristics can be obtained by applying the technique of the present invention.

  Hereinafter, a powder filling method and a filling apparatus to which the present invention is applied will be described in detail with reference to the drawings, taking as an example the case of application to the production of a rare earth sintered magnet.

  In this embodiment, the rare earth sintered magnet to be manufactured is mainly composed of rare earth element R, transition metal element T, and boron B, and is extremely excellent in magnetic properties. The downsizing and high performance can be realized.

  The magnet composition of the rare earth sintered magnet to be manufactured is not particularly limited, and may be arbitrarily selected according to the application. For example, the rare earth element R specifically means Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu. 1 type (s) or 2 or more types can be used. Among these, it is preferable that the main component as the rare earth element R is Nd because it is abundant in resources and relatively inexpensive. Moreover, as the transition metal element T, any conventionally used transition metal element can be used. For example, one or more of Fe, Co, Ni and the like can be used. Among these, Fe and Co are preferable from the viewpoint of sinterability, and it is particularly preferable to mainly include Fe from the viewpoint of magnetic characteristics. In addition to the rare earth element R, transition metal element T, and boron B, for the purpose of improving characteristics such as coercive force, an element such as Al may be added. In addition to these elements, for example, carbon and oxygen may be contained as inevitable impurities or trace additives.

  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 used to manufacture the aforementioned rare earth sintered magnet. The manufacturing process of rare earth sintered magnets by powder metallurgy is basically an alloying process, coarse pulverization process, fine pulverization process, magnetic field forming process, sintering process, aging process, processing process, and surface treatment process. 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, a raw material metal or alloy is blended in accordance with 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, but is not limited thereto. It is not a thing. As the raw material metal (alloy), pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof can be used.

  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. However, in consideration of mixing properties, mixing with an alloy is desirable.

  In the coarse pulverization step, first, a 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, hydrogen is occluded in the alloy lump and pulverization is performed. 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, 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 is completed, a pulverization aid is usually added to the coarsely pulverized raw material alloy coarse powder. As the grinding aid, for example, a fatty acid compound or the like can be used. By using such a 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 mass. 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, a fine pulverization step is performed. The fine pulverization step is performed by airflow pulverization 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 inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, and the high-speed carrier gas flow accelerates the 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. In addition, fine pulverization may be performed by wet pulverization using a ball mill, an attritor, or the like using a solvent such as toluene. In that case, a drying step for vaporizing the solvent is required.

  After the above pulverization step, the rare earth alloy fine powder is formed in the magnetic field in the magnetic field forming step. Specifically, the rare earth alloy fine powder obtained in the fine pulverization step is filled into a mold in which an electromagnet is arranged using a so-called feeder, and is molded in a magnetic field in a state where crystal axes are 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 50 to 260 MPa in a magnetic field of 400 to 1600 kA / m, for example. For the magnetic field orientation, a pulse magnetic field may be used, or a combination of a static magnetic field and a pulse magnetic field may be used. The pulse magnetic field is preferably 2400 kA / m or more.

  It is effective to use the present invention for filling rare earth metal magnet powder. This is because the rare earth magnet raw material powder needs to be filled in the mold in the molding step, but the die opening tends to become narrower as the rare earth sintered magnet becomes smaller and thinner. Is a big problem. Rare earth magnet raw material powder has poor fluidity, and when filling into a mold cavity with a small opening diameter, a bridge is often formed, causing a filling failure that prevents a predetermined amount from being filled. Moreover, even if it can be filled, the filling state becomes non-uniform, resulting in dimensional variations within the molded body and dimensional variations between the molded bodies.

  Therefore, in the present invention, a gas supply pipe is installed inside the powder, and the rare earth magnet raw material powder supplied into the feeder is mixed with the gas by ejecting the gas from the inside of the powder to the outside. By creating a mixture of powder and raw material powder, its fluidity is increased, bridge formation is eliminated, and filling properties are improved. As described above, by using a mixture of rare earth magnet raw material powder and gas, a state close to a fluid is obtained, and the interaction due to the surface energy between the powders is extremely small. At the same time, the bulk density can be reduced, the aggregation of the raw material powder is suppressed, the dispersibility between the particles is improved, and the fluidity of the raw material powder is greatly improved. In addition, no bridge is formed. Since the rare earth magnet raw material powder is agglomerated and easily forms a bridge, it is easily clogged. I could not. However, as in the present invention, by mixing the gas with the rare earth magnet raw material powder to form a mixture, aggregation and bridging can be eliminated, and the powder can be efficiently filled without stagnation. Become. Therefore, the filling property into the mold cavity becomes good, the filling time can be shortened, and the production efficiency can be improved by improving the molding cycle time.

  Here, it is preferable to use an inert gas such as nitrogen gas or argon gas that does not adversely affect the rare earth magnet raw material powder as the gas introduced (injected) into the rare earth magnet raw material powder. If air or the like is used, the rare earth magnet raw material powder may be oxidized and the characteristics may be deteriorated. Of course, if the target powder is not affected by oxidation or the like, air or the like can be used as the gas.

  When the gas is introduced into the rare earth magnet raw material powder, for example, the gas is introduced into the rare earth magnet raw material powder instead of blowing the gas from above the rare earth magnet raw material powder in the feeder. It is necessary to function as a mixture. Therefore, in the present invention, gas is ejected from the inside of the rare earth magnet raw material powder supplied and stored in the feeder to the outside of the powder, thereby improving the fluidity of the rare earth magnet raw material powder. Further, it is desirable that the gas supply port be disposed near the bottom surface of the feeder so that the gas is ejected upward from near the bottom of the rare earth magnet raw material powder. This is because, when filling, the raw material powder falls from the top to the bottom and is filled, while the gas is released from the bottom to the top, and the mixing effect can be enhanced. Moreover, since pressurization by gas can be prevented with respect to the raw material powder filled in the cavity, it is effective in reducing the filling density of the filled powder.

  In this case, it is only necessary that the gas be ejected upward from the horizontal direction, and thereby the gas can be evenly distributed to the rare earth magnet raw material powder in the feeder, and the fluidity of the rare earth magnet raw material powder. Can be improved efficiently. Note that the gas ejection direction may be any angle as long as it is directed upward from the horizontal direction, and the gas ejection direction is preferably 10 ° or more with respect to the horizontal direction. It is more preferable that at least a part of the ejection direction of the above form an angle of 10 ° to 60 ° with respect to the horizontal direction.

  When the gas is introduced, if the flow rate of the introduced gas is too small, the predetermined effect may not be obtained. That is, the fluidity of the rare earth magnet raw material powder 4 is deteriorated, and even if a bridge is formed, clogging may occur or uneven filling may occur. On the other hand, if the flow rate of the introduced gas is too large, the gas becomes bubble-like and the rare earth magnet raw material powder 4 is entrained and ejected upward, which may deteriorate the filling property. Further, channeling and slugging are likely to occur, and there is a possibility that the mixing property and fluidity of the powder and gas may be lowered. Therefore, in the present invention, the above problem is solved by appropriately setting the amount of gas introduced.

  In this case, the amount of gas introduced may be set as appropriate in consideration of surrounding conditions such as the density of the rare earth magnet raw material powder, the particle size (surface area), the material properties such as adhesion (surface energy), and the cavity shape. However, the optimum gas flow rate varies depending on the amount of rare earth magnet raw material powder in the feeder. Also, it is necessary to change the gas flow rate control method depending on the volume fluctuation of the rare earth magnet raw material powder supplied into the feeder. For example, when the volume of the powder supplied into the feeder is substantially constant or the fluctuation is small, the gas flow rate may be set constant according to the volume of the feeder. Specifically, when the feeder volume is V0 (L) and the gas flow rate is V1 (L / min), 1 ≦ V1 / V0 ≦ 30, preferably 1.5 ≦ V1 / V0 ≦ 16, Preferably, the gas flow rate is set so as to satisfy 1.5 ≦ V1 / V0 ≦ 10. If it is less than 1, the amount of gas is less than that of the raw material powder in the feeder, and sufficient fluidity of the raw material powder cannot be obtained. On the other hand, if it exceeds 30, the amount of gas becomes too large, and raw material powder may spill out of the feeder or filling into the cavity may be delayed. On the other hand, when the volume of the powder supplied into the feeder fluctuates with time, or when the volume of the feeder and the volume of the rare earth magnet raw material powder supplied therein are greatly different, the powder in the feeder It is preferable to set the gas flow rate according to the volume. That is, when the volume (= mass / bulk density) of the powder in the feeder is V2 (L) and the gas flow rate is V1 (L / min), 1.5 ≦ V1 / V2 ≦ 95, preferably 2 The gas flow rate is set so as to satisfy ≦ V1 / V0 ≦ 50. If it is less than 1.5, the amount of gas is less than that of the raw material powder in the feeder, and sufficient fluidity of the raw material powder cannot be obtained. On the other hand, if it exceeds 60, the amount of gas becomes too large, and raw material powder may spill out of the feeder or the filling into the cavity may be delayed.

  1 and 2 show an example of a filling apparatus for realizing the filling method. In the molding process, the rare earth magnet raw material powder 4 in the feeder 3 is filled in the cavity (molding space) 2 of the mold 1 and magnetic field orientation is performed, followed by pressure molding. When the rare earth magnet raw material powder 4 is filled, the lower punch 5 is inserted into the cavity 2 of the mold 1 called a die, and the rare earth magnet raw material powder 4 is filled with the tip surface of the lower punch 5 as the bottom surface. Is called. As shown in FIG. 1, the mold 1 has two cavities 2, and two molded bodies are molded simultaneously by one filling operation and molding operation.

  In the present embodiment, the opening shape of the cavity 2 is a rectangular shape, but is not limited thereto, and may be an arbitrary shape such as a C shape, a ring shape, or a disk shape. Further, the present invention is particularly effective when the shape of the cavity 2 is a shape in which the opening is narrow and the filling depth is deep, but there are no particular restrictions on the shape of the cavity 2 in application. In the present embodiment, two cavities are provided. However, the number of cavities is not limited, and may be one cavity or three or more cavities.

  The feeder 3 which is a filling device has a housing shape with the upper part opened. In this example, the so-called funnel-like shape (inverted truncated pyramid shape) in which the opening size gradually increases upward. Presents. Therefore, the rare earth magnet powder 4 supplied into the feeder 3 slides down on the wall surface and is guided from the bottom surface of the feeder 3 into the cavity 2.

  In addition, the feeder 3 is provided with a gas supply pipe 6 for supplying gas into the rare earth magnet raw material powder 4 supplied to the inside of the feeder 3. Is smoothly filled in the cavity 2.

  The gas supply pipe 6 includes a gas introduction part 6a disposed near the bottom surface of the feeder 3, and a gas supply side pipe 6b and a gas discharge side pipe 6c connected to both ends thereof. In this case, as shown in FIGS. 3A and 3B, the feeder 3 is installed at two locations on both sides of the powder feeding port 7 in the sliding direction of the feeder 3 (in the direction of the arrow x in the drawing). The installation interval L1 of the gas supply pipe 6 is arbitrary, but it is preferable to install it at intervals of 20 to 50 mm in the sliding direction. As a result, the gas can be distributed throughout the rare earth magnet raw material powder 4. The gas supply side pipe 6b and the gas discharge side pipe 6c are made of a material having flexibility, and are configured to follow the slide of the feeder 3.

  As shown in FIG. 4A, the gas introduction part 6a of the gas supply pipe 6 preferably has a plurality of gas introduction holes 6d. This is because the mixing of the raw material powder and the gas increases. The gas supplied to the gas introduction part 6a from the gas supply side pipe 6b is introduced (injected) into the rare earth magnet raw material powder 4 through these gas introduction holes 6d. Excess gas is discharged from the gas introduction part 6 a to the gas discharge side pipe 6.

  Further, the gas introduction holes 6d provided in the gas introduction part 6a are arranged in the gas introduction part 6a at regular intervals, and three gas introduction holes 6d are formed for each arrangement part. Here, the gas introduction part 6a is installed at a position as close as possible to the bottom surface of the feeder 3, and as shown in FIG. 4B, each gas introduction hole 6d is opened upward from the horizontal direction. The introduced gas is in the form of blowing up the rare earth magnet raw material powder 4 from below, and is configured to efficiently improve the fluidity of the rare earth magnet raw material powder 4.

  The opening direction of the gas introduction hole 6d is preferably upward from the horizontal direction. For example, as shown in FIG. 4B, if the angle θ from the horizontal direction is θ> 0 °. Good. Preferably, the angle θ is 10 ° or more, and the angle θ in at least a part of the gas introduction hole 6d is more preferably 10 ° to 60 °. By setting to such an angle, it is possible to distribute the gas evenly to the rare earth magnet raw material powder 4 in the vicinity of the inclined surface of the feeder 3 and to obtain fluidity stably throughout the rare earth magnet raw material powder 4. On the other hand, if the angle θ exceeds 60 ° in all the gas introduction holes 6d, the fluidization efficiency may be deteriorated. In the case of the present embodiment, two gas introduction holes 6d having an angle θ of 45 ° and one gas introduction hole 6d having an angle θ of 90 ° are formed at each arrangement location, for a total of three gas introduction holes 6d. Has been.

  Furthermore, in the case of the present embodiment, as described above, the three gas introduction holes 6d are provided for each arrangement location, but each arrangement location is preferably provided with an interval L2 of 5 to 30 mm. . If the distance L2 between the arrangement portions is less than 5 mm, the gas flow becomes too dense and it is easy to cause boiling and slugging. On the other hand, if the interval exceeds 30 mm, the gas flow becomes too sparse and channeling is likely to occur.

  The cavity 2 of the mold 1 is filled with the rare earth magnet raw material powder 4 using the filling device having the above-described configuration, and is molded into a predetermined shape. At the time of filling, the feeder 3 is reciprocated in the direction of arrow x in FIGS. 1 and 2 to fill the cavity 2 with the rare earth magnet raw material powder 4 from the bottom surface side of the feeder 3. The filling may be performed by using natural fall due to weight, suction filling due to external energy such as a magnetic field, or the like.

  In the present embodiment, since the gas is introduced into the rare earth magnet raw material powder 4 at an appropriate flow rate from the gas introduction hole 6d provided in the gas introduction portion 6a of the gas supply pipe 6, the rare earth magnet raw material powder 4 The fluidity can be improved, and smooth filling without bridge clogging is possible. In particular, even a space having a small opening shape or a space having a depth larger than that of the opening shape can be uniformly filled, and a plurality of (for example, two) molding spaces can be filled in one time. Even when filling, uniform filling is possible. Further, according to the filling method and filling apparatus of the present embodiment, it is not necessary to use a liquid for improving the fluidity of the rare earth magnet raw material powder 4, and there is no need for a special feed mechanism, a stirring bar, a shaker or the like, and simple equipment. Smooth filling is possible. Further, since the packing density can be lowered, it can be expected to obtain a magnet with excellent orientation and improved characteristics.

  During the filling, the feeder 3 is reciprocated for the filling, and at the same time (in FIGS. 1 and 2, the direction of the arrow x in FIGS. 1 and 2) (in FIGS. The reciprocation may also be performed in the direction of arrow y). In this case, the feeder 3 may be provided with a second swing mechanism that performs the reciprocating motion in the orthogonal direction in addition to the first swing mechanism that performs the reciprocating motion for filling. Thereby, the rare earth magnet raw material powder 4 can be made to collide with the side wall of the feeder 3, channeling can be prevented, and the fluidity can be further enhanced.

  After the filling, pressure forming is performed to form a formed body, and further, sintering and aging treatment are performed on the formed body in a sintering process and an aging process. That is, in the sintering step, the rare earth alloy fine powder is formed in a magnetic field, and then 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 is an important step in 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. Then, the 1st cooling process cooled to the range of room temperature-200 degreeC is provided. In the second stage aging treatment step, the temperature is maintained at about 550 ° C. for 1 to 3 hours. Next, a second cooling step for cooling 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 advisable to perform aging treatment at around 600 ° C.

  After the sintering step and the aging step, a processing step and a surface treatment step are performed. The processing step is a step of mechanically processing into a desired shape. A surface treatment process is a process performed in order to suppress the oxidation of the obtained rare earth sintered magnet, and dropping of the surface, for example, forming a plating film and a resin film on the surface of a rare earth sintered magnet.

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

Example Nd 30%, Dy 3%, B 1%, Al 0.5%, Co 0.5%, Nd-Fe-B based raw material alloy coarse powder having the composition of the balance Fe is pulverized by a jet mill. It was. The average particle diameter of the obtained rare earth magnet raw material powder was about 4 μm.

  This rare earth magnet raw material powder was transferred into the feeder 3 having the structure shown in FIGS. 1 and 2 and filled in the cavity 2 of the mold 1 to perform molding in a magnetic field. The lower part of the feeder has a rectangular opening of 40 mm × 90 mm, and the upper part has a rectangular opening of 70 mm × 130 mm and is open. The height is 100 mm. Therefore, it can be seen that the feeder volume (V0) is 0.635L. The raw material powder was supplied to the feeder so as to be constantly maintained at a height of about 30 mm to 70 mm and an average of 50 mm with respect to the height direction of the feeder. Therefore, it turns out that the volume (V2) of raw material powder is about 0.11-0.45L and average 0.32L. The opening direction of the gas introduction hole 6d provided in the gas introduction portion 6a of the gas supply pipe 6 installed in the feeder 3 is as shown in FIG. 4B, and opens upward from the horizontal direction. ing. The opening of the cavity 2 is an elongated rectangular shape of 6.1 mm × 43 mm, and the depth is 70 mm. During filling, nitrogen gas was supplied to the gas supply pipe 6 at a flow rate of 1 L / min (sample 1), 5 L / min (sample 2), and 10 L / min (sample 3).

  The rare earth magnet raw material powder was filled by reciprocating the feeder 3 in the direction of the arrow x, and the cavity 2 was rubbed and filled. In Sample 1 and Sample 2, the number of reciprocations was 8 (filling time 11 seconds), and in Sample 3, the number of reciprocations was 12 (filling time 17 seconds). After filling, the mold 1 was raised, and an upper punch was inserted from above, and it was pressed and molded at 200 MPa while applying a static magnetic field of 1000 kA / m.

  About the molded object 10 after shaping | molding, as shown in FIG. 5, the dimension of three places of AC was measured. This direction is a pressing direction during molding, and is a direction in which filling variation is easily reflected. The measurement was performed on 20 molded body samples obtained by filling and molding 10 times, and the average dimension and dimensional variation at each measurement location and the average dimension and dimensional variation in the filling direction of the molded body were obtained. The results are shown in Table 1. At the same time, the average weight and weight variation of 20 molded body samples were determined. Further, the packing density was determined from the cavity space size and the average weight, and the compact density was determined from the compact dimensions and weight. The results are also shown in Table 1.

  As is apparent from Table 1, when gas is introduced into the powder, both the dimensional variation and the weight variation in the compact 10 are reduced, and it can be seen that the rare earth magnet raw material powder is uniformly filled. In particular, Sample 3 having V1 / V2 of 22.2 to 90.9 was very excellent because both dimensional variation and weight variation were reduced. However, under the conditions of Sample 3, the number of reciprocating times of the feeder necessary for scraping and filling was 12 times, which was an increase compared to the case where the flow rate was small. In addition, boiling was generated, the raw material powder was partially scattered in the feeder, and the raw material powder spilled from the gap between the feeder and the mold, so handling was necessary. Sample 2 with V1 / V2 of 11.1 to 45.4 and Sample 1 with V1 / V2 of 2.2 to 9.1 show excellent results in both dimensional variation and weight variation, and is excellent. It has been found. Further, it was found that the number of reciprocating times of the feeder necessary for rubbing and filling is 8 times, and that the filling can be performed in about half the time when no gas is introduced. It has been found that there is no phenomenon such as boiling, slugging, or channeling, and extremely good filling is possible. Therefore, it can be said from the above result that the gas flow rate is preferably set so that V1 / V2 satisfies 1.5 ≦ V1 / V2 ≦ 95, and further 2 ≦ V1 / V0 ≦ 50. The same applies to V1 / V0, and it can be said that it is preferable to set the gas flow rate so as to satisfy 1 ≦ V1 / V0 ≦ 30, and further 1.5 ≦ V1 / V0 ≦ 10.

  In all cases, the packing density was smaller than that without gas introduction. Therefore, in this case, an improvement in orientation in magnetic field molding can be predicted, and good results were obtained. The density of the compact was increased in all cases compared to the case without gas introduction. This is presumed to be densely packed by pressurization as a result of uniform powder filling.

Comparative Example 1
Using the same feeder as in the previous example, the same filling and molding were attempted without introducing nitrogen gas into the gas supply pipe. However, the rare earth magnet raw material powder aggregated in the feeder to form a bridge, and sufficient filling could not be performed.

Comparative Example 2
The shape of the feeder was changed from a funnel shape to a rectangular parallelepiped shape (no taper), and the same filling and molding as in the example were attempted without introducing nitrogen gas into the gas supply pipe. In this case, the filling could not be completed unless the feeder was reciprocated 14 times (filling time 20 seconds). Moreover, the dimension of three places of AC was measured about the molded object (10 samples) after a shaping | molding similarly to the Example. The results are shown in Table 1.

  In Comparative Example 2, it was found that both the intra-cavity dimensional variation and the inter-cavity dimensional variation were larger than the Example, and the filling was non-uniform.

It is a front view which shows typically the example of 1 structure of the filling apparatus to which this invention is applied. It is a side view of the filling apparatus shown in FIG. (A) is a top view which shows the installation state in the cavity of a gas supply pipe, (b) is a side view. (A) is a top view which shows the external appearance shape of the gas introduction part of a gas supply pipe, (b) is sectional drawing of the part in which the gas introduction hole was formed. It is a figure which shows the dimension measurement location of the molded object in an Example and the comparative example 2. FIG.

Explanation of symbols

1 Mold, 2 cavity, 3 feeder, 4 rare earth magnet raw material powder, 5 lower punch, 6 gas supply pipe, 6a gas introduction part, 6b gas supply side pipe, 6c gas discharge side pipe, 6d gas introduction hole, 7 powder supply Mouth, 10 molded body

Claims (5)

A powder filling method for introducing gas into powder supplied into a feeder and filling the mold cavity with the powder in the feeder,
Powder filling, characterized in that the gas flow rate is set so as to satisfy 1 ≦ V1 / V0 ≦ 30 when the volume of the feeder is V0 (L) and the gas flow rate is V1 (L / min) Method. A powder filling method for introducing gas into powder supplied into a feeder and filling the mold cavity with the powder in the feeder,
The gas flow rate is set so as to satisfy 1.5 ≦ V1 / V2 ≦ 95, where V2 (L) is the powder volume in the feeder and V1 (L / min) is the gas flow rate. The powder filling method.   3. The powder filling method according to claim 1, wherein the gas is ejected upward from the horizontal direction and introduced into the powder.   4. The powder filling method according to claim 1, wherein the powder is filled by reciprocating the feeder in a predetermined direction.   The powder filling method according to any one of claims 1 to 4, wherein the powder is a rare earth magnet raw material powder.

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