JP2007196282A - Powder compacting method and powder compacting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder compacting method where compactness is not deteriorated even if continuous compacting is performed without providing an adsorption member. <P>SOLUTION: The powder compacting method where a compact is produced from a powder composition in a cavity formed at the die hole of a die using an upper punch and a lower punch comprises: a stage where a liquid lubricant is fed to the inner wall face of the die facing to the die hole from the side wall face of the lower punch; a stage where a prescribed amount of powder composition is fed to the cavity; and a stage where the powder composition fed into the cavity is subjected to press compacting by the upper punch and the lower punch, and in the period of either or both of the powder composition feeding stage and the press compacting stage, a gas is fed to the inner wall face of the die facing to the die hole from the side wall face of the lower punch. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a powder molding method and a powder molding apparatus for pressure-molding a powder composition, and in particular, a powder is added using a lubricant in order to prevent a phenomenon that the powder composition to be molded is galling. The present invention relates to a pressure forming method and apparatus.

  Conventionally, sintered magnets and the like have been produced using powder metallurgy. In a general powder metallurgy method, raw material alloy powder that has been micronized to several hundred microns or less is pressure-formed, and the resulting powder compact (green compact) is heated and held at a predetermined temperature and sintered. A sintered body such as a sintered magnet is produced.

In particular, Nd—Fe—B based sintered magnets that are frequently used for motors or the like first pulverize and finely pulverize the raw material alloy to a micron order. Next, the fine powder is pressure-molded in a magnetic field, and then sintered and aged to produce an Nd—Fe—B based sintered magnet.
This pressure molding is a powder comprising a die having a die hole penetrating in the vertical direction, an upper punch capable of advancing and retreating from above in the die hole, and a lower punch disposed in the die hole so as to be movable relative to the die. This is done using a molding device. Then, a cavity is formed in the die hole of the die by arranging the lower punch at a predetermined position in the die hole, and the fine powder (magnet powder) is dropped into the cavity from above and filled, and then the upper punch is attached to the die hole. It inserts in and presses in cooperation with a lower punch, and a molded object is obtained.

  Rare earth magnet powders typified by Nd-Fe-B magnet powders have poor fluidity, and there is a problem of galling in the die during the compression molding process. This galling means that a small amount of powder, which is a molded body, adheres to the die due to frictional heat. Since the powder adhering to the die has a strong adhesive force, if the molding is continued as it is, scratches, cracks, cracks and the like are generated in the molded body due to the adhered powder, and the quality of the molded body is deteriorated.

  In order to solve the above-described problems, Patent Document 1 discloses a technique for adding a lubricant to magnet powder. In this Patent Document 1, the Fe-R-B magnet powder is mixed with a lubricant (including at least one of stearic acid, zinc stearate and bisamide) to improve moldability and galling. It is disclosed that it is possible to suppress the occurrence of scratches and the like on the molded body due to the above. In Patent Document 1, a liquid lubricant obtained by dissolving or dispersing a solid lubricant in a solvent is added to a magnet powder to be molded.

  The method of adding a lubricant to magnet powder as in Patent Document 1 has a certain effect on improving moldability. However, in order to further improve the moldability, it is necessary to add an excessive amount of lubricant. This is because, in the method of adding to the magnet powder, there is a considerable amount of lubricant that does not contribute to the improvement of moldability. Since the lubricant is composed of an organic substance, the addition of an excessive amount of lubricant leads to an increase in the amount of carbon, which is one of the factors that reduce magnetic properties such as coercive force.

On the other hand, a method of applying a lubricant to a die is also disclosed. For example, Patent Document 2 discloses a technique in which a groove is provided around the upper side wall surface of the lower punch, and liquid lubricant flows out from nozzles as a plurality of supply ports in the groove toward the inner wall surface of the die. Has been.
Patent Document 3 discloses a powder press apparatus provided with a supply port for supplying a liquid lubricant to a die hole inner wall surface together with a gas from a supply port provided on a side wall surface of a lower punch. In this powder press apparatus, a lubricant adsorbing member made of a fiber such as felt is disposed so as to cover the upper periphery of the lower punch and the supply port, and the atomized lubricant is supplied to the adsorbing member. The lubricant is applied to the side wall surface of the die hole through the adsorption member.

JP-A-4-214803 JP-A-3-291307 JP 2000-197997 A

  When the lubricant is supplied by the methods described in Patent Document 2 and Patent Document 3, when the number of molding cycles is relatively small, good moldability can be obtained. However, according to the study by the present inventors, magnet powder becomes clogged in the supply port for supplying the lubricant as the molding cycle increases, or magnet powder gets into the attracting member, so that the lubricant supply port is clogged. Will occur. Due to such a phenomenon, the supply of the lubricant is insufficient, so that the moldability is deteriorated and scratches, cracks, cracks and the like are generated in the molded body, leading to molding defects. That is, the conventional powder molding apparatus has an insufficient effect on long-term continuous pressure molding.

  Moreover, the technique which provides an adsorption member like patent document 3 is not suitable when obtaining a thin molded object. Since the suction member is disposed around the lower punch, the lower punch needs to have a thickness obtained by subtracting the thickness of the suction member. When the thickness of the molded body to be molded is as thin as 15 mm or less, for example, the thickness of the lower punch must be made thinner than that, making it difficult to withstand the stress applied during pressing. In particular, it is practically difficult to employ a technique for disposing an adsorbing member on a thin molded body in consideration of making a path for supplying a lubricant into the lower punch.

  Then, an object of this invention is to provide the powder shaping | molding method and powder shaping | molding apparatus which a moldability does not deteriorate even if it forms continuously, without providing an adsorption member.

  The present inventors examined a method of supplying a liquid lubricant from a supply port provided in the lower punch, in particular, prevention of clogging of the magnetic powder into the supply port. As a result, it was difficult to remove the clogged magnet powder. In order to remove the magnet powder clogged in the supply port, it may be possible to eject the lubricant at a high pressure, but the magnet powder could not be removed even if the lubricant was ejected at a considerable pressure. This was the same even if it tried to remove magnet powder using gas. Further, ejecting the lubricant at a high pressure leads to supplying the lubricant into the cavity more than necessary, which is not preferable for the magnetic characteristics.

  Therefore, the present inventors have studied not to remove the clogged magnet powder after the fact but to prevent clogging itself. As a result, it was possible to prevent clogging of the magnet powder into the supply port formed in the lower punch by supplying the gas from the lower punch during the period when the magnet powder is filled in the cavity. Moreover, even if the pressure of the gas to be supplied is very small, the effect can be sufficiently obtained, and it has been found that there is almost no adverse effect on molding.

  The powder molding method of the present invention based on the above examination results is a powder molding method for producing a molded body using the upper punch and the lower punch from the powder composition in the cavity formed in the die hole of the die. A supply step of supplying a liquid lubricant from the side wall surface of the lower punch to the inner wall surface of the die facing, a step of supplying a predetermined amount of powder composition to the cavity, and a powder composition supplied into the cavity And pressing the upper punch and the lower punch, and the inner wall surface of the die facing the die hole during one or both of the step of supplying the powder composition and the step of pressing The gas is supplied from the side wall surface of the lower punch.

  In the powder molding method of the present invention, the gas is supplied from the side wall surface of the lower punch to the inner wall surface of the die facing the die hole during either or both of the powder filling step and the pressure molding step. Clogging of the powder composition into the lubricant supply port formed in the lower punch can be prevented.

In the powder molding method of the present invention, the supply pressure of the lubricant is preferably 0.01 to 0.5 MPa, and the supply pressure of the gas is preferably 0.03 to 3 MPa.
In the powder molding method of the present invention, the raw powder of the RTB-based sintered magnet can be used as the powder composition. In this case, the gas is preferably a non-oxidizing gas. In particular, when the oxygen concentration of the raw material powder is 3000 ppm or less, it is important that the gas is a non-oxidizing gas in order to prevent an increase in oxygen concentration.

  The present invention provides a powder molding apparatus capable of realizing the powder molding method described above. The powder molding apparatus for producing a molded body by pressure molding the powder composition includes a die having a die hole penetrating in the vertical direction, an upper punch for applying pressure to the powder composition supplied into the die hole, and A lubricant supply path for supplying lubricant supplied from the outside to a plurality of first supply ports opened in the side wall surface of the lower punch, and supplying from the outside A gas supply path is formed for supplying the generated gas to a plurality of second supply ports opened in the side wall surface of the lower punch.

  In the powder molding apparatus of the present invention, before supplying the powder composition into the die hole, the lubricant is supplied from the first supply port toward the inner wall surface of the die through the lubricant supply path, and then the gas is supplied. A controller for controlling the powder molding apparatus to supply gas from the second supply port to the inner wall surface of the die through the supply path and then supply the powder composition into the die hole can be provided. Thus, the controller can prevent clogging with the powder composition at the first supply port for supplying the lubricant by controlling the supply of the lubricant and the supply of the gas.

Here, the lubricant supply path is connected to the lubricant vertical supply path for supplying the lubricant in the vertical direction of the lower punch and the lubricant vertical supply path, and the lubricant supplied from the lubricant vertical supply path is horizontally aligned. And it can be set as the structure provided with the lubricant horizontal supply path supplied to a 1st supply port. Similarly, the gas supply path is connected to the gas vertical supply path for supplying gas in the vertical direction of the lower punch and the gas vertical supply path, and the gas supplied from the gas vertical supply path is horizontally extended to the second supply port. It can be set as the structure provided with the gas horizontal supply path to supply.
In the above configuration, the lubricant vertical supply path and the gas vertical supply path are independent, but the lubricant horizontal supply path can also serve as the gas horizontal supply path.
Furthermore, in the above configuration, the lubricant horizontal supply path can form a lattice-like path branched from the lubricant vertical supply path, and the gas horizontal supply path can form a lattice-like path branched from the gas vertical supply path.

  As described above, according to the present invention, gas is supplied from the side wall surface of the lower punch to the inner wall surface of the die facing the die hole during one or both of the powder filling step and the pressure forming step. By doing so, clogging of the powder composition into the lubricant supply port formed in the lower punch can be prevented.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of a powder molding apparatus 10 according to an embodiment of the present invention. In addition, although the powder shaping | molding apparatus 10 press-molds, applying the magnetic field of a predetermined direction to the magnetic powder P which is a powder composition, in the following description, description of the coil etc. for applying a magnetic field, mention etc. Is omitted.
The powder molding apparatus 10 is fitted into the die 11 having a die hole 12 penetrating in the vertical direction, an upper punch 13 configured to be able to advance and retreat from above the die hole 12 of the die 11, and the die hole 12 of the die 11. And a lower punch 14.

In the powder molding apparatus 10, the lower punch 14 is fixed to the base 15, but the die 11 is configured to be moved up and down by an actuator (not shown). Therefore, the lower punch 14 can be moved up and down relative to the die 11 in the vertical direction.
As shown in FIG. 1, when the die 11 is raised to a predetermined position with respect to the lower punch 14, a cavity 16 is formed in the die hole 12 of the die 11 by the lower punch 14.

A feeder box 17 is disposed on the upper surface of the die 11. The feeder box 17 accommodates the magnetic powder P which is a molding object inside. As the magnetic powder P, for example, magnet powder that is a raw material of a rare earth sintered magnet can be used. However, the molding object of the present invention is not limited to this magnet powder, and any other powder composition for molding can be used. The feeder box 17 can slide the upper surface of the die 11 left and right in the drawing by an actuator (not shown).
The magnetic powder P in the feeder box 17 in contact with the upper surface of the die 11 is filled with the magnetic powder P in the feeder box 17 freely falling into the cavity 16 when the feeder box 17 is slid to the upper side of the cavity 16. Is done. The magnetic powder P filled in the cavity 16 is pressure-formed by the upper punch 13 and the lower punch 14 inserted in the die hole 12.

2 is a front view of the lower punch 14, and FIG. 3 is a cross-sectional view taken along the line AA in FIG.
The lower punch 14 includes a punch head 14a having a rectangular cross section corresponding to the die hole 12, and a base 14b having a rectangular cross section positioned below the punch head 14a. A plurality of supply ports 30 which are openings for supplying a lubricant or a non-oxidizing gas are formed on the side wall surface of the punch head 14a. Each supply port 30 communicates with a punch head supply path 34 disposed in a grid and in the horizontal direction in the punch head 14a. A lubricant or a non-oxidizing gas is supplied to the punch head supply path 34.

Two lubricant supply paths 31, 33 are formed from the base 14b of the lower punch 14 to the punch head 14a. Further, a non-oxidizing gas supply path 32 is formed from the base portion 14b of the lower punch 14 to the punch head 14a. In the punch head 14 a, the upper ends of the lubricant supply paths 31 and 33 and the upper end of the non-oxidizing gas supply path 32 are communicated with the punch head supply path 34. Therefore, the lubricant supplied in the vertical direction through the lubricant supply paths 31 and 33 is further supplied in the horizontal direction through the punch head supply path 34 and discharged from the supply ports 30 toward the inner wall surface of the die 11. Further, the non-oxidizing gas supplied in the vertical direction through the non-oxidizing gas supply path 32 is further supplied in the horizontal direction through the punch head supply path 34 and discharged from the supply ports 30 toward the inner wall surface of the die 11. The
As described above, in the lower punch 14, the lubricant supply paths 31, 33 and the non-oxidizing gas supply path 32 are independent, but the punch head supply path 34 is provided with the lubricant supply path and the non-oxidizing gas. It also serves as a supply channel. Accordingly, the supply port 30 also serves as a lubricant supply and a non-oxidizing gas supply.

  As shown in FIG. 1, a lubricant supply pipe 18 is connected to the lubricant supply path 31 formed in the lower punch 14. A lubricant reservoir 24 is connected to the other end of the lubricant supply pipe 18. A first pump 22 and a first valve 20 are disposed on the lubricant supply pipe 18 from the lubricant reservoir 24 side. The lubricant stored in the lubricant storage layer 24 is supplied onto the lubricant supply pipe 18 by the first pump 22. When the first valve 20 is open, the oil is supplied to the lubricant supply path 31 of the lower punch 14, but remains on the lubricant supply pipe 18 when the first valve 20 is closed. Thus, the first valve 20 controls the supply of the lubricant to the lower punch 14.

  A non-oxidizing gas supply pipe 19 is connected to the non-oxidizing gas supply path 32 formed in the lower punch 14. A non-oxidizing gas storage layer 25 is connected to the other end of the non-oxidizing gas supply pipe 19. A second pump 23 and a second valve 21 are disposed on the non-oxidizing gas supply pipe 19 from the non-oxidizing gas storage layer 25 side. The non-oxidizing gas stored in the non-oxidizing gas storage layer 25 is supplied onto the non-oxidizing gas supply pipe 19 by the second pump 23. And when the 2nd valve | bulb 21 is open, it supplies with respect to the non-oxidizing gas supply path 32 of the lower punch 14, but when the 2nd valve | bulb 21 is closed, it remains on the non-oxidizing gas supply piping 19. FIG. As described above, the second valve 21 controls the supply of the non-oxidizing gas to the lower punch 14.

  The powder molding apparatus 10 includes a controller 26 for controlling the operation thereof. That is, the controller 26 controls the raising / lowering of the die 11, the raising / lowering of the upper punch 13, and the sliding operation of the feeder box 17 through the actuators attached thereto. In addition, the opening / closing operation of the first valve 20 and the second valve 21 is controlled.

The operation of the powder molding apparatus 10 configured as described above will be described with reference to FIGS. 9 and 10. This operation is controlled by the controller 26.
Initially, the previous series of steps is completed, and as shown in FIG. 9A, the die 11 is positioned at the lower end and the upper punch 13 is retracted to the upper end. This state is called an initial state as shown in FIG.
In the initial state, the feeder box 17 is also retracted and is not shown in FIG.
In this initial state, the first valve 20 on the lubricant supply pipe 18 is open ("ON" in FIG. 10, the same applies hereinafter), and the second valve 21 on the non-oxidizing gas supply pipe 19 is It is closed ("OFF" in FIG. 10, the same applies hereinafter). Accordingly, the lubricant is discharged from the supply port 30 provided in the punch head 14 a of the lower punch 14. This lubricant can use fatty acid or a derivative of fatty acid, for example, a stearic acid-based or oleic acid-based zinc stearate, calcium stearate, stearic acid amide, oleic acid amide, etc., and the solvent is ethanol or the like The organic solvent is used and mixed with the fatty acid. Even if the auxiliary agent is dissolved in the solvent, it can be used in a so-called mixed state, and the liquid lubricant of the present invention includes both. In the present invention, since an adsorbing member (for example, felt) as disclosed in Patent Document 3 is not used, a mixed state of a lubricant and a solvent can be used. The supply pressure of the lubricant is preferably 0.01 to 0.5 MPa. If the supply pressure is too low, it takes time to supply a predetermined amount of lubricant. Conversely, if the supply pressure is too high, the lubricant is scattered when discharged to the inner wall surface of the die 11 and supply is not possible. This is because it becomes stable. The supply pressure is preferably 0.05 to 0.3 MPa.

  When the supply of the predetermined amount of lubricant is finished, the controller 26 next raises the die 11 to the rising end for forming the cavity 16 (FIG. 9B). As the die 11 rises, a lubricant is applied to a predetermined region of the inner wall surface of the die 11. In order to make the application of the lubricant more reliable, it is also effective to perform an operation of raising the die 11 to the rising end, lowering the die 11 to the lowering end, and raising the die 11 to the rising end again.

At the timing when the die 11 is raised to the rising end, the controller 26 turns off the first valve 20 and turns on the second valve 21. Accordingly, the non-oxidizing gas is discharged from the supply port 30 provided in the punch head 14a of the lower punch 14. This non-oxidizing gas flows through the gap between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14. More specifically, in the gap between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14, the non-oxidizing gas flows upward and downward with reference to the supply port 30 formed in the punch head 14a. When a non-oxidizing gas is used, the magnetic powder P is effective in preventing oxidation against a material that is easily oxidized, such as a raw powder of an RTB-based sintered magnet. However, in the case of an oxidation-resistant powder composition, an oxidizing gas such as air can be used. Nitrogen gas or argon gas can be used as the non-oxidizing gas. When the gas supply pressure is high, powder filling into the cavity 16 in the next process is hindered. On the other hand, when the gas supply pressure is low, the powder can easily enter the gap between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14, and the effect of preventing the supply port 30 from clogging is lost. Therefore, 0.03 to 3 MPa is preferable, and more preferably about 0.05 to 2 MPa.
At the stage of forming the cavity 16, the upper punch 13 and the feeder box 17 are controlled to the retracted position.

Next, after the die 11 reaches the rising end, the controller 26 slides the feeder box 17 onto the cavity 16 as shown in FIG. As a result, the magnetic powder P housed in the feeder box 17 falls into the cavity 16.
At this time, the controller 26 keeps the first valve 20 OFF and the second valve 21 ON. Therefore, the magnetic powder P filled in the cavity 16 is formed between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14 by the resistance force of the non-oxidizing gas discharged from the supply port 30 formed in the lower punch 14. It does not easily enter the gap.
In this powder filling stage, the upper punch 13 remains controlled at the retracted position.

After the feeder box 17 moves onto the cavity 16 and a predetermined time elapses, the controller 26 retracts the feeder box 17 from the cavity 16. At this time, the magnetic powder P is scraped off at the lower surface of the feeder box 17, and a predetermined amount of the magnetic powder P is filled in the cavity 16.
After the retraction of the feeder box 17 is completed, the magnetic powder P is pressure-molded. For pressure molding, the controller 26 lowers the upper punch 13. As shown in FIG. 9D, the upper punch 13 is inserted into the die hole 12 (cavity 16) of the die 11 and press-molds the magnetic powder P in the cavity 16 in cooperation with the lower punch 14. The applied pressure at this time is about 30 to 300 MPa.

  In the process of pressure molding, the controller 26 continues the state where the first valve 20 is OFF and the second valve 21 is ON. Therefore, the magnetic powder P filled in the cavity 16 is formed between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14 by the resistance force of the non-oxidizing gas discharged from the supply port 30 formed in the lower punch 14. It does not easily enter the gap.

  When the predetermined pressure molding is completed, the controller 26 lowers the die 11 to the lower end while maintaining the positions of the upper punch 13 and the lower punch 14 as shown in FIG. The molded body C is discharged out of the cavity 16. At this time, the controller 26 continues the state in which the first valve 20 is OFF and the second valve 21 is ON.

  Thereafter, as shown in FIG. 9 (f), the controller 26 can take out the molded body C by retracting the upper punch 13 to a predetermined position. If the upper punch 13 is retracted to a predetermined position, the controller 26 switches the first valve 20 on and the second valve 21 off, sets the powder molding apparatus 10 to the initial state, and the subsequent pressure molding cycle Prepare for.

  In the present embodiment, the lower punch 14 is provided with a lubricant supply path 31 and a non-oxidizing gas supply path 32 independently, and the magnetic powder P is formed on the inner wall surface of the die 11 and the outer wall surface of the lower punch 14. The non-oxidizing gas is continuously supplied during the period when the magnetic powder P is most likely to enter the gap, and the lubricant is supplied during other predetermined periods. When the non-oxidizing gas is supplied, the lubricant is preferably filled up to the upper part in the lubricant supply path 31. By doing so, there is an advantage that the lubricant can be supplied instantaneously when the first valve 20 is turned on.

  In addition, the lower punch 14 is provided with two lubricant supply paths 31 and 33 because the lower punch 14 has a rectangular cross section. That is, when there is only one lubricant supply path, when the lower punch 14 has a rectangular cross section, the pressure of the lubricant discharged from each supply port 30 is not uniform. It is also assumed that it cannot be applied uniformly. On the other hand, the lower punch 14 of the present embodiment is provided with the two lubricant supply paths 31 and 33, so that the pressure of the lubricant discharged from each supply port 30 can be made more uniform. . Providing such two lubricant supply paths 31, 33 or three or more lubricant supply paths 31, 33 is particularly effective for a lower punch having a rectangular section with a long longitudinal length.

  The punch head supply path 34 of the lower punch 14 has a lattice shape. Therefore, even if the lubricant or the non-oxidizing gas is supplied to the plurality of supply ports 30 formed on the outer wall surface of the punch head 14a, the lubricant supply path 31 or the non-oxidizing gas supply path 32 is minimized. The number of Further, since the punch head supply path 34 is shared by the lubricant and the non-oxidizing gas, the configuration of the punch head supply path 34 can be simplified.

The powder molding apparatus 10 according to the present embodiment is characterized by the structure of the lower punch 14, but may also have the structure of the lower punch 40 shown in FIGS. 4 and 5, for example.
FIG. 4 shows a front view of the lower punch 40, and FIG.
The lower punch 40 includes a punch head 40a having a rectangular cross section corresponding to the die hole 12, and a base 40b having a rectangular cross section located at the lower portion of the punch head 40a. A plurality of supply ports 50 which are openings for supplying a lubricant or a non-oxidizing gas are formed on the side wall surface of the punch head 40a. Each supply port 50 communicates with a first punch head supply path 53 and a second punch head supply path 54 which are arranged in a lattice shape in the punch head 40a. The lower punch 40 is different from the punch head supply path 34 of the lower punch 14 in that it includes a first punch head supply path 53 and a second punch head supply path 54 that are independent of each other.

  Two lubricant supply paths 51 and two non-oxidizing gas supply paths 52 are formed from the base 40b of the lower punch 40 to the punch head 40a. In the punch head 40 a, the upper ends of the one lubricant supply path 51 and the non-oxidizing gas supply path 52 communicate with the first punch head supply path 53. In the punch head 40 a, the upper ends of the other lubricant supply path 51 and the non-oxidizing gas supply path 52 communicate with the second punch head supply path 54. Therefore, the lubricant or the non-oxidizing gas supplied through one lubricant supply path 51 or the non-oxidizing gas supply path 52 passes through the first punch head supply path 53 from each supply port 50 to the inner wall surface of the die 11. It is discharged toward. The lubricant or non-oxidizing gas supplied through the other lubricant supply path 51 or the non-oxidizing gas supply path 52 passes through the second punch head supply path 54 from each supply port 50 to the inner wall surface of the die 11. It is discharged toward.

  Similarly to the lower punch 14, the lower punch 40 has a lubricant supply pipe 51 connected to the lubricant supply path 51, and a non-oxidizing gas supply pipe 19 connected to the non-oxidizing gas supply path 52.

  The lower punch 40 has the following characteristics in addition to the same effects as the lower punch 14. That is, the lower punch 40 includes a first punch head supply path 53 and a second punch head supply path 54 that are independent from each other, and the lubricant is supplied to the first punch head supply path 53 and the second punch head supply path 54, respectively. Is done. Since the lubricant supply path 51 for supplying the lubricant to the first punch head supply path 53 and the second punch head supply path 54 is provided, respectively, the supply port 50 via the first punch head supply path 53 is provided. The uniformity of the pressure of the discharged lubricant and the uniformity of the pressure of the lubricant discharged from the supply port 50 via the second punch head supply path 54 can be improved. Moreover, as shown in FIG. 5, the lubricant supply path 51 is positioned substantially at the center of the plane of the first punch head supply path 53 and the second punch head supply path 54, so that the discharge pressure of the lubricant is reduced. Uniformity can be further improved. Therefore, the lubricant can be more uniformly applied to the inner wall surface of the die 11. In this way, since uniform lubricant application can be performed with a smaller amount of lubricant, it is possible to produce an RTB-based sintered magnet with a small amount of C that causes a decrease in magnetic properties. To do.

In the present invention, it is also effective to use the lower punch 60 in the form shown in FIGS.
6 is a front view of the lower punch 60, FIG. 7 is a cross-sectional view taken along the line CC in FIG. 6, and FIG. 8 is a cross-sectional view taken along the line DD in FIG.
The lower punch 60 includes a punch head 60a having a rectangular cross section corresponding to the die hole 12, and a base 60b having a rectangular cross section located at the lower portion of the punch head 60a. A plurality of supply ports 70a, which are openings for supplying a lubricant, are formed on the side wall surface of the punch head 60a on substantially the same plane. A plurality of supply ports 70b, which are openings for supplying non-oxidizing gas, are formed on the side wall surface of the punch head 60a on substantially the same plane. As shown in FIG. 6, a supply port 70b for supplying a non-oxidizing gas is disposed above a supply port 70a for supplying a lubricant.

The supply port 70a communicates with a first punch head supply path 73 and a second punch head supply path 74 that are arranged in a lattice pattern in the punch head 60a. The first punch head supply path 73 and the second punch head supply path 74 are independent of each other.
Further, the supply port 70b communicates with a third punch head supply path 75 disposed in a lattice shape in the punch head 60a. The third punch head supply path 75 is formed in an upper layer than the first punch head supply path 73 and the second punch head supply path 74, and with respect to the first punch head supply path 73 and the second punch head supply path 74. being independent.
Thus, the lower punch 60 is independent of the third punch head supply path 75 for supplying the non-oxidizing gas to the first punch head supply path 73 and the second punch head supply path 74 for supplying the lubricant. This is different from the lower punch 14 and the lower punch 40.

  From the base 60b of the lower punch 60 to the punch head 60a, two lubricant supply paths 71 and one non-oxidizing gas supply path 72 are formed. In the punch head 60a, the upper end of one lubricant supply path 71 communicates with the first punch head supply path 73, and the upper end of the other lubricant supply path 71 communicates with the second punch head supply path 74. . In the punch head 60 a, the upper end of the non-oxidizing gas supply path 72 communicates with the third punch head supply path 75. Accordingly, the lubricant supplied through one lubricant supply path 71 is discharged from each supply port 70 a toward the inner wall surface of the die 11 through the first punch head supply path 73. Further, the lubricant supplied through the other lubricant supply path 71 is discharged from each supply port 70 a toward the inner wall surface of the die 11 through the second punch head supply path 74. Further, the non-oxidizing gas supplied through the non-oxidizing gas supply path 72 is discharged from each supply port 70 b toward the inner wall surface of the die 11 through the third punch head supply path 75.

  Similarly to the lower punch 14, the lower punch 60 has the lubricant supply path 71 connected to the lubricant supply pipe 18 and the non-oxidizing gas supply path 72 connected to the non-oxidizing gas supply pipe 19.

The lower punch 60 has the following characteristics in addition to the same effects as the lower punch 14. That is, in the lower punch 60, the first punch head supply path 73 and the second punch head supply path 74 for supplying the lubricant and the third punch head supply path 75 for supplying the non-oxidizing gas are independent. Therefore, in the lower punch 14 and the lower punch 40 that share the lubricant supply path and the non-oxidizing gas supply path, the timing of switching between the lubricant supply and the non-oxidizing gas supply is strictly controlled. On the other hand, in the lower punch 60, even if the supply of the lubricant and the supply of the non-oxidizing gas are somewhat overlapped, no special trouble occurs.
Further, since the lower punch 60 is provided with the supply port 70b for discharging the non-oxidizing gas above the supply port 70a for discharging the lubricant, the lower punch 60 has an inner wall surface of the die 11 and an outer wall surface of the lower punch 60 from above. It is possible to effectively prevent the magnetic powder P that has entered between them from moving to the supply port 70a that discharges the lubricant.
Further, similarly to the lower punch 40, the first punch head supply path 73 and the second punch head supply path 74 are independent from each other, and the lubricant supply path 71 is the first punch head supply path 73, the second punch head. Since the head supply path 74 is positioned substantially at the center of the plane, the uniformity of the lubricant discharge pressure can be ensured.

  In the above embodiment, the non-oxidizing gas is supplied from the formation stage of the cavity 16 to the end of the molding, which is most effective for preventing the supply port 30 from being clogged with the magnetic powder P. The form is not limited. The non-oxidizing gas may be supplied only during a period in which the magnetic powder P is most likely to enter the gap between the inner wall surface of the die 11 and the outer wall surface of the lower punch 14, or from the stage of forming the cavity 16 to the end of molding. The non-oxidizing gas may be supplied intermittently.

  In the above embodiment, the cross section of the lower punch 14 is rectangular, but it is needless to say that it may be other polygonal shapes or circular shapes. Further, in the above embodiment, the example in which the lower punch 14 is fixed and the die 11 can be moved up and down has been described. However, the die 11 may be fixed and the lower punch 14 may be moved up and down in the vertical direction.

Next, a rare earth sintered magnet to which the present invention is applied will be described. The present invention is particularly preferably applied to an RTB-based sintered magnet.
This RTB-based sintered magnet contains 25 to 37 wt% of a rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. A preferable amount of R is 28 to 35 wt%, and a more preferable amount of R is 29 to 33 wt%.

Moreover, the RTB-based sintered magnet contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A preferable amount of B is 0.5 to 1.5 wt%, and a more preferable amount of B is 0.8 to 1.2 wt%.
T in the RTB-based sintered magnet means Fe or Fe and Co. Here, when Co is contained, it is 3.0 wt% or less (not including 0), preferably 0.1 to 1.0 wt%, more preferably 0.3 to 0.7 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.

Furthermore, the RTB-based sintered magnet can contain one or two of Al and Cu in a range of 0.02 to 0.5 wt%. By containing one or two of Al and Cu in this range, it is possible to increase the coercive force, increase the corrosion resistance, and improve the temperature characteristics of the obtained sintered magnet. In the case of adding Al, a preferable amount of Al is 0.03 to 0.3 wt%, and a more preferable amount of Al is 0.05 to 0.25 wt%. In addition, in the case of adding Cu, the preferable amount of Cu is 0.15 wt% or less (not including 0), and the more preferable amount of Cu is 0.03 to 0.12 wt%.
The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is preferable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is set to 5000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated. Further, when obtaining high magnetic properties, the amount is 3000 ppm or less, preferably 2000 pp or less, more preferably 1000 ppm or less. The present invention is preferably applied to pressure molding of an RTB-based sintered magnet with a small amount of oxygen.

Although the present invention is preferably applied to an RTB-based sintered magnet, the present invention can also be applied to other rare earth sintered magnets. For example, the present invention can be applied to an R—Co based sintered magnet.
The R—Co based sintered magnet contains R, one or more elements selected from Fe, Ni, Mn, and Cr, and Co. In this case, it preferably further contains one or more elements selected from Cu or Nb, Zr, Ta, Hf, Ti and V, and particularly preferably from Cu and Nb, Zr, Ta, Hf, Ti and V. Containing one or more selected elements. Among these, in particular, an intermetallic compound of Sm and Co, preferably an Sm ₂ Co ₁₇ intermetallic compound, is the main phase, and a subphase mainly composed of SmCo ₅ is present at the grain boundary.

The above RTB-based sintered magnet is manufactured as follows.
A raw material alloy can be obtained by strip casting the raw metal in a vacuum or non-oxidizing gas, preferably in an Ar atmosphere. As a raw material metal for obtaining a raw material alloy, a rare earth metal or a rare earth alloy, pure iron, ferroboron, or an alloy thereof can be used.

  After the raw material alloys are produced, these raw material alloys are pulverized. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, each mother alloy is coarsely pulverized until the particle size becomes about several hundred μm. In order to improve the coarse pulverization property, it is effective to perform coarse pulverization after occlusion of hydrogen. Further, after hydrogen storage, hydrogen can be released to perform coarse pulverization without using mechanical means.

  In order to obtain high magnetic properties, it is preferable to suppress the atmosphere in each step from pulverization (recovery after pulverization) to sintering (put into a sintering furnace) to an oxygen concentration of less than 100 ppm. By doing so, the amount of oxygen contained in the sintered body can be controlled to 3000 ppm or less.

  After the coarse pulverization process, the process proceeds to the fine pulverization process. In the fine pulverization, a jet mill is mainly used, and a coarsely pulverized powder having a particle size of about several hundred μm is pulverized until the average particle size becomes 1 to 8 μm. By using the raw material alloy of the present invention, finely pulverized powder having a narrow particle size distribution width can be obtained. 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 the high-speed gas flow accelerates the coarsely pulverized powder. This is a method of crushing by generating a collision with a target or a container wall. By adding about 0.01 to 0.3 wt% of additives such as zinc stearate at the time of fine pulverization, fine powder having high orientation can be obtained at the time of molding.

  Next, the finely pulverized magnetic powder is molded in a magnetic field with its crystal axis oriented by applying a magnetic field. In the powder molding apparatus 10 described above, description and reference of a coil or the like which is an element for applying a magnetic field is omitted. The molding pressure may be constant from the start to the end of molding, may increase or decrease gradually, or may vary irregularly. The lower the molding pressure is, the better the orientation is. However, if the molding pressure is too low, the strength of the molded body is insufficient and a handling problem occurs. Therefore, the molding pressure is selected in consideration of this point. The final relative density of the molded body obtained by molding in a magnetic field is usually 50 to 60%. Further, the applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can also be used in combination.

  Here, when the atmosphere of each step from the pulverization process is suppressed to an oxygen concentration of less than 100 ppm, the amount of oxygen contained in the magnetic powder P that is the object of molding in the magnetic field is also low. As described above, the magnetic powder P having a low oxygen content has a high degree of activity, so that the die 11 is very likely to be galling. Therefore, the present invention is particularly effective when manufacturing an RTB-based sintered magnet at a low oxygen concentration.

After molding in a magnetic field, the compact is sintered in a vacuum or non-oxidizing gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, a particle size, and a particle size distribution difference, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. The aging treatment is important for controlling the coercive force. In the case where the aging treatment is performed in two stages, it is effective to maintain a predetermined time in the vicinity of 800 to 900 ° C. and in the vicinity of 600 to 700 ° C.

A high purity raw material was prepared, and a raw material alloy was produced by a strip casting method. Next, after hydrogen was occluded in the raw material alloy at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere. The alloy that had been subjected to hydrogen pulverization was finely pulverized to obtain finely pulverized powder having an average particle size of 4 μm. The fine pulverization was performed with a jet mill. The composition of the finely pulverized powder is as follows.
30.2 wt% Nd-1.4 wt% Dy-1 wt% B-0.1 wt% Cu-0.2 wt% Al-0.5 wt% Co-bal. Fe

  The finely pulverized powder (oxygen amount: 4000 ppm, carbon amount: 1000 ppm) obtained above was used in the form shown in FIGS. The pulverized powder was continuously molded so that the compact density was 4.2 g / cc (Example). The size of the cavity 16 (lower punch 14) is 60 mm × 10 mm. Further, the lower punch 14 is provided with five supply ports 30 of φ1.5 mm on the 60 mm side and two on the 10 mm side. Further, nitrogen gas was used as the non-oxidizing gas, and zinc stearate mixed with an ethanol solvent was used as the lubricant. The supply pressure of nitrogen gas is 0.05 MPa, and the supply pressure of lubricant is 0.1 MPa.

  As a comparative example, continuous molding was performed under the same conditions as described above except that one supply port for supplying lubricant was provided on each side of the lower punch. In this comparative example, nitrogen gas was not supplied, but only lubricant was supplied at a supply pressure of 0.1 MPa.

  In the comparative example, galling or cracking occurred at 800 shots, so the process was interrupted. In the example, no galling occurred even after 10,000 shots elapsed.

Continuous molding was performed in the same manner as in Example 1 except that the alloy composition was as follows and the atmosphere from the pulverization treatment to molding was suppressed to an oxygen concentration of less than 100 ppm (Example 2). The obtained sintered body had an oxygen content of 1000 ppm and a carbon content of 1000 ppm.
24.9 wt% Nd-5.9 wt% Pr-0.4 wt% Dy-1 wt% B-0.05 wt% Cu-0.2 wt% Al-0.5 wt% Co-bal. Fe
In the comparative example in which one supply port for supplying the lubricant is provided on each side of the lower punch, galling or cracking occurred in 500 shots. There was no galling.
As described above, it has been found that by adopting the molding method according to the present invention, the occurrence of galling can be prevented even in long-term continuous molding in a low oxygen atmosphere.

It is a schematic block diagram of the powder shaping | molding apparatus by this Embodiment. It is a front view which shows the structure of the lower punch by this Embodiment. It is AA arrow sectional drawing of FIG. It is a front view which shows the other structure of the lower punch by this Embodiment. It is a BB arrow sectional view of Drawing 4. It is a front view which shows further another structure of the lower punch by this Embodiment. It is CC sectional view taken on the line of FIG. It is DD sectional view taken on the line of FIG. It is a figure explaining operation | movement of the powder shaping | molding apparatus by this Embodiment. It is a figure which shows the operation | movement flow of the main element of the powder shaping | molding apparatus by this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Powder shaping | molding apparatus, 11 ... Die, 12 ... Die hole, 13 ... Upper punch, 14, 40, 60 ... Lower punch, 14a, 40a, 60a ... Punch head, 14b, 40b, 60b ... Base, 15 ... Base DESCRIPTION OF SYMBOLS 16 ... Cavity, 17 ... Feeder box, 18 ... Lubricant supply piping, 19 ... Non-oxidizing gas supply piping, 20 ... First valve, 21 ... Second valve, 22 ... First pump, 23 ... Second pump, 24 ... lubricant storage layer, 25 ... non-oxidizing gas storage layer, 26 ... controller, 30, 50, 70a, 70b ... supply port, 31, 33, 51, 71 ... lubricant supply path, 32, 52, 72 ... non Oxidizing gas supply path 34... Punch head supply path 53 and 73. First punch head supply path 54 and 74. Second punch head supply path 75.

Claims (9)

A powder molding method for producing a molded body by using an upper punch and a lower punch from a powder composition in a cavity formed in a die hole of a die,
Supplying a liquid lubricant from the side wall surface of the lower punch to the inner wall surface of the die facing the die hole;
Supplying a predetermined amount of the powder composition to the cavity;
Pressing the powder composition supplied into the cavity with the upper punch and the lower punch, and
Gas is supplied from the side wall surface of the lower punch to the inner wall surface of the die facing the die hole during one or both of the step of supplying the powder composition and the pressure forming step. A powder molding method characterized by the above. The supply pressure of the lubricant is 0.01 to 0.5 MPa,
2. The powder forming method according to claim 1, wherein a supply pressure of the gas is 0.03 to 3 MPa. The powder composition is an R-T-B system sintered magnet raw material powder,
The powder molding method according to claim 1 or 2, wherein the gas is a non-oxidizing gas.
However, R represents one or more rare earth elements, and T represents Fe or Fe and Co.   The powder molding method according to claim 3, wherein the raw material powder has an oxygen concentration of 3000 ppm or less. A powder molding apparatus for producing a compact by pressure molding a powder composition,
A die having a die hole penetrating in a vertical direction;
An upper punch and a lower punch that apply pressure to the powder composition supplied into the die hole,
Inside the lower punch,
A lubricant supply path for supplying a lubricant supplied from the outside to a plurality of first supply ports opened in the side wall surface of the lower punch;
A powder forming apparatus characterized in that a gas supply path for supplying a gas supplied from the outside to a plurality of second supply ports opened in a side wall surface of the lower punch is formed. Before supplying the powder composition into the die hole, supplying the lubricant from the first supply port to the inner wall surface of the die via the lubricant supply path,
Thereafter, the gas is supplied from the second supply port to the inner wall surface of the die through the gas supply path,
6. The powder molding apparatus according to claim 5, further comprising a controller that controls the powder molding apparatus so as to supply the powder composition into the die hole. The lubricant supply path is connected to the lubricant vertical supply path for supplying the lubricant in the vertical direction of the lower punch and the lubricant vertical supply path, and the lubricant supplied from the lubricant vertical supply path is A lubricant horizontal supply path for supplying the horizontal direction and the first supply port;
The gas supply path is connected to a gas vertical supply path for supplying the gas in the vertical direction of the lower punch and the gas vertical supply path, and the gas supplied from the gas vertical supply path is horizontally and second The powder shaping | molding apparatus of Claim 5 or 6 provided with the gas horizontal supply path which supplies to the supply port of this.   The powder forming method according to claim 5, wherein the lubricant vertical supply path and the gas vertical supply path are independent, and the lubricant horizontal supply path also serves as the gas horizontal supply path. apparatus. The lubricant horizontal supply path is a lattice-like path branched from the lubricant vertical supply path,
The powder forming apparatus according to any one of claims 5 to 8, wherein the gas horizontal supply path forms a lattice-like path branched from the gas vertical supply path.

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