WO2002060677A1

WO2002060677A1 - Powder molding method

Info

Publication number: WO2002060677A1
Application number: PCT/JP2002/000617
Authority: WO
Inventors: Atsushi Ogawa; Shuhei Okumura
Original assignee: Sumitomo Special Metals Co., Ltd.
Priority date: 2001-01-29
Filing date: 2002-01-28
Publication date: 2002-08-08
Also published as: JPWO2002060677A1; CN1248811C; CN1484578A

Abstract

A powder molding method capable of increasing the orientationality of a molded body (39), comprising the steps of filling powder for magnet manufactured by a quenching method into a cavity (28) formed in a through-hole (24) of a die (16), and applying an orienting magnetostatic field to the powder inside the cavity (28) by a magnetic field generating device (40) while vibrating a lower punch (26) in the through-hole (24) in pressing direction by a vibrating device (30) to pressingly mold the powder inside the cavity (28) by an upper punch (34) and the lower punch (26) so as to provide the molded body (39), the pressing direction being vertical to the magnetic field orienting direction, or being allowed to be parallel with the magnetic field orienting direction.

Description

Description Powder molding method Technical field

The present invention relates to a powder molding method, and more particularly to a powder molding method for breath-forming a powder for a rare earth magnet. Background art

One example of this kind of prior art is disclosed in Japanese Patent Application Laid-Open No. 61-25008. Here, there has been proposed a vibration press forming machine which supports a pressing plate so as to be able to move up and down and a shaping table so as to be able to vibrate freely. In this vibrating breath forming machine, a vibrator is arranged and supported on the molding table side and the press plate side, respectively, and a pressurized cylinder which can move up and down is arranged on the press plate side and the molding table side. Supported.

However, in the above-mentioned prior art, there is no mention of a technique for orienting the powder raw material filled in the molding die, and it is not possible to improve the orientation of the powder raw material and thus the obtained molded body.

Therefore, a main object of the present invention is to provide a powder molding method capable of improving the orientation of the obtained molded article. Disclosure of the invention

According to an aspect of the present invention, there is provided a filling step of filling a cavity formed in a through hole of a die with a powder for magnets, and pressing at least one of an upper punch and a lower punch in a through hole during a magnetic field orientation. And a press step of press-forming the magnet powder in the cavity by an upper punch and a lower punch to obtain a molded body.

According to the present invention, at least one of the upper punch and the lower punch is vibrated in the press direction in the through hole of the die during the press forming, so that the friction acting on the magnet powder in the cavity changes from static friction to dynamic friction. Reduce the frictional force between the magnet powders Since it can be reduced, the fluidity of the magnet powder increases. If the orientation magnetic field is applied while the punch is vibrated in this manner, the magnet powder moves so as to be aligned in the magnetic field orientation direction, and the orientation of the magnet powder is improved. Therefore, if the magnet powder in that state is pressed, a compact having high orientation can be obtained.

Preferably, the orientation magnetic field in the pressing step is a static magnetic field. When a static magnetic field is applied during press molding, the powder can be pressed while securing the time required for the powder to flow, so that the orientation of the magnet powder and thus the compact can be improved.

Preferably, the pressing direction is perpendicular to the magnetic field orientation direction. In this case, since the magnetic field generating mechanism can be easily separated from the press mechanism, the orientation of the magnet powder and thus the compact can be improved with a simple configuration.

The present invention is suitable when the pressing direction is parallel to the magnetic field orientation direction. In the case where the pressing direction is parallel to the direction of the magnetic field than in the case where it is perpendicular to the direction of the magnetic field, the pressing is performed while the orientation during the application of the magnetic field is broken. However, in the present invention, the adverse effect can be suppressed by vibrating at least one of the upper punch and the lower punch in the through hole.

Further, the present invention is suitable when the magnet powder is manufactured by a quenching method. In the case where magnet powder produced by the quenching method is used, the frictional force acting between the powders is larger than that of other powders because the powder has a square shape in the past. As a result, the flowability of the powder during magnetic field orientation deteriorated, and improvement in the orientation property was hindered. However, in the present invention, even with such a magnet powder, the frictional force acting between the magnet powders in the cavity is reduced by vibrating the punch in the pressing direction in the through hole in the through hole during the magnetic field orientation and pressing. As a result, the fluidity of the magnet powder can be improved, so that the orientation of the magnet powder and thus the compact can be improved.

The rare earth sintered magnet, in order to reduce the crystal grain size of the R ₂ F e _{1 4} B phase after sintering tends to reduce the powder碎粉after milling. When the powder particle size is less than 5 / m (FSSS particle size) or less, even if a strong orientation magnetic field is applied, the degree of orientation is reduced because the rotating force generated in each powder becomes small. According to the present invention, it is possible to improve the degree of orientation even in such a powder having a small particle diameter.

Further, the present invention is suitable for a case where the molded article has an irregular shape. The resulting molded body is In the case of a different shape such as an arc shape, the compression ratio at the time of pressing differs depending on the forming part. Therefore, in the related art, at the end of the molded body having a high compression ratio, a gap occurs due to a difference from the compression ratio of other portions, and the orientation varies depending on the molding portion. However, in the present invention, even when a molded article having a different shape is obtained, the fluidity of the magnet powder is increased by vibration, and the density variation of the magnet powder within the cavity is reduced. Therefore, it is possible to mold a molded article of a different shape in which the density of each molded portion after molding is substantially uniform, and it is possible to suppress the occurrence of deformation and improve the orientation.

According to another aspect of the present invention, there is provided a method of manufacturing a rare earth magnet, including the above-described powder molding method. By using the above-mentioned powder molding method, a molded body with improved orientation can be obtained. Therefore, in the present invention, a rare earth magnet having high magnetic properties can be obtained. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is a perspective view showing an example of the obtained molded body,

FIG. 3 is a timing chart showing an example of the operation of the embodiment of FIG. 1, and FIG. 4 is a table showing an example of the experimental result.

FIG. 5 is a graph obtained from the experimental results shown in FIG.

FIG. 6 is an illustrative view showing one example of a measurement point of a magnetic property of a magnet in an experiment, and FIG. 7 is an illustrative view showing another embodiment of the present invention.

FIG. 8 is a timing chart showing an example of the operation of the embodiment of FIG. 7, and FIG. 9 is an illustrative view showing another embodiment of the present invention;

FIG. 10 is an illustrative view showing still another embodiment of the present invention, and FIG. 11 is a waveform diagram showing an example of each of a static magnetic field and a pulse magnetic field. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a powder molding apparatus 10 according to one embodiment of the present invention is a powder molding apparatus for magnets of a withdrawal type in which a pressing direction is perpendicular to a magnetic field orientation direction. You.

The powder molding apparatus 10 includes a base plate 12, which is supported by a plurality of legs 14. A die 16 is arranged above the single plate 12. The lower surface of the die 16 is connected to the connecting plate 20 via a pair of guide posts 18 penetrating the base plate 12. The connecting plate 20 is connected to a lower hydraulic cylinder (not shown) via a cylinder load 22. Therefore, the die 16 can be moved vertically by the lower hydraulic cylinder.

At a substantially central portion of the die 16, a through hole 24 penetrating in the vertical direction is formed. A lower punch 26 is inserted into the through hole 24 from below, and a cavity 28 is formed in the through hole 24. The powder for magnets, such as rare earth alloy powder, is supplied to the cavity 28 by a powder supply device (not shown) that can move in and out of the cavity 28. As the powder feeding device, for example, a powder feeding device described in Japanese Patent Application Laid-Open No. 2000-248301 is used. The packing density of the powder filled in the cavity 28 is, for example, 2.2 g / cm ³ or more and 2.5 g / cm ³ or less.

The lower punch 26 is disposed on the vibrator 30, and the vibrator 30 is disposed on the die plate 12. Therefore, the lower punch 26 is fixed on the base plate 12, but the upper punch plate 32 is arranged above the die 16 which can be vibrated in the vertical direction, that is, the press direction by the vibrating device 30. You. An upper punch 34 is provided on the lower surface of the upper punch plate 32 at a position where it can be inserted into the cavity 28. A cylinder rod 36 is provided on the upper surface of the upper punch plate 32. An upper hydraulic cylinder (not shown) is connected to the cylinder rod 36. A pair of guide posts 38 provided in the vertical direction are passed through the vicinity of both ends of the upper punch plate 32, and the lower end of the guide post 38 is connected to the upper surface of the die 16.

Therefore, the upper punch plate 32 can be moved vertically by the upper hydraulic cylinder while being guided by the guide post 38, and accordingly, the upper punch 34 can be moved vertically so that the upper punch plate 32 is moved into the cavity 28. Can be imported. At the time of press molding, the powder is compressed by the lower punch 26 and the upper punch 34 in the cavity 28 to form a compact 39. In this embodiment, as shown in FIG. An arc-shaped molded body 39 for producing a silver magnet is formed. In this case, the upper surface 39 a of the molded body 39 is a contact surface with the upper punch 34, and the lower surface 39 b of the molded body 39 is a contact surface with the lower punch 26.

A magnetic field generator 40 for orienting the powder in the cavity 28 is provided near the die 16. The magnetic field generator 40 includes a pair of yokes 42 a and 42 b symmetrically arranged so as to sandwich the die 16 from both sides. The yokes 42a and 42b are made of a material having high magnetic permeability such as carbon steel. Coils 44a and 44b are wound around the yokes 42a and 42b, respectively. When the coils 44a and 44b are energized, a static magnetic field is generated in the direction indicated by the arrow X, and the powder in the cavity 28 is oriented.

Thus, in the powder molding apparatus 10 described above, the pressing direction is perpendicular to the magnetic field orientation direction. The applied magnetic field strength is, for example, approximately 0.8ΜΑ7Π1 or more and 1.3 MA / m or less.

Here, a rare earth alloy powder such as an Nd-Fe-B powder is used as the powder.

The rare earth alloy powder is produced, for example, as follows. First, quenching method (cooling rate 1 0 ^ C / sec or more 1 0 ⁴ ° C / sec or less) US Patent No. 5 by the manufacturing method of the alloy, 3 8 3, 9 7 scan as shown in No. 8 A piece is produced by using a trip casting method.

Specifically, Nd: 30 wt%, B: 1.0 wt%, Dy: 1.2 wt%, A1: 0.2 wt%, Co: 0.9 wt% produced by a known method. An alloy having a composition consisting of the balance Fe and inevitable impurities is melted by high frequency melting. After the molten metal was kept at 1,350 ° C, the peripheral speed of the nozzle was about 1m / s, the cooling speed was 500 ° C / sec, and the supercooling was 200 ° C. It is quenched on a single roll to obtain a flake-like alloy ingot with a thickness of about 0.3 mm.

Next, the alloy ingot is roughly pulverized by a hydrogen storage method, and then finely pulverized in a nitrogen gas atmosphere using a jet mill to obtain an alloy powder having an average particle size of 3.5 m. A lubricant is added to the powder. In this case, for example, a fatty acid ester is used as a lubricant, and a petroleum-based solvent is used as a solvent. And rare earth 0.3 wt% (lubricant base) of fatty acid ester diluted with petroleum solvent is added to the alloy powder and mixed, and the lubricant is coated on the surface of the rare earth alloy powder. Next, the operation of the powder molding apparatus 10 will be described.

Initially, as shown in period A, die 16 is located at the lower end and upper punch 34 is located at the upper end, and the upper surfaces of die 16 and lower punch 26 are flush with each other. Is done. Next, as shown in a period B, the die 16 is raised to form a cavity 28 in the through hole 24. Thereafter, as shown in period C, the powder feeding device (not shown) is moved onto the cavity 28, and the powder in the powder feeding device is moved into the cavity 28 by slightly swinging the powder feeding device back and forth. After filling, the powder feeding device is moved out. Then, as shown in the period D, the die 16 is further raised, and the upper punch 34 is lowered, and as shown in the period E, the orientation magnetic field is applied by the magnetic field generator 40 and the vibrator 30 is applied. The vibration of the lower punch 26 starts. Further, as shown in a period F, the powder is pressed in the cavity 28 by the lower punch 26 and the upper punch 34 inserted into the through hole 24 from above while applying an orientation magnetic field and applying vibration. In the state of demagnetization and vibration stopped during period G, press molding of the powder is continued at the maximum pressing pressure. Thereafter, as shown in a period H, the upper punch 34 is gradually raised to gradually reduce the pressure, and the press forming is completed to form a molded body 39. Then, as shown in period I, the molded body 39 in the cavity 28 is pulled out to the upper surface of the die 16 by lowering the die 16 to the lower end. Further, as shown in the period J, after the upper punch 34 is raised to the rising end, the molded body 39 is taken out at the time K, and is prepared for the next press molding process. The powder is press-molded by repeating the above processing.

According to the powder molding apparatus 10, the lower punch 26 is oscillated in the press direction in the through hole 24 at the time of press molding, whereby the frictional force between the powders in the cavity 28 can be reduced, and the fluidity of the powders can be reduced. Get higher. If an orientation magnetic field is applied to the powder while oscillating the lower punch 26 in this way, the powder moves so as to be aligned with the direction of the magnetic field orientation, and the orientation of the powder is improved. In addition, since the powder moves so as to fill the gaps, the powder can be more evenly distributed in the cavity, so that the orientation during compression molding can be reduced. Can be suppressed. By pressing the powder in that state, a molded body 39 with high orientation can be obtained.

Even if the powder is filled at a high density of 2.5 g / cm ³ or more and press-molded, the powder moves to fill the gap due to vibration. Accordingly, the molding density for obtaining the desired magnetic properties can be reached at a low press pressure, so that the magnetic field alignment can be prevented from being broken by the press pressure, and a pressed compact can be produced while maintaining the magnetic field orientation state. Further, variation in the orientation in the height direction can be suppressed, which is particularly effective when a molded body 39 having a height of 20 mm or more is obtained.

In addition, by applying a static magnetic field during press molding, the powder can be pressed while securing the time required for the powder to flow, so that the orientation of the powder and thus the compact 39 can be improved. 0 can be separated from the press mechanism such as the die 16 and the upper punch 34, so that the configuration of the powder molding apparatus 10 is simplified.

In general, Nd-Fe-B-based powder produced by the quenching method has a greater frictional force acting between the powders than Nd-Fe-B-based granulated powder, and it is difficult to improve the orientation. This is because the Nd-Fe-B powder produced by the quenching method has a much smaller particle size and a narrower and sharper particle size distribution, so that the gap between the powders is smaller and the surface area of the powder is larger. This is because the grain shape is angular. Recently, the average particle size of powder has been reduced to 5 zm (FSSS particle size) for the purpose of improving magnetic properties. However, according to the powder molding apparatus 10, even the fine powder produced by the quenching method can be pressed by vibrating the lower punch 26 in the press direction in the through hole 24 during the magnetic field orientation, and pressing. Since the frictional force acting between the powders in the powders 28 can be reduced and the fluidity of the powders can be improved, the orientation of the powders and thus the compact 39 can be improved.

Further, when a lubricant is added to the Nd-Fe-B powder, friction between the powders is reduced and the fluidity of the powder is improved, so that the orientation is further improved.

In addition, even when a molded article having a different shape such as a bow such as the molded article 39 is obtained, the fluidity of the powder in the cavity 28 is increased by the vibration, and the powder is more evenly distributed in the cavity 28. Is done. Therefore, the density (green density) of each molded part after molding ) Can produce a molded article having a substantially uniform shape.

The compact obtained as described above was pressed in a state where the variation in the density of the powder in the cavity 28 was reduced and the magnetic anisotropy was more uniform. When this green body is sintered, the variation in the amount of shrinkage is reduced, and the degree of contour of the obtained sintered body is improved as compared with the conventional one. Therefore, the processing cost required for correction in the molded product is small. By subjecting such a sintered body to further aging treatment, a magnet such as a rare earth magnet having good magnetic properties can be obtained.

Next, an experimental example will be described.

Here, a magnet obtained by using a powder molding apparatus 10 and a magnet obtained by using a powder molding apparatus (hereinafter, referred to as a “comparative apparatus”) obtained by removing the vibration device 30 from the powder molding apparatus 10 are described. The magnetic properties of each of them were compared. That is, the magnetic properties of the magnets with and without vibration were compared. The magnet was obtained by subjecting a compact produced by a powder compacting machine to sintering and aging.

The experimental conditions are shown below.

As the powder, Nd-Fe-B-based alloy powder (for example, NE OMAX-48BH: manufactured by Sumitomo Special Metals Co., Ltd.) manufactured by the strip casting method to have an average particle size of 2 to 3 / m is used. Lubricants such as zinc stearate were added. As the die 16, a die in which one molded product of 51.3 mm x 53.3 mm x 25 mm was formed in one cycle (for taking one piece) was used. The molding density is 4. O g / cm ³ or more and 4.5 g / cm ³ or less, the feeding method is feeder filling (injection filling), the orientation magnetic field is the core center magnetic field 1.66 T, and the vibration frequency is about 50 The vibration was about 0.02 mm, and the vibration device 26 was made by Daiichi Corporation. Then, the obtained compact is sintered at 150 ° C. for 5.5 hours in an Ar atmosphere, and further aged for 3 hours at 500 ° C. in an Ar atmosphere. A magnet (Nd-Fe-B magnet) was obtained.

Under the above conditions, the magnetic properties of the Nd-Fe-B-based magnet obtained using the powder molding apparatus 10 and the Nd-Fe-B-based magnet obtained using the comparative apparatus were measured. Figures 4 and 5 show the results.

Specifically, the magnetic properties were measured as follows. First, a compact having a desired compacting density was formed using a powder compacting apparatus. A total of two compacts were obtained by two press moldings. After sintering and aging treatment of the obtained two compacts, they were cut to obtain nine magnets. For each of the nine magnets, the residual magnetic flux density Br and the maximum energy product (BH) max of the central part S were measured as shown in FIG. 6, and the nine values were averaged. Such a treatment was performed for each of the molding densities as shown in FIG. 4 for the powder molding apparatus 10 and the comparison apparatus, and the results shown in FIGS. 4 and 5 were obtained.

As can be seen from Fig. 5 (a), when comparing at the same molding density, the case using the powder molding apparatus 10 (with vibration) is better than the case using the comparison apparatus (without vibration). However, the residual magnetic flux density Br increases. In addition, as can be seen from Fig. 5 (b), when comparing at the same molding density, the case using the powder molding apparatus 10 (with vibration) is the case using the comparison apparatus (without vibration). ), The maximum energy product (BH) max becomes larger.

Therefore, when the compacting densities are the same, it can be seen that the magnetic properties of the obtained magnet are improved when the powder compacting apparatus 10 is used as compared with the case where the comparative apparatus is used. Therefore, in order to obtain magnets having the same magnetic characteristics, a smaller molding pressure is required when using the powder molding apparatus 10 than when using the comparison apparatus.

According to the present invention, by performing the magnetic field molding while applying vibration, it is possible to suppress the variation in the molding density of the compact and the deformation due to sintering. Therefore, for filling the powder, a method is used in which the powder corresponding to each cavity is weighed and the powder is dropped into the cavity and filled as disclosed in Japanese Patent Publication No. 2001-9595. Next, a powder molding apparatus 10a according to another embodiment of the present invention will be described with reference to FIG.

The powder compacting apparatus 10a is a double-push magnet powder compacting apparatus in which the pressing direction is perpendicular to the magnetic field orientation direction.

In the powder molding apparatus 10a, the die 16 is fixed on the base plate 12 via a plurality of legs 46, the vibrating apparatus 30 is disposed on the table 48, and the table 48 is provided with the guide post 50. To the connecting plate 20 via For other configurations, refer to Since the configuration is the same as that of the powder molding apparatus 10 shown in FIG. 1, the overlapping description will be omitted. Therefore, in the powder molding apparatus 10a, the lower punch 26 and the upper punch 34 move up and down in the through hole 24 of the die 16 to press the powder in the cavity 28.

The operation of the powder molding apparatus 10a will be described with reference to FIG.

In the powder molding apparatus 10a, the die 16 is fixed, and the lower punch 26 moves vertically. As can be seen by comparing FIG. 8 with FIG. 3, the lower punch 26 in the powder molding apparatus 10a operates substantially in the opposite direction to the die 16 in the powder molding apparatus 10, and Are pressed by the lower punch 26 and the upper punch 34. The extraction of the upper punch 34 from the cavity 28 is started from the period I. Except for these points, the operation of the powder compacting apparatus 10a is the same as that of the powder compacting apparatus 10, so that the overlapping description will be omitted.

The same effects as those of the powder molding apparatus 10 can be obtained with the powder molding apparatus 10a. Further, a powder molding apparatus 10b according to another embodiment of the present invention will be described with reference to FIG.

The powder compacting device 10b is a magnet type powder compacting device of a wide-open Al type in which the pressing direction is parallel to the magnetic field orientation direction.

In the powder molding apparatus 10b, the die 16 moves in the vertical direction, as in the powder non-molding apparatus 10, and the lower punch 26 vibrates in the vertical direction. A duplicate description of this point will be omitted. The powder molding device 10b includes a magnetic field generator 52. The magnetic field generator 52 includes a yoke 54 disposed above the die 16 and substantially parallel to the die 16. An upper punch 34 is provided on a lower surface of the yoke 54 at a position where it can be inserted into the through hole 24. Die 16 functions as a yoke paired with yoke 54. Coils 56a and 56b are wound on the yoke 54 and the die 16, respectively. Therefore, when the coils 56a and 56b are energized, a static magnetic field is generated in the direction indicated by the arrow Y, and the powder in the cavity 28 is oriented. Thus, in the powder molding apparatus 10b, the pressing direction is parallel to the magnetic field direction.

When the compact 39 shown in FIG. 2 is formed by the powder compacting apparatus 1 Ob, the side surface 39 c of the compact 39 becomes a contact surface with the upper punch 34, and the side surface 39 of the compact 39 is formed. d Is the contact surface with the lower punch 26. Therefore, the shapes of the upper punch 34 and the lower punch 26 and the cross-sectional shape of the through hole 24 in the powder molding device 10b are different from those of the powder molding device 10.

The powder molding apparatus 10b operates as shown in FIG. 3 similarly to the powder molding apparatus 10, and thus the duplicated description is omitted.

The same effect as in the powder molding apparatus 10 can be obtained in the powder molding apparatus 10b. In general, when the pressing direction is parallel to the magnetic field orientation direction, since the pressing direction and the magnetic field orientation direction are the same, the magnetic field orientation in the molded body is easily broken by the molding pressure. However, according to the powder molding apparatus 10b, the adverse effect can be suppressed by vibrating the lower punch 26 in the pressing direction in the through hole 24, and the effect becomes more remarkable.

In particular, the powder molding apparatus 10b is effective in forming a thin compact with a narrow through-hole 24 (in either the length direction or the width direction), a large cavity depth, and the like. It is.

In the case of forming a thin compact as described above in which the pressing direction is parallel to the direction of the magnetic field orientation, conventionally, it was necessary to press at a low compacting density in order to secure magnetic properties. This is because the magnetic properties decrease as the molding density increases. However, when the molding density is reduced, the strength of the molded body is reduced, and the molded body is easily crushed when it is extracted from the cavity, and it becomes difficult to extract the molded body, and productivity is reduced. On the other hand, if the molding density is set high to ensure the strength of the molded body, a molding pressure higher than usual is applied to the powder in the cavity, and the molding is performed while losing the orientation.

By using the powder molding apparatus 10b, a magnet having high magnetic properties can be obtained even if the molding density is relatively high. For example, magnetic properties of magnets molded density obtained by using a powder molding apparatus 1 0 b 4. 4 g / cm ^3, the molded density obtained without vibration 4.1 of g / cm ³ of the magnet Equivalent to magnetic properties.

Therefore, according to the powder molding apparatus 1 Ob, even when a thin compact (magnet) is obtained, the compact density can be increased so as not to be crushed when the compact is extracted from the cavity, and good magnetic properties can be obtained. Can be obtained. With reference to FIG. 10, a description will be given of a powder molding apparatus 10c according to still another embodiment of the present invention.

The powder compacting apparatus 10c is a double-push magnet powder compacting apparatus in which the pressing direction is parallel to the magnetic field orientation direction.

In the powder molding apparatus 10c, the die 16 is fixed on the base plate 12 via a plurality of legs 46, the vibrating apparatus 30 is arranged on the table 48, and the table 48 is connected to the guide post 50. To the connecting plate 20 via The rest of the configuration is the same as that of the powder molding apparatus 10b shown in FIG. 9, and a duplicate description thereof will be omitted. Therefore, the lower punch 26 and the upper punch 34 move up and down in the through hole 24 of the die 16 to press the powder in the cavity 28, and the pressing direction becomes parallel to the magnetic field orientation direction.

The powder compacting apparatus 10c operates as shown in FIG. 8 similarly to the powder compacting apparatus 10a, and therefore, redundant description is omitted.

The same effects as those of the powder molding apparatus 10 can be obtained in the powder molding apparatus 10c. In addition, the effect of the non-powder molding apparatus 10c is more remarkable because the pressing direction is parallel to the direction of the magnetic field orientation, as in the case of the powder molding apparatus 10b, and is particularly effective when a thin compact is formed. It is a target.

In each of the powder non-molding apparatuses 10, 10 a, 10 b, and 10 c, the amplitude of the lower punch 26 is preferably in the range of 0.001 mm to 0.2 mm. If the amplitude is less than 0.01 mm, the friction generated between the powders during molding cannot be reduced, while if the amplitude exceeds 0.2 mm, for example, the die 16 and the lower punch 26 This is because the powder is likely to be caught between them and the die 16 and the lower punch 26 are damaged.

In each of the powder molding apparatuses 10, 10 a, 10 b, and 10 c, it is preferable that the vibration frequency of the lower punch 26 be 5 Hz or more and 100 Hz or less. If the vibration frequency is less than 5 Hz, it is not possible to reduce the friction between the powders during molding.On the other hand, if the vibration frequency exceeds 100 Hz, the cost of the vibration device 30 becomes too high and practical. It is not.

The present invention is not limited to the case where only the lower punch 26 is vibrated in the through hole 24. The upper and lower punches 34, 26 may both be vibrated in the through hole 24, or only the upper punch 34 may be vibrated.

In addition, the present invention is not limited to the case of forming the shaped body 39 having a different shape, but can be applied to the case of obtaining a shaped body having an arbitrary shape such as a ring shape or a stepped shape.

As the alignment magnetic field, not only a static magnetic field but also a pulse magnetic field may be used. Here, the static magnetic field refers to a magnetic field in which the magnetic field intensity does not change with time as shown in FIG. 11 (a). The pulse magnetic field is a kind of dynamic magnetic field in which the magnetic field strength changes with time, and refers to a magnetic field generated temporarily as shown in Fig. 11 (b).

Claims

The scope of the claims

1. Filling process for filling the cavity formed in the die through hole with magnet powder, and

At the time of magnetic field orientation, at least one of the upper punch and the lower punch is vibrated in the pressing direction in the through hole, and the magnet powder in the cavity is press-formed by the upper punch and the lower punch to obtain a molded body. A powder molding method comprising a pressing step.

2. The powder molding method according to claim 1, wherein the orientation magnetic field in the pressing step is a static magnetic field.

3. The powder molding method according to claim 1, wherein the pressing direction is perpendicular to a magnetic field orientation direction.

4. The powder molding method according to claim 1, wherein the pressing direction is parallel to a magnetic field orientation direction.

5. The powder molding method according to claim 1 or 2, wherein the magnet powder is produced by a quenching method.

6. The powder molding method according to claim 1, wherein the molded body has a different shape.

7. A method for producing a rare earth magnet, comprising the powder molding method according to claim 1 or 2.