JPS63155605A - Manufacture of radially anisotropic bond magnet - Google Patents

Abstract

PURPOSE:To obtain a high orientation bond magnet wherein the magnetic characteristics are improved by forming rare earth magnet powder in a radial orientation magnetic field when the powder has coercive force of, 6 kOe or less before aging treatment and then by aging it. CONSTITUTION:2-17: system rare earth magnet power is formed in a radial orientation magnetic field when the powder has 6 kOe or less low coercive force before age treatment. Then, the formed powder is aged. The 2-17 system rare earth magnet powder has a main component of a composition shown by R2TM17 (where, R is one or two or more of rare earth elements such as Sn, Ce, Pr and Nd, including Y and TM is one or two or more of transition metal elements such as Fe, Co, and Ni). This enables obtaining a high orientation bond magnet wherein the magnetic characteristics are improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a bonded magnet in which magnetic powder is bonded using a resin or the like, and more specifically, the present invention relates to a method for manufacturing a bonded magnet in which magnetic powder is bonded using a resin or the like. The present invention relates to a method for manufacturing a radially anisotropic bonded magnet, which is formed in a radial orientation magnetic field before being molded, and then subjected to an aging treatment.

[Prior Art] Bonded magnets in which rare earth magnet powder is composited with a binder are conventionally known. As the binder, in addition to thermoplastic or thermosetting resins, metals, alloys, or glass-based inorganic substances are used. It is then manufactured by a molding method such as injection, compression, or extrusion.

Such rare earth bonded magnets have advantages such as high magnetic properties, excellent mass production, easy dimensional accuracy, and a large degree of freedom in shape, and are rapidly being used in a variety of applications in recent years.

In the conventional manufacturing method of radial anisotropic rare earth bonded magnets, the raw material alloy is crushed, shaped, and sintered, then subjected to aging treatment as it is, then crushed, and the aged powder is used. Molding is performed in a radial orientation magnetic field.

[Problems to be solved by the invention] In order to completely orient the magnetic powder when molding is performed in a magnetic field, the strength of the applied magnetic field must be at least 4 to 5 times the coercive force of the magnetic powder that is the material. is said to be necessary. For this reason, in the prior art, for example, in the case of S m 2 CO17 resin bonded magnets, a strong magnetic field of 40 to 50 kOe or more must be applied during molding.

However, the strength of the magnetic field obtained by the currently widely used magnetic press cannot satisfy the above values (generally, the magnetic field that can be applied on the production line is about 15 kOe), so In this case, the raw material powder cannot be oriented sufficiently.

Particularly in the case of radial orientation, the center rod passing through the center of the compact is one pole (for example, the N pole), and the die surrounding the compact is the opposite pole (in this case, the S pole).
Since the gap is filled with magnetic powder and molded while applying a magnetic field, if the axial length is longer than the diameter of the compact, the part filled with the magnetic powder in the gap during molding A problem arises in that the cross-sectional area of the magnetic path increases and the strength of the applied magnetic field decreases. Empirically, the shape ratio L/D is 3
/20 or more, the degree of orientation is extremely reduced, making it impossible to manufacture such a cylindrical radially anisotropic bonded magnet.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above,
A method for producing a 2-17 series radially anisotropic rare earth bonded magnet with excellent magnetic properties, especially with improved orientation and high coercive force, even if it has a cylindrical shape with a long axial length relative to the diameter. It is about providing.

[Means for solving the problems] The present invention, which can achieve the above objects, has the following features:
Radial anisotropy using -17 series rare earth magnet powder, molded in a radial orientation magnetic field when the coercive force is low (6 kOe or less before aging treatment), and then subjected to aging treatment. This is a method for manufacturing pound magnets.

The raw material 2-17 rare earth magnet powder is R2TM1
7 (However, R includes Y, Sm, Ce.

One or more rare earth elements such as Pr and Nd, TM
The main component is one or more transition metal elements such as Fe, Co, and Ni. Such raw materials are usually obtained by pulverizing an alloy having a predetermined composition, forming it into a predetermined shape and sintering it, and, if necessary, solution-treating it under predetermined conditions.

In 2-17 rare earth magnets, precipitation hardening occurs due to aging treatment and a high coercive force appears. The present inventors conducted various experiments on the relationship between the coercive force of magnet powder before magnetic field forming and the magnetic properties of bonded magnets after aging, and bonded by the method of the present invention using magnet powder with a coercive force of 6 kOe or less. The inventors discovered that the magnetic properties of the produced magnet were much better than that of bonded magnets obtained by conventional methods, and based on this knowledge, they completed the present invention.

As shown in Figure 1, in the present invention, the raw material sintered body as described above is first pulverized, and when the coercive force before aging treatment is in a small state of 6 kOe or less, it is molded in a radial orientation magnetic field, and then molded. A high coercive force is developed by aging the material while maintaining its original shape. As described above, a major feature of the present invention is that forming is performed in a radial orientation magnetic field in a state of low coercive force, and then aging treatment is performed. Regarding the prior art, as shown in FIG. 2, a raw material sintered body is first subjected to an aging treatment, and then pulverized magnet powder is used to perform molding in a radially oriented magnetic field.

When obtaining resin bonded magnets, after aging treatment,
It is integrated with a thermosetting synthetic resin such as epoxy resin, phenol resin, or acrylic resin by impregnation or immersion. PVA (polyvinyl alcohol) is used during molding to improve magnetic properties, especially residual magnetic flux density, and improve moldability.

Molding aids such as PVB (polyvinyl butyral), CMC (carboxymethyl cellulose), PEG (polyethylene glycol), paraffin, etc. may be used and the shaping aids may be heated and scattered before or during the aging treatment.

When using an inorganic binder such as glass or a metal binder such as a low-melting point metal or alloy, the powder is mixed with the inorganic binder or metal binder, formed in a magnetic field, and then subjected to aging treatment. Sometimes these binders are melted and integrated.

In the present invention, a radially oriented magnetic field press similar to the conventional one, for example as shown in cross-sectional view in FIG. 3, can be used. The center rod 12, the yoke 20 are made of ferromagnetic material, the mortar 10, the lower bunch 14. The upper bunch 16 is made of non-magnetic material. A center rod 12 is inserted through the center of the mortar 10, and a lower punch 14 and an upper punch 16 are fitted between them. And mortar 10, center rod 1
2. Magnet powder 18 is filled in the area surrounded by the lower bunch 14, and electromagnets 22 arranged on the upper and lower sides of the center rod 12 generate a yoke 20 with the center rod 12 side being the north pole.
A magnetic field (the lines of magnetic force are shown by broken lines) is applied so that the side becomes the south pole. As a result, a radial magnetic field acts on the magnet powder 18. In this state, the upper punch 16 is lowered to perform pressure forming, thereby obtaining a cylindrical molded body 24 having anisotropy in the radial direction as shown in FIG.

[Function] As can be seen from the model diagram of the 4πT-H loop in each process shown in Figure 1, the magnetic powder used when forming in a magnetic field is a powder before aging treatment, so the coercive force is 6 kOe. Small as below. Therefore, in the present invention, sufficient orientation can be achieved even with a small magnetic field.

Since the aging treatment is performed in that state, the orientation state is maintained as is even if the coercive force of the magnet powder after the aging treatment increases.

For comparison, the conventional technology is as shown in Figure 2. Magnet powder with a high coercive force after aging is molded in a magnetic field, so the strength of the magnetic field required for orientation must be extremely large to ensure sufficient variation. Cannot be polarized.

As a result, according to the present invention, a pound magnet with excellent magnetic properties can be manufactured even in a much weaker magnetic field than in the past. Furthermore, if molding is performed in a larger magnetic field (e.g. comparable to that of the conventional technology), a high degree of orientation, which could not be achieved in the past, can be obtained. It is possible to produce a bonded magnet.

Especially in the case of such radially oriented magnets, if the diameter of the cylindrical compact is small, the center rod 1 of the magnetic press
As the cross-sectional area of the molded body 2 becomes smaller, magnetic saturation is more likely to occur.On the other hand, when the axial length of the molded body 24 becomes longer, the magnetic path cross-sectional area during molding becomes larger, so that only a weak magnetic field can be applied. Even with such a weak magnetic field, a sufficient degree of orientation can be achieved, resulting in extremely remarkable effects.

Furthermore, by varying the aging treatment conditions for the compact, permanent magnets with different coercive forces can be easily manufactured, which has the advantage of being easily compatible with multi-product production.

[Example Co Samarium-cobalt (S m
, COI7) alloy was jet milled to an average particle size of 4μ.
m, and the powder was compacted in a magnetic field and then sintered to serve as the raw material in this example.

In this example, this raw material sintered body was crushed using a show crusher and sieved to obtain magnet powder having an average particle size of 200 μm. Without using a molding aid, this magnet powder was molded by radial orientation magnetic field pressing while varying the strength of the orientation magnetic field over several stages (from 0 to 15 kOe).

The obtained molded body was heated at 800°C in a vacuum.

Aging treatment was performed for 1 hour. Finally, an epoxy resin was impregnated in a vacuum, and after-curing was performed at 120° C. for 1 hour to harden the resin to produce a radial anisotropic bonded magnet.

Further, for comparison, a comparative sample was manufactured based on the conventional technology. In this method, the same raw material sintered body as in the above example was first aged under the same conditions as in the above example, and then pulverized and the average particle size was 20.
Magnet powder of 0 μm was obtained, molded using a radial orientation magnetic field press in which the strength of the orientation magnetic field was varied over several stages, and similarly impregnated with epoxy resin and integrated.

The shape of the prototype molded body has an outer diameter of 20 mmφ and an inner diameter of 16 mm.
It has a cylindrical shape with mmφ and axial length of 31 mm. Table 1 shows the properties of the magnet powder before magnetic field forming.

Table 1 The magnetic properties of the anisotropic bonded magnet thus obtained are shown in Table 2.

Table 2 The magnetic properties in Table 2 are determined by cutting out nine parts (shaded areas) of a cylindrical magnet as shown in Figure 6A and aligning the orientation direction as shown in Figure 6B. The measurements were taken by stacking nine pieces.

Further, FIG. 5 shows the change in (BH)max with respect to the strength of the orientation magnetic field.

From this result, 15kO has the best magnetic properties in the conventional method.
Br and bHc of the sample in case e.

It can be seen that (BH)max is located between the values of the samples obtained when the orientation magnetic field is 4 kOe and 6 kOe when the method of the present invention is implemented. In other words, according to the present invention, a magnetic field strength of about 5.5 kOe is sufficient to produce the magnetic properties obtained by applying 15 kOe in the conventional method.

Furthermore, if the strength of the orienting magnetic field is increased to 6 kOe or more using the method of the present invention, the magnetic properties and loops will be superior to those achieved by the conventional method at 15 kOe.

In the above example, the axial length of the compact is relatively small compared to the diameter of the compact, and in a magnetic field of 15 kOe, even with the conventional method, fairly good properties are obtained; however, the axial length of the compact is The effect of the present invention becomes even more pronounced as the length becomes longer.

In fact, the strength of the magnetic field that can be applied is limited by the dimensions of the compact, and as the length of the compact in the axial direction increases, the strength of the magnetic field that can be applied to the compact decreases relatively. For example, if the length of a molded body of the above shape is doubled, the magnetic field that can be applied will be approximately 1/2 (7.5 kOe), and if the length is tripled, the magnetic field that can be applied will be approximately 1/3 (5 kOe). It becomes. In the conventional method, when the height becomes 6 mm or 9 mm, the orientation magnetic field becomes only 7.5 kOe or 5 kOe, so as can be seen from Figure 5, there is almost no effect of anisotropy due to radial orientation, and it is essentially isotropic. It remains as it is. However, according to the method of the present invention, the anisotropic effect is sufficiently produced even if the axial length is 6 mm or 9 mm. In other words, it can be seen that by the method of the present invention, it is possible to obtain a radially anisotropic bonded magnet having a longer axial length than that obtained by the conventional method.

Since the strength of the orientation magnetic field of 15 kOe is considered to be the maximum value that can be applied industrially on a production line, the method of the present invention will prove to be extremely effective.

[Effects of the Invention] As described above, the present invention molds magnet powder that undergoes precipitation hardening by aging treatment to radial anisotropy before precipitation hardening, that is, in a state of low coercive force of 6 kOe or less, and then changes its shape. Since this is a method of precipitation hardening while holding the magnetic field and creating a high coercive force, it is possible to achieve the same magnetic properties as before with a much smaller magnetic field than before, and also to significantly improve the magnetic properties by applying the same large magnetic field as before. This has an excellent effect of producing a bonded magnet with an improved degree of orientation and a high degree of orientation.

According to the present invention, as described above, a much smaller magnetic field is required than in the prior art, so it has an extremely excellent effect of being able to obtain a radially oriented magnet with a long axial length.

[Brief explanation of the drawing]

Fig. 1 is a process explanatory diagram showing the main parts of the bonded magnet manufacturing process by the method of the present invention, Fig. 2 is a process explanatory diagram showing the main parts of the conventional process, and Fig. 3 is an explanatory diagram showing an example of radial orientation magnetic field press. Figure 4 is an explanatory diagram of the molded body obtained thereby,
FIG. 5 is a diagram showing the change in (BH)may with respect to the radial alignment magnetic field, and FIGS. 6A and 6B are explanatory diagrams showing the structure of the sample used in the experiment. 10... Mortar, 12... Center rod, 14...
Lower punch, 16... Upper bunch, 18... Magnetic powder,
20... Yoke, 22... Electromagnet, 24... Molded body. Patent Applicant: Fuji Electrochemical Co., Ltd. Agent: Minoru Shigemi Figure 1 Figure 2

Claims (1)

[Claims] 1. A radial anisotropic bonded magnet characterized in that 2-17 rare earth magnet powder is molded in a radial alignment magnetic field when the coercive force is 6 kOe or less before aging treatment, and then aging treatment is performed. Production method.