JPH0444402B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a permanent magnet in which magnetic powder is bonded using a resin binder, and more specifically,
2-17 rare earth magnet powder is molded in a magnetic field in a low coercive force state before aging treatment, and then subjected to aging treatment and impregnated and solidified with a polymer resin with specific properties, resulting in excellent magnetic properties and The present invention relates to a method for manufacturing resin-bonded permanent magnets with high mechanical strength.

[Prior Art] Conventionally, the method for manufacturing resin-bonded rare earth permanent magnets is to first crush, shape and sinter the raw material rare earth magnet alloy, then subject it to an aging treatment, and then crush it. After that, the aging-treated powder and an organic binder are kneaded and formed in a magnetic field, and then the organic binder contained therein is generally solidified. Here, as the organic binder, a thermoplastic resin or a thermosetting resin is used.

Such resin-bonded rare earth magnets have relatively high magnetic properties, are easy to mass-produce, can easily achieve dimensional accuracy, and have a large degree of freedom in shape.
In recent years, it is rapidly being used for various purposes.

[Problems to be solved by the invention] In order to sufficiently orient the magnetic powder when molding is performed in a magnetic field, the strength of the applied magnetic field must be 4 to 5 times the coercive force of the magnetic powder that is the material. It is said that more than that is necessary. For this reason, in the prior art, for example, in the case of Sm ₂ Co ₁₇ based resin-bonded permanent 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 with the currently widely used magnetic press equipment 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 sufficiently oriented.

In order to solve such problems, the present inventors proposed a method in which magnet powder with a coercive force of 6 kOe or less before being subjected to aging treatment is first formed in a magnetic field, and then subjected to aging treatment. This method has the advantage that a resin-bonded permanent magnet with high magnetic properties can be easily produced because magnet powder can be sufficiently oriented even in a low magnetic field during molding.

However, with this manufacturing method, it is necessary to impregnate and solidify a polymer resin after aging treatment, and the resulting resin-bonded magnet may contain magnet powder and polymer resin depending on the conditions (properties) of the polymer resin used. It is difficult to adhere to the resin in a uniformly distributed state, which may lead to a decrease in mechanical strength.

The purpose of the present invention is to further develop the method previously proposed by the present inventors in which magnet powder with a coercive force of 6 kOe or less before aging is subjected to forming in a magnetic field and then subjected to aging treatment. It goes without saying that the magnetic properties can be further improved compared to conventional technology, but the magnet powder and polymer resin are evenly distributed and bonded together, resulting in resin-bonded permanent magnets with excellent mechanical strength. The purpose is to provide a method for manufacturing.

[Means for Solving the Problems] The present invention, which can achieve the above objects, forms 2-17 rare earth magnet powder in a magnetic field when its coercive force is 6 kOe or less before aging treatment. death,
Thereafter, the obtained molded body is subjected to an aging treatment, and then impregnated with a polymer resin having a viscosity of 20 to 3000 cp (centipoise) and solidified.

The raw material is 2-17 rare earth stone powder.
R ₂ TM ₁₇ (However, R is Sm, Ce, Pr, Nd including Y
One or more rare earth elements such as TM is Fe,
One or more transition metal elements such as Co, Ni, etc.)
The main component is the composition represented by: Such raw materials are usually obtained by pulverizing an alloy having a predetermined composition, shaping it into a predetermined shape, sintering it, and, if necessary, subjecting it to solution treatment under predetermined conditions.

2-17 rare earth magnets undergo precipitation hardening due to aging treatment and develop a high coercive force. The present invention effectively utilizes this phenomenon.

In the present invention, the raw material sintered body as described above is first pulverized. The magnet powder thus obtained has a low coercive force of 6 kOe or less before aging treatment. The reason for using such low coercive force magnet powder is that 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 resin-bonded permanent magnets after aging. As a result, we found that if a resin-bonded permanent magnet is made using magnet powder with a coercive force of 6 kOe or less, the magnetic properties are significantly higher than that of a resin-bonded permanent magnet with the same coercive force obtained by conventional methods.
This is due to the discovery that Br and (BH)max are improved.

Then, the magnet powder is molded in a magnetic field and subjected to an aging treatment while maintaining the molded shape to develop a high coercive force. Then the viscosity is 20~3000cp
Impregnated with polymer resin and solidified.

The feature of the present invention is that, as described above, magnet powder is molded in a magnetic field with a low coercive force, and after aging treatment, it is impregnated with a polymer resin with a viscosity in the range of 20 to 3000 cp and solidified. .

As the polymer resin used here, any type of resin can be used as long as its viscosity is in the range of 20 to 3000 cp, such as epoxy resin, phenolic resin, acrylic resin, and anaerobic resin. The reason why the viscosity of the polymer resin is set to 20 to 3000 cp in the present invention is as follows, which was derived from experimental results. In other words, if it is less than 20 cp, the resin will flow out after impregnation or during curing, and if it exceeds 3,000 cp, the viscosity will become too high and impregnation will not be able to be carried out sufficiently, leaving a residue of impregnation in the center. This is because, as shown, the mechanical strength is extremely reduced.

In particular, in order to improve residual magnetic flux density and enhance moldability, PVA, PVB, CMC, PEG,
A molding aid such as paraffin may be added and the molding aid may be blown off by heating before or during the aging treatment.

[Function] In the present invention, since magnetic field compaction is performed using magnet powder in a low coercive force state before aging treatment, sufficient orientation can be achieved even if a magnetic field press device such as that used in a general production line is used. . Since the aging treatment is performed in this state, even if the coercive force of the magnet powder increases after the aging treatment, the good orientation state is maintained as it is, and high magnetic properties can be generated.

Then, since it is impregnated with a polymer resin with a viscosity of 20 to 3000 cp, the magnet powder is evenly distributed throughout the molded body and the resin is solidified, creating a resin-bonded permanent magnet with excellent mechanical strength. Can be manufactured.

[Example] As a raw material, a samarium-cobalt alloy in a low coercive force state represented by Sm (Co _0.68 Fe _0.20 Cu _0.10 Zr _0.02 ) _7.75 was ground in a jet mill, formed in a magnetic field, and then sintered.

This raw material sintered body was crushed with a geocrusher and sieved to obtain magnet powder with an average particle size of 250 μm. Next, without using a forming aid, this magnetic powder was
Compression molding was performed at 3 tons/cm ² in a magnetic field of 11 kOe to a size of 10 mm x 20 mm (orientation direction).

This compact was then aged in vacuum at 800°C for 1 hour to increase its coercive force. after that,
Epoxy resins of various viscosities were impregnated and solidified to produce resin-bonded rare earth magnets. Here, the treatment conditions for impregnation and solidification are as follows. First, the molded body is degassed in a vacuum tank with a vacuum level of 1 × 10 ^-3 Torr, immersed in an epoxy resin solution in the same tank, held for 30 minutes, and then transferred to another tank and pressurized to 5 atmospheres. 30 with
It was held for a minute to allow impregnation. After impregnation, heat curing treatment was performed at 120°C for 2 hours.

The magnetic properties and mechanical strength properties of the resin-bonded rare earth magnet obtained are shown in FIG. The following is clear from the results of this experiment. First, magnetic properties such as maximum energy product (BH) max and residual magnetic flux density Br are almost constant regardless of the viscosity η of the epoxy resin used. However, the bending strength is extremely reduced when the viscosity η is less than 20 cp or exceeds 3000 cp. The reason for this is that if the viscosity is less than 20cp, the polymer resin will flow out during solidification;
This is thought to be because if the resin exceeds 100%, the resin cannot be sufficiently impregnated into the interior due to its high viscosity, and unbonded parts remain, making it difficult for the resin to bond sufficiently.

For comparison, a resin-bonded rare earth magnet was manufactured using the same materials and conditions as above based on the conventional method, and it was found that the method of the present invention is superior to the conventional method in all aspects of magnetic properties and mechanical strength characteristics. It was confirmed that there is.

[Effects of the Invention] As described above, the present invention forms magnet powder that undergoes precipitation hardening through aging treatment in a magnetic field when it is in a low coercive force state before precipitation hardening, and then precipitation hardens it while maintaining its shape to obtain a high coercive force. Since this is a method of making magnetic particles appear, it has the effect of further improving magnetic properties compared to conventional techniques.

Furthermore, in the present invention, a polymer resin with a specific viscosity range of 20 to 3000 cp is used as the resin to be impregnated and solidified to bond the magnet powder, so that the magnet powder and the polymer resin are uniformly distributed. It has the excellent effect of producing a resin-bonded permanent magnet that can be fixed with a resin bond and has excellent mechanical strength.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the viscosity η of the polymer resin used in the method of the present invention and the magnetic properties and bending strength of the prepared resin-bonded rare earth magnet.

Claims (1)

[Claims] 1 2-17 rare earth magnet powder is molded in a magnetic field when its coercive force is 6 kOe or less before aging treatment, and then the obtained molded body is aged, and then a polymer with a viscosity of 20 to 3000 centipoise is formed. A method for manufacturing a resin-bonded permanent magnet, characterized by impregnating it with a resin and solidifying it.