JP2696100B2 - Manufacturing method of magnetic anisotropic sintered magnet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniaxial anisotropic magnet and a radial anisotropic permanent magnet manufactured by powder metallurgy and a method for manufacturing the same.

[Summary of the Invention]

The present invention relates to an anisotropic permanent magnet manufactured by powder metallurgy, in which a microcapsule (hereinafter simply referred to as a capsule) in which a binder is encapsulated is mixed with a magnet powder (hereinafter simply referred to as a powder), and a magnetic field molding press is used. After the powder is subjected to magnetic field orientation molding, the capsule is broken by pressure and the powder is bound with a binder without deteriorating the crystal axis alignment state (hereinafter abbreviated as the orientation ratio). (Abbreviated as). As a result, the handling of the green is facilitated, the production yield is improved, and the degree of freedom in handling the green is improved.

Further, by improving the strength of the green, it is possible to manufacture a radially anisotropic permanent magnet.

[Conventional technology]

Permanent magnets manufactured by the powder metallurgy method are made magnetically anisotropic by shaping powder crushed into a single crystal state in a magnetic field while arranging the directions of easy magnetization in order to improve magnetic properties.
Further, in order to improve green strength and facilitate handling, a method of adding a small amount of a binder such as paraffin that binds the powders to the finely pulverized powder has been used.

[Problems to be solved by the invention]

However, in the above-described conventional manufacturing method, (1) the binder has a property of adhering the powders to each other, and when the powder to which the binder is added is oriented in a magnetic field and molded, the slip between the powder particles is poor. However, there is a problem that the magnetic properties are deteriorated due to the difficulty in orientation.

(2) In the prior art, in order to improve the magnetic orientation ratio of the powder and obtain high magnetic properties, a lubricant that improves the slip between the powders is mixed. Therefore, there is a problem that the green strength is weak, the green is chipped or cracked due to handling, and the production yield is reduced. In addition, there is a problem that the handling of the green is restricted because the strength of the green is weak, and the automation means is also limited.

(3) In some cases, a binder and a lubricant are mixed and added in order to obtain high magnetic properties due to a high orientation ratio while improving the green strength. However, the effect of the binder and the lubricant cancel each other out. Few.

(4) When manufacturing a thin ring-shaped permanent magnet radially oriented by powder metallurgy, the green powders oriented in the magnetic field have the same polarity and repel each other, causing cracks in the green or, in extreme cases, the green. Was difficult to manufacture because of its destruction.

The present invention is directed to overcoming these problems.

[Means for solving the problem]

To solve the above problems, the present invention relates to a magnetic anisotropic permanent magnet manufactured by a powder metallurgy method, in which finely pulverized powder, a capsule encapsulating a binder were mixed, and the powder was oriented by a magnetic forming press. Afterwards, a method of breaking the capsule by pressing force. Alternatively, a method in which an additive is mixed with the powder as needed, the capsule is further mixed, granulated, the powder is oriented by a magnetic forming press, and the capsule is broken by a pressing force. This is a method for producing a permanent magnet that obtains green strength without lowering the magnetic field orientation ratio of the green by binding the powder with a binder by these destructions, and is a uniaxial anisotropy or radial produced by these methods. The present invention provides an anisotropic permanent magnet.

[Action]

According to the invention, the powder before molding is mixed with a capsule in which a binder is enclosed. Therefore, when the magnetic field is oriented, the powders are separated one by one without being bonded by the binder. Therefore, good orientation can be obtained by applying a magnetic field with a magnetic field molding machine.

〔Example〕

Example 1 A raw material (hereinafter referred to as a SmCo _5- based alloy) adjusted and weighed so as to have a composition of S5.8 wt% Co residue was melted in an arc furnace in an Ar atmosphere, and then roughly crushed to # 32 mesh through with a crusher mill. Then, a material pulverized to a particle size of 3 μm in N ₂ gas by a jet mill was used as a starting alloy.

Granulate the starting alloy with stearic acid as a lubricant.
1w capsules mixed with 05wt% and filled with liquid paraffin
The mixture was molded at a pressure of 1 ton / cm ^{2 in} a magnetic field of 10 kOe. At this time, the dimensions of the capsule were fixed to an outer diameter of 20 μm,
The film thickness was made into five types of 0.2, 0.5, 1, 2, and 3 μm. The material of the capsule was polyurethane.

The strength ratio of the green was represented by the remaining weight ratio after 100 rotations with a Rattler tester. Further, the green is degassed in vacuum at 500 ° C. for 1 hour to evaporate the capsule and the binder.
After sintering in Ar gas at 20 ° C., it was cooled to 830 ° C. at a rate of 1 ° C./min, kept at 830 ° C. for 2 hours, and quenched, and the orientation ratio of the sintered body was measured with a vibration sample type magnetometer.

The orientation ratio is calculated using the residual magnetic flux density (Br11) when magnetized in the easy magnetization direction and the residual magnetic flux density (Br⊥) when magnetized in the hard magnetization direction. I asked more. The dependence of the green strength ratio and the orientation ratio of the sintered body on the capsule film thickness is shown in the characteristic diagram of FIG.

According to Example 1, if the capsule film thickness is too thin, the capsule is broken by the pressure at which the powder is mixed to orientate in a magnetic field, and the binder flows out of the capsule, whereby the powders adhere to each other before being oriented by the magnetic field, and the orientation ratio decreases. I do. It was also found that if the film thickness was too large, the capsule could not be broken by the molding pressure and the binder did not flow out, so that the powders did not adhere to each other at the end of molding, and the green strength was not different from the conventional one.

Example 2 A capsule having a film thickness of 1 μm, an outer diameter of 20 μm, a material of polyurethane, and a binder of liquid paraffin, camphor,
The orientation ratio of the binder was 1.5, 1, 2, 3, 4, 5 wt% as polyvinyl butyral (hereinafter referred to as PVB). The SmCo ₅ alloy was manufactured as a sample in accordance with Example 1, and the results of measuring the green strength ratio and the magnetic properties are shown in the characteristic diagram of FIG. 2, and the magnetic properties when the binder was PVB are shown in Table 1. . Since camphor and PVB are solids, they were dissolved in methanol, greased and encapsulated.

As a comparison, when a sample containing only stearic acid as a lubricant and a granulator without any binder was measured, the coercive force was 19 kOe and the green strength ratio was 70.

According to Example-2, it was found that the magnetic properties and green strength exhibited values that were practically satisfactory when the binder compounding ratio was 0.5 to 5 wt%. In the case where the binder was paraffin, when the mixing ratio was 5 wt%, a decrease in the magnetic properties considered to be due to the residual carbon was observed. However, it was found that the characteristics of PVB were stable over a wide range.

Since the capsule thickness and optimal binding agent for the alloys of SmCo ₅ from Example -3 Example 1,2 is obtained, Sm26.75Co residue Fe15Cu8
Adjusted and weighed to Zr1.77wt% (hereinafter Sm ₂ Co
_The alloy prepared in accordance with Example 1 was used as a starting alloy, and 1.5% by weight of the PVB-filled capsule used in Example 2 was mixed, and a pressure of 1 ton / cm ² was applied in a magnetic field of 10 kOe. After demagnetizing in a magnetic field at 500 ° C. for 1 hour in a vacuum to evaporate the capsule and binder, sintering in Ar at 1200 ° C. for 1 hour, 1170
After quenching for 2 hours at ℃, the solution was quenched by quenching Ar and further 800 ℃
After holding for 4 hours, the mixture was cooled at a rate of 0.5 ° C./min, and aged at 400 ° C. for 8 hours. At this time, granulation and lubricant are stearic acid 0.
05 wt%, 2.5 wt% of di-n-butyl phthalate, and 0.05 wt% of magnesium stearate were blended.
As a comparative material, a sample was prepared in the same manner without mixing a capsule enclosing PVB.

 Table 2 shows the green intensity ratio and the magnetic properties.

According to Example 3, it was found that the present invention is also effective for Sm ₂ Co _17- based magnets. It was also found that the same effect can be obtained even if the type of granulation and the type of the lubricant were changed.

Example-4 An alloy adjusted and weighed so that the remaining amount of Nd34Fe is B1 wt% (hereinafter referred to as "the alloy").
Nd-Fe-based alloy) was prepared according to Example 1 as a starting alloy, and 1.5 wt% of the PVB-encapsulated capsule used in Example 2 was mixed and mixed at 1 ton / cm ^{2 in} a magnetic field of 10 kOe. After forming the magnetic field under pressure, the capsule and binder were evaporated as degassed in vacuum at 500 ° C. for 1 hour, sintered at 1070 ° C. for 1 hour, cooled at 1 ° C./min after sintering for 1 hour, and rapidly cooled after holding at 600 ° C. for 2 hours. .
At this time, as the granulation and lubricant, magnesium stearate, magnesium stearate and polyethylene glycol mixed at a ratio of 1: 1 were mixed at 0.05 wt% each.

A sample was prepared in the same manner without mixing a capsule into which PVB was inserted as a comparative material.

Table 3 shows the green intensity ratio and the magnetic properties. According to Example-4, it was found that the present invention is also effective for Nd-Fe-based magnets.

It was also found that the same effect can be obtained by mixing two types of granulation and lubricant.

Example -5 SmCo ₅ alloy, Sm ₂ Co ₁₇ alloy, dissolved according to the respective embodiments -1 Nd-Fe-based alloy, and pulverizing, capsules PVB encapsulation used in Example -2 mixed 1.5 wt% The powder sample was mixed with a fluorinated hydrocarbon to form a slurry, and the slurry was formed in a magnetic field under a pressure of 1 ton / cm ² . The resulting green was dried in a vacuum at room temperature for 12 hours or more and degassed, sintered, and aged according to Examples 1, 3, and 4 for each composition.

As a comparative example, a sample without mixing a binder was manufactured. Table 4 shows the green intensity ratio and the magnetic properties.

According to Example-5, it was found that the present invention is also effective in magnetic field molding by a wet method.

Example -6 Example -2, -3, SmCo ₅ alloy used at -4, the PVB Capsule 1.5 wt% used in Example -2 Sm ₂ Co ₁₇ alloy and Nd-Fe-based alloy mixture Then, a ring-shaped green, which was radially magnetically oriented under a pressure of 1 ton / cm ² in a magnetic field of 10 kOe, was degassed, sintered, and aged according to Examples 1, 3, and 4 for each composition. Was given.

As a comparative example, a sample without mixing a binder was manufactured. Table 5 shows the green strength and magnetic properties.

From Example-6, it was found that the present invention is also effective for radially oriented sintered magnets.

Example -7 0.05 wt% of stearic acid was mixed with the alloy mixed with the PVB-encapsulated capsule used in Example-6, and ring-shaped greens formed in a magnetic field according to Example-6 were prepared for each composition. Degassing, sintering and aging were performed according to -1, -3 and -4. As a comparative material, a sample not mixed with a binder was manufactured.

 Table 6 shows the green strength and the magnetic properties.

From Example-6, it was found that the present invention is also effective for radially oriented sintered magnets in which a lubricant is mixed with the raw material fine powder to improve the orientation ratio.

[Effects of the Invention] According to the present invention, the green strength can be greatly improved without lowering the magnetic properties, so that the handling of the green is facilitated, and defects such as cracking and chipping of the green during molding are reduced, and at the same time, the green Since the degree of freedom of handling is improved, the effect of man-hour reduction by automation can be expected.
In addition, a practical effect is very large, for example, a radially anisotropic sintered magnet, which was difficult to manufacture conventionally, can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of the dependence of the green intensity ratio and the orientation ratio on the capsule film thickness, and FIG. 2 is a characteristic diagram of the dependence of the green intensity ratio and the magnetic characteristics (coercive force) on the blending ratio of the binder.

Claims (2)

(57) [Claims] 1. A magnetically anisotropic sintered magnet manufactured by a powder metallurgy method, comprising: a step of mixing and granulating a microcapsule containing a binder with finely ground magnet powder; and a step of orienting the magnet powder. Pressure-forming a magnetic powder containing microcapsules encapsulating a binder; degassing the powder compact in a vacuum to evaporate the capsule and the binder; and forming the degassed powder. And sintering the body. 2. The magnetic anisotropic sintered magnet according to claim 1, further comprising a step of mixing one or more additives for improving the granulating property and lubricity with the magnet powder. Production method.