JPS5946081B2 - Permanent magnet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rare earth cobalt permanent magnet.

Conventionally, methods for manufacturing rare earth cobalt permanent magnets include (1) SmCo6 or general formula R(Co-Cu)5.
(2) SmCo5
There is a method of manufacturing a dust magnet by pulverizing the powder into fine powder particles, molding the powder into a desired shape in a magnetic field, and then subjecting the powder to isostatic pressing.

However, although the method (1) using sintering provides excellent magnetic properties, it is difficult to machine because it is hard and brittle, and is not suitable for manufacturing magnets that require dimensional accuracy.

In addition, the method (2) using compaction has excellent workability, but has the problem of inferior magnetic properties compared to sintered magnets. Furthermore, both methods (1) and (2) have drawbacks such as high raw material costs because the alloy components contain large amounts of expensive rare earth metals. In view of the above, the present invention was developed as a result of conducting various studies, and as a result, one or more rare earth metals are combined into 10
~30% by weight, 5-20% by weight of copper, 0.2-3% by weight of titanium, and further 2-15% by weight of iron as required, with the balance being cobalt, and heat treated at 1100-1250°C. After that, it is cooled to room temperature, and then crushed to form fine powder particles.Then, these particles are magnetically arranged and pressure molded into a desired shape, resulting in excellent workability and magnetic properties. The object of the present invention is to provide a method for manufacturing a permanent magnet with a reduced content of expensive rare earth metals. The present invention will be explained in detail below step by step.

The magnetic alloy in the present invention is yttrium, samarium,
10-30% of rare earth metals such as cerium and lanthanum (
% indicates weight %), 5 to 20% copper, and 0 titanium.
．． It is an alloy consisting of 2 to 3% iron and, if necessary, 2 to 15% iron, with the remainder being cobalt. First, a magnetic alloy with the above composition is melted and cast into an ingot, which is then heated for 1 hour in a non-oxidizing atmosphere such as vacuum or argon gas.
Heat treatment is performed by heating to 100 to 1250°C, and then cooled to room temperature.

In this case, since the cooling rate sensitively affects the magnetic properties,
A large coercive force can be obtained by adjusting this cooling rate to 120 to 5000 C/min. The reason why the temperature range of the heat treatment is limited is that if the temperature is lower than 1100'C, the alloy will not be sufficiently solutionized and a high coercive force will not be obtained even if it is subsequently magnetized. This is because, if it exceeds this, a portion of the alloy will begin to melt, and even if it is subsequently magnetized, it will no longer be possible to obtain a high coercive force. Furthermore, if necessary, the magnetic alloy cooled to room temperature is heated to 650 to 85 "C".
The magnetic properties can be further improved by heating the material to an aging treatment. By performing aging treatment in this way, the alloy structure that has been solutionized into one phase becomes R-CO5.
It is considered that this separated state exhibits excellent magnetic properties. The heat-treated ingot is then ground into fine powder particles in a non-oxidizing atmosphere such as argon, nitrogen or liquid ethyl alcohol while preventing the formation of oxides.

In this case, since the coercive force of the magnet is due to the fine structure in the alloy formed by heat treatment, it is desirable to grind to an extent that this structure is not destroyed, that is, to a particle size of 2 to 10 μm. Note that if the particle size is less than 2 μm, the microstructure formed by heat treatment will be destroyed, resulting in a decrease in coercivity.
Moreover, if the thickness exceeds 10 μm, there is a problem that both coercive force and residual magnetic flux density decrease. An organic binder, such as a solution of nylon dissolved in methyl alcohol, is added to the fine powder particles obtained in this way, and the mixture is mixed to the extent that it becomes slightly moist. A magnetic field of 10,000 to 30,000 G is applied to magnetically arrange the particles while pressure molding is performed at a pressure of 2 to 6 tons/Cli to produce a permanent magnet that is compacted into a desired shape. It is something.

Note that the pressure molding method is not limited to the method of pressure molding in a magnetic field as described above, but may also be a method in which particles are magnetically arranged in advance and then pressure molded into a desired shape to form a permanent magnet. . If necessary, the pressure-molded permanent magnet may be placed in a water-impermeable flexible container made of plastic or rubber, and further hydrostatically formed at a pressure of 3 to 6 tons to create a three-dimensional shape. By applying a certain stress, it is possible to obtain a permanent magnet that has uniform characteristics without magnetostriction and has excellent mechanical strength.

However, according to the present invention, by adding copper to the alloy composition, the content of expensive rare earth metals can be reduced without deteriorating the magnetic properties, and by adding titanium, the coercive force can be increased. be able to. By further adding iron, a permanent magnet with high magnetic flux density and high coercive force can be obtained. The reason why the amount of rare earth metal added in the present invention is limited to the above range is that 10%
If it is less than 300, it is impossible to increase the coercive force.
When exceeding 1), the magnetic flux density decreases to 5,300G or less,
This is because the maximum energy product becomes 5MG0e or less.

Note that the rare earth metal is not limited to one type, but may be added in combination of two or more types, and the same effect can be obtained even if Mitsushi metal, which is an alloy of these metals, is added. Also, copper is 5
If it is less than 20%, no increase in coercive force is observed, and if it exceeds 20%, the magnetic flux density will decrease. Also, titanium is 0.
If it is less than 2, there is no effect of improving the coercive force, and if it exceeds 30 I), the magnetic flux density will decrease. Further, if the iron content is less than 2%, no increase in magnetic flux density and coercive force can be obtained, and if it exceeds 15%, the coercive force decreases. Next, examples of the present invention will be described.

Example 1 Alloy 209 having the composition shown in Table 1 was heated to 12% in argon gas.
After heat treatment at 00'C for 1 hour, the cooling rate was 3000C/
Cooled in minutes.

Next, this alloy was wet-milled in ethyl alcohol using a ball mill to obtain fine powder particles with an average particle size of 5 μm.

After mixing these fine powder particles with a 4% nylon-methanol solution, they were filled into a mold made of a non-magnetic material, and a magnetic field of 15,000 (0e) was applied from above and below using a punch made of a magnetic material. (A pressure of 7ii was applied and uniaxial pressing was performed to obtain a disc-shaped green compact with a diameter of 12 folds and a height of 8 mm.Then, this green compact was placed in a rubber container and further pressed for 50 minutes.
A permanent magnet was produced by performing isostatic pressing at a pressure of t0n/Cd and compacting the powder. Example 2 A permanent magnet was produced by powder molding using a magnetic alloy having a composition as shown in Table 1 in which iron was added as in Example 1, except for the same conditions.

Example 3 In Example 2 above, a permanent magnet was produced by heat treatment at 1200° C. for 1 hour, cooling to room temperature, and further aging treatment at 850° C. for 30 minutes, and powder molding under the same conditions as above.

Example 4 A permanent magnet was produced by powder molding using the magnetic alloy of the composition shown in Table 1 in Example 1 above, and under the same conditions as above.

Example 5 A permanent magnet was manufactured by powder molding under the same conditions as in Example 4 except that the heat treatment conditions were 1180° C. for 1 hour.

Comparative Examples 1 to 3 In Examples 1, 2, and 4, the heat treatment was omitted, and powder-molded permanent magnets were manufactured under the same conditions except for the heat treatment.

In order to examine the characteristics of the permanent magnets obtained in these Examples and Comparative Examples, the magnetic flux density, coercive force, and maximum energy product were measured for each, and the results are also listed in Table 1.

As is clear from the above results, according to the method for manufacturing a permanent magnet according to the present invention, by heat-treating a magnetic alloy having the composition specified in the present invention, the magnetic properties are improved by about 2 times compared to those without this heat treatment. Not only can the magnetic properties be improved by a factor of 2, but also the magnetic properties can be further improved especially when iron is added.

Claims (1)

[Scope of Claims] 1. A magnetic alloy consisting of 10 to 30% by weight of one or more rare earth metals, 5 to 20% by weight of copper, 0.2 to 3% by weight of titanium, and the balance cobalt at 1100 to 1250°C. 1. A method for producing a permanent magnet, which comprises heat-treating the magnet, cooling it to room temperature, pulverizing it into fine powder particles, magnetically arranging the particles, and press-molding the particles. 2 10 to 30% by weight of one or more rare earth metals, 5 to 20% by weight of copper, 0.2 to 3% by weight of titanium, iron 2
110% magnetic alloy consisting of ~15% by weight, balance cobalt
Manufacture of a permanent magnet characterized by heat treatment at 0 to 1250°C, cooling to room temperature, then pulverizing this into fine powder particles, and then magnetically arranging the particles and press-molding them. Method.