JPH03214606A - Manufacture of bonded magnet - Google Patents

Abstract

PURPOSE:To obtain a bonded magnet whose magnetic characteristic is high by a method wherein a permanent-magnet bulk body is collapsed by hydrogen, a thin film of a rare-earth element is applied to the surface of an obtained raw-material particle, a molding operation is then executed in a magnetic field and a heat treatment is executed. CONSTITUTION:A permanent-magnet bulk body obtained by quenching and, after that, hot- working the molten solution of an alloy whose fundamental components are a rare-earth element, iron and boron is collapsed by hydrogen; in addition, it is crushed mechanically and classified. A thin film of a rare-earth element is applied to the surface of a classified pulverized body. The body is molded in a magnetic field; after that, it is heat-treated in an inert atmosphere; then, it is impregnated with a resin. That is to say, when the permanent- magnet bulk body is placed in an atmosphere of hydrogen, it occludes hydrogen and is collapsed. In addition, when it is crushed mechanically, a crystal particle 11 is split into a plurality of particles 11a, 11b. However, the particles are placed in the atmosphere of hydrogen and are not subjected to a bad influence such as oxidation or the like. The thin film of the rare-earth element is applied; split faces and the like are protected; the body is molded to a desired shape in the magnetic field and heat-treated. The crystal particles 11a, 11b are bonded at the split faces; a bad influence on a chemical activity by the split faces is eliminated. Thereby, it is possible to obtain a bonded magnet which can display a high magnetic characteristic.

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a method for manufacturing a bonded magnet in which magnetic material powder containing rare earth elements diiron and boron as basic components is bonded with a synthetic resin. The present invention relates to a method of manufacturing an anisotropic bonded magnet made of the above-mentioned basic components that exhibits magnetic properties.

<<Prior Art>> Conventionally, bonded magnets, particularly Nd type anisotropic bonded magnets, have been manufactured, for example, by the following method.

First, the melted alloy adjusted to the desired composition is quenched into liquid, and the quenched powder is placed in a graphite container and heat-treated while applying uniaxial pressure in a vacuum or inert atmosphere to create a high density. After molding, a die-up setting method is performed in which uniaxial plastic working is applied while heating again to produce a bulk anisotropic magnet.

Next, as shown in FIG. 1(B), the above bulk body is pulverized and classified according to particle size. A synthetic resin (for example, epoxy resin), which is an adhesive for this powder (Nd type anisotropic alloy powder), is mixed with the classified powder and kneaded uniformly. After the crosstalk is molded into a predetermined shape in a magnetic field, the molded body is cured.

In addition, the above-mentioned molding in a magnetic field generally employs a compression molding method, increases the density of the molded body, and manufactures a bonded magnet having good magnetic properties.

<<Problem to be solved by the invention>> However, bonded magnets manufactured by the conventional manufacturing method,
In particular, Nd type anisotropic bonded magnets do not have sufficient magnetic properties.

Compared to SmCo type bonded magnets, the above Nd
This type of anisotropic bonded magnet clearly has inferior magnetic properties.

The reason for this is thought to be as follows.

This type of powder (Nd-type anisotropic alloy powder) is chemically very active, so the powder generated by crushing the bulk material mentioned above is oxidized at the same time as it is generated (i.e., during crushing). , and is greatly affected by the stress caused by crushing. The large influence of these oxidation and stress significantly deteriorates the squareness of the 4πI-H loop of the product bonded magnet, and deteriorates the magnetic properties. In other words, it is thought that the above-mentioned oxidation and stress have a large influence on the magnetic properties.

The present invention has been made in view of the above points, and
The purpose is to propose a method for manufacturing bonded magnets, especially Nd type anisotropic bonded magnets, that can prevent significant deterioration of the squareness of the 4πI-H loop and exhibit high magnetic properties. .

<<Means for Solving the Problems>> In order to achieve the above object, the present invention provides a method for manufacturing a bonded magnet whose basic components are rare earth elements, iron, and boron, in which a solution of an alloy consisting of the basic components is dissolved. The permanent magnet bulk body obtained by hot processing after quenching is hydrogen-disintegrated, further mechanically crushed and classified, a thin film of a rare earth element is deposited on the surface of the classified powder, and the thin film-coated powder is It is characterized in that after molding in a magnetic field, it is heat-treated in a vacuum or an inert atmosphere, and then the heat-treated molded product is impregnated with a resin.

3 Preferably, the hydrogen decay described above is carried out at 30 Torr.
Hydrogen gas pressure of r ~50 K g/atl. room temperature~
It is to be carried out at 500°C.

Furthermore, the above heat treatment in vacuum or inert atmosphere is
The heating may be carried out at 00 to 900'C for up to 3 hours.

<<Function>> The present invention focuses on the fact that, as mentioned above, the magnetic properties of bonded magnets are greatly affected by the oxidation and stress of the raw material powder, and defects in the raw material powder (particles) such as oxidation and stress ■ Obtaining a permanent magnetic bulk body from the raw material powder by so-called hydrogen decay; ■ Protecting the surface of the obtained raw material particles; ■ Molding and heat-treating the raw material powder with the surface protected in a magnetic field before adding and mixing the resin. This can be resolved by doing something.

That is, as shown in Figure 2 (A-1), a permanent magnet bulk body obtained by hot processing a solution of an alloy consisting of the basic components after quenching has crystals of about 0.50 mm or less consisting of Nd2Fe14B. Grains 11 are surrounded by Nd-rich 4 phase 12. And Figure 2 (A-2)
It shows good squareness of the 4πI-H loop as shown in FIG.

When such a permanent magnet bulk body is placed in a hydrogen atmosphere, absorbs hydrogen, collapses, and is further mechanically crushed, a second
As shown in Figure (B-1), each crystal grain 11 is
It cracks into multiple parts as shown in a and llb, and this crack surface exhibits high chemical activity.

In the present invention, which employs hydrogen decay, this chemically active surface is under a hydrogen atmosphere and is not subject to adverse effects such as oxidation. In addition, although the reason is not clear, Figure 2 (
As shown in B-1), the coercive force (iHe) of the powder (particles) obtained by breaking the water cable is extremely low. This extremely low coercive force has the effect of significantly improving the distribution of particles during magnetic field molding.

Furthermore, in the present invention, by depositing a thin film of a rare earth element on the crack surface, the surface of the crystal grains 11a and llb other than the crack surface, and the surface of the crystal grain 11 that was not cracked by the hydrogen decay or mechanical crushing, , protecting these surfaces and eliminating the negative effects of chemical activity.

Thereafter, the rare earth element thin film-coated particles are molded into a desired shape in a magnetic field, and then heat treated.

As a result of this magnetic field molding and heat treatment, the crystal grains 11a and 1lb, which have been split into two, are combined approximately at the cracked surfaces, as shown in Figure 2 (C-1), and the crystal grains 11a and 1lb are combined with each other approximately at the crack surfaces, as shown in Figure 2 (A-1). ).

As a result, the squareness of the 4πI-H loop also changes as shown in Figure 2 (C
- As shown in 2), the condition will be good.

On the other hand, according to the conventional manufacturing method of bonded magnets described above, resin is added and mixed into the state shown in Figure 2 (B-1), so the chemical reaction caused by the above-mentioned crack surface 4 of product bonded magnets due to unresolved negative effects of physical activity.
The squareness of the π1-}I loop deteriorates significantly, as shown in FIG. 2 (B-2).

On the other hand, if the hydrogen gas pressure and temperature during the hydrogen decay described above are too low, hydrogen absorption takes too long and is impractical; conversely, if the hydrogen gas pressure and temperature are too high, the equipment used for hydrogen decay Since this may cause a safety problem, the present invention uses 30T, which allows hydrogen decay to occur well and provides the above-mentioned oxidation prevention effect on the cracked surface and the effect of significantly lowering the coercive force.
o r r~50kg/c4 hydrogen gas pressure 1 normal temperature~50
The temperature is set at 0°C.

Furthermore, if the thin film of the rare earth element is too thin, it will not be able to provide protection to the cracked surfaces and particle surfaces, and if it is too thick, the protective effect will become saturated, making it uneconomical. Therefore, it is preferable to have a thickness of about 0.005 to 3 μs.

These rare earth elements include Nd, Ce, La, Pr, D
y, Ho, Tb, etc. are preferably used, and the rare earth elements are not limited to the same type as the rare earth elements constituting the particles, but may be different types, or two or more types may be used in combination.

These thin films of rare earth elements are diffused into the particles by the heat treatment described above, and do not have any adverse effect on the magnetic properties of the product bonded magnet.

Thin films of rare earth elements can be produced by vapor deposition, sputtering, and method. It can be applied by a coating method or other appropriate method.

In order to obtain the effect shown in FIG.
The temperature is preferably 0°C. That is, when the temperature is lower than 400°C, the crystal grains 11a. Atomic diffusion between 11b and at the grain interface is insufficient, and the above-mentioned effect does not occur. On the other hand, if the temperature is higher than 900°C, the crystal grain size will become coarser,
Magnetic properties deteriorate rapidly.

Further, the time for the above heat treatment is appropriately selected depending on the above heat treatment temperature, but if it exceeds 3 hours, the crystal grain size will become coarse and the magnetic properties will deteriorate, so in the present invention, it is set to within 3 hours. It is.

Note that if the heat treatment time is shorter than 0.2 hours, atomic diffusion between the particles and at the grain interface may become insufficient, so the lower limit of the heat treatment time is preferably 0.2 hours.

Furthermore, the reason why the above heat treatment is performed in a vacuum or an inert atmosphere is to prevent the above-mentioned oxidation of the crack surfaces and crystal grain surfaces, which is promoted by heat.

In addition, the above heat treatment is not limited to continuous heat treatment as shown in FIG. 3(A), but as shown in FIG. 3(B), A+B+C+D...=-3 hours. The above effects can be obtained even with discontinuous heat treatment within the range.

In the present invention, resin impregnation is performed after the above heat treatment.

As a result, the resin penetrates between the particles after molding, locking the particles together, and making it possible to firmly maintain the shape after molding.

<<Examples>> Example 1 The method according to the present invention was carried out according to the flow shown in FIG. 1(A), and Nd+s. 3Fe7s. , Co2. s B5.4
An anisotropic bonded magnet having the composition was manufactured.

That is, a solution of an alloy consisting of rare earth elements (Nd), Fe, Co and B is rapidly cooled to obtain a thin ribbon, which is crushed,
The permanent magnet bulk body obtained by hot pressing and die-up setting is placed in a closed furnace (in this example, a hydrogen atmosphere electric furnace), and the air in this electric furnace is sufficiently filled with H2 gas. After replacing, it was kept at 250°C and a H2 gas pressure of 1 kg/ca for 4 hours.

The powder thus subjected to hydrogen collapse was further crushed using a jaw crusher and classified to obtain a powder having a particle size of 125-300.

This classified powder is inserted into a vacuum evaporation device, and the degree of vacuum is increased to IX.
Set at 10-6 Torr, with a thickness of 1000 N per minute
The operation of vapor-depositing d on the surface of the classified powder was performed 8 times in total, once every 2 minutes.

After that, this Nd thin film (0.5 cup) was applied to the adhering powder in a magnetic field of 15
Pressure molding was carried out at 4.5 ton/c+ff while orienting in KOe, and the molded body was heat-treated in vacuum at 750° C. for 1 hour. Note that the heat treatment method was the method shown in FIG. 3(A).

The molded body after heat treatment is immersed in an epoxy resin with a viscosity of 10 cps, transferred to a desiccator, and kept in a vacuum state for about 3 minutes to ensure that the molded body is sufficiently saturated with epoxy resin. lko.

Next, curing was performed at 100°C for 60 minutes.

Five samples were manufactured as described above.

For comparison, the conventional process shown in Figure 1 (B), i.e., without hydrogen decomposition and Nd thin film deposition, was applied to the classified powder obtained by mechanical crushing using a jaw crusher with a viscosity of 10 cps. After mixing the epoxy resin and kneading it uniformly, 4,5 to
Pressure molded at n/c♂ and heated at 100°C. Curing was performed for 60 minutes to produce five samples of anisotropic bonded magnets having the compositions described above.

The residual magnetic flux density Br maximum energy product (
BH) ■ The squareness of the 8 and 4πI-H loops was measured.

The results are shown in Table 1.

1 1 As is clear from Table 1, the method according to the present invention significantly improves the squareness and residual magnetic flux density compared to the conventional method. It can be seen that it is possible to obtain a bonded 1 2 magnet having high magnetic properties that could not be obtained using the bonded 1 2 magnet.

Example 2 The method according to the present invention was carried out in exactly the same manner as in Example 1 except that the heat treatment temperature was variously changed, and the magnetic properties of the obtained bonded magnets were measured.

The results are shown in FIG.

As is clear from the figure, temperatures below 400°C and temperatures below 900°C
At temperatures higher than °C, a decrease in magnetic properties is observed, with temperatures ranging from 600 to
It can be seen that the magnetic properties reach a peak at 800°C.

Example 3 The method according to the present invention was carried out in the same manner as in Example 1 except that the heat treatment time was varied, and the magnetic properties of the obtained bonded magnets were measured.

The results are shown in FIG.

As is clear from the figure, if the heating time is longer than 3 hours, the magnetic properties will be degraded, and if the heating time is shorter than 1 hour at 750° C., the magnetic properties will also be degraded.

Example 4 As a method of depositing a rare earth element thin film on the surface of classified powder, an organometallic compound containing 8% by weight of Nd (a complex salt having a chelate bond in the molecule, in addition to 8% by weight of Nd, a non-volatile A method was adopted in which 5% by weight of the classified powder was added (containing 33% by weight of 10% by weight and dissolved in toluene) and mixed for 0 minutes in an inert atmosphere, and the heat treatment conditions were set to 7%.
The method according to the present invention was carried out in exactly the same manner as in Example 1 except that the temperature was 00°C for 1 hour, and the obtained bonded magnets (5 pieces)
The magnetic properties of the material were measured.

The results are shown in Table 2.

Table 2 Example 5 The method of depositing the rare earth element thin film on the surface of the classified powder was the same as that of Example 1 except that the method of sputtering the classified powder with Nd metal as the cathode target material was adopted under the following conditions. The method according to the present invention was carried out in exactly the same manner, and the magnetic properties of the obtained bonded magnets (5 pieces) were measured.

Sputtering conditions Vacuum degree: IX10-2 Torr Input voltage: 150W Sputtering time: 2 hours The above results are shown in Table 3.

Table 3 1 5 Example 6 As a hydrogen decay method for a permanent magnet bulk body, the bulk body was placed in a hydrogen atmosphere electric furnace, the inside of this electric furnace was evacuated, and then H2 gas was introduced to create an H2 gas atmosphere. After that, 5
H2 gas pressure of 0 kg/c♂. Example 1 except that a method of holding at room temperature for 1 hour was adopted, and the vacuum degree was set to 1 × 10 Torr as a method of depositing a Nd thin film on powder surface blood, and the operation was performed once for 2 minutes for a total of 4 times. The method according to the present invention was carried out in exactly the same manner as described above, and the magnetic properties of the obtained bonded magnets (5 pieces) were measured.

The results are shown in Table 4.

Table 4 1 6 Example 7 The method according to the present invention was carried out in the same manner as in Example 1 except that hydrogen decay was carried out at 30 Torr, 500'C, for 4 hours, and the obtained bonded magnets (5 pieces ) was measured.

The results were similar to those in Table 1 of Example 1.

<<Effects of the Invention>> According to the method according to the present invention detailed above, since the raw material powder (particles) is obtained by hydrogen decay of the permanent magnet bulk body, defects caused by the chemical activity of the raw material particles are removed from the hydrogen gas atmosphere. and a thin film of rare earth elements deposited on the surface.
Next, by molding in a magnetic field and heat treatment, the defects in the raw material particles mentioned above can be eliminated through particle interaction, and since this is followed by resin impregnation, it is possible to obtain bonded magnets with magnetic properties that could not be obtained with conventional methods. can.

As a result, the method according to the present invention can provide a bonded magnet that has good squareness and is also excellent in both residual magnetic flux density and maximum energy product.

Further, according to the method of the present invention, it is possible to manufacture a ring-shaped bonded magnet with a high coercive force, which was previously impossible.

[Brief explanation of drawings]

FIG. 1(A) is a diagram showing the method according to the present invention in the order of steps, FIG. 1(B) is a diagram showing the conventional method in the order of steps, FIG. 2 is a diagram explaining the action of the method according to the present invention, Figure 3 (A), (B)
4 is an explanatory diagram showing how to perform heat treatment in the method according to the present invention.
5 and 5 are diagrams showing the basis of the heat treatment conditions of the method according to the present invention.

Claims (3)

[Claims] (1) In a method for manufacturing a bonded magnet whose basic components are rare earth elements, iron, and boron, a permanent magnet bulk body obtained by rapidly cooling and hot working a solution of an alloy consisting of the basic components is subjected to hydrogen collapse, Further, the classified powder is mechanically crushed and classified, a thin film of a rare earth element is deposited on the surface of the classified powder, the thin film-coated powder is molded in a magnetic field, and then heat treated in a vacuum or an inert atmosphere. A method for manufacturing a bonded magnet, which comprises impregnating a heat-treated molded body with a resin. (2) The hydrogen decay is controlled at 30 Torr to 50 Kg/cm
2. The method for manufacturing a bonded magnet according to claim 1, wherein the bonded magnet manufacturing method is carried out at a hydrogen gas pressure of ^2 and at room temperature to 500°C. (3) The heat treatment in vacuum or inert atmosphere is performed for 40 minutes.
3. The method for manufacturing a bonded magnet according to claim 1, wherein the manufacturing method is carried out at 0 to 900[deg.] C. for less than 3 hours.