JPH0472702A - Rare earth element-fe-b plastic magnet - Google Patents

Abstract

PURPOSE:To make it possible to conduct a electroless plating operation without performing a palladium chloride treatment by a method wherein a non-magnetic Ni-P electroless plating operation is conducted on the outside surface of a plastic magnet formed by compounding phenol-containing resin into the rare earth element-Fe-B magnet alloy powder consisting of specific composition. CONSTITUTION:A magnet alloy resin composition is formed by mixing 8 to 30atom% rare-earth element, 2 to 29atom% B, 0 to 3atom% Ga, 0 to 40atom% Co, and the remaining part composed of rare earth element-Fe-B magnet alloy powder, consisting of 50 to 96vol.% Fe and the resin, containing 10vol.% or more phenol against the entire resin quantity, of 5 to 50vol.%. After the above- mentioned mixture has been molded, non-magnetic Ni-P electroless plating is provided on the surface of the obtained molded body.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a rare earth element -Fe- which has improved corrosion resistance and reduced deterioration of magnetic properties and dimensional changes after high temperature aging.
Regarding B series plastic magnets.

(Prior Art) Plastic magnets have the advantage that they do not require a sintering process in their manufacture, and can be processed into magnets with high dimensional accuracy by economical molding process, rather than grinding process, which is expensive. Therefore, it is suitable for applications such as motor rotors that require high dimensional accuracy and economical efficiency.

Rare earth element-Fe-B alloy plastic magnets, which are the most common plastic magnets, have the drawback that the magnet powder itself has poor corrosion resistance, and even if it is made into a plastic magnet, it easily rusts. Generally, the surface is coated with resin to improve corrosion resistance.

However, although the salt spray resistance of resin-coated plastic magnets (sprayed with 5% salt water at 35°C) is good,
Moisture resistance (left in an environment of 80°C and 90%) is poor.

Furthermore, the resin used as a binder in plastic magnets and the resin coating/layer are permeable to oxygen, so if a resin-coated plastic magnet is used in an oxygen-containing atmosphere at a relatively high temperature, the magnet powder may permeate. Oxidized by oxygen, plastic magneto
Soto has the disadvantage of expanding. For example, if a motor using such a plastic magnet in its rotor is operated for a long time, the rotor expands and comes into contact with the stator, causing an accident in which the motor stops rotating.

In order to prevent dimensional changes from occurring, it is necessary to perform high temperature aging. Therefore, in advance, the plastic magnet is in an over-aged state (heated mustard state).
The process to prevent dimensional changes during use is
Traditionally done.

However, when a plastic magnet is overaged, its magnetic properties deteriorate at the same time, so this overaging treatment is used to suppress dimensional changes.
It has the disadvantage that the magnetic strength must be reduced by about 1 to 2 MGOe at the expense of magnetic properties.

On the other hand, as a protective film that improves corrosion resistance and prevents dimensional changes and deterioration of magnetic properties at high temperatures, a metal plating layer that does not allow oxygen to pass through is superior to a resin coating layer. In a plastic magnet formed from a mixed composition of magnetic powder and resin, the resin component surrounds the magnetic powder, making it impossible to establish electrical continuity between the outside and the magnet powder.

Therefore, electroplating cannot be applied, and electroless plating must be performed. Conventionally, when performing electroless plating, plastic magnets were treated with baradium chloride, making electroless plated products extremely expensive.
Therefore, its uses were limited.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned problems of plastic magnets, and to create magnets that have high corrosion resistance, less dimensional change and less deterioration of magnetic properties at high temperatures, and are economical in price. Our goal is to provide plastic magnets.

(Means for Solving the Problems) The present inventor has proposed that if a rare earth element-FeB plastic magnet is made using a phenol resin or a resin containing a phenol resin, electroless plating can be performed without palladium chloride treatment. The inventors have found that it is possible to do this, and have solved the above-mentioned object with a configuration according to the present invention having the following features.

That is, the plastic magnet according to the present invention contains 8 to 30 at% of rare earth elements, 2 to 28 at% of B,
Ga is 0 to 3 at%, CO is 0 to 40 at%,
50 to 95% by volume of a rare earth element -Fe-B magnet alloy powder, the balance of which is Fe, and 5 to 50% by volume of a resin containing phenolic resin in an amount of 10% by volume or more based on the total resin amount. to produce a magnet alloy resin composition,
After molding, non-magnetic Ni-P is applied to the surface of the obtained molded body.
This is a rare earth element-Fe-B plastic magnet characterized by being subjected to electroless plating.

The composition of the magnetic alloy powder is 8 to 30 at% rare earth element, 2 to 28 at% B, 0 to 3 at% Ga, 0 to 40 at% CO, and the balance is Fe.
The reason for limiting the elemental composition and composition range is that magnetic alloy powder having a composition outside this range cannot exhibit predetermined magnetic properties.

The plastic magnet made of a magnet alloy resin composition using a resin containing less than 10% by volume of phenolic resin is limited to a resin containing 10% by volume or more of phenolic resin based on the total amount of resin.

This is because Ni--P electroless plating cannot be applied to the surface of the substrate unless the conventional expensive baradium chloride treatment is applied to the surface. .

The total amount of resin in the magnet alloy resin composition is 5 to 50% by volume.
This is because if the resin amount is less than 5% by volume, the resin cannot function as a binder, and if it is more than 50% by volume, the resulting plastic magnet will not have the desired magnetic properties.

After the magnet alloy resin composition is molded into a predetermined plastic magnet, curing is preferably performed at a temperature of 50 to 250°C. This is because a curing temperature of less than 50°C is too low and the curing effect is weak, and aging at a temperature of 80°C or higher causes dimensional changes. When the curing temperature is 250° C. or higher, the magnetic properties of the plastic magnet deteriorate, and at the same time, the resin component softens, causing deformation of the plastic magnet.

In order to improve the corrosion resistance of plastic magnets, block the permeation of oxygen, and prevent dimensional changes at high temperatures, a Ni plating layer, which has particularly excellent properties among metal plating layers, is molded into plastic magnets. Apply to the product. However, if a magnet is coated with a magnetic layer with low coerciveness, such as a Ni plating layer, the magnetic flux will be short-circuited in the magnetic circuit, and the magnetic properties of the magnet will deteriorate.
To plate Ni, it is necessary to perform nonmagnetic plating. Therefore, in the present invention, nonmagnetic N1-P electroless plating is applied to the molded plastic magnet molded product using a known method. The film thickness is preferably around 20 μm.

(Example) EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Example 1 Nd: 14 at%, B: 6 at%, Co: 15 at%,
A magnet alloy consisting of 0.75% Ga and the balance Fe is melted at high frequency in a vacuum to produce a molten magnet alloy, and then the produced molten magnet alloy is sprayed onto a Cu piece roll in an Ar atmosphere to form a ribbon. A sample was obtained. This ribbon sample was ground in a ball mill to obtain a powder of 42 meshes or less, and then annealed at 650° C. for 30 minutes to obtain a magnet alloy powder.

According to the magnet composition described in Example 1 in Table 1, 77% by volume of the obtained magnet alloy powder and 23% by volume of phenol resin were mixed and ground, and the pulverized magnet alloy resin composition was heated to the mold temperature. A cylindrical body with a diameter of 10 mm and a height of 10 mm and an outer diameter of 19
Mold into a ring with an inner diameter of 17 mm and a height of 10 mm.
Next, curing was performed under the curing conditions listed in Table 1, ie, at 125°C for 3 hours, to obtain a cylindrical sample and a ring sample. Next, the obtained sample was subjected to non-magnetic N1-P electroless plating with a film thickness of 20 μm to obtain a test sample of Example 1 according to the present invention.The cylinder sample was used for magnetic measurement, and the ring sample was used for dimensional change and corrosion resistance. It was used for measurement.

A corrosion resistance test was conducted by exposing the ring test sample to an environment of 80° C. temperature and 90% humidity, and the time required for rust to occur was measured.

The ring test sample was aged at 125° C. for 100 hours, and the dimensional changes of the ring test sample before and after aging were measured.

The cylindrical samples were aged for 100 hours at the same <125°C, and the magnetic properties of the aged cylindrical test samples were measured with a B-H curve tracer.

The results of each of the above tests are shown in Table 1.

Examples 2 to 5 Magnet alloy powder having the same composition as in Example 1 obtained in the same manner as in Example 1 and phenol resin were prepared in the same manner as in Example 1 according to the magnet composition in Table 1, mixed, crushed, and molded. Then, it was cured under the conditions listed in the curing conditions in Table 1, and then subjected to the same non-magnetic N1-P electroless plating as in Example 1.
These were used as test samples of Examples 2 to 5, respectively.

Corrosion resistance, dimensional change, and magnetic properties of these test samples were similarly measured under the same conditions as in Example 1. The results of each test were as shown in Table 1.

Example 6 Magnet alloy powder having the same composition as Example 1 obtained in the same manner as Example 1 and an epoxy resin blended so that the volume percentage of phenol resin of the total resin amount was 15% were mixed at a volume ratio of 7.
The test sample of Example 6 was prepared by mixing 7% and 23%, pulverizing and molding, then curing under the same curing conditions as in Example 1, and then applying non-magnetic NiP electroless plating in the same manner as in Example 1. And so.

Corrosion resistance, dimensional change, and magnetic properties of this test sample were similarly measured under the same conditions as in Example 1.

The results of each test were as shown in Table 1.

Comparative Example 1 Magnet alloy powder having the same composition as Example 1 obtained in the same manner as Example 1 and phenol resin were mixed at a volume ratio of 55% and 4%.
They were mixed at 5%, pulverized and molded, then cured under the same curing conditions as in Example 1, and then subjected to the same non-magnetic Ni-P electroless plating as in Example 1 to obtain the test sample of Comparative Example 1. did.

Corrosion resistance, dimensional change, and magnetic properties of this test sample were similarly measured under the same conditions as in Example 1.

The results of each test were as shown in Table 1.

Comparative Example 1 exhibited significantly inferior magnetic properties because the volume % of the resin was greater than the range of the present invention.

Comparative Example 2 Magnet alloy powder having the same composition as Example 1 obtained in the same manner as Example 1 and an epoxy resin blended so that the volume percent of the phenol resin of the total resin amount was 5% were mixed at a volume ratio of 77.
% and 23%, respectively, were mixed, crushed and molded, and then cured under the same curing conditions as in Example 1.

In the sample of Comparative Example 2, the content of phenol resin in the total resin amount was outside the range of the required amount of phenol resin specified by the present invention, and the amount of phenol resin was insufficient, so that electroless plating could not be performed.

Comparative Example 3 This is the same example as Example 1 except that the sample was not subjected to non-magnetic Ni--P electroless plating.

It showed significantly poor corrosion resistance.

Comparative Example 5 This is the same example as Example 1, except that the sample was not subjected to non-magnetic Ni--P electroless plating, but instead was coated with an epoxy resin coating having a thickness of 20 μm.

Corrosion resistance was extremely poor, and dimensional changes due to aging were large.

All of the examples shown in Table 1 have a dimensional change of at most 10 μm.
The corrosion resistance test showed a value of around 1000 hours, showing even better magnetic properties.

(Effects of the Invention) As is clear from the test results of the examples, the plastic magnet according to the present invention has excellent corrosion resistance, maintains good magnetic properties even after high temperature aging, and exhibits very small dimensional change. It has characteristics. Such characteristics are optimal for use in magnets such as motor rotors, for example.

On the other hand, the present invention, in which non-magnetic Ni-P electroless plating, which has low processing cost and is easy to process, is applied to plastic magnet composition components that can be easily and inexpensively obtained, has excellent characteristics that have wide industrial applications. Plastic magnets can be supplied at a low price, and the range of use of plastic magnets can be expanded.

Claims (1)

[Claims] 1. 8 to 30 at% of rare earth elements, 2 to 2 of B
8 atomic%, Ga 0 to 3 atomic%, Co 0 to 4
Rare earth element -Fe- with 0 atomic % and the balance consisting of Fe-
A plastic magnet consisting of 50 to 95 volume % of B-based magnet alloy powder and 5 to 50 volume % of a resin containing 10 volume % or more of phenolic resin based on the total resin amount has no non-magnetic Ni-P on its outer surface. Electrolytically plated,
A rare earth element-Fe-B plastic magnet.