JPS59213104A - Permanent magnet - Google Patents

Abstract

PURPOSE:To obtain an excellent permanent magnet by a method wherein magnetic powder of R2-Mz14-17 having the specific value or more of true magnetic coercive force and thermoplastic resin are mixed, and the permanent magnet is formed by performing an injection molding method, thereby enabling to increase the number of reuse of the permanent magnet. CONSTITUTION:Magnetic powder of R2-Mz14-17 (R is the alloy having one kind or more of rare-earth element and Mz is the alloy containing cobalt as a main component) having 6,000 oersted or more of true magnetic coercive force iHc, is formed into the permanent magnet by performing an injection molding method using thermoplastic resin as a binder. As a result, the number of reuse of injection-molded permanent magnet can be increased even when the manufactured articles of product volumetric efficiency of 30% are manufactured, thereby enabling to obtain excellent permanent magnets.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet formed by injection molding R-MZ magnet powder using a thermoplastic resin as a binder.

An object of the present invention is to improve the number of reuses of injection molded permanent magnets and to obtain good permanent magnets.

Traditionally, permanent magnets are ferrite magnets and alnico magnets.
It was mainly used as a magnet, but in recent years, R-
Co magnets have shown rapid growth. This is because they have higher performance than ferrite magnets. For reference, these three types of hysteresis loops are shown in FIG. In the figure, 1 is a ferrite magnet, 2 is an alnico magnet, and 3 is an R-M Z magnet.Also, unlike the sintering method that has been the mainstream for ferrite magnets and R-M Z magnets in recent years, thermoplastic Magnets manufactured by injection molding using resin as a binder have been increasing. This is because it is relatively easy to manufacture thin-walled magnets and magnets with radial anisotropy, which are difficult to manufacture using the sintering method.Therefore, production of ferrite injection molded magnets began several years ago. Currently, it has developed to the point where it has formed a large market for products such as centering magnets for cathode ray tubes.

However, R-Mz magnets have not yet reached the industrial base. One of the major reasons for this is the issue of whether or not the spool runner can be reused.

For reference, Fig. 2 shows a sketch of the injection molding process.

In the figure, 4 is a spool, 5 is a runner, and 6 is a product. Generally, the product volume ratio, that is, is around 30%.

In the case of ferrite, the cost of raw material ferrite powder is generally low at 3 to 0.5 yen/1, so it is discarded and
Even if it was not reused, the impact on product cost was minimal and did not pose a major problem for industrialization.

However, in the case of R-Mz magnets, the cost of raw material powder is
Generally, it costs 20 to 50 yen/2, which is almost 100 times that of ferrite, and does not reuse 70% of the spool + runner.
Disposing of the product results in high product costs (and industrialization is impossible. Therefore, the number of times the spool and runner can be reused is the key to putting R-MZ injection molded magnets on an industrial basis. The point is whether or not.

Generally, in injection molding, the temperature is raised to 230 to 320° C. and then the material is injected, so the performance deteriorates due to oxidation of the magnet powder and the effect on the pinning effect of the domain wall, making it impossible to reuse it.

The present invention is intended to overcome these drawbacks and bring R-Mz injection molded magnets onto an industrial basis.

Conventionally, injection molding was performed mainly with the composition R1-MZ, but this magnet has single domain anisotropy, so the raw material powder particle size must be 10 microns or less, and because the particle size is fine, However, in the present invention, this raw material is converted into R2-MZI with a 1Hc of 6000 millimeter or more, ~
, 7, it was successful.

Before going into the description of the present invention, I would like to clarify the general criteria for reusability.

Currently, the standard tolerance for magnet performance is ±5%.
It is allowed to become 10% softer in the microwave. However, this is a fluctuation that includes all factors, and performance degradation due to reuse when manufacturing products with a product volume ratio of around 60% (2%, or half of this, 5%) will result in stable production. Tomuma Nanashi'10 Now, when performing this molding, the first time (I used 100% virgin material, but the next time I reused part of the spool and runner, I used Jijin 3302,
If it is repeated once, the ratio will be as follows.

Precept-1 Here, the performance degradation is approximately proportional to the number of reuses, so
When the performance when molded only with virgin material is A, the number of times of reuse is L, and the performance deterioration coefficient is a, the performance Bn when molded only with the second reprint product is Bn-AxarL (1 formula).

Therefore, the difference between performance A when molded only with virgin material and performance C when it is repeatedly reused and becomes as shown in Table 1 must be 5% or less, and in that case, the performance deterioration coefficient α is approximately 0.98. Substituting this into equation 1, we get 1
Performance B1o when molded only with materials that have been reused 0 times is:
Performance must be 80% of A.

Therefore, in the present invention, the reusable criterion is B1
o≧A X O, 8.

In the present invention, from the conventional RI M zH material amount: R2-Mz engineering, ~1. The material was changed to R, -MZl, ~17 material is a magnet that utilizes the pinning effect, and the particle size of the magnetic powder is R1-MzB.
This is because the surface area is about 10 times larger than that of wood, and its surface area is 1/100, reducing deterioration due to surface oxidation.

However, this alone is insufficient, and it has been found that even in this magnet material, performance deterioration due to reuse differs depending on the magnitude of iHc. As a result, B10≧A
In order to satisfy X 0.8, it is necessary that iHc≧6000 or more.

This will be explained in detail below using examples.

The raw materials of Example Sm(Co, Ou, Fe, Zr) s, t were aged to 1Hc==2000°40 by changing the aging treatment conditions.
00.6000,8000,10000゜15000.
20000. Ørsted material.

Seven types of powder were made, mixed with 40% nylon by volume, and each was reused 10 times by molding at 280°C to form a 4110mm x 10 round bar.The surface magnetic flux was measured and the performance was evaluated. We investigated the decline. The data are shown in FIG.

As you can see, the reusability is 1Hc6000
Below Oersted, it deteriorates extremely and is difficult to reuse.

Note that the present invention specifies the composition of the raw material and the iHc, and is effective regardless of the type of binder or its percentage.

[Brief explanation of the drawing]

Figure 1 shows the hysteresis curves of three types of magnets. 1 is ferrite, 2 is alnico, 3 is R-MZ. Figure 2 is a sketch of the injection molded product. 4 is a spool, 5 is a runner, 6 is a product, Fig. 3 shows i
Graph showing the decrease in BIO with respect to A due to differences in Hc. Applicant: Suwa Seikosha Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] R-MZ (R is one or more rare earth elements,
Mz is R2-M214 to . I. A permanent magnet characterized in that it uses raw material powder and has a true coercive force (iHc) of 6,000 degrees or more.