JPS6033287B2 - Magnetic field forming method for powdered permanent magnets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to molding powdered magnet materials in a magnetic field, and more particularly to a method for producing rare-cobalt powder permanent magnets.

Rare-cobalt intermetallic compounds have recently been developed such as Sm2Co., which has a high saturation magnetization. 7 series and its large magnetic anisotropy, it is made into a powder and molded under pressure in a magnetic field to become a permanent magnet.

An object of the present invention is to obtain an extremely high degree of orientation.

When powder is compacted excessively in a magnetic field, the easy magnetization direction of each particle and the direction of the magnetic field applied during compaction are compacted in parallel, resulting in a residual magnetic moment. r
is the saturation magnetic moment of the material. s (all 〇 are 1)
Ideally, it should be equal to the magnetic moment (magnetic moment per gram). However, in reality, each magnetic fine particle cannot be aligned completely parallel to the direction of the magnetic field applied by the interaction between the particles, and is formed with a certain angular dispersion. As a result, the molded magnet body. r is the material. It becomes smaller than s. Generally, in order to indicate the orientation of each fine particle of a magnet with respect to the direction of the magnetic field, the degree of orientation K of the particles is defined as K=groove, and it is necessary to devise a molding method in a magnetic field so that the particle becomes close to chest. Especially Sm2Co. The crystal structure of the 7 powder magnet is rhombohedral or hexagonal, and the coercive force generation mechanism is fundamentally different from that of conventional SmC magnets.

That is, Sm2Co. Type 7 is based on the movement of domain walls and their pinning, so when molding magnetic powder, a large oriented magnetic field and a molding method that holds the oriented powder are required. The conventional molding method in a magnetic field is generally widely used for heterogeneous barium ferrite magnets, etc., and its principle is as shown in Fig. 1, where a mold 6 is placed between electromagnets with variable magnetic pole spacing, and upper and lower punches 4 are placed. , 5, a magnetic field is applied with the magnetic powder placed between them, and the distance between the magnetic poles is shortened to form a powder molded body.

Generally, excitation coils 3 are attached to the upper and lower rams 1 and 2 of the compressor so that the electromagnet and the compression device are integrated, and molding is performed in a magnetic field. This method is characterized in that the direction of the magnetic field and the direction of pressing the powder are parallel. Conventionally, in order to obtain a high magnetic flux for SmC method powder, the magnetic field was compressed for rare metal-cobalt powder magnets, that is, SmC method magnets, as disclosed in Japanese Patent Publication No. 47-34852 (see Japanese Patent Publication No. 54-25637). It is stated that it is effective when applied perpendicular to the direction.

However, the present inventor has recently developed a high-performance magnet R2TM, type 7,
For example, Sm(Coo.672, Cuo.08, Feo.
02, Zro. 028) We have been researching alloys consisting of 6.0 to 9.3 coarse alloys, and as shown in the 41-H curve in Figure 2, we have found that there is a clear difference in the coercive force mechanism. It's here. Conventionally, based on the mechanism of one rotation of single magnetic domain particles in fine powder, the initial magnetization curve was (b)
As shown in Figure 2, there is a sudden rise. On the other hand, Sm (Coo.672, Cuo.08 Fe o.22
, Zro. 028) Initial magnetization curve of 4ml-HZ curve of 8.4 alloy {a)' Well, the magnitude of the external magnetic field, which is the energy for movement of the domain wall, is almost completed near 1 skin Ce. In this way, the SmC method and the Sm2Co. 7, the coercive force mechanism is fundamentally different, especially in Sm2Co. For type 7 permanent magnets, a higher orientation magnetic field and molding method are desired. As mentioned above, Tokupusho No. 47-134852 does not mention this at all. The present invention provides Sm2T
In the case of an M,7 magnet, it has been found that the degree of orientation K can be improved by press-molding in a direction perpendicular to the magnetic field and applying a magnetic field strength of 10 KOe or more.

Further, in the present invention, the Sm2TM, 7 alloy ingot is subjected to solution treatment and aging treatment, and then pulverized so that the particle size is distributed in the range of 5 to 80 mm, mixed with an epoxy resin as a binder, and then molded by the above method. It is something. In general, Sm2TM,7 alloy has the disadvantage that when it comes into contact with air, it oxidizes and its magnetic properties tend to deteriorate. Therefore, if the particle size of the powder becomes too small, the surface area will increase, making it more likely to oxidize, making the treatment for oxidation prevention complicated, increasing the number of manufacturing steps and cost, so it is desirable to have at least 5 grains. Also, if the particle size exceeds 80 Buddhas,
The roughness of the magnet surface increases after molding, which reduces the commercial value in terms of appearance, and also causes problems such as particles becoming more likely to fall off due to post-processing polishing or impact, so it is desirable to keep it within the above range. . The present invention is not simply an application of known technology, but also relates to a unique magnetic field forming method for improving the performance of powder magnets, taking into account the magnetic properties of Sm2TM,7 powder magnets. Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows the powder pressing device used in the example, and the mold 6 and punch 4, which correspond to the electromagnetic surface, are made of a stellite alloy, which is a non-magnetic metal.

Next, the raw material alloy has a composition formula of Sm(Co70.672,
Cuo. 08, Fe o. 22, Zro. 028)8.
4, and lk9 was high-frequency melted in an argon gas atmosphere. First, the mass of this cast ingot is
Solution treatment was performed in a tube furnace for 1160 qo x 6 hours while flowing Ar gas, and the material was rapidly cooled. The cooling rate is 10~
It took about 50,301 minutes. Subsequently, the sample was subjected to a two-step treatment of 800 qo x IH and 70,000 x bait in a gas atmosphere. Next, this raw material is coarsely pulverized to a particle size of -8
0# (mesh), and then a powder with a particle size of 51 to 65 was made in a ball mill under a non-oxidizing atmosphere.

This fine powder and an epoxy-based organic resin having a viscosity of 1000 to 1500 P (centiboise) as a binder were added in an amount of approximately W%, and the mixture was kneaded in a mortar to prepare a sample. The order of the molding method using the mixed powder will be shown below. 1 Sm (C
oo. 672, Cuo. 08, Feo. 22, Zro.
028) Add mixed powder 7 consisting of 8.4 and a binder.

2 Place the outer peripheral surface of the mold 6 in close contact with the magnetic pole 8 of the electromagnet.

3 Excite the electromagnet and apply a magnetic field.

4 Push rod 1 directly connected to hand jack or hydraulic pressure
Press and 2 to apply pressure to the powder evenly from both sides. 5 After the pressurization is finished, apply a reverse magnetic field to demagnetize the pressurized powder magnet.

6 Remove the resin-bonded powder magnet from the pressurizing device.

The magnet is taken out and the magnet powder is loaded by removing one of the moving punches 4 and 5 and pushing it out from one side. The shape of the sample (molded body) is 8 x 15 x 7 m
/ It has a prismatic shape and weighs 150 qo after being removed from the mold.
Heat curing treatment was performed for x1 hour to solidify. The above-described apparatus and operation are merely one method taken to embody the compression perpendicular to the direction of the magnetic field of the present invention. Figure 4 shows Sm (Coo.67) with an average particle size of 30〃.
2, Cuo. 08, Fe o. 22, Zro. 028)
The residual magnetic moment of the magnet with respect to the volume filling factor P of the powder magnet with the degree of compaction for the Sm2TM, 7 alloy of 8.4. This shows how r changes. When molding is performed according to the embodiment of the present invention, the curve [a] shows how r changes. It shows the case. Here, the curves (a-, (b) are for the case where the strength of the orienting magnetic field is 1 arc○e. Also, the x mark on the curve {a' is for the case where the strength of the magnetic field is 10KOe.The following is , or does not change much even if the strength of the magnetic field is changed.In other words, it is possible that the magnetic moment is fluctuating due to the pressurizing operation.Next, s is a vibrating sample magnetometer and the external magnetic field 16. Song oe
When measured, the os was 11 ratio mu/t. Therefore, if the orientation degree K is taken as an example when the volume filling rate is 80%, in the conventional magnetic field forming method, K = 0.81 from the curve 'b-.
, in the embodiment of the present invention, the curve {from a-, K=0.90;
It has been obtained. Furthermore, in the traditional magnetic field forming method, the residual magnetic moment of the powder magnet rapidly increases as the volume filling rate increases. Compared to the case where r decreases, the residual magnetic moment decreases even when the volume filling rate increases in the magnetic field forming method of the present invention. It is noteworthy that r is not significantly affected. Fifth
The figure shows a particle size close to the conventional alloy SmC single-domain particle powder (approximately 4 degrees), and the binder is 3.5% epoxy resin.
The mixed powder to which was added was molded using the pressure device shown in FIG. 3 in a strong magnetic field.

Curve b was obtained at that time. r (emu/evening). The marks (x) in the figure are cracked during molding and cannot be made into a permanent magnet shape, so they cannot be manufactured industrially. On the other hand, the method of the present invention has the advantage that a high degree of orientation, that is, a high-performance permanent magnet can be easily provided without any problems up to a wide range of filling rates. This difference is due to the particle size and holding power (
This can be explained by the fact that the relationship between iHc) is completely different. Conventional SmC wide alloy powder relies on a coercive force generation mechanism based on simultaneous rotation of single magnetic domain particles, and therefore exhibits best performance when its particle size is around 4 on average. For this reason, the amount of binder increases and the frictional force between the powder particles due to pressure increases to a maximum, which disturbs the orientation or causes stress concentration, making it easy to crack, making it impossible to increase the volumetric filling rate. On the other hand, the method of the present invention is applied to Sm2TM, 7 alloy, and as shown in Figure 7, the coercive force has no particle size dependence, so the size and shape of the powder can be freely controlled, resulting in extremely high The greatest advantage is that the degree of orientation can be expanded to a region with a high filling rate. As described in detail in the Examples above, the method of the present invention is of great industrial significance for improving the performance of R2TM, 7 alloy magnets, which are explained in terms of domain wall movement and pinning models.

It is clear that the application will be extremely effective industrially, as it will easily bring out the high performance of small magnets for precision machinery, including rotors for crystal clock motors, coreless motors, cartridges, and meters. .

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the conventional pressure forming method in a magnetic field, where the direction of the magnetic field and the direction of pressure are parallel.
-day curve, a diagram in which the dotted line shows the 4ml-day curve of the conventional alloy. Figure 3 is an outline of the magnetic field pressurizing device used to carry out the method of the present invention, and Figures 4 and 5 are the volume filling factor and magnetic properties of magnetic field powder in the applied magnetic field of 15 K in the method of the present invention and the conventional method. A glass showing the relationship between. FIG. 6 is a graph showing the relationship between grain size and coercive force (iHc) of a conventional SmC alloy. The average particle size is approximately 4 Buddhas. Figure 7 shows Sm(C) of the method of the present invention.
oo. 572,Cu o. 08, Fe o. 22, Zr
o. 028) A graph showing the relationship between viscosity and coercive force (iHc) of 8.4 alloy, and the symbols used in the figure are as follows. 1, 2...Push stick, 3...
Excitation coil, 4, 5... Upper and lower punch, 6...
... Mold, 7... Powder. Figure 1 Figure 2 Figure 3 Figure 6 Figure 7 Figure 4 Figure 5

Claims (1)

[Claims] 1 R_ where the ratio of Sm and transition metal TM consisting of Co, Cu, Fe and Zr is 1:6.0 to 9.5 in atomic ratio
After solution treatment and aging treatment of the 2TM_1_7 alloy ingot, it is pulverized so that the particle size is distributed in the range of 5 to 80μ, and after mixing epoxy resin as a binder, a magnetic field of 10KCe or more is applied almost perpendicular to the pressing direction. 1. A method for forming a powdered permanent magnet in a magnetic field, the method comprising: forming the powdered alloy in a magnetic field.