JPH04314315A - Manufacture of bond magnet - Google Patents

Abstract

PURPOSE:To provide a bond magnet which is made of baked type permanent magnet bulk which is cheap and excellent in magnetic characteristics. CONSTITUTION:A permanent magnet bulk consisting of partially baked alloy whose basic components are rare earth elements, iron and boron is molded by magnetic field applied molding and the resulting compact is impregnated with resin. Or, the same permanent magnet bulk is molded by after magnetic field applied molding and then thermally treated in an inert atmosphere, and the resulting compact is impregnated with resin. The partially baked alloy is thermally treated in a vacuum or inert atmosphere. The treatment is made at 700-1000 deg.C for 3 hours or less so that the density may be 60-95% of theoretical one.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing bonded magnets in which magnetic materials whose basic components are rare earth elements (R), iron, and boron are bonded together using synthetic resin, and in particular, sintered R-Fe. The present invention relates to a method of manufacturing a bonded magnet exhibiting high magnetic properties using a B-based permanent magnet bulk body as a raw material.

0002

[Prior Art] Conventionally, as a rare earth magnet, R-Fe-B
permanent magnets have been developed. There are two types of R-Fe-B magnets: sintering method and high-speed quenching method.Currently,
The sintered type is said to be the most excellent as it is low cost and has high magnetic properties. On the other hand, bonded magnets have conventionally been manufactured, for example, by the following method.

[0003] The above-mentioned high-speed quenching type R-Fe-B permanent magnet bulk body is used as a raw material, which is pulverized and classified according to particle size. A synthetic resin (such as an epoxy resin) as an adhesive for the powder is added to and mixed with the classified powder, and the mixture is uniformly kneaded. After the kneaded material is molded into a predetermined shape in a magnetic field, the obtained molded product is cured.

[0004] In the above-mentioned magnetic field molding, a compression molding method is generally employed to increase the density of the molded body and produce a bonded magnet having good magnetic properties. in this way,
Conventional bonded magnets are made from high-speed quenched bulk R-Fe-B permanent magnets; unknown.

Therefore, as mentioned above, sintered R-Fe
- B-based permanent magnet bulk bodies are low in cost and have high magnetic properties, so it is desired to develop bonded magnets using them as raw materials. The manufacturing had technical challenges as explained below.

[0006]

[Problem to be Solved by the Invention] In other words, in a method for manufacturing a bonded magnet using a sintered type as a raw material, when the material is crushed, mechanical distortion occurs in the resulting powder (particles) due to the crushing. In addition, oxidation occurs due to chemical activity on the particle crushing surface, and the magnetic properties (coercive force iHc) of the particles are drastically reduced due to the effects of distortion and oxidation. Bonded magnets obtained using particles with drastically reduced magnetic properties are
Naturally, the magnetic properties are not sufficient, and according to the experiments of the present inventors, the iHc is about 2KOe, and the maximum energy product (BH) m
The ax was only about 3MGOe, which meant that it was not practical.

The present invention has been made in view of the above points, and its purpose is to develop a sintered R-Fe-B permanent magnet, which has not been used as a raw material for bonded magnets in the past. It is an object of the present invention to provide a method for stably manufacturing bonded magnets that are simple, low cost, and have high magnetic properties using bulk materials as raw materials.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a permanent magnet bulk body made of a semi-sintered alloy whose basic components are rare earth elements, iron and boron in a magnetic field, and It is characterized by impregnating the molded body with resin.

In addition, as a second invention, a permanent magnet bulk body made of a semi-sintered alloy whose basic components are rare earth elements, iron and boron is molded in a magnetic field, then heat treated in a vacuum or an inert atmosphere, and then The method is characterized by impregnating the obtained heat-treated molded body with a resin. The above-mentioned semi-sintered alloy is semi-sintered at a temperature of 700 to 1000°C in a vacuum or an inert atmosphere for less than 3 hours, and its density is reduced to 60% of the theoretical density.
It is desirable to set it to ~95%. The heat treatment in vacuum or in an inert atmosphere is preferably performed at a temperature of 400 to 1000° C. for less than 3 hours.

0010

[Operation] As mentioned above, the present invention focuses on the fact that the magnetic properties of bonded magnets are greatly affected by the oxidation and mechanical distortion of the sintered R-Fe-B permanent magnet bulk powder, which is the raw material. However, this defect such as oxidation and mechanical distortion can be eliminated by
This can be reduced by limiting the sintering temperature (hereinafter referred to as semi-sintering), placing the semi-sintered bulk body in a mold of the desired shape, and molding it in a magnetic field in a form that combines pulverization and molding, and heat treatment as necessary. It can be resolved by doing something like this.

FIG. 1 shows a comparison between the structure of a conventional sintered body and the structure of the semi-sintered body of the present invention. The figure shows that grain growth is suppressed in the present invention. In addition, as shown in the same figure, the structure of the present invention has a low density because it has a structure that contains a large number of pores, and since the pores become the core of crack development and even fracture, it can be easily processed by small stress. Can be crushed. Specifically, the bending strength of the conventional sintered body is 2.5
ton/cm2 or more, whereas the semi-sintered body of the present invention has a very small weight of less than 1 ton/cm2.

The present invention takes advantage of the above advantages. That is, the semi-sintered body is put into a mold of a desired shape in a bulk state without being pulverized, and molding is performed in a magnetic field in a manner that combines pulverization and molding.

[0013] In the conventional technology, the grinding and classification processes are easily affected by mechanical distortion and oxidation, and the magnetic properties (particularly iHc) deteriorate and vary greatly. However, the present invention is less susceptible to these influences, so the magnetic properties are high and there are few variations. By taking advantage of the advantages described above, it is possible to reduce costs as shown below. If the desired characteristics are satisfied by semi-sintering, aging treatment can be omitted. Further, if the semi-sintered body satisfies the desired characteristics after being molded in a magnetic field, the heat treatment in FIG. 2 can be omitted. Furthermore, if heat treatment is carried out without omitting it, a bonded magnet with extremely high characteristics can be obtained. In addition, there is no pulverization or classification process, resulting in significant cost reductions.

[0014] In the present invention, in order to more effectively exhibit the above-mentioned effects, the above-mentioned semi-sintering temperature is 700 to 1
000°C (corresponding to 60 to 95% of the theoretical density), particularly preferably 800 to 950°C (corresponding to 70 to 85% of the theoretical density). That is, if the temperature is lower than 700° C., almost no iHc is generated in the semi-sintered body, and the above-mentioned effect does not occur. If the temperature is higher than 1000°C, the theoretical density exceeds 95% and the bending strength exceeds 2 ton/cm2, and the advantages such as little mechanical distortion and suppressed grain growth are lost, so the temperature was set at 700 to 1000°C.

[0015] Further, the above-mentioned semi-sintering time is appropriately selected depending on the above-mentioned semi-sintering temperature, but in the present invention, it should be within 3 hours because the coarsening of the crystal grain size deteriorates the magnetic properties. is desirable. In this case, if the time is shorter than 1 hour, the effect of semi-sintering may be insufficient, so it is preferable that the lower limit of the semi-sintering time is 1 hour.

Furthermore, in FIG. 2, the heat treatment temperature is 400
The temperature is preferably 600 to 800°C, particularly 600 to 800°C. That is, if the temperature is lower than 400° C., atomic diffusion between particles and at crystal grain interfaces is insufficient, and the effect of improving iHc cannot be obtained. On the other hand, if the temperature is higher than 1000° C., the crystal grain size becomes coarse and oxidation occurs, which not only deteriorates the magnetic properties but also causes problems such as changes in the shape of the molded product.

Further, the heat treatment time is appropriately selected depending on the above heat treatment temperature, but if it exceeds 3 hours, the magnetic properties will deteriorate due to coarsening of crystal grain size and oxidation, so in the present invention, the time is within 3 hours. It is desirable to do so. Note that if the heat treatment time is shorter than 1 hour, atomic diffusion between particles and at grain interfaces may become insufficient, so the lower limit of the heat treatment time is 1 hour.
It is preferable to set it as time. Furthermore, if the above-mentioned semi-sintering and heat treatment are performed in a vacuum or an inert atmosphere, oxidation is not promoted by heat and is effective for preventing this oxidation.

In the present invention, as a sintered R-Fe-B permanent magnet bulk body which is a raw material for exhibiting the above effects, R (R is at least one of Nd, Pr, Dy, Ho, and Tb) is used. One or more La, Ce, Sm, Gd, Er
, Eu, Tm, Yb, Lu, Y) 8 to 30 at%, B2 to 28 at%, Fe42
Those having a composition of 90 atomic % are preferably used. Furthermore, for the purpose of improving the Curie point, etc., up to 50% of Co may be substituted for Fe.

[0019]

[Example] *Production of bulk body for bonded magnet Composition formula Nd1
Nd-Fe-B alloys represented by 6Fe78B6 and Nd18Fe76B6 were ground using a jet mill to form fine powder with an average particle size of 3 μm. After molding this fine powder in a magnetic field, it was semi-sintered and aged under the conditions shown in Table 1. provided.

Table 2 shows the magnetic properties of the obtained bulk body under each condition. In addition, as a comparative example, a sample having the same composition but subjected to normal sintering and aging treatment is also shown. (Note that the average grain size is the value measured by mirror polishing the obtained bulk body and using a metallurgical microscope.) From Table 2, it can be seen that grain growth is suppressed and iHc is large in the semi-sintered alloy.

[0021]

[0022]

* Confirmation of semi-sintering temperature range Composition Nd18Fe76B6 (semi-sintering condition 800°C x 2
h, aging conditions (600°C x 1 h), a plurality of semi-sintered samples were produced in exactly the same manner as the bulk body manufacturing method described above, except that the semi-sintering temperature was variously changed, and various properties of the obtained semi-sintered bodies were determined. was measured. The results are shown in FIG.

[0024] The figure shows that iHc depends on the semi-sintering temperature, iHc hardly appears at temperatures lower than 700°C, and sufficient iHc is obtained at temperatures above 700°C. 1000
When the temperature exceeds 95% of the theoretical density, the advantages of semi-sintered alloys (low mechanical strain, etc.) are lost. From the above, it can be seen that the semi-sintering temperature is 700 to 1000°C, preferably 800 to 950°C.

*Confirmation of semi-sintering time Composition Nd18Fe76B6 (semi-sintering condition 800°C x 2
h, aging conditions (600°C x 1 h), a plurality of semi-sintered samples were produced in exactly the same manner as the bulk body manufacturing method described above, except that the semi-sintering time was varied, and the magnetic properties of the obtained semi-sintered bodies were was measured.

The results are shown in FIG. As is clear from the figure, when the time is longer than 3 hours, a decrease in iHc is observed, and when the time is shorter than 1 hour, a decrease in iHc is also observed.

*Example 1 Each bulk body obtained in Table 1 above was compression molded at 3 tons/cm 2 while being oriented in a magnetic field of 15 KOe, and this molded body was immersed in an epoxy resin with a viscosity of 10 cps.
The molded product was transferred to a desiccator and kept in a vacuum state for about 3 minutes to sufficiently impregnate the epoxy resin into the molded product. Then 100℃, 60℃
A sample was prepared by performing an after-cure for 1 minute (manufacturing method in which heat treatment was omitted in Figure 2).

Table 3 shows the magnetic properties of the bonded magnet obtained. From Table 3, it is possible to mold only semi-sintered bulk bodies with low mechanical strength, and none of the comparative examples could be molded. In addition, regarding magnetic properties, i
It can be seen that since the deterioration of Hc is small, it is sufficiently practical.

[0029]

*Squareness: Hc/iH at 0.9Br
c *Both Comparative Example A and Comparative Example B cannot be molded.

[0031]*
Example 2 Each bulk body obtained in Table 1 above was compression molded at 3 ton/cm 2 while oriented in a magnetic field of 15 KOe, and the molded body was heat treated at 700°C for 1 hour in a vacuum of 1 x 10 -6 Torr. did. This molded body was immersed in an epoxy resin having a viscosity of 10 cps, transferred to a desiccator, and kept under vacuum for about 3 minutes to sufficiently impregnate the epoxy resin into the molded body. Next, after-cure was performed at 100°C for 60 minutes. A sample was prepared as described above (see FIG. 2).

For comparison, a sintered bulk body of the same composition was crushed with a jaw crusher and classified to have a particle size of 125 to 300.
The classified powder was compression molded at 3 ton/cm 2 while being oriented in a magnetic field of 15 KOe, and the molded body was bonded using the method described above to prepare a sample.

Table 4 shows the magnetic properties of each sample. Table 4 shows that bonded magnets with very high characteristics can be obtained by the semi-sintering-molding-heat treatment operation of the present invention.

[0034]

*Squareness: Hc/iH at 0.9Br
c * Comparative example A: Same composition as ■, ■ * Comparative example B: Same composition as ■, ■

*Example 3 Composition Nd18Fe76B6 (semi-sintering condition 800°C x 2
The manufacturing method according to the present invention was carried out in exactly the same manner as in Example 2, except that the semi-sintering 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, the magnetic properties are highly dependent on the heat treatment temperature.
The effect appears at temperatures above 400°C. Also, as the temperature rises, both iHc and (BH)max increase, and (BH)max reaches its maximum at 700°C, reaching 10
It decreases sharply when the temperature exceeds 00℃. iHc increases up to 1000°C and decreases sharply when it exceeds 1000°C (iHc
The difference in peak position between and (BH)max is due to a slight difference in squareness. ).

[0038] As a result of the above, the heat treatment effect is 400 to 1000
℃, preferably 600 to 800℃.

*Example 4 Composition Nd18Fe76B6 (semi-sintering condition 800°C x 2
The method according to the present invention was carried out in exactly the same manner as in Example 3, except that the heat treatment time was varied under the aging conditions (600° C. x 1 h), and the magnetic properties of the obtained bonded magnets were measured.

The results are shown in FIG. As is clear from the figure, when the time is longer than 3 hours, the magnetic properties are degraded, and when the time is shorter than 1 hour, the magnetic properties are also degraded.

[0041]

[Effects of the Invention] According to the method according to the present invention described in detail above, it is possible to obtain a large iHc in a semi-sintered state with respect to the bulk body, which is a raw material of a bonded magnet, so that the desired iHc can be satisfied. For example, the aging process can be omitted. Furthermore, regarding the production of bonded magnets, since the deterioration of iHc is small even after pulverization, heat treatment can be omitted if the desired characteristics are satisfied. Furthermore, the grinding and classification steps are omitted. Therefore, a bonded magnet having good magnetic properties can be provided at low cost.

[0042] Furthermore, if the aging treatment and heat treatment are not omitted, it is possible to produce a magnet with extremely high performance that cannot be achieved with the current technology.

[Brief explanation of drawings]

FIG. 1 is an enlarged schematic explanatory view of the surface of a bulk body used in the conventional manufacturing method and the manufacturing method of the present invention.

FIG. 2 is a block diagram sequentially showing the steps of the manufacturing method of the present invention.

FIG. 3 is a graph showing the relationship between sintering temperature, iHc, and density.

FIG. 4 is a graph showing the relationship between sintering time and iHc.

FIG. 5 is a graph showing the relationship between heat treatment temperature and iHc.

FIG. 6 is a graph showing the relationship between heat treatment time and (BH)max.

Claims (4)

[Claims] [Claim 1] Production of a bonded magnet characterized by molding a permanent magnet bulk body made of a semi-sintered alloy whose basic components are rare earth elements, iron, and boron in a magnetic field, and impregnating the obtained molded body with a resin. Method. [Claim 2] A permanent magnet bulk body made of a semi-sintered alloy whose basic components are rare earth elements, iron, and boron is molded in a magnetic field, and then heat treated in a vacuum or inert atmosphere, and then the resulting heat-treated molded product A method for manufacturing a bonded magnet, which comprises impregnating a bonded magnet with a resin. 3. The semi-sintered alloy is semi-sintered in a vacuum or an inert atmosphere at a temperature of 700 to 1000°C for up to 3 hours, and the density thereof is made to be 60 to 95% of the theoretical density. The method for manufacturing a bonded magnet according to claim 1 or 2. 4. The method of manufacturing a bonded magnet according to claim 2, wherein the heat treatment in vacuum or an inert atmosphere is carried out at a temperature of 400 to 1000° C. for less than 3 hours.