JPS59179703A - Manufacture of rare earth cobalt alloy powder having two-phase separation type coercive force producing mechanism - Google Patents

Abstract

PURPOSE:To obtain the titled alloy powder capable of forming a permanent magnet having large coercive force by reducing an oxide as a starting material with metallic Ca under heating to a specified temp. CONSTITUTION:Powder of the oxide of a rare earth metal and other starting material are mixed with metallic Ca, and the mixture is heated to >=1,050 deg.C in a nonoxidizing atmosphere. The oxide of a rare earth metal is reduced to the metal with the metallic Ca, and the constituent metallic elements of the titled alloy are uniformly diffused at once in the particles at >=1,050 deg.C. In this method, the heating temp. of said mixture is important. When reduction and diffusion are carried out at about 950 deg.C for a long time, a phase in which the constituent elements are uniformly dispersed like a molten state is not obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a method for producing rare earth cobalt alloy powder having a two-phase separation type holding force generation mechanism. Rare earth cobalt alloys are known to have promising properties as permanent magnets.
A large amount of research has been conducted on two-phase separation type magnets, typified by compounds replaced with u and Fe, because of their high energy product.

It is thought that the coercive force of this magnet is caused by a two-phase separation reaction caused by heat treatment. Below this alloy is 2
It is abbreviated as phase-separated Kijisei cobalt alloy. Two-phase separation type rare earth cobalt alloy (generally, a molten metal with a desired composition is prepared, solidified as an alloy, and then the resulting powder is sintered through the steps of coarse pulverization and fine pulverization. embodiment,
It's a statute of limitations.

Which heat treatment is used to obtain the desired permanent magnet. In recent years, many methods have been developed to obtain a powder of a two-phase separated rare earth cobalt alloy by directly reducing G and H without using the molten metal preparation-pulverization process.

(2) Explanation of the prior art and its problems In the production of rare earth cobalt alloy powder, a method in which raw material hexaanide is mixed with metallic calcium and the oxide is analyzed at a temperature of less than 100°C to obtain the desired composition. However, this method is useful for producing RCo5 type powders other than two-phase separated Fudochi Cobalt Ajaku, but it is not suitable for producing two-phase separated rare earth cobalt alloy powders. The inventor's research has revealed that the magnetic properties are unsatisfactory.In other words, in a two-phase separated rare earth cobalt alloy, the rare earth element, Cobalt, iron, copper, and other additive elements must form a homogeneous phase.However, 10
A temperature of less than 00°C is higher than 840°C, which is necessary for liquid-phase reduction with liquid-phase calcium, but is insufficient to homogenize the components within the powder particles. Even if the two-phase separated alloy powder obtained at a temperature of less than 1000°C is heated at a high temperature and/or for a long time in the subsequent steps of sintering, solution treatment, and aging treatment, ,
It is now extremely difficult to obtain sufficient holding force. Therefore, in the production of rare earth cobalt alloy permanent magnets using rare earth oxides as raw materials by the reduction diffusion method, it is important to know at what temperature the first powder production step is carried out.
Even if the powder obtained at a reduction temperature below 000°C is formed into a permanent magnet, it is not possible to obtain a holding force comparable to that of a permanent magnet obtained through a conventional grinding process, or even if it is possible, The conditions for sintering etc. are extremely long or at high temperatures, making it impossible to use in reality.

(3) Purpose of the Invention The purpose of the present invention is to develop a permanent magnet with a high coercive force using a two-phase separated rare earth cobalt alloy 'J'9j powder manufactured using an inexpensive oxide as a starting material. The objective is to improve the manufacturing method.

(4) Structure of the Invention The object of the present invention is to mix metallic calcium with rare earth metal oxide powder and other raw material powder in a method for producing rare earth cobalt alloy powder having a two-phase separation type coercive force generation structure, and The mixture is heated to 1050°C or higher in a non-oxidizing atmosphere to reduce at least the rare earth gold @ oxide metal with metallic calcium, and then immediately heated to 1050°C or higher in a non-oxidizing atmosphere to dissolve each constituent metal element of the iU2 alloy into powder particles. A manufacturing method characterized by uniform diffusion has been achieved by one person.

The constituent elements of the present invention will be explained in detail below. The method of the present invention requires the use of inexpensive rare earth metal oxide powder as a raw material, and other raw material powders include metal iron,
It may be in a metallic state, such as cobalt, or may be in an oxide state, such as cobalt oxide. In addition to the commonly used Sm, 'La' is used as a rare earth chorus.
+ Ce + P r r Nd + may be used in place of a part or all of Sm, or Mitsushi metal or the like may be used. Raw materials other than rare earth metal oxides include various elements that can be used as constituent metal elements of two-phase separated rare earth cobalt alloys, such as iron, manganese, touge, titanium, zirconium, and niobium. This includes: The particle size of these raw materials is not particularly limited, but is preferably in the range of several microns to several hundred microns.

Thoroughly mix granular metallic calcium with the above raw material powder,
It is important to perform heating at a temperature of 1050° C. or higher. Even if the reduction-diffusion reaction is carried out at 950° C. for a long time, only an equilibrium state on the phase diagram will be obtained, and a phase in which the constituent elements are uniformly dispersed, such as the molten state (4), will not be obtained.

Generally, in a two-phase separation type dilute ten-box cobalt alloy, two-phase separation occurs due to spinodal decomposition in the homogeneous phase, creating a pinning site of the domain wall and generating coercive force, but in this case, the initial homogeneous phase must be sufficiently homogeneous. It is a must. Therefore,
For example, if the temperature is kept at 950° C. for a long time, reduction begins and further diffusion progresses. However, the phase state obtained here is only a stable state at 950°C on the phase diagram, and detailed analysis shows that the distribution of each constituent element in the alloy is sufficient to cause spinodal decomposition. It can be seen that uniformity is not maintained. Therefore, 1050 according to the present invention
A heating temperature of 0.degree. C. or higher is very important for sufficiently developing the characteristics of the two-phase Fuki type 1 cobalt alloy powder. Moreover, by performing this heating to 1050° C. or more immediately after the reduction and diffusion, that is, at the same time in the processing equipment where the reduction and diffusion is not carried out, a remarkable improvement in coercive force can be seen. In the present invention, the preferred heating time is 0.5 to 1 hour at 1050°C or higher. The heating temperature is particularly preferably 1100°C or higher, but 130°C
The upper limit is 1300℃ because the alloy will melt if it exceeds 0℃.
shall be. Furthermore, the determination of the heating temperature will be explained with reference to FIG. 1, which shows an experiment conducted by the present inventor. Figure 1 shows that the final composition is approximately 25% Sms, approximately 50% CO, approximately 15% Fe, approximately 8% Cu.
% and about 1.6% Zr, and further contains about 0.1% oxygen as an impurity. This shows the relationship between the heating temperature and the coercive force of the alloy. It is a graph. In the production of this alloy, the holding time at the heating temperature during production of the alloy powder was 30 minutes, after which the powder was made into a permanent magnet by a known process. That is, sintering was performed at 1200°C for 60 minutes, then sintered at 830°C for 40 minutes.
A permanent magnet was obtained by performing aging treatment in multiple stages: 40 minutes at 700°C, 1 hour at 600°C, 2 hours at 500°C, and 10 hours at 400°C.

From FIG. 1, it can be seen that there is a difference in coercive force of about 1.5 koe between heating temperatures of less than 1000°C and those of 1050°C or more. This difference is determined by how uniformly each constituent metal element is distributed within the alloy powder particles. Therefore, it can be seen that when the heating temperature is less than 1000° C., the original coercive force of the two-phase separation type alloy cannot be sufficiently generated.

Next, in the above experiment, the heating temperature during powder production was 1150
For two cases: ℃ and 950°C, the obtained alloy powder was blasted within a predetermined particle size range to examine how uniformly the constituent metal elements were dispersed between the particles of each particle size. The results are shown in Tables 1 and 2.

Table 1 (1050℃ x 05 hours) Table 2 (950℃ x 05 hours) Table 1 shows the case where the heating temperature is 1150℃, and Co + 8m, Fe, Cu + Zr are uniformly distributed between the particles of each particle size. You can see that it is distributed. On the other hand, 950℃
In the case of Table 2 which shows, it can be seen that the variation from the average composition is extremely large. Therefore, if an attempt is made to pulverize alloy powders whose compositions vary as shown in Table 2 before compression molding, some powder will come out that cannot be pulverized using conventional methods.

The method according to the present invention described above is carried out each time a heat treatment is carried out in an ordinary heating furnace in an inert atmosphere using argon gas, hydrogen gas, or a mixture thereof. Then, the obtained alloy powder was washed with water using a known method such as Example 1 Sm203130. ! i', Co218.9. Fe66
．． 9+Cu 35 g, Zr 8,! i' powder of 200 # or less, and 67 g of granular Ca (this is S
5 of the Ca stoichiometric amount required to reduce m203
0% increase) and fill it into the stainless steel heat. Konohitowo, 1100 in argon gas atmosphere
It was heated at ℃ for 2 hours. The reaction product is crushed in water, stirred in an acidic solution to remove Ca, and dried under vacuum.

The obtained powder was molded in a magnetic field and heated at 1200"C for 1.5 hours.
After sintering, it was cooled and aged at a temperature ranging from 850°C to 400°C. The coercive force of the sample at that time was 70,000e.

Example 2 (Comparative Example) The same powder as in Example 1 and Ca powder were heated at 900° C. for 6 hours and subjected to the same treatment as in Example 1. The coercive force of the obtained sample was 35000e.

Example 3 5m203130g + Coo 277g, C
u2O40g.

Powders of Fe20393.5 g, ZrO210,7El, and Ca423I were mixed and heated and treated in the same manner as in Example 1. The coercive force of the obtained long angle is 6900
It was 0e.

(6) Effects According to the present invention, since an inexpensive oxide is used as a starting material and the high coercive force of the two-phase separated rare earth cobalt alloy is fully brought out, the industrial effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between heating degree and coercive force during the production of two-phase separation type rare earth angle cobalt alloy powder. Patent applicant TDC Co., Ltd. Patent application agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Higashi Murai Patent attorney Akira Yamaguchi

Claims (1)

[Claims] °1. In a method for producing rare earth cobalt alloy powder with a two-phase separation magnetic force generation mechanism, metallic calcium is mixed with rare earth metal oxide powder and other raw material powder, and the mixture is heated to 1050°C or higher in a non-oxidizing atmosphere. Heat it with
A manufacturing method characterized by reducing at least a rare earth metal oxide to a metallic state with metallic calcium, and further immediately uniformly diffusing each constituent metal element of the alloy in powder particles at 1050° C. or higher.