JPH01289101A - Manufacture of rare earth transition metallic magnet alloy powder - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance and the temperature characteristics without deteriorating the magnetic characteristics by a method wherein a mixture in the specific composition containing rare earth oxide is heat-treated and then washed away to remove any by-product of reaction. CONSTITUTION:A mixture meeting the following requirements is prepared i.e. a material powder comprising respective powders such as rare earth element (Rem) oxide containing Y, ferroboron, boron oxide, iron, cobalt, nickel, ferrocobalt alloy, cobalt nickel alloy, ferronickel, iron oxide, cobalt oxide and nickel oxide is properly selected so that the mixture may contain Rem:8-30 at.%, B:2-20at.% with the residual parts substantially comprising Fe, Co, Ni subject to respective blended amount of Fe:10-75at.%, Co:7-50at.%, Ni:8-30at.% as well as (Fe+Co+Ni):50-90at.%. Then, metallic Ca or CaH2 is blended with the mixture to be heated in inert gas atmosphere up to 800-1200 deg.C causing reduction.diffusion reaction and after being cooled down, a reaction product is washed away to remove any by-product of the reaction.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing a rare earth transition metal magnet alloy powder, and in particular aims to obtain an alloy powder with excellent corrosion resistance using an inexpensive rare earth oxide as a starting material. It is something to do.

(Prior Art) The main magnet materials currently occupying the market include alnico magnets, ferrite magnets, and rare earth magnets. Among them, rare earth magnets have superior magnetic properties compared to other magnets, and therefore meet the demands of the times for miniaturization and higher performance of electrical and electronic equipment, and their production continues to increase.

As such rare earth MN stone, Sm-Co [stone was first developed, but this Sm-Co magnet is made of S which is scarce in resources.
11 and Co, whose supply is unstable, as the main components.
The recent SI
This is increasing due to the rise in the price of I. Therefore, development of new rare earth magnets that do not use large amounts of SaI or Co has been actively carried out, and as a result, magnets have been developed using ternary and stable alloys made by the sintering method (Japanese Patent Publication No. 61-34242).
, J. J. Croat et al. focused on metastable phases and non-equilibrium phases, and developed alloys with high coercive force by liquid quenching (Japanese Patent Application Laid-Open No. 59-64739). These are alloys made of rare earth elements-Fe-B, and their magnetic properties are superior to those of conventional Sm-Co (4 stones).

However, such rare earth-Fe-B magnet alloys contain a large amount of extremely active rare earth metals and rust-prone iron in their components, so they are easily oxidized, and such oxidation greatly deteriorates the magnetic properties. There was a problem.

By the way, as a method for producing such rare earth magnet alloy powder, there is a method in which rare earth metals and other metals or alloys are blended to a desired composition, melted, and the resulting ingot is crushed (Japanese Patent Laid-Open No. 59-215460). (Japanese Patent Application Laid-Open No. 102271/1983), a method of obtaining a magnet alloy powder with a desired composition by using an inexpensive rare earth oxide as a starting material, adding a reducing agent such as metal Ca, and causing a reduction diffusion reaction Public bulletin) has been proposed.

In rare earth-Fe-B magnet alloys, as mentioned above, if oxygen is included in the magnet alloy, the magnetic properties will be significantly degraded, so it is important not only in the magnet manufacturing process but also in the manufacturing process of the alloy powder that is the raw material. It is also necessary to avoid contamination with oxygen as much as possible.

(Problem to be solved by the invention) However, when producing alloy powder according to the conventional method,
In particular, when producing rare earth element -Be-B (i-stone alloy powder) using the reduction diffusion method, significant oxidation occurs during the manufacturing process shown in Figure 1, especially during the water washing and drying steps, resulting in a change in magnetic properties. Deterioration was inevitable.

(Means for Solving the Problems) The inventors conducted intensive studies to improve the corrosion resistance of rare earth-Fe-B magnets, and found that Fe@ in the alloy
It has been found that by partially substituting Ni and further CO, corrosion resistance and temperature characteristics can be significantly improved without substantially deteriorating magnetic properties.

Furthermore, alloys with such compositions do not lose their corrosion resistance even when they are pulverized, so even when using inexpensive rare earth oxide powders as starting materials and producing alloy powders with the above compositions through reduction reactions, special We have found that a magnetic alloy powder with excellent magnetic properties can be obtained at low cost without requiring extensive oxidation prevention treatment.

This invention is based on the above knowledge.

That is, this invention provides powders of Rem (a rare earth element containing Y) oxide, ferroboron, boron oxide, iron, cobalt, nickel, iron-cobalt alloy, cobalt-nickel alloy, ferronickel, iron oxide, cobalt oxide, and nickel oxide. Re III: 8 to 30 at%.

B: Contains 2 to 20 at%, the remainder substantially consists of Fe, Co, and Ni, and the blending amounts of Fe, Co, and L are respectively Fe
: 1.0-75 at%.

Co: 7 to 50 at%.

Ni: More than 8 to 30 at% and (Fe+Co+Ni): After blending into a mixed powder with a composition satisfying 50 to 10 at%, metallic Ca or C is mixed.
After adding and mixing aH, the mixture is heated to 800-1200°C in an inert gas atmosphere to cause a reduction-diffusion reaction, then cooled, and the resulting reaction product is washed with water to remove reaction by-products. This is a method for producing rare earth transition metal magnet alloy powder, which comprises removing materials.

This invention will be explained in detail below.

Now, in this invention, the above-mentioned inexpensive oxide powder is mainly used as the raw material powder, but the composition of the mixed powder to be prepared using such raw material powder is limited to the above range. This is due to the following reasons.

Rem (rare earth element including Y): 8 to 30 at% Rel
1L is an essential element for obtaining high coercive force, but if the content is less than 8 at%, its addition effect will be poor, while if it exceeds 30 at%, the proportion of non-magnetic phase will increase and the residual magnetic flux density will decrease. Therefore, it was added in an amount of 8 to 30 at%.

B: 2 to 20 at% B is an essential element for forming the main phase that produces ferromagnetism and for expressing sufficient coercive force, but if it is less than 2 at%, high coercive force cannot be obtained, whereas at 20 at% Since the residual magnetic flux density decreases when the content exceeds 2 to 20 at%.

Fe: 10 to 75 at% Fe is essential to obtain high saturation magnetic flux density, and if it is less than 10 at%, the effect is poor;
If it exceeds at%, the amounts of Rem and B will be relatively reduced and the coercive force will be lowered, so it was limited to a range of IO to 75 at%.

Ni: more than 8 at% to 30 at%, Co Ni at% to 50
At%Nj effectively contributes to improving corrosion resistance by suppressing the oxygen content of magnetic powder, but if the content is less than 8at%, the addition effect is poor, while if it exceeds 30at%, the coercive force and residual magnetic flux density will decrease. Because it deteriorates rapidly, more than 8 at% ~ 30
It is necessary to add it within the range of at%.

Co is a useful element that not only effectively improves the magnetic properties, especially the coercive force, without deteriorating the corrosion resistance improvement effect of Ni addition, but also effectively contributes to improving the Chierly temperature and therefore the temperature characteristics. . However, if the content is less than 7 at%, the effect of addition is poor, and on the other hand, if it is added in a large amount exceeding 50 at%, the coercive force and residual magnetic flux density will be reduced, so it is limited to a range of 7 to 50 at%.

(Fe+Ni+Co): 50-10 at%Fe
The total amount of transition metal elements such as , Ni and Co is relatively related to the amount of rare earth elements, and if the amount of transition metals is large, the amount of rare earth elements will inevitably be small, making it difficult to obtain high coercive force. Conversely, if the amount of Pe, Ni and Co is small, the proportion occupied by the non-magnetic phase rich in rare earth elements will increase, leading to a decrease in the residual magnetic flux density. and 50~1
The content was set to be in the range of 0 at%.

Next, the manufacturing method of this invention will be explained.

Now, in this invention, first, an appropriate selection is made from raw material powders and blended so as to obtain an alloy powder having a preferable component composition as described above to obtain a mixed powder.

Furthermore, Ca or CaH is added to this mixed powder as a reducing agent. The amount of reducing agent added is 1.5 of the stoichiometric amount necessary to reduce rare earth oxides, iron oxide, cobalt oxide, nickel oxide, boron oxide, and other oxides contained in the mixed powder. It is preferable to set it to about 4.0 times to 4.0 times.

This is because if the amount of reducing agent is less than 1.5 times the stoichiometric amount, the oxides in the raw material mixture will not be reduced sufficiently, and the amount of oxygen remaining in the alloy will increase. This is because if it exceeds 4.0 times, the amount of Ca increases in the alloy and the magnetic properties deteriorate on the contrary.

After a predetermined amount of the above raw material mixed powder and reducing agent are blended, they are mixed in an inert gas atmosphere.

Next, the mixed powder is heated in an inert gas atmosphere and held at a temperature range of 800 to 1200°C for 1 to 40 hours, and during the soaking treatment, a reduction reaction is carried out, and the reduced rare earth elements, etc. Proceed with alloying by interdiffusing with other component elements. In such a soaking process, if the holding temperature is lower than 800'C, not only will the reduction of the oxide be insufficient and a large amount of oxygen will remain, but also the diffusion will not proceed sufficiently and an alloy powder with the desired composition will not be obtained. do not have. On the other hand, if the temperature exceeds 1200°C, the amount of Ca remaining in the reaction product increases, making it impossible to obtain a high-performance magnetic alloy powder. Therefore, the holding temperature for carrying out the reduction-diffusion reaction needs to be 800 to 1200°C.

After the reduction-diffusion reaction is completed, the reaction product is cooled to room temperature in the same inert gas atmosphere.

The cooled reaction product is then poured into water to react the by-product CaO and the remaining Ca with H2O to convert Ca.
(OH) z and remove by repeating leaching. Adding a weak acid to water when repeating leaching
Although it is effective in reducing the oxygen content by pickling the surface of the alloy powder, adding too much of it has the opposite effect as it lowers the yield of the product.

The obtained alloy powder is in the form of a slurry, and a magnet alloy powder is obtained by washing this slurry with a low boiling point organic solvent and then drying it under vacuum at room temperature.

(Example) NdzOi powder with soil purity of 99.7 wt%: 124.6
g, ferroboron powder with B content of 20 wt%:
21.8 g, 99 wt% pure nickel oxide powder:
38.1 g, 99.9 wt% pure cobalt powder:
92.1 g and 99.9 wt% purity iron oxide powder: 1
22. Purity: 99ht% to Og-t-mixed powder
After adding 329.3 g of Ca powder, the mixture was mixed in Ar gas using a type mixer, and then heated at 5'C/min in an electric furnace under Ar gas atmosphere to 1080°C.
After holding for 1.5 hours to perform a reduction-diffusion reaction, the mixture was cooled to room temperature in the furnace.

The obtained reaction product was poured into water and stirred, the supernatant liquid was removed, water was added and leaching was repeated, and then pickled with acetic acid diluted to 0.1 vol 1% or less, and after washing with water, Alcohol washing was repeated several times, and the slurry was vacuum dried at room temperature for 36 hours to obtain a magnet alloy powder.

This alloy powder was finely pulverized with a jet mill in N2 to obtain a powder with an average particle size of 4.0 μm. Table 1 shows the composition of the powder obtained.

Next, this alloy powder was oriented in a magnetic field of 12.5 kOe and then pressure-molded at 2 L/cI112, and then sintered in a vacuum at 1060°C for 11 hours and then in an Ar gas stream for 1 hour. Cooled to room temperature.

Thereafter, it was heat-treated at 600° C. for 1 hour in Ar gas, and then cooled to room temperature to obtain a permanent magnet.

The magnetic properties of the permanent magnet thus obtained are also shown in Table 1.

Nd2O3 powder with purity of 99.7%: 136.5
g, purity 99.8 wt% D)'gos powder: 16.
1 g, 99.9 wL% purity iron powder: 123.8 g, 99.9 wt% purity nickel powder: 12.0 g
, B2O3 powder with purity 99.8 wt% = 15.9 g
and Ni content is 20. Owt% Co-Ni powder: 129.1g of pure powder was added to the mixed powder with a purity of 99wt%.
In Example 1, 2.8 g of 1B metal Ca powder was added.
(However, the reduction-diffusion reaction is performed at 800゛C12
Then, the mixture was heated to 1080° C. for 12 hours) to obtain an alloy powder.

The composition of the alloy powder thus obtained is shown in Table 1.
Table 1 shows the magnetic properties of permanent magnets obtained by molding and sintering this alloy powder in the same manner as in Example 1.

Disaster control purity 99.7 wt% Nd, 0. Powder: I38.1g
, purity 99.8 wt% PrzO=: 18. Og
, 99% pure cobalt oxide powder = 139.5 g,
Ferroboron powder with B content of 20.0gt%: 23.
After further adding 312.5 g of metallic Ca powder with a purity of 99-t% to the mixed powder of 144.4 g of Ferroninkel powder with a Ni content of 20 wt% and 20 wt% of Ni content, The reaction was carried out at 100°C for 11 hours and then at 1100°C for 11 hours) to obtain an alloy powder.

The composition of the alloy powder thus obtained is shown in Table 1.

Table 1 shows the magnetic properties of permanent magnets obtained by molding and sintering this alloy powder in the same manner as in Example 1.

Comparison ■ NdZOn powder with purity 99.7 wt%: 140.4
9 g, iron powder with purity of 99.9 t%: 220.8 g,
Ferroboron powder with B content of 20 t%: 23.
7 g and 99-t% purity metallic Ca powder: 110.
4 g of the mixed powder was treated in the same manner as in Example 1 to obtain an alloy powder.

Table 1 shows the composition of the obtained alloy powder and the magnetic properties of a permanent magnet obtained by shaping and sintering this alloy powder in the same manner as in Example 1.

As is clear from the table, all of the permanent magnets obtained according to the present invention have significantly improved magnetic properties than the comparative materials obtained by the conventional method.

(Effects of the Invention) Thus, according to the present invention, a rare earth transition metal magnet alloy powder with a low oxygen content can be easily produced using an inexpensive rare earth oxide as a starting material.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the process of manufacturing alloy powder by the reduction diffusion method.

Claims (1)

[Claims] 1. Raw material powder consisting of Rem (rare earth element containing Y) oxide, ferroboron, boron oxide, iron, cobalt, nickel, iron-cobalt alloy, cobalt-nickel alloy, ferronickel, iron oxide, cobalt oxide and nickel oxide powder. Rem: 8 to 30 at%, B: 2 to 20 at%, selected appropriately from among them, and the remainder substantially consists of Fe, Co, and Ni, and the blending amounts of Fe, Co, and Ni are respectively Fe: After preparing a mixed powder with a composition satisfying 10 to 75 at%, Co: 7 to 50 at%, Ni: more than 8 to 30 at%, and (Fe + Co + Ni): 50 to 10 at%, metal Ca or CaH_2 is added and mixed. is heated to 800-1200°C in an inert gas atmosphere to cause a reduction-diffusion reaction, then cooled, and then the resulting reaction product is washed with water to remove reaction by-products. A method for producing rare earth transition metal magnet alloy powder.