JPH04188805A - Manufacture of rare-earth bonded magnet - Google Patents

Abstract

PURPOSE:To manufacture an anisotropic R-Fe-B rare-earth bonded magnet, having a high energy product, in a highly efficient manner by treating an alloy consisting of R (contains at least a kind selected from rare-earth elements containing Y)-Fe-B raw material as the fundamental component. CONSTITUTION:R (provided that R contains at least a kind selected from rare- earth elements containing Y), Fe and B are used as the raw material of the fundamental component of a substrate, the alloy composed of the above- mentioned fundamental component is melted, cast, and after the cast alloy has been hot-processed, it is heat-treated in a hydrogen gas atmosphere, and hydrogen is occluded. Then, after a dehydrogenization operation has been conducted in a vacuum atmosphere, the alloy is crushed and used as magnetic powder. In this case, after the crystal axis of coarse crystal grains have been lined up using a hot-processing method, the crystal grains are microscopically formed by conducting a hydrogen treatment, and the direction of crystal axis of the microscopic crystal of the magnetic powder after pulverization is made uniform still more. As a result, a bonded magnet, having high residual magnetic flux density and high coercive force and a high energy product, can be manufactured.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a rare earth bonded magnet.

[Prior art] Conventional methods for manufacturing R-Fe-B rare earth bonded magnets include:
There are the following:

(1) JP-A-59-211549, R, W, Le
e; Appl, Phys, Lett, Vol, 46 (
8), 15 April 1985. p750 is a R-
Fe-B magnets are disclosed.

This permanent magnet is manufactured by making a quenched thin piece with a thickness of about 30 μm using a quenched ribbon manufacturing apparatus used for manufacturing an amorphous alloy, kneading the thin piece with a resin, and press-molding the thin piece.

(2) JP-A-60-100402, R, W, Le
e; Appl, Phys, Lett, Vol, 48 (
8), 15 April 1985. For p750, an R-Fe-B magnet having anisotropy is obtained by using the quenched ribbon used in the method (1) above in a vacuum or in an inert atmosphere by a method called a two-step hot pressing method, and then It is disclosed that a bonded magnet can be obtained by crushing, kneading with resin, and press-molding.

(3) Summary of general lectures at the Autumn Conference of the Japan Institute of Metals (1990)
Then, by heat-treating an alloy ingot in a hydrogen gas atmosphere to absorb hydrogen into the alloy, and then dehydrogenating it in a vacuum, uniform and fine ferromagnetic crystal grains are obtained, and bonded magnets obtained by crushing this alloy and It also improves the coercive force when
Elements such as r, Hf, and Ga have the effect of aligning the C axes of fine ferromagnetic R-Fe-B crystals when they are formed by dehydrogenation, and reduce the residual magnetic flux when formed into a bonded magnet. It has been disclosed that it has the effect of increasing density.

(4) In JP-A No. 62-276803, an R-Fe-B alloy is melted, cast, hot worked, absorbed hydrogen gas at room temperature, dehydrogenated in vacuum, and then crushed and bonded. A method of forming into a magnet is disclosed.

[Problem M to be Solved by the Invention] However, the method for manufacturing the R-Fe-B rare earth bond magnet described above has the following drawbacks.

The rare earth bonded magnet manufactured by the method (1) is isotropic in principle, so it has a low energy product, and the squareness of the hysteresis loop is also poor, which is disadvantageous in terms of use.

The rare earth bonded magnet manufactured by method (2) is a unique method of using hot pressing in two stages, but it is inefficient when considering mass production.

Although the method (3) is a very effective means, the orientation by the added element is insufficient, and the residual magnetic flux density cannot be said to be sufficient.

In method (4), the crystal axes are oriented by hot working and a high residual magnetic flux density can be obtained, but the coercive force is greatly reduced by pulverization and is insufficient for practical use.

Therefore, the present invention solves the above-mentioned problems.
The purpose is to provide a method for efficiently manufacturing an anisotropic, high energy product R-Fe-B rare earth bonded magnet.

[Means for Solving the Problems] The method for manufacturing a rare earth bonded magnet of the present invention includes R (however, R
is at least one rare earth element containing Y), Fe,
B is used as a basic raw material component, and an alloy containing the basic component is melted,
It is possible to use magnet powder that has been cast, hot worked, or hot worked a quenched ribbon of the basic components, then heat treated in a hydrogen gas atmosphere to absorb hydrogen, and then dehydrogenated in a vacuum. Features.

According to Conventional Example (3), when a cast ingot is heat-treated in hydrogen, ferromagnetic crystals of several tens of micrometers initially absorb hydrogen and decompose into compounds such as RH2, Fe, and Fe2B. Thereafter, by dehydrogenation in vacuum, the decomposed elements are recombined to form a fine R-Fe-B compound on the order of 0.3 μm. If trace elements such as Ga, Zr, and Hf are present at this time, the recombined fine R--Fe--B crystals tend to align their crystal axes in the direction of the crystal axes before being decomposed by hydrogen. Therefore, the fine crystals produced by hydrogen treatment have their crystal axes aligned within a range of several tens of micrometers, and when a bonded magnet is manufactured by this method, a certain degree of anisotropy can be obtained. However, with crystal grain orientation in such a narrow range, it is inevitable that fine crystals with different crystal axis directions coexist within the crushed magnetic powder, which reduces anisotropy when made into a bonded magnet. It's going to happen.

Therefore, in the present invention, the crystal axes of coarse crystal grains are aligned in advance by the hot working method according to conventional example (4), and then the crystal grains are refined by the above-mentioned hydrogen treatment. We discovered that by aligning more of the crystal axis directions of the crystals, it is possible to produce bonded magnets with high residual magnetic flux density, high coercive force, and high energy product.

The preferred composition range of the rare earth bonded magnet in the present invention will be explained below.

Rare earths include Y, La, Ce, Pr,
Nd.

Sm, Eu, Gd, Tb, Dy,
Candidates include Ho, Er, Tm, Yb, and Lu, and one or more of these may be used in combination.

The highest magnetic properties are obtained with Pr, so in practical terms,
Pr, Pr-Nd alloy, Cr-Pr-Nd alloy, etc. are used. Small amounts of heavy rare earth elements, e.g. Dy, 'rb
etc. are effective for improving coercive force.

The main phase of the R-Fe-B magnet is R2FezB.

Therefore, if R is less than 8 at %, the above compound is no longer formed and high magnetic properties cannot be obtained. On the other hand, R is 30 atomic%
If the value exceeds 100%, the amount of nonmagnetic R-rich phase increases and the magnetic properties deteriorate significantly. Therefore, the appropriate range for R is 8 to 30 W and %. However, for high residual magnetic flux density, preferably R8 to 25 at % is suitable.

B is an essential element for forming the R2Fe+tB phase, and if it is less than 2 atomic %, it becomes a rhombohedral R-Fe system, so a high coercive force cannot be expected. Moreover, when it exceeds 28 at %, the amount of B-rich nonmagnetic phase increases, and the residual magnetic flux density decreases significantly. However, in order to obtain a high coercive force, preferably B
It is better to have 88 atoms or less, and if it is more than 88 atoms, fine R2Fe+a
It is difficult to obtain phase B, and the coercive force is small.

Elements such as Cu, Ag, Au, and Pd have the effect of significantly increasing coercive force. However, since these elements are non-magnetic elements, increasing the amount will reduce the residual magnetic flux density, so it is preferably 6 at % or less.

Co is an effective element for increasing the Curie point of the present magnet, but since it reduces the coercive force, it is preferably 50 atomic % or less.

Elements such as Zr, Hf, and Ga have the effect of aligning the C axes of fine ferromagnetic R-Fe-B crystals when they are generated by dehydrogenation, but these elements are nonmagnetic. Therefore, if the content is too large, the residual magnetic flux density will decrease and at the same time, the coercive force will decrease, so the content is preferably 5 at % or less.

The temperature during hot working is desirably higher than the recrystallization temperature, preferably 500°C in the R-Fe-B alloy of the present invention.
That's all.

The temperature at which hydrogen absorption and dehydrogenation occur is determined by the reaction temperature between the rare earth element in the ferromagnetic phase and hydrogen, but with hydrogen and alloys at atmospheric pressure, the reaction to produce fine crystals does not occur below 500°C. , and when the temperature exceeds 1000℃, R2F
E-port B rapidly grows grains and loses coercive force, so it is desirable that it is less than that.

[Example] (Example 1) Using an induction heating furnace in an argon atmosphere, alloys having the compositions shown in Table 1 were melted and left to stand. At this time, rare earth, iron and copper raw materials with a purity of 99.9% were used.
Ferroboron was used as boron.

The cast ingot thus obtained was placed in an iron capsule, degassed, and sealed. To this, processing degree 3 at 950℃
0% hot rolling was performed four times in air to give a final working degree of 76%.

Further, during this hot working, the axis of easy magnetization of the crystal was oriented parallel to the direction in which the alloy was pressed.

After putting this rolled material into a stainless steel electric furnace where the atmosphere can be controlled, the electric furnace was evacuated to 10-'Torr.
It was replaced with hydrogen gas at 0 Torr.

After that, it was heated to 800°C and held for 3 hours to absorb hydrogen into the alloy, and then heated again for 1 hour at 10-'T.

The reactor was evacuated to rr to perform dehydrogenation and quenched with argon gas. The hydrogen-treated alloy ingot was crushed in a stamp mill for 10 minutes and in a Raikai machine for 30 minutes, resulting in 1.5wt%.
7 tons/kneaded with epoxy resin in a 15 koe magnetic field.
A bonded magnet was produced by pressing and curing at cm-2.

In addition, in order to compare the effects of hydrogen treatment, an alloy with the same composition was heat treated at 1000°C for 24 hours in an argon gas atmosphere, and then an ingot that was heat treated at 475°C for 2 hours was crushed in the same way, kneaded with resin, Molded.

Furthermore, in order to compare the effects of hot working, a bonded magnet was also produced by hydrogen-treating the cast ingot without hot working and molding it under similar conditions.

The magnetic properties of the molded bonded magnet are determined by applying a maximum magnetic field of 25 kO.
Table 2 shows the results measured using the B-H tracer of e.

As shown in Table 1, Table 2, and Table 2, the bonded magnet made from the magnet powder that was hydrogen-treated after hot working of the present invention had a higher coercive force than other comparative examples. It can also be seen that a high residual magnetic flux density can be obtained by hot working, and a bonded magnet with a high energy product can be obtained.

(Example 2) An alloy having the composition shown in Table 1 was made into a quenched ribbon using a single roll vacuum melt spinning device at a roll speed of about 20 m/sec. This quenched ribbon was packed into an iron capsule, degassed, and sealed. This was then hot-rolled four times in air at 950°C with a working degree of 30%, so that the final working degree was 76%.

Further, during this hot working, the axis of easy magnetization of the crystal was oriented parallel to the direction in which the alloy was pressed.

Thereafter, hydrogen was absorbed by heat treatment at 750°C for 3 hours in a hydrogen atmosphere in the same manner as in Example 1, and the rolled material was dehydrogenated by exhaust gas and rapidly cooled.
In the same manner as above, it was crushed, mixed with resin, molded, and its magnetic properties were measured.

In addition, in order to compare the effects of hydrogen treatment, a sample of quenched ribbon with the same composition was heat-treated at 1000°C for 24 hours in an argon atmosphere after rolling, and then heat-treated at 475°C for 2 hours, and then formed into a bonded magnet in the same way. The characteristics were created.

Furthermore, in order to compare the effects of hot working, a bonded magnet was also produced by hydrogen-treating the manufactured ingot without hot working and molding it under similar conditions.

The magnetic properties of the molded bonded magnet are determined by applying a maximum magnetic field of 25 kO.
Table 3 shows the results measured using the B-H tracer of e.

Table 3 As shown in Table 3, even when a quenched ribbon is used, the bonded magnet made from the magnet powder subjected to hydrogen treatment after hot processing of the present invention is superior to other comparative examples. It can be seen that a high coercive force is obtained, a high residual magnetic flux density is obtained by hot working, and a bonded magnet with a high energy product can be obtained.

[Effects of the Invention] As described above, according to the present invention, R (where R is at least one rare earth element including Y), Fe, and B are used as basic raw material components, and an alloy containing the basic components is melted, Magnet powder is produced by on-site production, hot processing, or by hot processing a quenched ribbon of the basic component, then heat-treated in a hydrogen gas atmosphere to absorb hydrogen, and then dehydrogenated in a vacuum. Manufacturing bonded magnets has the following effects.

(1) Coercive force iHc can be increased by making ferromagnetic crystal grains finer by hydrogen treatment. In addition, by mechanically orienting the crystal axes through hot working, bonded magnets with high residual magnetic flux density and high energy product can be realized. I can do it.

In addition, the stable supply of magnets with high magnetic properties has a great effect on downsizing and improving the reliability of motors and electronic devices incorporating motors.

that's all Applicant: Seiko Epson Corporation

Claims (2)

[Claims] (1) R (where R is at least one rare earth element including Y), Fe, and B are used as basic raw material components, and after melting and casting the alloy as the basic components and hot working the cast alloy, A method for producing a rare earth bonded magnet, which uses magnet powder that is heat-treated in a hydrogen gas atmosphere to absorb hydrogen, dehydrogenated in a vacuum, and then ground. (2) Use magnet powder obtained by hot processing a quenched ribbon having the composition described in claim 1, then heat-treating it in a hydrogen gas atmosphere to absorb hydrogen, dehydrogenating it in a vacuum, and then pulverizing it. A method for producing a rare earth bonded magnet, which is characterized by: