JPH01706A - Rare earth magnet manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a permanent magnet made of rare earth metals (represented by NdFe-B permanent magnets) and transition metals (transition metals) and boron (B) as main components. R2T14B intermetallic compound magnet.

In particular, extremely high magnetic properties (BH) max 50M-
The present invention relates to a method for manufacturing a high-performance magnet having a G.08 or higher.

[Conventional technology]

Methods for manufacturing R-Fe-B magnets are roughly divided into two methods. One type is a liquid quenched magnet, which is manufactured by ultra-quenching a molten alloy and then molding pulverized magnet powder. One is a sintered magnet, which is manufactured by finely pulverizing an ingot of a magnetic alloy obtained by melting, shaping it in a magnetic field, and then sintering it. The present invention relates to sintered magnets.

Generally, the manufacturing process for two-piece magnets using the powder metallurgy method involves melting, crushing, orienting the raw material alloy in a magnetic field, and compression molding.

The process proceeds in the order of sintering, 9 aging. Melting is usually performed in a vacuum or inert atmosphere using arc, high frequency, etc., and the raw material ingot is obtained by casting into a water-cooled copper mold or the like. Grinding is divided into coarse grinding and fine grinding, and coarse grinding is performed using a soyota crusher, an iron mortar, a disc mill, a roll mill, etc.

Fine pulverization is performed using a burr mill, vibration mill, jet mill, etc.

Orientation in a magnetic field and compression molding are usually performed simultaneously using a mold, in which the C-axis directions of the crystals exhibiting large magnetic anisotropy are aligned. Namely.

High-performance anisotropic sintered magnets can be realized by highly oriented the zero plane of the crystal. Sintering 2 Usually from 1000℃
It is carried out in an inert atmosphere at a temperature in the range of 1150°C. Aging contributes to the improvement of IHC and is performed as needed2, usually at a temperature around 600°C.

Increasing Br is an essential condition for improving the performance of this system magnet. Br is achieved mainly by reducing the R value and improving the degree of C-plane orientation of crystal grains.

The raw material ingots used so far have been cast to a thickness of usually 10 mm or more.

[Problem that the invention seeks to solve]

However, in the above manufacturing method, when the R content in the ingot composition is about 35 wt% or less, the R2Fe 14 B phase (main phase)
There is a tendency for the Fe phase to precipitate inside, and as 9R decreases, its increase becomes remarkable. This precipitation of Fe phase is a factor that reduces the degree of crystal orientation of the sintered body, and as the amount of precipitation increases, the anisotropy tends to decrease, and the improvement in +Br is extremely large compared to the potential increase in 4π■8. It was getting smaller.

Furthermore, when the R value in the raw material decreases, the sinterability of the compact decreases, and it becomes necessary to increase the sintering temperature in order to obtain the required sintered density (d).

However, as the sintering temperature increases, the crystal grains of the sintered body grow! It becomes necessary to limit the range to a range where the decrease in Hc is small. By reducing the R value,
The disadvantage is that the suitable sintering range gradually becomes narrower, progressing in a direction that is industrially disadvantageous.

In view of the above drawbacks, one technical object of the present invention is to prevent the precipitation of the F'e phase in the R2T14B phase, which is a factor that reduces the degree of crystal orientation of a sintered body.

It is an object of the present invention to provide a method for manufacturing a rare earth magnet in which sinterability is improved to suppress the growth of crystal grains in a sintered body.

[Means for solving problems]

According to the present invention, in a method for manufacturing an R2T14B magnet containing Nd, Fe, and B as main components (herein, R represents yttrium and rare earth elements, in which case transition metal is used) by a powder metallurgy method, R is 28 .5-33.5
By using a crystallized liquid quenched alloy containing 0.85 to 1.35 wt% B and the balance T as a starting material, pulverizing it, forming it in a magnetic field, and sintering it, (BH
) A method for manufacturing a rare earth magnet is obtained, which is characterized in that aX obtains magnetic properties of 50 M-G·00 or more.

That is, as a result of various experiments, the inventor of the present invention improved the cooling rate of the raw material alloy during these steps. By using an R-T-B alloy with a certain composition range, a highly oriented sintered body can be obtained because the Fe phase does not precipitate.
Because sinterability is improved, it can be used in a wide sintering temperature range (BH)
I discovered that it is possible to achieve more than 50M-G.00. That is, the method for producing the raw material alloy is to obtain a suitably crystallized rapidly solidified alloy by a liquid quenching method. The metal structure in this case is.

The Ndrich phase surrounds the fine main phase particles that have grown in a columnar shape, and no Fe phase is observed to precipitate.

In this case, the minor axis direction of the main phase crystal is about 3 to 10 μm.

This is a suitable range for melting, taking into consideration the sinterability and degree of orientation of the sintered body. When a liquid quenched alloy is produced using the single roll method, it becomes a thin strip (thin piece, thin plate) with a thickness of about 1 to 3 mm.
When fabricated by the two-roll method, the same effect is shown up to a thickness of about 5 Wrm.

Also, the composition of alloy 1 is related to 4πIBK.

If high magnetic properties are to be obtained, it must be limited.

Including the relationship with yHc, (BH)max50M-G-
The composition range where R is 28.5 to 33.00 or more is obtained.
5 wt%.

B needs to be limited to a range of 0.85 to 1.35 wt% and the balance T.

The present invention is simple and has not been easily obtained in the past (B
H) m, x50M-G.00 or higher, which is an extremely high magnetic property that can be achieved, and is very useful industrially.

Below is Itohichi 〔Example〕 An embodiment of the present invention will be described.

Example 1 Nd with a purity of 97 wt% (the remainder is a rare earth element mainly consisting of Ce and Pr), ferroboron (B purity about 20 wt%)
) and electrolytic iron, the rare earth element (8) is 30. O
wt%.

B is 1. The alloy was melted by high-frequency heating in an argon atmosphere so that the remaining content was Fe, and a double-sided water-cooled mold made of Cu was used to obtain an alloy ingot with a thickness of about 10 mm.

Next, this ingot is used to remelt by high frequency heating in an r Ar atmosphere, and after that, the one round speed is about 2 m/s.
Spray onto EC Cu roll and use one-piece roll method.

A liquid quenched alloy ribbon having a width of about 1 oan and a thickness of about 1.0 μm was obtained.

The photographs show the metallographic structures of these ingots and the plane parallel to the cooling surface inside the liquid-quenched alloy ribbon. The ingot consists of coarse main phase crystals, Fe phase particles precipitated therein, and Ndrich phase crystal grains unevenly distributed between the main phase particles. The liquid quenched alloy consists of fine main phase crystals that have grown into columnar shapes and a Ndrich grain boundary phase that surrounds them.
The Ndrich phase with a low melting point has good dispersibility, and no precipitation of Fe phase, which causes a decrease in crystal orientation, is observed.

Next, sintered magnets were produced using these ingots and liquid quenched alloy as raw materials. After coarsely pulverizing each raw material alloy,
It was pulverized using a ball mill to have an average particle size of about 2.5 μm. Next, this powder is placed in a magnetic field of about 25 koe,
It was molded at a pressure of ton/cm2. 10 pieces of this molded body
00℃, 1020℃, 1040℃, 1060℃.

After holding each temperature in vacuum for 1 hour at 1080°C and 1100°C, it was held in Ar for 91 hours and rapidly cooled.

These sintered bodies were aged at 660°C for 3 hours.

A magnetic field of approximately 30 koe was applied to this sintered body.

The magnetic properties were measured. The results are shown in FIG.

Using liquid quenched raw materials improves sinterability.

Regarding the sintered density (d), the sintering temperature is reduced by about 50°C.

Furthermore, Br shows a significantly high value, and IHc also tends to be high, so +(BH)max is significantly improved.

As a result of measuring the degree of crystal orientation of the sintered body by X-ray diffraction,
When the liquid quenched raw material was used, the C-plane of the Nd2Fe14B crystal was clearly more highly oriented.

Example 2 Same as Example 1, R was set to 28.0.29.0°30
．． 0.31.0.32.0, 33.0, 34.0wt%
B changes to 1. After obtaining an ingot with Q wt% and the balance being Fe, a liquid quenched alloy ribbon with a thickness of about 1 inch was obtained using a Cu roll. Sintered magnets were produced using these ingots and liquid quenched alloy as raw materials.

However, the aging of the sintered body is 25°C between 550°C and 700°C.
Each temperature was changed by ℃ and held for 3 hours.

Among the above, the highest magnetic properties (
(BH)maX) is shown in FIG.

(BH) For values of 50 M-G・Oe or more, R is 2
It was obtained in the range of 8.5 to aX 33.5 wt%.

Example 3 In the same manner as in Example 2, R is 3 Q, Q wt%, B
0.8.0.9, 1.0, 1.1, 1.2.1
．． 3. Comparison of the characteristics of a sintered magnet with a composition of 1.4 wt% and the balance being Fe when ingots and liquid quenched alloys are used as raw materials.

The results are shown in FIG. (BH) 50 M-G-
Values equal to or higher than OeaX are obtained when B is in the range of 0.85 to 1.35 wt%.

Example 4 Pr, Nd and ferroboron with a purity of 99% or more.

Using electrolytic iron, R as (Nd[18·P r O,2) was 31.0 wt% and B was 1.0 wt%. Owt%, balance Fe.

An ingot was obtained in the same manner as in Example 1.

Next, in the same manner as in Example 1, the circumferential speed of 9 was approximately 1"l/see.
A liquid quenched alloy ribbon having a thickness of approximately 2 ran was obtained using a Cu roll of 1. Using these ingots and rapidly solidified alloy ribbons as raw materials, they were subjected to coarse pulverization, fine pulverization, compaction in a magnetic field, sintering and 1 aging in the same manner as in Example 2, and then their magnetic properties were measured. Among the samples for each raw material, the highest (BH
) is shown in Table 1 as maX.

Table 1 below shows that sintered magnets using liquid quenched alloys as raw materials exhibit significantly higher magnetic properties.BH) max 50M-G-
This value significantly exceeds Oe.

Example 5 Nd and Dy and ferrozeron with a purity of 97 wt% or more.

'(Nd(197) using scrap iron and electrolytic cobalt
・R as Dy0.03) is 31.0 wt% and B is 1.0 wt%.

An ingot was obtained in the same manner as in Example 1 so that (Fe, .Col11o) was the remainder.

Next, in the same manner as in Example 4, a liquid quenched alloy ribbon was obtained.

These ingots and rapidly solidified alloy ribbons were used as raw materials and coarsely ground in the same manner as in Example 2.

After pulverization, molding in porcelain hot water, sintering and aging for 1 time, magnetic properties were measured. The highest (BH) among the samples for each raw material
The values indicating max are shown in Table 2.

Table 2 Sintered magnets using liquid quenched alloy as raw material showed significantly higher magnetic properties, (BH) 50M-G・Oe
The value exceeds that of aX.

〔Effect of the invention〕

As shown in the above examples, R is 28.5 to 33,
5 wt%, B 0.85 to 1.35 wt%, balance T
A crystallized liquid quenched alloy is used as a raw material.

By pulverizing this, forming it in a magnetic field, sintering it and aging it for 1 time,
, (BH)maxsoM-G-oe or higher magnetic properties can be obtained at n.

In the above embodiments, only the manufacture of liquid quenched alloys by the single roll method has been described, but the same effect can be obtained by the twin roll method.

Also, Nd-Fe-B system, Nd-Pr-Fe-B system, Nd-Fe-B system,
Although only the d-Dy-Fe/C0-B system was mentioned14
It can be easily inferred that magnetic properties of (BH) 50M-G·00 or more can be obtained even if the substitution is made with other elements to the extent that the decrease in πI 5 (Br ) is not significant. (Theoretically, Br is 14.15
It should be at least kG. )

[Brief explanation of drawings]

Figure 1 shows the sintering temperature and density (d) of the sintered body in Example 1.
) and magnetic properties (Br, He + (BH) mB
In Figure 1, the ○ mark (solid line) indicates the sample using liquid quenched alloy as the raw material, and the Δ mark (dashed line) indicates the relationship between
The figure shows a sample using In and T as raw materials. FIG. 2 shows the relationship between the rare earth element composition value @) and the magnet properties (Br, IHC+ (BH)max) in Example 2. Figure 3 shows the B composition value and magnetic properties (Br
, rHc* (BH) ). max Figures 4(a) and 4(b) show the metal structure inside the sintered magnet raw material alloy (plane parallel to the cooling surface) used in Example 1. (a) is an ingot, and the gray crystals are the main phase (Nd2Fe1
4B phase), the dendrites in the gray crystals are Fe phase, and the black crystals are Ndrich phase. (b) is a liquid rapidly solidified alloy, and the gray crystals are the main phase (Nd2F0
14B phase), the black crystals are Ndrich phase. Figure 1 Sintering temperature (C) Figure 2 R (wt, %) Figure 3 B (Wzem) Figure 4

Claims (1)

[Claims] 1. R_2T_ containing Nd, Fe, and B as main components
In a method for producing a 1_4B magnet (where R represents yttrium and a rare earth element, and T represents a transition metal) by a powder metallurgy method, R is 28.5 to 33.5 wt%, B is 0.85 to 1. 3
A crystallized liquid quenched alloy of 5 wt% and the balance T is used as a starting material, and by pulverizing, forming in a magnetic field, and sintering, magnetic properties of (BH)_m_a_x50M・G・Oe or more are obtained. A method for manufacturing a rare earth magnet.