JPH04369203A - Rare-earthe permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a magnet wherein N atoms or C atoms have been introduced and its magnetic characteristic is high by a method wherein an R2Fe17 type magnet alloy powder-molded body is sintered and heat-treated in the atmosphere of a mixed gas by N2 gas, NH3 gas and CH4 gas and by exerting a specific gas pressure. CONSTITUTION:A magnet alloy ingot which has been formed by melting, at a high frequency, and casting the composition raw material of an R2Fe17 type magnet is crushed fine and made uniaxially anisotropic. Then, fine powders are oriented in a magneto-static field, pressed, molded and sintered temporarily. After that, this temporarily sintered body is sintered formally and heat-treated in a mixed gas formed of one or two or more kinds out of N2 gas, NH3 gas and CH4 gas at a gas pressure of 10 Pa or higher. At this time, R represents one or two or more kinds of rare-earth elements such as La, Ce, Pr, Nd and the like including Y. Thereby, it is possible to obtain an R2Fe17 type anisotropic bulklike sintered magnet whose cost is low and which is provided with a high magnetic characteristic.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates to an R2Fe17 type bulk sintered magnet into which interstitial atoms having high magnetic properties are introduced, and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION Conventional R2Fe17 compounds were unsuitable as magnet materials because they did not satisfy three conditions for magnets. The three conditions for the magnet are that saturation magnetization (Ms), magnetocrystalline anisotropy constant (Ku), and Curie temperature (Tc) all exhibit high values. Although these three conditions are necessary conditions and not sufficient conditions, when they are satisfied, there is a possibility that magnetization can be achieved. Among R2Fe17 compounds, especially S
When C or N atoms are introduced into m2Fe17 between the lattices, K
It is known that u increases significantly (X.P.ZH
ONG, et al. , J. Magn. Magn. M
ater. 86, 333 (1990). , J. M. D
．． Coey and Hong SUN, J. Mag
n. Magn. Mater. 87, L251 (1990
). , Hiroshi Nagata, Hironobu Fujii, Abstracts of the 14th Annual Meeting of the Japanese Society of Applied Magnetics, 491 (1990). , Japanese Patent Publication No. 3-1
(See Publication No. 6102). Among these compounds, Sm2
Since Fe17Nx has a Ku value that is almost equal to or higher than that of Nd2Fe14B, and completely satisfies the above three conditions,
It is attracting a lot of attention as a new magnetic material. In this way, in rare earth-iron compounds, introducing interstitial atoms to widen the distance between Fe and Fe is very effective in improving magnetic properties.

0003

However, the problem lies in the stability of interstitial atoms at high temperatures. For example, Sm2Fe1
When a 7Nx alloy or powder is heated under atmospheric gas pressure, the N atoms dissolved in the alloy will be eliminated at temperatures above 650°C. Therefore, even if an anisotropic sintered magnet is produced using the powder sintering method, it is necessary to sinter at a temperature of 1000°C or higher, making it impossible to introduce N atoms into the sintered body. Even if the sintered body is heat-treated in N2 gas, only the surface is nitrided, and it is difficult to introduce N atoms into the interior. For this reason, we have achieved a microstructure with a single magnetic domain particle size or smaller using liquid ultra-quenching method and mechanical alloying method.
The limit is to use the nitrided powder as an isotropic bonded magnet, and a method for producing bulk anisotropic sintered magnets has not yet been found. The present invention provides N and/or
Another object of the present invention is to provide an R2Fe17 type anisotropic bulk sintered magnet with high magnetic properties into which C atoms are introduced, and a method for manufacturing the same.

0004

[Means for Solving the Problems] In order to solve the problems, the present inventors have completed the present invention by studying the manufacturing conditions in detail. (here R represents a rare earth element) is N2
, NH3, CH4 gas, sintering and heat treatment at a gas pressure of 107 Pa or more in an atmosphere of one or more mixed gases, and a rare earth magnet produced by this manufacturing method. Located in a permanent magnet.

[0005] The present invention will be explained in detail below. Equilibrium decomposition pressure-temperature diagrams are known for many metal hydrides and intermetallic compounds. For example, “Osaka Science Center: Research report on hydrogen storage alloy materials,
p. 6 (1984)'' describes equilibrium decomposition pressure-temperature diagrams for various alloys and H2, and it can be seen that the decomposition temperature increases by increasing the equilibrium decomposition pressure. In the case of metal hydrides, to facilitate hydrogen absorption and dissociation,
The challenge is to lower the dissociation temperature, but in the case of magnetic materials, it is important to raise the dissociation temperature so that N2 does not dissociate even at high temperatures during sintering.

[0006] Sm2Fe17NX compounds etc. can also be expected to exhibit the same behavior as hydrides, so at 1000°C
As a result of research on the equilibrium dissociation pressure of N2 and rare earth/intermetallic compounds at the above-mentioned high temperatures, it was found that if sintering is performed at an N2 gas pressure of 107 Pa or higher, preferably 106 Pa or higher, dissociation of N2 does not occur. Since such a high temperature and high pressure environment cannot be achieved with a normal sintering furnace, we were able to solve this problem by using a hot isostatic press (HIP) device.

[0007] As for the manufacturing method, magnet composition raw materials are high-frequency melted, a cast magnet alloy ingot is pulverized to a particle size of 3 to 5 μm by a wet or dry method, and then uniaxial anisotropy is first performed. This is N2 gas under atmospheric pressure or N2
300~ in a mixed gas atmosphere of +NH3, N2+CH4
Heat treatment is performed at a temperature range of 600°C for 8 to 24 hours,
After nitriding or nitriding the fine powder, it is rapidly cooled. The mixing ratio of the mixed gas is preferably in the range of 90/10 to 50/50 for both N2/NH3 and N2/CH4 in volume %. Next, the fine powder was oriented in a static magnetic field of 10 to 15 KOe, and
After press forming at a pressure of on/cm2 or more,
The compact is pre-sintered for 1 to 2 hours at 500 to 600 DEG C. below the N2 dissociation temperature in a common sintering furnace for producing rare earth magnets or a hot press.

[0008] After that, the temporary sintered body is heated in a HIP machine for 10 minutes.
Main sintering and heat treatment are performed at a temperature range of 950 to 1150° C. for 1 to 2 hours under N2 gas pressure of 7 Pa or higher. In addition, in some cases, 800 ~
The sintered body, which has been densified by main sintering at 1,150° C. for 1 to 2 hours, may be heat-treated in HIP (under the same conditions as above) to be nitrided again. If the N2 gas pressure during main sintering in the HIP apparatus is less than 107 Pa, the N2 dissociation temperature will not reach 1,000° C. and sintering will not be possible, and the pressure is preferably 107 Pa or more. There is no particular upper limit for the gas pressure, but due to mechanical limitations of the HIP device, it is 109 Pa.
The following are practical limits. Once N2 has dissociated and the sintered body has become highly dense, even if it is heat-treated at a low N2 gas pressure, only the surface will be nitrided, and it is difficult to introduce N atoms into the interior of the sintered body. However, by nitriding in a high temperature and high pressure atmosphere, it is possible to nitride the inside of the sintered body.

The scope of application of this manufacturing method is effective for R2Fe17 type alloys. Here R includes Y La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
One or more rare earth elements selected from y, Ho, Er, Tm, Yb, Lu, etc., preferably S
Two or more elements mainly consisting of m or Sm.

0010

[Examples] Hereinafter, the embodiments of the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. (Example) An alloy mainly composed of Sm metal with a purity of 99% by weight and Fe with a purity of 99.9% by weight and having a basic composition of Sm2Fe17 was high-frequency melted and cast in an inert gas. After coarsely pulverizing the ingot, use a jet mill in N2 gas to reduce the particle size to 3.
Finely ground to ~5 μm. The fine powder was heat-treated in an atmosphere of N2 gas or a mixture of N2 gas and NH3 gas or CH4 gas at atmospheric pressure in a temperature range of 300 to 600°C for one hour or more, and then rapidly cooled. Then, the fine powder was divided into 1
1Ton/c when oriented in a static magnetic field of 5KOe
After press forming at a pressure of m2, 500~6
Preliminary sintering was performed at 00°C, and the sintered body was sintered using a HIP device at a temperature range of 950 to 1150°C under atmospheric pressure (105 Pa) to 108 Pa in a N2 atmosphere.
Heat treatment was performed. Table 1 shows these conditions and the magnetic properties of the obtained sintered magnet. As shown in Table 1,
Those heat-treated under a pressure of less than 107 Pa are
Magnetic properties are inferior to those heat-treated under pressures of Pa or more.

[0011]

[Table 1]

0012

[Effects of the Invention] The present invention has made it possible to sinter N interstitial magnet alloys, which were difficult to increase in density, and the resulting Sm
2Fe17NxCy magnets are less expensive than conventional SmCo magnets and have high magnetic properties without using expensive Co, so they have extremely high industrial utility value.

Claims (2)

[Claims] Claim 1: An R2Fe17 type magnet alloy powder compact (here R represents a rare earth element) is heated under a gas pressure of 1 in an atmosphere of one or more mixed gases of N2, NH3, and CH4 gases.
A method for producing a rare earth permanent magnet, characterized by sintering and heat treatment at a pressure of 0.07 Pa or higher. 2. A rare earth permanent magnet produced by the manufacturing method according to claim 1.