JPS5923803A - Production of magnet consisting of rare earth element - Google Patents

Abstract

PURPOSE:To produce a permanent magnet having high residual magnetic flux density and high max. energy product in production of a magnet alloy consisting of a rare earth element and a transition element by sintering the alloy dividedly in two stages: low pressure and high pressure. CONSTITUTION:An R2T17 magnet alloy (R: yttrium, rare earth element, T: transition metal), for example, Sm-Co permanent magnet, is first sintered in a non-oxidative atmosphere kept at 10<-3>-760Torr until the voids among the particles of a molded body turn into open cells. The variance of magnetic characteristics is reduced by the above-mentioned sintering. The alloy is then sintered in an inert atmosphere kept at 760-1520Torr to prevent the incorporation of oxidative gas such as air and to provide >= about 8.2 (gr/cc) sintered density in the final. The permanent magnet material having high performance is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is typified by an Sm-Co permanent magnet. The present invention relates to a method for manufacturing an R2T17 intermetallic compound magnet made of a rare earth metal (R) and a transition metal (T), and particularly relates to improving the characteristics of this type of magnet manufactured by powder metallurgy.

The mainstream of conventional Sm-Co-based permanent magnets has been the intermetallic compound SmCo5 (hereinafter referred to as 1-5 system), but in recent years, the intermetallic compound 5m2Co17 (hereinafter referred to as 2-5 system) has been improved in magnetic properties. 17 series) is being put into practical use.

Practically, in this 2-17 system, a part of Co is replaced with Fe.
, Co, Cu + Ti + Zr and the like. and these S
m-Co permanent magnets are manufactured by powder metallurgy. In general, this type of magnet is manufactured through the following manufacturing processes: melting, crushing, orientation in a magnetic field, compression molding, sintering solution, and heat treatment (aging). The melting is carried out in an inert atmosphere by means such as Levitation, arc, radio frequency, etc. Grinding can be divided into coarse grinding and fine grinding, and coarse grinding is done in an iron mortar or brown mill.

Fine pulverization is performed using a ball mill, vibration mill, jet mill, etc. Orientation in a magnetic field and compression molding are usually performed at the same time when a mold is used.

The magnetic field required for orientation is 8-20 KOe and the molding pressure is 2-20 KOe.
It is 7712 in l Oton/. The sintering is carried out in a non-oxidizing atmosphere, that is, an inert atmosphere such as fi, r, He, etc. or in vacuum at a temperature in the range of 1180 to 1250°C. Solution treatment generally proceeds simultaneously with sintering, but it is possible to separate both steps if necessary.

However, the permanent magnetic mantle obtained by the above-mentioned conventional manufacturing method has a disadvantage that the square shape of the second quadrant of the hysteresis curve is poor, and a high energy product cannot be obtained.

In order to obtain a high-performance magnet, it is necessary to have high Br and high He monthly, and high Br is the first condition.

In order to obtain high Br, it is necessary to increase saturation magnetization, crystal grain orientation, density, etc.

The purpose of the present invention is to improve the rectangular shape of the second quadrant of the hysteresis curve in the above-mentioned prior art, provide a method for manufacturing a permanent magnet with an extremely high energy product, and improve the sintered density of a 2-17 rare earth cobalt magnet. The performance is improved by improving the performance. The above purpose.

To achieve this, the present invention involves a sintering process in which the powder is sintered in a non-oxidizing atmosphere of 10 to 760 Torr until the voids between the powders become closed, and then sintered in a non-oxidizing atmosphere of 760 to 1520 Torr.
It is characterized by sintering in an inert gas atmosphere of r.

In addition, the sintering atmosphere at the initial stage of sintering is 10 to 760T.
orr (1 atm) because it eliminates the need for expensive vacuum equipment and reduces fluctuations in magnetic properties caused by compositional variations due to evaporation of Sm, etc. in high vacuum. It's for the sake of things. The reason for setting the sintering atmosphere in the second half at 760 to 1520 Torr is that by increasing the pressure higher than the outside air, it is possible to prevent the mixing of oxidizing gases such as air due to accidents, and to reduce the
This is not possible considering industrial advantages, such as if the l-force exceeds 1520 Torr, the equipment would be expensive.

Sintering of rare earth cobalt magnets is generally carried out in an inert (Il gas) atmosphere, but it is easy to obtain a higher sintered density in the case of ■-5 series, or in the case of 2-17 series. Even if the sintering temperature is increased, the sintering temperature is only about 15%, and as the He decreases, the magnetic properties deteriorate. It is important to obtain a sintered body with high density.

FIG. 1 shows the relationship between the sintering temperature program and the atmospheric pressure during sintering of the present invention. As shown in the figure, in the present invention, the initial stage of sintering (time L + 'l) is made to have a void of 1 month or less, and sintering is accelerated and the pores become closed.
This is done by applying a positive pressure of 2 atmospheres. Creating an atmosphere of negative pressure of 1 atm or less at the initial stage prevents air from escaping from the voids between particles in the press-molded product. This is to sinter the capsule while defoaming it, and apply negative pressure until the pores are closed.

In this state (fi, 7.8~8.0 (9r/cc
) pore size iU, then switch to positive pressure of 1 to 2 atm;
ξIn addition, s-even more forcefully eliminates the stomata.''
, sea urchin, finally 8.2 (,!9r/cc) j
I'L? Shi1! It is something that I do.

4＼ Inventive cow'i Q, (r soil, negative Jf = binding at the first 1υ1 stage, then 11j [Tozuchi is important to increase the porosity, 1', Q also θJ'1 This makes it possible to obtain the density of the soil in a soil condition of 8.-1 (l gr/cc).

Two embodiments of the present invention will be described below.

Example I Sm is 26 wt%, Cu is 9 wt%, Fe is 15
．． 5wL%.

The main components were pulverized to an average particle diameter of about 4 μm by surface frequency heating in an argon atmosphere so that Zr was 1.5 wt%, Ti was 0.1 wt%, and Co remained. This powder was compacted at a pressure of 1 tqn and 4 m2 in a magnetic field of 10 KOe/ζ. When the moon powder is sintered at 1210°C, the sintering atmosphere is changed to a non-oxidizing atmosphere of 760 Torr or less during the initial sintering process, in which the voids between the powders in the green compact become closed pores. Inert gas atmosphere or 3!4: Empty, then fill with Ar gas and set at 760-1.520 Torr for 11
Sintering was carried out by holding for Rj. This sintered body was subjected to solution treatment at 80'C, and then heated at 800C for 1
[Run heat treatment J'llll between I+i fj:I.

5°C/min, cooling rate below 400 Ut) I
IL Buko.

The magnetic properties of this sample are shown in Figure 2.
1 corresponds to an atmospheric pressure of 760 Torr at the initial stage of sintering.

As is clear from Figure 2, sintering occurs at the initial stage of sintering) 5-The lower the surrounding pressure, the higher the density, and high density means that the gaps between particles become closed, resulting in residual magnetic flux density B
r has been improved and the maximum energy product (1■) IllaX
becomes larger, leading to improved magnetic properties.

Although the present invention has been described in detail above, the following is a description of the production of an R2T17 magnet alloy using a powder metallurgy method.

In the sintering process, 10'~7' until the voids between the powders become closed pores.
By employing a method for manufacturing rare earth cobalt magnets characterized by sintering in an atmospheric pressure of 6 (1 Torr) and then pressurizing the sintering atmosphere to 7 (io-1520 Torr), the density can be brought closer to the true density than conventionally obtained. It is possible to obtain a high residual magnetic flux density and a high maximum energy product, which was previously not possible.
We have developed an excellent permanent magnet 4J material mainly consisting of R2Co17 intermetallic compound.

[Brief explanation of drawings]

FIG. 1 is a graph showing temporal changes in sintering atmospheric pressure and sintering temperature according to the present invention, and FIG. 2 is a diagram showing the relationship between magnetic properties and initial sintering atmospheric pressure of two embodiments of the present invention. .

Claims (1)

[Claims] In a method for manufacturing a JR2T17-based magnetic alloy (where R represents yttrium and a rare earth element, and T represents a transition element) by a powder metallurgy method, a sintering process is first carried out for 10
~ 760 Torr in a non-oxidizing atmosphere until the voids between the particles of the molded body become closed, and then 760 ~ 15 Torr.
A method for producing a rare earth magnet, characterized in that it is carried out in an inert atmosphere of 20 Torr.