JPS5919453B2 - intermetallic compound magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an alloy RC0z (z=
4.0 to 5.8) with Cr added thereto.

The purpose of the present invention is, firstly, to improve the corrosion resistance of RCo2 magnets, and secondly, to impart viscosity to a hard and brittle magnet alloy.

Y, La, Ce, which are generally known as rare earth elements,
Among Sm, Pr, etc., compounds of Sm and transition elements smc
It is theoretically predicted that o5 has high magnetic properties,
After passing through the research and development stage, it is now widely used industrially.

There are generally three known methods for manufacturing such RCo5 magnets: sintering, casting, and resin bonding.
Of these three methods, the sintering method has the best magnetic properties, and the resin bonding method has about the same level of magnetic properties as the sintering method.
/2. However, in terms of machinability, the resin bonding method is the best, while the sintering method has the disadvantage of being hard and brittle. In the casting method, the brittleness of the sintering method is somewhat improved by the inclusion of Cu. Furthermore, in terms of corrosion resistance and weather resistance during processing and long-term use of magnets, the resin bonding method, in which magnetic powder is bonded while being coated with resin, is far superior to the sintering method. In this way, RCo5 manufactured by the sintering method
Although magnets have excellent magnetic properties, they have many drawbacks in other respects. The present invention is aimed at magnets produced by such a sintering method, and achieves improved corrosion resistance and toughness while minimizing deterioration in magnetic properties.

Rare earth elements, represented by Sm, are extremely susceptible to oxidation and have the property of reacting even at room temperature.
Compounds with also have this tendency. However, in addition to this, a few percent of Cr
When added, corrosion resistance is greatly improved, and no oxidation is observed at room temperature. Furthermore, the reduction in magnetic properties, especially the residual magnetic flux density 5 degrees Br, due to the addition of Cr is about the same as when Cu is added in the casting method, and there is no significant reduction in properties as in the resin bonding method. Furthermore, in terms of toughness, the same or better effect than the casting method can be obtained. Therefore, the properties of the magnet can be adjusted to zero by adjusting the amount of Cr added. If the atomic ratio of Cr to Co is less than 0.03, practically sufficient corrosion resistance cannot be obtained, and if it exceeds 0.3, the magnetic properties will deteriorate significantly. A range of 0.3 is desirable. 5 In addition, for the compound RCo2, R is other than sm&CCe
3 Michel metal, Pr, or their compounds are considered, and in addition to Co alone, a part of it may be Cu.
Alternatively, those in which Fe is substituted have also been put into practical use.

Furthermore, regarding z, z = 5 is the ideal stoichiometric composition, but as is well known, RCO compounds have a wide range in phase diagram, and z can change depending on the component composition. Therefore, if z is within the range of 4.0 to 5.8, R
It can be said to be a CO5 magnet. The details will be explained below based on examples.

Example 1. As the rare earth transition metal compound RMz, an alloy with a composition of SmcO4.8 and a part of CO in this alloy are replaced with Cr.
Sm substituted with (COl=XCrX) 4.8, where X is 0.01, 0.03, 0.1, 0.
3 and 0.4 alloys were weighed, melted, crushed, and
Multiple types of magnets were manufactured through the various steps of molding, sintering, and heat treatment.

First, we investigated the changes in magnetic properties and bending strength, which is one of the parameters representing toughness, depending on the amount of Cr added to the obtained magnet.
As shown in the figure. As is clear from FIG. 1, the residual magnetic flux density Br and coercive force BHc, which represent magnetic properties, decrease as the amount of Cr increases, and the rate of decrease becomes large when the atomic ratio of Cr is around 0.3. On the other hand, the bending strength σ increases almost in proportion to the atomic ratio of Cr, indicating that addition of Cr improves toughness. Next, in order to examine the corrosion resistance of these magnets, they were left in a circulating atmosphere at +60°C. Table 1 shows the changes in the appearance of the magnet at that time. As is clear from Table 1, not only in the case without Cr addition,
Even when the atomic ratio is 0.01, the corrosion resistance is not significantly improved, but when the atomic ratio is 0.03 or more, there is a noticeable difference compared to the case without additives.

Therefore, by minimizing the deterioration of magnetic properties,
In order to obtain sufficient toughness and corrosion resistance for practical use,
The amount of Cr added is preferably in the range of 0.03 to 0.3 in terms of atomic ratio. As described above, the present invention has the advantage of adding Cr to the RCOz alloy.
By adding , it is possible to improve corrosion resistance and mechanical properties, and the practical effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a diagram showing changes in magnetic properties and bending strength with respect to the amount of Cr added in Example 1.

Claims (1)

[Claims] 1 RC mainly composed of a compound in which the ratio of R selected from one or more rare earth elements and Co is 1:5
oz (z = 4.0 to 5.8), a part of the Co is 0.03 to 0.3 in atomic ratio.
An intermetallic compound magnet characterized in that Cr is substituted with Cr.