JPH0441652A - Rare earth magnetic alloy - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and to obtain a rare earth magnetic alloy excellent in magnetic properties by adding new light rare earth oxide to an alloy containing R2TM14B1 type tetragonal crystal as main phase. CONSTITUTION:Light rare earth oxide (La2O3, Ce2O3, Pr2O3, Nb2O3, Sm2O3)is incorporated by 0.1-1.0wt.% into a rare earth permanent magnet containing R2TM14B1, (R is Ce, Pr, Nd, Gd, Tb, or Dy and TM is Fe or Co) type tetragonal crystal as main phase, by which the rare earth permanent magnet alloy excellent in corrosion resistance and magnetic properties can be produced.

Description

[Detailed Description of the Invention] [Industrial Application Field 1 Rare earth magnets have superior magnetic properties compared to ferrite magnets, and are very advantageous for downsizing industrial products by utilizing high magnetic force. It is applied in a wide range of fields, from child-type watches to computer terminals. The present invention relates to this rare earth magnet, and more specifically to improving its corrosion resistance.

[Summary of the invention] R2T1114 Bl (R=Ce, Pr, Nd, G
d, Tb or D y , T y = Fe or CO) type tetragonal as the main phase, m
SmCo-based magnets have a high saturation rate and have the highest maximum energy product ((BH)max) among the rare earth magnets currently in the market due to their high content of Fe or Co, which is the source of the SmCo-based moment. Compared to other rare earth permanent magnets such as
Since the volume fraction with one stone becomes large, the maximum energy product (BH) max decreases significantly, and the above-mentioned magnet cannot exhibit a higher value than other types of magnets in terms of magnetic properties.

Therefore, in the present invention, the problem of corrosion resistance is not solved by surface treatment, but by adding a new light rare earth oxide to an alloy whose main phase is R2T, 4B, type tetragonal.
We have discovered a rare earth magnet alloy that has improved corrosion resistance and excellent magnetic properties.

Considering that the increase in the cost of magnet products due to the addition of a small amount of light rare earth oxide to this alloy is negligible, its industrial value is extremely large.

[Conventional technology] Conventionally, as a method for making rare earth iron magnets corrosion resistant, NdFe
Surface treatment methods such as vapor phase plating or forming a chromic acid film on the surface of B-based sintered magnets are used.

[Issue to be solved by the invention I11 In the conventional surface treatment method, only in the case of a magnet with a relatively large volume, the decrease in magnetic properties (especially maximum energy product (BH) max) due to the surface protective layer is relatively small. However, as the volume of the magnet becomes smaller (the smaller the volume of the magnet, the greater the influence of the surface protective layer on the magnetic properties. For example, a stepping motor rotor for a wristwatch with a volume of approximately 5 The conventional magnet had a drawback that the maximum energy product (BH) max decreased by about 30% or more, making it unusable for practical use.

[Means for Solving the Problems 1 In order to solve the above problems, the present invention uses light rare earth oxides (Lag Os, Cez Ox, Pry O
s, NdtOs, SmaOs) from 0.1 to 1
．． By containing 0 wt%, a rare earth permanent magnet alloy has been found that has excellent corrosion resistance and magnetic properties.

[Function and Examples] Example: 1 Light rare earth oxide (La
gOx, CezOx, PryOs.

Ndx Os, Sma Os) powder (average particle size 2
5 μm) was added in an amount of 0 to 5.0 wt% and mixed for 1 hour in an organic solvent using a low energy rotary ball mill.

This mixed powder was formed under pressure at a pressure of 10 t/cm 2 while applying a magnetic field of 15 KOe in a direction perpendicular to the pressure direction. The obtained molded body was heated at 1070°C for 1
After sintering for an hour and then cooling to room temperature, the
A sample was subjected to time aging treatment.

Furthermore, X-ray diffraction analysis revealed that the sintered alloy contains a large amount of Nd2.
It was confirmed that the product consisted of an F 6148 + tetragonal product, an Nd-rich phase, and a light rare earth oxide.

The prepared samples were left in a constant temperature environment of 80° C. and 95% humidity for 0 to 1000 hours, and changes in weight of the samples were measured, which was used as an evaluation of corrosion resistance. In addition, the magnetic characteristics are DC type B
l (measured using a tracer.

Example 2 An alloy having the composition shown in Table 1 below was melted by arc melting, coarsely pulverized, and then finely pulverized using a vibrating ball mill to an average particle size of 3.0 μm. The obtained fine powder was coated with Sm20. 0.5wt
Add and mix. The subsequent steps are the same as in Example 1.

In Example 2, all alloys were RtT-4B, tetragonal, R-rich phase (R is a rare earth element) phase, and Sm
It was confirmed by X-ray diffraction that it consisted of a mixed phase of tOs.

[Effects of the Invention 1 From the above examples, the following effects can be mentioned as effects of the present invention.

Figure 1 shows N d + @ F e a? Light rare earth oxides (Lag 03, Ce20S, Pr
201. Nd, Ox, Sm20. ) is a characteristic diagram showing the relationship between leaving time at a constant temperature F4 boundary and weight change when 0.5 wt% of It has become clear that corrosion resistance is improved by the addition of

FIG. 2 is a characteristic diagram showing the relationship between the amount of S m 203 added and the weight change after a standing time of 500 hours, and it is recognized from this that the corrosion resistance is improved when O, 1 wt % or more of S m *Os is added.

Figure 3 is a characteristic diagram showing the demagnetization curve and the effect on the maximum energy product (BH) max depending on the amount of S m 20 s added. It is recognized that there are few. A similar tendency is observed for other oxides as well.

The above results suggest that the addition of light rare earth oxides is effective in achieving both improved corrosion resistance and high magnetic properties.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the weight change with addition of the light rare earth oxide of the present invention. FIG. 2 is a characteristic diagram showing the addition of samarium oxide (SmmO3) and weight change according to the present invention. Figures 3 (A) and (B) are Sm, O, Ganto Hamada of the present invention.
Seiko Electronics Industries Co., Ltd. Representative Patent Attorney Keisuke Hayashi m203 Addition amount (w t '/J Figure Removal time bar (h) H (to Oe)

Claims (1)

[Claims] R_2T_M_1_4B_1 (R is Ce, Pr, Nd
, a combination of one or more of Gd, Tb, or Dy; T_M is a combination of one or two of Fe or Co) type tetragonal crystal is the main phase, and light rare earth oxides (La_2O_3, Ce_2O_3, Pr_2O_
3, Nd_2O_3, Sm_2O_3) from 0.1 to 1.
A rare earth magnet alloy characterized by containing 0 wt%.