JPH06231920A - Rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To provide an alloy high in coercive force consisting of a main phase and a rich phase by adding V and Si into an R-Fe magnet alloy. CONSTITUTION:This is a rare earth permanent magnet which is shown by the composition formula RxFe100-x-y(V1-aSia)y [among the formula, Y is one or more kinds of rare earth elements including Y x=5.5-18%, Y=8-20% (% is atom percentage), and a =0.05-0.7 (atom ratio)] and the main phase of which has ThMn12-type body-centered tetragonal structure. This composition of compound can easily form structure useful for a nucleus production type of magnet by a short time of heat treatment so a rare earth permanent magnet, which has excellent magnetic property, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth permanent magnet having excellent magnetic properties, which is useful as a material for various electric machines and electronic devices.

[0002]

2. Description of the Related Art With the miniaturization and higher performance of motors related to electronic equipment, the demand for rare earth permanent magnets is expanding faster than ferrite magnets. Among the rare earth permanent magnets that have been well known and mass-produced, Sm-Co magnets are widely used in speakers, motors, measuring instruments, and so on. However, since an expensive SmCo-based alloy is used, there is a cost problem, and replacing Co with inexpensive Fe is a development issue. On the other hand, Nd-Fe-B based magnets have been developed, which are made of Nd and Fe, which are rich in resources, as the main raw materials and have higher performance than Sm-Co based magnets (see Japanese Patent Laid-Open No. 59-46008). But this Nd-F
The e-B magnet is very rusty and requires some kind of coating. It was put into practical use for the first time by the development of an inexpensive and reliable rust preventive method such as Ni plating.

By the way, recently, inexpensive Fe was used as a main raw material for Sm-
Th with magnetic properties equivalent to or better than Co magnets
A magnet having an Mn ₁₂ type body-centered tetragonal structure (hereinafter referred to as 1-12 type structure) was discovered (see Japanese Patent Laid-Open No. 1-175205). The 1-12 type compound which is the main phase of this magnet is R-Fe-M
(R is a rare earth element including Y, M is Ti, V, Si, Cr, Mn, W,
(Including Mo, Al, etc.) ternary system, R-Fe (Co)
It cannot exist stably in the binary system, but the 1-12 type structure is stabilized only by the introduction of the third element. This compound is stable without containing expensive Co, has saturation magnetization, anisotropic magnetic field, Curie temperature, etc., which are almost the same as those of the Nd ₂ Fe ₁₄ B compound, and is mainly Fe. It has high corrosion resistance.

[0004]

As described above, it is very difficult to obtain a compound single phase from the 1-12 type compound having excellent magnetic properties, and it requires a heat treatment for a long time of several days.
When making a nucleation type magnet using the liquid phase sintering method typified by Nd-Fe-B based magnets, in addition to the main phase, a rare earth rich phase (which contains a lot of rare earths and contributes to densification by melting during sintering) However, in the case of 1-12 type magnet, if the amount of rare earth is more than the stoichiometric composition of the compound, it becomes a source of reverse magnetic domain R ₂
The Fe ₁₇ type compound (2-17 type compound) is likely to crystallize, which causes a decrease in coercive force. The 1-12 type magnet has not been industrialized yet due to these problems. The present invention is intended to solve such obstacles, to investigate a 1-12 type compound having excellent magnetic properties from the viewpoint of composition, and to provide a relatively easy production method.

[0005]

In order to solve such a problem, the inventors of the present invention have to melt-solution the ingot of a 1-12 type magnet into an alloy composed of a main phase and a rich phase in a short time. The present invention has been completed by solving this problem from the viewpoint of the composition of a magnet alloy, and the gist thereof is the composition formula R _x Fe _100-xy (V _1-a Si _a ) _y (where R includes Y). One or more rare earth elements, x = 5.5-18%, y =
8 to 20% (% is an atomic percentage) and a = 0.05 to 0.7 (atomic ratio), and the main phase is a rare earth permanent magnet characterized by having a ThMn ₁₂ type body-centered tetragonal structure.

The present invention will be described in detail below. The greatest feature of the present invention is that the third element (Ti, V, Si, Cr, Mn, W, etc.) for realizing the body-centered tetragonal ThMn ₁₂ type structure in the R-Fe system is used.
Among various combinations of Mo, Al, etc., in particular, the composite addition of V and Si2 elements stabilizes the main phase 1-12 type body-centered tetragonal structure,
It has been found that an alloy composed of a main phase and a rare earth-rich phase can be easily obtained by heat treatment for a short time.

[0007]

In the nucleation-type magnet represented by the Nd-Fe-B system magnet, the rare earth-rich phase is melted at a temperature lower than the melting temperature of the main phase during the sintering step in powder metallurgy, and the rare earth-rich liquid phase Densifies while encasing the main phase. As a result, it is possible to obtain a uniform fine structure without the individual isolated main phases being enlarged. The nucleation type magnet having such a structure is characterized in that the initial magnetization curve rises steeply from the heat demagnetized state, and the domain wall is very easy to move within the grains of the main phase. Therefore, when a reverse magnetic domain bud is generated in the crystal grain, it quickly spreads throughout the crystal grain and magnetization reversal occurs. The high coercive force of the nucleation magnet causes the rare earth-rich phase surrounding the main phase to eliminate the source of the reverse domain at the grain boundary, making it difficult for domain walls generated in phases other than the main phase to enter the main phase, resulting in magnetization reversal. Is difficult to occur. Since the magnitude of the coercive force corresponds to the domain wall energy near the grain boundary, a large coercive force is produced with a large difference in domain wall energy between the main phase and the rare earth-rich phase surrounding it. Therefore, in this type of sintered magnet, the size of the coercive force determines how uniformly the main phase is surrounded by the rich phase.

The ingot melted in the above composition formula is heat-treated at 800 to 1,100 ° C. for 2 to 10 hours,
An alloy composed of a main phase having a 1-12 type structure and a rare earth-rich phase can be easily obtained. When sintered, the rare earth-rich phase densifies while encasing the 1-12 phase of the main phase, similar to the Nd-Fe-B based magnets described above, and the reverse magnetic domain generation source is incorporated into the rare earth-rich phase and the main phase and the rich phase A high coercive force can be obtained due to the large difference in domain wall energy between the two.

As the third element for stabilizing the body-centered tetragonal ThMn ₁₂ structure which is the main phase, in addition to V and Si, Ti, Cr, Mn, W,
Although there are Mo and Al, an alloy composed of a main phase and a rare earth-rich phase can be easily obtained particularly by combining V and Si. The reason for this dissolution, a structure of the alloy as-cast fine Therefore short-time heat treatment (meaning short range diffusion)
Then, disappearance of α-Fe and formation of ThMn ₁₂ type tetragonal crystal occur. In addition, 1-12 type compounds containing V and Si are very stable and preferentially generate in the equilibrium state.
Since it is contained in the type compound, the R ₂ Fe ₁₇ compound having a rare earth content more than the 1-12 type compound, the RFe ₂ compound, etc. are not formed,
It is considered that a rare earth-rich phase is formed.

In the composition formula R _x Fe _100-xy (V _1-a Si _a ) _y of the present invention, when x is less than 5.5 atom%, the rare earth is 1-12.
It is consumed to form the type compound, the rare earth-rich phase is hard to appear, and α-Fe remains after the solution treatment, so that sufficient coercive force cannot be obtained. Further, when it exceeds 18 atomic%, the saturation magnetization is greatly reduced, so that the above range is required. Further, when y is out of the range of 8 to 20 atomic%, the body-centered tetragonal ThMn ₁₂ structure is not stabilized.
2-17 phase and α-Fe phase are crystallized and large coercive force cannot be expected. On the other hand, when the value of a is less than 0.05 (atomic ratio), α-Fe does not easily disappear, and this becomes a source of reverse magnetic domain, and the coercive force decreases. Further, it takes a lot of time for heat treatment to completely eliminate α-Fe, which is not economical, and rare earth elements having a high vapor pressure are easily vaporized, and a desired composition cannot be obtained. When the value of a exceeds 0.7, the 2-17 phase tends to crystallize,
The coercive force is greatly reduced.

Although the present invention is based on the R-Fe-V-Si system,
Part of V and Si are Ti, Cr, Mn, W, Nb, Mo, Ta, Al,
It can also be replaced with Sn, Zr, Hf, Ge. However, addition of too much causes deterioration of magnetic properties, so the substitution amount is 5
Up to about atomic%. In addition, the rare earth element to which the present invention is applicable is La, Ce, Pr, Nd, Pm, Sm, Eu, Gc, Tb, Dy, H containing Y.
One or more of o, Er, Tm, Yb and Lu.

The permanent magnet alloy according to the present invention has excellent magnetic properties by melting, casting, solutionizing, crushing, molding in a magnetic field, sintering and aging a compound having the above alloy composition by a usual powder metallurgy method. Can be realized.

[0013]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1 of actual machine) Sm metal having a purity of 99.9% by weight, M = Si, V, Cr, Ti, Mo metals having a purity of 99.9% by weight and Fe are Sm 11.
0, Fe 76.0, M 15.0 Weigh each atomic% (15.0 atomic% in total when M is 2 or more), perform high frequency melting in an inert gas, cool the melt with a Cu mold, 1,10
It was solution-treated at 0 ° C. for 2 hours and was designated as Sample No. 2. As a result of the observation of this sample by X-ray diffraction and EPMA, the metal phase was identified. V + Si-containing 1-12 phase, rare earth-rich phase. Others: α-Fe phase, 1-12 phase, 2-17
Phase, rare earth rich phase. Fig. 1 shows Sm 11.0 and Fe 76.
0, M 15.0 (V 10.0, Si 5.0) A composition image by an electron probe X-ray microanalyzer (hereinafter abbreviated as EPMA) obtained by subjecting the compound (Sample No. 2) having a composition of each atomic% to the heat treatment. Show. In the figure, the gray part is the ThMn ₁₂ type body-centered tetragonal compound, and the white part around it is the Sm-rich phase. Separately, Table 1 shows the results of measuring the magnetic characteristics (coercive force) of the sintered body with a self-recording magnetometer.

(Example 2) Sm metal having a purity of 99.9% by weight,
Ferrovanadium containing 45% Si and Fe with a purity of 99.9% by weight
Fe was weighed as shown in Table 1 (Sample Nos. 1 to 5), subjected to high-frequency melting in an inert gas, the molten metal was cooled with a Cu mold, and thereafter solution-treated at 1,100 ° C. for 2 hours. The ingot was coarsely pulverized and then finely pulverized with a jet mill using N ₂ gas to an average particle size of 3 to 5 μm. After press-molding this fine powder in a static magnetic field of 12 kOe at a pressure of 1 t / cm ² , the molded body was sintered in an inert gas at a temperature of 1,150 ° C for 1 hour, and then kept at 600 ° C. It heat-processed at the temperature for 1 hour and then quenched. Table 1 shows the results of measuring the magnetic characteristics of the sintered body with a self-recording magnetometer.

(Comparative Example) Sample No. 6 was added with no Si, and sample N
A sintered body was prepared by treating in the same manner as in Example 1 except that O.7 was not added with V, and the magnetic properties were measured and are also shown in Table 1.

[0016]

[Table 1]

[0017]

According to the present invention, the compound of the composition easily forms a structure useful for a nucleated sintered magnet by heat treatment for a short time, and a rare earth permanent magnet having excellent magnetic properties by an ordinary powder metallurgy method. A magnet can be obtained, and its utility value is extremely high in industry.

[Brief description of drawings]

FIG. 1 is a drawing showing a metal structure by EPMA of the composition of Sample No. 2 of Example 1 of the present invention.

Claims (1)

[Claims] 1. A composition formula R _x Fe _100-xy (V _1-a Si _a ) _y (wherein R is one or more rare earth elements including Y, x =
5.5-18%, y = 8-20% (% is atomic percentage), a = 0.0
A rare earth permanent magnet characterized by having a main phase having a ThMn ₁₂ type body-centered tetragonal structure, which is represented by 5 to 0.7 (atomic ratio).