JPH0569906B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention relates to a low-cost, high-performance permanent magnet alloy consisting of or mainly based on cerium (Ce)-didimium (Di)-iron (Fe)-molybdenum (Mo)-boron (B). Regarding. However, didymium is a common name for Nd-Pr alloy. Table 1 shows the classification of the main types of magnets that have been put into practical use based on their chemical composition and manufacturing method.

[Table] In the table, ○ marks indicate items that are produced, and × marks indicate items that are not produced. In the Japanese market, five types of magnets other than sintered alnico are produced. These five types of magnets account for over 99% of the total shipment value and production weight in the Japanese market (1983).
If you think of a magnet, you can say that it is one of these. The reason there are so many types of magnets is that
Each thing has its own advantages and disadvantages,
This is because they are used differently depending on the specifications required by various applications. Let's list the advantages and disadvantages of these magnets. First is sintered ferrite magnets, which are currently used in large quantities (59,000 tons in Japan, estimated in 1983) because they are the cheapest compared to other magnets. Unit price is isotropic
0.5 to 1 yen/g, anisotropic 2 to 3 yen/g,
Performance is expressed as energy product (BH) max, which is about 1 MGOe for isotropic and about 3.5 to 4.0 MGOe for anisotropic. As described above, although the performance of sintered ferrite magnets is low, the unit price is more advantageous. However, since the main body is a ceramic magnet, it is hard, brittle, and has poor impact resistance. It also has the disadvantage of being difficult to process into complex shapes. Plastic bond type ferrite magnets are made to compensate for this drawback. This magnet, which is usually called a ferrite bond magnet, has high toughness and workability, so it is resistant to cracking and chipping and can easily be made into complex-shaped magnets.Isotropic magnets are (BH)max = 0.5 ~
The unit price for 1 MGOe is approximately 0.6 yen/g, and the unit price for an anisotropic magnet is approximately 2.8 yen/g at (BH)max=1.5.
It is. The reason why the unit price of the anisotropic material is the same or higher than that of sintered ferrite and its performance is lower is that it contains 40 to 50% of Vo1% of expensive engineered plastic as a binder material. However, despite the disadvantages of high unit price and low performance of ferrite bond magnets, demand for anisotropic magnets is rapidly increasing. The reason for this is that the above-mentioned advantages are effective. Next is alnico magnets, but before the advent of rare earth magnets, this was the only magnet available to obtain high magnetic flux density, and its production value was so large that it surpassed that of ferrite magnets. However, the inherent coercive force iHc
In 1979, the small size of cobalt, the instability of cobalt prices, the difficulty of processing, and the advent of rare earth magnets led to
Demand continued to decline from 1983 onwards, and in 1983, it was finally overtaken by rare earth magnets in terms of production value. This trend is likely to continue in the future. Finally, rare earth magnets began to be manufactured on a trial basis in 1970, and in 1976
Industrial production began in 2010. Japan's production in 1976 was only 5 tons, but it has rapidly increased since then, and is estimated to have reached 290 tons in 1983. The reason why rare earth magnets have grown this much is that their energy product is overwhelmingly higher than previous magnets (sintered
30MGOe) was a successful match with market needs. However, the unit price is an order of magnitude higher than other magnets, at 40 to 50 yen/g. Furthermore, sintered rare earth magnets have the disadvantage of being very brittle and are difficult to use because they are prone to cracking and chipping. Plastic bond rare earth magnets overcome this fragility. Items manufactured by powder molding are
(BH)max=10~18MGOe, and in this range it maintains an advantage over sintered magnets. Also, recently, techniques such as injection molding and extrusion molding have been adopted for this magnet, making it easier to use and expanding its range of applications. However, since a binder is mixed in, the magnetic performance is inevitably limited, and the unit price is not actually lower than that of sintering, so the cost performance does not improve much. Conventionally, an index calculated by dividing (BH)max (MGOe) by the unit price (yen/g) has been conveniently used to evaluate the cost performance of magnets, but when actually using magnets, weight is important. Since it is an energy product per volume rather than a hit, the cost performance index should also be per volume. Therefore, if the density is e, the index ID should be ID=(BH)max/(e・unit price). Based on this index, the cost performance of the five types of magnets described above was calculated (Table 2 a, b).

〔the purpose〕

The present invention solves these problems,
The objective is to provide a magnet with high performance and low cost. [Summary] The permanent magnet alloy according to the present invention is an alloy whose main components are cerium-cydium, iron, molybdenum, and boron. In a broad sense, they fall into the category of rare earth magnets, but their composition is completely different from conventional samarium-cobalt-based magnets. Generally, 15 kinds of rare earth elements are produced as a mixed rare earth. In order to extract individual elements, the mixed rare earth must be separated and refined, and if only a certain element is used in large quantities, other elements will be left over, which is inconvenient. Therefore, the price of rare earth elements is determined not only by their abundance and importance, but also by the order in which they are extracted, how difficult they are, and their balance with other elements. As a result, Sm is approximately 30,000 yen/Kg
Mitsushi Metal is priced at just over 3,000 yen/kg (both as of 1983). Ce−Di (dijim; Nd
-Pr alloy) is contained in the mixed rare earths of monazite and bastnaesite, respectively, at approximately 75% and 70%, and is extracted at the beginning of the smelting process, so no smelting man-hours are required. In recent years, the growth in heavy rare earths (elements ranging from Sm to Lu) and the decline in demand for Mitsushi Metals has resulted in a surplus.
No worries about balance. Therefore, if it becomes used in large quantities, it will become available at a price close to that of Mitsushi Metal. The first feature of the permanent magnet alloy according to the present invention is the use of such inexpensive rare earth metals. A second feature of the permanent magnet alloy according to the present invention is that cobalt, which is one of the main components of conventional rare earth magnets, is not used. Normally, Ce-Di-Fe alone cannot be used as a ferromagnetic material due to its low Kiuri point Tc, but by adding an appropriate amount of boron, the Tc increases and the ferromagnetism becomes stable. Boron with high purity may be used, and inexpensive ferroboron may also be used. Using iron instead of cobalt frees us from resource constraints and significantly reduces alloy costs. The third feature of the permanent magnet alloy according to the present invention is that molybdenum (Mo) is added to improve the coercive force and to make it possible to obtain a large coercive force even in a bulk state. By adding Mn, the coercive force iHc is increased to a level that does not pose a problem for practical use. Also, obtaining a large coercive force in the bulk state is especially important for application to resin bonded magnets, and
Since magnetic particles of m or more can be used without any problem, the reliability and characteristics of the magnet can be improved. In addition, being able to handle magnetic powder with large particle size is also advantageous for its production. Part of Mn is Ti, Hf, V, Nb,
The effect of Mo is enhanced when at least one element of Ta is substituted. In addition, a part of B in the Ce-Di-Fe-Mo-B alloy of the present invention may be Al, Ga, In, Si, Ge, P, S, Bi, Sn,
Substitution with at least one element of Pb and C further enhances the ferromagnetic stabilizing effect. Even if a small amount of rare earth elements are replaced with La, the magnetic force will not decrease. By adding La, the rare earth component can be manufactured more easily and the alloy can be made at a lower cost. Next, the reason for limiting the composition range will be described. Atomic ratio of elements in rare earth elements R=Ce ₁ −a−bNdaPrb
The coefficients a and b that indicate this are set within a composition range that allows the Ce-Di alloy to be produced industrially at low cost. Also M=
When Fe1−x−y Mox By, R, M, and the ratio Z (Z=M/R) must be between 4.0 and 9.0 in order to produce a coercive force of 5 KOe or more. in M
The effect of Mo starts to appear when the Mo amount X is 0.01 or more, and 0.2
This decision was made because the saturation magnetic flux density decreases significantly when the value exceeds . Similarly, the range of y is determined by the reason that the effect of boron starts to appear at 0.001 or more, and if it exceeds 0.15, the coercive force and saturation magnetization decrease rapidly. [Example] Hereinafter, the present invention will be described in detail based on Examples. Example 1 Eleven types of alloys (compositional formulas are atomic ratios) with a compositional formula of Ce _0.4 Nd _0.4 Pr _0.2 (Fe _0.8 Mo _0.1 B _0.1 ) where z is taken from 4.0 to 9.0 in 0.5 increments were heated in a low frequency induction furnace. It was dissolved using B previously prepared a master alloy with Fe to make it easier to melt. Each alloy was homogenized for 4 hours at an optimal temperature between 1100 and 1200° C. in an argon atmosphere and then quenched to room temperature. Thereafter, isothermal heat treatment was performed at 820°C for 6 hours and at 650°C for 4 hours, followed by gradual cooling to room temperature at a cooling rate of 1.5°C/mm. The alloy was then ground to an average particle size of 10-20 μm and compounded with 3 wt% epoxy resin. The kneaded magnetic powder is press-molded in a 15KOe magnetic field,
I cured epoxy resin and made it into a magnet. The magnetic properties of the obtained magnets are shown in FIG. 1 according to the Z value. It can be seen that when Z is between 4.0 and 9.0, a coercive force iHc, a high residual magnetic flux density Br, and an energy product (BH) max that do not pose a problem in practical use are obtained. Example 2 A magnet was produced using the same method as in Example 1 using an alloy having the composition shown in Table 3. Table 4 shows the magnetic performance of the obtained magnet.

【table】

【table】

[Table] For each composition, properties with (BH)max of 7 or more were obtained, and in some cases, properties equivalent to the highest performance of the Sm ₂ Co ₁₇ system were obtained. It is significant that such magnets can be made at low cost. Example 3 An alloy in which part of Mo was replaced with Ti, Zr, Hf, V, Nb, and Ta was melted by the method of Example 1. However, M
=Fe _0.82-W Mo _0.1 AwB _0.08 (A is the above six elements), take 11 types of W from 0 to 0.20 in 0.02 increments,
R=Ce _0.4 Nd _0.5 Pr _0.1 , and the ratio Z of R and M was 6.0. The magnet manufacturing method was the same as in Example 1. Figure 2 shows the results when A is Zr. However, in the heat treatment after homogenization, the addition of Hf improves iHc, so in order to obtain a high energy product, iHc was moderately suppressed and optimal conditions were adopted with the aim of improving hysteresis corner formation. It can be seen that better results were obtained when Zr was added to some extent than when Zr was not added. Table 5 shows how much the performance was improved by adding the above six elements compared to before addition.

[Table] Example 4 Part of B is Al, Ga, In, Si, Ge, P, Si,
The alloy substituted with Bi, Sn, and Pb was melted by the method of Example 1. However, M=Fe _0.75 Mo _0.1 B _0.15 −uQu(Q
are the above 10 elements), R=Ce _0.4 Md _0.5 Pr _0.1 and Z
= 6.5 (RM _6.5 ), and u is 0.1 in increments of 0.01 from 0.01.
There are 10 types of ivy. Magnet production was carried out in the same manner as in Example 1. Table 6 shows the improvement in the Curie point of the alloy with the highest improvement in the Curie point compared to before addition, for each element among the magnets obtained with each substitution element (BH) max 10 MGOe or higher. become that way.

〔effect〕

As described above, according to the present invention, high-performance plastic bonded magnets and sintered magnets can be produced even by using the inexpensive rare earth compound Ce-Di, and high-cost performance not found in conventional magnets can be achieved. have

[Brief explanation of drawings]

Figure 1 shows Ce _0.4 Nd _0.4 Pr _0.2 (Fe _0.8 Mo _0.1 B _0.1 )Z
The magnetic properties of plastic bonded magnets are shown when the ratio Z of rare earths and other elements is changed in terms of composition. Figure 2 shows Ce _0.4 Nd _0.5 Pr _0.1 (Fe _0.82-W Mo _0.1
ZrwB _0.08 ) _6.0 shows the energy product of a plastic magnet when the amount w of Zr is changed. Figure 3 shows Co _0.45-C Nd _0.45 Pr _0.1 Lac (Fe _0.82 Mo _0.1
This figure shows the changes in the squareness and energy product of a plastic bonded magnet when the amount c of La is changed with a composition of B _0.08 ) _6.5 . Figure 4 shows Ce _0.45-C Nd _0.45
The energy product of a magnet obtained by sintering an alloy with a composition of Pr _0.1 Lac (Fe _0.82 Mo _0.1 B _0.08 ) _6.5 is shown as a relationship with the change in the amount of La, c.

Claims (1)

[Claims] 1 (La _1-abc Ce _a Pr _b Nd _c ) (Fe _1-xy (Mo _1-s α _s )
_x (B _1-t β _t ) _y ) In the permanent magnet alloy represented by _z , the ratio of rare earth element R to other elements M is expressed as
number of atoms of M/number of atoms of R), the coefficient a,
b, c, x, y, z are in the following range of values, 0.01≦a≦0.9 0.05≦b≦0.5 0.05≦c≦0.8 0.01≦x≦0.3 0.001≦y≦0.15 3.5≦z≦9.0, α is at least one element selected from Ti, Zr, Hf, V, Nb, Ta; β is Al, Ga,
At least one element selected from In, Si, Ge, P, S, Bi, Sn, Pb, and C, and the coefficients s and t are in the following range of values, that is, 0.01≦s≦0.99 0.01≦t≦0.99 A permanent magnetic alloy characterized by: