JPS6223060B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a precipitation magnet using R ₂ Co ₁₇ type crystals. More specifically, when melting and casting an alloy in which the ratio of the rare earth metal R and the transition metal TM consisting of Co, Cu, Fe, and Zr is 1:7.0 to 9.0 in atomic ratio, the molten metal at the time of casting is This invention relates to a method of manufacturing a permanent magnet in which columnar crystals are exposed throughout the alloy ingot by pouring from the bottom of the mold. When melting and casting R(TM) _{7.0 to 9.0 alloy} , when pouring into the mold, the molten metal should be kept quiet,
It is characterized by the fact that the macrostructure of the ingot is made into columnar crystals by pouring. An object of the present invention is to improve magnetic performance and reduce variation, and another object is to improve mass productivity. In our patent application No. 55-3226, we proposed Sm―Co―Cu―
When the Fe-Zr alloy ingot is made into columnar crystals,
It was shown that the magnetic performance of magnets using this alloy is significantly better than that of equiaxed crystals and chill crystals. If we use exactly the same manufacturing method and make a magnet from a chilled crystal alloy using an equiaxed crystal alloy and a columnar crystal alloy, we find that the columnar crystal alloy has the same characteristics as the saturation magnetization 4πIs, the coercive force iHc, bHc, or the squareness of the hysteresis loop. It was found that the performance was excellent across the board. On the contrary, equiaxed crystal alloys and equiaxed chill crystal alloys are the worst in terms of performance. Columnar chill crystal alloys produce magnets with values intermediate between these. Since the crystals of columnar crystal alloys are aligned, they have good orientation in the uniaxial direction when made into a magnet. In addition, it is thought that in this alloy, precipitates formed by heat treatment are more uniform than in other alloys. This improves the squareness of the hysteresis. It is also believed that the crystal structure and morphology of the precipitates are formed in a way that increases iHc better than those of equiaxed crystals. The origin of equiaxed crystals was not well known before, but it is now believed that crystals formed in a mold or on a cooled surface of the liquid become free crystals, and these free crystals form equiaxed crystals. (A. Ohno, T. Motegi and H. Soda:
Trans ISIJ.11 (1971) 18). It has also become clear that the movement of the molten metal within the mold during pouring is very important for the formation of columnar crystals. As mentioned above, the present invention promotes columnar crystallization of an ingot.
It's something that can be easily obtained. Therefore, the method of the present invention consists in injecting hot water into the mold from the bottom of the mold. In this case, the molten metal is poured quietly into the mold, and no turbulent waves occur on the surface of the molten metal. Therefore, the crystals formed on the casting wall are not released, and the crystals tend to grow from the casting wall surface. Due to this, the columnar crystals grow to the inside of the ingot. The method of the present invention has very few chill crystals, mostly columnar crystals, and some equiaxed crystals.
Macrostructure including columnar crystals and chill crystals accounts for 50% of the total
The above is preferable. The composition of the alloy in the present invention is:
Contains 21 to 28% by weight of a rare earth metal R consisting of one or more of Sm, Y, La, Ce, and Pr, and the remainder is a transition metal TM consisting of Co, Cu, Fe, and Zr; and TM ratio is 1:7.0~9.0
It is an R ₂ TM ₁₇ series alloy. Of course, magnetic performance can also be improved using RTM ₅ alloy. Furthermore, the method of the present invention is applicable to resin-bonded magnets made using alloy ingot crystals as they are. Example 1 The composition of alloy ingot is Sm
(Co _0.61 Cu _0.07 Fe _{0.3 Zr 0.02} ) _It was melted in _a high _frequency furnace to give _{8.3 .} Figure 1 shows the conventional method of pouring molten metal, in which the molten metal was poured into mold 1 (S15C mold) from the top 3 at a temperature of 1550°C. At this time, the water surface 2 causes violent waves. The macrostructure of the ingot cooled and solidified in this way has columnar crystals near the casting wall surface, as shown in FIG. 2, but most of them are equiaxed crystals. The columnar crystal space factor is approximately
It was as low as 20%. On the other hand, the casting method of the present invention was
As shown in the figure. The raw material whose weight was adjusted to give the above composition alloy was melted in a high frequency furnace. This molten metal (water temperature 1600℃)
From the socket, 7 made of 8 alumina cement
It is introduced into the mold from the bottom of the mold through the runner runner No. 4. In this way, the molten metal 5 is gently pushed up the mold wall. Since the mold 4 is made of S15C material, it is cooled from the casting wall. The macrostructure of the ingot thus obtained is shown in FIG.
It was found that almost 60-70% of the ingots were columnar crystals, although there was a small amount of equiaxed crystals in the center of the ingot. Next, permanent magnets were made from 0.5 kg each of the alloy ingots made by the conventional method and the method of the present invention according to the magnet manufacturing process shown in FIG. First, in an Ar gas atmosphere,
The bulk ingot was subjected to solution treatment. The temperature is
The temperature was 1150°C for 10 hours, and the temperature was rapidly cooled to room temperature at a rate of 10 to 30°C/min. Subsequently, aging treatment for magnetic hardening was performed at 800°C for 24 hours. Next, the ingot was crushed into coarse powder (-80#) using a hammer crusher and then finely crushed in a ball mill under a non-oxidizing atmosphere. The powder particle size at this time is 3μm to 50μm
m, and the average particle size was 15 μm. The thus obtained magnetic powder was used to obtain a resin-bonded magnet according to Production Method 1. First, the binder is a one-component epoxy resin with a viscosity of 1000 CPS, added with 2.0 Wt%, mixed with magnetic powder, and magnetically oriented in an electromagnet with a magnetic field strength of 15 kg.
Further pressure molding was performed at 5 tons/cm ² . Next, the molded body was extracted from the mold, and the binder was cured by heating at 150°C for 2 hours. The dimensions of the molded body thus obtained are φ15×
This is a cylindrical sample with a diameter of 10m/m. In addition, 10 samples each were prepared for both the conventional method and the present invention method. The magnetic properties of this sample were examined using a DC magnetic flux meter (BH measuring device). The results are shown in Table 1.

[Table] As you can see from Table 1, resin bonded magnets are
It was found that the magnetic properties vary greatly depending on the degree of columnar crystallization of the cast structure. Therefore, the process of melting and casting is extremely important for improving the performance of magnets. According to the method of the present invention, even if the alloy has the same composition, its performance is approximately 1.2 in terms of (BH)max.
It was doubled. Also, regarding the variation in (BH)max, in terms of the average deviation σ, it was σ=0.05 for the method of the present invention and σ=0.15 for the conventional method. Example ₂ An alloy _of Sm( _{Co0.6Cu0.08Fe0.3Zr0.02} )z _composition (z _{is 7.0} to _9.0 ) was melted and cast into a mold in the same _manner as in Example 1. Next, a magnet was manufactured according to the same manufacturing process as in Example 1. The degree of columnar crystallization for each composition (change in Sm) is 20 to 30% in the conventional method;
The method of the present invention yielded 65% to 75%. FIG. 6 shows magnetic properties, and with respect to changes in Z, the method of the present invention
4πIs (saturation magnetization) and iHc (coercive force) compared to the conventional method
It is also excellent. In addition, iHc changes with respect to changes in Sm.
is slowing down. In other words, Sm generated during the process
It has the advantage of preventing deterioration of magnetic properties due to oxidation and paper-out. The other one is also on the row Z side.
Since iHc8KOe~10KOe can be obtained, high 4πIs
At the same time, there is also the advantage of being able to improve performance. In this way, the method of the present invention has the advantage of being able to increase the width of the composition range of the Sm ₂ Co ₁₇ type magnet and moving it to the lower Sm side (higher Z side). In the example, an example was shown in which Sm was used as the rare earth metal, but similar effects can be obtained even if a part of Sm is replaced with one or more of Y, La, Ce, and Pr. As described in detail in the Examples above, it has been found that promoting columnar crystallization of the alloy ingot is very effective in improving the performance of resin-bonded magnets. This has enabled the industry to improve the magnetic performance of Sm ₂ Co ₁₇ type magnets compared to conventional magnets, making it possible to manufacture low-cost, high-performance magnets.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 5 are graphs obtained in Example 1 of the method of the present invention. 1st
Figure 2 is a cross-sectional view showing the conventional pouring method and mold, and the macrostructure of the cast alloy. 1... Mold (S15C material), 2... Molten metal, 3... Pouring section, Figures 3 and 4 show the pouring method of the present invention, a cross-sectional view of the mold, and the macrostructure of the cast alloy. 4... Mold (S15C material), 5... Molten metal, 6... Molten metal pouring section, 7... Molten metal flow, 8... Mold for runner (alumina material), Figure 5 shows the production of resin-bonded magnets. A diagram showing the process.
Figure 6 shows the amount of Sm (Z value) obtained in Example 2.
A diagram showing magnetic properties.

Claims (1)

[Claims] 1 An alloy containing 21 to 28% by weight of rare earth metals consisting of one or more of Sm, Y, La, Ce, and Pr, and the balance consisting of Co, Cu, Fe, and Zr is powdered and a resin binder is prepared. In a method for producing a resin-bonded permanent magnet in which an alloy having the composition described above is melted and cast, the alloy ingot is formed by pouring the molten metal containing the alloy from the bottom of the mold and cooling it. A method for producing a permanent magnet, characterized in that the macrostructure of the permanent magnet is mainly amorphous.