JPH0137462B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a rare earth cobalt permanent magnet alloy mainly composed of Sm ₂ Co ₁₇ type crystals. An example will be explained using a resin bonded rare earth cobalt magnet. This magnet is produced by the manufacturing method shown in Figure 1, in which the alloy is melted and cast, hardened magnetically through container treatment and aging treatment, and then crushed into powder, after which a binder is mixed, Magnetization can be achieved by two methods: coating and molding or impregnation with a binder after molding. The magnetic performance of this magnet depends on the alloy composition, heat treatment, powder particle size and shape, binder type,
It has long been known that pressing in a magnetic field is affected by the strength of the magnetic field, the pressing pressure, and the molding method. This time, we newly discovered that the magnetic performance of a magnet changes significantly depending on the macrostructure of the cast ingot. Generally, when molten metal is poured into a mold from a crucible, the metal melt first contacts the walls of the mold and is rapidly cooled to the extent that extensive nucleation occurs, creating a chilled crystalline structure. Next, as heat flows into the mold, the columnar crystal structure extends inward perpendicular to the mold wall. When the heat flow gradually stops, the crystal structure changes to a columnar crystal structure and an equiaxed crystal structure appears, and solidification in the mold is completed. When we conducted various experiments on the three types of structures mentioned above using cast magnetic alloys, we found that the one with a columnar crystal structure was the most magnetically superior. These experiments were carried out using Sm−Co−Cu
An alloy with a five-element composition of -Fe-Nb was used. At this time, the effect of the columnar crystal structure became evident.
The composition had a Sm ₂ Co ₁₇ type crystal structure with an Sm content of 21 to 28 wt%. Example 1 An alloy having the composition of Alloy 1 in Table 1 was subjected to induction welding.

[Table] Using a melting furnace, 1 kg was melted in an alumina crucible and placed in an iron mold with a wall thickness of 10 mm as shown in Figure 2.
It was cast at a temperature of 1500℃. At that time, it took the form of an organization shown in Figure 3. FIG. 3 shows the structure when the ingot is cut at the center. Among these parts, the chill crystal structure is called A, and the columnar crystal structure is called B.
And let C be the equiaxed crystal structure. In this example, ingots were cut from cast ingots A, B, and C of Alloy 1, and they were solution-treated at an optimal temperature between 1140 and 1180°C, and then aged at 800°C. Magnetically hardened. It was crushed into powder and then kneaded with an organic binder. The kneaded mixture is press-molded in a magnetic field, and the resin in the molded body is cured by applying appropriate heat (cure treatment).
So, I completed the magnet. The relationship between the magnetic performance and the structure of the alloy is shown in FIGS. 4 and 5. FIG. 4 shows the relationship between the coercive force iHc and the aging time at 800°C, and the symbols A, B, and C in the figure indicate the chill crystal structure, columnar crystal structure, and equiaxed crystal structure, respectively. FIG. 5 shows the relationship between saturation magnetization Ms and aging time. As can be seen from FIGS. 4 and 5, higher magnetic performance was obtained in the columnar crystal structure area than in other areas. Example 2 Alloys 2 and 3 shown in Table 1 were melted in the same manner as in Example 1, and heated to 1500°C in the iron mold shown in Figure 6.
It was cast at a temperature of In Figure 6b, copper pipes are placed on the outside so that the mold can be cooled with water. Figure 6a shows an air-cooled mold. Both molds are the same size, shape, and material, except for the water cooling system. In addition, alloys 2 and 3 were melted in the same manner as in Example 1, and an ingot was obtained which was left to cool slowly in a crucible. Observing the structures of these three types of ingots with different cooling rates, we find that for both Alloys 1 and 3, the water-cooled ones are almost entirely chilled crystals, while the air-cooled ones are made up of columnar crystals at over 90 vol%. The crystals were coarse equiaxed crystals. For Alloys 1 and 3, three types of ingots were solution-treated at optimal conditions between 1140 and 1180°C, followed by 2 hours at 800°C and an additional 700°C.
It was aged at ℃ for 4 hours. Then, a resin-bonded magnet was manufactured in the same manner as in Example 1. The results are shown in Tables 2 and 3. Table 2 shows the results for Alloy 2, and Table 3 shows the results for Alloy 3.

【table】

[Table] As can be seen from Tables 2 and 3, it can be said that for Alloys 1 and 3, the air-cooled ingots made of columnar crystals have the best magnetic performance. As explained above, by utilizing the columnar crystal structure, the magnetic performance of Sm ₂ Co ₁₇ type magnets can be improved compared to conventional magnets, making it possible to manufacture inexpensive and high-performance magnets.

[Brief explanation of drawings]

FIG. 1 shows the manufacturing process of a resin-bonded magnet.
Figure 2 shows a round iron mold. Thickness is everything
It is 10mm. The unit of length is mm. Figure 3 shows
This is a cross section taken in the longitudinal direction through the center of the ingot cast into the mold shown in FIG. 2. A, B
And C indicates each structure of chill crystal, columnar crystal, and equiaxed crystal. D is a cross section of the mold. Fourth
The figure shows the relationship between aging time and coercive force (iHc) in the magnetic performance of magnets obtained from ingots of chill crystal A, columnar crystal B, and equiaxed crystal C. FIG. 5 shows the relationship between aging time and saturation magnetization (Ms) in a magnet similar to that in FIG. 4. Figure 6 shows a square iron mold. A
is iron, and B is water-cooled copper pipe. All units in the figure are mm.

Claims (1)

[Claims] 1 An alloy mainly composed of Sm ₂ Co ₁₇ type crystals is melted, cast, crushed into powder, and then mixed with a binder.
In the method for producing a rare earth cobalt permanent magnet alloy by coating or impregnating and forming, the alloy includes samarium (Sm), cobalt (Co), copper (Cu),
A rare earth cobalt permanent alloy consisting of iron (Fe) and niobium (Nb), with an Sm content in the range of 21 to 28% by weight, and a macrostructure having a columnar crystal structure. Method of manufacturing magnetic alloy.