JPH031803B2 - - Google Patents

Description

[Detailed description of the invention]

The purpose of the present invention is to provide Sm-Co-Cu-Fe-Ti-M
In order to improve the magnetic performance of alloys made of alloys, it is important to make the cast structure of the alloy ingot into columnar crystals as much as possible. In our patent application No. 55-3226, we proposed Sm-Co-Cu-
It was shown that when the Fe-Zr alloy ingot is made into a columnar crystal, the magnetic performance of a magnet using this alloy is much better than that of a special axis crystal or chill crystal. The present invention is based on the fact that Sm-Co-Cu-Fe
This shows that a similar effect can be obtained even if the special element M is added to a Ti-based alloy to increase the columnar structure. The present invention heat-treats a cast ingot lump as it is, crushes it, mixes it with a binder, molds it in a magnetic field,
It is extremely effective in improving the performance of resin, metal, or ceramic bonded magnets, which are produced by strengthening the binding of binders. In other words, the process before pulverization is the same as for cast magnets, and the crystalline state of the cast ingot is used as is, so the special element M added in a small amount to the cast ingot can be used to add the columnar crystals that provide the above-mentioned high-performance magnetic properties. Due to its effect, it is possible to obtain a high-performance magnet by producing as much as possible. Generally, when molten metal is poured from a crucible into a mold, it begins to solidify from the mold. This is explained by the fact that englios (crystal buds) in contact with a solid foreign material have a smaller energy barrier to stable formation than those floating in the melt without contact. Crystals formed in the mold grow into the molten metal while competing with neighboring crystals. The competitive growth region of crystals in the outermost layer of the ingot, as shown in FIG. 1, is called the chill layer. Since crystals have anisotropy in growth rate, crystals whose direction of maximum growth rate is parallel to the direction of heat flow grow preferentially, suppressing the growth of adjacent crystals. During crystal growth, the closer the preferred orientation is to the heat flow, the longer the crystals survive, and other crystals are weeded out.As a result, the number of crystals decreases toward the inside of the ingot, forming columnar crystal zones. When the conditions are right, the columnar crystal bands collide and solidification is completed, but as shown in FIG. 1, equiaxed crystals are usually formed inside the columnar crystals. Although the origin of equiaxed crystals was not well known before, it is now known that crystals formed in a mold or on a cooled liquid surface are liberated and become free crystals.
It has become clear that these free crystals form equiaxed crystals (A. Ohno, T. Motegi and H.
Soda: Trans. ISIJ.11 (1971) 18). A magnet using a Sm-Co-Cu-Fe-Ti-M six-element alloy is called a precipitation hardening type or a two-phase separation type magnet. This is because a different phase is precipitated in the matrix and magnetically hardened. This series of magnets was initially made of Sm-Co-Cu ternary alloy, mainly
Since it was magnetized with a composition using Sm ₂ Co ₁₇ crystals,
It has been widely developed today. It is known that when Co is replaced with Fe, the saturation magnetization 4πIs increases up to a certain amount. In the range where 4πIs increases, the crystal exhibits uniaxial ease because Sm ₂ (Co ₁ −
xFex) ₁₇ , X is in the range of 0 to 0.6. This fact does not change even if a certain amount of Cu is substituted for Co. When Ti is further added to Sm ₂ (Co Cu Fe) ₁₇ , the magnetic performance can be greatly improved even if the amount of Ti is minute. That is, by adding Ti, even if the amount of Cu is small or the amount of iron is large, a coercive force iHc sufficient for a practical magnet can be obtained, making it possible to create a magnet with a high energy product. As mentioned above, in this alloy, it has become clear that among the chill crystal zone, columnar crystal zone, and equiaxed crystal zone, the columnar crystal zone is the most suitable for making into a magnet. Furthermore, an ingot in which a small amount of special element M is added to the alloy to increase the columnar crystal zone in the ingot is superior to an ingot cast under the same conditions. An example will now be explained using a resin bonded rare earth cobalt magnet. This magnet is made from a magnetic alloy using the method shown in FIG. If we use the same manufacturing methods to make equiaxed crystal alloy, columnar crystal alloy, and chilled crystal alloy magnets, we find that columnar crystal alloy has all the advantages of saturation magnetization 4πIs, coercive force iHc, bHc, and squareness of hysteresis loop. It was found to be excellent in terms of performance. On the contrary, equiaxed crystal alloys and chill crystal alloys are inferior in performance. In addition, ingots cast under the same conditions but with a small amount of special element M added to increase the columnar crystal zone, and ingots without special element M added, the columnar crystal zone was increased by adding special element M. The performance is better. 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 direction that increases iHc better than that of equiaxed crystals. Therefore, in order to obtain a good magnet, it is important to manufacture this alloy in such a way that the chill crystals near the mold are made into columnar chill crystals, and the other parts are made into columnar crystals. Since the amount of chill crystal bands is small in the overall alloy, the most important thing in manufacturing is to prevent equiaxed crystal bands and increase the ratio of columnar crystal bands. For this reason, Sm−Co−Cu
-Fe-Ti alloys include S, Se, Te, Ce, Pb, Cd,
By casting with trace amounts of Bi, Si, etc. added,
Oxides that promote nucleation of crystallization from the melt,
Nitride, etc. is wrapped in sulfide, etc. to inactivate the nuclear action, and special element M and oxygen, nitrogen, etc. in the melt combine to generate oxides, nitrides, etc. that become the nucleus for crystal formation. The formation of equiaxed crystals is suppressed as much as possible. In this case, although the effects are not necessarily the same depending on the added elements, they play the same role in promoting columnar crystals. In addition, from a structural perspective, the most effective effect of columnar crystallization is expected when the composition is expressed as the composition formula Sm(Co _1-UVWX Cu _U Fe _V Ti _W M _V ) _Z using atomic ratios. , 0<U<0.3 0<V<0.6 0<W0.1 0<X<0.1 5.0Z9.0. Further, in order to obtain a high-performance magnet, a more preferable composition range is as follows: 0<U0.2 0<V0.5 0<W0.1 0<X<0.1 6.5Z9.0. This is the same composition range as shown in the claims. The reason for limiting the components and composition range will be explained below. In this alloy system and its composition range, Sm-
Co type is the basic type. Cu is added to the Sm ₂ Co ₁₇ type alloy to obtain coercive force, and adding Cu improves iHc. However, 4πIs decreases. Therefore, as a practical magnetic material, Sm
(Co _1-U Cu _U ) The value of U in _Z is limited to 0.2. When the value of Z is between 5Z8.5, Sm
-Co alloy is separated into SmCo ₅ type compound and Sm ₂ Co ₁₇ type compound. The value of 4πIs is 2% higher for Sm ₂ Co ₁₇ . Therefore, in order to realize high 4πIs, Z should be
6.5 or higher is desirable. On the other hand, when Z becomes 9.0 or more,
This is not preferable because the iHC is significantly reduced and a large amount of CoFe phase comes out, which impairs the squareness of the hysteresis loop. Ti is significantly alloyed
Since it lowers 4πIs, if more than 0.1 is added, there is no point in increasing Fe and reducing Cu to increase 4πIs. The effect of M varies somewhat depending on the added element, but if it exceeds a certain amount, 4πIs and iHc decrease, so taking this limit into consideration, the upper limit was set at 0.1. still,
These indicate the total amount of composite addition, and the ratio is not particularly specified. The binder can be a variety of polymers, such as epoxy, phenol, rubber, polyester, etc.
The metal binder is preferably a low melting point alloy with a melting point of 400°C or less. The present invention will be explained below with reference to Examples. Example 1 Raw materials having a composition of Sm (Co _0.6 Cu _0.07 Fe _0.3 Ti _0.02 S _0.01 ) _8.2 after casting were prepared, and a total of 1 kg of alloy was melted in an Ar gas atmosphere using a high frequency furnace.
Heat water at a temperature of 1600°C in an iron mold as shown in Figure 3.
I put it in. The molten metal is mainly cooled from the side wall, and the first
The structure was as shown in the figure. Figure 1 shows the structure when the ingot is cut at the center. In these parts, the chill layer is denoted as A, the columnar structure as B, and the equiaxed structure as C. Alloy ingots A, B,
Each cast ingot was cut out from section C, and a resin-bonded magnet was produced according to manufacturing method 1 shown in FIG. Solution treatment: 1150℃ for 15 hours, aging treatment: 800℃
The test was carried out in an argon atmosphere for 18 hours. 1.8 wt % of an epoxy resin as a binder was kneaded into fine magnet powder that had been ground to an average particle size of 12 μm using a ball mill method. This kneaded mixture was press-molded in a 16KG magnetic field, and a suitable amount of heat was applied to the molded body to harden the resin (cure treatment) to complete the magnet. The results are shown in Table 1. As can be seen from the table, the magnetic performance obtained from the columnar crystal zone in section B is much better than that obtained from the equiaxed crystal zone in section C. Although the chill crystal zone in part A is lower than that in part B,
better than the department.

[Table] However, SQ is an index indicating the squareness of the hysteresis loop, and is given by SQ = Hk/iHc. Hk is on the 4πI-H demagnetization curve
It is the magnitude of the magnetic field given by 0.9Br. From these results, it became clear that the columnar crystal part of part B had the best performance. The chill crystal zone in part A is generated only in the vicinity of the casting wall, and is very small in the whole ingot, so the most important thing in ingot production is how to suppress the formation of equiaxed crystals and form columnar crystals. The key is to develop crystals. Incidentally, it seems that part A used in this example contains a certain amount of columnar crystal B, judging from the occurrence of part A. Example 2 In the same manner as in Example 1, resin-bonded magnets were manufactured from alloys having the compositions shown in Table 2. However, the solution treatment was carried out at the most appropriate temperature between 1130 and 1180°C for 18 hours.

[Table] This example was carried out on ingots of sections B and C. The results are shown in Figure 4. Even as the amount of Fe increases, better magnetic performance is obtained in columnar zone B. This revealed that even if the amount of Fe is increased to a certain extent, a certain level of iHc can be obtained. Example 3 In exactly the same manner as in Example 2, resin-bonded magnets were manufactured from alloys having the compositions shown in Table 3. The results are shown in Figure 5. In Sm (CoCuFeTiM) type ₁₇ alloy, iHc decreases as the amount of Cu decreases, but in columnar crystals, iHc decreases even at low Cu compositions compared to equiaxed crystals.
It can be seen that a high value can be obtained. In addition, the columnar crystal portion has better squareness.

[Table] Example 4 In exactly the same manner as in Example 2, resin-bonded magnets were manufactured from alloys having the compositions shown in Table 4. The temperature of the hot water during alloy casting is 1650℃. The cast ingot has a cross-sectional macrostructure as shown in FIG. The proportion of columnar structure in B is approximately 55% in alloy No. 1, and in alloy No. 2 ~
It was 75-85% for Alloy No. 4 and 60-75% for Alloy No. 5-6. The proportion of columnar structure was estimated by observing the cross section of the ingot under a microscope and using the mesh method.

【table】

[Table] The results are shown in Table 5. As can be seen from Table 5,
The one with the most columnar structures has the best magnetic performance. In this way, the alloy composition includes S, Se, Te,
It can be seen that the magnetic performance is improved by adding a small amount of special elements M such as Ce, Pb, Cd, Bi, and Si to promote the columnar structure as much as possible.

[Table] Example 5 A resin-bonded magnet was manufactured using the alloy having the composition shown in Table 6 in exactly the same manner as in Example 2. The results are shown in Table 7.

【table】

[Table] As shown above, it was possible to obtain a magnet with sufficiently high magnetic performance even when the value of Z was changed. In this way, in the Sm-Co-Cu-Fe-Ti alloy,
By adding trace amounts of S, Se, Te, Bi, etc.
By further promoting columnar crystallization of alloy ingots, the performance of Sm ₂ Co ₁₇ type magnets bonded with resin, metal, or ceramic was improved. The high performance magnet of the present invention has wide industrial applications such as step motors for watches, micro speakers, coreless motors, and magnetic sensors.

[Brief explanation of the drawing]

FIG. 1 is a cross section of an ingot cast into a mold, taken along the center of the mold. A, B, C
represent the chilled layer, columnar layer, and equiaxed layer, respectively. D is the cross section of the mold. FIG. 2 shows the manufacturing process of the resin-bonded magnet. Figure 3 shows an iron mold. All walls are 15mm thick. Unit of length is mm
It is. Figure 4 shows Sm(Co _0.9-V Cu _0.07 Fe _V Ti _0.02
S _0.01 ) The magnetic performance of the resin-bonded magnet when V is changed in the composition of _8.2 is shown. Figure 5 shows Sm
(Co _0.75-U Cu _U Fe _0.22 Ti _0.02 S _0.01 ) In the composition of _8.3 ,
The magnetic performance of the resin-bonded magnet is shown when U is changed.

Claims (1)

[Claims] 1. A rare earth cobalt permanent magnet made by kneading a binder into powder of an alloy mainly composed of Sm ₂ Co ₁₇ type crystals and compacting the resultant powder, wherein the composition using atoms as the alloy is Sm ( Co _1-uvwx Cu _u Fe _v Ti _w Mx)z (0<u<0.2 0<v<0.5 0<w<0.1 0<x<0.1 6.5≦z≦9.0 M stands for S, Se, Te, and Bi. 1. A rare earth cobalt permanent magnet characterized by using an alloy represented by the following formula and whose ingot macrostructure at the time of casting is mainly a columnar crystal structure.