JPS629658B2 - - Google Patents

Description

[Detailed description of the invention]

Field of Application This invention relates to an improvement in the manufacturing method of rare earth cobalt permanent magnets of the R ₂ M ₁₇ series (R is a rare earth element, M is a transition metal element). Introducing a treatment process,
After that, pulverization, compression molding, sintering, and
The present invention relates to a method for manufacturing a permanent magnet, which improves and stabilizes magnetic properties by cooling to a specific temperature or lower at a specific cooling rate, and which eliminates an aging treatment step. Background technology Rare earth cobalt magnets have a higher
As a permanent magnet material with an extremely high coercive force and a large energy product, demand for it has increased rapidly in recent years, and its applications are wide-ranging, mainly in the electronics industry. These rare earth cobalt magnet alloys have both sufficiently high saturation magnetization strength (4ΠIs) and crystal magnetic anisotropy (K), making them excellent permanent magnet materials with high coercive force and energy product. It is known that there is. Among the above alloys, especially
RM ₅ series and R ₂ M ₁₇ series alloys have attracted attention, and their industrialization has been progressing. Among these, for rare earth cobalt magnets having an RM ₅ alloy composition, a magnet material with a maximum energy product of 20 MGOe, which is close to the theoretical energy product value, has already been obtained. Therefore, in order to obtain even higher magnetic properties,
High saturation magnetization, that is, high molar ratio of M
R ₂ M ₁₇ rare earth cobalt magnets have started to attract attention. However, if the amount of M is simply increased, the coercive force, which is one of the basic characteristics of the magnet, will be significantly reduced, and the characteristics of a practical permanent magnet will not be sufficiently obtained.
Therefore, conventionally, Sm was mainly used as the R component,
Regarding the constituent components of M, attempts were made to improve performance by varying the combinations and proportions of each component.
Many things have been done. Here, to explain the conventional manufacturing method of R ₂ M _17- based rare earth cobalt magnet alloy, this magnet alloy is manufactured through the following manufacturing steps: melting, crushing, press molding in a magnetic field, sintering, and aging treatment. Melting is performed in an inert atmosphere such as argon gas using an arc button melting furnace, a high frequency melting furnace, or the like. Grinding consists of coarse grinding and fine grinding processes, and after coarse grinding in a Jyokratuar iron mortar, etc., it is processed using a ball mill, vibration mill, jet mill,
Finely pulverize using a mill or the like. Press molding in a magnetic field uses a mold to produce 8kOe~
A compression molded body is made by orienting the powder in a 15kOe magnetic field. Sintering is performed in a non-oxidizing atmosphere such as argon, hydrogen, etc. or in vacuum at a temperature range of 1100°C to 1250°C. Subsequently, aging treatment is performed in a temperature range of 300°C to 950°C to obtain the final permanent magnet gold. However, the magnetic properties of the permanent magnets obtained by the above-mentioned conventional manufacturing method are low and highly variable, and various phases coexist in the metallographic structure, sometimes causing a knick on the demagnetization curve. There was a problem that it could not be used as a practical permanent magnet material and required many manufacturing steps. Purpose of the Invention The present invention solves the problems caused by the conventional manufacturing method described above, and has even higher holding power and higher energy product.
The purpose is to provide an R ₂ M ₁₇ -based rare earth cobalt permanent magnet material and to omit the aging treatment process. Composition of the Invention This invention consists of an R ₂ M _17- based magnetic alloy consisting of a rare earth element R and a transition metal M (where R is Y, La, Ce, Pr, Nb, Sm
and a combination of two or more of Mitsushi metals, M is one or two of Cu, Fe, or Ni.
Combinations of more than one species and a part of the M include Mn, Ti, Nb,
After melting and casting a combination of Zr, Ta, and Hf (substituted with one or more of the elements), solution treatment is performed at 1150°C to 1210°C for 1 to 12 hours, and then Rapid cooling is performed to generate 90% or more of the metallic phase RM ₇ phase, and the alloy is further crushed and compression molded, and this compression molded body is sintered in a vacuum or in an inert atmosphere,
After that, by cooling to below 800°C at a cooling rate of 20°C/min to 500°C/min, the conventional aging treatment process is omitted and the R ₂ M ₁₇ phase is reduced by 55% to 55% in terms of metal phase.
It is characterized by obtaining a permanent magnet with a residual RM of 85% and ₅ phases. Effects of the Invention By subjecting the present magnet alloy after melting and casting, which is a feature of this invention, to liquefaction treatment and rapid cooling treatment, and cooling it at a specific cooling rate to 880°C or less after sintering, the following can be achieved. It has a remarkable effect on improving the magnetic properties of permanent magnets such as. The mechanism by which the high magnetic properties of this R ₂ M ₁₇ -based magnet alloy appear is that the metal phase that makes up this magnet alloy becomes a single phase with a TbCu ₇ crystal structure (RM ₇ phase) during sintering. The Th ₂ Zn ₁₇ crystal structure phase (R ₂ M ₁₇
phase) and the CaCu ₅ crystal structure phase (RM ₅ phase) are finely decomposed and precipitated. This TbCu ₇ crystal structure phase is an essential metal phase for this alloy, and after melting or sintering,
If there is a small amount of TbCu ₇ crystal structure phase, high magnetic properties cannot be obtained no matter what magnetization process is performed afterwards. This is because the TbCu ₇ crystal structure phase is a metallic phase that is stable only at high temperatures and within a certain narrow composition range, and it cannot be dissolved or
As the temperature drops during the casting process, etc., the
Decomposed into Th ₂ Zn ₁₇ crystal structure phase and CaCu ₅ crystal structure phase.
This is because the TbCu ₇ crystal structure phase is precipitated, and once the TbCu 7 crystal structure phase is decomposed and precipitated, it does not easily recover to the original TbCu ₇ crystal structure phase. Moreover, in the normally used magnetization process of melting and casting, rapid cooling of the molten ingot is industrially difficult, and the solidification process differs depending on the cooling rate, so that other than the TbCu ₇ crystal structure phase already forms after casting. In addition, it contains a considerable amount of magnetically unfavorable Th ₂ Zn ₁₇ crystal structure phase, Fe-Corich primary crystal, and CaCu ₅ crystal structure phase. Furthermore, since rare earth elements have a high vapor pressure and are chemically active, ingots obtained by normal processes have significant compositional fluctuations and are likely to produce the above-mentioned undesirable metal phases. Therefore, the solution treatment process for melted and cast ingots, which is the first feature of the present invention, includes melting,
After casting, the ingot is held in a temperature range of 1150℃ to 1210℃ for 1 to 12 hours, and after treatment, it is rapidly cooled using liquid nitrogen, water, etc., and the metal phase is RM ₇ phase of 90% or more. That's true. Reason for limitation The reason why the solution treatment temperature was limited to 1150°C to 1210°C is that below 1150°C, the TbCu ₇ crystal structure phase, which is stable only at high temperatures, becomes ordered and immediately
This is to precipitate the Th ₂ Zn ₁₇ crystal structure phase and the CaCu ₅ crystal structure phase, and at temperatures above 1210℃,
An excess of about 10% or more of the melt phase is generated in the metallic phase, which increases _microscopic compositional fluctuations and significantly deteriorates the magnetic properties. In order to prevent this, the solution treatment temperature should be between 1150°C and 1210°C. Next, the reason why the solution treatment time was set to 1 hour to 12 hours is as follows. Generally, when producing large ingots, the ingots are slowly cooled during casting, so the Th ₂ Zn ₁₇ crystal structure phase and Fe
-Corich primary crystals tend to form a magnetically harmful metallic phase, which increases the solution treatment time.
If the solution treatment time is less than 1 hour, a sufficient TbCu ₇ crystal structure phase cannot be obtained. If the time exceeds 12 hours, it will take too long for industrial purposes, and compositional fluctuations due to evaporation and oxidation of R and generation of magnetically harmful metal phases will be significant. Therefore, the solution treatment time is set to 1 to 12 hours. By the above optimum solution treatment at 1150°C to 1210°C for 1 hour to 12 hours, the metal phase can be made into a RM ₇ phase of 90% or more. Ingots exhibiting a metallic phase of less than 90% of the _RM7 phase will not exhibit excellent magnetic properties no matter what magnetic process is performed. Next, sintering in the manufacturing process is performed at 1150°C or higher in a non-oxidizing atmosphere such as argon or hydrogen, or in air.
Sintering is carried out in a temperature range of 1210℃ to improve sintering density and magnetic properties. Here, in the metal phase after sintering,
It is essential for the amount of _RM7 phase to be at least 70%, preferably at least 90%, in order to obtain high magnetic properties. Further, sintering under the following conditions is effective in further improving the magnetic properties. That is, the sintering method is a sintering process in which the compression molded body obtained above is heated from room temperature to 800°C at a rate of 4 to 20°C/min in a vacuum atmosphere of 1 × 10 ^-2 Torr or less. It's a method. Regarding the temperature increase rate, if the temperature increase rate is less than 4℃/min, it will take more than 3 hours to reach 800℃, which is industrially unsuitable, and if the temperature increase rate exceeds 20℃/min, cannot sufficiently remove adsorbed gases, moisture, etc. Further, the degree of vacuum during heating is preferably 1×10 ⁻² Torr or less in order to prevent oxidation of the compression molded body during the heating process. Next, the sintering atmosphere is changed to
During the heating time of 10 to 120 minutes from 800℃ or higher to the sintering temperature and the sintering temperature holding time of 0.5 to 4 hours, mutual diffusion of R and M components is promoted, and the TbCu ₇ crystal structure phase is formed. In order to stabilize the sintering density and improve magnetic properties by increasing the sintering density,
Create an argon gas atmosphere with a reduced pressure of 50 Torr to 350 Torr. If the argon gas atmosphere pressure is less than 50 Torr, the R component will evaporate preferentially, resulting in a composition that is considerably different from the final magnet composition, which will significantly impair the magnetic properties. The mutual diffusion of each component is insufficient, and the sintered density is low, resulting in poor magnetic properties. Next, regarding the cooling conditions after sintering, which is a feature of this invention, when cooling to a temperature of 800°C or less at a cooling rate in the range of 20 to 500°C/min, aging treatment after sintering, which is usually performed. There is no need to do this. The reason for limiting the cooling rate above is 20℃/min.
At a cooling rate of less _than
At cooling rates exceeding 500°C/min, the RM ₇ phase becomes R ₂ M ₁₇
Phase/RM Unfavorable because it does not fully decompose into ₅ phases. In this invention, in order to cause fine decomposition and precipitation of the R ₂ M ₁₇ phase and the RM ₅ phase, the optimum cooling rate is preferably 50 to 200° C./min. In this invention, cooling under the optimum cooling conditions means that the R ₂ M ₁₇ phase is 55 to 85% in terms of metal phase, and the remaining
The RM ₅ phase is essential for obtaining excellent magnetic properties, and the magnetic properties of magnets with metal phases other than this metal phase are extremely low. Examples Examples according to the present invention will be shown below to clarify its effects. Example 1 Sm26.9wt% with a purity of 99.9% or more, Co47.6wt% with a purity of 99.8% or more, Fe12.1wt%,
An alloy consisting of 5.5wt% Ni and 7.9wt% Cu was high-frequency melted in an argon gas atmosphere and cast. The resulting ingot was subjected to solution treatment at 1180℃ for 6 hours. After treatment, it was placed in liquid nitrogen. By rapid cooling, 94% of the metal phase was _RM7 . The obtained alloy was coarsely ground in an iron mortar and further finely ground in a ball mill in an organic solvent.
It was made into a μm powder. This powder was press-molded in a magnetic field of 12 kOe to obtain a compression-molded body. Next, the compression molded body is sintered at 1200°C for 2 hours in a hydrogen atmosphere, and after sintering, the permanent magnet according to the present invention is cooled at a cooling rate of 100°C/min to a temperature of 800°C or less. Obtained. In addition, as a comparative example, the same cast ingot as above was subjected to coarse pulverization, fine pulverization, press molding, and sintering under the same conditions as above without being subjected to solution treatment.
A comparative permanent magnet was obtained by solution treatment after sintering at 1160°C for 8 hours. Table 1 shows the magnetic properties of the two types of permanent magnets obtained.

[Table] Example 2 Sm25.6wt%, Y1.5wt% with a purity of 99.9% or higher, Co43.9wt%, Fe15.3wt% with a purity of 99.8% or higher,
An alloy consisting of 6.6wt% Ni and 7.1wt% Cu was arc melted and cast in an argon gas atmosphere.The obtained ingot was subjected to solution treatment at 1150℃ for 8 hours, and after treatment was placed in liquid nitrogen. By rapid cooling, 97% of the metal phase was _RM7 . The obtained alloy was roughly pulverized in an iron mortar, and further finely pulverized with a ball mill in an organic solvent.
It was made into a powder of 10 μm. This powder was press-molded in a magnetic field of 15 kOe to obtain a compression-molded body. Next, the compression molded body is placed in a reduced pressure argon atmosphere of 200Toor.
Sintered at 1200℃ for 2 hours, after sintering, 180℃
A permanent magnet according to the present invention was obtained by cooling to a temperature of 800°C or less at a cooling rate of °C/min. In addition, as a comparative example, the ingot was not subjected to solution treatment after casting, but was subjected to coarse pulverization, fine pulverization, press molding, and sintering under the above conditions, followed by solution treatment after sintering at 1160 ° C. for 6 hours. A comparative permanent magnet was obtained by heat treatment at 800°C for 3 hours. The magnetic properties of the two types of permanent magnets obtained are shown in Table 2.

[Table] As is clear from the above examples, by the method of the present invention, in which the ingot after casting is subjected to solution treatment, and after sintering, it is cooled to a specific temperature or less at a specific cooling rate.
The magnetic properties have been significantly improved, and excellent rare earth cobalt permanent magnets can be manufactured.

Claims (1)

[Claims] 1 R ₂ M _17- based magnetic alloy consisting of rare earth element R and transition metal M (wherein R is Y, La, Ce, Pr, Nb,
A combination of one or more of Sm and Mitsushi metal, M is a combination of one or more of Cu and Co, Fe or Ni, and a part of M is Mn,
A combination of Ti, Nb, Zr, Ta, and Hf in which one or more elements are substituted) was melted and cast, and solution treatment was performed at 1150°C to 1210°C for 1 to 12 hours. Afterwards, rapid cooling is performed to generate 90% or more of the metallic RM ₇ phase, and the alloy is further crushed and compression molded. After sintering this compression molded body in vacuum or in an inert atmosphere, the alloy is heated to 800°C. A method for manufacturing a permanent magnet, characterized by cooling at a cooling rate of 20°C/min to 500°C/min.