JPH0122970B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improvement in the manufacturing method of R ₂ M ₁₇ series (R is a rare earth element, M is a transition metal element) permanent magnet, and a new solution treatment process is introduced after alloy melting and casting in the manufacturing process. The present invention relates to a method for producing a rare earth cobalt permanent magnet, which is then subjected to pulverization, compression molding and sintering, and then a solution treatment after sintering, thereby improving and stabilizing the permanent magnet properties. R ₂ M ₁₇ series permanent magnet alloys are widely used mainly in the electronic industry as excellent permanent magnets with extremely high coercive force and maximum energy product. However, in order to maximize the magnetic properties of this permanent magnet alloy, the manufacturing method is most important, and each process must be strictly controlled to manufacture the magnet. Therefore, as a method for improving and stabilizing the magnetic properties of the R ₂ M ₁₇ series permanent magnet alloy by improving this manufacturing method, the inventor of the present application previously proposed a method for alloy melting and casting in Japanese Patent Application No. 57-8035. He later proposed that ingot solution treatment was effective, and in Japanese Patent Application No. 57-21819, that special sintering treatment in the sintering process and post-sintering solution treatment were effective. However, the manufacturing method proposed above also had the following problems. In other words, in the former method, which only performs solution treatment on ingots, there tends to be large variations in the magnetic properties obtained between the molten ingots, and when large ingots are solution treated, it takes a long time, and the solution treatment Extremely rapid cooling is required in the subsequent rapid cooling, and it is difficult to maintain the TbCu ₇ crystal structure phase, which is a high-temperature stable phase, to room temperature, resulting in variations in the magnetic properties obtained. In addition, in the latter method of applying solution treatment after sintering, the R ₂ M ₁₇ alloy is slightly different in the cooling conditions or composition during melting and casting of the ingot, but there are some undesirable effects on the R ₂ M ₁₇ alloy magnet properties. It contains metal phases such as Th ₂ Zn ₁₇ crystal structure phase in which solidification occurs through multiple peritectic reactions, Fe-Co rich primary crystal, CaCu ₅ crystal structure phase, etc., which deteriorates magnetic properties. These metallic phases have mechanical strength,
Due to the difference in magnetic properties, the manufacturing process of this magnet alloy, such as crushing and orientation in a magnetic field, causes variations in magnetic properties and deterioration, and even after solution treatment after sintering, the magnetic properties are There was a tendency to not be able to recover in minutes. Furthermore, regarding the cooling rate after the post-sintering solution treatment, an extremely fast cooling rate is required, making it difficult to apply it to industrial mass production, and there is a problem that rapid cooling is not possible for large-sized magnets. This invention is the _result of various studies on improvements to improve and stabilize the magnetic properties of such _{R 2 M 17} series magnet alloys. The invention is characterized in that by first performing solution treatment on the ingot and then also using post-sintering solution treatment during the sintering process, the magnetic properties are further improved and stabilized than in the prior invention described above. do. That is, this invention provides R ₂ M ₁₇ consisting of a rare earth element R and a transition metal element M.
Permanent magnet alloy (where R is one or a combination of two or more of Y, La, Ce, Pr, Nb, Sm, and Mitsushi metal, M is one or two of Cu, Co, Fe, or Ni)
combinations of more than one species and combinations in which a part of the above M is replaced with one or more elements of each element of Mn and Zr)
is melted and cast, and subjected to ingot solution treatment at 1100 to 1250℃ for 1 to 10 hours to improve the metallographic structure.
The R ₂ M ₁₇ phase is made into a single phase, which is crushed and compression molded to form a molded body.The molded body is then sintered at a temperature range of 1100 to 1250℃ in a reduced pressure argon gas atmosphere of 50 to 350 Torr, and further This is a method for producing a rare earth cobalt permanent magnet, which is characterized by performing post-sintering solution treatment in a temperature range of ~1200°C, followed by rapid cooling at 100°C/min or more, and aging treatment. The ingot solution treatment after melting and casting, which is one of the features of the manufacturing method of this invention, is to heat the ingot after melting and casting in a non-oxidizing atmosphere in a temperature range of 1100 to 1250°C for 1 to 10 minutes. hold time,
After that, it is rapidly cooled using a refrigerant such as liquid nitrogen or water. Here, the ingot solution treatment temperature was limited to 1100 to 1250°C, although it varied slightly depending on the alloy composition. The reason for this is that at temperatures below 1100°C, the TbCu ₇ crystal structure phase, which is a high-temperature stable phase that is essential for exhibiting the excellent magnetic properties of this R ₂ M ₁₇ magnet alloy, cannot be completely obtained, and the composition The homogenization of the alloy does not proceed sufficiently, and therefore the obtained magnetic properties are poor. At solution treatment temperatures exceeding 1250°C, the alloy melts and forms a solution phase, so the alloy composition fluctuates widely and high magnetic properties are not obtained. This is so that you will not be affected. In order to stably obtain excellent magnetic properties by forming a single TbCu ₇ crystal structure phase and sufficiently promoting homogenization of the composition, the solution treatment temperature is most preferably 1150 to 1210°C. Next, the ingot solution treatment time was 1 to 10 hours, although it differed slightly depending on the alloy composition, ingot weight, and ingot cooling conditions. Generally, large ingots contain Th ₂ Zn ₁₇ crystal structure phase and Fe, which cause deterioration of magnetic properties during alloy melting and casting.
-Since Corich primary crystals are likely to form, the solution treatment time must be long. If the ingot solution treatment time is less than 1 hour, a sufficient single phase of TbCu ₁₇ crystal structure cannot be obtained, and excellent magnetic properties cannot be expected.
Furthermore, if the ingot solution treatment time exceeds 10 hours, there is no industrial advantage in that it requires a long time, and the evaporation and oxidation of R gradually progresses, so that the magnetic properties obtained decrease with the treatment time. Therefore 1~
The processing time was 10 hours. In order to homogenize the ingot composition, sufficiently obtain a single TbCu ₇ crystal structure phase, and prevent evaporation and oxidation of R as much as possible, the industrial ingot solution treatment time is preferably 2 to 8 hours. In addition, in this invention, in addition to the ingot solution treatment, a post-sintering solution treatment is performed, so the ingot solution treatment time 1 of the above-mentioned Japanese Patent Application No. 8035/1983 is applied.
Another improvement is that the ingot solution treatment time was shortened compared to ~20 hours. Next, sintering in a reduced pressure argon atmosphere and post-sintering solution treatment, which are another excellent feature of the manufacturing method of the present invention, will be explained. Sintering is performed at a temperature of 50~
1100~ in a reduced pressure argon atmosphere of 350Torr
Perform in a temperature range of 1250℃. Here, the reason for limiting the argon gas atmosphere pressure is that when the pressure is lower than 50 Torr, the vapor pressure of the components of the rare earth cobalt magnet alloy, especially the rare earth components, is 20 to 30 Torr at 800°C or higher, which is quite high among metal elements. The rare earth metal preferentially evaporates into the atmosphere, and the final sintered body has a composition different from the predetermined composition, resulting in significant deterioration of magnetic properties. Further, if the pressure is higher than 350 Torr, sufficient improvement in density is not observed and ultimately excellent magnetic properties cannot be obtained, so the pressure is set at 50 to 350 Torr. In addition, the reason for limiting the sintering temperature range is that the optimum sintering temperature range for rare earth cobalt magnet alloys varies depending on the constituent components and the proportions of each component, but it is less than 1100℃. A sufficient sintered density cannot be obtained at a sintering temperature of 1250°C, and a sintered magnet body with good characteristics cannot be obtained because the alloy melts at a sintering temperature exceeding 1250°C. In order to obtain sufficient sintered density and excellent magnetic properties without forming an excessive melt phase, the most desirable sintering temperature is 1160 to 1230°C. Solution treatment after sintering is slightly lower than the sintering temperature
Sintering is carried out in an argon atmosphere under reduced pressure or normal pressure at a temperature range of 1100 to 1200°C to fully react the melt phase generated during sintering with the sintered crystal phase, homogenize the composition, and form the TbCu ₇ crystal structure phase. Single phase. This solution treatment can be carried out either by cooling to room temperature after sintering and then raising the temperature again for solution treatment, or by cooling the temperature to the solution treatment temperature without cooling to room temperature after sintering. However, the obtained magnetic properties are the same. In order to exhibit excellent magnetic properties by homogenizing the composition and forming a single-phase TbCu ₇ crystal structure, the most desirable temperature for the post-sintering solution treatment is 1150 to 1190°C. After the post-sintering solution treatment is completed, rapid cooling is required to maintain the TbCu ₇ crystal structure single phase, which is a high-temperature stable phase, to room temperature in order to obtain excellent magnetic properties. In the prior invention patent application No. 57-21319, the cooling rate was required to be 200°C/min or more when only the solution treatment was performed after sintering, but the cooling rate was not less than 200°C/min. In the present invention, where both treatments are performed, the cooling rate is
At 100°C/min or higher, stable and excellent magnetic properties can be obtained. Next, after the solution treatment, an aging treatment is performed to obtain a rare earth cobalt permanent magnet. Further, in the manufacturing method of the present invention, especially in the sintering step, if the following special temperature raising process is used, it is effective to further improve the magnetic properties. During the temperature raising process from room temperature to 800℃ or less, the temperature is slowly raised at a rate of 4 to 20℃/min in a vacuum atmosphere of 1×10 ^-2 Torr or less to prevent oxidation while degassing. . The reason for limiting the heating rate is 4.
At a temperature increase rate of less than ℃/min, it takes more than 3 hours to raise the temperature to 800℃, and the molded product oxidizes during that time even in a vacuum atmosphere, which is too time-consuming for industrial purposes. In addition, if the heating rate exceeds 20℃/min, the temperature rising is too fast and the adsorbed/occluded gas in the molded body cannot be removed sufficiently, so the subsequent heating in a reduced pressure argon atmosphere is necessary. No effect of property improvement due to sintering. In particular, in the above heating process, a large amount of gas, which accounts for approximately 90% of the adsorbed/occluded gas in the molded body, is released in the temperature range of 200 to 600°C, so the heating rate in this temperature range is 4 to 10°C.
It is preferable to carry out the degassing treatment effectively while preventing oxidation in a high vacuum atmosphere of 1×10 ⁻⁴ to 1×10 −5 Torr at a temperature of 1×10 −4 to 1×10 ⁻⁵ Torr. The present invention will be explained below using examples. Example 1 Sm26.0wt% with purity of 99.9% or more, purity of 99.8%
Co47.3wt%, Fe12.8wt%, Ni5.3wt%, and
After high-frequency melting and casting of an alloy consisting of 8.6wt% Cu in an argon atmosphere,
The ingot was subjected to solution treatment at 1180°C for 4 hours, and after the solution treatment, it was rapidly cooled with liquid nitrogen. Next, the solution-treated ingot was coarsely ground in an iron mortar, and then ground into fine powder with an average particle size of 2 to 10 μm using a ball mill in an organic solvent. The obtained fine powder was pressed in a magnetic field of 15 KOe to form a compression molded body. This compression molded body was sintered at 1210℃ for 2 hours in an argon atmosphere of 200Torr, and then at 1190℃ for 2 hours.
After solution treatment after sintering for an hour, 150℃/
Rapid cooling was performed at a cooling rate of min. Furthermore, 800℃,
A permanent magnet according to the present invention was obtained by aging for 4 hours. Further, as a comparative example (1), a permanent magnet was obtained by the same manufacturing method as in Example 1 above, without performing ingot solution treatment at 1180° C. for 4 hours. Further, as Comparative Example (2), a permanent magnet was obtained by the same manufacturing method as in Example 1 above without performing post-sintering solution treatment at 1190° C. for 2 hours. Table 1 summarizes the results of the magnet characteristics obtained.

[Table] Example 2 Sm24.0wt%, Y1.8wt% with a purity of 99.9% or higher, Co43.6wt%, Fe16.2wt% with a purity of 99.8% or higher,
An ingot obtained by high-frequency melting and casting of an alloy consisting of 6.3 wt% Ni, 7.6 wt% Cu, and 0.5 wt% Zr in an argon atmosphere was subjected to solution treatment at 1170°C for 5 hours. Rapidly cooled in nitrogen. This alloy was coarsely ground in an iron mortar and then made into a fine powder of 2 to 10 μm in size using a jet mill. This fine powder was pressed in a magnetic field of 15 KOe to form a compression molded body. This compression molded body is
From room temperature to 800℃ in a vacuum atmosphere of 10 ^-4 Torr
After increasing the temperature at a rate of 10°C/min to 200 Torr, sintering was performed at 1200°C for 2 hours in a reduced pressure argon atmosphere of 200 Torr, followed by post-sintering solution treatment at 1185°C for 3 hours. Afterwards, it was rapidly cooled at a cooling rate of 160°C/min. Furthermore, 800℃ x 2 hours, 700℃ x 4 hours, 600℃
A multi-stage aging treatment of 8 hours at 500°C and 16 hours at 500°C was performed to obtain a permanent magnet according to the present invention. Further, as a comparative example (1), a permanent magnet was obtained by the same manufacturing method as in Example 2 above without performing ingot solution treatment at 1170° C. for 5 hours. Further, as Comparative Example (2), a permanent magnet was obtained by the same manufacturing method as in Example 2 above without performing post-sintering solution treatment at 1185° C. for 3 hours. Table 2 summarizes the results of the magnet characteristics obtained.

[Table] Example 3 Sm25.3wt%, Y1.0wt% with a purity of 99.9% or more, Co43.8wt%, Fe16.1wt% with a purity of 99.8% or more,
Ni4.8wt%, Cu7.7wt%, Mn0.3wt%, Zr1.0wt%
An ingot obtained by high-frequency melting and casting in an argon atmosphere was subjected to solution treatment at 1195°C for 3 hours, and after the treatment was rapidly cooled in liquid nitrogen. This alloy was coarsely ground in an iron mortar and then made into a fine powder of 2 to 10 μm in size using a jet mill. This fine powder was pressed in a magnetic field of 15 KOe to form a compression molded body. 5×
800°C from room temperature in a vacuum atmosphere of 10 ^-4 Torr.
After heating at a rate of 10℃/min to 180Torr
Sintered at 1205℃ for 2 hours in a reduced pressure argon atmosphere, followed by post-sintering solution treatment at 1190℃ for 3 hours, and then rapidly cooled at a cooling rate of 150℃/min. . Furthermore, 800℃×4 hours, 700℃×8
A permanent magnet according to the present invention was obtained by performing multi-stage aging treatment at 600°C for 16 hours and at 500°C for 32 hours. Further, as Comparative Example (1), a permanent magnet was obtained by the same manufacturing method as in Example 3 without performing ingot solution treatment at 1195° C. for 3 hours. As Comparative Example (2), a permanent magnet was obtained by the same manufacturing method as in Example (3) above, without performing post-sintering solution treatment at 1190° C. for 3 hours. Table 3 summarizes the results of the magnet characteristics obtained.

[Table] As shown in the above examples, the manufacturing method of rare earth cobalt permanent magnets, which uses both the ingot solution treatment after melting and casting and the solution treatment after sintering, which are the characteristics of this invention, It is clear that this method is extremely effective in improving magnetic properties.

Claims (1)

[Claims] 1 Consisting of rare earth element R and transition metal element M
R ₂ M ₁₇ series permanent magnet alloy (However, R is one or a combination of two or more of Y, La, Ce, Pr, Nb, Sm and Mitsushi metal, M is one or more of Cu, Co, Fe or Ni 2
combinations of more than one species and combinations in which a part of the above M is replaced with one or more elements of each element of Mn and Zr)
is melted and cast, and subjected to ingot solution treatment at 1100 to 1250℃ for 1 to 10 hours to improve the metallographic structure.
The R ₂ M ₁₇ phase is made into a single phase, which is crushed and compression molded to form a molded body.The molded body is then sintered at a temperature range of 1100 to 1250℃ in a reduced pressure argon gas atmosphere of 50 to 350 Torr, and further A method for producing a rare earth cobalt permanent magnet, which comprises performing post-sintering solution treatment in a temperature range of ~1200°C, followed by rapid cooling at 100°C/min or more, and aging treatment.