CN115910512A - Low-flux-loss permanent magnet material and preparation method thereof - Google Patents
Low-flux-loss permanent magnet material and preparation method thereof Download PDFInfo
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- CN115910512A CN115910512A CN202211569892.8A CN202211569892A CN115910512A CN 115910512 A CN115910512 A CN 115910512A CN 202211569892 A CN202211569892 A CN 202211569892A CN 115910512 A CN115910512 A CN 115910512A
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Abstract
The invention belongs to the technical field of magnetic materials, and relates to a low-flux-loss permanent magnetic material and a preparation method thereof. The preparation method comprises the following steps: preparing raw materials, smelting, pulverizing, orientation molding, primary sintering solid solution, cooling, secondary sintering solid solution, cooling and aging treatment. In the preparation process of the samarium cobalt permanent magnet material, secondary sintering and secondary solid solution processes are added, the grain size of the permanent magnet material is increased, the solid solution structure is homogenized, the grain boundary area with weak pinning of magnetic domains is reduced, the structure uniformity is improved, and therefore the magnetic flux loss after high-temperature heat preservation is reduced.
Description
Technical Field
The invention belongs to the technical field of magnetic materials, and relates to a low-flux-loss permanent magnetic material and a preparation method thereof.
Background
With the continuous development of high and new technologies such as aerospace, high-speed railways, communication equipment and the like, the service temperature of a permanent magnet material is gradually improved, and meanwhile, the requirement on the magnetic loss performance of the permanent magnet material is more and more strict. In the commercialized magnet material, sm 2 Co 17 The magnet has higher magnetic energy product, high Curie temperature and good temperature stability, and has the development potential in the high temperature field.
The magnetic flux loss can be classified into 3 types, the first type is reversible magnetic flux loss, and the reversible magnetic flux loss can be spontaneously recovered after being cooled to room temperature; the second type is irreversible magnetic flux loss which can be recovered after being recharged with magnetism; the third type is unrecoverable magnetic flux loss, which cannot be recovered after re-magnetization. The document "induction of the final heat treatment on the magnetic properties of Sm (Co, fe, cu, zr) z high temperature magnetic properties" considers that when the secondary aging temperature is increased to be equal to or more than the high temperature heat preservation temperature of the magnet, the thermal stability of the microstructure can be improved, and the third type of magnetic flux loss is obviously reduced.
While the second type of flux loss arises from a change in the domain structure, sm 2 Co 17 The phenomenon of Cu deficiency often exists at the magnet grain boundary, the cellular structure is incomplete, the first region becomes a region for forming nuclei and expanding of the anti-magnetization domain, and the reduction of the area with the incomplete grain boundary cellular structure becomes the key for reducing the magnetic flux loss.
Disclosure of Invention
The invention aims to provide a low-flux-loss permanent magnetic material and a preparation method thereof, aiming at the defects of the prior art.
One purpose of the invention is realized by the following technical scheme:
the average grain size of the low-flux-loss permanent magnetic material is larger than 90 mu m, and the flux loss after heat preservation in air at 525 ℃ for 2 hours is smaller than 3.5 percent.
More preferably, the average grain size of the low-flux-loss permanent magnetic material is more than 100 mu m, and the flux loss after the permanent magnetic material is kept in air at 525 ℃ for 2 hours is less than 3 percent.
Optionally, the low flux loss permanent magnet material is a samarium cobalt permanent magnet material.
The other purpose of the invention is realized by the following technical scheme:
a preparation method of a low-flux loss permanent magnetic material comprises the following steps:
preparing raw materials, smelting, pulverizing, orientation molding, primary sintering and solid solution, cooling, secondary sintering and solid solution, cooling and aging treatment.
Preferably, the raw materials comprise the following components in percentage by weight: sm:24.0 to 27.0%, co: 55.0-60.0%, fe:5.0 to 8.0%, cu:5.0 to 8.0 percent, and the balance of Zr.
Preferably, the sintering temperature of the primary sintering and solid solution is 1190-1240 ℃, and the holding time is 2-5 h.
Preferably, the solid solution temperature of the primary sintering solid solution is 1150-1200 ℃, and the holding time is 2-5 h. The solid solution temperature is lower than the sintering temperature.
Preferably, the sintering temperature of the secondary sintering and solid solution is 1190-1240 ℃, and the holding time is 2-5 h.
Preferably, the solid solution temperature of the secondary sintering solid solution is 1150-1200 ℃, and the holding time is 2-5 h. The solid solution temperature is lower than the sintering temperature.
The sintering temperature and time and the solid solution temperature and time of the first sintering solid solution and the second sintering solid solution may be the same or different, and the values may be within the above ranges.
Optionally, the cooling modes after the primary sintering solid solution and the secondary sintering solid solution are fast cooling modes such as air cooling, water cooling and the like.
Preferably, in the primary sintering solid solution process, the step-wise temperature rise is performed by raising the temperature to the sintering temperature in a step-wise manner, and the step-wise temperature rise includes: raising the temperature to 300-400 ℃ at room temperature, and keeping the temperature for 1-3 h; then heating to 800-950 ℃, and preserving the heat for 1-3 h; then heating to 1100-1190 ℃, and preserving the heat for 1-3 h; then the temperature is raised to the sintering temperature of 1190 to 1240 ℃, and the temperature is preserved for 2 to 5 hours.
Preferably, in the secondary sintering solid solution process, the sintering temperature is raised in stages, and the stage raising includes: raising the temperature to 300-400 ℃ at room temperature, and keeping the temperature for 1-3 h; then heating to 800-950 ℃, and preserving the heat for 1-3 h; then heating to 1100-1190 ℃, and preserving the heat for 1-3 h; then the temperature is raised to the sintering temperature of 1190 to 1240 ℃, and the temperature is preserved for 2 to 5 hours.
The temperature may be increased in stages by the first sintering solid solution and the second sintering solid solution, or may be increased in stages by the second sintering solid solution.
Preferably, the aging treatment comprises primary aging and secondary aging, wherein the primary aging temperature is 800-850 ℃, the heat preservation time is 20-40 h, the secondary aging temperature is 400-600 ℃, and the heat preservation time is 10-20 h.
Preferably, after the first-stage aging heat preservation treatment, the temperature is reduced to the second-stage aging temperature at a cooling rate of 0.3-0.8 ℃/min.
Compared with the prior art, the invention has the following beneficial effects:
1. the samarium cobalt permanent magnet material provided by the invention has the average grain size of more than 90 mu m, and the magnetic flux loss after heat preservation in air at 525 ℃ for 2h is less than 3.5%;
2. in the preparation process of the samarium cobalt permanent magnet material, secondary sintering and secondary solid solution processes are added, the grain size of the permanent magnet material is increased, the solid solution state structure is homogenized, the grain boundary area with weak pinning of magnetic domains is reduced, the structure uniformity is improved, and thus the magnetic flux loss after high-temperature heat preservation is reduced;
3. in the primary sintering solid solution process and the secondary sintering solid solution process, the magnetic flux loss after high-temperature heat preservation can be reduced by adopting stage temperature rise to the sintering temperature;
4. the method for reducing the magnetic flux loss of the samarium cobalt permanent magnet material after high-temperature heat preservation is simple, and the obtained low-magnetic-flux-loss permanent magnet material has a great application prospect in the high-temperature field.
Drawings
Fig. 1 is an SEM image of a samarium cobalt permanent magnet prepared in example 1 and a samarium cobalt permanent magnet prepared in comparative example 1.
Detailed Description
The technical solutions of the present invention are further described and illustrated in the following specific embodiments and the accompanying drawings, it should be understood that the specific embodiments described herein are only for the purpose of facilitating understanding of the present invention, and are not intended to limit the present invention specifically. And the drawings used herein are for the purpose of illustrating the disclosure better and are not intended to limit the scope of the invention. The raw materials used in the examples of the present invention are those commonly used in the art, and the methods used in the examples are those conventional in the art, unless otherwise specified.
In the present specification, "crystal grain size" means the maximum distance among arbitrary 2-point distances on the contour line of a crystal grain observed using an observation apparatus such as a Scanning Electron Microscope (SEM) or a metallographic microscope (OM). The "average crystal grain size" is an average value obtained by counting the crystal grain sizes observed in several fields of view using an observation device such as SEM or OM, and calculating the number of counted crystal grains to be greater than 100.
In this specification, magnetic flux loss = (initial magnetic flux — magnetic flux after holding a specific temperature for a specific time)/initial magnetic flux = 100%.
Example 1
The low-flux-loss permanent magnetic material of the embodiment is prepared by the following method:
(1) Preparing raw materials: sm used in the embodiment 2 Co 17 The samarium cobalt permanent magnet material comprises the following raw materials in percentage by weight: 26.62 percent of samarium, 55.04 percent of cobalt, 6.96 percent of iron, 7.13 percent of copper and the balance of zirconium, wherein the purity of Sm, co and Cu is more than or equal to 99.9 percent, and the purity of Fe and Zr is more than or equal to 99.5 percent;
(2) Smelting to obtain an ingot: smelting the prepared raw materials in a vacuum high-frequency induction furnace in high-purity argon at the smelting temperature of 1500 ℃, melting the raw materials to form a uniform alloy solution, and pouring the uniform alloy solution into a cooling copper mold to obtain an alloy ingot;
(3) Powder preparation and oriented blank making: mechanically crushing the cast ingot into powder of 50-200 mu m, further grinding the powder into powder with the average grain diameter of 4.5 mu m by using an air flow grinding process, then carrying out orientation molding under a magnetic field of 2T, packaging, keeping the pressure for 20s by using a cold isostatic press under 160MPa, and compacting to obtain a blank;
(4) Primary sintering and solid solution: heating the blank to 350 ℃ in an argon atmosphere, and preserving the heat for 1h; then heating to 850 ℃, and preserving heat for 1h; then heating to 1180 ℃, and preserving heat for 1h; then heating to a sintering temperature of 1225 ℃, and sintering for 2 hours under the protection of argon atmosphere; finally, cooling to 1180 ℃ and carrying out argon protection solution treatment for 2 hours, and then air cooling to room temperature;
(5) Secondary sintering and solid solution: in the argon atmosphere, heating the blank after primary sintering and solid solution to 355 ℃, and preserving heat for 1h; then raising the temperature to 855 ℃, and keeping the temperature for 1h; then heating to 1190 ℃, and preserving the heat for 1h; then heating to a sintering temperature of 1220 ℃, and sintering for 2h under the protection of argon atmosphere; finally, cooling to 1175 ℃, carrying out argon protection solution treatment for 2 hours, and then air-cooling to room temperature;
(6) Aging treatment: and (3) carrying out argon protection aging treatment for 20h at 830 ℃, then cooling to 500 ℃ at the cooling speed of 0.5 ℃/min, preserving heat for 10h, and then air-cooling to room temperature to obtain the samarium-cobalt permanent magnet.
Example 2
The low-flux-loss permanent magnetic material of the embodiment is prepared by the following method:
(1) Preparing raw materials: sm used in the embodiment 2 Co 17 The samarium cobalt permanent magnet material comprises the following raw materials in percentage by weight: 24.65% of samarium, 57.08% of cobalt, 6.92% of iron, 7.15% of copper and the balance of zirconium, wherein the purity of Sm, co and Cu is more than or equal to 99.9%, and the purity of Fe and Zr is more than or equal to 99.5%;
(2) Smelting to obtain an ingot: smelting the prepared raw materials in a vacuum high-frequency induction furnace in high-purity argon at the smelting temperature of 1520 ℃, melting the raw materials to form uniform alloy solution, and pouring the uniform alloy solution into a cooling copper mold to obtain an alloy ingot;
(3) Powder making and oriented blank making: mechanically crushing the cast ingot into powder of 50-200 microns, further grinding the powder into powder with the average particle size of 4.6 microns by using an air flow grinding process, then carrying out orientation molding under a magnetic field of 1.8T, packaging, then maintaining the pressure for 18s by using a cold isostatic press under 170MPa, and compacting to obtain a blank;
(4) Primary sintering and solid solution: in the argon atmosphere, heating the blank to 360 ℃, and preserving the heat for 1h; then heating to 880 ℃, and preserving heat for 1.5h; then heating to 1190 ℃, and preserving the heat for 1h; then heating to a sintering temperature of 1233 ℃, and sintering for 2h under the protection of argon atmosphere; finally, cooling to 1190 ℃ and carrying out argon protection solution treatment for 2 hours, and then air-cooling to room temperature;
(5) Secondary sintering and solid solution: in the argon atmosphere, heating the blank after primary sintering and solid solution to 380 ℃, and preserving heat for 1.5h; then heating to 860 ℃, and preserving heat for 1h; then heating to 1185 ℃, and preserving heat for 1h; then heating to a sintering temperature of 1230 ℃, and sintering for 2h under the protection of argon atmosphere; finally, cooling to 1180 ℃ and carrying out argon protection solution treatment for 2 hours, and then air cooling to room temperature;
(6) And (3) aging treatment: and (3) carrying out argon protection aging treatment for 20h at 840 ℃, then cooling to 400 ℃ at a cooling speed of 0.5 ℃/min, preserving heat for 10h, and then air-cooling to room temperature to obtain the samarium-cobalt permanent magnet.
Example 3
The low-flux-loss permanent magnetic material of the embodiment is prepared by the following method:
(1) Preparing raw materials: sm used in the embodiment 2 Co 17 The samarium cobalt permanent magnet material comprises the following raw materials in percentage by weight: 25.60% of samarium, 56.15% of cobalt, 6.89% of iron, 7.2% of copper and the balance of zirconium, wherein the purity of Sm, co and Cu is more than or equal to 99.9%, and the purity of Fe and Zr is more than or equal to 99.5%;
(2) Smelting to obtain an ingot: smelting the prepared raw materials in a vacuum high-frequency induction furnace in high-purity argon at the smelting temperature of 1550 ℃, melting the raw materials to form a uniform alloy solution, and pouring the uniform alloy solution into a cooling copper mold to obtain an alloy ingot;
(3) Powder preparation and oriented blank making: mechanically crushing the cast ingot into powder of 50-200 microns, further grinding the powder into powder with the average particle size of 4.0 microns by using an air flow grinding process, then carrying out orientation molding under a magnetic field of 2.2T, packaging, then maintaining the pressure for 22s by using a cold isostatic press under 150MPa, and compacting to obtain a blank;
(4) Primary sintering and solid solution: in the argon atmosphere, heating the blank to a sintering temperature of 1225 ℃, and sintering for 2.5h under the protection of the argon atmosphere; finally cooling to 1180 ℃ and carrying out argon protection solution treatment for 2 hours, and then air cooling to room temperature;
(5) Secondary sintering and solid solution: in argon atmosphere, heating the blank after primary sintering and solid solution to the sintering temperature of 1230 ℃, and sintering for 2.5h under the protection of argon atmosphere; finally, cooling to 1185 ℃ and carrying out argon protection solution treatment for 2 hours, and then air cooling to room temperature;
(6) Aging treatment: and (3) carrying out argon protection aging treatment for 22h at 820 ℃, then cooling to 450 ℃ at a cooling speed of 0.5 ℃/min, preserving heat for 12h, and then air-cooling to room temperature to obtain the samarium-cobalt permanent magnet.
Comparative example 1
The difference between the method for preparing samarium cobalt permanent magnet of comparative example 1 and example 1 is that the green body is not subjected to secondary sintering solid solution after primary sintering solid solution, and is directly aged. The rest is the same as in example 1.
Comparative example 2
The difference between the method for preparing samarium cobalt permanent magnet of comparative example 2 and example 2 is that the green body was not subjected to secondary sintering solid solution after primary sintering solid solution, and was subjected to direct aging treatment. The rest is the same as in example 2.
Comparative example 3
The samarium cobalt permanent magnet of comparative example 3 was prepared as described in example 3 except that the primary sintering and solution treatment was not followed by a secondary sintering and solution treatment, and the aging treatment was conducted directly. The rest is the same as in example 3.
Comparative example 4
The samarium cobalt permanent magnet of comparative example 4 was prepared by the method described in example 1, except that:
the primary sintering solid solution in the step (4) is as follows: heating the blank to 360 ℃ in an argon atmosphere, and preserving heat for 1h; then heating to 880 ℃, and preserving heat for 1.5h; then heating to 1190 ℃, and preserving the heat for 1h; then heating to a sintering temperature of 1233 ℃, and sintering for 2h under the protection of argon atmosphere; finally, air cooling to room temperature;
the rest is the same as in example 1.
Comparative example 5
The samarium cobalt permanent magnet of comparative example 5 was prepared by the method described in example 1, except that:
the secondary sintering solid solution in the step (5) is as follows: in the argon atmosphere, heating the blank subjected to primary sintering and solid solution to 355 ℃, and keeping the temperature for 1h; then raising the temperature to 855 ℃, and preserving the temperature for 1h; then heating to 1190 ℃, and preserving the heat for 1h; then heating to a sintering temperature of 1220 ℃, and sintering for 2h under the protection of argon atmosphere; finally, air cooling to room temperature;
the rest is the same as in example 1.
The average grain size of samarium-cobalt permanent magnets of examples 1-3 and comparative examples 1-5 and the magnetic flux before and after 2 hours of heat preservation in air at 525 ℃ were tested, and the magnetic flux loss was calculated, and the test results are shown in table 1.
TABLE 1 samarium cobalt permanent magnet average grain size and flux loss for examples 1-3 and comparative examples 1-5
Fig. 1 is an SEM image of the samarium cobalt permanent magnet prepared in example 1 and the samarium cobalt permanent magnet prepared in comparative example 1, and it can be seen from table 1 and fig. 1 that the samarium cobalt permanent magnet had been solid-solubilized by the secondary sintering, and the crystal grain size was increased relative to the samarium cobalt permanent magnet that had not been subjected to the secondary sintering. As can be seen from Table 1, the average grain size of examples 1-3 was > 90 μm, and the magnetic flux loss after 2 hours of heat preservation in air at 525 ℃ was < 3.5%; comparative examples 1-5 have an average grain size of < 90 μm and a magnetic flux loss of > 3.5% after 2h incubation in air at 525 ℃. The experimental results show that the samarium cobalt permanent magnet can increase the grain size and effectively reduce the magnetic flux loss after secondary sintering and solid solution.
The aspects, embodiments, features of the present invention should be considered in all respects as illustrative and not restrictive, the scope of the invention being defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
In the preparation method of the present invention, the order of the steps is not limited to the listed order, and for those skilled in the art, the order of the steps is not changed without creative efforts, and the invention is also within the protection scope of the present invention. Further, two or more steps or actions may be performed simultaneously.
Finally, it should be noted that the specific examples described herein are merely illustrative of the invention and do not limit the embodiments of the invention. Those skilled in the art may now make numerous modifications of, supplement, or substitute for the specific embodiments described, all of which are not necessary or desirable to describe herein. While the invention has been described with respect to specific embodiments, it will be appreciated that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.
Claims (10)
1. The low-flux-loss permanent magnet material is characterized in that the average grain size of the low-flux-loss permanent magnet material is larger than 90 mu m, and the flux loss after heat preservation in air at 525 ℃ for 2 hours is smaller than 3.5%.
2. A method for preparing the low flux loss permanent magnetic material of claim 1, comprising the steps of:
preparing raw materials, smelting, pulverizing, orientation molding, primary sintering and solid solution, cooling, secondary sintering and solid solution, cooling and aging treatment.
3. The preparation method according to claim 2, wherein the raw materials comprise the following components in percentage by weight: sm:24.0 to 27.0%, co: 55.0-60.0%, fe:5.0 to 8.0%, cu:5.0 to 8.0 percent, and the balance of Zr.
4. The preparation method according to claim 2, characterized in that the sintering temperature of the primary sintering solid solution is 1190-1240 ℃, and the holding time is 2-5 h.
5. The preparation method according to claim 2 or 4, characterized in that the solid solution temperature of the primary sintering solid solution is 1150-1200 ℃, and the holding time is 2-5 h.
6. The preparation method of claim 2, wherein the sintering temperature of the secondary sintering solid solution is 1190-1240 ℃, and the holding time is 2-5 h.
7. The preparation method according to claim 2 or 6, characterized in that the solid solution temperature of the secondary sintering solid solution is 1150-1200 ℃, and the holding time is 2-5 h.
8. The preparation method according to claim 2, 4 or 6, characterized in that in the primary sintering solid solution process, the sintering temperature is raised in stages, and the stage temperature raising comprises the following steps: raising the temperature to 300-400 ℃ at room temperature, and keeping the temperature for 1-3 h; then heating to 800-950 ℃, and preserving the heat for 1-3 h; then heating to 1100-1190 ℃, and preserving the heat for 1-3 h; then heating to the sintering temperature of 1190-1240 ℃, and preserving the heat for 2-5 h;
and/or in the secondary sintering solid solution process, the sintering temperature is raised in a staged way, and the staged temperature rise comprises the following steps: raising the temperature to 300-400 ℃ at room temperature, and keeping the temperature for 1-3 h; then heating to 800-950 ℃, and preserving the heat for 1-3 h; then heating to 1100-1190 ℃, and preserving the heat for 1-3 h; then the temperature is raised to the sintering temperature of 1190 to 1240 ℃, and the temperature is preserved for 2 to 5 hours.
9. The preparation method according to claim 2, wherein the aging treatment comprises primary aging and secondary aging, wherein the primary aging temperature is 800-850 ℃, the holding time is 20-40 h, the secondary aging temperature is 400-600 ℃, and the holding time is 10-20 h.
10. The preparation method according to claim 9, characterized in that after the primary aging heat preservation treatment, the temperature is reduced to the secondary aging temperature at a cooling rate of 0.3-0.8 ℃/min.
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