CN117790157A - Preparation method of high-performance self-protection rare earth permanent magnet material - Google Patents
Preparation method of high-performance self-protection rare earth permanent magnet material Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 106
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 100
- 239000000463 material Substances 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 229910001172 neodymium magnet Inorganic materials 0.000 claims abstract description 66
- 238000005496 tempering Methods 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims description 50
- 239000002184 metal Substances 0.000 claims description 50
- 238000000034 method Methods 0.000 claims description 30
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 20
- 238000004140 cleaning Methods 0.000 claims description 17
- 238000001816 cooling Methods 0.000 claims description 16
- 238000007254 oxidation reaction Methods 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 11
- 229910052786 argon Inorganic materials 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 238000004381 surface treatment Methods 0.000 claims description 8
- 238000009210 therapy by ultrasound Methods 0.000 claims description 8
- 238000004321 preservation Methods 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 6
- 230000009471 action Effects 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 238000005324 grain boundary diffusion Methods 0.000 claims description 6
- 150000002500 ions Chemical class 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 238000005554 pickling Methods 0.000 claims description 6
- 239000013077 target material Substances 0.000 claims description 6
- 229910052779 Neodymium Inorganic materials 0.000 claims description 4
- 238000004544 sputter deposition Methods 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 2
- 238000007605 air drying Methods 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 229910052718 tin Inorganic materials 0.000 claims description 2
- 238000011534 incubation Methods 0.000 claims 1
- 230000007797 corrosion Effects 0.000 abstract description 9
- 238000005260 corrosion Methods 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 230000008901 benefit Effects 0.000 abstract description 5
- 238000001755 magnetron sputter deposition Methods 0.000 abstract description 4
- 239000002131 composite material Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 10
- 238000005245 sintering Methods 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
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- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 description 2
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- 239000011248 coating agent Substances 0.000 description 2
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- 229910052742 iron Inorganic materials 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
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- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 1
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- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
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- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention relates to a preparation method of a high-performance self-protection rare earth permanent magnet material, a composite film layer which has good binding force and consists of non-rare earth metal, light rare earth metal and heavy rare earth metal is formed on the surface of a sintered NdFeB magnet in a magnetron sputtering mode, then the magnet is heated to 600-1000 ℃ in a vacuum environment, the temperature is kept for 2-48 hours, heavy rare earth, light rare earth and non-rare earth metal elements in the film layer diffuse into the magnet through a grain boundary at high temperature, and tempering treatment is carried out for 1-10 hours at 420-650 ℃ to obtain the NdFeB magnet with obviously improved magnetic performance and strong corrosion resistance on the surface of the magnet. The preparation method shortens the manufacturing period, reduces the manufacturing cost of the magnet, ensures that the NdFeB magnet has good corrosion resistance and has obvious production cost advantage.
Description
Technical Field
The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a preparation method of a high-performance self-protection rare earth permanent magnet material.
Background
The neodymium-iron-boron permanent magnet material is widely applied to fields of hybrid electric vehicles, wind power generation, energy-saving motors, variable-frequency air conditioners and the like, the fields require that a magnet works at high temperature for a long time, and the rare earth permanent magnet has higher intrinsic coercivity Hcj. An effective method for improving the Hcj of NdFeB (neodymium iron boron) sintered magnet is to replace the Nd of the main phase of the magnet by heavy rare earth elements such as Dy (dysprosium) and Tb (terbium) 2 Fe 14 Nd in B, formation (Nd, dy) 2 Fe 14 B，(Nd、Dy) 2 Fe 14 B has higher anisotropy than Nd 2 Fe 14 B, a step of preparing a composite material; thus, hcj of the magnet is significantly improved; but these heavy rare earth elements are scarce in resources and expensive. On the other hand, the magnetic moments of Nd and Fe are aligned in parallel, while Dy and Fe are aligned antiparallel. Thus, the remanence Br (remanence) and the maximum magnetic energy product (BH) max of the magnet are reduced.
At present, the research on the improvement of the magnet performance by utilizing the principle of grain boundary diffusion at home and abroad has been carried out for more than ten years. The grain boundary diffusion treatment technology mainly adopts modes of coating, depositing, plating, sputtering, sticking and the like, so that metal powder (Dy, tb or other rare earth elements) or a compound is attached to the outer surface of the magnet, and the metal powder or the compound is diffused into a main phase of the sintered magnet through the grain boundary by heat treatment.
In recent years, various processes for diffusing rare earth elements from the surface of a magnet to the inside of a matrix have been studied. The process method ensures that the permeated rare earth elements are distributed preferentially along the grain boundary and the surface area of the main phase grains, thereby not only improving the coercive force, but also saving the using amount of noble rare earth, and ensuring that the remanence and the magnetic energy product are not obviously reduced, so as to solve the influence of the grain boundary diffusion technology on the magnetic performance of the sintered NdFeB magnet to a certain extent. However, the process has low efficiency by using an evaporation or sputtering method in mass production, and a large amount of rare earth metal is scattered in a heating furnace chamber in the evaporation process, so that unnecessary waste of heavy rare earth metal is caused. And the problem that the coercivity is limited by coating rare earth oxide or fluoride on the surface for heating diffusion exists.
Disclosure of Invention
In order to overcome the defects of the existing detection method, the invention adopts a combined cathode target, a composite film layer which has good binding force and consists of non-rare earth metal, light rare earth metal and heavy rare earth metal is formed on the surface of a sintered NdFeB magnet in a magnetron sputtering mode, then the magnet is heated to 600-1000 ℃ in a vacuum environment, the temperature is kept for 2-48 hours, heavy rare earth, light rare earth and non-rare earth metal elements in the film layer diffuse into the magnet through a grain boundary at high temperature, and tempering treatment is carried out for 1-10 hours at 420-650 ℃ to obtain the NdFeB magnet with obviously improved magnetic property and strong corrosion resistance on the surface of the magnet.
The technical scheme adopted by the invention is that the preparation method of the high-performance self-protection rare earth permanent magnet material comprises the following steps:
step 1): preparation of a combined target, wherein the combined target has the following chemical formula A x B y C 100-x-y ；
Wherein A is light rare earth metal Nd, pr, la or Ce, B is heavy rare earth metal Dy, tb or Ho, C is non-rare earth metal Al, cu, ga, zn or Sn; x and y are the atomic percentage content of each component in the combined target material, and x=0-20 and y=0-80; the prepared combined target is used as a cathode;
step 2): processing the sintered NdFeB magnet into a shape to be treated, and then cleaning and drying the surface of the sintered NdFeB magnet to obtain a clean NdFeB magnet with surface treatment;
step 3): placing the NdFeB magnet with clean surface treatment on a metal plate, and taking the whole as an anode; placing an anode and the cathode prepared in the step 1) in a treatment cabin, introducing argon, applying direct current to the anode and the cathode, enabling ionized argon positive ions to accelerate to strike the cathode, sputtering cathode metal, and directionally attaching the cathode metal on the surface of the NdFeB magnet under the action of a magnetic field so as to form a deposited metal film;
step 4): placing the NdFeB magnet with the metal film in the step 3) in a vacuum heat treatment furnace, generating high-temperature grain boundary diffusion under the specified condition, and cooling along with the furnace; thereby obtaining a diffused NdFeB magnet; the specified conditions are: preserving heat for 2-48 h at 600-1000 ℃;
step 5): tempering the NdFeB magnet diffused in the step 4), and then carrying out low-temperature surface micro-oxidation treatment and heat preservation to obtain the magnet with improved performance.
Further, the purity requirements of the light rare earth metal, the heavy rare earth metal and the non-rare earth metal in the combined target in the step 1) are not lower than 99.99%.
Further, in the step 1), the light rare earth metal, the heavy rare earth metal and the non-rare earth metal in the combined target are formed into the combined target through arrangement and size control, and the physical contact between the targets is kept within 0.5 mm.
Further, the combined target is Nd 10 Tb 80 Cu 10 、Nd 10 Dy 80 Cu 10 、Nd 15 Tb 80 Al 5 Or Nd 15 Dy 80 Al 5 。
Further, the surface cleaning process in the step 2) is as follows:
immersing the NdFeB magnet in an oil removal tank for 10-15min to remove greasy dirt on the surface of the magnet; and then sequentially carrying out first water washing, acid washing, second water washing and ultrasonic treatment, and finally air-drying the surface of the NdFeB magnet.
Further, the pickling time is 20-45s, and the ultrasonic treatment time is 20-45s.
Further, in the step 2), the sintered NdFeB magnet is processed into a shape to be treated, and the orientation direction is controlled to be 1-20mm thick.
Further, in the step 3), the vacuum degree of the treatment chamber is pumped to 10 -2 Pa, then introducing argon to 10 -1 Pa, direct current of 32.5A and 480V is applied to the anode and the cathode.
Further, the film thickness of the deposited metal film in the step 3) is 2-40 μm.
Further, in the step 4), the vacuum degree in the vacuum heat treatment furnace is less than 10 -3 Pa, cooling to not higher than 50 ℃ along with the furnace.
Further, in step 5), the tempering treatment conditions are: tempering temperature is 420-650 ℃; tempering treatment time is 1-10h, and then cooling to 320-380 ℃ at a speed of 5 ℃/min.
Further, in the step 5), the conditions of the low-temperature surface micro-oxidation treatment and heat preservation are as follows: cooling to 320-380deg.C, introducing mixed gas with oxygen content of 1-6% and nitrogen content of 94-99%, and maintaining for 30-100min.
The invention adopts a combined target magnetron sputtering method to form a plurality of layers of multi-type metal combined adhesion layers on the surface of the magnet; the combined surface adhesion layer has remarkable effect of improving the magnetic performance of the magnet after high-temperature grain boundary diffusion, medium-temperature aging treatment and low-temperature surface micro-oxidation treatment. Meanwhile, a protective layer with high protection capability is generated on the surface of the magnet, so that the magnet is self-protected, and a new protective layer film is not required to be added outside the magnet. In addition, the preparation method shortens the manufacturing period, reduces the manufacturing cost of the magnet, ensures that the NdFeB magnet has good corrosion resistance and has obvious production cost advantage.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows Nd in an embodiment of the invention 15 Tb 80 Al 5 Schematic diagram of a combined target setting mode;
FIG. 2 shows Nd in an embodiment of the invention 15 Dy 80 Al 5 Schematic diagram of a combined target setting mode;
FIG. 3 shows Nd in an embodiment of the invention 10 Tb 80 Cu 10 Schematic diagram of a combined target setting mode;
FIG. 4 shows Nd in an embodiment of the invention 10 Dy 80 Cu 10 Schematic diagram of the combined target arrangement.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The NdFeB magnets to be treated used in the following methods were sintered NdFeB magnets, and the same batch and same brand sintered NdFeB magnets were used in each example.
The invention relates to a preparation method of a high-performance self-protection rare earth permanent magnet material, which mainly comprises the steps of preparing a combined target, cleaning the surface of a sintered magnet NdFeB, diffusing at a high temperature grain boundary, aging at a medium temperature, micro-oxidizing at a low temperature and the like, and particularly comprises the steps of attaching heavy rare earth, non-rare earth metals and the like on the surface of the NdFeB magnet by a magnetron sputtering combined cathode target method, and then optimizing the microstructure of the magnet by diffusing at the grain boundary when the high temperature is carried out, and improving the anti-demagnetizing capability of an epitaxial layer of NdFeB magnet grains, thereby improving the coercivity characteristics of the NdFeB magnet. The method not only realizes the high-efficiency utilization of rare earth elements in the preparation process, but also improves the magnetic performance of the magnet; meanwhile, a protective layer with high protection capability is generated on the surface of the magnet, so that the magnet is self-protected, and a new protective layer film is not required to be added outside the magnet.
Example 1
1) Preparation of Nd 15 Tb 80 Al 5 And (3) combining a target material: the arrangement mode of the combined target is shown in fig. 1, and the combined target is a combination of pure metal targets, wherein the proportion of light rare earth metal Nd is 15% (atomic percent), the proportion of heavy rare earth metal Tb is 80% (atomic percent), and the proportion of non-rare earth metal Al is 5% (atomic percent). In fig. 1, the heavy rare earth metal Tb is arranged in the middle and has two parts, the light rare earth metal Nd and the non-rare earth metal Al are arranged at two sides, the light rare earth metal Nd and the heavy rare earth metal Tb, the heavy rare earth metal Tb and the heavy rare earth metal Tb, and the heavy rare earth metal Tb and the non-rare earth metal Al form a combined target through arrangement and size control, the physical contact between the targets is kept within 0.5 mm. It should be noted that the metal purity of the light rare earth metal Nd, the heavy rare earth metal Tb and the non-rare earth metal Al is required to be 99.99%, and the surfaces are required to be dried and kept clean before bonding. Nd prepared according to the structure shown in FIG. 1 15 Tb 80 Al 5 The combined target acts as a cathode.
2) Sintered NdFeB magnets were machined to the shape to be treated (specification 20 x 15 x 2 mm) with the orientation direction controlled to a thickness of 2mm, and then subjected to a cleaning surface procedure. The surface cleaning procedure is as follows: soaking the magnet in an oil removal tank for 10min to remove greasy dirt on the surface of the magnet; then cleaning the surface with clear water, and then using dilute HNO with the mass concentration of 0.4wt% 3 Pickling for 20s, washing with water and performing ultrasonic treatment for 20s, and then rapidly drying the surface of the magnet by strong wind to obtain the NdFeB magnet with clean surface treatment.
3) Placing the NdFeB magnet with the clean surface treated in the step 2) on a metal plate, and taking the whole as an anode; the whole anode and the cathode obtained in the step 1) are placed in a treatment cabin, and the vacuum degree of the treatment cabin is pumped to 10 by a mechanical pump, a molecular pump and the like -2 Pa, then introducing argon gas to the pressure of 10 -1 Pa, a direct current of 32.5A, 480V was applied to both the anode and the cathode, thereby discharging between the cathode and the anode. The positive ions of the ionized gas are accelerated to strike the cathode, cathode metal is sputtered, and under the action of magnetic fieldOriented attachment to the NdFeB magnet surface, thereby forming a deposited metal film. The surface of the NdFeB magnet is uniformly deposited with a film rich in rare earth and pure metal (namely, a metal film composed of NdTb and Al), and the film thickness is about 12 mu m.
4) Placing the NdFeB magnet with the attached metal film prepared in the step 3) in a vacuum heat treatment furnace, wherein the vacuum degree in the vacuum heat treatment furnace is less than 10 -3 Pa, preserving heat for 10h at 935 ℃ to enable heavy rare earth, light rare earth and non-rare earth metal elements in the film layer to diffuse into the magnet through grain boundary at high temperature; and then cooling to not higher than 50 ℃.
5) Loading the NdFeB magnet diffused in the step 4) into a material box, placing the material box in a single layer, and placing the material box into a vacuum sintering furnace for tempering treatment, wherein the vacuum degree in the vacuum sintering furnace is 10 -2 pa, tempering treatment temperature is 490 ℃, and heat preservation is carried out for 4 hours; then cooling to 380 ℃ according to 5 ℃/min, and carrying out low-temperature surface micro-oxidation treatment; the low-temperature surface micro-oxidation treatment conditions are as follows: and (3) introducing mixed gas with the oxygen content of 3% and the nitrogen content of 97% and preserving heat for 50min to obtain the magnet with good corrosion resistance and remarkably improved magnetic property.
Example 1 magnet Performance changes before and after treatment are shown in Table 1, the coercivity is improved by 1200Oe, the remanence is slightly reduced, 165Gs is reduced, and the 24-hour weight loss performance is reduced from 5mg/cm 2 Reduced to 0.8mg/cm 2 。
Example 2
1) Preparation of Nd 15 Dy 80 Al 5 And (3) combining a target material: the arrangement mode of the combined target is shown in fig. 2, and the combined target is a combination of pure metal targets, wherein the proportion of light rare earth metal Nd is 15% (atomic percent), the proportion of heavy rare earth metal Dy is 80% (atomic percent), and the proportion of non-rare earth metal Al is 5% (atomic percent). The preparation process of the combined target is the same as that of example 1, and will not be described in detail here. It should be noted that the metal purity of the light rare earth metal Nd, the heavy rare earth metal Tb and the non-rare earth metal Al is required to be 99.99%, and the surfaces are required to be dried and kept clean before bonding. Nd prepared according to the structure shown in FIG. 2 15 Tb 80 Al 5 The combined target acts as a cathode.
2) The sintered NdFeB magnet was machined to the shape to be treated (specification 25 x 15 x 3 mm) with an orientation direction of 3mm thickness, and then subjected to a cleaning surface procedure. The cleaning surface procedure is as follows: and placing the magnet into a degreasing tank for soaking for 10min to remove greasy dirt on the surface of the magnet. Cleaning the surface with clear water, and then using dilute HNO with the mass concentration of 0.4wt% 3 Pickling for 20s, washing with water and performing ultrasonic treatment for 20s, and then rapidly drying the surface of the magnet by strong wind to obtain the NdFeB magnet with clean surface treatment.
3) Placing the NdFeB magnet with the clean surface treated in the step 2) on a metal plate, and taking the whole as an anode; the whole anode and the cathode obtained by the treatment in the step 1) are placed in a treatment cabin, and the vacuum degree of the treatment cabin is pumped to 10 by a mechanical pump, a molecular pump and the like -2 Pa, then introducing argon to 10 -1 Pa, direct current of 32.5A and 480V is applied to the anode and the cathode, so that the cathode and the anode discharge, positive ions of ionized gas are accelerated to strike the cathode, cathode metal is sputtered, and the cathode metal is directionally attached to the surface of the NdFeB magnet under the action of a magnetic field, so that a deposited metal film is formed. The surface of the NdFeB magnet is uniformly deposited with a film rich in rare earth and pure metal (namely, a metal film consisting of NdDy and Al) and the film thickness is about 18 mu m.
4) Placing the NdFeB magnet with the metal film obtained in the step 3) in a vacuum heat treatment furnace, wherein the vacuum degree is less than 10 -3 Pa, preserving heat for 10h at 940 ℃ to enable heavy rare earth, light rare earth and non-rare earth metal elements in the film layer to diffuse into the magnet through grain boundaries at high temperature; cooling to not higher than 50 ℃ along with the furnace.
5) Loading the NdFeB magnet diffused in the step 4) into a material box, placing the material box in a single layer, placing the material box into a vacuum sintering furnace for tempering treatment, and controlling the vacuum degree in the vacuum sintering furnace to be 10 -2 pa, tempering treatment temperature is 490 ℃, and heat preservation is carried out for 4 hours; then cooling to 380 ℃ according to 5 ℃/min, and carrying out low-temperature surface micro-oxidation treatment; the low-temperature surface micro-oxidation treatment conditions are as follows: and (3) introducing mixed gas with the oxygen content of 3% and the nitrogen content of 97% and preserving heat for 50min to obtain the magnet with good corrosion resistance and remarkably improved magnetic property.
Example 2 before and after treatment of magnetic PropertiesThe change is shown in Table 1, the coercive force is improved by 750Oe, the residual magnetism is slightly reduced, 175Gs is reduced, and the weight loss performance of 24 hours is reduced from 5mg/cm 2 Reduced to 1.2mg/cm 2 。
Example 3
1) Preparation of Nd 10 Tb 80 Cu 10 And (3) combining a target material: the arrangement mode of the combined target is shown in fig. 3, and the combined target is a combination of pure metal targets, wherein the proportion of light rare earth metal Nd is 10% (atomic percent), the proportion of heavy rare earth metal Tb is 80% (atomic percent), and the proportion of non-rare earth metal Cu is 10% (atomic percent). In fig. 3, the light rare earth metal Nd and the heavy rare earth metal Tb are arranged at intervals on the left side and are divided into two parts, the non-rare earth metal Cu is arranged on the right side and is divided into only one part, the light rare earth metal Nd and the heavy rare earth metal Tb and the non-rare earth metal Cu form a combined target through arrangement and size control, physical contact is carried out between the targets, and the gap is kept within 0.5 mm. It should be noted that the metal purity of the light rare earth metal Nd, the heavy rare earth metal Tb and the non-rare earth metal Cu is required to be 99.99%, and the surfaces thereof should be dried and kept clean before bonding. Nd prepared according to the structure shown in FIG. 3 10 Tb 80 Cu 10 The combined target acts as a cathode.
2) The sintered NdFeB magnet was machined to the shape to be treated (specification 25 x 15 x 5 mm) with an orientation direction of 5mm thickness, and then subjected to a cleaning surface procedure. The cleaning surface procedure is as follows: and placing the magnet into a degreasing tank for soaking for 10min to remove greasy dirt on the surface of the magnet. Cleaning the surface with clear water, and then using dilute HNO with the mass concentration of 0.4wt% 3 Pickling for 35s, washing with water and performing ultrasonic treatment for 35s, and rapidly drying the surface of the magnet by strong wind to obtain the NdFeB magnet with clean surface treatment.
3) Placing the NdFeB magnet with the clean surface treated in the step 2) on a metal plate, and taking the whole as an anode; the whole anode and the cathode prepared by the step 1) are placed in a treatment cabin, and the vacuum degree of the treatment cabin is pumped to 10 by a mechanical pump, a molecular pump and the like -2 Pa, then introducing argon to 10 -1 Pa, applying 32.5A, 480V direct current to the anode and cathode, thereby discharging between the cathode and anode, and ionizingThe positive ions of the gas of (2) are accelerated to strike the cathode, cathode metal is sputtered, and the cathode metal is directionally attached to the surface of the NdFeB magnet under the action of a magnetic field, so that a deposited metal film is formed. The surface of the NdFeB magnet is uniformly deposited with a film rich in rare earth and pure metal (namely, a metal film consisting of NdTb and Cu), and the film thickness is about 30 mu m.
4) Placing the magnet with the metal film attached obtained in the step 3) in a vacuum heat treatment furnace, wherein the vacuum degree is less than 10 -3 Pa, preserving heat for 25h at 940 ℃ to enable heavy rare earth, light rare earth and non-rare earth metal elements in the film layer to diffuse into the magnet through grain boundaries at high temperature; cooling to not higher than 50 ℃ along with the furnace.
5) Loading the NdFeB magnet diffused in the step 4) into a material box, placing the material box in a single layer, placing the material box into a vacuum sintering furnace for tempering treatment, and controlling the vacuum degree in the vacuum sintering furnace to be 10 -2 pa, tempering treatment temperature is 490 ℃, and heat preservation is carried out for 5h; cooling to 380 ℃ at a speed of 5 ℃/min, and performing low-temperature surface micro-oxidation treatment; the low-temperature surface micro-oxidation treatment conditions are as follows: and (3) introducing mixed gas with the oxygen content of 3% and the nitrogen content of 97% and preserving heat for 70min to obtain the magnet with good corrosion resistance and remarkably improved magnetic property.
The magnet performance change before and after the treatment in example 3 is shown in Table 1, the coercive force is improved by 1100Oe, the remanence is slightly reduced, and 170Gs and 24h are reduced; the weight loss performance of 24 hours is 5mg/cm 2 Reduced to 0.82mg/cm 2 。
Example 4
1) Preparation of Nd 10 Dy 80 Cu 10 And (3) combining a target material: the arrangement mode of the combined target is shown in fig. 4, and the combined target is a combination of pure metal targets, wherein the proportion of light rare earth metal Nd is 10% (atomic percent), the proportion of heavy rare earth metal Dy is 80% (atomic percent), and the proportion of non-rare earth metal Cu is 10% (atomic percent). The preparation process of the combined target is the same as that of example 3, and will not be described in detail here. It should be noted that the metal purity of the light rare earth metal Nd, the heavy rare earth metal Tb and the non-rare earth metal Cu is required to be 99.99%, and the surfaces thereof should be dried and kept clean before bonding. Nd prepared according to the Structure shown in FIG. 4 10 Tb 80 Cu 10 The combined target acts as a cathode.
2) The sintered NdFeB magnet was machined to the shape to be treated (specification 25 x 15 x 3 mm) with an orientation direction of 5mm thickness, and then subjected to a cleaning surface procedure. The cleaning surface procedure is as follows: and placing the magnet into a degreasing tank for soaking for 10min to remove greasy dirt on the surface of the magnet. Cleaning the surface with clear water, and then using dilute HNO with the mass concentration of 0.4wt% 3 Pickling for 30s, washing with water and performing ultrasonic treatment for 30s, and then rapidly drying the surface of the magnet by strong wind to obtain the NdFeB magnet with clean surface treatment.
3) Placing the NdFeB magnet with the clean surface treated in the step 2) on a metal plate, and taking the whole as an anode; the whole anode and the cathode prepared by the step 1) are placed in a treatment cabin, and the vacuum degree of the treatment cabin is pumped to 10 by a mechanical pump, a molecular pump and the like -2 Pa, then introducing argon to 10 -1 Pa, direct current of 32.5A and 480V is applied to the anode and the cathode, so that the cathode and the anode discharge, positive ions of ionized gas are accelerated to strike the cathode, cathode metal is sputtered, and the cathode metal is directionally attached to the surface of the NdFeB magnet under the action of a magnetic field, so that a deposited metal film is formed. The surface of the NdFeB magnet is uniformly deposited with a film rich in rare earth and pure metal (namely, a metal film consisting of NdDy and Cu) with a film thickness of about 30 mu m.
4) Placing the magnet with the metal film attached obtained in the step 3) in a vacuum heat treatment furnace, wherein the vacuum degree is less than 10 -3 Pa, preserving heat for 25h at 920 ℃ to enable heavy rare earth, light rare earth and non-rare earth metal elements in the film layer to diffuse into the magnet through grain boundaries at high temperature; cooling to not higher than 50 ℃ along with the furnace.
5. Loading the NdFeB magnet diffused in the step 4) into a material box, placing the material box in a single layer, placing the material box into a vacuum sintering furnace for tempering treatment, and controlling the vacuum degree in the vacuum sintering furnace to be 10 -2 pa, tempering treatment temperature is 490 ℃, and heat preservation is carried out for 5h; then cooling to 380 ℃ according to 5 ℃/min, and carrying out low-temperature surface micro-oxidation treatment; the low-temperature surface micro-oxidation treatment conditions are as follows: and (3) introducing mixed gas with the oxygen content of 3% and the nitrogen content of 97% and preserving heat for 70min to obtain the magnet with good corrosion resistance and remarkably improved magnetic property.
Example 4 magnet Performance Change before and after treatment As shown in Table 1, coercivity was improved by 8500Oe, remanence was reduced by 170Gs, and 24h weight loss performance was improved from 5mg/cm 2 Reduced to 1.29mg/cm 2 。
Table 1 examples 1-4 data on changes in magnet properties before and after treatment
By the preparation method, the coercive force of the magnet can be improved by 30-90%, the residual magnetism is reduced by 1-2%, the usage amount of heavy rare earth can be saved by 30-50% by the magnet with the same performance, the magnetic performance can be obviously improved, and the magnetic performance of the NdFeB magnet with strong corrosion resistance can be formed on the surface of the magnet.
Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (12)
1. The preparation method of the high-performance self-protection rare earth permanent magnet material comprises the following steps:
step 1): preparation of a combined target, wherein the combined target has the following chemical formula A x B y C 100-x-y ；
Wherein A is light rare earth metal Nd, pr, la or Ce, B is heavy rare earth metal Dy, tb or Ho, C is non-rare earth metal Al, cu, ga, zn or Sn; x and y are the atomic percentage content of each component in the combined target material, and x=0-20 and y=0-80; the prepared combined target is used as a cathode;
step 2): processing the sintered NdFeB magnet into a shape to be treated, and then cleaning and drying the surface of the sintered NdFeB magnet to obtain a clean NdFeB magnet with surface treatment;
step 3): placing the NdFeB magnet with clean surface treatment on a metal plate, and taking the whole as an anode; placing an anode and the cathode prepared in the step 1) in a treatment cabin, introducing argon, applying direct current to the anode and the cathode, enabling ionized argon positive ions to accelerate to strike the cathode, sputtering cathode metal, and directionally attaching the cathode metal on the surface of the NdFeB magnet under the action of a magnetic field so as to form a deposited metal film;
step 4): placing the NdFeB magnet with the metal film in the step 3) in a vacuum heat treatment furnace, generating high-temperature grain boundary diffusion under the specified condition, and cooling along with the furnace; thereby obtaining a diffused NdFeB magnet; the specified conditions are: preserving heat for 2-48 h at 600-1000 ℃;
step 5): tempering the NdFeB magnet diffused in the step 4), and then carrying out low-temperature surface micro-oxidation treatment and heat preservation to obtain the magnet with improved performance.
2. The method of claim 1, wherein the combined target in step 1) has a purity requirement of not less than 99.99% for light rare earth metals, heavy rare earth metals, and non-rare earth metals.
3. The method of claim 2, wherein in step 1), the light rare earth metal, the heavy rare earth metal and the non-rare earth metal in the combined target are formed into the combined target through arrangement and size control, and physical contact is kept between the targets, and a gap is kept within 0.5 mm.
4. A method according to any one of claims 1 to 3, wherein the combined target is Nd 10 Tb 80 Cu 10 、Nd 10 Dy 80 Cu 10 、Nd 15 Tb 80 Al 5 Or Nd 15 Dy 80 Al 5 。
5. The method of claim 1, wherein the surface cleaning in step 2) is performed by:
immersing the NdFeB magnet in an oil removal tank for 10-15min to remove greasy dirt on the surface of the magnet; and then sequentially carrying out first water washing, acid washing, second water washing and ultrasonic treatment, and finally air-drying the surface of the NdFeB magnet.
6. The method of claim 5, wherein the pickling time is 20-45s and the ultrasonic treatment time is 20-45s.
7. The process according to claim 1, wherein in step 2) the sintered NdFeB magnet is processed into a shape to be treated, the orientation direction of which is controlled to a thickness of 1-20 mm.
8. The method according to claim 1, wherein in step 3), the vacuum of the process chamber is pumped to 10 -2 Pa, then introducing argon to 10 -1 Pa, direct current of 32.5A and 480V is applied to the anode and the cathode.
9. The method according to claim 1 or 8, wherein the deposited metal film in step 3) has a film thickness of 2-40 μm.
10. The method according to claim 1, wherein in the step 4), the degree of vacuum in the vacuum heat treatment furnace is less than 10 -3 Pa, cooling to not higher than 50 ℃ along with the furnace.
11. The method of claim 1, wherein in step 5), the tempering conditions are: tempering temperature is 420-650 ℃; tempering treatment time is 1-10h, and then cooling to 320-380 ℃ at a speed of 5 ℃/min.
12. The method of claim 11, wherein in step 5), the conditions for the low temperature surface micro-oxidation treatment and incubation are: cooling to 320-380deg.C, introducing mixed gas with oxygen content of 1-6% and nitrogen content of 94-99%, and maintaining for 30-100min.
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