CN113345708B - Heat treatment equipment and diffusion method of neodymium iron boron magnet - Google Patents
Heat treatment equipment and diffusion method of neodymium iron boron magnet Download PDFInfo
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- 238000009792 diffusion process Methods 0.000 title claims abstract description 122
- 238000010438 heat treatment Methods 0.000 title claims abstract description 116
- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 66
- 239000000463 material Substances 0.000 claims abstract description 14
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 30
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 20
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- 229910010271 silicon carbide Inorganic materials 0.000 claims description 6
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 6
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 239000011733 molybdenum Substances 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
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- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Abstract
The invention discloses a heat treatment device and a diffusion method of a neodymium iron boron magnet, wherein the heat treatment device comprises: the furnace body comprises a heating chamber and a low-temperature chamber, the heating chamber and the low-temperature chamber are separated by an intercepting net, and the mesh size of the intercepting net is smaller than that of the neodymium iron boron magnet; and the lifting part is arranged at one end of the furnace body, and lifts the heating chamber through the lifting part, so that other materials except the magnet in the heating chamber enter the low-temperature chamber. The diffusion method based on the heat treatment equipment can be used for grain boundary diffusion of small-size magnets and special-shaped magnets, has high diffusion efficiency, reduces adhesion between the magnets and diffusion sources, reduces consumption of the diffusion sources, reduces collision between the magnets, and reduces corner missing of the magnets.
Description
Technical Field
The invention belongs to the field of magnetic material preparation, and particularly relates to heat treatment equipment for neodymium iron boron magnet diffusion, and further relates to a neodymium iron boron magnet diffusion method.
Background
As a third generation rare earth permanent magnet material, a sintered Nd-Fe-B magnet is called as "Magang" because of its extremely high magnetic performance, and is an alloy formed by smelting rare earth elements RE (Nd, pr, etc.), transition metals TM (Fe, co, etc.) and B according to a certain component proportion, then is pressed and formed by adopting a powder metallurgy method, and is sintered to obtain a high-performance magnetic material. With the increasingly wide application of sintered neodymium iron boron materials, especially the application in high temperature fields such as automobile motors, the neodymium iron boron materials are required to have high coercive force so as to meet the requirement of continuous high temperature application. Therefore, the improvement of the coercive force of the magnet to widen the high-temperature application field of the neodymium iron boron magnet becomes the requirement of industry development.
The traditional method for improving the sintered neodymium iron boron is mainly to add heavy rare earth element Dy or Tb into neodymium iron boron alloy in the smelting process. On one hand, however, dy and Tb have an anti-ferromagnetic coupling effect with Fe, so that the remanence and the magnetic energy product of the material can be reduced; on the other hand, dy and Tb are low in the crust and belong to non-renewable resources.
The grain boundary diffusion technology is a new technology developed in the industry for improving the performance of sintered neodymium iron boron, in particular improving the coercivity. The grain boundary diffusion is a new technology for greatly improving the coercive force of the magnet by diffusing heavy rare earth elements in a diffusion source to the edge of a main phase grain boundary of the magnet at a certain temperature. In recent years, various grain boundary diffusion methods are developed in the industry to improve the coercive force of a magnet, and the methods mainly comprise coating, electrodeposition, magnetron sputtering and the like. However, these methods require that the magnet be placed on a plate and then the coating process is completed, which not only makes the operation complicated, but also has high requirements for equipment. Especially for small-sized magnets, the wobble plate needs to consume a lot of time, which is not suitable for industrialization. In addition, for special-shaped magnets such as circular rings and circular tube type magnets, the inner ring surface of the magnet is difficult to be coated, so that the coercive force of the magnet is not greatly improved. Therefore, the conventional grain boundary diffusion technology has many limitations.
The rotary diffusion developed to solve the above problems has well solved the problems faced by grain boundary diffusion of small magnets and shaped magnets, for example, in chinese patent applications CN112802677A and CN109192489A, it is disclosed that a grain boundary diffusion process is completed by mixing a magnet with a heavy rare earth metal or alloy, and then placing the mixture in a rotary furnace for heat treatment. The rotation of the furnace body can make the contact between the magnet and the heavy rare earth diffusion source more uniform. However, the current rotational diffusion technology still has the following problems: (1) the diffusion temperature is limited, the effect of greatly improving the coercive force is usually achieved by adopting a method of raising the temperature and prolonging the time, but when the temperature reaches more than 750 ℃, adhesion can be generated between the magnet and a diffusion source; (2) the furnace body rotates for a long time, and the magnet is seriously collided, so that the unfilled corner is more easily generated; (3) the magnet contacts with the diffusion source for a long time, heavy rare earth is excessively consumed, and the phenomenon of over-diffusion is generated, so that the residual magnetism of the magnet is obviously reduced.
Disclosure of Invention
In view of the above, the present invention is directed to a heat treatment apparatus and a diffusion method for ndfeb magnets, which can be used for grain boundary diffusion of small-sized magnets and irregular magnets, and has high diffusion efficiency, reduced adhesion between the magnets and the diffusion source, reduced consumption of the diffusion source, reduced collision between the magnets, and reduced occurrence of corner chipping of the magnets.
In order to achieve the purpose, the invention adopts the following technical scheme:
the present invention provides a heat treatment apparatus comprising:
the device comprises a rotatable furnace body, wherein the furnace body comprises a heating chamber and a low-temperature chamber, the heating chamber and the low-temperature chamber are separated by an interception net, and the mesh size of the interception net is smaller than that of the neodymium iron boron magnet;
and the lifting part is arranged at one end of the furnace body, and the furnace body is lifted up through the lifting part, so that materials except the magnet in the heating chamber enter the low-temperature chamber, and the separation of the magnet and other materials is realized.
Furthermore, the periphery of the furnace body is sleeved with a heating body for heating the heating chamber.
Further, the interception net is a molybdenum net.
The invention further provides a neodymium iron boron magnet diffusion method based on any one of the above, which comprises the following steps:
mixing the cleaned neodymium-iron-boron magnet and a diffusion source, and then carrying out rotary heating under a vacuum condition, wherein the heating temperature is 600-750 ℃, and the heat preservation time is 1-5 hours;
stopping rotating, separating the NdFeB magnet from the diffusion source, continuously heating the NdFeB magnet to perform high-temperature diffusion treatment at the temperature of 800-950 ℃, and preserving heat for 1-20h.
Further, the diffusion source is a heavy rare earth metal ball, and the heavy rare earth metal is selected from Dy or Tb.
Furthermore, the diameter of the heavy rare earth metal ball is 0.5-5mm.
Further, the mass ratio of the neodymium iron boron magnet to the heavy rare earth metal ball is 1:0.5 to 5.
Further, the vacuum condition in the furnace body is that the air pressure is less than 1 x 10 -2 Pa; the rotating speed of the furnace body is 1-20r/min.
Further, the diffusion source also comprises a stirring aid, wherein the stirring aid is selected from at least one of zirconia, silicon nitride, silicon carbide and boron nitride, and is spherical with the particle size not exceeding 5 mm; the mass ratio of the neodymium iron boron magnet to the stirring aid is 1:0.1 to 3.
Further, the neodymium iron boron magnet still includes aging treatment after high temperature diffusion treatment, aging treatment specifically is: and taking out the neodymium iron boron magnet subjected to high-temperature diffusion treatment, and preserving the heat at 450-550 ℃ for 3-5h.
Compared with the prior art, the invention has the following beneficial effects:
in the heat treatment equipment, the furnace body can rotate, so that the rotary diffusion is conveniently realized; the heating chamber and the low-temperature chamber are arranged in the furnace body, and the magnet and the diffusion source can be separated by matching with the lifting part outside the furnace body, so that the grain boundary diffusion of the magnet can be carried out in two parts.
The diffusion method based on the heat treatment equipment reduces the contact temperature and time of the magnet and the diffusion source in the first stage, and then separates the diffusion source from the magnet and carries out secondary high-temperature diffusion, so that the adhesion between the magnet and the diffusion source is reduced, and the consumption of the diffusion source is reduced. According to the diffusion method, the rotation is started only in a short time when the magnet is in contact with the diffusion source, and the magnet is not rotated any more after being separated from the diffusion source in the second stage, so that the collision between the magnets is reduced, and the unfilled corner of the magnet is reduced.
The diffusion method can be used for grain boundary diffusion of small-size magnets and special-shaped magnets, and has high diffusion efficiency.
Drawings
FIG. 1 is a schematic view showing the structure of the heat treatment apparatus according to a preferred embodiment of the present invention in an operating state.
In the figure: 10-furnace body, 101-heating chamber, 102-low temperature chamber, 103-interception net, 104-heating body, 105-magnetofluid and 106-rotation driving device;
20-a lifting part.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
As shown in fig. 1, a first aspect of the present invention discloses a heat treatment apparatus comprising a furnace body 10 and an elevating portion 20, the furnace body 10 being horizontally disposed to be rotatable along an axial line thereof.
The furnace body 10 comprises a heating chamber 101 and a low-temperature chamber 102 inside, the heating chamber 101 can be heated, the low-temperature chamber 102 refers to a chamber which is not heated, in the embodiment, the heating chamber 101 and the low-temperature chamber 102 are separated by an interception net 103, wherein the size and the shape of the meshes of the interception net 103 are not particularly limited as long as neodymium iron boron magnets can be ensured not to pass through, and diffusion sources and the like can pass through, furthermore, the selection of the material of the interception net 103 is not particularly limited as long as adhesion with the diffusion sources can be ensured not to occur at high temperature, and in some embodiments of the invention, a molybdenum net is adopted as the interception net 103. A pair of magnetic fluids 105 is arranged at two ends of the furnace body 10, the magnetic fluids 105 are connected with the furnace body 10 through flanges, and the magnetic fluids 105 are used for transmitting rotary motion to the furnace body 10 and simultaneously realizing vacuum sealing on the furnace body 10. The heat treatment equipment further comprises a rotary driving device 106, the rotary driving device 106 is positioned at the lower part of the furnace body 10 and arranged between the magnetic fluids 105, the rotary driving device comprises a driving motor, the driving motor and the furnace body 10 are in chain transmission, and the magnetic fluids 105 are matched with the rotary driving device 106 to realize the rotation and the sealing of the whole furnace body 10. Further, in order to ensure that only the heating chamber 101 is heated when the heating temperature rises, as shown in fig. 1, a heating body 104 is sleeved on the outer periphery of the furnace body 10 for heating the heating chamber 101 in the present embodiment. Specifically, the magnetic fluid 105, the rotation driving device 106, the heating body 104, and the lifting unit 20 are all connected to a computer control system of the apparatus, so as to control the rotation and heating of the furnace body 10 and the lifting of the furnace body 10. The method specifically comprises the following steps: (1) rotation: the equipment control panel is clicked to start rotation, and the rotation driving device 106 drives the motor to operate to drive the magnetic fluid 105 and the furnace body 10 to start rotation. (2) heating: heating is started by clicking on the control panel of the equipment, and the heating body 104 can perform heating. (3) lifting: when the equipment control panel is clicked to rise, the lifting part 20 is lifted, so that one side of the furnace body 10 is lifted to a required height and then stopped. The lifting part 20 may be a mechanism capable of lifting and lowering, which is conventionally used in the art, and the connection between each computer control system and each mechanism is known in the art, and will not be described in detail here.
Further, referring to fig. 1, the elevating portion 20 is located at one end of the furnace body 10, and the specific position thereof is adjusted according to the heating chamber 101, on one hand, the elevating portion 20 is used to maintain the furnace body 10 in a horizontal state, and on the other hand, the elevating portion 20 is raised to lift the heating chamber 101 in the furnace body 10, so that the diffusion source in the heating chamber 101 enters the low temperature chamber 102 from the heating chamber 101, and the ndfeb magnet continues to remain in the heating chamber 101.
In addition, the furnace body 10 can be connected with an external vacuum system to realize the control of the vacuum state in the furnace body 10. Through the heat treatment equipment, the high-efficiency diffusion of the neodymium iron boron magnet can be realized, the neodymium iron boron magnet which has high coercive force and good thermal stability and is reduced in unfilled corners is obtained, and the consumption of a diffusion source can be saved.
The second aspect of the present invention provides a method for diffusing a neodymium iron boron magnet based on the heat treatment apparatus of the first aspect of the present invention, comprising the following steps:
mixing the cleaned neodymium-iron-boron magnet and a diffusion source, and then carrying out rotary heating under a vacuum condition, wherein the heating temperature is 600-750 ℃, and the heat preservation time is 1-5 hours;
stopping rotating, separating the neodymium iron boron magnet from the diffusion source, continuously heating the neodymium iron boron magnet to perform high-temperature diffusion treatment, keeping the temperature at 800-950 ℃, and preserving the heat for 1-20h.
Specifically, the cleaned ndfeb magnet and the diffusion source are added into a heating chamber 101 in the heat treatment equipment according to the first aspect of the present invention;
vacuumizing the furnace body 10, heating and rotating the furnace body 10 to make the temperature inside the heating chamber 101 reach 600-750 ℃, and preserving heat for 1-5h;
stopping rotating the furnace body 10, lifting the heating chamber 101, and enabling the diffusion source to enter the low-temperature chamber 102, and then enabling the furnace body 10 to be horizontal;
heating the heating chamber 101 to 800-950 ℃, and preserving the heat for 1-20h for high-temperature diffusion treatment.
According to the invention, the NdFeB magnet and the diffusion source are firstly rotated at a lower temperature, then the NdFeB magnet and the diffusion source are separated, the temperature is raised, the rotation is stopped, and the high-temperature diffusion treatment is carried out, so that the diffusion source is prevented from being adhered to the magnet at a high temperature, the rotation time is short, the problem of corner defect caused by long-time collision of the magnet is greatly avoided, in addition, the consumption of the diffusion source is reduced, the cost is saved, the coercive force of the diffused NdFeB magnet is greatly improved, and the problems of corner defect and adhesion are improved.
Further, in the present invention, before diffusion, the ndfeb magnet and the diffusion source are preferably cleaned and surface cleaned, where the cleaning of the ndfeb magnet is not particularly limited, and may adopt a conventional cleaning manner in the art, and in one or more embodiments of the present invention, the cleaning of the ndfeb magnet includes oil removal, acid cleaning, ultrasound, and blow drying, and further, the oil removal, acid cleaning, ultrasound, and blow drying may adopt a conventional manner in the art, and in one or more embodiments of the present invention, the oil removal process specifically includes: removing oil in NaOH solution with pH value of 10-11 and temperature of 60-70 ℃ for 13-15 min; the pickling process specifically comprises the following steps: pickling for 30-90 s by using nitric acid with the mass concentration of 3% -5%; the ultrasonic and blow-drying process specifically comprises the following steps: and (3) placing the acid-washed neodymium-iron-boron magnet in distilled water, ultrasonically cleaning for 1-3 min, and drying for later use.
Further, the diffusion source in the present invention refers to any diffusion substance that can be used for grain boundary diffusion of neodymium iron boron magnet, and is a heavy rare earth metal that is more commonly used in the art, and in one or more embodiments of the present invention, the diffusion source is a heavy rare earth metal ball, and the heavy rare earth metal is selected from Dy or Tb, further significantly increasing the coercivity of the magnet, and the shape of the diffusion source in the present invention is not particularly limited, and the shape of the diffusion source can be matched with the mesh of the interception net, and in some preferred embodiments of the present invention, in order to make the diffusion source easily and smoothly enter the low temperature chamber, preferably, the diffusion source is spherical.
The diameter of the heavy rare earth metal ball in the invention is generally not more than 5mm, so that the contact effect of the diffusion source and the surface of the magnet is increased, and the diffusion effect is obviously improved, and in one or more embodiments of the invention, the diameter of the heavy rare earth metal ball is 0.5-5mm.
In one or more embodiments of the present invention, the mass ratio of the neodymium-iron-boron magnet to the heavy rare-earth metal ball is 1:0.5 to 5.
In order to avoid the phenomena of high-temperature diffusion and oxidation of the product during the heat treatment, the diffusion in the invention is carried out under the vacuum condition, and in one or more embodiments of the invention, the vacuum state in the furnace body is the air pressure less than 1 x 10 - 2 Pa。
Further, the rotating speed of the furnace body is not particularly limited, and the conventional rotating diffusion parameters are adopted, so that the rotating speed is not too high, the serious collision of the magnet and the corner defect are avoided, and in one or more embodiments of the invention, the rotating speed of the furnace body is 1-20r/min.
Further, preferably, the diffusion source further comprises a stirring aid, so as to play a role of buffering during rotation, reduce direct collision between the magnets and further reduce the probability of generating unfilled corners of the magnets, and in one or more embodiments of the invention, the stirring aid is selected from at least one of zirconia, silicon nitride, silicon carbide and boron nitride, and is in a spherical shape with a particle size not exceeding 5mm.
The amount of the mixing aid is not particularly limited, and can be adjusted according to the experience of a person skilled in the art, on one hand, the amount of the mixing aid is not too much, so that the diffusion effect is diluted, and on the other hand, the mixing aid does not further reduce the unfilled corner of the magnet when the amount of the mixing aid is too little, and in one or more embodiments of the invention, the mass ratio of the neodymium iron boron magnet to the mixing aid is 1.
More preferably, in one or more embodiments of the present invention, after the high-temperature diffusion treatment, the neodymium iron boron magnet further includes an aging treatment, so as to further improve the coercivity of the magnet, where the aging treatment specifically is: and taking out the neodymium iron boron magnet subjected to high-temperature diffusion treatment, and preserving the heat at 450-550 ℃ for 3-5h.
The technical solution of the present invention will be more clearly and completely described below with reference to specific embodiments.
Example 1
Pretreatment of neodymium iron boron magnet
A commercial Nd-Fe-B magnet was cut into cylindrical blocks of phi 4X 10 (mm) (the axial direction was the orientation direction, and the mark was N50) for several uses.
And (3) removing oil, pickling, ultrasonically treating and blow-drying the cylindrical sample block. Wherein, the degreasing process comprises the following steps: adopting NaOH solution with pH value of 10, wherein the oil removing temperature is 60 ℃, and the oil removing time is 13min; the pickling process comprises the following steps: adopting nitric acid with the concentration of 3% for pickling for 90s; then, ultrasonically cleaning the product after acid washing in distilled water for 2min; finally, the product was blow dried for use and labeled as sample A0.
Diffusion treatment of neodymium-iron-boron magnet
A sample A0, zirconia balls having a diameter of 2mm, and Dy ball particles having a diameter of 1mm were placed in a heating chamber 101 in a furnace body 10 shown in fig. 1 at a mass ratio of 1 -3 After Pa, heating the heating chamber 101 to 600 ℃, preserving heat for 2h, and rotating the furnace body 10 at the speed of 1 r/min while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Dy balls and the zirconia balls from the magnet, wherein the Dy balls and the zirconia balls enter the low-temperature chamber 102 from the intercepting net 103, and the magnet is intercepted by the intercepting net 103 and is continuously remained in the heating chamber 101;
returning the furnace body 10 to the horizontal position, stopping rotating, continuously raising the temperature of the heating chamber 101 to 800 ℃, preserving the temperature for 5 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 450 ℃ for 3 h.
Comparative example 1
This comparative example applied the same diffusion treatment to the magnet as in example 1, except that: the lifting system was not started, the diffusion source was not separated from the magnet, and the other parameters and steps were the same as in example 1.
Comparative example 2
This comparative example applied the same diffusion treatment to the magnet as in example 1, except that: after the furnace body 10 is returned to the horizontal state, in the high-temperature diffusion stage, the rotation is still started until the diffusion is finished, and other parameters are the same as those in embodiment 1.
Example 2
Pretreatment of neodymium iron boron magnet
The same as in example 1.
Diffusion treatment of neodymium-iron-boron magnet
Will try outSample A0, silicon nitride spheres with a diameter of 5mm, tb spheres with a diameter of 0.5mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 according to a mass ratio of 1 -3 After Pa, heating the heating chamber 101 to 750 ℃, preserving heat for 5 hours, and rotating the furnace body 10 at 10 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Tb ball and the silicon nitride ball from the magnet, enabling the Tb ball and the silicon nitride ball to enter the low-temperature chamber 102 from the blocking net 103, blocking the magnet by the blocking net 103, and continuously remaining in the heating chamber 101;
returning the furnace body 10 to the horizontal position, stopping rotating, continuously raising the temperature of the heating chamber 101 to 900 ℃, preserving the heat for 3 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 500 ℃ for 3 h.
Comparative example 3
This comparative example applied the same diffusion treatment to the magnet as in example 2, except that: and (3) starting the lifting part 20, separating the Tb ball and the zirconia ball from the magnet, and then performing diffusion treatment on the magnet by still adopting 750 ℃ and keeping the temperature for 5 hours in the subsequent diffusion stage without increasing the temperature, wherein other steps and parameters are the same as those in the embodiment 2.
Test example 1
The magnets of examples 1-2 and comparative examples 1-3 were subjected to appearance inspection, and the magnetic properties of the magnet of blank A0 and those of the magnets of examples 1-2 and comparative examples 1-3 were measured by a permanent magnet material measuring system in accordance with the requirements of GB/T3217-2013 permanent magnet (hard magnetic) material-magnetic test method, and the results are shown in Table 1.
TABLE 1 comparison of the performances of N50 Nd-Fe-B permanent-magnet materials after treatment under different conditions
Note: the missing angle ratio% = number of missing angle magnets/total number of magnets in table 1.
As can be seen from the results in table 1, compared with the comparative example, the neodymium iron boron magnet obtained by diffusion through the diffusion method of the present invention has a greatly improved coercive force with almost no loss of remanence of the magnet, and the magnet is not bonded to the diffusion source, and the corner missing condition of the magnet is significantly improved.
Example 3
Pretreatment of neodymium iron boron magnet
Cutting a commercial neodymium iron boron magnet into annular sample blocks with the diameter of (phi 20-phi 10) multiplied by 10 (mm) (the state is axial orientation, non-magnetization and the mark is 42 SH) for standby;
and (3) carrying out oil removal, acid cleaning, ultrasonic treatment and blow drying on the circular sample block. Wherein, the oil removing process comprises the following steps: adopting NaOH solution with pH value of 11, wherein the oil removing temperature is 70 ℃, and the oil removing time is 15min; the pickling process comprises the following steps: adopting nitric acid with the concentration of 5 percent, and pickling for 60s; then, ultrasonically cleaning the product after acid washing in distilled water for 3min; finally, the product was blow dried for use and labeled as sample B0.
Diffusion treatment of neodymium-iron-boron magnets
Sample B0, zirconia balls having a diameter of 5mm, and Dy ball particles having a diameter of 3mm were placed in a heating chamber 101 in a furnace body 10 as shown in fig. 1 at a mass ratio of 2 -3 Heating to 700 ℃ after Pa, preserving heat for 1h, and rotating the furnace body 10 at the speed of 10 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Dy balls and the zirconia from the magnet, wherein the Dy balls and the zirconia enter the low-temperature chamber 102 from the interception net 103, and the magnet is intercepted by the interception net 103 and continuously left in the heating chamber 101;
returning the furnace body 10 to the horizontal position, closing the furnace body to rotate, continuously raising the temperature of the heating chamber 101 to 950 ℃, preserving the heat for 15 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 550 ℃ for 3 h.
Comparative example 4
This comparative example uses the same embodiment as example 3 except that: the steps and parameters were the same as those of example 3, except that the elevating unit 20 was not started and the diffusion source and the magnet were not separated.
Comparative example 5
This comparative example uses the same embodiment as example 3 except that: after the Dy ball and the zirconia ball were separated from the magnet by starting the elevating unit 20, the rotation was still started until the end of the diffusion treatment in the high-temperature diffusion stage, and the other steps and parameters were the same as those in example 3.
Example 4
Pretreatment of neodymium iron boron magnet
The same as in example 3.
Diffusion treatment of neodymium-iron-boron magnet
A sample B0, zirconia balls with a diameter of 2mm, tb ball particles with a diameter of 0.5mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 in a mass ratio of 1 -3 Heating to 700 ℃ after Pa, preserving heat for 5 hours, and rotating the furnace body 10 at the speed of 3 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Tb ball and the zirconia ball from the magnet, wherein the Tb ball and the zirconia ball enter the low-temperature chamber 102 from the blocking net 103, and the magnet is blocked by the blocking net 103 and continuously remained in the heating chamber 101;
returning the furnace body 10 to the horizontal position, closing and rotating, continuously raising the temperature of the heating chamber 101 to 850 ℃, preserving heat for 3 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 480 ℃ for 3 h.
Comparative example 6
This comparative example uses the same embodiment as example 4 except that: after the lifting part 20 is started to separate the Tb ball and the zirconia ball from the magnet, in the subsequent diffusion stage, the temperature is not increased, the temperature is maintained at 700 ℃ for 5 hours, and other steps and parameters are the same as those in the embodiment 4.
Comparative example 7
This comparative example is the same as example 4, except that: no diffusion source was added to the system, and the other steps and parameters were the same as in example 4.
Example 5
Pretreatment of neodymium iron boron magnet
The same as in example 3.
Diffusion treatment of neodymium-iron-boron magnet
A sample B0 and Tb pellets with the diameter of 0.5mm are placed in a heating chamber 101 of a furnace body 10 shown in figure 1 according to the mass ratio of 1 -3 Heating to 700 ℃ after Pa, preserving heat for 5 hours, and rotating the furnace body 10 at the speed of 3 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Tb ball from the magnet, wherein the Tb ball enters the low-temperature chamber 102 from the blocking net 103, and the magnet is blocked by the blocking net 103 and continues to be left in the heating chamber 101;
returning the furnace body 10 to the horizontal position, closing the furnace body to rotate, continuously raising the temperature of the heating chamber 101 to 850 ℃, preserving the heat for 3 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 480 ℃ for 3 h.
Example 6
Pretreatment of neodymium iron boron magnet
The same as in example 3.
Diffusion treatment of neodymium-iron-boron magnets
A sample B0, silicon carbide spheres having a diameter of 3mm and Dy sphere particles having a diameter of 5mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 at a mass ratio of 1.1 -3 Heating to 700 ℃ after Pa, preserving heat for 3h, and rotating the furnace body 10 at the speed of 20 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Dy balls and the silicon carbide balls from the magnets, wherein the Dy balls and the silicon carbide balls enter the low-temperature chamber 102 from the interception net 103, and the magnets are intercepted by the interception net 103 and are continuously remained in the heating chamber 101;
returning the furnace body 10 to the horizontal position, closing the furnace body to rotate, continuously raising the temperature of the heating chamber 101 to 950 ℃, preserving the heat for 1 hour, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 550 ℃ for 3 h.
Example 7
Pretreatment of neodymium iron boron magnet
The same as in example 3.
Diffusion treatment of neodymium-iron-boron magnets
A sample B0, boron nitride spheres with the diameter of 1mm and Tb sphere particles with the diameter of 2mm are placed in a heating chamber 101 of a furnace body 10 shown in figure 1 according to the mass ratio of 1 -3 Heating to 680 ℃ after Pa, preserving heat for 4 hours, and rotating the furnace body 10 at the speed of 5 revolutions per minute while heating;
starting the lifting part 20, lifting the heating chamber 101 to separate the Tb ball and the boron nitride ball from the magnet, wherein the Tb ball and the boron nitride ball enter the low-temperature chamber 102 from the blocking net 103, and the magnet is blocked by the blocking net 103 and is continuously remained in the heating chamber 101;
returning the furnace body 10 to the horizontal position, closing the furnace body to rotate, continuously raising the temperature of the heating chamber 101 to 800 ℃, preserving the heat for 20 hours, and performing high-temperature diffusion treatment on the magnet;
and finally, taking out the magnet and performing low-temperature aging treatment at 500 ℃ for 5h.
Test example 2
The magnets of examples 3 to 7 and comparative examples 4 to 7 were subjected to appearance inspection, and magnetic properties of the blank sample B0 and examples 3 to 7 and comparative examples 4 to 7 were measured using a permanent magnet material measuring system in accordance with the requirements of GB/T3217-2013 "permanent magnet (hard magnetic) material-magnetic test method", and the test results are shown in Table 2.
TABLE 2 comparison of performances of 42SH Nd-Fe-B permanent-magnet materials after treatment under different conditions
Note: the missing angle ratio% = number of missing angle magnets/total number of magnets in table 2.
As can be seen from the results in table 2, compared with the comparative example, the coercivity of the neodymium iron boron magnet prepared by the method of the present invention is greatly improved, and the unfilled corner condition of the magnet is improved. Better magnetic performance can be obtained by optimizing the process parameters such as temperature, time and the like. All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (10)
1. The method for diffusing the neodymium iron boron magnet is characterized by being carried out in heat treatment equipment and comprising the following steps of:
mixing the cleaned neodymium iron boron magnet and a diffusion source, and then carrying out rotary heating under a vacuum condition, wherein the heating temperature is 600-750 ℃, and the heat preservation time is 1-5h;
stopping rotating, separating the NdFeB magnet from the diffusion source, continuously heating the NdFeB magnet to perform high-temperature diffusion treatment at the temperature of 800-950 ℃, and preserving heat for 1-20h.
2. The diffusion method of claim 1, wherein the heat treatment apparatus comprises:
the device comprises a rotatable furnace body, wherein the furnace body comprises a heating chamber and a low-temperature chamber, the heating chamber and the low-temperature chamber are separated by an interception net, and the mesh size of the interception net is smaller than that of the neodymium iron boron magnet;
and the lifting part is arranged at one end of the furnace body, and the furnace body is lifted up through the lifting part, so that materials except the magnet in the heating chamber enter the low-temperature chamber, and the separation of the magnet and other materials is realized.
3. The diffusion method according to claim 2, wherein a heating body is provided around the furnace body to heat the heating chamber.
4. The diffusion method of claim 2, wherein the interception mesh is a molybdenum mesh.
5. The diffusion method of claim 2, wherein the vacuum condition in the furnace body is a gas pressure of less than 1 x 10 -2 Pa; the rotating speed of the furnace body is 1-20r/min.
6. The diffusion method of claim 1, wherein the diffusion source is a heavy rare earth metal sphere, the heavy rare earth metal being selected from Dy or Tb.
7. The diffusion method of claim 6, wherein the heavy rare earth metal spheres have a diameter of 0.5mm to 5mm.
8. The diffusion method of claim 6, wherein the mass ratio of the neodymium-iron-boron magnet to the heavy rare earth metal ball is 1:0.5 to 5.
9. The diffusion method of claim 1, wherein the diffusion source further comprises a co-stirring agent selected from at least one of zirconia, silicon nitride, silicon carbide, boron nitride, and having a spherical shape with a particle size of not more than 5 mm; the mass ratio of the neodymium iron boron magnet to the stirring aid is 1:0.1 to 3.
10. The diffusion method of claim 1, wherein the ndfeb magnet further comprises an aging treatment after the high temperature diffusion treatment, and the aging treatment specifically comprises: and taking out the neodymium iron boron magnet subjected to high-temperature diffusion treatment, and preserving the heat at 450-550 ℃ for 3-5h.
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