CN113345708A - 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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- CN113345708A CN113345708A CN202110680889.2A CN202110680889A CN113345708A CN 113345708 A CN113345708 A CN 113345708A CN 202110680889 A CN202110680889 A CN 202110680889A CN 113345708 A CN113345708 A CN 113345708A
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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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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 mainly comprises the step of adding 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 ring magnets and circular tube 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 publication nos. CN112802677A and CN109192489A, the disclosed method is to mix a magnet with a heavy rare earth metal or alloy, and then place the mixture in a rotary furnace to perform heat treatment, thereby completing the grain boundary diffusion process. The rotation of the furnace body can make the magnet contact with the heavy rare earth diffusion source more uniformly. However, the current rotational diffusion technology still has the following problems: diffusion temperature is limited, the effect of greatly improving coercive force is achieved by generally adopting a method of raising temperature and prolonging time, but when the temperature reaches more than 750 ℃, adhesion is generated between a magnet and a diffusion source; secondly, the furnace body rotates for a long time, the magnet is seriously collided, and unfilled corners are more easily generated; and thirdly, the magnet is in contact 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 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 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 h;
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 at the temperature of 800-950 ℃, and preserving heat for 1-20 h.
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 0.5-5 mm.
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 10-2Pa; the rotating speed of the furnace body is 1-20 r/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: taking out the neodymium iron boron magnet after the high-temperature diffusion treatment, and preserving the heat for 3-5h at the temperature of 550 ℃ of 450-.
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, then separates the diffusion source from the magnet and carries out secondary high-temperature diffusion, reduces the adhesion between the magnet and the diffusion source, and reduces the consumption of the diffusion source. 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 specific embodiments illustrated. 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 including a furnace body 10 and an elevating part 20, the furnace body 10 being horizontally placed to be rotatable along an axial line thereof.
The furnace body 10 includes a heating chamber 101 and a low temperature chamber 102, 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 mesh size and shape of the interception net 103 are not particularly limited as long as the neodymium iron boron magnet can not pass through, but the diffusion source can pass through, furthermore, the selection of the material of the interception net 103 is not particularly limited as long as the diffusion source can not be adhered at high temperature, so that the diffusion source can pass through smoothly, in some embodiments of the invention, the interception net 103 is a molybdenum net. 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) rotating: 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: the heating is started by clicking on the control panel of the device, and the heating body 104 can perform heating. (3) Lifting: clicking on the equipment control panel to lift, the lifting part 20 can be lifted, so that the furnace body 10 stops after one side is lifted to the required height. 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 h;
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 at the temperature of 800-950 ℃, and preserving heat for 1-20 h.
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;
after the furnace body 10 is vacuumized, the furnace body 10 is heated and rotated, so that the temperature in the heating chamber 101 reaches 600-;
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 ℃ and 950 ℃, and preserving the heat for 1-20h to perform 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 both cleaned and surface-cleaned, wherein the cleaning of the ndfeb magnet is not particularly limited, and a conventional cleaning manner in the art may be adopted, in one or more embodiments of the present invention, the cleaning of the ndfeb magnet includes degreasing, pickling, ultrasound, and blow-drying, and further, the degreasing, pickling, ultrasound, blow-drying and the like may be realized by a conventional means in the art, and in one or more embodiments of the present invention, the degreasing process specifically includes: deoiling in NaOH solution with the pH value of 10-11 and the temperature of 60-70 ℃ for 13-15 min; the pickling process specifically comprises the following steps: pickling with nitric acid with the mass concentration of 3% -5% for 30-90 s; 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 0.5-5 mm.
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- 2Pa。
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 1-20 r/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 5 mm.
The addition amount of the stirring aid is not particularly limited, and can be adjusted according to experience of a person skilled in the art, on one hand, the amount of the stirring aid cannot be too much, so that the diffusion effect can be diluted, and on the other hand, the magnet unfilled corner cannot be further reduced if the amount of the stirring aid is too little, and in one or more embodiments of the invention, the mass ratio of the neodymium iron boron magnet to the stirring aid is 1: 0.1-3.
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: taking out the neodymium iron boron magnet after the high-temperature diffusion treatment, and preserving the heat for 3-5h at the temperature of 550 ℃ of 450-.
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
Commercial Nd-Fe-B magnets were cut into cylindrical blocks of 4X 10 mm (axial direction is the direction of orientation, brand: N50) for several uses.
And (3) removing oil, pickling, ultrasonically treating and blow-drying the cylindrical sample block. Wherein, the oil removing 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 13 min; the pickling process comprises the following steps: nitric acid with the concentration of 3% is adopted, and the pickling time is 90 s; then, ultrasonically cleaning the product after acid washing in distilled water for 2 min; finally, the product was blow dried and ready for use and labeled as sample a 0.
Diffusion treatment of neodymium-iron-boron magnets
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 1:1:1, and then the furnace body 10 was evacuated to a vacuum of 9X 10-3After 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 interception net 103, and the magnet is intercepted by the interception net 103 and continuously remained in the heating chamber 101;
returning the furnace body 10 to the horizontal position, stopping rotating, continuously increasing the temperature of the heating chamber 101 to 800 ℃, preserving the heat 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 magnets
A sample 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 at a mass ratio of 1:2:3, and the furnace body was evacuated to 8X 10-3After 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 increasing 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 carrying out diffusion treatment on the magnet by adopting 750 ℃ and heat preservation for 5 hours without increasing the temperature in the subsequent diffusion stage, 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 visual inspection and the magnetic properties of the blank A0 and the magnets of examples 1-2 and comparative examples 1-3 were tested using a permanent magnet material measurement system as per the requirements of GB/T3217-2013 "permanent magnet (hard magnetic) material-magnetic test method", the test results being given in Table 1.
TABLE 1 comparison of the properties of N50 Nd-Fe-B permanent-magnet material treated under different conditions
Note: in table 1,% of missing angle of magnet is the number of missing angle magnets/total number of magnets.
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 42SH) for standby;
and (3) carrying out oil removal, acid cleaning, ultrasonic treatment and blow drying on the annular 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 15 min; the pickling process comprises the following steps: adopting nitric acid with the concentration of 5 percent, and pickling for 60 s; then, ultrasonically cleaning the product after acid washing in distilled water for 3 min; finally, the product was blow dried and ready for use and labeled as sample B0.
Diffusion treatment of neodymium-iron-boron magnets
Sample B0, zirconia balls having a diameter of 5mm, Dy ball grains 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 2:1:2Then the furnace body 10 is vacuumized to 9 x 10-3Heating 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 lifting unit 20 was not started, and the diffusion source and the magnet were not separated, and the other steps and parameters were the same as those of example 3.
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 magnets
Placing sample B0, zirconia balls with diameter of 2mm and Tb ball particles with diameter of 0.5mm in a mass ratio of 1:0.3:5 in a heating chamber 101 of a furnace body 10 shown in FIG. 1, and vacuumizing the furnace body 10 to 8X 10-3Heating 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, the temperature is not increased in the subsequent diffusion stage, the temperature is still maintained at 700 ℃ for 5h, and other steps and parameters are the same as those in example 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 magnets
Sample B0 and Tb pellets with a diameter of 0.5mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 at a mass ratio of 1:5, and the furnace body 10 was evacuated to 8X 10-3Heating 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 interception net 103, and the magnet is intercepted by the interception net 103 and continuously stays 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.
Example 6
Neodymium-iron-boron magnetPretreatment of bodies
The same as in example 3.
Diffusion treatment of neodymium-iron-boron magnets
Sample B0, silicon carbide pellets having a diameter of 3mm and Dy pellets having a diameter of 5mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 in a mass ratio of 1:0.1:0.5, and the furnace body 10 was evacuated to a vacuum of 8X 10-3Heating 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 1h, 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 pellets having a diameter of 1mm and Tb pellets having a diameter of 2mm were placed in a heating chamber 101 of a furnace body 10 shown in FIG. 1 in a mass ratio of 1:3:2, and the furnace body 10 was evacuated to 8X 10-3Heating 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 to lift 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 5 h.
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 blank B0 and examples 3 to 7 and comparative examples 4 to 7 were measured using a permanent magnet material measuring system as required by GB/T3217-2013 "permanent magnet (hard magnetic) material-magnetic test method", and the test results are shown in Table 2.
TABLE 242 SH comparison of performances of Nd-Fe-B permanent-magnet materials treated under different conditions
Note: in table 2,% of missing angle of magnet is the number of missing angle magnets/total number of magnets.
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. The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification 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 more specific and detailed, but not construed 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 shall be subject to the appended claims.
Claims (10)
1. A thermal processing apparatus comprising:
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 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.
2. The heat treatment apparatus according to claim 1, wherein a heating body is provided around the furnace body to heat the heating chamber.
3. The thermal processing apparatus of claim 1, wherein said interception mesh is a molybdenum mesh.
4. A method for diffusing a neodymium iron boron magnet based on the heat treatment equipment of any one of claims 1 to 3, which is characterized by 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 h;
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 at the temperature of 800-950 ℃, and preserving heat for 1-20 h.
5. The diffusion method of claim 4, wherein the diffusion source is a heavy rare earth metal sphere, the heavy rare earth metal being selected from Dy or Tb.
6. The diffusion method of claim 5, wherein the heavy rare earth metal spheres have a diameter of 0.5 to 5 mm.
7. The diffusion method of claim 5, wherein the mass ratio of the neodymium-iron-boron magnet to the heavy rare earth metal ball is 1:0.5 to 5.
8. The diffusion method of claim 4, wherein the vacuum condition in the furnace body is a gas pressure of less than 1 x 10-2Pa; the rotating speed of the furnace body is 1-20 r/min.
9. The diffusion method of claim 4, wherein the diffusion source further comprises a co-stirring agent selected from at least one of zirconia, silicon nitride, silicon carbide, and boron nitride, and the co-stirring agent is spherical 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 4, wherein the NdFeB magnet further comprises an aging treatment after the high-temperature diffusion treatment, and the aging treatment specifically comprises: taking out the neodymium iron boron magnet after the high-temperature diffusion treatment, and preserving the heat for 3-5h at the temperature of 550 ℃ of 450-.
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