CN113948303A - High-yield and high-performance sintered NdFeB radiation ring and preparation method thereof - Google Patents
High-yield and high-performance sintered NdFeB radiation ring and preparation method thereof Download PDFInfo
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- 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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- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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Abstract
The invention belongs to the technical field of permanent magnet materials, and particularly relates to a sintered NdFeB radiation ring with high yield and high performance and a preparation method thereof. By proportioning the magnetic powder with different particle sizes, the coarse powder and the fine powder are reasonably matched, so that the compactness of a pressed blank is improved; by adopting nano MoS2Organic matters are combined to serve as a lubricant, so that the addition amount of the organic lubricant is reduced, the carbon content is effectively reduced, and the coercive force of the magnet is improved; in the isostatic pressing process, hard tungsten-cobalt alloy is selected as a core mold material to support the radiation ring, so that the inner diameter and the outer diameter of the radiation ring are ensured to be shrunk consistently in the cold isostatic pressing process; reasonably regulating and controlling the sintering process, carrying out multistage tempering heat treatment step by step to eliminate stress and reduce the crack rate. The sintered NdFeB radiation ring prepared by the method has the characteristics of excellent magnetic property, difficult cracking, high yield and good processing performance, and is simple to operate, high in production efficiency and suitable for batch production.
Description
Technical Field
The invention belongs to the field of magnetic materials, and particularly relates to a sintered NdFeB radiation ring with high yield and high performance and a preparation method thereof.
Background
With the development of artificial intelligence and automation technology, more and more finely controlled electromechanical products are used, and miniaturization, light weight and high efficiency are development trends of the motor industry. Compared with the traditional electric excitation motor, the permanent magnet motor has the remarkable advantages of simple structure, small volume, light weight, small loss, high efficiency, high power factor and the like, thereby being widely applied to various fields of aerospace, national defense and military industry, industrial and agricultural production, daily life and the like.
At present, the stator or rotor structure of the neodymium iron boron permanent magnet motor is mostly of a magnetic tile/strip insertion type or an embedded type: the magnetized sintered Nd-Fe-B magnetic tiles are embedded in a frame structure made of soft magnetic materials and spliced into a ring. However, the mode of splicing the magnetic shoes into a ring has the following problems: the magnetic field directions in the single magnet are consistent, the magnetic field intensity of the ring formed by splicing the magnetic shoes is not uniformly distributed along the circle of the excircle, so that the dynamic balance of the spliced magnetic ring is poor, the transition area between the magnetic poles is large, the motor generates noise and vibration, and the operation efficiency is reduced. To improve this phenomenon, the angle difference is usually reduced by increasing the number of magnetic poles in the production process. However, as the number of magnetic poles increases, the dimensional tolerance of the magnet becomes more critical. Because the machining precision difficulty such as the angle of tile shape magnet is big, the size has the difference between different fritter magnets, can appear the clearance during concatenation or piece incomplete phenomenon. The assembly process is usually performed first, and the satisfactory magnets are packaged individually as a group, resulting in a significant increase in installation costs.
The neodymium iron boron radiation magnetic ring developed in recent years well overcomes the defects of the spliced magnetic ring, can replace the traditional tile-shaped block, and becomes a key new direction for developing neodymium iron boron permanent magnet materials. The magnetic field direction of the neodymium iron boron radiation magnetic ring is in a radiation state of continuous distribution by taking the ring center as the center, the magnetic field inside the whole magnetic ring is continuously and uniformly distributed, a magnetic pole transition area does not exist, the noise and heat generated by vibration caused by magnetic field jumping during the operation of the motor are greatly reduced, and the operation efficiency of the motor is obviously improved. The advantages of the magnetic neodymium iron boron radiation magnetic ring are mainly reflected in the following aspects: firstly, a magnetic conduction frame is not needed for supporting connection, so that the energy density is increased; the complete circular ring structure avoids falling off and breaking; the original iron core rotor is replaced, so that the motor is smaller in size, high in rotating speed and easy to control; the high-precision control device is more suitable for controlling the motor at high rotating speed and high precision, has the advantages of high precision, stable operation, low noise and the like, reduces the assembly difficulty and time, is an important component for future electromechanical development, is very suitable for severe working conditions such as high-speed vibration of the electric automobile and the like, and also provides guarantee for the research and development of novel hub motors and wheel-side motors for vehicles.
However, the prior sintered NdFeB radiation ring has the problems of easy cracking, low toughness and poor processability: firstly, because NdFeB is a brittle material, the tetragonal phase crystal structure is complex, the sliding system is few, the deformation performance is poor, and the maximum deformation amount before the mechanical sample is broken is less than 1 mm; secondly, in the cold isostatic pressing process, the shrinkage of the inner diameter and the outer diameter of the radiation ring is inconsistent, and the radiation ring is easy to break along the radial direction; thirdly, the sintered NdFeB radiation ring has different thermal expansion coefficients along the radial direction and the axial direction, the axial direction and the radial direction generate non-free strain due to the thermal expansion of the closed circular ring in the temperature reduction process, and the cracking is caused when a large amount of circumferential stress is accumulated in the temperature reduction process to exceed the fracture strength of a sintered body.
Chinese patent 201811014250.5 discloses a high-toughness sintered neodymium-iron-boron radiation ring and a preparation method thereof, which is characterized in that micron-sized PrCu alloy is added to a radiation ring magnet as toughening powder, thereby improving the bending strength and fracture toughness of the radiation ring, but still solving the problem of low yield of the sintered radiation ring.
Chinese patent 201310753909.X discloses a neodymium iron boron radiation orientation ring and a preparation method thereof, which is characterized in that heavy rare earth alloy is added into a radiation ring magnet to obtain a neodymium iron boron radiation ring with excellent magnetic performance, but the problem of low yield of the radiation ring is still not solved, and the heavy rare earth alloy is expensive and is not beneficial to large-scale production.
Chinese patent 201610732581.7 provides a method for preparing a radiation-oriented sintered neodymium-iron-boron magnet ring, which is characterized in that the magnetic powder is subjected to twice jet milling, and a lubricant is added twice, so that the powder fluidity is improved, and a neodymium-iron-boron radiation ring with a low cracking rate is obtained, but the residual carbon content of the magnet is high, the magnetic performance of the radiation ring is low, and the applicability is poor.
Therefore, in view of the above disadvantages, it is necessary to provide a method for preparing a sintered NdFeB radiation ring with high yield and high performance, so that the radiation ring has excellent magnetic properties while having high yield.
Disclosure of Invention
The invention aims to solve the problems of low yield and poor performance of a sintered NdFeB radiation ring, and provides a sintered NdFeB radiation ring with high yield and high performance and a preparation method thereof.
The technical scheme adopted by the invention for realizing the technical purpose is as follows:
a preparation method of a sintered NdFeB radiation ring with high yield and high performance comprises the following steps:
1) preparing fine powder: vacuum melting to obtain NdFeB permanent magnetic alloy A, carrying out hydrogen crushing on the A to obtain hydrogen crushed powder B, and carrying out batch jet milling on the hydrogen crushed powder B at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes;
2) particle size regulation: the air current milled powder C1-C4 with different average particle sizes is proportioned according to a certain proportion to obtain mixed magnetic powder D, the coarse powder and the fine powder are reasonably matched, the compaction compactness of a pressed compact is improved, the shrinkage rate of a radiation ring is reduced in the sintering process, the residual stress is reduced, and the finished product rate is high.
3) Adding a lubricant: adding nano MoS into the mixed magnetic powder D after the granularity is regulated and controlled2As an inorganic lubricant, adding a small amount of organic lubricant, and uniformly mixing to obtain mixed magnetic powder E;
4) orientation forming and cold isostatic pressing: adding the mixed magnetic powder E into a radiation ring die, and performing compression molding in a magnetic field to obtain a green body F; inserting a core mold into the green body F, carrying out vacuum packaging and carrying out cold isostatic pressing treatment to obtain a radiation ring green body G;
5) sintering and aging: and removing the core mold after cold isostatic pressing is finished, performing vacuum sintering on the radiation ring pressed compact G, filling argon after sintering is finished, cooling along with the furnace, performing air cooling, and performing multi-stage tempering heat treatment to obtain the sintered NdFeB radiation ring.
Further, in the step 1), the NdFeB permanent magnet alloy a comprises the following components: (PrNd)xFe1-x-y-zMyBzWherein M is one or more of Al, Cu, Ga, Co and Zr, x is more than or equal to 28.5 percent and less than or equal to 31.5 percent, y is more than or equal to 0.2 percent and less than or equal to 2 percent, z is more than or equal to 0.95 percent and less than or equal to 1.1 percent, and the percentages are weight percentages; the hydrogen fragmentation conditions were: the permanent magnet alloy A absorbs hydrogen in a saturated mode at room temperature, and is dehydrogenated at 500-600 ℃ to prepare hydrogen crushed powder; the average particle size of the airflow milled powder C1-C4 is 1.0-2.0 μm, 2.0-3.0 μm, 3.0-4.0 μm and 4.0-5.0 μm in sequence.
Further, the mass ratio of the magnetic powder with different particle sizes in the mixed magnetic powder D in the step 2) satisfies the following conditions: 20% < C1< 30%, 20% < C2< 30%, 20% < C3< 25%, 20% < C4< 25%.
Further, in the step 3), the nano MoS in the step of adding a lubricant2The addition amount of the magnetic powder is 0.5 to 2 percent of the mixed magnetic powder D; the organic lubricant comprises an organic solvent and a lubricant, wherein the mass ratio of the organic solvent to the lubricant is 1-3: 1, and the addition amount of the organic lubricant is 0.1-0.3% of the mixed magnetic powder D.
Preferably, in step 3), the organic solvent is one or more of ethanol, xylene, petroleum ether, acetone, dichloromethane and n-propanol; the lubricant is one or more of zinc stearate, sodium stearate, lithium stearate, calcium stearate and polytetrafluoroethylene wax.
Further, in step 4), the uniformly mixed magnetic powder E is subjected to radiation orientation molding in a 2T magnetic field, a columnar hard tungsten cobalt alloy with the same height is selected as a core mold material, the diameter of the core mold is 93-97% of the inner diameter of the radiation ring, and after the core mold is inserted into the core part of the radiation ring, cold isostatic pressing treatment at 200MPa or more is performed.
Further, in step 5), the vacuum sintering process comprises: and (3) sequentially preserving heat at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1020-1080 ℃ and preserving heat for 3-5 h, wherein the heating rate is controlled at 5 ℃/min, argon is cooled to 400-500 ℃ along with the furnace, and then argon is air-cooled to room temperature.
Further, in step 5), the aging treatment process of the multi-stage tempering heat treatment comprises the following steps: the temperature of the first tempering treatment is 850-950 ℃, the heat preservation time is 2-3 h, after the first tempering treatment is finished, argon is filled into the furnace to be cooled to 200 ℃, second tempering is carried out, the temperature is increased to 500-600 ℃, the heat preservation time is 2-3 h, the argon is air-cooled to 200 ℃, then third tempering is carried out, the temperature is increased to 300-400 ℃, the heat preservation time is 2-3 h, and finally the argon is air-cooled to the room temperature.
Compared with the prior art, the invention has the following advantages:
1. by regulating and controlling the powder granularity, the coarse powder and the fine powder are reasonably matched, and the fine powder is filled in gaps of the coarse powder, the compaction degree of a pressed compact is improved, the shrinkage rate of a radiation ring is reduced in the sintering process, the residual stress is reduced, and the finished product rate is high.
2. Adding nano MoS2Can partially replace organic lubricant, reduce the dosage of the organic lubricant and greatly reduce the content of residual carbon. In addition, nano MoS2The material has a higher melting point, can play a role in inhibiting the growth of crystal grains and refining the crystal grains in a crystal boundary phase, and effectively improves the coercive force of the radiation ring magnet.
3. The hard tungsten-cobalt alloy is selected as the core mold, plays a supporting role in the cold isostatic pressing process, and shrinks synchronously with the radiation ring, so that the problem that the inner diameter and the outer diameter of the radiation ring shrink inconsistently to crack is effectively solved, and the sintering yield of the radiation ring is greatly improved.
4. The internal stress of the radiation ring is reduced by optimizing the sintering process and reasonably controlling the cooling process, and then the residual internal stress of the radiation ring is further reduced by multi-step tempering heat treatment, so that the machinability of the radiation ring is improved, and the problem that the sintered NdFeB radiation ring is easy to break during processing is effectively solved.
Drawings
FIG. 1 is a graph illustrating a Nd-Fe-B radial ring sintering process.
Fig. 2 is a schematic diagram of a neodymium iron boron radiation loop annealing process curve.
Detailed Description
The present invention is described in further detail below with reference to examples, which are intended to facilitate the understanding of the present invention and are not intended to limit the present invention in any way.
Example 1:
(1) vacuum rapid hardening smelting (Pr, Nd)31.5Fe65.72Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated absorbing hydrogen at room temperature, and dehydrogenating at 550 ℃ to produce hydrogen crushed powder; and (3) carrying out batch jet milling on the hydrogen crushed powder at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes, wherein the average particle sizes of the jet milled powder C1-C4 are 1.8 mu m, 2.4 mu m, 3.5 mu m and 4.4 mu m in sequence.
(2) C1-C4 are proportioned to finally obtain powder with the mass ratio: 28% of C1, 27% of C2, 23% of C3 and 22% of C4.
(3) The mixed magnetic powder is mixed with nano MoS with the total mass of 0.5 percent2As an inorganic lubricant, and a mixture of petroleum ether and sodium stearate in a mass ratio of 1:1 in total of 0.2% by mass as an organic lubricant, and uniformly mixed.
(4) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 93 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(5) And (3) preserving the green compact subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h in sequence, exhausting and presintering, finally heating to 1060 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 500 ℃ along with the furnace, and then cooling to room temperature by air cooling to obtain the sintered radiation ring.
(6) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 900 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering at 500 ℃ for 2h, carrying out air cooling on the ring to 200 ℃ after finishing the tempering, carrying out third tempering at 350 ℃ for 2h, and finally carrying out air cooling on the ring to room temperature; and (5) preparing a finished product of the radiation ring.
Comparative example 1:
(1) vacuum rapid hardening smelting (Pr, Nd)31.5Fe65.72Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated absorbing hydrogen at room temp., dehydrogenating at 550 deg.C to obtain hydrogen broken powder, and making the hydrogen broken powder into powder by gas-flow grinding at same speed of sorting wheel, and its average grain size is 2.8 micrometers.
(2) The nanometer MoS with the total mass of 0.5 percent is doped into the jet mill magnetic powder2As an inorganic lubricant, and a mixture of petroleum ether and sodium stearate in a mass ratio of 1:1 in total of 0.2% by mass as an organic lubricant, and uniformly mixed.
(3) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 93 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(4) And (3) preserving the green compact subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h in sequence, exhausting and presintering, finally heating to 1060 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 500 ℃ along with the furnace, and then cooling to room temperature by air cooling to obtain the sintered radiation ring.
(5) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 900 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering at 500 ℃ for 2h, carrying out air cooling on the ring to 200 ℃ after finishing the tempering, carrying out third tempering at 350 ℃ for 2h, and finally carrying out air cooling on the ring to room temperature; and (5) preparing a finished product of the radiation ring.
Example 2:
(1) vacuum rapid hardening smelting (Pr, Nd)31Fe66.22Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated in hydrogen at room temperature, and dehydrogenated at 560 ℃ to produce hydrogen crushed powder; and (3) carrying out jet milling on the hydrogen crushed powder at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes, wherein the average particle sizes of the jet milled powder C1-C4 are 1.3 mu m, 2.7 mu m, 3.4 mu m and 4.2 mu m in sequence.
(2) C1-C4 are proportioned to finally obtain powder with the mass ratio: 25% of C1, 27% of C2, 24% of C3 and 24% of C4.
(3) The mixed magnetic powder is mixed with nano MoS with the total mass of 0.8 percent2As an inorganic lubricant, and a mixture of petroleum ether and zinc stearate as an organic lubricant in a mass ratio of 1.5:1 in total of 0.2% by mass, wherein the petroleum ether and the zinc stearate are uniformly mixed.
(4) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 94 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(5) And (3) preserving the green compact subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h in sequence, exhausting and presintering, finally heating to 1050 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 450 ℃ along with the furnace, and then cooling to room temperature by air cooling to obtain the sintered radiation ring.
(6) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 880 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering, keeping the temperature at 550 ℃ for 2h, cooling the ring to 200 ℃ with air by using argon after finishing the tempering, carrying out third tempering, keeping the temperature at 350 ℃ for 2h, and finally cooling the ring to room temperature with air by using argon; and (5) preparing a finished product of the radiation ring.
Comparative example 2:
(1) the same magnetic powder as in example 2 was selected, and the magnetic powder distribution after compounding was also the same as in example 2.
(2) The mixed magnetic powder is mixed with a mixture of petroleum ether and zinc stearate with the total mass of 0.2 percent as an organic lubricant, wherein the mass ratio of the petroleum ether to the zinc stearate is 1.5:1, and the mixture is uniformly mixed.
(3) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 94 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(4) And (3) preserving the formed pressed compact for 1h at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ in sequence, exhausting and presintering, finally heating to 1050 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 450 ℃ along with a furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(5) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 880 ℃ for 3h, cooling the sintered radiation ring to 200 ℃ by argon air after finishing, carrying out second tempering at 550 ℃ for 2h, cooling the sintered radiation ring to 200 ℃ by argon air after finishing, carrying out third tempering at 350 ℃ for 2h, and finally cooling the sintered radiation ring to room temperature by argon air; and (5) preparing a finished product of the radiation ring.
Example 3:
(1) vacuum rapid hardening smelting (Pr, Nd)30.5Fe66.72Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated absorbing hydrogen at room temperature, and dehydrogenating at 580 deg.C to obtain hydrogen crushed powder; and (3) carrying out jet milling on the hydrogen crushed powder at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes, wherein the average particle sizes of the jet milled powder C1-C4 are 1.5 mu m, 2.6 mu m, 3.9 mu m and 4.7 mu m in sequence.
(2) C1-C4 are proportioned to finally obtain powder with the mass ratio: 26% of C1, 26% of C2, 24% of C3 and 24% of C4.
(3) The mixed magnetic powder is mixed with nano MoS with the total mass of 1.2 percent2As an inorganic lubricant, and a mixture of acetone and lithium stearate in a mass ratio of 0.2% of the total mass as an organic lubricantIs 2:1, and is mixed evenly.
(4) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 95 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(5) And (3) preserving the heat of the pressed blank subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h in sequence, exhausting and presintering, finally heating to 1055 ℃ and preserving the heat for 3h, filling argon after sintering, cooling to 450 ℃ along with the furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(6) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 880 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering, keeping the temperature at 550 ℃ for 2h, cooling the ring to 200 ℃ with air by using argon after finishing the tempering, carrying out third tempering, keeping the temperature at 350 ℃ for 2h, and finally cooling the ring to room temperature with air by using argon; and (5) preparing a finished product of the radiation ring.
Comparative example 3:
(1) the same magnetic powder as in example 3 was selected, and the magnetic powder distribution after compounding was also the same as in example 3.
(2) The mixed magnetic powder is mixed with nano MoS with the total mass of 1.2 percent2As an inorganic lubricant, and a mixture of acetone and lithium stearate as an organic lubricant in a mass ratio of 2:1 in a total mass of 0.2%, and uniformly mixed.
(3) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting an iron column with the diameter of 95 percent of the inner diameter of the radiation ring into the core of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment at 220MPa after vacuum packaging.
(4) And (3) preserving the heat of the pressed blank subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h in sequence, exhausting and presintering, finally heating to 1055 ℃ and preserving the heat for 3h, filling argon after sintering, cooling to 450 ℃ along with the furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(5) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 880 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering, keeping the temperature at 550 ℃ for 2h, cooling the ring to 200 ℃ with air by using argon after finishing the tempering, carrying out third tempering, keeping the temperature at 350 ℃ for 2h, and finally cooling the ring to room temperature with air by using argon; and (5) preparing a finished product of the radiation ring.
Example 4:
(1) vacuum rapid hardening smelting (Pr, Nd)30Fe67.22Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated absorbing hydrogen at room temperature, and dehydrogenating at 575 deg.C to obtain hydrogen crushed powder; and (3) carrying out jet milling on the hydrogen crushed powder at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes, wherein the average particle sizes of the jet milled powder C1-C4 are 1.3 mu m, 2.2 mu m, 3.5 mu m and 4.3 mu m in sequence.
(2) C1-C4 are proportioned to finally obtain powder with the mass ratio: 28% of C1, 24% of C2, 24% of C3 and 24% of C4.
(3) The mixed magnetic powder is mixed with nano MoS with the total mass of 1.5 percent2As an inorganic lubricant, and a mixture of n-propanol and calcium stearate in a mass ratio of 2.5:1 in total of 0.2% by mass as an organic lubricant, and uniformly mixed.
(4) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 96 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment under 225MPa after vacuum packaging.
(5) And (3) sequentially preserving the pressed blank subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1065 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 480 ℃ along with the furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(6) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 920 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering at 570 ℃ for 2h, carrying out air cooling to 220 ℃ with argon after finishing the tempering, carrying out third tempering at 380 ℃ for 2h, and finally carrying out air cooling to room temperature with argon; and (5) preparing a finished product of the radiation ring.
Comparative example 4:
(1) the same magnetic powder as in example 4 was selected, and the magnetic powder distribution after compounding was also the same as in example 4.
(2) The mixed magnetic powder is mixed with nano MoS with the total mass of 1.5 percent2As an inorganic lubricant, and a mixture of n-propanol and calcium stearate in a mass ratio of 2.5:1 in total of 0.2% by mass as an organic lubricant, and uniformly mixed.
(3) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 96 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment under 225MPa after vacuum packaging.
(4) And (3) sequentially preserving the pressed compact subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1065 ℃ and preserving heat for 3h, and filling argon after sintering to cool to room temperature to obtain the sintered radiation ring.
(5) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 920 ℃ for 3h, filling argon after finishing the tempering, cooling the ring to 200 ℃ along with the furnace, carrying out second tempering at 570 ℃ for 2h, carrying out air cooling to 220 ℃ with argon after finishing the tempering, carrying out third tempering at 380 ℃ for 2h, and finally carrying out air cooling to room temperature with argon; and (5) preparing a finished product of the radiation ring.
Example 5:
(1) vacuum rapid hardening smelting (Pr, Nd)29.5Fe67.72Co1Cu0.2Al0.2Ga0.2Zr0.2B0.98(wt.%) alloy, saturated absorbing hydrogen at room temperature, and dehydrogenating at 565 ℃ to produce hydrogen crushed powder; carrying out jet milling on the hydrogen crushed powder at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes, wherein the average particle sizes of the jet milled powder C1-C4 are 1 in sequence.4μm、2.5μm、3.4μm、4.7μm。
(2) C1-C4 are proportioned to finally obtain powder with the mass ratio: 27% of C1, 26% of C2, 23% of C3 and 24% of C4.
(3) The mixed magnetic powder is mixed with nano MoS with the total mass of 2 percent2As an inorganic lubricant, and a mixture of n-propanol and calcium stearate in a total mass of 0.2% as an organic lubricant, wherein the mass ratio of n-propanol to calcium stearate is 3:1, and uniformly mixed.
(4) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, after coating the film, inserting a hard tungsten-cobalt alloy column with the diameter of 97 percent of the inner diameter of the radiation ring into the core part of the radiation ring to be used as a core mold, and carrying out cold isostatic pressing treatment under 225MPa after vacuum packaging.
(5) And (3) sequentially preserving the pressed blank subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1065 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 480 ℃ along with the furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(6) Carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 930 ℃ for 3h, filling argon after finishing, cooling to 200 ℃ along with the furnace, carrying out second tempering, keeping the temperature at 560 ℃ for 2h, cooling to 220 ℃ with argon after finishing, carrying out third tempering, keeping the temperature at 380 ℃ for 2h, and finally cooling to room temperature with argon; and (5) preparing a finished product of the radiation ring.
Comparative example 5:
(1) the same magnetic powder as in example 5 was selected, and the magnetic powder distribution after compounding was also the same as in example 5.
(2) The mixed magnetic powder is mixed with nano MoS with the total mass of 2 percent2As an inorganic lubricant, and a mixture of n-propanol and calcium stearate in a total mass of 0.2% as an organic lubricant, wherein the mass ratio of n-propanol to calcium stearate is 3:1, and uniformly mixed.
(3) And placing the uniformly mixed magnetic powder in a rotating magnetic field with the magnetic field intensity of 2T, orienting and molding, coating the film, inserting hard tungsten-cobalt alloy with the diameter of 97 percent of the inner diameter of the radiation ring into the core of the radiation ring to be used as a core mold, and carrying out 225MPa cold isostatic pressing treatment after vacuum packaging.
(4) And (3) sequentially preserving the pressed blank subjected to cold isostatic pressing at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1065 ℃ and preserving heat for 3h, filling argon after sintering, cooling to 480 ℃ along with the furnace, and then performing air cooling to room temperature to obtain the sintered radiation ring.
(5) And (3) carrying out first tempering treatment on the sintered radiation ring, keeping the temperature at 930 ℃ for 3h, carrying out argon air cooling to room temperature after finishing the tempering treatment, carrying out second tempering, keeping the temperature at 560 ℃ for 2h, and carrying out argon air cooling to room temperature after finishing the tempering treatment to obtain the finished radiation ring.
A plurality of batches of tests were carried out according to examples 1 to 5 and comparative examples 1 to 5, and the results were as follows:
from the results given in the table above it can be seen that: the sintered NdFeB radiation ring prepared by the technology has very high sintering yield and processing yield, effectively reduces the defective rate and the cost of the sintered NdFeB radiation ring, has excellent magnetic performance, and is suitable for large-scale production.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (9)
1. A preparation method of a sintered NdFeB radiation ring with high yield and high performance is characterized in that: the method comprises the following steps:
1) preparing fine powder: vacuum melting to obtain NdFeB permanent magnetic alloy A, carrying out hydrogen crushing on the A to obtain hydrogen crushed powder B, and carrying out batch jet milling on the hydrogen crushed powder B at different sorting wheel rotating speeds to obtain jet milled powder C1-C4 with different average particle sizes;
2) particle size regulation: mixing airflow milled powder C1-C4 with different average particle sizes according to a certain proportion to obtain mixed magnetic powder D;
3) adding a lubricant: adding nano MoS into the mixed magnetic powder D after the granularity is regulated and controlled2As an inorganic lubricant, adding a small amount of organic lubricant, and uniformly mixing to obtain mixed magnetic powder E;
4) orientation forming and cold isostatic pressing: adding the mixed magnetic powder E into a radiation ring die, and performing compression molding in a magnetic field to obtain a green body F; inserting a core mold into the green body F, carrying out vacuum packaging and carrying out cold isostatic pressing treatment to obtain a radiation ring green body G;
5) sintering and aging: and removing the core mold after cold isostatic pressing is finished, performing vacuum sintering on the radiation ring pressed compact G, filling argon after sintering is finished, cooling along with the furnace, performing air cooling, and performing multi-stage tempering heat treatment to obtain the sintered NdFeB radiation ring.
2. The preparation method according to claim 1, wherein the NdFeB permanent magnet alloy a in step 1) has the following composition: (PrNd)xFe1-x-y-zMyBzWherein M is one or more of Al, Cu, Ga, Co and Zr, x is more than or equal to 28.5 percent and less than or equal to 31.5 percent, y is more than or equal to 0.2 percent and less than or equal to 2 percent, and z is more than or equal to 0.95 percent and less than or equal to 1.1 percent; the hydrogen fragmentation conditions were: the permanent magnet alloy A absorbs hydrogen in a saturated mode at room temperature, and is dehydrogenated at 500-600 ℃ to prepare hydrogen crushed powder; the average particle size of the airflow milled powder C1-C4 is 1.0-2.0 μm, 2.0-3.0 μm, 3.0-4.0 μm and 4.0-5.0 μm in sequence.
3. The preparation method according to claim 1, wherein the mass ratio of the magnetic powder with different particle sizes in the mixed magnetic powder D in the particle size regulation step satisfies: 20% < C1< 30%, 20% < C2< 30%, 20% < C3< 25%, 20% < C4< 25%.
4. The method of claim 1, wherein the nano MoS is in the step of adding a lubricant2The addition amount of the magnetic powder is 0.5 to 2 percent of the mixed magnetic powder D; the organic lubricant comprises an organic solvent and a lubricant, wherein the mass ratio of the organic solvent to the lubricant is 1-3: 1, and the addition amount of the organic lubricant is 0.1-0.3% of the mixed magnetic powder D.
5. The method according to claim 4, wherein the organic solvent is one or more of ethanol, xylene, petroleum ether, acetone, dichloromethane, and n-propanol; the lubricant is one or more of zinc stearate, sodium stearate, lithium stearate, calcium stearate and polytetrafluoroethylene wax.
6. The production method according to claim 1, wherein in the orientation molding and cold isostatic pressing steps, the uniformly mixed magnetic powder E is subjected to radiation orientation molding in a 2T magnetic field, a columnar hard tungsten-cobalt alloy with the same height is selected as a core mold material, the diameter of the core mold is 93-97% of the inner diameter of the radiation ring, and after the core mold is inserted into a core part of the radiation ring, cold isostatic pressing treatment at 200MPa or more is performed.
7. The preparation method according to claim 1, wherein in the step 5), the vacuum sintering process comprises: and (3) sequentially preserving heat at 350 ℃, 500 ℃, 650 ℃, 820 ℃ and 980 ℃ for 1h, exhausting and presintering, finally heating to 1020-1080 ℃ and preserving heat for 3-5 h, wherein the heating rate is controlled at 5 ℃/min, argon is cooled to 400-500 ℃ along with the furnace, and then argon is air-cooled to room temperature.
8. The method according to claim 1, wherein in step 5), the aging treatment process of the multi-stage tempering heat treatment is as follows: the temperature of the first tempering treatment is 850-950 ℃, the heat preservation time is 2-3 h, after the first tempering treatment is finished, argon is filled into the furnace to be cooled to 200 ℃, second tempering is carried out, the temperature is increased to 500-600 ℃, the heat preservation time is 2-3 h, the argon is air-cooled to 200 ℃, then third tempering is carried out, the temperature is increased to 300-400 ℃, the heat preservation time is 2-3 h, and finally the argon is air-cooled to the room temperature.
9. A sintered NdFeB radiative ring prepared according to the method of any one of claims 1 to 8.
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