Preparation method of high-comprehensive-performance sintered neodymium-iron-boron permanent magnet material for new energy automobile

Abstract

The invention relates to a preparation method of a high-comprehensive-performance sintered neodymium-iron-boron permanent magnet material for a new energy automobile, and the method comprises the following steps: (1) obtaining an easy-to-diffuse high-performance precursor through the optimization of a component system and the regulation and control of an intrinsic organization structure; (2) a multi-component co-diffusion technology is adopted, the diffusion advantages of different components are cooperatively utilized, and a multi-target magnetron sputtering technology is adapted, so that the diffusivity and coercive force optimization effect of the diffusion source are effectively improved; and (3) performing low-temperature diffusion and aging treatment on the neodymium-iron-boron magnet attached with the heavy rare earth layer to obtain the high-comprehensive-performance sintered neodymium-iron-boron permanent magnet material for the new energy automobile. Different from high-temperature heat diffusion in the prior art, the neodymium-iron-boron magnet adopts relatively low temperature for diffusion, so that the energy consumption and the cost are reduced, and meanwhile, the neodymium-iron-boron magnet with high comprehensive performance is used for a new energy automobile.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a preparation method of a sintered NdFeB permanent magnet material with high comprehensive performance for new energy vehicles. Background Art

[0002] High-performance NdFeB rare earth permanent magnet materials have boosted the rapid development of the new energy vehicle field. In 2023, the global sales volume of new energy vehicles exceeded 13 million, and the industrial scale has developed rapidly. At the same time, it also faces increasingly fierce competition. Under the development requirements of fast charging, high efficiency, and high stability, the "double high" NdFeB magnets with both ultra-high coercivity and ultra-high remanence, especially the high serviceability series magnets, have become the core components urgently needed for the technological upgrading of the new generation of new energy vehicle drive motors. Based on the intrinsic "competing" relationship between coercivity and remanence, the current traditional process cannot achieve batch and stable production of high serviceability magnets for new energy vehicles. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a preparation method of a sintered NdFeB permanent magnet material with high comprehensive performance for new energy vehicles, which not only reduces energy consumption and cost, but also obtains high comprehensive magnetic properties of the sintered NdFeB permanent magnet material for new energy vehicles.

[0004] The present invention provides a preparation method of a sintered NdFeB permanent magnet material with high comprehensive performance for new energy vehicles, including the following steps:

[0005] (1) Prepare a NdFeB permanent magnet rapid solidification sheet by using a rapid solidification technology process;

[0006] (2) Subject the rapid solidification sheet obtained in step (1) to two-stage powder making by hydrogen explosion and air flow milling to obtain NdFeB permanent magnet powder;

[0007] (3) Orient and sinter the NdFeB permanent magnet powder obtained in step (2) under a magnetic field of 1.5 - 2.0 T to form an easily diffusible high-performance precursor;

[0008] (4) Adhere a heavy rare earth layer to the easily diffusible high-performance precursor obtained in step (3) by using multi-pole target magnetron sputtering;

[0009] (5) Perform low-temperature diffusion and aging treatment on the NdFeB magnet adhered with the heavy rare earth layer in step (4) to obtain a sintered NdFeB permanent magnet material with high comprehensive performance for new energy vehicles.

[0010] Preferably, the microstructure of the rapid solidification sheet in step (1) has complete columnar crystals, no α-Fe segregation phase, and the rare earth-rich phase is diffusely distributed.

[0011] Preferably, the average thickness of the quick-setting sheet in step (1) is 0.20 - 0.40 mm.

[0012] Preferably, the average particle size of the NdFeB permanent magnet magnetic powder in step (2) is SMD = 2.8 - 3.2 um, X10 = 1.6 - 2.0 um, and X99 ≤ 10 um.

[0013] Preferably, the sintering in step (3) is specifically as follows:

[0014] 1) Put the NdFeB powder compact into the furnace;

[0015] 2) Evacuate the air. Use a pump set consisting of a sliding vane vacuum pump and a Roots pump. Open the roughing valve to evacuate the vacuum degree inside the sintering equipment to 1.0×10 -1 Pa;

[0016] 3) Heat up and exhaust gas. The target temperature is 600 °C. After holding for 0.5 h, raise the temperature to the final exhaust gas temperature point of 950 °C. After the exhaust gas vacuum degree reaches 1.0×10 -1 Pa, then continue to heat up to 1080 °C and hold for 4 h. At this time, the pump set continues to work to maintain the vacuum degree of 1.0×10 -1 Pa;

[0017] 4) Temper. Cool down to 900 °C and hold for 2 h. Then cool down to 490 °C and hold for 4 h;

[0018] 5) Turn off the pump set, turn on the fan, and cool down to room temperature and take out of the furnace.

[0019] Preferably, the multi-pole target magnetron sputtering in step (4) uses a multi-component co-mixed single target or target material group of heavy rare earth Dy / Tb, light rare earth Pr / Nd, and non-magnetic metals Al, Cu, Ga, and is completed using a multi-target magnetron sputtering automated production line.

[0020] Preferably, the low-temperature diffusion and aging treatment in step (5) is specifically as follows:

[0021] 1) Sinter and heat up, hold the temperature;

[0022] 2) Turn off the heating, fill the sintering equipment with inert gas and cool it down to the first-stage aging temperature of 900 °C ± 20 °C by self-cooling. The inert gas is heated by the high-temperature product, and then heat exchange is carried out through a heat exchanger. Then the sintering equipment directly holds the temperature for 1.5 h - 2.5 h under a vacuum degree of 0.05 pa;

[0023] 3) After the first-stage aging heat preservation is completed, fill it with inert gas again and air-cool it to below 80 °C;

[0024] 4) When the vacuum degree of the sintering equipment is 0.05 pa, turn off the vacuum pump set, raise the temperature to the second-stage aging temperature of 510 °C ± 30 °C, and hold the temperature for 4 h - 5 h;

[0025] 5) Fill with inert gas and air-cool the furnace to discharge.

[0026] Beneficial effects

[0027] The present invention first starts from the optimization design of the composition system and microstructure of NdFeB materials, regulates the distribution of grain boundary channels and physical properties of the magnet, and develops a high-performance precursor conducive to the efficient grain boundary diffusion of heavy rare earths; further from the perspective of the design and modification of the diffusion source, develops a multi-component diffusion system, comprehensively regulates the shell structure of the diffusion magnet, the distribution of grain boundary phases and the diffusion depth, and develops an efficient grain boundary diffusion technology based on multi-target magnetron sputtering to realize the preparation of sintered NdFeB permanent magnet steel with high comprehensive performance for new energy vehicles; the present invention uses a relatively low temperature for sintering and diffusion aging, which not only reduces energy consumption and costs, but also obtains high comprehensive magnetic properties of the sintered NdFeB permanent magnet material for new energy vehicles. Specific embodiments

[0028] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0029] Example 1

[0030] This example provides a preparation method of a sintered NdFeB permanent magnet material with high comprehensive performance for new energy vehicles, including the following steps:

[0031] (1) Weigh the ingredients according to the chemical composition PrNd 28.5 Dy 0.5 Tb 0.5 Co 1.00 Ga 0.2 Al 0.1 Cu 0.2 Zn 0.1 B 0.95 Fe 67.95 to prepare the ingredients, and use the rapid solidification technology to obtain a rapid solidification sheet with an average thickness of 0.25 mm. No obvious α-Fe segregation phase is found in the metallographic structure test.

[0032] (2) Use the hydrogen explosion and air jet milling of the rapid solidification sheet in step (1) to obtain NdFeB magnetic powder; the average particle size of the magnetic powder SMD = 3.12um, X10 = 1.72um, X99 = 9.91um.

[0033] (3) Orient and compact the NdFeB magnetic powder in step (2) under a magnetic field of 1.8 T, with a pressure of 20 MPa, and form a NdFeB magnet precursor through high-temperature sintering.

[0034] The specific high-temperature sintering process is as follows:

[0035] 1) Put the NdFeB powder compact into the furnace;

[0036] 2) Evacuate the air. Use a pump set consisting of a rotary vane vacuum pump and a Roots pump. Open the roughing valve to evacuate the vacuum degree inside the sintering equipment to 1.0×10 -1 Pa;

[0037] 3) Heat up and exhaust gas. The target temperature is 600°C. After keeping the temperature for 0.5 h, raise the temperature to the final exhaust temperature point of 950°C. After the exhaust vacuum degree reaches 1.0×10 -1 Pa, continue to raise the temperature to 1080°C and keep the temperature for 4 h. At this time, the pump set continues to work to maintain the vacuum degree of 1.0×10 -1 Pa;

[0038] 4) Temper. Cool down to 900°C and keep the temperature for 2 h. Then cool down to 490°C and keep the temperature for 4 h;

[0039] 5) Turn off the pump set, turn on the fan, and cool down to room temperature and then take out the product from the furnace.

[0040] (4) Perform slicing processing on the precursor obtained in step (3) to obtain square or circular slices with a thickness of 3.5 mm.

[0041] (5) Coat the magnetic steel sheets obtained in step (4) by multi-pole target magnetron sputtering. The coating weight gain ratio is Tb 0.3% (wt%) + Dy 0.2% (wt%).

[0042] (6) Perform low-temperature diffusion and aging treatment on the coated magnetic steel sheets obtained in step (5), and finally obtain a sintered NdFeB permanent magnetic material with high comprehensive performance for new energy vehicles.

[0043] The specific low-temperature diffusion and aging treatment in step (5) is as follows:

[0044] 1) Sinter, heat up and keep the temperature;

[0045] 2) Turn off the heating, fill the sintering equipment with inert gas and cool it down to the first-stage aging temperature of 900°C by self-cooling. The inert gas is heated by the high-temperature product, and then heat exchange is carried out through a heat exchanger. Then the sintering equipment directly keeps the temperature for 2 h under a vacuum degree of 0.05 Pa;

[0046] 3) After the first-stage aging and heat preservation are completed, fill the inert gas again and cool it down to below 80°C by air cooling;

[0047] 4) When the vacuum degree of the sintering equipment is 0.05 Pa, turn off the vacuum pump set, raise the temperature to the second-stage aging temperature of 510°C, and keep the temperature for 4 h;

[0048] 5) Fill the inert gas and cool it down by air cooling and then take out the product from the furnace.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that: without undergoing the step (5) film covering treatment, two-stage aging treatment of the traditional process is directly carried out.

[0051] Table 1 Material magnetic properties of Example 1 and Comparative Example 1

[0052] Br (kGs) Hcj (kOe) (BH)max (MGOe) Example 1 14.67 26.86 53.87 Comparative Example 1 14.52 18.12 52.21

Claims

1. A preparation method of a sintered neodymium iron boron permanent magnet material with high comprehensive performance for new energy vehicles, comprising the following steps: (1) Prepare a neodymium iron boron permanent magnet rapid solidification sheet by using a rapid solidification technology process; (2) Subject the rapid solidification sheet obtained in step (1) to two-stage powder making through hydrogen explosion and air flow milling to obtain neodymium iron boron permanent magnet powder; (3) Orient and sinter the neodymium iron boron permanent magnet powder obtained in step (2) under a magnetic field of 1.5 - 2.0 T to form a high-performance precursor with easy diffusion; (4) Adhere a heavy rare earth layer to the high-performance precursor with easy diffusion obtained in step (3) by using multi-pole target magnetron sputtering; (5) Perform low-temperature diffusion and aging treatment on the neodymium iron boron magnet with a heavy rare earth layer attached in step (4), and thus obtain a sintered neodymium iron boron permanent magnet material with high comprehensive performance for new energy vehicles.

2. The preparation method according to claim 1, wherein: The microstructure of the rapid solidification sheet in step (1) has complete columnar crystals, no α-Fe segregation phase, and the rare earth-rich phase is dispersed.

3. The preparation method according to claim 1, wherein: The average thickness of the rapid solidification sheet in step (1) is 0.20 - 0.40 mm.

4. The preparation method according to claim 1, characterized in that: The average particle size of the neodymium iron boron permanent magnet powder in step (2) is SMD = 2.8 - 3.2 μm, X10 = 1.6 - 2.0 μm, and X99 ≤ 10 μm.

5. The preparation method according to claim 1, characterized in that: The sintering in step (3) is specifically as follows: 1) Put the neodymium iron boron powder compact into the furnace; 2) Evacuate the air. Use a pump set consisting of a sliding vane vacuum pump and a Roots pump. Open the roughing valve to evacuate the vacuum degree inside the sintering equipment to 1.0×10 -1 Pa; 3) Heat up and exhaust gas. The target temperature is 600 °C. After holding for 0.5 h, it is raised to the final exhaust gas temperature point of 950 °C. After the exhaust gas vacuum degree reaches 1.0×10 -1 Pa, then continue to heat up to 1080 °C and hold for 4 h. At this time, the pump set continues to work to maintain the vacuum degree of 1.0×10 - 1 Pa; 4) Temper, cool down to 900 °C, hold for 2 h, and then cool down to 490 °C and hold for 4 h; 5) Close the pump group, turn on the fan, and cool to room temperature and take out of the furnace.

6. The preparation method according to claim 1, characterized in that: The multi-pole target magnetron sputtering in step (4) uses a multi-component co-mixed single target or target group of heavy rare earth Dy / Tb, light rare earth Pr / Nd, and non-magnetic metals Al, Cu, Ga, and is completed by using a multi-target magnetron sputtering automated production line.

7. The preparation method according to claim 1, characterized in that: The low-temperature diffusion and aging treatment in step (5) is specifically as follows: 1) Sinter and heat up and hold; 2) Turn off the heating, fill the sintering equipment with an inert gas and self-cool to the first-stage aging temperature of 900 °C ± 20 °C. The inert gas is heated by the high-temperature product, then heat exchange is carried out through a heat exchanger, and then the sintering equipment directly holds for 1.5 h - 2.5 h under a vacuum degree of 0.05 Pa; 3) After the first-stage aging holding is completed, fill with an inert gas and air-cool to below 80 °C; 4) When the vacuum degree of the sintering equipment is 0.05 Pa, close the vacuum pump group, raise the temperature to the second-stage aging temperature of 510 °C ± 30 °C, and hold for 4 h - 5 h; 5) Fill with an inert gas and air-cool and take out of the furnace.