Disclosure of Invention
The invention provides a method for diffusing heavy rare earth on the surface of a sintered neodymium-iron-boron permanent magnet, which solves the defects and problems of the existing permeation and diffusion method, particularly the embedding method.
The invention is realized by adopting the following technical scheme: the method for diffusing the heavy rare earth on the surface of the sintered neodymium-iron-boron permanent magnet is realized by the following steps:
1) immersing the sintered Nd-Fe-B permanent magnet with clean surface into the heavy rare earth alloy R in a vacuum environmentTPerforming infiltration treatment in the molten liquid of M;
2) sintering neodymium iron boron permanent magnet after permeation treatment is made from heavy rare earth alloy RTSeparating the M from the molten liquid, and then performing diffusion treatment;
3) and (4) carrying out aging treatment on the sintered neodymium iron boron permanent magnet after diffusion treatment.
Compared with the prior art: a) compared with vacuum sputtering, the utilization rate of the target material of the vacuum sputtering is low, generally 45-50 percent, and the cost is high; sputtering each surface of the workpiece respectively, and sending the workpiece into a vacuum furnace for vacuum diffusion treatment, so that the efficiency is low; the equipment is complex and the investment is large. b) Compared with surface coating, workpieces are sprayed, printed and dipped one by one, and the efficiency is low; the adhesive is added and is finally stuck on the surface and difficult to remove; the coating layer peels off during diffusion, and the reliability is poor. c) Compared with an embedding method, the existing embedding method can cause surface over-penetration because the workpiece and the powder are always contacted after the penetration and before the cooling is finished; because of cooling during contact, the rare earth-rich phase precipitated on the surface of the magnet adheres to the powder, causing waste of heavy rare earth materials and difficulty in cleaning. D) The invention is liquid phase infiltration, so the infiltration depth and speed are much higher than those of solid phase infiltration. The diffusion method optimizes the process steps and process parameters, and achieves the same result as the prior art, namely, the remanence is reduced very little, and the coercive force is greatly improved; but because the separation of the workpiece and the permeable metal liquid can be automatically and immediately realized after the one-time permeation is finished, the utilization rate of the heavy rare earth material is improved by 55-60%, the heavy rare earth material and labor are saved, the equipment investment is reduced, and the comprehensive cost is reduced.
Detailed Description
The method for diffusing heavy rare earth on the surface of the sintered neodymium-iron-boron permanent magnet is realized by the following steps as shown in figures 1-5:
1) immersing the sintered Nd-Fe-B permanent magnet with clean surface into the heavy rare earth alloy R in a vacuum environmentTPerforming infiltration treatment in the molten liquid of M;
2) sintering neodymium iron boron permanent magnet after permeation treatment is made from heavy rare earth alloy RTSeparating the M from the molten liquid, and then performing diffusion treatment;
3) and (4) carrying out aging treatment on the sintered neodymium iron boron permanent magnet after diffusion treatment.
In specific implementation, the vacuum environment in the step 1) is vacuum degree of 1Pa to 0.003Pa (such as 1Pa, 0.5 Pa, 0.1 Pa, 0.05 Pa, 0.01 Pa, 0.008 Pa and 0.003 Pa); the time of the infiltration treatment is 0.2-10 (e.g., 0.2 hour, 0.5 hour, 1 hour, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 5.5 hours, 6 hours, 7 hours, 8 hours, 8.8 hours, 9 hours, 10 hours), the infiltration temperature is 600-950 ℃ (e.g., 600 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃);
in step 2), the temperature of the diffusion treatment is 820-950 ℃ (e.g., 820 ℃, 850 ℃, 900 ℃, 950 ℃) and the diffusion treatment time is 1-10 hours (e.g., 1 hour, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 5.5 hours, 6 hours, 7 hours, 8 hours, 8.8 hours, 9 hours, 10 hours);
in step 3), the temperature of the aging treatment is 450-650 ℃ (450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃) and the vacuum degree is 10-1-10-2Pa (e.g., 0.1 Pa, 0.08 Pa, 0.05 Pa, 0.01 Pa); the time for the aging treatment is 4 to 12 hours (e.g., 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours).
Steps 1) -2) are achieved as follows: putting a sintered Nd-Fe-B permanent magnet with a clean surface into a permeation box 1, arranging an isolation net 2 with the periphery fixed with the permeation box above the sintered Nd-Fe-B permanent magnet, and placing a heavy rare earth alloy R on the isolation net 2TM block 3, then heavy rare earth alloy RTAn inverted crucible 4 is buckled on the M blocks 3, the periphery of the crucible 4 is hermetically connected with the infiltration material box 1, thereby the heavy rare earth alloy R is obtainedTM blocks 3 and sintered Nd-Fe-B permanent magnets are covered in a permeation material box 1, the permeation material box 1 covered with a crucible 4 is placed into a vacuum furnace for heating, the vacuum degree in the furnace is 1 Pa-0.003 Pa, and the heavy rare earth alloy R is madeTM blocks 3 are melted and flow into a penetration material box 1 (through an isolation net 2) to enable the sintered Nd-Fe-B permanent magnet to be immersed into the heavy rare earth alloy RTPerforming infiltration treatment in the molten liquid of M, wherein the temperature of the infiltration treatment is 600-950 ℃, and the time of the infiltration treatment is 0.2-10 hours; then, the infiltration material box 1 in the vacuum furnace is turned over for 180 degrees, so that the heavy rare earth alloy R in the infiltration material box 1TThe M molten state liquid flows into the crucible 4 to realize sintering the Nd-Fe-B permanent magnet from the heavy rare earth alloy RTSeparating the M from the molten liquid, and then performing diffusion treatment at 820-950 ℃ for 1-10 hours. After diffusion treatment, the infiltration material box 1 is moved out of the vacuum furnace to a cooling chamber, and the heavy rare earth alloy R in the crucible 4 is recoveredTM, starting a gas circulation cooling system to cool the sintered neodymium iron boron permanent magnet to 50-200 ℃; then, the infiltration material box 1 is sent into the vacuum furnace again for aging treatment, the temperature of the aging treatment is 450-650 ℃, and the vacuum degree is 10-1-10-2Pa, and the time of aging treatment is 4-12 hours. The infiltration material box 1 is connected with the crucible 4 through a flange, and the periphery of the separation net 2 is pressed on the connecting flangeIn the meantime.
In order to conveniently realize the overturning of the permeation cartridge, the steps 1) to 2) are realized as follows: putting a sintered Nd-Fe-B permanent magnet with a clean surface into a permeation box 1, arranging an isolation net 2 with the periphery fixed with the permeation box 1 above the sintered Nd-Fe-B permanent magnet, and placing a heavy rare earth alloy R on the isolation net 2TM block 3, then heavy rare earth alloy RTAn inverted crucible 4 is buckled on the M blocks 3, the infiltration material box 1 with the crucible 4 buckled thereon is arranged in the furnace pipe and is pressed between the upper inner wall and the lower inner wall of the furnace pipe, thereby realizing the sealing connection of the periphery of the crucible 4 and the infiltration material box 1, and the heavy rare earth alloy R isTM block 3 and sintered Nd-Fe-B permanent magnet are covered in the permeating material box, the vacuum degree in the furnace pipe reaches 1 Pa-0.003 Pa, the furnace pipe is rotatablely supported in the heating furnace, the heating furnace heats the furnace pipe, so that the heavy rare earth alloy RTM blocks 3 are melted and flow into a penetration material box 1 (through an isolation net 2) to enable the sintered Nd-Fe-B permanent magnet to be immersed into the heavy rare earth alloy RTPerforming infiltration treatment in the molten liquid of M at the infiltration temperature of 600-950 ℃ for 0.2-10 hours; then, the furnace pipe is turned over 180 degrees to enable the heavy rare earth alloy R in the infiltration material box 1 to permeateTThe M molten state liquid flows into the crucible 4 to realize sintering the Nd-Fe-B permanent magnet from the heavy rare earth alloy RTSeparating the M from the molten liquid, and then performing diffusion treatment at 820-950 ℃ for 1-10 hours. After diffusion treatment, the infiltration material box 1 is moved out of the furnace pipe to a cooling chamber, and the heavy rare earth alloy R in the crucible 4 is recoveredTM, starting a gas circulation cooling system to cool the sintered neodymium iron boron permanent magnet to 50-200 ℃; then, the infiltration material box 1 is sent into the furnace pipe again for aging treatment, the temperature of the aging treatment is 450-650 ℃, and the vacuum degree is 10-1-10-2Pa, and the time of aging treatment is 4-12 hours. The heating furnace is of a split structure, as shown in fig. 5, the two furnace bodies are folded when heating, and the two furnace bodies are separated when heating is not needed. The infiltration material box 1 is connected with the crucible 4 through a flange, and the periphery of the isolation net 2 is pressed between the connecting flanges; because the crucible 4 and the permeation material box 1 are pressed between the upper inner wall and the lower inner wall of the furnace pipe, the permeation material box 1 and the connecting flange of the crucible 4 can be fastened without bolts.
Heavy rare earth alloy RTR of MTIs one or more of Dy, Tb and Ho in any proportion, M is one or more of Fe, Al, Cu and Ga in any proportion, and the proportion is designed according to the principle that the heavy rare earth alloy RTThe melting temperature of M is 10 degrees below the infiltration temperature, so as to ensure better fluidity at the infiltration temperature. Preferably, the heavy rare earth alloy RTR of MTThe content of (B) is 75-95%, and the content of M is 5-25%.
The sintered Nd-Fe-B permanent magnets are arranged in a multi-layer manner in the penetration material box 1, each layer is provided with a plurality of sintered Nd-Fe-B permanent magnets, the upper layer and the lower layer and the sintered Nd-Fe-B on the same layer are isolated by high temperature resistant grids to leave gaps, and the sintered Nd-Fe-B permanent magnets are ensured to be sufficient and heavy rare earth alloy RTMolten liquid contact of M.
Example 1
Preparation of heavy rare earth alloy R of 88wt% Dy and 12wt% CuTM, melting point about 810 ℃. The diffusion method of the invention is used for carrying out surface diffusion on the sheet sintered NdFeB permanent magnet with the performance of N52 being 3X 15X 20, and finally the magnet with the surface of 50H is obtained, and the surface is clean and tidy.
Example 2
A high Tb-permeable alloy having a Tb content of 80 wt%, a Cu content of 10 wt%, a Ga content of 5 wt% and an Al content of 5 wt% was prepared, and the remainder was subjected to the same procedure as in example 1 to obtain a 50UH magnet.