Neodymium-iron-boron sintering method facilitating decarburization

Abstract

Disclosed is a neodymium-iron-boron sintering method facilitating decarburization. The chemical formula of a neodymium-iron-boron magnet is RX1T(100-X1-X2-X3-X4)MX3AX4BX2. The sintering method comprises the following main steps: blending raw materials of neodymium, iron and boron at a ratio; melting same to form an alloy melt, casting same into strip-cast flakes, and grinding same to form a powder; loading the powder into a tank protected by an inert gas, and fully stirring same; compacting the powder and performing oriented forming; performing vacuum encapsulation, water-based isostatic pressing, sintering and film stripping, wherein the sintering is carried out by means of multi-stage heating and soaking, the inert gas is introduced and withdrawn during the soaking to form alternating soak sintering by an inert-gas pressure differential; and after the sintering is completed, cooling is performed to no more than 100°C. A central part of the sintered magnet is collected to determine the contents of nitrogen, oxygen and carbon in the compact. Provided is a neodymium-iron-boron sintering method facilitating decarburization, wherein the carbon is removed by means of the sintering process during the neodymium-iron-boron sintering.

Description

A NdFeB sintering method that facilitates decarburization Technical Field

[0001] This invention relates to the field of NdFeB production, specifically to a NdFeB sintering method that facilitates decarburization. Background Technology

[0002] With the rapid development of rare earth permanent magnet applications, the demand for high-performance, low-cost NdFeB permanent magnets is increasing rapidly. Therefore, improving the magnetic properties of NdFeB and developing high-performance sintered NdFeB has become a primary technical challenge. One of the main applications of rare earth permanent magnet materials is in the manufacture of various permanent magnet motors. Compared with traditional motors, permanent magnet motors are characterized by light weight, small size, high efficiency and energy saving, and high reliability. Sintered NdFeB permanent magnets are small in size and high in performance, which can effectively reduce motor weight and improve motor efficiency, making them more suitable for the miniaturization and weight reduction of automobiles.

[0003] Currently, improving coercivity (H) CJ The most effective method is to replace neodymium (Nd) in the alloy with the heavy rare earth elements terbium (Tb) and dysprosium (Dy) to form (Nd,Tb)2Fe. 14 B or (Nd,Dy)2Fe 14 B. Among them, grain boundary diffusion technology and grain boundary doping technology are effective ways to prepare high coercivity materials with no or low heavy rare earth elements.

[0004] Since its inception, grain boundary diffusion technology has attracted widespread attention in the industry and has been rapidly industrialized in recent years. In actual industrial production, the use of grain boundary diffusion can reduce the consumption of heavy rare earth elements by more than 50%. However, the grain boundary diffusion process places higher demands on the substrate; the lower the carbon, oxygen, and nitrogen content in the substrate, the easier it is to ensure unobstructed channels for grain boundary diffusion.

[0005] For matrices with grain boundary diffusion, the introduction of carbon elements should be intentionally reduced during the powder preparation and molding stages, such as by reducing the use of lubricants and surface modifiers. However, in order to ensure the flowability and formability of the powder, it is unavoidable to add antioxidants, air jet mill protectants, etc. Therefore, this unavoidable introduction of carbon elements affects the performance of the matrix and also affects the smooth flow of grain boundary diffusion channels. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a NdFeB sintering method that facilitates decarburization by removing carbon elements during the NdFeB sintering process.

[0007] The technical solution adopted by this invention to solve the above problems is: a sintering method for NdFeB magnets that facilitates decarburization, wherein the chemical formula of the NdFeB magnet is R X1 T (100-X1-X2-X3-X4) MX3 A X4 B X2 During sintering, a multi-stage heating and holding platform is used. Inert gas is introduced and extracted during the holding period to create an alternating inert gas pressure difference for sintering, thereby reducing the carbon content inside the billet. The steps are as follows:

[0008] S1: Mix NdFeB raw materials in a specified proportion;

[0009] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0010] S3: Cast the molten alloy into a sheet;

[0011] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0012] S5: Press the powder into a compact and shape it according to orientation;

[0013] S6: Vacuum sealed;

[0014] S7: Perform isostatic pressure testing of water;

[0015] S8: Sintering and peeling are carried out. The sintering adopts a multi-stage heat preservation and heating method. During the heat preservation, inert gas is introduced and extracted to form an inert gas pressure difference for alternating heat preservation and sintering.

[0016] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0017] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0018] Compared with the prior art, the advantages of the present invention are as follows: through step S8, during the sintering process, a staged heat preservation is adopted to avoid the formation of a high-temperature reaction isolation layer, ensuring that the internal and external temperatures of the billet are consistent, thereby ensuring that the diffusion channels are open; at the same time, the alternating pressure difference of inert gas in the heat preservation section promotes the interaction between organic gas and inert gas, and then a vacuum pump is used to form a negative pressure to remove more carbides.

[0019] As an improvement of the present invention, step S8 includes the following steps:

[0020] S8.1: Start heating from room temperature;

[0021] S8.2: Increase the temperature to 100℃~400℃;

[0022] S8.3: Keep warm for 1-4 hours;

[0023] S8.4: Increase the temperature to 400℃~600℃;

[0024] S8.5: Keep warm for 1-4 hours;

[0025] S8.6: Heat to 600℃~900℃;

[0026] S8.7: Keep warm for 1-4 hours;

[0027] Through the aforementioned improvements, in conventional sintered NdFeB materials, organic matter such as release agents adsorbed on the surface of the billet can vaporize at 100℃-400℃ and be discharged from the billet through the diffusion channels. Therefore, a long initial preheating is performed in steps S8.2 and S8.3. Then, the temperature is raised again in steps S8.4 and S8.5. During this stage, the gaps between particles in the billet are further reduced, and hydrogen, carbon, and oxygen-containing substances that are strongly bonded to the powder particles escape. Then, in steps S8.6 and S8.7, the temperature is raised from 600℃ to 900℃, and a liquid phase begins to appear in the sintered NdFeB. Particle rearrangement occurs, and the diffusion channels narrow. This stage requires a relatively long time to reach the lowest temperature gradient inside and outside the billet, eliminating the phenomenon that the channels are blocked due to the high temperature and large amount of liquid phase outside the billet, thus preventing the organic matter from being discharged.

[0028] As an improvement to the present invention, steps S8.3, S8.5, and S8.7 all include the following steps:

[0029] A1: After the insulation process begins, inert gas is introduced;

[0030] A2: After maintaining this position for a period of time, vacuum the system.

[0031] A3: After being kept in a vacuum for a period of time;

[0032] A4: Repeat steps A1-A3 at least twice;

[0033] Through the aforementioned improvements, the carbon elements removed from the billet during the sintering process mainly volatilize directly or form carbide gases. Therefore, steps A1-A4 can enhance the mobility of the volatilized carbon and carbide gases and provide sufficient diffusion time for them to quickly diffuse throughout the sintering equipment. Then, by introducing inert gas, the volatilized carbon and carbide gases are diluted, allowing them to fully diffuse into the inert gas. This reduces the difficulty of removing the volatilized carbon and carbide gases during vacuuming, thereby reducing their inhibitory effect on subsequent decarburization reactions.

[0034] With the aforementioned improvement, after step S8.7, the method further includes step S8.8: evacuating to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1050±50℃, and the holding time is 4 to 15 hours. Through the above improvement, the billet is sintered and shaped.

[0035] As an improvement of the present invention, in step S9, after sintering is completed, a high-purity inert gas is introduced to cool it to below 100°C. Through this improvement, after the billet is sintered in a vacuum, the introduction of a high-purity inert gas can not only rapidly cool the billet, but also ensure that the sintered billet tends to be in a stable state by cooling it to below 100°C, thus ensuring the sintering quality of the billet.

[0036] As an improvement of the present invention, after step S9, step S9.1 is further included: aging treatment is performed on the sintered magnet, and the magnetic properties of the magnet are enhanced by the aging treatment.

[0037] As an improvement of the present invention, step S4 includes step S4.1: adding a powder modifier at a ratio of 0.05wt%-0.5wt% and stirring thoroughly. This improvement provides an anti-oxidation protection effect, isolating the magnetic powder from air and significantly reducing the oxidation risk of the NdFeB powder before sintering; it improves powder flowability, as the oleophilic hydrocarbon chain structure of the modifier reduces the forces between powder particles, inhibits agglomeration, and makes the powder easier to flow and uniformly fill the mold; it enhances flame retardancy and safety, as the modifier reduces powder surface activity during processing such as air jet milling, preventing combustion accidents caused by friction or collision of the magnetic powder; and it promotes magnetic field orientation, as the lubricating effect of the modifier makes the magnetic powder particles more easily rotate and align in a consistent manner in the magnetic field, thereby increasing the remanence B of the magnet. r And the maximum magnetic energy product (BH) max .

[0038] As an improvement of the present invention, step S5 includes step S5.1: spraying a release agent during the molding process, thereby facilitating the demolding of the blank after molding.

[0039] As an improvement to the present invention, the following steps are also included:

[0040] S11: The sintered magnet is processed into thin sheets and subjected to grain boundary diffusion;

[0041] S12: Use a magnetic tester to test the magnetic properties before and after diffusion. Through the aforementioned improvement, grain boundary diffusion is performed on the sintered magnet to further improve the magnetic properties of the magnet, and then the change in magnetic properties is measured. Attached Figure Description

[0042] Figure 1 is a schematic diagram of the sintering curve and the pressure change curve of the sintering equipment according to the present invention. Detailed Implementation

[0043] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0044] A sintering method for NdFeB magnets that facilitates decarburization, the chemical formula of NdFeB magnets is R X1 T (100-X1-X2-X3-X4) M X3 A X4 B X2 ;

[0045] Where X1, X2, X3, and X4 are the mass percentages of the corresponding elements;

[0046] R is selected from one or more rare earth elements, and 28.5wt%≤X1≤32.5wt%;

[0047] T is selected from Fe and Co, with Co content ranging from 0 to 1.0 wt% and the balance being Fe;

[0048] M is selected from one or more of Ti, Zr and Nb, with 0.1wt% ≤ X3 ≤ 0.35wt%;

[0049] A is selected from Cu, Ga and Al, 0.0wt% ≤ X4 ≤ 1.2wt%;

[0050] B is B, and its content is 0.88wt% ≤ X2 ≤ 0.98wt%.

[0051] A multi-stage heating and holding platform is used during sintering. Inert gas is introduced and extracted during the holding period to create an alternating inert gas pressure difference for sintering, thereby reducing the carbon content inside the billet. The steps are as follows:

[0052] S1: Mix NdFeB raw materials in a specified proportion;

[0053] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0054] S3: Cast the molten alloy into a sheet;

[0055] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0056] S4.1: Add powder modifier at a ratio of 0.05wt%-0.5wt%, and stir thoroughly;

[0057] S5: Press the powder into a compact and shape it according to orientation;

[0058] S5.1: A release agent is sprayed in during the molding process;

[0059] S6: Vacuum sealed;

[0060] S7: Perform isostatic pressure testing of water;

[0061] S8: Sintering and peeling are carried out. The sintering adopts a multi-stage heat preservation and heating method. During the heat preservation, inert gas is introduced and extracted to form an inert gas pressure difference for alternating heat preservation and sintering.

[0062] S8.1: Start heating from room temperature;

[0063] S8.2: Increase the temperature to 100℃~400℃;

[0064] S8.3: Keep warm for 1-4 hours;

[0065] S8.3.1: Fill with inert gas;

[0066] S8.3.2: After maintaining this position for a period of time, apply a vacuum.

[0067] S8.3.3: After maintaining a vacuum state for a period of time;

[0068] S8.3.4: Repeat steps S8.3.1-S8.3.3 at least once;

[0069] S8.4: Increase the temperature to 400℃~600℃;

[0070] S8.5: Keep warm for 1-4 hours;

[0071] S8.5.1: Fill with inert gas;

[0072] S8.5.2: After maintaining this position for a period of time, apply a vacuum.

[0073] S8.5.3: After maintaining a vacuum state for a period of time;

[0074] S8.5.4: Repeat steps S8.5.1-S8.5.3 at least once;

[0075] S8.6: Heat to 600℃~900℃;

[0076] S8.7: Keep warm for 1-4 hours;

[0077] S8.7.1: Fill with inert gas;

[0078] S8.7.2: After maintaining this position for a period of time, apply a vacuum.

[0079] S8.7.3: After maintaining a vacuum state for a period of time;

[0080] S8.7.4: Repeat steps S8.7.1-S8.7.3 at least once;

[0081] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1050±50℃, and the holding time is 4 to 15 hours;

[0082] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0083] S9.1: Aging treatment is performed on the sintered magnet;

[0084] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0085] S11: Take the sintered magnet and process it into a thin sheet of 10mm×10mm×5mm, and then perform grain boundary diffusion;

[0086] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0087] Example 1.1: The casting formulation is: (PrNd) 30% B 0.94% Ti 0.2% (Al+Cu+Ga) 0.35% Co 1%, with the remainder being Fe.

[0088] The steps are as follows:

[0089] S1: Mix NdFeB raw materials in a specified proportion;

[0090] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0091] S3: Cast the molten alloy into a sheet;

[0092] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0093] S4.1: Add powder modifier at a ratio of 0.1 wt% and stir thoroughly;

[0094] S5: Press the powder into a compact and shape it according to orientation;

[0095] S5.1: A release agent is sprayed in during the molding process at a weight ratio of 0.1 wt%.

[0096] S6: Vacuum sealed;

[0097] S7: Perform isostatic pressure testing of water;

[0098] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0099] S8.1: Start heating from room temperature;

[0100] S8.2: Heat to 200℃;

[0101] S8.3: Keep warm for 2 hours;

[0102] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0103] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0104] S8.3.3: Maintain in a vacuum for 30 minutes;

[0105] S8.3.4: Repeat steps S8.3.1-S8.3.3 once more;

[0106] S8.4: Heat to 560℃;

[0107] S8.5: Keep warm for 2 hours;

[0108] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0109] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0110] S8.5.3: Maintain in a vacuum for 30 minutes;

[0111] S8.5.4: Repeat steps S8.5.1-S8.5.3 once more;

[0112] S8.6: Heat to 820℃;

[0113] S8.7: Keep warm for 3 hours;

[0114] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0115] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0116] S8.7.3: Maintain in a vacuum for 30 minutes;

[0117] S8.7.4: Repeat steps S8.7.1-S8.7.3 twice more;

[0118] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature was raised to 1082℃, and the holding time was 7 hours;

[0119] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0120] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0121] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0122] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.62wt%.

[0123] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0124] Example 1.2: The casting formulation is: (PrNd) 30% B 0.94% Ti 0.2% (Al+Cu+Ga) 0.35% Co 1%, with the remainder being Fe.

[0125] The steps are as follows:

[0126] S1: Mix NdFeB raw materials in a specified proportion;

[0127] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0128] S3: Cast the molten alloy into a sheet;

[0129] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0130] S4.1: Add powder modifier at a ratio of 0.1 wt% and stir thoroughly;

[0131] S5: Press the powder into a compact and shape it according to orientation;

[0132] S5.1: A release agent is sprayed in during the molding process at a weight ratio of 0.1 wt%.

[0133] S6: Vacuum sealed;

[0134] S7: Perform isostatic pressure testing of water;

[0135] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0136] S8.1: Start heating from room temperature;

[0137] S8.2: Heat to 200℃;

[0138] S8.3: Keep warm for 3 hours;

[0139] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0140] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0141] S8.3.3: Maintain in a vacuum for 30 minutes;

[0142] S8.3.4: Repeat steps S8.3.1-S8.3.3 twice more;

[0143] S8.4: Heat to 560℃;

[0144] S8.5: Keep warm for 3 hours;

[0145] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0146] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0147] S8.5.3: Maintain in a vacuum for 30 minutes;

[0148] S8.5.4: Repeat steps S8.5.1-S8.5.3 twice more;

[0149] S8.6: Heat to 820℃;

[0150] S8.7: Keep warm for 4 hours;

[0151] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0152] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0153] S8.7.3: Maintain in a vacuum for 30 minutes;

[0154] S8.7.4: Repeat steps S8.7.1-S8.7.3 three times;

[0155] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature was raised to 1082℃, and the holding time was 7 hours;

[0156] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0157] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0158] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0159] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.62wt%.

[0160] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0161] Comparative Example 1: The casting formulation is: (PrNd) 30%B 0.94%Ti 0.2%(Al+Cu+Ga) 0.35%Co 1%, with the remainder being Fe.

[0162] The steps are as follows:

[0163] S1: Mix NdFeB raw materials in a specified proportion;

[0164] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0165] S3: Cast the molten alloy into a sheet;

[0166] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0167] S4.1: Add powder modifier at a ratio of 0.1 wt% and stir thoroughly;

[0168] S5: Press the powder into a compact and shape it according to orientation;

[0169] S5.1: A release agent is sprayed in during the molding process at a weight ratio of 0.1 wt%.

[0170] S6: Vacuum sealed;

[0171] S7: Perform isostatic pressure testing of water;

[0172] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0173] S8.1: Start heating from room temperature;

[0174] S8.2: Heat to 200℃;

[0175] S8.3: Keep warm for 3 hours;

[0176] S8.4: Heat to 560℃;

[0177] S8.5: Keep warm for 3 hours;

[0178] S8.6: Heat to 820℃;

[0179] S8.7: Keep warm for 4 hours;

[0180] S8.8: The sintering temperature is raised to 1082℃ and held for 7 hours;

[0181] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0182] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0183] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0184] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.62wt%.

[0185] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0186] Example 2.1: The casting formulation is: (PrNd) 28.5% Gd 2.5% B 0.95% Ti 0.2% (Al+Cu+Ga) 0.5% Co 0.8%, with the remainder being Fe.

[0187] The steps are as follows:

[0188] S1: Mix NdFeB raw materials in a specified proportion;

[0189] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0190] S3: Cast the molten alloy into a sheet;

[0191] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0192] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0193] S5: Press the powder into a compact and shape it according to orientation;

[0194] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0195] S6: Vacuum sealed;

[0196] S7: Perform isostatic pressure testing of water;

[0197] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0198] S8.1: Start heating from room temperature;

[0199] S8.2: Heat to 200℃;

[0200] S8.3: Keep warm for 2 hours;

[0201] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0202] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0203] S8.3.3: Maintain in a vacuum for 30 minutes;

[0204] S8.3.4: Repeat steps S8.3.1-S8.3.3 once more;

[0205] S8.4: Heat to 560℃;

[0206] S8.5: Keep warm for 2 hours;

[0207] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0208] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0209] S8.5.3: Maintain in a vacuum for 30 minutes;

[0210] S8.5.4: Repeat steps S8.5.1-S8.5.3 once more;

[0211] S8.6: Heat to 820℃;

[0212] S8.7: Keep warm for 3 hours;

[0213] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0214] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0215] S8.7.3: Maintain in a vacuum for 30 minutes;

[0216] S8.7.4: Repeat steps S8.7.1-S8.7.3 twice more;

[0217] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1076℃, and the holding time is 5 hours;

[0218] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0219] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0220] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0221] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.56wt%.

[0222] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0223] Example 2.2: The casting formulation is: (PrNd) 28.5% Gd 2.5% B 0.95% Ti 0.2% (Al+Cu+Ga) 0.5% Co 0.8%, with the remainder being Fe.

[0224] The steps are as follows:

[0225] S1: Mix NdFeB raw materials in a specified proportion;

[0226] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0227] S3: Cast the molten alloy into a sheet;

[0228] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0229] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0230] S5: Press the powder into a compact and shape it according to orientation;

[0231] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0232] S6: Vacuum sealed;

[0233] S7: Perform isostatic pressure testing of water;

[0234] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0235] S8.1: Start heating from room temperature;

[0236] S8.2: Heat to 200℃;

[0237] S8.3: Keep warm for 3 hours;

[0238] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0239] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0240] S8.3.3: Maintain in a vacuum for 30 minutes;

[0241] S8.3.4: Repeat steps S8.3.1-S8.3.3 twice more;

[0242] S8.4: Heat to 560℃;

[0243] S8.5: Keep warm for 3 hours;

[0244] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0245] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0246] S8.5.3: Maintain in a vacuum for 30 minutes;

[0247] S8.5.4: Repeat steps S8.5.1-S8.5.3 twice more;

[0248] S8.6: Heat to 820℃;

[0249] S8.7: Keep warm for 4 hours;

[0250] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0251] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0252] S8.7.3: Maintain in a vacuum for 30 minutes;

[0253] S8.7.4: Repeat steps S8.7.1-S8.7.3 three times;

[0254] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1076℃, and the holding time is 5 hours;

[0255] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0256] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0257] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0258] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.56wt%.

[0259] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0260] Comparative Example 2: The casting formulation is: (PrNd) 28.5% Gd 2.5% B 0.95% Ti 0.2% (Al+Cu+Ga) 0.5% Co 0.8%, with the remainder being Fe.

[0261] The steps are as follows:

[0262] S1: Mix NdFeB raw materials in a specified proportion;

[0263] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0264] S3: Cast the molten alloy into a sheet;

[0265] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0266] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0267] S5: Press the powder into a compact and shape it according to orientation;

[0268] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0269] S6: Vacuum sealed;

[0270] S7: Perform isostatic pressure testing of water;

[0271] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0272] S8.1: Start heating from room temperature;

[0273] S8.2: Heat to 200℃;

[0274] S8.3: Keep warm for 3 hours;

[0275] S8.4: Heat to 560℃;

[0276] S8.5: Keep warm for 3 hours;

[0277] S8.6: Heat to 820℃;

[0278] S8.7: Keep warm for 4 hours;

[0279] S8.8: The sintering temperature is raised to 1076℃ and held for 5 hours;

[0280] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0281] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0282] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0283] S11: The sintered magnet is processed into a 10mm x 10mm x 5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.56wt%.

[0284] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0285] Example 3.1: The casting formulation is: (PrNd) 28.8%, (Dy+Gd) 2.1%, B 0.95%, Ti 0.2%, (Al+Cu+Ga) 1.0%, Co 0.5%, and the remainder is Fe.

[0286] The steps are as follows:

[0287] S1: Mix NdFeB raw materials in a specified proportion;

[0288] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0289] S3: Cast the molten alloy into a sheet;

[0290] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0291] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0292] S5: Press the powder into a compact and shape it according to orientation;

[0293] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0294] S6: Vacuum sealed;

[0295] S7: Perform isostatic pressure testing of water;

[0296] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0297] S8.1: Start heating from room temperature;

[0298] S8.2: Heat to 200℃;

[0299] S8.3: Keep warm for 2 hours;

[0300] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0301] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0302] S8.3.3: Maintain in a vacuum for 30 minutes;

[0303] S8.3.4: Repeat steps S8.3.1-S8.3.3 once more;

[0304] S8.4: Heat to 560℃;

[0305] S8.5: Keep warm for 2 hours;

[0306] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0307] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0308] S8.5.3: Maintain in a vacuum for 30 minutes;

[0309] S8.5.4: Repeat steps S8.5.1-S8.5.3 once more;

[0310] S8.6: Heat to 820℃;

[0311] S8.7: Keep warm for 3 hours;

[0312] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0313] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0314] S8.7.3: Maintain in a vacuum for 30 minutes;

[0315] S8.7.4: Repeat steps S8.7.1-S8.7.3 twice more;

[0316] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1073℃, and the holding time is 5 hours;

[0317] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0318] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0319] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0320] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.65wt%.

[0321] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0322] Example 3.2: The casting formulation is: (PrNd) 28.8%, (Dy+Gd) 2.1%, B 0.95%, Ti 0.2%, (Al+Cu+Ga) 1.0%, Co 0.5%, with the remainder being Fe.

[0323] The steps are as follows:

[0324] S1: Mix NdFeB raw materials in a specified proportion;

[0325] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0326] S3: Cast the molten alloy into a sheet;

[0327] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0328] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0329] S5: Press the powder into a compact and shape it according to orientation;

[0330] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0331] S6: Vacuum sealed;

[0332] S7: Perform isostatic pressure testing of water;

[0333] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0334] S8.1: Start heating from room temperature;

[0335] S8.2: Heat to 200℃;

[0336] S8.3: Keep warm for 3 hours;

[0337] S8.3.1: Inert gas is introduced at a pressure of 0.05 MPa;

[0338] S8.3.2: After holding for 30 minutes, evacuate the vacuum.

[0339] S8.3.3: Maintain in a vacuum for 30 minutes;

[0340] S8.3.4: Repeat steps S8.3.1-S8.3.3 twice more;

[0341] S8.4: Heat to 560℃;

[0342] S8.5: Keep warm for 3 hours;

[0343] S8.5.1: Fill with inert gas at a pressure of 0.05 MPa;

[0344] S8.5.2: After holding for 30 minutes, evacuate the vacuum.

[0345] S8.5.3: Maintain in a vacuum for 30 minutes;

[0346] S8.5.4: Repeat steps S8.5.1-S8.5.3 twice more;

[0347] S8.6: Heat to 820℃;

[0348] S8.7: Keep warm for 4 hours;

[0349] S8.7.1: Fill with inert gas at a pressure of 0.05 MPa;

[0350] S8.7.2: After holding for 30 minutes, evacuate the vacuum.

[0351] S8.7.3: Maintain in a vacuum for 30 minutes;

[0352] S8.7.4: Repeat steps S8.7.1-S8.7.3 three times;

[0353] S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1073℃, and the holding time is 5 hours;

[0354] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0355] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0356] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0357] S11: The sintered magnet is processed into a 10mm×10mm×5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.65wt%.

[0358] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0359] Comparative Example 3: The casting formulation is: (PrNd) 28.8%, (Dy+Gd) 2.1%, B 0.95%, Ti 0.2%, (Al+Cu+Ga) 1.0%, Co 0.5%, with the remainder being Fe.

[0360] The steps are as follows:

[0361] S1: Mix NdFeB raw materials in a specified proportion;

[0362] S2: Melt the neodymium iron boron raw materials into an alloy liquid;

[0363] S3: Cast the molten alloy into a sheet;

[0364] S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly;

[0365] S4.1: Add powder modifier at a ratio of 0.08 wt% and stir thoroughly;

[0366] S5: Press the powder into a compact and shape it according to orientation;

[0367] S5.1: A release agent is sprayed during the molding process at a weight ratio of 0.075 wt%.

[0368] S6: Vacuum sealed;

[0369] S7: Perform isostatic pressure testing of water;

[0370] S8: Perform sintering and peeling, and the sintering adopts a multi-stage heat preservation and heating method;

[0371] S8.1: Start heating from room temperature;

[0372] S8.2: Heat to 200℃;

[0373] S8.3: Keep warm for 3 hours;

[0374] S8.4: Heat to 560℃;

[0375] S8.5: Keep warm for 3 hours;

[0376] S8.6: Heat to 820℃;

[0377] S8.7: Keep warm for 4 hours;

[0378] S8.8: The sintering temperature is raised to 1073℃ and held for 5 hours;

[0379] S9: After sintering, high-purity inert gas is introduced to cool the temperature to below 100°C;

[0380] S9.1: After a two-stage aging process of holding at 900℃ for 2-3 hours and at 500℃ for 3-6 hours, high-purity inert gas is introduced to cool it to below 100℃;

[0381] S10: Take the center part of the sintered magnet and use pulse infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

[0382] S11: The sintered magnet is processed into a 10mm x 10mm x 5mm thin sheet, and grain boundary diffusion is performed by printing. The diffusion source is pure Tb, and the weight gain ratio is 0.65wt%.

[0383] S12: Use a NIM62000 magnetic tester to test the magnetic properties before and after diffusion.

[0384] Both the pulsed infrared absorption method and the high-frequency infrared absorption method mentioned above are conventional testing methods.

[0385] As shown in Figure 1, the figure shows the sintering curves and pressure change curves of the sintering equipment in Examples 1.2, 2.2, and 3.2.

[0386] Table 1. Carbon and oxygen content in the center of the magnet blank in each embodiment and comparative example.

[0387]

[0388] Table 2. Increase in magnetic properties and coercivity before and after diffusion in each embodiment and comparative example.

[0389]

[0390] Magnets manufactured using a NdFeB sintering method that facilitates decarburization offer the following improvements:

[0391] 1. As can be seen from Table 1, among the same type of neodymium iron boron magnets, the carbon and oxygen content will decrease significantly after repeated filling with inert gas and vacuuming.

[0392] 2. As shown in Table 2, among neodymium iron boron magnets of the same type, those that have undergone repeated filling with inert gas and evacuation have higher H values. CJ The magnetic properties of the magnet have been improved.

[0393] By employing a multi-stage heating and holding platform during sintering, and alternating holding sintering with the introduction and extraction of inert gas to create an inert gas pressure difference, the carbon content inside the billet can be effectively reduced. This reduces the blockage of grain boundary diffusion by carbon elements, increases the diffusion range of grain boundaries, and thus improves the magnetic properties of the iron boron magnet.

[0394] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A sintering method for NdFeB magnets that facilitates decarburization, wherein the chemical formula of the NdFeB magnet is R X1 T (100-X1-X2-X3-X4) M X3 A X4 B X2 Its characteristics are, The sintering process employs a multi-stage heating and holding platform. During the holding period, inert gas is introduced and extracted to create an alternating inert gas pressure difference for sintering, thereby reducing the carbon content inside the billet. The main steps are as follows: S1: Mix NdFeB raw materials in a specified proportion; S2: Melt the neodymium iron boron raw materials into an alloy liquid; S3: Cast the molten alloy into a sheet; S4: Grind the cast sheet into powder, put it into a container protected by inert gas, and stir it thoroughly; S5: Press the powder into a compact and shape it according to orientation; S6: Vacuum sealed; S7: Perform isostatic pressure testing of water; S8: Sintering and peeling are carried out. The sintering adopts a multi-stage heat preservation and heating method. During the heat preservation, inert gas is introduced and extracted to form an inert gas pressure difference for alternating heat preservation and sintering. S9: After sintering is complete, cool to below 100°C; S10: Take the center part of the sintered magnet and use pulsed infrared absorption method to test the nitrogen and oxygen content in the billet, and use high frequency infrared absorption method to test the carbon content in the billet.

2. The NdFeB sintering method for decarburization according to claim 1, characterized in that, Step S8 includes the following steps: S8.1: Start heating from room temperature; S8.2: Increase the temperature to 100℃~400℃; S8.3: Keep warm for 1-4 hours; S8.4: Increase the temperature to 400℃~600℃; S8.5: Keep warm for 1-4 hours; S8.6: Heat to 600℃~900℃; S8.7: Keep warm for 1 to 4 hours.

3. The NdFeB sintering method for decarburization according to claim 2, characterized in that, In steps S8.3, S8.5, and S8.7, all Includes the following steps: A1: After the insulation process begins, inert gas is introduced; A2: After maintaining this position for a period of time, vacuum the system. A3: After being kept in a vacuum for a period of time; A4: Repeat steps A1-A3 at least once more.

4. The NdFeB sintering method for decarburization according to claim 3, characterized in that, The following steps are included after step S8.7: S8.8: Evacuate to a vacuum level of less than 10. -2 Pa, the sintering temperature is raised to 1050±50℃, and the holding time is 4 to 15 hours.

5. The NdFeB sintering method for decarburization according to claim 4, characterized in that, In step S9, after sintering is completed, high-purity inert gas is introduced to cool the temperature to below 100°C.

6. The NdFeB sintering method for decarburization according to claim 1, characterized in that, After step S9, step S9.1 is also included: aging treatment of the sintered magnet.

7. The NdFeB sintering method for decarburization according to claim 1, characterized in that, Step S4 includes step S4.1: adding powder modifier at a ratio of 0.05wt%-0.5wt% and stirring thoroughly.

8. The NdFeB sintering method for decarburization according to claim 1, characterized in that, Step S5 includes step S5.1: spraying a release agent during the orientation molding process.

9. The NdFeB sintering method for decarburization according to claim 1, characterized in that, It also includes the following steps: S11: The sintered magnet is processed into thin sheets and subjected to grain boundary diffusion; S12: Use a magnetic tester to test the magnetic properties before and after diffusion.

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