Neodymium iron gallium bialloy heavy rare earth-free 54H sintered neodymium iron boron magnet and its preparation method

Abstract

This invention discloses a neodymium-iron-gallium dual-alloy 54H sintered neodymium-iron-boron magnet and its preparation method, relating to the field of neodymium-iron-boron magnet preparation technology. The preparation includes the following raw materials: 170-175 kg of PrNd (praseodymium-neodymium alloy), 25-30 kg of BFe (ferrocopper), 1-5 kg ​​of Co (cobalt), 0.1-2 kg of Cu (copper), 1-5 kg ​​of Zr (zirconium), 0.1-1 kg of Ga (gallium), and 380-420 kg of Fe (iron). This neodymium-iron-gallium dual-alloy 54H sintered neodymium-iron-boron magnet and its preparation method utilize a dual-alloy process with neodymium-iron-gallium as an auxiliary alloy, without adding scarce heavy rare-earth elements such as dysprosium and terbium, to prepare 54H sintered neodymium-iron-boron magnets, achieving optimized performance and cost of neodymium-iron-boron magnets.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron magnet preparation technology, specifically to neodymium iron gallium dual alloy sintered neodymium iron boron magnet without heavy rare earth 54H and its preparation method. Background Technology

[0002] Neodymium iron boron (NdFeB) magnets are tetragonal crystals formed from neodymium, iron, and boron (Nd₂Fe₁₄B). Belonging to the third generation of rare-earth permanent magnet materials, they are characterized by their small size, light weight, and strong magnetism, making them the best performance-to-price ratio magnets currently available. The (BH)max value of NdFeB magnets is 5-12 times that of ferrite magnets and 3-10 times that of AlNiCo magnets; their coercivity is equivalent to 5-10 times that of ferrite magnets and 5-15 times that of AlNiCo magnets. Their potential magnetic properties are extremely high, capable of attracting objects weighing up to 640 times their own weight.

[0003] Since its discovery by Masato Sagawa of Sumitomo Special Metals Corporation in Japan in 1983, the application fields of neodymium iron boron (NdFeB) magnets have been continuously expanding. This material is now widely used in electronics, electrical machinery, medical devices, toys, packaging, hardware machinery, aerospace, and other fields. Common applications include permanent magnet motors, loudspeakers, magnetic separators, computer disk drives, and magnetic resonance imaging equipment. In particular, with the development of the knowledge economy, represented by information technology, new applications are constantly emerging for functional materials such as rare-earth permanent magnet NdFeB, bringing even broader market prospects to the NdFeB industry.

[0004] my country began mass production of sintered NdFeB magnets around 1985, but its overall production technology still lags far behind Europe, America, and Japan. The resulting products are of lower quality, and the coercivity is typically improved by adding relatively expensive rare earth elements such as dysprosium and terbium, which increases material costs and puts the country at a significant disadvantage in market competition. How to improve material performance without adding these rare earth elements through process innovation has become a crucial research direction for sintered NdFeB magnet development. Based on the current research status and direction, this invention further studies and improves sintered NdFeB magnets and their preparation methods. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a neodymium iron gallium dual alloy sintered neodymium iron boron magnet without heavy rare earth 54H and its preparation method, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a neodymium iron gallium dual alloy sintered neodymium iron boron magnet without heavy rare earth elements (54H), comprising the following raw materials:

[0007] PrNd (praseodymium-neodymium alloy), BFe (iron-copper alloy), Co (cobalt), Cu (copper), Zr (zirconium), Ga (gallium), Fe (iron);

[0008] Based on the mass ratio:

[0009] PrNd (praseodymium-neodymium alloy) 170-175kg, BFe (iron-copper alloy) 25-30kg, Co (cobalt) 1-5kg, Cu (copper) 0.1-2kg, Zr (zirconium) 1-5kg, Ga (gallium) 0.1-1kg, Fe (iron) 380-420kg.

[0010] Optional, the specific quality of the raw materials is as follows:

[0011] The total weight of PrNd is 172.2 kg, BFe is 28.42 kg, Co is 3.18 kg, Cu is 0.96 kg, Zr is 1.92 kg, Ga is 0.6 kg, and Fe is 392.7 kg, for a total of 600 kg.

[0012] Optionally, the raw materials are polished and derusted before batching, and the batching is weighed on an electronic scale to ensure accurate weight as much as possible.

[0013] The preparation method of NdFeB magnets with heavy rare earth 54H sintering, which are made of NdFeB dual alloy, includes the following specific steps:

[0014] S1. Alloy smelting, including main alloy smelting and auxiliary alloy smelting;

[0015] S101, Main alloy smelting, details are as follows:

[0016] (1) Place the weighed raw materials into a 600kg vacuum spinning furnace. The order of loading the furnace is as follows: the bottom layer is pure iron, which should be dense but not compact; the middle layer is ferroborone, cobalt, and zirconium; the upper layer is praseodymium and neodymium; and the top layer is gallium and copper.

[0017] (2) After the furnace is loaded, start smelting. After the vacuum belt furnace is evacuated to below 10 Pa, preheat the furnace charge. The power requirement is 120-150 kW. During the process, the vacuum is continuously evacuated, the furnace charge temperature gradually increases, and the vacuum degree gradually decreases. When it reaches below 4.0 Pa, turn off the power.

[0018] (3) Inject argon gas into the furnace to 27 kPa-29 kPa;

[0019] (4) The next step is to start melting the raw materials. The initial power is 180kW, which is increased to 250kW in 10 minutes, and then increased by 50kW every 5 minutes to 450kW. Start using a stopwatch to record the time it takes for the raw materials to melt completely.

[0020] (5) After all the raw materials have melted, start refining and increase the power to 530kw. After reaching 530kw, continue timing and observe the liquid level and refining time to determine whether the required temperature of 1450-1480℃ has been reached.

[0021] (6) Start temperature measurement. After reaching the specified temperature, reduce the power to 120kW and keep it warm for 5 minutes. Reduce the power to zero and cool down for 3 minutes. At this time, measure the low temperature, which is about 1400℃. Increase the power to 530kW. The temperature continues to rise while measuring the temperature. After reaching the pouring temperature of 1450℃, start pouring.

[0022] (7) The initial power of the casting is 120kW, which decreases proportionally with the increase of the crucible tilt angle. During the casting process, the casting observation window and the casting display screen are used to determine whether manual point control of the casting is required. The thickness of the casting sheet is 0.2mm~0.35mm, and the casting time is 12min±30s.

[0023] (8) Then start crushing for 5 minutes, fill with argon gas to 80 kPa, turn on the fan for cooling, and cool for 90 min to 120 min; observe the product temperature display, and remove the product from the furnace when the temperature of the spun sheet is below 45°C;

[0024] (9) The furnace charge is placed into a sealed bag and stored under argon gas;

[0025] S102, Auxiliary alloy material smelting, details are as follows:

[0026] (1) Preparation of auxiliary alloy smelting: PrNd weight 207.8kg, Ga weight 20kg, Fe weight 172.2kg; the surface of the raw materials is polished and rust removed before batching. The batching should be weighed on an electronic scale to ensure the weight is as accurate as possible.

[0027] (2) Place the weighed raw materials into a 600kg vacuum spinning furnace. The loading order is as follows: put pure iron at the bottom, which should be dense but not compact; put praseodymium and neodymium in the middle; and put gallium at the top.

[0028] (3) After the furnace is loaded, start smelting. After the vacuum belt furnace is evacuated to below 10 Pa, preheat the furnace charge. The power requirement is 70-90 kW. During the process, continue to evacuate the furnace charge. The furnace charge temperature gradually increases and the vacuum degree gradually decreases. Turn off the power when it is below 4.0 Pa.

[0029] (4) Inject argon gas into the furnace to 27 kPa-29 kPa;

[0030] (5) The next step is to start melting the raw materials. The initial power is 150kW, which is increased to 250kW in 10 minutes, and then increased by 50kW every 5 minutes to 400kW. Start using a stopwatch to record the time it takes for the raw materials to melt completely.

[0031] (6) After all the raw materials have melted, start refining and increase the power to 450kW. After reaching 450kW, continue timing and observe the liquid level and refining time to determine whether the required temperature of 1480-1510℃ has been reached.

[0032] (7) Start temperature measurement. After reaching the specified temperature, reduce the power to 75kW and keep it warm for 5 minutes. Reduce the power to zero and cool down for 3 minutes. At this time, measure the low temperature, which is about 1480℃. Increase the power to 450kW. The temperature continues to rise. At the same time, measure the temperature. After reaching the pouring temperature of 1490℃, start pouring.

[0033] (8) The initial power of the pouring is 80kW, which decreases proportionally with the increase of the crucible tilt angle; during the pouring process, the pouring observation window and pouring display screen are used to determine whether manual point control of the pouring is required; the pouring time is 7min±30s.

[0034] (9) Then start crushing for 5 minutes, introduce argon gas to 80 kPa, turn on the fan for cooling, and cool for 60 minutes; observe the product temperature display, and remove the product from the furnace when the temperature of the spun sheet is below 45°C.

[0035] S2, hydrogen fragmentation, as detailed below:

[0036] S201. Weigh the main alloy spool (600kg) and auxiliary alloy spool (36kg). After confirming that the weights are correct, place the feeding hopper and argon gas pipe to protect the feeding. When feeding, slowly and evenly put the main and auxiliary alloy spools into the furnace to prevent waste.

[0037] S202. After the material is added, the furnace body rotates for 5 minutes to ensure that the alloy is mixed evenly. Then, the vacuum is evacuated to below 1 Pa, and the equipment automatically maintains the pressure for about 15 seconds to prepare for entering the hydrogen absorption state. Then, hydrogen absorption begins. The hydrogen absorption requires the furnace to reach above 100 kPa, and the hydrogen absorption time is 120 minutes.

[0038] S203. After hydrogen absorption is completed, the hydrogen replenishment state begins. Observe the pressure gauge reading. If the fluctuation range is below 0.1 kPa, confirm that hydrogen absorption is saturated, and then enter the dehydrogenation stage.

[0039] S204, dehydrogenation speed 28 revolutions, dehydrogenation temperature 500℃, stop the engine and start the pump for 30 minutes, start the pump and turn off the electric furnace for 75 minutes, delay for 30 minutes after turning off the furnace, observe the vacuum count value range of 5pa-50pa, then the furnace door can be opened, dehydrogenation is completed, prepare to enter the cooling state, cooling time 120 minutes, furnace outlet temperature below 30℃.

[0040] S205. After the coarse powder is removed from the furnace, it is placed into a coarse powder container and stored under argon gas.

[0041] S3, air jet mill, details are as follows:

[0042] S301. Pour the coarse powder after hydrogen crushing and weighing into the coarse powder tank of the air jet mill after oxygen removal; according to the powder weight, add 0.1% antioxidant and 70g of 120# gasoline, hoist it into the three-dimensional mixer, and mix the coarse powder for 45min±10min; hoist the mixed coarse powder into the air jet mill feeding platform, ready for feeding; the grinding weight in the grinding chamber is 35kg±2kg, the grinding pressure is 0.55Mpa±0.02Mpa, the bottom spray pressure is 0.45Mpa±0.02mpa, the sorting wheel speed is 4000±100 rpm, the oxygen content is 0±5ppm, and the grinding time is 4~5h;

[0043] S302. After the powder is discharged, add 0.1% antioxidant and 0.1% lubricant, then hoist it into the three-dimensional mixer and mix for 90 min ± 10 min.

[0044] S303. Hoist the mixed fine powder tank into the feeding platform of the sieving machine, connect the cleaned and oxygen-removed fine powder tank to the discharge port of the sieving machine, and start sieving for 3 hours, with the oxygen content controlled below 400ppm.

[0045] S304. After sieving, nitrogen gas is introduced and the powder is stored in a powder storage chamber.

[0046] S4. Molding, as detailed below:

[0047] S401. Take fine powder from the fine powder warehouse and use vertical molding followed by isostatic pressing molding process; control the oxygen content of the pressed powder to below 400ppm, the molding magnetic field is 1.8T, mechanical control of dimensions, pressing pressure is about 8Mpa, the product size is 47*45*31, no release agent is added to ensure dimensional accuracy, after pressing, the product is wrapped and inner sealed in the glove box.

[0048] S402. After the material is discharged, during the outer packaging stage, first put it in a protective bag, then put it in an outer packaging bag for outer packaging.

[0049] S403, Finally, isostatic pressure, isostatic pressure 230 MPa;

[0050] S5. Sintering and heat treatment: The green body is sintered in a vacuum sintering furnace (heating start condition: vacuum degree below 0.5 Pa). In order to remove harmful gases, additives and impurities from the green body, the sintering process is set as follows: 250℃ for 2 hours, 600℃ for 2.5 hours (vacuum degree controlled below 10 Pa), 850℃ for 3.5 hours (vacuum degree controlled below 1 Pa), 1000℃ for 30 minutes, the highest temperature of 1090℃-1100℃ for 6 hours, slow cooling to 1000℃, continuing to heat up to 1060℃ for 4 hours, slow cooling to 1000℃, heating up again to 1055℃ for 4 hours, and finally slow cooling to 600℃ and air cooling to below 70℃ before being taken out of the furnace.

[0051] The tempering process employs a two-stage tempering treatment. The first stage involves heating to 900℃-930℃ (heating start conditions: vacuum degree below 0.5pa), holding at that temperature for 2-4 hours, slowly cooling to 100℃-700℃, and then air-cooling to below 70℃ before removing from the furnace. The second stage involves heating to 450℃-650℃ and holding at that temperature for 5 hours (heating start conditions: vacuum degree below 0.5pa; argon gas is purged three minutes before heating is completed), and then air-cooling to below 70℃.

[0052] Optionally, the criteria for judging the temperature required by the process during the raw material melting process in step S101 are: the liquid surface gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 5 minutes.

[0053] Optionally, the criteria for judging the temperature required by the process during the raw material melting process in step S102 are: the liquid surface gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 3 minutes.

[0054] Optionally, in step S301, fine powder is taken from the sampling port of the air jet mill at the start of grinding, after 2 hours of grinding, and after grinding is completed to measure the particle size. Particle size between 2.6um and 3.2um is considered qualified.

[0055] Optionally, the nitrogen pressure in step S304 is 0.1 MPa to 0.15 MPa.

[0056] This invention provides a neodymium iron gallium dual alloy sintered neodymium iron boron magnet without heavy rare earth 54H and its preparation method, which has the following beneficial effects:

[0057] This invention relates to a method for preparing a NdFeB magnet using a dual alloy without heavy rare earth elements (54H), comprising a main alloy and an auxiliary alloy (SC) sheet. The main and auxiliary alloys are mixed in a certain proportion and coarsely crushed using a hydrogen crushing process. The resulting powder is then milled into fine powder, which is oriented and pressed into a mold. Finally, it undergoes continuous vacuum sintering and vacuum heat treatment. Compared with conventional dual alloy processes, this method improves the remanence and coercivity of the blank. It also enables the preparation of 54H grade NdFeB magnets without heavy rare earth elements, achieving both performance and cost reduction while ensuring a reasonable balance in the comprehensive utilization of rare earth metals. Detailed Implementation

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0059] Neodymium iron gallium dual alloy 54H sintered neodymium iron boron magnets without heavy rare earth elements are prepared using the following raw materials:

[0060] The total weight of PrNd is 172.2 kg, BFe is 28.42 kg, Co is 3.18 kg, Cu is 0.96 kg, Zr is 1.92 kg, Ga is 0.6 kg, and Fe is 392.7 kg, for a total of 600 kg.

[0061] Before mixing, the raw materials are polished and rust-removed. The ingredients are weighed on an electronic scale to ensure accurate weight as much as possible.

[0062] The preparation method of NdFeB magnets with heavy rare earth 54H sintering, which are made of NdFeB dual alloy, includes the following specific steps:

[0063] S1. Alloy smelting, including main alloy smelting and auxiliary alloy smelting;

[0064] S101, Main alloy smelting, details are as follows:

[0065] (1) Place the weighed raw materials into a 600kg vacuum spinning furnace. The order of loading the furnace is as follows: the bottom layer is pure iron, which should be dense but not compact; the middle layer is ferroborone, cobalt, and zirconium; the upper layer is praseodymium and neodymium; and the top layer is gallium and copper.

[0066] (2) After the furnace is loaded, start smelting. After the vacuum belt furnace is evacuated to below 10 Pa, preheat the furnace charge. The power requirement is 120-150 kW. During the process, the vacuum is continuously evacuated, the furnace charge temperature gradually increases, and the vacuum degree gradually decreases. When it reaches below 4.0 Pa, turn off the power.

[0067] (3) Inject argon gas into the furnace to 27 kPa-29 kPa;

[0068] (4) The next step is to start melting the raw materials. The initial power is 180kW, which is increased to 250kW in 10 minutes, and then increased by 50kW every 5 minutes to 450kW. Start using a stopwatch to record the time it takes for the raw materials to melt completely.

[0069] (5) After all the raw materials have melted, start refining and increase the power to 530kw. After reaching 530kw, continue timing and observe the liquid level and refining time to determine whether the required process temperature of 1450-1480℃ has been reached. (The criteria for determining the required process temperature are: the liquid level gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 5min).

[0070] (6) Start temperature measurement. After reaching the specified temperature, reduce the power to 120kW and keep it warm for 5 minutes. Reduce the power to zero and cool down for 3 minutes. At this time, measure the low temperature, which is about 1400℃. Increase the power to 530kW. The temperature continues to rise while measuring the temperature. After reaching the pouring temperature of 1450℃, start pouring.

[0071] (7) The initial power of the casting is 120kW, which decreases proportionally with the increase of the crucible tilt angle. During the casting process, the casting observation window and the casting display screen are used to determine whether manual point control of the casting is required. The thickness of the casting sheet is 0.2mm~0.35mm, and the casting time is 12min±30s.

[0072] (8) Then start crushing for 5 minutes, fill with argon gas to 80 kPa, turn on the fan for cooling, and cool for 90 min to 120 min; observe the product temperature display, and remove the product from the furnace when the temperature of the spun sheet is below 45°C;

[0073] (9) The furnace charge is placed into a sealed bag and stored under argon gas;

[0074] S102, Auxiliary alloy material smelting, details are as follows:

[0075] (1) Preparation of auxiliary alloy smelting: PrNd weight 207.8kg, Ga weight 20kg, Fe weight 172.2kg; the surface of the raw materials is polished and rust removed before batching. The batching should be weighed on an electronic scale to ensure the weight is as accurate as possible.

[0076] (2) Place the weighed raw materials into a 600kg vacuum spinning furnace. The loading order is as follows: put pure iron at the bottom, which should be dense but not compact; put praseodymium and neodymium in the middle; and put gallium at the top.

[0077] (3) After the furnace is loaded, start smelting. After the vacuum belt furnace is evacuated to below 10 Pa, preheat the furnace charge. The power requirement is 70-90 kW. During the process, continue to evacuate the furnace charge. The furnace charge temperature gradually increases and the vacuum degree gradually decreases. Turn off the power when it is below 4.0 Pa.

[0078] (4) Inject argon gas into the furnace to 27 kPa-29 kPa;

[0079] (5) The next step is to start melting the raw materials. The initial power is 150kW, which is increased to 250kW in 10 minutes, and then increased by 50kW every 5 minutes to 400kW. Start using a stopwatch to record the time it takes for the raw materials to melt completely.

[0080] (6) After all the raw materials have melted, start refining and increase the power to 450kW. After reaching 450kW, continue timing and observe the liquid level and refining time to determine whether the required process temperature of 1480-1510℃ has been reached. (The criteria for determining the required process temperature are: the liquid level gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 3min).

[0081] (7) Start temperature measurement. After reaching the specified temperature, reduce the power to 75kW and keep it warm for 5 minutes. Reduce the power to zero and cool down for 3 minutes. At this time, measure the low temperature, which is about 1480℃. Increase the power to 450kW. The temperature continues to rise. At the same time, measure the temperature. After reaching the pouring temperature of 1490℃, start pouring.

[0082] (8) The initial power of the pouring is 80kW, which decreases proportionally with the increase of the crucible tilt angle; during the pouring process, the pouring observation window and pouring display screen are used to determine whether manual point control of the pouring is required; the pouring time is 7min±30s.

[0083] (9) Then start crushing for 5 minutes, introduce argon gas to 80 kPa, turn on the fan for cooling, and cool for 60 minutes; observe the product temperature display, and remove the product from the furnace when the temperature of the spun sheet is below 45°C.

[0084] S2, hydrogen fragmentation, as detailed below:

[0085] S201. Weigh the main alloy spool (600kg) and auxiliary alloy spool (36kg). After confirming that the weights are correct, place the feeding hopper and argon gas pipe to protect the feeding. When feeding, slowly and evenly put the main and auxiliary alloy spools into the furnace to prevent waste.

[0086] S202. After the material is added, the furnace body rotates for 5 minutes to ensure that the alloy is mixed evenly. Then, the vacuum is evacuated to below 1 Pa, and the equipment automatically maintains the pressure for about 15 seconds to prepare for entering the hydrogen absorption state. Then, hydrogen absorption begins. The hydrogen absorption requires the furnace to reach above 100 kPa, and the hydrogen absorption time is 120 minutes.

[0087] S203. After hydrogen absorption is completed, the hydrogen replenishment state begins. Observe the pressure gauge reading. If the fluctuation range is below 0.1 kPa, confirm that hydrogen absorption is saturated, and then enter the dehydrogenation stage.

[0088] S204, dehydrogenation speed 28 revolutions, dehydrogenation temperature 500℃, stop the engine and start the pump for 30 minutes, start the pump and turn off the electric furnace for 75 minutes, delay for 30 minutes after turning off the furnace, observe the vacuum count value range of 5pa-50pa, then the furnace door can be opened, dehydrogenation is completed, prepare to enter the cooling state, cooling time 120 minutes, furnace outlet temperature below 30℃.

[0089] S205. After the coarse powder is removed from the furnace, it is placed into a coarse powder container and stored under argon gas.

[0090] S3, air jet mill, details are as follows:

[0091] S301. Pour the coarse powder after hydrogen crushing and weighing into the coarse powder tank of the air jet mill after oxygen removal; according to the powder weight, add 0.1% antioxidant and 70g of 120# gasoline, hoist it into the three-dimensional mixer, and mix the coarse powder for 45min±10min; hoist the mixed coarse powder into the air jet mill feeding platform, ready for feeding; the grinding weight in the grinding chamber is 35kg±2kg, the grinding pressure is 0.55Mpa±0.02Mpa, the bottom spray pressure is 0.45Mpa±0.02mpa, the sorting wheel speed is 4000±100 rpm, the oxygen content is 0±5ppm, and the grinding time is 4~5h; (at the beginning of grinding, after 2 hours of grinding, and at the end of grinding, take fine powder samples from the sampling port of the air jet mill to measure the particle size. The particle size is 2.6um-3.2um, which is considered qualified).

[0092] S302. After the powder is discharged, add 0.1% antioxidant and 0.1% lubricant, then hoist it into the three-dimensional mixer and mix for 90 min ± 10 min.

[0093] S303. Hoist the mixed fine powder tank into the feeding platform of the sieving machine, connect the cleaned and oxygen-removed fine powder tank to the discharge port of the sieving machine, and start sieving for 3 hours, with the oxygen content controlled below 400ppm.

[0094] S304. After sieving, fill the powder with nitrogen and store it in the powder silo (nitrogen pressure 0.1Mpa-0.15Mpa).

[0095] S4. Molding, as detailed below:

[0096] S401. Take fine powder from the fine powder warehouse and use vertical molding followed by isostatic pressing molding process; control the oxygen content of the pressed powder to below 400ppm, the molding magnetic field is 1.8T, mechanical control of dimensions, pressing pressure is about 8Mpa, the product size is 47*45*31, no release agent is added to ensure dimensional accuracy, after pressing, the product is wrapped and inner sealed in the glove box.

[0097] S402. After the material is discharged, during the outer packaging stage, first put it in a protective bag, then put it in an outer packaging bag for outer packaging.

[0098] S403, Finally, isostatic pressure, isostatic pressure 230 MPa;

[0099] S5. Sintering and heat treatment: The green body is sintered in a vacuum sintering furnace (heating start condition: vacuum degree below 0.5 Pa). In order to remove harmful gases, additives and impurities from the green body, the sintering process is set as follows: 250℃ for 2 hours, 600℃ for 2.5 hours (vacuum degree controlled below 10 Pa), 850℃ for 3.5 hours (vacuum degree controlled below 1 Pa), 1000℃ for 30 minutes, the highest temperature of 1090℃-1100℃ for 6 hours, slow cooling to 1000℃, continuing to heat up to 1060℃ for 4 hours, slow cooling to 1000℃, heating up again to 1055℃ for 4 hours, and finally slow cooling to 600℃ and air cooling to below 70℃ before being taken out of the furnace.

[0100] The tempering process employs a two-stage tempering treatment. The first stage involves heating to 900℃-930℃ (heating conditions: vacuum degree below 0.5pa), holding at this temperature for 2-4 hours, slowly cooling to 100℃-700℃, and finally air-cooling to below 70℃ before removing from the furnace. The second stage involves heating to 450℃-650℃ and holding at this temperature for 5 hours (heating conditions: vacuum degree below 0.5pa; argon gas is purged three minutes before heating is complete), followed by air-cooling to below 70℃.

[0101] The sintered NdFeB rare earth permanent magnet material prepared in this embodiment was finally measured to have a remanence of 14.42 kGs-14.46 kGs and an intrinsic coercivity of 17.36 kOe-17.69 kOe.

[0102] The comparative case used conventional dual-alloy sintered NdFeB, with terbium hydride coarse powder as the auxiliary alloy, grade 52MT.

[0103] Preparation of main alloy materials: PrNd weight 174kg, BFe weight 27.3kg, Tb weight 1.8kg, Co weight 5.4kg, Cu weight 0.72kg, Zr weight 0.72kg, Ga weight 1.8kg, Fe weight 388.26kg, totaling 600kg; Before batching, the surface of the raw materials is polished and rust-removed. The materials must be weighed on an electronic scale to ensure the weight is as accurate as possible.

[0104] (1) Main alloy smelting: The weighed raw materials are placed into a 600kg vacuum spinning furnace. The loading order is as follows: pure iron is placed at the bottom, which should be dense but not compacted; ferroborone, cobalt, and zirconium are placed in the middle; praseodymium and neodymium are placed on the upper layer; and gallium and copper are placed on the top layer. After loading, smelting begins. The vacuum spinning furnace is evacuated to below 10pa, and the furnace charge is preheated. The power requirement is 120-150kW. During the process, the vacuum is continuously evacuated, the furnace charge temperature gradually increases, and the vacuum degree gradually decreases. The power is turned off when the pressure drops below 4.0pa. Argon gas is introduced into the furnace to 27-29 kPa; the next step is to begin material melting, with an initial power of 180 kW, increasing to 250 kW after 10 minutes, and then increasing by 50 kW every 5 minutes until reaching 450 kW; a stopwatch is used to record the time it takes for the raw materials to completely melt; after the raw materials are completely melted, refining begins, increasing the power to 530 kW, and timing continues after reaching 530 kW, observing the liquid level and refining time to determine if the required process temperature of 1450-1480℃ has been reached; (reaching...) The process requires temperature judgment criteria: the liquid surface gradually changes from red to silvery-white, and the white scum on the surface gradually decreases (refining time reaches 5 minutes). At this point, temperature measurement begins. After reaching the specified temperature, the power is reduced to 120kW and held for 5 minutes; the power is then reduced to zero and the temperature is lowered for 3 minutes. At this point, the low temperature is measured, approximately 1400℃; the power is increased to 530kW, and the temperature continues to rise while temperature measurement continues. Once the casting temperature of 1450℃ is reached, casting begins. The initial casting power is 120kW, which decreases proportionally with the increase of the crucible tilt angle. During casting, the casting observation window and casting display screen are used to determine whether manual point-controlled casting is required. The casting thickness is 0.2mm~0.35mm, and the casting time is 12min±30s. Afterward, crushing begins for 5 minutes, argon gas is introduced to 80kPa, and the fan is turned on for cooling, with a cooling time of 90min~120min. The product temperature display is observed, and the casting temperature drops below 45℃ before the product is removed from the furnace. The removed material is placed in a sealing bag and stored under argon gas.

[0105] (2)Hydrogen Crushing: Weigh 600 kg of the master alloy flakes. After confirmation, place the feeding hopper and argon pipe to protect the feeding. When feeding, slowly and evenly put the master alloy flakes into the furnace body to prevent waste; after feeding, rotate the furnace body for 5 minutes to mix the alloy evenly, then evacuate the air to below 1 Pa, and the equipment automatically maintains the pressure for about 15 s to prepare to enter the hydrogen absorption state; then start hydrogen absorption. It is required that the pressure in the furnace reaches above 100 kPa at the beginning of hydrogen absorption, and the hydrogen absorption time is 120 minutes; after the hydrogen absorption ends, enter the continuous hydrogen state, observe that the fluctuation range of the pressure gauge value is below 0.1 kPa, confirm that the hydrogen absorption is saturated, and enter the dehydrogenation stage; the dehydrogenation rotation speed is 28 turns, the dehydrogenation temperature is 550 °C, rotate stop to pump on for 30 minutes, pump on to electric furnace off for 75 minutes, delay for 30 minutes after closing the furnace, observe that the vacuum gauge value range is 5 Pa - 50 Pa, then the furnace door can be opened, the dehydrogenation ends, and prepare to enter the cooling state. The cooling time is 120 minutes, and the furnace outlet temperature is below 30 °C; after the coarse powder is taken out of the furnace and loaded into the coarse powder tank, add 3.6 kg of auxiliary alloy coarse powder and store it by filling with argon;

[0106] (3)Jet Mill: Pour the coarse powder after hydrogen crushing and weighing into the coarse powder tank of the jet mill after exhausting oxygen; according to the powder weight, add 0.1% antioxidant and 70 g of 120# gasoline, lift it into the three-dimensional mixer, and mix the coarse powder for 45 min ± 10 min; lift the mixed coarse powder to the feeding platform of the jet mill and prepare for feeding; the grinding chamber grinding weight is 35 kg ± 2 kg, the grinding pressure is 0.55 Mpa ± 0.02 Mpa, the bottom spray pressure is 0.45 Mpa ± 0.02 mpa, the sorting wheel rotation speed is 4000 ± 100 turns, the oxygen content is 30 ± 5 ppm, and the powder grinding time is 4 - 5 h; (When starting grinding, at 2 h of grinding, and when grinding is completed, take fine powder from the sampling port of the jet mill to measure the particle size. The particle size between 2.6 um - 3.2 um is a qualified product) After the powder discharging is completed, add 0.1% antioxidant and 0.1% lubricant, lift it into the three-dimensional mixer, and mix the powder for 90 min ± 10 min; lift the mixed fine powder tank to the feeding platform of the sieving machine, connect the cleaned and oxygen-exhausted small fine powder tank to the discharge port of the sieving machine, and start sieving for 3 h, and control the oxygen content below 400 ppm; after sieving is completed, fill it with nitrogen and store it in the powder warehouse (nitrogen pressure 0.1 Mpa - 0.15 Mpa);

[0107] (4)Pressing: Receive the fine powder from the fine powder warehouse, adopt the forming process of vertical die pressing and isostatic pressing; control the oxygen content during pressing below 400 ppm, the forming magnetic field is 1.8 T, mechanically control the size, the pressing pressure is about 8 Mpa, the product size is 47*45*31, and no mold release agent is added to ensure accurate size. After pressing, carry out film coating and inner encapsulation in the glove box; after discharging, in the outer encapsulation stage, first put on a protective bag, then load it into the outer encapsulation bag for outer encapsulation; finally, isostatic pressing, the isostatic pressure is 230 Mpa;

[0108] (5)Sintering and Heat Treatment

[0109] The green body is sintered in a vacuum sintering furnace (heating conditions: vacuum degree below 0.5 Pa). To remove harmful gases, additives and impurities from the green body, the sintering process is set as follows: hold at 250℃ for 2 hours, hold at 600℃ for 2.5 hours (vacuum degree controlled below 10 Pa), hold at 850℃ for 3.5 hours (vacuum degree controlled below 1 Pa), hold at 1000℃ for 30 minutes, hold at the highest temperature of 1050℃-1060℃ for 6 hours, slowly cool to 600℃, and air cool to below 70℃ before being removed from the furnace.

[0110] The tempering process employs a two-stage tempering treatment. The first stage involves heating to 900℃-930℃ (heating conditions: vacuum degree below 0.5 Pa), holding at this temperature for 2-4 hours, then slowly cooling to 100℃-700℃, and finally air-cooling to below 70℃ before removing from the furnace. The second stage involves heating to 450℃-650℃ and holding at this temperature for 5 hours (heating conditions: vacuum degree below 0.5 Pa; argon gas is purged three minutes before heating is complete), and then air-cooling to below 70℃.

[0111] This type of dual-alloy sintered NdFeB rare earth permanent magnet material has a Tb content of 0.9%, a remanence of 14.35 kGs, and an intrinsic coercivity of 16.43 kJ / s to 16.59 kJ / s.

[0112] Analysis of the experimental results and evaluation and comparison of magnet performance showed that the remanence and coercivity of the blank prepared by the NdFeB dual alloy process were improved compared with those prepared by the conventional dual alloy process. At the same time, it achieved the preparation of 54H grade NdFeB magnets without heavy rare earth elements, and the overall material cost was lower, which has a very obvious advantage.

[0113] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of producing a neodymium-iron-gallium double alloy heavy rare earth-free 54H sintered neodymium-iron-boron magnet, characterized by, The steps are as follows: S1. Alloy smelting, including main alloy smelting and auxiliary alloy smelting; S101, Main alloy smelting, specifically: (1) Prepare the following raw materials by weight: praseodymium-neodymium alloy PrNd 170-175kg, ferroborone BFe 25-30kg, cobalt Co 1-5kg, copper Cu 0.1-2kg, zirconium Zr 1-5kg, gallium Ga 0.1-1kg, and iron Fe 380-420kg. Place the weighed raw materials into a vacuum spinning furnace in the following order: The bottom layer contains iron (Fe), the middle layer contains boron iron (BFe), cobalt (Co), and zirconium (Zr), the top layer contains praseodymium-neodymium alloy (PrNd), and the top layer contains gallium (Ga) and copper (Cu). (2) Smelting: After the vacuum belt spinning furnace is evacuated to below 10 Pa, the furnace charge is preheated. During the process, the vacuum is continuously evacuated and the vacuum level is gradually reduced to below 4.0 Pa before being shut off. (3) Fill the furnace with argon gas to 27 kPa-29 kPa; (4) Chemical processing, initial power 180kW, increased to 250kW in 10min, and then increased by 50kW every 5min to 450kW; (5) After all the raw materials are melted, the refining power is increased to 530kw. After reaching 530kw, the timing continues until the process requires a temperature of 1450-1480℃. (6) After reaching the specified temperature, reduce the power to 120kW and keep it warm for 5 minutes; then reduce the power to zero and cool down for 3 minutes, then increase the power to 530kW. The temperature continues to rise while the temperature is measured. After reaching the pouring temperature of 1450℃, pouring begins. (7) The initial power of casting is 120kW, which decreases proportionally with the increase of the crucible tilt angle; the thickness of the casting sheet is 0.2mm~0.35mm, and the casting time is 12min±30s; (8) Then start crushing for 5 minutes, fill with argon gas to 75-85 kPa, turn on the fan for cooling, and cool for 90-120 minutes; observe the product temperature display, and remove the sheet from the furnace when the temperature drops below 45°C; (9) The furnace charge is placed into a sealed bag and stored under argon gas; S102, Auxiliary alloy material smelting, specifically: (1) Preparation of auxiliary alloy smelting: praseodymium-neodymium alloy PrNd 207.8kg, gallium Ga 20kg, iron Fe 172.2kg; the surface of the raw materials is polished and derusted before batching; (2) Place the weighed raw materials into the vacuum spinning furnace. The loading order is as follows: put Fe at the bottom, PrNd in the middle, and Ga at the top. (3) After the furnace is loaded, start smelting. After the vacuum belt furnace is evacuated to below 10 Pa, preheat the furnace charge. The power requirement is 70-90 kW. During the process, continue to evacuate the furnace charge. The furnace charge temperature gradually increases and the vacuum degree gradually decreases to below 4.0 Pa before turning off the power. (4) Fill the furnace with argon gas to 27 kPa-29 kPa; (5) Chemical processing, initial power 150kW, increased to 240-280kW in 10min, and then increased by 50kW every 5min to 400kW; (6) After all the raw materials have been melted, the refining process begins and the power is increased to 450kW. After reaching 450kW, the timing continues until the required process temperature of 1480-1510℃ is reached. (7) After reaching the specified temperature, reduce the power to 75kW and keep it warm for 5 minutes; after the power is reduced to zero and the temperature is lowered for 3 minutes, increase the power to 450kW and the temperature continues to rise. At the same time, measure the temperature. After reaching the pouring temperature of 1490℃, start pouring. (8) The initial power for casting is 80kW, which decreases proportionally with the increase of the crucible tilt angle; the casting time is 7min±30s; (9) Then start crushing for 5 minutes, introduce argon gas to 80 kPa, turn on the fan for cooling, and cool for 60 minutes; observe the product temperature display, and remove the product from the furnace when the temperature of the spun sheet is below 45°C. S2, hydrogen breakup, specifically: S201. Weigh the main alloy spool (600kg) and auxiliary alloy spool (36kg). After confirming that the weights are correct, place them in the feeding hopper and argon gas pipe to protect the feeding process. When feeding, slowly and evenly place the main and auxiliary alloy spools into the furnace body. S202. After the material is added, the furnace body rotates for 5 minutes to ensure that the alloy is mixed evenly. Then, the vacuum is drawn to below 1 Pa. The equipment automatically maintains the pressure for 15 seconds and enters the hydrogen absorption state. The hydrogen absorption requires the furnace to reach above 100 kPa and the hydrogen absorption time is 120 minutes. S203. Enter the hydrogen replenishment state and observe that the pressure gauge reading fluctuates within a range of less than 0.1 kPa to confirm hydrogen absorption saturation. S204. Enter the dehydrogenation stage. The dehydrogenation speed is 25-30 revolutions per minute, and the dehydrogenation temperature is 480-520℃. The time from stopping the engine to starting the pump is 25-35 minutes. The time from starting the pump to turning off the electric furnace is 65-80 minutes. After turning off the furnace, delay for 30 minutes. Observe the vacuum count value in the range of 5pa-50pa. Then open the furnace door. Dehydrogenation is completed and prepare to enter the cooling state. The cooling time is 90-120 minutes. The furnace outlet temperature is below 28-32℃. S205. After the coarse powder is removed from the furnace, it is placed into a coarse powder container and stored under argon gas. S3, airflow mill, specifically: S301. Pour the coarse powder after hydrogen crushing and weighing into the coarse powder tank of the air jet mill after oxygen removal; according to the powder weight, add 0.1% antioxidant and 70g of 120# gasoline, hoist it into the three-dimensional mixer, and mix the coarse powder for 45min±10min; hoist the mixed coarse powder into the air jet mill feeding platform, ready for feeding; the grinding weight in the grinding chamber is 35kg±2kg, the grinding pressure is 0.55Mpa±0.02Mpa, the bottom spray pressure is 0.45Mpa±0.02mpa, the sorting wheel speed is 4000±100 rpm, the oxygen content is 0±5ppm, and the grinding time is 4~5h; S302. After the powder is discharged, add 0.1% antioxidant and 0.1% lubricant, then hoist it into the three-dimensional mixer and mix for 90 min ± 10 min. S303. Hoist the mixed fine powder container into the feeding platform of the sieving machine, connect the cleaned and oxygen-removed fine powder container to the discharge port of the sieving machine, and start sieving for 2.5-3 hours, with the oxygen content controlled below 400ppm. S304. After sieving, nitrogen gas is introduced and the powder is stored in a powder storage chamber. S4, molding, specifically: S401. Take fine powder from the fine powder warehouse and use vertical molding followed by isostatic pressing molding process; control the oxygen content of the pressed powder to below 400ppm, the molding magnetic field is 1.8T, the pressing pressure is 6-10Mpa, the product size is 47*45*31, no release agent is added to ensure dimensional accuracy, and after pressing, the product is wrapped and inner sealed in the glove box. S402. After the material is discharged, during the outer packaging stage, first put it in a protective bag, then put it in an outer packaging bag for outer packaging. S403, Finally, isostatic pressure, isostatic pressure 230 MPa; S5. Sintering and heat treatment: The green billets are sintered in a vacuum sintering furnace to remove harmful gases, additives and impurities from the green billets. The sintering process is set as follows: hold at 240-260℃ for 2 hours, hold at 580-620℃ for 2.5 hours, hold at 800-900℃ for 3.5 hours, hold at 900-1050℃ for 30 minutes, hold at 1090℃-1100℃ for 6 hours, slowly cool to 950-1050℃, continue to heat up to 1040-1080℃ and hold for 4 hours, slowly cool to 950-1020℃, heat up again to 1055℃ and hold for 4 hours, and finally slowly cool to 600℃ and then air cool to below 70℃ before being taken out of the furnace. The tempering process employs a two-stage tempering process. The first stage involves heating the temperature to 900℃-930℃ and holding it for 2-4 hours, then slowly cooling it to 100℃-700℃ and finally air-cooling it to below 60-80℃ before removing it from the furnace. The second stage involves heating the temperature to 450℃-650℃ and holding it for 5 hours, then air-cooling it to below 65-75℃.

2. The method for preparing the NdFeB magnet with no heavy rare earth 54H sintered from a NdFeB dual alloy according to claim 1, characterized in that, The specific quality of the raw materials is as follows: Praseodymium-neodymium alloy PrNd 172.2kg, Boron-iron BFe 28.42kg, Cobalt Co 3.18kg, Copper Cu 0.96kg, Zirconium Zr 1.92kg, Gallium Ga 0.6kg, Iron Fe 392.7kg, totaling 600kg.

3. The method for preparing the NdFeB magnet with no heavy rare earth 54H sintered structure according to claim 1, characterized in that, Before mixing, the surface of the raw materials must be polished and rust-removed.

4. The method for preparing the NdFeB magnet with heavy rare earth-free 54H sintered structure of NdFeB dual alloy according to claim 1, characterized in that, The criteria for judging the temperature required by the process during the raw material melting process in step S101 are: the liquid surface gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 5 minutes.

5. The method for preparing a NdFeB magnet with no heavy rare earth 54H sintered from a NdFeB dual alloy according to claim 1, characterized in that, The criteria for judging the temperature required by the process during the raw material melting process in step S102 are: the liquid surface gradually changes from red to silvery-white, the white scum on the surface gradually decreases, and the refining time reaches 3 minutes.

6. The method for preparing a NdFeB magnet with no heavy rare earth 54H sintered from a NdFeB dual alloy according to claim 1, characterized in that, In step S301, fine powder is taken from the sampling port of the air jet mill at the start of grinding, after 2 hours of grinding, and after grinding is completed to measure the particle size. Particle size between 2.6μm and 3.2μm is considered qualified.

7. The method for preparing a NdFeB magnet with no heavy rare earth 54H sintered from a NdFeB dual alloy according to claim 1, characterized in that, In step S304, the nitrogen pressure is 0.1 MPa - 0.15 MPa.