An on-line crystallization integrated preparation method of high-cobalt rapidly quenched neodymium-iron-boron magnetic powder

Abstract

This application relates to the field of magnetic material preparation technology, and in particular to an integrated online crystallization preparation method for high-cobalt rapidly quenched NdFeB magnetic powder. The method includes: melting Pr-Nd, B, Co, Ga, and other raw materials into rods in an induction furnace according to a specified ratio, with a Co mass percentage of 3.0%–4.5%; forming the alloy rods into a rapidly quenched strip in a rapid quenching furnace and directly introducing it into the same cavity for online induction heating crystallization, where the crystallization temperature and Co content satisfy a quantitative linear relationship, followed by rapid cooling with high-purity argon gas; real-time monitoring of magnetic properties and feedback of data to a PLC system to automatically adjust the process parameters for the next batch; and finally, crushing and pulverizing under a protective atmosphere. This application, through an integrated online process and closed-loop control, solves the problems of high energy consumption, coarse grains, and poor uniformity caused by offline crystallization, achieving precise control of grain size and significantly improving the coercivity and temperature stability of the magnetic powder.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet material preparation technology, specifically to an online crystallization integrated preparation method for high cobalt fast-quenched NdFeB magnetic powder. Background Technology

[0002] Rare earth permanent magnet materials are key functional materials for strategic emerging industries such as new energy vehicles, wind power generation, and energy-saving home appliances, and their performance optimization and preparation process improvement have always been research hotspots. Rapidly quenched and bonded rare earth permanent magnet materials, due to their near-net-shape forming, low eddy current loss, and good corrosion resistance, have broad application prospects in fields such as electric vehicle drive motors, servo motors, and robot joint motors. In recent years, the application fields of rapidly quenched NdFeB magnetic powder have been continuously expanding, and the demand for magnetic properties in high-end manufacturing is constantly increasing. Therefore, developing magnetic powder preparation processes with high magnetic properties and good temperature stability is of great significance.

[0003] In existing technologies, high-cobalt formulations are considered an important means to improve the Curie temperature and thermal stability of rare-earth permanent magnet materials. Patent CN116344139B discloses a high-cobalt rare-earth permanent magnet material and its preparation method. It achieves improved coercivity through optimized composition design. However, this technical solution still adopts the traditional offline crystallization annealing process, and the energy consumption of secondary heat treatment is as high as 0.85 kWh / kg. Moreover, the Nd3Co phase formed by Co enrichment at the grain boundary is prone to growth during secondary heating, resulting in uneven magnetic properties and batch consistency that is difficult to meet the requirements of high-end applications.

[0004] Patent CN118098741A discloses a method for preparing rare-earth permanent magnet materials, which utilizes precursor powder mixing and sintering to obtain high squareness magnets. However, the traditional sintering process used in this method has insufficient control over the grain size of the high-cobalt system, and the process window is narrow, resulting in poor batch consistency. The key to the preparation process lies in the control of microstructure; therefore, developing a low-energy-consumption preparation method capable of precisely controlling grain size is urgently needed.

[0005] The performance of rare-earth permanent magnet materials hinges on the synergy between composition and processing. While partial substitution of Fe with Co can raise the Curie temperature of the main phase, it also shifts the crystallization temperature window upwards. Single offline processing methods in high-cobalt systems suffer from insufficient crystallization and easy carbon deposition and oxidation. Heteroatom doping and online processing are common modification techniques, allowing for real-time control of process parameters to modulate the phase properties, grain size, and performance of magnetic powders. However, under high-temperature crystallization conditions, the grain size of high-cobalt systems is prone to drastic fluctuations. Therefore, developing an integrated online crystallization preparation method with high coercivity, high consistency, and low energy consumption is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an integrated online crystallization preparation method for high-cobalt rapidly quenched NdFeB magnetic powder.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides an online integrated crystallization preparation method for high-cobalt rapidly quenched NdFeB magnetic powder, comprising:

[0009] The high-cobalt fast-quenching NdFeB magnetic powder is a magnetic powder with Pr-Nd, B, Co and Ga as alloy components. The magnetic powder uses NdFeB alloy with iron as the balance as the basic framework. The magnetic powder is based on the total mass of the magnetic powder, and the mass percentage of cobalt is 3.0% to 4.5%. The process includes the following steps:

[0010] S1: The alloy raw materials are melted in a vacuum induction furnace according to the proportion, and the melting temperature is controlled at 1480±10℃. After being uniformly stirred by electromagnetic stirring, the alloy rods are cast into alloy bars.

[0011] S2: The alloy rod is placed in a high vacuum rapid quenching furnace and rapidly quenched into a rapid quenching strip. The formed rapid quenching strip is directly introduced into the induction heating zone in the same cavity for online crystallization. The crystallization temperature is controlled at 680±10℃, and rapid cooling is performed by high-purity argon gas.

[0012] S3: The material after online crystallization is subjected to real-time magnetic property detection and the data is fed back to the PLC control system. The process parameters of the next batch are automatically adjusted according to the detection results. Finally, the material is crushed and pulverized by air jet mill under nitrogen protection to obtain the final product.

[0013] The Pr-Nd is a praseodymium-neodymium mixed rare earth element, the B is a boron-iron alloy, the Co is electrolytic cobalt, and the Ga is metallic gallium. The PLC control system is connected to the signal output terminal of the magnetic property detection device. The weight percentage of Pr-Nd, B, Co, Ga and Fe in S1 is (30.0-31.5): (0.8-1.2): (3.0-4.5): (0.3-0.8): balance.

[0014] Furthermore, in step S1, the stirring power is adjusted to 30kW and the frequency to 50Hz via electromagnetic stirring, and the alloy rod has the following specifications: 50±1mm.

[0015] Furthermore, in S2, the roller speed for rapid quenching is 35±2m / s and the roller surface temperature is 120±20℃.

[0016] Furthermore, the cooling rate of the online crystallization in S2 is 120±30℃ / s and the holding time is 80±20s.

[0017] Furthermore, the crystallization temperature T and the cobalt content [Co] in S2 satisfy a quantitative relationship:

[0018] T = 630 + 13.2 × [Co]

[0019] The spraying pressure of the rapid quenching strip in S2, which is sprayed onto the surface of the beryllium copper alloy roller through a nozzle, is 0.40±0.05MPa.

[0020] Furthermore, the adjustment logic of the PLC control system in S3 is as follows:

[0021] If the coercivity is below 2.0T, increase the roller speed of the next batch by 0.3m / s. The particle size of the crushed magnetic powder... It is 80-120μm.

[0022] Furthermore, the crushing environment in S3 is a nitrogen atmosphere and the crushing medium is helium, and the final grain size of the magnetic powder microstructure in S3 is 0.18±0.03μm.

[0023] Furthermore, the PLC control system is electrically connected to the frequency converter of the rapid quenching furnace to achieve closed-loop regulation of the roller speed.

[0024] Furthermore, in the praseodymium-neodymium mixed rare earth element used in the Pr-Nd, the mass percentage of Pr is 25% and the mass percentage of Nd is 75%.

[0025] Furthermore, the intrinsic coercivity of the high-cobalt rapidly quenched NdFeB magnetic powder ≥2.20T, and the consistency index of magnetic properties for 30 consecutive batches. ≤2.8%.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention utilizes an online integrated process for synthesis. The first step involves obtaining a rapidly quenched zone through vacuum melting and high-vacuum rapid quenching. The second step involves direct induction heating crystallization within the same vacuum chamber, achieving precise control of grain size under high-temperature conditions. Simultaneously, PLC closed-loop control is introduced into the preparation process. Compared to traditional technologies, this method achieves lower production energy consumption and higher batch consistency, while simplifying the process steps and stabilizing the composition system. When applied to the manufacture of drive motors for new energy vehicles, it can achieve high coercivity and high temperature stability of magnetic powder, demonstrating significant economic value and promising market application prospects. Attached Figure Description

[0028] Figure 1 This diagram compares the method proposed in this invention with existing methods. Detailed Implementation

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Performance evaluation method: The magnetic properties of the magnetic powder were evaluated using a pulsed magnetic field magnetometer (PFM) and a superconducting quantum interference device (SQUID). The sample chamber was protected with high-purity helium. The magnetic powder sample was mixed with epoxy resin at a mass ratio of 10:1 and then placed into a cylindrical tube with an inner diameter of 5 mm and a length of 10 mm. The mixture was oriented and cured under an external magnetic field of 2.5 T. The cured sample was then placed at the center of the magnetometer measurement, and the demagnetization curves were measured at room temperature (25℃) and high temperature (50℃) to obtain the remanence. Innate self-control and maximum magnetic energy product Through statistical continuous Each batch Data, calculate batch consistency index The calculation formula is as follows:

[0033] ,

[0034] in, This is a batch consistency index for magnetic properties. The smaller the value of this index, the smaller the performance fluctuation between batches produced continuously, and the better the consistency. The standard deviation of the intrinsic coercivity data samples from consecutive test batches reflects the dispersion of the data; The arithmetic mean of intrinsic coercivity data from consecutive test batches; To determine the total number of batches, data from 30 consecutive batches is used here. ; For the first Intrinsic coercivity in each batch The actual measured value; The test batch number is a variable with a value range from 1 to... Energy consumption assessment uses an intelligent power monitoring instrument to record the total power consumption of the online crystallization module and the rapid quenching module in real time, which is converted to kWh / kg.

[0035] like Figure 1 As shown, an online crystallization integrated preparation method for high-cobalt fast-quenching NdFeB magnetic powder includes magnetic powder with Pr-Nd, B, Co and Ga as alloy components, with NdFeB alloy as the basic framework of the magnetic powder with iron as the balance, the magnetic powder is based on the total mass of the magnetic powder, and the mass percentage of cobalt is 3.0% to 4.5%.

[0036] Includes the following steps:

[0037] S1: The alloy raw materials are melted in a vacuum induction furnace according to the proportion, and the melting temperature is controlled at 1480±10℃. After being uniformly stirred by electromagnetic stirring, the alloy rods are cast into alloy bars.

[0038] S2: The alloy rod is placed in a high vacuum rapid quenching furnace and rapidly quenched into a rapid quenching strip. The formed rapid quenching strip is directly introduced into the induction heating zone in the same cavity for online crystallization. The crystallization temperature is controlled at 680±10℃, and rapid cooling is performed by high-purity argon gas.

[0039] S3: The material after online crystallization is subjected to real-time magnetic property detection and the data is fed back to the PLC control system. The process parameters for the next batch are automatically adjusted according to the detection results. Finally, the material is crushed and pulverized by air jet mill under nitrogen protection to obtain the final product.

[0040] Example 1:

[0041] Weigh 30.80 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 3.80 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 63.90 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 35 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 120℃ / s. The crystallization temperature T is determined according to the formula:

[0042] T = 630 + 13.2 × [Co]

[0043] The calculation was set at 680℃, held for 80 seconds, then rapidly cooled with argon gas. A sample was taken and the coercivity was measured at 2.25T. The data was transmitted back to the PLC, and the system entered the nitrogen crushing program, where the material was pulverized using an air jet mill to... =105mum.

[0044] Example 2:

[0045] Weigh 30.00 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 0.80 kg of ferroborone alloy (B content 20%), 3.00 kg of electrolytic cobalt (purity 99.9%), 0.30 kg of metallic gallium, and 65.90 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Melt at 1470℃ under vacuum for 5 minutes, then turn on the electromagnetic stirring device, adjust the power to 30kW and the frequency to 50Hz, stir for 4 minutes, and then cast into a φ50mm alloy rod. Place the alloy rod in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 33 m / s and a surface temperature of 100°C. The resulting rapid quenching zone is directly introduced into the induction heating zone within the same cavity, with a cooling rate of 120°C / s. The crystallization temperature T is determined according to the formula:

[0046] T = 630 + 13.2 × [Co]

[0047] The calculation was set at 670℃, held for 100 seconds, then rapidly cooled with argon gas. A sample was taken and the coercivity was measured at 2.21T. The data was transmitted back to the PLC, and the system entered the nitrogen crushing program, where the material was pulverized using an air jet mill to... =80μm.

[0048] Example 3:

[0049] Weigh 31.50 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.20 kg of ferroborone alloy (B content 20%), 4.50 kg of electrolytic cobalt (purity 99.9%), 0.80 kg of metallic gallium, and 62.00 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1490℃, the temperature was raised to 1490℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller. The nozzle-roller distance is 0.35 mm, and the roller speed is 37 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 150 °C / s. The crystallization temperature T is determined according to the formula:

[0050] T = 630 + 13.2 × [Co]

[0051] The calculation was set at 689℃, held at that temperature for 60 seconds, then rapidly cooled with argon gas. A sample was taken and the squareness was measured at 0.96, meeting the set range. The data was transmitted back to the PLC, and the process entered the nitrogen crushing program, where the material was pulverized using an air jet mill to... =120μm.

[0052] Example 4:

[0053] Weigh 31.00 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.10 kg of ferroborone alloy (B content 20%), 3.50 kg of electrolytic cobalt (purity 99.9%), 0.40 kg of metallic gallium, and 64.00 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 35 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 120℃ / s. The crystallization temperature T is determined according to the formula:

[0054] T = 630 + 13.2 × [Co]

[0055] The calculation was set at 676℃, and after holding at that temperature for 80 seconds, rapid argon cooling was performed. Sampling and testing showed a coercivity of 1.98T. Based on the adjustment logic, the PLC control system triggered feedback, increasing the roller speed of the next batch by 0.3m / s to 35.3m / s. After adjustment, the coercivity of the next batch increased to 2.22T, and it entered the nitrogen crushing process, being pulverized by an air jet mill to... =100μm.

[0056] Example 5:

[0057] Weigh 30.50 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 0.90 kg of ferroborone alloy (B content 20%), 4.00 kg of electrolytic cobalt (purity 99.9%), 0.60 kg of metallic gallium, and 64.00 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 36 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 130℃ / s. The crystallization temperature T is determined according to the formula:

[0058] T = 630 + 13.2 × [Co]

[0059] The temperature was calculated and set at 683℃. After holding at this temperature for 70 seconds, the crystallization temperature was rapidly reduced with argon gas. Sampling and testing showed a squareness below 0.95. The PLC control system, based on its adjustment logic, triggered feedback and increased the crystallization temperature for the next batch to 688℃. The finished grain size, observed by TEM, was 0.18±0.02 μm. The crystals then entered a nitrogen crushing process, being pulverized by an air jet mill to... =110μm.

[0060] Example 6:

[0061] Weigh 30.80 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 3.20 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 64.50 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 34 m / s and a surface temperature of 110°C. The resulting rapid quenching zone is directly introduced into the induction heating zone within the same cavity, with a cooling rate of 120°C / s. The crystallization temperature T is determined according to the formula:

[0062] T = 630 + 13.2 × [Co]

[0063] The calculation was set at 672℃, held at that temperature for 90 seconds, and then rapidly cooled with argon gas. Batch consistency (σ / μ) was measured at 2.5% during sampling. Data was transmitted back to the PLC, and the system entered a nitrogen crushing program, where the material was pulverized using an air jet mill. =95μm.

[0064] Example 7:

[0065] Weigh 31.20 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 3.80 kg of electrolytic cobalt (purity 99.9%), 0.70 kg of metallic gallium, and 63.30 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.45 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 35 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 120℃ / s. The crystallization temperature T is determined according to the formula:

[0066] T = 630 + 13.2 × [Co]

[0067] The calculation was set at 680℃, held for 80 seconds, then rapidly cooled with argon gas. A sample was taken and the coercivity was measured at 2.26T. The data was transmitted back to the PLC, and the system entered the nitrogen crushing program, where the material was pulverized using an air jet mill to... =105μm, the finished magnetic powder has an upper limit of working temperature of 155℃ as tested, showing excellent high temperature stability.

[0068] Example 8:

[0069] Weigh 30.20 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 0.90 kg of ferroborone alloy (B content 20%), 4.20 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 64.20 kg of pure iron. Place the raw materials in a vacuum induction melting furnace. Under vacuum of 1480℃, the temperature was raised to 1480℃ and melted for 5 minutes. The electromagnetic stirring device was then turned on, with the power adjusted to 30kW and the frequency 50Hz. After stirring for 5 minutes, the mixture was cast into a φ50mm alloy rod. The alloy rod was then placed in a high-vacuum rapid quenching furnace. At a pressure of 0.40 MPa, the material is sprayed onto the surface of a beryllium copper alloy roller at a speed of 35 m / s. The resulting rapid quenching zone is directly introduced into the induction heating zone of the same cavity, with a cooling rate of 125℃ / s. The crystallization temperature T is determined according to the formula:

[0070] T = 630 + 13.2 × [Co]

[0071] The calculation was set at 685℃, held for 75 seconds, then rapidly cooled with argon gas. Under PLC closed-loop control, the coercivity range was less than 0.05T for 30 consecutive batches. The data was then transmitted back to the PLC, and the nitrogen crushing program was initiated, where the material was pulverized by an air jet mill to... =100μm, which fully verifies the high consistency and repeatability of the process.

[0072] Comparative Example 1:

[0073] Weigh 30.80 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 3.80 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 63.90 kg of pure iron. Place the raw materials in a vacuum induction melting furnace, melt them at 1480℃, and electromagnetically stir until homogeneous. Then cast them into φ50 mm alloy rods. Place the alloy rods in a high-vacuum rapid quenching furnace... Under a vacuum of 0.40 MPa, a beryllium copper alloy roller was sprayed onto its surface at a speed of 35 m / s to obtain a rapid quenching strip. Unlike Example 1, the rapid quenching strip was cooled to room temperature and then transferred to a separate heat treatment vacuum furnace for offline crystallization. The crystallization process involved heating to 680°C at a heating rate of 10°C / min, holding at that temperature for 80 seconds, cooling with the furnace, and finally crushing and grinding under nitrogen protection using an air jet mill. The final magnetic powder was obtained with a particle size of 105 μm. The coercivity of the obtained magnetic powder was then tested. 2.05T, batch consistency The percentage is 4.8%, and the energy consumption is 0.85 kWh / kg.

[0074] Comparative Example 2:

[0075] Weigh 30.80 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 3.80 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 63.90 kg of pure iron. The smelting and rapid quenching processes are the same as in Example 1. The online crystallization process is also carried out in the same chamber, with the crystallization temperature fixed at 680℃ and held for 80 seconds. Unlike Example 1, no PLC closed-loop control system is introduced in the preparation process. Fixed process parameters are used throughout the process: roller speed 35 m / s and crystallization temperature 680℃. The process parameters for subsequent furnaces are not adjusted based on the magnetic property test results. Finally, the mixture is crushed and pulverized by air jet milling under nitrogen protection. The final magnetic powder was obtained with a particle size of 100 μm. The coercivity of the obtained magnetic powder was then tested. 2.15T, batch consistency The percentage is 4.2%, and the energy consumption is 0.58 kWh / kg.

[0076] Comparative Example 3:

[0077] Weigh 30.80 kg of praseodymium-neodymium mixed rare earth (Pr content 25%, Nd content 75%), 1.00 kg of ferroborone alloy (B content 20%), 0.80 kg of electrolytic cobalt (purity 99.9%), 0.50 kg of metallic gallium, and 66.90 kg of pure iron, wherein the mass percentage of cobalt is 0.8%, and the balance is iron. Use the same online integrated process as in Example 1, with a melting temperature of 1480℃, a rapid quenching roller speed of 35 m / s, a spraying pressure of 0.40 MPa, and an online crystallization temperature according to the formula:

[0078] T = 630 + 13.2 × [Co]

[0079] The calculation was set at 640℃, held for 80 seconds, and finally crushed and pulverized using an air jet mill under nitrogen protection. The final magnetic powder was obtained with a particle size of 105 μm. The coercivity of the obtained magnetic powder was then tested. 1.85T, batch consistency The efficiency is 3.5%, and the energy consumption is 0.52 kWh / kg.

[0080] The magnetic properties of each embodiment and comparative example were analyzed using PFM and statistical methods. The results are shown in Table 1 below:

[0081] Table 1: Results of Magnetic Powder Performance and Consistency Tests

[0082]

[0083] It should be noted that this invention utilizes an online integrated process. The first step involves vacuum melting and high-vacuum rapid quenching to obtain a rapidly quenched band with a uniform microstructure. The second step involves instantaneous crystallization directly within the same vacuum chamber using induction heating, effectively suppressing Co segregation at grain boundaries and grain coarsening in the high-cobalt system. Simultaneously, a PLC closed-loop control system enables precise control of process parameters. Compared to traditional technologies, this method achieves significantly reduced energy consumption and greatly improved batch stability. Applying it to the manufacture of drive motors for new energy vehicles can achieve extremely low demagnetization rates under high-temperature environments, demonstrating high economic value and promising market application prospects.

[0084] The foregoing describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An on-line crystallization integrated preparation method of high cobalt melt-spun neodymium-iron-boron magnetic powder, characterized in that, The high-cobalt rapidly quenched NdFeB magnetic powder is a magnetic powder with Pr-Nd, B, Co, and Ga as alloy components. The magnetic powder uses an NdFeB alloy with iron as the balance as the basic framework. The total mass of the magnetic powder is used as a basis, and the mass percentage of cobalt is 3.0% to 4.5%. Includes the following steps: S1: The alloy raw materials are melted in a vacuum induction furnace according to the proportion, and the melting temperature is controlled at 1480±10℃. After being uniformly stirred by electromagnetic stirring, the alloy rods are cast into alloy bars. S2: The alloy rod is placed in a high vacuum rapid quenching furnace and rapidly quenched into a rapid quenching strip. The formed rapid quenching strip is directly introduced into the induction heating zone in the same cavity for online crystallization. The crystallization temperature is controlled at 680±10℃, and rapid cooling is performed by high-purity argon gas. S3: The material after online crystallization is subjected to real-time magnetic property detection and the data is fed back to the PLC control system. The process parameters of the next batch are automatically adjusted according to the detection results. Finally, the material is crushed and pulverized by air jet mill under nitrogen protection to obtain the final product. The Pr-Nd is a praseodymium-neodymium mixed rare earth element, the B is a boron-iron alloy, the Co is electrolytic cobalt, and the Ga is metallic gallium. The PLC control system is connected to the signal output terminal of the magnetic property detection device. The weight percentage of Pr-Nd, B, Co, Ga and Fe in S1 is (30.0-31.5): (0.8-1.2): (3.0-4.5): (0.3-0.8): balance.

2. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, In the S1, the stirring power is adjusted to 30 kW and the frequency is adjusted to 50 Hz by electromagnetic stirring, and the specification of the alloy bar is 50 ± 1 mm.

3. The method according to claim 1, wherein the method is characterized by: In S2, the roller speed for rapid quenching is 35±2m / s and the roller surface temperature is 120±20℃.

4. The on-line crystallization integrated preparation method of high-Co rapid-quench Nd-Fe-B magnetic powder according to claim 1, characterized in that, The cooling rate of online crystallization in S2 is 120±30℃ / s and the holding time is 80±20s.

5. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The crystallization temperature T in S2 and the cobalt content [Co] satisfy a quantitative relationship: T = 630 + 13.2 × [Co] The spraying pressure of the rapid quenching strip in S2, which is sprayed onto the surface of the beryllium copper alloy roller through a nozzle, is 0.40±0.05MPa.

6. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The adjustment logic of the PLC control system in S3 is as follows: If the coercivity is below 2.0T, increase the roller speed of the next batch by 0.3m / s. The particle size of the crushed magnetic powder... It is 80-120μm.

7. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The crushing environment in S3 is a nitrogen atmosphere and the crushing medium is helium. The final grain size of the magnetic powder in S3 is 0.18±0.03μm.

8. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The PLC control system is electrically connected to the frequency converter of the rapid quenching furnace to achieve closed-loop regulation of the roller speed.

9. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The praseodymium-neodymium mixed rare earth element used in the Pr-Nd method has a Pr mass percentage of 25% and a Nd mass percentage of 75%.

10. The method for online integrated crystallization preparation of high-cobalt rapidly quenched NdFeB magnetic powder according to claim 1, characterized in that, The intrinsic coercivity of the high-cobalt rapidly quenched NdFeB magnetic powder ≥2.20T, and the consistency index of magnetic properties for 30 consecutive batches. ≤2.8%.

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