High remanence neodymium iron boron magnet, its manufacturing method and applications

Abstract

The present invention provides a high remanence NdFeB magnet and its manufacturing method and application. The NdFeB magnet of the present invention has crystal grains with RTB type compound as the main structure and grain boundary phase. The NdFeB magnet of the present invention can obtain a relatively high volume ratio of main phase crystal grains by adjusting the ratio relationship of elements such as B, Cu, Ga, RE, Ti, etc., and can effectively suppress the ratio of B-rich phase in the grain boundary phase, so that the magnet has a relatively high Br and excellent Hcj and squareness performance at the same time.

Description

Detailed Description of the Invention

[0001] [Priority and Related Applications] This application claims priority from a prior application bearing patent application number 202111107088.3 and entitled "High remanence neodymium iron boron magnet, its manufacturing method and application," filed with the State Intellectual Property Office of the People's Republic of China on September 22, 2021. The above prior application is incorporated herein by reference in its entirety.

[0002] [Technical Field] The present invention relates to the field of neodymium-iron-boron magnets, and more particularly to neodymium-iron-boron sintered magnets, their manufacturing methods, and applications.

[0003] [Background technology] Neodymium-iron-boron sintered magnets are a fourth-generation permanent magnet material known as the "king of magnetism" due to their excellent magnetic properties, and are widely used in many fields, including automobiles, wind power generation, compressors, elevators, and industrial automation.

[0004] Since the beginning of the 21st century, there has been increasing interest in improving the coercive force performance of magnetic steel. In particular, due to cost issues caused by an imbalance in the supply of heavy rare earth resources, which are relatively scarce, and the rapid rise in raw material prices, many scholars and companies have been conducting research on techniques such as grain refinement and grain boundary diffusion to maintain and further improve coercive force performance and ensure the demagnetization resistance of magnetic steel at operating temperatures, on the premise of reducing the amount of heavy rare earth used.

[0005] With the growth of the new energy vehicle market and new policies for high-efficiency, energy-saving home appliances, motor miniaturization and high efficiency indicators have become new points of interest. In order to ensure that motors are miniaturized as much as possible and that the output power of the motor is maintained or even improved, the magnetic steel that is the power center needs to have high energy density, i.e., high remanence.

[0006] Theoretically, the maximum remanence of a pure neodymium-iron-boron magnet is 1.61 T, and currently, the maximum remanence achievable under laboratory conditions is 1.56 T. However, due to process difficulties and equipment precision, this is far from being mass-produced. At the same time, the mainstream remanence range of magnetic steel used in fields such as new energy vehicles and energy-saving home appliances is between 1.10 and 1.40 T, and further improvement of remanence would effectively promote the demand for smaller motors and higher efficiency levels.

[0007] Patent CN111724985A In this study, a sintered magnet (or diffused magnet) was produced by smelting an alloy with a low B composition (0.80-0.93 wt%) and incorporating a certain amount of transition metal phase (R6T13M). The sintered magnet (or diffused magnet) was then heat-treated at a temperature between 400°C and 600°C for between 10 seconds and 30 minutes, resulting in high remanence and high Hcj, with the remanence reaching 1.41 T. The use of a low B composition results in the formation of a relatively wide R6T13M phase at the grain boundaries. However, due to the requirements of the theoretical formula for remanence of NdFeB magnets, the volume fraction of the main phase is reduced, inevitably reducing its Br. Furthermore, the R6T13M phase at the grain boundaries helps improve Hcj, but the stability of this grain boundary phase is relatively low, requiring difficult control of the equipment process. Magnet squareness is prone to fluctuation and cannot be consistently greater than 0.95, directly impacting the motor's resistance to high-temperature demagnetization.

[0008] Patent CN107424699AThe company smelts an alloy with a low B content (0.94 wt%) to produce alloy sheet with a columnar crystal ratio of over 95%, processes it in a rotary hydrogen crushing furnace, and uses high-pressure nitrogen gas to produce jet-milled powder with a size of 3.75-3.9 μm. This enables the production of ultra-high-performance neodymium-iron-boron magnets with Br of 1.44-1.48 T and Hcj of 14-16 kOe. By controlling the columnar crystal ratio of the alloy flakes, optimizing the HD production process, controlling the particle size range of the jet-milled powder, and further matching it with the sintering process, magnets with high Br and high Hcj can be obtained. However, the RE content is extremely low, and there is not enough Nd-rich phase to uniformly surround the main phase crystal grains during sintering and promote sintering. At the same time, there is no grain boundary phase such as Zr or Ti borides, which makes it easy for the crystal grains to grow abnormally. The magnet crystal grains are non-uniform in size, which deteriorates the squareness. Although the magnet has high Br and Hcj, the areas where the crystal grains have grown abnormally are very susceptible to reverse magnetization, which reduces the magnet's demagnetization resistance.

[0009] Summary of the Invention To solve the above technical problems, the present invention proposes a high remanence neodymium iron boron magnet, its manufacturing method and application.

[0010] The present invention provides a neodymium-iron-boron magnet, which has crystal grains whose main structure is an RTB type compound and a grain boundary phase, and the neodymium-iron-boron magnet is: R is 28wt% or more and 30wt% or less, T of 63 wt% or more and 70 wt% or less, B is 0.98 wt% or more and 1.05 wt% or less, M1 is greater than 0 wt% and less than or equal to 0.3 wt%; 0.04 wt% or more and 0.15 wt% or less of M2; R represents a rare earth element, and is Nd, or Nd and at least one rare earth element selected from Pr, La, Ce, Dy, Tb, and Ho; T is selected from Fe and / or Co, and among them, Fe accounts for 99 wt% or more of the total amount of T; M1 is selected from Cu and Ga, and Ga accounts for 75 wt% or more of the total amount of M1; M2 is at least one selected from Zr, Ti, and Nb.

[0011] Preferably, M2 is selected from Ti.

[0012] According to an embodiment of the present invention, the atomic numbers of elements in the raw materials for manufacturing the neodymium-iron-boron magnet further satisfy the following condition.

[0013] 2.15≦[R] / ([B]-2[M2])≦2.35

[0014] Wherein, [R] is the atomic percentage of R, [B] is the atomic percentage of B, and [M2] is the atomic percentage of M2. In the present invention, atomic percentage means [the number of a certain atom] / [the total number of each atom in the raw material].

[0015] Illustratively, [R] / ([B]-2[M2]) is 2.15, 2.2, 2.24, 2.29, and 2.3.

[0016] According to an embodiment of the present invention, when R is at least one selected from Nd and rare earth elements Pr, La, Ce, Dy, Tb, and Ho, the total mass of heavy rare earth elements such as Dy, Tb, and Ho accounts for 1 wt% or less of the mass of the magnet, and preferably 0.5 wt% or less.

[0017] According to an embodiment of the present invention, the magnet has the following magnetic properties: (1) Perpendicularity ≧ 0.95, for example, 0.95, 0.96, 0.97, 0.98, 0.99; (2) Br≧1.44T, for example, 1.45T, 1.46T, 1.47T, 1.48T, 1.49T, 1.5T; (3) Hcj≧1100kA / m, for example, 1100kA / m, 1110kA / m, 1120kA / m, 1130kA / m, 1140kA / m, 1150kA / m, 1160kA / m, 1170kA / m, 1180kA / m, 1190kA / m, and 1200kA / m.

[0018] The present invention strictly limits the content of each element in the manufacturing raw materials, specifically, Because the magnetic polarization strength of the RTB-based main phase crystal grains made of rare earth elements such as Pr, Dy, Tb, and Ho is lower than that of Nd, the Br of the magnet is significantly reduced, ensuring a high Br. At the same time, the Hcj of the magnet can be increased by using small amounts of heavy rare earth elements such as Dy, Tb, and Ho. If the R in the magnet is too high, the neodymium-rich phase in the magnet increases and Br decreases. If the R is too low, it is not possible to form a uniform, continuous Nd-rich phase in the magnet for magnetic insulation of the main phase crystal grains, resulting in a rapid deterioration in the Hcj and squareness of the magnet.

[0019] Co occupies the position of Fe in the main phase crystal grains, and its atomic magnetic moment is smaller than that of Fe. Adding Co reduces the Br of the magnet. Therefore, Fe is controlled to account for 99% or more of the total T. At the same time, by controlling other components and optimizing the process, the corrosion resistance and temperature resistance of the Co in the magnet are compensated for and improved.

[0020] Conventional techniques produce high-performance NdFeB magnets with low B content (≦0.95 wt%), increasing the thickness of the grain boundary phase by forming an RT-Ga type grain boundary phase, thereby improving the Hcj of the magnet. However, as the grain boundary phase becomes thicker, the volume ratio of the main phase crystal grains inevitably decreases, significantly reducing the Br performance of the magnet. This invention controls the B content to increase the volume ratio of the main phase crystal grains and improve the Br of the magnet. If the B content is too low, a relatively high proportion of the B-rich or Nd-rich phase is formed, and the volume ratio of the main phase crystal grains is small, resulting in a relatively low Br of the magnet. If the B content is too high, the volume ratio of the B-rich phase increases significantly, significantly reducing the magnetic properties.

[0021] M1 mainly concentrates in the grain boundary phase, improving the structure of the grain boundary phase and significantly increasing Hcj. If a magnet does not contain Cu or Ga, the main phase crystal grains and B-rich phase of the magnet will become relatively coarse, significantly reducing the magnetic properties of the magnet. If the Cu and Ga content in the magnet is too high, grain growth will be inhibited, and at the same time, the grain boundary phase will become thicker, reducing the volume ratio of the main phase crystal grains and reducing the Br of the magnet. When the Ga content reaches the level of the present invention, the Hcj of the magnet can be significantly improved and has a significant optimization effect on the magnet's temperature coefficient, avoiding the impact of a low Co content on the temperature resistance of the magnet.

[0022] M2 and B form A2B type compounds, which exist in the grain boundary phase and suppress the abnormal growth of magnet crystal grains. If the M2 content is too low, the A2B type compounds cannot be effectively formed, and the abnormal growth of the main phase crystal grains of the magnet cannot be suppressed. If the M2 content is too high, the A2B type compounds exist as grain boundary phases, reducing the volume ratio of the main phase crystal grains and preventing the magnet from achieving a high Br.

[0023] The present invention further provides a method for producing the above-mentioned neodymium-iron-boron magnet, comprising: (a) a smelting step of melting the raw materials for producing the neodymium-iron-boron magnet at a high temperature, casting the materials, and forming an alloy sheet after secondary cooling; (b) a milling step of pulverizing the alloy sheet to form an alloy powder; (c) a press-molding step of press-molding the alloy powder under the action of a magnetic field to obtain a billet; and (d) a sintering step of sintering the billet at a high temperature.

[0024] According to an embodiment of the present invention, the (a) smelting step specifically includes fully melting the raw materials for producing the NdFeB magnet into a molten alloy steel in a vacuum or inert gas atmosphere, followed by rapid cooling to form an alloy sheet, and then secondary cooling, wherein the interval between the secondary cooling and the rapid cooling does not exceed 10 seconds, and the cooling rate of the secondary cooling is 5 to 20°C / s. Preferably, the melting is performed by medium-frequency induction heating in a vacuum induction smelting furnace. In the present invention, the rapid cooling can be performed using any rapid cooling method commonly used in the art, as long as the desired alloy sheet is obtained. Illustratively, the rapid cooling is performed using a chill roll.

[0025] In the present invention, the secondary cooling can be performed by using a cooling method and a cooling device commonly used in the art. Illustratively, the secondary cooling is performed using a cooling device selected from a low-temperature inert gas spray, a water-cooled disk, or other types of cooling devices.

[0026] Preferably, the cooling rate of the secondary cooling is 5 to 20° C. / s.

[0027] Preferably, the alloy sheet has a thickness of 0.15 to 0.45 mm.

[0028] According to an embodiment of the present invention, the milling step (b) includes coarse grinding and fine grinding.

[0029] Preferably, the coarse grinding is selected from hydrogen grinding and / or medium grinding.

[0030] Preferably, the pulverization is performed using a jet mill. Preferably, the jet milling is performed in an inert gas atmosphere. Preferably, the inert gas is selected from nitrogen gas, helium gas, etc.

[0031] In the present invention, the above-mentioned hydro-crushing, medium crushing or jet milling can be carried out by any of the methods known in the art.

[0032] Preferably, it is obtained after the above-mentioned fine grinding and by screening such as grading wheel screening.

[0033] Preferably, the particle size SMD of the alloy powder is between 2.0 and 3.4 μm, and X90 / X10≦4.5, where SMD is the area mean particle size, the smaller the SMD, the smaller the particle size of the powder particles, and the larger the SMD, the larger the particle size of the powder particles, X90 represents the particle size value corresponding to the cumulative distribution percentage reaching 90%, that is, all particles have a particle size equal to or smaller than this particle size, and the number of particles larger than this particle size value is 0, and X10 represents the cumulative distribution percentage reaching 90%. 10 %, the particle size value corresponds to the particle size value, i.e., the particle sizes of all particles are equal to or smaller than this particle size value, and the number of particles larger than this particle size value is 0. Here, X90 / X10 represents the particle size distribution of the powder, and the smaller X90 / X10 means that the particle size distribution of the powder is more concentrated.

[0034] Preferably, a lubricant should be added during pulverization, and preferably added both before and after jet milling. Adding a lubricant before jet milling can improve the flowability of the powder, improving the flowability and uniformity of the powder during jet milling, while adding a lubricant after jet milling can improve the uniformity and flowability of the powder, facilitating uniform powder filling and pressing.

[0035] Preferably, the lubricant is selected from reagents and amounts known in the art so as to thoroughly and uniformly mix the powder and facilitate compaction. Exemplarily, the lubricant is selected from volatile organic solvents such as lipids or alcohols, e.g., zinc stearate. Exemplarily, the amount of the lubricant added is 0.1 to 1 wt% of the total mass of the raw materials.

[0036] Preferably, after adding the lubricant, further mixing is required, and the mixing time is preferably 3 to 6 hours.

[0037] The mixing according to the present invention can be carried out using methods known in the art, such as mixing in a mixer.

[0038] According to an embodiment of the present invention, the press-molding step (c) specifically includes press-molding the alloy powder under the action of a magnetic field to obtain a billet.

[0039] Preferably, the pressing is carried out in a press die cavity.

[0040] Preferably, before press molding, it is necessary to orient and magnetize the material under a magnetic field strength of 2 T and then mold it.

[0041] Preferably, after press molding, the material is demagnetized by applying an inverse magnetic field.

[0042] Preferably, the compacted billet can be further processed in a cold isostatic press to further increase the billet density.

[0043] According to an embodiment of the present invention, the sintering step (d) includes a first sintering, a first cooling, a second sintering, and a second cooling. The sintering step in the present invention can be performed using a method known in the art. Illustratively, the billet is sintered in a sintering furnace.

[0044] Preferably, the sintering step is carried out in a vacuum atmosphere, and the degree of vacuum during heating is preferably 10-1 Pa or less.

[0045] Preferably, the sintering temperature in the first sintering is 1000 to 1050°C, and the temperature-retention time in the first sintering is 240 to 360 minutes.

[0046] Preferably, the second sintering temperature is 30 to 70°C higher than the first sintering temperature, and is preferably 1030 to 1100°C.

[0047] Preferably, the temperature retention time for the second sintering is 270 to 360 minutes.

[0048] Preferably, both the first and second cooling steps are performed at temperatures below 200°C.

[0049] According to an embodiment of the present invention, the sintering step further includes an aging treatment performed after the second cooling.

[0050] Preferably, the aging treatment is selected from primary aging treatment or secondary aging treatment.

[0051] Preferably, the conditions for the primary aging treatment are that the aging temperature is between 500 and 700°C and the temperature-holding time is between 240 and 420 minutes.

[0052] Preferably, the secondary aging treatment includes a first aging treatment in which the temperature is increased to 800 to 950°C and the temperature is maintained for 180 to 300 minutes, and a second aging treatment in which the temperature is increased to 450 to 600°C after cooling to 150°C or below and the temperature is maintained for 240 to 360 minutes.

[0053] According to an embodiment of the present invention, a diffusion treatment may also be performed after the sintering step.

[0054] Preferably, the diffusion treatment includes applying a diffusion material to the magnet surface, and performing a vacuum high-temperature diffusion treatment, diffusion cooling, and diffusion aging treatment.

[0055] Preferably, the diffusion material is selected from pure metals of Dy and / or Tb, or alloys such as hydrides, oxides, hydroxides, fluorides, etc. of Dy and / or Tb.

[0056] Preferably, the diffusion treatment can be carried out by using a method such as vacuum deposition, magnetron sputtering, coating or embedding.

[0057] Preferably, the temperature of the high-temperature diffusion is 850 to 950° C., and the time of the high-temperature diffusion is 10 to 30 hours.

[0058] Preferably, the diffusion cooling temperature is less than 100°C.

[0059] Preferably, the temperature of the diffusion aging treatment is 450 to 600°C, and the time of the diffusion aging treatment is 4 to 8 hours.

[0060] According to embodiments of the present invention, the billet may be machined to a target size after the sintering process and before the diffusion process.

[0061] The present invention requires strict limitations on the conditions for each process in the magnet production method. Specifically, when molten alloy steel is rapidly cooled, for example, using a chill roll, nucleation points form on the alloy sheet on the surface of the chill roll, and crystal grains form and grow from the nucleation points. The alloy sheet falls off the chill roll, and its temperature drops from the melting temperature to about 800°C. In this case, the crystal grains grow gradually, so secondary cooling must be carried out in a timely manner to reduce the temperature of the alloy sheet. If the secondary cooling time is too long, the main phase crystal grains on the alloy sheet will continue to grow, and the temperature of the alloy sheet will disperse unevenly, resulting in secondary crystals. The existence of these secondary crystals will result in poor uniformity in the grain size of the main phase crystal grains, which will in turn result in poor squareness of the magnet. If the cooling rate is too slow, a large amount of B-rich phase will form in the grain boundary phase around the main phase crystal grains, and the B-rich phase formed at this time cannot be effectively removed or reduced during processes such as milling and sintering, inevitably resulting in a rapid deterioration of magnetic properties. If the cooling rate is too fast, the alloy sheet will cool too quickly, causing the growth of the main phase crystal grains to stop and preventing them from melting and absorbing the surrounding grain boundary phase and B-rich phase and continuing to grow, resulting in a relatively small volume ratio and a decrease in the Br of the magnet.

[0062] As can be seen from the above, the relatively low R content in the magnet manufacturing raw materials results in the presence of binary and ternary grain boundary phases between main phase grains in the alloy sheet. In addition, some of the main phase grains are in direct contact with each other, resulting in extremely high bonding strength between these directly contacting main phase grains. If the alloy powder particle size is too small, the alloy powder particles will fracture primarily at the grain boundary phase. While internal fractures of the main phase grains occur to achieve the desired powder particle size, these fractured powder particles will have irregular sizes and surfaces. After sintering, demagnetization points are likely to form at the contact points between adjacent grains and the grain boundary phase, resulting in low magnet squareness and magnet demagnetization at high temperatures or under the influence of other external magnetic fields. If the powder particle size is too large, the grain boundary phase will not be able to fully separate from the main phase grains. Consequently, the Nd-rich phase, which melts and adheres to the main phase grains, grows during sintering. This results in insufficient Nd-rich phase to encase the main phase grains, significantly reducing the Hcj of the magnet. When the powder particle size distribution X90 / X10 is within the range of the present invention, a magnet with uniform and consistent particle size can be obtained, with relatively high Br and Hcj. However, if the particle size distribution X90 / X10 is too large, the magnet's crystal grain size will vary greatly, and fine powder particles will easily aggregate and melt to form triangular grain boundary phases, and adjacent coarse powder particles will melt to form large crystal grains, all of which will have a significant impact on the squareness of the magnet.

[0063] At the same time, the present invention uses a secondary sintering process to significantly improve magnet performance and effectively suppress abnormal grain growth. In the NdFeB magnet manufacturing method of the present invention, the second sintering temperature is higher than the first sintering temperature, and the first sintering is performed at a relatively low temperature, improving the magnet's density but avoiding the presence of some gaps and the resulting abnormal growth of the main phase grains. The second sintering temperature is significantly higher than the first sintering temperature, promoting sufficient growth of the main phase grains without causing abnormal grain growth and resulting in a rapid deterioration of magnetic properties. If the temperature difference between the two sintering temperatures is too low, the primary sintering temperature is too high to ensure the sintered magnet's density, resulting in a relatively dense grain arrangement. The relatively low secondary sintering temperature does not fully reorganize and optimize the magnet's grain structure, preventing the magnet from achieving relatively high magnetic properties. If the temperature difference between the two sintering temperatures is too large, the primary sintering temperature is too low, the gaps are too large, and the secondary sintering temperature is too high, resulting in abnormal grain growth in some areas and resulting in poor magnetic properties.

[0064] The present invention further provides an application of the above magnet in the field of motors.

[0065] The present invention further provides a motor including the above magnet.

[0066] The present invention further provides applications of the above motor, preferably, the above motor can be applied to new energy vehicles and energy-saving home appliances.

[0067] [Beneficial Effects] The neodymium-iron-boron magnet of the present invention achieves a relatively high volume ratio of main phase crystal grains by adjusting the ratios of elements such as B, Cu, Ga, RE, and Ti, effectively suppressing the proportion of B-rich phase in the grain boundary phase. The structure of the grain boundary phase is optimized and adjusted by adding transition metal elements M1 (e.g., Ga) and M2 (e.g., Ti), giving the magnet a relatively high Br and simultaneously providing excellent Hcj and squareness performance.

[0068] In the present invention, the B content is higher than that of typical NdFeB-based sintered magnets. Typical NdFeB magnets, when simultaneously achieving high Br and Hcj performance, have a ratio of [R] / ([B]-2[M2]) slightly greater than 2.35, but greater than 2.5, resulting in relatively little or no B-rich phase. In the present invention, by setting this ratio between 2.15 and 2.35, theoretically more B-rich phase is formed compared to typical NdFeB magnets. However, within this ratio range, the volume fraction of the magnet's main phase crystal grains can be increased in conjunction with secondary cooling in the manufacturing method of the present invention, suppressing excessive formation of the B-rich phase. This ensures the magnet's Br while also providing excellent Hcj and squareness index.

[0069] The magnet of the present invention achieves high remanence and coercivity with extremely small amounts of heavy rare earth elements such as Dy / Tb, or even no heavy rare earth elements at all, and has a magnet squareness of ≥ 0.95. The manufacturing process is simple and mass production is highly stable.

[0070] Magnets manufactured using the manufacturing method of the present invention have high remanence, Br≧1.44T, and very high energy density. When applied to motors, this effectively improves the power output per unit volume and reduces the volume of the motor, saving material waste in other motor components and playing an important role in making motors smaller and less expensive.

[0071] [Mode for Carrying Out the Invention] The technical solutions of the present invention will be described in more detail below with reference to specific examples. It should be understood that the following examples are merely for illustrative purposes and should not be construed as limiting the scope of the claims of the present invention. Any technology realized based on the above content of the present invention is included within the scope of the claims of the present invention.

[0072] Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0073] In the following examples, atomic percentage means [number of atoms] / [total number of each atom in the raw material], where M1 is selected from Cu and Ga, M2 is at least one selected from Zr, Ti, and Nb, and R is at least one selected from Nd and rare earth elements Pr, La, Ce, Dy, Tb, and Ho.

[0074] Examples 1 to 4 (1) The raw materials were blended according to the target composition of the magnet in Table 1, and a neodymium-iron-boron alloy sheet was produced by a melt spinning casting process. The alloy sheet was cooled by a quenching roll and dropped off, and then secondary cooling was performed by injecting low-temperature argon gas. By adjusting the flow rate and temperature of the low-temperature argon gas, the alloy sheet was obtained by secondary cooling at a cooling rate of 10°C / s, and the alloy sheet was dropped onto a water-cooled disk and collected, producing an alloy sheet with a thickness of 0.15 to 0.45 mm.

[0075] [Table 1]

[0076] (2) The alloy sheet was coarsely crushed by hydrogen crushing to obtain powder, and zinc stearate (0.1 wt% of the raw material mass) was added to the powder as a lubricant and mixed for 60 min. The mixed material was then finely crushed in a fluidized bed jet mill using nitrogen gas as the grinding gas, and equipment parameters such as the rotation speed of the grading wheel and grinding pressure were adjusted to obtain jet mill powder with a target particle size of SMD = 2.5 μm.

[0077] (3) Zinc stearate, the mass of which is 0.2 wt% of the raw materials, is further added as a lubricant to the jet mill powder of the target particle size produced, and after thorough mixing, it is pressed under a magnetization magnetic field strength of 2 T to form a billet, and the density of the billet is further improved by oil cold isostatic pressing.

[0078] (4) The billet was placed in a sintering furnace and subjected to secondary sintering in a vacuum atmosphere. The sintering temperature was maintained for 270 minutes each time. When the sintering cooling temperature was below 80°C, the billet was heated to 890°C and maintained at that temperature for 240 minutes. After cooling, secondary aging was performed, with the optimal aging temperature adjusted according to the composition. The aging temperature was 280 minutes. The specific sintering aging regime is shown in Table 2.

[0079] [Table 2]

[0080] The magnets after sintering and aging treatment were processed into standard sample columns with a diameter of 10 mm and a height of 10 mm, and the magnetic performance was measured using a BH analyzer. The specific magnetic property measurement results are shown in Table 3.

[0081] [Table 3]

[0082] As can be seen from the results in Table 3, when the composition of each element is within the controlled range, the magnet has a relatively high remanence and coercive force, while at the same time ensuring a squareness of ≥ 0.95, which ensures that the magnet can provide stable power output during motor operation.

[0083] Comparative Examples 1 and 2 The raw materials were blended according to the target composition of the magnet in Table 4, and a neodymium-iron-boron alloy sheet was produced by a melt spinning process. The alloy sheet was cooled by a quenching roll and dropped off, and then secondary cooling was performed by injecting low-temperature argon gas. By adjusting the flow rate and temperature of the low-temperature argon gas, the alloy sheet was secondary cooled at a cooling rate of 10°C / s to obtain an alloy sheet. The alloy sheet was then dropped onto a water-cooled disk and collected, thereby obtaining the alloy sheet.

[0084] Comparative Example 3 The raw materials were blended according to the target magnet composition in Table 4, and a neodymium-iron-boron alloy sheet was produced by a melt spinning casting process. The alloy sheet was quenched by a chill roll and then directly dropped onto a water-cooled disk for cooling and recovery.

[0085] Comparative Example 4 The raw materials were blended according to the target magnet composition in Table 4, and a neodymium-iron-boron alloy sheet was produced by a melt spinning casting process. The alloy sheet was quenched by a chill roll and then directly dropped onto a water-cooled disk for cooling and recovery.

[0086] [Table 4]

[0087] The alloy sheets obtained in Comparative Examples 1 to 4 were jet-milled to produce powder with a target SMD of 2.5 μm using the same process as in Examples, and then pressed and sintered and aged. The specific process parameters are shown in Table 5.

[0088] [Table 5]

[0089] The magnets manufactured in Comparative Examples 1 to 4 were processed into standard sample columns with a diameter of 10 mm and a height of 10 mm, and the magnetic performance was measured using a BH analyzer.

[0090] [Table 6]

[0091] As can be seen from Comparative Example 1, when the ratio of [R], [B], and [M2] exceeds 2.35, Hcj improves slightly, but Br decreases significantly, and the squareness is less than 0.95, so the demagnetization resistance fluctuates and the motor cannot output a stable magnetic field during high-speed operation.

[0092] Because the ratio of [Cu] to [Ga] in Comparative Example 2 is much smaller than 0.75, the Br and Hcj of the magnet are both significantly lower than those of the Examples, and it is not possible to simultaneously achieve high remanence and high coercivity.

[0093] The target magnet in Comparative Example 3 had the same composition as in Example 1, but the alloy sheet was not subjected to secondary cooling during the smelting process as in the method claimed in the present patent application. As can be seen from Table 3, when secondary cooling of the alloy sheet was omitted, the alloy sheet experienced significant grain growth and an increase in thickness. When jet mill polishing was performed, jet-milled powder with the target SMD was obtained, but the particle size distribution (X90 / X10) was significantly worsened, the ratio of coarse powder to fine powder increased, and the powder uniformity was low. In addition, only primary sintering was performed during the sintering process, without a secondary sintering process, and the remanence and coercivity of the magnet were both significantly reduced.

[0094] As can be seen from Comparative Example 4, when the ratio of [Cu] to [Ga] is less than 0.75 and the secondary cooling and secondary sintering processes described in the present invention are not used, the Hcj is significantly reduced and the squareness is far lower than 0.95, so the demagnetization resistance fluctuates and the motor cannot output a stable magnetic field when operating at high speed.

[0095] Example 5 The sintered and aged magnets from Example 1 were processed into sheet products measuring 20 mm in length, 20 mm in width, and 5 mm in thickness. A thin film of metallic Dy was applied to the magnet surface using a dip coating process. The magnets were then subjected to a diffusion treatment at 900°C for 15 hours. After cooling to a temperature below 100°C, the diffusion temperature was further increased to 500°C and aging treatment was performed for 5 hours. The magnetic properties and composition of the final magnets were measured. The final composition and magnetic property results are shown in Tables 9 and 10.

[0096] [Table 7]

[0097] [Table 8]

[0098] As can be seen from the above results, the coercive force of the magnet after diffusion is significantly improved, and Br does not obviously decrease, so the magnet of the present invention can also be used as a diffusion substrate.

[0099] Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A neodymium-iron-boron magnet, The neodymium-iron-boron magnet has crystal grains whose main structure is an R-T-B type compound and a grain boundary phase, R of 28 wt% or more and 30 wt% or less, T of 63 wt% or more and 70 wt% or less; 0.98 wt% or more and 1.05 wt% or less of B; M1 is greater than 0 wt% and less than or equal to 0.3 wt%; M2 of 0.04 wt% or more and 0.15 wt% or less and impurity elements, R represents a rare earth element, and is Nd, or Nd and at least one selected from the rare earth elements Pr, La, Ce, Dy, Tb, and Ho; T is selected from Fe and Co, and among them, Fe accounts for 99 wt % or more of the total amount of T; M1 is selected from Cu and Ga, and Ga accounts for 75 wt % or more of the total amount of M1; M2 is at least one selected from Zr, Ti, and Nb; In the neodymium-iron-boron magnet, the atomic numbers of the elements further satisfy the following conditions: 2.15≦[R] / ([B]-2[M2])≦2.35, Wherein, [R] is the atomic percentage of R, [B] is the atomic percentage of B, and [M2] is the atomic percentage of M2; when R is at least one selected from Nd and rare earth elements Pr, La, Ce, Dy, Tb, and Ho, the total mass of the heavy rare earth elements Dy, Tb, and Ho accounts for 1 wt % or less of the mass of the magnet; The neodymium-iron-boron magnet is (1) perpendicularity ≧ 0.95; (2) Br≧1.44T, (3) Having magnetic properties of Hcj≧1100 kA / m; Neodymium iron boron magnet.

2. the total mass of the heavy rare earth elements Dy, Tb, and Ho accounts for 0.5 wt% or less of the mass of the magnet; M2 is selected from Ti; 2. The neodymium-iron-boron magnet according to claim 1.

3. (a) a smelting step in which the raw materials for producing the neodymium-iron-boron magnet are melted at high temperature, cast, rapidly cooled, and then secondary cooled to form an alloy sheet; (b) milling the alloy sheet to form an alloy powder; (c) a press molding step of press-molding the alloy powder under the action of a magnetic field to obtain a billet; (d) sintering the billet at a high temperature; 2. The method for producing a neodymium-iron-boron magnet according to claim 1.

4. Specifically, the (a) smelting step includes: fully melting the raw materials for producing the neodymium-iron-boron magnet into a molten alloy steel in a vacuum or inert gas atmosphere, followed by rapid cooling and secondary cooling to form an alloy sheet; the interval between the secondary cooling and the rapid cooling is not more than 10 seconds; and the cooling rate of the secondary cooling is 5 to 20°C / s. The method according to claim 3 .

5. The rapid cooling is performed using a quench roll, the secondary cooling is carried out using any one cooling device selected from a low-temperature inert gas spray and a water-cooled disk; the cooling rate of the secondary cooling is 5 to 20°C / s, The thickness of the alloy sheet is 0.15 to 0.45 mm. The method according to claim 4 .

6. The (b) milling step includes coarse pulverization and fine pulverization, The coarse crushing is carried out by hydrogen crushing, The fine pulverization is performed by a jet mill, the jet mill is performed in an inert gas atmosphere, and the inert gas is selected from nitrogen gas and helium gas; the particle size SMD of the alloy powder is between 2.0 and 3.4 μm, and X90 / X10≦4.5, where X90 represents the particle size value corresponding to a cumulative distribution percentage of 90%, and X10 represents the particle size value corresponding to a cumulative distribution percentage of 10%, During fine grinding, a lubricant is added, After adding the lubricant, further mixing is carried out, and the mixing time is 3 to 6 hours. The press-molding step (c) specifically includes press-molding the alloy powder under the action of a magnetic field to obtain a billet, Before press molding, the material is magnetized and oriented under a magnetic field strength of 2T, and then molded. After press molding, a reverse magnetic field is applied to demagnetize the material. The formed billet is further processed in a cold isostatic press to further increase the billet density. The manufacturing method according to any one of claims 3 to 5.

7. the (d) sintering step includes a first sintering, a first cooling, a second sintering, and a second cooling; The sintering process is carried out in a vacuum atmosphere, and the degree of vacuum during heating is 10-1 Pa or less; The sintering temperature of the first sintering is 1000 to 1050°C, and the temperature retention time of the first sintering is 240 to 360 minutes; The second sintering temperature is 30 to 70°C higher than the first sintering temperature, ie, 1030 to 1100°C. The second sintering temperature retention time is 270 to 360 minutes. The first cooling and the second cooling are both below 200°C, The sintering step further includes an aging treatment performed after the second cooling, The aging treatment is selected from one-step aging treatment or two-step aging treatment, The conditions of the single-step aging treatment are that the aging treatment temperature is between 500 and 700°C and the heat-retention time is between 240 and 420 minutes, The two-stage aging treatment includes: performing a first aging treatment by increasing the temperature to 800 to 950°C and holding the temperature for 180 to 300 minutes; and performing a second aging treatment by cooling the steel to 150°C or less and then increasing the temperature to between 450 to 600°C and holding the temperature for 240 to 360 minutes. After the sintering process, a diffusion treatment is carried out. The diffusion treatment includes applying a diffusion material to the magnet surface, and performing a vacuum high-temperature diffusion treatment, a diffusion cooling treatment, and a diffusion aging treatment; the diffusion material is selected from pure metals of Dy and / or Tb, or hydrides, oxides, hydroxides, and fluorides of Dy and / or Tb; The diffusion treatment is carried out by selecting a method such as vacuum deposition, magnetron sputtering, coating or embedding. The temperature of the high-temperature diffusion is 850 to 950°C, and the time of the high-temperature diffusion is 10 to 30 hours. The diffusion cooling temperature is less than 100°C, The temperature of the diffusion aging treatment is 450 to 600°C, and the time of the diffusion aging treatment is 4 to 8 hours. The method according to claim 3 .

8. A neodymium iron boron magnet as described in claim 1 or 2, used in the manufacture of a motor.

9. A motor comprising the neodymium-iron-boron magnet according to claim 1 or 2.

10. A motor as described in claim 9, which is applied to a new energy vehicle or an energy-saving home appliance.

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