Sintered magnet based on rare earth iron-carbon alloy and preparation process thereof

Abstract

The invention discloses a sintered magnet based on a rare earth iron-carbon alloy and a preparation process of the sintered magnet, and belongs to the technical field of permanent magnet materials. The sintered magnet based on the rare earth-iron-carbon alloy is prepared through a method of orientation profiling, sintering and two-stage heat treatment, and the sintered magnet based on the rare earth-iron-carbon alloy prepared through the technology is prepared from a main phase RE2 (Fe, M) 14 (C, N)-2 (Fe, M) 14 (C, N)-2 (Fe, M)-2 (Fe, M)-4 (C, N)-2 (Fe The sintered rare earth permanent magnet is composed of a rare earth element (A, B), a grain boundary phase (including a rare earth element, a rare earth oxide and a transition metal-rich phase (such as a Zr-rich phase), alpha-Fe, a RE2Fe17Cx (x = 1, 2 or 3) phase and a rare earth carbide (such as REC2 and RE2C3), has high magnetic energy product and coercive force, and is a novel high-performance sintered rare earth permanent magnet.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth permanent magnet materials, and in particular relates to a sintered magnet based on a rare earth iron-carbon alloy and a preparation process thereof. Background Art

[0002] Permanent magnetic materials are widely used in energy, transportation, medical and other fields. Compared with samarium cobalt permanent magnets, neodymium iron boron permanent magnets have a higher magnetic energy product and stronger comprehensive magnetic properties. However, their anisotropy field is lower, making it difficult to obtain high coercive force. In addition, the large-scale production of neodymium iron boron has led to an unbalanced utilization of rare earth resources. 14 C permanent magnet material has the same 14 B has the same tetragonal crystal structure and similar magnetic properties. 14 Compared with B permanent magnet materials, light rare earth iron carbon compounds have higher magnetocrystalline anisotropy field and can obtain high coercivity without adding heavy rare earth. 14 C permanent magnet materials are very important for solving the problems faced by rare earth resources.

[0003] Traditional preparation of RE2Fe 14 The main methods for C-based compounds are melting ingots with long annealing time, rapid quenching of melts with short annealing time, and mechanical alloying. 14 The C phase has poor stability and can only be obtained through slow solid phase transformation within a specific temperature range. Some researchers have obtained RE2Fe by annealing the ingot for 4 weeks. 14 C phase, but due to the long annealing time, the grains grow excessively and its coercivity is very low. The melt rapid quenching method is to first melt the ingot into an amorphous or nanocrystalline ribbon. Due to the small grains, the solid phase reaction speed is greatly accelerated, so a short annealing time is performed to obtain RE2Fe 14 C phase. As for the mechanical alloying method, although the preparation process is simple, the coercive force and magnetic energy product obtained are not high. 14 C compound, it needs to be further prepared into magnets before it can be truly applied. Currently, most researchers choose to use rapid quenching strips as precursors and prepare RE2Fe through hot pressing and hot deformation processes. 14 C-based magnets, but this method is difficult to produce in bulk, resulting in low production efficiency. Furthermore, the magnetic energy product still lags behind sintered magnets, limiting the further application of RE-Fe-C compounds. Currently, methods for preparing rare earth iron-carbon alloys can only produce alloys, but are still unable to produce magnets suitable for industrial mass production. Therefore, a process for preparing sintered magnets based on rare earth iron-carbon alloys is needed. Summary of the Invention

[0004] In order to solve the problems in the prior art that rare earth iron-carbon based alloys cannot be quickly mass-produced and that the magnets in the prior art have many defects and poor magnetic energy product, the present invention proposes a sintered magnet based on rare earth iron-carbon alloy and a preparation process thereof. The preparation process of the present invention can be applied in engineering.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] The present invention provides a sintered magnet based on a rare earth iron-carbon alloy, the general chemical formula of which is RE x Fe y M 100-y-x-z- w B w C z , wherein x, y, z and w are the atomic percentages of each element, x refers to the sum of the atomic percentages of all rare earth elements, 10≤x≤20, 70≤y≤81, 2≤z≤8, 0<w≤2; RE is at least two of Y, La, Ce, Pr, Nd, and Sm; M is at least four of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Zr, Nb, Ag, Hf, Mo, W, and Ta.

[0007] Compared with the existing rare earth permanent magnet alloy, the present invention adds carbon, so the quick-setting sheet and the final magnet contain RE2 (Fe, M) 14 (C,B),α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase, grain boundary phase (including rare earth element, rare earth oxide and transition metal-rich phase (such as Zr-rich phase)) and rare earth carbide (such as REC2, RE2C3), combined with the step of annealing the rapid solidification sheet, greatly increases RE2(Fe,M) 14 The content of (C, B) improves the performance of the sintered magnet. In the sintered magnet based on the rare earth iron-carbon alloy of the present invention, the carbon content is greater than 2 at.%, preferably the carbon content is 2-8 at.%, and more preferably the carbon content is 3-6 at.%. The C element enters the alloy during the smelting process and can be added in the form of an alloy or a single substance to participate in the formation of RE2(Fe, M) 14 (C, B) main phase. The sintered magnet based on the rare earth iron-carbon alloy of the present invention contains a certain amount of dispersed α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbide (such as REC2, RE2C3) phase, these phases are generated during the smelting and rapid solidification process, rather than external addition, and the α-Fe, R2Fe 17 C x(x=1, 2 or 3) phase and rare earth carbide phase (such as REC2, RE2C3), thereby forming different α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbide (such as REC2, RE2C3) phase content magnets, thereby improving the performance of the magnets.

[0008] Exemplarily, the chemical formula of the sintered magnet based on rare earth iron carbon alloy is Pr 14 Nd4Fe 72.48 Al 0.96 Cu 0.20 Ga 0.20 Zr 0.16 B2C6、LaCe2Pr5Nd3Fe 80.4 V 1.01 Si 0.2 Ti 0.2 Nb 0.1 Mo 0.04 Ta 0.04 W 0.01 B1C6 or Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 BC5.

[0009] The present invention also provides a process for preparing the above-mentioned sintered magnet based on rare earth iron-carbon alloy, comprising the following steps:

[0010] Weigh the raw materials according to the general chemical formula, wherein the amount of rare earth is increased by 1-5 wt.% based on the theoretical amount of rare earth calculated according to the general chemical formula;

[0011] The raw materials are smelted and then rapidly solidified after smelting to obtain rapid solidification sheets. The rapid solidification sheets prepared by the present invention mainly contain RE2(Fe, M) 14 (C,B) phase (main phase), α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase, rare earth carbide (such as REC2, RE2C3) phase and grain boundary phase (including rare earth element, rare earth oxide and transition metal-rich phase (such as Zr-rich phase)), among which RE2(Fe,M) 14 The (C, B) phase content is above 75wt.%, the α-Fe content is below 3wt.%, and the R2Fe 17 C xThe content of (x=1, 2 or 3) phase is less than 22wt.%, the content of rare earth carbide is less than 6wt.%, and the rest is grain boundary phase; the thickness of the quick-setting sheet is 150-350μm, and the main phase grains and rare earth-rich phase grains inside are columnar crystals, arranged alternately in radial patterns; α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbides are dispersed inside and at the boundaries of the main phase grains;

[0012] The quick-setting sheet is sequentially annealed and rapidly cooled, and the rapidly cooled quick-setting sheet is subjected to hydrogen crushing and air flow milling to obtain air flow milled powder;

[0013] The jet milled powder is subjected to orientation pressing, sintering and two-stage heat treatment to obtain the sintered magnet based on the rare earth iron-carbon alloy.

[0014] The sintered magnet based on rare earth iron carbon alloy prepared by the process of the present invention is composed of the main phase RE2 (Fe, M) 14 (C, B), grain boundary phase (including rare earth elements, rare earth oxides and transition metal-rich phases (such as Zr-rich phases)) and α-Fe, R2Fe 17 C x phase and rare earth carbide; among which sintered magnet RE2(Fe,M) 14 The (C, B) phase content is above 86wt.%, the α-Fe content is below 2wt.%, and the R2Fe 17 C x The content of (x=1, 2 or 3) phase is less than 12wt.%, the content of rare earth carbide is less than 4wt.%, and the rest is grain boundary phase; the main phase is equiaxed micron crystal with a length of 1-6μm; α-Fe and R2Fe 17 C x (x = 1, 2 or 3) phase is dispersed in the main phase grains and boundaries; the grain boundary phase is distributed in the thin layer grain boundaries and triangular grain boundaries; rare earth carbides are distributed in the main phase grain boundaries and grain boundaries in agglomerates. RE2(Fe,M) 14 The (C,B) phase is the most abundant phase in sintered magnets and also has a high magnetocrystalline anisotropy field and remanent magnetization. The higher the magnetocrystalline anisotropy field, the larger the reverse magnetic field required for magnetization reversal, thus having the potential to achieve a higher coercive force. Therefore, increasing the mass fraction of this phase is very helpful in improving the remanence and coercive force of sintered magnets. α-Fe, R2Fe 17 C x The content of (x=1, 2 or 3) and rare earth carbides can be controlled by annealing the quick-setting sheet, sintering the magnet and heat treating the magnet. α-Fe has a certain contribution to the relative saturation magnetic moment, but it is easy to cause the coercive force to decrease, so its content needs to be controlled at a low level. 17 C x(x=1, 2 or 3) and rare earth carbides have an adverse effect on coercivity, so their content also needs to be controlled.

[0015] Exemplarily, the melting is selected from arc melting or induction melting.

[0016] Preferably, the preparation process of the quick-setting sheet is as follows: the weighed raw materials are placed in a vacuum induction melting quick-setting crucible, and the cavity is evacuated to a vacuum degree of 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum degree in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2 When the pressure drops below 400 Pa, the vacuum system is turned off, and then argon is filled into the cavity, and the power is increased to 13.5kW for smelting. When all the raw materials are melted, the power is reduced to 10kW for refining for 3 minutes to make the alloy liquid composition fully uniform. After refining, the quick-setting system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller with a rotation speed of 0.5-2m / s. Finally, a quick-setting sheet with uniform thickness of 150-350μm is obtained.

[0017] The present invention does not limit the annealing method, as long as the annealing effect can be achieved. Exemplarily, the annealing method includes but is not limited to being carried out in a non-vacuum muffle furnace with protective gas purge, in a vacuum muffle furnace, and in a sintering furnace filled with protective gas. Preferably, the annealing in the present invention is carried out using a vacuum sintering furnace, a muffle furnace, or a tubular furnace under argon protection, and the annealing temperature of the quick-setting sheet is 600-1150°C, and the annealing time is 1-20h. Preferably, the annealing temperature is 900-1050°C, and the annealing time is 1-5h.

[0018] The present invention does not limit the rapid cooling method, as long as it can achieve the rapid cooling effect. Exemplary rapid cooling methods include but are not limited to ice water quenching, purging with cold protective gas, etc. The present invention preferably uses cold argon purging as the rapid cooling process.

[0019] Hydrogen crushing is used to coarsely pulverize the quick-setting flakes. Other coarse crushing methods may also be used, including but not limited to mortar pounding and mechanical crushing with a jaw crusher. After coarse crushing, the powder has a particle size of 45-355 μm. Hydrogen crushing is the preferred coarse crushing method in this invention, with a hydrogen absorption temperature of room temperature and a dehydrogenation temperature of 400°C-650°C.

[0020] Jet milling is used to obtain a finer powder (i.e., fine pulverization). Ball milling can also be used instead of jet milling. After fine pulverization, the powder has a particle size of 1-7 μm. The preferred fine pulverization method for this invention is jet milling, performed in an atmosphere with an oxygen content of less than 80 ppm, at a rotation speed of 3600-5000 rpm, using nitrogen or argon as the gas.

[0021] In the present invention, after obtaining the alloy powder, the densification method is as follows: pressing it into a green body in an orientation press, the magnetic field strength of the press is preferably 1T-2T, the pressure is 20-30MPa, and the pressing time can be the time commonly used in the art, such as 5-30s.

[0022] After orientation pressing, the density of the green compact is relatively low. To further increase the density of the green compact, it is necessary to perform cold isostatic pressing. During the cold isostatic pressing process, the vacuum-sealed green compact is placed in a cylinder and pressurized to 200-300 MPa, preferably 225 MPa, for 0.5-5 minutes, preferably 3 minutes.

[0023] Furthermore, the sintering temperature is 1000-1100° C., and the sintering time is 1-20 hours, preferably the sintering temperature is 1020-1080° C. The sintering atmosphere is preferably a vacuum or argon atmosphere.

[0024] Furthermore, the two-stage heat treatment (two-stage aging heat treatment) includes a primary heat treatment and a secondary heat treatment, wherein the temperature of the primary heat treatment is 450-970°C, and the holding time is 3 hours; the temperature of the secondary heat treatment is 480-660°C, and the holding time is 4 hours; preferably, the temperature of the primary heat treatment is 880-970°C; and the temperature of the secondary heat treatment is 540-660°C.

[0025] The present invention also provides applications of the rare earth iron-carbon alloy-based sintered magnet in the fields of energy, consumer electronics, transportation and / or medical treatment.

[0026] Exemplarily, the sintered magnets based on the rare earth iron-carbon alloy are used to prepare motors, household appliances, medical devices, drives, or magnetic separation equipment. For example, the sintered magnets based on the rare earth iron-carbon alloy of the present invention can be used to prepare high-efficiency and energy-saving motors (such as permanent magnet motors), new energy vehicle motors, and micromotors (such as mobile phone vibration motors and micro fans). They can also be used to prepare permanent magnet direct-drive generator sets for wind power generation, household appliances such as variable-frequency air conditioners and variable-frequency refrigerators, magnetic resonance imaging (MRI) equipment, hard disk drives, aerospace sensors, and suspension systems for magnetic levitation trains.

[0027] The principle of the present invention is:

[0028] The present invention prepares alloy powder through the process of batching-melting-rapid solidification-annealing-quenching-crushing, and then prepares sintered magnet based on rare earth iron carbon alloy through the method of orientation pressing-sintering-two-stage heat treatment. The sintered magnet based on rare earth iron carbon alloy prepared by the process of the present invention is composed of main phase RE2 (Fe, M) 14 (C, B), grain boundary phase (including rare earth elements, rare earth oxides and transition metal-rich phases (such as Zr-rich phases)) and α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbide; wherein the sintered magnet RE2(Fe,M) 14 The (C, B) phase content is above 86wt.%, the α-Fe content is below 2wt.%, and the R2Fe 17 C x The content of (x=1, 2 or 3) phase is less than 12wt.%, the content of rare earth carbide is less than 4wt.%, and the rest is grain boundary phase; the main phase is equiaxed micron crystal with a length of 1-6μm; α-Fe and R2Fe 17 C x The (x=1, 2 or 3) phase is dispersed inside and at the boundaries of the matrix phase grains; the rare earth-rich phase is distributed in the thin layer grain boundaries and the triangular grain boundaries; transition metal carbides and / or borides are mostly distributed in the triangular grain boundaries in the form of rods; rare earth carbides are distributed in the form of agglomerates at the grain boundaries of the main phase and in the rare earth-rich phase.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] The present invention provides a sintered magnet based on a rare earth iron-carbon alloy and a preparation process thereof. First, a large amount of rare earth iron-carbon based alloy powder is obtained through the process of smelting-rapid solidification-annealing-quenching-crushing, and then sintering and two-stage heat treatment are performed to obtain a sintered magnet based on a rare earth iron-carbon alloy. The sintered magnet is a high-performance rare earth iron-carbon based magnet containing a certain amount of dispersed α-Fe and R2Fe. 17 C x phase, and the α-Fe and R2Fe phases can be adjusted by heat treatment process. 17 C x (x = 1, 2 or 3) phase content, thereby forming different α-Fe and R2Fe 17 C x (x=1, 2 or 3) phase content magnets. This type of magnet does not require the addition of heavy rare earth elements, which can reduce the production cost of magnets and save scarce resources.

[0031] The sintered magnet based on the rare earth iron carbon alloy of the present invention has high magnetic energy product and squareness, which shows that the method and process of the present invention are relatively reasonable and can prepare high-performance rare earth iron carbon based sintered magnets. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 The XRD test results and powder XRD refinement pattern of the quick-setting sheet obtained in S2 in Example 1, wherein (a) is the XRD test result and (b) is the powder XRD refinement pattern;

[0034] Figure 2 The backscattered diffraction electron images of the roller-attached surface and the cross-sectional backscattered diffraction electron images of the quick-setting sheet obtained in S2 in Example 1 are shown, where (a) and (b) are backscattered diffraction electron images of the roller-attached surface, and (c) and (d) are backscattered diffraction electron images of the cross-sectional backscattered diffraction electron images;

[0035] Figure 3 Backscattered diffraction electron images of the free surface and cross section of the medium-speed solidified sheet in Example 1 after annealing at 1050°C for 2 hours, (a) is 10 μm, (b) is 1 μm;

[0036] Figure 4 X-ray diffraction spectra of sintered magnets obtained from S7 in Examples 1 to 7 (a) and XRD refinement patterns of sintered magnets obtained from S7 in Example 2 at a sintering temperature of 1020°C (b), from S7 in Example 1 at a sintering temperature of 1070°C (c), and from S7 in Example 3 at a sintering temperature of 1080°C (d);

[0037] Figure 5 Backscattered diffraction electron images of the sintered magnet obtained in Example 1 at a sintering temperature of 1070°C in S7, (a) is 10 μm, (b) is 1 μm;

[0038] Figure 6 The backscattered diffraction electron image and elemental surface scanning results of the sintered magnet based on the rare earth iron-carbon alloy in Example 1, where (a) and (b) are backscattered diffraction electron images, and the image on the right is the elemental surface scanning result of area (b);

[0039] Figure 7 The XRD spectra and XRD refinement patterns of the roller-attached surface and free surface of the quick-setting sheet obtained in Example 22, wherein (a) is the XRD spectrum and (b) is the XRD refinement pattern;

[0040] Figure 8 is the X-ray diffraction spectrum of the sintered magnets in Example 22 and Example 23;

[0041] Figure 9The XRD spectra of the roller surface and free surface of the rapid solidification sheet and the powder XRD refinement pattern of Comparative Example 1, where (a) is the XRD spectrum and (b) is the XRD refinement pattern;

[0042] Figure 10 The X-ray diffraction spectrum and powder XRD refinement pattern of the sintered magnet of Comparative Example 1, wherein (a) is the X-ray diffraction spectrum of the sintered magnet of Comparative Example 1, and (b) is the powder XRD refinement pattern of the sintered magnet of Comparative Example 1;

[0043] Figure 11 This is the backscattered diffraction electron image of the sintered magnet of Comparative Example 1. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0046] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0050] All raw materials used in the examples of the present invention are commercially available.

[0051] In the embodiment of the present invention, “high-purity argon gas” refers to argon gas with a purity of 99.999% or more.

[0052] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0053] The technical solution of the present invention is further illustrated by the following examples.

[0054] Example 1

[0055] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, and the steps are as follows:

[0056] S1. According to the chemical formula Pr 14 Nd4Fe 72.48 Al 0.96 Cu 0.20 Ga 0.20 Zr 0.16 The stoichiometric ratio of B2C6 is such that the mass of all rare earth elements is increased by 1.5 wt.% compared to the mass calculated according to the above general chemical formula;

[0057] S2. Place Pr, Nd, Fe, Al, Cu, Ga, Zr, FeC alloy, and FeB alloy with a purity higher than 99% in a water-cooled crucible of a medium-frequency induction melting furnace, close the chamber, and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum degree in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2 When the pressure drops below 0.05 Pa, the vacuum system is turned off, and argon is then filled into the chamber. The power is increased to 13.5kW for smelting. When all the raw materials are melted, the power is reduced to 10kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid solidification system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller with a rotation speed of 1.8m / s. Finally, a rapid solidification sheet with uniform thickness of about 280μm is obtained.

[0058] S3. Anneal the quick-setting sheet under argon protection and air-cool it. The specific steps are as follows: put the prepared large batch of quick-setting sheets into a vacuum sintering furnace and evacuate to 5×10 -3 Pa and filled with high-purity argon, heated to 1050 ° C and kept for 2 h (i.e. annealed at 1050 ° C for 2 h), and after annealing, the sample was purged with cold argon for air cooling;

[0059] S4. After annealing, the quick-setting sheets were manually crushed and placed in a stainless steel container and placed in a rotary hydrogen treatment furnace, and then vacuumed to 5×10 -3 Pa, close the vacuum system, introduce 99.999% pure hydrogen to 75kPa, and absorb hydrogen for 1 hour at room temperature. During the hydrogen absorption process, the hydrogen pressure in the furnace must be maintained. After the hydrogen absorption is completed, open the vacuum system to discharge the remaining hydrogen in the furnace. When the vacuum degree drops to 5×10 -2 After the temperature is below Pa, the heating system is turned on, and the temperature is raised to 550℃ and kept for 5 hours for dehydrogenation treatment. After the dehydrogenation is completed, argon is filled and air-cooled to room temperature. Under nitrogen protection, the hydrogen explosion powder is taken out and placed in a sealed can for standby use;

[0060] S5. The airflow mill was filled with nitrogen. After the oxygen content dropped below 70 ppm, the hydrogen explosion powder was poured into the airflow mill. The speed was set to 4800 rpm. After 1 h of grinding, the airflow mill was removed.

[0061] S6. After the oxygen content in the pulsed magnetic field forming press was reduced to below 200 ppm using nitrogen, the press was pressed under a 1.8 T magnetic field. The vacuum-sealed green compact was then placed in a cold isostatic press and pressurized to 225 MPa for 3 minutes.

[0062] S7. The compact was placed in a vacuum sintering furnace and heated in a stepwise manner at 430°C, 600°C, and 800°C for 1 hour, and then heated to 1070°C for 3 hours (i.e., the sintering temperature in this embodiment is 1070°C). The compact was then cooled to room temperature with argon gas to obtain a sintered magnet.

[0063] S8. The magnet sintered at 1070°C was placed in a vacuum sintering furnace, heated to 950°C and held for 3 hours for primary heat treatment, and then cooled to room temperature with argon gas.

[0064] S9. Place the magnet sintered at 1070°C and subjected to primary heat treatment at 950°C into a vacuum sintering furnace, raise the temperature to 600°C and maintain the temperature for 4 hours for secondary heat treatment, and then cool it to room temperature with argon gas to obtain a sintered magnet based on a rare earth iron-carbon alloy.

[0065] The XRD test results of the quick-setting sheet and the powder XRD refinement pattern obtained in step S2 are as follows: Figure 1 As shown, it can be seen that the main diffraction peak in the quick-setting sheet corresponds to Pr2Fe 14 The diffraction peaks of (C, B) are shown in Figure 2, in which the main phase accounts for about 90wt.%, and the rest contains rare earth-rich phase (including Pr, Pr2O3, PrO2), as well as a small amount of α-Fe (black spots), Pr2Fe 17 C x(dark gray phase) and rare earth carbide (lumpy white contrast phase, including PrC2 and Pr2C3). The mass fractions of different phases in the XRD refinement results of the quick-setting sheet are shown in Table 1; the lattice constants and unit cell volumes of the main phases in the XRD refinement results of the quick-setting sheet are shown in Table 2. For comparison, the Pr2Fe 14 B and Pr2Fe 14 C 0.95 B 0.05 The lattice parameters of the two phases are also listed in Table 2. It can be seen that the lattice constant c and unit cell volume of the quick-setting sheet are between the two phases (Pr2Fe 14 B and Pr2Fe 14 C 0.95 B 0.05 ), indicating that the C element has entered the main phase lattice.

[0066] Table 1 Mass fraction of different phases in the XRD refinement results of the rapid solidification sheet

[0067]

[0068]

[0069] Table 2 Lattice constants and unit cell volumes of the main phase in the XRD refinement results of the rapid solidification sheet

[0070]

[0071] The backscattered diffraction electron image of the quick-setting sheet roller surface and the cross-section backscattered diffraction electron image obtained in step S2 are as follows: Figure 2 As shown, the roller surface shows a flower-like distribution of nucleation points (such as Figure 2 As shown in the red circle in (a), Figure 2 The white contrast in (b) corresponds to the Pr-rich phase or Pr-C phase, which is unevenly distributed and partially exists in the form of clumps. Figure 2 In images (c) and (d), columnar crystals of the primary phase (grey contrast) grow radially from the nucleation point, alternating between the primary phase and the rare-earth-rich phase. Notably, diffusely distributed black particles are observed in both the backscattered diffraction (BSD) electron images of the roller surface and the cross-sectional BSD electron images. Based on the energy spectrum, these particles correspond to the α-Fe phase.

[0072] Step S3: After annealing at 1050℃ for 2h, the backscattered diffraction electron images of the free surface and cross section of the quick-setting sheet are as follows: Figure 3 As shown in the figure, it can be seen that the black particles in the free surface and cross section of the quick-setting sheet after annealing have basically disappeared, indicating that the α-Fe content in the sample can be adjusted through appropriate annealing treatment.

[0073] Example 2

[0074] This embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the sintering temperature in S7 is 1020°C.

[0075] Example 3

[0076] This embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the sintering temperature in S7 is 1080°C.

[0077] Example 4

[0078] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the sintering temperature in S7 is 1030°C.

[0079] Example 5

[0080] This embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the sintering temperature in S7 is 1040°C.

[0081] Example 6

[0082] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of embodiment 1, except that the sintering temperature in S7 is 1060°C.

[0083] Example 7

[0084] This embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the sintering temperature in S7 is 1050°C.

[0085] The X-ray diffraction spectra of the sintered magnets obtained by S7 in Examples 1 to 7 are as follows: Figure 4 As shown in the figure, the orientation of the magnets is relatively good at all sintering temperatures. Compared with the quick-setting sheets, the α-Fe and 2:17 phases in the sintered magnet samples have been greatly reduced or even disappeared, indicating that the sintering process can continue to adjust the content of α-Fe and 2:17 phases while achieving densification.

[0086] The mass fractions of different phases in the XRD refinement results of the sintered magnets obtained when the sintering temperature of S7 in Example 2 is 1020°C, the sintering temperature of S7 in Example 1 is 1070°C, and the sintering temperature of S7 in Example 3 is 1080°C are shown in Table 3. The lattice constants and unit cell volumes of the main phases of the sintered magnets obtained when the sintering temperature of S7 in Example 2 is 1020°C, the sintering temperature of S7 in Example 1 is 1070°C, and the sintering temperature of S7 in Example 3 is 1080°C are shown in Table 4. The lattice constants (c) and unit cell volumes of the sintered magnets are not much different from those of the quick-setting sheets, and are still between Pr2Fe 14 B and Pr2Fe 14 C 0.95 B 0.05 This shows that after the homogenization treatment of sintering, the C element still exists in the main phase lattice.

[0087] Table 3 Mass fractions of different phases in XRD refinement results of magnets sintered at different sintering temperatures

[0088]

[0089] Table 4 Lattice constants and unit cell volumes of the main phase in XRD refinement results of magnets sintered at different sintering temperatures

[0090]

[0091] The magnetic properties and density (ρ) of the sintered magnets obtained at different sintering temperatures S7 in Examples 1 to 7 are shown in Table 5. The coercive force (H cj ), remanence (B r ) and magnetic energy product ((BH) max ) all reach their maximum values when sintered at 1070℃, which are 12.29kOe, 13.24kGs and 43.76MGOe respectively.

[0092] Table 5 Magnetic properties and density of sintered magnets of Example 1 to Example 7

[0093]

[0094]

[0095] The backscattered diffraction electron image of the sintered magnet obtained by sintering S7 at a temperature of 1070°C in Example 1 is as follows: Figure 5 As shown in the figure, it can be seen that there are more thin-layer grain boundary phases in the sintered magnet, the grain size in the magnet is small, and the distribution is relatively uniform.

[0096] Example 8

[0097] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 970°C.

[0098] Example 9

[0099] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 930°C.

[0100] Example 10

[0101] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 910°C.

[0102] Example 11

[0103] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 880°C.

[0104] Example 12

[0105] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 850°C.

[0106] Example 13

[0107] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 820°C.

[0108] Example 14

[0109] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 480°C.

[0110] Example 15

[0111] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the primary heat treatment temperature in S8 is 450°C.

[0112] The magnetic properties of the magnets obtained by primary heat treatment at different temperatures are shown in Table 6. The magnet heat treated at 950℃ obtained the maximum coercivity, remanence and magnetic energy product, reaching 14.48kOe, 13.45kG and 45.15MGOe respectively.

[0113] Table 6 Magnetic properties of magnets obtained by primary heat treatment at different temperatures

[0114]

[0115] Note: "1070℃" in Table 6 refers to the sintered magnet obtained in step S7 of Example 1 without the primary heat treatment; "1070℃-450℃" refers to the sintering temperature of 1070℃ and the primary heat treatment temperature of 450℃, and so on.

[0116] Example 16

[0117] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the secondary heat treatment temperature in S9 is 630°C.

[0118] Example 17

[0119] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the secondary heat treatment temperature in S9 is 660°C.

[0120] Example 18

[0121] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of embodiment 1, except that the secondary heat treatment temperature in S9 is 570°C.

[0122] Example 19

[0123] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the secondary heat treatment temperature in S9 is 540°C.

[0124] Example 20

[0125] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the secondary heat treatment temperature in S9 is 510°C.

[0126] Example 21

[0127] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, which is the same as that of Example 1, except that the secondary heat treatment temperature in S9 is 480°C.

[0128] The magnetic properties of sintered magnets obtained by secondary heat treatment at different temperatures are shown in Table 7. The secondary heat treatment significantly optimizes the microstructure of the magnet, further enhances the demagnetizing coupling effect, and makes the magnetization reversal of the magnet more consistent.

[0129] Table 7 Magnetic properties of sintered magnets obtained by secondary heat treatment at different temperatures

[0130]

[0131]

[0132] Note: In Table 7, 1070℃ in “1070℃-950℃-480℃” means the sintering temperature is 1070℃, 950℃ means the primary heat treatment temperature is 950℃, 480℃ means the secondary heat treatment temperature is 480℃, and so on.

[0133] The backscattered diffraction electron image and element surface scanning results of the sintered magnet based on rare earth iron carbon alloy in Example 1 are as follows: Figure 6 As shown in the figure, the distribution of the rare earth-rich phase is significantly improved after the secondary heat treatment, with more thin grain boundary phases appearing and increasing in thickness. This helps further enhance the demagnetizing coupling between adjacent grains and improves the coercivity. Furthermore, Zr enrichment is observed in this sample. This Zr-rich phase appears within the grain boundary phase and appears as a dark, island-like structure in the backscattered diffraction electron image.

[0134] Example 22

[0135] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy, and the steps are as follows:

[0136] S1. According to the chemical formula LaCe2Pr5Nd3Fe 80.4 V 1.01 Si 0.2 Ti 0.2 Nb 0.1 Mo 0.04 Ta 0.04 W 0.01 The stoichiometric ratio in B1C6, wherein the mass of each rare earth element is increased by 1.5 wt.% compared to the mass calculated according to the above chemical formula;

[0137] S2. Place Pr, La, Ce, Nd, V, Si, Ti, Nb, Mo, Ta, and W elements with a purity higher than 99% (i.e., the purity of the above elements is higher than 99%), FeC alloy, and FeB alloy in a water-cooled crucible of a medium-frequency induction melting furnace, close the chamber, and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum degree in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2When the pressure drops below 0.05 Pa, the vacuum system is turned off, and argon is then filled into the chamber. The power is increased to 13.5kW for smelting. When all the raw materials are melted, the power is reduced to 10kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid solidification system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller with a rotation speed of 1.8m / s. Finally, a rapid solidification sheet with uniform thickness of about 290μm is obtained.

[0138] Steps S3-S6 are the same as in Example 1;

[0139] S7. The compact was placed in a vacuum sintering furnace and heated in a stepwise manner at 430°C, 600°C, and 800°C for 1 hour, and then heated to 1020°C for 3 hours (i.e., the sintering temperature in this embodiment is 1020°C). The compact was then cooled to room temperature with argon gas to obtain a sintered magnet.

[0140] S8. The sintered magnet was placed in a vacuum sintering furnace, heated to 805°C and held for 3 hours for primary heat treatment, and then cooled to room temperature with argon gas.

[0141] S9. Place the magnet that has undergone primary heat treatment into a vacuum sintering furnace, raise the temperature to 600°C and keep it at this temperature for 4 hours for secondary heat treatment, and then cool it to room temperature with argon gas to obtain a sintered magnet based on a rare earth iron-carbon alloy.

[0142] Example 23

[0143] This embodiment provides a preparation process for a sintered magnet based on a rare earth iron-carbon alloy. The specific steps are the same as those in Example 22, with the only difference being that the sintering temperature in S7 is 1040°C.

[0144] The XRD spectra (a) and XRD refinement patterns (b) of the roller surface and free surface of the quick-setting sheet obtained in Example 22 are as follows: Figure 7 As shown in the figure, it can be seen that the roller surface of the quick-setting sheet still shows a strong (00L) surface c-axis texture.

[0145] The mass fractions of different phases in the XRD refinement results of the medium-speed solidification sheet in Example 22 are shown in Table 8.

[0146] Table 8 Mass fractions of different phases in the XRD refinement results of the rapid solidification sheet of Example 22

[0147]

[0148] The X-ray diffraction spectra of the sintered magnets in Example 22 and Example 23 are as follows: Figure 8 As shown, it can be seen that the sample still exhibits the diffraction peak of the main phase.

[0149] The magnetic properties and density of the sintered magnets and the magnets after the primary heat treatment in Example 22 and Example 23 are shown in Table 9. It can be seen that the coercive force of the magnets is improved after the primary heat treatment.

[0150] Table 9 Magnetic properties and density of sintered magnets and magnets after primary heat treatment in Example 22 and Example 23

[0151]

[0152] Note: In Table 9, “1020℃” refers to the sintered magnets obtained at a sintering temperature of 1020℃, and “1020℃-805℃” refers to the magnets obtained at a sintering temperature of 1020℃ and a primary heat treatment temperature of 805℃; and so on.

[0153] Example 24

[0154] S1. According to the chemical formula Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 The stoichiometric ratio in BC5 is such that the mass of each rare earth element is increased by 1.5 wt.% compared to the mass calculated according to the above general chemical formula;

[0155] S2. Place Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, Ag (all of which have a purity higher than 99%), FeC alloy, and FeB alloy in a water-cooled crucible in a medium-frequency induction melting furnace, close the chamber, and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum degree in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2 When the pressure drops below 0.05 Pa, the vacuum system is turned off, and argon is then filled into the chamber. The power is increased to 13.5kW for smelting. When all the raw materials are melted, the power is reduced to 10kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid solidification system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller with a rotation speed of 1.8m / s. Finally, a rapid solidification sheet with uniform thickness of about 275μm is obtained.

[0156] Steps S3-S6 are the same as in Example 1;

[0157] S7. The compact was placed in a vacuum sintering furnace and heated in steps at 430°C, 600°C, and 800°C for 1 hour, and then heated to 1030°C for 3 hours (i.e., the sintering temperature in this embodiment is 1030°C). The compact was then cooled to room temperature with argon gas to obtain a sintered magnet.

[0158] S8. The sintered magnet is placed in a vacuum sintering furnace, heated to 750°C and held for 3 hours for primary heat treatment, and then cooled to room temperature with argon gas.

[0159] S9. The magnets that had undergone primary heat treatment were placed in a vacuum sintering furnace, heated to 450°C and held there for 4 hours for secondary heat treatment. The magnets were then cooled to room temperature with argon gas to produce sintered magnets based on a rare earth iron-carbon alloy. The magnetic properties of the sintered magnets, and the magnets that underwent primary and secondary heat treatments in Example 24 are shown in Table 10.

[0160] Table 10 Magnetic properties of the sintered magnet and the magnet after two-stage heat treatment in Example 24

[0161]

[0162] Note: In Table 10, “1030℃” refers to the sintered magnets obtained at a sintering temperature of 1030℃; “1030℃-750℃” refers to the magnets obtained at a sintering temperature of 1030℃ and a primary heat treatment temperature of 750℃; “1030℃-750℃-450℃” refers to the magnets obtained at a sintering temperature of 1030℃, a primary heat treatment temperature of 750℃, and a secondary heat treatment temperature of 450℃.

[0163] Comparative Example 1

[0164] This comparative example provides a preparation process for a sintered magnet, and the specific steps are as follows:

[0165] S1. According to the stoichiometric ratio Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 BC5 ratio, where the mass of Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, and Ag is the same as the general formula Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 Compared with the mass calculated for BC5, it increased by 1.5wt.%;

[0166] S2. Place Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, and Ag (all of which have a purity higher than 99%), FeC alloy, and FeB alloy into a water-cooled crucible in a medium-frequency induction rapid solidification furnace, close the chamber, and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2 When the pressure drops below 0.05 Pa, the vacuum system is shut off. Argon is then introduced into the chamber, and the power is increased to 13.5 kW for smelting. Once all the raw materials have melted, the power is reduced to 10 kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid setting system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller rotating at a speed of 1.8 m / s. Finally, a uniform rapid setting sheet with a thickness of approximately 290 μm is obtained.

[0167] The rapidly solidified sheet was not annealed, and hydrogen explosion, airflow milling, and orientation pressing were directly performed (i.e., step S3 in Example 24 was not performed, and steps S4 to S6 were performed directly after step S2). The process was the same as that of Example 24. Sintering was performed by stepwise heating, with temperatures of 430°C, 600°C, and 800°C being maintained for 1 hour, respectively, to further remove residual hydrogen and impurities. Finally, the temperature was raised to 1030°C and maintained for 3 hours (i.e., the sintering temperature in this comparative example was 1030°C), and then cooled to room temperature with argon gas.

[0168] The XRD spectra (a) of the roller surface and free surface of the quick-setting sheet obtained in this comparative example and the XRD refined pattern of the powder (b) are shown in FIG. Figure 9 shown.

[0169] The mass fractions of different phases in the XRD refinement results of the rapid solidification sheet obtained in this comparative example are shown in Table 11. 17 The Cx (x=1, 2 or 3) phase content is relatively high, reaching 20.214 wt.%.

[0170] S8. The sintered magnet is placed in a vacuum sintering furnace, heated to 750°C and held for 3 hours for primary heat treatment, and then cooled to room temperature with argon gas.

[0171] S9. Place the magnet that has undergone primary heat treatment into a vacuum sintering furnace, raise the temperature to 450°C and keep it at that temperature for 4 hours for secondary heat treatment, and then cool it to room temperature with argon gas to obtain a sintered magnet based on rare earth iron-carbon alloy.

[0172] The mass fractions of different phases in the XRD refinement results of the sintered magnet of Comparative Example 1 are shown in Table 12. X-ray diffraction spectrum and XRD refinement spectrum of the sintered magnet of Comparative Example 1 Figure 10 As shown, the magnetic properties of the sintered magnet, primary and secondary heat-treated magnets in Comparative Example 1 are shown in Table 13. After heat treatment, the coercive force of the magnet reaches a maximum of 10.01 kOe, and the magnetic energy product is 30.32 MGOe, which is lower than that of the sample in Example 24.

[0173] The backscattered diffraction electron image of the sintered magnet of Comparative Example 1 is as follows: Figure 11 As shown, the dark gray contrast is RE2Fe 17 C x Phase, the large black area is α-Fe phase, which shows that the sintered magnet also contains a lot of RE2Fe 17 C x phase and α-Fe phase, which is consistent with the refinement results.

[0174] Comparative Example 1: The pellets were crushed, pulverized and sintered without annealing, resulting in the presence of a large amount of α-Fe and RE2Fe in the sintered magnets. 17 C x phase, excessive α-Fe and RE2Fe 17 C x On the one hand, the phase reduces the mass fraction of the main phase, and on the other hand, the magnetocrystalline anisotropy field of these two phases is low, which is not conducive to achieving high coercive force of the magnet.

[0175] Table 11 Mass fractions of different phases in the XRD refinement results of the rapid solidification sheet of comparative example 1

[0176]

[0177] Table 12 Mass fractions of different phases in XRD refinement results of sintered magnet of comparative example 1

[0178]

[0179] Table 13 Magnetic properties of sintered magnets and magnets subjected to two-stage heat treatment in Comparative Example 1

[0180]

[0181] Note: In Table 13, “1030℃” refers to the sintered magnets obtained at a sintering temperature of 1030℃; “1030℃-750℃” refers to the magnets obtained at a sintering temperature of 1030℃ and a primary heat treatment temperature of 750℃; “1030℃-750℃-450℃” refers to the magnets obtained at a sintering temperature of 1030℃, a primary heat treatment temperature of 750℃, and a secondary heat treatment temperature of 450℃.

[0182] Comparative Example 2

[0183] This comparative example provides a preparation process for a sintered magnet, and the specific steps are as follows:

[0184] S1. According to the stoichiometric ratio Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 B6 ratio, in which the mass of Y, Pr, LaCe, Nd, Cr, Co, Fe, Ni, Ti, Zn, and Ag is the same as that of the general formula Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 Compared with the mass calculated for B6, it increased by 1.5wt.%;

[0185] S2. Place Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, and Ag (all of which have a purity higher than 99%) and FeB alloy into a water-cooled crucible in a medium-frequency induction rapid solidification furnace, close the chamber, and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2 When the pressure drops below 0.05 Pa, the vacuum system is shut off. Argon is then introduced into the chamber, and the power is increased to 13.5 kW for smelting. Once all the raw materials have melted, the power is reduced to 10 kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid setting system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller rotating at a speed of 1.8 m / s. Finally, a uniform rapid setting sheet with a thickness of about 285 μm is obtained.

[0186] The process of steps S3-S9 is the same as that of Example 24.

[0187] The magnetic properties of the sintered magnet, primary and secondary heat-treated magnets in Comparative Example 2 are shown in Table 14. After heat treatment, the coercive force of the magnet reaches a maximum of 13.88 kOe, and the magnetic energy product is 37.29 MGOe, which is lower than the sample in Example 24.

[0188] Table 14 Magnetic properties of sintered magnets of Comparative Example 2

[0189]

[0190] Note: In Table 14, “1030℃” refers to the sintered magnets obtained at a sintering temperature of 1030℃; “1030℃-750℃” refers to the magnets obtained at a sintering temperature of 1030℃ and a primary heat treatment temperature of 750℃; “1030℃-750℃-450℃” refers to the magnets obtained at a sintering temperature of 1030℃, a primary heat treatment temperature of 750℃, and a secondary heat treatment temperature of 450℃.

[0191] Comparative Example 2 Compared with Example 24, all C is replaced by B, and the process remains unchanged. The sintered magnet has poor magnetic properties and its coercive force is significantly lower than that of the sample prepared under the same process in Example 24. This is because when RE is a light rare earth, RE2Fe 14 The magnetocrystalline anisotropy field of B is much lower than that of RE2Fe 14 Caused by C.

[0192] Comparative Example 3

[0193] This comparative example provides a preparation process for a sintered magnet, and the specific steps are as follows:

[0194] S1. According to the chemical formula Pr6Nd3Dy3Tb3HoFe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 The stoichiometric ratio of B6 is such that the mass of the individual elements Pr, La, Ce, Nd, Dy, Tb, Ho, Cr, Co, Fe, Ni, Ti, Zn, and Ag is increased by 1.5 wt.% compared to the mass calculated according to the above general chemical formula;

[0195] S2. Place Pr, La, Ce, Nd, Dy, Tb, Ho, Cr, Co, Fe, Ni, Ti, Zn, and Ag (all of which have a purity higher than 99%), FeC alloy, and FeB alloy into a water-cooled crucible in a medium-frequency induction rapid solidification furnace. Close the chamber and evacuate to 3×10 -2 Pa, turn on the power and use low power (2kW) to preheat to remove moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum in the furnace will rise slightly to 8×10 -2 Pa, and when the vacuum degree begins to drop again, increase the power to 5kW to dry the material, and wait until the vacuum degree drops to 3×10 -2When the pressure drops below 0.05 Pa, the vacuum system is shut off. Argon is then introduced into the chamber, and the power is increased to 13.5 kW for smelting. Once all the raw materials have melted, the power is reduced to 10 kW for refining for 3 minutes to fully homogenize the alloy liquid. After refining, the rapid setting system is turned on, and the crucible is tilted to allow the alloy liquid to be cast through the runner onto the surface of a water-cooled copper roller rotating at a speed of 1.8 m / s. Finally, a uniform rapid setting sheet with a thickness of approximately 290 μm is obtained.

[0196] The process of steps S3-S9 is the same as that of Example 24.

[0197] The magnetic properties of the sintered magnet, primary and secondary heat-treated magnets in Comparative Example 3 are shown in Table 15.

[0198] Table 15 Magnetic properties of sintered magnets and magnets subjected to two-stage heat treatment in Comparative Example 3

[0199]

[0200] Note: In Table 15, “1030℃” refers to the sintered magnets obtained at a sintering temperature of 1030℃; “1030℃-750℃” refers to the magnets obtained at a sintering temperature of 1030℃ and a primary heat treatment temperature of 750℃; “1030℃-750℃-450℃” refers to the magnets obtained at a sintering temperature of 1030℃, a primary heat treatment temperature of 750℃, and a secondary heat treatment temperature of 450℃.

[0201] Comparative Example 3, compared to Example 24, reduces the light rare earth elements Y, La, and Ce, adds heavy rare earth elements Tb, Dy, and Ho, and does not add carbon. The process remains unchanged, resulting in a slightly lower coercivity than the rare earth iron-carbon magnet sample without the heavy rare earth element. This demonstrates that the present invention can produce a magnet with a higher coercivity without the addition of heavy rare earth elements, which is of great significance for the balanced utilization of rare earth resources and reducing the manufacturing cost of high-performance magnets.

[0202] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A sintered magnet based on a rare earth iron-carbon alloy, characterized in that: The general chemical formula is RE x Fe y M 100-y-x-z-w B w C z , wherein x, y, z and w are the atomic percentages of each element, x refers to the sum of the atomic percentages of all rare earth elements, 10≤x≤20, 70≤y≤81, 2≤z≤8, 0<w≤2; RE is at least two of Y, La, Ce, Pr, Nd, and Sm; M is at least four of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Zr, Nb, Ag, Hf, Mo, W, and Ta.

2. The sintered magnet based on rare earth iron carbon alloy according to claim 1, characterized in that The chemical formula is Pr 14 Nd4Fe 72.48 Al 0.96 Cu 0.20 Ga 0.20 Zr 0.16 B2C6、LaCe2Pr5Nd3Fe 80.4 V 1.01 Si 0.2 Ti 0.2 Nb 0.1 Mo 0.04 Ta 0.04 W 0.01 B1C6 or Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 BC5.

3. A process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to any one of claims 1 to 2, characterized in that: The following steps are involved: Weigh the raw materials according to the general chemical formula, wherein the amount of rare earth is increased by 1-5 wt.% based on the theoretical amount of rare earth calculated according to the general chemical formula; The raw materials are melted, and after melting, they are rapidly solidified to obtain rapid solidification sheets; The quick-setting sheet is sequentially annealed and rapidly cooled, and the rapidly cooled quick-setting sheet is subjected to hydrogen crushing and air flow milling to obtain air flow milled powder; The jet milled powder is subjected to orientation pressing, sintering and two-stage heat treatment to obtain the sintered magnet based on the rare earth iron-carbon alloy.

4. The process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to claim 3, characterized in that: The melting is selected from arc melting or induction melting.

5. The process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to claim 3, characterized in that: The annealing temperature of the quick-setting sheet is 600-1150° C., and the annealing time is 1-20 hours.

6. The process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to claim 3, characterized in that: The sintering temperature is 1000-1100°C.

7. The process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to claim 3, characterized in that: The two-stage heat treatment includes a primary heat treatment and a secondary heat treatment. The temperature of the primary heat treatment is 450-970°C; the temperature of the secondary heat treatment is 480-660°C.

8. The process for preparing a sintered magnet based on a rare earth iron-carbon alloy according to claim 7, characterized in that: The temperature of the primary heat treatment is 880-970°C; the temperature of the secondary heat treatment is 540-660°C.

9. Use of the rare earth iron-carbon alloy-based sintered magnet according to any one of claims 1 to 2 in the fields of consumer electronics, energy, transportation and / or medical care.

10. The use according to claim 9, characterized in that The sintered magnet based on the rare earth iron-carbon alloy is used for preparing motors, household appliances, medical equipment, drives or magnetic separation equipment.

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