A sintered magnet based on rare earth iron-carbon alloy and a preparation process thereof

Abstract

The application discloses a sintered magnet based on rare earth iron-carbon alloy and a preparation process thereof, and belongs to the technical field of permanent magnet materials. 14 (C,B), a grain boundary phase (containing rare earth elements, rare earth oxides and transition metal-rich phases (such as Zr-rich phases)) and alpha-Fe, RE2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbides (such as REC2 and RE2C3), has high magnetic energy product and coercive force, and is a new type of high-performance sintered rare earth permanent magnet.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a sintered magnet based on a rare earth iron-carbon alloy and a preparation process thereof. BACKGROUND

[0002] Permanent magnet materials have a wide range of applications in the fields of energy, transportation, and medical treatment. Compared with samarium-cobalt permanent magnets, neodymium-iron-boron permanent magnets have high magnetic energy products and strong comprehensive magnetic properties, but have low anisotropy fields and are difficult to obtain high coercivity. In addition, the large-scale production of neodymium-iron-boron permanent magnets leads to unbalanced utilization of rare earth resources. RE2Fe 14 C permanent magnet materials have the same tetragonal crystal structure and similar magnetic properties as RE2Fe 14 B permanent magnet materials. Compared with traditional Nd2Fe 14 B permanent magnet materials, light rare earth iron-carbon compounds have higher magnetic crystal anisotropy fields and can obtain very high coercivity without adding heavy rare earths. Therefore, the preparation of high-performance RE2Fe 14 C permanent magnet materials is very important to solve the problems faced by rare earth resources.

[0003] Traditional methods for preparing RE2Fe 14 C-based compounds mainly include three methods: smelting ingot plus long-time annealing, melt quenching plus short-time annealing, and mechanical alloying. Since the RE2Fe 14 C phase has poor stability, it must be obtained through slow solid-phase transformation within a specific temperature range. Some researchers obtained the RE2Fe 14 C phase by annealing an ingot for 4 weeks, but the coercivity is very low due to the excessive grain growth caused by the long annealing time. The melt quenching method is to melt the ingot into an amorphous or nanocrystalline ribbon, and since the grains are small, the solid-phase reaction speed is greatly accelerated, so that the RE2Fe 14 C phase can be obtained through short-time annealing. As for the mechanical alloying method, although the preparation process is simple, the obtained coercivity and magnetic energy product are not high. After obtaining the RE2Fe 14 C compound, it needs to be further prepared into a magnet to be truly applied. At present, researchers mostly choose to use a rapidly quenched ribbon as a precursor to prepare a RE2Fe 14 C-based magnet through a hot-pressing and hot-deformation process, but this method is difficult to produce large blocks of magnets, resulting in low production efficiency, and the magnetic energy product is still lower than that of sintered magnets, which limits the further application of RE-Fe-C compounds. At present, the methods for preparing rare earth iron-carbon alloys can only prepare alloys, and cannot prepare magnets for industrial mass production. Therefore, a process for preparing sintered magnets based on rare earth iron-carbon alloys is needed. SUMMARY

[0004] In order to solve the problems of the rare earth iron-carbon based alloy in the prior art that cannot be quickly and batch produced, and the magnet in the prior art that has many defects and poor magnetic energy product, the application provides a sintered magnet based on a rare earth iron-carbon alloy and a preparation process thereof.

[0005] In order to achieve the above-mentioned purpose, the application provides the following technical scheme.

[0006] The application provides a sintered magnet based on a rare earth iron-carbon alloy, which has a general chemical formula of RE x Fe y M 100-y-x-z- w B w C z wherein x, y, z and w are atomic percentages of respective elements, x represents the sum of atomic percentages of all rare earth elements, 10<=x<=20, 70<=y<=81, 2<=z<=8, and 0

[0007] Compared with the existing rare earth permanent magnet alloy, the application adds carbon, so that the RE2(Fe,M) 14 (C,B) phase, the alpha-Fe phase, the R2Fe 17 C x (x=1, 2 or 3) phase, a grain boundary phase (containing rare earth elements, rare earth oxides and transition metal-rich phases (such as Zr-rich phases)) and rare earth carbides (such as REC2 and RE2C3), and a step of annealing the rapidly solidified flake, so that the content of RE2(Fe,M) 14 (C,B) is greatly increased, and the performance of the sintered magnet is improved. In the sintered magnet based on the rare earth iron-carbon alloy, the content of carbon is greater than 2at.%, preferably the content of carbon is 2-8at.%, and more preferably the content of carbon is 3-6at.%. The carbon element enters the alloy in the smelting process, and can be added in the form of an alloy or in the form of a single element to participate in the formation of the RE2(Fe,M) 14 (C,B) main phase. The sintered magnet based on the rare earth iron-carbon alloy contains a certain amount of dispersed alpha-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and rare earth carbides (such as REC2 and RE2C3) phase, which are generated in the smelting and rapid solidification process instead of being externally added, and can be adjusted by a heat treatment process. 17 C x(x=1, 2 or 3) phase and the content of rare earth carbide phase (such as REC2, RE2C3), thereby forming sintered magnets with different α-Fe, R2Fe 17 C x (x=1, 2 or 3) phase and the content of rare earth carbide (such as REC2, RE2C3) phase, thereby improving the performance of the magnet.

[0008] Exemplarily, the sintered magnet based on rare earth iron carbon alloy has a chemical formula of 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 application also provides a preparation process of the sintered magnet based on rare earth iron carbon alloy, comprising the following steps:

[0010] The raw materials are weighed according to the 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 chemical formula;

[0011] The raw materials are smelted, and then quenched after the smelting is completed to obtain a quenched piece, wherein the quenched piece prepared by the application mainly contains 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 (containing rare earth element, rare earth oxide and transition metal-rich phase (such as Zr-rich phase)), wherein RE2(Fe,M) 14 (C,B) phase content is more than 75 wt.%, α-Fe content is less than 3 wt.%, R2Fe 17 C x(x = 1, 2 or 3) phase content is below 22wt.%, the rare earth carbide content is below 6wt.%, and the rest is grain boundary phase; the thickness of the rapidly solidified sheet is 150-350μm, the internal main phase grain and the rare earth-rich phase grain are columnar crystals, and are arranged in a radial direction alternately; the main phase is α-Fe, R2Fe 17 C x (x = 1, 2 or 3) phase and the rare earth carbide are dispersedly distributed in the main phase grain and the boundary;

[0012] The rapidly solidified sheet is sequentially subjected to annealing and quenching, and the quenched rapidly solidified sheet is subjected to hydrogen crushing and air-jet milling to obtain the air-jet milled powder.

[0013] After the air-jet milled powder is subjected to orientation compression, sintering and two-stage heat treatment, the rare earth iron-carbon alloy-based sintered magnet is obtained.

[0014] The rare earth iron-carbon alloy-based sintered magnet prepared by the process of the application is mainly composed of a main phase RE2(Fe,M) 14 (C,B), grain boundary phase (containing rare earth element, rare earth oxide and transition metal-rich phase (such as Zr-rich phase)) and α-Fe, R2Fe 17 C x phase and rare earth carbide; wherein the sintered magnet RE2(Fe,M) 14 (C,B) phase content is above 86wt.%, α-Fe content is below 2wt.%, R2Fe 17 C x (x = 1, 2 or 3) phase content is below 12wt.%, the rare earth carbide content is below 4wt.%, and the rest is grain boundary phase; the main phase is equiaxed micrometer crystal with a length of 1-6μm; α-Fe and R2Fe 17 C x (x = 1, 2 or 3) phase is dispersedly distributed in the main phase grain and the boundary; the grain boundary phase is distributed in the thin layer grain boundary and the triangular grain boundary; the rare earth carbide is distributed in the main phase grain boundary and the grain boundary in the form of a lump. RE2(Fe,M) 14 (C,B) phase is the phase with the largest content in the sintered magnet, and also has a relatively high magnetic crystal anisotropy field and residual magnetization. The higher the magnetic crystal anisotropy field, the larger the reverse magnetic field required for magnetization reversal, thus having the potential to realize a larger coercive force. Therefore, increasing the mass fraction of this phase is of great help to improving the residual magnetism and coercive force of the sintered magnet. α-Fe, R2Fe 17 C x The content of (x = 1, 2 or 3) and the rare earth carbide can be controlled by processes such as annealing of the rapidly solidified sheet, sintering and heat treatment of the magnet. The α-Fe phase has a certain contribution to the saturation magnetic moment, but is easy to cause the coercive force to decrease, and thus its content needs to be controlled at a low level, R2Fe 17 C x(x = 1, 2 or 3) and the rare earth carbide have an adverse effect on the coercivity, and thus the content thereof also needs to be controlled.

[0015] The melting is exemplarily selected from arc melting or induction melting.

[0016] Preferably, the preparation process of the rapid solidification sheet is as follows: the weighed raw materials are loaded into a vacuum induction melting rapid solidification crucible, the cavity is vacuumized, the vacuum degree reaches 3x10 -2 Pa, the power is increased to 5kW for drying the raw materials when the vacuum degree starts to decrease again, and the power is decreased to 10kW for refining for 3min when the vacuum degree is below 3x10 -2 Pa, the vacuum system is turned off, then argon is filled into the cavity, and the power is increased to 13.5kW for melting, the power is decreased to 10kW for refining for 3min when the raw materials are completely melted, the composition of the alloy liquid is fully homogenized, the rapid solidification system is opened after the refining is completed, the crucible is tilted to make the alloy liquid cast onto the surface of a water-cooled copper roller with a rotation speed of 0.5-2m / s, and finally the rapid solidification sheet with uniform thickness is obtained, and the thickness is 150-350μm. -2

[0017] The annealing method is not limited in the present application, and any method that can achieve the annealing effect is acceptable. Exemplarily, the annealing method includes but is not limited to being performed in a vacuum-free muffle furnace with protective gas blowing, in a vacuum muffle furnace, or in a sintering furnace filled with protective gas. Preferably, the annealing in the present application is performed in a vacuum sintering furnace or a muffle furnace or a tube furnace under the protection of argon, the annealing temperature of the rapid solidification sheet is 600-1150℃, the annealing time is 1-20h, preferably the annealing temperature is 900-1050℃, and the annealing time is 1-5h.

[0018] The quenching method is not limited in the present application, and any method that can achieve the quenching effect is acceptable. Exemplarily, the quenching method includes but is not limited to ice water quenching and blowing with cold protective gas. Preferably, the quenching process in the present application is blowing with cold argon.

[0019] The hydrogen crushing is for rough crushing of the rapid solidification sheet, and other rough crushing methods can also be used, including but not limited to pounding with a mortar and mechanical crushing with a jaw crusher. After the rough crushing, the particle size of the powder is 45-355μm. Preferably, the rough crushing method in the present application is hydrogen crushing, the hydrogen absorption temperature is room temperature, and the hydrogen desorption temperature is 400℃-650℃.

[0020] ​The air flow mill pulverization is to obtain finer powder (i.e. fine pulverization), and the air flow mill can be replaced by a ball mill. After the fine pulverization, the particle size of the powder is 1-7 μm. The preferred fine pulverization method in the present application is air flow mill pulverization, which is carried out in an atmosphere with oxygen content less than 80 ppm, at a rotation speed of 3600 rpm-5000 rpm, and the gas used can be nitrogen or argon.

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

[0022] The density of the pressed body after the orientation pressing is low, and in order to further improve the density of the pressed body, the pressed body needs to be subjected to cold isostatic pressing. In the cold isostatic pressing process, the vacuum packaged pressed body is placed in an oil cylinder and pressurized to 200-300 MPa, preferably 225 MPa, and maintained for 0.5 min-5 min, preferably 3 min.

[0023] Further, the sintering temperature is 1000-1100 ℃, and the sintering time is 1-20 h; preferably, the sintering temperature is 1020-1080 ℃. The sintering atmosphere is preferably vacuum or argon atmosphere.

[0024] Further, the two-stage heat treatment (two-stage aging heat treatment) is a first-stage heat treatment and a second-stage heat treatment, the temperature of the first-stage heat treatment is 450-970 ℃, and the holding time is 3 h; the temperature of the second-stage heat treatment is 480-660 ℃, and the holding time is 4 h; preferably, the temperature of the first-stage heat treatment is 880-970 ℃; the temperature of the second-stage heat treatment is 540-660 ℃.

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

[0026] For example, the sintered magnet based on rare earth iron-carbon alloy in the present application can be used to prepare high-efficiency energy-saving motors (such as permanent magnet motors), new energy automobile motors, micro motors (such as mobile phone vibration motors, micro fans, etc.); 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) devices, hard disk drives, aerospace sensors, suspension systems for maglev trains, etc.

[0027] The principle of the present application is:

[0028] The application prepares alloy powder through a process of batching-melting-rapid solidification-annealing-quenching-crushing, and then prepares a sintered magnet based on rare earth iron-carbon alloy through a method of oriented compacting-sintering-two-stage heat treatment. The sintered magnet based on rare earth iron-carbon alloy prepared by the process of the application is mainly composed of a main phase RE2(Fe,M) 14 (C,B), a grain boundary phase (containing rare earth element, rare earth oxide and transition metal-rich phase (such as Zr-rich phase)) 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 (C,B) phase is more than 86wt.%, the content of α-Fe is less than 2wt.%, the content of R2Fe 17 C x (x=1, 2 or 3) phase is less than 12wt.%, the content of rare earth carbide is less than 4wt.%, and the rest is the grain boundary phase; the main phase is equiaxed micrometer crystal with a length of 1-6μm; α-Fe and R2Fe 17 C x (x=1, 2 or 3) phase is dispersedly distributed in the grain boundary and the boundary of the matrix phase; the rare earth-rich phase is distributed in the thin layer grain boundary and the triangular grain boundary; the transition metal carbide and / or boride is mostly distributed in the triangular grain boundary in the form of rod; the rare earth carbide is distributed in the form of lump in the grain boundary of the main phase and the rare earth-rich phase.

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

[0030] The application provides a sintered magnet based on rare earth iron-carbon alloy and a preparation process thereof. A large amount of rare earth iron-carbon alloy powder is obtained through a process of melting-rapid solidification-annealing-quenching-crushing, and then sintering and two-stage heat treatment are performed to prepare a sintered magnet based on rare earth iron-carbon alloy. The sintered magnet based on rare earth iron-carbon alloy is a high-performance rare earth iron-carbon-based magnet, which contains a certain amount of dispersedly distributed α-Fe and R2Fe 17 C x phases, and the content of the α-Fe and R2Fe 17 C x (x=1, 2 or 3) phase can be adjusted through a heat treatment process, so as to form a magnet with different α-Fe and R2Fe 17 C x (x=1, 2 or 3) phase content. Such a magnet does not need to add heavy rare earth elements, can reduce the production cost of the magnet, and save scarce resources.

[0031] The magnetic energy product and squareness of the sintered magnet based on rare earth iron-carbon alloy of the application are both high, which indicates that the method process of the application is reasonable, and a high-performance rare earth iron-carbon-based sintered magnet can be prepared. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the application. In the drawings:

[0033] Figure 1 XRD test results and powder XRD refinement patterns of the green compact obtained in Example 1, S2, wherein (a) is the XRD test results, (b) is the powder XRD refinement patterns;

[0034] Figure 2 Backscattered electron images of the surface and cross-section of the green compact obtained in Example 1, S2, wherein (a) and (b) are the backscattered electron images of the surface, (c) and (d) are the backscattered electron images of the cross-section;

[0035] Figure 3 Backscattered electron images of the surface and cross-section of the green compact obtained in Example 1, S2, wherein (a) and (b) are the backscattered electron images of the surface, (c) and (d) are the backscattered electron images of the cross-section;

[0036] Figure 4 XRD patterns of the sintered magnets obtained in Example 1-7, S7, and XRD refinement patterns of the sintered magnets obtained in Example 2, S7 sintered at 1020°C (b), Example 1, S7 sintered at 1070°C (c), and Example 3, S7 sintered at 1080°C (d);

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

[0038] Figure 6 Backscattered electron images and elemental mapping of the sintered magnets based on rare earth iron-carbon alloy obtained in Example 1, wherein (a) and (b) are the backscattered electron images, and the right side of the figure is the elemental mapping of the area (b);

[0039] Figure 7 XRD patterns and XRD refinement patterns of the green compact obtained in Example 22, wherein (a) is the XRD pattern, (b) is the XRD refinement pattern;

[0040] Figure 8 XRD patterns of the sintered magnets obtained in Example 22 and Example 23;

[0041] Figure 9XRD spectra and powder XRD refinement patterns of the roll face and free face of the Example 1 speeded green sheet, where (a) is the XRD spectra and (b) is the XRD refinement patterns;

[0042] Figure 10 X-ray diffraction spectra and powder XRD refinement patterns of the sintered magnet of Comparative Example 1, where (a) is the X-ray diffraction spectra of the sintered magnet of Comparative Example 1 and (b) is the powder XRD refinement patterns of the sintered magnet of Comparative Example 1;

[0043] Figure 11 Backscattered electron image of the sintered magnet of Comparative Example 1. DETAILED DESCRIPTION

[0044] The following detailed description of various example embodiments of the application will not be considered to limit the application, but rather to provide a more detailed description of the various aspects, features, and embodiments of the application.

[0045] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for the purposes of the present application, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. It is to be understood that the terms "comprising", "including", "containing", "characterized by" and "having" are inclusive and do not exclude other

[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict between the present specification and any document incorporated by reference, the present specification will control.

[0047] Various modifications and changes can be made to the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0048] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended and do not exclude additional, unrecited elements or method steps.

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

[0050] The raw materials used in the embodiments of the present application are all commercially available.

[0051] In the embodiments of the present application, the "high-purity argon" refers to argon with a purity of 99.999% or above.

[0052] It should be noted that the details not described in the present application are all conventional operating means in the art and are not the focus of the present application.

[0053] The technical solutions of the present application are further illustrated by the following examples.

[0054] Example 1

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

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

[0057] S2. The Pr, Nd, Fe, Al, Cu, Ga, Zr elements with a purity of more than 99%, FeC alloy and FeB alloy are placed in the water-cooled crucible of the medium-frequency induction melting furnace, the chamber is closed and vacuumed to 3×10 -2 Pa, the power is turned on to preheat and remove the moisture and volatile impurities on the surface of the raw materials, during which the vacuum degree in the furnace rises slightly to 8×10 -2 Pa, when the vacuum degree starts to decrease again, the power is increased to 5kW to heat the raw materials, and when the vacuum degree decreases to 3×10 -2 Pa again, the vacuum system is turned off, then argon is filled into the chamber, and the power is increased to 13.5kW to melt, when the raw materials are completely melted, the power is reduced to 10kW to refine for 3min, so that the composition of the alloy liquid is fully homogenized. After refining, the rapid solidification system is opened, the crucible is tilted to cast the alloy liquid onto the surface of the water-cooled copper roller with a rotation speed of 1.8m / s, and finally a rapid solidification sheet with uniform thickness is obtained, and the thickness is about 280μm;

[0058] S3. The rapid solidification sheet is annealed and air-cooled under argon protection, and the specific steps are as follows: a large batch of prepared rapid solidification sheets are placed in a vacuum sintering furnace, vacuumed to 5×10 -3 Pa and filled with high-purity argon, heated to 1050℃ and kept for 2h (i.e. annealed at 1050℃ for 2h), and after annealing, the sample is blown with cold argon for air cooling.

[0059] S4. After the annealing, the quenched piece was manually broken into pieces and then put into a stainless steel container and placed in a rotary hydrogen treatment furnace, and then vacuumized to 5x10 -3 Pa, the vacuum system was closed, and hydrogen gas with a purity of 99.999% was introduced to 75 kPa, and hydrogen absorption was carried out at room temperature for 1 h, and the hydrogen pressure in the furnace needed to be maintained during the hydrogen absorption process. After the hydrogen absorption was completed, the vacuum system was opened to discharge the remaining hydrogen in the furnace, and when the vacuum degree decreased to 5x10 -2 Pa, the heating system was opened, and the temperature was raised to 550°C for 5 h for dehydrogenation treatment. After dehydrogenation, argon was filled to cool to room temperature, and the hydrogen explosion powder was taken out under nitrogen protection and put into a sealed tank for standby;

[0060] S5. Nitrogen was filled in the jet mill, and after the oxygen content was reduced to below 70 ppm, the hydrogen explosion powder was poured into the jet mill, the speed was set to 4800 rpm, and after 1 h of grinding, the jet mill powder was taken out;

[0061] S6. After the oxygen content in the pulse magnetic field forming press was discharged to below 200 ppm using nitrogen, pressing was carried out under a magnetic field of 1.8 T, and then the vacuum packaged compact was put into a cold isostatic pressing machine and pressurized to 225 MPa for 3 minutes;

[0062] S7. The compact was put into a vacuum sintering furnace, and a stepwise temperature rise was adopted, and the temperature was kept at 430°C, 600°C and 800°C for 1 h respectively, and then the temperature was raised to 1070°C for 3 h (i.e. the sintering temperature in this embodiment is 1070°C), and then argon was introduced to cool to room temperature, and a sintered magnet was obtained;

[0063] S8. The magnet sintered at 1070°C was put into a vacuum sintering furnace, and the temperature was raised to 950°C and kept for 3 h for primary heat treatment, and then argon was introduced to cool to room temperature;

[0064] S9. The magnet sintered at 1070°C and subjected to primary heat treatment at 950°C was put into a vacuum sintering furnace, and the temperature was raised to 600°C and kept for 4 h for secondary heat treatment, and then argon was introduced to cool to room temperature, and a sintered magnet based on rare earth iron-carbon alloy was obtained.

[0065] The XRD test and powder XRD refinement spectrum results of the quenched piece obtained in step S2 are shown in Figure 1 It can be seen that the main diffraction peaks in the quenched piece correspond to the diffraction peaks of Pr2Fe 14 (C,B), wherein the main phase content is about 90 wt.%, and the remaining part contains rich rare earth phase (including Pr, Pr2O3, PrO2) and a small amount of α-Fe (black spots), Pr2Fe 17 C x(Dark gray phase) and rare earth carbides (massive white contrast phase, containing PrC2 and Pr2C3). The mass fractions of different phases in the XRD refinement results of the rapidly solidified sheets are shown in Table 1; the lattice constants and cell volumes of the principal phases in the XRD refinement results of the rapidly solidified sheets are shown in Table 2. For comparison, Pr2Fe from the standard PDF database... 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 cell volume of the rapidly solidified sheet are between those of the two phases (Pr2Fe). 14 B and Pr2Fe 14 C 0.95 B 0.05 The spaces between ) indicate that the C element has entered the main phase lattice.

[0066] Table 1 shows the mass fraction of different phases in the XRD refinement results of the quick-setting tablets.

[0067]

[0068]

[0069] Table 2 shows the lattice constants and cell volumes of the main phases in the XRD refinement results of the rapidly solidified sheets.

[0070]

[0071] The backscattered electron image and cross-sectional backscattered electron image of the rapid-curing sheet obtained in step S2 are as follows: Figure 2 As shown, the roller surface exhibits nucleation points distributed in a flower-like pattern (e.g. Figure 2 (as shown in the red circle in (a)) Figure 2 The white contrast in (b) corresponds to a Pr-rich or Pr-C phase, which is unevenly distributed and partially exists in agglomerate form. From the cross-sectional diagram ( Figure 2 In (c) and (d), it can be seen that the main phase (gray contrast) columnar crystals grow radially from the nucleation point, with the main phase and rare earth-rich phase columnar crystals alternating. Notably, diffusely distributed black particles can be observed in both the backscattered electron diffraction (RSD) images of the roller surface and the cross-sectional backscattered electron diffraction (RSD) images, which, based on the energy dispersive spectroscopy (EDS) results, can correspond to the α-Fe phase.

[0072] Backscattered electron images of the free surface and cross-section of the rapidly solidified sheet after annealing at 1050℃ for 2 hours in step S3 are as follows: Figure 3 As shown, the black particles in the free surface and cross-section of the annealed quick-setting sheet have basically disappeared, indicating that the content of α-Fe in the sample can be adjusted by appropriate annealing treatment.

[0073] Example 2

[0074] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1020℃.

[0075] Embodiment 3

[0076] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1080℃.

[0077] Embodiment 4

[0078] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1030℃.

[0079] Embodiment 5

[0080] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1040℃.

[0081] Embodiment 6

[0082] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1060℃.

[0083] Embodiment 7

[0084] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is same as that in the embodiment 1, with the difference that the sintering temperature in S7 is 1050℃.

[0085] The X-ray diffraction spectra of the sintered magnets obtained in S7 in the embodiments 1-7 are shown in the following table, and the XRD refinement patterns of the sintered magnets obtained in the embodiment 2 with the sintering temperature of 1020℃ in S7, the embodiment 1 with the sintering temperature of 1070℃ in S7 and the embodiment 3 with the sintering temperature of 1080℃ in S7 are shown in the following table. Figure 4 As shown in the table, the orientation degrees of the magnets are good at all sintering temperatures. Compared with the rapid solidification flakes, the α-Fe and 2:17 phases in the sintered magnet samples are greatly reduced or even disappeared, which indicates that the content of the α-Fe and 2:17 phases can be continuously adjusted by the sintering process while densifying.

[0086] The mass fraction of different phases in the XRD refinement results of the sintered magnets obtained by sintering temperature of S7 at 1020°C in Example 2, sintering temperature of S7 at 1070°C in Example 1 and sintering temperature of S7 at 1080°C in Example 3 are shown in Table 3, the lattice constant and the cell volume of the main phase of the sintered magnets given by the XRD refinement results of the sintered magnets obtained by sintering temperature of S7 at 1020°C in Example 2, sintering temperature of S7 at 1070°C in Example 1 and sintering temperature of S7 at 1080°C in Example 3 are shown in Table 4, the lattice constant (c) and the cell volume of the sintered magnets are not much different from those of the green sheet, and are still between Pr2Fe 14 B and Pr2Fe 14 C 0.95 B 0.05 After sintering, the C element still exists in the main phase lattice.

[0087] Table 3 The mass fraction of different phases in the XRD refinement results of the sintered magnets obtained by different sintering temperatures

[0088]

[0089] Table 4 The lattice constant and the cell volume of the main phase in the XRD refinement results of the sintered magnets obtained by different sintering temperatures

[0090]

[0091] The magnetic properties and the density (p) of the sintered magnets obtained by S7 at different sintering temperatures in Example 1-Example 7 are shown in Table 5. The coercivity (H cj ), the remanence (B r ) and the magnetic energy product ((BH) max ) of the sintered magnets all reach the maximum values at 1070°C, which are 12.29kOe, 13.24kGs and 43.76MGOe respectively.

[0092] Table 5 The magnetic properties and the density of the sintered magnets in Example 1-Example 7

[0093]

[0094]

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

[0096] Example 8

[0097] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 970 DEG C.

[0098] Embodiment 9

[0099] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 930 DEG C.

[0100] Embodiment 10

[0101] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 910 DEG C.

[0102] Embodiment 11

[0103] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 880 DEG C.

[0104] Embodiment 12

[0105] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 850 DEG C.

[0106] Embodiment 13

[0107] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 820 DEG C.

[0108] Embodiment 14

[0109] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 480 DEG C.

[0110] Embodiment 15

[0111] The embodiment provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy, which is identical to that in the embodiment 1, except that the first heat treatment temperature in S8 is 450 DEG C.

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

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

[0114]

[0115] Note: "1070°C" in Table 6 means no first heat treatment, i.e. the sintered magnet obtained in step S7 of Example 1; "1070°C-450°C" means the sintering temperature is 1070°C and the first heat treatment temperature is 450°C, and so on.

[0116] Example 16

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

[0118] Example 17

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

[0120] Example 18

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

[0122] Example 19

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

[0124] Example 20

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

[0126] Example 21

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

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

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

[0130]

[0131]

[0132] Note: In Table 7, 1070°C in 1070°C-950°C-480°C refers to the sintering temperature of 1070°C, 950°C refers to the first heat treatment temperature of 950°C, 480°C refers to the second heat treatment temperature of 480°C, and so on.

[0133] The backscattered electron image and elemental mapping results of the sintered magnet based on rare earth iron-carbon alloy in Example 1 are shown in FIG. 1, and it can be seen that the distribution of rare earth-rich phase is obviously improved after the second heat treatment, and there are more thin layer grain boundary phases, and the thickness increases, which helps to further enhance the demagnetization coupling effect between adjacent grains and improve the coercivity. In addition, Zr enrichment appears in the sample. This zirconium-rich phase appears in the grain boundary phase, and in the backscattered electron image, it appears as a dark island structure. Figure 6

[0134] Example 22

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

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

[0137] S2. Put the pure Pr, La, Ce, Nd, V, Si, Ti, Nb, Mo, Ta, W elements (i.e. the purity of the above elements is higher than 99%), FeC alloy and FeB alloy into the water-cooled crucible of the medium-frequency induction melting furnace, close the cavity and vacuumize to 3x10 -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 which the vacuum degree in the furnace will rise slightly to 8x10 -2 Pa, when the vacuum degree starts to decrease again, increase the power to 5kW to bake the material, and when the vacuum degree decreases to 3x10 -2 ​When the pressure is below 0.01 Pa, the vacuum system is closed, then argon is filled into the chamber, and the power is increased to 13.5 kW for melting. When the raw materials are completely melted, the power is decreased to 10 kW for 3 min for refining, so that the composition of the alloy liquid is fully homogenized. After the refining is completed, the rapid solidification system is opened, the crucible is tilted to make the alloy liquid cast onto the surface of a water-cooled copper roller with a rotation speed of 1.8 m / s, and finally a rapid solidification sheet with uniform thickness is obtained, and the thickness is about 290 μm;

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

[0139] S7. The green compact is placed into a vacuum sintering furnace, and stepwise heating is adopted. The temperature is maintained at 430 ℃, 600 ℃ and 800 ℃ respectively for 1 h. Finally, the temperature is increased to 1020 ℃ and maintained for 3 h (i.e. the sintering temperature in this example is 1020 ℃), and then argon is blown to cool to room temperature, to obtain a sintered magnet;

[0140] S8. The sintered magnet is placed into a vacuum sintering furnace, heated to 805 ℃ and maintained for 3 h for primary heat treatment, and then argon is blown to cool to room temperature;

[0141] S9. The magnet subjected to the primary heat treatment is placed into a vacuum sintering furnace, heated to 600 ℃ and maintained for 4 h for secondary heat treatment, and then argon is blown to cool to room temperature, to obtain a sintered magnet based on a rare earth iron-carbon alloy.

[0142] Example 23

[0143] This example provides a preparation process of a sintered magnet based on a rare earth iron-carbon alloy. The specific steps are the same as in Example 22, except that the sintering temperature in S7 is 1040 ℃.

[0144] The XRD spectra of the adhering roller surface and the free surface of the rapid solidification sheet obtained in Example 22 are shown in Figs. 8(a) and 8(b), respectively. It can be seen that the adhering roller surface still exhibits strong c-axis texture of the (00L) plane. Figure 7

[0145] The mass fractions of different phases in the XRD refinement results of the rapid 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 in Example 22

[0147]

[0148] The X-ray diffraction spectra of the sintered magnets in Example 22 and Example 23 are shown in Figs. 9(a) and 9(b), respectively. It can be seen that the samples still exhibit diffraction peaks of the main phase. Figure 8

[0149] ​​The magnetic properties and densities of the sintered magnets and the magnets after the first heat treatment in Example 22 and Example 23 are shown in Table 9. It can be seen that the coercivity of the magnets after the first heat treatment is improved.

[0150] Table 9 Magnetic properties and densities of the sintered magnets and the magnets after the first 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℃, "1020℃-805℃" refers to the magnets obtained at a sintering temperature of 1020℃ and a first 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 increased by 1.5wt.% compared with the mass of each rare earth element calculated according to the above chemical formula;

[0155] S2. The Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, Ag elements (i.e. the purity of the above elements is higher than 99%) with a purity higher than 99%, FeC alloy and FeB alloy are placed in the water-cooled crucible of the intermediate frequency induction melting furnace, the chamber is closed and vacuumed to 3x10 -2 Pa, the power is turned on to preheat and remove the moisture and volatile impurities on the surface of the raw materials, and the vacuum degree in the furnace will slightly rise to 8x10 -2 Pa, when the vacuum degree starts to decrease again, the power is increased to 5kW to bake the materials, and when the vacuum degree is again decreased to 3x10 -2 Pa, the vacuum system is turned off, then argon is filled into the chamber, and the power is increased to 13.5kW to melt, and when the raw materials are completely melted, the power is reduced to 10kW to refine for 3min to make the composition of the alloy liquid fully homogenized. After the refining is completed, the rapid solidification system is opened, the crucible is tilted to make the alloy liquid cast through the sprue to the surface of the water-cooled copper roller with a rotation speed of 1.8m / s, and finally a rapid solidification sheet with uniform thickness is obtained, and the thickness is about 275μm;

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

[0157] S7. Put the green compact into a vacuum sintering furnace, adopt stepwise heating, respectively keep at 430℃, 600℃ and 800℃ for 1h, then respectively heat to 1030℃ for 3h (i.e. the sintering temperature in this embodiment is 1030℃), after that, cool to room temperature by argon gas, to obtain sintered magnet;

[0158] S8. Put the sintered magnet into a vacuum sintering furnace, heat to 750℃ and keep for 3h for primary heat treatment, after that, cool to room temperature by argon gas;

[0159] S9. Put the magnet after primary heat treatment into a vacuum sintering furnace, heat to 450℃ and keep for 4h for secondary heat treatment, after that, cool to room temperature by argon gas, to obtain sintered magnet based on rare earth iron-carbon alloy. The magnetic properties of sintered magnet, primary and secondary heat treated magnet in Example 24 are shown in Table 10.

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

[0161]

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

[0163] Comparative Example 1

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

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

[0166] S2. The Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, Ag single elements (i.e. the purity of the above single elements is higher than 99%), FeC alloy and FeB alloy with purity higher than 99% are loaded into the water-cooled crucible of the intermediate frequency induction rapid solidification furnace, the chamber is closed and vacuumed to 3 x 10 -2 Pa, the power is turned on to preheat the raw material surface to remove moisture and volatile impurities at a low power (2 kW), and the vacuum in the furnace rises slightly to 8 x 10 -2 Pa, the power is turned on to preheat the raw material surface to remove moisture and volatile impurities at a low power (2 kW), and the vacuum in the furnace rises slightly to 8 x 10 -2 Pa, the power is turned on to preheat the raw material surface to remove moisture and volatile impurities at a low power (2 kW), and the vacuum in the furnace rises slightly to 8 x 10 17 Pa, the power is turned on to preheat the raw material surface to remove moisture and volatile impurities at a low power (2 kW), and the vacuum in the furnace rises slightly to 8 x 10

[0167] The rapid solidification sheet is not annealed, but directly subjected to hydrogen explosion, airflow milling and oriented compression (i.e. step S3 in Example 24 is not performed, and steps S4-S6 are directly performed after step S2 is completed), and the process is the same as that in Example 24. The sintering is performed by stepwise heating, and the temperature is maintained at 430°C, 600°C and 800°C for 1 h respectively, to further remove residual hydrogen and impurities, and finally the temperature is raised to 1030°C for 3 h (i.e. the sintering temperature of this comparative example is 1030°C), and then argon gas is blown to cool to room temperature.

[0168] The XRD spectra of the rapid solidification sheet obtained in this comparative example, which is attached to the roller surface and the free surface, and the powder XRD refinement spectrum are shown in Figure 9

[0169] The mass fraction of different phases in the XRD refinement results of the rapid solidification sheet obtained in this comparative example is shown in Table 11. The RE2Fe 17 Cx(x = 1, 2 or 3) phase content is relatively high, reaching 20.214wt.%.

[0170] S8. The sintered magnet is placed into a vacuum sintering furnace, heated to 750°C and maintained for 3 h for primary heat treatment, and then argon gas is blown to cool to room temperature;

[0171] S9. The magnet subjected to primary heat treatment is placed into a vacuum sintering furnace, heated to 450°C and maintained for 4 h for secondary heat treatment, and then argon gas is blown to cool to room temperature, to obtain a sintered magnet based on rare earth iron-carbon alloy.

[0172] The mass fraction of different phases in the XRD refinement results of the sintered magnet of Comparative Example 1 is shown in Table 12. The X-ray diffraction spectrum and the XRD refinement pattern of the sintered magnet of Comparative Example 1 are shown in Figure 6. Figure 10 The magnetic properties of the sintered magnet, the first-stage heat-treated magnet and the second-stage heat-treated magnet in Comparative Example 1 are shown in Table 13. The coercivity of the heat-treated magnet is up to 10.01 kOe and the magnetic energy product is 30.32 MGOe, which are lower than those of the sample in Example 24.

[0173] The backscattered electron image of the sintered magnet of Comparative Example 1 is shown in Figure 7, in which the dark gray contrast is the RE2Fe Figure 11 17 C x phase and the large black area is the a-Fe phase, which indicates that the sintered magnet also contains a large amount of RE2Fe 17 C x phase and a-Fe phase, which is consistent with the refinement results.

[0174] The sintered magnet of Comparative Example 1 is not annealed before being crushed, powdered and sintered, which results in a large amount of a-Fe and RE2Fe 17 C x phase in the sintered magnet. The excessive a-Fe and RE2Fe 17 C x phase reduces the mass fraction of the main phase on the one hand and the magnetic anisotropy field of the two phases is low, which is not conducive to achieving high coercivity of the magnet.

[0175] Table 11 The mass fraction of different phases in the XRD refinement results of the sintered magnet of Comparative Example 1

[0176]

[0177] Table 12 The mass fraction of different phases in the XRD refinement results of the sintered magnet of Comparative Example 1

[0178]

[0179] Table 13 The magnetic properties of the sintered magnet and the heat-treated magnet of Comparative Example 1

[0180]

[0181] Note: In Table 13, “1030℃” refers to the sintered magnet obtained at a sintering temperature of 1030℃, “1030℃-750℃” refers to the magnet obtained at a sintering temperature of 1030℃ and a first-stage heat treatment temperature of 750℃, and “1030℃-750℃-450℃” refers to the magnet obtained at a sintering temperature of 1030℃, a first-stage heat treatment temperature of 750℃ and a second-stage heat treatment temperature of 450℃.

[0182] Comparative Example 2​

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

[0184] S1. The Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 B6is mixed in a stoichiometric ratio, and the mass of Y, Pr, LaCe, Nd, Cr, Co, Fe, Ni, Ti, Zn, and Ag is calculated according to the general formula Y2LaCe4Pr6Nd3Fe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 B6is increased by 1.5wt.%;

[0185] S2. The Y, Pr, La, Ce, Nd, Cr, Co, Fe, Ni, Ti, Zn, Ag elements (i.e., the purity of the above elements is higher than 99%) and FeB alloy with a purity higher than 99% are loaded into the water-cooled crucible of the medium-frequency induction rapid solidification furnace, the chamber is closed and vacuumized to 3x10 -2 Pa, the power is turned on to preheat and remove the moisture and volatile impurities on the surface of the raw materials. During this period, the vacuum in the furnace will rise slightly to 8x10 -2 Pa, and when the vacuum degree starts to decrease again, the power is increased to 5kW for drying the raw materials. When the vacuum degree is again below 3x10 -2 Pa, the vacuum system is turned off, then argon is filled into the chamber, and the power is increased to 13.5kW for smelting. When the raw materials are completely melted, the power is reduced to 10kW for refining for 3min to make the alloy liquid composition fully homogenized. After refining, the rapid solidification system is opened, the crucible is tilted to make the alloy liquid cast onto the surface of the water-cooled copper roller with a rotation speed of 1.8m / s, and finally a rapid solidification sheet with uniform thickness is obtained, with a thickness of about 285μm.

[0186] Steps S3-S9 are the same as in Example 24.

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

[0188] Table 14 Magnetic properties of the sintered magnet in Comparative Example 2

[0189]

[0190] Note: In Table 14, "1030°C" refers to a sintered magnet obtained at a sintering temperature of 1030°C, "1030°C-750°C" refers to a magnet obtained at a sintering temperature of 1030°C and a first heat treatment temperature of 750°C, and "1030°C-750°C-450°C" refers to a magnet obtained at a sintering temperature of 1030°C, a first heat treatment temperature of 750°C, and a second heat treatment temperature of 450°C.

[0191] Example 24, all C is replaced by B, the process is unchanged, the sintered magnet has poor magnetic properties, and the coercivity is significantly lower than the sample prepared under the same process of Example 24, which is due to the fact that when RE is light rare earth, RE2Fe 14 The magnetic crystal anisotropy field of B is much lower than that of RE2Fe 14 C.

[0192] Comparative Example 3

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

[0194] S1. The stoichiometric ratio of Pr6Nd3Dy3Tb3HoFe 73 CoCr 1.06 Ni 2.4 Ti 0.4 Zn 0.1 Ag 0.04 B6, wherein the mass of 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 chemical formula;

[0195] S2. The pure Pr, La, Ce, Nd, Dy, Tb, Ho, Cr, Co, Fe, Ni, Ti, Zn, and Ag elements (i.e., the purity of the above elements is higher than 99%), FeC alloy, and FeB alloy are loaded into the water-cooled crucible of the medium-frequency induction rapid cooling furnace, the chamber is closed and vacuumed to 3x10 -2 Pa, the power is turned on to preheat and remove the moisture and volatile impurities on the surface of the raw materials at a low power (2 kW), and during this period, the vacuum in the furnace will rise slightly to 8x10 -2 Pa, and when the vacuum degree starts to decrease again, the power is increased to 5 kW to bake the materials, and when the vacuum degree decreases to 3x10 -2When the pressure in the vacuum system is below 1 Pa, the vacuum system is closed, then argon is filled into the cavity, and the power is increased to 13.5 kW for smelting. When the raw materials are completely melted, the power is reduced to 10 kW for refining for 3 min, so that the composition of the alloy liquid is fully homogenized. After the refining is completed, the rapid solidification system is opened, the crucible is tilted to make the alloy liquid cast through the sprue to the surface of the water-cooled copper roller with a rotation speed of 1.8 m / s, and finally the rapid solidification sheet with uniform thickness is obtained, and the thickness is about 290 μm.

[0196] Steps S3-S9 are the same as those in Example 24.

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

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

[0199]

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

[0201] Compared with Example 24, the light rare earth Y, La and Ce are reduced, the heavy rare earth Tb, Dy and Ho are added, and the C element is not added in Comparative Example 3, and the process is unchanged. The coercivity of the finally obtained magnet is slightly smaller than that of the rare earth iron-carbon based magnet sample without adding heavy rare earth. It is shown that the magnet with high coercivity can be obtained without adding heavy rare earth according to the present application, which has important significance for the balanced use of rare earth resources and the reduction of the manufacturing cost of high-performance magnets.

[0202] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A preparation process for sintered magnets based on rare earth iron-carbon alloys, characterized in that, Includes the following steps: Weigh each raw material 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, wherein the general chemical formula is RE. x Fe y M 100-y-x-z-w B w C z Where 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. The raw materials are melted and then rapidly solidified to obtain rapid solidification sheets. The quick-setting sheets were annealed and quenched in sequence, and the quenched quick-setting sheets were then subjected to hydrogen crushing and air jet milling to obtain air jet mill powder. The airflow milling process involves orientation pressing, sintering, and two-stage heat treatment to obtain the sintered magnet based on rare earth iron-carbon alloy. The sintering temperature is 1000-1100℃; The two-stage heat treatment consists of a primary heat treatment and a secondary heat treatment. The temperature of the primary heat treatment is 450-970℃, and the temperature of the secondary heat treatment is 480-660℃. The sintered magnet based on rare earth iron-carbon alloy consists of the main phase RE2(Fe,M). 14 (C,B), grain boundary phases and α-Fe, R2Fe 17 C x The phase and rare earth carbides are composed of x=1, 2 or 3, and the grain boundary phase includes rare earth elements, rare earth oxides and transition metal-rich phases; wherein RE2(Fe,M) 14 The (C,B) phase content is above 86 wt.%, the α-Fe content is below 2 wt.%, and R2Fe... 17 C x The phase content is below 12 wt.%, the rare earth carbide content is below 4 wt.%, and the remainder is grain boundary phase; the main phase is equiaxed microcrystals with a length of 1-6 μm; α-Fe and R2Fe 17 C x The phase is dispersed within the main phase grains and at their boundaries; the grain boundary phase is distributed in thin-layer grain boundaries and triangular grain boundaries; rare earth carbides are distributed in agglomerate form at the boundaries and grain boundaries of the main phase grains.

2. The preparation process of the sintered magnet based on rare earth iron-carbon alloy according to claim 1, characterized in that, The general 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. The preparation process of the sintered magnet based on rare earth iron-carbon alloy according to claim 1, characterized in that, The smelting process is selected from electric arc smelting or induction smelting.

4. The preparation process of the sintered magnet based on rare earth iron-carbon alloy according to claim 1, characterized in that, The annealing temperature of the quick-setting sheet is 600-1150℃, and the annealing time is 1-20h.

5. The preparation process of the sintered magnet based on rare earth iron-carbon alloy according to claim 1, characterized in that, The temperature of the first-stage heat treatment is 880-970℃; the temperature of the second-stage heat treatment is 540-660℃.

6. An application of a sintered magnet based on a rare-earth iron-carbon alloy in consumer electronics, energy, transportation, and / or medical fields, characterized in that... The sintered magnet based on rare earth iron-carbon alloy is prepared according to the preparation process described in any one of claims 1-5.

7. The application according to claim 6, characterized in that, The sintered magnets based on rare earth iron-carbon alloys are used to manufacture motors, home appliances, medical devices, drivers, or magnetic separation equipment.

Images