Preparation method of sintered neodymium iron boron with high bending strength

Abstract

The invention relates to the technical field of sintered titanium-iron-boron magnets, and discloses a preparation method of sintered neodymium-iron-boron with high bending strength, and main alloy elements comprise 27.2-29.3% by mass of R (R is a rare earth element which must contain any one of Nd and Pr), 0.93-1.0% by mass of B, 0.03-0.1% by mass of Ti, # imgabs 0 # by mass% Cu, 0.03-0.1% by mass of Al, # imgabs 1 # by mass% Ga and # imgabs 2 # by mass% Co. According to the preparation method of the high-bending-strength sintered neodymium iron boron, when main alloy elements meet the formula (1), the R2Fe14B main phase main body in a main alloy casting piece reaches 98.5% or above, and high residual magnetism can be kept; when the auxiliary alloy elements meet the formula (2) and the formula (3), the formed low-melting-point magnet intergranular phase is good in wettability and beneficial for improving the intrinsic coercive force of the magnet, most importantly, Al-Cu elements are mainly distributed in the grain boundary, the interface mismatching degree of the main phase and the thin-layer Nd-rich phase is obviously reduced, and then the bending strength of the magnet is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of sintered titanium iron boron magnets, in particular to a preparation method of sintered neodymium iron boron with high bending strength. Background Art

[0002] Coreless motors, with their small size, light weight, high efficiency, and fast response, are widely used in drones, robotics, medical devices, and other fields. With the advancement of industrial automation and intelligentization, market demand continues to grow. Coreless motors are expected to see increasing demand in new energy vehicles, smart manufacturing, and other fields, and the industry has broad prospects. The radial NdFeB magnets used in coreless motors require high bending strength and good rotational performance. Because they rotate at 130,000 rpm, the motor generates significant centrifugal forces during operation, and the manufacturing process is complex. Sintered NdFeB magnets are a brittle material with mechanical properties characterized by hardness and brittleness, meaning they have high strength and low toughness. They exhibit almost no plastic deformation before breaking, breaking during the elastic deformation phase and exhibiting low bending strength. The processing of radial magnetic rings for coreless cups requires complex processes such as strip cutting, squaring, rounding, drilling, and hole washing, resulting in a low pass rate of less than 90%. Furthermore, as the speed of coreless cup motors continues to increase, currently reaching a maximum of 130,000 rpm, this creates enormous centrifugal forces, requiring NdFeB magnets to have high bending strength and good machinability. Summary of the Invention

[0003] (1) Technical problems solved

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing sintered NdFeB with high bending strength, which solves the problems raised in the above background technology.

[0005] (2) Technical solution

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing sintered NdFeB with high bending strength, comprising the following steps:

[0007] Step 1: Main alloy smelting process;

[0008] Step 2: Main alloy hydrogen cracking process;

[0009] Step 3: Flour making process;

[0010] Step 4: Auxiliary alloy smelting process;

[0011] Step 5: auxiliary alloy hydrogen cracking process;

[0012] Step 6: Auxiliary alloy powder making process;

[0013] Step 7: Mixing process;

[0014] Step 8: Molding process;

[0015] Step 9: Sintering process;

[0016] Step 10: Heat treatment process;

[0017] The main alloying element ratio requirements are: 27.2-29.3 mass% R (R must include any one of Nd and Pr rare earth elements), 0.93-1.0 mass% B, 0.03-0.1 mass% Ti, mass% Cu, 0.03-0.1 mass% Al, Mass%Ga, The main alloying element ratio satisfies the following formula (1):

[0018] 2.15<(([R]÷143.41)÷([B]÷10.81))<2.30 (1);

[0019] The auxiliary alloy element ratio requirements are: 87.45-89.92 mass% Nd, 0.08-0.15 mass% B, 0.5-0.8 mass% Ti, % Cu by mass, 5.0-6.0% Al by mass, and when the mass percentages of Nd, B, Ti, Cu, and Al in the composition are respectively recorded as [Nd], [B], [Ti], [Cu], and [Al], the main alloying element ratios satisfy the following formulas (2) and (3):

[0020] 1.95<(([Nd]÷144.24)÷([Al]÷26.98+[Cu]÷63.55))<2.43 (2)

[0021] ([Al]÷26.98)÷(2×([Cu]÷63.55))≥1.2 (3).

[0022] Preferably, the main alloy composition is prepared by mixing the required raw materials, heating and melting the main alloy liquid in a rapid-setting sheet vacuum induction melting furnace under argon protection, and then pouring it onto a rotating copper roller to obtain a solidified alloy sheet.

[0023] Preferably, the main alloy liquid is poured onto the rotating copper roll at 1430-1500°C, and the rotating speed of the rotating copper roll is The thickness of the quick-setting alloy sheet is

[0024] Preferably, the required raw materials are prepared according to the ratio requirements of the auxiliary alloy elements, heated and melted in a vacuum medium frequency induction melting furnace under argon protection, and then poured onto a rotating copper roller to obtain a solidified alloy sheet. The auxiliary alloy liquid is poured onto the rotating copper roll at 1030℃-1100℃, and the casting power of the auxiliary alloy is 0.7-0.9 times the refining power to ensure smooth casting.

[0025] Preferably, the rotating speed of the copper roller is

[0026] Preferably, the thickness of the quick-setting alloy sheet is

[0027] Preferably, the step of preparing one or more main alloy fine powders and one or more auxiliary alloy fine powders;

[0028] The step of mixing the one or more additional alloy powders so as to account for 1.5 mass % or more and 5.0 mass % or less in 100 mass % of the mixed alloy powder to obtain a mixed alloy powder of the one or more main alloy powders and the one or more auxiliary alloy powders.

[0029] Preferably, a V-shaped mixer is used and the mixing time is 180-360 minutes.

[0030] Preferably, 1 mL / kg of antioxidant is added to the mixed powder.

[0031] (3) Beneficial effects

[0032] Compared with the prior art, the present invention provides a method for preparing sintered NdFeB with high bending strength, which has the following beneficial effects:

[0033] 1. The preparation method of sintered NdFeB with high bending strength is as follows: when the main alloying elements satisfy formula (1), the main R2Fe14B phase in the main alloy casting reaches more than 98.5%, which is conducive to maintaining high remanence; when the auxiliary alloying elements satisfy formula (2) and formula (3), the low melting point magnet intergranular phase formed has good wettability, which is conducive to improving the intrinsic coercive force of the magnet. Most importantly, the Al-Cu elements are mainly distributed at the grain boundaries, and the mismatch between the main phase and the thin layer of Nd-rich phase interface is significantly reduced, thereby significantly improving the bending strength of the magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the bending strength testing tool of the present invention;

[0035] Figure 2 This is a schematic diagram of the radial anti-explosion force detection tooling of the radial magnetic ring of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] See also Figure 1-2 The present invention provides a technical solution: a method for preparing high flexural strength sintered NdFeB, characterized in that it comprises the following steps:

[0038] Step 1: Main alloy smelting process;

[0039] Step 2: Main alloy hydrogen cracking process;

[0040] Step 3: Flour making process;

[0041] Step 4: Auxiliary alloy smelting process;

[0042] Step 5: auxiliary alloy hydrogen cracking process;

[0043] Step 6: Auxiliary alloy powder making process;

[0044] Step 7: Mixing process;

[0045] Step 8: Molding process;

[0046] Step 9: Sintering process;

[0047] Step 10: Heat treatment process;

[0048] The main alloying element ratio requirements are: 27.2-29.3 mass% R (R must include any one of the rare earth elements Nd and Pr), 0.93-1.0 mass% B, 0.03-0.1 mass% Ti, mass% Cu, 0.03-0.1 mass% Al, Mass%Ga, The composition is composed of 2.0% by mass of Co, the balance of Fe and other elements, and the total content of heavy rare earth elements is less than 2.0% by mass. The mass percentage of the rare earth elements in the composition is recorded as [R], the mass percentage of the B element is recorded as [B], and the main alloying element ratio satisfies the following formula (1):

[0049] 2.15<(([R]÷143.41)÷([B]÷10.81))<2.30 (1);

[0050] Auxiliary alloy element ratio requirements: 87.45-89.92 mass% Nd, 0.08-0.15 mass% B, 0.5-0.8 mass% Ti, % Cu by mass, 5.0-6.0% Al by mass, and when the mass percentages of Nd, B, Ti, Cu, and Al in the composition are expressed as [Nd], [B], [Ti], [Cu], and [Al], respectively, the main alloying element ratios satisfy the following formulas (2) and (3):

[0051] 1.95<(([Nd]÷144.24)÷([Al]÷26.98+[Cu]÷63.55))<2.43 (2)

[0052] ([Al]÷26.98)÷(2×([Cu]÷63.55))≥1.2 (3).

[0053] A process for preparing one or more main alloy fine powders and one or more auxiliary alloy fine powders;

[0054] A step of mixing one or more additional alloy powders so as to account for 1.5% to 5.0% by mass in 100% by mass of the mixed alloy powder to obtain a mixed alloy powder of one or more main alloy powders and one or more auxiliary alloy powders;

[0055] The NdFeB sintered magnet composition of the embodiment of the present invention is such that when the main alloying elements satisfy formula (1), the main R2Fe14B phase in the main alloy casting reaches more than 98.5%, which is conducive to maintaining high remanence; when the auxiliary alloying elements satisfy formula (2) and formula (3), the low-melting-point magnet intergranular phase formed has good wettability, which is conducive to improving the intrinsic coercive force of the magnet. Most importantly, the Al-Cu elements are mainly distributed at the grain boundaries, and the mismatch between the main phase and the thin layer of Nd-rich phase interface is significantly reduced, thereby significantly improving the bending strength of the magnet;

[0056] Main alloy smelting process:

[0057] Prepare the required raw materials according to the above main alloy composition, heat and melt them into alloy liquid in a rapid solidification vacuum induction melting furnace under argon protection, and then pour them onto a rotating copper roller to obtain solidified alloy sheets;

[0058] Preferably, the alloy liquid is poured onto the rotating copper plate at 1430-1500°C;

[0059] Preferably, the rotating speed of the copper roller is

[0060] As a preference, the thickness of the quick-setting alloy sheet is

[0061] Main alloy hydrogen cracking process:

[0062] Using a hydrogen cracking furnace, hydrogen is absorbed under hydrogen pressure and then dehydrogenated. Before hydrogen absorption, the hydrogen cracking furnace is evacuated to 1.1×10-2Pa, then filled with argon to 1KPa~1.5KPa, and the temperature is raised to 150~200℃ and kept warm for 0.5~1.5 hours to preheat and activate the casting. Then, the furnace is evacuated to 1×10-2Pa, filled with hydrogen to 0.2MPa~0.25MPa to absorb hydrogen, and dehydrogenated at 450-600℃;

[0063] Flour making process:

[0064] The coarse particles with a particle size of less than 1.5 mm obtained by hydrogen crushing are crushed into particles with a particle size of As a preferred method, the air flow milling process is as follows: nitrogen pressure 0.5MPa~0.65MPa, separation wheel speed 3200~4200 rpm;

[0065] Auxiliary alloy smelting process:

[0066] According to the above auxiliary alloy element ratio requirements, the required raw materials are prepared, heated and melted in a vacuum medium frequency induction melting furnace under argon protection, and then poured onto a rotating copper roller to obtain a solidified alloy sheet;

[0067] Preferably, the alloy liquid is poured onto the rotating copper plate at 1030°C-1100°C;

[0068] As a preference, the casting power of the auxiliary alloy is 0.7-0.9 times the refining power to ensure smooth casting;

[0069] Preferably, the rotating speed of the copper roller is

[0070] As a preference, the thickness of the quick-setting alloy sheet is

[0071] Auxiliary alloy hydrogen cracking process:

[0072] Using a hydrogen furnace, hydrogen is absorbed under hydrogen pressure and then dehydrogenated. Before hydrogen absorption, the hydrogen furnace is evacuated to 1.1×10-2Pa, then filled with argon to 1KPa~1.5KPa, and the temperature is raised to 200~300℃ and kept warm for 1~3 hours to preheat and activate the casting. Then, the furnace is evacuated to 1×10-2Pa, and hydrogen is filled to 0.2MPa~0.25MPa to absorb hydrogen for 23-36 hours. The furnace is dehydrogenated at 450-600℃ for 0.5-1 hour, and then filled with argon for protection and cooled. After cooling to 25℃, the casting is taken out of the furnace.

[0073] Auxiliary alloy powder making process:

[0074] The coarse particles with a particle size of less than 1.5 mm obtained by hydrogen crushing are crushed into particles with a particle size of As a preferred method, the air flow milling process is as follows: nitrogen pressure 0.5MPa~0.65MPa, separation wheel speed 4200~5100 rpm;

[0075] Mixing process:

[0076] A process for preparing one or more main alloy fine powders and one or more auxiliary alloy fine powders;

[0077] A step of mixing one or more additional alloy powders so as to account for 1.5% to 5.0% by mass in 100% by mass of the mixed alloy powder to obtain a mixed alloy powder of one or more main alloy powders and one or more auxiliary alloy powders;

[0078] As a preference, a V-shaped mixer is used with a mixing time of 180-360 minutes;

[0079] Preferably, 1 mL / kg of antioxidant is added to the mixed powder;

[0080] Molding process:

[0081] The obtained alloy powder is formed in a magnetic field of 1.5 to 1.8 T to obtain a formed green body;

[0082] Sintering process:

[0083] The sintered body (sintered magnet) is obtained by sintering the formed body. The sintering is preferably carried out in a vacuum atmosphere at a sintering temperature of 1050-1080°C and a holding time of 6-12 hours.

[0084] Heat treatment process:

[0085] The obtained sintered magnet is subjected to heat treatment for the purpose of improving magnetic properties and high bending strength. A two-stage tempering system can be used, such as Next level tempering exist Secondary tempering Finally, a sintered magnet is obtained.

[0086] The sintered blank was produced and machined to produce a 47×20×6mm black sheet sample (with a tolerance of plus or minus 0.05mm). Figure 1 The tooling is tested for bending strength using the three-point bending method to judge its bending strength. The bending strength calculation formula is as follows:

[0087] Calculate the bending strength of rare earth permanent magnet materials according to the formula:

[0088]

[0089] Where:

[0090] σ bb ——Flexural strength of rare earth permanent magnet material, in megapascals (MPa);

[0091] F bb ——maximum bending force, in Newton (N);

[0092] L s ——span, in millimeters (mm);

[0093] b——width of the specimen, in millimeters (mm);

[0094] h——Height of the specimen, in millimeters (mm).

[0095] The flexural strength reaching above 360MPa is defined as the high flexural strength sintered NdFeB magnet of this patent.

[0096] The sintered blank is made into radial magnetic ring for hollow cup motor with the size of D12×D5×10. Figure 2 The radial anti-burst force of the magnetic ring is tested on the tooling to judge its radial anti-burst capability; and the radial anti-burst force greater than 1800N is defined as meeting the standard.

[0097] The electrical components mentioned in this article are all connected to an external main controller and 220V AC power, and the main controller can be a conventional known device that performs control such as a computer.

[0098] The present invention will be further described below with reference to specific embodiments and comparative examples, but the present invention is not limited to the following embodiments:

[0099] Main alloy smelting process:

[0100] Main alloys A1-A7 were prepared according to the element ratios in Table 1. Pr, Nd, pure iron, electrolytic Co, Al, Cu, Ga, Ti, and ferroboron alloys with a purity of 99.5% or more were used, and the main alloy compositions were formulated according to the components shown in Table 1.

[0101] Table 1:

[0102]

[0103]

[0104] Note: U = ([R] ÷ 143.41) ÷ ([B] ÷ 10.81)

[0105] Prepare the required raw materials according to the above main alloy composition, heat and melt them into alloy liquid in a rapid solidification vacuum induction melting furnace under argon protection, and then pour them onto a rotating copper roller to obtain solidified alloy sheets;

[0106] Preferably, the alloy liquid is poured onto the rotating copper plate at 1430-1500°C;

[0107] Preferably, the rotating speed of the copper roller is

[0108] As a preference, the thickness of the quick-setting alloy sheet is

[0109] Main alloy hydrogen cracking process:

[0110] Using a hydrogen cracking furnace, hydrogen is absorbed under hydrogen pressure and then dehydrogenated. Before hydrogen absorption, the hydrogen cracking furnace is evacuated to 1.1×10-2Pa, then filled with argon to 1KPa~1.5KPa, and the temperature is raised to 150~200℃ and kept warm for 0.5~1.5 hours to preheat and activate the casting. Then, the furnace is evacuated to 1×10-2Pa, filled with hydrogen to 0.2MPa~0.25MPa to absorb hydrogen, and dehydrogenated at 450-600℃;

[0111] Flour making process:

[0112] The coarse particles with a particle size of less than 1.5 mm obtained by hydrogen crushing are crushed into particles with a particle size of As a preferred method, the air flow milling process is as follows: nitrogen pressure 0.5MPa~0.65MPa, separation wheel speed 3200~4200 rpm;

[0113] Auxiliary alloy smelting process:

[0114] According to the element ratios in Table 2, B1-B4 were prepared. Using Nd, Co, Al, Cu, Ti, and BCu alloys with a purity of 99.5% or higher by mass, the required raw materials were prepared according to the auxiliary alloy element ratio requirements described above. Melted in a vacuum medium-frequency induction melting furnace under argon protection, the refining temperature was controlled at 1080°C for 8-10 minutes, and then cast onto a rotating copper roller to obtain B1-B4 solidified alloy flakes.

[0115] In addition, based on the corresponding compositions, the values ​​of formula (2) (expressed as V values) and the values ​​of formula (3) (expressed as W values) are calculated and listed in the table.

[0116] Table 2:

[0117] alloy powder B1 B2 B3 B4 Alloy Type Auxiliary alloy powder Auxiliary alloy powder Auxiliary alloy powder Auxiliary alloy powder Nd 89.37 88.45 88.00 88.45 B 0.08 0.10 0.15 0.10 Cu 4.80 5.10 5.40 5.8 Al 5.20 5.80 5.90 5.1 Ti 0.55 0.55 0.55 0.55 V 2.32 2.09 2.02 2.20 W 1.28 1.34 1.29 1.04 Does it satisfy formula (2)? √ √ √ √ Does it satisfy formula (3)? √ √ √ ×

[0118] According to the above auxiliary alloy element ratio requirements, the required raw materials are prepared, heated and melted in a vacuum medium frequency induction melting furnace under argon protection, and then poured onto a rotating copper roller to obtain a solidified alloy sheet;

[0119] Auxiliary alloy hydrogen cracking process:

[0120] A hydrogen cracking furnace is used to absorb hydrogen under hydrogen pressure and then dehydrogenate. Before hydrogen absorption, the hydrogen cracking furnace is evacuated to 1.1×10-2Pa, and then filled with argon to 1KPa~1.5KPa. The temperature is raised to 200~300℃ and kept warm for 1~3 hours to preheat and activate the casting. Then, the furnace is evacuated to 1×10-2Pa, and hydrogen is filled to 0.2MPa~0.25MPa to absorb hydrogen. The hydrogen absorption time is 23-36 hours. Dehydrogenation is carried out at 450-600℃ for 0.5-1 hour, and argon is filled for protection and cooled. After cooling to 25℃, the casting is taken out of the furnace.

[0121] Auxiliary alloy powder making process:

[0122] The coarse particles with a particle size of less than 1.5 mm obtained by hydrogen crushing are crushed into particles with a particle size of As a preferred method, the air flow milling process is as follows: nitrogen pressure is 0.5MPa to 0.65MPa, and the speed of the separation wheel is 4200 to 5100 rpm.

[0123] Mixing process:

[0124] According to Table 3, the main alloy fine powder and the auxiliary alloy fine powder are mixed in the proportions shown in the table, and the mixing time is 240 minutes;

[0125] Table 3:

[0126]

[0127]

[0128] Molding process:

[0129] The alloy powders obtained in Examples 1-10 and Comparative Examples 11-15 in Table 3 were formed in a magnetic field of 1.5 to 1.8 T to obtain formed green bodies.

[0130] Sintering process:

[0131] The green body is sintered to obtain a sintered green body (sintered magnet). The sintering is preferably carried out in a vacuum atmosphere at a temperature of 1050-1080°C and a holding time of 6-8 hours.

[0132] Heat treatment process:

[0133] The obtained sintered magnet is preferably subjected to heat treatment for the purpose of improving magnetic properties and high bending strength. Next level tempering exist Secondary tempering Finally, a sintered magnet is obtained.

[0134] The sintered blank was made and machined to produce a 47×20×6mm black sheet sample (with a tolerance of plus or minus 0.05mm). Figure 1 The tooling was tested for flexural strength using the three-point flexural method to evaluate its flexural strength, see Table 4 for details;

[0135] The sintered blank is made into radial magnetic ring for hollow cup motor with the size of D12×D5×10. Figure 2 The radial bursting resistance of the magnetic ring was tested using the tooling, and the results are shown in Table 4.

[0136] Table 4:

[0137]

[0138] As shown in Figure 4, in Examples 1-10, the main alloy powder meets the requirements of formula (1), and the auxiliary alloys meet the requirements of formula (2) and formula (3). The sintered blanks have a bending strength of 360 MPa, which is relatively high. The corresponding blanks are processed into radial magnetic rings with a diameter of D12×D5×10, and their radial explosion resistance is higher than 1800N.

[0139] In Comparative Example 11 in Table 4, the main alloy powder meets the requirements of formula (1), and the auxiliary alloys all meet the requirements of formula (2) and formula (3), but the main-auxiliary alloy ratio is 94:6, resulting in excessive auxiliary alloys. The neodymium-rich phase of the sintered magnet is mostly accumulated in the intergranular triangle, while the neodymium-rich phase at the two-phase boundary is relatively small and thin, with a thickness of less than 10 nanometers, which leads to its bending strength being only 258 MPa; in Comparative Examples 12-14, the main alloy powders do not meet the requirements of formula (1), and the measured bending strengths are all lower than 360 MPa, and the radial explosion resistance of the radial rings is all lower than 1800 N; in Comparative Example 15, the auxiliary alloy does not meet formula (3), its AlCu ratio is too low, the melting point of the auxiliary alloy is too high, the wettability is poor, and the intergranular phase distribution is uneven, resulting in the bending strength failing to reach 360 MPa.

[0140] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high flexural strength sintered NdFeB, characterized by: The method comprises the following steps: Step 1: Main alloy smelting process; Step 2: Main alloy hydrogen cracking process; Step 3: Flour making process; Step 4: Auxiliary alloy smelting process; Step 5: auxiliary alloy hydrogen cracking process; Step 6: Auxiliary alloy powder making process; Step 7: Mixing process; Step 8: Molding process; Step 9: Sintering process; Step 10: Heat treatment process; The main alloying element ratio requirements are: 27.2-29.3 mass% R (R must include any one of Nd and Pr rare earth elements), 0.93-1.0 mass% B, 0.03-0.1 mass% Ti, mass% Cu, 0.03-0.1 mass% Al, Mass%Ga, The main alloying element ratio satisfies the following formula (1): 2.15<(([R]÷143.41)÷([B]÷10.81))<2.30 (1); The auxiliary alloy element ratio requirements are: 87.45-89.92 mass% Nd, 0.08-0.15 mass% B, 0.5-0.8 mass% Ti, % Cu by mass, 5.0-6.0% Al by mass, and when the mass percentages of Nd, B, Ti, Cu, and Al in the composition are respectively recorded as [Nd], [B], [Ti], [Cu], and [Al], the main alloying element ratios satisfy the following formulas (2) and (3): 1.95<(([Nd]÷144.24)÷([Al]÷26.98+[Cu]÷63.55))<2.43 (2) ([Al]÷26.98)÷(2×([Cu]÷63.55))≥1.2 (3).

2. The method for preparing high flexural strength sintered NdFeB according to claim 1, wherein: The main alloy composition is prepared by mixing the required raw materials, heating and melting the main alloy liquid in a rapid solidification vacuum induction melting furnace under argon protection, and then pouring it onto a rotating copper roller to obtain a solidified alloy sheet.

3. The method for preparing high flexural strength sintered NdFeB according to claim 2, wherein: The main alloy liquid is poured onto the rotating copper roll at 1430-1500°C. The rotating speed of the rotating copper roll is The thickness of the quick-setting alloy sheet is 4. The method for preparing high flexural strength sintered NdFeB according to claim 3, wherein: According to the requirements of the auxiliary alloy element ratio, the required raw materials are prepared, heated and melted in a vacuum medium frequency induction melting furnace under argon protection, and then poured onto a rotating copper roller to obtain a solidified alloy sheet. The auxiliary alloy liquid is poured onto the rotating copper roll at 1030℃-1100℃. The casting power of the auxiliary alloy is 0.7-0.9 times the refining power to ensure smooth casting.

5. The method for preparing high flexural strength sintered NdFeB according to claim 4, wherein: The rotating speed of the copper roller is 6. The method for preparing high flexural strength sintered NdFeB according to claim 5, wherein: The thickness of the quick-setting alloy sheet is 7. The method for preparing high flexural strength sintered NdFeB according to claim 6, wherein: The step of preparing one or more main alloy fine powders and one or more auxiliary alloy fine powders; The step of mixing the one or more additional alloy powders so as to account for 1.5 mass % or more and 5.0 mass % or less in 100 mass % of the mixed alloy powder to obtain a mixed alloy powder of the one or more main alloy powders and the one or more auxiliary alloy powders.

8. The method for preparing high flexural strength sintered NdFeB according to claim 7, wherein: The V-shaped mixer is selected and the mixing time is 180-360 minutes.

9. The method for preparing high flexural strength sintered NdFeB according to claim 8, characterized in that: 1 mL / kg of antioxidant was added to the mixed powder.

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