A high-aluminum high-gadolinium low-indium sintered neodymium-iron-boron permanent magnet and a preparation method thereof

Abstract

The application provides a high-aluminum high-gadolinium low-indium sintered neodymium-iron-boron permanent magnet and a preparation method thereof, and belongs to the technical field of permanent magnets.The main alloy raw material and the auxiliary alloy raw material with specific compositions are separately subjected to rapid solidification casting to obtain main alloy castings and auxiliary alloy castings; the main alloy castings and the auxiliary alloy castings with specific proportions are subjected to double-alloy hydrogen crushing to obtain coarse powder; the coarse powder is mixed with an antioxidant and subjected to airflow milling to obtain fine powder; the fine powder is mixed with a lubricant and sequentially subjected to orientation forming, sintering and tempering to obtain the high-aluminum high-gadolinium low-indium sintered neodymium-iron-boron permanent magnet.In the application, the Al and Gd element contents in the sintered neodymium-iron-boron permanent magnet are high, and the low-melting-point In element is added in the form of an alloy to improve the grain boundary distribution of the magnet; without adding Dy and Tb heavy rare earth elements, the sintered neodymium-iron-boron permanent magnet with a magnetic property of 12kGs remanence and a coercive force of 23kOe can be obtained, and the production cost is saved.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet technology, specifically to a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet and its preparation method. Background Technology

[0002] The sintered NdFeB permanent magnet industry is currently facing fierce competition and a challenging situation, with relatively scarce rare earth resources and significant financial pressure on companies. In existing technologies, the Al content in sintered NdFeB permanent magnets with a coercivity of 23 kOe is generally no more than 1%, and the Gd content is generally no more than 5%. It is necessary to add heavy rare earth elements such as Dy and Tb to improve product performance. Given the scarcity of Dy and Tb heavy rare earth resources and the tight financial situation, developing low-cost sintered NdFeB permanent magnets free of Dy and Tb heavy rare earth elements is of great significance. Summary of the Invention

[0003] The purpose of this invention is to provide a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet and its preparation method. The high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet prepared by the method of this invention does not contain Dy and Tb heavy rare earth elements and has low cost.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet, comprising the following steps:

[0006] The main alloying material and the auxiliary alloying material are rapidly solidified and cast separately to obtain main alloy castings and auxiliary alloy castings; the main alloying material comprises M by mass fraction. 1 23-26%, Gd 5-8%, Co 2-3%, Cu 0.2-0.4%, Ga 0.1-0.3%, B 0.9-0.94%, Al 2-2.5%, balance Fe, M 1 The auxiliary alloying material consists of Pr and Nd; the composition of the auxiliary alloying material includes M. 2 28-31%, Ti 0.5-1%, In 0.1-0.5%, B 0.9-0.94%, balance Fe, M 2 For Pr and Nd;

[0007] The main alloy casting and the auxiliary alloy casting are subjected to bi-alloy hydrogen crushing to obtain coarse powder; the mass of the auxiliary alloy casting is 9-15% of the mass of the main alloy casting.

[0008] The coarse powder is mixed with an antioxidant and then subjected to air jet milling to obtain fine powder;

[0009] The fine powder is mixed with a lubricant and then subjected to orientation molding, sintering and tempering processes to obtain a high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnet.

[0010] Preferably, the M 1 The mass ratio of Pr to Nd in the medium was (4.6–5.2):(18.4–20.8); M 2 The mass ratio of Pr to Nd in the medium is (5.6–6.2):(22.4–24.8).

[0011] Preferably, the conditions for preparing the main alloy casting include: refining the main alloy raw material at 1440-1460°C for 2-5 minutes, then cooling it to 1360-1390°C at a rate of 5-8°C / min, holding it at that temperature for 3-6 minutes, and then casting it; the copper roller rotation speed is 35-45 rpm; and the thickness of the main alloy casting is 0.1-0.3 mm.

[0012] Preferably, the conditions for preparing the auxiliary alloy casting include: refining the auxiliary alloy raw material at 1470-1500℃ for 2-5 minutes, then cooling it to 1430-1450℃ at a rate of 3-7℃ / min, holding it at that temperature for 5-9 minutes, and then casting it; the copper roller speed is 35-45 rpm; and the thickness of the auxiliary alloy casting is 0.1-0.3 mm.

[0013] Preferably, the hydrogen decomposition of the dual alloy includes sequential hydrogen absorption and dehydrogenation treatments; the hydrogen absorption treatment is performed at room temperature for 150–210 min; the dehydrogenation treatment is performed at 550–640 °C for 3–5 h.

[0014] Preferably, the antioxidant is 0.4 to 0.6‰ of the mass of the coarse powder; the grinding pressure of the air jet mill is 5.9 to 6.1 MPa, and the powder output speed is 190 to 220 kg / h; the particle size d50 of the fine powder is 3.9 to 4.3 μm.

[0015] Preferably, the mass of the lubricant is 0.5–0.7‰ of the mass of the fine powder; the orientation molding is carried out under conditions of magnetic induction intensity of 1.9–2.3T and molding pressure of 3–6MPa; the density of the green body obtained after orientation molding is 4.1–4.25 g / cm³. 3 .

[0016] Preferably, the sintering operating conditions include: vacuum degree ≤ 5 × 10⁻⁶. -2 Pa, temperature 1050~1075℃, heat preservation time 3~5h.

[0017] Preferably, the tempering treatment includes a first tempering treatment and a second tempering treatment performed sequentially; the conditions for the first tempering treatment include: vacuum degree ≤ 5 Pa, temperature 860~920℃, and holding time 3~5 h; the conditions for the second tempering treatment include: vacuum degree ≤ 5 Pa, temperature 550~630℃, and holding time 4~7 h.

[0018] This invention provides a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet prepared by the preparation method described in the above technical solution.

[0019] This invention provides a method for preparing a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet, comprising the following steps: rapidly solidifying and casting the main alloy raw material and the auxiliary alloy raw material separately to obtain the main alloy casting and the auxiliary alloy casting; the main alloy raw material, by mass fraction, comprises M 1 23-26%, Gd 5-8%, Co 2-3%, Cu 0.2-0.4%, Ga 0.1-0.3%, B 0.9-0.94%, Al 2-2.5%, balance Fe, M 1 The auxiliary alloying material consists of Pr and Nd; the composition of the auxiliary alloying material includes M. 2 29-31%, Ti 0.5-1%, In 0.1-0.5%, B 0.9-0.94%, balance Fe, M 2 The main alloy casting and auxiliary alloy casting are subjected to bi-alloy hydrogen crushing to obtain coarse powder; the mass of the auxiliary alloy casting is 9-15% of the mass of the main alloy casting; the coarse powder is mixed with an antioxidant and subjected to air jet milling to obtain fine powder; the fine powder is mixed with a lubricant and subjected to orientation forming, sintering and tempering treatment in sequence to obtain a high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnet. In this invention, the sintered NdFeB permanent magnet has a high content of Al and Gd elements, and low-melting-point In element is added in an alloying manner to improve the magnet grain boundary distribution and enhance (PrNd)2-Fe. 14 -B phase and Gd2-Fe 14 The anisotropy of the -B phase can improve product performance. Without adding Dy and Tb heavy rare earth elements and with a small amount of praseodymium and neodymium, sintered NdFeB permanent magnets with a remanence of 12 kGs and a coercivity of 23 kOe can be obtained. This reduces the consumption of Dy and Tb heavy rare earth resources, saves production costs, and enhances product competitiveness. Furthermore, the method provided by this invention is suitable for mass production, and the prepared products have good stability. Detailed Implementation

[0020] This invention provides a method for preparing a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet, comprising the following steps:

[0021] The main alloying material and the auxiliary alloying material are rapidly solidified and cast separately to obtain main alloy castings and auxiliary alloy castings; the main alloying material comprises M by mass fraction. 1 23-26%, Gd 5-8%, Co 2-3%, Cu 0.2-0.4%, Ga 0.1-0.3%, B 0.9-0.94%, Al 2-2.5%, balance Fe, M 1 The auxiliary alloying material consists of Pr and Nd; the composition of the auxiliary alloying material includes M. 2 28-31%, Ti 0.5-1%, In 0.1-0.5%, B 0.9-0.94%, balance Fe, M 2 For Pr and Nd;

[0022] The main alloy casting and the auxiliary alloy casting are subjected to bi-alloy hydrogen crushing to obtain coarse powder; the mass of the auxiliary alloy casting is 9-15% of the mass of the main alloy casting.

[0023] The coarse powder is mixed with an antioxidant and then subjected to air jet milling to obtain fine powder;

[0024] The fine powder is mixed with a lubricant and then subjected to orientation molding, sintering and tempering processes to obtain a high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnet.

[0025] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0026] This invention involves rapidly solidifying and casting the main alloying material and the auxiliary alloying material separately to obtain main alloy castings and auxiliary alloy castings. In this invention, the main alloying material, by mass fraction, comprises M... 1 23-26%, Gd 5-8%, Co 2-3%, Cu 0.2-0.4%, Ga 0.1-0.3%, B 0.9-0.94%, Al 2-2.5%, balance Fe; preferably including M 1 24-25%, Gd 6-7%, Co 2.2-2.5%, Cu 0.2-0.3%, Ga 0.1-0.2%, B 0.9-0.92%, Al 2-2.2%; specifically, M can be... 1 24%, Gd 6%, Co 2%, Cu 0.3%, Ga 0.2%, B 0.92%, Al 2.2%, balance Fe; or it can be M 1 26%, Gd 5%, Co 2.2%, Cu 0.3%, Ga 0.2%, B 0.92%, Al 2.5%, balance Fe; or it could be M 123%, Gd 8%, Co 2%, Cu 0.3%, Ga 0.2%, B 0.92%, Al 2%, balance Fe. In this invention, the M 1 For Pr and Nd, the M 1 The preferred mass ratio of Pr to Nd is (4.6–5.2):(18.4–20.8), specifically 4.8:19.2, 5.2:20.8, or 4.6:18.4. In this invention, the auxiliary alloying material comprises M... 2 28-31%, Ti 0.5-1%, In 0.1-0.5%, B 0.9-0.94%, balance Fe; preferably including M 2 29-30%, Ti 0.5-0.7%, In 0.3-0.5%, B 0.9-0.92%, balance Fe; specifically, M 2 29%, Ti 0.5%, In 0.3%, B 0.92%, balance Fe; or it can be M 2 30%, Ti 0.5%, In 0.5%, B 0.92%, balance Fe. In this invention, the M... 2 For Pr and Nd, the M 2 The preferred mass ratio of Pr to Nd is (5.6–6.2):(22.4–24.8), and more preferably 5.8:23.2.

[0027] This invention involves batching ingredients according to a formula design to obtain main alloy raw materials and auxiliary alloy raw materials. These materials are then rapidly solidified and cast into sheets to obtain main alloy sheets and auxiliary alloy sheets, respectively. In this invention, the preferred conditions for preparing the rapidly solidified main alloy sheets include: refining the main alloy raw materials at 1440–1460°C for 2–5 minutes, then cooling them to 1360–1390°C at a rate of 5–8°C / min, holding at this temperature for 3–6 minutes, and then casting. The refining temperature is further preferably 1450–1445°C, and the casting temperature is further preferably 1370–1380°C. The copper roller rotation speed is preferably 35–45 rpm, more preferably 40–42 rpm. In this invention, the thickness of the main alloy sheet is preferably 0.1–0.3 mm, more preferably 0.26 mm. In this invention, the preferred conditions for preparing the auxiliary alloy casting include: refining the auxiliary alloy raw material at 1470–1500°C for 2–5 minutes, then cooling it to 1430–1450°C at a rate of 3–7°C / min, holding it at that temperature for 5–9 minutes, and then casting it; wherein the refining temperature is further preferably 1480–1490°C, and the casting temperature is further preferably 1435–1440°C; the copper roller speed is preferably 35–45 rpm, more preferably 40–42 rpm. In this invention, the thickness of the auxiliary alloy casting is preferably 0.1–0.3 mm, more preferably 0.26 mm.

[0028] After obtaining the main alloy casting and the auxiliary alloy casting, the present invention performs bi-alloy hydrogen crushing on the main alloy casting and the auxiliary alloy casting to obtain coarse powder. In the present invention, the mass of the auxiliary alloy casting is preferably 9-15% of the mass of the main alloy casting, more preferably 12-13%. In the present invention, the bi-alloy hydrogen crushing preferably includes sequential hydrogen absorption and dehydrogenation treatments; the temperature of the hydrogen absorption treatment is preferably room temperature, specifically 25°C in the embodiments of the present invention; the time of the hydrogen absorption treatment is preferably 150-210 min, more preferably 160-175 min; the temperature of the dehydrogenation treatment is preferably 550-640°C, more preferably 570-595°C, further preferably 580-590°C, and the holding time is preferably 3-5 h, more preferably 4-5 h. After the dehydrogenation treatment, the present invention preferably cools to <40°C to obtain coarse powder. The present invention does not have a special limitation on the particle size of the coarse powder. In the embodiments of the present invention, the bi-alloy hydrogen crushing is specifically carried out in a hydrogen crushing furnace.

[0029] After obtaining coarse powder, the present invention mixes the coarse powder with an antioxidant and performs air jet milling to obtain fine powder. In the present invention, the antioxidant is preferably a lipid-based No. 3 antioxidant, and the mass of the antioxidant is preferably 0.4-0.6‰ of the mass of the coarse powder, more preferably 0.5‰. In the present invention, the grinding pressure of the air jet mill is preferably 5.9-6.1 MPa, more preferably 6 MPa; the powder output speed is preferably 190-220 kg / h, more preferably 203-217 kg / h, and even more preferably 205-210 kg / h. In the present invention, the d50 of the fine powder is preferably 3.9-4.3 μm, more preferably 4.04-4.20 μm, and even more preferably 4.1-4.16 μm.

[0030] After obtaining the fine powder, the present invention mixes the fine powder with a lubricant and performs orientation molding to obtain a green body. In the present invention, the lubricant is preferably a grease-based lubricant, and the mass of the lubricant is preferably 0.5-0.7‰ of the mass of the fine powder, more preferably 0.6‰. In the present invention, the orientation molding is preferably carried out under conditions of a magnetic induction intensity of 1.9-2.3T and a molding pressure of 3-6MPa, the magnetic induction intensity is further preferably 2.1T, and the molding pressure is further preferably 4MPa. In the present invention, the density of the green body is preferably 4.1-4.25 g / cm³. 3 More preferably, it is 4.13–4.18 g / cm³. 3 In an embodiment of the present invention, the orientation forming is specifically performed in a magnetic field press.

[0031] After obtaining the green blank, the present invention sintersulates the green blank to obtain a sintered material. In the present invention, the sintering conditions preferably include: a vacuum degree preferably ≤5×10⁻⁶. -2 Pa, more preferably 6 × 10 Pa -3 Pa; the preferred temperature is 1050–1075℃, more preferably 1065–1068℃; the preferred holding time is 3–5 h, more preferably 4–5 h. In this invention, the heating rate from room temperature to the required sintering temperature is preferably 3–5℃ / min, more preferably 4℃ / min. In this invention, after the holding period during sintering is completed, the temperature is preferably reduced to 50–70℃ at a rate of 9–12℃ / min to obtain the sintered material; more preferably, it is reduced to 60℃ at a rate of 10℃ / min to obtain the sintered material. In an embodiment of this invention, the sintering is specifically carried out in a sintering furnace.

[0032] After obtaining the sintered material, the present invention tempers the sintered material to obtain a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet. In the present invention, the tempering treatment includes a first tempering treatment and a second tempering treatment performed sequentially. In the present invention, the conditions for the first tempering treatment preferably include: a vacuum degree preferably ≤5 Pa, more preferably 3 Pa; a temperature preferably 860–920℃, more preferably 890–900℃; and a holding time preferably 3–5 h, more preferably 3.5 h. In the present invention, the heating rate to the temperature required for the first tempering treatment is preferably 3–6℃ / min, more preferably 4℃ / min; after the holding time in the first tempering treatment, it is preferably cooled to 40–60℃, preferably 55℃, using continuous argon gas cooling, before proceeding with the second tempering treatment. In this invention, the conditions for the second tempering treatment preferably include: a vacuum degree preferably ≤5 Pa, more preferably 3 Pa; a temperature preferably 550–630 °C, more preferably 620 °C; and a holding time preferably 4–7 h, more preferably 5 h. In this invention, the heating rate to the temperature required for the second tempering treatment is preferably 3–6 °C / min, more preferably 4 °C / min; after the holding time in the second tempering treatment is completed, it is preferably cooled to 35–45 °C, preferably 40 °C, using a continuous argon-filled air cooling method, to obtain a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet.

[0033] This invention provides a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet prepared by the preparation method described in the above technical solution.

[0034] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Example 1

[0036] The ingredients are formulated according to the design composition. By mass fraction, the main alloy raw material consists of 24% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 4.8:19.2), 6% Gd, 2% Co, 0.3% Cu, 0.2% Ga, 0.92% B, 2.2% Al, and the balance Fe. The auxiliary alloy raw material consists of 29% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 5.8:23.2), 0.5% Ti, 0.3% In, 0.92% B, and the balance Fe.

[0037] The main alloy raw material is rapidly solidified and cast to obtain a main alloy casting sheet with a thickness of 0.26 mm. The conditions for the rapid solidification casting sheet include: refining the main alloy raw material at 1460°C for 4 min, then cooling it to 1380°C at a rate of 6°C / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 40 rpm.

[0038] The auxiliary alloy raw material is subjected to rapid solidification casting to obtain an auxiliary alloy casting sheet with a thickness of 0.26 mm. The conditions for rapid solidification casting include: refining the auxiliary alloy raw material at 1500℃ for 5 min, then cooling it to 1430℃ at a rate of 6℃ / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 40 rpm.

[0039] The main alloy casting and the auxiliary alloy casting are placed in a hydrogen crushing furnace. The mass of the auxiliary alloy casting is 15% of the mass of the main alloy casting. The hydrogen crushing is carried out by a dual alloy process. Specifically, the hydrogen is absorbed at room temperature (25°C) for 175 min, and then dehydrogenation is carried out at 595°C for 5 h. After that, the mixture is cooled to <40°C to obtain coarse powder.

[0040] The coarse powder is mixed with lipid-based antioxidant #3, wherein the mass of lipid-based antioxidant #3 is 0.5‰ of the mass of the coarse powder. The resulting mixture is then subjected to air jet milling to obtain fine powder. The grinding pressure of the air jet milling is 6 MPa, and the powder output speed is 210 kg / h. The d50 of the fine powder is 4.1 μm.

[0041] The fine powder was mixed with a grease lubricant for 2 hours, the mass of which was 6‰ of the fine powder mass. The resulting mixture was then placed in a magnetic field press and oriented under conditions of a magnetic induction intensity of 2.1T and a molding pressure of 4MPa, resulting in a density of 4.18 g / cm³. 3 raw blanks;

[0042] The green blank was placed in a sintering furnace and heated from room temperature to 1068°C at a rate of 4°C / min, while maintaining a temperature of 1068°C and a vacuum degree of 6×10⁻⁶. -3 Sintering was carried out under Pa conditions for 5 hours, and then the temperature was lowered to 60°C at a rate of 10°C / min to obtain sintered material. Then, the temperature was raised to 890°C at a rate of 4°C / min, and a first tempering treatment was carried out at 890°C and a vacuum degree of 3Pa for 3.5 hours. The temperature was then cooled to 55°C by continuous air cooling with argon gas, and then raised to 620°C at a rate of 4°C / min. A second tempering treatment was carried out at 620°C and a vacuum degree of 3Pa for 5 hours. The temperature was then cooled to 40°C by continuous air cooling with argon gas to obtain high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnets.

[0043] Three high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet samples were prepared repeatedly according to the method in Example 1, and then subjected to 20°C. The cylindrical test specifically measured the remanence (Br), coercivity (Hcb), intrinsic coercivity (Hcj), magnetic energy product ((BH)max), reverse magnetic field (Hk) at J=0.9Jr on the J-demagnetization curve of the magnet, and squareness (Hk / Hcj). The specific results are shown in Table 1. Table 1 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention, after testing, exhibit a remanence of 12 kGs and an intrinsic coercivity of 23 kOe. Furthermore, Table 1 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention have good product stability.

[0044] Table 1. Performance test results of three high-aluminum, high-gadolinium, low-indium sintered NdFeB permanent magnet samples in Example 1.

[0045]

[0046] Example 2

[0047] The ingredients are formulated according to the design composition. By mass fraction, the main alloy raw material consists of 26% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 5.2:20.8), 5% Gd, 2.2% Co, 0.3% Cu, 0.2% Ga, 0.92% B, 2.5% Al, and the balance Fe; the auxiliary alloy raw material consists of 30% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 5.8:23.2), 0.5% Ti, 0.5% In, 0.92% B, and the balance Fe.

[0048] The main alloy raw material is rapidly solidified and cast to obtain a main alloy casting sheet with a thickness of 0.24 mm. The conditions for the rapid solidification casting sheet include: refining the main alloy raw material at 1450°C for 5 min, then cooling it to 1370°C at a rate of 6°C / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 42 rpm.

[0049] The auxiliary alloy raw material is rapidly solidified and cast to obtain an auxiliary alloy casting sheet with a thickness of 0.24 mm. The conditions for the rapid solidification casting sheet include: refining the auxiliary alloy raw material at 1490°C for 5 min, then cooling it to 1435°C at a rate of 6°C / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 42 rpm.

[0050] The main alloy casting and the auxiliary alloy casting are placed in a hydrogen crushing furnace. The mass of the auxiliary alloy casting is 13% of the mass of the main alloy casting. The hydrogen crushing is carried out by a dual alloy process. Specifically, the hydrogen is absorbed at room temperature (25°C) for 175 min, and then dehydrogenation is carried out at 590°C for 5 h. After that, it is cooled to <40°C to obtain coarse powder.

[0051] The coarse powder was mixed with lipid-based antioxidant #3, wherein the mass of lipid-based antioxidant #3 was 0.5‰ of the mass of the coarse powder. The resulting mixture was then subjected to air jet milling to obtain fine powder. The grinding pressure of the air jet milling was 6 MPa, and the powder output speed was 203 kg / h. The d50 of the fine powder was 4.04 μm.

[0052] The fine powder was mixed with a grease lubricant for 2 hours, the mass of which was 6‰ of the fine powder mass. The resulting mixture was then placed in a magnetic field press and oriented under conditions of a magnetic induction intensity of 2.1T and a molding pressure of 4MPa, resulting in a density of 4.13 g / cm³. 3 raw blanks;

[0053] The green blank was placed in a sintering furnace and heated from room temperature to 1068°C at a rate of 4°C / min, while maintaining a temperature of 1068°C and a vacuum degree of 6×10⁻⁶. -3 Sintering was carried out under Pa conditions for 5 hours, and then the temperature was lowered to 60°C at a rate of 10°C / min to obtain sintered material. Then, the temperature was raised to 890°C at a rate of 4°C / min, and a first tempering treatment was carried out at 890°C and a vacuum degree of 3Pa for 3.5 hours. The temperature was then cooled to 55°C by continuous air cooling with argon gas, and then raised to 620°C at a rate of 4°C / min. A second tempering treatment was carried out at 620°C and a vacuum degree of 3Pa for 5 hours. The temperature was then cooled to 40°C by continuous air cooling with argon gas to obtain high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnets.

[0054] Three high-aluminum, high-gadolinium, low-indium sintered NdFeB permanent magnet samples were prepared repeatedly according to the method in Example 2, and then subjected to 20°C. The cylindrical test specifically measured the remanence (Br), magnetic coercivity (Hcb), intrinsic coercivity (Hcj), magnetic energy product ((BH)max), reverse magnetic field (Hk) at J=0.9Jr on the J-demagnetization curve of the magnet, and squareness (Hk / Hcj). The specific results are shown in Table 2. Table 2 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention, after testing, exhibit a remanence of 12 kGs and an intrinsic coercivity of 23 kOe. Furthermore, Table 2 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention have good product stability.

[0055] Table 2. Performance test results of three high-aluminum, high-gadolinium, low-indium sintered NdFeB permanent magnet samples in Example 2.

[0056]

[0057] Example 3

[0058] The ingredients are formulated according to the design composition. By mass fraction, the main alloy raw material consists of 23% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 4.6:18.4), 8% Gd, 2% Co, 0.3% Cu, 0.2% Ga, 0.92% B, 2% Al, and the balance Fe. The auxiliary alloy raw material consists of 29% praseodymium and neodymium (of which, the mass ratio of Pr to Nd is 5.8:23.2), 0.5% Ti, 0.3% In, 0.92% B, and the balance Fe.

[0059] The main alloy raw material is rapidly solidified and cast to obtain a main alloy casting sheet with a thickness of 0.24 mm. The conditions for the rapid solidification casting sheet include: refining the main alloy raw material at 1445℃ for 5 min, then cooling it to 1360℃ at a rate of 6℃ / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 42 rpm.

[0060] The auxiliary alloy raw material is rapidly solidified and cast to obtain an auxiliary alloy casting sheet with a thickness of 0.24 mm. The conditions for the rapid solidification casting sheet include: refining the auxiliary alloy raw material at 1490°C for 5 min, then cooling it to 1435°C at a rate of 6°C / min, holding it at that temperature for 5 min, and then casting it; the copper roller speed is 42 rpm.

[0061] The main alloy casting and the auxiliary alloy casting are placed in a hydrogen crushing furnace. The mass of the auxiliary alloy casting is 15% of the mass of the main alloy casting. The hydrogen crushing is carried out by a dual alloy process. Specifically, the hydrogen is absorbed at room temperature (25°C) for 175 min, and then dehydrogenation is carried out at 595°C for 5 h. After that, the mixture is cooled to <40°C to obtain coarse powder.

[0062] The coarse powder was mixed with lipid-based antioxidant #3, wherein the mass of lipid-based antioxidant #3 was 0.5‰ of the mass of the coarse powder. The resulting mixture was then subjected to air jet milling to obtain fine powder. The grinding pressure of the air jet milling was 6 MPa, and the powder output speed was 217 kg / h. The d50 of the fine powder was 4.16 μm.

[0063] The fine powder was mixed with a grease lubricant for 2 hours, the mass of which was 6‰ of the fine powder mass. The resulting mixture was then placed in a magnetic field press and oriented under conditions of a magnetic induction intensity of 2.1T and a molding pressure of 4MPa, resulting in a density of 4.18 g / cm³. 3 raw blanks;

[0064] The green blank was placed in a sintering furnace and heated from room temperature to 1065°C at a rate of 4°C / min, while maintaining a temperature of 1065°C and a vacuum degree of 6×10⁻⁶. -3 The material was sintered for 5 hours under Pa conditions, then cooled to 60°C at a rate of 10°C / min to obtain the sintered material. The temperature was then increased to 920°C at a rate of 4°C / min, and subjected to a first tempering treatment of 3.5 hours at 920°C and a vacuum of 3 Pa. It was then cooled to 55°C using continuous argon air cooling, followed by a second tempering treatment of 5 hours at 620°C and a vacuum of 3 Pa. Finally, it was cooled to 40°C using continuous argon air cooling to obtain a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet.

[0065] Three high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet samples were prepared repeatedly according to the method in Example 3, and then subjected to 20°C. The cylindrical test specifically measured the remanence (Br), magnetic coercivity (Hcb), intrinsic coercivity (Hcj), magnetic energy product ((BH)max), reverse magnetic field (Hk) at J=0.9Jr on the J-demagnetization curve of the magnet, and squareness (Hk / Hcj). The specific results are shown in Table 3. Table 3 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention, after testing, exhibit a remanence of 12 kGs and an intrinsic coercivity of 23 kOe. Furthermore, Table 3 shows that the high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnets prepared using the method provided by this invention have good product stability.

[0066] Table 3. Performance test results of three high-aluminum, high-gadolinium, low-indium sintered NdFeB permanent magnet samples in Example 3.

[0067]

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet, comprising the following steps: The main alloying material and the auxiliary alloying material are rapidly solidified and cast separately to obtain main alloy castings and auxiliary alloy castings; the main alloying material comprises M by mass fraction. 1 23-26%, Gd 5-8%, Co 2-3%, Cu 0.2-0.4%, Ga 0.1-0.3%, B 0.9-0.94%, Al 2-2.5%, balance Fe, M 1 For Pr and Nd, the M 1 The mass ratio of Pr to Nd is (4.6~5.2):(18.4~20.8); the composition of the auxiliary alloying material includes M. 2 28~31%, Ti 0.5~1%, In 0.1~0.5%, B 0.9~0.94%, balance Fe, M 2 For Pr and Nd, the M 2 The mass ratio of Pr to Nd in the medium was (5.6~6.2):(22.4~24.8). The main alloy casting and auxiliary alloy casting are subjected to bi-alloy hydrogen crushing to obtain coarse powder; the mass of the auxiliary alloy casting is 9-15% of the mass of the main alloy casting. The coarse powder is mixed with an antioxidant and then subjected to air jet milling to obtain fine powder; The fine powder is mixed with a lubricant and then subjected to orientation molding, sintering and tempering processes to obtain a high-alumina, high-gadolinium, and low-indium sintered NdFeB permanent magnet.

2. The preparation method according to claim 1, characterized in that, The conditions for preparing the main alloy casting include: refining the main alloy raw material at 1440~1460℃ for 2~5 min, then cooling it to 1360~1390℃ at a rate of 5~8℃ / min, holding it at that temperature for 3~6 min, and then casting it; the copper roller speed is 35~45 rpm; and the thickness of the main alloy casting is 0.1~0.3 mm.

3. The preparation method according to claim 1, characterized in that, The conditions for preparing the auxiliary alloy casting include: refining the auxiliary alloy raw material at 1470~1500℃ for 2~5 min, then cooling it to 1430~1450℃ at a rate of 3~7℃ / min, holding it at that temperature for 5~9 min, and then casting it; the copper roller speed is 35~45 rpm; and the thickness of the auxiliary alloy casting is 0.1~0.3 mm.

4. The preparation method according to claim 1, characterized in that, The hydrogen decomposition of the dual alloy includes sequential hydrogen absorption and dehydrogenation treatments; the hydrogen absorption treatment is performed at room temperature for 150-210 min; the dehydrogenation treatment is performed at 550-640℃ for 3-5 h.

5. The preparation method according to claim 1, characterized in that, The antioxidant is 0.4-0.6‰ of the mass of the coarse powder; the grinding pressure of the air jet mill is 5.9-6.1 MPa, and the powder output speed is 190-220 kg / h; the particle size d50 of the fine powder is 3.9-4.3 μm.

6. The preparation method according to claim 1, characterized in that, The mass of the lubricant is 0.5-0.7‰ of the mass of the fine powder; the orientation molding is carried out under conditions of magnetic induction intensity of 1.9-2.3T and molding pressure of 3-6MPa; the density of the green body obtained after orientation molding is 4.1-4.25 g / cm³. 3 .

7. The preparation method according to claim 1, characterized in that, The sintering conditions include: vacuum degree ≤ 5 × 10⁻⁶ -2 Pa, temperature 1050~1075℃, heat preservation time 3~5h.

8. The preparation method according to claim 1 or 7, characterized in that, The tempering process includes a first tempering process and a second tempering process performed sequentially. The conditions for the first tempering process are: vacuum degree ≤ 5 Pa, temperature 860~920℃, and holding time 3~5 h. The conditions for the second tempering process are: vacuum degree ≤ 5 Pa, temperature 550~630℃, and holding time 4~7 h.

9. The high-alumina, high-gadolinium, low-indium sintered NdFeB permanent magnet prepared by the preparation method according to any one of claims 1 to 8.

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