A manufacturing process of neodymium iron boron magnet and transformer manufactured therefrom

Abstract

The present invention discloses a manufacturing process for NdFeB magnets and a transformer manufactured therefrom, comprising the following steps: (1) mixing and smelting alloy raw materials and preparing alloy flakes by a rapid solidification thin-sheet method; (2) subjecting the alloy flakes to hydrogen explosion, adding additives, and then jet milling to form alloy powder; (3) banburying the alloy powder with a lubricant and an antioxidant, and then subjecting the alloy powder to segmented pressing using a combination of isostatic pressing and variable pressure pressing under magnetic field orientation to form a compact; (4) subjecting the compact to variable temperature sintering and multi-stage aging treatment in a protective gas atmosphere to obtain NdFeB magnets. The present invention can solve the problem of poor temperature characteristics of NdFeB magnets and alleviate the difficulties faced by enterprises due to the scarcity and high price of rare earth resources.

Description

Technical Field

[0001] The invention relates to a manufacturing process of NdFeB magnetic steel and a transformer manufactured therefrom, belonging to the technical field of permanent magnetic materials. Background Art

[0002] Neodymium iron boron magnets are commonly used rare earth magnets with excellent magnetic properties. They are widely used in permanent magnet motors, electric vehicle motors, intelligent large-scale DC power supply systems, fast charging systems, aerospace and military industries, such as intelligent large-scale DC converter transformers, intelligent reactors and other transformers, rectifiers and inductors.

[0003] Sintered NdFeB magnets, key components of transformers, rectifiers, and inductors, are experiencing increasing market demand. The heat generated by these devices during high-speed operation subjects them to relatively high operating temperatures, requiring them to possess higher thermal stability and coercivity. However, existing sintered NdFeB magnets have poor temperature characteristics, weakening their magnetic properties at high temperatures. Other approaches to improving the performance of sintered NdFeB magnets include adding heavy rare earths to form an anisotropic shell on the surface of the NdFeB magnets. However, the scarcity and high cost of heavy rare earth resources increase the cost of NdFeB magnets.

[0004] Therefore, it is necessary to develop a manufacturing process for NdFeB steel to solve the above problems. Summary of the Invention

[0005] In order to address at least one problem existing in the above-mentioned prior art, the present invention provides a manufacturing process for NdFeB magnets, which can solve the problem of poor temperature characteristics of NdFeB magnets; and alleviate the difficulties brought to enterprises by the scarcity and high price of rare earth resources; the NdFeB magnets of the present invention are used to manufacture transformers, rectifiers, inductors, etc.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a manufacturing process of NdFeB magnet steel, comprising the following steps:

[0007] (1) Mixing and smelting the cleaned raw materials of neodymium iron alloy, boron iron alloy, pure iron, niobium hafnium alloy, neodymium copper alloy, aluminum gallium alloy, aluminum powder and copper powder to form an alloy liquid, and then preparing the alloy liquid into an alloy sheet by a rapid solidification thin sheet method;

[0008] (2) The alloy flakes are hydrogen-blasted, carbonyl iron powder and zirconium carbide particles are added, and then jet milled to form alloy powder;

[0009] (3) The alloy powder is mixed with a lubricant and an antioxidant through internal kneading, and then is subjected to segmented pressing by combining isostatic pressing and variable pressure pressing under magnetic field orientation to form a compact;

[0010] (4) Under a protective gas atmosphere, the compact is subjected to variable temperature sintering and then to multi-stage aging treatment to obtain NdFeB magnets.

[0011] Preferably, in step (1), the thickness of the alloy sheet is 0.15 to 0.3 mm, preferably 0.18 mm, 0.22 mm, or 0.28 mm.

[0012] Preferably, in step (1), the alloy sheet comprises the following raw material composition and its mass ratio: the mass ratio of neodymium iron alloy, boron iron alloy, pure iron, niobium hafnium alloy, neodymium copper alloy, aluminum gallium alloy, aluminum powder and copper powder is 32:10~12:15~18:5~6:2~4:0.3~0.4:0.1~0.15:0.2~0.25; preferably 32:11.2:16:5.6:3.2:0.35:0.13:0.22.

[0013] Preferably, in step (2), the amount of carbonyl iron powder added is 0.28-0.49% of the weight of the alloy flakes.

[0014] Preferably, in step (2), the amount of zirconium carbide particles added is 0.37-0.62% of the weight of the alloy flakes.

[0015] Preferably, in step (2), the particle size of the alloy powder is 3.2 to 4.8 μm, preferably 3.5 μm, 4.2 μm, or 4.6 μm.

[0016] Preferably, in step (3), the lubricant is Kenolube P11; and the amount added is 0.12 to 0.18% of the weight of the alloy powder.

[0017] Preferably, in step (3), the antioxidant is composed of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 5:1-2, and the added amount is 0.14-0.22% of the weight of the alloy powder.

[0018] Preferably, the hindered phenol antioxidant is antioxidant 3224, and the phosphite antioxidant is antioxidant 626.

[0019] Preferably, in step (3), the segmented pressing process is: maintaining at constant temperature and constant pressure - maintaining at a constant temperature and then increasing the pressure - maintaining at a constant temperature and then decreasing the pressure - maintaining at a constant temperature and then decreasing the pressure - maintaining at a constant temperature and then decreasing the pressure - maintaining at a constant temperature and then releasing the pressure.

[0020] Preferably, in step (3), the segmented pressing process is: maintaining a temperature of 110-120°C and a pressure of 70-80 MPa for 10-15 minutes, keeping the temperature constant, gradually increasing the pressure to 300-310 MPa and maintaining it for 5-10 minutes, then increasing the temperature and reducing the pressure to a temperature of 455-475°C and a pressure of 65-75 MPa, maintaining it for 20-30 seconds, then reducing the temperature and increasing the pressure to a temperature of 90-100°C and a pressure of 160-170 MPa, maintaining it for 5-10 minutes, keeping the temperature constant, gradually reducing the pressure to 100-110 MPa, maintaining it for 5-10 minutes, and then keeping the temperature and releasing the pressure to normal pressure.

[0021] Preferably, the rate of gradual pressure increase is 5 to 8 MPa / min; the heating rate of temperature increase and pressure reduction is 5.5 to 6.5°C / min and the pressure reduction rate is 3.5 to 4.5 MPa / min; the cooling rate of temperature decrease and pressure increase is 8 to 10°C / min and the pressure increase rate is 2 to 3 MPa / min; the rate of gradual pressure reduction is 1.5 to 2.5 MPa / min.

[0022] Preferably, in step (4), the variable temperature sintering process is: gradually heating up and then keeping warm - accelerating heating up and then keeping warm - gradually cooling down and then keeping warm - accelerating cooling down and then keeping warm - gradually heating up and then keeping warm.

[0023] Preferably, in step (4), the variable temperature sintering process is: first gradually heating to 220-240°C, keeping warm for 1-2 hours, then accelerating heating to 1560-1620°C, keeping warm for 0.5-1.5 hours, then gradually cooling to 1360-1400°C, keeping warm for 1-2 hours, then accelerating cooling to 760-800°C, keeping warm for 2-3 hours, then gradually heating to 1230-1280°C, keeping warm for 1-2 hours.

[0024] Preferably, the rate of gradual heating is 5-10°C / min; the rate of accelerated heating is 15-20°C / min; the rate of gradual cooling is 10-15°C / min; and the rate of accelerated cooling is 20-25°C / min.

[0025] Preferably, in step (4), the multi-stage aging treatment includes primary aging treatment, secondary aging treatment and tertiary aging treatment.

[0026] Preferably, in step (4), the multi-stage aging treatment process is: first, a primary aging treatment is performed at a temperature of 980-1020°C for 0.5-1.5 hours, then a secondary aging treatment is performed at a temperature of 760-800°C for 2-3 hours, and finally a tertiary aging treatment is performed at a temperature of 420-460°C for 1-2 hours.

[0027] Preferably, in step (4), the protective gas is composed of a combination of carbon dioxide and argon.

[0028] The NdFeB magnet manufactured by the present invention is used as a magnetic core and is applied to manufacturing transformers, rectifiers and inductors.

[0029] Beneficial effects of the present invention:

[0030] 1. The manufacturing process of the present invention uses neodymium iron alloy, ferroboron alloy, pure iron, niobium hafnium alloy, neodymium copper alloy, aluminum gallium alloy, aluminum powder and copper powder as raw materials, which are crushed by hydrogen, and then carbonyl iron powder and zirconium carbide particles are added for air flow milling, and then lubricant and antioxidant are added for mixing, and then subjected to segmented pressing combining isostatic pressing and variable pressure, variable temperature sintering and multi-stage aging treatment. The obtained neodymium iron boron magnet has more excellent thermal stability and corrosion resistance, and good magnetic properties; 2. The neodymium iron boron magnet manufactured by the present invention maintains good magnetic properties at high temperatures and has good temperature characteristics; 3. The neodymium iron boron magnet of the present invention has higher thermal stability and higher coercive force, which can not only reduce the input of rare earth metals, reduce costs and save resources, but also has excellent market application prospects in the application of intelligent large-scale DC converter transformers, intelligent reactors and other transformers, rectifiers and inductors manufacturing. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the implementation of the present invention. The embodiments described 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 work are within the scope of protection of the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer.

[0032] Example 1

[0033] A manufacturing process of NdFeB magnets, including the following steps:

[0034] (1) The cleaned NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCu alloy, AlGa alloy, aluminum powder and copper powder raw materials were mixed and melted in a mass ratio of 32:11.2:16:5.6:3.2:0.35:0.13:0.22 to form an alloy liquid, and then the alloy liquid was prepared into an alloy sheet with a thickness of 0.22 mm by a rapid solidification thin sheet method;

[0035] (2) The alloy flakes were hydrogen-blasted, and then 0.35% by weight of carbonyl iron powder and 0.48% by weight of zirconium carbide particles were added to the alloy flakes, followed by jet milling to form an alloy powder with a particle size of 4.2 μm;

[0036] (3) The alloy powder is mixed with 0.15% of Kenolube P11 by weight of the alloy powder and 0.18% of the antioxidant by weight of the alloy powder through banburying, and then subjected to segmented pressing in a magnetic field orientation in the manner of constant temperature and constant pressure holding - holding after heat preservation and pressure increase - holding after heat preservation and pressure reduction - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release to form a green compact.

[0037] The antioxidant is composed of antioxidant 3224 and antioxidant 626 in a mass ratio of 5:1.5;

[0038] Segmented pressing conditions: maintain at a temperature of 115°C and a pressure of 75MPa for 12min, keep the temperature constant, gradually increase the pressure to 305MPa at a rate of 5-8MPa / min and maintain for 8min, then increase the temperature at a rate of 5.5-6.5°C / min and reduce the pressure at a rate of 3.5-4.5MPa / min to a temperature of 465°C and a pressure of 70MPa, maintain for 25s, then reduce the temperature at a rate of 8-10°C / min and increase the pressure at a rate of 2-3MPa / min to a temperature of 95°C and a pressure of 165MPa, maintain for 8min, keep the temperature constant, gradually reduce the pressure to 105MPa at a rate of 1.5-2.5MPa / min, maintain for 8min, then keep the temperature and release the pressure to normal pressure.

[0039] (4) In a protective gas atmosphere composed of carbon dioxide and argon, the compact is subjected to variable temperature sintering in a manner of gradually heating up and then holding the temperature - accelerating heating up and then holding the temperature - gradually cooling down and then holding the temperature - accelerating cooling down and then holding the temperature - gradually heating up and then holding the temperature, and then subjected to primary, secondary, and tertiary aging treatment to obtain NdFeB magnets;

[0040] Among them, the variable temperature sintering conditions are: first gradually increase the temperature to 230°C at a rate of 5-10°C / min, keep warm for 1.5 hours, then accelerate the temperature to 1600°C at a rate of 15-20°C / min, keep warm for 1 hour, then gradually decrease the temperature to 1380°C at a rate of 10-15°C / min, keep warm for 1.5 hours, then accelerate the temperature to 780°C at a rate of 20-25°C / min, keep warm for 2.5 hours, then gradually increase the temperature to 1255°C at a rate of 5-10°C / min, and keep warm for 1.5 hours;

[0041] Multi-stage aging treatment conditions: first, perform primary aging treatment at a temperature of 1000°C for 1 hour, then perform secondary aging treatment at a temperature of 780°C for 2.5 hours, and finally perform tertiary aging treatment at a temperature of 440°C for 1.5 hours.

[0042] Example 2

[0043] A manufacturing process of NdFeB magnets, including the following steps:

[0044] (1) The cleaned NdFe alloy, FeB alloy, pure iron, niobium hafnium alloy, NdCu alloy, AlGa alloy, aluminum powder and copper powder raw materials were mixed and melted in a mass ratio of 32:10:15:5:2:0.3:0.1:0.2 to form an alloy liquid, and then the alloy liquid was prepared into an alloy sheet with a thickness of 0.28 mm by a rapid solidification thin sheet method;

[0045] (2) The alloy flakes were hydrogen-blasted, and then 0.28% by weight of carbonyl iron powder and 0.37% by weight of zirconium carbide particles were added to the alloy flakes, followed by jet milling to form an alloy powder with a particle size of 4.6 μm;

[0046] (3) The alloy powder is mixed with 0.12% of Kenolube P11 by weight of the alloy powder and 0.14% of the antioxidant by weight of the alloy powder through banburying, and then subjected to segmented pressing in a magnetic field orientation in the manner of constant temperature and constant pressure holding - holding after heat preservation and pressure increase - holding after heat preservation and pressure reduction - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release to form a green compact.

[0047] The antioxidant is composed of antioxidant 3224 and antioxidant 626 in a mass ratio of 5:1;

[0048] The conditions for segmented pressing are as follows: maintain the temperature at 110°C and the pressure at 70MPa for 15min, keep the temperature constant, gradually increase the pressure to 300MPa at a rate of 5-8MPa / min and maintain for 10min, then increase the temperature at a rate of 5.5-6.5°C / min and reduce the pressure at a rate of 3.5-4.5MPa / min to a temperature of 455°C and a pressure of 65MPa, maintain for 30s, then reduce the temperature at a rate of 8-10°C / min and increase the pressure at a rate of 2-3MPa / min to a temperature of 90°C and a pressure of 160MPa, maintain for 10min, keep the temperature constant, gradually reduce the pressure to 100MPa at a rate of 1.5-2.5MPa / min, maintain for 10min, then keep the temperature and release the pressure to normal pressure.

[0049] (4) In a protective gas atmosphere composed of carbon dioxide and argon, the compact is subjected to variable temperature sintering in a manner of gradually heating up and then holding the temperature - accelerating heating up and then holding the temperature - gradually cooling down and then holding the temperature - accelerating cooling down and then holding the temperature - gradually heating up and then holding the temperature, and then subjected to primary, secondary, and tertiary aging treatment to obtain NdFeB magnets;

[0050] Among them, the variable temperature sintering conditions are: first gradually increase the temperature to 220°C at a rate of 5-10°C / min, keep warm for 2 hours, then accelerate the temperature to 1560°C at a rate of 15-20°C / min, keep warm for 1.5 hours, then gradually decrease the temperature to 1360°C at a rate of 10-15°C / min, keep warm for 2 hours, then accelerate the temperature to 760°C at a rate of 20-25°C / min, keep warm for 3 hours, then gradually increase the temperature to 1230°C at a rate of 5-10°C / min, and keep warm for 2 hours;

[0051] Multi-stage aging treatment conditions: first, perform primary aging treatment at a temperature of 980-1020°C for 0.5-1.5h, then perform secondary aging treatment at a temperature of 760-800°C for 2-3h, and finally perform tertiary aging treatment at a temperature of 420-460°C for 1-2h.

[0052] Example 3

[0053] A manufacturing process of NdFeB magnets, including the following steps:

[0054] (1) The cleaned NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCu alloy, AlGa alloy, aluminum powder and copper powder raw materials were mixed and melted in a mass ratio of 32:12:18:6:4:0.4:0.15:0.25 to form an alloy liquid, and then the alloy liquid was prepared into an alloy sheet with a thickness of 0.18 mm by a rapid solidification thin sheet method;

[0055] (2) hydrogen explosion of the alloy flakes, adding 0.49% by weight of carbonyl iron powder and 0.62% by weight of zirconium carbide particles to the alloy flakes, and then jet milling to form an alloy powder with a particle size of 3.5 μm;

[0056] (3) The alloy powder is mixed with 0.18% of Kenolube P11 by weight of the alloy powder and 0.22% of an antioxidant by weight of the alloy powder through banburying, and then subjected to segmented pressing in a magnetic field orientation in the manner of constant temperature and constant pressure holding - temperature maintenance and pressure increase holding - temperature increase and pressure reduction holding - temperature reduction and pressure increase holding - temperature maintenance and pressure reduction holding - temperature maintenance and pressure release to form a green compact.

[0057] The antioxidant is composed of antioxidant 3224 and antioxidant 626 in a mass ratio of 5:2;

[0058] The conditions for segmented pressing are as follows: maintain the temperature at 120°C and the pressure at 80 MPa for 10 min, keep the temperature constant, gradually increase the pressure to 310 MPa at a rate of 5-8 MPa / min and maintain for 5 min, then increase the temperature at a rate of 5.5-6.5°C / min and reduce the pressure at a rate of 3.5-4.5 MPa / min to a temperature of 475°C and a pressure of 75 MPa, maintain for 20 s, then reduce the temperature at a rate of 8-10°C / min and increase the pressure at a rate of 2-3 MPa / min to a temperature of 100°C and a pressure of 170 MPa, maintain for 5 min, keep the temperature constant, gradually reduce the pressure to 110 MPa at a rate of 1.5-2.5 MPa / min, maintain for 5 min, then keep the temperature and release the pressure to normal pressure.

[0059] (4) In a protective gas atmosphere composed of carbon dioxide and argon, the compact is subjected to variable temperature sintering in a manner of gradually heating up and then holding the temperature - accelerating heating up and then holding the temperature - gradually cooling down and then holding the temperature - accelerating cooling down and then holding the temperature - gradually heating up and then holding the temperature, and then subjected to primary, secondary, and tertiary aging treatment to obtain NdFeB magnets;

[0060] Among them, the variable temperature sintering conditions are: first gradually increase the temperature to 240°C at a rate of 5-10°C / min, keep warm for 1 hour, then accelerate the temperature to 1620°C at a rate of 15-20°C / min, keep warm for 0.5 hour, then gradually decrease the temperature to 1400°C at a rate of 10-15°C / min, keep warm for 1 hour, then accelerate the temperature to 800°C at a rate of 20-25°C / min, keep warm for 2 hours, then gradually increase the temperature to 1280°C at a rate of 5-10°C / min, keep warm for 1 hour;

[0061] Multi-stage aging treatment conditions: first, perform primary aging treatment at a temperature of 1020°C for 0.5h, then perform secondary aging treatment at a temperature of 800°C for 2h, and finally perform tertiary aging treatment at a temperature of 460°C for 1h.

[0062] Example 4

[0063] A manufacturing process of NdFeB magnets, including the following steps:

[0064] (1) The cleaned NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCu alloy, AlGa alloy, aluminum powder and copper powder raw materials were mixed and melted in a mass ratio of 32:11:18:5:2:0.4:0.1:0.2 to form an alloy liquid, and then the alloy liquid was prepared into an alloy sheet with a thickness of 0.22 mm by a rapid solidification thin sheet method;

[0065] (2) The alloy flakes were hydrogen-blasted, and then 0.3% of carbonyl iron powder and 0.6% of zirconium carbide particles were added to the alloy flakes, and then jet milled to form an alloy powder with a particle size of 4.2 μm;

[0066] (3) The alloy powder is mixed with 0.15% of Kenolube P11 by weight of the alloy powder and 0.2% of the antioxidant by weight of the alloy powder through banburying, and then subjected to segmented pressing in a magnetic field orientation in the manner of constant temperature and constant pressure holding - holding after heat preservation and pressure increase - holding after heat preservation and pressure reduction - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release to form a green compact.

[0067] The antioxidant is composed of antioxidant 3224 and antioxidant 626 in a mass ratio of 5:1;

[0068] The conditions for segmented pressing are as follows: maintain the temperature at 115°C and the pressure at 75MPa for 10min, keep the temperature constant, gradually increase the pressure to 300MPa at a rate of 5-8MPa / min and maintain for 5min, then increase the temperature at a rate of 5.5-6.5°C / min and reduce the pressure to a temperature of 460°C and a pressure of 65MPa at a rate of 3.5-4.5MPa / min, maintain for 25s, then reduce the temperature at a rate of 8-10°C / min and increase the pressure to a temperature of 100°C and a pressure of 160MPa at a rate of 2-3MPa / min, maintain for 5min, keep the temperature constant, gradually reduce the pressure to 105MPa at a rate of 1.5-2.5MPa / min, maintain for 5min, then keep the temperature and release the pressure to normal pressure.

[0069] (4) In a protective gas atmosphere composed of carbon dioxide and argon, the compact is subjected to variable temperature sintering in a manner of gradually heating up and then holding the temperature - accelerating heating up and then holding the temperature - gradually cooling down and then holding the temperature - accelerating cooling down and then holding the temperature - gradually heating up and then holding the temperature, and then subjected to primary, secondary, and tertiary aging treatment to obtain NdFeB magnets;

[0070] Among them, the variable temperature sintering conditions are: first gradually increase the temperature to 225°C at a rate of 5-10°C / min, keep warm for 1 hour, then accelerate the temperature to 1610°C at a rate of 15-20°C / min, keep warm for 1.5 hours, then gradually decrease the temperature to 1370°C at a rate of 10-15°C / min, keep warm for 1 hour, then accelerate the temperature to 760°C at a rate of 20-25°C / min, keep warm for 2.5 hours, then gradually increase the temperature to 1265°C at a rate of 5-10°C / min, and keep warm for 2 hours;

[0071] Multi-stage aging treatment conditions: first, perform primary aging treatment at a temperature of 990°C for 0.5h, then perform secondary aging treatment at a temperature of 790°C for 2h, and finally perform tertiary aging treatment at a temperature of 450°C for 1.5h.

[0072] Comparative Example 1

[0073] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: (1) cleaned NdFe alloy, ferroboron alloy, pure iron, NdCo alloy, AlGa alloy, aluminum powder, and copper powder are mixed and melted in a mass ratio of 32:11.2:16:53.2:0.35:0.13:0.22 to form an alloy liquid, and then the alloy liquid is prepared into an alloy sheet with a thickness of 0.22 mm by a rapid solidification thin sheet method; the rest of the steps are the same.

[0074] Comparative Example 2

[0075] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: cleaned NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCo alloy, aluminum powder, and copper powder raw materials are mixed and melted in a mass ratio of 32:11.2:16:5.6:3.2:0.13:0.22 to form an alloy liquid, and the alloy liquid is then prepared into an alloy sheet with a thickness of 0.22 mm by a rapid solidification thin sheet method; the rest of the steps are the same.

[0076] Comparative Example 3

[0077] A manufacturing process for NdFeB magnets, wherein the specific process steps are different from those in Example 1 in that: (2) the alloy flakes are hydrogen-blasted and then jet-milled to form alloy powder with a particle size of 4.2 μm; the rest are the same.

[0078] Comparative Example 4

[0079] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: (2) the alloy flakes are hydrogen-blasted, and then 0.83% of the weight of the alloy flakes is added with carbonyl iron powder, which is then jet-milled to form an alloy powder with a particle size of 4.2 μm; the rest of the steps are the same.

[0080] Comparative Example 5

[0081] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: (2) the alloy flakes are hydrogen-blasted, zirconium carbide is added in an amount of 0.83% by weight of the alloy flakes, and then the alloy powder is jet-milled to form a 4.2 μm alloy powder; the rest of the steps are the same.

[0082] Comparative Example 6

[0083] A manufacturing process for NdFeB magnets, wherein the specific process steps are different from those in Example 1 in that: (3) isostatic pressing is adopted, wherein the conditions are: first, a first-stage pressing at a temperature of 100°C and a pressure of 250 MPa for 25 minutes, then a second-stage pressing at a temperature of 515°C and a pressure of 80 MPa for 40 seconds, then a third-stage pressing at a temperature of 110°C and a pressure of 125 MPa for 20 minutes, and finally a fourth-stage pressing at a temperature of 80°C and a pressure of 100 MPa for 20 minutes; the rest are the same.

[0084] Comparative Example 7

[0085] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: (3) variable pressure segmented pressing is adopted, wherein the conditions are as follows: at a temperature of 115°C, the pressure is gradually increased from normal pressure to 305 MPa at a rate of 3 to 5 MPa / min, the temperature is then increased at a rate of 5.5 to 6.5°C / min and the pressure is decreased at a rate of 3 to 4 MPa / min to a temperature of 465°C and a pressure of 70 MPa, the temperature is then decreased at a rate of 8 to 10°C / min and the pressure is increased at a rate of 1 to 2 MPa / min to a temperature of 95°C and a pressure of 165 MPa, and the pressure is finally gradually decreased at a rate of 1 to 2 MPa / min to 105 MPa and the pressure is released; the rest of the steps are the same.

[0086] Comparative Example 8

[0087] A manufacturing process of NdFeB magnets, the specific process steps are different from those of Example 1 in that: (4) constant temperature sintering is adopted, and the conditions are: sintering at a temperature of 1100° C. for 5 hours; the rest are the same.

[0088] Comparative Example 9

[0089] A manufacturing process for NdFeB magnets, wherein the specific process steps differ from those of Example 1 in that: (4) variable temperature sintering with uniform heating and cooling is adopted, wherein the temperature is first raised to 230°C at a rate of 5-10°C / min and kept at this temperature for 1.5 hours, then raised to 1600°C and kept at this temperature for 1 hour, then lowered to 1380°C at a rate of 10-15°C / min and kept at this temperature for 1.5 hours, then lowered to 780°C and kept at this temperature for 2.5 hours, and finally raised to 1255°C at a rate of 5-10°C / min and kept at this temperature for 1.5 hours; the rest of the steps are the same.

[0090] Comparative Example 10

[0091] A manufacturing process for NdFeB magnets, the specific process steps are different from those in Example 1 in that: (4) a two-stage aging treatment condition is adopted: first, a secondary aging treatment is performed at a temperature of 880°C for 3 hours, and finally a tertiary aging treatment is performed at a temperature of 500°C for 2.5 hours; the rest are the same.

[0092] The NdFeB magnets manufactured in the above Examples 1 to 4 and Comparative Examples 1 to 10 are used as magnetic cores to manufacture transformers, rectifiers and inductors, and then the performance of these NdFeB magnet cores is tested.

[0093] Performance Testing

[0094] The NdFeB magnets manufactured in Examples 1 to 4 and Comparative Examples 1 to 10 were used as magnetic cores, and their performance was characterized after saturation magnetization. The results are shown in Table 1 for magnetic properties and Table 2 for thermal stability.

[0095] 1. Determine the remanence (Br), maximum magnetic energy product ((BH)max) and coercive force (Hcb) of the original sample at room temperature (20±1℃).

[0096] 2. Calculate the remanence temperature coefficient (αBrT) in each interval starting from 25°C for the original sample.

[0097] 3. Real-world corrosion simulation: In a chlorine-rich environment, the original sample was heated to 100°C on an open constant-temperature heating table and exposed to air for 25 days to form a corrosion sample. The remanence temperature coefficient (αBrT) in each interval was then calculated starting from 25°C.

[0098] Table 1 Magnetic properties

[0099] Br / T Hcb / KHcb Example 1 1.35 26.6 Example 2 1.36 26.4 Example 3 1.34 26.8 Example 4 1.34 26.7 Comparative Example 1 1.30 25.2 Comparative Example 2 1.31 25.4 Comparative Example 3 1.15 22.1 Comparative Example 4 1.34 25.3 Comparative Example 5 1.31 25.5 Comparative Example 6 1.32 24.9 Comparative Example 7 1.31 25.3 Comparative Example 8 1.28 24.5 Comparative Example 9 1.32 25.0 Comparative Example 10 1.33 25.7

[0100] Table 2 Thermal stability

[0101]

[0102]

[0103] From Tables 1 and 2 above, it can be seen that the NdFeB magnets manufactured in Examples 1 to 4 have a remanence intensity ≥1.34T and a coercive force ≥26.4KOe, and have good magnetic properties. Moreover, the remanence temperature coefficient of the original NdFeB magnet sample in the ranges of 25°C to 60°C, 25°C to 120°C, and 25°C to 180°C is ≥-0.05% / °C. After exposure to a chlorine-rich environment at 100°C for 25 days, the remanence intensity is ≥1.31T, and the remanence temperature coefficient is ≥-0.051% / °C. The NdFeB magnets exhibit good heat resistance and the heat resistance does not significantly decrease under the action of composite corrosion. Therefore, the NdFeB magnets manufactured by the present invention have more excellent thermal stability and corrosion resistance, enabling the NdFeB magnets to maintain good magnetic properties at high temperatures and have good temperature characteristics.

[0104] Compared with Comparative Examples 1 to 5, the NdFeB magnet of Example 1 uses NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCopper alloy, aluminum-gallium alloy, aluminum powder and copper powder as alloy raw materials, which are hydrogen crushed, and then carbonyl iron powder and zirconium carbide particles are added for air flow milling. The niobium-hafnium alloy, aluminum-gallium alloy, appropriate carbonyl iron powder and zirconium carbide and other raw materials cooperate with each other to form a thin layer of continuous grain boundary phase, which hinders the growth of main phase grains, is beneficial to improving the coercive force and remanence strength of the magnetic force, and can also inhibit the occurrence of grain boundary corrosion, thereby improving thermal stability and corrosion resistance.

[0105] Compared with Comparative Examples 6 to 10, the NdFeB magnet manufacturing process of Example 1 adopts segmented pressing of constant temperature and constant pressure holding - holding after heat preservation and pressure increase - holding after heat preservation and pressure reduction - holding after temperature reduction and pressure increase - holding after heat preservation and pressure reduction - holding after heat preservation and pressure release, gradually heating and then keeping warm - keeping warm after accelerated heating - keeping warm after gradual cooling - keeping warm after accelerated cooling - gradually heating and then keeping warm, variable temperature sintering, and three-stage multi-stage aging treatment are combined to make the NdFeB magnet have higher density, enhance the infiltration and linking effect, form a thin layer of continuous grain boundary phase, promote the improvement of the coercive force and residual magnetic strength of the NdFeB magnet, and improve the thermal stability and corrosion resistance.

[0106] In summary, the manufacturing process of the present invention uses neodymium iron alloy, boron iron alloy, pure iron, niobium hafnium alloy, neodymium copper alloy, aluminum gallium alloy, aluminum powder and copper powder as raw materials, which are crushed by hydrogen, and then carbonyl iron powder and zirconium carbide particles are added for air flow milling, and then lubricant and antioxidant are added for mixing, and the neodymium iron boron magnet is subjected to segmented pressing, variable temperature sintering and multi-stage aging treatment combined with isostatic pressing and variable pressure. The neodymium iron boron magnet has more excellent thermal stability and corrosion resistance, good magnetic properties, maintains good magnetic properties at high temperatures, and has good temperature characteristics; the neodymium iron boron magnet of the present invention has higher temperature resistance and higher coercive force, which not only solves the problem of poor temperature characteristics of neodymium iron boron magnet; it can also reduce the input of rare earth metals, alleviate the difficulties brought to enterprises by the scarcity and high price of rare earth resources. In addition, the neodymium iron boron magnet manufactured by the present invention has excellent market application prospects in the application of intelligent large-scale DC converter transformers, intelligent reactors and other transformers, rectifiers and inductor manufacturing.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be embodied in other specific forms without departing from the spirit and essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0108] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A process for manufacturing NdFeB magnets, characterized in that: The following steps are involved: (1) The cleaned NdFe alloy, FeB alloy, pure iron, niobium-hafnium alloy, NdCu alloy, AlGa alloy, aluminum powder and copper powder are mixed and smelted to form an alloy liquid, and then the alloy liquid is prepared into alloy sheets by a rapid solidification thin sheet method; (2) The alloy flakes are hydrogen-blasted, carbonyl iron powder and zirconium carbide particles are added, and then the alloy powder is formed by jet milling; (3) The alloy powder is mixed with a lubricant and an antioxidant through internal kneading, and then is subjected to segmented pressing by combining isostatic pressing and variable pressure pressing under magnetic field orientation to form a green compact; (4) Under a protective gas atmosphere, the compact is subjected to variable temperature sintering, and then subjected to multi-stage aging treatment to obtain NdFeB magnets; The segmented pressing process is as follows: constant temperature and constant pressure maintenance - heat preservation and pressure increase and then maintenance - heat preservation and pressure reduction and then maintenance - heat preservation and pressure increase and then maintenance - heat preservation and pressure release; The variable temperature sintering process is: gradually heating up and then keeping warm - accelerating heating up and then keeping warm - gradually cooling down and then keeping warm - accelerating cooling down and then keeping warm - gradually heating up and then keeping warm; The multi-stage aging treatment includes primary, secondary and tertiary aging treatments.

2. The manufacturing process of NdFeB magnet according to claim 1, characterized in that: In step (1), the alloy sheet comprises the following raw material composition and their mass ratio: the mass ratio of neodymium iron alloy, boron iron alloy, pure iron, niobium hafnium alloy, neodymium copper alloy, aluminum gallium alloy, aluminum powder and copper powder is 32:10~12:15~18:5~6:2~4:0.3~0.4:0.1~0.15:0.2~0.

25.

3. The manufacturing process of NdFeB magnet according to claim 1, characterized in that: In step (2), the amount of carbonyl iron powder added is 0.28-0.49% of the weight of the alloy flakes; the amount of zirconium carbide particles added is 0.37-0.62% of the weight of the alloy flakes.

4. The manufacturing process of NdFeB magnet according to claim 1, characterized in that: In step (3), the segmented pressing process is as follows: maintain the temperature at 110-120°C and the pressure at 70-80 MPa for 10-15 minutes, keep the temperature constant, gradually increase the pressure to 300-310 MPa and maintain it for 5-10 minutes, then increase the temperature and reduce the pressure to 455-475°C and 65-75 MPa, maintain it for 20-30 seconds, then reduce the temperature and increase the pressure to 90-100°C and 160-170 MPa, maintain it for 5-10 minutes, keep the temperature constant, gradually reduce the pressure to 100-110 MPa, maintain it for 5-10 minutes, and then keep the temperature and release the pressure to normal pressure.

5. The manufacturing process of NdFeB magnet according to claim 4, characterized in that: The rate of gradual pressure increase is 5~8MPa / min; the heating rate of temperature increase and pressure reduction is 5.5~6.5℃ / min and the pressure reduction rate is 3.5~4.5MPa / min; the cooling rate of temperature decrease and pressure increase is 8~10℃ / min and the pressure increase rate is 2~3MPa / min; the rate of gradual pressure reduction is 1.5~2.5MPa / min.

6. The manufacturing process of NdFeB magnet according to claim 1, characterized in that: In step (4), the multi-stage aging treatment process is: first, a primary aging treatment is performed at a temperature of 980-1020°C for 0.5-1.5 hours, then a secondary aging treatment is performed at a temperature of 760-800°C for 2-3 hours, and finally a tertiary aging treatment is performed at a temperature of 420-460°C for 1-2 hours.

7. The manufacturing process of NdFeB magnet according to claim 1, characterized in that: In step (4), the variable temperature sintering process is: first gradually increase the temperature to 220~240℃, keep it warm for 1~2h, then accelerate the temperature increase to 1560~1620℃, keep it warm for 0.5~1.5h, then gradually cool down to 1360~1400℃, keep it warm for 1~2h, then accelerate the temperature decrease to 760~800℃, keep it warm for 2~3h, then gradually increase the temperature to 1230~1280℃, keep it warm for 1~2h.

8. The manufacturing process of NdFeB magnet according to claim 7, characterized in that: The rate of gradual heating is 5~10℃ / min; the rate of accelerated heating is 15~20℃ / min; the rate of gradual cooling is 10~15℃ / min; the rate of accelerated cooling is 20~25℃ / min.

9. A transformer, characterized in that: A transformer is manufactured by using the manufacturing process according to any one of claims 1 to 8 to obtain neodymium iron boron magnetic steel.

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