Grain boundary diffusion process method of high-performance sintered neodymium-iron-boron permanent magnet

Abstract

The invention relates to the field of neodymium iron boron, in particular to a grain boundary diffusion process method of a high-performance sintered neodymium iron boron permanent magnet. The method comprises the steps that sintered neodymium-iron-boron substrates subjected to surface treatment are stacked on a plane tool disc in order, and a product stacking area is subjected to flange fixing; the fixed tool disc with the product is conveyed to a feeding cabin A chamber, mold cavity fixing is conducted on a to-be-coated area on the surface of the product, an automatic feeder weighs sufficient diffusion source powder and places the powder into a mold cavity of the to-be-coated surface of the product, and the tool disc is vibrated in an intermediate frequency mode till the powder on the surface of the product is evenly spread; a pressure condition is set, the selected pole head is matched with the mold cavity to press downwards, diffusion source powder on the surface of the product is pressed into a dense metal thin layer with high binding force, and then demolding is conducted; and a layer of adhesive is uniformly sprayed on the surface of the metal film layer, the metal film layer is conveyed to a curing cabin B chamber after completion, and the surface adhesive is heated and cured through infrared radiation of an infrared curing oven channel, so that the compact protective film layer is rapidly formed.

Description

Technical Field

[0001] The invention relates to the field of NdFeB, and in particular to a grain boundary diffusion process method for high-performance sintered NdFeB permanent magnets. Background Art

[0002] In recent years, the domestic NdFeB industry has experienced rapid development, and many original achievements have emerged in the grain boundary diffusion technology, showing a trend of catching up. Currently, most high-performance NdFeB on the market are prepared by grain boundary diffusion, such as high-performance magnetic steel in wind power and new energy vehicles.

[0003] The basic process of sintered NdFeB grain boundary diffusion technology is to first use different methods to coat the metal, alloy or compound (diffusant) to be diffused on the surface of the sintered magnet, and then use an optimized heat treatment process to allow the diffusant to enter the magnet along the grain boundary. For grain boundary diffusion technology, it is necessary to develop diffusants and diffusion processes. At present, the diffusants used in industry are mainly fluorides, hydrides and pure metals of heavy rare earths. The current process technologies for diffusant coating mainly include adhesive coating, electrodeposition and vapor deposition. The adhesive coating method mainly mixes the diffusant with a suspension or a thermoplastic adhesive and applies it to the surface of the magnet by different processes, mainly including dipping, spraying, roller coating and printing. Adhesive coating has no special restrictions on the type of deposited diffusant, but the thickness and uniformity of the diffusant coating are difficult to control, which easily leads to waste of diffusant. Summary of the invention

[0004] The present application provides a grain boundary diffusion process for high-performance sintered NdFeB permanent magnets, which adopts the following technical solutions:

[0005] A grain boundary diffusion process for high-performance sintered NdFeB permanent magnets, comprising:

[0006] Step S1: neatly stack the surface-treated sintered NdFeB substrates on a flat tooling tray, and fix the stacked product area with sidewalls;

[0007] Step S2: The fixed tooling tray with the product is transferred to the feed cabin A, and the mold cavity is fixed on the surface area of ​​the product to be coated. The automatic feeder weighs a sufficient amount of diffusion source powder and puts it into the mold cavity of the product surface to be coated. The tooling tray is vibrated at a medium frequency until the powder on the surface of the product is evenly spread;

[0008] Step S3: setting the pressure conditions, the selected pole matches the mold cavity and presses down to press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force and then demolds;

[0009] Step S4: spray a layer of adhesive evenly on the surface of the metal film layer, and then transfer it to the curing chamber B. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer to protect the underlying metal film layer from oxidation, thereby preparing a coated magnetic steel with uniform surface coating, strong scratch resistance and oxidation resistance.

[0010] Optionally, the surface treatment in step S1 is to use 100 mesh alumina to shot peen the product surface under 0.3 atmosphere pressure.

[0011] Optionally, the chamber in step S2A is an inert gas protection chamber.

[0012] Optionally, in step S2A, the depth of the mold cavity in the coating area is 5 cm.

[0013] Optionally, the tip pressure in step S3 is 15-35 MPa, and a pressure of 20 MPa is used for a 3 mm product with a weight gain of 0.6 wt% Dy / Tb diffusion source.

[0014] Optionally, the adhesive in step S4 is a mixture of epoxy resin and organic solvent.

[0015] Optionally, the spraying amount of the adhesive in step S4 is 5-15wt% of the diffusion source.

[0016] Optionally, the magnetic steel obtained in step S4 is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 860-930°C for 800-1900 min and aging treatment at 430-650°C for 300-500 min to obtain the diffused magnetic steel.

[0017] Optionally, the magnetic steel is cut into a cylinder with a diameter of 10 mm by an electric spark wire cutting machine, and the surface of the cylinder is polished to remove the oxide layer.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention proposes a new sintered NdFeB dry powder coating diffusion process. First, the conventional pickling cleaning process is abandoned for the substrate surface, and the surface treatment is performed by shot blasting to increase the bonding force between the coating and the product surface. There is no acid intervention, which avoids the damage of the rare earth-rich layer on the product surface. The surface coating of the product is coated with powder and pressurized to optimize the controllability of the coating amount. Compared with the oil quantity defect in the spraying air pressure control process and the screen printing white edge defect of screen printing, the uniformity of the powder-covered coating is further improved, and it is not affected by the viscosity of the slurry. The fallen edge diffusion source powder is not polluted and can be recycled and reused, which effectively improves the utilization rate of heavy rare earths. The infrared light curing process is adopted, and the product coating has a fast curing speed and high efficiency. The surface organic film layer is uniform and more protective of heavy rare earths. This method is suitable for a variety of diffusion areas such as full-surface diffusion and selected-area diffusion, and is adapted to the current industry-oriented status of reducing the use of heavy rare earths and reducing processing and manufacturing costs.

[0020] The diffusion coating thickness of the sintered NdFeB magnet prepared by the method of the present invention is uniform, the coating bonding force is strong, the surface coating has good scratch resistance and oxidation resistance, the magnetic property stability of the sintered NdFeB after diffusion is excellent, the diffusion source is economically utilized, and it is suitable for industrial manufacturing. No harmful gas is released during the curing process, which meets environmental protection requirements. DETAILED DESCRIPTION

[0021] The technical solutions of the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] An embodiment of the present invention provides a grain boundary diffusion process method for high-performance sintered NdFeB permanent magnets.

[0023] Embodiment 1:

[0024] The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are treated with hydrogen cracking and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled and isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into three sizes of products: 30*20*3mm, 30*20*5mm, and 30*20*7mm.

[0025] 1)① After the surface of the three sizes of products (30*20*3mm, 30*20*5mm, and 30*20*7mm) was shot peened with 100 mesh alumina and 0.3Mpa air pressure, the three sizes of products were stacked on the tooling tray respectively, and the products were fixed with 600*600 side guards.

[0026] ②Transfer the fixed product tooling tray with a size of 30*20*3mm to the feeding cabin A room, fix the product surface area to be coated with a 600*600*5mm cavity, weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated, and vibrate the tooling tray at a medium frequency until the powder on the product surface is evenly spread, among which the A cabin is an inert gas protection cabin; set the pressure condition of 20MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the product surface into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and after completion, transfer it to the curing cabin B room, and heat and cure the surface adhesive through the infrared radiation of the infrared curing furnace channel to quickly form a dense protective film layer;

[0027] ③Transfer the fixed product tooling tray with a size of 30*20*5mm to the feeding cabin A room, fix the surface area of ​​the product to be coated with a 600*600*5mm cavity, and weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated. Vibrate the tooling tray at a medium frequency until the powder on the surface of the product is evenly spread. Among them, the A cabin is an inert gas protection cabin; set the pressure condition of 22MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and then transfer it to the curing cabin B room after completion. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer;

[0028] ④Transfer the fixed product tooling tray with a size of 30*20*7mm to the feeding cabin A room, fix the product surface area to be coated with a 600*600*5mm cavity, weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated, and vibrate the tooling tray at a medium frequency until the powder on the product surface is evenly spread, among which cabin A is an inert gas protection cabin; set the pressure condition of 24MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the product surface into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and after completion, transfer it to the curing cabin B room, and heat and cure the surface adhesive through the infrared radiation of the infrared curing furnace channel to quickly form a dense protective film layer;

[0029] Repeat ② to ④ to complete the second side coating of the product, and obtain the coated magnetic steel with a total weight gain of 0.6% Dy alloy;

[0030] The 30*20*3mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 900 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel a;

[0031] The 30*20*5mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1200 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel b;

[0032] The 30*20*3mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1500 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel c;

[0033] The magnetic steels a, b and c obtained in 2) are sampled and cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surfaces of the cylinders are polished to remove the oxide layer;

[0034] The magnetic properties of the a, b, and c magnetic sample columns obtained in 3) were tested using NIM62000, and the test data were recorded in Table 1.

[0035] Comparative Example 1

[0036] The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are treated with hydrogen cracking and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled and isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into three sizes of products: 30*20*3mm, 30*20*5mm, and 30*20*7mm.

[0037] 1) After treating the surfaces of products of three sizes (30*20*3mm, 30*20*5mm, and 30*20*7mm) with a water ultrasonic process, the three sizes of products were stacked on 600*600mm tooling trays respectively;

[0038] The three sizes of products were respectively subjected to 0.3% Dy alloy diffusion source spray coating treatment using a conventional spraying process. The composition of the Dy alloy diffusion source was the same as that of the diffusion source in Example 1 (the actual slurry spraying weight gain was 0.9%, and the ratio of the Dy alloy diffusion source to the organic solvent in the slurry was 2:1);

[0039] Repeat the coating steps to complete the coating on the second side of the product, and obtain a coated magnetic steel with a weight gain of 0.6% Dy alloy;

[0040] 2) The 30*20*3mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 900 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel d;

[0041] The 30*20*5mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1200 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel e;

[0042] The 30*20*3mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1500 minutes and aging at 490°C for 300 minutes to obtain a diffused magnetic steel f;

[0043] 3) The magnetic steel samples d, e and f obtained in 2) are cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surfaces of the cylinders are polished to remove the oxide layer;

[0044] 4) The magnetic properties of the magnetic sample columns d, e, and f obtained in 3) were tested using NIM62000, and the test data were recorded in Table 1.

[0045] Comparative Example 2

[0046] 1) The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are treated with hydrogen cracking and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled and isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into three sizes of products: 30*20*3mm, 30*20*5mm, and 30*20*7mm.

[0047] After treating the surfaces of products of three sizes (30*20*3mm, 30*20*5mm, and 30*20*7mm) with a water ultrasonic process, the three sizes of products are stacked on a 400*200mm workpiece tray respectively;

[0048] The three sizes of products were respectively subjected to screen printing coating treatment with a Dy alloy diffusion source having a weight gain of 0.3% by using a conventional screen printing process. The composition of the Dy alloy diffusion source was the same as that of the diffusion source in Example 1 (the actual slurry spraying weight gain was 0.72%, and the ratio of the Dy alloy diffusion source to the adhesive in the slurry was 5:1);

[0049] Repeat the coating steps to complete the coating on the second side of the product, and obtain a coated magnetic steel with a weight gain of 0.6% Dy alloy;

[0050] 2) The 30*20*3mm coated magnetic steel obtained above is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900℃ for 900min and aging at 490℃ for 300min to obtain the diffused magnetic steel g;

[0051] The obtained 30*20*5mm coated magnetic steels were neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1200 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel h;

[0052] The 30*20*3mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1500 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel i;

[0053] 3) The magnetic steels g, h and i obtained in 2) are sampled and cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surfaces of the cylinders are polished to remove the oxide layer;

[0054] 4) The g, h, and i magnetic sample columns obtained in 3) were tested for magnetic properties using NIM62000, and the test data were recorded in Table 1.

[0055] Embodiment 2:

[0056] The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are subjected to hydrogen cracking treatment and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into a product with a size of 30*20*4mm.

[0057] ① After the surface of the 30*20*4mm product is shot peened with 100-mesh alumina and 0.3Mpa air pressure, the product is stacked on the tooling tray and fixed with 600*600 sidewalls.

[0058] ②Transfer the fixed product tooling tray with a size of 30*20*4mm to the feeding cabin A room, fix the surface area of ​​the product to be coated with a 600*600*5mm cavity, and weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (the Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated. Vibrate the tooling tray at a medium frequency until the powder on the surface of the product is evenly spread. Among them, the A cabin is an inert gas protection cabin; set the pressure condition of 21MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and then transfer it to the curing cabin B room after completion. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer;

[0059] Repeat ② to complete the coating on the second side of the product, and obtain a coated magnetic steel with a weight gain of 0.6% Dy alloy;

[0060] 2) The 30*20*4mm coated magnetic steel obtained above is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900℃ for 1100min and aging at 490℃ for 300min to obtain the diffused magnetic steel x;

[0061] 3) The magnetic steel x obtained in 2) is sampled and cut into a cylinder with a diameter of 10 mm by an electric spark wire cutting machine, and the surface of the cylinder is polished to remove the oxide layer;

[0062] 4) The x magnet sample column obtained in 3) was subjected to magnetic property test using NIM62000, and the test data were recorded in Table 1.

[0063] Comparative Example 1

[0064] The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are subjected to hydrogen cracking treatment and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into a product with a size of 30*20*4mm.

[0065] 1)① After the surface of the 30*20*4mm product is shot peened with 100 mesh alumina and 0.3Mpa air pressure, the product is stacked on the tooling tray and fixed with 600*600 sidewalls.

[0066] ②Transfer the fixed product tooling tray with a size of 30*20*4mm to the feeding cabin A room, fix the surface area of ​​the product to be coated with a 600*600*5mm cavity, and weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (the Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated. Vibrate the tooling tray at a medium frequency until the powder on the surface of the product is evenly spread. Among them, the A cabin is an inert gas protection cabin; set the pressure condition of 21MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and then transfer it to the curing cabin B room after completion. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer;

[0067] Repeat ② to complete the coating on the second side of the product, and obtain a coated magnetic steel with a weight gain of 0.6% Dy alloy;

[0068] 2) The 30*20*4mm coated magnetic steel obtained above is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 860℃ for 1100min and aging at 490℃ for 300min to obtain diffused magnetic steel x1;

[0069] The 30*20*4mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 880°C for 1100 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel x2;

[0070] The 30*20*4mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 930°C for 1100 minutes and aging at 490°C for 300 minutes to obtain diffused magnetic steel x3;

[0071] 3) The magnetic steels x1, x2 and x3 obtained in 2) are sampled and cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surfaces of the cylinders are polished to remove the oxide layer;

[0072] 4) The magnetic properties of the x1, x2, and x3 magnetic sample columns obtained in 3) were tested using NIM62000, and the test data were recorded in Table 1.

[0073] Comparative Example 2

[0074] The composition ratio is The raw materials are configured with a vacuum quick-setting furnace with a melting temperature of 1500±10℃ and a casting temperature of 1460±5℃ to melt and spin into thin sheets. The thin sheets are subjected to hydrogen cracking treatment and made into powder with a particle size of D50=3.8㎛ by air flow milling under argon protection. The obtained powder is evenly stirred and oriented in a 2T magnetic field. It is water-cooled isostatically pressed under a pressure of 225MPa. The pressed green sheet is sintered at 1090℃ for 5h, annealed at 900℃ for 3h, and tempered at 500℃ for 3h to obtain a sintered NdFeB matrix. The matrix is ​​processed into a product with a size of 30*20*4mm.

[0075] 1)① After the surface of the 30*20*4mm product is shot peened with 100 mesh alumina and 0.3Mpa air pressure, the product is stacked on the tooling tray and fixed with 600*600 sidewalls.

[0076] ②Transfer the fixed product tooling tray with a size of 30*20*4mm to the feeding cabin A room, fix the surface area of ​​the product to be coated with a 600*600*5mm cavity, and weigh the Dy alloy diffusion source powder with a production weight gain of 0.3% (Dy alloy diffusion source contains Dy and one or more alloy elements such as Cu, Al, Pr, Gd, Co, Ti, Zr, etc.) with an automatic feeder and put it into the product surface cavity to be plated. Vibrate the tooling tray at a medium frequency until the powder on the surface of the product is evenly spread. Among them, the A cabin is an inert gas protection cabin; set the pressure condition of 21MPa, and the selected pole head matches the 600*600*5mm cavity to press down, press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force, and then demold; spray 0.06% adhesive evenly on the surface of the metal film layer, and then transfer it to the curing cabin B room after completion. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer;

[0077] Repeat ② to complete the coating on the second side of the product, and obtain a coated magnetic steel with a weight gain of 0.6% Dy alloy;

[0078] 2) The 30*20*4mm coated magnetic steel obtained above is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900℃ for 1100min and aging at 430℃ for 300min to obtain the diffused magnetic steel y1;

[0079] The 30*20*4mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1100 minutes and aging at 520°C for 300 minutes to obtain diffused magnetic steel y2;

[0080] The 30*20*4mm coated magnetic steel obtained above was neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 900°C for 1100 minutes and aging at 650°C for 300 minutes to obtain diffused magnetic steel y3;

[0081] 3) The magnetic steels y1, y2 and y3 obtained in 2) are sampled and cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surfaces of the cylinders are polished to remove the oxide layer;

[0082] 4) The magnetic properties of the y1, y2, and y3 magnetic sample columns obtained in 3) were tested using NIM62000, and the test data were recorded in Table 1;

[0083] Table 1

[0084] Br(kGs) Hcj(kOe) Hk / Hcj(%) Substrate 14.60 14.24 99.4 a 14.41 23.21 98.9 b 14.46 22.67 98.5 c 14.49 22.34 97.6 d 14.39 21.29 98.2 e 14.43 20.96 97.4 f 14.47 20.32 97.1 g 14.42 21.55 97.8 h 14.46 21.16 96.9 i 14.52 20.59 95.6 x 14.43 22.87 99.0 x1 14.45 21.71 98.2 x2 14.42 22.15 98.6 x3 14.36 21.04 99.1 y1 14.38 20.27 89.7 y2 14.43 21.79 96.5 y3 14.46 20.10 93.0

[0085] It can be seen from the above table that the preparation method of the grain boundary diffusion sintered NdFeB permanent magnet material of the present invention can significantly improve the magnetic properties of the sintered NdFeB permanent magnet material.

[0086] Sintered NdFeB magnets are used in air-conditioning compressors, wind turbines, elevators, new energy vehicles, artificial intelligence motors and other fields.

[0087] 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 implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive from any point of view. The scope of the present invention is defined by the appended claims, rather than the above description, and it is intended that all changes within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0088] In addition, it should be understood that although this specification is described in accordance with the implementation methods, not every implementation method contains only one independent technical solution. This description is only for the sake of clarity. Those skilled in the art should take 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. A grain boundary diffusion process method for high-performance sintered NdFeB permanent magnets.

Claims

1. A grain boundary diffusion process for high performance sintered NdFeB permanent magnets, characterized in that: The following steps are involved: Step S1: neatly stack the surface-treated sintered NdFeB substrates on a flat tooling tray, and fix the stacked product area with sidewalls; Step S2: The fixed tooling tray with the product is transferred to the feed cabin A, and the mold cavity is fixed on the surface area of ​​the product to be coated. The automatic feeder weighs a sufficient amount of diffusion source powder and puts it into the mold cavity of the product surface to be coated. The tooling tray is vibrated at a medium frequency until the powder on the surface of the product is evenly spread; Step S3: setting the pressure conditions, the selected pole matches the mold cavity and presses down to press the diffusion source powder on the surface of the product into a dense metal thin layer with strong bonding force and then demold; Step S4: spray a layer of adhesive evenly on the surface of the metal film layer, and then transfer it to the curing chamber B. The surface adhesive is cured by infrared radiation heating in the infrared curing furnace channel to quickly form a dense protective film layer to protect the underlying metal film layer from oxidation, thereby preparing a coated magnetic steel with uniform surface coating, strong scratch resistance and oxidation resistance.

2. The grain boundary diffusion process of a high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: The surface treatment in step S1 is to use 100 mesh aluminum oxide to shot peen the product surface under 0.3 kPa pressure.

3. The grain boundary diffusion process for high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: The chamber in step S2A is an inert gas protection chamber.

4. The grain boundary diffusion process for high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: Step S2A: The depth of the coating area cavity is 5 cm.

5. The grain boundary diffusion process for high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: The tip pressure in step S3 is 15~35MPa, and the pressure of 20MPa is used for the 3mm product with 0.6wt% Dy / Tb diffusion source.

6. The grain boundary diffusion process for high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: The adhesive in step S4 is a mixture of epoxy resin and organic solvent.

7. The grain boundary diffusion process of a high performance sintered NdFeB permanent magnet according to claim 1, characterized in that: The adhesive spraying amount in step S4 is 5-15wt% of the diffusion source.

8. The grain boundary diffusion process for high performance sintered NdFeB permanent magnets according to claim 1, characterized in that: The magnetic steel obtained in step S4 is neatly stacked in a graphite box, placed in a vacuum heat treatment furnace for diffusion at 860-930°C for 800-1900 min and aging treatment at 430-650°C for 300-500 min to obtain a diffused magnetic steel.

9. The grain boundary diffusion process of a high performance sintered NdFeB permanent magnet according to claim 8, characterized in that: The magnetic steel is cut into cylinders with a diameter of 10 mm by an electric spark wire cutting machine, and the surface of the cylinder is polished to remove the oxide layer.

10. A neodymium iron boron magnet, characterized in that: The high-performance sintered NdFeB permanent magnet is prepared by the grain boundary diffusion process described in any one of claims 1 to 9.