Production process of neodymium-iron-boron magnetic ring

Abstract

This invention relates to the field of magnetic ring manufacturing technology, specifically a manufacturing process for neodymium iron boron (NdFeB) magnetic rings. The raw materials used in the NdFeB magnetic rings, by mass percentage, consist of the following: B: 1.6–3.8%, Nb: 1.2–3.3%, PrNd: 23–28%, Ga: 0.8–2.5%, Al: 0.15–3.0%, with the balance being Fe. The functional protective agent of this invention is composed of nano-alumina microspheres and nano-titanium dioxide, which greatly enhances its wear resistance. The surface of the pretreated inorganic substrate is also "grafted" with methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which effectively enhances its antioxidant properties. Its synergistic effect with pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] further improves its oxidation performance. The NdFeB magnetic ring produced by this invention not only has good wear resistance but also good corrosion resistance, which extends its service life to a certain extent while ensuring the quality of the NdFeB magnetic ring.

Description

Technical Field

[0001] This invention relates to the field of magnetic ring manufacturing technology, specifically a manufacturing process for neodymium iron boron magnetic rings. Background Technology

[0002] A magnetic ring is a ring-shaped conductive material. It is a commonly used anti-interference component in electronic circuits, effectively suppressing high-frequency noise. Magnetic rings exhibit different impedance characteristics at different frequencies; generally, the impedance is very small at low frequencies, and increases sharply as the signal frequency rises. Typically, the higher the signal frequency, the easier it is to radiate. Since most signal lines are unshielded, they become excellent antennas, receiving various stray high-frequency signals from the surrounding environment. These stray signals can superimpose on the original transmitted signal and even alter the intended signal. Magnetic rings, however, allow the normal, useful signal to pass through while effectively suppressing high-frequency interference signals.

[0003] Currently, there are many types of magnetic rings. Due to their advantages such as high magnetic properties, high cost-effectiveness, strong machinability, and wide range of applications, neodymium iron boron magnetic rings are increasingly being used as raw materials for magnetic ring production. Although neodymium iron boron magnetic rings have many advantages, they also have disadvantages such as poor hardness and weak corrosion resistance, which not only affect their quality but also shorten their service life to some extent.

[0004] Therefore, the present invention provides a manufacturing process for neodymium iron boron magnetic rings to solve this technical problem. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing process for neodymium iron boron (NdFeB) magnetic rings. The NdFeB magnetic rings produced by this invention not only have good wear resistance but also good corrosion resistance, which extends their service life to a certain extent while ensuring the quality of the NdFeB magnetic rings.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A manufacturing process for neodymium iron boron magnetic rings includes the following steps:

[0008] Step 1: Prepare materials according to the following mass percentages: B: 1.6-3.8%, Nb: 1.2-3.3%, PrNd: 23-28%, Ga: 0.8-2.5%, Al: 0.15-3.0%, with the balance being Fe; then, use a vacuum melting process to heat the prepared raw materials into molten metal using medium-frequency induction heating; pour the resulting molten metal into a double-sided water-cooled mold to prepare ingots for later use;

[0009] Step 2: Place the ingot obtained in Step 1 in a vacuum heat treatment furnace, evacuate and heat to 1130-1200℃, fill with argon gas to a pressure of -0.08MPa, and maintain the furnace temperature for 18-22 hours; then fill with argon gas to a pressure of -0.04MPa, and then cool it down to 880-920℃ within 12-15 minutes, and maintain this temperature for 100-150 minutes; then lower the furnace temperature to 580-630℃ within 40-50 minutes, and maintain this temperature for 100-150 minutes; finally, air cool it down to room temperature before removing it from the furnace.

[0010] Step 3: Perform HDDR treatment on the ingot obtained in Step 2. The resulting magnetic powder with a hydrogen content ≤550ppm is sent to an air jet mill for grinding. The resulting air jet mill magnetic powder with an average particle size of 1-6μm is stored for later use.

[0011] Step 4: Add 0.06-0.85 wt% of a lubricant, which is a compound of triglycerides and calcium stearate in a mass ratio of 1:1.0-1.5, to the air jet mill magnetic powder. After mixing and stirring for 3-7 hours, transfer the resulting mixture into a magnetic ring magnetic field press for orientation molding. Then, after isostatic pressing, high-temperature sintering, cooling and tempering heat treatment, a protective coating is applied to the surface of the resulting magnetic ring. After the protective coating dries, the final product is a highly irregular square magnetic ring.

[0012] Furthermore, the coating used in the protective coating is composed of component A and component B; wherein,

[0013] Component A is composed of the following raw materials in parts by weight: 24-30 parts bisphenol A type epoxy resin, 8-12 parts o-cresol epoxy resin, 0.6-1.8 parts EFKA-4320 wetting and dispersing agent, 6-9 parts γ-aminopropyltriethoxysilane, 2.8-3.6 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10-16 parts functional protective agent, 12-16 parts toluene, 2.3-3.5 parts bentonite, 22-28 parts filler, and 8-13 parts pigment;

[0014] Component B is composed of the following raw materials in parts by weight: 8-12 parts xyleneamine, 20-30 parts YD-8115 polyamide curing agent, 8-12 parts tetraethylenepentamine, 3.6-4.8 parts N-(2,5-dihydro-2,5-dioxo-1H-imidazol-4-yl)urea, 23-28 parts phthalic anhydride, and 45-65 parts mixed solvent.

[0015] Furthermore, the preparation method of the functional protective agent is as follows: methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is stirred and melted at a temperature of 68-73°C. Then, 8-12% by mass of pretreated inorganic substrate and 0.3-0.5% by mass of dioctyltin oxide are added to the resulting melt. After mixing and stirring evenly, the temperature of the resulting mixed melt is raised to 115-125°C, and the mixture is stirred and reacted for 3-4 hours under nitrogen protection. After the reaction is completed, the resulting reaction product is filtered. The resulting filter cake is washed 3-4 times with N,N-dimethylformamide and then dried in a vacuum drying oven. The final product is the functional protective agent.

[0016] Furthermore, the preparation method of the pretreated inorganic substrate is as follows: the inorganic substrate is immersed in a mixed acid solution with a mass of 5 to 8 times that of the substrate, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3, and the mixture is refluxed at a temperature of 90 to 95°C for 6 to 10 hours; after the reaction is completed, the resulting product components are subjected to centrifugal filtration, deionized water washing and drying treatment in sequence, and the final product is the pretreated inorganic substrate.

[0017] Furthermore, the method for preparing the inorganic substrate includes the following steps:

[0018] I. The nano-carrier was uniformly dispersed in anhydrous ethanol at a solid-liquid ratio of 0.003–0.005 g / mL. While stirring, an ethanol solution of zirconium dichloride with a volume of 20–30% anhydrous ethanol and a concentration of 0.1–0.15 mol / L was added. After stirring for 25–40 min, an appropriate amount of glycerol was added under magnetic stirring. After mechanical stirring for 30–40 min, the pH of the resulting mixture was adjusted to 10.5–11.8. The mixture was then transferred to a reaction vessel and kept at 170–200 °C for 12–16 h.

[0019] II. After the heat preservation treatment is completed, the mixture in the reactor is naturally cooled to room temperature, and then vacuum filtered 3 to 4 times. The obtained filter material is dried and then calcined at 450 to 560°C for 2 to 3 hours under nitrogen atmosphere protection. The final product is the inorganic substrate. The mass concentration of glycerol in the mixture is 5 to 8 times that of zirconium dichloride.

[0020] Furthermore, the preparation method of the nanocarrier includes the following steps:

[0021] i. Add 0.2-0.3% (by mass) citric acid and 50-90 times the molar amount of N,N-dimethylformamide to an aqueous solution of aluminum nitrate with a concentration of 0.02-0.04 mol / L. After mixing and stirring evenly, raise the temperature to 80-90°C and maintain this temperature for 2-3 hours. Then transfer the mixture to a high-pressure reactor and raise the reactor temperature to 230-250°C, maintaining this temperature for 3-5 hours. After treatment, allow it to cool naturally to room temperature. Store the resulting mixture for later use.

[0022] ii. While stirring, add ferric nitrate in a molar amount 2-3 times that of aluminum nitrate to the mixed components. After stirring to ensure the ferric nitrate is uniformly dissolved, add N,N-dimethylformamide in a molar amount 40-55 times that of ferric nitrate. Under stirring conditions, raise the temperature to 80-96℃ and maintain the reaction at this temperature for 3-6 hours. After the reaction is complete, filter the resulting product. Wash the filter cake 2-3 times with deionized water and anhydrous ethanol, then dry and sinter at high temperature. Wash the resulting solid material with nitric acid at 80-90℃ and a concentration of 5.5-6.5 mol / L to remove impurities, then remove impurity ions by centrifugation. Finally, dry the material to obtain the finished nanocarrier.

[0023] Furthermore, the pigment is any one of iron oxide red, iron oxide black, cadmium red, cadmium yellow, carbon black, phthalocyanine blue, and ultramarine.

[0024] Furthermore, the filler is composed of nano-silica and quartz powder in a mass ratio of 8 to 10:1.

[0025] Furthermore, the mixed solvent is prepared by compounding toluene, anhydrous ethanol and acetone in a volume ratio of 4-6:1:0.8-1.2.

[0026] Furthermore, the specific operations of the HDDR processing in step three are as follows:

[0027] S1. Place the ingot in the HDDR furnace, check the airtightness of the equipment and evacuate the furnace to below 0.18 Pa. Then raise the furnace temperature to 175-195°C, fill the furnace with hydrogen to increase the furnace pressure to 96-98 kPa, and maintain this condition for 40-55 minutes.

[0028] S2. Evacuate the furnace again to below 0.8 Pa, while raising the furnace temperature to 825-845°C. Introduce hydrogen to raise the furnace pressure to 31-34 kPa and maintain this condition for 80-90 min. Then, adjust the furnace temperature to 885-900°C, introduce hydrogen to raise the furnace pressure to 73-78 kPa, and maintain this condition for 30-40 min.

[0029] S3. Within 4-5 minutes, reduce the hydrogen pressure inside the furnace from 73-78 kPa to 5.5-6.5 kPa, then within 6-8 minutes, reduce it to 4-4.5 kPa, and maintain the hydrogen pressure inside the furnace at 3.5-4.3 kPa for 15-20 minutes. Finally, reduce the furnace temperature to 860-870℃, and simultaneously force hydrogen venting to reduce its pressure to below 0.15 Pa. Turn off the heating and allow it to cool naturally to below 30℃.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention uses aluminum nitrate, citric acid, and ferric nitrate as raw materials and employs a specific chemical process to prepare a spherical nanocarrier, essentially nano-alumina microspheres. These microspheres are then immersed in anhydrous ethanol, with the addition of an ethanol solution of zirconium dichloride and glycerol. This results in the deposition of a large amount of nano-zirconia on the surface of the nanocarrier, achieving a tight coating of the nanocarrier with zirconium dichloride and preparing an inorganic substrate. Immersing the prepared inorganic substrate in a mixed acid solution effectively "modifies" it, generating a significant amount of -OH groups on the exposed surfaces of the nanocarrier and nano-zirconia, facilitating subsequent reactions. Under the action of dioctyltin oxide, the hydroxyl groups on the surface of the pretreated inorganic substrate react chemically with molten methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ultimately connecting through chemical bonds. This allows methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to be successfully "grafted" onto the surface of the pretreated inorganic substrate, resulting in the final functional protective agent.

[0032] The functional protective agent of this invention is composed of nano-alumina microspheres and nano-titanium dioxide, which greatly improves its wear resistance. Furthermore, the surface of the pretreated inorganic substrate is "grafted" with methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, effectively enhancing its antioxidant properties. Its synergistic effect with pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] results in even better oxidation resistance.

[0033] In summary, using functional protective agents as raw materials for protective coatings not only effectively improves the wear resistance of the prepared NdFeB magnetic rings, but also effectively improves their corrosion resistance, extending their service life to a certain extent while effectively ensuring the quality of the NdFeB magnetic rings. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] A manufacturing process for neodymium iron boron magnetic rings includes the following steps:

[0037] Step 1: Prepare materials according to the following mass percentages: B: 1.6%, Nb: 1.2%, PrNd: 23%, Ga: 0.8%, Al: 0.15%, with the balance being Fe; then use a vacuum melting process to heat the prepared raw materials into molten metal by medium-frequency induction heating; pour the resulting molten metal into a double-sided water-cooled mold to prepare an ingot for later use;

[0038] Step 2: Place the ingot obtained in Step 1 in a vacuum heat treatment furnace, evacuate and heat to 1130℃, fill with argon gas to a pressure of -0.08MPa, and maintain the furnace temperature for 18 hours; then fill with argon gas to a pressure of -0.04MPa, and then cool it down to 880℃ within 12 minutes, and maintain this temperature for 100 minutes; then lower the furnace temperature to 580℃ within 40 minutes, and maintain this temperature for 100 minutes; finally, air cool it down to room temperature before removing it from the furnace.

[0039] Step 3: Perform HDDR treatment on the ingot obtained in Step 2. The resulting magnetic powder with a hydrogen content of 550ppm is sent to an air jet mill for grinding. The resulting air jet mill magnetic powder with an average particle size of 1μm is stored for later use.

[0040] Step 4: Add 0.06 wt% of a lubricant, which is a compound of triglycerides and calcium stearate, to the air jet mill magnetic powder. After mixing and stirring for 3 hours, transfer the resulting mixture into a magnetic ring magnetic field press for orientation molding. Then, after isostatic pressing, high-temperature sintering, cooling and tempering heat treatment, a protective coating is applied to the surface of the resulting magnetic ring. After the protective coating dries, the final product is a highly irregular square magnetic ring.

[0041] The protective coating consists of component A and component B; among which,

[0042] Component A consists of the following raw materials in parts by weight: 240 parts bisphenol A type epoxy resin, 8 parts o-cresol epoxy resin, 0.6 parts EFKA-4320 wetting and dispersing agent, 6 parts γ-aminopropyltriethoxysilane, 2.8 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10 parts functional protective agent, 12 parts toluene, 2.3 parts bentonite, 22 parts filler, and 8 parts iron oxide red;

[0043] The filler is composed of nano-silica and quartz powder in a mass ratio of 8:1.

[0044] Component B consists of the following raw materials in parts by weight: 8 parts xyleneamine, 20 parts YD-8115 polyamide curing agent, 8 parts tetraethylenepentamine, 3.6 parts N-(2,5-dihydro-2,5-dioxo-1H-imidazol-4-yl)urea, 23 parts phthalic anhydride and 45 parts mixed solvent.

[0045] The mixed solvent is composed of toluene, anhydrous ethanol and acetone in a volume ratio of 4:1:0.8.

[0046] The preparation method of the functional protective agent is as follows: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is stirred and melted at 68°C. Then, 8% by mass of pretreated inorganic substrate and 0.3% by mass of dioctyltin oxide are added to the resulting melt. After mixing and stirring evenly, the temperature of the resulting mixed melt is raised to 115°C and stirred for 3 hours under nitrogen protection. After the reaction is completed, the resulting reaction product is filtered. The resulting filter cake is washed three times with N,N-dimethylformamide and then dried in a vacuum drying oven. The final product is the functional protective agent.

[0047] The preparation method of the pretreated inorganic substrate is as follows: the inorganic substrate is immersed in a mixed acid solution with a mass of 5 times that of the substrate, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3, and the mixture is refluxed at 90°C for 6 hours. After the reaction is completed, the resulting product components are centrifuged, filtered, washed with deionized water, and dried in sequence. The final product is the pretreated inorganic substrate.

[0048] The method for preparing inorganic substrates includes the following steps:

[0049] I. The nanocarrier was uniformly dispersed in anhydrous ethanol at a solid-liquid ratio of 0.003 g / mL. While stirring, an ethanol solution of 0.1 mol / L zirconium dichloride (20% by volume of anhydrous ethanol) was added. After stirring for 25 min, an appropriate amount of glycerol was added under magnetic stirring. After mechanical stirring for 30 min, the pH of the resulting mixture was adjusted to 10.5. Then, it was transferred to a reaction vessel and kept at 170℃ for 12 h.

[0050] II. After the heat preservation treatment is completed, the mixture in the reactor is naturally cooled to room temperature, and then vacuum filtered three times. The resulting filter material is dried and then calcined at 450°C for 2 hours under nitrogen atmosphere. The final product is the inorganic substrate. The mass concentration of glycerol in the mixture is 5 times that of zirconium dichloride.

[0051] The preparation method of nanocarriers includes the following steps:

[0052] i. Add citric acid (0.2% by mass of aluminum nitrate) and N,N-dimethylformamide (50 times the molar amount of aluminum nitrate) to a 0.02 mol / L aqueous solution of aluminum nitrate. After mixing and stirring thoroughly, raise the temperature to 80°C and maintain this temperature for 2 hours. Then transfer the mixture to a high-pressure reactor, raise the reactor temperature to 230°C, and maintain this temperature for 3 hours. After the treatment is complete, allow it to cool naturally to room temperature. Store the resulting mixture for later use.

[0053] ii. While stirring, add ferric nitrate in a molar amount twice that of aluminum nitrate to the mixed components. After stirring to dissolve the ferric nitrate evenly, add N,N-dimethylformamide in a molar amount 40 times that of ferric nitrate. Under stirring conditions, raise the temperature to 80°C and maintain the reaction at this temperature for 3 hours. After the reaction is complete, filter the resulting product. Wash the filter cake twice with deionized water and anhydrous ethanol, then dry and sinter it at high temperature. Wash the resulting solid material with nitric acid at 80°C and a concentration of 5.5 mol / L to remove impurities, then centrifuge to remove impurity ions, and finally dry it to obtain the finished nanocarrier.

[0054] The specific operations for HDDR processing in step three are as follows:

[0055] S1. Place the ingot in the HDDR furnace, check the airtightness of the equipment and evacuate the furnace to below 0.18Pa. Then raise the furnace temperature to 175°C, fill the furnace with hydrogen to increase the furnace pressure to 96kPa, and maintain this condition for 40 minutes.

[0056] S2. Evacuate the furnace again to below 0.8 Pa, and at the same time raise the furnace temperature to 825°C. Introduce hydrogen to increase the furnace pressure to 31 kPa and maintain this condition for 80 min. Then, adjust the furnace temperature to 885°C and introduce hydrogen to increase the furnace pressure to 73 kPa and maintain this condition for 30 min.

[0057] Within S3 and S4 minutes, reduce the hydrogen pressure in the furnace from 73 kPa to 5.5 kPa, then within 6 minutes, reduce it to 4 kPa, and maintain the hydrogen pressure in the furnace at 3.5 kPa for 15 minutes. Finally, reduce the furnace temperature to 860°C, and simultaneously force hydrogen venting to reduce its pressure to 0.15 Pa. Turn off the heating and allow it to cool naturally to 30°C.

[0058] Example 2

[0059] The manufacturing process of the NdFeB magnetic ring in this embodiment is basically the same as that in Example 1. The difference lies in the specific proportions of the raw materials used for the NdFeB magnetic ring and the protective coating, as well as the preparation method of the functional protective agent. The specific proportions of the raw materials used and the preparation method of the functional protective agent in this embodiment are as follows:

[0060] The raw materials used for neodymium iron boron magnetic rings are: B: 3.0%, Nb: 2.5%, PrNd: 25%, Ga: 1.8%, Al: 2.0%, with the balance being Fe;

[0061] The protective coating consists of component A and component B; among which,

[0062] Component A consists of the following raw materials in parts by weight: 28 parts bisphenol A type epoxy resin, 10 parts o-cresol epoxy resin, 1.3 parts EFKA-4320 wetting and dispersing agent, 8 parts γ-aminopropyltriethoxysilane, 3.2 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 14 parts functional protective agent, 14 parts toluene, 3.0 parts bentonite, 25 parts filler, and 10 parts cadmium yellow;

[0063] The filler is composed of nano-silica and quartz powder in a mass ratio of 9:1.

[0064] Component B consists of the following raw materials in parts by weight: 10 parts xyleneamine, 25 parts YD-8115 polyamide curing agent, 10 parts tetraethylenepentamine, 4.2 parts N-(2,5-dihydro-2,5-dioxo-1H-imidazol-4-yl)urea, 25 parts phthalic anhydride and 55 parts mixed solvent.

[0065] The mixed solvent is composed of toluene, anhydrous ethanol and acetone in a volume ratio of 5:1:1.

[0066] The preparation method of the functional protective agent is as follows: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is stirred and melted at 70°C. Then, 10% of the mass of the pretreated inorganic substrate and 0.4% of dioctyltin oxide are added to the resulting melt. After mixing and stirring evenly, the temperature of the resulting mixed melt is raised to 120°C and stirred for 4 hours under nitrogen protection. After the reaction is completed, the resulting reaction product is filtered. The resulting filter cake is washed 4 times with N,N-dimethylformamide and then dried in a vacuum drying oven. The final product is the functional protective agent.

[0067] The preparation method of the pretreated inorganic substrate is as follows: the inorganic substrate is immersed in a mixed acid solution with a mass of 6 times that of the substrate, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3, and the mixture is refluxed at 93°C for 8 hours. After the reaction is completed, the resulting product components are centrifuged, filtered, washed with deionized water, and dried in sequence. The final product is the pretreated inorganic substrate.

[0068] The method for preparing inorganic substrates includes the following steps:

[0069] I. The nanocarrier was uniformly dispersed in anhydrous ethanol at a solid-liquid ratio of 0.004 g / mL. While stirring, an ethanol solution of 0.12 mol / L zirconium dichloride (25% by volume of anhydrous ethanol) was added. After stirring for 30 min, an appropriate amount of glycerol was added under magnetic stirring. After mechanical stirring for 35 min, the pH of the resulting mixture was adjusted to 11.2. Then, it was transferred to a reaction vessel and kept at 190℃ for 14 h.

[0070] II. After the heat preservation treatment is completed, the mixture in the reactor is naturally cooled to room temperature, and then vacuum filtered 4 times. The obtained filter material is dried and then calcined at 500°C for 2 hours under nitrogen atmosphere. The final product is the inorganic substrate. The mass concentration of glycerol in the mixture is 6 times that of zirconium dichloride.

[0071] The preparation method of nanocarriers includes the following steps:

[0072] i. Add citric acid (0.25% by mass of aluminum nitrate) and N,N-dimethylformamide (70 times the molar amount of aluminum nitrate) to a 0.03 mol / L aqueous solution of aluminum nitrate. After mixing and stirring thoroughly, raise the temperature to 85°C and maintain this temperature for 3 hours. Then transfer the mixture to a high-pressure reactor, raise the reactor temperature to 240°C, and maintain this temperature for 4 hours. After the treatment is complete, allow it to cool naturally to room temperature. Store the resulting mixture for later use.

[0073] ii. While stirring, add ferric nitrate in a molar amount 2.5 times that of aluminum nitrate to the mixed components. After stirring to dissolve the ferric nitrate evenly, add N,N-dimethylformamide in a molar amount 50 times that of ferric nitrate. Under stirring conditions, raise the temperature to 90°C and maintain the reaction at this temperature for 4 hours. After the reaction is complete, filter the resulting product. Wash the filter cake twice with deionized water and anhydrous ethanol, then dry and sinter it at high temperature. Wash the resulting solid material with nitric acid at 85°C and a concentration of 6 mol / L to remove impurities, then centrifuge to remove impurity ions, and finally dry it to obtain the finished nanocarrier.

[0074] Example 3

[0075] The manufacturing process of the NdFeB magnetic ring in this embodiment is basically the same as that in Example 1. The difference lies in the specific proportions of the raw materials used for the NdFeB magnetic ring and the protective coating, as well as the preparation method of the functional protective agent. The specific proportions of the raw materials used and the preparation method of the functional protective agent in this embodiment are as follows:

[0076] The raw materials used for neodymium iron boron magnetic rings are: B: 3.8%, Nb: 3.3%, PrNd: 28%, Ga: 2.5%, Al: 3.0%, with the balance being Fe;

[0077] The protective coating consists of component A and component B; among which,

[0078] Component A consists of the following raw materials in parts by weight: 30 parts bisphenol A type epoxy resin, 12 parts o-cresol epoxy resin, 1.8 parts EFKA-4320 wetting and dispersing agent, 9 parts γ-aminopropyltriethoxysilane, 3.6 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 16 parts functional protective agent, 16 parts toluene, 3.5 parts bentonite, 28 parts filler, and 13 parts ultramarine.

[0079] The filler is composed of nano-silica and quartz powder in a mass ratio of 10:1;

[0080] Component B consists of the following raw materials in parts by weight: 12 parts xyleneamine, 30 parts YD-8115 polyamide curing agent, 12 parts tetraethylenepentamine, 4.8 parts N-(2,5-dihydro-2,5-dioxo-1H-imidazol-4-yl)urea, 28 parts phthalic anhydride and 65 parts mixed solvent.

[0081] The mixed solvent is composed of toluene, anhydrous ethanol and acetone in a volume ratio of 6:1:1.2.

[0082] The preparation method of the functional protective agent is as follows: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is stirred and melted at 73°C. Then, 12% by mass of pretreated inorganic substrate and 0.5% by mass of dioctyltin oxide are added to the resulting melt. After mixing and stirring evenly, the temperature of the resulting mixed melt is raised to 125°C and stirred for 4 hours under nitrogen protection. After the reaction is completed, the resulting reaction product is filtered. The resulting filter cake is washed 4 times with N,N-dimethylformamide and then dried in a vacuum drying oven. The final product is the functional protective agent.

[0083] The preparation method of the pretreated inorganic substrate is as follows: the inorganic substrate is immersed in a mixed acid solution with a mass of 8 times that of the substrate, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3, and the mixture is refluxed at 95°C for 10 hours. After the reaction is completed, the resulting product components are centrifuged, filtered, washed with deionized water, and dried in sequence. The final product is the pretreated inorganic substrate.

[0084] The method for preparing inorganic substrates includes the following steps:

[0085] I. The nanocarrier was uniformly dispersed in anhydrous ethanol at a solid-liquid ratio of 0.005 g / mL. While stirring, an ethanol solution of zirconium dichloride with a volume of 30% anhydrous ethanol and a concentration of 0.15 mol / L was added. After stirring for 40 min, an appropriate amount of glycerol was added under magnetic stirring. After mechanical stirring for 40 min, the pH of the resulting mixture was adjusted to 11.8. Then, it was transferred to a reaction vessel and kept at 200℃ for 16 h.

[0086] II. After the heat preservation treatment is completed, the mixture in the reactor is naturally cooled to room temperature, and then vacuum filtered 4 times. The obtained filter material is dried and then calcined at 560°C for 3 hours under nitrogen atmosphere. The final product is the inorganic substrate. The mass concentration of glycerol in the mixture is 8 times that of zirconium dichloride.

[0087] The preparation method of nanocarriers includes the following steps:

[0088] i. Add citric acid (0.3% by mass of aluminum nitrate) and N,N-dimethylformamide (90 times the molar amount of aluminum nitrate) to a 0.04 mol / L aqueous solution of aluminum nitrate. After mixing and stirring thoroughly, raise the temperature to 90°C and maintain this temperature for 3 hours. Then transfer the mixture to a high-pressure reactor, raise the reactor temperature to 250°C, and maintain this temperature for 5 hours. After the treatment is complete, allow it to cool naturally to room temperature. Store the resulting mixture for later use.

[0089] ii. While stirring, add ferric nitrate in a molar amount three times that of aluminum nitrate to the mixed components. After stirring to dissolve the ferric nitrate evenly, add N,N-dimethylformamide in a molar amount 55 times that of ferric nitrate. Under stirring conditions, raise the temperature to 96°C and maintain the reaction at this temperature for 6 hours. After the reaction is complete, filter the resulting product. Wash the filter cake three times with deionized water and anhydrous ethanol, then dry and sinter it at high temperature. Wash the resulting solid material with nitric acid at 90°C and a concentration of 6.5 mol / L to remove impurities, then centrifuge to remove impurity ions, and finally dry it to obtain the finished nanocarrier.

[0090] The difference between Comparative Example 1 and Example 1 is that the raw materials of the coating used in the protective coating in this example do not contain functional protective agents.

[0091] Comparative Example 2 differs from Example 1 in that an equal amount of inorganic substrate is used instead of the functional protective agent in this example.

[0092] Comparative Example 3 differs from Example 1 in that the inorganic substrate was not pretreated in this example; that is, when preparing the functional protective agent, an equal amount of inorganic substrate was directly used to replace the pretreated inorganic substrate.

[0093] Comparative Example 4 differs from Example 1 in that an equal amount of nanocarrier is used instead of the functional protective agent in this example.

[0094] Performance Testing: The performance of the NdFeB magnetic rings with a protective coating thickness of 35±3μm provided in Examples 1-3 and Comparative Examples 1-4 was tested as follows, and the experimental data are recorded in the table below:

[0095]

[0096] Note 1: Impact resistance test is conducted in 5cm intervals;

[0097] 2. The impact resistance test standard is GB / T1732-1993; the cross-cut test standard is GB / T9286-1998; the comprehensive aging performance test standard for the protective coating is GB / T1766-2008; the oxidation resistance test method is: high temperature treatment at 180℃ for 72 hours, and then observe whether cracks appear on the surface of the magnetic ring.

[0098] By comparing and analyzing the relevant data in the table, it can be seen that the NdFeB magnetic rings produced by this invention not only have good wear resistance but also good corrosion resistance, which extends their service life to a certain extent while ensuring the quality of the NdFeB magnetic rings. Therefore, it is evident that the production process of the NdFeB magnetic rings provided by this invention has a broader market prospect and is more suitable for widespread application.

[0099] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0100] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A manufacturing process for neodymium iron boron magnetic rings, characterized in that, Includes the following steps: Step 1: Prepare materials according to the following mass percentages: B: 1.6-3.8%, Nb: 1.2-3.3%, PrNd: 23-28%, Ga: 0.8-2.5%, Al: 0.15-3.0%, with the balance being Fe; then, use a vacuum melting process to heat the prepared raw materials into molten metal using medium-frequency induction heating; pour the resulting molten metal into a double-sided water-cooled mold to prepare ingots for later use; Step 2: Place the ingot obtained in Step 1 in a vacuum heat treatment furnace, evacuate and heat to 1130-1200℃, fill with argon gas to a pressure of -0.08MPa, and maintain the furnace temperature for 18-22 hours; then fill with argon gas to a pressure of -0.04MPa, and then cool it down to 880-920℃ within 12-15 minutes, and maintain this temperature for 100-150 minutes; then lower the furnace temperature to 580-630℃ within 40-50 minutes, and maintain this temperature for 100-150 minutes; finally, air cool it down to room temperature before removing it from the furnace. Step 3: Perform HDDR treatment on the ingot obtained in Step 2. The resulting magnetic powder with a hydrogen content ≤550ppm is sent to an air jet mill for grinding. The resulting air jet mill magnetic powder with an average particle size of 1-6μm is stored for later use. Step 4: Add 0.06-0.85 wt% of a lubricant made of triglycerides and calcium stearate in a mass ratio of 1:1.0-1.5 to the air jet mill magnetic powder. After mixing and stirring for 3-7 hours, transfer the resulting mixture into a magnetic ring magnetic field press for orientation molding. Then, after isostatic pressing, high-temperature sintering, cooling and tempering heat treatment, a protective coating is applied to the surface of the resulting magnetic ring. After the protective coating dries, the final product is a highly irregular square magnetic ring. The protective coating is composed of component A and component B. Component A is composed of the following raw materials in parts by weight: 24-30 parts bisphenol A epoxy resin, 8-12 parts o-cresol epoxy resin, 0.6-1.8 parts EFKA-4320 wetting and dispersing agent, 6-9 parts γ-aminopropyltriethoxysilane, 2.8-3.6 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10-16 parts functional protective agent, 12-16 parts toluene, 2.3-3.5 parts bentonite, 22-28 parts filler, and 8-13 parts pigment. Component B is composed of the following raw materials in parts by weight: 8-12 parts xyleneamine, 20-30 parts YD-8115 polyamide curing agent, 8-12 parts tetraethylenepentamine, 3.6-4.8 parts N-(2,5-dihydro-2,5-dioxo-1H-imidazol-4-yl)urea, 23-28 parts phthalic anhydride, and 45-65 parts mixed solvent; The preparation method of the functional protective agent is as follows: methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is stirred and melted at a temperature of 68-73°C. Then, 8-12% by mass of pretreated inorganic substrate and 0.3-0.5% by mass of dioctyltin oxide are added to the resulting melt. After mixing and stirring evenly, the temperature of the resulting mixed melt is raised to 115-125°C, and the mixture is stirred and reacted for 3-4 hours under nitrogen protection. After the reaction is completed, the resulting reaction product is filtered. The resulting filter cake is washed 3-4 times with N,N-dimethylformamide and then dried in a vacuum drying oven. The final product is the functional protective agent.

2. The manufacturing process of a neodymium iron boron magnetic ring according to claim 1, characterized in that, The method for preparing the pretreated inorganic substrate is as follows: the inorganic substrate is immersed in a mixed acid solution of 5 to 8 times its mass, which is composed of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:3, and the mixture is refluxed at a temperature of 90 to 95°C for 6 to 10 hours; after the reaction is completed, the resulting product components are centrifuged, filtered, washed with deionized water, and dried in sequence, and the final product is the pretreated inorganic substrate.

3. The manufacturing process of a neodymium iron boron magnetic ring according to claim 2, characterized in that, The method for preparing the inorganic substrate includes the following steps: I. The nanocarrier was uniformly dispersed in anhydrous ethanol at a solid-liquid ratio of 0.003–0.005 g / mL. While stirring, an ethanol solution of zirconium dichloride with a volume of 20–30% anhydrous ethanol and a concentration of 0.1–0.15 mol / L was added. After stirring for 25–40 min, an appropriate amount of glycerol was added under magnetic stirring. After mechanical stirring for 30–40 min, the pH of the resulting mixture was adjusted to 10.5–11.

8. The mixture was then transferred to a reaction vessel and kept at 170–200 °C for 12–16 h. II. After the heat preservation treatment is completed, the mixture in the reactor is naturally cooled to room temperature, and then vacuum filtered 3 to 4 times. The obtained filter material is dried and then calcined at 450 to 560°C for 2 to 3 hours under nitrogen atmosphere protection. The final product is the inorganic substrate. The mass concentration of glycerol in the mixture is 5 to 8 times that of zirconium dichloride.

4. The manufacturing process of a neodymium iron boron magnetic ring according to claim 3, characterized in that, The preparation method of the nanocarrier includes the following steps: i. Add 0.2-0.3% (by mass) citric acid and 50-90 times (by molar amount) N,N-dimethylformamide to an aqueous solution of aluminum nitrate with a concentration of 0.02-0.04 mol / L. After mixing and stirring thoroughly, raise the temperature to 80-90°C and maintain this temperature for 2-3 hours. Then transfer the mixture to a high-pressure reactor and raise the reactor temperature to 230-250°C, maintaining this temperature for 3-5 hours. After treatment, allow it to cool naturally to room temperature. Store the resulting mixture for later use. ii. While stirring, add ferric nitrate in a molar amount 2-3 times that of aluminum nitrate to the mixed components. After stirring to ensure the ferric nitrate is uniformly dissolved, add N,N-dimethylformamide in a molar amount 40-55 times that of ferric nitrate. Under stirring conditions, raise the temperature to 80-96℃ and maintain the reaction at this temperature for 3-6 hours. After the reaction is complete, filter the resulting product. Wash the filter cake 2-3 times with deionized water and anhydrous ethanol, then dry and sinter at high temperature. Wash the resulting solid material with nitric acid at 80-90℃ and a concentration of 5.5-6.5 mol / L to remove impurities, then remove impurity ions by centrifugation. Finally, dry the material to obtain the finished nanocarrier.

5. The manufacturing process of a neodymium iron boron magnetic ring according to claim 1, characterized in that: The pigment is any one of iron oxide red, iron oxide black, cadmium red, cadmium yellow, carbon black, phthalocyanine blue, and ultramarine.

6. The manufacturing process of a neodymium iron boron magnetic ring according to claim 1, characterized in that: The filler is composed of nano-silica and quartz powder in a mass ratio of 8 to 10:

1.

7. The manufacturing process of a neodymium iron boron magnetic ring according to claim 1, characterized in that: The mixed solvent is prepared by mixing toluene, anhydrous ethanol and acetone in a volume ratio of 4-6:1:0.8-1.

2.

8. The manufacturing process of a neodymium iron boron magnetic ring according to claim 1, characterized in that, The specific operations of the HDDR processing in step three are as follows: S1. Place the ingot in the HDDR furnace, check the airtightness of the equipment and evacuate the furnace to below 0.18 Pa. Then raise the furnace temperature to 175-195°C, fill the furnace with hydrogen to increase the furnace pressure to 96-98 kPa, and maintain this condition for 40-55 minutes. S2. Evacuate the furnace again to below 0.8 Pa, while raising the furnace temperature to 825-845°C. Introduce hydrogen to raise the furnace pressure to 31-34 kPa and maintain this condition for 80-90 min. Then, adjust the furnace temperature to 885-900°C, introduce hydrogen to raise the furnace pressure to 73-78 kPa, and maintain this condition for 30-40 min. S3. Within 4-5 minutes, reduce the hydrogen pressure inside the furnace from 73-78 kPa to 5.5-6.5 kPa, then within 6-8 minutes, reduce it to 4-4.5 kPa, and maintain the hydrogen pressure inside the furnace at 3.5-4.3 kPa for 15-20 minutes. Finally, reduce the furnace temperature to 860-870℃, and simultaneously force hydrogen venting to reduce its pressure to below 0.15 Pa. Turn off the heating and allow it to cool naturally to below 30℃.

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