Preparation process for high-performance sintered neodymium-iron-boron magnet

Abstract

The present invention provides a preparation process for a high-performance sintered neodymium-iron-boron magnet. The preparation process for a high-performance sintered neodymium-iron-boron magnet comprises the following steps: adding organic silicon to modify an epoxy resin; adding nanocrystalline Ni-Zn ferrite powder to prepare a magnetically conductive coating; smelting metal raw materials, and carrying out jet milling to prepare powder; adding metal holmium and the like, and carrying out compression molding; carrying out vacuumizing and static pressing; and carrying out vacuum sintering, and spraying the magnetically conductive coating. According to the present invention, the nanocrystalline Ni-Zn ferrite powder and other auxiliaries are added into the modified epoxy resin to prepare the magnetically conductive coating having excellent magnetic conductivity, and after the magnetically conductive coating is sprayed on the surface of a neodymium-iron-boron magnet, the influence, of direct coating of the epoxy resin on the surface of the neodymium-iron-boron magnet, on the magnetism of the neodymium-iron-boron magnet can be reduced.

Description

A preparation process for high-performance sintered NdFeB magnets Technical Field

[0001] The present invention relates to the field of rare earth functional materials, and in particular to a preparation process of a high-performance sintered NdFeB magnet. Background Art

[0002] NdFeB magnets are tetragonal crystals formed by neodymium, iron, and boron. They are permanent magnets with magnetic properties second only to absolute zero holmium magnets and are also the most commonly used rare earth magnets. NdFeB is divided into sintered NdFeB and bonded NdFeB. Sintered NdFeB permanent magnets have excellent magnetic properties and are widely used in electronics, power machinery, medical equipment, hardware machinery, aerospace, and other fields. However, sintered NdFeB has poor corrosion resistance and usually requires surface coating for protection.

[0003] At present, methods such as electroplating Ni, Zn, etc. on the surface of NdFeB magnets, performing cathodic electrophoretic coating, or spraying epoxy resin have been adopted to protect NdFeB magnets and improve their corrosion resistance. However, electroplating Ni, Zn, etc. or performing cathodic electrophoretic coating have poor protective effects on NdFeB magnets and the degree of improvement in the corrosion resistance of the magnets is relatively weak. Although spraying epoxy resin can better protect NdFeB magnets, the magnetic conductivity of NdFeB magnets after spraying epoxy resin is poor, that is, spraying epoxy resin will reduce the magnetism of NdFeB magnets.

[0004] Therefore, we propose a high-performance sintered NdFeB magnet that can reduce the influence of epoxy resin sprayed on the surface of the NdFeB magnet on the magnetic properties of the NdFeB magnet.

[0005] Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a preparation process for high-performance sintered NdFeB magnets.

[0007] A process for preparing high-performance sintered NdFeB magnets comprises the following steps:

[0008] S1: Modification of epoxy resin by adding silicone

[0009] The epoxy resin and butyl acetate are stirred and mixed and heated, and then silicone and dibutyltin dilaurate are added to carry out a modification reaction;

[0010] S2: Add nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating

[0011] Triethylamine is added for neutralization reaction, and then a modified epoxy resin is prepared by vacuum distillation. Then, nanocrystalline Ni-Zn ferrite powder, a curing agent, a film-forming aid, and a defoaming agent are added to the modified epoxy resin, and after shearing and dispersion, a magnetic conductive coating is obtained.

[0012] S3: Melting metal raw materials and air flow grinding powder

[0013] The metal raw materials such as neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum and copper are mixed and smelted, and then roughly crushed. Then, under the protection of nitrogen, air flow milling is carried out to obtain alloy powder;

[0014] S4: Add metal holmium and press into shape

[0015] The metal holmium and dysprosium oxide are mixed into the alloy powder, and then added into a forming mold. Under the protection of nitrogen, a magnetic field is applied for orientation, and the mold is pressed to obtain an alloy blank.

[0016] S5: Vacuum and static pressure

[0017] Start the vacuum valve on the forming mold to evacuate the forming mold containing the alloy blank, then place the vacuumed forming mold into a static press and press for 1-2 hours to obtain an alloy green body;

[0018] S6: Vacuum sintering and spraying magnetic conductive paint

[0019] After demoulding the alloy green body, vacuum sintering is performed to prepare a NdFeB magnet. After cooling, a textured magnet is obtained by laser texturing. Then, the magnetic conductive coating is evenly sprayed on the surface of the textured magnet to obtain a high-performance sintered NdFeB magnet.

[0020] Furthermore, step S1 of adding silicone to modify the epoxy resin specifically includes the following steps:

[0021] S1.1: Add epoxy resin and butyl acetate solvent into the reactor at a material-liquid ratio of 1-2:1 kg / L. After the gravity sensor in the reactor detects the addition of the epoxy resin and butyl acetate, it sends a signal to the controller.

[0022] S1.2: After receiving the signal from the gravity sensor, the controller controls the agitator and heater in the reactor to start. The agitator stirs at a rate of 600-750 rpm for 1-2 hours, and the heater heats at a rate of 5-10°C / min.

[0023] S1.3: After the stirring is completed, the controller controls the feed assembly to open, and the feed assembly mixes the silicone and catalyst in a mass ratio of 10-15:1 and adds them to the reactor to carry out the modification reaction. At the same time, the feed assembly sends a signal to the controller;

[0024] S1.4: After receiving the signal sent by the feeding component, the controller controls the stirrer to stir at a rate of 800-1000 r / min for 20-30 minutes.

[0025] Furthermore, the step S2 of adding nanocrystalline Ni-Zn ferrite powder to prepare the magnetic conductive coating specifically includes the following steps:

[0026] S2.1: After the stirring is completed, the controller controls the feeder to start, and the feeder adds triethylamine to the reactor to carry out the neutralization reaction. At the same time, the controller controls the stirring speed of the stirrer to 200-300 r / min, and continues stirring for 4-5 hours;

[0027] S2.2: After the reaction is completed, the controller controls the opening of the pressure reducing valve to adjust the pressure in the reactor to 0.02-0.05 MPa. At the same time, the controller controls the heating temperature of the heater to increase to 70-85°C, and the reactor is subjected to reduced pressure distillation to obtain a modified epoxy resin.

[0028] S2.3: The distilled modified epoxy resin flows into the high-shear disperser through the liquid conduit until a liquid volume sensor in the high-shear disperser detects that the volume of the modified epoxy resin in the high-shear disperser reaches a preset range, and the liquid volume sensor sends a signal to the controller;

[0029] S2.4: After receiving the signal from the liquid volume sensor, the controller controls the feeding assembly to add the nanocrystalline Ni-Zn ferrite powder into the high shear disperser;

[0030] S2.5: The controller then starts the high shear disperser and shears and disperses at 1000-1200 r / min for 0.5-1 h.

[0031] S2.6: After the shear dispersion is completed, the controller controls the feeding component to add the curing agent, film-forming aid and defoaming agent into the high shear disperser. The controller adjusts the speed of the high shear disperser to 800-1000r / min, and shear dispersion is performed for 2-3 hours to obtain the magnetic conductive coating.

[0032] Furthermore, step S3 of smelting the metal raw material and grinding it into powder by air flow grinding specifically includes the following steps:

[0033] S3.1: Using a batching machine, metal raw materials such as neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum, and copper are mixed according to mass ratio, and then placed in a vacuum induction furnace for smelting to obtain an alloy ingot;

[0034] S3.3: Add the alloy ingot to a crusher for coarse crushing to obtain alloy scrap;

[0035] S3.4: Nitrogen is introduced into the airflow mill until a first nitrogen detector in the airflow mill detects that the nitrogen concentration in the airflow mill is 95-99%, and the first nitrogen detector sends a signal to the controller;

[0036] S3.5: After receiving the signal from the first nitrogen detector, the controller controls the crusher discharge valve to open, feeding the alloy crumbs into the airflow mill. After the gravity sensor in the airflow mill detects the addition of the alloy crumbs, it sends a signal to the controller.

[0037] S3.6: After receiving the signal from the gravity sensor, the controller controls the airflow mill to operate for 45-55 minutes to perform airflow milling to obtain alloy powder.

[0038] Furthermore, step S4 of adding metal holmium and the like and pressing into shape specifically includes the following steps:

[0039] S4.1: After the airflow milling is completed, the controller controls the airflow mill to stop operating. At the same time, the hopper controls the hopper to add holmium metal and dysprosium oxide into the airflow mill in a mass ratio of 2-3:1, and stirs and mixes them with the stirrer to obtain a mixed powder.

[0040] S4.2: Nitrogen is introduced into the molding press until a second nitrogen detector in the molding press detects that the nitrogen concentration in the molding press is 90-99%, and the second nitrogen detector sends a signal to the controller;

[0041] S4.3: After receiving the signal from the second nitrogen detector, the controller controls the airflow mill to open the discharge valve and add the mixed powder into the pressing mold;

[0042] S4.4: Place the pressing die containing the mixed powder into a forming press, apply a magnetic field to orient the alloy powder in the forming die, and simultaneously start the forming press to press the alloy powder into a shape to obtain an alloy blank.

[0043] Furthermore, the vacuum sintering and spraying of magnetic conductive coating in step S6 specifically includes the following steps:

[0044] S6.1: Demolding the alloy green body obtained in step S5, placing the alloy green body into a graphite box, and then placing the graphite box containing the alloy green body into a vacuum sintering furnace. Adjust the temperature of the vacuum sintering furnace to 300-500°C and pre-sinter for 2-3 hours;

[0045] S6.2: Adjust the temperature of the vacuum sintering furnace to 1000-1200°C and vacuum sinter for 4-5 hours to obtain NdFeB magnets;

[0046] S6.3: When the temperature sensor in the vacuum sintering furnace detects that the temperature in the furnace is 20-30°C, the temperature sensor sends a signal to the controller;

[0047] S6.4: After receiving the signal from the temperature sensor, the controller controls the conveying assembly of the vacuum sintering furnace to start, and conveys the NdFeB magnet into the laser texturing machine through the conveying assembly;

[0048] S6.5: Then, the laser texturing machine is started to perform laser texturing on the NdFeB magnet to obtain a texturized magnet;

[0049] S6.6: The magnetic conductive coating obtained in step S2.6 is loaded into a spray gun, and the magnetic conductive coating is evenly sprayed on the surface of the above-mentioned roughened magnet using the spray gun. After the magnetic conductive coating is solidified, a high-performance sintered NdFeB magnet is obtained.

[0050] Furthermore, after the air flow mill produces the alloy powder, the nitrogen in the air flow mill is extracted by an exhaust pump, and the nitrogen is then introduced into the forming press to discharge the air in the forming press for compression molding. After the compression molding is completed, the nitrogen in the forming press is extracted by an exhaust pump again, and introduced into the air flow mill again to discharge the air in the air flow mill, and the cycle is continued.

[0051] Furthermore, the organosilicon is dimethyldichlorosilane, and the catalyst is dibutyltin dilaurate.

[0052] Furthermore, the pressure of the static press is 120-180 MPa.

[0053] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0054] 1. The present invention prepares a magnetic conductive coating with excellent magnetic conductivity by adding nanocrystalline Ni-Zn ferrite powder and other additives to modified epoxy resin. After the magnetic conductive coating is sprayed on the surface of NdFeB magnets, the effect of directly coating the epoxy resin on the surface of NdFeB magnets can be reduced.

[0055] 2. The present invention improves the corrosion resistance, heat resistance and UV aging resistance of epoxy resin by modifying epoxy resin with organic silicon. After the modified epoxy resin is made into a coating, it is sprayed on the surface of the NdFeB magnet, which can effectively protect the NdFeB magnet and extend its service life.

[0056] 3. The present invention adds metal holmium and dysprosium oxide to the alloy powder obtained by smelting and crushing the metal raw material, which can make the grain distribution of the NdFeB magnet obtained by subsequent sintering uniform and increase the density, thereby improving the stability of the NdFeB magnet.

[0057] 4. The present invention utilizes an air pump to recycle the nitrogen in the airflow mill and the forming press, thereby achieving the effect of effectively utilizing resources and reducing waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG1 is a flow chart of a process for preparing a high-performance sintered NdFeB magnet used in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The present invention is further described in detail below with reference to specific embodiments.

[0060] Example 1

[0061] A preparation process for high-performance sintered NdFeB magnets, as shown in FIG1 , comprises the following steps:

[0062] S1: Modification of epoxy resin by adding silicone

[0063] Epoxy resin and butyl acetate solvent are added to the reactor at a material-liquid ratio of 1:1 kg / L. After the gravity sensor in the reactor detects the addition of the above two, the gravity sensor sends a signal to the controller. After the controller receives the signal sent by the gravity sensor, it controls the agitator and heater in the reactor to turn on. The agitator stirs at a rate of 600 r / min for 1-2 hours, and the heater is heated at a rate of 5°C / min. After the stirring is completed, the controller controls the feeding component to turn on. The feeding component mixes dimethyldichlorosilane and dibutyltin dilaurate at a mass ratio of 10:1 and adds them to the reactor to carry out a modification reaction. At the same time, the feeding component sends a signal to the controller. After the controller receives the signal sent by the feeding component, it controls the agitator to stir at a rate of 800 r / min for 20 minutes. By modifying the epoxy resin with silicone, the corrosion resistance, heat resistance and UV aging resistance of the epoxy resin can be improved. After the modified epoxy resin is made into a coating, it is sprayed on the surface of the NdFeB magnet, which can effectively protect the NdFeB magnet and extend its service life.

[0064] S2: Add nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating

[0065] After the stirring is completed, the controller controls the feeder to start, and the feeder adds triethylamine to the reactor to carry out the neutralization reaction. At the same time, the controller controls the stirring rate of the stirrer to 200r / min, and continues stirring for 4h. After the reaction is completed, the controller controls the pressure reducing valve to open, and the pressure reducing valve adjusts the pressure in the reactor to 0.02MPa. At the same time, the controller controls the heating temperature of the heater to increase to 70°C, and performs vacuum distillation in the reactor to obtain a modified epoxy resin. The distilled modified epoxy resin flows into the high shear disperser through the liquid conduit until the liquid volume sensor in the high shear disperser detects that the volume of the modified epoxy resin in the high shear disperser reaches a preset range. The liquid volume sensor sends a signal to the controller, and the controller receives the liquid volume sensor. After receiving the signal sent by the device, the feeding component is controlled to add the nanocrystalline Ni-Zn ferrite powder into the high shear disperser, and then the controller controls the high shear disperser to start, and shear disperses at 1000r / min for 0.5h. After the shear dispersion is completed, the controller controls the feeding component to add the curing agent, film-forming aid and defoaming agent into the high shear disperser, and the controller adjusts the speed of the high shear disperser to 800r / min, and shear disperses for 2h to obtain a magnetic conductive coating. By adding the nanocrystalline Ni-Zn ferrite powder and other additives to the modified epoxy resin, a magnetic conductive coating with excellent magnetic conductive properties is prepared. After the magnetic conductive coating is sprayed on the surface of the NdFeB magnet, the influence of directly coating the epoxy resin on the surface of the NdFeB magnet on the magnetic properties of the NdFeB magnet can be reduced;

[0066] S3: Melting metal raw materials and air flow grinding powder

[0067] Neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum, copper and other metal raw materials are mixed in a mass ratio through a batching machine, and then put into a vacuum induction furnace for smelting to obtain an alloy ingot, and then the alloy ingot is added to a crusher for coarse crushing to obtain alloy scraps, and then nitrogen is introduced into the air flow mill until the first nitrogen detector in the air flow mill detects that the nitrogen concentration in the air flow mill is 95%, and the first nitrogen detector sends a signal to the controller. After receiving the signal sent by the first nitrogen detector, the controller controls the discharge valve of the crusher to open, and the alloy scraps are put into the air flow mill. After the gravity sensor in the air flow mill detects the addition of the alloy scraps, it sends a signal to the controller. After receiving the signal sent by the gravity sensor, the controller controls the air flow mill to operate for 45 minutes, performs air flow grinding, and obtains alloy powder.

[0068] S4: Add metal holmium and press into shape

[0069] After the air flow grinding is completed, the controller controls the air flow mill to stop operating, and at the same time controls the hopper to add metal holmium and dysprosium oxide into the air flow mill in a mass ratio of 2:1, and stir and mix them through the agitator to obtain a mixed powder, and then the nitrogen in the air flow mill is extracted by the vacuum pump, and the nitrogen is then introduced into the molding press to discharge the air in the molding press until the second nitrogen detector in the molding press detects that the nitrogen concentration in the molding press is 90%. The second nitrogen detector sends a signal to the controller. After receiving the signal sent by the second nitrogen detector, the controller controls the air flow mill to open the discharge valve, and adds the above mixed powder into the pressing mold, and then The pressing die containing the mixed powder is placed in a forming press, and a magnetic field is applied to the alloy powder in the forming die for orientation. At the same time, the forming press is started to press the alloy powder into a shape to obtain an alloy blank. After the pressing and molding is completed, the nitrogen in the forming press is extracted by an exhaust pump and introduced into the air flow mill in step S3 again to discharge the air in the air flow mill. This is continuously circulated to achieve the effect of effectively utilizing resources and reducing waste. In addition, by adding metallic holmium and dysprosium oxide to the alloy powder obtained after smelting and crushing the metal raw material, the grain distribution of the NdFeB magnet obtained by subsequent sintering can be uniform, the density is increased, and the stability of the NdFeB magnet is improved.

[0070] S5: Vacuum and static pressure

[0071] Start the vacuum valve on the forming mold to evacuate the forming mold containing the alloy blank, then place the vacuumed forming mold into a static press, adjust the pressure of the static press to 120-180 MPa, and press for 1-2 hours to obtain an alloy green body;

[0072] S6: Vacuum sintering and spraying magnetic conductive paint

[0073] The alloy green body obtained in step S5 is demolded, and then the alloy green body is placed in a graphite box, and then the graphite box containing the alloy green body is placed in a vacuum sintering furnace, the temperature of the vacuum sintering furnace is adjusted to 300°C, and after pre-sintering for 2 hours, the temperature of the vacuum sintering furnace is adjusted to 1000°C, and vacuum sintering is performed for 4 hours to obtain a NdFeB magnet. When the temperature sensor in the vacuum sintering furnace detects that the temperature in the furnace is 20°C, the temperature sensor sends a signal to the controller. After receiving the signal sent by the temperature sensor, the controller controls the transmission component of the vacuum sintering furnace to start, and the NdFeB magnet is sent to the laser texturing machine through the transmission component. Subsequently, the laser texturing machine is started to perform laser texturing on the NdFeB magnet to obtain a texturized magnet. Then, the magnetic conductive coating obtained in step S2 is loaded into a spray gun, and the magnetic conductive coating is evenly sprayed on the surface of the texturized magnet by the spray gun. After the magnetic conductive coating is cured, a high-performance sintered NdFeB magnet is obtained.

[0074] Example 2

[0075] A preparation process for high-performance sintered NdFeB magnets, as shown in FIG1 , comprises the following steps:

[0076] S1: Modification of epoxy resin by adding silicone

[0077] Epoxy resin and butyl acetate solvent are added to the reactor at a material-liquid ratio of 2:1 kg / L. After the gravity sensor in the reactor detects the addition of the above two, the gravity sensor sends a signal to the controller. After the controller receives the signal sent by the gravity sensor, it controls the agitator and heater in the reactor to turn on. The agitator stirs at a rate of 600 r / min for 1 hour, and the heater is heated at a rate of 5°C / min. After the stirring is completed, the controller controls the feeding component to turn on. The feeding component mixes dimethyldichlorosilane and dibutyltin dilaurate at a mass ratio of 15:1 and adds them to the reactor to carry out a modification reaction. At the same time, the feeding component sends a signal to the controller. After the controller receives the signal sent by the feeding component, it controls the agitator to stir at a rate of 1000 r / min for 20 minutes. By modifying the epoxy resin with silicone, the corrosion resistance, heat resistance and UV aging resistance of the epoxy resin can be improved. After the modified epoxy resin is made into a coating, it is sprayed on the surface of the NdFeB magnet, which can effectively protect the NdFeB magnet and extend its service life.

[0078] S2: Add nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating

[0079] After the stirring is completed, the controller controls the feeder to start, and the feeder adds triethylamine to the reactor to carry out a neutralization reaction. At the same time, the controller controls the stirring rate of the stirrer to 300r / min, and continues stirring for 4h. After the reaction is completed, the controller controls the pressure reducing valve to open, and the pressure reducing valve adjusts the pressure in the reactor to 0.02MPa. At the same time, the controller controls the heating temperature of the heater to increase to 70°C, and performs vacuum distillation in the reactor to obtain a modified epoxy resin. The distilled modified epoxy resin flows into the high shear disperser through the liquid conduit until the liquid volume sensor in the high shear disperser detects that the volume of the modified epoxy resin in the high shear disperser reaches a preset range. The liquid volume sensor sends a signal to the controller, and the controller receives the signal from the liquid volume sensor. After the signal is sent, the feeding component is controlled to add the nanocrystalline Ni-Zn ferrite powder into the high shear disperser, and then the controller controls the high shear disperser to start, and shear disperses at 1200r / min for 0.5h. After the shear dispersion is completed, the controller controls the feeding component to add the curing agent, film-forming aid and defoaming agent into the high shear disperser, and the controller adjusts the speed of the high shear disperser to 1000r / min, and shear disperses for 2h to obtain a magnetic conductive coating. By adding the nanocrystalline Ni-Zn ferrite powder and other additives to the modified epoxy resin, a magnetic conductive coating with excellent magnetic conductive properties is prepared. After the magnetic conductive coating is sprayed on the surface of the NdFeB magnet, the influence of directly coating the epoxy resin on the surface of the NdFeB magnet on the magnetic properties of the NdFeB magnet can be reduced;

[0080] S3: Melting metal raw materials and air flow grinding powder

[0081] Neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum, copper and other metal raw materials are mixed in a mass ratio through a batching machine, and then put into a vacuum induction furnace for smelting to obtain an alloy ingot, and then the alloy ingot is added to a crusher for coarse crushing to obtain alloy scraps, and then nitrogen is introduced into the air flow mill until the first nitrogen detector in the air flow mill detects that the nitrogen concentration in the air flow mill is 99%, and the first nitrogen detector sends a signal to the controller. After receiving the signal sent by the first nitrogen detector, the controller controls the discharge valve of the crusher to open, and the alloy scraps are put into the air flow mill. After the gravity sensor in the air flow mill detects the addition of the alloy scraps, it sends a signal to the controller. After receiving the signal sent by the gravity sensor, the controller controls the air flow mill to operate for 45 minutes, performs air flow grinding, and obtains alloy powder.

[0082] S4: Add metal holmium and press into shape

[0083] After the air flow grinding is completed, the controller controls the air flow mill to stop operating, and at the same time controls the hopper to add metal holmium and dysprosium oxide into the air flow mill in a mass ratio of 3:1, and stir and mix them through the agitator to obtain a mixed powder, and then the nitrogen in the air flow mill is extracted by the vacuum pump, and the nitrogen is then introduced into the molding press to discharge the air in the molding press until the second nitrogen detector in the molding press detects that the nitrogen concentration in the molding press is 90%. The second nitrogen detector sends a signal to the controller. After receiving the signal sent by the second nitrogen detector, the controller controls the air flow mill to open the discharge valve, and adds the above mixed powder into the pressing mold, and then The pressing die containing the mixed powder is placed in a forming press, and a magnetic field is applied to the alloy powder in the forming die for orientation. At the same time, the forming press is started to press the alloy powder into a shape to obtain an alloy blank. After the pressing and molding is completed, the nitrogen in the forming press is extracted by an exhaust pump and introduced into the air flow mill in step S3 again to discharge the air in the air flow mill. This is continuously circulated to achieve the effect of effectively utilizing resources and reducing waste. In addition, by adding metallic holmium and dysprosium oxide to the alloy powder obtained after smelting and crushing the metal raw material, the grain distribution of the NdFeB magnet obtained by subsequent sintering can be uniform, the density is increased, and the stability of the NdFeB magnet is improved.

[0084] S5: Vacuum and static pressure

[0085] The vacuum valve on the forming mold was started to evacuate the forming mold containing the alloy blank, and then the vacuum-evacuated forming mold was placed in a static press. The pressure of the static press was adjusted to 180 MPa and pressed for 1 hour to obtain an alloy green body.

[0086] S6: Vacuum sintering and spraying magnetic conductive paint

[0087] The alloy green body obtained in step S5 is demolded, and then the alloy green body is placed in a graphite box, and then the graphite box containing the alloy green body is placed in a vacuum sintering furnace, the temperature of the vacuum sintering furnace is adjusted to 500°C, and after pre-sintering for 2 hours, the temperature of the vacuum sintering furnace is adjusted to 1200°C, and vacuum sintering is performed for 4 hours to obtain a NdFeB magnet. When the temperature sensor in the vacuum sintering furnace detects that the temperature in the furnace is 20°C, the temperature sensor sends a signal to the controller. After receiving the signal sent by the temperature sensor, the controller controls the transmission component of the vacuum sintering furnace to start, and the NdFeB magnet is sent to the laser texturing machine through the transmission component. Subsequently, the laser texturing machine is started to perform laser texturing on the NdFeB magnet to obtain a texturized magnet. Then, the magnetic conductive coating obtained in step S2 is loaded into a spray gun, and the magnetic conductive coating is evenly sprayed on the surface of the texturized magnet by the spray gun. After the magnetic conductive coating is cured, a high-performance sintered NdFeB magnet is obtained.

[0088] Example 3

[0089] A preparation process for high-performance sintered NdFeB magnets, as shown in FIG1 , comprises the following steps:

[0090] S1: Modification of epoxy resin by adding silicone

[0091] Epoxy resin and butyl acetate solvent are added to the reactor at a material-liquid ratio of 1:1 kg / L. After the gravity sensor in the reactor detects the addition of the above two, the gravity sensor sends a signal to the controller. After the controller receives the signal sent by the gravity sensor, it controls the agitator and heater in the reactor to turn on. The agitator stirs at a rate of 600 r / min for 2 hours, and the heater is heated at a rate of 5°C / min. After the stirring is completed, the controller controls the feeding component to turn on. The feeding component mixes dimethyldichlorosilane and dibutyltin dilaurate at a mass ratio of 15:1 and adds them to the reactor to carry out a modification reaction. At the same time, the feeding component sends a signal to the controller. After the controller receives the signal sent by the feeding component, it controls the agitator to stir at a rate of 800 r / min for 30 minutes. By modifying the epoxy resin with silicone, the corrosion resistance, heat resistance and UV aging resistance of the epoxy resin can be improved. After the modified epoxy resin is made into a coating, it is sprayed on the surface of the NdFeB magnet, which can effectively protect the NdFeB magnet and extend its service life.

[0092] S2: Add nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating

[0093] After the stirring is completed, the controller controls the feeder to start, and the feeder adds triethylamine to the reactor to carry out a neutralization reaction. At the same time, the controller controls the stirring rate of the stirrer to 200r / min, and continues stirring for 5h. After the reaction is completed, the controller controls the pressure reducing valve to open, and the pressure reducing valve adjusts the pressure in the reactor to 0.05MPa. At the same time, the controller controls the heating temperature of the heater to increase to 70°C, and performs vacuum distillation in the reactor to obtain a modified epoxy resin. The distilled modified epoxy resin flows into the high shear disperser through the liquid conduit until the liquid volume sensor in the high shear disperser detects that the volume of the modified epoxy resin in the high shear disperser reaches a preset range. The liquid volume sensor sends a signal to the controller, and the controller receives the liquid volume sensor. After the sensor sends a signal, the feeding component is controlled to add the nanocrystalline Ni-Zn ferrite powder into the high shear disperser, and then the controller controls the high shear disperser to start, and shear disperses at 1000r / min for 1h. After the shear dispersion is completed, the controller controls the feeding component to add the curing agent, film-forming aid and defoaming agent into the high shear disperser, and the controller adjusts the speed of the high shear disperser to 800r / min, and shear disperses for 3h to obtain a magnetic conductive coating. By adding the nanocrystalline Ni-Zn ferrite powder and other additives to the modified epoxy resin, a magnetic conductive coating with excellent magnetic conductive properties is prepared. After the magnetic conductive coating is sprayed on the surface of the NdFeB magnet, the influence of directly coating the epoxy resin on the surface of the NdFeB magnet on the magnetic properties of the NdFeB magnet can be reduced;

[0094] S3: Melting metal raw materials and air flow grinding powder

[0095] Neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum, copper and other metal raw materials are mixed in a mass ratio through a batching machine, and then put into a vacuum induction furnace for smelting to obtain an alloy ingot, and then the alloy ingot is added to a crusher for coarse crushing to obtain alloy scraps, and then nitrogen is introduced into the air flow mill until the first nitrogen detector in the air flow mill detects that the nitrogen concentration in the air flow mill is 95%, and the first nitrogen detector sends a signal to the controller. After receiving the signal sent by the first nitrogen detector, the controller controls the discharge valve of the crusher to open, and the alloy scraps are put into the air flow mill. After the gravity sensor in the air flow mill detects the addition of the alloy scraps, it sends a signal to the controller. After receiving the signal sent by the gravity sensor, the controller controls the air flow mill to operate for 55 minutes, performs air flow grinding, and obtains alloy powder.

[0096] S4: Add metal holmium and press into shape

[0097] After the air flow grinding is completed, the controller controls the air flow mill to stop operating, and at the same time controls the hopper to add metal holmium and dysprosium oxide into the air flow mill in a mass ratio of 2:1, and stir and mix them through the agitator to obtain a mixed powder, and then the nitrogen in the air flow mill is extracted by the vacuum pump, and the nitrogen is then introduced into the molding press to discharge the air in the molding press until the second nitrogen detector in the molding press detects that the nitrogen concentration in the molding press is 99%. The second nitrogen detector sends a signal to the controller. After receiving the signal sent by the second nitrogen detector, the controller controls the air flow mill to open the discharge valve, and adds the above mixed powder into the pressing mold, and then The pressing die containing the mixed powder is placed in a forming press, and a magnetic field is applied to the alloy powder in the forming die for orientation. At the same time, the forming press is started to press the alloy powder into a shape to obtain an alloy blank. After the pressing and molding is completed, the nitrogen in the forming press is extracted by an exhaust pump and introduced into the air flow mill in step S3 again to discharge the air in the air flow mill. This is continuously circulated to achieve the effect of effectively utilizing resources and reducing waste. In addition, by adding metallic holmium and dysprosium oxide to the alloy powder obtained after smelting and crushing the metal raw material, the grain distribution of the NdFeB magnet obtained by subsequent sintering can be uniform, the density is increased, and the stability of the NdFeB magnet is improved.

[0098] S5: Vacuum and static pressure

[0099] The vacuum valve on the forming mold was started to evacuate the forming mold containing the alloy blank, and then the vacuum-evacuated forming mold was placed in a static press, the pressure of the static press was adjusted to 120 MPa, and the pressing was carried out for 2 hours to obtain an alloy green body;

[0100] S6: Vacuum sintering and spraying magnetic conductive paint

[0101] The alloy green body obtained in step S5 is demolded, and then the alloy green body is placed in a graphite box, and then the graphite box containing the alloy green body is placed in a vacuum sintering furnace, the temperature of the vacuum sintering furnace is adjusted to 300°C, and after pre-sintering for 3 hours, the temperature of the vacuum sintering furnace is adjusted to 1000°C, and vacuum sintering is performed for 5 hours to obtain a NdFeB magnet. When the temperature sensor in the vacuum sintering furnace detects that the temperature in the furnace is 20°C, the temperature sensor sends a signal to the controller. After receiving the signal sent by the temperature sensor, the controller controls the transmission component of the vacuum sintering furnace to start, and the NdFeB magnet is sent to the laser texturing machine through the transmission component. Subsequently, the laser texturing machine is started to perform laser texturing on the NdFeB magnet to obtain a texturized magnet. Then, the magnetic conductive coating obtained in step S2 is loaded into a spray gun, and the magnetic conductive coating is evenly sprayed on the surface of the texturized magnet by the spray gun. After the magnetic conductive coating is cured, a high-performance sintered NdFeB magnet is obtained.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A process for preparing high performance sintered NdFeB magnets, characterized in that: The steps include: S1: Modification of epoxy resin by adding silicone The epoxy resin and butyl acetate are stirred and mixed and heated, and then silicone and dibutyltin dilaurate are added to carry out a modification reaction; S2: Adding nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating Triethylamine is added for neutralization reaction, and then a modified epoxy resin is prepared by vacuum distillation. Then, nanocrystalline Ni-Zn ferrite powder, a curing agent, a film-forming aid and a defoaming agent are added to the modified epoxy resin, and a magnetic conductive coating is obtained after shearing and dispersion. S3: Melting metal raw materials and air flow grinding Mixing metal raw materials such as neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum and copper, smelting, coarsely crushing, and then air-milling under the protection of nitrogen to obtain alloy powder; S4: Add metal holmium and press into shape The metal holmium and dysprosium oxide are mixed into the alloy powder, and then added into a forming mold, and oriented by a magnetic field under the protection of nitrogen, and pressed into a mold to obtain an alloy blank; S5: Vacuuming and static pressure Start the vacuum valve on the forming mold to evacuate the forming mold containing the alloy blank, and then put the vacuum-evacuated forming mold into a static press and press for 1-2 hours to obtain an alloy green billet; S6: Vacuum sintering and spraying magnetic conductive paint After demoulding the alloy green body, the NdFeB magnet is prepared by vacuum sintering. After cooling, the textured magnet is obtained by laser texture processing. Then, the magnetic conductive coating is evenly sprayed on the surface of the textured magnet to obtain a high-performance sintered NdFeB magnet.

2. The process for preparing a high performance sintered NdFeB magnet according to claim 1, characterized in that: Step S1 of adding silicone to modify the epoxy resin specifically includes the following steps: S1.1: Add epoxy resin and butyl acetate solvent into the reactor at a material-liquid ratio of 1-2:1 kg / L. After the gravity sensor in the reactor detects the addition of the above two, the gravity sensor sends a signal to the controller; S1.2: After receiving the signal sent by the gravity sensor, the controller controls the agitator and heater in the reactor to turn on, the agitator stirs at a rate of 600-750r / min for 1-2h, and the heater heats at a rate of 5-10℃ / min; S1.3: After the stirring is completed, the controller controls the feed component to start, and the feed component mixes the silicone and the catalyst in a mass ratio of 10-15:1 and adds them to the reactor to perform a modification reaction. At the same time, the feed component sends a signal to the controller; S1.4: After receiving the signal sent by the feeding component, the controller controls the agitator to stir at a rate of 800-1000r / min for 20-30min.

3. The process for preparing a high performance sintered NdFeB magnet according to claim 2, characterized in that: Step S2 of adding nanocrystalline Ni-Zn ferrite powder to prepare magnetic conductive coating specifically comprises the following steps: S2.1: After the stirring is completed, the controller controls the feeder to start, and the feeder adds triethylamine into the reactor to carry out a neutralization reaction. At the same time, the controller controls the stirring rate of the stirrer to 200-300r / min, and continues stirring for 4-5h; S2.2: After the reaction is completed, the controller controls the pressure reducing valve to open, and the pressure reducing valve adjusts the pressure in the reactor to 0.02-0.05MPa. At the same time, the controller controls the heating temperature of the heater to increase to 70-85°C, and the reactor is subjected to reduced pressure distillation to obtain a modified epoxy resin; S2.3: The distilled modified epoxy resin flows into the high shear disperser through the liquid guide tube until the liquid volume sensor in the high shear disperser detects that the volume of the modified epoxy resin in the high shear disperser reaches a preset range, and the liquid volume sensor sends a signal to the controller; S2.4: After the controller receives the signal sent by the liquid volume sensor, it controls the feeding component to feed the nanocrystals. Ni-Zn ferrite powder is added into a high shear disperser; S2.5: The controller then starts the high shear disperser and shears and disperses at 1000-1200 r / min for 0.5-1 h; S2.6: After the shear dispersion is completed, the controller controls the feeding component to add the curing agent, film-forming aid and defoaming agent into the high shear disperser. The controller adjusts the speed of the high shear disperser to 800-1000r / min, and shears and disperses for 2-3h to obtain the magnetic conductive coating.

4. The process for preparing a high performance sintered NdFeB magnet according to claim 1, characterized in that: Step S3 of smelting the metal raw material and grinding it into powder by air flow includes the following steps: S3.1: Mix metal raw materials such as neodymium-praseodymium alloy, boron, iron, dysprosium, aluminum and copper according to mass ratio through a batching machine, and then put them into a vacuum induction furnace for smelting to obtain an alloy ingot; S3.3: adding the alloy ingot to a crusher for coarse crushing to obtain alloy scraps; S3.4: nitrogen is introduced into the airflow mill until the first nitrogen detector in the airflow mill detects that the nitrogen concentration in the airflow mill is 95-99%, and the first nitrogen detector sends a signal to the controller; S3.5: After receiving the signal sent by the first nitrogen detector, the controller controls the discharge valve of the crusher to open, and puts the alloy scraps into the airflow mill. After the gravity sensor in the airflow mill detects the addition of the alloy scraps, it sends a signal to the controller; S3.6: After receiving the signal sent by the gravity sensor, the controller controls the airflow mill to operate for 45-55 minutes to perform airflow milling to obtain alloy powder.

5. The process for preparing a high performance sintered NdFeB magnet according to claim 4, characterized in that: Step S4 of adding metal holmium and the like and pressing into shape specifically comprises the following steps: S4.1: After the airflow grinding is completed, the controller controls the airflow grinding mill to stop operating, and at the same time controls the hopper to add metal holmium and dysprosium oxide into the airflow grinding mill at a mass ratio of 2-3:1, and stirs them through the stirrer mixing to obtain mixed powder; S4.2: nitrogen is introduced into the molding press until the second nitrogen detector in the molding press detects that the nitrogen concentration in the molding press is 90-99%, and the second nitrogen detector sends a signal to the controller; S4.3: After receiving the signal sent by the second nitrogen detector, the controller controls the airflow mill to open the discharge valve and add the mixed powder into the pressing mold; S4.4: Place the pressing die containing the mixed powder into a forming press, apply a magnetic field to orient the alloy powder in the forming die, and start the forming press to press the alloy powder into a shape to obtain an alloy blank.

6. The process for preparing a high performance sintered NdFeB magnet according to claim 3, characterized in that: The vacuum sintering and spraying of magnetic conductive coating in step S6 specifically includes the following steps: S6.1: demolding the alloy green body obtained in step S5, placing the alloy green body into a graphite box, and then placing the graphite box containing the alloy green body into a vacuum sintering furnace, adjusting the temperature of the vacuum sintering furnace to 300-500° C., and pre-sintering for 2-3 hours; S6.2: adjusting the temperature of the vacuum sintering furnace to 1000-1200°C, vacuum sintering for 4-5 hours, and obtaining a NdFeB magnet; S6.3: When the temperature sensor in the vacuum sintering furnace detects that the temperature in the furnace is 20-30°C, the temperature sensor sends a signal to the controller; S6.4: After receiving the signal sent by the temperature sensor, the controller controls the conveying component of the vacuum sintering furnace to start, and conveys the NdFeB magnet into the laser texturing machine through the conveying component; S6.5: Then, the laser texturing machine is started to perform laser texturing on the NdFeB magnet to obtain a texturized magnet; S6.6: The magnetic conductive coating obtained in step S2.6 is loaded into a paint spray gun, and the magnetic conductive coating is evenly sprayed on the surface of the roughened magnet through the paint spray gun. After the magnetic conductive coating is solidified, a high-performance sintered NdFeB magnet is obtained.

7. The process for preparing a high performance sintered NdFeB magnet according to claim 5, characterized in that: After the air flow mill obtains the alloy powder, the nitrogen in the air flow mill is extracted through a vacuum pump, and the nitrogen is then introduced into the forming press to discharge the air in the forming press for compression molding. After the compression molding is completed, the nitrogen in the forming press is extracted through a vacuum pump and introduced into the air flow mill again to discharge the air in the air flow mill, and the cycle is continued.

8. The process for preparing a high performance sintered NdFeB magnet according to claim 2, characterized in that: The organosilicon is dimethyldichlorosilane and the catalyst is dibutyltin dilaurate.

9. The process for preparing a high performance sintered NdFeB magnet according to claim 1, characterized in that: The pressure of the static press is 120-180MPa.

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