A method for additive manufacturing of sintered neodymium-iron-boron

Abstract

The present application relates to a kind of sintered neodymium iron boron additive preparation methods, comprising the following steps: configuration slurry;Filament;Model slice;Printing;Degreasing;Sintering;Magnetization.The present application can simultaneously adapt granular material printer and wire printer, and universality is strong.The present application produces sintered neodymium iron boron by 3D printing mode, solves the problem that sintered neodymium iron boron is too fragile and thus difficult to carry out complex secondary processing to shape.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing of magnetic printing, specifically relating to a method for sintering NdFeB additive manufacturing. Background Technology

[0002] Additive manufacturing (also known as 3D printing) is an emerging manufacturing technology that uses digital models as a basis to build up materials layer by layer to create physical objects. It will have a profound impact on traditional processes, production lines, factory models, and supply chain combinations, and is a representative disruptive technology in the manufacturing industry. Additive manufacturing can produce magnets that are superior to those made by traditional methods in terms of mechanical properties, microstructure, and magnetic properties.

[0003] Neodymium magnets, also known as NdFeB magnets, are tetragonal crystals composed of neodymium, iron, and boron (Nd₂Fe₁₄B). These magnets are the second strongest permanent magnets known to date, after holmium magnets at absolute zero, and are the most commonly used rare-earth magnets. Neodymium magnets are widely used in electronic products such as hard drives, mobile phones, headphones, and battery-powered tools.

[0004] Neodymium iron boron (NdFeB) magnets are classified into two types: sintered NdFeB and bonded NdFeB. Bonded NdFeB exhibits magnetism in all directions and is corrosion-resistant; while sintered NdFeB is prone to corrosion and requires surface plating, typically zinc, nickel, environmentally friendly zinc, environmentally friendly nickel, nickel-copper-nickel, or environmentally friendly nickel-copper-nickel plating. Sintered NdFeB permanent magnets possess excellent magnetic properties and are widely used in electronics, power machinery, medical devices, toys, packaging, hardware machinery, aerospace, and other fields. Common applications include permanent magnet motors, loudspeakers, magnetic separators, computer disk drives, and magnetic resonance imaging equipment. While additive manufacturing technology for bonded NdFeB has made some progress, how to use additive manufacturing techniques to produce sintered NdFeB remains a challenge. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for preparing sintered NdFeB additive manufacturing.

[0006] This invention is achieved through the following technical solution: This invention provides a method for preparing sintered NdFeB additive manufacturing, comprising the following steps:

[0007] 1) Preparation of slurry: The demagnetized sintered NdFeB powder is modified, mixed with the base material and thickener is added to obtain the slurry;

[0008] 2) Fiber production: The prepared slurry is fed into an extruder to be made into wire;

[0009] 3) Model slicing: The printing model is sliced ​​using slicing software, and the resulting gcode file is then imported into the magnetic printing control system for processing.

[0010] 4) Printing: Printing is performed using an additive manufacturing magnetic printing device;

[0011] 5) Degreasing: Degrease the printed model from step 4);

[0012] 6) Sintering: Place the degreased model from step 5) into a sintering furnace for controlled shaping and sintering;

[0013] 7) Magnetization: The sintered neodymium iron boron is magnetized.

[0014] Preferably, in step 1), the base material is a paraffin system and / or a water-based system.

[0015] Preferably, in step 1), the denaturation includes cleaning, mixing with a coupling agent, heating, washing, drying, pulverizing, and sieving;

[0016] Preferably, in step 1), the base material is a paraffin system consisting of 70%-90% paraffin wax and 10-30% PP by volume; or a paraffin system consisting of 80% paraffin wax and 20% PP by volume.

[0017] Preferably, in step 1), the base material is a water-based polyethylene glycol system;

[0018] Preferably, in step 1), the base material is an aqueous system of methylcellulose aqueous solution;

[0019] Preferably, in step 1), the base material is PLA or PETG thermoplastic plastic;

[0020] Preferably, in step 1), the mass fraction of the thickener is 0.5-20% of the total mass;

[0021] Preferably, in step 1), the thickener is selected from one or more of carbomer 940, carbomer 950, methylcellulose, and polyamide wax.

[0022] Preferably, the cleaning temperature is room temperature;

[0023] Preferably, the coupling agent is a silane with a mass fraction of 1-10%;

[0024] Preferably, when mixing with the coupling agent, the mass ratio of the added alcohol to the demagnetized sintered NdFeB powder is 2:3-4:1.

[0025] Preferably, the heating temperature is 40-75°C;

[0026] Preferably, the heating time is 1-4 hours;

[0027] Preferably, the washing agent is 99% alcohol;

[0028] Preferably, the pulverizing equipment is a ball mill.

[0029] Preferably, step 2) further includes adding no more than 50% of the total mass of a polymer material such as PLA to the prepared slurry for blending;

[0030] Preferably, in step 2), the wire diameter is 1.75-3.75mm.

[0031] Preferably, in step 5), when the base material is a paraffin system, the degreasing solution is petroleum ether and ethanol;

[0032] Preferably, in step 2), when the base material is a water-based system, the degreasing is performed by heating to boiling.

[0033] Preferably, when the base material is PLA or PETG, the degreasing solution is ethanol and / or chloroform;

[0034] Preferably, the volume ratio of petroleum ether to ethanol is 1:1.

[0035] Preferably, the degreasing solution is added, heated to 75°C, and soaked for 4-6 hours;

[0036] Preferably, the degreasing solution is added and the soaking is carried out at room temperature for 18-36 hours;

[0037] Preferably, the heating time is 2-4 hours;

[0038] Preferably, it also includes the addition of antioxidants;

[0039] Preferably, the degreasing solution is added, heated to 75°C, and soaked for 6-12 hours;

[0040] Preferably, the antioxidant is one of at least hydroxyphenols, naphthols, and benzenesulfinic acid;

[0041] Preferably, the printed model is heated in a water bath and boiled for about 2-4 hours;

[0042] Preferably, it also includes the addition of an FeCl3 catalyst.

[0043] Preferably, the sintering includes high-temperature sintering, gas ventilation, and vacuuming processes.

[0044] Preferably, the heating includes a first high-temperature sintering, a second high-temperature sintering, and a third high-temperature sintering. The first high-temperature sintering temperature is 1060-1120℃, the second high-temperature sintering temperature is 780-820℃, and the second high-temperature sintering time is 2-4 hours. The third high-temperature sintering temperature is 280-320℃, and the third sintering time is 2-4 hours. The gas supply is first hydrogen gas, then argon gas.

[0045] As described above, the sintered NdFeB additive manufacturing method provided by the present invention has the following beneficial effects:

[0046] 1) This invention can be adapted to both granule printers and filament printers, making it highly versatile.

[0047] 2) This invention produces sintered NdFeB using 3D printing, which solves the problem that sintered NdFeB is too brittle and therefore requires complex secondary processing to shape. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the preparation method of the present invention.

[0049] Figure 2 This is a hysteresis loop diagram of Embodiment 1 of the present invention. Detailed Implementation

[0050] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0051] A method for preparing sintered NdFeB additive manufacturing includes the following steps:

[0052] 1) Preparation of slurry: The demagnetized sintered NdFeB powder is modified, mixed with the base material and thickener is added to obtain the slurry;

[0053] 2) Fiber production: The prepared slurry is fed into an extruder to be made into wire;

[0054] 3) Model slicing: The printing model is sliced ​​using slicing software, and the resulting gcode file is then imported into the magnetic printing control system for processing.

[0055] 4) Printing: Printing is performed using an additive manufacturing magnetic printing device;

[0056] 5) Degreasing: Degrease the printed model from step 4);

[0057] 6) Sintering: Place the degreased model from step 5) into a sintering furnace for controlled shaping and sintering;

[0058] 7) Magnetization: The sintered neodymium iron boron is magnetized.

[0059] During the printing process, the base material softens and becomes highly fluid, allowing printing to proceed and enabling the NdFeB particles to rotate within it. These NdFeB particles possess a microstructure called magnetic domains, giving them an easily magnetized direction and a difficult-to-magnetize direction. When an electric current is applied to generate a magnetic field, the easily magnetized direction is first magnetized and aligned with the magnetic field direction. Then, due to the reduced rheological properties of the cooled base material, it is fixed in that direction. At this point, the easily magnetized direction of the NdFeB particles can be controlled by rotating the direction of the applied magnetic field, thus forming a specific magnetic domain orientation.

[0060] A gcode file is an intermediate format file that a 3D model must be processed by a slicer before it can be printed by a 3D printer. Each line of this intermediate file contains commands that the 3D printer's firmware can understand. These commands, also known as gcode commands, are the most important command interface between the 3D printer and the computer.

[0061] In the degreasing process, the main task is to remove most of the organic matter in the materials. The organic matter is the base material and thickener added when preparing the slurry. In order to generate the necessary air gap before the sintering process without affecting the sintering process, this part of the organic components of non-NdFeB particles must be removed before sintering. This step must correspond to the base material system used to prepare the slurry.

[0062] The reason for this magnetization is that all magnetic materials have a magnetization curve. In order to achieve their maximum remanence, they need to be magnetized using a magnetizing clamp or magnetizer before leaving the factory to reach their saturation magnetization intensity, and then reach their maximum remanence after the magnetic field is removed.

[0063] In a preferred embodiment, step 1) includes the denaturation process, which includes cleaning, mixing with a coupling agent, heating, washing, drying, pulverizing, and sieving.

[0064] In a preferred embodiment, the heating temperature is 40-75°C;

[0065] In a preferred embodiment, the heating time is 1-4 hours;

[0066] In a preferred embodiment, the washing agent is 99%-99.8% alcohol;

[0067] In a preferred embodiment, the pulverizing device is a ball mill.

[0068] Specifically, the denaturation process involves cleaning the demagnetized sintered NdFeB powder at room temperature, mixing it with 1%-10% silane coupling agent by mass, adding alcohol at a mass ratio of 2:3-4:1 to the material, heating to 40-75°C and holding for 1-4 hours, then washing with alcohol of 99% or higher, drying, pulverizing with a ball mill, and sieving to complete the denaturation.

[0069] In a preferred embodiment, in step 1), the base material is a paraffin-based system and / or a water-based system.

[0070] In a preferred embodiment, in step 1), the base material is a paraffin system consisting of 80% paraffin wax and 20% PP by volume.

[0071] Polypropylene (PP) is a colorless, odorless, non-toxic, and translucent solid. It is a high-performance thermoplastic synthetic resin, a colorless, translucent, lightweight, general-purpose plastic. It possesses chemical resistance, heat resistance, electrical insulation, high mechanical strength, and good abrasion resistance during processing. PP degrades very slowly, making it a relatively user-friendly material during processing.

[0072] In a preferred embodiment, in step 1), the base material is a water-based polyethylene glycol system;

[0073] In a preferred embodiment, in step 1), the base material is an aqueous system of methylcellulose aqueous solution;

[0074] In a preferred embodiment, in step 1), the base material is PLA or PETG thermoplastic.

[0075] PLA is an abbreviation for polylactic acid, a thermoplastic polymer derived from renewable resources, more specifically from corn starch or sugarcane. PLA plastics are known as bio-based polymers. PLA is widely used in small-scale 3D printing. The material is processed very well in most cases.

[0076] PET resin is a linear homopolymer polyester formed by the condensation polymerization of diol (ethylene glycol, EG) and diacid (terephthalic acid, TPA). Copolyesters are polyesters modified with alcohols or acids, including PETG, PCTG, PCTA, and biodegradable copolyesters. PETG is a non-crystalline copolyester. During its production process, a certain amount of ethylene glycol is replaced by 1,4-cyclohexanedimethanol (CHDM), which prevents crystallization and improves processing and transparency. Its products are highly transparent, have excellent impact resistance, and are particularly suitable for molding thick-walled transparent products. Its processing and molding performance is excellent, allowing for arbitrary shapes to be designed according to the designer's intentions. It can be formed using traditional extrusion, injection molding, blow molding, and vacuum forming methods. It can be widely used in the markets for sheets, high-performance shrink films, bottles, and profiles. Furthermore, it has excellent secondary processing performance and can be subjected to conventional machining and finishing. PETG is an amorphous PET grade, generally suitable for 3D printing.

[0077] In a preferred embodiment, in step 1), the mass fraction of the thickener is 0.5-20% of the total mass;

[0078] In a preferred embodiment, in step 1), the thickener is selected from one or more of carbomer 940, carbomer 950, methylcellulose, and polyamide wax. Adding a thickener ensures the rheological shear properties of the particles during the printing process, maintaining a viscosity of 10-10000 Pas at approximately 200-220 degrees Celsius, thus making it as shear-thinned a non-Newtonian fluid as possible.

[0079] In a preferred embodiment, step 2) further includes adding no more than 50% of polymer materials such as PLA to the prepared slurry for blending, taking into account the difficulty of later material preparation.

[0080] In a preferred embodiment, in step 2), the wire diameter is 1.75-3.75 mm, and the wire color is usually gray-black due to the addition of neodymium iron boron particles.

[0081] In a preferred embodiment, in step 5), when the base material is a paraffin system, the degreasing solution is petroleum ether and ethanol;

[0082] In a preferred embodiment, in step 2), when the base material is a water-based system, the degreasing is performed by heating to boiling.

[0083] In a preferred embodiment, when the base material is PLA or PETG, the degreasing solution is ethanol and / or chloroform;

[0084] In a preferred embodiment, the volume ratio of petroleum ether to ethanol is 1:1;

[0085] In a preferred embodiment, the degreasing solution is added, the mixture is heated to 75°C, and soaked for 4-6 hours.

[0086] In a preferred embodiment, the degreasing solution is added, and the soaking is carried out at room temperature for 18-36 hours;

[0087] In a preferred embodiment, the heating time is 2-4 hours;

[0088] In a preferred embodiment, an antioxidant is also included;

[0089] In a preferred embodiment, the defatting solution is added, heated to 75°C, and soaked for 6-12 hours;

[0090] In a preferred embodiment, the antioxidant is at least one of hydroxyphenols, naphthols, and benzenesulfinic acid;

[0091] In a preferred embodiment, the printed model is heated in a water bath and boiled for about 2-4 hours;

[0092] In a preferred embodiment, the addition of a FeCl3 catalyst is also included.

[0093] Specifically, the degreasing process corresponds to the base material system in the slurry preparation process. If using a paraffin system of 80% paraffin and 20% PP, the printed sample obtained in step 4) should first be soaked in a solution of petroleum ether and ethanol in approximately a 1:1 ratio, heated to about 75°C, and maintained for about 4-6 hours. If no heating is applied, it should be soaked for about 18 hours in a laboratory environment at about 20°C. After soaking, it should be placed in a degreasing furnace and heated at 170-240°C for about 3 hours (a second heating and holding can be performed, but the efficiency will differ). If using a water-based system, it can be directly heated to boiling in a water bath for about 2 hours. However, considering the ease of oxidation, approximately 10% of antioxidants such as hydroxyphenols, naphthols, and benzenesulfinates are generally added. If using PLA or PETG, it should first be soaked in ethanol or chloroform, heated to 75°C, and maintained for six hours. Considering environmental factors, ethanol is used for indoor preparation, and approximately 1% of FeCl3 is generally added as a catalyst, which can remove 95% of the organic components, with the remaining 5% being removed during sintering.

[0094] In a preferred embodiment, the sintering includes high-temperature sintering, gas ventilation, and vacuuming processes. These processes are to ensure the density of the magnetic material and the formation of the magnetic structure.

[0095] In a preferred embodiment, the high-temperature sintering includes a first high-temperature sintering, a second high-temperature sintering, and a third high-temperature sintering. The first high-temperature sintering temperature is 1060-1120℃, the second high-temperature sintering temperature is 780-820℃, the second high-temperature sintering time is 2-4 hours, the third high-temperature sintering temperature is 280-320℃, the third sintering time is 2-4 hours, and the gas supply is first hydrogen gas and then argon gas.

[0096] The magnetization is performed to magnetize the magnetic material.

[0097] Example 1

[0098] The material is sintered NdFeB powder, which is prepared using the additive manufacturing method of sintered NdFeB of the present invention. According to the national standard GB / T13560-2009 for sintered NdFeB permanent magnet materials, the main magnetic properties of the product, including remanence (Br) and intrinsic coercivity (Hcj), are measured.

[0099] The measurement was performed using a standard Helmholtz coil with h = R = 0.5m. The two stages of the Helmholtz coil were connected to an active oscilloscope, and then...

[0100]

[0101] The change in current in an oscilloscope can be converted into a change in magnetic field. This allows for the indirect measurement of the hysteresis loop of sintered NdFeB products, ultimately leading to the determination of the product's remanence and intrinsic coercivity. The specific measurement steps are as follows:

[0102] 1) Connect the two ends of a standard Helmholtz coil to an oscilloscope.

[0103] 2) Zero the oscilloscope, ensuring the Helmholtz coil is in the correct position before zeroing. This process minimizes interference from the Earth's magnetic field on the Helmholtz coil itself.

[0104] 3) Use a fixture to place the printed product, i.e., the 1cm*1cm*1cm sintered NdFeB cube, at the midpoint of the central axis of the two circular coils. This is because this is where the magnetic field non-uniformity generated by the Helmholtz coil is minimized, which can ensure that the measured product is as consistent as possible with the theory. However, due to the existence of the non-zero differential term of the fourth derivative of B with respect to z, the measurement should still have at least 7% systematic error, and this error cannot be eliminated.

[0105] 4) Set the oscilloscope to 24V and gradually increase the applied current, from 0V to 2500mA. This process should be as slow as possible to reduce the potential impact of Helmholtz resonance on the measurement.

[0106] 5) Input R = 0.5m into the oscilloscope, and the current will be directly converted into a magnetic field in the oscilloscope's built-in parameters for display.

[0107] 6) The obtained hysteresis loop is as follows Figure 2 As shown.

[0108] from Figure 2 It can be concluded that the remanence Br of the printed product is 1.21T and the intrinsic coercivity Hcj is 2.57T, both of which are greatly improved compared with the built-in parameters.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing sintered NdFeB additive manufacturing, characterized in that, Includes the following steps: 1) Preparation of slurry: The demagnetized sintered NdFeB powder is modified, mixed with the base material, and a thickener is added to obtain a slurry; wherein, the modification includes washing, mixing with a coupling agent, heating, washing, drying, pulverizing, and sieving; the coupling agent is silane with a mass fraction of 1-10%; the thickener has a mass fraction of 0.5-20% of the total mass; the thickener is selected from one or more of carbomer 940, carbomer 950, methylcellulose, and polyamide wax; 2) Fiber production: The slurry is fed into an extruder to be made into wire; 3) Model slicing: The printing model is sliced ​​using slicing software, and the resulting gcode file is then imported into the magnetic printing control system for processing; 4) Printing: Printing is performed using an additive manufacturing magnetic printing device; 5) Degreasing: Degrease the printed model from step 4); 6) Sintering: Place the degreased model from step 5) into a sintering furnace for controlled molding and sintering; the sintering includes high-temperature sintering, gas ventilation, and vacuuming processes; the high-temperature sintering includes a first high-temperature sintering, a second high-temperature sintering, and a third high-temperature sintering, the first high-temperature sintering temperature is 1060-1120℃, the second high-temperature sintering temperature is 780-820℃, the second high-temperature sintering time is 2-4h, the third high-temperature sintering temperature is 280-320℃, the third high-temperature sintering time is 2-4h, and the gas ventilation is performed by first introducing hydrogen gas and then argon gas; 7) Magnetization: Magnetize the sintered neodymium iron boron.

2. The method for preparing sintered NdFeB additive manufacturing as described in claim 1, characterized in that, Step 1) includes any of the following technical features: A2) The base material is a paraffin system consisting of 70%-90% paraffin wax and 10-30% PP by volume; A3) The base material described is a water-based polyethylene glycol system; A4) The base material is an aqueous system of methylcellulose aqueous solution; A5) The base material is PLA or PETG thermoplastic.

3. The method for preparing sintered NdFeB additive manufacturing as described in claim 2, characterized in that, In A2), the base material is a paraffin system consisting of 80% paraffin wax and 20% PP by volume.

4. The method for preparing sintered NdFeB additive manufacturing as described in claim 1, characterized in that, Includes at least one of the following technical features: A11) The cleaning temperature is room temperature; A13) When mixing with the coupling agent, the mass ratio of alcohol to demagnetized sintered NdFeB powder is 2:3-4:

1. A14) The heating temperature is 40-75℃; A15) The heating time is 1-4 hours; A16) The washing reagent is 99%-99.8% alcohol; The crushing equipment mentioned in A17 is a ball mill.

5. The method for preparing sintered NdFeB additive manufacturing as described in claim 1, characterized in that, In step 2), B1) also includes blending no more than 50% by total mass of PLA polymer material into the prepared slurry; B2) The wire diameter is 1.75-3.75mm.

6. The method for preparing sintered NdFeB additive manufacturing as described in claim 2, characterized in that, In step 5), any of the following technical features are included: C1) When the base material is a paraffin system, the degreasing solution is petroleum ether and ethanol; C2) When the base material is a water-based system, the degreasing is performed by heating to boiling; C3) When the base material is PLA or PETG, the degreasing solution is ethanol and / or chloroform.

7. The method for preparing sintered NdFeB additive manufacturing as described in claim 6, characterized in that, Includes one or more of the following technical features, In C1), the volume ratio of petroleum ether to ethanol is 0.5:1 to 2:1; C12) In C1), add defatting solution, heat to 75℃ and soak for 4-6 hours; C13) Add defatting solution to C1) and soak at room temperature for 18-36 hours; In C2), the heating time is 2-4 hours; C22) In C2), antioxidants are also added; In C3), add a degreasing solution, heat to 75°C and soak for 6-24 hours.

8. The method for preparing sintered NdFeB additive manufacturing as described in claim 7, characterized in that, In C1), the volume ratio of petroleum ether to ethanol is 1:

1.

9. The method for preparing sintered NdFeB additive manufacturing as described in claim 7, characterized in that, Includes any of the following technical features: In C321, the antioxidant is one of at least hydroxyphenols, naphthols, and benzenesulfinic acid; Heat the printed model in a water bath and boil for 2-24 hours; In C31), the addition of FeCl3 catalyst is also included.

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