Device and process for preparing rare earth metal hydride powder

Abstract

The present invention discloses a preparation device and process for rare earth metal hydride powder. The preparation device includes a main reaction chamber, a vacuum system, and a stainless-steel material tank. In its preparation process, the reaction device is automatically leak-tested. First, an inert gas argon is filled, and then hydrogen is filled to ensure the safety and controllability of the reaction. After the hydrogen absorption reaction is completed, dehydrogenation is not carried out. Argon is filled again, and water cooling and air cooling are turned on. After cooling, the vacuum is first pumped, and then the bucket containing the crude rare earth metal hydride powder is taken out. Absolute ethanol is pressed into the bucket and stirred and mixed. Then, it is ball-milled to form spherical particle powder with a size of 0.5-1 μm. Then, the wet rare earth metal hydride powder is put into the material tank and stored by filling an inert gas. The preparation device and process for rare earth metal hydride powder of the present invention ensure that the powder is not in contact with air throughout the process, and fully consider the operation and storage safety during the preparation process.

Description

Technical Field

[0001] The present invention relates to a preparation device and process for rare earth metal hydride powder, and is particularly applicable to the preparation of rare earth hydride powders such as dysprosium hydride and terbium hydride for grain boundary penetration or double alloy secondary phases of sintered neodymium iron boron magnets. Background Art

[0002] With the increasingly mature application of the sintered neodymium iron boron grain boundary penetration process, it has been found that the effect of coating with dysprosium hydride or terbium hydride is better than using dysprosium oxide or terbium oxide, dysprosium fluoride or terbium fluoride; and it has also been found that in the traditional double alloy process, adding dysprosium hydride or terbium hydride as the secondary phase can also significantly improve Hcj, and the consumption of heavy rare earths decreases significantly compared to adding during melting. With the application of the grain boundary penetration or double alloy process, the demand for rare earth metal hydrides by enterprises has increased. Currently, the demand for rare earth metal hydrides by sintered neodymium iron boron enterprises is mostly achieved through procurement. Since rare earth hydrides need to be hydrogenated, the production, transportation, and safety costs are high, resulting in high procurement costs for enterprises on the one hand. On the other hand, the particle size of the purchased rare earth metal hydride powder is not completely suitable for direct production, and the rare earth metal hydride powder is flammable, posing safety hazards during transportation and storage. Therefore, self-producing the required rare earth metal hydrides has become the most economical option for enterprises. However, the existing equipment for producing rare earth metal hydride powder is large in volume and relatively expensive, making it unlikely to be used as self-produced equipment. Therefore, it is very necessary to design a preparation device and process for rare earth metal hydride powder with low cost and easy implementation. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the purpose of the design of the present invention is to provide a preparation device and process for rare earth metal hydride powder.

[0004] The present invention is achieved through the following technical solutions:

[0005] The described preparation device for rare earth metal hydride powder is characterized in that the preparation device includes two symmetrically arranged triangular brackets, a main reaction chamber arranged between the two brackets, a flipping mechanism, a stainless steel material tank, and a vacuum system. One end of the main reaction chamber is closed, and the other end is provided with an opening. The stainless steel material tank is connected with a first butterfly valve through a self-locking nut, and the flange at the opening end of the main reaction chamber is connected with a second butterfly valve through a self-locking nut. The pipeline flange port in the middle of the main reaction chamber is connected with a third butterfly valve through a nut. The third butterfly valve and the vacuum system, as well as between the first butterfly valve and the second butterfly valve, are all connected through quick connectors. A hydrogen pipeline interface and an argon pipeline interface are installed on the main reaction chamber.

[0006] The described preparation device for rare earth metal hydride powder is characterized in that the flipping mechanism includes a motor and a rotating shaft. One end of the rotating shaft is fixedly connected with the main reaction chamber, and the other end of the rotating shaft is connected with the output shaft of the motor.

[0007] The described preparation device for rare earth metal hydride powder is characterized in that the vacuum system comprises a vacuum pipeline, a vacuum pump, a vacuum valve and a pressure gauge. The pressure gauge is installed on the main reaction chamber, and a vacuum gauge is installed on the vacuum pipeline.

[0008] The described preparation device for rare earth metal hydride powder is characterized in that the main reaction chamber is provided with a water-cooled interlayer, and water-cooled copper pipes are coiled around the connection positions of the first butterfly valve, the second butterfly valve and the third butterfly valve.

[0009] A process for preparing rare earth metal hydride powder by using the preparation device for rare earth metal hydride powder comprises the following steps:

[0010] 1) Cut the rare earth material into small pieces and put them into the main reaction chamber. The turning mechanism rotates the main reaction chamber to the horizontal position, i.e., the position during the hydrogenation reaction.

[0011] 2) Connect and lock the first butterfly valve and the stainless steel material tank with a self-locking nut, connect and lock the flange at the open end of the main reaction chamber and the second butterfly valve with a self-locking nut. Then place a gasket between the first butterfly valve and the second butterfly valve. After the gasket is placed, clamp and lock it with a quick connector; Connect and lock the pipeline flange opening in the middle of the main reaction chamber and the third butterfly valve with a nut. Place a gasket between the third butterfly valve and the vacuum pipeline flange, and clamp and lock it with a quick connector. After installation, open the first butterfly valve, the second butterfly valve and the third butterfly valve.

[0012] 3) Fill with 0.5 MPa of argon gas to conduct a positive pressure leak rate detection on the reaction device, and require that the pressure drop does not exceed 1 Pa within 10 minutes.

[0013] 4) After the positive pressure leak rate detection is completed, start the vacuum pump and the vacuum valve to start pumping vacuum.

[0014] 5) When the vacuum is lower than 0.1 Pa, close the vacuum valve to conduct a negative pressure leak rate detection, and require that the pressure does not rise beyond 0.2 Pa after 10 minutes.

[0015] 6) After the leak rate detection is completed, open the vacuum valve and continue to pump vacuum to 0.1 Pa.

[0016] 7) Close the vacuum valve, fill with 30 - 50 Kpa of argon gas, close the first butterfly valve, the second butterfly valve and the third butterfly valve, and then introduce hydrogen gas to 150 - 300 KPa.

[0017] 8) The rare earth metal starts to absorb hydrogen. During this process, the pressure in the furnace is lower than 100 Kpa, and hydrogen gas is replenished.

[0018] 9) After filling with hydrogen gas for 1 - 3 hours, stop replenishing hydrogen gas.

[0019] 10) After 1 hour of hydrogen absorption delay, argon is filled to 0.2 - 0.5 MPa, and the circulating water in the reaction chamber sandwich is turned on for cooling. At the same time, a fan can be used to assist in accelerating air cooling to speed up the cooling rate;

[0020] 12) After 5 - 12 hours of cooling, the first butterfly valve, the second butterfly valve, and the third butterfly valve are opened, and the vacuum pump is turned on to pump out the remaining mixed gas in the main reaction chamber. Then, the vacuum pump, the vacuum valve, and the third butterfly valve are closed, the quick - fitting joint between the third butterfly valve and the vacuum pipeline is loosened, the turning mechanism rotates the main reaction chamber to the vertical state, which is the discharging position, and the prepared crude rare - earth metal hydride powder is poured into the stainless - steel feed tank. The first butterfly valve is closed, the quick - fitting joint between the first butterfly valve and the second butterfly valve is loosened, the cooling water of the water - cooled copper pipe at the stainless - steel feed tank opening is turned off, and the stainless - steel feed tank is removed;

[0021] 13) An inert gas is used to press anhydrous ethanol into the stainless - steel feed tank. After stirring and mixing for 0.5 - 2 hours, the stainless - steel feed tank is connected to the ball mill, and the crude powder is added to the ball mill. The crude rare - earth metal hydride powder is ground into wet powder of spherical particles with a size of 0.5 - 1 μm by ball milling. The powder is put into the stainless - steel feed tank and stored by filling with an inert gas. Preferably, the crude rare - earth metal hydride powder is added to the ball mill, and then anhydrous ethanol is isobarically pressed into the ball mill with an inert gas, and the pressure is controlled at 0.2 - 0.5 Mpa. The ball - milling equipment is started, and the ball - milling time is set according to the required particle size. Particle - size detection can be carried out by sampling. Preferably, after ball milling, 1 - 5 ml / kg of anhydrous ethanol is pressed into the ball mill again with an inert gas, and then filled with an inert gas to 0.5 MPa, and then the pressure is released to 0.1 MPa. After repeated cleaning for many times, the rare - earth metal hydride powder mixed with anhydrous ethanol is taken out.

[0022] The process for preparing rare - earth metal hydride powder described above is characterized in that the rare - earth purity is 99.5 - 99.9%.

[0023] The main reaction chamber of the present invention is made of stainless steel with a water - cooled sandwich layer. When the hydrogen absorption reaction ends, circulating water can be passed through for water cooling. Preferably, it is stainless steel SUS316, the stainless - steel thickness is 8 mm, and it is welded by argon arc welding. Preferably, for the water - cooled sandwich layer, the water flow rate is not less than 1 L / s. The pipeline at the connection with the butterfly valve and the vacuum valve is coiled with copper pipe and cooled by passing cooling water to prevent seal failure caused by heat conduction during the reaction. Preferably, the water flow rate of the coiled copper pipe is not less than 0.5 L / s.

[0024] The pipeline flange opening in the middle of the main reaction chamber is connected and locked with the third butterfly valve using nuts. A gasket is placed between the third butterfly valve and the vacuum pipeline flange, and a quick connector is used to clamp and lock it. After the reaction is completed, the quick connector between the main reaction chamber and the vacuum pipeline can be disconnected, and then the main reaction chamber rotation mechanism is used to flip the reaction chamber to facilitate pouring the coarse powder into the stainless steel feed tank. Preferably, the vacuum pump uses the PKS030 model, and the entire vacuum system is connected to the PLC and automatically controlled by the PLC, effectively improving the operation accuracy and realizing program interlock to prevent entering the next step under non-conforming conditions, resulting in potential safety hazards.

[0025] A gasket is added between the first butterfly valve and the second butterfly valve, and a quick connector is used to clamp and lock it. After the reaction is completed, the first butterfly valve and the second butterfly valve are opened, the main reaction chamber is rotated to the discharging position, the coarse powder is poured into the stainless steel feed tank, the first butterfly valve is closed, and then the quick connector between the first butterfly valve and the second butterfly valve is disconnected, and the stainless steel feed tank with the poured coarse powder is removed. Preferably, the butterfly valve seal uses polytetrafluoroethylene or fluororubber to prevent seal aging due to long-term contact with hydrogen.

[0026] The utility model conducts positive pressure detection of 0.5 MPa and negative pressure detection of 0.1 Pa on the reaction device to ensure that there is no positive or negative pressure leakage in the reaction device and ensure the safety of the hydrogen absorption reaction. Preferably, the reaction device is leak-tested using a helium leak detector before the first use or regularly. In the vacuum state, first, an inert gas argon is filled to 30 - 50 KPa, and then hydrogen is filled to 150 - 300 KPa. When the pressure in the furnace is lower than 100 KPa during the process, hydrogen is automatically replenished. By filling argon first and then introducing hydrogen, it can ensure that hydrogen reacts with rare earth metals under safe and controllable conditions. Preferably, 50 KPa of argon is filled first, and then 220 KPa of hydrogen is filled.

[0027] The device of the present invention adopts hydrogen absorption for 1 - 3 hours, and after a 1-hour delay without dehydrogenation, argon is filled to 0.2 - 0.5 MPa, and the cooling water in the main reaction chamber sandwich is directly opened, and the fan can be simultaneously opened to assist in accelerating cooling. Preferably, hydrogen absorption is carried out for 1.5 hours, without dehydrogenation, 0.5 MPa of argon is filled, and the fan is directed at the reaction chamber for auxiliary cooling.

[0028] The device of the present invention has a simple structure, small volume, low assembly cost, is convenient for assembly, and is easy to implement; its preparation process flow is simple, and the powder is not in contact with air throughout the preparation process, improving the safety of operation and storage. Description of the Drawings

[0029] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 is Figure 1 the side view of;

[0031] In the figure, 1 - support, 2 - main reaction chamber, 3 - flipping mechanism, 4 - stainless steel feed tank, 5 - first butterfly valve, 6 - second butterfly valve, 7 - third butterfly valve, 8 - hydrogen pipeline interface, 9 - argon pipeline interface, 10 - motor, 11 - rotating shaft, 12 - vacuum pipeline, 13 - vacuum pump, 14 - vacuum valve, 15 - pressure gauge, 16 - vacuum gauge tube, 17 - water cooling pipe. Specific implementation mode

[0032] The present invention will be further described in detail below with reference to the accompanying drawings of the specification and specific embodiments. The embodiments described below are only a part of the embodiments of the present invention for patents, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments modified or polished by those skilled in the art belong to the scope of protection of the present invention.

[0033] As Figure 1-2 shown, a preparation device for rare earth metal hydride powder includes two symmetrically arranged triangular supports, a main reaction chamber arranged between the two supports, a flipping mechanism for the main reaction chamber, a stainless steel feed tank, and a vacuum system. One end of the main reaction chamber is closed and the other end is provided with an opening. The stainless steel feed tank is connected with a first butterfly valve through a self-locking nut, the flange at the opening end of the main reaction chamber is connected with a second butterfly valve through a self-locking nut, and the pipeline flange at the middle of the main reaction chamber is connected with a third butterfly valve through a nut. The connection between the third butterfly valve and the vacuum system and the connection between the first butterfly valve and the second butterfly valve are both realized through quick connectors. A hydrogen pipeline interface and an argon pipeline interface are installed on the main reaction chamber.

[0034] Among them, the flipping mechanism includes a motor and a rotating shaft. One end of the rotating shaft is fixedly connected to the main reaction chamber, and the other end of the rotating shaft is connected to the output shaft of the motor. This flipping mechanism is mainly used for the 90-degree flipping of the main reaction chamber. The detailed structure for realizing the flipping is prior art and will not be described in detail. The vacuum system includes a vacuum pipeline, a vacuum pump, a vacuum valve, and a pressure gauge. The pressure gauge is installed on the main reaction chamber, and a vacuum gauge tube is installed on the vacuum pipeline. The main reaction chamber has a water cooling interlayer, and water cooling copper tubes are coiled around the connection positions of the first butterfly valve, the second butterfly valve, and the third butterfly valve for cooling.

[0035] The preparation process of rare earth metal hydride powder using the above device is shown in the following embodiments.

[0036] Example 1

[0037] Cut the metal terbium with a purity of 99.5% into small pieces and place them in the main reaction chamber of the rare earth metal hydride powder preparation device. Rotate the main reaction chamber to the position during the hydrogenation reaction. Connect and lock the first butterfly valve and the stainless steel drum with a self-locking nut. Connect and lock the flange at the open end of the main reaction chamber and the second butterfly valve with a self-locking nut. Place the gasket between the first butterfly valve and the second butterfly valve and lock it with a quick connector. Connect and lock the pipe flange opening in the middle of the main reaction chamber and the third butterfly valve with a nut. Place the gasket between the third butterfly valve and the vacuum pipe flange and lock it with a quick connector.

[0038] Open the first butterfly valve, the second butterfly valve and the third butterfly valve; fill with argon at 0.5 MPa and conduct a positive pressure test on the reaction device. It is required that the pressure drop does not exceed 1 Pa within 10 minutes. After the positive pressure leak rate test is completed, turn on the vacuum pump and the vacuum valve and start pumping vacuum. When the vacuum is lower than 0.1 Pa, close the vacuum valve and conduct a negative pressure leak rate test. It is required that the pressure does not rise by more than 0.2 Pa after 10 minutes.

[0039] After the leak rate test is completed, open the vacuum valve and continue to pump vacuum to 0.1 Pa; close the vacuum valve, fill with argon at 50 Kpa, close the first butterfly valve, the second butterfly valve and the third butterfly valve, and then introduce hydrogen to 220 KPa; the rare earth metal starts to absorb hydrogen. During this process, the pressure in the furnace is lower than 100 Kpa, and hydrogen is replenished; after hydrogen is filled for 3 hours, stop replenishing hydrogen.

[0040] After 1 hour of hydrogen absorption delay, fill with argon to 0.5 MPa, turn on the circulating water in the reaction chamber jacket for cooling. At the same time, a fan can be used to assist in accelerating air cooling to speed up the cooling rate; after 6 hours of cooling, open the first butterfly valve, the second butterfly valve and the third butterfly valve, turn on the vacuum pump, and pump out the remaining mixed gas in the furnace. Then close the vacuum pump, the vacuum valve and the third butterfly valve, loosen the quick connector between the third butterfly valve and the vacuum pipe, rotate the main reaction chamber to the discharging position, pour the prepared crude rare earth metal hydride powder into the stainless steel tank, close the first butterfly valve, loosen the quick connector between the first butterfly valve and the second butterfly valve, close the cooling water of the water-cooled copper pipe at the bucket mouth, and remove the stainless steel drum.

[0041] Press anhydrous ethanol into a stainless-steel drum using an inert gas. After stirring and mixing for 1 hour, connect the stainless-steel drum to a ball mill. Add the coarse powder to the ball mill, and use the ball mill to crush the coarse powder of rare-earth metal hydride into wet powder of spherical particles with a size of 0.5 μm. Put the powder into a stainless-steel storage tank and store it by filling with an inert gas. Preferably, add the coarse powder of rare-earth metal hydride to the ball mill, then press anhydrous ethanol and the like into the ball mill using an inert gas, control the pressure at 0.5 Mpa, start the ball mill equipment, set the ball milling time, which is determined according to the required particle size, and particle size detection can be carried out by sampling. Preferably, after the ball milling is completed, press 3 ml / kg of anhydrous ethanol into the ball mill again using an inert gas, then fill with an inert gas to 0.5 MPa, and then release the pressure to 0.1 MPa. After repeated cleaning for many times, take out the rare-earth metal hydride powder mixed with anhydrous ethanol.

[0042] Further configure and stir the terbium hydride powder into a suspension mixture for dysprosium and terbium infiltration by the coating method. Then spray the suspension mixture on the sintered neodymium iron boron workpiece, followed by curing and baking, and then use a grain boundary infiltration furnace for infiltration and aging. The following is a comparison of the magnetic properties before infiltration and after infiltration by the coating method using terbium hydride prepared by the device and process of the present invention:

[0043]

[0044] Through comparison, it is found that Br only decreases by 190 Gs, while Hcj increases by 668.65 KA / m. We use an ICP plasma mass spectrometer to detect the composition of the sintered neodymium iron boron magnet before and after infiltration. The contents of heavy rare earths dysprosium and terbium in the magnet before infiltration can be basically ignored, and the weight percentage content of terbium after infiltration is only 0.255%. The performance of the sintered neodymium iron boron after infiltration using terbium hydride prepared by the device and process of the present invention has reached 52SH, with obvious cost advantages.

[0045] Example 2

[0046] Cut the metal dysprosium with a purity of 99.5% into small pieces and put them into the main reaction chamber of the rare-earth metal hydride powder preparation device. Rotate the main reaction chamber to the position for the hydrogenation reaction; connect the first butterfly valve and the stainless-steel drum with a self-locking nut and lock them tightly. Connect the flange at the open end of the main reaction chamber and the second butterfly valve with a self-locking nut and lock them tightly. Place the gasket between the first butterfly valve and the second butterfly valve, and use a quick-connect fitting to clamp and lock it; connect the pipe flange opening in the middle of the main reaction chamber and the third butterfly valve with a nut and lock them tightly. Place the gasket between the third butterfly valve and the vacuum pipe flange, and use a quick-connect fitting to clamp and lock it.

[0047] Open the first butterfly valve, the second butterfly valve and the third butterfly valve; fill with argon at 0.5 MPa, and conduct a positive pressure test on the reaction device. It is required that the pressure drop does not exceed 1 Pa within 10 minutes; after the positive pressure leak rate test is completed, turn on the vacuum pump and the vacuum valve, and start pumping vacuum; when the vacuum is lower than 0.1 Pa, close the vacuum valve and conduct a negative pressure leak rate test. It is required that the pressure does not exceed 0.2 Pa after 10 minutes.

[0048] After the leak rate test is completed, open the vacuum valve and continue to pump vacuum to 0.1 Pa; close the vacuum valve, fill with argon at 50 Kpa, close the first butterfly valve, the second butterfly valve and the third butterfly valve, and then introduce hydrogen to 220 KPa; the rare earth metal starts to absorb hydrogen. During this process, the pressure in the furnace is lower than 100 Kpa, and hydrogen is replenished; after filling with hydrogen for 2.5 hours, stop replenishing hydrogen.

[0049] After 1 hour of hydrogen absorption delay, fill with argon to 0.5 MPa, turn on the circulating water in the reaction chamber sandwich for cooling, and at the same time, a fan can be used to assist in accelerating air cooling to speed up the cooling rate; after 6 hours of cooling, open the first butterfly valve, the second butterfly valve and the third butterfly valve, turn on the vacuum pump, and pump out the remaining mixed gas in the furnace. Then close the vacuum pump, the vacuum valve and the third butterfly valve, loosen the quick connection joint between the third butterfly valve and the vacuum pipeline, rotate the main reaction chamber to the discharging position, pour the prepared crude rare earth metal hydride powder into the stainless steel feed tank, close the first butterfly valve, loosen the quick connection joint between the first butterfly valve and the second butterfly valve, close the cooling water of the water-cooled copper pipe at the mouth of the feed barrel, and remove the stainless steel feed barrel.

[0050] Use inert gas to press anhydrous ethanol into the stainless steel feed tank. After stirring and mixing for 2 hours, connect the stainless steel feed tank to the ball mill, add the crude powder to the ball mill, and use ball milling to crush the crude rare earth metal hydride powder into wet powder of spherical particles with a size of 0.5 um. Put the powder into the stainless steel feed tank and store it by filling with inert gas. Preferably, add the crude rare earth metal hydride powder to the ball mill, and then use inert gas to press anhydrous ethanol or the like into the ball mill, and control the pressure at 0.5 Mpa. Start the ball milling equipment and set the ball milling time. The ball milling time is determined according to the required particle size, and particle size detection can be carried out by sampling. Preferably, after the ball milling is completed, press 2 ml / kg of anhydrous ethanol into the ball mill again with inert gas, then fill with inert gas to 0.5 MPa, and then release the pressure to 0.1 MPa. After repeated cleaning for many times, take out the rare earth metal hydride powder mixed with anhydrous ethanol.

[0051] Take the dysprosium hydride powder as the secondary phase and uniformly mix it into the main phase powder with a low total rare earth content at a weight percentage of 0.2 - 1%, and then orient, mold and sinter to prepare a magnet.

[0052] The following is a comparison of the magnetic properties of sintered Nd-Fe-B magnets prepared without adding the secondary phase and with the dysprosium hydride secondary phase prepared by the device and process of the present invention:

[0053]

[0054] Through comparison, it is found that when adding 0.5% of dysprosium hydride prepared by the device and process of the present invention, the Br decreases by only 210 Gs, while the Hcj increases by 349.3 kA / m. Through research and analysis, it is found that when the proportion of the added dysprosium hydride or terbium auxiliary phase is small, the heavy rare earths are mainly distributed at the grain boundaries and the epitaxial layer of the main phase, which is related to the characteristics of the rare earth hydride powder prepared by using the preparation device and process of the present invention. Since the auxiliary phase has a high hydrogen content and a low melting point, it is easy to form liquid-phase sintering, and the heavy rare earth elements Dy / Tb diffuse into the edges of the main-phase grains to form a (Nd, Dy)2Fe14B hard shell phase, increasing the anisotropy of the magnet and greatly improving the intrinsic coercivity of the magnet. When adding 1% of dysprosium hydride, the Hcj still increases but significantly, only slightly higher than that of direct melting in Tianjin, but the Br decreases significantly. We believe through research and analysis that this is mainly caused by too much dysprosium entering the main phase.

[0055] Example 3

[0056] Cut the praseodymium-neodymium metal with a purity of 99% into small pieces and put them into the main reaction chamber of the rare earth hydride metal powder preparation device. Rotate the main reaction chamber to the position during the hydrogenation reaction; connect the first butterfly valve and the stainless steel material barrel with a self-locking nut and lock them tightly. Connect the flange at the open end of the main reaction chamber and the second butterfly valve with a self-locking nut and lock them tightly. Place the gasket between the first butterfly valve and the second butterfly valve and lock it tightly with a quick connector; connect the pipe flange at the middle of the main reaction chamber and the third butterfly valve with a nut and lock them tightly. Place the gasket between the third butterfly valve and the vacuum pipe flange and lock it tightly with a quick connector.

[0057] Open the first butterfly valve, the second butterfly valve and the third butterfly valve; fill in argon gas at 0.5 MPa to conduct a positive pressure detection on the reaction device, and require that the pressure drop does not exceed 1 Pa within 10 minutes; after the positive pressure leak rate detection is completed, turn on the vacuum pump and the vacuum valve to start pumping vacuum; when the vacuum is lower than 0.1 Pa, close the vacuum valve to conduct a negative pressure leak rate detection, and require that the pressure does not rise beyond 0.2 Pa after 10 minutes.

[0058] After the leak rate detection is completed, open the vacuum valve and continue to pump vacuum to 0.1 Pa; close the vacuum valve, fill in argon gas at 50 kPa, close the first butterfly valve, 2, 3, and then introduce hydrogen gas to 220 kPa; the rare earth metal starts to absorb hydrogen. During this process, the pressure in the furnace is lower than 100 kPa, and hydrogen gas is replenished; after filling in hydrogen gas for 1.5 hours, stop replenishing hydrogen gas.

[0059] After the hydrogen absorption is delayed for 1 hour, argon is filled to 0.5 MPa, and the circulating water in the interlayer of the reaction chamber is turned on for cooling. At the same time, a fan can be used to assist in accelerating air cooling to speed up the cooling rate. After 6 hours of cooling, the first butterfly valve, the second butterfly valve, and the third butterfly valve are opened, and the vacuum pump is turned on to pump out the remaining mixed gas in the furnace. Then, the vacuum pump, the vacuum valve, and the third butterfly valve are closed, the quick-connect joint between the third butterfly valve and the vacuum pipeline is loosened, the main reaction chamber is rotated to the discharging position, the prepared crude rare earth metal hydride powder is poured into a stainless steel feed tank, the first butterfly valve is closed, the quick-connect joint between the first butterfly valve and the second butterfly valve is loosened, the cooling water of the water-cooled copper pipe at the mouth of the feed bucket is turned off, and the stainless steel feed bucket is removed.

[0060] Use inert gas to press anhydrous ethanol into the stainless steel feed tank. After stirring and mixing for 1 hour, connect the stainless steel feed tank to the ball mill, add the crude powder into the ball mill, and use ball milling to crush the crude rare earth metal hydride powder into wet powder of spherical particles with a size of 1 μm. The powder is put into a stainless steel storage tank and filled with inert gas for storage. Preferably, add the crude rare earth metal hydride powder into the ball mill, then use inert gas to press anhydrous ethanol or the like into the ball mill, control the pressure at 0.5 Mpa, start the ball milling equipment, set the ball milling time, and the ball milling time is determined according to the required particle size. Particle size detection can be carried out by sampling. Preferably, after the ball milling is completed, 1 ml / kg of anhydrous ethanol is pressed into the ball mill again with inert gas, and then filled with inert gas to 0.5 MPa, and then the pressure is released to 0.1 MPa. After repeated cleaning for many times, the rare earth metal hydride powder mixed with anhydrous ethanol is taken out.

[0061] Take the praseodymium-neodymium hydride powder as the secondary phase and uniformly mix it into the main phase powder with a low total rare earth content according to the weight percentage of 0.2 - 1%, and then orient, form, and sinter to prepare a magnet.

[0062] The following is a comparison of the magnetic properties of sintered NdFeB magnets prepared without adding the secondary phase and with the praseodymium-neodymium hydride secondary phase prepared by the device and process of the present invention:

[0063]

[0064] Through comparison, it is found that when 0.5% of the praseodymium-neodymium hydride prepared by the device and process of the present invention is added, the Br only decreases by 250 Gs, and the Hcj increases by 110.7 kA / m, which has certain application significance.

[0065] The preparation device of the rare earth metal hydride powder of the present invention is relatively simple, and institutions and individuals with slightly equipment manufacturing capabilities can make it by themselves. Those with capabilities can achieve automatic control by using a touch screen and a PLC, and those without conditions can also achieve it by manual operation. The preparation process of the rare earth metal hydride powder of the present invention has strong operability, and the prepared powder is a wet rare earth metal hydride powder mixed with absolute ethanol, which does not affect subsequent penetration by the coating method or use as an auxiliary phase in the double alloy process. The preparation process of the rare earth metal hydride powder of the present invention fully considers the operation and storage safety during the preparation process. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A process for preparing rare earth metal hydride powder, which is prepared by the following device: The device includes two symmetrically arranged triangular brackets (1), a main reaction chamber (2) arranged between the two brackets (1), a turning mechanism (3), a stainless steel material tank (4), and a vacuum system. The main reaction chamber (2) has a water-cooled interlayer, one end is closed, and the other end is provided with an opening. The stainless steel material tank (4) is connected with a first butterfly valve (5) through a self-locking nut, and the flange at the opening end of the main reaction chamber (2) is connected with a second butterfly valve (6) through a self-locking nut. The pipeline flange opening in the middle of the main reaction chamber (2) is connected with a third butterfly valve (7) through a nut. The connection between the third butterfly valve (7) and the vacuum system and the connection between the first butterfly valve (5) and the second butterfly valve (6) are both realized through quick connectors. A hydrogen pipeline interface (8) and an argon pipeline interface (9) are installed on the main reaction chamber (2); The vacuum system includes a vacuum pipeline (12), a vacuum pump (13), a vacuum valve (14), and a pressure gauge (15). The pressure gauge (15) is installed on the main reaction chamber (2), and a vacuum gauge tube (16) is installed on the vacuum pipeline (12); It is characterized in that The process specifically adopts the following steps: 1) Cut the rare earth material into small pieces and put them into the main reaction chamber (2). The flipping mechanism rotates the main reaction chamber (2) to the horizontal position, i.e., the position during the hydrogenation reaction. 2) Connect and lock the first butterfly valve (5) and the stainless steel material tank (4) with self-locking nuts, and connect and lock the flange at the open end of the main reaction chamber (2) and the second butterfly valve (6) with self-locking nuts. Then place a gasket between the first butterfly valve (5) and the second butterfly valve (6), and use a quick connector to clamp and lock it after the gasket is placed. Connect and lock the pipe flange opening in the middle of the main reaction chamber (2) and the third butterfly valve (7) with nuts. Place a gasket between the third butterfly valve (7) and the flange of the vacuum pipe (12), and use a quick connector to clamp and lock it. After installation, open the first butterfly valve (5), the second butterfly valve (6), and the third butterfly valve (7). 3) Fill in argon gas at 0.5 MPa to conduct a positive pressure leak rate test on the reaction device, and require that the pressure drop does not exceed 1 Pa within 10 minutes. 4) After the positive pressure leak rate test is completed, start the vacuum pump (13) and the vacuum valve (14) to start pumping vacuum. 5) When the vacuum is lower than 0.1 Pa, close the vacuum valve (14) to conduct a negative pressure leak rate test, and require that the pressure does not rise beyond 0.2 Pa after 10 minutes. 6) After the negative pressure leak rate test is completed, open the vacuum valve (14) and continue to pump vacuum to 0.1 Pa. 7) Close the vacuum valve (14), fill in argon gas at 30 - 50 Kpa, close the first butterfly valve (5), the second butterfly valve (6), and the third butterfly valve (7), and then introduce hydrogen gas to 150 - 300 KPa. 8) The rare earth metal starts to absorb hydrogen. During this process, the pressure in the furnace is lower than 100 Kpa, and hydrogen gas is replenished. 9) After filling in hydrogen gas for 1 - 3 hours, stop replenishing hydrogen gas. 10) After 1 hour of hydrogen absorption delay, fill in argon gas to 0.2 - 0.5 MPa, open the circulating water in the interlayer of the main reaction chamber, and conduct cooling. Or at the same time, use a fan to assist in accelerating air cooling to speed up the cooling rate. 12) After cooling for 5 - 12 hours, open the first butterfly valve (5), the second butterfly valve (6), and the third butterfly valve (7), start the vacuum pump (13), and pump out the remaining mixed gas in the main reaction chamber (2). Then close the vacuum pump (13), the vacuum valve (14), and the third butterfly valve (7), loosen the quick connector between the third butterfly valve (7) and the vacuum pipe (12), rotate the main reaction chamber (2) to the vertical position, i.e., the discharging position, pour the prepared crude powder of hydrogenated rare earth metal into the stainless steel material tank (4), close the first butterfly valve (5), loosen the quick connector between the first butterfly valve (5) and the second butterfly valve (6), close the cooling water of the water-cooled copper pipe at the opening of the stainless steel material tank, and remove the stainless steel material tank. 13) Use inert gas to press anhydrous ethanol into the stainless steel material tank (4), stir and mix for 0.5 - 2 hours, then connect the stainless steel material tank (4) to the ball mill, add the crude powder to the ball mill, use ball milling to crush the crude powder of hydrogenated rare earth metal into wet powder of spherical particles with a size of 0.5 - 1 μm, put the powder into the stainless steel material tank, and store it by filling in inert gas.

2. The process for preparing rare earth metal hydride powder according to claim 1, characterized in that The flipping mechanism includes a motor (10) and a rotating shaft (11). One end of the rotating shaft (11) is fixedly connected to the main reaction chamber (2), and the other end of the rotating shaft (11) is connected to the output shaft of the motor.

3. The process for preparing rare earth metal hydride powder as claimed in claim 1, characterized in that Water-cooled copper tubes (17) are coiled around the connection positions of the first butterfly valve (5), the second butterfly valve (6) and the third butterfly valve (7).

4. The process for preparing rare earth metal hydride powder according to claim 1, characterized in that The rare earth purity is 99.5 - 99.9%.

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