Rare earth alloy diffusion source powder and preparation method and application thereof

Abstract

The invention provides diffusion source powder and a preparation method and application thereof, and belongs to the technical field of metal materials and powder metallurgy. Rare earth alloy raw materials are sequentially smelted and crushed, obtained fragments are sequentially subjected to hydrogen demolishing treatment and dehydrogenation treatment, and dehydrogenated alloy powder is obtained; the dehydrogenated alloy powder is refined, the obtained refined alloy powder is soaked in a mixed solvent, rare earth alloy diffusion source powder is obtained, and the mixed solvent comprises an oil film forming substance and an antioxidant. According to the method, the residual hydrogen element achieves the anti-oxidation effect through hydrogen demolishing treatment, a uniform and compact protection layer is formed on the surface of the dehydrogenated alloy powder in combination with the sealing effect of the mixed solvent, the oxidation resistance, activity loss resistance and stability of the rare earth alloy diffusion source powder are improved, and the service life of the rare earth alloy diffusion source powder is prolonged. A more reliable diffusion source material is provided for magnet diffusion heat treatment, and the method is particularly suitable for sintered neodymium-iron-boron grain boundary diffusion treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials and powder metallurgy, and particularly relates to a rare earth alloy diffusion source powder, a preparation method thereof, and an application thereof. Background Art

[0002] As a method to effectively improve the performance of sintered Nd-Fe-B magnets without significantly increasing the material cost, the grain boundary diffusion technology has been proven to be an economical and efficient improvement strategy. The core raw material of the grain boundary diffusion technology is the diffusion source powder. However, due to their high surface activity, the commonly used rare earth hydride and rare earth alloy powders are extremely prone to oxidation, resulting in the effect of grain boundary diffusion being far lower than expected, and even possibly completely failing. In order to reduce contact with oxygen, the operation of these powders must be carried out in a protective gas environment, such as nitrogen or argon, which undoubtedly increases the technical cost. In addition, the diffusion source powders obtained by traditional preparation techniques are prone to caking and agglomeration during long-term storage or use, which further affects the stable performance of their performance. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a rare earth alloy diffusion source powder, a preparation method thereof, and an application thereof. The rare earth alloy diffusion source powder prepared by the present invention has good antioxidant performance and stability.

[0004] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: The present invention provides a preparation method of a rare earth alloy diffusion source powder, including the following steps: Successively melting and crushing the rare earth alloy raw material to obtain fragments; Successively performing hydrogen breaking treatment and dehydrogenation treatment on the fragments to obtain dehydrogenated alloy powder; Refining the dehydrogenated alloy powder to obtain refined alloy powder; Soaking the refined alloy powder in a mixed solvent to obtain the rare earth alloy diffusion source powder, and the mixed solvent includes an oil film-forming substance and an antioxidant.

[0005] Preferably, the temperature of the hydrogen breaking treatment is 100-350°C.

[0006] Preferably, the oil film-forming substance includes one or more of kerosene, silicone oil, and gasoline.

[0007] Preferably, the mass of the antioxidant is 0.07-0.5% of the mass of the dehydrogenated alloy powder.

[0008] Preferably, the antioxidant includes fatty acid and / or organic phosphate ester.

[0009] Preferably, the particle size of the fragments is 1-2 mm.

[0010] Preferably, a fresh fracture surface is reserved before the hydrogen decrepitation treatment of the fragments.

[0011] Preferably, the average particle size of the alloy powder after dehydrogenation is 20 - 150 μm.

[0012] Preferably, the average particle size of the alloy powder after refinement is 3 - 20 μm.

[0013] The present invention also provides a rare earth alloy diffusion source powder prepared by the preparation method described in the above technical solution.

[0014] The present invention also provides an application of the rare earth alloy diffusion source powder described in the above technical solution in the diffusion heat treatment of magnets.

[0015] The present invention provides a preparation method of a rare earth alloy diffusion source powder, comprising the following steps: successively melting and crushing rare earth alloy raw materials to obtain fragments; successively performing hydrogen decrepitation treatment and dehydrogenation treatment on the fragments to obtain alloy powder after dehydrogenation; refining the alloy powder after dehydrogenation to obtain refined alloy powder; soaking the refined alloy powder in a mixed solvent to obtain the rare earth alloy diffusion source powder, and the mixed solvent comprises an oil film-forming substance and an antioxidant.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention utilizes hydrogen decrepitation treatment to make the residual hydrogen element play an antioxidant role, combined with the sealing effect of the mixed solvent, to form a uniform and dense protective layer (including an oil film and an antioxidant film) on the surface of the alloy powder after dehydrogenation, improving the antioxidant performance, anti-activity loss and stability of the rare earth alloy diffusion source powder, providing a more reliable diffusion source material for the diffusion heat treatment of magnets, being particularly suitable for the grain boundary diffusion treatment of sintered neodymium iron boron, and further improving the coercivity of the magnet.

[0017] The present invention also provides a rare earth alloy diffusion source powder prepared by the preparation method described in the above technical solution, which has good antioxidant performance and stability, and solves the problems of easy oxidation and poor stability of the rare earth alloy diffusion source powder in the related art. Detailed Embodiments

[0018] The present invention provides a preparation method of a rare earth alloy diffusion source powder, comprising the following steps: Successively melting and crushing rare earth alloy raw materials to obtain fragments; Successively performing hydrogen decrepitation treatment and dehydrogenation treatment on the fragments to obtain alloy powder after dehydrogenation; Refining the alloy powder after dehydrogenation to obtain refined alloy powder; Soak the refined alloy powder in a mixed solvent to obtain the rare earth alloy diffusion source powder, where the mixed solvent includes an oil film-forming substance and an antioxidant.

[0019] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well-known to those skilled in the art.

[0020] In the present invention, the rare earth alloy raw materials are successively melted and crushed to obtain fragments.

[0021] In the present invention, the content of rare earth elements in the rare earth alloy raw materials is preferably 60 - 95 wt%.

[0022] The present invention has no special limitation on the chemical composition of the rare earth alloy diffusion source powder. The types of rare earth alloy diffusion source powders well-known to those skilled in the art can be used. Specifically, such as Tb - Al - Ga alloy. In the specific embodiments of the present invention, it is more preferably Tb 70 Al 24 Ga6 (wt.%).

[0023] The present invention has no special limitation on the source of the rare earth alloy raw materials. According to the required ratio of the rare earth alloy diffusion source powder, weigh and mix the rare earth alloy raw materials. In the present invention, in order to ensure the purity of the rare earth alloy diffusion source powder, it is preferred to perform impurity removal treatment on the rare earth alloy raw materials before use. The present invention has no special limitation on the specific method of the impurity removal treatment, and the methods well-known to those skilled in the art can be used.

[0024] In the present invention, the melting is preferably carried out in an inert gas environment, and the melting process preferably uses a rapid solidification technique to form a cast sheet or prepare an ingot.

[0025] In the present invention, the particle size of the fragments is preferably 1 - 2 mm. The present invention has no special limitation on the specific method of the crushing, and the methods well-known to those skilled in the art can be used.

[0026] In the present invention, before the hydrogenation and dehydrogenation treatment of the fragments, it is preferably further included to retain a fresh fracture surface to prevent the fragments from oxidizing.

[0027] The present invention preferably soaks the fragments in a liquid to retain a fresh fracture surface. The liquid is preferably a liquid that does not react with the fragments and can isolate air, and will volatilize when heated to within 300 °C. In the specific embodiments of the present invention, it is preferred to soak the fragments in alcohol or kerosene.

[0028] After obtaining the fragments, the present invention successively performs hydrogenation and dehydrogenation treatment on the fragments to obtain the dehydrogenated alloy powder.

[0029] In the present invention, the temperature of the hydrogen desorption treatment is preferably 100-350 °C, specifically it can be 100, 150, 200, 250, 280, 300 or 350 °C, and the time is preferably until the fragments no longer absorb hydrogen. During the hydrogen desorption treatment, the fragments are induced to absorb hydrogen, causing hydrogen embrittlement of the alloy particles.

[0030] In the present invention, the temperature of the dehydrogenation treatment is preferably lower than the liquid-phase transformation temperature of the fragments, more preferably 400-600 °C, specifically it can be 400, 500 or 600 °C, and the time is preferably 3-8 h, specifically it can be 3, 4, 5, 6, 7 or 8 h.

[0031] In the present invention, the hydrogen desorption treatment and dehydrogenation treatment are preferably carried out in a hydrogen desorption furnace. The present invention preferably raises the furnace body temperature of the hydrogen desorption furnace to the temperature of the hydrogen desorption treatment, then stops heating, allows the furnace body to cool naturally, and at the same time introduces hydrogen into the furnace to start the hydrogen absorption reaction. After the metal is fully saturated with hydrogen absorption (i.e., the air pressure in the hydrogen desorption furnace remains constant), the furnace body is heated to carry out the dehydrogenation treatment.

[0032] In the present invention, the average particle size of the alloy powder after dehydrogenation is preferably 20-150 μm, specifically it can be 20, 50, 75, 100, 120 or 150 μm.

[0033] After obtaining the alloy powder after dehydrogenation, the present invention refines the alloy powder after dehydrogenation to obtain the refined alloy powder.

[0034] In the present invention, the particle size of the refined alloy powder is preferably 3-20 μm, specifically it can be 3, 5, 10, 15 or 20 μm.

[0035] The present invention preferably transfers the alloy powder after dehydrogenation to a glove box immediately, and carries out the refinement in the glove box using a grinder. The glove box can prevent the coarse powder from being oxidized in the air for a long time, and the glove box is preferably filled with argon or nitrogen. In the present invention, the grinder is preferably a ball mill or a jet mill.

[0036] After obtaining the alloy powder after dehydrogenation, the present invention immerses the alloy powder after dehydrogenation in a mixed solvent to obtain the rare earth alloy diffusion source powder, and the mixed solvent includes an oil film-forming substance and an antioxidant.

[0037] In the present invention, the oil film-forming substance preferably includes kerosene and / or gasoline.

[0038] In the present invention, the dosage of the oil film-forming substance is preferably sufficient to completely immerse the alloy powder after dehydrogenation.

[0039] In the present invention, the mass of the antioxidant is preferably 0.05% to 1% of the mass of the alloy powder after dehydrogenation, more preferably 0.07% to 0.5%, and specifically can be 0.05%, 0.07%, 0.1%, 0.5% or 1%.

[0040] In the present invention, the antioxidant preferably includes fatty acids and / or organophosphates. In a specific embodiment of the present invention, the antioxidant is preferably a commercial antioxidant for NdFeB powder.

[0041] In the present invention, it is preferred to soak the alloy powder after dehydrogenation in a mixed solvent, and then stir to form a uniform and dense protective layer (including an oil film and an antioxidant film). The protective layer adheres tightly to the surface layer of the powder, and there is no other substance in the middle. The obtained rare earth alloy diffusion source powder is sealed and stored, thereby effectively preventing oxidation and improving stability.

[0042] The present invention also provides a rare earth alloy diffusion source powder prepared by the preparation method described in the above technical solution.

[0043] The present invention also provides an application of the rare earth alloy diffusion source powder described in the above technical solution in the diffusion heat treatment of magnets.

[0044] The present invention has no special limitation on the specific manner of the application, and the manner well-known to those skilled in the art can be adopted.

[0045] In the present invention, it is preferred to dilute the rare earth alloy diffusion source powder with alcohol to obtain a slurry, spray the slurry on the surface of the magnet to be diffused, and then perform diffusion heat treatment.

[0046] In the present invention, the magnet to be diffused is preferably a sintered neodymium iron boron magnet.

[0047] In the present invention, the spraying is preferably carried out in an atmospheric environment.

[0048] The present invention has no special limitation on the specific parameters of the dilution, spraying and diffusion heat treatment, and the manner well-known to those skilled in the art can be adopted.

[0049] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0050] Example 1 Step 1: Taking the Tb-Al-Ga alloy as an example, first according to the nominal composition Tb 70 Al 24Ingredients are prepared with Ga6 (wt.%). All raw materials should have impurities removed before use.

[0051] Step 2: The prepared raw materials are melted. They are melted into alloy cast sheets using a rapid solidification melting method, and the melting should be carried out in an inert gas environment.

[0052] Step 3: A hydraulic shear is used to crush the melted alloy cast sheets into particles with a particle size of 1 - 2 mm. Then, the crushed particles are quickly soaked in alcohol to retain a fresh fracture surface and prevent oxidation.

[0053] Step 4: The alloy cast sheets soaked in alcohol after crushing are placed in a hydrogen breaking furnace for hydrogen breaking treatment and dehydrogenation treatment. First, the furnace body temperature is raised to 280 °C and held for heat preservation. Then, the heating is stopped, and the furnace body is allowed to cool naturally. At the same time, hydrogen is introduced into the furnace to start the hydrogen absorption reaction.

[0054] Step 5: After the metal is fully saturated with hydrogen absorption, the furnace body is heated for dehydrogenation. The dehydrogenation temperature is 500 °C, and the dehydrogenation time is 3 h.

[0055] Step 6: The average particle size of the alloy powder after dehydrogenation is 75 μm, and it is immediately transferred to a glove box filled with argon.

[0056] Step 7: In the glove box, a grinder is used to refine the alloy powder after dehydrogenation to 10 μm, obtaining refined alloy powder.

[0057] Step 8: The refined alloy powder is immediately soaked in a mixed solvent of kerosene and a commercial NdFeB powder antioxidant. The kerosene should cover the powder, and the addition amount of the commercial NdFeB powder antioxidant is 0.07 wt.% of the powder. Then, it is fully stirred to obtain rare earth alloy diffusion source powder, which is then sealed and stored.

[0058] Step 9: After obtaining the rare earth alloy diffusion source powder treated by soaking, 10 g of the rare earth alloy diffusion source powder is diluted with 30 mL of alcohol and then sprayed on the surface of the magnet to be diffused (sintered NdFeB magnet) for diffusion heat treatment. The specific steps are as follows: The sintered NdFeB magnet is cut into cubes of 10 × 10 × 5 mm, and it is sprayed on two 10 × 10 surfaces. Then, it is dried by blowing with a hot air blower at 100 °C for 20 min, and the sprayed magnet is weighed. The weight of the magnet increases by 0.8 wt.% after spraying. The spraying process is carried out in the atmospheric environment.

[0059] Comparative Example 1 Steps 1 - 3 are the same as those in Example 1; Step 4: The alloy cast sheets soaked in alcohol after crushing are refined by ball milling to obtain ball - milled powder; Step 5: The same as Step 8 in Example 1.

[0060] Step 6: The same as Step 9 of Example 1.

[0061] Comparative Example 2 Steps 1 to 7 are the same as those of Example 1; Step 8: The same as Step 9 of Example 1.

[0062] Table 1 shows the comparison of magnetic property parameters after coating diffusion of the examples and comparative examples. It can be seen from Table 1 that after the sintered NdFeB magnet is diffusion-treated with the rare earth alloy diffusion source powder prepared by the method of the present invention, a large increase in coercivity of 12.7 kOe is obtained. Under the same environment and process variables, without anti-oxidation treatment (Comparative Example 2) or only using simple alcohol for anti-oxidation treatment (Comparative Example 1), the increase in coercivity decreases to varying degrees. This is because the rare earth alloy diffusion source powder is extremely easy to oxidize in the air, and the oxidized alloy is very difficult to diffuse into the magnet due to its stable structure, thus it is difficult to improve the coercivity of the magnet.

[0063] Table 1 Comparison of Magnetic Property Parameters after Coating Diffusion of Examples and Comparative Examples

[0064] The above is only the preferred embodiment of the present invention, and it is not intended to limit the present invention in any form. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a rare earth alloy diffusion source powder, characterized in that, It includes the following steps: Successively smelt and crush the rare earth alloy raw materials to obtain fragments; Successively perform hydrogen breaking treatment and dehydrogenation treatment on the fragments to obtain dehydrogenated alloy powder; Refine the dehydrogenated alloy powder to obtain refined alloy powder; Soak the refined alloy powder in a mixed solvent to obtain the rare earth alloy diffusion source powder, and the mixed solvent includes an oil film-forming substance and an antioxidant.

2. The preparation method according to claim 1, characterized in that, The temperature of the hydrogen breaking treatment is 100-350°C.

3. The preparation method according to claim 1, wherein The oil film-forming substance includes one or more of kerosene, silicone oil and gasoline.

4. The preparation method according to claim 1, wherein The mass of the antioxidant is 0.07-0.5% of the mass of the dehydrogenated alloy powder.

5. The preparation method according to claim 1 or 4, characterized in that, The antioxidant includes fatty acid and / or organic phosphate ester.

6. The preparation method according to claim 1, wherein The average particle size of the dehydrogenated alloy powder is 20-150μm.

7. The preparation method according to claim 1, characterized in that, The particle size of the fragments is 1-2mm.

8. The preparation method according to claim 1 or 7, characterized in that Before the fragments are subjected to hydrogen breaking treatment, it also includes retaining a fresh fracture surface.

9. The rare earth alloy diffusion source powder prepared by the preparation method according to any one of claims 1-8.

10. The application of the rare earth alloy diffusion source powder according to claim 9 in the diffusion heat treatment of magnets.

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