Fine-grain molybdenum-lanthanum alloy molybdenum powder and preparation method thereof

Abstract

The invention discloses fine-grain molybdenum-lanthanum alloy molybdenum powder and a preparation method thereof.The preparation method specifically comprises the steps that rare earth lanthanum salt hydrate and deionized purified water are put into a stirring tank to be mixed and stirred, and a rare earth lanthanum salt solution is obtained; preparing doped molybdenum dioxide by using a rare earth lanthanum salt solution and MoO2; and the sample doped with molybdenum dioxide is put into a high-temperature reduction furnace, hydrogen is used for reduction, screening is conducted, and the molybdenum-lanthanum alloy molybdenum powder is obtained. According to the preparation method of the fine-grain molybdenum-lanthanum alloy molybdenum powder, molybdenum dioxide serves as a raw material, the molybdenum-lanthanum alloy molybdenum powder is prepared by adopting soluble rare earth lanthanum salt solution to atomize doped molybdenum dioxide and adopting hydrogen to reduce the doped molybdenum dioxide, La2O3 is dispersed and evenly distributed among fine-grain molybdenum-lanthanum alloy molybdenum powder grains, sintered molybdenum-lanthanum alloy is of a compact and even fine-grain structure, and therefore the fine-grain molybdenum-lanthanum alloy molybdenum powder is obtained. And the plastic-brittle transition temperature of the processed molybdenum metal is reduced, and the toughness and strength of the molybdenum-lanthanum alloy are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of molybdenum metal material preparation, and specifically relates to a method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder, and also relates to fine-grained molybdenum-lanthanum alloy molybdenum powder. Background Art

[0002] A molybdenum-lanthanum alloy is formed by adding lanthanum compounds to the matrix metal molybdenum, which is composed of La2O3 present as dispersed particles in the matrix. The dispersed La2O3 refines the grains, strengthens the molybdenum-lanthanum alloy, reduces the plastic-brittle transition temperature (DBTT) of molybdenum, and improves the toughness and strength of the molybdenum-lanthanum alloy.

[0003] At present, there are three main methods for producing and preparing molybdenum-lanthanum alloy molybdenum powder at home and abroad: (1) Liquid-liquid doping to prepare molybdenum-lanthanum alloy molybdenum powder, prepare ammonia paramolybdate solution in proportion, prepare an aqueous solution of rare earth metal salt, add an aqueous solution of rare earth metal salt to prepare doped ammonium paramolybdate when the ammonium paramolybdate solution evaporates and crystallizes to a certain extent, and hydrogen is used in two stages to prepare doped molybdenum-lanthanum alloy molybdenum powder, and prepare molybdenum alloy molybdenum powder with uniform distribution of rare earth elements. However, the use of lanthanum nitrate solution for doping produces a large amount of NO pollution, and due to the high decomposition temperature of rare earth metal salts, it takes a long time to roast them to completely decompose them. In addition, its production process is complicated, costly, energy-intensive, and difficult to control in large-scale production, which is not suitable for large-scale production of molybdenum-lanthanum alloy molybdenum powder. (2) Liquid-solid doping to prepare molybdenum-lanthanum alloy molybdenum powder, using molybdenum dioxide as raw material, using lanthanum nitrate solution to spray dope molybdenum dioxide, hydrogen reduction dope molybdenum dioxide to prepare molybdenum-lanthanum alloy molybdenum powder, the production of molybdenum-lanthanum alloy molybdenum powder La2O3 is relatively uniform, but in the process of preparing lanthanum nitrate solution, acid mist is generated, and in the process of mixing doped molybdenum dioxide vacuum drying, La(NO3)3 decomposes high-concentration, pungent yellow NO, NO2 and other nitrogen oxides are discharged, causing serious pollution to the work site and the surrounding environment. Domestic and foreign companies producing molybdenum-lanthanum alloy molybdenum powder have tried to add environmental protection equipment to the doping operation room and doping equipment to solve the problem of harm to operators and environmental pollution at the work site during the process of doping molybdenum dioxide with lanthanum nitrate solution, but the addition of environmental protection equipment failed to meet the national safety and environmental protection standards for employees and the work site environment. (3) Solid-solid + water doping is used to prepare molybdenum-lanthanum alloy molybdenum powder. Molybdenum dioxide is added to La2O3 to prepare a premixed doped molybdenum dioxide matrix. Then a certain amount of doped molybdenum dioxide matrix is ​​added to a certain amount of molybdenum dioxide, and water is sprayed to dope the molybdenum dioxide. However, the La2O3 in the prepared molybdenum-lanthanum alloy molybdenum powder is unevenly distributed, which weakens the La2O3 dispersion strengthening of the molybdenum alloy and the grain refinement effect of La2O3. The sintered molybdenum-lanthanum alloy products have coarse grains, the plastic-brittle transition temperature of the processed molybdenum metal is high, and the strength and toughness of the molybdenum-lanthanum alloy are poor. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder, which solves the problems of uneven La2O3 dispersion distribution in the molybdenum-lanthanum alloy molybdenum powder prepared by the existing method and coarse grains of the sintered molybdenum-lanthanum alloy.

[0005] Another object of the present invention is to provide the above-mentioned fine-grained molybdenum-lanthanum alloy molybdenum powder.

[0006] The technical solution adopted by the present invention is a method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder, which is specifically implemented according to the following steps: Step 1, placing rare earth lanthanum salt hydrate and deionized pure water into a stirring tank, mixing and stirring to obtain a rare earth lanthanum salt solution; Step 2, preparing doped molybdenum dioxide by mixing a rare earth lanthanum salt solution and MoO2; Step 3, putting the doped molybdenum dioxide into a high-temperature reduction furnace, reducing it with hydrogen, screening it, and mixing it to obtain molybdenum-lanthanum alloy molybdenum powder.

[0007] The present invention is also characterized in that: In step 1, the stirring time is 30-60 min.

[0008] In step 1, the mass fraction of the rare earth lanthanum salt solution is 5%-10%; the rare earth lanthanum salt hydrate is specifically lanthanum acetate.

[0009] In step 2, specifically: start the peristaltic pump to infuse the pipeline, open the compressed air pipeline valve at the same time, start the vacuum dryer, turn on the heating system to start heating the water tank to 80°C-90°C, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of a two-stream spray method to mix with MoO2, rotate and spray the liquid, after the injection is completed, turn on the vacuum system, vacuumize after 3-5 hours, and after the material is dried, complete the doping of molybdenum dioxide.

[0010] In step 3, the reduction temperature is 880°C-980°C, the time is 8h-10h; the sieving mesh is 250 and 280 mesh; the molybdenum powder mixing time is 5-10 hours.

[0011] Another technical solution adopted by the present invention is the fine-grained molybdenum-lanthanum alloy molybdenum powder prepared by the preparation method of fine-grained molybdenum-lanthanum alloy molybdenum powder.

[0012] The beneficial effects of the present invention are as follows: the preparation method of fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention uses molybdenum dioxide as a raw material, adopts a soluble rare earth lanthanum salt solution to atomize and dope molybdenum dioxide, and hydrogen reduces and dopes the molybdenum dioxide to prepare the molybdenum-lanthanum alloy molybdenum powder, La2O3 is dispersed and evenly distributed between the grains of the fine-grained molybdenum-lanthanum alloy molybdenum powder, and the sintered molybdenum-lanthanum alloy is a dense and uniform fine-grained structure, which reduces the plastic-brittle transition temperature of the processed molybdenum metal and improves the toughness and strength of the molybdenum-lanthanum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is an electron microscope scanning image of molybdenum-lanthanum alloy molybdenum powder prepared by solid-solid + water doping; Figure 2 It is the organization diagram of molybdenum-lanthanum alloy molybdenum powder sintered molybdenum alloy products prepared by solid-solid + water doping; Figure 3 This is an electron microscope scanning image of the rare earth lanthanum salt solution sprayed with molybdenum dioxide to prepare fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention; Figure 4 It is a structure diagram of a molybdenum alloy product prepared by spraying a rare earth lanthanum salt solution and doping molybdenum dioxide to prepare fine-grained molybdenum-lanthanum alloy molybdenum powder sintered; Figure 5 The present invention is an electron microscope scanning image of the preparation of fine-grained molybdenum-lanthanum alloy molybdenum powder sintered molybdenum alloy by spraying rare earth lanthanum salt solution doped with molybdenum dioxide. DETAILED DESCRIPTION

[0014] The present invention is described in detail below in conjunction with specific implementation modes and accompanying drawings.

[0015] The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder provided by the present invention uses molybdenum dioxide as a raw material, adopts a soluble rare earth lanthanum salt solution to atomize and dope molybdenum dioxide, and hydrogen reduces and dopes the molybdenum dioxide to prepare molybdenum-lanthanum alloy molybdenum powder, and La2O3 is dispersed and evenly distributed between the grains of the molybdenum-lanthanum alloy molybdenum powder. The sintered molybdenum alloy product is a dense fine-grained structure, which reduces the plastic-brittle transition temperature of the processed molybdenum metal and improves the toughness and strength of the molybdenum-lanthanum alloy. Rare earth lanthanum hydrate is selected as a dopant. The rare earth lanthanum hydrate is a white or colorless crystal, which is easily soluble in water at room temperature of 18°C ​​and decomposes into lanthanum oxide when heated to 760°C. The preparation of rare earth lanthanum salt solution is convenient and environmentally friendly, meeting the needs of industrial-scale production.

[0016] The method of the present invention solves the problem of the prior art of "solid-solid + water" doping molybdenum dioxide to prepare molybdenum-lanthanum alloy molybdenum powder, uneven dispersion distribution of La2O3, sintering of coarse grains of molybdenum-lanthanum alloy molybdenum rods to roll molybdenum rods for multi-mode stretching of molybdenum wires, poor toughness of wires and easy brittle wire breakage, low tensile strength of stretched 0.18mm molybdenum wires, uneven sintering grain size structure, and even "ring crystal" molybdenum-lanthanum alloy molybdenum rolled molybdenum rods to stretch thick molybdenum wires will have "hollow" wire breakage, and stretched thin molybdenum wires will split, which reduces production efficiency and affects the performance of molybdenum wires. At the same time, it solves the problem of NO, NO2 and other nitrogen oxide pollutants generated in the process of liquid preparation, doping mixing and reduction of solid-liquid and liquid-liquid doping, which endangers operators and pollutes the on-site working environment.

[0017] The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention is specifically implemented according to the following steps: Step 1, placing rare earth lanthanum salt hydrate and deionized pure water into a stirring tank, mixing and stirring to obtain a rare earth lanthanum salt solution; The stirring time is 30-60 minutes; The mass fraction of the rare earth lanthanum salt solution is 5%-10%; the rare earth lanthanum salt hydrate is specifically lanthanum acetate; the purity of the rare earth lanthanum salt hydrate is 99.99%; Step 2, preparing doped molybdenum dioxide; Start the peristaltic pump to infuse the pipeline, open the valve of the compressed air pipeline at the same time, start the vacuum dryer, turn on the heating system to start heating the water tank to 80℃-90℃, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of two-stream spray and mix it with MoO2, rotate and spray the liquid, after the liquid injection is completed, turn on the vacuum system, vacuumize after 3-5 hours, and stop the equipment after the material is dried, and the doping of molybdenum dioxide is completed; The mass fraction of MoO2 is 5%-10%; The existing doping technology solid-solid + water doping molybdenum dioxide reduction to prepare molybdenum-lanthanum alloy molybdenum powder lacks the uniformity of La2O3 distribution, resulting in less lanthanum content in some parts of the produced molybdenum-lanthanum alloy, or even no lanthanum, and all pure molybdenum. The sintered molybdenum-lanthanum alloy molybdenum rod has coarse grains and uneven grain structure. Coarse grain molybdenum-lanthanum alloy molybdenum rods are rolled molybdenum rods for multi-mode drawn molybdenum wires. The wire has poor toughness and is prone to brittle wire breakage. The tensile strength of stretched 0.18mm molybdenum wire is low; uneven grain molybdenum-lanthanum alloy molybdenum rolled molybdenum rods will cause "hollow" wire breakage when stretching thick molybdenum wires, and splitting occurs when stretching thin molybdenum wires, which reduces production efficiency and affects the performance of molybdenum wires.

[0018] Step 3, preparing molybdenum-lanthanum alloy molybdenum powder; The sample doped with molybdenum dioxide is placed in a flat four-tube high-temperature reduction furnace, reduced with hydrogen, and then sieved with an overhead sieving machine to obtain molybdenum-lanthanum alloy molybdenum powder; The reduction temperature is 880℃-980℃, and the time is 8h-10h; The mesh size during screening is 250 and 280 mesh; the mixing time of molybdenum powder is 5-10 hours.

[0019] The method of the present invention selects rare earth lanthanum hydrate as a dopant, and the rare earth metal salt is white or colorless crystals, which are easily soluble in water at room temperature of 18°C ​​and decomposed into lanthanum oxide when heated to 760°C. The preparation of the rare earth lanthanum salt solution is convenient and environmentally friendly.

[0020] The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention has the following advantages: First, environmentally friendly dopants are selected: the preparation of rare earth lanthanum salt solution is convenient and environmentally friendly, and the two-stream liquid-solid spray doping molybdenum dioxide reduction is used to prepare fine-grained molybdenum-lanthanum alloy molybdenum powder with dispersed and uniformly distributed La2O3; this solves the problem that the domestic main production of molybdenum-lanthanum alloy molybdenum powder uses lanthanum nitrate as a dopant, and solid-liquid doping is used to prepare molybdenum-lanthanum alloy molybdenum powder, which produces NO, NO2 and other nitrogen oxides that endanger operators and pollute the on-site working environment.

[0021] Second, solve the problem of broken wires in the process of drawing molybdenum-lanthanum alloy rolled molybdenum rods, especially in the last process of multi-mode high-speed cold-drawn molybdenum wires; The present invention is the first to adopt a two-stream atomization doping process for molybdenum dioxide, and the fineness of the sprayed liquid is between 30-50um, ensuring that the liquid is evenly sprayed on the material. At present, the main domestic production of molybdenum-lanthanum alloys still adopts a single-stream spray doping method, which has a poor spray atomization effect and cannot ensure that the liquid is evenly sprayed on the sandblasted material.

[0022] The present invention adopts a two-flow method to prepare molybdenum-lanthanum alloy molybdenum powder by liquid mist doping with molybdenum dioxide reduction, La2O3 is dispersed and evenly distributed, fine grains strengthen the molybdenum-lanthanum alloy, and the plasticity and toughness of the molybdenum wire are improved.

[0023] The effect of grain refinement and strengthening has a significant improvement on the plasticity and toughness of the material. On the one hand, the fine grains enable the material to undergo plastic deformation more evenly when subjected to stress, avoiding local stress concentration and excessive deformation, thereby delaying the initiation and expansion of cracks. On the other hand, grain refinement can also make the material consume more energy before breaking, improving the toughness of the material. It can solve the problem of broken wires in multi-mode, especially in the last process of multi-mode high-speed cold-drawn molybdenum wire drawing during the molybdenum-lanthanum alloy rolling molybdenum rod drawing process.

[0024] Thirdly, the molybdenum-lanthanum alloy molybdenum powder is prepared by a two-stream method of atomization doping molybdenum dioxide reduction. La2O3 is dispersed evenly, and the fine grains strengthen the molybdenum-lanthanum alloy, thereby improving the strength of the molybdenum-lanthanum alloy.

[0025] Grain refinement can significantly improve the strength of materials. Grain boundaries are effective barriers to dislocation movement. The finer the grains, the larger the grain boundary area, and the greater the barrier to dislocation movement. Therefore, grain refinement can increase the resistance to dislocation slip, thereby improving the strength of the material.

[0026] Example 1 The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention comprises the following steps: Step 1, selection of raw materials and liquid preparation; Take 600kg of molybdenum dioxide as raw material and 99.99% pure rare earth lanthanum salt hydrate as dopant.

[0027] Weigh 3500g of rare earth lanthanum hydrate into a stirring tank, add 40L of deionized pure water, turn on the stirrer and stir for 60 minutes to prepare a rare earth lanthanum salt solution; Step 2, preparing doped molybdenum dioxide; Turn on the peristaltic pump to infuse the pipeline, open the valve of the compressed air pipeline, turn on the vacuum dryer, turn on the heating system to heat the water tank to 80°C, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of two-stream spray and mix it with MoO2, rotate and spray the liquid, and after the liquid injection is completed, turn on the vacuum system, vacuumize for 3 hours, and stop the equipment after the material is dried, and the doping of molybdenum dioxide is completed.

[0028] Step 3, preparing molybdenum-lanthanum alloy molybdenum powder; The doped molybdenum dioxide is put into a flat four-tube high-temperature reduction furnace to reduce the molybdenum-lanthanum alloy molybdenum powder with hydrogen. The elevated screening machine screens the molybdenum-lanthanum alloy molybdenum powder, and the molybdenum-lanthanum alloy molybdenum powder is mixed and packaged.

[0029] The reduction temperature is 880°C and the time is 10h; The mesh size during screening is 280 mesh; The existing solid-solid + water doping method is used to prepare molybdenum-lanthanum alloy molybdenum powder. The La2O3 distribution in the prepared molybdenum-lanthanum alloy powder is uneven, which weakens the effect of La2O3 on grain refinement. The alloy molybdenum powder has large grains and is mixed with fine particles, such as Figure 1 As shown in Figure 2, the fracture of the sintered molybdenum-lanthanum alloy shows a coarse grain structure. Figure 2 As shown, the plastic-brittle transition temperature of processed molybdenum metal is high, and the strength and toughness of molybdenum-lanthanum alloy are poor.

[0030] In this embodiment, rare earth metal salt solution is sprayed to dope molybdenum dioxide, which is convenient, environmentally friendly and pollution-free. The electron microscope scanning image of fine-grained molybdenum-lanthanum alloy powder is prepared, as shown in FIG. Figure 3 As shown in the figure, La2O3 is dispersed evenly on the fine grains, and the sintered molybdenum alloy product has a dense, uniform, fine-grained structure. Figure 4 and Figure 5 As shown, from the electron microscope morphology of the molybdenum-lanthanum alloy, La2O3 is dispersed on the grain boundaries and between the grain boundaries (the white dots and point-like objects in the figure are La2O3 particles), which reduces the plastic-brittle transition temperature of the processed molybdenum metal and improves the toughness and strength of the molybdenum alloy.

[0031] Example 2 The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention is specifically implemented according to the following steps: Step 1, placing rare earth lanthanum salt hydrate and deionized pure water into a stirring tank, mixing and stirring to obtain a rare earth lanthanum salt solution; the stirring time is 60 min; The mass fraction of the rare earth lanthanum salt solution is 5%; the rare earth lanthanum salt hydrate is specifically lanthanum acetate; the purity of the rare earth lanthanum salt hydrate is 99.99%; Step 2, preparing doped molybdenum dioxide; Turn on the peristaltic pump to infuse the pipeline, open the valve of the compressed air pipeline, turn on the vacuum dryer, turn on the heating system to start heating the water tank to 90°C, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of a two-stream spray method to mix with MoO2, rotate and spray the liquid, and after the liquid injection is completed. Turn on the vacuum system, vacuum for 5 hours, and stop the equipment after the material is dried, and the doping of molybdenum dioxide is completed; Step 3, preparing molybdenum-lanthanum alloy molybdenum powder; The sample doped with molybdenum dioxide is placed in a flat four-tube high-temperature reduction furnace, reduced with hydrogen, and then sieved with an overhead sieving machine to obtain molybdenum-lanthanum alloy molybdenum powder; The reduction temperature is 980°C and the time is 8h; The mesh size during screening is 250 mesh.

[0032] Example 3 The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder of the present invention is specifically implemented according to the following steps: Step 1, placing rare earth lanthanum salt hydrate and deionized pure water into a stirring tank, mixing and stirring to obtain a rare earth lanthanum salt solution; The stirring time is 30 min; The mass fraction of the rare earth lanthanum salt solution is 10%; the rare earth lanthanum salt hydrate is specifically lanthanum acetate; the purity of the rare earth lanthanum salt hydrate is 99.99%; Step 2, preparing doped molybdenum dioxide; Turn on the peristaltic pump to infuse the pipeline, open the valve of the compressed air pipeline, turn on the vacuum dryer, turn on the heating system to heat the water tank to 80°C, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of two-stream spray and mix it with MoO2, rotate and spray the liquid, and after the liquid injection is completed. Turn on the vacuum system, vacuumize for 3 hours, and stop the equipment after the material is dried, and the doping of molybdenum dioxide is completed; Step 3, preparing molybdenum-lanthanum alloy molybdenum powder; The sample doped with molybdenum dioxide is placed in a flat four-tube high-temperature reduction furnace, reduced with hydrogen, and then sieved with an overhead sieving machine to obtain molybdenum-lanthanum alloy molybdenum powder; The reduction temperature is 880°C and the time is 8h; the mesh size during screening is 280 mesh.

Claims

1. A method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder, characterized in that: Follow the steps below to implement it: Step 1, placing rare earth lanthanum salt hydrate and deionized pure water into a stirring tank, mixing and stirring to obtain a rare earth lanthanum salt solution; Step 2, preparing doped molybdenum dioxide using a rare earth lanthanum salt solution and MoO2; Step 3, putting the sample doped with molybdenum dioxide into a high-temperature reduction furnace, reducing it with hydrogen, and sieving it to obtain molybdenum-lanthanum alloy molybdenum powder.

2. The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder according to claim 1, characterized in that: In the step 1, the stirring time is 30-60 min.

3. The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder according to claim 1, characterized in that: In step 1, the mass fraction of the rare earth lanthanum salt solution is 5%-10%; the rare earth lanthanum salt hydrate is specifically lanthanum acetate.

4. The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder according to claim 1, characterized in that: In the step 2, specifically: start the peristaltic pump to infuse the pipeline, open the compressed air pipeline valve at the same time, start the vacuum dryer, turn on the heating system to start heating the water tank to 80°C-90°C, inject the rare earth lanthanum salt solution into the vacuum dryer in the form of a two-stream spray method to mix with MoO2, rotate and spray the liquid, after the injection is completed, turn on the vacuum system, vacuumize for 3-5 hours, and after the material is dried, complete the doping of molybdenum dioxide.

5. The method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder according to claim 1, characterized in that: In the step 3, the reduction temperature is 880° C.-980° C., the time is 8 h -10 h; and the mesh size during sieving is 250-280 mesh.

6. The fine-grained molybdenum-lanthanum alloy molybdenum powder prepared by the method for preparing fine-grained molybdenum-lanthanum alloy molybdenum powder according to any one of claims 1 to 5.

Images