Low-cost and high-efficiency large-diameter electrode induction gas atomization spherical powder preparation method

Abstract

The invention discloses a low-cost and high-efficiency large-diameter electrode induction gas atomization spherical powder preparation method, which belongs to the technical field of metal powder preparation, and comprises the following steps of: (1) heating and melting the end part of a metal bar with the diameter of 100mm-300mm to form metal liquid drops with the size of millimeter level; (2) the metal liquid drops drop to a supersonic spraying disc internally provided with a liquid guide pipe under the action of gravity, meanwhile, inert gas is sprayed out through the supersonic spraying disc, the metal liquid drops dropping to the spraying disc are impacted, and secondary liquid drops with the size being in the micron order are obtained; and (3) the secondary liquid drops slowly drop into the atomizing chamber along the liquid guide pipe, move and solidify under the action of gravity and airflow, and circulate in this way, so that the metal spherical powder is obtained. The method not only can meet the requirement for preparing the spherical powder from the large-diameter metal bar, but also is low in cost and high in efficiency, and fully meets the application requirements of the fields of additive manufacturing, cladding, powder metallurgy, spraying and the like on the metal spherical powder.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder preparation, and in particular relates to a low-cost and high-efficiency method for preparing large-diameter electrode induction atomization spherical powder. Background Art

[0002] Due to the development of additive manufacturing, cladding, powder metallurgy, spraying and other fields, nearly spherical powders of various metals are needed. However, the existing powder making methods are difficult to achieve low-cost and high-quality powder preparation for the following reasons:

[0003] Alloys can react chemically with ceramic crucibles, and the components of the crucible will also enter the liquid metal, which will cause pollution, and then the powder will produce composition deviation, increased oxygen content, and the formation of inclusions. Therefore, vacuum induction melting gas atomization (VIGA method) with crucibles, and even water atomization, rotating disk atomization and other atomization methods using ceramic crucibles are difficult to obtain high-purity, low-pollution spherical powders. If active elements such as Ti and rare earth are contained, this method cannot be used for powder preparation.

[0004] The raw material of plasma wire atomization equipment (PA) must be wire, and methods such as PREP (plasma rotating electrode atomization) need to be pre-processed into round rods and made into threads. This type of method has high requirements for the shape of the raw material and processing accuracy, and not all materials that need to be prepared into powder can meet them. The raw material of the radio frequency plasma spheroidization method must even be in powder form, which adds necessary steps, not only increasing the preparation cost, but also limiting the range of materials that can be prepared into powder.

[0005] In addition to using a crucible to melt metal raw materials, the water atomization method is a non-vacuum atomization method. The non-vacuum atmosphere and the water flow used will increase the oxygen content of the powder and bring impurities. The prepared powder is not spherical and is difficult to use in fields such as additive manufacturing.

[0006] Crucible-free vacuum electrode induction melting gas atomization (EIGA method) does not contact the crucible and does not cause reactions or impurities. Therefore, it can produce low-impurity, high-purity metal powders, and even alloy powders containing active elements, but its preparation cost is relatively high. Therefore, the current EIGA method mainly reduces the diameter of metal bars (usually below 70 mm) and combines gas recovery and reuse, peak electricity consumption, human resources and other measures to reduce preparation costs, but it has gradually approached its limit and is difficult to reduce further; and if gas recovery and reuse, such as hydrogenation and dehydrogenation technology routes, are used, the quality of metal powders is difficult to guarantee. The above factors also affect the promotion and application of the metal powder back-end market. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and to provide a low-cost and high-efficiency method for preparing large-diameter electrode-induced atomized spherical powders.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A low-cost, high-efficiency method for preparing large-diameter electrode-induced atomized spherical powders comprises the following steps:

[0010] (1) In a vacuum environment and inert atmosphere, the end of a metal bar with a diameter of 100 mm to 300 mm is heated and melted to form metal droplets with a size of millimeters;

[0011] (2) The metal droplets drip onto a supersonic spray plate with a liquid guide tube under the action of gravity. At the same time, an inert gas is sprayed through the supersonic spray plate to impact the metal droplets dripping onto the spray plate, thereby obtaining secondary droplets of micron size; the inert gas pressure is 0.1-20 MPa, and the duration of the gas impact does not exceed 300 seconds;

[0012] (3) The secondary droplets slowly drip into the atomization chamber along the liquid guide tube, move and solidify under the action of gravity and airflow, and repeat this cycle to obtain metal spherical powder with an average particle size range of 5-300 μm.

[0013] Specifically, the metal bar material is made of a single metal or an alloy.

[0014] Furthermore, the end of the metal bar is in the shape of a cone, and the taper thereof is 10°-170°.

[0015] Furthermore, the preparation process of the metal bar material is: the raw material is prepared into a metal ingot by a smelting ingot casting or a powder metallurgy method, and then the metal ingot is obtained by surface treatment.

[0016] Preferably, in step (1), the vacuum degree of the vacuum environment is 10 -7 -100MPa.

[0017] Preferably, the inert gas in step (1) is at least one of nitrogen, argon and helium.

[0018] Specifically, in step (1), the power used for heating and melting the end of the metal bar is 50-800 kW.

[0019] Furthermore, in the step (2), one of the methods selected from the group consisting of induction heating, electric arc and electron beam is used to heat and melt the end of the metal bar to form metal droplets with a size of millimeters.

[0020] Furthermore, in step (3), the atomization gas consumption is 500-2000 cubic meters per hour.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention adopts a secondary gas atomization method, cooperates with the design of the taper of the end of the metal bar, and the effects of the vacuum environment, supersonic spray disc, inert gas, liquid guide tube and atomization chamber. First, the end of the metal bar is melted into millimeter-level primary droplets, and then the gas impact of the supersonic spray disc is used to form micrometer-level secondary droplets from the primary droplets. Then, through the control of the liquid guide tube, the secondary droplets are slowly dripped into the atomization chamber, and finally solidified into powder under the action of the airflow in the atomization chamber. This scheme designed by the present invention can not only meet the requirements of preparing spherical powders from large-diameter metal bars (more than 100mm, up to 300mm), but also has low cost and high efficiency.

[0023] Experiments show that since large diameter metal bars can be used, the scheme of the present invention effectively increases the output of metal powder. Specifically, under the same length of metal bars for electrodes, the output of metal powder in a single furnace of a metal bar with a diameter of 100 mm is 4 times that of a metal bar with a diameter of 50 mm, and the output of metal powder in a single furnace of a metal bar with a diameter of 300 mm is 36 times that of a metal bar with a diameter of 50 mm.

[0024] Moreover, based on the current market situation, when the scheme of the present invention is adopted, when the diameter of the metal bar is above 100 mm, the unit cost shows a trend of greatly decreasing and then slowly increasing, as shown in Table 1.

[0025]

[0026] Table 1

[0027] Therefore, the present invention fully meets the application requirements of metal spherical powder in the fields of additive manufacturing, cladding, powder metallurgy, spraying, etc.

[0028] (2) The preparation method of the present invention does not contact the crucible, uses an inert gas to impact the metal droplets, and designs the pressure and impact duration of the inert gas. Therefore, it not only effectively avoids the chemical reaction between the crucible and active metal elements such as rare earth, IVB group (zirconium and hafnium), VB group (vanadium, niobium and tantalum), beryllium, and chromium, but also reduces the pollution caused by the crucible and reduces the oxygen content. It also effectively avoids the introduction of impurities and fully improves the quality of the metal spherical powder.

[0029] (3) The raw materials required in the preparation method of the present invention can be recycled materials, thereby further reducing production costs.

[0030] (4) The various links of the present invention are closely linked, complementary and related, and provide a good reference basis for the low-cost and high-efficiency preparation of metal spherical powders. Therefore, the present invention is very suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM image of pure tungsten (melting point: 3422° C.) metal spherical powder prepared in Example 1 of the present invention;

[0032] Figure 2 Schematic diagram of the melting of a TC4 titanium alloy bar with a diameter of 150 mm into droplets in Example 2 of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the materials and reagents used in the examples can be obtained from commercial sources.

[0035] The content of active metal elements in the metal powder finally prepared in the embodiment of the present invention is measured by a conventional chemical quantitative method in the art, and the oxygen increment and nitrogen increment are measured by an oxygen, nitrogen and hydrogen analyzer.

[0036] In the present invention, the powder raw material is WMoTaNbV refractory high entropy alloy, and single substance and alloy with melting point in the range of 30°C to 3600°C. The preparation method of metal spherical powder is as follows:

[0037] (1) A metal ingot is prepared by smelting ingots (using vacuum magnetic levitation induction melting, vacuum induction water-cooled copper crucible condensation furnace melting, vacuum arc melting or vacuum induction melting to melt the alloy, and the melting temperature of the alloy melting is 50°C-6000°C), powder metallurgy (using sintering, hot pressing sintering and other methods; the temperature of powder metallurgy is 30°C-3000°C, and the pressure is 0-500Mpa); and then surface treatment (mechanical grinding or chemical cleaning to clean the surface oil, impurities, oxide scale pollution layer to expose the metal) to obtain a metal bar with a diameter of 100mm-300mm, the front end of the bar is a cone, and the taper is 10°-170°;

[0038] (2) Use a vacuum pump to evacuate the furnace body so that the metal bar is in a vacuum environment with a vacuum degree of 10 -7-100MPa, and filled with at least one of nitrogen, argon and helium with a gas purity of 99.99%, and repeated replacement times 1-2 times;

[0039] (3) Using induction heating, electric arc, electron beam and other methods, the end of the metal bar is heated and melted to obtain molten metal droplets (primary droplets, the size is millimeter level); the heating and melting temperature is 30-3600°C, and the power supply power is 50-800kW;

[0040] (4) A secondary gas atomization method is used to first form metal droplets into micron-sized secondary droplets, and then pass through an atomization chamber to finally solidify into spherical powder; wherein the gas atomization gas pressure for forming secondary droplets is 0.1-20 MPa, the duration of each impact does not exceed 300 seconds, and the gas consumption in the atomization chamber is 500-2000 cubic meters / hour.

[0041] The present invention will be further described below in conjunction with embodiments and drawings.

[0042] Example 1

[0043] Powder making raw material: tungsten metal element, melting point is 3422℃.

[0044] The preparation method is as follows:

[0045] S1. A tungsten metal single substance ingot is prepared by a hot isostatic pressing sintering method in a powder metallurgy method, wherein the temperature of the powder metallurgy is 3000°C and the pressure is 500Mpa; and then a tungsten metal rod with a diameter of 100mm is obtained by mechanical processing, and the front end of the rod is a cone with a taper of 170°;

[0046] S2. Use a vacuum pump to evacuate the furnace body so that the tungsten metal rod is in a vacuum environment. The vacuum degree is set to 10 -7 MPa, and filled with helium with a gas purity of 99.99%, and replaced repeatedly twice;

[0047] S3, using electron beam heating method to heat and melt the end of the tungsten metal rod to obtain molten metal droplets (size is millimeter level); the heating and melting temperature is 3600°C, and the power supply power is 800kW;

[0048] S4, the metal droplets drip onto the supersonic spray plate under the action of gravity. At the same time, the inert gas (helium) is sprayed through the supersonic spray plate to impact the metal droplets dripping onto the spray plate, and secondary droplets with a size of micrometers are obtained; the inert gas pressure is 20MPa, and each gas impact lasts for 300 seconds;

[0049] S5. The secondary droplets slowly drip into the atomization chamber along the liquid guide tube, move and solidify under the action of gravity and airflow, and repeat this cycle to obtain tungsten metal spherical powder with an average particle size of 70μm. The gas consumption is 2000 cubic meters per hour.

[0050] The SEM of the above tungsten metal spherical powder is as follows Figure 1 shown.

[0051] Example 2

[0052] Powder making raw material: TC4 alloy, melting point is 1660°C. Composition is by mass percentage: aluminum content 5.5-6.75wt%, vanadium content 3.5-4.5wt%, titanium content balance.

[0053] The preparation method is as follows:

[0054] S1. The alloy is melted by vacuum arc melting in the ingot, and the melting temperature of the alloy is 1700°C; then, an alloy bar with a diameter of 150 mm is obtained by mechanical processing, and the front end of the bar is a cone with a taper of 90°;

[0055] S2. Use a vacuum pump to evacuate the furnace body so that the alloy bars are in a vacuum environment. The vacuum degree is set to 10 -3 MPa, and filled with argon gas with a gas purity of 99.99%, and the number of replacements was 1;

[0056] S3, using induction heating to heat and melt the end of the alloy bar to obtain molten alloy droplets (size is millimeter level); the heating and melting temperature is 2000°C, and the power is 200kW;

[0057] S4, the alloy droplets drip onto the supersonic spray plate under the action of gravity, and at the same time, the inert gas (argon) is sprayed through the supersonic spray plate to impact the alloy droplets dripping onto the spray plate, and secondary droplets with a size of micrometers are obtained; the inert gas pressure is 5MPa, and each gas impact lasts for 300 seconds;

[0058] S5. The secondary droplets slowly drip into the atomization chamber along the liquid guide tube, move and solidify under the action of gravity and airflow, and repeat this cycle to obtain TC4 alloy spherical powder with an average particle size of 300μm. The gas consumption is 1000 cubic meters per hour.

[0059] Example 3

[0060] Powder making raw materials: cesium metal element, melting point is 28.4℃.

[0061] The preparation method is as follows:

[0062] S1. Vacuum magnetic suspension induction melting is used to melt ingots at a melting temperature of 50°C. Then, cesium metal bars with a diameter of 300 mm are obtained through mechanical processing. The front end of the bars is a cone with a taper of 10°.

[0063] S2. Use a vacuum pump to evacuate the furnace body so that the tungsten metal rod is in a vacuum environment. The vacuum degree is set to 10 -7 MPa, and filled with nitrogen with a gas purity of 99.99%, and the replacement frequency was 1;

[0064] S3, using an arc heating method to heat and melt the end of the cesium metal rod to obtain molten metal droplets (size is millimeter level); the heating and melting temperature is 30°C, and the power supply power is 50kW;

[0065] S4, the metal droplets drip onto the supersonic spray plate under the action of gravity, and at the same time, the inert gas (nitrogen) is sprayed through the supersonic spray plate to impact the metal droplets dripping onto the spray plate, and obtain secondary droplets with a size of micrometers; the inert gas pressure is 0.1MPa, and each gas impact lasts for 300 seconds;

[0066] S5. The secondary droplets slowly drip into the atomization chamber along the liquid guide tube, move and solidify under the action of gravity and airflow, and repeat this cycle to obtain cesium metal spherical powder with an average particle size of 5μm. The gas consumption is 500 cubic meters per hour.

[0067] The present invention significantly reduces the preparation cost while ensuring the quality of the metal spherical powder through reasonable scheme design (including the selection of the metal bar diameter and the setting of the end shape and taper, the gas atomization method and the setting of the process parameters), and well breaks through the limitations of the prior art. Therefore, compared with the prior art, the present invention has outstanding substantive features and significant progress.

[0068] The above-mentioned embodiments only express the specific implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the protection scope of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powders, characterized in that: The following steps are involved: (1) In a vacuum environment and inert atmosphere, the end of a metal bar with a diameter of 100 mm to 300 mm is heated and melted to form metal droplets with a size of millimeters; (2) The metal droplets drip onto a supersonic spray plate with a liquid guide tube under the action of gravity. At the same time, an inert gas is sprayed through the supersonic spray plate to impact the metal droplets dripping onto the spray plate, thereby obtaining secondary droplets of micron size; the inert gas pressure is 0.1-20 MPa, and the duration of the gas impact does not exceed 300 seconds; (3) The secondary droplets slowly drip into the atomization chamber along the liquid guide tube, move and solidify under the action of gravity and airflow, and repeat this cycle to obtain metal spherical powder with an average particle size range of 5-300 μm.

2. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 1, characterized in that: The metal bar material is made of a single metal or an alloy.

3. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 2, characterized in that: The end of the metal bar is in the shape of a cone, and the taper is 10°-170°.

4. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 3, characterized in that: The preparation process of the metal bar material is: the raw material is prepared into a metal ingot by a smelting ingot casting or a powder metallurgy method, and then the metal ingot is prepared by surface treatment.

5. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to any one of claims 1 to 4, characterized in that: In the step (1), the vacuum degree of the vacuum environment is 10 -7 -100MPa.

6. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 5, characterized in that: The inert gas in step (1) is at least one of nitrogen, argon and helium.

7. A low-cost, high-efficiency method for preparing large-diameter electrode-induced atomized spherical powder according to claim 6, characterized in that: In the step (1), the power used for heating and melting the end of the metal bar is 50-800 kW.

8. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 1, 2, 3, 4, 6 or 7, characterized in that: In the step (2), one of the methods of induction heating, electric arc and electron beam is used to heat and melt the end of the metal bar to form metal droplets with a size of millimeters.

9. A low-cost, high-efficiency method for preparing large-diameter electrode-induced aerosolized spherical powder according to claim 8, characterized in that: In the step (3), the atomization gas consumption is 500-2000 cubic meters per hour.

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