Preparation method of spherical tungsten powder by plasma rotating electrode atomization

Abstract

The present invention relates to the field of metal powder preparation, and in particular to a method for preparing spherical tungsten powder by plasma rotating electrode atomization. Among them, a method for preparing spherical tungsten powder by plasma rotating electrode atomization comprises the following steps: preparing a doped tungsten alloy electrode rod by isostatic pressing, medium frequency sintering, forging and machining the doped tungsten powder, wherein the boiling point of the doped component in the doped tungsten alloy electrode rod is less than the melting point of tungsten or not higher than 500°C of the melting point of tungsten; and atomizing the doped tungsten alloy electrode rod by plasma rotating electrode to obtain spherical tungsten powder by plasma rotating electrode atomization. The method for preparing spherical tungsten powder by plasma rotating electrode atomization provided by the present invention adopts a doped tungsten alloy electrode rod to replace a pure tungsten electrode rod, and obtains spherical tungsten powder with a lower particle size without changing the rotation speed of the equipment and the diameter of the electrode rod, thereby effectively improving the yield of spherical tungsten powder prepared by plasma rotating electrode atomization that meets the medium and low particle size requirements of EBM and the particle size requirements of SLM.

Description

Technical Field

[0001] The invention relates to the field of metal powder preparation, and in particular to a method for preparing spherical tungsten powder by plasma rotating electrode atomization. Background Art

[0002] Tungsten is the metal with the highest melting point. It has the advantages of low saturated vapor pressure, small thermal expansion coefficient, good thermal and electrical conductivity, high high-temperature strength, large atomic coefficient, high density, and strong resistance to radiation. It is widely used in electrical vacuum, thermal field, medical, nuclear power, military industry and other fields.

[0003] However, tungsten has a high plastic-brittle transition temperature, low plasticity, and is relatively difficult to process by pressure and machining, which greatly limits its application. In the traditional powder metallurgy + pressure processing + machining process, the use of doping with rare earth oxides and potassium can improve the forming performance of tungsten and obtain better performance advantages such as improved high-temperature strength, plasticity, and reduced electron work function. The development of metal 3D printing technology has provided a new way for the forming and application of tungsten. It is currently known that spherical tungsten powder is used as the raw material, and complex-shaped tungsten products printed by two printing methods, laser selective melting (SLM) and electron beam selective melting (EBM) based on powder bed, have been successfully used in medical, nuclear power and military industries in batches, and have broad prospects. In terms of the comparison of the two processes, SLM accounts for a larger proportion in actual applications.

[0004] Different printing technologies have different requirements for the particle size of spherical powders, which are generally SLM: 15-53μm, EBM: 45-106μm. There are also many processes for preparing spherical metal powders, but there are not many choices for the metal with the highest melting point - tungsten (melting point 3410℃). There are only three industrialized technologies at present, radio frequency plasma spheroidization (with powder as raw material), plasma rotating electrode atomization (with rods as raw material), and electric explosion method (with wire as raw material). In terms of cost, the radio frequency plasma spheroidization process should be the lowest, and the powder particle size coverage can also cover the two printing processes. If the particle size of the raw material powder is well controlled, the yield of the finished spherical powder can reach more than 90%. However, the powder sphericity, spheroidization rate, and hollow spherical powder prepared by this process have relatively poor performance, especially coarse-grained spherical tungsten powder (≥53μm) needs to be made of granulated tungsten powder as raw material, which is costly and has a high hollow ball ratio. The electric explosion method uses wire with a diameter of about 0.3mm as raw material. As mentioned above, tungsten is a difficult metal to process. The wire is produced by powder metallurgy and pressure processing. The process is long, the cost is high, and the availability of raw materials is poor. At the same time, this process is suitable for making nano powders and relatively small micron powders for SLM. The powder sphericity, spheroidization rate, and hollow ball powder are all very good, and the quality consistency is also high. However, the yield of powder in the target particle size range will be relatively low, about 50%. Plasma rotating electrode atomization uses machined rods as raw materials. The cost and availability of raw materials are between powders and wires. The performance indicators of powders made by this process are comparable to those of the electric explosion method. However, the only drawback is that it is limited by the capacity of the equipment (mainly the rotation speed and the maximum electrode rod diameter and weight that the equipment can clamp). It can only prepare powders in the medium and coarse particle size range for EBM, and the yield rate is also insufficient. As for the fine micron powder used for SLM, it is basically negligible, which greatly limits its application and commercial value.

[0005] There have been continuous attempts to prepare finer spherical powders by plasma rotating electrode atomization, and the main focus of current improvements is on powder making equipment.

[0006] The formula for calculating the average particle size of plasma rotating electrode atomized powder is as follows:

[0007]

[0008] Where: n is the rotation speed of the electrode rod, D is the diameter of the electrode rod, δ is the surface tension of the droplet, ρ is the density, and η is the dimensionless correction factor.

[0009] From the formula, it can be seen that increasing the rotation speed of the electrode rod and increasing the diameter of the electrode rod can reduce the powder particle size. The progress in this regard depends on the design and manufacturing capabilities of the equipment, how to obtain a higher rotation speed, or how to clamp an electrode rod with a larger diameter.

[0010] Increasing the rotation speed places high demands on the rotating system and is difficult to manufacture. Increasing the electrode rod diameter will also increase the load and heat dissipation requirements on the rotating system. The density of tungsten is 19.2g / cm 3 , the increase in diameter will lead to a significant increase in weight. At the same time, for tungsten electrode rods produced by powder metallurgy (powder-isostatic pressing / compression molding-sintering) plus pressure processing (rolling, forging) plus machining, the increase in diameter also brings the risk of poor sintering uniformity and easy cracking during pressure processing, reducing the availability of the final product. Therefore, the equipment on the market usually has a high speed, and the diameter of the electrode rod is small. On the contrary, if the speed is low, a larger diameter electrode rod can be used. However, if the diameter is large, the length often needs to be shortened to avoid the adverse effects of excessive load on the equipment. Due to the loss of the fixed length of the clamping end, this will also lead to a decrease in the powder yield.

[0011] Therefore, there is still a long way to go for plasma rotating electrode atomization to better meet the medium and low particle size requirements of EBM and the particle size requirements of SLM through equipment improvement. How to jump out of the scope of equipment improvement and enable plasma rotating electrode atomization technology to obtain spherical tungsten powder with lower particle size has become a major research hotspot. Summary of the invention

[0012] In order to solve the problem that the plasma rotating electrode atomization technology in the prior art cannot meet the medium and low particle size requirements of EBM and the particle size requirements of SLM, and the yield is low, the present invention provides a method for preparing spherical tungsten powder by plasma rotating electrode atomization, and the steps are as follows:

[0013] The doped tungsten powder is subjected to isostatic pressing, medium frequency sintering, forging and machining to obtain a doped tungsten alloy electrode rod, wherein the boiling point of the doping component in the doped tungsten alloy electrode rod is lower than the melting point of tungsten or is not higher than 500° C. of the melting point of tungsten;

[0014] The doped tungsten alloy electrode rod is subjected to plasma rotating electrode atomization to obtain plasma rotating electrode atomized spherical tungsten powder.

[0015] In one embodiment, the processes of isostatic pressing, medium frequency sintering, forging, and machining are as follows:

[0016] Isostatic pressing: After the doped tungsten powder is mixed evenly, it is placed in a cold isostatic press for pressing. The maximum isostatic pressing pressure is 180-220 MPa, and the holding time is 80-160 seconds. After pressing, a green body is obtained.

[0017] Medium frequency sintering: Place the green body into a medium frequency sintering furnace and sinter under hydrogen protection. The maximum sintering temperature is 1900-2300℃, and the high temperature insulation time is 5-10h. After medium frequency sintering, sintered tungsten bars are obtained.

[0018] Forging: Forging the sintered tungsten bar on a fast forging machine or an air hammer, with a forging heating temperature of 1200-1700° C. and a deformation amount of 15%-30% to obtain a forged tungsten bar.

[0019] Machining: According to the requirements of the drawings, the forged tungsten rod is machined to obtain the doped tungsten alloy electrode rod.

[0020] In one embodiment, the operating temperature of the doped tungsten alloy electrode rod during the plasma rotating electrode atomization process is less than the boiling point of tungsten and higher than the boiling point of the doping component.

[0021] In one embodiment, the doping component is potassium and / or rare earth oxide.

[0022] In one embodiment, the rare earth oxide is one or a combination of lanthanum oxide, cerium oxide, and yttrium oxide.

[0023] In one embodiment, in the doped tungsten alloy electrode rod, the potassium content is 30-150 ppm by mass; and the rare earth oxide content is 0.1%-5%.

[0024] Preferably, when the doping component is potassium, the potassium content is 60 to 80 ppm;

[0025] Preferably, when the doping component is a rare earth oxide, the content of the rare earth oxide is 1% to 1.5%.

[0026] Preferably, when the doping components are potassium and rare earth oxides, the potassium content is 60-80 ppm, and the rare earth oxide content is 1%-1.5%.

[0027] In one embodiment, after the doped tungsten alloy electrode rod is subjected to plasma rotating electrode atomization, the obtained powder is subjected to surface treatment, and the surface treatment process is ultrasonic alcohol cleaning followed by vacuum drying.

[0028] In one embodiment, the doped tungsten powder is prepared by dry doping and / or wet doping.

[0029] Specifically, the wet doping process is:

[0030] When the doping component is a rare earth oxide, the raw material is a nitrate (such as lanthanum nitrate) or ammonium salt (such as lanthanum ammonium) of the corresponding rare earth element, which is configured in proportion to form a doping solution; when the doping component is potassium, the raw material is an aqueous solution of potassium silicate and aluminum nitrate, which is configured in proportion to form a doping solution. The doping process can specifically use a pressure spray gun to spray the dopant solution in the form of a spray onto the blue tungsten placed in the doping pot while stirring, and drying after the spraying is completed to obtain doped blue tungsten; the doped blue tungsten is reduced to obtain doped tungsten powder. Preferably, the doped tungsten powder with the doping component of potassium is reduced and then pickled to remove excess auxiliary agents. Specifically, the pickling process includes first washing with a hydrochloric acid solution, then washing with a hydrofluoric acid solution, and finally washing with deionized water and drying.

[0031] The dry doping process can be:

[0032] Directly add the rare earth oxide powder into the pure tungsten powder according to the proportion, stir and mix evenly with a high-speed mixer to obtain the doped tungsten powder.

[0033] Specifically, the specific methods of wet doping and dry doping can be adjusted by those skilled in the art according to actual conditions without limitation.

[0034] Furthermore, when the doping components are potassium and rare earth oxides, potassium can only be doped by wet doping. Then, the potassium-doped tungsten powder after acid washing can be added with rare earth oxides by dry doping, or the potassium-doped tungsten powder after acid washing and the rare earth oxide-doped tungsten powder after wet doping reduction can be mixed in proportion to obtain the doped tungsten powder with potassium and rare earth oxide as the doping components.

[0035] In one embodiment, the forming process of the doped tungsten alloy electrode rod is as follows: the doped tungsten powder is mixed evenly, isostatically pressed to obtain a green billet, and then sintered in a medium frequency induction furnace under hydrogen protection to obtain a billet with a relative density of more than 90%, and then the billet is forged to make the billet density reach more than 95%, and then the doped tungsten alloy electrode rod of the required specifications is machined.

[0036] In some embodiments, the plasma rotating electrode atomization is performed under argon protection, and the argon pressure is 0.04-0.12 MPa; the plasma rotating electrode atomization feed speed is 1.0-1.4 mm / s, the current is 3800-4000 A, and the rotation speed is 18000-20000 RPM.

[0037] In some embodiments, the tungsten content in the spherical tungsten powder atomized by the plasma rotating electrode is greater than 99.95%.

[0038] Based on the above, compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The method for preparing spherical tungsten powder by plasma rotating electrode atomization provided in an embodiment of the present invention adopts a doped tungsten alloy electrode rod instead of a pure tungsten electrode rod. In the process of plasma rotating electrode atomization powder making, without changing the equipment rotation speed and the electrode rod diameter, the method starts from the link of breaking the molten liquid film, and vaporizes the doped components in the doped tungsten alloy electrode rod while the tungsten material is melted, thereby blasting the liquid film, thereby achieving the effect of reducing the particle size of the final spherical tungsten powder, and then obtaining spherical tungsten powder with a lower particle size, effectively improving the yield of spherical tungsten powder prepared by plasma rotating electrode atomization that meets the low and medium particle size requirements of EBM and the particle size requirements of SLM.

[0040] 2. The method for preparing spherical tungsten powder by plasma rotating electrode atomization provided by the embodiment of the present invention uses potassium and / or rare earth oxide as doping components. During the plasma rotating electrode atomization process, the molten liquid film can be gasified to explode, thereby reducing the particle size of the spherical tungsten powder finally obtained. At the same time, the use of potassium and / or rare earth oxide as doping components can avoid alloying with tungsten, and most of the doping components will volatilize and escape during the plasma rotating electrode atomization process, which will not cause adverse effects on use.

[0041] 3. The method for preparing spherical tungsten powder by plasma rotating electrode atomization provided in an embodiment of the present invention adopts potassium and / or rare earth oxides as doping components, and at the same time controls the feed speed and current size of the plasma rotating electrode atomization process, so that the working temperature of the doped tungsten alloy electrode rod during the plasma rotating electrode atomization process is lower than the boiling point of tungsten and higher than the boiling point of the doping component, so that the doping component is vaporized without affecting the melting of tungsten and the performance of the spherical tungsten powder finally obtained.

[0042] 4. The plasma rotating electrode atomization spherical tungsten powder preparation method provided in the embodiment of the present invention adopts doping components and doped tungsten alloy electrode rods, which have a wide source of materials, mature technology, low overall improvement cost, and good promotion and application value.

[0043] Other features and beneficial effects of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other beneficial effects of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. The positional relationships described in the drawings in the following description are based on the directions in which the components are drawn in the diagrams, unless otherwise specified.

[0045] Figure 1 This is a photo of cracks on a tungsten alloy electrode rod due to excessive doping components.

[0046] Figure 2 This is a photo of a doped tungsten alloy electrode rod that was scrapped due to excessive doping.

[0047] Figure 3 This is a photo of a tungsten alloy electrode rod with too many doping components showing blocky peeling during the plasma rotating electrode atomization process.

[0048] Figure 4 The rare earth oxide distribution and energy spectrum of the spherical tungsten powder of Example 2.

[0049] Figure 5 The rare earth oxide distribution and energy spectrum of the spherical tungsten powder surface in Example 2.

[0050] Figure 6 This is the rare earth oxide distribution and energy spectrum of the spherical tungsten powder surface of Comparative Example 1. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; 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.

[0052] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and cannot be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in the present invention.

[0053] The present invention provides the following embodiments and comparative examples:

[0054] Example 1

[0055] The doped tungsten powder was prepared into a doped tungsten alloy electrode rod of φ50*L260mm, and then subjected to plasma rotating electrode atomization powder making. The plasma rotating electrode atomization powder making process was carried out at a feed rate of 1.2mm / s, a current of 3850A, and a rotation speed of 18500RPM to obtain spherical tungsten powder.

[0056] The doping component in the doped tungsten alloy electrode rod is potassium, and the potassium content is 42ppm.

[0057] Example 2

[0058] Except that the doping component in the doped tungsten alloy electrode rod is 0.87 wt % of lanthanum oxide, the rest is the same as Example 1.

[0059] Example 3

[0060] Except that the doping component in the doped tungsten alloy electrode rod is 30 ppm of potassium, the rest is the same as Example 1.

[0061] Example 4

[0062] Except that the doping component in the doped tungsten alloy electrode rod is 150 ppm of potassium, the rest is the same as Example 1.

[0063] Example 5

[0064] Except that the doping component in the doped tungsten alloy electrode rod is 0.1wt% of lanthanum oxide, the rest is the same as Example 1.

[0065] Example 6

[0066] Except that the doping component in the doped tungsten alloy electrode rod is 5 wt % of lanthanum oxide, the rest is the same as that in Example 1.

[0067] Example 7

[0068] Except that the doping component in the doped tungsten alloy electrode rod is 5 wt% of yttrium oxide, the rest is the same as that in Example 1.

[0069] Example 8

[0070] Except that the doping components in the doped tungsten alloy electrode rod are 0.1wt% lanthanum oxide and 150ppm potassium, the rest is the same as Example 1.

[0071] Example 9

[0072] Except that the doping components in the doped tungsten alloy electrode rod are 5wt% of lanthanum oxide and 30ppm of potassium, the rest is the same as Example 1.

[0073] Example 10

[0074] Except that the doping components in the doped tungsten alloy electrode rod are 1.5wt% of lanthanum oxide and 60ppm of potassium, the rest is the same as Example 1.

[0075] Embodiment 11

[0076] Except that the doping components in the doped tungsten alloy electrode rod are 1wt% of lanthanum oxide and 80ppm of potassium, the rest is the same as Example 1.

[0077] Comparative Example 1

[0078] Except for using pure tungsten electrode rods, the rest is the same as Example 1.

[0079] Comparative Example 2

[0080] Except that the doping component in the doped tungsten alloy electrode rod is 20 ppm of potassium, the rest is the same as Example 1.

[0081] Comparative Example 3

[0082] Except that the doping component in the doped tungsten alloy electrode rod is 180 ppm of potassium, the rest is the same as Example 1.

[0083] The forging of the doped tungsten alloy electrode rods resulted in cracks, which led to scrapping. At the same time, the plasma rotating electrode atomization process caused peeling, which caused equipment pollution. Figures 1 to 3 shown.

[0084] Comparative Example 4

[0085] Except that the doping component in the doped tungsten alloy electrode rod is 0.05wt% of lanthanum oxide, the rest is the same as Example 1.

[0086] Comparative Example 5

[0087] Except that the doping component in the doped tungsten alloy electrode rod is 5.5 wt % of lanthanum oxide, the rest is the same as that in Example 1.

[0088] The forging of the doped tungsten alloy electrode rods resulted in cracks, which led to scrapping. At the same time, the plasma rotating electrode atomization process caused peeling, which caused equipment pollution. Figures 1 to 3 At the same time, spherical tungsten powder with hollow interior appears in the final product, and the yield rate decreases.

[0089] The doping components in the doped tungsten alloy electrode rods used in the examples and comparative examples are shown in Table 1. The specific preparation method is as follows:

[0090] The doped tungsten powder of a set proportion is obtained by wet doping. After the doped tungsten powder is evenly mixed, it is put into a cold isostatic press for pressing. The maximum pressure is 200 MPa and the holding time is 120 s. After pressing, a green body is obtained.

[0091] The green body is placed in a medium frequency sintering furnace and sintered under hydrogen protection. The maximum sintering temperature is 2100°C and the high temperature holding time is 8 hours. After medium frequency sintering, a sintered tungsten bar is obtained. The relative density of the sintered tungsten bar is 90%.

[0092] The sintered tungsten bar is forged on a fast forging machine with a forging heating temperature of 1500°C and a pass deformation of 20%. After the density is 95%, a forged tungsten bar is obtained.

[0093] The forged tungsten bar is machined to obtain a doped tungsten alloy electrode rod of φ50*L260mm.

[0094] Table 1 Doping component contents of examples and comparative examples

[0095]

[0096]

[0097] The spherical tungsten powders of Examples 1 to 11 and Comparative Examples 1 to 5 were subjected to a 100-mesh primary sieving and a 140-mesh secondary sieving, and the yield and particle size distribution of the spherical tungsten powders obtained by the two sieving were statistically analyzed. The specific results are shown in Table 2.

[0098] Table 2 Particle size distribution and yield of examples and comparative examples

[0099]

[0100] Note: -140 mesh yield is the yield of spherical tungsten powder sieved through 100 mesh and then sieved through 140 mesh.

[0101] As shown in Table 2, it can be seen from Examples 1 to 11 and Comparative Example 1 that the particle size distribution of the spherical tungsten powders of Examples 1 to 11 is significantly lower than that of the spherical tungsten powders prepared from the pure tungsten electrode rod. At the same time, it can be seen that the overall yield of the spherical tungsten powders of Examples 1 to 11 after continuous 100 mesh and 140 mesh screening is higher than that of Comparative Example 1, indicating that the plasma rotating electrode atomization spherical tungsten powder preparation method provided by the present invention can effectively reduce the particle size of the spherical tungsten powder while improving the yield of the spherical tungsten powder of the target specification, and can effectively reduce the cost.

[0102] At the same time, according to the data in Table 2 and Figures 1 to 3It can be seen that when the content of doping components in the doped tungsten alloy electrode rod is small, the effect of improving the particle size of the final spherical tungsten powder is not obvious, resulting in poor overall economic efficiency; when the content of doping components in the doped tungsten alloy electrode rod is too large, the processing performance of the doped tungsten alloy electrode rod will be poor, and it is easy to crack and scrap. In addition, block peeling occurs during the plasma spheroidization powder making process, resulting in a low spherical powder yield. And when the doping component is a rare earth oxide, the content of the doping component is likely to lead to an increase in hollow sphere powder, causing difficult-to-remove pollution to the plasma spheroidization powder making equipment.

[0103] Moreover, it can be seen from the data in Table 2 that the D10 of the spherical tungsten powder after 140 mesh screening in the embodiments has been able to be reduced to a scale of 50 μm or even 40 μm, indicating that at least 10% of the spherical tungsten powder in some embodiments can fully meet the particle size range of 15 to 53 μm required by SLM, effectively improving the yield of spherical tungsten powder prepared by plasma rotating electrode atomization that meets the medium and low particle size requirements of EBM and the particle size requirements of SLM.

[0104] The spherical tungsten powders of Examples 1 to 11 and Comparative Examples 1 to 5 were tested for element content after surface treatment. The specific results are shown in Table 3.

[0105] Table 3 Element contents of examples and comparative examples

[0106]

[0107]

[0108] Note: Except for the rare earth oxide in Example 7 which is yttrium oxide, the others are all lanthanum oxide. Meanwhile, the element contents are all tested after surface treatment.

[0109] It can be seen from the data in Table 3 that the element contents of Examples 1 to 11 are not much different from those of Comparative Example 1, and both meet the standard of tungsten content ≥ 99.95%.

[0110] At the same time, it can be seen from Example 1 and Examples 3 to 4 that when the doping component is only potassium, the element content of the spherical tungsten powder in the example is equivalent to the spherical tungsten powder made from the pure tungsten electrode rod in Comparative Example 1, and only a very small amount of potassium remains, indicating that most of the doped potassium is vaporized and leaves the spherical tungsten powder, with little effect on the element content.

[0111] The rare earth oxide in the doping component only slightly increases the content of rare earth oxide and oxygen in the elements, and the overall tungsten content still meets the standard of ≥99.95%.

[0112] Further, electron microscope scanning and energy spectrum analysis were performed on Example 2 and Comparative Example 1, and the specific results are as follows: Figures 4 to 6The element contents of the doped tungsten alloy electrode rod, the spherical tungsten powder and the spherical tungsten powder after surface treatment in Example 2 were analyzed, and the specific data are shown in Table 4.

[0113] Table 4 Element contents of doped tungsten alloy electrode rod and before and after surface treatment in Example 2

[0114]

[0115] Depend on Figures 4 to 6 As can be seen from Table 4, in the final spherical tungsten powder, only a trace amount of rare earth oxide remains inside the spherical powder, most of it is extracted after volatilization, and a small amount adheres to the surface of the spherical tungsten powder in the form of nano floccules. After surface treatment, only a trace amount of rare earth oxide remains, making the product meet the standards.

[0116] Furthermore, surface treatment may be performed to improve the purity of the spherical tungsten powder; or surface treatment may not be performed to retain the nano-flocculated rare earth oxide on the surface of the spherical tungsten powder, thereby obtaining new printed product performance. Those skilled in the art may make a choice according to needs.

[0117] Furthermore, by comparing the element contents before and after surface treatment when the doping component is only potassium, it is found that the surface treatment has almost no effect on the element content. When the doping component is only potassium, the surface treatment step can be omitted, and technicians in this field can make adjustments based on actual conditions.

[0118] In summary, compared with the prior art, the method for preparing spherical tungsten powder by plasma rotating electrode atomization provided by the present invention adopts a doped tungsten alloy electrode rod instead of a pure tungsten electrode rod, and obtains spherical tungsten powder with a lower particle size without changing the equipment rotation speed and the electrode rod diameter, thereby effectively improving the yield of spherical tungsten powder prepared by plasma rotating electrode atomization that meets the low and medium particle size requirements of EBM and the particle size requirements of SLM.

[0119] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention can be improved in only one or several aspects, without having to solve all the technical problems listed in the prior art or background technology at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be used as a limitation on the claim.

[0120] Although the terms such as doped tungsten powder, doped tungsten alloy electrode rod, plasma rotating electrode atomization, etc. are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention; the terms "first", "second", etc. (if any) in the description and claims of the embodiments of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing spherical tungsten powder by plasma rotating electrode atomization, characterized in that: Here are the steps: The doped tungsten powder is subjected to isostatic pressing, medium frequency sintering, forging and machining to obtain a doped tungsten alloy electrode rod, wherein the doping component in the doped tungsten alloy electrode rod is potassium and / or rare earth oxide; the rare earth oxide is one or a combination of lanthanum oxide, cerium oxide and yttrium oxide; The doped tungsten alloy electrode rod is subjected to plasma rotating electrode atomization to obtain plasma rotating electrode atomized spherical tungsten powder; the operating temperature of the doped tungsten alloy electrode rod during the plasma rotating electrode atomization process is less than the boiling point of tungsten and higher than the boiling point of the doping component; In the doped tungsten alloy electrode rod, the potassium content is 30 to 150 ppm by mass; the rare earth oxide content is 0.1% to 5%.

2. The method for preparing spherical tungsten powder by plasma rotating electrode atomization according to claim 1, characterized in that: After the doped tungsten alloy electrode rod is subjected to plasma rotating electrode atomization, the obtained powder is subjected to surface treatment, and the surface treatment process comprises ultrasonic alcohol cleaning followed by vacuum drying.

3. The method for preparing spherical tungsten powder by plasma rotating electrode atomization according to claim 1, characterized in that: The doped tungsten powder is prepared by dry doping and / or wet doping.

4. The method for preparing spherical tungsten powder by plasma rotating electrode atomization according to claim 1, characterized in that: The uniformly mixed doped tungsten powder is isostatically pressed to obtain a green billet, which is then sintered in a medium frequency induction furnace under hydrogen protection to obtain a billet with a relative density of more than 90%. The billet is then forged to achieve a density of more than 95%, and then machined into the doped tungsten alloy electrode rod.

5. The method for preparing spherical tungsten powder by plasma rotating electrode atomization according to claim 1, characterized in that: The plasma rotating electrode atomization is carried out under the protection of argon gas, and the argon gas pressure is 0.04-0.12 MPa; the plasma rotating electrode atomization feed speed is 1.0-1.4 mm / s, the current is 3800-4000 A, and the rotation speed is 18000-20000 RPM.

6. The method for preparing spherical tungsten powder by plasma rotating electrode atomization according to claim 1, characterized in that: The tungsten content in the plasma rotating electrode atomized spherical tungsten powder is greater than 99.95%.

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