Manufacturing process of spherical titanium alloy powder

Abstract

The invention provides a manufacturing process of spherical titanium alloy powder, which comprises the following steps: mixing titanium hydride powder and an adhesive, internally mixing, granulating, primarily shaping, screening, drying, mixing with an active metal simple substance, performing vacuum degreasing and sintering to obtain a sintered block, and performing chemical corrosion, crushing, fine grinding and secondary shaping to finally obtain high-sphericity titanium alloy powder. According to the process, the sphericity degree of the powder reaches 50% or above in the primary shaping process and is further improved to 70% or above in the secondary shaping process, and the flowability, the filling density and the sintering uniformity of the powder are effectively improved. Meanwhile, active metal elementary substances are introduced in the vacuum degreasing and sintering process to serve as sacrificial agents, the dehydrogenation and deoxidation efficiency is improved, oxygen impurity residues are reduced, and the compactness and purity of titanium alloy products are improved. Besides, by accurately controlling the drying temperature, humidity and time and optimizing the temperature, the heating rate and the vacuum degree of each stage of vacuum degreasing sintering, the uniformity and the material performance of the sintered block are remarkably enhanced. The process is efficient, low in energy consumption and suitable for titanium alloy near-net forming, and has good industrial application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy powder metallurgy, in particular to a process for preparing spherical titanium alloy powder. BACKGROUND

[0002] Titanium hydride is a metal compound formed by titanium and hydrogen, which is usually prepared by hydrogenation process such as calcium reduction method, and is mainly used as a raw material precursor of titanium alloy products. Through subsequent dehydrogenation treatment, high-purity titanium powder can be obtained, which avoids the oxidation problem caused by high temperature in the traditional smelting process. In powder metallurgy, titanium hydride powder needs to go through processes such as ball milling, vacuum degreasing and sintering, and finally forms a dense titanium alloy component. This process route has the advantages of high efficiency and low energy consumption, and is an important technical path for near-net-shape forming of titanium alloy.

[0003] Although titanium hydride powder has good chemical activity, its particle morphology is often irregular polyhedron or flaky structure with low sphericity. Titanium hydride powder has low toughness and high brittleness, and is prone to fracture rather than plastic deformation during mechanical ball milling. It is difficult to achieve spheroidization through conventional impact energy. In addition, the rapid escape of hydrogen during vacuum degreasing stage will cause the collapse of the internal structure of the particles, further damage the surface integrity, and exacerbate the irregularity of the shape, resulting in insufficient sphericity, which directly affects the flowability, packing density and sintering uniformity of the powder, and becomes a key factor restricting the performance of titanium alloy products.

[0004] Titanium hydride powder needs to be sintered in a high-temperature inert environment, but there is still a risk of oxygen absorption in the actual process. On the one hand, trace amounts of water or residual oxides adsorbed on the surface of the powder may release active oxygen during the heating process. On the other hand, the fresh titanium surface generated after the dehydrogenation of titanium hydride is prone to react with residual oxygen to form an oxide layer such as titanium oxide. The introduction of oxygen impurities will significantly reduce the plasticity and fatigue life of titanium alloy, and the adsorption of oxygen impurities will also cause the adhesion of titanium alloy powder, which will reduce the sphericity and affect the densification process of the sintered body. Although existing vacuum or atmosphere protection measures can alleviate the problem, they cannot completely eliminate oxygen pollution, which limits the purity and performance of the product. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, provide a process for preparing spherical titanium alloy powder, and improve the sphericity of titanium hydride powder to facilitate the production of titanium alloy products with better quality through vacuum sintering and other methods.

[0006] To achieve the above-mentioned purpose, the technical solutions provided by the present application are as follows.

[0007] A process for preparing spherical titanium alloy, comprising the following steps: S1, mixing titanium hydride powder with a binder and performing banbury mixing; S2, granulating the mixed titanium hydride powder; S3, primary shaping the granulated titanium hydride powder; S4, sieving the primary shaped titanium hydride powder to obtain titanium hydride powder within a certain particle size range for standby; S5, drying the sieved titanium hydride powder; S6, mixing the dried titanium hydride powder with active metal elements and vacuum debinding sintering to obtain sintered blocks; S7, sequentially performing chemical etching, crushing, fine grinding, and secondary shaping on the vacuum debinding sintered blocks, wherein the etching is used to remove the hydride and oxide of the active metal elements.

[0008] The titanium hydride powder is an intermetallic compound formed by the combination of titanium and hydrogen, which has good chemical activity and low sintering temperature, and is often used as a precursor for preparing titanium alloy powder. In the present application, it specifically includes but is not limited to semi-hydrogenated or semi-dehydrogenated titanium alloy. The binder refers to an organic or inorganic material used to enhance the bonding force between powder particles during the mixing process, which helps subsequent granulation and forming operations. In the mixing step, the titanium hydride powder is mixed with the binder under high temperature and high shear conditions to uniformly coat the binder on the surface of the powder, thereby improving the plasticity and fluidity of the powder and laying a foundation for subsequent granulation.

[0009] The granulation stage breaks the mixed powder lumps and forms particles with a certain particle size through a granulation process. The purpose of this step is to obtain granular powder suitable for subsequent processing, so that it has good fluidity and bulk density, and at the same time avoids the problems of caking or uneven dispersion of the powder in subsequent processing. The particle size of the granulated powder is usually controlled between 10-75 μm to meet the needs of shaping and sieving. Here, the particle size control can be for fine powder with a particle size below 25 μm, or coarse powder with a particle size of 25-75 μm; it is worth noting that the particle size control at this time needs to consider the particle size reduction caused by subsequent crushing process, so it is necessary to appropriately increase the particle size in raw material selection compared to the target particle size.

[0010] Primary shaping is to improve the sphericity of the powder by mechanical force or thermal action, so that the corners of the powder particles are removed and the shape tends to be regularized, with a sphericity of more than 50%. The purpose of this step is to improve the flowability and filling performance of the powder, and to provide protection for obtaining uniform and dense structure in the subsequent sintering process. Sieving is a particle size screening of the shaped powder to ensure that the powder particle size distribution entering the next stage is concentrated and uniform.

[0011] The term "sphericity" refers to the ratio of the surface area of a sphere with the same volume as the object to the surface area of the object.

[0012] The drying step is a dehydration treatment of the sieved powder under controlled temperature, humidity, and time conditions to remove water or other volatile substances that may be adsorbed in the powder, preventing the destruction of the powder structure or the decline of the sintering quality due to water evaporation in the subsequent vacuum debinding sintering process.

[0013] After the dried titanium hydride powder is mixed with the active metal element, it undergoes four stages of dehydration, debinding, dehydrogenation and sintering in vacuum. The active metal element acts as a "sacrificial agent" in this process, reacting with hydrogen and oxygen to form easily removable hydrides and oxides, thereby effectively reducing the oxygen impurity content in the powder, improving the dehydrogenation efficiency and the purity and density of the final product. Vacuum debinding sintering not only removes the binder, but also completes the dehydrogenation reduction and sintering densification of titanium hydride, ultimately forming a sintered block with certain strength.

[0014] The post-processing step includes chemical etching, crushing, fine grinding, and secondary shaping. Chemical etching removes the hydrides and oxides left after the reaction of the active metal element by acid or alkali washing, ensuring high purity of the powder.

[0015] As a preferred technical solution, in S1, the particle size of the titanium hydride powder ranges from 0.1 to 45 μm, and the mass ratio of the binder to the titanium hydride powder is 1-10:100.

[0016] The titanium hydride powder, as the core raw material of the present application, has a particle size range of 0.1-45 μm, which can effectively ensure its uniform mixing with the binder during the banburying process, and has good plasticity and formability, which is conducive to the smooth progress of subsequent steps such as granulation, shaping and sintering. The specific surface area of the powder in this particle size range is moderate, which can effectively prevent the agglomeration phenomenon caused by too small particle size, and can also prevent the influence on the denseness and sphericity of the final product caused by too large particle size.

[0017] The binder plays the role of enhancing the bonding force between the titanium hydride powder particles in this step, improving the flowability and formability of the powder, and thus improving the granulation efficiency and shaping effect. The mass ratio of the binder to the titanium hydride powder is controlled within the range of 1-10:100. If the proportion of the binder is too low, the adhesion between the particles cannot be effectively enhanced, resulting in poor granulation effect; if the proportion is too high, the binder may be difficult to completely remove in the subsequent debinding stage, affecting the sintering quality, even introducing impurities or causing an increase in internal porosity, reducing the density and purity of the final titanium alloy powder.

[0018] As a preferred technical solution, in S2, the particle size of the granulated titanium hydride powder after banburying ranges from 10 to 75 μm. Compared with S1, the particle size increases due to the agglomeration, surface adhesion of the binder, etc. of the titanium hydride powder after banburying.

[0019] In the granulation process, the particle size control can be achieved by adjusting the speed of the granulator, the amount of spraying, the drying temperature and other parameters. The particle size range of 10-75 μm is suitable for various granulation methods such as spray granulation, extrusion granulation, high-speed shearing granulation, etc. This particle size range also provides good basic conditions for the subsequent screening and drying steps. The screening is easy to separate the powder with the qualified particle size range, avoiding the density unevenness or sintering defects in the subsequent sintering process due to the large difference in particle size. In the drying process, the particles with moderate particle size have good thermal conductivity and volatile matter removal efficiency, which helps to reduce the internal structural defects of the powder.

[0020] As a preferred technical solution, in S3, the sphericity of the titanium hydride powder obtained by the first shaping is ≥ 50%.

[0021] The method of first shaping can adopt existing technologies including but not limited to ball milling, jet milling, plasma spheroidization, etc. The particle morphology is corrected by physical, chemical, mechanical and other methods. Herein, no further description is given.

[0022] Titanium hydride powder is not easy to achieve spheroidization in conventional mechanical processing due to its characteristics of large brittleness and poor plasticity. Therefore, it must be effectively shaped by specific process means. Usually, mechanical ball milling, air flow impact or centrifugal granulation is used. The principle is to control the impact force, friction force or heat to round the corners of the powder particle surface, so as to gradually approach the spherical structure.

[0023] As a preferred technical solution, in S4, the particle size range of the titanium hydride powder after screening is 10-75 μm.

[0024] In order to ensure that the titanium hydride powder entering the subsequent drying and vacuum debinding sintering stage has a uniform and suitable particle size distribution, thereby ensuring the stability of the entire process and the consistency of the performance of the final product. After completing S3 first shaping, the sphericity of the powder particles has been improved, but there may still be a large difference in particle size between the particles. The second screening controls the particle size in the range of 10-75 μm, removes the unqualified particles that are too large or too small, and ensures that the titanium hydride powder entering the next stage has good particle size consistency.

[0025] It should be noted that the particle size screening range in S4 is the same as that in S2, and the purpose is to obtain titanium hydride powder with a preset particle size. In S2, the titanium hydride powder in S1 is obtained, such as 90wt.% of the particle size range. After S4 treatment, titanium hydride powder in S1 may be obtained, such as 80wt.% of the particle size range. Although the particle size ranges are the same, in fact, it refers to the second screening relative to S2, rather than repeating the steps or limiting the technical effect of S3 first shaping.

[0026] As a preferred technical solution, in the S5, the drying temperature is 35-90 DEG C, the drying humidity is 1-10%, and the drying time is 20-60 minutes.

[0027] The drying temperature is controlled in the range of 35-90 DEG C, which is based on the balance between the thermal stability of titanium hydride powder and the water removal efficiency; the relative humidity of the drying environment is controlled in the range of 1-10%, in order to create a low humidity environment, which is beneficial to the rapid escape of water and prevents the powder from reabsorbing moisture during the drying process.

[0028] As a preferred technical solution, in the S6, the vacuum debinding and sintering is carried out by using a vacuum debinding and sintering furnace, including a dehydration stage, a debinding stage, a dehydrogenation and deoxygenation stage, and a sintering stage. The temperature of the dehydration stage is 35-120 DEG C, and the dehydration is completed when the vacuum degree is reduced to 50-500 pa; The temperature of the debinding stage is 120-500 DEG C, and the debinding is completed when the vacuum degree is reduced to 50-1000 pa; The dehydrogenation and deoxygenation stage adopts a heating rate of 2-20 DEG C / h to 600-800 DEG C, and the dehydrogenation and deoxygenation are completed when the vacuum degree is reduced to 50-1000 pa; The temperature of the sintering stage is 1000-1300 DEG C, and the sintering is completed when the vacuum degree is reduced to 10-200 pa after the temperature is maintained at a preset temperature.

[0029] The dehydration stage is to remove the physical water absorbed by the titanium hydride powder and the binder mixture and part of the volatile impurities. The temperature of this stage should not be too high, so as to prevent the binder from decomposing or producing intense volatilization, causing the powder structure to be damaged or partially hollow. The debinding stage makes the binder gradually decompose and volatilize under high-temperature vacuum conditions.

[0030] Since the binder is mostly organic, its decomposition process has stages, so a step-by-step heating method can be used to avoid the rupture of powder particles or loose structure caused by the expansion of internal gas due to rapid heating. In the dehydrogenation and deoxygenation stage, the titanium hydride powder releases hydrogen elements at high temperature, and at the same time, the active metal elements react with oxygen elements to generate volatile hydrides and oxides, thereby realizing efficient dehydrogenation and deoxygenation. Slow heating is beneficial to the uniform reaction, avoiding local overheating or intense reaction, and ensuring the complete removal of hydrogen and oxygen impurities.

[0031] In the sintering stage, the powder particles diffuse and recrystallize at high temperature, gradually densify, and form a sintered block with certain strength. The vacuum environment helps maintain the purity of the system and prevents the titanium alloy from reacting with oxygen or water vapor at high temperature to form an oxide layer, affecting the final material performance. The sintering temperature needs to be adjusted according to the composition of the titanium hydride powder and the type of active metal element to ensure maximum densification without melting.

[0032] As a preferred technical solution, in S6, the active metal element includes at least one of lithium, potassium, barium, calcium, sodium, magnesium, and aluminum, and the mixing mass ratio of the active metal element to the titanium hydride powder is (1-5):100.

[0033] The active metal elements listed in the application are all metal elements with high chemical activity and low electronegativity. They can react with hydrogen and oxygen in the titanium hydride powder under high-temperature vacuum conditions to form corresponding metal hydrides and metal oxides.

[0034] The active metal element needs to react with hydrogen and oxygen in the titanium hydride. If the addition ratio is too low, it cannot provide enough reactants, leading to insufficient dehydrogenation and deoxidation, and high residual impurity content. If the addition ratio is too high, it may cause an excess of active metal elements, not only increasing the cost, but also making it difficult to completely remove the reaction products in the subsequent chemical corrosion process, affecting the purity of the final titanium alloy powder.

[0035] As a preferred technical solution, in S6, the holding time of the sintering stage meets the condition that the effective output power of the vacuum debinding sintering furnace is greater than or equal to 1.2 times the sintering calculation power.

[0036] In the above technical features, by introducing the power matching principle, it is ensured that the vacuum debinding sintering furnace has sufficient heating capacity in the sintering stage to maintain uniform heating and densification of the powder at high temperature.

[0037] The effective output power calculation process of the vacuum debinding sintering furnace considers the theoretical required heat (J) as Q=mC p ΔT, m is the mass of the material (kg), C p is the specific heat capacity (J / g·℃), and ΔT is the temperature rise range (℃). The calculated power P (W) is considered after considering the thermal efficiency, and the required power is the sintering calculation power.

[0038] As a preferred technical solution, in S7, the chemical corrosion method includes pickling and / or alkali washing, and after pickling and / or alkali washing, the sintered block is vacuum dried.

[0039] The above technical features aim to remove active metal elements and their reaction products such as metal hydride and metal oxide introduced in the vacuum debinding sintering process, so as to obtain high-purity titanium alloy powder. Since these impurities are difficult to be physically removed in the subsequent crushing, grinding and shaping processes, it is necessary to effectively remove them by chemical corrosion to ensure the performance stability and application reliability of the final product.

[0040] It should be noted that when the acid or alkali dosage is relatively low, such as the total amount of active metal elements being less than 5% of the total mass of titanium hydride powder, the residual acid or alkali can be left without cleaning, and no obvious adverse effects are found in subsequent experiments. However, for relatively high dosages, deionized water can be used to remove the residual acid or alkali under a protective atmosphere.

[0041] The active metal elements can have a certain amount of surface oxidation, corrosion, etc., but as a sacrificial agent, they should have sufficient elemental substances to combine with the free hydrogen or free oxygen of the titanium hydride powder. For different active metal elements, the dosage, especially the content of elemental substances, is preferably not less than the hydrogenation amount of titanium hydride, which can be 1.05-2 times the hydrogenation equivalent of titanium hydride. Using active metal elements with high oxidation properties, the container containing the active metal elements can be transferred to a vacuum box for operation, or it can be crushed into powder again in the vacuum box to retain the role of the sacrificial agent without excessive oxidation impurities. Although the industrial dosage can be increased to 3-5% to overcome this problem, it will also cause inconvenience in subsequent chemical corrosion.

[0042] As a preferred technical solution, in S7, the sintered block is crushed to a particle size range of 0.3-3 mm by a jaw crusher.

[0043] The above technical features aim to preliminarily crush the dense sintered block formed after vacuum debinding sintering, so as to convert it into intermediate granular material suitable for subsequent grinding and secondary shaping operations. Since the sintered block usually has high hardness and strength, it is difficult to grind or shape directly, so it is necessary to control the particle size within a reasonable range through the crushing process to improve the subsequent processing efficiency and powder quality. If the particle size is too small, it means that the crushing strength is too high, which may cause excessive crushing of the particles, resulting in a large amount of fine powder and affecting the subsequent screening and shaping efficiency. If the particle size is too large, it is not conducive to uniform processing by subsequent jet milling or ball milling shaping, which may cause local overheating, increased energy consumption or uneven powder particle size distribution.

[0044] As a preferred technical solution, in the S7, the fine grinding adopts an air flow crusher to finely grind the particles after the completion of the crushing to a particle size range of 1-75 mu m. Through the air flow crushing process, the titanium alloy particles after the crushing treatment are efficiently and finely controlled in particle size, so as to reach the required particle size range for subsequent shaping, powder laying, sintering or 3D printing and other applications, to provide an adaptive particle size for the secondary shaping, and the powder with a moderate particle size is more easily to remove the corners and improve the sphericity in the shaping process.

[0045] As a preferred technical solution, in the S7, the secondary shaping adopts a horizontal ball mill or an air flow mill to remove the corners of the powder, and the oxygen content in the horizontal ball mill and / or the air flow mill is ≤100 ppm, so that the sphericity of the titanium hydride powder is ≥70%.

[0046] The above technical features aim to further improve the sphericity of the titanium hydride powder on the basis of the primary shaping through the secondary shaping process, so that the sphericity is ≥70%, thereby significantly improving the flowability, packing density, powder laying uniformity and sintering density of the powder, and meeting the needs of the high-end manufacturing field such as powder metallurgy, near-net shaping and 3D printing for high-performance titanium alloy powder.

[0047] Specifically, the horizontal ball mill drives the grinding medium (such as zirconia ball) to collide and rub with the powder particles through the rotation of the cylinder, gradually rounding the corners of the particles, and can realize continuous production. The air flow mill utilizes high-speed airflow to drive the powder particles to collide and rub with each other, remove the corners and improve the sphericity, without grinding medium to avoid the introduction of impurities.

[0048] The advantages and beneficial effects of the present application are that the multiple shaping process is introduced, the sphericity is ≥50% in the primary shaping process, and is further improved to ≥70% in the secondary shaping. After improving the sphericity of the powder, the flowability, packing density and sintering uniformity of the powder are improved. In the process of vacuum debinding and sintering, the active metal element is introduced, in the process of vacuum sintering, the active metal element acts as a sacrificial agent and reacts with titanium hydride to enrich hydrogen and oxygen elements, improve the dehydrogenation and deoxygenation efficiency, reduce the residual oxygen impurities, and improve the densification process of the sintered block. In the subsequent process, the active metal element after the reaction is removed by chemical corrosion, so as to retain the titanium hydride powder with low hydrogen and oxygen element contents, and improve the purity and performance of the final titanium alloy product. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a process flow chart of the spherical titanium alloy powder preparation process shown in the present application. DETAILED DESCRIPTION

[0050] In order to enable the above-mentioned objects, features and advantages of the present application to be more clearly understood, further specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0052] In order to enable the above-mentioned objects, features and advantages of the present application to be more clearly understood, further specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0053] Embodiment 1 The embodiment provides a manufacturing process of a spherical titanium alloy, and specifically comprises the following steps. S1, titanium hydride powder with a particle size of 25-45 μm is mixed with a binder (acrylic resin) at a mass ratio of 1:100, and then is subjected to mixing in a mixer at 60°C for 1 hour. The mixing process ensures that the titanium hydride powder is fully combined with the binder, thereby improving the subsequent granulation efficiency and powder uniformity.

[0054] S2, the mixed titanium hydride powder is subjected to a granulation process, so that the particle size of the granulated powder is controlled within the range of 10-75 μm. This particle size range facilitates the subsequent shaping and screening operations.

[0055] S3, the granulated titanium hydride powder is subjected to primary shaping, so that the sphericity of the powder particles reaches ≥50%. This step can significantly improve the flowability and filling performance of the powder.

[0056] S4, the primary shaped titanium hydride powder is screened, and the qualified powder with a particle size within the range of 10-75 μm is selected as the raw material for the subsequent drying treatment.

[0057] S5, the screened titanium hydride powder is subjected to drying treatment in a dry environment with a temperature of 35°C and a humidity of 10%, and the drying time is controlled within 30 minutes, so as to ensure that the powder is fully dehydrated and the subsequent vacuum degreasing stage is avoided.

[0058] S6, the dried titanium hydride powder is mixed with active metal elements (magnesium) at a mass ratio of (1-5):100, and then is placed in a vacuum degreasing sintering furnace for sintering. The specific sintering process comprises the following stages: dehydration stage, the temperature is controlled at 100°C, and the vacuum degree is reduced to 1000 Pa to complete the dehydration; degreasing stage, the temperature is increased to 300°C, and the vacuum degree is reduced to 500 Pa to complete the degreasing; Dehydrogenation and deoxidation stage, the temperature is raised to 800℃ at a rate of 2-20℃ / h, and the vacuum degree is reduced to 100Pa to complete the dehydrogenation and deoxidation; Sintering stage, the temperature is raised to 1300℃ at a rate of 2℃ / min, and the vacuum degree is reduced to 10Pa to complete the sintering, and the holding time is set according to the effective output power of the sintering furnace being greater than or equal to 1.2 times the calculated sintering power.

[0059] S7, the sintered block is sequentially subjected to the following treatments: Chemical corrosion, using 0.1mol / L dilute nitric acid to remove hydride and oxide of active metal elements, and after corrosion, vacuum drying is performed to remove the residual dilute nitric acid solution on the surface of the sintered block, and the small amount of residual nitrate and hydrogen ions on the surface of the sintered block can be ignored; Crushing, using a jaw crusher to crush the sintered block to a particle size of 0.3-3mm; Fine grinding, using an air jet mill to fine grind the particles to a particle size of 1-75μm; Secondary shaping, using a horizontal ball mill or an air jet mill to remove powder edges, the oxygen content in the equipment is ≤100ppm, and finally the sphericity of the titanium hydride powder is ≥70%, thereby obtaining a titanium alloy powder with high sphericity and high purity.

[0060] Preferably, the binder can be selected from thermoplastic resins such as polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), etc.; cellulose derivatives such as hydroxypropyl methylcellulose (HPMC), ethyl cellulose (EC); waxes such as paraffin wax, polyethylene wax (PE Wax), and a compounded system of the above. The selection of the binder requires good compatibility with the titanium hydride powder; it can be completely pyrolyzed and removed at a relatively low temperature, especially at 300℃, to avoid residual as much as possible; at the same time, it does not or is difficult to chemically react with the metal powder; it is easy to disperse uniformly, and does not affect the subsequent shaping and sintering process.

[0061] Preferably, in the process of vacuum debinding and sintering, the active metal elements are used as "sacrificial agents" to capture hydrogen and oxygen elements, thereby improving the dehydrogenation and deoxidation efficiency, reducing the oxygen content in the final powder, and improving the material performance. The active metal elements suitable for this process include alkali metals such as sodium (Na), potassium (K); alkaline earth metals such as calcium (Ca), barium (Ba), magnesium (Mg); transition metals such as aluminum (Al), and mixtures or alloys of the above metals. The selection of the active metal elements requires strong reaction ability with oxygen and hydrogen, and the reaction products are easy to remove by chemical corrosion, and at the same time, do not introduce impurity elements that are difficult to remove; the activity of the active metal should not be too high, and it should mildly react with the titanium hydride powder to avoid violent heat release or structural damage.

[0062] Preferably, the chemical corrosion method can be selected from acid washing, such as dilute hydrochloric acid (HCl), dilute sulfuric acid (H2SO4), dilute nitric acid (HNO3), hydrofluoric acid (HF), etc.; alkali washing such as sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.; acid washing followed by alkali washing, or alternating use, can also be used to improve removal efficiency; if necessary, ultrasonic assistance can be introduced to improve corrosion effect; when some metal oxide residues are difficult to remove, complexing agents such as ethylenediaminetetraacetic acid (EDTA) can be used to remove residual metal ions.

[0063] It is necessary to control the concentration of the corrosion solution and the processing time to prevent the titanium alloy powder from being excessively corroded. After corrosion, the powder should be thoroughly cleaned to remove the acid / alkali residues. The chemical corrosion operation should be carried out in a sealed protective condition such as a vacuum glove box to avoid re-oxidation of the titanium hydride powder during the corrosion process, resulting in poor effect. After the corrosion is completed, vacuum drying is performed to prevent the powder from absorbing moisture and oxidizing.

[0064]

Example 2

[0065] In S6, the active metal element is aluminum, and the mixing mass ratio of the aluminum to the titanium hydride powder is 3:100. The vacuum debinding and sintering are as follows.

[0066] In the dehydration stage, the temperature is 80℃, and the dehydration is completed when the vacuum degree is reduced to 300 Pa; In the debinding stage, the temperature is 400℃, and the debinding is completed when the vacuum degree is reduced to 800 Pa; In the dehydrogenation and deoxidation stage, the temperature is increased to 700℃ at a rate of 10℃ / h, and the dehydrogenation and deoxidation are completed when the vacuum degree is reduced to 500 Pa; In the sintering stage, the temperature is 1200℃, and the sintering is completed when the vacuum degree is reduced to 50 Pa. The holding time is set according to the effective output power of the sintering furnace being ≥1.2 times the calculated sintering power.

[0067] In S7, chemical corrosion is performed using a mixture of 1 mol / L hydrofluoric acid and nitric acid (volume ratio 1:3) for acid washing. After the corrosion is completed, vacuum drying is performed to remove the residual acid.

[0068]

Example 3

[0069] In S2, the particle size of the granulated powder is controlled to be 50 μm.

[0070] The drying temperature in S5 is 60℃, the humidity is 5%, and the drying time is 40 minutes.

[0071] In S6, the active metal element is calcium, and the mixing mass ratio of calcium to titanium hydride powder is 4:100. The vacuum debinding and sintering stage is as follows.

[0072] The dehydration stage is at a temperature of 110℃, and the vacuum degree is reduced to 200Pa; The debinding stage is at a temperature of 450℃, and the vacuum degree is reduced to 600Pa; The dehydrogenation and deoxidation stage is to increase the temperature to 750℃ at a rate of 5℃ / h, and the vacuum degree is reduced to 300Pa; The sintering stage is at a temperature of 1150℃, the vacuum degree is reduced to 80Pa, and the holding time meets the power requirement of the furnace body.

[0073] In S7, the particle size after crushing is 1.5mm, the particle size after fine grinding is 30μm, the secondary shaping uses an air flow grinding machine, and the oxygen content is controlled to be 80ppm. The final powder sphericity is ≥70%.

[0074]

Example 4

[0075] In S2, the particle size after granulation is 60μm.

[0076] In S5, the drying temperature is 90℃, the humidity is 1%, and the drying time is 20 minutes.

[0077] In S6, the active metal element is sodium, and the mixing mass ratio of sodium to titanium hydride powder is 2:100. The vacuum debinding and sintering stage is as follows.

[0078] The dehydration stage is at a temperature of 120℃, and the vacuum degree is reduced to 100Pa; The debinding stage is at a temperature of 500℃, and the vacuum degree is reduced to 400Pa; The dehydrogenation and deoxidation stage is to increase the temperature to 800℃ at a rate of 15℃ / h, and the vacuum degree is reduced to 200Pa; The sintering stage is at a temperature of 1300℃, the vacuum degree is reduced to 15Pa, and the holding time is set according to the power of the furnace body.

[0079] In S7, chemical corrosion is carried out by alkali washing with sodium hydroxide solution (concentration 0.5mol / L), and vacuum drying is carried out after corrosion. The particle size after crushing is 2.5mm, the particle size after fine grinding is 50μm, the secondary shaping uses a horizontal ball mill, the oxygen content is controlled to be 90ppm, and the final powder sphericity is ≥70%.

[0080] Example 5 A process for producing a spherical titanium alloy, which differs from Example 1 only in that, In S1, the average particle size of the titanium hydride powder is 10 μm, and the mass ratio of the binder to the titanium hydride powder is 2:100.

[0081] In S2, the particle size after granulation is 20 μm.

[0082] In S5, the drying temperature is 50°C, the humidity is 8%, and the drying time is 50 minutes.

[0083] In S6, the active metal element is barium, and the mass ratio of the barium to the titanium hydride powder is 1:100. The vacuum debinding and sintering stage is as follows.

[0084] In the dehydration stage, the temperature is 90°C, and the vacuum degree is reduced to 400 Pa. In the debinding stage, the temperature is 350°C, and the vacuum degree is reduced to 700 Pa. In the dehydrogenation and deoxidation stage, the temperature is increased to 650°C at a rate of 3°C / h, and the vacuum degree is reduced to 600 Pa. In the sintering stage, the temperature is 1100°C, the vacuum degree is reduced to 100 Pa, and the holding time is set according to the power of the furnace body.

[0085] In S7, the particle size after crushing is 1.0 mm, the particle size after fine grinding is 20 μm, the secondary shaping is performed using an air jet mill, the oxygen content is controlled to be 70 ppm, and the final powder sphericity is ≥70%.

[0086] Example 6 A process for producing a spherical titanium alloy, which differs from Example 1 only in that, In S1, the particle size of the titanium hydride powder is 30 μm, and the mass ratio of the binder to the titanium hydride powder is 9:100.

[0087] In S2, the particle size after granulation is 70 μm.

[0088] In S5, the drying temperature is 70°C, the humidity is 3%, and the drying time is 60 minutes.

[0089] In S6, the active metal element is potassium, and the mass ratio of the potassium to the titanium hydride powder is 5:100. The vacuum debinding and sintering stage is as follows.

[0090] In the dehydration stage, the temperature is 100°C, and the vacuum degree is reduced to 200 Pa. In the debinding stage, the temperature is 400°C, and the vacuum degree is reduced to 500 Pa. In the dehydrogenation and deoxidation stage, the temperature is increased to 700°C at a rate of 10°C / h, and the vacuum degree is reduced to 400 Pa. Sintering stage: temperature is 1250 DEG C, vacuum degree is reduced to 30Pa, and holding time is set according to furnace power.

[0091] The particle size of the broken particles in S7 is 2.0 mm, the particle size after fine grinding is 40 mu m, the secondary shaping adopts a horizontal ball mill, the oxygen content is controlled to be 100 ppm, and the final powder sphericity is greater than or equal to 70%.

[0092] The application provides a high-efficiency and low-energy-consumption spherical titanium alloy powder manufacturing process, which introduces multiple shaping, active metal element assisted dehydrogenation and deoxidation, and fine vacuum degreasing and sintering control, and significantly improves the sphericity and purity of titanium hydride powder.

[0093] In the vacuum degreasing and sintering process, the added active metal element acts as a "sacrificial agent" and reacts with hydrogen and oxygen in the titanium hydride powder to form corresponding hydrides and oxides, thereby effectively reducing the residual oxygen impurities and improving the dehydrogenation and deoxidation efficiency. Subsequently, these impurities are removed by chemical corrosion (pickling or alkaline washing) to retain high-purity titanium alloy powder, significantly improving the density and mechanical properties of the final product. In addition, by accurately controlling the drying temperature, humidity and time, and optimizing the temperature, heating rate and vacuum degree of each stage of vacuum degreasing and sintering, the uniformity and structural stability of the sintered block are further ensured.

[0094] In summary, the application not only solves the technical problems of low sphericity of titanium hydride powder and difficulty in removing oxygen impurities, but also realizes stable preparation of high-purity and high-sphericity titanium alloy powder through systematic optimization of process parameters, has good industrial application prospect, and is especially suitable for high-end manufacturing fields such as 3D printing and powder metallurgy.

[0095] The above description is only a preferred embodiment of the application, but the protection scope of the application is not limited thereto, and any skilled person in the art can make equivalent replacement or change within the technical range disclosed by the application according to the technical solution and inventive concept of the application, which should be covered within the protection scope of the application.

Claims

1. A process for making a spherical titanium alloy powder, characterized in that The method comprises the following steps: S1, mixing titanium hydride powder with a binder and performing compounding; S2, performing granulation on the compounded titanium hydride powder; S3, performing primary shaping on the granulated titanium hydride powder; S4, performing screening on the primary shaped titanium hydride powder to obtain titanium hydride powder in a certain particle size range for standby; S5, performing drying on the screened titanium hydride powder; S6, performing vacuum degreasing sintering on the dried titanium hydride powder mixed with active metal elements to obtain sintered blocks; S7, sequentially performing chemical etching, crushing, fine grinding, and secondary shaping on the sintered blocks, wherein the chemical etching is used to remove hydrides and oxides of the active metal elements.

2. The process of claim 1, wherein: In step S1, the particle size of the titanium hydride powder is 0.1-45 μm, and the mass ratio of the binder to the titanium hydride powder is 1-10:

100.

3. The process of claim 1, wherein: In step S2, the particle size of the compounded titanium hydride powder after granulation is 10-75 μm.

4. The process of claim 1, wherein: In step S3, the sphericity of the primary shaped titanium hydride powder is ≥50%.

5. The process of claim 1, wherein: In step S4, the particle size of the screened titanium hydride powder is 10-75 μm.

6. The process of claim 1, wherein: In step S5, the drying temperature is 35-90℃, the humidity is 1-10%, and the drying time is 20-60 minutes.

7. The process of claim 1, wherein: In step S6, the vacuum degreasing sintering comprises the following stages: dehydration stage, temperature 35-120℃, vacuum degree reduced to 50-500 Pa to complete dehydration; degreasing stage, temperature 120-500℃, vacuum degree reduced to 50-1000 Pa to complete degreasing; dehydrogenation and deoxidation stage, temperature increased to 600-800℃ at a rate of 2-20℃ / h, vacuum degree reduced to 50-1000 Pa to complete dehydrogenation and deoxidation; sintering stage, temperature 1000-1300℃, vacuum degree reduced to 10-200 Pa to complete sintering.

8. The process of claim 1 wherein: In step S6, the active metal elements include at least one of lithium, potassium, barium, calcium, sodium, magnesium, and aluminum, and the mixing mass ratio of the active metal elements to the titanium hydride powder is (1-5):

100.

9. The process of claim 7, wherein: In the sintering stage of step S6, the holding time is consistent with the effective output power of the vacuum degreasing sintering furnace being ≥1.2 times the calculated sintering power.

10. The process of claim 1-9, wherein: In step S7, the chemical etching is completed by acid washing and / or alkali washing, and vacuum drying is required after etching.

11. The process of claim 1-9, wherein: In the crushing process of step S7, a jaw crusher is used to crush the sintered blocks to a particle size range of 0.3-3 mm.

12. The process of claim 1-9, wherein: In the fine grinding process of step S7, an air flow pulverizer is used to fine grind the crushed particles to a particle size range of 1-75 μm.

13. The process of claim 1-9, wherein: In the secondary shaping of step S7, a horizontal ball mill or an air flow grinder is used to remove the edges and corners of the powder, and the oxygen content in the equipment is ≤100 ppm, so that the sphericity of the titanium hydride powder is ≥70%.

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