A low-oxygen small-size titanium alloy powder and its preparation method and application

Abstract

A low-oxygen, small-size titanium alloy powder, its preparation method, and its applications. This invention belongs to the field of titanium alloy powder preparation. The purpose of this invention is to solve the technical problems of high cost and poor mechanical stability of existing rotating electrode powder preparation methods, which reduce powder particle size by increasing electrode rotation speed and electrode size. The method of this invention: A rotating electrode powder preparation method is used, with a radio frequency hydrogen plasma emitter as the heat source. The plasma arc is placed within a dynamic rotating magnetic field generated by two orthogonally arranged electromagnetic coils. After the consumable electrode reaches a preset rotation speed, the heat source is activated. After vacuuming, powder is prepared in an argon-hydrogen mixed atmosphere. The prepared powder is then subjected to high-temperature isothermal sintering under vacuum conditions to obtain low-oxygen, small-size titanium alloy powder. This method promotes fluid granulation and fine powder generation, effectively reduces the oxygen impurity content in the alloy powder, and results in lower cost, stronger mechanical stability, and lower impurity content.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy powder preparation, specifically relating to a low-oxygen, small-size titanium alloy powder, its preparation method, and its application. Background Technology

[0002] Titanium alloys are widely used in basic industries such as aerospace, petroleum energy, medical devices, and marine vessels due to their high specific strength, low coefficient of thermal expansion, strong corrosion resistance, and good biocompatibility. However, factors restricting their further application include complex manufacturing processes, low material utilization, simple part forming structures, and difficulties in machining deformation. In recent years, hot isostatic pressing powder metallurgy and powder titanium alloy additive manufacturing technology have gradually developed into important processes for the preparation of complex titanium alloy parts. These technologies place high demands on the chemical composition, sphericity, and flowability of the raw material spherical powder. However, titanium alloy powders differ from conventional metal powders; their extremely strong room-temperature oxygen absorption characteristics and high-temperature reactivity make the preparation process of titanium alloy powders different from that of conventional metal powders. Therefore, the preparation process of spherical titanium powder is an important foundation for titanium alloy production and manufacturing.

[0003] The Plasma Rotating Electrode Process (PREP) is a commonly used method for preparing spherical titanium alloy powder. It is a centrifugal atomization method where the master alloy is processed into an electrode rod, and an electric arc is used as a heat source to continuously melt the high-speed rotating metal rod. In the molten state, molten metal droplets on the end face of the alloy rod are ejected under centrifugal force and rapidly cooled and solidified into spherical powder under a protective gas environment. The PREP method completely avoids slag formation and contact with refractory materials during the melting and atomization of the metal, thus eliminating sources of non-metallic inclusion contamination. This preparation process can produce high-purity powder, meeting the requirements of titanium alloy powder in various application fields, such as aerospace and medical devices. The application of the PREP method improves the quality and usability of titanium alloy powder, promoting the further development and application of titanium alloy materials.

[0004] Typically, methods to reduce powder particle size include increasing electrode rotation speed and enlarging electrode size. However, increasing rotation speed to reduce powder size is somewhat ineffective, and it also increases production costs, reduces the mechanical stability of the equipment, and can even generate friction debris contamination. Furthermore, while increasing the diameter of the rotating electrode can reduce powder size, this places high demands on the equipment. Therefore, new methods are needed to more effectively reduce alloy powder contamination, decrease powder particle size, and provide higher quality titanium alloy powder materials. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of high cost and poor mechanical stability of the device caused by the existing rotating electrode powder preparation method, which reduces the powder particle size by increasing the electrode rotation speed and increasing the electrode size. The invention provides a low-oxygen small-size titanium alloy powder, its preparation method and application.

[0006] One objective of this invention is to provide a method for preparing low-oxygen, small-size titanium alloy powder, the method comprising the following steps:

[0007] S1: The rotating electrode powder making method is adopted. The radio frequency hydrogen plasma emitter is used as the heat source. The plasma arc is placed in the dynamic rotating magnetic field generated by two orthogonally set electromagnetic coils. After the rotating consumable electrode reaches the preset speed, the heat source is started. After vacuuming, powder is made in an argon-hydrogen mixed atmosphere.

[0008] S2: The powder is sintered at high temperature under vacuum to obtain low-oxygen, small-sized titanium alloy powder.

[0009] Further restrictions are imposed, with the diameter of the rotating consumable electrode in S1 being 70-80 mm. The roundness deviation is required to be <0.05 mm, and the straightness deviation <0.01 mm / m.

[0010] Further specified, the vacuum degree in S1 is ≤5×10-3Pa.

[0011] Further specified, the partial pressure of hydrogen in the argon-hydrogen mixture in S1 is 1-50%, and the gas is filled to 0.04-0.05 MPa.

[0012] Further specified, the feeding speed of the rotating consumable electrode in S1 is 1-2 mm / s, the rotation speed is 15000-20000 r / min, and the current is 2000-2500 A.

[0013] Further specified, the plasma arc rotation oscillation frequency in S1 is 10-50Hz, and the deflection angle is 5-45°.

[0014] Further specified, the vacuum degree in S2 is ≤5×10-3Pa.

[0015] Further specified, the sintering temperature in S2 is 600-800℃, and the time is 5-7h.

[0016] The second objective of this invention is to provide a titanium alloy powder prepared by the above method, wherein the titanium alloy powder has a particle size of <200μm and an oxygen content of ≤1100ppm.

[0017] The third objective of this invention is to provide an application of titanium alloy powder prepared by the above method in hot isostatic pressing powder metallurgy and powder additive manufacturing.

[0018] The significant advantages of this invention compared to existing technologies are:

[0019] This invention uses a radio frequency hydrogen plasma emitter as a heat source, avoiding the electrode contamination that may occur with traditional tungsten electrodes. It introduces magnetic arc oscillation into the radio frequency hydrogen plasma emitter, increasing fluid disturbance and promoting fluid granulation and fine powder generation. Furthermore, it effectively reduces the oxygen impurity content in the alloy powder, and the hydrogen element is dissolved in the titanium alloy, improving its viscosity and surface tension, thereby reducing the size of the ejected droplets. Compared with traditional methods, this improved method is lower in cost, has stronger mechanical stability, and contains fewer impurities. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the apparatus for preparing low-oxygen, small-sized titanium alloy powder according to the present invention; wherein 1-electric arc, 2-powder, 3-electromagnetic coil, 4-rotating consumable titanium alloy electrode, 5-plasma torch, and 6-radio frequency hydrogen plasma emitter. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0023] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0024] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0025] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] Example 1: The preparation method of low-oxygen small-size titanium alloy powder in this example is carried out according to the following steps:

[0027] (1) TC4 titanium alloy bar stock Install it into the rotary feed device and ensure it is sealed. Evacuate the atomization chamber to a vacuum level ≤ 5 × 10⁻⁶. -3 After Pa, argon gas is introduced to 0.05 MPa and the circulation pump is started, followed by the cooling system. The argon gas purity is ≥99.999%.

[0028] (2) Start the rotary button to gradually accelerate the rotation of the bar. When it reaches 18000 r / min, turn on the power supply of the radio frequency hydrogen plasma emitter at 2200A. At this time, a high-temperature plasma arc is generated between the bar and the electrode. The end face of the bar melts instantly to form a liquid metal film. Under the combined action of centrifugal force and surface tension, the film detaches from the bar and forms tiny droplets, which solidify into metal powder under the cooling effect of the cooling gas. Subsequently, start the rotary feed button to adjust the feed rate to 1.5 mm / s to ensure continuous feeding of the bar and maintain the continuous powder-making process. During the powder-making process, the equipment operation should be observed at all times and records should be kept.

[0029] (3) The prepared powder was subjected to isothermal dehydrogenation treatment in a high-temperature vacuum sintering furnace. The process was 700℃ / 6h, and the vacuum degree was controlled at 5×10⁻⁶ during the dehydrogenation process. -3 Within Pa, after the constant temperature period ends, turn off the heating system and allow it to cool naturally to 30℃.

[0030] The hydrogen and oxygen content of the product powder were determined using a hydrogen and oxygen content analyzer, and the powder particle size was also measured. The test results are shown in Table 1.

[0031] Example 2: The preparation method of low-oxygen small-size titanium alloy powder in this example is carried out according to the following steps:

[0032] (1) TC4 titanium alloy bar stock Install it into the rotary feed device and ensure it is sealed. Evacuate the atomization chamber to a vacuum level ≤ 5 × 10⁻⁶. -3 After Pa, an argon-hydrogen mixture is introduced to 0.05 MPa and the circulation pump is started. The argon-hydrogen partial pressure ratio is 8:2. Then the cooling system is started. The argon purity is ≥99.999%.

[0033] (2) Start the rotary button to gradually accelerate the rotation of the bar. When it reaches 18000 r / min, turn on the power supply of the radio frequency hydrogen plasma emitter at 2200A. At this time, a high-temperature plasma arc is generated between the bar and the electrode. The end face of the bar melts instantly to form a liquid metal film. Under the combined action of centrifugal force and surface tension, the film detaches from the bar and forms tiny droplets, which solidify into metal powder under the cooling effect of the cooling gas. Subsequently, start the rotary feed button to adjust the feed rate to 1.5 mm / s to ensure continuous feeding of the bar and maintain the continuous powder-making process. During the powder-making process, the equipment operation should be observed at all times and records should be kept.

[0034] (3) The prepared powder was subjected to isothermal dehydrogenation treatment in a high-temperature vacuum sintering furnace. The process was 700℃ / 6h, and the vacuum degree was controlled at 5×10⁻⁶ during the dehydrogenation process. -3 Within Pa, after the constant temperature period ends, turn off the heating system and allow it to cool naturally to 30℃.

[0035] The hydrogen and oxygen content of the product powder were determined using a hydrogen and oxygen content analyzer, and the powder particle size was also measured. The test results are shown in Table 1.

[0036] Example 3: The preparation method of low-oxygen small-size titanium alloy powder in this example is carried out according to the following steps:

[0037] (1) TC4 titanium alloy bar stock Install it into the rotary feed device and ensure it is sealed. Evacuate the atomization chamber to a vacuum level ≤ 5 × 10⁻⁶. -3 After Pa, an argon-hydrogen mixture is introduced to 0.05 MPa and the circulation pump is started. The argon-hydrogen partial pressure ratio is 8:2. Then the cooling system is started. The argon purity is ≥99.999%.

[0038] (2) Start the rotary button to gradually accelerate the rotation of the rod. When it reaches 18000 r / min, turn on the power supply of the radio frequency hydrogen plasma emitter at 2200A. The plasma arc is placed within the dynamic rotating magnetic field generated by two orthogonally arranged electromagnetic coils, causing the plasma arc to rotate and oscillate at a frequency of 10 Hz and a deflection angle of 25°. At this time, a high-temperature plasma arc is generated between the rod and the electrode. The end face of the rod melts instantly to form a liquid metal film. Under the combined action of centrifugal force and surface tension, the film detaches from the rod and forms tiny droplets, which solidify into metal powder under the cooling effect of the cooling gas. Subsequently, start the rotary feed button to adjust the feed rate to 1.5 mm / s to ensure continuous feeding of the rod and maintain the continuous powder-making process. During the powder-making process, the equipment operation should be observed at all times and records should be kept.

[0039] (3) The prepared powder was subjected to isothermal dehydrogenation treatment in a high-temperature vacuum sintering furnace. The process was 700℃ / 6h, and the vacuum degree was controlled at 5×10⁻⁶ during the dehydrogenation process. -3 Within Pa, after the constant temperature period ends, turn off the heating system and allow it to cool naturally to 30℃.

[0040] The hydrogen and oxygen content of the product powder were determined using a hydrogen and oxygen content analyzer, and the powder particle size was also measured. The test results are shown in Table 1.

[0041] Table 1. Oxygen content and particle size of titanium alloy powders prepared in Examples 1-3

[0042] Example 1 Example 2 Example 3 Oxygen content / ppm 1600 1100 800 Average powder particle size / μm 232 168 132

[0043] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing low-oxygen, small-size titanium alloy powder, characterized in that, The method described: S1: The rotating electrode powder making method is adopted, with a radio frequency hydrogen plasma emitter as the heat source. The plasma arc is placed in the dynamic rotating magnetic field generated by two orthogonally set electromagnetic coils. After the rotating consumable electrode reaches the preset speed, the heat source is started. After evacuation, powder is made in an argon-hydrogen mixed atmosphere. The hydrogen partial pressure in the argon-hydrogen mixed gas is 1-50%, and the gas is filled to 0.04-0.05MPa. The plasma arc rotation oscillation frequency is 10-50Hz, and the deflection angle is 5-45°. S2: The powder is sintered at a high temperature under vacuum conditions. The sintering temperature is 600-800℃ and the time is 5-7h to obtain low oxygen small-sized titanium alloy powder.

2. The method according to claim 1, characterized in that, The diameter of the rotating consumable electrode in S1 is 70-80 mm.

3. The method according to claim 1, characterized in that, Vacuum degree in S1 ≤ 5 × 10 -3 Pa.

4. The method according to claim 1, characterized in that, The feed speed of the rotating consumable electrode in S1 is 1-2 mm / s, the rotation speed is 15000-20000 r / min, and the current is 2000-2500 A.

5. The method according to claim 1, characterized in that, Vacuum degree in S2 ≤ 5 × 10 -3 Pa.

6. The titanium alloy powder prepared by the method according to any one of claims 1-5, characterized in that, The titanium alloy powder has a particle size of <200μm and an oxygen content of ≤1100ppm.

7. The application of the titanium alloy powder according to claim 6 in hot isostatic pressing powder metallurgy and powder additive manufacturing.

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