Method for accurate determination of oxygen increment and oxygen content control of high-quality titanium alloy powder

Abstract

This invention belongs to the field of aerospace titanium alloy powder technology, and relates to a method for accurately measuring the oxygen increment and controlling the oxygen content of high-quality titanium alloy powder. It obtains the difference between the oxygen content of the master alloy ingot and the oxygen content of the whole titanium alloy powder immediately after it exits the furnace by measuring the oxygen content of the master alloy ingot and the oxygen content of the whole powder. The method further measures the change in oxygen content of the whole powder in air over time. In practice, powder of different particle sizes is used. After a period of air sieving, the oxygen content of the powder of the required particle size range is measured, and the oxygen content of the whole powder in the same furnace at the same time is measured using parallel samples. The difference in oxygen content between the particle size range powder and the whole powder is obtained, and the oxygen content of the particle size range powder is corrected to obtain the oxygen increment of the practical particle size range powder immediately after exiting the furnace. The main influencing factors of oxygen increment during powder preparation are identified. Low-oxygen-content master alloy ingots and high-purity argon are used to prepare titanium alloy powder with a high content of active elements, providing support for the effective control and accurate measurement of oxygen increment of powders in different application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of aerospace titanium alloy powder, and relates to a method for efficient determination of oxygen increment and precise control of oxygen content in the preparation process of high-quality titanium alloy powder, specifically a method for precise determination of oxygen increment and control of oxygen content in high-quality titanium alloy powder. Background Technology

[0002] High-quality 3D-printed titanium alloys have been applied to aircraft parts, and titanium alloy powder is the material basis for high-performance titanium alloy 3D-printed components. High-quality titanium alloy powder has high fluidity, high sphericity (above 90%), and low oxygen content (below 700 ppm). Titanium alloys, due to their chemical reactivity, readily combine with oxygen, leading to increased oxygen content and adversely affecting the performance of the alloy and components. To effectively control the oxygen content of 3D-printed titanium alloy components, it is essential to first clarify the contribution of oxygen increment at different stages of the manufacturing process and identify key oxygen content control factors. Titanium alloys easily combine with oxygen during the melting and preparation process, causing an increase in the oxygen content of the master alloy ingot. In the gas atomization powder preparation process, the master alloy ingot needs to be remelted and then dispersed, broken, and solidified into micron-sized spherical particles through high-speed gas dispersion. During these processes, contact between the melt and oxygen in the furnace environment also increases oxygen content. Furthermore, because the specific surface area of ​​the powder is 1-2 orders of magnitude higher than that of the bulk alloy, its oxygen content is even higher. These factors are all important contributors to the increased oxygen content of titanium alloy powder. Previous studies have shown that, in some cases, the oxygen content of titanium alloy powder is close to that of the final 3D printed component. This indicates that oxygen content control should be based on tracing back to the preceding fabrication process, using the powder stage as a reference. Therefore, accurately identifying the contribution of oxygen content increments at each stage of the fabrication process to the overall oxygen content of the component is crucial for oxygen control. To address the above problems, existing technologies have certain limitations: (1) Previous work often tended to control the overall oxygen content in the final result, with insufficient understanding of the oxygen increment at each stage of the process, and also lacked relevant detection methods; (2) For every 100 ppm decrease in oxygen content, the production difficulty and cost increase significantly, and the price also increases exponentially. The price of Grade 0 sponge titanium is 50% or more higher than that of traditional Grade 2, making the preparation of high-quality titanium alloys technically and costly; (3) Powders have a much larger specific surface area than bulk materials, causing a surge in oxygen content. Combined with the fact that titanium is an active metal, oxygen control becomes even more difficult; (4) In industrial production, after powder preparation, it is often sieved in the air to the target particle size range before oxygen content testing. This makes it impossible to identify and distinguish the oxygen increment contribution from the preparation process of the master alloy rod or the powder's atomization preparation process. Therefore, developing efficient methods for determining the oxygen increment and accurately controlling the oxygen content of high-quality titanium alloy powder is an effective means to solve the above-mentioned technical limitations and bottlenecks. Summary of the Invention

[0003] The purpose of this invention is to propose a method for efficient determination of oxygen increment and precise control of oxygen content in high-quality titanium alloy powder, aiming to solve the problem of determining and precisely controlling oxygen increment during the storage process of titanium alloy powder.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for accurately determining the oxygen increment and controlling the oxygen content of high-quality titanium alloy powder, characterized by comprising the following steps: Step 1: Titanium alloy powder was prepared by electrode induction melting gas atomization method, and the original oxygen content of the master alloy ingot was measured; Step 2: After the gas atomization powdering is completed, titanium alloy powder of all particle sizes is taken out from the powder hopper under a protective atmosphere, and its oxygen content is measured at the first time (T0) after exiting the furnace (powder sample 1). The difference between this oxygen content and the original oxygen content of the master alloy ingot is defined as the "exit oxygen increment" of the titanium alloy powder (i.e., the oxygen increment of the titanium alloy powder). Step 3: Expose the full-size titanium alloy powder from the same furnace (powder sample 2) to the atmosphere, while simultaneously sieving another portion of the powder from the same furnace in the air to obtain the target practical particle size powder (powder sample 3); Samples 1 and 2 are used for subsequent sampling at different times. Sample 3 is the sieved sample. Sample 1 is measured at time T0 for the first time, and Samples 2 and 3 are measured simultaneously at time T1 for the second and third times.

[0005] Step 4: Record the time point (T1) when the sieving is completed in Step 3. Measure the oxygen content of the full-size powder (sample 2) exposed to the atmospheric environment at this time and the oxygen content of the target practical particle size powder (sample 3) obtained by sieving. Calculate the difference between the two as the "particle size-to-full powder oxygen content correction value". Step 5: Use the “Particle size segment - total powder oxygen content correction value” to calibrate the oxygen content of the target practical particle size segment powder at the furnace exit time (T0) (sample 1) to obtain the calibrated target practical particle size segment powder exit oxygen content. Combine this with the original oxygen content of the master alloy ingot to obtain the “practical particle size segment powder exit oxygen increment”. In step two, the oxygen increment of titanium alloy powder is defined as the difference in oxygen content between the original bar stock and the finished powder (powder sample 1). In step five, the oxygen content difference between powder sample 2 and powder sample 3 is aligned according to time to obtain the oxygen increment from the bar stock to the powder of the target practical particle size range. Step 6: By comparing the test results of low-oxygen-content master alloy ingots and high-oxygen-content master alloy ingots, the main influencing factors of oxygen increment during powder preparation are identified. Titanium alloy powder is prepared using low-oxygen-content master alloy ingots and high-purity argon gas, and the prepared powder is vacuum-sealed for preservation.

[0006] In step two, the first time (T0) is the time interval between removing the powder from the pulverizing furnace and starting the oxygen content measurement, which is less than 10 minutes, preferably 1 minute. In step two, the powder removed from the pulverizing furnace is divided into no less than two portions, which will be used for subsequent gas content measurement.

[0007] In step two, the oxygen content of the full-size titanium alloy powder was measured using an oxygen and nitrogen gas analyzer, with the measurement time being within 0.5 minutes.

[0008] The target practical particle size range of powder mentioned in step three includes, but is not limited to, a particle size range of 15~53μm suitable for 3D printing powder spreading process, a particle size range of 53~150μm suitable for 3D printing coaxial powder feeding process, or a particle size range of ≤63μm suitable for powder metallurgy process.

[0009] The oxygen content of the low-oxygen content master alloy ingot mentioned in step six is ​​350-1200 ppm, and the purity of the high-purity argon gas is 99.999% (weight fraction).

[0010] The process parameters for preparing titanium alloy powder by electrode induction melting gas atomization method are: melting power 15-35kw, bar feed rate 30mm / min-50mm / min, and atomization pressure 2-4MPa.

[0011] The protective atmosphere described in step two is argon. After the gas atomization powder preparation is completed, the furnace is kept under argon pressure for at least 20 minutes for cooling before the powder is poured into a vacuum with a vacuum degree of less than 10. -3 The powder container inside Pa.

[0012] The vacuum sealing described in step six involves using a vacuum container for large-capacity storage or using a multi-layer vacuum sealing structure for small sample storage, in order to avoid the powder coming into contact with air during transportation and storage, which would cause an increase in oxygen levels.

[0013] The main contributing factor to the oxygen increment in the powder stage was identified as the air exposure from the time the powder exits the furnace until the subsequent transfer process. Therefore, a vacuum sealing method was adopted to control the oxygen increment in the powder stage.

[0014] By comparing the test results of low-oxygen-content and high-oxygen-content master alloy ingots, it was identified that the original oxygen content of the master alloy ingot is the key factor affecting the overall oxygen content of the final titanium alloy powder. The oxygen increase caused by the powder preparation and sieving process is unrelated to the original oxygen content of the master alloy. Therefore, a low-oxygen-content master alloy ingot combined with a high-purity argon atomization process can be used to achieve overall control of the oxygen content of the titanium alloy powder.

[0015] The present invention has the following beneficial effects: Technicians need to understand the oxygen increment at the actual application particle size range during powder preparation. However, the untimely testing of oxygen content at the actual application particle size range (oxygenation rapidly increases from the time the powder exits the furnace to the time it is sieved, and actual measurement results also show that the oxygen content of titanium alloy powder quickly reaches its extreme value within a short period of time) is a limitation that existing technologies cannot solve. This application innovatively combines the timeliness of powder testing across the entire powder particle size range with the calibration of oxygen content in the entire powder / actual application particle size range. It accurately obtains the oxygen increment at the moment the powder exits the furnace at the actual application particle size range (within the preparation furnace), identifies the main controlling factors of oxygen increment in the powder preparation process, and provides support for oxygen content control in the titanium alloy powder preparation process. Specifically: 1. The gas content of the full-size powder produced in real time before the furnace is measured in a timely manner to obtain accurate data on the oxygen increment during the powder preparation stage.

[0016] 2. Since sieving in an atmospheric environment inevitably causes the powder to come into contact with oxygen in the environment, resulting in additional oxygen increase, an innovative time alignment method is used to compare the difference between the whole titanium alloy powder and the powder after sieving to determine the oxygen increase of the target practical particle size segment.

[0017] 3. It can identify the main factors affecting the oxygen increment of titanium alloy powder for 3D printing, such as the master alloy rod, powder preparation process, and transport process.

[0018] 4. Identifying the key processes for oxygen enrichment in the preparation of the master alloy ingot and the subsequent powder atomization preparation process, the master alloy ingot is prepared using high-quality sponge titanium raw materials and high-vacuum melting.

[0019] 5. The oxygen content of titanium alloy powder is controlled by combining high-purity bar melting and high-purity argon atomization processes.

[0020] 6. High-purity argon gas is used to prepare titanium alloy powder. The titanium alloy powder is stored in a vacuum container (large capacity) or a vacuum multilayer packaging structure (small sample) to avoid oxygen increase caused by contact between the powder and air during transportation.

[0021] 7. For powders prepared using the same preparation process, the oxygen content of the powder across the entire particle size range can be measured, and combined with the original oxygen content of the bar stock, the oxygen increment of the powder in the target actual particle size range can be determined.

[0022] 8. Ensures high purity of titanium alloy powder, timely oxygen increase testing (full particle size powder), and availability of oxygen increase data (target practical particle size range powder).

[0023] 9. This method combines high purity, timeliness, and usability (particle size range). Total powder oxygen content - rod feed oxygen content = powder oxygen increment. 10. The oxygen increment of titanium alloy powder is controlled by combining high-purity smelting and high-purity argon atomization process (room temperature atomization).

[0024] 11. A protective atmosphere, timely measurement, and time-aligned method were used to accurately determine the oxygen increment of titanium alloy powder with high active element content. The oxygen increment of high oxygen content bar stock was compared.

[0025] 12. It was found that the oxygen increase in titanium alloy powder is greatly related to the timeliness of gas testing. The oxygen content in the powder reaches its maximum value within one day and hardly changes thereafter.

[0026] 13. A titanium alloy powder with high activity elements was prepared using a low oxygen content master alloy ingot and high-purity argon (Ar purity 99.999%), providing support for the effective control and accurate measurement of oxygen increment in powders for different applications (such as 3D printing or powder metallurgy).

[0027] 14. Existing technological bottlenecks (It is necessary to understand the oxygen increment of the actual application particle size range during powder preparation, but the oxygen content testing of the powder in the actual application particle size range is not timely (the oxygen content increases rapidly from the time the powder exits the furnace to the time the powder is sieved, and the actual measurement results also show that the oxygen content of titanium alloy powder reaches its extreme value rapidly in a short period of time, and the existing technology cannot solve the above limitations). The innovation and technical effects of this application (Combining the timeliness of powder testing across the entire powder particle size range with the calibration of the oxygen content of the entire powder / actual application particle size range. Accurately obtaining the oxygen increment at the moment the powder exits the furnace (within the preparation furnace) in the actual application particle size range, identifying the main controlling factors of oxygen increment in the powder preparation process, and providing support for oxygen content control in the titanium alloy powder preparation process). Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention. In the following description, well-known structures and techniques are not shown to avoid unnecessarily obscuring the invention.

[0030] Example 1 S1. Titanium alloy powder was prepared by electrode induction melting gas atomization. The oxygen content of the titanium alloy bar was 393 ppm, the argon purity was 99.999% (weight fraction), the melting power was 20 kW, the bar feed rate was 40 mm / min, and the atomization pressure was 3 MPa.

[0031] S2. After the gas atomization powdering is completed, maintain the argon pressure inside the furnace, cool for 25 minutes, open the ball valve, and pour the powder into a vacuum with a pressure <10. -3 Pa has a smooth inner cavity powder container.

[0032] S3. Prepare the gas analyzer during atomization and powder production, including standard sample testing and calibration.

[0033] S4. Take out the full-size titanium alloy powder from the protective atmosphere powder container. After a 1-minute interval from taking it out of the powder pulverizer, divide the powder into at least two portions and pack them in sealed plastic bags.

[0034] S5. The oxygen content of the titanium alloy powder across the entire particle size range (powder sample 1) was analyzed using an oxygen-nitrogen gas analyzer and found to be 441 ppm, with a typical test time of less than 0.5 min. Simultaneously, another number of alloy powder samples were exposed to the atmosphere (powder sample 2). All samples were taken from powder prepared in the same batch.

[0035] S6. Simultaneously send the powder container into the screening workshop for particle size screening under normal atmospheric conditions to the target practical particle size range of 15~53μm (powder sample 3). This particle size range of powder is suitable for 3D printing powder spreading process (particle size range 15~53μm).

[0036] S7. After a period of sieving, the powder of the particle size range (powder sample 3) was placed into a gas analyzer, and its oxygen content was analyzed to be 714 ppm. The time was recorded. At the same time, the oxygen content of the previously stored full-powder titanium alloy powder of the particle size range (powder sample 2) was tested and found to be 591.5 ppm. The difference in oxygen content between the two was calculated, and the oxygen content of the initial particle size range powder was obtained as 529 ppm based on this ratio.

[0037] S8. The oxygen increment of titanium alloy powder is defined as the "bar-to-powder oxygen increment" between the original bar stock and the finished powder (powder sample 1), which is the oxygen content difference of 441-393=48ppm. Then, based on the time-aligned oxygen content difference between powder sample 2 and powder sample 3, the initial "bar-to-powder oxygen increment" from the bar stock to the target practical particle size range (particle size range 15~53μm) is obtained as 529-393=136ppm.

[0038] S9. The oxygen increment from rod to powder after 7 days of air exposure is 591.5-393=198.5ppm; the oxygen increment from rod to powder for the particle size range measured after air sieving is 714-393=321ppm.

[0039] Example 2 Titanium alloy powder was prepared by electrode induction melting gas atomization and the oxygen increment from rod to powder was measured. The difference from Example 1 is that the initial oxygen content of the titanium alloy rod was 1150 ppm, and the oxygen content of the powder in the particle size range measured after air sieving was 1460 ppm. The exposure time was 7 days, and the oxygen increment from rod to powder in the 15-53 μm particle size range of titanium alloy after air exposure sieving was 1460-1150=310 ppm.

[0040] The initial oxygen increments in the powder's initial stage across the entire particle size range and in the actual usable particle size range were measured to be 48 ppm and 136 ppm, respectively. After exposure for a period of time, these values ​​reached 198.5 ppm and 321 ppm, respectively. It was identified that the oxygen increment in the powder stage mainly occurred after the powder exited the furnace and during subsequent transfer processes. Therefore, multi-layer vacuum sealing or protective atmosphere canister storage of the powder can effectively control the oxygen content in the powder stage. It was also found that regardless of whether the ingot was low-oxygen or high-oxygen, the oxygen increment in the final powder stage was similar (310~321 ppm) after considering the exposure time during the sieving process. However, in terms of contribution to the total oxygen content, the oxygen in the low-oxygen ingot (393 ppm) and the high-oxygen ingot (1150 ppm) both contribute to the final powder (529 ppm and 1460 ppm, respectively). Therefore, the oxygen content contribution of the alloy ingot is identified as a significant factor in the overall oxygen content contribution of the titanium alloy. Low-oxygen titanium alloy ingots should be prepared using grade 0 sponge titanium, and low-oxygen electrode rods should be used as the raw material for powder preparation. This method also showed that there is a certain oxygen increment in the rod-to-powder process. Therefore, high-purity argon should be used for atomization powder preparation to achieve overall control of the oxygen content of titanium alloy powder.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A method for accurately determining the oxygen increment and controlling the oxygen content of high-quality titanium alloy powder, characterized in that, Includes the following steps: Step 1: Titanium alloy powder was prepared by electrode induction melting gas atomization method, and the original oxygen content of the master alloy ingot was measured; Step 2: After the gas atomization powdering is completed, titanium alloy powder of all particle sizes is taken out from the powder hopper under a protective atmosphere, and its oxygen content is measured at the first time T0 after exiting the furnace. The difference between this oxygen content and the original oxygen content of the master alloy ingot is defined as the "exit oxygen increment" of the titanium alloy powder. Step 3: Expose the full range of titanium alloy powder from the same furnace to the atmosphere, while sieving another portion of the powder from the same furnace in the air to obtain the target practical particle size range powder. Step 4: Record the time point T1 when the sieving is completed in Step 3. Measure the oxygen content of the powder of the full particle size range exposed to the atmospheric environment at this time and the oxygen content of the target practical particle size range powder obtained by sieving. Calculate the difference between the two as the "particle size range - full powder oxygen content correction value". Step 5: Use the "particle size segment - total powder oxygen content correction value" to calibrate the oxygen content of the target practical particle size segment powder at the furnace exit time T0, and obtain the calibrated oxygen content of the target practical particle size segment powder at the furnace exit. Then, combine it with the original oxygen content of the master alloy ingot to obtain the "practical particle size segment powder at the furnace exit oxygen increment". Step 6: Prepare titanium alloy powder using a low-oxygen-content master alloy ingot and high-purity argon gas, and then preserve the prepared powder by vacuum packaging.

2. The method according to claim 1, characterized in that, In step two, the first time (T0) is the time interval from taking the powder out of the powder mill to starting to measure the oxygen content, which is less than 10 minutes.

3. The method according to claim 1, characterized in that, In step two, the oxygen content of the full-size titanium alloy powder was measured using an oxygen and nitrogen gas analyzer, with the measurement time being within 0.5 minutes.

4. The method according to claim 1, characterized in that, The target practical particle size range of powder mentioned in step three includes, but is not limited to, a particle size range of 15~53μm suitable for 3D printing powder spreading process, a particle size range of 53~150μm suitable for 3D printing coaxial powder feeding process, or a particle size range of ≤63μm suitable for powder metallurgy process.

5. The method according to claim 1, characterized in that, The oxygen content of the low-oxygen content master alloy ingot mentioned in step six is ​​350-1200 ppm, and the purity of the high-purity argon gas is 99.999%.

6. The method according to claim 1, characterized in that, The process parameters for preparing titanium alloy powder by electrode induction melting gas atomization method are: melting power 15-35kw, bar feed rate 30mm / min-50mm / min, and atomization pressure 2-4MPa.

7. The method according to claim 1, characterized in that, The protective atmosphere described in step two is argon. After the gas atomization powdering is completed, the furnace is kept under argon pressure for at least 20 minutes for cooling before the powder is poured into a vacuum with a vacuum degree of less than 10. -3 Pa is in a powder container with a smooth inner cavity.

8. The method according to claim 1, characterized in that, The vacuum sealing described in step six involves using a vacuum container for large-capacity storage or using a multi-layer vacuum sealing structure for small sample storage, in order to avoid the powder coming into contact with air during transportation and storage, which would cause an increase in oxygen levels.

9. The method according to claim 2, characterized in that, The time interval is 1 minute.