A method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization and its application

Abstract

The present invention belongs to the technical field of metal ball powder preparation, and specifically relates to a method for improving the fine powder rate of titanium alloy ball powder in electrode induction gas atomization and its application, the method comprising the following steps: A. preparing a molten titanium alloy with a hydrogen content of 300ppm to 10000ppm; B. atomizing and powdering the molten titanium alloy with a hydrogen content of 300ppm to 10000ppm to obtain titanium alloy ball powder. The present invention can obtain a powder yield of 80% for powders with a particle size less than 53μm, which is higher than 30% of the existing process, and reduces the process cost while improving the fine powder rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal ball powder preparation, and specifically relates to a method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization and an application thereof, and is particularly applicable to the field of titanium alloy ball powder preparation in additive manufacturing and powder metallurgy industries. Background Art

[0002] Titanium alloys have the advantages of high specific strength, good corrosion resistance and good biocompatibility, and are widely used in aviation, aerospace, shipbuilding, chemical industry and biomedicine. The use of traditional machining manufacturing technology to process titanium alloys has problems such as high processing difficulty and low material utilization, resulting in high processing costs. The prepared titanium alloys are expensive and difficult to use on a large scale.

[0003] Applying 3D printing (additive manufacturing) technology to titanium alloy processing can effectively circumvent the difficulty of traditional machining. At the same time, combining 3D printing technology with topological design, by using a high-energy heating device to sinter titanium alloy ball powder layer by layer using the designed data model to make components of the expected shape, can achieve structural weight reduction, thereby improving material utilization, greatly reducing the manufacturing cost of titanium alloy parts, and promoting the application of titanium alloy products in a wider range of fields such as aerospace, biomedicine, etc.

[0004] Electrode induction gas atomization (EIGA) is the most widely used method for producing titanium alloy ball powder. Compared with other process methods such as inert gas atomization and ultrasonic atomization, it has the advantages of low production cost and high production efficiency. However, 3D printing can only use titanium alloy ball powder with a particle size of less than 53 microns, and the qualified rate of titanium alloy ball powder prepared by electrode induction gas atomization is only about 30%, resulting in a high price of titanium alloy ball powder and a high cost of 3D printing of titanium alloy.

[0005] The technical principle of the electrode induction gas atomization method (EIGA) is: using high-speed and high-pressure argon gas flow to impact the titanium alloy melt. The high-speed gas flow can overcome the surface tension of the titanium alloy melt, atomize the melt droplets to form fine metal droplets, and the fine metal droplets cool and solidify under the action of the tension to form spherical powder. At present, additive manufacturing technology can only use titanium alloy ball powder with a particle size of less than 53 microns, and the titanium alloy ball powder prepared by the electrode induction gas atomization method with a particle size of less than 53 microns only accounts for about 30% of the total powder, resulting in a higher price for titanium alloy ball powder, which in turn increases the cost of 3D printing of titanium alloy.

[0006] The key to increasing the fine powder rate in the EIGA atomization process is to provide sufficiently high gas kinetic energy to overcome the surface tension of the melt and atomize the molten metal flow to form fine droplets. However, the cost of increasing the gas kinetic energy is high. Currently, the fine powder rate is mainly increased by high-power smelting to increase the melt temperature and reduce the melt surface tension, or by improving the nozzle structure to improve the melt flow stability.

[0007] Guo Kuai Kuai, Liu Changsheng, Chen Suiyuan and others disclosed the influence of power on the properties of TC4 alloy powder for 3D printing prepared by EIGA, and the patent document with application number 202210679586.3 disclosed a titanium alloy and a method for preparing atomized powder for improving the fine powder recovery ratio of inert gas atomized powder in electrode induction melting. By increasing the high-frequency induction melting power and the temperature of the molten metal flow, according to the relationship between the surface tension and temperature of the metal material, increasing the temperature of the melt of the metal material can reduce the surface tension. Under the same high-pressure airflow impact force, the low melt surface tension is easier to be atomized to form fine powder. However, although increasing the temperature can reduce the surface tension of the titanium alloy material melt to a certain extent, it has little effect on pure titanium metal. For titanium alloys, too high a molten state temperature can easily lead to serious loss of low melting point components in the alloy, resulting in abnormal composition of the alloy.

[0008] In the literature published by Xie Bo et al., the EIGA atomization method for preparing TC4 alloy powder for laser 3D printing was used to increase the kinetic energy of the airflow by increasing the impact high-pressure airflow pressure, thereby overcoming the surface tension of the metal melt and improving the atomization effect. Research by the Panzhihua Iron and Steel Group Research Institute showed that increasing the impact airflow pressure can increase the fine powder rate; however, due to process limitations, the increase in impact kinetic energy is relatively limited. At the same time, excessive air flow exchanges heat with the melt, and the melt cools down and solidifies too quickly, which can easily cause problems such as ellipsoids, reducing the performance and quality of the powder. Excessive air flow will also increase the loss of high-purity high-pressure argon gas, increasing the process cost. Summary of the invention

[0009] In order to improve the deficiencies of the prior art, the present invention provides a method for improving the fine powder rate of titanium alloy ball powder in electrode induction gas atomization, combining the thermal hydrogen treatment process of titanium with the EIGA method, and utilizing the weak bond effect of hydrogen to reduce the surface tension and viscosity of the molten titanium alloy, so that it is easier to be broken up into fine metal droplets and solidified to form fine ball powder under the erosion of high-pressure airflow.

[0010] In a first aspect, the present invention provides a method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization, comprising the following steps:

[0011] A. preparing a molten titanium alloy having a hydrogen content of 300 ppm to 10000 ppm;

[0012] B. Atomize and powderize a molten titanium alloy having a hydrogen content of 300ppm to 10000ppm to obtain titanium alloy ball powder.

[0013] According to an embodiment of the present invention, the hydrogen content in the molten titanium alloy is 1000ppm~8000ppm, preferably, the hydrogen content in the molten titanium alloy is 2000ppm~5000ppm, for example, 1000ppm, 1500ppm, 2000ppm, 2500ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm or 7000ppm.

[0014] According to an embodiment of the present invention, step A comprises the following steps: subjecting the titanium alloy raw material to a high-temperature hydrogen treatment and then melting it, or subjecting the titanium alloy raw material to a liquid hydrogen treatment after melting it.

[0015] According to an embodiment of the present invention, the high temperature hydrogen treatment of the titanium alloy raw material comprises the following steps:

[0016] a. Place the titanium alloy raw material into a tubular hydrogen treatment furnace, evacuate and heat to 400-800°C, fill with high-purity hydrogen until the hydrogen partial pressure in the furnace is 5-60KPa and stop charging;

[0017] b. Keep warm for 5-24 hours, and cool to room temperature to obtain a titanium alloy material with a hydrogen content of 300ppm to 10000ppm.

[0018] According to an embodiment of the present invention, the following step is included before step a: cleaning the surface of the titanium alloy raw material, preferably using an organic solvent to clean the surface of the titanium alloy raw material.

[0019] According to an embodiment of the present invention, the organic solvent includes at least one of methanol, ethanol and acetone, for example, acetone.

[0020] According to an embodiment of the present invention, heating to 400-800° C. in step a comprises: heating to 400-800° C. at a heating rate of 5-15° C. / min.

[0021] According to an embodiment of the present invention, the heating temperature is 500-600°C.

[0022] According to an embodiment of the present invention, the inflation is stopped when the hydrogen partial pressure in the furnace is 10-30 KPa.

[0023] According to an embodiment of the present invention, the high-temperature hydrogen treatment and re-melting of the titanium alloy raw material comprises the following steps: placing the titanium alloy material with a hydrogen content of 300ppm to 10000ppm into a gas atomization device for melting.

[0024] As an example, melting the titanium alloy material includes the following steps: placing the titanium alloy material in a clamping piece of a gas atomization device, clamping the bottom conical area of ​​the titanium alloy material in an induction coil, evacuating the cavity of the gas atomization device, introducing high-purity argon gas into the melting zone and the atomization zone, increasing the melting power to 30 to 80 kW, and raising the temperature until the titanium alloy material is melted.

[0025] According to an embodiment of the present invention, the step B comprises the following steps: spraying an inert gas into a molten titanium alloy having a hydrogen content of 300ppm to 10000ppm through an atomizer nozzle to perform atomization and powdering to obtain atomized powder.

[0026] According to an embodiment of the present invention, the angle at which the nozzle sprays gas is 5° to 80°.

[0027] According to an embodiment of the present invention, the gas flow rate of the nozzle is 5 to 35 Nm 3 / min.

[0028] According to an embodiment of the present invention, step B further includes the following step: collecting atomized powder.

[0029] In a second aspect, the present invention also provides a titanium alloy atomized powder prepared by the above method, wherein the particle size distribution of the titanium alloy atomized powder is 5 to 150 microns, and the powder yield of powder with a particle size less than 53 microns is higher than 30%, preferably, the powder yield of powder with a particle size less than 53 microns is higher than 40%, for example, any point value among 35%, 40%, 45%, 50%, 55%, 60%, 68%, 70%, 74%, 80% or any value in the range composed of any point value.

[0030] In a third aspect, the present invention also provides an application of the above-mentioned titanium alloy atomized powder in 3D printing, for example, for 3D printing to prepare aviation, aerospace, shipbuilding, chemical or biomedical devices.

[0031] In a fourth aspect, the present invention further provides a method for processing titanium alloy using the above-mentioned additive manufacturing, comprising the following steps: forming a titanium alloy device by 3D printing the above-mentioned titanium alloy atomized powder.

[0032] According to an embodiment of the present invention, before processing the titanium alloy, the following step is also included: sieving the titanium alloy atomized powder to obtain a powder with a particle size less than 53 microns.

[0033] Beneficial Effects

[0034] 1. The present invention unexpectedly discovered that by melting a titanium alloy rod with a hydrogen content of 300ppm to 10000ppm to obtain titanium alloy droplets with a high hydrogen content; or by first melting the titanium alloy rod and then subjecting it to liquid hydrogenation to obtain titanium alloy droplets with a high hydrogen content, and then atomizing it, the surface tension and viscosity of the titanium alloy with a high hydrogen content in the molten state are greatly reduced, and the reduced viscosity of the molten metal flow is conducive to the formation of a finer liquid flow, which is conducive to more sufficient atomization to form fine droplets under the impact of high-pressure airflow in the atomization zone; the reduced surface tension of the liquid flow is conducive to the high-pressure airflow in the atomization zone to disperse the atomization into finer droplets, thereby obtaining atomized powder with a low fine powder rate. The powder rate of powder with a particle size less than 53μm obtained after high-pressure airflow atomization reaches 80%, which is higher than the 30% of the existing process; the present invention reduces the process cost while increasing the fine powder rate.

[0035] 2. In the present invention, the titanium alloy droplets with a high hydrogen content react with the oxygen mixed in the inert gas at a high temperature, which can reduce the effect of reducing the oxygen increase in the powder. During the smelting process of titanium alloy bars with a hydrogen content of 300ppm to 10000ppm, the hydrogen contained in the melt can remove the oxygen contained in the atomizing gas, and the oxygen increase in the powder is reduced to less than 100ppm, which is significantly lower than the oxygen increase of 200ppm in pure argon atmosphere smelting, thereby improving the quality of the powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the structure of the aerosol device in an embodiment of the present invention;

[0037] Figure 2 This is an electron microscope image of the titanium alloy ball powder prepared in Example 1 of the present invention;

[0038] Figure 3 1 is the relationship between the hydrogen content of the prefabricated titanium alloy rod and the oxygen content of the prepared ball powder in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The preparation method of the present invention will be described in further detail below in conjunction with specific examples. It should be understood that the following examples are only exemplary illustrations and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0040] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0041] The electrode-induced atomization in the following embodiments of the present invention is carried out as follows Figure 1 The aerosolization device shown in FIG. Figure 1As shown, the gas atomization equipment includes a clamping member, an induction zone and an atomization zone which are arranged in sequence from top to bottom. The inductor is provided with a coil, and the atomization zone is provided with a nozzle. The atomization angle of the nozzle is 5° to 80°. The clamping member is used to clamp the titanium alloy bar, and the conical area of ​​the clamped titanium alloy bar is located in the induction coil. The droplets heated by the induction coil enter the atomization bin and are atomized by the airflow sprayed from the nozzle to form spherical atomized powder.

[0042] Example 1

[0043] S101. Use acetone to clean the titanium alloy rod to remove the oil on the surface of the sample, put it into the hydrogen treatment heating furnace, and evacuate to 10 -3 Pa, and then heated to 650°C at a heating rate of 10°C / min, and filled with high-purity argon and high-purity hydrogen respectively until the hydrogen partial pressure in the furnace reached 60KPa, and then stopped charging, kept warm for 10 hours, and cooled to room temperature to obtain a titanium alloy rod with a hydrogen content of 5000ppm.

[0044] S102, use Figure 1 The aerosolization device shown clamps and fixes the titanium alloy rod with a hydrogen content of 5000 ppm prepared in step S101, and the conical area at the bottom of the titanium alloy rod is located in the induction coil, and the aerosolization equipment cavity is evacuated.

[0045] S103, high-purity argon gas is introduced into the smelting zone and the atomizing zone to increase the smelting power to 60kw.

[0046] S104, when the titanium alloy metal melts into a liquid flow and falls, high-purity argon is introduced into the atomizer nozzle at a gas flow rate of 20Nm 3 / min under the condition of atomization powder making, finally the desired spherical atomized powder is obtained.

[0047] See also Figure 2 As shown, the spherical atomized powder prepared in this embodiment has a particle size distribution of 5 to 150 microns, and the content of particles with a size less than 53 microns is 80%.

[0048] Example 2

[0049] S201. Use acetone to clean the titanium alloy rod to remove the oil on the surface of the sample, put it into the hydrogen treatment heating furnace, and evacuate to 10 -3 Pa, and then heated to 650°C at a heating rate of 10°C / min, and filled with high-purity argon and high-purity hydrogen respectively until the hydrogen partial pressure in the furnace reached 50KPa, and then stopped charging, kept warm for 10 hours, and cooled to room temperature to obtain a titanium alloy rod with a hydrogen content of 3000ppm.

[0050] S202, clamp and fix the titanium alloy rod, with the conical area at the bottom of the titanium alloy rod located in the induction coil, and evacuate the cavity of the atomization equipment.

[0051] S203, high-purity argon gas is introduced into the smelting zone and the atomizing zone to increase the smelting power to 60kw.

[0052] S204, when the titanium alloy metal melts into a liquid flow and falls, high-purity argon is introduced into the atomizer nozzle at a gas flow rate of 20Nm 3 / min under the condition of atomization powder making, finally the desired spherical atomized powder is obtained.

[0053] S205. The spherical atomized powder is collected by a cyclone separation system.

[0054] The spherical atomized powder prepared in this embodiment has a particle size distribution of 5 to 150 microns, and the content of particles with a size less than 53 microns is 74%.

[0055] Example 3

[0056] S301. Use acetone to clean the titanium alloy rod to remove the oil on the surface of the sample, put it into the hydrogen treatment heating furnace, and evacuate to 10 -3 Pa, and then heated to 600°C at a heating rate of 10°C / min, and filled with high-purity argon and high-purity hydrogen respectively until the hydrogen partial pressure in the furnace reached 40KPa, and then stopped charging. The furnace was kept warm for 10 hours and cooled to room temperature to obtain a titanium alloy rod with a hydrogen content of 1500ppm.

[0057] S302, clamp and fix the pre-charged hydrogen titanium alloy rod, the conical area at the bottom of the titanium alloy rod is located in the induction coil, and the atomization equipment cavity is evacuated.

[0058] S303, high-purity argon gas is introduced into the smelting zone and the atomizing zone to increase the smelting power to 60kw.

[0059] S304, when the titanium alloy metal melts into a liquid flow and falls, high-purity argon is introduced into the atomizer nozzle at a gas flow rate of 20Nm 3 / min under the condition of atomization powder making, finally the desired spherical atomized powder is obtained.

[0060] S305, collecting the spherical atomized powder through a cyclone separation system.

[0061] The spherical atomized powder prepared in this embodiment has a particle size distribution of 5 to 150 microns, and the content of particles with a size less than 53 microns is 68%.

[0062] Example 4

[0063] S401. Use acetone to clean the titanium alloy rod to remove the oil on the surface of the sample, put it into the hydrogen treatment heating furnace, and evacuate it to 10 -3Pa, and then heated to 500°C at a heating rate of 10°C / min, and filled with high-purity argon and high-purity hydrogen respectively until the hydrogen partial pressure in the furnace reached 30KPa, and then stopped charging, kept warm for 10 hours, and cooled to room temperature to obtain a titanium alloy rod with a hydrogen content of 300ppm.

[0064] S402, clamp and fix the pre-set hydrogen titanium alloy rod, the conical area at the bottom of the titanium alloy rod is located in the induction coil, and the atomization equipment cavity is evacuated.

[0065] S403, high-purity argon gas is introduced into the smelting zone and the atomizing zone to increase the smelting power to 60kw.

[0066] S404, when the titanium alloy metal melts into a liquid flow and falls, high-purity argon is introduced into the atomizer nozzle at a gas flow rate of 20Nm 3 / min under the condition of atomization powder making, finally the desired spherical atomized powder is obtained.

[0067] S405, collecting the spherical atomized powder through a cyclone separation system.

[0068] The spherical atomized powder prepared in this embodiment has a particle size distribution of 5 to 150 microns, and the content of particles with a size less than 53 microns is 35%.

[0069] Comparative Example 1

[0070] This comparative example directly uses non-hydrogenated titanium alloy rods as titanium alloy rod materials, and the preparation steps are the same as those of Examples S102-S104.

[0071] The spherical atomized powder prepared in this comparative example has a particle size distribution of 5 to 250 microns, and the content of particles with a size less than 53 microns is 28%.

[0072] Comparative Example 2

[0073] In this comparative example, except that the hydrogen content in the titanium alloy rod is 150 ppm, the remaining steps are the same as those of Example 1.

[0074] The spherical atomized powder prepared in the comparative example has a particle size distribution of 5 to 250 microns, and the content of particles with a particle size less than 53 microns is 30%.

[0075] Comparative Example 3

[0076] In this comparative example, except that the hydrogen content in the titanium alloy rod is 1000 ppm, the remaining steps are the same as those of Example 1.

[0077] The spherical atomized powder prepared in this comparative example has a particle size distribution of 5 to 150 microns, and the content of particles with a size less than 53 microns is 40%.

[0078] The present invention obtains a titanium alloy rod with a hydrogen content controlled within the range of 300ppm to 10000ppm by placing hydrogen on a titanium alloy rod, and introduces high-purity argon gas into a high-frequency induction melting zone of an EIGA device. The titanium alloy rod is heated and melted under the action of an electromagnetic field to form a molten liquid flow that falls into an atomization zone. The metal liquid flow entering the atomization zone is broken under the impact of a high-pressure airflow at high speed, so that it is atomized into fine metal droplets. The droplets are changed into spherical particles in the air by surface tension, and are rapidly cooled and solidified into metal powder in an atomization chamber. The metal powder is then collected by a cyclone separation system, and the residual hydrogen in the powder can be simultaneously removed in a vacuum heat treatment process after additive manufacturing. In the present invention, the surface tension and viscosity of the titanium alloy with a high hydrogen content in a molten state are greatly reduced, and the reduced viscosity of the molten metal liquid flow is conducive to the formation of a finer liquid flow, which is conducive to more sufficient atomization to form fine droplets under the impact of a high-pressure airflow in the atomization zone; the reduced surface tension of the liquid flow is conducive to the high-pressure airflow in the atomization zone to disperse and atomize the finer droplets, thereby increasing the fine powder rate and reducing the process cost.

[0079] In addition, the hydrogenation of the titanium alloy rod in the present invention can also adopt a liquid hydrogenation process, or by introducing hydrogen into the molten titanium alloy and diffusing hydrogen into the titanium alloy material, the same effect of the hydrogenation process in the present invention can be achieved; wherein, the introduction of hydrogen into the molten titanium alloy can be achieved by introducing an argon-hydrogen mixture into the smelting zone during the EIGA atomization process to achieve the liquid hydrogenation effect of the titanium alloy, which can also achieve the effect of the surface tension and viscosity of the titanium alloy melt, and has a positive effect on increasing the fine powder rate, which has been described in the above embodiments and will not be repeated.

[0080] The above examples are used to illustrate the specific implementation of the present invention. However, the protection scope of the present invention is not limited to the above exemplary implementation. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for increasing the fine powder rate of titanium alloy ball powder in electrode induction atomization, characterized in that: The method comprises the following steps: A. Put titanium alloy rods with a hydrogen content of 300ppm to 10000ppm into a tubular hydrogen treatment furnace, evacuate and heat to 400~800℃, fill with high-purity hydrogen until the hydrogen partial pressure in the furnace is 5~60KPa, stop filling, keep warm for 5~24h, cool to room temperature, and obtain titanium alloy droplets with a hydrogen content of 5000ppm~10000ppm; or melt the titanium alloy rods first and then place hydrogen in liquid form to obtain a molten titanium alloy with a hydrogen content of 5000ppm~10000ppm; B. atomizing a molten titanium alloy having a hydrogen content of 5000ppm to 10000ppm to obtain titanium alloy ball powder; The method of melting the titanium alloy rod and then placing hydrogen in liquid state comprises the following steps: melting the titanium alloy rod, introducing a mixed gas of inert gas and hydrogen into molten titanium alloy droplets, and obtaining a molten titanium alloy with a hydrogen content of 5000ppm to 10000ppm.

2. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to claim 1 is characterized in that: The following steps are included before step A: cleaning the surface of the titanium alloy rod.

3. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to claim 1 is characterized in that: The heating to 400-800° C. in step A includes: heating to 400-800° C. at a heating rate of 5-15° C. / min.

4. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to any one of claims 1 to 3, characterized in that: When the hydrogen partial pressure in the tubular hydrogen treatment furnace is 10-30 KPa, the inflation is stopped.

5. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to any one of claims 1 to 3, characterized in that: In the mixed gas of the inert gas and hydrogen, the volume ratio of hydrogen to the inert gas is in the range of 0.1-5%.

6. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to any one of claims 1 to 3, characterized in that: The step B comprises the following steps: spraying an inert gas into a molten titanium alloy having a hydrogen content of 5000ppm to 10000ppm through an atomizer nozzle to perform atomization and powdering to obtain atomized powder.

7. The method for improving the fine powder rate of titanium alloy ball powder in electrode induction atomization according to claim 6 is characterized in that: The angle of the gas sprayed by the atomizer nozzle is 5°~80°, and the gas flow rate of the atomizer nozzle is 5~35Nm 3 / min.

8. A titanium alloy atomized powder prepared by the method according to any one of claims 1 to 7, characterized in that: The particle size distribution of the titanium alloy atomized powder is 5-150 μm, and the powder rate with a particle size less than 53 μm is higher than 40%.

9. Use of the titanium alloy atomized powder prepared by the method according to any one of claims 1 to 7 or the titanium alloy atomized powder according to claim 8 in 3D printing.

10. The use according to claim 9, characterized in that: Including 3D printing for the preparation of aviation, aerospace, shipbuilding, chemical or biomedical devices.

11. A method for processing titanium alloy by additive manufacturing, characterized in that: The method comprises the following steps: forming a titanium alloy device by 3D printing the titanium alloy atomized powder prepared by the method described in any one of claims 1 to 7 or the titanium alloy atomized powder described in claim 8.

Images