Low-oxygen small-size titanium alloy powder and preparation method and application thereof

Abstract

The invention discloses low-oxygen small-size titanium alloy powder and a preparation method and application thereof. The invention belongs to the field of titanium alloy powder preparation. The invention aims to solve the technical problems of high cost and poor mechanical stability of the device due to the fact that the particle size of powder is reduced by increasing the rotating speed of an electrode and increasing the size of the electrode in the conventional rotating electrode pulverizing method. The method comprises the following steps: adopting a rotating electrode powder preparation method, taking a radio frequency hydrogen plasma emitter as a heat source, placing a plasma arc in a dynamic rotating magnetic field generated by two orthogonally arranged electromagnetic coils, starting the heat source after a rotating consumable electrode reaches a preset rotating speed, vacuumizing and then preparing powder in an argon-hydrogen mixed atmosphere; and carrying out high-temperature and constant-temperature sintering on the prepared powder under a vacuum condition to obtain the low-oxygen small-size titanium alloy powder. According to the method, fluid granulation and fine powder generation are promoted, the oxygen element impurity content in the alloy powder is effectively reduced, the cost is lower, the mechanical stability is higher, and the impurity content is lower.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloy powder preparation, and in particular relates to a low-oxygen small-size titanium alloy powder and a preparation method and application thereof. Background Art

[0002] Titanium alloys are widely used in basic industrial fields such as aerospace, petroleum energy, medical equipment, and marine ships due to their advantages such as high specific strength, low thermal expansion coefficient, strong corrosion resistance, and good biocompatibility. However, factors that restrict its further application include complex preparation process, low material utilization, simple part forming structure, and difficult cutting deformation processing. In recent years, hot isostatic pressing powder metallurgy method and powder titanium alloy additive manufacturing technology have gradually developed into important processes for solving the preparation of complex titanium alloy parts. These technologies have put forward high requirements on the chemical composition, sphericity, and fluidity of the raw material spherical powder. However, titanium alloy powder is different from conventional metal powder. Its extremely strong room temperature oxygen absorption characteristics and high temperature reaction activity make the preparation process of titanium alloy powder different from that of conventional metal powder. Therefore, the preparation process of spherical titanium powder is an important basis for the production and manufacturing of titanium alloys.

[0003] Plasma Rotating Electrode Process (PREP) is one of the commonly used methods for preparing spherical titanium alloy powder. It is a centrifugal atomization method, the principle of which is to process the master alloy into an electrode rod, and use the electric arc as a heat source to continuously melt the high-speed rotating metal rod. In the molten state, the molten metal droplets on the end of the alloy rod are thrown out under the action of centrifugal force, and are 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 atomizing of the metal, thereby eliminating the pollution source of non-metallic inclusions. Such a preparation process can produce high-cleanliness powder, which meets the requirements of titanium alloy powder in various application fields, such as aerospace, medical equipment, etc. The application of the PREP method improves the quality and availability of titanium alloy powder and promotes the further development and application of titanium alloy materials.

[0004] Generally, the method to reduce the powder particle size is to increase the electrode rotation speed and increase the electrode size. However, the method of reducing the powder size by increasing the rotation speed is ineffective to a certain extent, and increasing the rotation speed will increase the production cost, reduce the mechanical stability of the device, and even produce friction debris pollution. At the same time, although increasing the diameter of the rotating electrode can reduce the powder size, this places high demands on the equipment. Therefore, it is necessary to develop new methods to more effectively reduce alloy powder contamination, reduce powder particle size, and provide higher quality titanium alloy powder materials. Summary of the invention

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

[0006] One of the purposes of the present invention is to provide a method for preparing low-oxygen small-size titanium alloy powder, the method being carried out according to the following steps:

[0007] 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 a dynamic rotating magnetic field generated by two orthogonal electromagnetic coils. The heat source is started after the rotating consumable electrode reaches a preset speed, and the powder is made in an argon-hydrogen mixed atmosphere after vacuuming;

[0008] S2: The prepared powder is subjected to high temperature constant temperature sintering under vacuum conditions to obtain low-oxygen small-sized titanium alloy powder.

[0009] It is further defined that the diameter of the rotating consumable electrode in S1 is 70-80 mm, and the roundness deviation is required to be less than 0.05 mm, and the straightness deviation is required to be less than 0.01 mm / m.

[0010] It is further defined that the vacuum degree in S1 is ≤5×10-3Pa.

[0011] It is further defined that the hydrogen partial pressure in the argon-hydrogen mixed gas in S1 is 1-50%, and the gas is filled to 0.04-0.05 MPa.

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

[0013] It is further defined that the plasma arc rotation oscillation frequency in S1 is 10-50 Hz and the deflection angle is 5-45°.

[0014] It is further defined that the vacuum degree in S2 is ≤5×10-3Pa.

[0015] It is further defined that the sintering temperature in S2 is 600-800°C and the sintering time is 5-7h.

[0016] A second object of the present invention is to provide a titanium alloy powder prepared according to the above method, wherein the particle size of the titanium alloy powder is less than 200 μm and the oxygen content is ≤1100 ppm.

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

[0018] Compared with the prior art, the present invention has the following significant effects:

[0019] The present invention uses a radio frequency hydrogen plasma emitter as a heat source, avoiding the electrode contamination that may exist in traditional tungsten electrodes; magnetic arc oscillation is introduced on the basis of the radio frequency hydrogen plasma emitter, and the disturbance of the fluid is increased by magnetic arc oscillation, which promotes fluid granulation and the generation of fine powder; in addition, the oxygen impurity content in the alloy powder is effectively reduced, and the hydrogen element is dissolved in the titanium alloy, which improves its viscosity and surface tension, thereby reducing the particle size of the ejected droplets. Compared with the traditional method, this improved method has lower cost, stronger mechanical stability, and less impurity content. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

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

[0024] The "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present invention. The "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0025] The endpoints and any values ​​of the ranges disclosed in the 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

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

[0027] (1) TC4 titanium alloy bar Install it into the rotary feed device and seal it. Evacuate the atomization chamber to a vacuum degree of ≤5×10 -3 After Pa, argon is filled to 0.05MPa and the circulation pump is started, and then the cooling system is started. The purity of argon is ≥99.999%.

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

[0029] (3) The prepared powder is subjected to a constant temperature dehydrogenation treatment in a high temperature vacuum sintering furnace. The process is 700°C / 6h, and the vacuum degree is controlled at 5×10 -3 After the constant temperature is over, the heating system is turned off and the temperature drops naturally to 30℃.

[0030] The hydrogen and oxygen contents of the product powder were measured 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 of this example is carried out according to the following steps:

[0032] (1) TC4 titanium alloy bar Install it into the rotary feed device and seal it. Evacuate the atomization chamber to a vacuum degree of ≤5×10 -3 After Pa, fill in argon and hydrogen mixed gas to 0.05MPa and start the circulation pump. The argon and hydrogen partial pressure ratio is 8:2. Then start the cooling system. The argon purity is ≥99.999%.

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

[0034] (3) The prepared powder is subjected to a constant temperature dehydrogenation treatment in a high temperature vacuum sintering furnace. The process is 700°C / 6h, and the vacuum degree is controlled at 5×10 -3 After the constant temperature is over, the heating system is turned off and the temperature drops naturally to 30℃.

[0035] The hydrogen and oxygen contents of the product powder were measured 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 the low-oxygen small-size titanium alloy powder of this example is carried out according to the following steps:

[0037] (1) TC4 titanium alloy bar Install it into the rotary feed device and seal it. Evacuate the atomization chamber to a vacuum degree of ≤5×10 -3 After Pa, fill in argon and hydrogen mixed gas to 0.05MPa and start the circulation pump. The argon and hydrogen partial pressure ratio is 8:2. Then start the cooling system. The argon purity is ≥99.999%.

[0038] (2) Start the rotation button to gradually accelerate the rotation of the rod. When it reaches 18000r / min, start the power supply of the radio frequency hydrogen plasma transmitter with a current of 2200A. The plasma arc is placed in a dynamic rotating magnetic field generated by two orthogonal electromagnetic coils to make the plasma arc rotate and oscillate. The frequency of the plasma arc rotation oscillation is 10Hz and the deflection angle is 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 metal liquid film, which is separated from the rod and forms tiny droplets under the combined action of centrifugal force and surface tension. It solidifies into metal powder under the cooling action of the cooling gas. Subsequently, start the rotary feed button and adjust the feed rate to 1.5mm / s to feed the rod continuously to ensure the continuous progress of the powder making process. During the powder making process, the operation of the equipment should be observed at any time and records should be kept.

[0039] (3) The prepared powder is subjected to a constant temperature dehydrogenation treatment in a high temperature vacuum sintering furnace. The process is 700°C / 6h, and the vacuum degree is controlled at 5×10 -3 After the constant temperature is over, the heating system is turned off and the temperature drops naturally to 30℃.

[0040] The hydrogen and oxygen contents of the product powder were measured 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 powder obtained 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 are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing low-oxygen small-size titanium alloy powder, characterized in that: The method: 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 a dynamic rotating magnetic field generated by two orthogonal electromagnetic coils. The heat source is started after the rotating consumable electrode reaches a preset speed, and the powder is made in an argon-hydrogen mixed atmosphere after vacuuming; S2: The prepared powder is subjected to high temperature constant temperature sintering under vacuum conditions 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 The vacuum degree in S1 is ≤5×10-3Pa.

4. The method according to claim 1, characterized in that: The hydrogen partial pressure in the argon-hydrogen mixed gas in S1 is 1-50%, and the gas is filled to 0.04-0.05MPa.

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

6. The method according to claim 1, characterized in that The plasma arc rotation oscillation frequency in S1 is 10-50Hz, and the deflection angle is 5-45°.

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

8. The method according to claim 1, characterized in that The sintering temperature in S2 is 600-800°C and the sintering time is 5-7h.

9. The titanium alloy powder prepared by the method according to any one of claims 1 to 8, characterized in that: The particle size of the titanium alloy powder is less than 200 μm, and the oxygen content is less than or equal to 1100 ppm.

10. Use of the titanium alloy powder according to claim 9 in hot isostatic pressing powder metallurgy and powder additive manufacturing.

Images