A superalloy capillary tube and an electro-assisted preparation method thereof

Abstract

The present invention discloses a superalloy capillary tube and an electro-assisted preparation method thereof, comprising the following steps: preparing an initial microtube with an outer diameter of 2.0±0.1 mm and a wall thickness of 50±3 μm from a superalloy blank by using a traditional process; cleaning, drying, tip rolling and lubricating the initial microtube; performing two or three passes of drawing on the microtube by using an electro-assisted hollow drawing process, and performing one pass of electro-assisted annealing treatment on the drawn microtube to eliminate work hardening; repeating the processes of lubrication, two or three passes of electro-assisted drawing, and one pass of electro-assisted annealing to complete the preparation of the capillary tube; straightening, cutting, cleaning and drying the capillary tube, and then performing aging heat treatment to improve the service strength, so as to obtain the final capillary tube product. The electro-assisted hollow drawing and electro-assisted annealing treatment alternately performed in the preparation method of the superalloy capillary tube proposed by the present invention have the advantages of high efficiency, low cost, good product performance, etc., and effectively realize the simultaneous forming and property manufacturing of the superalloy capillary tube.

Description

Technical Field

[0001] The present invention belongs to the technical field of capillary tube preparation, and particularly relates to a superalloy capillary tube and an electro-assisted preparation method thereof. Background Art

[0002] The superalloy capillary tube is a key and core component of a strongly pre-cooled engine heat exchanger. Its outer diameter is at the millimeter level and its wall thickness is at the micron level, which can ensure that the heat exchanger cools the oncoming flow at Mach 5 from 1000 °C to 100 °C in an instant of 0.05 s. The working conditions of high temperature and high pressure and the use requirements of high heat transfer efficiency pose extremely high requirements for the cross-scale manufacturing technology of superalloy capillary tubes.

[0003] Affected by multiple factors such as materials, structures, and processes, traditional manufacturing processes lack methods for precise forming of microstructural features and coordinated control of properties, and need to repeatedly try and error, making it difficult to achieve high-performance target control. Therefore, there is an urgent need to develop a precise, efficient, integrated microfabrication technology for forming and property control suitable for superalloy capillary tubes to improve product quality and comprehensive mechanical properties and solve the key technical bottlenecks restricting the research and development of strongly pre-cooled engines.

[0004] The electro-assisted preparation process may be an effective method for realizing the coordinated manufacturing of the shape and properties of superalloy capillary tubes. This process can use the action of current excitation to change the microscopic physical nature and macroscopic deformation characteristics of superalloys, reduce the deformation resistance of materials, improve the atomic activity inside the materials, and improve the processing performance and plastic deformation ability of materials. At present, this process has been widely used in the preparation of wires such as copper, stainless steel, tungsten, and titanium. However, due to the unique high melting point and hollow thin-wall structure of superalloy capillary tubes, the temperature distribution, process configuration, microstructure evolution, and deformation mode in the electro-assisted tube preparation process are different from those of ordinary metal wire preparation, and the process route needs to be redesigned.

[0005] The superalloy capillary tube preparation method proposed in the invention patent "A Method and System for Preparing Alloy Capillary Tubes" with the publication number CN112934995A only uses electro-assisted annealing and does not apply current to the deformation process. The current-assisted drawing method proposed in the invention patent "Device and Processing Method for Pulse Current-Assisted Drawing of Metal Composite Tubes" with the publication number CN110340165A is liner drawing, which is suitable for preparing metal tubes with larger diameters. However, when using the liner drawing method to prepare capillary tubes with smaller diameters, the capillary tubes will break. At present, there is no process method for simultaneously using electro-assisted annealing and electro-assisted hollow drawing methods to prepare metal capillary tubes, and there is a lack of an effective electro-assisted preparation process route for superalloy capillary tubes. Summary of the Invention

[0006] The present invention provides a superalloy capillary tube and an electro-assisted preparation method thereof. This method uses electro-assisted hollow drawing and electro-assisted annealing to solve the technical problems of high processing difficulty, poor dimensional accuracy, and unstable performance during the micro-forming process of superalloy capillary tubes.

[0007] A superalloy capillary tube prepared by the present invention, the dimensions of the superalloy capillary tube are: outer diameter 0.9 ± 0.03 mm, wall thickness 58 ± 3 μm; the average grain size of the superalloy capillary tube is less than 3 μm, the tensile strength ≥ 1700 MPa, the yield strength ≥ 1200 MPa, and the elongation ≥ 10%.

[0008] The electro-assisted preparation method for preparing a superalloy capillary tube that meets the above dimensions and performance indicators includes the following steps:

[0009] S1: Using traditional processes to prepare a superalloy microtube with an outer diameter of 2.0 ± 0.1 mm and a wall thickness of 50 ± 3 μm from a superalloy billet, and using it as the initial microtube for the electro-assisted preparation process;

[0010] S2: Cleaning, drying, and tip-rolling the initial microtube, and lubricating the outer surface of the microtube with 20,000-mesh graphite powder;

[0011] S3: Conducting two or three passes of electro-assisted hollow drawing on the microtube, with an average diameter reduction of less than 20% per pass. During drawing, the positive and negative electrodes are located between the drawing dies, and the temperature of the drawn area during the drawing process is 550 - 650 °C;

[0012] S4: Conducting electro-assisted annealing treatment on the drawn microtube, with an annealing temperature of 800 - 900 °C and an annealing time of 15 - 20 s;

[0013] S5: Judging whether the diameter of the microtube reaches the target diameter of the capillary tube. If it reaches, proceed to the next step. If not, after lubricating the current microtube, repeat steps S3 and S4;

[0014] S6: Straightening the capillary tube to improve the straightness of the capillary tube;

[0015] S7: Cutting off the excess part of the capillary tube, and cleaning and drying the capillary tube;

[0016] S8: Conducting age heat treatment on the capillary tube to improve the service strength of the capillary tube and obtain the final capillary tube.

[0017] In the electro-assisted preparation method of the superalloy capillary tube provided by the present invention, an infrared thermal imager is used for real-time temperature measurement during the electro-assisted drawing and electro-assisted annealing processes.

[0018] In the above-mentioned electro-assisted preparation method of the superalloy capillary tube provided by the present invention, in step S3, two or three passes of electro-assisted hollow drawing are carried out, which specifically include the following steps:

[0019] S31: Set the drawing speed of the drawing machine to 300 mm / min;

[0020] S32: Install the drawing die, and draw the microtube about 120 mm by conventional hollow drawing;

[0021] S33: Add a positive electrode power supply device and a negative electrode power supply device to the non-drawn and drawn areas of the microtube respectively. The distance between the positive electrode power supply device and the drawing die is 50 mm, and the distance between the negative electrode power supply device and the drawing die is 100 mm. Place the infrared thermal imager between the negative electrode power supply device and the drawing die;

[0022] S34: Energize the microtube, and start electro-assisted hollow drawing after the drawn area stabilizes to 550-650 °C;

[0023] S35: Stop energizing when the microtube is about to pass through the positive electrode power supply device, and complete the final drawing process by conventional drawing;

[0024] S36: Repeat steps S32 to S35 to complete the next pass of electro-assisted hollow drawing.

[0025] In the above-mentioned electro-assisted preparation method of the superalloy capillary tube provided by the present invention, in step S4, one pass of electro-assisted annealing treatment is carried out, which specifically includes the following steps:

[0026] S41: Remove the drawing die, adjust the distance between the positive and negative electrode power supply devices to 100 mm, and the drawing speed of the drawing machine remains 300 mm / min;

[0027] S42: Energize, and start moving the microtube driven by the drawing machine after the temperature stabilizes to 800-900 °C. During this period, the microtube is annealed for 15-20 s;

[0028] S43: Stop energizing when the microtube is about to pass through the positive electrode power supply device to complete the annealing treatment.

[0029] In the above-mentioned electro-assisted preparation method of the superalloy capillary tube provided by the present invention, in step S7, the redundant part of the capillary tube includes the conventional drawing areas in the early and late stages of drawing and the tip rolling positions, and it should be ensured that the remaining part is a uniform area after electro-assisted drawing + electro-assisted treatment.

[0030] Advantages of the present invention over the prior art:

[0031] (1) Based on the characteristics of the superalloy capillary material, structure, and process, and leveraging the advantages of electro-assisted hollow drawing and electro-assisted annealing, the present invention optimizes process parameters such as the number of drawing passes, drawing speed, annealing temperature, and annealing time, and for the first time proposes an electro-assisted preparation process route for superalloy capillaries that combines two or three passes of electro-assisted hollow drawing with one pass of electro-assisted annealing.

[0032] (2) The present invention limits the temperature of electro-assisted hollow drawing to 550 - 650 °C. At this temperature, the electroplastic effect brought by the current can improve the uniform deformation ability of superalloy grains, reduce the drawing force, and effectively enhance the surface quality and geometric accuracy of the capillary. In addition, the speed of electro-assisted hollow drawing is limited to 300 mm / min, which is significantly higher than the drawing speed of 50 mm / min in Patent CN112934995A, improving the processing efficiency while ensuring the processing accuracy of the capillary.

[0033] (3) Based on electro-assisted hollow drawing, the present invention limits the temperature and time of electro-assisted annealing to 800 - 900 °C and 15 - 20 s respectively. Compared with the traditional superalloy annealing temperature of 1050 °C and annealing time of 30 min, the temperature is lower and the time is shorter, with advantages such as low cost and high efficiency. At the same time, the electroplastic effect of the current is used to quickly achieve complete recrystallization of the capillary and prevent grain growth. The average grain size of the superalloy capillary is less than 3 μm, effectively enhancing the strength and toughness of the capillary.

[0034] (4) The process route proposed by the present invention, where electro-assisted annealing is performed once every two or three passes of electro-assisted hollow drawing, can eliminate work hardening while ensuring processing efficiency, and avoid defects such as wrinkling and cracking during the drawing process of the capillary.

[0035] (5) The electro-assisted preparation process route for superalloys proposed by the present invention can effectively form superalloy capillaries that meet the usage requirements, and is very suitable for the efficient and precision forming manufacturing of thin-walled capillaries made of difficult-to-deform superalloy materials. Description of the Drawings

[0036] Figure 1 It is a process route diagram for the electro-assisted preparation of superalloy capillaries provided by the present invention;

[0037] Figure 2 It is a diagram of the electro-assisted drawing and annealing passes of the GH4169 capillary in Example 1 of the present invention;

[0038] Figure 3 It is a schematic diagram of the electro-assisted hollow drawing of the capillary provided by the present invention;

[0039] Figure 4 It is the GH4169 capillary obtained in Example 1 of the present invention;

[0040] Figure 5 This is the microstructure diagram of the GH4169 capillary in Embodiment 1 of the present invention. Specific Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are merely examples and are not used to limit the present invention.

[0042] Embodiment 1:

[0043] In this embodiment, the specific material of the superalloy capillary to be prepared is GH4169, with an outer diameter of 0.9 ± 0.03 mm and a wall thickness of 58 ± 3 μm. A superalloy capillary electro-assisted preparation process route provided by the present invention is as Figure 1 shown, and the specific processing passes are as Figure 2 shown, including six passes of electro-assisted hollow drawing, three passes of electro-assisted annealing treatment, and one pass of direct aging heat treatment. The specific steps are as follows:

[0044] S1: Using traditional processes, prepare a semi-hard superalloy microtube with an outer diameter of about 2.0 mm and a wall thickness of about 50 μm from a superalloy billet, and use it as the initial microtube for the electro-assisted preparation process;

[0045] S2: Clean, dry, and tip the initial microtube, and lubricate the outer surface of the microtube with 20,000-mesh graphite powder;

[0046] S3: Conduct the first pass of electro-assisted hollow drawing, and the specific steps include:

[0047] (1) Set the drawing speed of the drawing machine to 300 mm / min;

[0048] (2) Install the drawing die, and draw the microtube about 120 mm using conventional hollow drawing;

[0049] (3) Add a positive power supply device and a negative power supply device to the non-drawn and drawn areas of the microtube respectively. The distance between the positive power supply device and the drawing die is 50 mm, and the distance between the negative power supply device and the drawing die is 100 mm. Place the infrared thermal imager between the negative power supply device and the drawing die. The schematic diagram of electro-assisted hollow drawing is as Figure 3 shown.

[0050] (3) Energize the microtube, and start electro-assisted hollow drawing after the drawn area stabilizes to 600 °C;

[0051] (4) Stop energizing when the microtube is about to pass through the positive power supply device, and complete the final drawing process using conventional drawing methods;

[0052] S4: Installation Install the drawing die and perform the second-pass electro-assisted tube drawing. The specific steps are the same as those in S3;

[0053] S5: Perform the first-pass electro-assisted annealing treatment. The specific steps include:

[0054] (1) Remove the drawing die, adjust the distance between the positive and negative power supply devices to 100 mm, and the drawing speed of the drawing machine remains 300 mm / min;

[0055] (2) Apply electricity. After the temperature stabilizes at 850 °C, the drawing machine drives the microtube to start moving. During this period, the microtube is annealed for 15 - 20 s;

[0056] (3) Stop applying electricity when the microtube is about to pass through the positive power supply device to complete the annealing treatment;

[0057] S6: Installation Install the drawing die and perform the third-pass electro-assisted tube drawing. The specific steps are the same as those in S3;

[0058] S7: Installation Install the drawing die and perform the fourth-pass electro-assisted tube drawing. The specific steps are the same as those in S3;

[0059] S8: Perform the second-pass electro-assisted annealing treatment. The specific steps are the same as those in S5.

[0060] S9: Installation Install the drawing die and perform the fifth-pass electro-assisted tube drawing. The specific steps are the same as those in S3;

[0061] S10: Installation Install the drawing die and perform the sixth-pass electro-assisted tube drawing. The specific steps are the same as those in S3;

[0062] S11: Perform the third-pass electro-assisted annealing treatment. The specific steps are the same as those in S5.

[0063] S12: Straighten the capillary tube, cut off the conventional drawing area and the tip position at the early and late stages of capillary tube drawing, and ensure that the remaining part is the uniform area after electro-assisted drawing + electro-assisted treatment.

[0064] S13: Clean the capillary tube. After drying, perform direct aging heat treatment on the capillary tube. The heat treatment route is 720 °C ± 5 °C, 8 h, furnace cooling to 620 °C ± 5 °C at 50 °C / h, 8 h, and air cooling to obtain the final capillary tube.

[0065] The superalloy capillary tube prepared in this embodiment is as Figure 4As shown, the outer diameter is 0.895 mm, the wall thickness is 58.04 μm, the surface roughness Ra is 0.131 μm, the yield strength is 1272 MPa, the tensile strength is 1740 MPa, and the elongation is 13.2%. Compared with the superalloy capillary tubes manufactured by traditional processes, the wall thickness of the superalloy capillary tubes manufactured by the electro-assisted process is reduced by 2 μm, the surface quality is improved by 129.0%, the tensile strength is increased by 31.1%, and the elongation is increased by 9.4%. In addition, the electro-assisted manufacturing process achieves significant fine grain strengthening, the average grain size is less than 3 μm, and its tissue uniformity is significantly improved, as Figure 5 shown.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A method for electro-assisted preparation of a superalloy capillary tube, characterized in that, It includes the following steps: S1: Prepare a superalloy microtube with an outer diameter of 2.0 ± 0.01 mm and a wall thickness of 50 ± 3 μm from a superalloy billet using traditional processes, and use it as the initial microtube for the electro-assisted preparation process; S2: Clean, dry, and tip-roll the initial microtube, and lubricate the outer surface of the microtube with 20,000-mesh graphite powder; S3: Conduct two or three passes of electro-assisted hollow drawing on the microtube, with an average diameter reduction of less than 20% in each pass. During drawing, the positive and negative electrodes are located between the drawing dies, and the temperature of the drawn area during the drawing process is 550 - 650 °C; S4: Conduct electro-assisted annealing treatment on the drawn microtube, with an annealing temperature of 800 - 900 °C and an annealing time of 15 - 20 s; S5: Determine whether the diameter of the microtube reaches the target diameter of the capillary. If it does, proceed to the next step. If not, after lubricating the current microtube, repeat steps S3 and S4; S6: Straighten the capillary to improve its straightness; S7: Cut off the excess part of the capillary, and clean and dry the capillary; S8: Conduct age heat treatment on the capillary to improve its service strength and obtain the final capillary; In step S3, when conducting two or three passes of electro-assisted hollow drawing, it specifically includes the following steps: S31: Set the drawing speed of the drawing machine to 300 mm / min; S32: Install the drawing die, and draw the microtube about 120 mm using conventional hollow drawing; S33: Add a positive electrode power supply device and a negative electrode power supply device to the undrawn and drawn areas of the microtube respectively. The distance between the positive electrode power supply device and the drawing die is 50 mm, and the distance between the negative electrode power supply device and the drawing die is 100 mm. Place the infrared thermal imager between the negative electrode power supply device and the drawing die; S34: Energize the microtube, and start electro-assisted hollow drawing after the drawn area stabilizes at 550 - 650 °C; S35: Stop energizing when the microtube is about to pass through the positive electrode power supply device, and complete the final drawing process using the conventional drawing method; S36: Repeat steps S32 to S35 to complete the next pass of electro-assisted hollow drawing.

2. The electro-assisted preparation method of the superalloy capillary tube according to claim 1, characterized in that During the electro-assisted drawing and electro-assisted annealing processes, an infrared thermal imager is used for real-time temperature measurement.

3. The electro-assisted preparation method of the superalloy capillary tube according to claim 1, wherein In step S4, when conducting one pass of electro-assisted annealing treatment, it specifically includes the following steps: S41: Remove the drawing die, adjust the distance between the positive and negative electrode power supply devices to 100 mm, and the drawing speed of the drawing machine remains 300 mm / min; S42: Energize, and start moving the microtube driven by the drawing machine after the temperature stabilizes at 800 - 900 °C. During this period, the microtube is annealed for 15 - 20 s; S43: Stop energizing when the microtube is about to pass through the positive electrode power supply device to complete the annealing treatment.

4. The electro-assisted preparation method of the superalloy capillary according to claim 1, wherein, In step S7, the excess part of the capillary includes the conventional drawing areas and the tip-rolled positions in the early and late stages of drawing, and it should be ensured that the remaining part is a uniform area after electro-assisted drawing + electro-assisted treatment.

5. A superalloy capillary tube, characterized in that, Obtained by the method for electro-assisted preparation of superalloy capillary tubes described in claim 1, the dimensions of the superalloy capillary tubes are: outer diameter 0.9 ± 0.03 mm, wall thickness 58 ± 3 μm; the average grain size of the superalloy capillary tubes is less than 3 μm, the tensile strength ≥ 1700 MPa, the yield strength ≥ 1200 MPa, and the elongation ≥ 10%.

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