Preparation method of titanium alloy wire in compressive stress state
By combining conductive pipes with pulse current, compressive stress titanium alloy wires are prepared, which solves the problem of tensile stress elimination of titanium alloy wires after cold drawing, and achieves efficient stress state conversion and performance improvement.
Patent Information
- Application Number
- CN202510380639.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art is difficult to effectively eliminate the tensile stress in the cold-drawn titanium alloy wire material and convert it into compressive stress, resulting in a decrease in its service strength and life, and a brittle oxide layer is easily formed with high-temperature heat treatment.
The conductive pipe material is used as a fixed mold, and the titanium alloy wire is instantly heat-expanded and subjected to extrusion restrictions through pulse current. Using the difference in the thermal expansion coefficient of the material, compressive stress titanium alloy wire material is prepared in a short time.
While eliminating tensile stress, titanium alloy wire material with compressive stress distribution is prepared, which improves its comprehensive mechanical properties and service life. It has a simple process, environmentally friendly and suitable for mass production.
Smart Images
Figure CN120249854A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a preparation method of titanium alloy wire, belonging to the technical field of alloy material processing. Background Art
[0002] After cold drawing, there are inevitable tensile stresses inside the titanium alloy wire, which reduces its service strength and life and limits its further application in human implant devices. If the internal stress state of the wire is compressive stress, not only the alloy strength and life will be improved, but also its surface wear resistance will be significantly improved.
[0003] Currently, an effective method to eliminate the tensile stress of cold-drawn titanium alloy wire is: high-temperature heat treatment in a vacuum furnace for several hours or even dozens of hours. Although this kind of process can eliminate most of the residual tensile stress, it is extremely easy to form a brittle oxide layer on the surface of the titanium alloy wire and cannot induce the generation of compressive stress. Summary of the Invention
[0004] Aiming at the above-mentioned defects of the prior art, the task of the present invention is to provide a preparation method of titanium alloy wire in a compressive stress state, which solves the problems of difficult elimination of tensile stress of traditional treated titanium alloy wire and inability to generate compressive stress.
[0005] The technical solution of the present invention is: a preparation method of titanium alloy wire in a compressive stress state, including: using a conductive pipe as a fixed mold, threading the titanium alloy wire into the fixed mold and tensioning it, the inner diameter of the pipe of the fixed mold being the same as the wire diameter of the titanium alloy wire; connecting electrodes at both ends of the conductive pipe to make the titanium alloy wire pass through a pulsed current, the pulsed current causing the titanium alloy wire to heat and expand and being restricted by the extrusion of the fixed mold; after the pulsed current passes, keeping the titanium alloy wire tensioned and passing it through the fixed mold.
[0006] Further, the coefficient of thermal expansion of the conductive pipe is less than that of the titanium alloy wire.
[0007] Further, the conductive pipe is a hafnium alloy pipe.
[0008] Further, the inner diameter of the conductive pipe is not more than 1 mm.
[0009] Further, the pulsed current is 0.5 - 1.0 A, the frequency is 50 - 200 Hz, preferably 100 - 150 Hz.
[0010] Further, the passing time of the pulsed current is 1 - 5 s, preferably 1 - 3 s.
[0011] Further, when the titanium alloy wire passes through the fixed mold, it passes through at a uniform speed not higher than 15 m / min.
[0012] Furthermore, the tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire.
[0013] The advantages of the present invention compared with the prior art are as follows:
[0014] By virtue of the principle that the degree of thermal expansion during instantaneous heating and slow cooling of the material does not match, the present invention restricts the expansion through a fixed mold during heat treatment. While eliminating the internal tensile stress in the cold-drawn titanium alloy wire, a titanium alloy wire with a compressive stress distribution state is prepared, optimizing the stress distribution in the alloy. This compressive stress helps to hinder the propagation of fatigue cracks, effectively improving the comprehensive mechanical properties of the titanium alloy and extending the service life of titanium alloy medical devices.
[0015] The magnitude of the compressive stress of the titanium alloy wire prepared by the present invention can be quantitatively regulated through the above parameters, which is suitable for product customization.
[0016] Based on the characteristics of self-resistance direct heating and fast heating rate of the titanium alloy, the preparation time of the present invention is within several seconds, with significantly reduced energy consumption and no pollution to the environment. At the same time, the process steps are simple, making it suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic structural diagram of the device for preparing a titanium alloy wire with a compressive stress state.
[0018] Figure 2 It is a microstructural photograph of the titanium alloy wire with a compressive stress state prepared in Example 1.
[0019] Figure 3 It is a microstructural photograph of the titanium alloy wire with a compressive stress state prepared in Example 2.
[0020] Figure 4 It is a microstructural photograph of the titanium alloy wire with a compressive stress state prepared in Example 3.
[0021] Figure 5 It is a microstructural photograph of the titanium alloy wire with a compressive stress state prepared in Example 4.
[0022] Figure 6 It is a microstructural photograph of the titanium alloy wire with a compressive stress state prepared in Example 5.
[0023] Figure 7 It is a microstructural photograph of the titanium alloy wire prepared in the comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] The present invention will be further described below with reference to the embodiments, but it is not intended to limit the present invention.
[0025] The mass percentage components of the cold-drawn bright titanium alloy wire processed in each of the following examples are: the Ti content is 50%, the Ni content is 36%, the copper content is 14%, the wire diameter of the titanium alloy wire is 0.2 mm, and the coefficient of thermal expansion is about 8.0×10 -6 / K. High-temperature resistant and high-strength hafnium alloy tubes are selected as the fixed die. The inner diameter of the hafnium alloy tube is 0.2 mm, the length is 800 mm, the surface roughness of the inner surface is Ra of 0.03 μm, and the coefficient of thermal expansion is about 6.5×10 -6 / K.
[0026] Example 1
[0027] A preparation method of a titanium alloy wire in a compressive stress state, as Figure 1 shown, pass the titanium alloy wire 1 through the fixed die 2. One end of the titanium alloy wire 1 is wound on the pay-off reel 3, and the other end is connected to the take-up reel 4 to make the titanium alloy wire 1 taut. The tension of the titanium alloy wire 1 is not higher than 1 / 50 of the yield stress of the titanium alloy wire 1. The take-up reel 4 can rotate at a constant speed. When the take-up reel 4 rotates, it drives the titanium alloy wire 1 to pass through the fixed die 2 stably.
[0028] At both ends of the fixed die 2, a pulsed current is applied through the electrode fixture, and the following pulsed current parameters are used: the frequency is 100 Hz, the voltage is 25 V, and the overall treatment time is 1 s. The titanium alloy wire 1 is instantaneously heated through a millisecond time interval. The titanium alloy wire 1 expands due to heat, but is restricted by the size of the fixed die 2, so that compressive stress is generated inside the titanium alloy wire 1. When the current is applied, the take-up reel 4 stops rotating.
[0029] Let the titanium alloy wire 1 cool naturally within 3 s after the pulsed current application ends, and water quenching cooling is not allowed. After 3 s from the end of the pulsed current application, the take-up reel 4 rotates to make the titanium alloy wire pass through the fixed die 2 at a speed of 10 m / min, and make the next section of the titanium alloy wire 1 enter the fixed die 2, and so on until all the titanium alloy wires 1 are processed.
[0030] Figure 2 It is a microstructural photograph of the titanium alloy wire prepared in Example 1. From Figure 2 it can be seen that the microstructure has not changed significantly. After measurement, the inside of the titanium alloy wire has shown a compressive stress state, and the stress is -27.8 MPa.
[0031] Example 2
[0032] A preparation method of a titanium alloy wire in a compressive stress state, pass the titanium alloy wire through the fixed die, one end of the titanium alloy wire is wound on the pay-off reel, and the other end is connected to the take-up reel to make the titanium alloy wire taut. The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire. The take-up reel can rotate at a constant speed. When the take-up reel rotates, it drives the titanium alloy wire to pass through the fixed die stably.
[0033] At both ends of the fixed mold, a pulsed current is applied through electrode clamps, and the following pulsed current parameters are used: the frequency is 100 Hz, the voltage is 25 V, and the overall processing time is 3 s. The titanium alloy wire is instantaneously heated through a millisecond time interval. The titanium alloy wire expands due to heat, but is restricted by the extrusion of the fixed mold size, thereby generating compressive stress inside the titanium alloy wire. The take-up reel stops rotating when the current is applied.
[0034] Within 5 s after the pulsed current application ends, the titanium alloy wire is allowed to cool naturally, and water quenching cooling is not allowed. After 5 s from the end of the pulsed current application, the take-up reel rotates to make the titanium alloy wire pass through the fixed mold at a speed of 10 m / min, and the next section of the titanium alloy wire enters the fixed mold, and so on until all the titanium alloy wires are processed.
[0035] Figure 3 Radial compressive stress values and microstructural photographs of the titanium alloy wire prepared for Example 2. From Figure 3 it can be seen that the microstructure has not changed significantly. After measurement, the inside of the titanium alloy wire has shown a compressive stress state, and the stress is -52.3 MPa.
[0036] Example 3
[0037] A method for preparing a titanium alloy wire in a compressive stress state. The titanium alloy wire is passed through a fixed mold. One end of the titanium alloy wire is wound around a pay-off reel, and the other end is connected to a take-up reel to make the titanium alloy wire taut. The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire. The take-up reel can rotate at a constant speed, and when the take-up reel rotates, it drives the titanium alloy wire to pass through the fixed mold stably.
[0038] At both ends of the fixed mold, a pulsed current is applied through electrode clamps, and the following pulsed current parameters are used: the frequency is 150 Hz, the voltage is 25 V, and the overall processing time is 1 s. The titanium alloy wire is instantaneously heated through a millisecond time interval. The titanium alloy wire expands due to heat, but is restricted by the extrusion of the fixed mold size, thereby generating compressive stress inside the titanium alloy wire. The take-up reel stops rotating when the current is applied.
[0039] Within 3 s after the pulsed current application ends, the titanium alloy wire is allowed to cool naturally, and water quenching cooling is not allowed. After 3 s from the end of the pulsed current application, the take-up reel rotates to make the titanium alloy wire pass through the fixed mold at a speed of 10 m / min, and the next section of the titanium alloy wire enters the fixed mold, and so on until all the titanium alloy wires are processed.
[0040] Figure 4 Radial compressive stress values and microstructural photographs of the titanium alloy wire prepared for Example 3. From Figure 4It can be seen that the microstructure has not changed significantly. After measurement, the internal of the titanium alloy wire has shown a compressive stress state, and the stress is -180.9 MPa.
[0041] Example 4
[0042] A method for preparing a titanium alloy wire in a compressive stress state. Pass the titanium alloy wire through a fixed die. One end of the titanium alloy wire is wound around a wire pay-off reel, and the other end is connected to a wire take-up reel to make the titanium alloy wire taut. The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire. The wire take-up reel can rotate at a constant speed, and when the wire take-up reel rotates, it drives the titanium alloy wire to pass through the fixed die stably.
[0043] At both ends of the fixed die, apply a pulsed current through electrode clamps, and use the following pulsed current parameters: the frequency is 200 Hz, the voltage is 25 V, and the overall treatment time is 1 s. Instantly heat the titanium alloy wire through a millisecond time interval. The titanium alloy wire expands due to heat, but is restricted by the size of the fixed die, so that compressive stress is generated inside the titanium alloy wire. When applying the current, the wire take-up reel stops rotating.
[0044] Let the titanium alloy wire cool naturally within 3 s after the pulsed current application ends, and water quenching cooling is not allowed. After 3 s from the end of the pulsed current application, the wire take-up reel rotates to make the titanium alloy wire pass through the fixed die at a speed of 10 m / min, and make the next section of the titanium alloy wire enter the fixed die, and so on until all the titanium alloy wires are processed.
[0045] Figure 5 Radial compressive stress value and microstructure photo of the titanium alloy wire prepared for Example 4. From Figure 5 It can be seen that the microstructure has not changed significantly. After measurement, the internal of the titanium alloy wire has shown a compressive stress state, and the stress is -402.3 MPa.
[0046] Example 5
[0047] A method for preparing a titanium alloy wire in a compressive stress state. Pass the titanium alloy wire through a fixed die. One end of the titanium alloy wire is wound around a wire pay-off reel, and the other end is connected to a wire take-up reel to make the titanium alloy wire taut. The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire. The wire take-up reel can rotate at a constant speed, and when the wire take-up reel rotates, it drives the titanium alloy wire to pass through the fixed die stably.
[0048] At both ends of the fixed die, apply a pulsed current through electrode clamps, and use the following pulsed current parameters: the frequency is 200 Hz, the voltage is 25 V, and the overall treatment time is 3 s. Instantly heat the titanium alloy wire through a millisecond time interval. The titanium alloy wire expands due to heat, but is restricted by the size of the fixed die, so that compressive stress is generated inside the titanium alloy wire. When applying the current, the wire take-up reel stops rotating.
[0049] Let the titanium alloy wire cool naturally within 3 s after the pulse current application ends, and water quenching is not allowed. After 3 s from the end of the pulse current application, the take-up reel rotates to make the titanium alloy wire pass through the fixed die at a speed of 10 m / min, and the next section of the titanium alloy wire enters the fixed die, and so on until all the titanium alloy wires are processed.
[0050] Figure 6 Microstructure photograph of the titanium alloy wire prepared in Example 5. From Figure 6 it can be seen that the microstructure has changed significantly and coarse grains appear.
[0051] Comparative example
[0052] A preparation method of a titanium alloy wire, passing the titanium alloy wire through a fixed die, winding one end of the titanium alloy wire on a pay-off reel, and connecting the other end to a take-up reel to make the titanium alloy wire taut. The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire. The take-up reel can rotate at a constant speed, and when the take-up reel rotates, it drives the titanium alloy wire to pass through the fixed die stably.
[0053] At both ends of the fixed die, a pulse current is applied through electrode clamps, and the following pulse current parameters are used: the frequency is 50 Hz, the voltage is 25 V, and the overall processing time is 1 s. The titanium alloy wire is instantaneously heated through a millisecond time interval. The titanium alloy wire expands due to heat, but is restricted by the extrusion of the fixed die size, so that compressive stress is generated inside the titanium alloy wire. When the current is applied, the take-up reel stops rotating.
[0054] Let the titanium alloy wire cool naturally within 5 s after the pulse current application ends, and water quenching is not allowed. After 5 s from the end of the pulse current application, the take-up reel rotates to make the titanium alloy wire pass through the fixed die at a speed of 10 m / min, and the next section of the titanium alloy wire enters the fixed die, and so on until all the titanium alloy wires are processed.
[0055] Figure 7 Microstructure photograph of the titanium alloy wire prepared in the comparative example. From Figure 7 it can be seen that the microstructure has not changed significantly. After measurement, the internal tensile stress state of the titanium alloy wire is +113.5 MPa.
Claims
1. A preparation method of a titanium alloy wire in a compressive stress state, characterized in that, Comprising: Taking a conductive pipe as a fixed mold, threading a titanium alloy wire into the fixed mold and tensioning it, the inner diameter of the pipe of the fixed mold being the same as the wire diameter of the titanium alloy wire; connecting electrodes to both ends of the conductive pipe to pass a pulsed current through the titanium alloy wire, the pulsed current causing the titanium alloy wire to heat and expand and be restricted by the extrusion of the fixed mold; after the pulsed current passes, keeping the titanium alloy wire in tension and passing it through the fixed mold.
2. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The thermal expansion coefficient of the conductive pipe is less than that of the titanium alloy wire.
3. The preparation method of the compressive stress state titanium alloy wire according to claim 2, characterized in that, The conductive pipe is a hafnium alloy pipe.
4. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The inner diameter of the conductive pipe is not greater than 1 mm.
5. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The pulsed current is 0.5 - 1.0 A and the frequency is 50 - 200 Hz.
6. The preparation method of the compressive stress state titanium alloy wire according to claim 5, characterized in that, The frequency of the pulsed current is 100 - 150 Hz.
7. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The passing time of the pulsed current is 1 - 5 s.
8. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The passing time of the pulsed current is 1 - 3 s.
9. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, When the titanium alloy wire passes through the fixed mold, it passes through at a uniform speed not higher than 15 m / min.
10. The preparation method of the compressive stress state titanium alloy wire according to claim 1, characterized in that, The tension of the titanium alloy wire is not higher than 1 / 50 of the yield stress of the titanium alloy wire.