A nickel-titanium memory alloy pipe and a preparation method and application thereof

Abstract

The application discloses a kind of nickel-titanium memory alloy pipe and its preparation method, application.The preparation method includes: providing a nickel-titanium memory alloy bar material, the content of nickel in bar material is: 54%-58%;The bar material is opened, and the pipe material of preset inner diameter is obtained;Using air-drawing reducing technology is drawn to pipe material several times, to reduce the diameter of pipe material, wherein, after each drawing, the area variable of pipe material is not more than 15%;The pipe material after reducing diameter is profiled, to obtain profiled pipe material;Profiled pipe material is placed into profiled forming die group and heat treated, to activate the memory alloy function of profiled pipe material, to obtain target pipe material with phase transition temperature of-20℃-60℃, wherein, the temperature of profiled forming die group heat treatment is 500-530 degrees, and the setting time is 25-35 minutes.The preparation method of the application is simple, and the target pipe material obtained can form a uniform and delicate metal luster surface, so it can be directly used as a structural appearance part, and has good environmental adaptability.

Description

Technical Field

[0001] This application relates to the field of materials processing technology, and in particular to a nickel-titanium shape memory alloy pipe, its preparation method, and its application. Background Technology

[0002] Nickel-titanium shape memory alloys have been applied in aerospace, aviation, construction, biomedicine and daily life due to their shape memory effect and related superelasticity, especially in the biomedical field.

[0003] Currently, nickel-titanium shape memory alloy tubing is rarely used in products, especially shaped nickel-titanium alloy tubing. Through extensive research and practice, the inventors of this application have discovered that the processing of shaped nickel-titanium alloy tubing in existing technologies is complex, has a low yield rate, and the resulting shaped tubing is difficult to use as structural or aesthetic components. Summary of the Invention

[0004] This application provides a nickel-titanium shape memory alloy tube, its preparation method, and its application, in order to solve the technical problems in the prior art where the processing of nickel-titanium alloy irregular-shaped tubes is complicated, the yield is low, and the obtained irregular-shaped tubes are difficult to use as structural appearance parts.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: a method for preparing nickel-titanium shape memory alloy tubing, the method comprising: providing a nickel-titanium shape memory alloy rod, wherein the nickel content in the rod is 54%-58%; making holes in the rod to obtain a tubing with a preset inner diameter; drawing the tubing several times using a vacuum drawing reduction technique to reduce the diameter of the tubing, wherein the tubing is heat-treated in a vacuum furnace after each drawing, and the area change of the tubing after each drawing does not exceed 15%; subjecting the reduced-diameter tubing to a shaped process to obtain a shaped tubing; placing the shaped tubing into a shaped forming module for heat treatment to activate the shape memory alloy function of the shaped tubing to obtain a target tubing with a phase transformation temperature of -20℃ to 60℃, wherein the heat treatment temperature of the shaped forming module is 500-530 degrees Celsius, and the shaping time is 25-35 minutes.

[0006] Furthermore, the steps for shaping the reduced-diameter pipe include: shaping the reduced-diameter pipe through the through hole of the drawing die, and bending the shaped pipe to obtain the shaped pipe.

[0007] Furthermore, the drawing die includes at least two drawing sub-dies, the width of the through holes of the at least two drawing sub-dies gradually decreases, and the preparation method includes: drawing the reduced diameter tube sequentially through the drawing sub-dies with gradually decreasing through hole widths.

[0008] Furthermore, after the reduced diameter tube passes through the through hole of each drawing die, the change in its area is less than 2%.

[0009] Furthermore, the drawing die also includes at least two inner dies, the outer diameters of the at least two inner dies gradually decreasing, and at least two drawing sub-dies corresponding one-to-one with the at least two inner dies. The preparation method further includes: inserting the inner dies with gradually decreasing outer diameters into the tube after the diameter reduction in sequence, so as to draw them through the corresponding drawing sub-dies respectively.

[0010] Furthermore, the step of drilling holes in the bar stock includes drilling holes in the bar stock through electrode drilling and wire cutting processes to obtain a tube with an arithmetic mean roughness of less than or equal to 0.3.

[0011] Furthermore, the steps of drawing the pipe several times using the air-drawing diameter reduction technology include: drawing the pipe 15-30 times using cold drawing, and heat-treating it in a vacuum furnace at a temperature of 600-700 degrees Celsius, with the vacuum furnace filled with argon gas.

[0012] Furthermore, the preparation method also includes: roughing the target pipe by magnetic needle polishing / brown corundum polishing process; and fine polishing the roughened target pipe by manual wire wheel in conjunction with polishing wax.

[0013] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a nickel-titanium shape memory alloy tube, which is prepared by the preparation method of any of the above embodiments.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide an application of nickel-titanium shape memory alloy tubing in earphone clips, medical supplies, toys or couplings.

[0015] Beneficial Effects: Unlike existing technologies, this application provides a method for preparing nickel-titanium shape memory alloy tubing. The method includes: providing a nickel-titanium shape memory alloy rod with a nickel content of 54%-58%; drilling a hole in the rod to obtain a tubing with a predetermined inner diameter; drawing the tubing several times using a vacuum drawing technique to reduce its diameter, wherein the tubing is heat-treated in a vacuum furnace after each drawing, and the area change of the tubing after each drawing does not exceed 15%; subjecting the reduced-diameter tubing to a shaped process to obtain a shaped tubing; placing the shaped tubing into a shaping module for heat treatment to activate the shape memory alloy function of the shaped tubing, thereby obtaining a target tubing with a phase transformation temperature of -20℃ to 60℃, wherein the heat treatment temperature of the shaping module is 500-530℃, and the shaping time is 25-35 minutes. The preparation method provided by this application can obtain shaped nickel-titanium alloy tubing. This preparation method is simple, has a high yield, and is low in cost. The resulting target pipe can form a uniform and delicate metallic luster surface, making it suitable for direct use as a structural appearance component. Furthermore, the target pipe has good environmental adaptability, which expands its application range. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of a method for preparing a nickel-titanium shape memory alloy tube provided in this application;

[0018] Figure 2 This is a schematic diagram of the structure of a bar stock to be processed according to this application;

[0019] Figure 3 Through Figure 2 A schematic diagram of a structure of a tube obtained from the shown bar material;

[0020] Figure 4 yes Figure 3 The diagram shows the structure of the pipe after diameter reduction;

[0021] Figure 5 yes Figure 4 A schematic diagram of an embodiment of the irregularly shaped pipe obtained after bending the pipe shown;

[0022] Figure 6 yes Figure 4 The diagram shows the cross-sectional changes of a pipe as it is processed from a round pipe into a flat pipe.

[0023] Figure 7 yes Figure 6 The diagram shows the structure of the irregularly shaped pipe obtained after bending the pipe. Detailed Implementation

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0025] The terms "first," "second," etc., used in this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] This application provides a method for preparing nickel-titanium shape memory alloy tubing, which can process nickel-titanium alloy shaped tubing and achieve a high-gloss finish on both the inner and outer walls of the formed tubing. The preparation method for nickel-titanium shape memory alloy tubing provided in this application will be described in detail below.

[0028] Please see Figure 1 As shown, Figure 1 This is a schematic flowchart of an embodiment of a method for preparing a nickel-titanium shape memory alloy tube provided in this application. Specifically, the preparation method includes:

[0029] S11: Provide a nickel-titanium shape memory alloy rod, wherein the nickel content in the rod is 54%-58%.

[0030] First, obtain a nickel-titanium shape memory alloy rod to be processed. The obtained rod is as follows: Figure 2As shown in the figure, the rod 10 can be cylindrical. In other embodiments, the rod 10 can also be cuboid.

[0031] If the outer diameter of bar 10 does not meet the requirements, it can be processed to the required specifications using a diameter reduction technique. For example, bar 10 can be drawn using cold drawing and tempering processes to reduce its diameter to the required specifications while maintaining its original phase transformation and memory function. If the outer diameter of bar 10 meets the requirements, then step S12 below can be performed directly.

[0032] Furthermore, the nickel content in rod 10 is 55%-58%, for example, in a specific embodiment, the nickel content in rod 10 can be 56.06%. The nickel content in the nickel-titanium shape memory alloy rod has a crucial impact on its shape memory function and superelasticity. Through extensive experimentation, the inventors have confirmed that by selecting nickel-titanium alloy rods of the above specifications and combining them with specific subsequent processing techniques, shape memory tubing with a wide phase transition temperature range can be obtained, thereby improving the temperature adaptability of the tubing.

[0033] S12: Drill holes in the bar to obtain a tube with a preset inner diameter.

[0034] After obtaining the nickel-titanium shape memory alloy rod, holes are drilled in the rod to obtain a tube with a predetermined inner diameter. For example, for... Figure 2 By drilling holes in the bar 10 shown, we can obtain... Figure 3 Pipe 11 is shown.

[0035] Alternatively, holes can be drilled in the bar using electrode drilling and wire cutting processes to obtain a tube with an arithmetic mean roughness of less than or equal to 0.3 μm.

[0036] Electrode drilling is a non-contact machining technique that uses the principle of electro-spark etching to create tiny holes in conductive materials. It is suitable for precision drilling requirements in materials with high hardness, high toughness, or complex shapes. During electro-spark etching, a tiny gap (approximately 0.01–0.1 mm) is maintained between the electrode (tool electrode) and the rod material. A high-frequency pulse voltage is applied in an insulating medium (such as deionized water or kerosene). This generates instantaneous high temperatures (locally reaching 10,000°C), causing the rod material to locally melt and vaporize, forming a hole through electrical discharge etching. Electrode drilling involves no mechanical stress and can be used for thin-walled structures.

[0037] When drilling electrodes, use a low discharge current (e.g., less than 4A) to reduce the energy of a single discharge and decrease the depth of the surface pit; shorten the pulse time (<5μs) to reduce the size of the discharge pit; select high-purity copper or graphite electrodes to reduce the impact of electrode wear on accuracy; and use low-viscosity, high-cleanliness deionized water or kerosene to ensure that the etching products are discharged in a timely manner.

[0038] After drilling holes in the rod, in order to further reduce the roughness of the inner wall of the rod after drilling, this application uses wire cutting technology for further finishing. Wire cutting is a process of cutting the profile by moving a metal wire (electrode wire) through electrical discharge. The wire cutting process may include: (1) guiding the electrode wire into the interior of the rod through a pre-machined wire hole (completed by the above-mentioned electrode drilling). (2) inputting the pre-generated cutting path and setting the offset (to compensate for the electrode wire diameter and discharge gap). (3) removing the material quickly with high energy parameters (the surface roughness Ra can reach 1.0 to 2.0 μm). (4) gradually reducing the energy and performing 1 to 3 finishing passes, the final roughness can reach Ra≤0.3 μm. (5) after cutting, the electrode wire is cut off or retracted to separate the tube from the waste. The wire cutting process has high precision and controllable surface quality.

[0039] For example, in one embodiment, the pipe has a wall roughness of 0.2 μm.

[0040] The electrode drilling and wire cutting processes described above can produce low-roughness holes, which can delay fatigue crack propagation, facilitate subsequent processing, and significantly extend the service life of the pipe by reducing friction, corrosion, and fatigue.

[0041] In other embodiments, holes can also be drilled in the nickel-titanium alloy rod using a laser. These will not be listed here.

[0042] S13: The tube is drawn several times using the air-drawing diameter reduction technology to reduce its diameter. After each drawing, the tube is heat-treated in a vacuum furnace, and the area change of the tube after each drawing does not exceed 15%.

[0043] like Figure 3 As shown, after obtaining the pipe 11, the dimensions of the pipe 11 may not meet the usage requirements. This application uses a drawing reduction technique to reduce the diameter of the pipe 11, and the resulting pipe can be referenced. Figure 4 The tube 11 shown is an example. For instance, in some specific embodiments, the original outer diameter of the tube is 5 mm and the inner wall thickness is 1 mm. After 17 drawing cycles, the outer diameter of the tube becomes 15 mm and the inner wall thickness becomes 0.2 mm.

[0044] Air-drawing reduction is a tube drawing process without a mandrel. This application employs air-drawing reduction technology, which avoids friction and wear of the mandrel, reduces process complexity, minimizes the risk of internal surface scratches, and improves the surface quality of the finished product.

[0045] After each drawing, the tube is heat-treated in a vacuum furnace to ensure its elongation, allowing it to withstand multiple stretching operations. The area variation of the tube after each drawing does not exceed 15%, reducing lattice distortion accumulation, resulting in a smoother surface and preventing cracking. Maintaining consistent area variation after each drawing ensures uniform deformation during the process, reduces residual stress concentration, improves tube stability, and increases product yield.

[0046] Each drawing process causes plastic deformation of the tube, increasing dislocation density, exacerbating lattice distortion, and gradually increasing material strength and hardness (work hardening effect). Ductility (elongation) decreases with increasing drawing cycles, and repeated cumulative deformation may increase material brittleness. This application performs an annealing process after each drawing, using a vacuum furnace heat treatment at 600-700 degrees Celsius to maintain a high elongation of the tube. Annealing in a vacuum furnace allows for stable annealing temperatures, and the argon-filled furnace ensures a high level of cleanliness in the tube's appearance.

[0047] The number of drawing cycles directly affects the mechanical properties and microstructure of the pipe. In this application, cold drawing is used to draw the pipe 15-30 times, which can maintain the original phase transformation and memory function of the pipe.

[0048] S14: The reduced-diameter pipe is subjected to special-shaped processing to obtain special-shaped pipe.

[0049] After the pipe diameter is reduced, the pipe is then subjected to special-shaped processing.

[0050] In some specific embodiments, the pipe can be cut first to obtain a pipe of a predetermined length. Then, as... Figure 5 As shown, the cut pipe is directly heat-bent into a bent pipe to obtain the irregular pipe 16.

[0051] In other embodiments, the cylindrical tube can be first pressed into a flat tube, and then the flat tube can be bent to obtain a shaped tube.

[0052] Alternatively, the reduced-diameter tube can be shaped by passing it through the through-hole of a drawing die to press the round tube into a flat tube.

[0053] Specifically, the drawing die may include at least two drawing sub-dies, and the width of the through holes in the at least two drawing sub-dies may gradually decrease. The reduced-diameter tube is sequentially drawn through the drawing sub-dies with gradually decreasing through hole widths.

[0054] For example, a drawing die may include three drawing sub-dies, with through-hole shapes of ellipse, waist-shaped, and rectangular, respectively, to progressively draw a round tube into a flat tube. Figure 6As shown, after passing through three drawing dies, the tube 11 is successively transformed into a tube 12 with an elliptical cross section, a tube 13 with a waist-shaped cross section, and a tube 14 with a rectangular cross section.

[0055] The above method can avoid excessive local thinning or cracking of the pipe wall caused by a single large deformation. The processing technology of this application releases the work hardening effect in stages, reducing the cumulative elongation loss of the pipe.

[0056] Furthermore, the drawing die also includes at least two inner dies, the outer diameter of which gradually decreases. At least two drawing sub-dies correspond one-to-one with the two inner dies. The inner dies with gradually decreasing outer diameters are sequentially inserted into the reduced-diameter tube, so that they are drawn through the corresponding drawing sub-dies. That is, a corresponding inner die is inserted into the inner hole of the tube to pass through the corresponding drawing sub-dies, thus further shaping the tube during the deformation process and improving the deformation effect of the tube.

[0057] After the reduced-diameter tube passes through the through-hole of each drawing die, the area change is less than 2%. By promoting dynamic recrystallization through each small deformation, the retention rate of the shape memory properties of the nickel-titanium alloy tube can be greatly improved.

[0058] After the pipe is flattened, it can be hot-bent to obtain a special-shaped pipe, such as the shape shown in Figure 7, which is semi-circular.

[0059] S15: The irregularly shaped tube is placed into the irregularly shaped forming module for heat treatment to activate the shape memory alloy function of the irregularly shaped tube, so as to obtain the target tube with a phase transformation temperature of -20℃ to 60℃. The heat treatment temperature of the irregularly shaped forming module is 500-530 degrees and the shaping time is 25-35 minutes.

[0060] The bent irregularly shaped tubes are placed into the irregularly shaped forming module for heat treatment to set their shape. The shape memory alloy function is activated directionally through heat treatment.

[0061] The non-standard forming module can include an upper forming mold and a lower forming mold. The lower surface of the upper forming mold forms an upper non-standard forming surface, and the upper surface of the lower forming mold forms a lower non-standard forming surface that matches the shape of the upper non-standard forming surface. The setting temperature of the non-standard forming module is 500-530℃, and the setting time is 25-35 minutes, for example, 30 minutes. Through the above method, the phase change temperature range of the obtained target pipe can be -20℃ to 60℃, the elongation is greater than 10%, and the tensile strength is greater than 1240 MPa. This target pipe has a memory function, a large phase change temperature range, and can achieve multi-scenario adaptability of "low-temperature flexible shaping, body temperature rigid locking, and high-temperature strong driving".

[0062] S16: The target pipe is roughened using a magnetic needle polishing / brown corundum polishing process, and then finely polished using a manual wire wheel and polishing wax.

[0063] In some embodiments, after obtaining the target pipe, the target pipe can be further polished. Optionally, the target pipe can be roughened first, and then finely polished.

[0064] For example, the target pipe can be roughened using a magnetic needle polishing process. This involves using an electromagnetic field to drive magnetic grinding needles (such as steel needles or iron-based abrasive grains) at high speed, impacting and cutting the surface of the pipe. The magnetic needles form a dynamic grinding flow in the magnetic field, achieving uniform removal of surface oxide layers, weld scars, and burrs. Alternatively, the target pipe can be roughened using a brown fused alumina polishing process. Using brown fused alumina as the abrasive, mechanical vibration or centrifugal force drives the abrasive grains to cut the surface of the target pipe.

[0065] Furthermore, the target pipe can be finely polished using a manual thread wheel and polishing wax.

[0066] The material of the polishing wheel can be pure cotton, wool, or a blend. Coarse polishing wax can contain diamond micron powder (3-6μm) to eliminate scratches with a roughness of 0.4μm. Coarse polishing wax can also contain cerium oxide or diatomaceous earth to achieve a mirror finish with a roughness of less than or equal to 0.1μm. The manual polishing pressure can be 2-4 N / cm², but excessive pressure can cause surface overheating. During polishing, the polishing wheel can be used at a 45° angle along the tube axis to avoid unidirectional texture (reducing surface anisotropy). Using these methods, the surface roughness can be improved from 0.4μm to 0.02-0.05μm (mirror finish). The polishing wax fills micropores, reducing surface porosity to less than 0.1%.

[0067] Alternatively, the polished target pipe can be coated with a film on its surface using physical vapor deposition methods, such as ion vacuum plating, to control the appearance and color of the target pipe and ensure that its appearance meets the user's requirements. Physical vapor deposition technology and ion vacuum plating methods are within the scope of understanding for those skilled in the art and will not be elaborated upon here.

[0068] In this application, the preparation method of nickel-titanium shape memory alloy is simple, low-cost, and has a high yield. The resulting target tube can form a uniform and delicate metallic luster surface, making it suitable for use as a structural appearance component. The elimination of the need for an outer coating on the tube shortens the manufacturing cycle, effectively controls production costs, and enhances the overall metallic appearance of the product. The target tube exhibits a wide phase transformation temperature range, improving the environmental adaptability of the nickel-titanium alloy and expanding its application scope.

[0069] This application also provides a nickel-titanium shape memory alloy tube, which can be prepared by the preparation method of any of the above embodiments. For the preparation method, please refer to the description of any of the above embodiments, which will not be repeated here.

[0070] The nickel-titanium shape memory alloy tubing provided in this application can be used in various types and fields of products. For example, it can be used in 3C smart functional components such as earphone clips, medical supplies, toys, or couplings. The inner and outer walls of the nickel-titanium shape memory alloy tubing provided in this application can both achieve a high-gloss finish; therefore, it can be used in the exposed metal parts of the aforementioned products.

[0071] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing a nickel-titanium shape memory alloy tube, characterized in that, The preparation method includes: A nickel-titanium shape memory alloy rod is provided, wherein the nickel content in the rod is 54%-58%; The rod is perforated to obtain a tube with a preset inner diameter; The tube is drawn several times using air-drawing diameter reduction technology to reduce its diameter. After each drawing, the tube is heat-treated in a vacuum furnace, and the area change of the tube after each drawing does not exceed 15%. The reduced-diameter pipe is then subjected to a special-shaped process to obtain a special-shaped pipe. The irregularly shaped tube is placed into the irregularly shaped forming module for heat treatment to activate the shape memory alloy function of the irregularly shaped tube, so as to obtain the target tube with a phase transformation temperature of -20℃ to 60℃. The heat treatment temperature of the irregularly shaped forming module is 500-530 degrees and the shaping time is 25-35 minutes.

2. The preparation method according to claim 1, characterized in that, The step of shaping the reduced-diameter pipe includes: The reduced-diameter tube is shaped by passing it through the through hole of a drawing die, and then the shaped tube is bent to obtain the shaped tube.

3. The preparation method according to claim 2, characterized in that, The drawing die includes at least two drawing sub-dies, the width of the through holes in the at least two drawing sub-dies gradually decreasing, and the preparation method includes: The reduced-diameter tubes are sequentially drawn through drawing dies with progressively smaller through-hole widths.

4. The preparation method according to claim 3, characterized in that, The area change of the reduced-diameter tube after passing through the through hole of each drawing die is less than 2%.

5. The preparation method according to claim 3, characterized in that, The drawing die further includes at least two inner dies, the outer diameters of which gradually decrease, and the at least two drawing sub-dies correspond one-to-one with the at least two inner dies. The preparation method further includes: The inner molds with gradually decreasing outer diameters are inserted into the reduced-diameter pipe in sequence, so that they can be drawn by the corresponding drawing sub-dies.

6. The preparation method according to claim 1, characterized in that, The step of drilling holes in the rod includes... Holes are made in the bar material by electrode drilling and wire cutting processes to obtain a tube with an arithmetic mean roughness of less than or equal to 0.

3.

7. The preparation method according to claim 1, characterized in that, The step of drawing the pipe several times using the air-drawing diameter reduction technique includes: The tube is cold-drawn 15-30 times, and the vacuum furnace heat treatment temperature is 600-700 degrees Celsius, and the vacuum furnace is filled with argon gas.

8. The preparation method according to claim 1, characterized in that, The preparation method further includes: The target pipe is roughened using a magnetic needle smoothing / brown corundum smoothing process; The rough-cut target pipe is finely polished using a manual thread wheel and polishing wax.

9. A nickel-titanium shape memory alloy pipe, characterized in that, The nickel-titanium shape memory alloy tubing is prepared according to the preparation method described in any one of claims 1-8.

10. The application of the nickel-titanium shape memory alloy tubing as described in claim 9 in earphone clips, medical supplies, toys, or couplings.

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