Nickel-titanium-based shape memory alloy stranded wire processing method

Abstract

The invention discloses a nickel-titanium-based shape memory alloy stranded wire processing method, which comprises the following steps of: 1, feeding a plurality of second wire blanks through an inlet of each side line pay-off mechanism, and discharging a stranded wire through an outlet of a stranding machine; or when a plurality of second wire blanks are fed, the first wire blanks are fed through an inlet of a core wire pay-off mechanism to serve as core wires; wherein the pay-off tension of the core wire and the pay-off tension of the side wire are both 5-30 MPa; 2, feeding the stranded wire into an annealing furnace; and step 3, sequentially feeding the annealed stranded wire into a cooling mechanism and a take-up machine to finish the processing of the stranded wire. The nickel-titanium-based shape memory alloy solves the problems that the existing nickel-titanium-based shape memory alloy cannot be twisted due to large resilience when being twisted and has poor characteristics after being twisted.

Description

[Technical field]

[0001] The invention belongs to the technical field of shape memory alloy processing, and in particular relates to a method for processing nickel-titanium based shape memory alloy stranded wires. [Background technology]

[0002] Shape memory alloy as a smart material has attracted great attention, especially its unique superelasticity and memory properties, which make it have unparalleled advantages over other materials in some specific usage occasions. With the continuous research of scholars, various shape memory alloy products continue to emerge and have been widely used in engineering and civil fields such as biomedicine, mechanical electronics, and aerospace.

[0003] Currently, nickel-titanium-based shape memory alloys are used in many forms, such as guide wires made of wires, bolts made of rods, bone plates made of plates, vascular stents made of pipes, and actuators made of springs. These memory alloy materials can fully release their superelastic and memory properties by selecting specific processing methods and heat treatment systems, and can meet the needs of many special occasions, such as mechanical fastening, dental orthopedics, and elastic eyeglass frames.

[0004] Stranded wire is a multi-strand twisted wire element formed by a certain number of wires according to different winding methods. In engineering applications, stranded wire has good torsion and bending properties. This property makes it possible for each wire of the stranded wire to bear tensile loads in parallel when subjected to external forces, providing a safer failure mode. It is foreseeable that nickel-titanium-based shape memory alloy stranded wire can be composed of various possible diameters and twisting methods to form different cross-sectional geometries, with great flexibility, and nickel-titanium-based shape memory alloy stranded wire can withstand greater forces, is easier to handle than wires or rods with the same cross-sectional area, is more convenient and flexible to use, has better fatigue performance under cyclic loads, has signs of damage, and can avoid sudden damage. However, due to the large elasticity of nickel-titanium-based shape memory alloy wire, unlike stainless steel or other metal wires, which can be well twisted by plastic deformation during twisting, nickel-titanium-based shape memory alloy wire has large rebound when twisted, and will rebound loose without special heat treatment after twisting, and cannot be twisted. At the same time, nickel-titanium-based shape memory alloys are very sensitive to heat treatment systems, and only appropriate heat treatment systems can give full play to the characteristics of nickel-titanium-based shape memory alloys. In addition, the composite material composed of nickel-titanium-based shape memory alloy wires and other metal wires can have the superelasticity of memory alloys and other properties, and can also have the high stiffness of other metal materials. For example, stainless steel wires are used as core wires and memory alloy wires are used as side wires for twisting. The nickel-titanium-based shape memory alloy composite strands have both the superelasticity of memory alloys and the high stiffness of stainless steel, which has great engineering value potential. At present, there is no similar nickel-titanium-based shape memory alloy composite strands. [Summary of the invention]

[0005] The purpose of the present invention is to provide a method for processing nickel-titanium-based shape memory alloy stranded wires, so as to solve the problem that the existing nickel-titanium-based shape memory alloys have large springback when stranded and cannot be stranded, and have poor properties after stranding.

[0006] The present invention adopts the following technical scheme: a method for processing a nickel-titanium-based shape memory alloy stranded wire, which is based on a stranding machine, an annealing furnace, a cooling mechanism and a wire take-up machine that are sequentially connected; one side of the stranding machine is an inlet for wire blanks, and the inlet includes a core wire pay-off mechanism inlet located in the center, and a plurality of side wire pay-off mechanism inlets surrounding the core wire pay-off mechanism inlet; the other side of the stranding machine is an outlet for wire blanks, and the outlet is used to send out the stranded wires;

[0007] Processing methods include the following:

[0008] Step 1, feeding a plurality of second wire blanks through the entrance of each side wire pay-off mechanism, and sending the stranded wires after stranding through the outlet of the stranding machine; at this time, the second wire blanks are nickel-titanium-based shape memory alloy wires;

[0009] Or, while feeding in a plurality of second wire blanks, the first wire blank is fed in through the entrance of the core wire pay-off mechanism as the core wire; at this time, the first wire blank and the second wire blank are both nickel-titanium-based shape memory alloy wires; or the first wire blank is a nickel-titanium-based shape memory alloy wire, and the second wire blank is other alloy wires; or the first wire blank is other alloy wires, and the second wire blank is a nickel-titanium-based shape memory alloy wire;

[0010] Among them, the tension of the core wire pay-off and the tension of the side wire pay-off are both 5 to 30 MPa;

[0011] Step 2, sending the stranded wire into an annealing furnace;

[0012] Step 3: Send the annealed stranded wire to the cooling mechanism and the wire take-up machine in turn, thus completing the processing of the stranded wire.

[0013] Furthermore, the annealing temperature in step 2 is 300-600° C., the stranded wire is kept warm in the furnace for 2-30 min, and the annealing furnace is filled with inert gas with a gas flow rate of 3-5 L / min.

[0014] Furthermore, the length of the annealing furnace in step 2 is 3 to 10 m, and the wire-taking speed of the wire-taking machine is 0.1 to 5 m / min.

[0015] Furthermore, the cooling method of the cooling mechanism is spray or immersion rapid water cooling, or slow air cooling.

[0016] The second technical solution adopted by the present invention is a nickel-titanium-based shape memory alloy stranded wire, the structure of which includes:

[0017] at least two side wires made of nickel-titanium-based shape memory alloy wires, without a core wire;

[0018] or at least two side wires made of nickel-titanium-based shape memory alloy wires, and a core wire made of other alloy wires;

[0019] Or at least two side wires made of other alloy wires, and a core wire made of nickel-titanium-based shape memory alloy wire.

[0020] The beneficial effects of the present invention are as follows: a method for processing nickel-titanium-based shape memory alloy stranded wires of the present invention organically combines the processes of wire unwinding, wire twisting, annealing and shaping, cooling, and wire winding, provides specific process parameter requirements, and according to the specifications of the memory alloy stranded wires, the superelasticity, mechanical properties and other characteristics of the stranded wires can be regulated by controlling the annealing and shaping parameters, so that the memory alloy stranded wires exhibit optimal superelasticity and other characteristics; high-quality nickel-titanium-based shape memory alloy stranded wires can be produced simply, conveniently, and at low cost, solving the problem that the existing nickel-titanium-based shape memory alloys have large springback when twisted and cannot be twisted, and have poor characteristics after twisting.

Brief Description of the Drawings

[0021] Figure 1 A system structure diagram of a nickel-titanium-based shape memory alloy stranded wire processing method of the present invention;

[0022] Figure 2-Figure 4 Schematic diagrams of cross-sections of the stranded wires obtained in Examples 1 to 3 of the present invention respectively;

[0023] Figure 5 This is a superelasticity curve diagram of the nickel-titanium-based shape memory alloy stranded wire obtained in Example 1.

[0024] Among them, 1. core wire, 2. side wire, 3. stranding machine, 31. core wire pay-off mechanism, 32. side wire pay-off mechanism, 4. annealing furnace, 5. cooling mechanism, 6. wire take-up machine, 7. controller. [Specific implementation method]

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] A method for processing a nickel-titanium-based shape memory alloy stranded wire, such as Figure 1 As shown, it is based on a stranding machine 3, an annealing furnace 4, a cooling mechanism 5 and a wire take-up machine 6 which are connected in sequence; the horizontal center and the vertical center of each device coincide with each other, and when processing the stranded wire, the core wire passes through the center of each mechanism to finally form a finished stranded wire. One side of the stranding machine 3 is the inlet of the wire blank, and the inlet includes a core wire pay-off mechanism 31 inlet located in the center, and a plurality of side wire pay-off mechanism 32 inlets surrounding the core wire pay-off mechanism 31 inlet; the other side of the stranding machine 3 is the outlet of the wire blank, and the outlet is used to send out the stranded wire.

[0027] The machine also includes a controller 7, which is used to set the speed and tension parameters of the pay-off mechanism, the twisting mechanism and the take-up mechanism, and to start and stop these devices. After the wire blank passes through the pay-off machine, the twisting machine, the annealing furnace, the cooling mechanism and the take-up machine, the parameters of the devices are set on the controller, and the devices are started through the controller to complete the twisting process.

[0028] Processing methods include the following:

[0029] Step 1: Feed a plurality of second wire blanks into each of the edge wire pay-off mechanisms 32 through an inlet, and deliver the stranded wires through an outlet of the stranding machine after stranding; at this time, the second wire blanks are nickel-titanium-based shape memory alloy wires.

[0030] Or while feeding in a plurality of second wire blanks, the first wire blank is fed in through the entrance of the core wire pay-off mechanism 31 as the core wire; at this time, the first wire blank and the second wire blank are both nickel-titanium-based shape memory alloy wires; or the first wire blank is a nickel-titanium-based shape memory alloy wire, and the second wire blank is other alloy wire; or the first wire blank is other alloy wire, and the second wire blank is a nickel-titanium-based shape memory alloy wire.

[0031] When the finished stranded wire has no core wire, only the side wire pay-off mechanism 32 is needed to pay out the wire. When the finished stranded wire has both core wire and side wire, one core wire pay-off mechanism 31 is used for the core wire pay-off, and the rest are side wire pay-off mechanisms 32. There is no limit on the number of side wire pay-off mechanisms 32, that is, the number of strands of the stranded wire is not limited. The diameter of the blank placed by the side wire pay-off mechanism 32 and the diameter of the blank placed by the core wire pay-off mechanism may be the same or different.

[0032] When the blank is a nickel-titanium-based shape memory alloy wire during processing, the finished product is a nickel-titanium-based shape memory alloy stranded wire. When the blank is composed of nickel-titanium-based shape memory alloy wire and other alloy wires, the finished product is a nickel-titanium-based shape memory alloy composite stranded wire. In addition, the blank can also be composed of stranded wire or stranded wire and wire, for example, the core wire is a stranded wire and the side wire is a single wire; the number of strands of the stranded wire is greater than or equal to two. When the number of strands of the stranded wire exceeds two, the finished product is a nickel-titanium-based shape memory alloy stranded wire or a nickel-titanium-based shape memory alloy composite stranded wire with a more complex cross-section.

[0033] The tension of the core wire pay-off is 5-30MPa, and the tension of the side wire pay-off is 5-30MPa. The pay-off process refers to installing the wire blank in the pay-off mechanism and paying the wire blank into the stranding machine 3 at a stable and uniform speed; there are multiple pay-off mechanisms for pay-off, one of which is located in the center as the core wire pay-off mechanism 31, and the others are the side wire pay-off mechanisms 32.

[0034] When the pay-off tension is below 5MPa, the elastic deformation of the alloy wire is small, and the alloy wire cannot be tightened to maintain stability. When the pay-off tension is above 30MPa, it is easy to cause plastic deformation of the wire, especially the torsional deformation during twisting, which will cause the wire to deform too much, exceeding the elastic deformation range, and causing irreversible plastic deformation, thereby damaging the superelastic properties of the memory alloy stranded wire, and excessive tension will cause the wire size to become smaller; the pay-off tension is controlled at 5-30MPa, which can ensure that the material undergoes elastic deformation during the processing of the stranded wire, effectively increase the stability of the pay-off, avoid the phenomenon of looseness and tightness due to excessive or insufficient tension, resulting in uneven stranding, and through such a pay-off tension, it can be ensured that the elastic deformation of the memory alloy during twisting can rebound within the allowable size after annealing and shaping, and the setting of multiple pay-off mechanisms can produce two or more strands of stranded wire, so that multiple stable pay-offs are conducive to the production of uniform and non-loose strands.

[0035] The stranding process refers to winding the side wire blanks released by the pay-off mechanism around the core wire in a spiral shape clockwise or counterclockwise around the forward direction of the core wire at a certain speed to form stranded wire; in this way, stranded wires with different parameters such as lay length and different lay directions can be produced by controlling different speeds.

[0036] The core wire pay-off mechanism 31 can be set separately, and the side wire pay-off mechanism 32 can be set integrally with the stranding machine 3. The side wire pay-off mechanism 32 is set at equal angles and distances around the core wire forward direction on the stranding machine 3. Such a design is conducive to processing uniform and non-loose strands.

[0037] Step 2: Send the stranded wires into the annealing furnace 4. The annealing and shaping process refers to passing the stranded wires through the annealing furnace 4 at a specific temperature and then rapidly cooling them to achieve a shaping effect.

[0038] Step 3: Send the annealed strands to the cooling mechanism 5 and the wire take-up machine 6 in sequence, and the processing of the strands is completed. The cooling process refers to cooling the strands that have passed through the annealing furnace 4 at a specific temperature. The cooling is mainly a water cooling cycle. The cooling mechanism 5 is installed at the strand outlet of the annealing furnace 4. The wire taking-up process refers to collecting the cooled strands in the wire take-up machine 6 at a stable, uniform, and certain take-up speed.

[0039] In some embodiments, the annealing temperature is 300-600°C, the stranded wire is kept in the furnace for 2-30 minutes, the annealing furnace is filled with inert gas, and the gas flow rate is 3-5 L / min. The annealing equipment has the conditions of filling inert gas, with air entering at one end and air leaving at the other end. When the surface of the finished stranded wire is bright or slightly oxidized, the surface of the blank needs to be bright or slightly oxidized, and inert gas is passed during the annealing of the stranded wire, so as to prevent the surface of the stranded wire from changing color during annealing.

[0040] There are two purposes for annealing. First, the memory alloy is twisted and shaped by temperature, and second, the performance of the memory alloy strand is regulated. The memory alloy has high elasticity and is difficult to twist. When the annealing temperature is lower than 300°C, the memory alloy strand will explode and become loose due to the large rebound after twisting, and it is impossible to achieve effective twisting, that is, it is difficult to twist the memory alloy at low temperature. The density of dislocations and the morphology of second-phase precipitates inside the memory alloy structure have a great influence on the properties of the memory alloy. The higher the dislocation density and the finer and more uniform the second-phase precipitates, the stronger the strengthening of the memory alloy matrix, that is, the better the superelasticity of the memory alloy. When the annealing temperature is lower than 300°C, the structure of the memory alloy strand is in the recovery stage. The temperature at this time is too low to affect the significant change of dislocations inside the structure, the formation of second-phase precipitates and the control of the morphology of precipitates, that is, the performance of the memory alloy strand cannot be regulated. When the annealing temperature of the memory alloy strand is higher than 600℃, recrystallization and grain growth occur inside the strand, forming coarse equiaxed grains, significantly reducing the internal dislocation density, coarse second phase precipitates, and the coherence between the precipitated second phase and the matrix is ​​destroyed, which significantly reduces the yield strength of the memory alloy strand, seriously reducing the strength and hardness of the strand. When the alloy is subjected to external force, it undergoes irreversible plastic deformation before elastic deformation occurs, causing the alloy to lose superelasticity, and ultimately causing the strand to fail to meet the use requirements. When the annealing temperature of the memory alloy strand is controlled at 300℃ to 600℃, the dislocation density in the structure is large, and the fine second phase precipitates are dispersed in the alloy matrix, forming a coherent interface with the matrix, so that the dislocations in the structure and the precipitated phases are well matched, thereby improving the superelastic properties of the memory alloy strand. If the annealing setting time is less than 2 minutes, the internal stress of the stranded wire is not fully released and the purpose of twisting and shaping cannot be achieved. If the annealing setting time is kept within 30 minutes, the internal stress of the stranded wire can be fully released, which is conducive to shaping. If the time is longer, the impact on twisting and shaping will become smaller and smaller, and the production efficiency will be seriously reduced. Therefore, the annealing setting time is controlled by controlling the wire taking-up speed of the wire taking-up mechanism to be kept at 2 minutes to 30 minutes, so as to achieve full shaping while improving wire efficiency. In addition, different annealing parameters should be selected for stranded wires of different sizes. The larger the stranded wire size, the more complicated the twisting, the greater the internal stress during twisting, the greater the torque during twisting, and the more difficult it is to twist. Therefore, in order to effectively twist the stranded wire, the higher the annealing temperature should be, and the longer the annealing time should be, so that the dislocation inside the alloy can be fully released and the internal stress can be reduced to achieve the twisting of the memory alloy; the annealing parameters can adjust the flexibility and superelastic properties of the memory alloy stranded wire. The higher the temperature and the longer the time, the lower the dislocation inside the stranded wire and the more second phase precipitates, which reduces the strength of the memory alloy stranded wire, improves the flexibility of the stranded wire, and improves the superelastic properties of the stranded wire.Therefore, according to the specifications of the memory alloy stranded wire, the superelasticity, mechanical properties and other characteristics of the stranded wire can be regulated by controlling the annealing parameters, so that the memory alloy stranded wire can exhibit the best superelasticity and other characteristics.

[0041] In addition, different annealing parameters should be selected for strands of different sizes. The larger the strand size, the more complicated the stranding, the greater the elasticity during stranding, and the more difficult it is to strand. Therefore, in order to effectively strand the strands, the higher the annealing temperature should be, and the longer the annealing time should be. The annealing parameters can adjust the flexibility and memory characteristics of the strands. The higher the temperature and the longer the time, the more flexible the strands are, and the better the memory characteristics of the strands are. Therefore, the superelasticity, memory characteristics, mechanical properties and other characteristics of the finished strands can be adjusted by controlling the annealing parameters.

[0042] In some embodiments, the annealing furnace in step 2 is 3m to 10m long, and the take-up speed of the take-up machine 6 is 0.1 to 5m / min. In practice, the holding time of the stranded wire in the annealing furnace is regulated according to the take-up speed, so that the stranded wire is annealed and shaped by a specific temperature, cooling and take-up speed after stranding, and the superelasticity or memory characteristics of the stranded wire are regulated.

[0043] In some embodiments, the cooling mechanism is a spray or immersion rapid water cooling, or a slow air cooling. The speed of cooling will affect the organizational state of the memory alloy strand during annealing and shaping. The faster the cooling speed, the smaller the organizational change. Rapid cooling with water can keep the organizational state obtained after annealing and shaping at room temperature.

[0044] The present invention also provides a nickel-titanium-based shape memory alloy stranded wire, the structure of which includes the following three forms:

[0045] at least two side wires 2 made of nickel-titanium-based shape memory alloy wires, without a core wire 1;

[0046] or at least two side wires 2 made of nickel-titanium-based shape memory alloy wires, and a core wire 1 made of other alloy wires;

[0047] Or at least two side wires 2 made of other alloy wires, and a core wire 1 made of nickel-titanium-based shape memory alloy wire.

[0048] Example

[0049] The present invention is carried out in accordance with the following method in Example 1 to Example 3. The parameters in each example are shown in Table 1. The schematic diagram of the finished stranded wire structure of each example is shown in Figure 2-Figure 4 shown.

[0050] Step 1: Feed a plurality of second wire blanks through the entrance of each side wire pay-off mechanism 32, and at the same time, if there is a core wire, feed the first wire blank through the core wire pay-off entrance mechanism 31 as the core wire; and send the stranded wires after stranding through the outlet of the stranding machine;

[0051] Step 2, sending the stranded wire into an annealing furnace 4 for annealing treatment;

[0052] Step 3: Send the annealed stranded wires to the cooling mechanism 5 and the wire take-up machine 6 in sequence, thus completing the processing of the stranded wires.

[0053] Table 1 Process parameters of three embodiments

[0054]

[0055]

[0056] The superelastic curve of the memory alloy strand produced in Example 1 is as follows: Figure 5 As shown in the figure, the stress of the superelastic upper platform is 493MPa, the stress of the lower platform is 238MPa, and the stress hysteresis between the upper and lower platforms is as high as 255MPa. The larger the stress hysteresis of the superelastic curve, the more energy it can absorb. The alloy stranded wire has excellent energy storage performance. In addition, the residual strain of the stranded wire is only 0.12%, and the recoverable superelastic strain is as high as 5.88%. That is, when the stranded wire is subjected to a large external force during use, it can undergo a large elastic deformation and absorb a large amount of energy. After the external force is removed, it can rely on its superelastic properties to perform elastic recovery and can be used repeatedly. It can be repeatedly used as an energy-absorbing material and has great potential in engineering applications.

[0057] The mechanical property data of the stranded wires processed in the above-mentioned embodiments are shown in Table 2.

[0058] Table 2 Mechanical properties data of the stranded wires of the three embodiments

[0059] Mechanical properties Example 1 Example 2 Example 3 Yield Strength 514MPa 540MPa 589MPa tensile strength 1245MPa 1360MPa 1580MPa Elongation 34％ 25％ 21％

[0060] As can be seen from Table 2, the stranded wire produced by Examples 1 to 3 has a relatively high yield strength of 514 MPa to 589 MPa. The high yield strength can enable the stranded wire to withstand greater elastic deformation without introducing plastic deformation, so that the stranded wire exhibits excellent superelasticity; the tensile strength is relatively high, at 1245 MPa to 1580 MPa, and the high tensile strength indicates that the stranded wire can withstand a large destructive force without breaking; the elongation is relatively high, at 21% to 34%, and the good elongation can cause the stranded wire to undergo a large deformation when subjected to an external force, and there are signs of damage, which can avoid sudden damage and provide early warning.

[0061] The nickel-titanium-based shape memory alloy stranded wire processing method of the present invention organically combines the processes of wire laying, stranding, annealing and shaping, cooling, and stranding, provides a specific parameter design, and produces high-quality nickel-titanium-based shape memory alloy stranded wire in a simple, convenient, and low-cost manner. The twist length, twist direction, cross-section, and other appearances of the final nickel-titanium-based shape memory alloy stranded wire product, as well as the superelasticity, memory properties, and mechanical properties of the finished product can be regulated by setting the stranding parameters. The nickel-titanium-based shape memory alloy stranded wire processed by the nickel-titanium-based shape memory alloy stranded wire processing method of the present invention has a simple process; the processed nickel-titanium-based shape memory alloy stranded wire has the same excellent superelasticity and other properties as the nickel-titanium-based shape memory alloy filament, but has better mechanical properties and cost advantages than nickel-titanium-based shape memory alloy rods of the same size, as well as better fatigue properties and failure forms, that is, the nickel-titanium-based shape memory alloy stranded wire has more potential for use in engineering than nickel-titanium-based shape memory alloy rods or wires.

Claims

1. A method for processing nickel-titanium-based shape memory alloy stranded wire, characterized in that: The invention is based on a wire stranding machine (3), an annealing furnace (4), a cooling mechanism (5) and a wire take-up machine (6) which are connected in sequence; one side of the wire stranding machine (3) is an inlet for wire blanks, and the inlet includes a core wire pay-off mechanism (31) inlet located in the center, and a plurality of side wire pay-off mechanism (32) inlets surrounding the core wire pay-off mechanism (31) inlet; the other side of the wire stranding machine (3) is an outlet for wire blanks, and the outlet is used to send out the stranded wires; The processing method comprises the following contents: Step 1, feeding a plurality of second wire blanks through the inlet of each of the edge wire pay-off mechanisms (32), and sending the stranded wires after stranding through the outlet of the stranding machine; at this time, the second wire blanks are nickel-titanium-based shape memory alloy wires; Or, while feeding in a plurality of second wire blanks, the first wire blank is fed in through the entrance of the core wire pay-off mechanism (31) as the core wire; at this time, the first wire blank and the second wire blank are both nickel-titanium-based shape memory alloy wires; or the first wire blank is a nickel-titanium-based shape memory alloy wire, and the second wire blank is other alloy wires; or the first wire blank is other alloy wires, and the second wire blank is a nickel-titanium-based shape memory alloy wire; Wherein, the tension of the core wire pay-off and the tension of the side wire pay-off are both 5 to 30 MPa; Step 2, feeding the stranded wire into the annealing furnace (4); Step 3: The stranded wire after annealing is sequentially fed into a cooling mechanism (5) and a wire take-up machine (6), thereby completing the processing of the stranded wire.

2. A method for processing nickel-titanium-based shape memory alloy stranded wire as claimed in claim 1, characterized in that: The annealing temperature in step 2 is 300-600° C., the stranded wire is kept warm in the furnace for 2-30 minutes, and the annealing furnace (4) is filled with inert gas with a gas flow rate of 3-5 L / min.

3. A method for processing nickel-titanium-based shape memory alloy stranded wire as claimed in claim 2, characterized in that: The length of the annealing furnace (4) in step 2 is 3 to 10 m, and the wire-taking speed of the wire-taking machine is 0.1 to 5 m / min.

4. A method for processing a nickel-titanium-based shape memory alloy stranded wire as claimed in any one of claims 1 to 3, characterized in that: The cooling method of the cooling mechanism (5) is spray or immersion rapid water cooling, or slow air cooling.

5. A nickel-titanium-based shape memory alloy stranded wire, characterized in that: Its structure includes: At least two side wires (2) made of nickel-titanium-based shape memory alloy wires, without a core wire (1); or at least two side wires (2) made of nickel-titanium-based shape memory alloy wires, and a core wire (1) made of other alloy wires; Or at least two side wires (2) made of other alloy wires, and a core wire (1) made of nickel-titanium-based shape memory alloy wire.

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