Heat treatment method of high-elasticity and high-strength nickel-titanium alloy braided tube

Abstract

The invention relates to the technical field of nickel-titanium alloy processing, and particularly discloses a heat treatment method after weaving of a high-elasticity and high-strength nickel-titanium alloy pipe. A heat treatment method after weaving of a high-elasticity and high-strength nickel-titanium alloy pipe is used for performing aging treatment on a nickel-titanium alloy woven pipe, and specifically comprises the steps that the nickel-titanium alloy woven pipe is subjected to heat preservation for 15-60 min under the conditions that the vacuum degree is smaller than or equal to 5 * 10 <-3 > Pa and the temperature is 480-600 DEG C, the heating rate is 3-5 DEG C / min, water cooling is performed to 25 + / -2 DEG C, and finally heat treatment is completed. According to the heat treatment method for the nickel-titanium alloy braided tube obtained through the heat treatment method for the braided nickel-titanium alloy tube, the elastic recovery rate is larger than or equal to 95%, the tensile strength is larger than or equal to 1000 MPa, and meanwhile the elasticity and strength of the nickel-titanium alloy braided tube are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of nickel-titanium alloy processing, in particular to a heat treatment method of a high-elasticity and high-strength nickel-titanium alloy braided tube. BACKGROUND

[0002] The nickel-titanium alloy braided tube has become a key material in the fields of medical treatment, aerospace, electronics and the like due to excellent shape memory effect and biocompatibility, and is widely applied to earphone connecting bridges connecting two earphone units in Bluetooth earphones. When applied to the field of earphone connecting bridges, repeated deformation and external force impact caused by human beings need to be coped with, and therefore the nickel-titanium alloy braided tube needs to meet high elasticity and high strength, so as to avoid damage of the earphone connecting bridge and ensure the service life of the Bluetooth earphone.

[0003] In the related art, the strength is improved by increasing the content of nickel, but the elasticity of the nickel-titanium alloy braided tube is reduced, which cannot adapt to the repeated deformation requirement of the earphone connecting bridge component. If the elasticity is optimized by reducing the transformation temperature and reducing the crosslinking density, the yield strength of the nickel-titanium alloy braided tube is reduced, and permanent deformation or even fracture is easily caused by external force extrusion in the use process, which is difficult to meet the quality and service life requirement of the product nickel-titanium alloy braided tube. SUMMARY

[0004] In order to simultaneously improve the elasticity and strength of the nickel-titanium alloy braided tube, the application provides a heat treatment method of a high-elasticity and high-strength nickel-titanium alloy braided tube.

[0005] In the first aspect, the application provides a heat treatment method of a high-elasticity and high-strength nickel-titanium alloy braided tube, which adopts the following technical scheme: The heat treatment method of the high-elasticity and high-strength nickel-titanium alloy braided tube is to perform aging treatment on the nickel-titanium alloy braided tube, specifically to perform aging treatment on the nickel-titanium alloy braided tube at a temperature of 480-600 DEG C and a pressure of 5*10 -3 Pa for 15-60 min at a temperature increasing rate of 3-5 DEG C / min, and then water-cooled to 25+ / -2 DEG C, and finally the heat treatment is completed.

[0006] By adopting the above technical scheme, the aging treatment can control the proportion of alloy phases, the temperature of 480-600 DEG C can promote the uniform precipitation of nanoscale second phases in the nickel-titanium alloy, compared with a higher aging temperature, this temperature range can avoid excessive growth of the second phases, so that the second phases are uniformly distributed in the matrix, and the temperature increasing rate is controlled at 3-5 DEG C / min, which can prevent uneven structure caused by too fast temperature increasing, water cooling can reduce the total amount of precipitated phases, avoid increase of brittleness, improve the strength, guarantee the stability of the microstructure, and overall improve the strength and elasticity of the nickel-titanium alloy braided tube.

[0007] As preferred: the aging treatment is preceded by a solid solution treatment, specifically: the nickel-titanium alloy braided tube is subjected to a solid solution treatment at a temperature of 850-950℃ for 0.5-2h, with a heating rate of 5-10℃ / min, and cooling. -3 Pa, 850-950℃, holding for 0.5-2h, heating rate 5-10℃ / min, cooling.

[0008] By adopting the above technical scheme, the nickel-titanium alloy braided tube is easy to produce residual stress and fiber-like distortion organization inside after braiding, and there may be small pores, so the solid solution treatment is carried out first to eliminate the processing stress produced in the braiding process, make the alloy elements uniformly solid solution, and ensure the composition uniformity. Solid solution at a temperature of 850-950℃ makes the atoms inside the alloy fully diffuse, and the fiber organization formed by braiding is converted into uniform equiaxed grains. The vacuum environment can avoid the oxidation of the pipe surface and the penetration of gas during heating, effectively eliminating the small pores and internal stress produced in the braiding process, and laying a foundation for subsequent improvement of elasticity and strength.

[0009] As preferred: the nickel-titanium alloy braided tube is pretreated before the solid solution treatment, specifically: first rinse the surface of the nickel-titanium alloy braided tube with deionized water, then soak it in the degreasing liquid for 10-15min, wash with water, then soak it in the pickling liquid for 5-10min, wash with water, neutralize, and dry at 60-80℃ for 15-20min.

[0010] By adopting the above technical scheme, the nickel-titanium alloy braided tube is pretreated by pickling, and the surface is washed and degreased before pickling, which is more conducive to pickling, and then soaked in the pickling liquid to dissolve the surface TiO2 and NiO oxide skin, avoiding the oxide skin hindering the uniform diffusion of the composition during solid solution, ensuring the formation of uniform organization after solid solution, and further improving the elasticity and strength.

[0011] In addition, pickling can also reduce the surface micro-cracks, oxidation inclusions and other defects of the nickel-titanium alloy braided tube, reduce the stress concentration points, avoid breaking from the surface defects when stressed, improve the strength, and also form a uniform surface roughness, enhance the consistency of the organization during subsequent heat treatment, avoid too large difference between the surface and the internal performance, and improve the overall performance of the nickel-titanium alloy braided tube.

[0012] As preferred: the degreasing liquid comprises the following raw materials by weight: sodium hydroxide 4-6 parts, sodium tripolyphosphate 2-3 parts, fatty alcohol polyoxyethylene ether 1-3 parts, and deionized water 90-95 parts.

[0013] By adopting the technical scheme, local stress concentration caused by oil stain residue is reduced, and elasticity and strength are reduced, so that oil removal is required. The sodium hydroxide in the oil removal agent decomposes polar components in rolling oil and cutting oil through saponification reaction and emulsification, so that the oil stain is stripped from the surface of the braided tube, and decomposition of the oil stain to produce carbide during subsequent heat treatment is avoided, so that the alloy brittleness is increased, and the elastic fracture is reduced. The fatty alcohol polyoxyethylene ether emulsifies and penetrates the oil stain, quickly decomposes and strips the oil stain on the surface and in the gap of the braided tube, the sodium tripolyphosphate prevents the oil stain from re-depositing, ensures no residue, and improves the oil removal effect.

[0014] As a preferred, the pickling solution comprises the following raw materials by weight: 5-10 parts of hydrofluoric acid with a concentration of 40%, 15-20 parts of nitric acid with a concentration of 68%, 1-2 parts of citric acid, 0.5-1 part of ammonium hydrogen fluoride, and 70-80 parts of deionized water.

[0015] By adopting the technical scheme, the hydrofluoric acid pickling dissolves TiO2, and reduces the corrosion of the nickel-titanium alloy braided tube. The nitric acid oxidizes and removes NiO, quickly forms a passivation film, and reduces the overall acid liquid corrosion. The citric acid forms a stable complex with Ti 4+ , Ni 2+ , promotes the dissolution of impurities in the gap, and avoids secondary deposition. The ammonium hydrogen fluoride can provide F - to supplement the complexing ability of the hydrofluoric acid, and achieve efficient dissolution of the surface oxide layer. At the same time, the buffering effect of the ammonium hydrogen fluoride is used to regulate the corrosion rate, avoid excessive corrosion of the alloy substrate, finally achieve the dual effect of rapid removal of the oxide layer and protection of the matrix, and also reduce the amount of hydrofluoric acid.

[0016] As a preferred, the weight ratio of the ammonium hydrogen fluoride to the hydrofluoric acid with a concentration of 40% is 1:(10-15).

[0017] By adopting the technical scheme, the weight ratio of the ammonium hydrogen fluoride to the hydrofluoric acid with a concentration of 40% is adjusted, which further improves the pickling effect and is beneficial to subsequent solid solution and aging treatment.

[0018] As a preferred, after the heat treatment of the nickel-titanium alloy braided tube under the condition of a vacuum degree of ≤5*10 -3 Pa and 850-950℃ for 0.5-2h, the heat treatment is followed by 2-4h of heat preservation at-80--100℃, and then 30-60min of heat preservation at 150-200℃.

[0019] By adopting the technical scheme, deep cryogenic treatment promotes complete transformation of martensite and refines martensite laths; low-temperature tempering eliminates deep cryogenic residual stress, while retaining fine martensite structure, which improves yield strength and maintains high elastic recovery rate.

[0020] As a preferred, preheating is performed before the aging treatment, specifically 10-15min of heat preservation at 430-460℃.

[0021] By adopting the technical scheme, the residual stress generated by braiding processing and solid solution cooling is gradually released, the residual stress and thermal stress are avoided from being superimposed during subsequent aging, stress concentration is reduced, elasticity and fatigue resistance are improved, and the second phase is promoted to uniformly precipitate, and the strength is further improved.

[0022] Preferably, the cooling rate of the water cooling is 5-10℃ / min.

[0023] By adopting the technical scheme, the residual stress caused by fast cooling is avoided, the slow cooling reduces the generation of secondary thermal stress, avoids the generation of cracks, stabilizes the phase change characteristics, and realizes the coordinated improvement of strength and elasticity.

[0024] Preferably, the nickel-titanium alloy braided tube is braided by any one of a nickel-titanium alloy wire, a nickel-titanium-vanadium alloy wire and a nickel-titanium-copper alloy wire; the nickel-titanium alloy wire comprises the following elements in mass fraction: nickel 51.5%-57.0%, titanium in the balance, and total impurity content ≤0.1%; the nickel-titanium-vanadium alloy wire comprises the following elements in mass fraction: nickel 52.5%-57%, vanadium 0.3%-2.7%, titanium in the balance, and total impurity content ≤0.1%; and the nickel-titanium-copper alloy wire comprises the following elements in mass fraction: nickel 41%-49%, copper 5%-10%, titanium in the balance, and total impurity content ≤0.1%.

[0025] By adopting the technical scheme, the nickel-titanium alloy wire can ensure the biocompatibility and super-elasticity basis; the vanadium is added in the nickel-titanium-vanadium alloy wire to improve the alloy strength and corrosion resistance through vanadium element doping. The copper is added in the nickel-titanium-copper alloy wire to reduce the phase change hysteresis period and improve the functional fatigue life. Any one of the nickel-titanium alloy wire, the nickel-titanium-vanadium alloy wire and the nickel-titanium-copper alloy wire can obtain the high-elasticity high-strength nickel-titanium alloy braided tube.

[0026] In addition, the heat treatment method of the nickel-titanium alloy braided tube is applicable to but not limited to any one of the following braiding processes: regular braiding structure, rhombus braiding structure, diamond braiding structure and three-way braiding structure. The regular braiding structure is that the thread pattern is 1-press-2 under the full spool state of the braiding machine, that is, one clockwise rotating yarn is pressed by two counterclockwise rotating yarns, and then two counterclockwise rotating yarns are pressed, as shown in Figure 1 ; the rhombus braiding structure is that the thread pattern is 1-press-1 under the half spool state of the braiding machine (that is, the even half of the clockwise and counterclockwise spools), that is, one clockwise rotating yarn is pressed by one counterclockwise rotating yarn, and then one counterclockwise rotating yarn is pressed, as shown in Figure 2 ; and the diamond braiding structure is that the thread pattern is 2-press-2 under the spool assembly sequence change (that is, two clockwise spools and two counterclockwise spools) of the braiding machine, that is, two closely arranged clockwise rotating yarns are pressed by two closely arranged counterclockwise rotating yarns, and then two counterclockwise rotating yarns are pressed, as shown in Figure 3Three-dimensional weaving involves adding yarns parallel to the weaving mandrel from the center of the impeller and fixing them in the middle of the weaving yarns; these yarns do not participate in interlacing. Figure 4 .

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. This application involves heat treatment of nickel-titanium alloy braided tubing to age it, and controlling the treatment parameters to achieve an elastic recovery rate of ≥95% and a tensile strength of ≥1000MPa, thereby improving the elasticity and strength of the nickel-titanium alloy braided tubing.

[0028] 2. In this application, the nickel-titanium alloy braided tubing is subjected to solution treatment before aging treatment, which improves the tensile strength of the nickel-titanium alloy braided tubing to 1022 MPa.

[0029] (3) This application pre-treats the nickel-titanium alloy braided tube with degreasing and pickling before solution treatment, and controls the formulation and dosage of degreasing solution and pickling solution, so that the tensile strength of the nickel-titanium alloy braided tube is 1071-1078 MPa and the elastic recovery rate is 98%, which further improves the elasticity and strength of the nickel-titanium alloy braided tube.

[0030] (4) This application applies a nickel-titanium alloy braided tube under a vacuum of 5×10 -3 After heat treatment at 900℃ for 1.5 hours, the tube was kept at -90℃ for 3 hours, and then kept at 180℃ for 45 minutes, which increased the tensile strength of the nickel-titanium alloy braided tube to 1085 MPa, thus further improving the strength of the nickel-titanium alloy braided tube.

[0031] (5) In this application, the nickel-titanium alloy braided tube is preheated before aging treatment, so that the tensile strength of the nickel-titanium alloy braided tube is 1100MPa, thereby further improving the strength of the nickel-titanium alloy braided tube.

[0032] (6) This application further controls the cooling rate of water cooling to 5-10℃ / min, so that the tensile strength of the nickel-titanium alloy braided tube is 1115-1132MPa, thereby improving the strength of the nickel-titanium alloy braided tube. Attached Figure Description

[0033] Figure 1 Regular weave structure Figure 2 diamond woven structure Figure 3 Diamond braided structure Figure 4 Three-way braided structure Detailed Implementation

[0034] The present application will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0035] The following raw materials used in this application are all commercially available products and are intended to fully disclose the raw materials used in this application. They should not be construed as limiting the source of the raw materials. Specifically: nickel-titanium alloy wire, medical grade standard; sodium hydroxide, 98% effective substance content; sodium tripolyphosphate, 96% effective substance content; fatty alcohol polyoxyethylene ether, 99% effective substance content; citric acid, 99% effective substance content; ammonium bifluoride, 99% effective substance content.

[0036] Example 1 Example 1 describes a heat treatment method for a high-elasticity, high-strength nickel-titanium alloy braided tubing, comprising the following steps: aging the nickel-titanium alloy braided tubing, specifically by subjecting the solution-treated nickel-titanium alloy braided tubing to a vacuum of 5×10⁻⁶. - 3 Heating was carried out at 550℃ for 1.5 hours at a heating rate of 4℃ / min, then water-cooled to 25℃ at a cooling rate of 4℃ / min to complete the heat treatment.

[0037] Example 2 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 2 differs from that in Example 1 in that a solution treatment is performed before the aging treatment. Specifically, the nickel-titanium alloy braided tubing is subjected to a vacuum of 5×10⁻⁶. -3 Heat treatment was performed at 900°C for 1.5 hours with a heating rate of 8°C / min. After cooling, the remaining steps were the same as in Example 1.

[0038] Example 3 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 3 differs from that in Example 2 in that the nickel-titanium alloy braided tubing is pretreated before solution treatment. Specifically, the surface of the nickel-titanium alloy braided tubing is first rinsed with deionized water, then immersed in a degreasing solution at 45°C for 13 minutes, washed with water, then immersed in an acid pickling solution for 8 minutes, washed with water, neutralized, and dried at 70°C for 18 minutes. The remaining steps are the same as in Example 2.

[0039] The degreasing solution is a 5% sodium hydroxide aqueous solution; the pickling solution is a mixed solution of 8 kg of 40% hydrofluoric acid, 18 kg of 68% nitric acid, and 75 kg of deionized water.

[0040] Example 4 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 4 differs from that in Example 3 in that the degreasing solution is a mixed solution of 5 kg sodium hydroxide, 2.5 kg sodium tripolyphosphate, 1.5 kg fatty alcohol polyoxyethylene ether, and 93 kg deionized water. The remaining steps are the same as in Example 3.

[0041] Example 5 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 5 differs from that in Example 3 in that the pickling solution is a mixed solution of 5 kg of 40% hydrofluoric acid, 18 kg of 68% nitric acid, 1.5 kg of citric acid, 1 kg of ammonium bifluoride, and 75 kg of deionized water. The remaining steps are the same as in Example 3.

[0042] Example 6 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 6 differs from that in Example 4 in that the pickling solution is a mixed solution of 5 kg of 40% hydrofluoric acid, 18 kg of 68% nitric acid, 1.5 kg of citric acid, 1 kg of ammonium bifluoride, and 75 kg of deionized water. The remaining steps are the same as in Example 4.

[0043] Examples 7-10 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Examples 7-10 differs from that in Example 6 in that the amounts of ammonium bifluoride and 40% concentration hydrofluoric acid are different, namely 8 kg and 0.8 kg, 13 kg and 0.7 kg, 7.5 kg and 0.5 kg, and 10 kg and 0.5 kg, respectively. The remaining steps are the same as in Example 6.

[0044] Example 11 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 11 differs from that in Example 7 in that the nickel-titanium alloy braided tubing is subjected to a vacuum of 5×10⁻⁶. -3 After heat treatment at 900℃ for 1.5 hours, the temperature was kept at -90℃ for 3 hours, followed by heat treatment at 180℃ for 45 minutes. The remaining steps were the same as in Example 7.

[0045] Example 12 The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Example 12 differs from that in Example 11 in that preheating is performed before aging treatment, specifically by holding at 450°C for 13 minutes. The remaining steps are the same as in Example 11.

[0046] Examples 13-16 The heat treatment methods for the high-elasticity, high-strength nickel-titanium alloy braided tubing in Examples 13-16 differ from those in Example 12 in that the water cooling rates during the aging treatment are 5°C / min, 7°C / min, 10°C / min, and 11°C / min, respectively, while the remaining steps are the same as in Example 12.

[0047] Comparative Example 1 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tube in Comparative Example 1 differs from that in Example 1 in that the solution treatment temperature is controlled at 800℃, while the remaining steps are the same as in Example 1.

[0048] Comparative Example 2 The heat treatment method of the high elasticity and high strength nickel-titanium alloy braided tube in Comparative Example 2 differs from that in Example 1 in that the solution treatment temperature is controlled at 1000℃, while the other steps are the same as in Example 1.

[0049] Comparative Example 3 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tubing in Comparative Example 3 differs from that in Example 1 in that the aging treatment temperature is controlled at 470°C, while the remaining steps are the same as in Example 1.

[0050] Comparative Example 4 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tubing in Comparative Example 4 differs from that in Example 1 in that the aging treatment temperature is controlled at 610°C, while the remaining steps are the same as in Example 1.

[0051] Comparative Example 5 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tube in Comparative Example 5 differs from that in Example 1 in that the aging treatment heating rate is 2℃ / min, while the other steps are the same as in Example 1.

[0052] Comparative Example 6 The heat treatment method of the high-elasticity, high-strength nickel-titanium alloy braided tube in Comparative Example 6 differs from that in Example 1 in that the aging treatment heating rate is 6℃ / min, while the other steps are the same as in Example 1.

[0053] The following is an example of the application of heat treatment methods in the preparation of nickel-titanium alloy braided tubing: Example 1. Application Example 1: The heat treatment method for nickel-titanium alloy braided tubing is used in the preparation of nickel-titanium alloy braided tubing, specifically as follows: S1. Selected binary nickel-titanium alloy wire (Ni-Ti wire), medical grade standard, wherein the nickel (Ni) content is 55% (mass fraction), the titanium (Ti) is the balance, the total impurity content is ≤0.1%; the diameter is 0.05mm.

[0054] S2. The strands are braided using a braiding machine, supported by a cylindrical mandrel (mandrel surface smoothness Ra=0.02μm). The strand tension (15N), braiding pitch (2.0mm), and braiding angle (45°) are precisely controlled to ensure the accuracy of the pipe's inner diameter. Figure 1 It is woven using a regular weaving structure. When the weaving machine is fully loaded, the pattern is 1 pressing 2, that is, a clockwise rotating yarn will be pressed down by two counterclockwise rotating yarns, and then pressed down by two more counterclockwise rotating yarns.

[0055] S3. After braiding, the heat treatment method of nickel-titanium alloy braided tube in Example 1 is used to finally obtain nickel-titanium alloy braided tube.

[0056] Application Example 2-16 The heat treatment method for nickel-titanium alloy braided tubing in Application Example 2-16 differs from that in Application Example 1 in that the heat treatment method for nickel-titanium alloy braided tubing adopts the method of Example 2-16, while the remaining steps are the same as in Application Example 1.

[0057] Application Comparative Examples 1-6 The difference between the heat treatment method of Comparative Examples 1-6 for preparing nickel-titanium alloy braided tubing and Application Example 1 is that the heat treatment method of Comparative Examples 1-6 is used, while the remaining steps are the same as in Application Example 1.

[0058] The performance testing was conducted using the following methods to test the nickel-titanium alloy braided tubing obtained in use cases 1-16 and application comparison examples 1-6. The specific test results are shown in Table 1.

[0059] Elastic recovery rate: The elastic recovery rate of nickel-titanium alloy braided tubing was tested according to ASTM F2063-15.

[0060] Tensile strength: Tested in accordance with the requirements of GB / T 228.1-2021 Metallic materials, tensile testing - Part 1: Test method at room temperature.

[0061] Table 1. Test results of different nickel-titanium alloy braided tubing The test results in Table 1 show that the nickel-titanium alloy braided tube obtained by the heat treatment method of this application has an elastic recovery rate of ≥95% and a tensile strength of ≥1000MPa, which improves the elasticity and strength of the nickel-titanium alloy braided tube.

[0062] Based on the test data of the nickel-titanium alloy braided tubing in Application Examples 1 and 2, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of Example 2 had a tensile strength of 1022 MPa, which was higher than that of Example 1. This improved the strength and elasticity of the nickel-titanium alloy braided tubing, indicating that solution treatment of the nickel-titanium alloy braided tubing before aging treatment can improve its strength.

[0063] Based on the test data of application examples 2 and 3, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of application example 3 had a tensile strength of 1032 MPa and an elastic recovery rate of 96%, both of which were higher than those of application example 2. This improved the strength and elasticity of the nickel-titanium alloy braided tubing, indicating that pretreatment of the nickel-titanium alloy braided tubing by degreasing and pickling before solution treatment can improve its strength and elasticity.

[0064] Based on the test data of application examples 3 and 4, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of application example 4 had a tensile strength of 1045 MPa, which improved the strength of the nickel-titanium alloy braided tubing. This indicates that when the degreasing solution is a mixed solution of sodium hydroxide, sodium tripolyphosphate, fatty alcohol polyoxyethylene ether and deionized water, the strength of the nickel-titanium alloy braided tubing can be improved.

[0065] Based on the test data of the nickel-titanium alloy braided tubing in Application Examples 3 and 5, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of Application Example 5 had a tensile strength of 1050 MPa, which was higher than that of Application Example 5. This improved the strength of the nickel-titanium alloy braided tubing, indicating that the strength of the nickel-titanium alloy braided tubing can be improved when the pickling solution is a mixed solution of 40% hydrofluoric acid, 68% nitric acid, citric acid, ammonium bifluoride, and deionized water.

[0066] Based on the test data of the nickel-titanium alloy braided tubing in Application Example 6 and Application Example 5, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of the nickel-titanium alloy braided tubing in Example 5 had a tensile strength of 1065 MPa and an elastic recovery rate of 97%, both of which were higher than those in Application Example 5. This improved the strength of the nickel-titanium alloy braided tubing, indicating that when the degreasing solution is a mixed solution of sodium hydroxide, sodium tripolyphosphate, fatty alcohol polyoxyethylene ether, and deionized water, and the pickling solution is a mixed solution of 40% hydrofluoric acid, 68% nitric acid, citric acid, ammonium bifluoride, and deionized water, the strength and elasticity of the nickel-titanium alloy braided tubing can be further improved.

[0067] Based on the test data of application examples 6 and 7-10, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of example 7-9 had a tensile strength of 1071-1078 MPa and an elastic recovery rate of 98%, both higher than those of application examples 6 and 10. This improved the strength of the nickel-titanium alloy braided tubing, indicating that when the weight ratio of ammonium bifluoride to 40% hydrofluoric acid in the pickling solution is 1:(10-15), the strength of the nickel-titanium alloy braided tubing can be further improved.

[0068] Based on the test data of Application Example 8 and Application Example 11, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of Application Example 11 had a tensile strength of 1085 MPa, which was higher than that of Application Example 8, indicating that the strength of the nickel-titanium alloy braided tubing was improved by heat treatment at a vacuum degree of 5×10⁻⁶ MPa. -3 After heat treatment at 900℃ for 1.5 hours, followed by heat treatment at -90℃ for 3 hours, and then heat treatment at 180℃ for 45 minutes, the strength of nickel-titanium alloy braided tubing can be further improved.

[0069] Based on the test data of the nickel-titanium alloy braided tubing in Application Examples 11 and 12, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of Example 12 had a tensile strength of 1100 MPa, which was higher than that in Application Example 11. This improved the strength of the nickel-titanium alloy braided tubing, indicating that preheating before aging treatment can further improve the strength of the nickel-titanium alloy braided tubing.

[0070] Based on the test data of the nickel-titanium alloy braided tubing in Application Examples 12 and 13-16, it was found that the nickel-titanium alloy braided tubing obtained by the heat treatment method of the nickel-titanium alloy braided tubing in Examples 13-15 had a tensile strength of 1115-1132 MPa, which was higher than that in Application Examples 12 and 16. This improved the strength of the nickel-titanium alloy braided tubing, indicating that controlling the cooling rate of water cooling during aging treatment at 5-10℃ / min can further improve the strength of the nickel-titanium alloy braided tubing.

[0071] Based on the test data of application example 1 and comparative examples 1-6, it was found that controlling the solution treatment temperature at 850-950℃, the aging treatment temperature at 500-600℃, and controlling the heating rate during aging treatment at 3-5℃ / min can improve the strength and elasticity of nickel-titanium alloy braided tubing to varying degrees.

[0072] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A heat treatment method for a high-elasticity, high-strength nickel-titanium alloy braided tube, characterized in that, The nickel-titanium alloy braided tubing undergoes an aging treatment, specifically by aging the tubing under a vacuum degree ≤ 5 × 10⁻⁶. -3 Heating at 480-600℃ for 15-60 minutes with a heating rate of 3-5℃ / min, followed by water cooling to 25±2℃, is then completed to finish the heat treatment.

2. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing according to claim 1, characterized in that, The solution treatment prior to the aging process specifically involves: preparing the nickel-titanium alloy braided tubing under a vacuum degree ≤ 5 × 10⁻⁶. -3 Heat treatment is carried out at 850-950℃ for 0.5-2 hours, with a heating rate of 5-10℃ / min, followed by cooling.

3. The heat treatment method for high-elasticity, high-strength nickel-titanium alloy braided tubing according to claim 2, characterized in that, The nickel-titanium alloy braided tubing is pretreated before solution treatment, specifically: first, the surface of the nickel-titanium alloy braided tubing is rinsed with deionized water, then immersed in a degreasing solution at 40-50℃ for 10-15 minutes, rinsed with water, then immersed in an acid pickling solution for 5-10 minutes, rinsed with water, neutralized, and dried at 60-80℃ for 15-20 minutes.

4. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing according to claim 3, characterized in that, The degreasing solution comprises the following raw materials in parts by weight: 4-6 parts sodium hydroxide, 2-3 parts sodium tripolyphosphate, 1-3 parts fatty alcohol polyoxyethylene ether, and 90-95 parts deionized water.

5. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tube according to claim 3, characterized in that, The pickling solution comprises the following raw materials in parts by weight: 5-10 parts of 40% hydrofluoric acid, 15-20 parts of 68% nitric acid, 1-2 parts of citric acid, 0.5-1 parts of ammonium bifluoride, and 70-80 parts of deionized water.

6. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tube according to claim 5, characterized in that, The weight ratio of ammonium bifluoride to 40% hydrofluoric acid is 1:(10-15).

7. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing according to claim 1, characterized in that, The nickel-titanium alloy braided tubing is subjected to a vacuum degree ≤5×10 -3 After heat treatment at 850-950℃ for 0.5-2 hours, the temperature is kept at -80-100℃ for 2-4 hours, followed by heat treatment at 150-200℃ for 30-60 minutes.

8. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tubing according to claim 1, characterized in that, The aging process involves preheating the equipment at 430-460℃ for 10-15 minutes.

9. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tube according to claim 1, characterized in that, The cooling rate of the water cooling system is 5-10℃ / min.

10. The heat treatment method for the high-elasticity, high-strength nickel-titanium alloy braided tube according to claim 1, characterized in that, The nickel-titanium alloy braided tubing is woven from any one of the following alloy wires: nickel-titanium alloy wire, nickel-titanium-vanadium alloy wire, or nickel-titanium-copper alloy wire. The nickel-titanium alloy wire comprises the following elements by mass fraction: nickel 51.5%~57.0%, titanium as the balance, and total impurities ≤0.1%. The nickel-titanium-vanadium alloy wire comprises the following elements by mass fraction: nickel 52.5%-57%, vanadium 0.3%-2.7%, titanium as the balance, and total impurities ≤0.1%. The nickel-titanium-copper alloy wire comprises the following elements by mass fraction: nickel 41%-49%, copper 5%-10%, titanium as the balance, and total impurities ≤0.1%.

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