Preparation method of super-elastic nickel-titanium alloy wire, super-elastic nickel-titanium alloy wire

Abstract

The application discloses a preparation method of super-elastic nickel-titanium alloy wire and the super-elastic nickel-titanium alloy wire. The preparation method comprises the following steps: providing a nickel-titanium alloy rod, then pre-oxidizing the nickel-titanium alloy rod; continuously heat-drawing the pre-oxidized nickel-titanium alloy rod to obtain a semi-finished wire; removing the oxidation layer on the surface of the semi-finished wire; sequentially performing room-temperature drawing, online vacuum annealing and water quenching on the semi-finished wire to obtain a nickel-titanium alloy wire; and performing online vacuum annealing and water quenching on the nickel-titanium alloy wire again to obtain the required super-elastic nickel-titanium alloy wire. The preparation method of the super-elastic nickel-titanium alloy wire can realize continuous heat-drawing without high-temperature annealing and water quenching in the middle, and the prepared super-elastic nickel-titanium alloy wire has excellent super-elasticity with a 6% loading strain and a residual less than 0.3%.

Description

Technical Field

[0001] This invention relates to the field of shape memory alloy wire processing technology, and in particular to a method for preparing a superelastic nickel-titanium alloy wire and the superelastic nickel-titanium alloy wire. Background Technology

[0002] Nickel-titanium alloys possess excellent and unique properties, including shape memory effect, superelasticity, damping characteristics, biocompatibility, radiation impermeability, non-influence of nuclear magnetic resonance, and corrosion resistance. They are currently widely used in aerospace, machinery, shipbuilding, and biomedical fields. Particularly in the medical device field, nickel-titanium alloys are primarily used in orthodontic wires, root canal files, spinal braces, bone plates, intramedullary nails, patellar claws, guidewires, guide needles, cardiac patches, vascular stents, thrombus filters, esophageal stents, respiratory stents, biliary stents, urethral stents, rectal stents, duodenal stents, and external auditory canal stents.

[0003] Superelasticity refers to the behavior of a nickel-titanium alloy that automatically recovers its deformation after being deformed in its parent phase state, undergoing a stress-induced martensitic transformation, and then recovering its original shape after unloading due to a reverse stress-induced martensitic transformation. Although superelasticity was recognized more than a decade later than shape memory effect, approximately 90% of the current medical and engineering applications of shape memory alloys utilize their superelastic properties to achieve their functions.

[0004] Currently, traditional superelastic nickel-titanium alloy wires are mainly produced through multiple cycles of hot drawing and cold drawing with fixed dies, with each drawing being a single-die drawing. This production method significantly increases the thickness of the oxide layer on the surface of the nickel-titanium alloy wire, increases material consumption, and results in low production efficiency and unstable performance. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for preparing superelastic nickel-titanium alloy wire that can solve the above problems.

[0006] In addition, it is necessary to provide a method for preparing the above-mentioned superelastic nickel-titanium alloy wire to obtain the superelastic nickel-titanium alloy wire.

[0007] A method for preparing a superelastic nickel-titanium alloy wire includes the following steps:

[0008] A nickel-titanium alloy rod is provided, and then the nickel-titanium alloy rod is pre-oxidized;

[0009] The pre-oxidized nickel-titanium alloy rod is continuously hot-drawn to obtain a semi-finished wire. The temperature of the continuous hot drawing is 600℃~900℃, the drawing speed is 0.5m / min~8m / min, and the single-pass deformation rate is 3%~25%.

[0010] Remove the oxide layer from the surface of the semi-finished yarn;

[0011] The semi-finished wire was sequentially subjected to room temperature drawing, online vacuum annealing, and water quenching to obtain a nickel-titanium alloy wire; and

[0012] The nickel-titanium alloy wire is subjected to online vacuum annealing and water quenching again to obtain the desired superelastic nickel-titanium alloy wire.

[0013] In one embodiment, the diameter of the nickel-titanium alloy rod is 6 mm to 18 mm;

[0014] In the pre-oxidation operation of the nickel-titanium alloy rod, the pre-oxidation temperature is 600℃~900℃ and the pre-oxidation time is 30min~120min.

[0015] In one embodiment, the diameter of the semi-finished filament is 1.5 mm to 4 mm;

[0016] In the continuous hot drawing operation of the pre-oxidized nickel-titanium alloy rod, the lubricant for the continuous hot drawing is a graphite emulsion with a concentration of 20wt% to 80wt%.

[0017] In one embodiment, the operation of removing the oxide layer on the surface of the semi-finished yarn is as follows: the oxide layer on the surface of the semi-finished yarn is removed by peeling it off using a centerless sewing machine or a mold.

[0018] In one embodiment, the operation of removing the oxide layer on the surface of the semi-finished yarn is as follows: the semi-finished yarn is pickled with an acidic solution to remove the oxide layer on the surface of the semi-finished yarn. The acidic solution is a mixture of hydrofluoric acid solution and nitric acid solution with a volume ratio of 1:2 to 4. The concentration of the hydrofluoric acid solution is 35wt% to 60wt%, the concentration of the nitric acid solution is 50wt% to 70wt%, the pickling is performed 2 to 5 times, and the pickling time for each time is 5 min to 30 min.

[0019] In one embodiment, the diameter of the nickel-titanium alloy wire is 0.025 mm to 0.8 mm;

[0020] In the sequential operations of room temperature drawing, online vacuum annealing, and water quenching of the semi-finished wire, the drawing die for room temperature drawing is a combined diamond die, the total deformation rate of the combined die is 25% to 80%, the deformation rate per pass of room temperature drawing is 5% to 30%, the drawing speed of room temperature drawing is 10 m / min to 30 m / min, the lubricant for room temperature drawing is a soap solution with a concentration of 20 wt% to 80 wt%, the wire feeding device for online vacuum annealing is a passive damping type wire feeding device, the wire feeding device for online vacuum annealing is a continuous double H-beam take-up device, the annealing temperature of online vacuum annealing is 400℃ to 900℃, and the annealing time of online vacuum annealing is 0.1 min to 10 min.

[0021] In one embodiment, during the online vacuum annealing and water quenching of the nickel-titanium alloy wire, the annealing temperature of the online vacuum annealing is 400℃~700℃, and the annealing time of the online vacuum annealing is 0.1min~10min.

[0022] In one embodiment, the nickel-titanium alloy rod is prepared by the following operation:

[0023] Provide nickel-titanium alloy ingots;

[0024] The nickel-titanium alloy ingot is peeled and inspected to remove the defective parts and obtain a qualified ingot.

[0025] The qualified ingots are subjected to a series of processes, including rough forging, precision forging, hot rolling, rounding, and peeling, to obtain the nickel-titanium alloy rods.

[0026] In one embodiment, the raw materials for the nickel-titanium alloy ingot are electrolytic nickel and sponge titanium, and the nickel-titanium alloy ingot comprises 55.0 wt% to 56.5 wt% nickel and the remainder titanium.

[0027] The nickel-titanium alloy ingot is prepared by the following operation: electrolytic nickel and sponge titanium are pressed into electrodes, and then subjected to vacuum induction melting and two vacuum consumable melting processes to obtain the nickel-titanium alloy ingot.

[0028] In the sequential processes of forging, precision forging, hot rolling, rounding, and peeling of the qualified ingot, the forging temperature is 1000℃~800℃, the forging holding time is 3h~4h, the precision forging temperature is 1000℃~800℃, the precision forging holding time is 2h~3h, the hot rolling temperature is 900℃~750℃, the hot rolling holding time is 2h~3h, and the peeling depth is 0.5mm~1mm.

[0029] A superelastic nickel-titanium alloy wire is prepared by the above-described method for preparing superelastic nickel-titanium alloy wire.

[0030] The method for preparing the superelastic nickel-titanium alloy wire of this invention employs hot drawing with controlled deformation and drawing speed. During the hot drawing heating process, the dislocation density from the previous processing pass is eliminated or complete annealing is achieved, enabling continuous hot drawing without intermediate high-temperature annealing or water quenching. The resulting superelastic nickel-titanium alloy wire exhibits excellent superelasticity with a 6% loaded strain and a residual strain of less than 0.3%. Compared to traditional single-die drawing methods, the method of this invention does not cause a significant increase in the oxide layer thickness on the surface of the nickel-titanium alloy wire, resulting in higher production efficiency and more stable performance of the prepared superelastic nickel-titanium alloy wire.

[0031] Furthermore, in a preferred embodiment of the present invention, the drawing die for room temperature drawing is a combined die, which realizes combined die drawing, resulting in a shorter production process, higher efficiency, and improved product stability. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] in:

[0034] Figure 1 This is a flowchart of a method for preparing a superelastic nickel-titanium alloy wire according to one embodiment.

[0035] Figure 2 The stress-strain test results are for the two samples prepared in Example 1.

[0036] Figure 3 The stress-strain test results are for the two samples prepared in Example 2.

[0037] Figure 4 The stress-strain test results are for the two samples prepared in Example 3.

[0038] Figure 5 The stress-strain test results are for the two samples prepared in Comparative Example 2. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0041] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of the stated features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0042] Combination Figure 5 This invention discloses a method for preparing a superelastic nickel-titanium alloy wire according to one embodiment, comprising the following steps:

[0043] S10. Provide a nickel-titanium alloy rod, and then pre-oxidize the nickel-titanium alloy rod.

[0044] In one embodiment, the diameter of the nickel-titanium alloy rod is 6 mm to 18 mm.

[0045] In the pre-oxidation process of nickel-titanium alloy rods, the pre-oxidation temperature is 600℃~900℃ and the pre-oxidation time is 30min~120min.

[0046] Nickel-titanium alloy rods are available for direct purchase.

[0047] In this embodiment, the nickel-titanium alloy rod can also be prepared by the following operation:

[0048] Provide nickel-titanium alloy ingots;

[0049] The nickel-titanium alloy ingot is peeled and inspected to remove the unqualified parts and obtain a qualified ingot.

[0050] The qualified ingots are sequentially subjected to forging, precision forging, hot rolling, rounding and peeling to obtain nickel-titanium alloy rods.

[0051] Preferably, the raw materials for the nickel-titanium alloy ingot are electrolytic nickel and sponge titanium, and the nickel-titanium alloy ingot includes 55.0 wt% to 56.5 wt% nickel and the remainder titanium.

[0052] Specifically, in this embodiment, a lathe can be used to peel off the outer layer of the nickel-titanium alloy ingot, and then a handheld ultrasonic flaw detector can be used to inspect the inside of the nickel-titanium alloy ingot and remove the defective parts.

[0053] Nickel-titanium alloy ingots can be prepared by pressing electrolytic nickel and sponge titanium into electrodes, followed by vacuum induction melting and two vacuum consumable melting processes to obtain nickel-titanium alloy ingots.

[0054] Specifically, in this embodiment, during the sequential operations of rough forging, precision forging, hot rolling, rounding, and peeling of qualified ingots, the forging temperature is 1000℃~800℃, the forging holding time is 3h~4h, the precision forging temperature is 1000℃~800℃, the precision forging holding time is 2h~3h, the hot rolling temperature is 900℃~750℃, the hot rolling holding time is 2h~3h, and the peeling depth is 0.5mm~1mm.

[0055] Specifically, in this embodiment, the rounding can be achieved by pulling.

[0056] Specifically, in this embodiment, a graphite crucible can be used for vacuum induction melting, and a water-cooled copper crucible can be used for vacuum consumable melting.

[0057] Specifically, in this embodiment, peeling and pre-oxidation treatment can remove defects such as material folding and polygons caused during the rolling process.

[0058] S20. The pre-oxidized nickel-titanium alloy rod obtained in S10 is continuously hot-drawn to obtain a semi-finished wire.

[0059] The continuous hot drawing temperature is 600℃~900℃, the continuous hot drawing speed is 0.5m / min~8m / min, and the single-pass deformation rate of continuous hot drawing is 3%~25%.

[0060] Preferably, in this embodiment, the diameter of the semi-finished yarn is 1.5mm to 4mm.

[0061] Specifically, in the continuous hot drawing operation of the pre-oxidized nickel-titanium alloy rod, the lubricant for continuous hot drawing is a graphite emulsion with a concentration of 20wt% to 80wt%.

[0062] Specifically, in this embodiment, a spool drawing machine, a straight drawing machine, or a roller mill drawing machine can be used to continuously hot draw the pre-oxidized nickel-titanium alloy rod.

[0063] By continuously hot-drawing nickel-titanium alloy bars and controlling the drawing speed, continuous drawing can be achieved, which greatly improves production efficiency and enables large-scale production.

[0064] S30: Remove the oxide layer from the surface of the semi-finished yarn obtained in S20.

[0065] Preferably, in this embodiment, the operation of removing the oxide layer on the surface of the semi-finished yarn can be: removing the oxide layer on the surface of the semi-finished yarn by peeling it off using a centerless sewing machine or a mold.

[0066] In other embodiments, the removal of the oxide layer on the surface of the semi-finished yarn can also be achieved by pickling the semi-finished yarn with an acidic solution, thereby removing the oxide layer on the surface of the semi-finished yarn. The acidic solution is a mixture of hydrofluoric acid solution and nitric acid solution with a volume ratio of 1:2 to 4. The concentration of the hydrofluoric acid solution is 35wt% to 60wt%, the concentration of the nitric acid solution is 50wt% to 70wt%, the pickling is performed 2 to 5 times, and the pickling time for each time is 5 min to 30 min.

[0067] S40, the semi-finished wire obtained from S30 is sequentially subjected to room temperature drawing, online vacuum annealing and water quenching to obtain nickel-titanium alloy wire.

[0068] Preferably, in this embodiment, the diameter of the nickel-titanium alloy wire is 0.025 mm to 0.8 mm;

[0069] In the sequential operations of room temperature drawing, online vacuum annealing, and water quenching of semi-finished wire, the drawing die for room temperature drawing is a combined die with a total deformation rate of 25%–80%. The deformation rate per pass of room temperature drawing is 5%–30%. The drawing speed for room temperature drawing is 10 m / min–30 m / min. The lubricant for room temperature drawing is a soap solution with a concentration of 20 wt%–80 wt%. The wire feeding device for online vacuum annealing is a passive damping type, and the wire feeding device for online vacuum annealing is a continuous double H-beam take-up device. The annealing temperature for online vacuum annealing is 400℃–900℃, and the annealing time for online vacuum annealing is 0.1 min–10 min.

[0070] Specifically, semi-finished wires can be intermediately annealed and water-quenched using an online vacuum annealing furnace.

[0071] The drawing die for room temperature drawing is a combination die, which enables combined die drawing, resulting in a shorter production process, higher efficiency, and improved product stability. Furthermore, combined die drawing allows for more uniform work hardening of the obtained wire, leading to a more uniform deformation process and more consistent and stable performance. Additionally, combined die drawing can reduce the total number of drawing passes, thereby increasing production efficiency.

[0072] The anti-dampening device uses passive damping for unwinding and continuous double H-beam reel for winding, which can increase the tension of the semi-finished yarn in the annealing furnace.

[0073] S50, the nickel-titanium alloy wire obtained from S40 is subjected to online vacuum annealing and water quenching again to obtain the desired superelastic nickel-titanium alloy wire.

[0074] Preferably, in the process of performing online vacuum annealing and water quenching on the nickel-titanium alloy wire, the annealing temperature of the online vacuum annealing is 400℃~700℃, and the annealing time of the online vacuum annealing is 0.1min~10min.

[0075] Specifically, nickel-titanium alloy wires can be subjected to intermediate annealing and water quenching again using an online vacuum annealing furnace.

[0076] The method for preparing the superelastic nickel-titanium alloy wire of the present invention enables continuous hot drawing without intermediate high-temperature annealing or water quenching. The resulting superelastic nickel-titanium alloy wire exhibits excellent superelasticity with a loaded strain of 6% and a residual strain of less than 0.3%. Compared with the traditional single-die drawing method, the method of the present invention does not cause a significant increase in the oxide layer thickness on the surface of the nickel-titanium alloy wire, has higher production efficiency, and produces more stable superelastic nickel-titanium alloy wire.

[0077] The present invention also discloses an embodiment of a superelastic nickel-titanium alloy wire prepared by the above-described method for preparing superelastic nickel-titanium alloy wire.

[0078] The following are specific examples.

[0079] In a specific embodiment, the sponge titanium was purchased from Grade 0 sponge titanium of Chaoyang Jinda Titanium Industry Co., Ltd., the electrolytic nickel was purchased from high-purity electrolytic nickel plates of Jinchuan Group Co., Ltd., and the graphite emulsion was purchased from Qingdao Xingyuan Graphite Emulsion Co., Ltd.

[0080] Example 1

[0081] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 200mm and a weight of 50kg.

[0082] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 198mm.

[0083] Step 3: After holding the ingot at 1000℃ for 3.5 hours, use a high-speed forging machine to forge the ingot to obtain a Φ80mm forging billet.

[0084] Step 4: After holding the forging billet at 900℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ50mm forging billet.

[0085] Step 5: After holding the forging billet at 900℃ for 2 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ9.5mm forging billet;

[0086] Step 6: Round and peel the Φ9.5mm rolled strip to obtain Φ9.0mm bar stock;

[0087] Step 7: Hold the bar obtained in Step 6 at 900℃ for 30 minutes to obtain a bar with a thin layer of oxide scale;

[0088] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 900℃, a drawing speed of 1m / min, a single-pass deformation rate of 10%, and a 50wt% graphite emulsion as the lubricant, drawing to Φ2.0mm.

[0089] Step 9: Peel the filament obtained in Step 8 using a mold, ensuring a surface roughness of less than or equal to 0.8 μm;

[0090] Step 10: The filament obtained in Step 9 is subjected to room temperature drawing, online vacuum annealing, and water quenching to a diameter of 0.2 mm. The drawing die is a combination die with a total deformation rate of 35%. The filament is immersed in a soap solution with a concentration of 30 wt%. The drawing speed is 10 m / min. The online intermediate annealing temperature is 700 ℃, and the online vacuum annealing time is 2 min.

[0091] Step 11: Perform online vacuum annealing and water quenching on the wire obtained in Step 10 again. The online intermediate annealing temperature is 550℃ and the online vacuum annealing time is 1.0 min to obtain a superelastic nickel-titanium alloy wire with no oxide layer on the surface.

[0092] Example 2

[0093] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 200mm and a weight of 50kg.

[0094] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 198mm.

[0095] Step 3: After holding the ingot at 950℃ for 3 hours, use a high-speed forging machine to forge the ingot to obtain a Φ80mm forging billet.

[0096] Step 4: After holding the forging billet at 950℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ50mm forging billet.

[0097] Step 5: After holding the forging billet at 900℃ for 2.5 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ12.0mm forging billet;

[0098] Step 6: Round and peel the Φ12.0mm rolled strip to obtain Φ11.5mm bar stock;

[0099] Step 7: Hold the bar obtained in Step 6 at 750℃ for 45 minutes to obtain a bar with a thin layer of oxide scale;

[0100] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 820℃, a drawing speed of 4m / min, a single-pass deformation rate of 12%, and a 30wt% graphite emulsion as the lubricant, drawing to Φ2.0mm.

[0101] Step 9: Pickle the filament obtained in Step 8 until the surface roughness is less than or equal to 0.8 μm;

[0102] Step 10: The filament obtained in Step 9 is subjected to room temperature drawing, intermediate vacuum annealing, and water quenching to a diameter of 0.1 mm. The drawing die is a combination die with a total deformation rate of 60%. The filament is immersed in a soap solution with a concentration of 40 wt%. The drawing speed is 10 m / min. The online intermediate annealing temperature is 750 ℃, and the online vacuum annealing time is 1.5 min.

[0103] Step 11: Perform vacuum annealing and water quenching on the wire obtained in Step 10 again at a temperature of 540℃. The annealing time for online vacuum annealing is 1.0 min to obtain a superelastic nickel-titanium alloy wire with no oxide layer on the surface.

[0104] Example 3

[0105] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 300mm and a weight of 80kg.

[0106] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 298mm.

[0107] Step 3: After holding the ingot at 1100℃ for 3 hours, use a high-speed forging machine to forge the ingot to obtain a Φ120mm forging billet.

[0108] Step 4: After holding the forging billet at 1000℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ60mm forging billet.

[0109] Step 5: After holding the forging billet at 900℃ for 2 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ10.0mm forging billet;

[0110] Step 6: Round and peel the Φ10.0mm rolled strip to obtain Φ9.5mm bar stock;

[0111] Step 7: Hold the bar obtained in Step 6 at 900℃ for 30 minutes to obtain a bar with a thin layer of oxide scale;

[0112] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 900℃, a drawing speed of 2m / min, a single-pass deformation rate of 15%, and a 60wt% graphite emulsion as the lubricant, drawing to Φ2.0mm.

[0113] Step 9: The filament obtained in Step 9 is drawn at room temperature, vacuum annealed in the middle and quenched in water to a diameter of 0.06 mm. The drawing die is a combination die with a total deformation rate of 65%. The filament is immersed in a soap solution with a concentration of 50 wt%. The drawing speed is 10 m / min. The online intermediate annealing temperature is 750 ℃ ​​and the online vacuum annealing time is 1.5 min.

[0114] Step 9: Pickle the filament obtained in Step 8 to remove the surface oxide layer. The surface roughness should be less than or equal to 0.8 μm. The pickling solution is a mixture of hydrofluoric acid solution and nitric acid solution with a volume ratio of 1:3. The concentration of hydrofluoric acid solution is 40 wt% and the concentration of nitric acid solution is 60 wt%. The pickling is performed 3 times, and the pickling time for each time is 15 min.

[0115] Step 11: Perform vacuum annealing and water quenching on the wire obtained in Step 10 again at a temperature of 530℃. The annealing time for online vacuum annealing is 0.5 min to obtain a superelastic nickel-titanium alloy wire with no oxide layer on the surface.

[0116] Comparative Example 1

[0117] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 200mm and a weight of 50kg.

[0118] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 198mm.

[0119] Step 3: After holding the ingot at 1000℃ for 3.5 hours, use a high-speed forging machine to forge the ingot to obtain a Φ80mm forging billet.

[0120] Step 4: After holding the forging billet at 900℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ50mm forging billet.

[0121] Step 5: After holding the forging billet at 900℃ for 2 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ9.5mm forging billet;

[0122] Step 6: Round and peel the Φ9.5mm rolled strip to obtain Φ9.0mm bar stock;

[0123] Step 7: Hold the bar obtained in Step 6 at 800℃ for 30 minutes to obtain a bar with a thin layer of oxide scale;

[0124] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 900℃ and a drawing speed of 1m / min. The single-pass deformation rate is 10%, and the lubricant is graphite emulsion with a concentration of 50wt%. After the total deformation reaches 45%, hold at 850℃ for 60min and gradually draw to Φ2.0mm.

[0125] Step 9: Peel the filament obtained in Step 8 using a mold, ensuring a surface roughness of less than or equal to 0.8 μm;

[0126] Step 10: The filament obtained in Step 9 is subjected to room temperature drawing, online vacuum annealing, and water quenching to a diameter of 0.2 mm. The drawing die is a combination die with a total deformation rate of 35%. The filament is immersed in a soap solution with a concentration of 30 wt%. The drawing speed is 10 m / min. The online intermediate annealing temperature is 700 ℃, and the online vacuum annealing time is 2 min.

[0127] Step 11: Perform online vacuum annealing and water quenching on the wire obtained in Step 10 again. The online intermediate annealing temperature is 550℃ and the online vacuum annealing time is 1.0 min to obtain a superelastic nickel-titanium alloy wire with no oxide layer on the surface.

[0128] Comparative Example 2

[0129] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 200mm and a weight of 50kg.

[0130] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 198mm.

[0131] Step 3: After holding the ingot at 1000℃ for 3.5 hours, use a high-speed forging machine to forge the ingot to obtain a Φ80mm forging billet.

[0132] Step 4: After holding the forging billet at 900℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ50mm forging billet.

[0133] Step 5: After holding the forging billet at 900℃ for 2 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ9.5mm forging billet;

[0134] Step 6: Round and peel the Φ9.5mm rolled strip to obtain Φ9.0mm bar stock;

[0135] Step 7: Hold the bar obtained in Step 6 at 800℃ for 30 minutes to obtain a bar with a thin layer of oxide scale;

[0136] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 900℃, a drawing speed of 1m / min, a single-pass deformation rate of 10%, and a 50wt% graphite emulsion as the lubricant, drawing to Φ2.0mm.

[0137] Step 9: Peel the filament obtained in Step 8 using a mold, ensuring a surface roughness of less than or equal to 0.8 μm;

[0138] Step 10: The filament obtained in Step 9 is subjected to room temperature drawing, online vacuum annealing, and water quenching to a diameter of 0.2 mm. The drawing die is a single fixed die with a die deformation rate of 15%. The filament is immersed in a soap solution with a concentration of 30 wt%. The drawing speed is 10 m / min. The online intermediate annealing temperature is 700 ℃, and the online vacuum annealing time is 2 min.

[0139] Step 11: Perform online vacuum annealing and water quenching on the wire obtained in Step 10 again. The online intermediate annealing temperature is 550℃ and the online vacuum annealing time is 1.0 min to obtain a superelastic nickel-titanium alloy wire with no oxide layer on the surface.

[0140] Comparative Example 3

[0141] Step 1: Mix Ni with a mass percentage of 55.5%, select grade 0 sponge titanium and high-purity electrolytic nickel for vacuum induction melting and two vacuum self-consumption melting to obtain an ingot with a diameter of 200mm and a weight of 50kg.

[0142] Step 2: Use a lathe to peel off the surface to a depth of 1mm, then use a handheld ultrasonic flaw detector to inspect the ingot for flaws, remove the defective parts, and obtain an ingot with a diameter of 198mm.

[0143] Step 3: After holding the ingot at 1000℃ for 3.5 hours, use a high-speed forging machine to forge the ingot to obtain a Φ80mm forging billet.

[0144] Step 4: After holding the forging billet at 900℃ for 2.5 hours, it is then precision forged using a radial precision forging machine to obtain a Φ50mm forging billet.

[0145] Step 5: After holding the forging billet at 900℃ for 2 hours, it is rolled at high temperature using a transverse rolling mill to obtain a Φ9.5mm forging billet;

[0146] Step 6: Round and peel the Φ9.5mm rolled strip to obtain Φ9.0mm bar stock;

[0147] Step 7: Hold the bar obtained in Step 6 at 800℃ for 30 minutes to obtain a bar with a thin layer of oxide scale;

[0148] Step 8: Perform hot drawing on the bar obtained in Step 7 at a temperature of 900℃, a drawing speed of 1m / min, a single-pass deformation rate of 10%, and a 40wt% graphite emulsion as the lubricant, drawing to Φ2.0mm.

[0149] Step 9: Peel the filament obtained in Step 8 using a mold, ensuring a surface roughness of less than or equal to 0.8 μm;

[0150] Step 10: The wire obtained in Step 9 is drawn at room temperature, annealed in the atmosphere online, and quenched in water until it reaches Φ0.2mm. The drawing die is a combination die with a total deformation rate of 35%. The wire is immersed in a soap solution with a concentration of 40wt%. The drawing speed is 10m / min. The online intermediate annealing temperature is 700℃, and the online vacuum annealing time is 2min.

[0151] Step 11: The wire obtained in Step 10 is subjected to online atmospheric annealing and water quenching again. The online intermediate annealing temperature is 550℃, and the online vacuum annealing time is 1.0 min, to obtain a superelastic nickel-titanium alloy wire with a thicker surface oxide layer.

[0152] Test case

[0153] Mechanical tests were performed on the two samples prepared in Example 1, and the results were obtained. Figure 2 and Table 1 below.

[0154] Table 1: Mechanical test data of the two samples obtained in Example 1

[0155] Tensile strength / MPa UPS / MPa LPS / MPa Residual strain / % Sample 1 1601 606 334 0.09 Sample 2 1604 606 342 0.09

[0156] Combination Figure 2 As shown in Table 1, the nickel-titanium alloy wire prepared in Example 1 has excellent superelasticity with a 6% loading strain and a residual strain of less than 0.3%, and the difference in mechanical strength is within 10 MPa. This indicates that the method in Example 1 can prepare nickel-titanium alloy wire with excellent superelasticity.

[0157] Mechanical tests were performed on the two samples prepared in Example 2, and the results were obtained. Figure 3 and Table 2 below.

[0158] Table 2: Mechanical test data of the two samples obtained in Example 2

[0159] Tensile strength / MPa UPS / MPa LPS / MPa Residual strain / % Sample 1 1536 502 196 0.06 Sample 2 1538 512 202 0.08

[0160] Combination Figure 3 As shown in Table 2, the nickel-titanium alloy wire prepared in Example 2 has excellent superelasticity with a 6% loading strain and a residual strain of less than 0.3%, and the difference in mechanical strength is within 10 MPa. This indicates that the method in Example 1 can prepare nickel-titanium alloy wire with excellent superelasticity.

[0161] Mechanical tests were performed on the two samples prepared in Example 3, and the results were obtained. Figure 4 and Table 3 below.

[0162] Table 3: Mechanical test data of the two samples obtained in Example 3

[0163] Tensile strength / MPa UPS / MPa LPS / MPa Residual strain / % Sample 1 1563 558 238 0.05 Sample 2 1560 566 248 0.08

[0164] Combination Figure 4 As shown in Table 3, the nickel-titanium alloy wire prepared in Example 3 has excellent superelasticity with a 6% loading strain and a residual strain of less than 0.3%, and the difference in mechanical strength is within 10 MPa. This indicates that the method in Example 1 can prepare nickel-titanium alloy wire with excellent superelasticity.

[0165] In the production process of Comparative Example 1, the cycle time was 2 to 3 times that of Example 1, which greatly reduced production efficiency.

[0166] Mechanical tests were performed on the two samples prepared in Comparative Example 2, and the results were obtained. Figure 5 and Table 4 below.

[0167] Table 4: Mechanical test data of the two samples prepared in Comparative Example 2

[0168] Tensile strength / MPa UPS / MPa LPS / MPa Residual strain / % Sample 1 1459 502 194 0.06 Sample 2 1532 511 189 0.09

[0169] Combination Figure 5 As shown in Table 4, the nickel-titanium alloy wire prepared in Comparative Example 2 has excellent superelasticity with a 6% loading strain and a residual strain of less than 0.3%, but its mechanical strength differs by 73 MPa, indicating that combined die drawing can effectively improve the mechanical stability of nickel-titanium alloy wire.

[0170] Scanning electron microscopy was performed on the sample prepared in Comparative Example 3. It was found that the oxide layer and graphite emulsion thickness on the surface of the nickel-titanium alloy wire prepared in Comparative Example 3 were between 8 μm and 12 μm, and the surface roughness was relatively large. This indicates that the method of Comparative Example 3 cannot obtain nickel-titanium alloy wire without an oxide layer.

[0171] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a superelastic nickel-titanium alloy wire, characterized in that, Includes the following steps: A nickel-titanium alloy rod is provided, and then the nickel-titanium alloy rod is pre-oxidized; The pre-oxidized nickel-titanium alloy rod is subjected to continuous hot drawing to obtain a semi-finished wire. The continuous hot drawing temperature is 600℃~900℃, the continuous hot drawing speed is 0.5m / min~8m / min, and the single-pass deformation rate of the continuous hot drawing is 3%~25%. Remove the oxide layer from the surface of the semi-finished yarn; The semi-finished wire was sequentially subjected to room temperature drawing, online vacuum annealing, and water quenching to obtain a nickel-titanium alloy wire; and The nickel-titanium alloy wire was subjected to online vacuum annealing and water quenching again to obtain the desired superelastic nickel-titanium alloy wire; The diameter of the semi-finished filament is 1.5mm to 4mm; In the continuous hot drawing operation of the pre-oxidized nickel-titanium alloy rod, the lubricant for the continuous hot drawing is a graphite emulsion with a concentration of 20wt%~80wt%. The diameter of the nickel-titanium alloy wire is 0.025mm to 0.8mm. In the sequential operations of room temperature drawing, online vacuum annealing, and water quenching of the semi-finished wire, the drawing die for room temperature drawing is a combined diamond die, the total deformation rate of the combined die is 25%~80%, the deformation rate of each pass of room temperature drawing is 5%~30%, the drawing speed of room temperature drawing is 10m / min~30m / min, the lubricant for room temperature drawing is a soap solution with a concentration of 20wt%~80wt%, the wire feeding device for online vacuum annealing is a passive damping type wire feeding device, the wire feeding device for online vacuum annealing is a continuous double H-beam take-up device, the annealing temperature of online vacuum annealing is 400℃~900℃, and the annealing time of online vacuum annealing is 0.1min~10min; In the process of performing online vacuum annealing and water quenching on the nickel-titanium alloy wire, the annealing temperature of the online vacuum annealing is 400℃~700℃, and the annealing time of the online vacuum annealing is 0.1min~10min.

2. The method for preparing the superelastic nickel-titanium alloy wire according to claim 1, characterized in that, The diameter of the nickel-titanium alloy rod is 6mm~18mm; In the pre-oxidation operation of the nickel-titanium alloy rod, the pre-oxidation temperature is 600℃~900℃ and the pre-oxidation time is 30min~120min.

3. The method for preparing the superelastic nickel-titanium alloy wire according to claim 2, characterized in that, The operation of removing the oxide layer on the surface of the semi-finished yarn is as follows: the oxide layer on the surface of the semi-finished yarn is removed by peeling with a centerless sewing machine or a mold.

4. The method for preparing the superelastic nickel-titanium alloy wire according to claim 2, characterized in that, The operation of removing the oxide layer on the surface of the semi-finished yarn is as follows: the semi-finished yarn is pickled with an acidic solution to remove the oxide layer on the surface of the semi-finished yarn. The acidic solution is a mixture of hydrofluoric acid solution and nitric acid solution with a volume ratio of 1:2~4. The concentration of the hydrofluoric acid solution is 35wt%~60wt%, and the concentration of the nitric acid solution is 50wt%~70wt%. The pickling is performed 2 to 5 times, and the pickling time for each time is 5min~30min.

5. The method for preparing the superelastic nickel-titanium alloy wire according to any one of claims 1 to 4, characterized in that, The nickel-titanium alloy rod is prepared by the following operation: Provide nickel-titanium alloy ingots; The nickel-titanium alloy ingot is peeled and inspected to remove the defective parts and obtain a qualified ingot. The qualified ingots are subjected to a series of processes, including rough forging, precision forging, hot rolling, rounding, and peeling, to obtain the nickel-titanium alloy rods.

6. The method for preparing the superelastic nickel-titanium alloy wire according to claim 5, characterized in that, The raw materials for the nickel-titanium alloy ingot are electrolytic nickel and sponge titanium, and the nickel-titanium alloy ingot includes 55.0~56.5wt% nickel and the remaining content of titanium; The nickel-titanium alloy ingot is prepared by the following operation: electrolytic nickel and sponge titanium are pressed into electrodes, and then subjected to vacuum induction melting and two vacuum consumable melting processes to obtain the nickel-titanium alloy ingot. In the sequential processes of forging, precision forging, hot rolling, rounding, and peeling of the qualified ingot, the forging temperature is 1000℃~800℃, the forging holding time is 3h~4h, the precision forging temperature is 1000℃~800℃, the precision forging holding time is 2h~3h, the hot rolling temperature is 900℃~750℃, the hot rolling holding time is 2h~3h, and the peeling depth is 0.5mm~1mm.

7. A superelastic nickel-titanium alloy wire, characterized in that, The superelastic nickel-titanium alloy wire is prepared by the preparation method of superelastic nickel-titanium alloy wire as described in any one of claims 1 to 6.

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