A method for processing Ti45Nb titanium alloy straight wire

Abstract

This invention provides a method for processing Ti45Nb titanium alloy straight wire. The method involves forging a Ti45Nb titanium alloy ingot that has passed composition inspection; repeatedly upsetting and drawing the forged billet; hot rolling the billet; cold drawing using a roll die; intermediate annealing; cold drawing again using a roll die; argon-filled online continuous annealing; and vertical electrical straightening. The Ti45Nb titanium alloy straight wire prepared using this method is simple to operate, has a stable and controllable process, exhibits straightness ≤2.0 mm / m, ellipticity ≤0.02 mm, surface roughness Ra ≤1.0 μm, uniform and fine microstructure, passes eddy current testing, and demonstrates consistent and stable room temperature mechanical properties in the annealed state, meeting relevant standard requirements.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material processing technology, and particularly relates to a processing method for Ti45Nb titanium alloy straight wire. Background Technology

[0002] The use of titanium alloys and composite materials has become a significant indicator of aircraft advancement. Advanced aircraft both domestically and internationally are increasingly employing these materials, leading to a corresponding increase in the use of titanium alloy fasteners as connectors in composite components. In recent years, titanium alloy fasteners have replaced heavier steel fasteners, resulting in significant weight reduction. They are widely used in mechanical connection structures in modern aviation and aerospace, further reducing aircraft weight, improving the reliability of connecting components, and extending the aircraft's design life. Furthermore, titanium alloys possess excellent corrosion resistance, particularly their positive potential properties, which perfectly match those of carbon fiber composites, effectively preventing galvanic corrosion of fasteners. This characteristic is irreplaceable by any other material, contributing to the rapid development and increasing use of titanium alloy fasteners.

[0003] Ti45Nb alloy is a rivet material widely used in US aerospace products. In the annealed state, it exhibits good tensile properties (441–490 MPa), shear strength (365 MPa), and high plasticity (elongation exceeding 20%, reduction of area as high as 60%–80%). It also possesses excellent cold-working properties, making it suitable for manufacturing rivet fasteners for composite materials. Among titanium alloys used for rivets, titanium-niobium rivets and pure titanium rivets are relatively easy to rivet. Furthermore, titanium-niobium alloys have higher shear and tensile strengths than pure titanium, but lower deformation resistance. Therefore, the US has switched to using titanium-niobium rivets with superior cold-working properties in all its aerospace products.

[0004] While Ti45Nb titanium alloy rivets are the best choice for joining composite materials, their low deformation resistance, high surface viscosity, and susceptibility to surface scratches make surface quality control of the wire material difficult. Ti45Nb titanium alloy rivets require high surface quality and dimensional accuracy of the wire material during continuous riveting. The preparation process required by the patent (CN107282688A - A method for preparing Ti45Nb alloy coiled wire) is cumbersome, and the tooling, such as a twelve-square-hole cold rolling mill, and equipment with complex parameter settings for gauge-shaped flat and round holes, places high demands on the equipment, hindering large-scale production and resulting in high processing costs. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a processing method for Ti45Nb titanium alloy straight wire. This method combines billet forging, repeated upsetting and drawing, hot rolling, cold drawing with roll die, intermediate annealing, argon-filled online annealing, and vertical electric straightening. It uses common and readily available equipment to achieve the processing of Ti45Nb titanium alloy straight wire with a bright surface and high dimensional accuracy. The operation is simple and the process is stable and controllable.

[0006] This invention provides a method for processing Ti45Nb titanium alloy straight wire, comprising the following steps:

[0007] 1) Heat the Ti45Nb titanium alloy ingot that has passed the composition inspection to 1000-1150℃, forge it into a billet, and air cool it to obtain a forged billet;

[0008] 2) Heat the forging billet to 800-900℃, forge by upsetting, and air cool to obtain a bar billet;

[0009] 3) The billet is heated to 800-900℃ and hot-rolled, then air-cooled to obtain wire rod with a diameter of Ф9.0mm-Ф10.0mm;

[0010] 4) After coating the surface of the wire rod with lubricant, perform multiple bright cold drawing processes to obtain round wire rod.

[0011] 5) The coiled wire is subjected to intermediate annealing, and after water cooling, the surface oxide scale is removed;

[0012] 6) After applying lubricant again, perform multiple bright cold drawing processes to obtain coiled wire.

[0013] 7) The coiled wire is subjected to argon-filled online continuous annealing to obtain straight wire, and then vertically electrically straightened to obtain Ti45Nb titanium alloy straight wire.

[0014] Preferably, in step 1), 1 to 2 forging passes are performed; the number of forging passes and pulls per pass does not exceed three passes and three pulls.

[0015] The upsetting deformation during the initial forging is controlled at 45-60%.

[0016] Preferably, in step 2), the forging process involves 2 to 3 repeated upsetting and drawing processes; the number of upsetting and drawing processes in each upsetting and drawing process does not exceed two upsetting and two drawing processes.

[0017] The upsetting deformation during the forging process is controlled at 40-55%.

[0018] Preferably, the diameter of the bar blank is Ф80.0mm~Ф100.0mm and the weight is 30.0~50.0kg.

[0019] Preferably, the speed of the multi-pass bright cold drawing in step 4) is 15-100 m / min, and the deformation per drawing pass is less than 20%.

[0020] The speed of the multi-pass bright cold drawing in step 6) is 20-150 m / min, and the deformation per drawing pass is less than 25%.

[0021] Preferably, the intermediate annealing temperature in step 5) is 750–850°C, and the holding time is 30–60 min;

[0022] The temperature of the argon-filled online continuous annealing process described in step 7) is 700–850°C, and the wire walking speed is 2–10 m / min.

[0023] Preferably, the heating temperature for vertical electric straightening in step 7) is controlled at 500-600°C.

[0024] Preferably, the lubricant is a graphite emulsion lubricant.

[0025] This invention provides a method for processing Ti45Nb titanium alloy straight wire, comprising the following steps: 1) heating a Ti45Nb titanium alloy ingot that has passed composition inspection to 1000-1150℃, forging it into a billet, and air-cooling it to obtain a forged billet; 2) heating the forged billet to 800-900℃, upsetting and drawing it, and air-cooling it to obtain a bar billet; 3) heating the bar billet to 800-900℃, hot-rolling it, and air-cooling it to obtain a wire with a diameter of Ф9.0mm-Ф10.0mm. 4) After coating the surface of the wire rod with lubricant, perform multiple bright cold drawing to obtain round wire; 5) Perform intermediate annealing on the round wire obtained in step 4), and clean the surface oxide scale after water cooling; 6) After coating with lubricant again, perform multiple bright cold drawing to obtain round wire; 7) Perform argon-filled online continuous annealing on the round wire to obtain straight wire, and then perform vertical electrical straightening to obtain Ti45Nb titanium alloy straight wire. The method provided by this invention is simple to operate, the process is stable and controllable, the straightness is ≤2.0mm / m, the ellipticity is ≤0.02mm, the surface roughness Ra≤1.0μm, the microstructure is uniform and fine, the eddy current flaw detection is qualified, and the room temperature mechanical properties in the annealed state are consistent and stable, meeting the relevant standard requirements. It effectively solves many problems existing in the current Ti45Nb titanium alloy wire, such as low dimensional control accuracy, insufficient surface roughness, uneven shape control, low production efficiency, and lax surface quality control. Attached Figure Description

[0026] Figure 1 The image shows the microstructure of the Ti45Nb titanium alloy straight wire prepared in Example 1 of this invention.

[0027] Figure 2The image shows the microstructure of the Ti45Nb titanium alloy straight wire prepared in Example 2 of this invention.

[0028] Figure 3 This is a microstructure diagram of the Ti45Nb titanium alloy straight wire prepared in Example 3 of the present invention. Detailed Implementation

[0029] This invention provides a method for processing Ti45Nb titanium alloy straight wire, comprising the following steps:

[0030] 1) Heat the Ti45Nb titanium alloy ingot that has passed the composition inspection to 1000-1150℃, forge it into a billet, and air cool it to obtain a forged billet;

[0031] 2) Heat the forging billet to 800-900℃, forge by upsetting, and air cool to obtain a bar billet;

[0032] 3) The billet is heated to 800-900℃ and hot-rolled, then air-cooled to obtain wire rod with a diameter of Ф9.0mm-Ф10.0mm;

[0033] 4) After coating the surface of the wire rod with lubricant, perform multiple bright cold drawing processes to obtain round wire rod.

[0034] 5) The coiled wire obtained in step 4) is subjected to intermediate annealing, and after water cooling, the surface oxide scale is removed.

[0035] 6) After applying lubricant again, perform multiple bright cold drawing processes to obtain coiled wire.

[0036] 7) The coiled wire obtained in step 6) is subjected to argon-filled online continuous annealing to obtain straight wire, and then vertically electrically straightened to obtain Ti45Nb titanium alloy straight wire.

[0037] The method provided by this invention effectively combines various processing techniques such as billet forging, repeated upsetting and drawing, hot rolling, roll-dip cold drawing, intermediate annealing, argon-filled online annealing, and vertical electrical straightening. It strictly controls the forging temperature, hot rolling time, and deformation per hot rolling pass, resulting in a sufficiently refined and homogenized microstructure of the Ti45Nb titanium alloy, which facilitates the smooth implementation of subsequent drawing processes. During the subsequent bright cold drawing process, strict control of deformation per pass and the provision of reasonable, feasible, and effective lubrication aids prevent cracks and defects that may occur during the drawing process. Even the occurrence of wire breakage was mitigated while ensuring the dimensional accuracy of the wire. During the drawing process, the intermediate annealing, argon-filled online continuous annealing, and vertical electric straightening processes were rationally arranged to effectively remove residual stress caused by uneven local deformation that may occur in the titanium alloy wire during the drawing process. At the same time, the straightness of the wire and the potential hydrogen permeation problem on the surface were ensured. This effectively solved many problems existing in the Ti45Nb titanium alloy wire, such as low dimensional control accuracy, insufficient surface roughness, uneven shape control, low production efficiency, and lax surface quality control.

[0038] This invention involves heating a Ti45Nb titanium alloy ingot to 1000–1150°C, forging it into a billet, and then air-cooling it to obtain a forged billet. Preferably, this invention involves 1–2 passes of forging; the number of upsetting and drawing passes in each pass does not exceed three passes; the upsetting deformation during the forging process is controlled at 45–60%; in a specific embodiment, two passes are used, with the first pass having an upsetting deformation of 50% or 55%; the second pass also has an upsetting deformation of 50% or 55%. In a specific embodiment, a Ti45Nb titanium alloy ingot with qualified chemical composition is used; the Ti45Nb titanium alloy ingot is heated to 1100°C, 1080°C, or 1050°C.

[0039] This invention heats the forging billet to 800–900°C, performs upsetting and drawing forging, and then air-cools it to obtain a bar billet. Preferably, this invention involves 2–3 rounds of repeated upsetting and drawing forging; the number of upsetting and drawing rounds per round does not exceed two upsettings and two drawing rounds; the upsetting deformation during the upsetting and drawing forging is controlled at 40–55%. The bar billet has a diameter of Ф80.0 mm to Ф100.0 mm, a weight of 30.0–50.0 kg, and no surface defects or damage. In specific embodiments, the forging billet is heated to 880°C, 850°C, or 860°C. In some embodiments, a two-pass, two-stage, two-stage repeated forging process is performed, with the deformation amount of the first stage being 50% and the deformation amount of the second stage being 45%. In some embodiments, a two-pass, two-stage, two-stage repeated forging process is performed, with the deformation amount of the first stage being 55% and the deformation amount of the second stage being 50%. In some embodiments, a three-pass, two-stage, two-stage repeated forging process is performed, with the deformation amount of the first stage being 45% and the deformation amount of the second stage being 50%.

[0040] In steps 1) and 2) of this invention, a fast forging machine with simple operation is used to perform initial forging and repeated upsetting and drawing forging of Ti45Nb titanium alloy ingot, so as to obtain sufficient refinement and homogenization of the microstructure of the alloy.

[0041] This invention involves heating the billet to 800–900°C, hot rolling it, and then air cooling it to obtain wire rod with a diameter of Ф9.0 mm to Ф10.0 mm. This invention uses hot rolling equipment to hot roll the Ti45Nb titanium alloy billet into wire rod suitable for subsequent roll drawing, thereby further refining and homogenizing the alloy's microstructure. In specific embodiments, the billet is heated to 850°C, 820°C, or 860°C. The diameter of the wire rod is Ф9.6 mm, Ф9.2 mm, or Ф9.3 mm.

[0042] This invention involves coating the surface of the wire rod with a lubricant and then performing multiple bright cold drawing passes to obtain coiled wire. The speed of the multiple bright cold drawing passes is 15–100 m / min, and the deformation per drawing pass is less than 20%. In some embodiments, three bright cold drawing passes are performed, and the wire diameters after each pass are Ф9.0 mm, Ф8.5 mm, and Ф8.2 mm, respectively. In some embodiments, four bright cold drawing passes are performed, and the wire diameters after each pass are Ф8.6 mm, Ф8.0 mm, Ф7.4 mm, and Ф6.8 mm, respectively. In some embodiments, seven bright cold drawing passes are performed, and the wire diameters after each pass are Ф8.8 mm, Ф8.0 mm, Ф7.2 mm, Ф6.5 mm, Ф6.0 mm, Ф5.5 mm, and Ф5.0 mm, respectively. The drawing speed is 60m / min, 85m / min or 120m / min; the diameter of the coarse coiled wire is Ф8.2mm, Ф6.8mm or Ф5.0mm.

[0043] This invention involves intermediate annealing of the coarse coiled wire, followed by water cooling and removal of surface oxide scale. The intermediate annealing temperature is 750–850°C, and the holding time is 30–60 minutes. In specific embodiments, the intermediate annealing temperatures are 780°C, 820°C, and 800°C; the holding times are 40 minutes, 35 minutes, and 45 minutes, respectively. The purpose of intermediate annealing is to eliminate residual stress caused by uneven deformation during continuous drawing of the wire. Intermediate annealing further refines the grain structure and improves process plasticity. Simultaneously, water cooling after annealing increases the surface hardness and reduces the surface viscosity of the wire, which is beneficial for removing surface defects.

[0044] After recoating with lubricant, the present invention performs multiple bright cold drawing passes to obtain coiled wire. The speed of the multiple bright cold drawing passes is 20-150 m / min, and the deformation per drawing pass is less than 25%. In some embodiments, when preparing coiled wire, four bright cold drawing passes are performed, and the wire diameters after each pass of roller drawing are Ф7.8 mm, Ф7.2 mm, Ф6.6 mm, and Ф6.0 mm, respectively. In some embodiments, five bright cold drawing passes are performed, and the wire diameters after each pass of roller drawing are Ф6.2 mm, Ф5.6 mm, Ф5.0 mm, Ф4.5 mm, and Ф4.0 mm, respectively. In some embodiments, six bright cold drawing passes are performed, and the wire diameters after each pass of roller drawing are Ф4.5 mm, Ф4.0 mm, Ф3.6 mm, Ф3.2 mm, Ф2.8 mm, and Ф2.5 mm, respectively. In a specific embodiment, the drawing speed is 100 m / min or 80 m / min. The diameter of the coiled wire is Ф6.0 mm, Ф4.0 mm, or Ф2.5 mm.

[0045] The lubricant used in this invention is graphite emulsion lubricant. This invention coats the surface of the wire rod with the lubricant and then performs multiple bright cold drawing passes. Compared to the traditional cold drawing process for eyepieces, the use of an advanced roller die drawing machine can increase the drawing speed and production efficiency. Simultaneously, due to the high precision of the die, the brightness of the wire surface can be effectively improved, while ensuring the diameter tolerance and ellipticity requirements of the wire. This solves problems such as rivet surface scratches and die jamming caused by insufficient dimensional accuracy of the wire.

[0046] This invention involves subjecting the coiled wire to argon-filled online continuous annealing to obtain straight wire, followed by vertical electrical straightening to obtain Ti45Nb titanium alloy straight wire. During the argon-filled online continuous annealing, the purity of the argon gas in the furnace is ≥99.99%, and a slight positive pressure is maintained to allow for the overflow of inert gas. The temperature of the argon-filled online continuous annealing is 700–850℃, and the wire travel speed is 2–10 m / min. The heating temperature for vertical electrical straightening is controlled at 500–600℃. In specific embodiments, the temperature of the argon-filled online continuous annealing is 750℃, 780℃, or 800℃; the wire travel speed is 8 m / min or 6 m / min. The diameter of the straight wire is Ф6.0 mm or Ф4.5 mm. The heating temperatures for vertical electrical straightening are specifically 560℃, 550℃, and 580℃.

[0047] This invention eliminates residual stress in the wire by performing argon-filled online continuous annealing. Simultaneously, by subjecting the coiled wire to nearly 100m of argon-filled online continuous annealing, it improves the straightness requirements of Ti45Nb titanium alloy straight wire, solving the problem that traditional vacuum annealing furnaces cannot guarantee straightness after annealing due to space limitations. It also effectively removes potential surface hydrogen contamination of the alloy wire during processing. This invention further improves the straightness of the wire through heating and vertical loading.

[0048] The Ti45Nb titanium alloy straight wire prepared by this invention is specifically a Ti45Nb titanium alloy wire with a diameter of 2.5 mm, a Ti45Nb titanium alloy wire with a diameter of 4.0 mm, or a Ti45Nb titanium alloy wire with a diameter of 6.0 mm.

[0049] To further illustrate the present invention, the following detailed description of a processing method for Ti45Nb titanium alloy straight wire provided by the present invention is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] The steps for preparing a 6.0 mm diameter Ti45Nb titanium alloy wire using the method of this invention are as follows:

[0052] Step 1: Heat the qualified Ti45Nb titanium alloy ingot to 1100℃ and perform two-pass forging with two upsetting and two drawing processes. The upsetting deformation in the first pass is 50%, and the upsetting deformation in the second pass is 55%. After air cooling, perform surface grinding to obtain the forging billet.

[0053] Step 2: Heat the forging billet described in Step 1 to 880℃ and perform repeated upsetting and drawing forging in two passes. The deformation amount of the first upsetting and drawing is 50%, and the deformation amount of the second upsetting and drawing is 45%. After air cooling, perform surface grinding to obtain the billet.

[0054] Step 3: Heat the billet obtained in Step 2 to 850℃, hot roll it, air cool it, and then perform surface grinding to obtain wire rod with a diameter of Ф9.6mm;

[0055] Step four: After coating the surface of the wire rod obtained in step three with an emulsion, perform three bright cold drawing passes on a roller drawing machine. The wire diameters after each pass of roller drawing are Ф9.0mm, Ф8.5mm, and Ф8.2mm, respectively. The drawing speed is controlled at 60m / min to obtain a Ф8.2mm wire rod.

[0056] Step 5: Place the coiled wire obtained in Step 4 into a pit-type annealing furnace for intermediate annealing. After holding at 780℃ for 40 minutes, water cool it. After cooling, clean the surface oxide scale and surface defects.

[0057] Step Six: After coating the surface of the coiled wire obtained in Step Five with emulsion, perform four bright cold drawing operations on a roller drawing machine. The wire diameters after each roller drawing operation are Ф7.8mm, Ф7.2mm, Ф6.6mm, and Ф6.0mm, respectively. The drawing speed is controlled at 100m / min to obtain a Ф6.0mm wire rod.

[0058] Step 7: Anneal the wire obtained in Step 6 in a continuous annealing furnace filled with high-purity argon gas at a temperature of 800℃ and a wire travel speed of 6m / min to obtain a Ф6.0mm Ti45Nb titanium alloy straight wire.

[0059] Step 8: Perform vertical electric straightening on the straight wire obtained in Step 7, heating at 580℃.

[0060] The Ti45Nb titanium alloy wire prepared using this embodiment has a straightness of 1.2 mm / m, a diameter deviation of -0.01 mm to 0.01 mm, an ellipticity of 0.01 mm, a surface roughness Ra of 0.8 μm, a tensile strength of 552 MPa at room temperature, a yield strength of 491 MPa, an elongation of 22.5%, a reduction of area of ​​76.8%, a shear strength of 382 MPa, and passes eddy current testing. The microstructure is as follows: Figure 1 As shown, it meets the relevant technical standards requirements.

[0061] Example 2

[0062] The steps for preparing Ti45Nb titanium alloy wire with a diameter of 4.0 mm using the method of this invention are as follows:

[0063] Step 1: Heat the Ti45Nb titanium alloy ingot that has passed the chemical composition test to 1080℃ and perform a three-stage forging process in one pass. The roughing deformation of the first pass is 50%, the roughing deformation of the second pass is 55%, and the roughing deformation of the third pass is 45%. After air cooling, perform surface grinding to obtain the forging billet.

[0064] Step 2: Heat the forging billet described in Step 1 to 850℃ and perform repeated upsetting and drawing forging in two passes. The deformation amount of the first upsetting and drawing is 55%, and the deformation amount of the second upsetting and drawing is 50%. After air cooling, perform surface grinding to obtain the billet.

[0065] Step 3: Heat the billet obtained in Step 2 to 820℃, hot roll it, air cool it, and then perform surface grinding to obtain wire rod with a diameter of Ф9.2mm;

[0066] Step four: After coating the surface of the wire rod obtained in step three with an emulsion, perform four bright cold drawing passes on a roller drawing machine. The wire diameters after each pass of roller drawing are Ф8.6mm, Ф8.0mm, Ф7.4mm and Ф6.8mm, respectively. The drawing speed is controlled at 85m / min to obtain a Ф6.8mm wire rod.

[0067] Step 5: Place the coiled wire obtained in Step 4 into a pit-type annealing furnace for intermediate annealing. After holding at 820℃ for 35 minutes, water cool it. After cooling, clean the surface oxide scale and surface defects.

[0068] Step Six: After coating the surface of the coiled wire obtained in Step Five with emulsion, perform five bright cold drawing passes on a roller drawing machine. The wire diameters after each pass of roller drawing are Ф6.2mm, Ф5.6mm, Ф5.0mm, Ф4.5mm, and Ф4.0mm, respectively. The drawing speed is controlled at 80m / min to obtain a Ф4.0mm wire rod.

[0069] Step 7: Anneal the wire obtained in Step 6 in a continuous annealing furnace filled with high-purity argon gas at a temperature of 780℃ and a wire travel speed of 8m / min to obtain a Ф4.0mm Ti45Nb titanium alloy straight wire.

[0070] Step 8: Perform vertical electric straightening on the straight wire obtained in Step 7, heating at 560℃.

[0071] The Ti45Nb titanium alloy wire prepared using this embodiment has a straightness of 1.5 mm / m, a diameter deviation of -0.01 mm to 0.01 mm, an ellipticity of 0.01 mm, a surface roughness Ra of 0.6 μm, a tensile strength of 568 MPa at room temperature, a yield strength of 511 MPa, an elongation of 24.6%, a reduction of area of ​​80.2%, a shear strength of 388 MPa, and passes eddy current testing. The microstructure is as follows: Figure 2 As shown, it meets the relevant technical standards requirements.

[0072] Example 3

[0073] The steps for preparing Ti45Nb titanium alloy wire with a diameter of 2.5 mm using the method of this invention are as follows:

[0074] Step 1: Heat the Ti45Nb titanium alloy ingot, which has passed the chemical composition test, to 1050℃ and perform two-pass, two-upsetting and two-drawing forging. The roughing deformation of the first pass is 55%, and the roughing deformation of the second pass is 55%. After air cooling, the surface is ground to obtain the forging billet.

[0075] Step 2: Heat the forging billet described in Step 1 to 860℃ and perform repeated upsetting and drawing forging in 3 passes. The deformation amount of the first upsetting and drawing is 45%, and the deformation amount of the second upsetting and drawing is 50%. After air cooling, perform surface grinding to obtain the billet.

[0076] Step 3: Heat the billet obtained in Step 2 to 860℃, hot roll it, air cool it, and then perform surface grinding to obtain wire rod with a diameter of Ф9.3mm;

[0077] Step four: After coating the surface of the wire rod obtained in step three with an emulsion, perform seven bright cold drawing passes on a roller drawing machine. The wire diameters after each pass of roller drawing are Ф8.8mm, Ф8.0mm, Ф7.2mm, Ф6.5mm, Ф6.0mm, Ф5.5mm, and Ф5.0mm, respectively. The drawing speed is controlled at 120m / min to obtain a Ф5.0mm wire rod.

[0078] Step 5: Place the coiled wire obtained in Step 4 into a pit-type annealing furnace for intermediate annealing. After holding at 800℃ for 45 minutes, water cool it. After cooling, clean the surface oxide scale and surface defects.

[0079] Step Six: After coating the surface of the coiled wire obtained in Step Five with emulsion, perform six bright cold drawing passes on a roller drawing machine. The wire diameters after each pass of roller drawing are Ф4.5mm, Ф4.0mm, Ф3.6mm, Ф3.2mm, Ф2.8mm, and Ф2.5mm, respectively. The drawing speed is controlled at 100m / min to obtain Ф2.5mm wire rod.

[0080] Step 7: Anneal the wire rod obtained in Step 6 in a continuous annealing furnace filled with high-purity argon gas at a temperature of 750℃ and a wire travel speed of 8m / min to obtain a Ф2.5mm Ti45Nb titanium alloy straight wire.

[0081] Step 8: Perform vertical electric straightening on the straight wire obtained in Step 7, heating at 550℃.

[0082] The Ti45Nb titanium alloy wire prepared using this embodiment has a straightness of 1.0 mm / m, a diameter deviation of -0.01 mm to 0.01 mm, an ellipticity of 0.01 mm, a surface roughness Ra of 0.5 μm, a tensile strength of 552 MPa at room temperature, a yield strength of 515 MPa, an elongation of 22.8%, a reduction of area of ​​77.4%, a shear strength of 378 MPa, and passes eddy current testing. The microstructure is as follows: Figure 3 As shown, it meets the relevant technical standards requirements.

[0083] As can be seen from the above embodiments, the Ti45Nb titanium alloy straight wire prepared by the method provided by the present invention is simple to operate, the process is stable and controllable, the straightness is ≤2.0mm / m, the ellipticity is ≤0.02mm, the surface roughness Ra≤1.0μm, the microstructure is uniform and fine, the eddy current flaw detection is qualified, and the room temperature mechanical properties in the annealed state are consistent and stable, meeting the relevant standard requirements.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for processing Ti45Nb titanium alloy straight wire, comprising the following steps: 1) Heat the Ti45Nb titanium alloy ingot that has passed the composition inspection to 1000~1150℃, forge it into a billet, and air cool it to obtain a forged billet; 2) Heat the forging billet to 800~900℃, forge by upsetting, and air cool to obtain a bar billet; 3) The billet is heated to 800~900℃ and hot-rolled, then air-cooled to obtain wire rod with a diameter of Ф9.0mm~Ф10.0mm; 4) After coating the surface of the wire rod with lubricant, perform multiple bright cold drawing processes to obtain round wire rod. 5) The coiled wire obtained in step 4) is subjected to intermediate annealing, and after water cooling, the surface oxide scale is removed. 6) After applying lubricant again, perform multiple bright cold drawing processes to obtain coiled wire; the lubricant is graphite emulsion lubricant; 7) The coiled wire obtained in step 6) is subjected to argon-filled online continuous annealing to obtain straight wire, and then vertically electrically straightened to obtain Ti45Nb titanium alloy straight wire; In step 1), perform 1-2 forging passes; the number of forging passes per pass shall not exceed three passes and three draws; The upsetting deformation during the initial forging is controlled at 45-60%. In step 2), the forging process involves 2-3 repeated upsetting and drawing operations; the number of upsetting and drawing operations per forging operation shall not exceed two upsetting and two drawing operations. The upsetting deformation during the forging process is controlled at 40-55%. The diameter of the billet is Ф80.0mm~Ф100.0mm, and the weight is 30.0~50.0kg; In step 4), the speed of the multi-pass bright cold drawing is 15~100m / min, and the deformation per drawing pass is less than 20%. In step 5), the intermediate annealing temperature is 750~850℃, and the holding time is 30~60min; In step 6), the speed of the multi-pass bright cold drawing is 20~150m / min, and the deformation per drawing pass is less than 25%. The temperature of the argon-filled online continuous annealing process in step 7) is 700~850℃, and the wire walking speed is 2~10m / min; The heating temperature for vertical electric straightening is controlled at 500~600℃.

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