A production method for small-diameter thick-wall seamless titanium alloy tubes

Abstract

The present invention provides a production method for small-diameter thick-wall titanium alloy seamless tubes, comprising: Step 1: obtaining a titanium alloy ingot through three times of VAR melting; Step 2: blooming, drawing out, and radial forging the titanium alloy ingot into a round bar, and machining the round bar into a hollow tube blank through deep hole drilling, internal honing, and external turning; Step 3: performing three passes of cold rolling on the hollow tube blank to produce a finished titanium alloy seamless tube; sampling the titanium alloy tube after each pass of cold rolling, observing its crack defects, removing the crack defects, and performing intermediate vacuum annealing after removing the crack defects; Step 4: performing vacuum annealing, straightening, pickling, ultrasonic testing, and packaging on the titanium alloy finished tube in Step 3 to produce a small-diameter thick-wall titanium alloy seamless tube. The present invention comprehensively formulates measures from aspects such as tube blank specification design, tube blank processing technology, titanium alloy tube cold rolling process design, vacuum annealing process design, and internal and external surface defect treatment technology of the tube blank to solve the problem of internal surface cracks in cold rolling of small-diameter thick-wall titanium alloy seamless tubes.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of non-ferrous metal seamless tubes, and specifically relates to a production method for small-diameter thick-wall titanium alloy seamless tubes. Background Art

[0002] Due to the poor plasticity, strong cold rolling texture and anisotropy of titanium alloys, dimensional accuracy and internal and external surface defects are likely to occur during the cold rolling of titanium alloy tubes.

[0003] For small-diameter thick-wall titanium alloy seamless tubes with an outer diameter ≤ 10 mm, a wall thickness ≥ 1 mm, and an outer diameter to wall thickness ratio ≤ 5.5, due to the influence of the specifications, cracks are extremely likely to occur on the inner surface during the cold rolling of titanium alloy tubes, resulting in product rejection, and there is no perfect solution in the existing preparation methods. Summary of the Invention

[0004] In view of the above technical problems, a production method for small-diameter thick-wall titanium alloy seamless tubes is provided. The present invention comprehensively formulates measures from aspects such as the design of the tube blank specifications, the processing technology of the tube blank, the design of the cold rolling process of the titanium alloy tube, the vacuum annealing process design, and the treatment process for internal and external surface defects of the tube blank to solve the internal surface cracks during the cold rolling of small-diameter thick-wall titanium alloy seamless tubes.

[0005] The technical means adopted by the present invention are as follows:

[0006] A production method for small-diameter thick-wall titanium alloy seamless tubes, comprising the following steps:

[0007] Step 1: Obtain a titanium alloy ingot through three times of VAR melting;

[0008] Step 2: Subject the titanium alloy ingot to 5 passes of three upsetting and three drawing to form a square billet, 1 pass of drawing to form a long bar, and 3 passes of radial forging to form a round bar, with the radial forging temperature being 840 °C to 850 °C. The round bar meets the AA level of the GB / T5193 standard for flaw detection. The round bar is machined into a hollow tube blank with an outer diameter of D and a wall thickness of S through deep hole drilling, internal honing, and external turning. The outer diameter to wall thickness ratio (D / S) ≤ 5.5; for internal honing, a green silicon carbide oilstone with a W40 grit bonded by a resin binder is used, with a working pressure of 1.3 Mpa, a honing speed of 18 to 21 meters per minute, and the surface roughness of the hollow tube blank after internal honing ≤ 0.4 micrometers.

[0009] Step 3: Subject the hollow tube blank to three passes of cold rolling to form a finished titanium alloy seamless tube with an outer diameter of D1 and a wall thickness of S1; the wall thickness S of the hollow tube blank is 3 times the wall thickness S1 of the finished titanium alloy seamless tube;

[0010] During the cold rolling process, the deformation rate ε and K value of each cold rolling pass are smaller than those of the previous pass, and the K value of each cold rolling pass is ≥1; a titanium alloy tube with an outer diameter of Da and a wall thickness of Sa is cold rolled into a titanium alloy tube with an outer diameter of Db and a wall thickness of Sb. The calculation formula for the deformation rate ε of this cold rolling pass is:

[0011] ε=((Da-Sa)×Sa-(Db-Sb)×Sb) / ((Da-Sa)×Sa);

[0012] The calculation formula of the K value of this cold rolling pass is: K = (Sa-Sb)×Da / (Da-Db)×Sa.

[0013] Before each cold rolling, a rolling lubricant prepared by mixing 900-mesh MoS2, paraffin wax and No. 32 anti-wear oil in a weight ratio of 1:1:8 is applied to the inner surface of the titanium alloy tube and the surface of the mandrel. The rolling mill lubricant is filtered before and during each cold rolling, with a filtration accuracy of 3 microns.

[0014] After each cold rolling, the titanium alloy tube is sampled, its crack defects are observed, and the crack defects are removed. The specific method is as follows: after each cold rolling of the titanium alloy tube, a 100 mm long tube section sample is taken, and after the wall thickness of the tube section sample is removed by pickling 0.01 mm, the inner and outer surfaces are cut open to observe, and the distribution, direction, and maximum defect position of the crack defects are confirmed. The longitudinal and transverse metallographic structure samples are taken at the maximum defect position, and the maximum depth of the crack defect is determined to be h and the opening distance of the crack defect is observed, and the crack defects are removed according to the opening distance and the maximum depth h. After removal, a 100 mm long tube section sample is taken, and after confirming that there are no defects on the inner and outer surfaces by using an imager and a stereo microscope, the titanium alloy tube is subjected to intermediate vacuum annealing and the next cold rolling;

[0015] For the inner surface defects with the opening distance of crack defects ≥0.02mm, internal honing is selected to remove the inner surface wall thickness of titanium alloy tube h+0.02mm; internal honing adopts W40 grain green silicon carbide oil stone bonded with resin binder, working pressure 1.3Mpa, honing speed 18-21 meters per minute;

[0016] For the external surface defects with the opening distance of crack defects ≥0.02mm, the outer surface wall thickness of the titanium alloy tube is removed by sanding belt polishing h+0.02mm;

[0017] For the inner and outer surface defects with the opening distance of crack defects less than 0.02mm, the inner and outer surface flow pickling is selected to remove the wall thickness of the titanium alloy tube h+0.02mm. For the inner surface flow pickling alone, the outer surface of the titanium alloy tube is covered with plastic bags, and for the outer surface flow pickling alone, plastic is used to block the two ends of the titanium alloy tube; the pickling liquid is made of HF acid: HNO3 acid: water in a weight ratio of 4:15:81, and flows through the inner and / or outer surface of the titanium alloy tube at a speed greater than or equal to 3 meters / minute.

[0018] After cold rolling for each pass, after removing crack defects, intermediate vacuum annealing is carried out. The intermediate vacuum annealing process for a titanium alloy tube with an outer diameter of Db and a wall thickness of Sb that has been cold rolled with a deformation rate of ε is as follows: the heating rate is 2 °C per minute, the intermediate annealing temperature is (600 + 300×ε) °C, the holding time is 55×Sb minutes, and the elongation of the titanium alloy tube after annealing is ≥30%.

[0019] Step 4: Vacuum anneal, straighten, pickling, ultrasonic inspection, and package the titanium alloy finished tube in Step 3 to produce a small-diameter thick-wall titanium alloy seamless tube with an outer diameter D2 ≤ 10 mm, a wall thickness S2 ≥ 1 mm, and an outer diameter to wall thickness ratio ≤ 5.5. The vacuum annealing in Step 4 is adjusted according to the performance requirements of the preset product.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The three - time VAR melting in the present invention ensures the uniform composition of the titanium alloy; the hot deformation process combination of 5 - fire three - pier three - draw forging, 1 - fire drawing, and 3 - fire sizing at 840°C - 850°C ensures the uniform structure, good performance, and good plasticity of the titanium alloy round bar, with the elongation rate ≥ 28%. The flaw detection of the round bar can reach Grade AA of the GB / T5193 standard, reducing the probability of defects in the cold rolling of titanium alloy tubes; the preparation of the hollow tube blank by deep - hole drilling, internal honing, and external turning machining completely avoids the internal and external surface defects of the tube blank; the preferred internal honing process ensures that the internal surface roughness of the hollow tube blank is less than or equal to 0.4 microns, reducing the probability of defects on the internal surface of the cold - rolled titanium alloy tube; at the same time, the machining of the tube blank can flexibly process the specifications of the tube blank according to the size specifications of the finished tube to facilitate the design of the cold - rolling process. The machined hollow tube blank has an outer - diameter - to - wall - thickness ratio ≤ 5.5, and the wall thickness S is 3 times the wall thickness S1 of the finished titanium alloy tube, ensuring that the K value of each cold - rolling pass from the tube blank to the finished tube ≥ 1, and the K value ≥ 1 in cold rolling is a necessary condition to ensure that no cracks appear on the internal surface of the cold - rolled titanium alloy tube; before cold rolling, lubricating oil is coated on the internal surface of the titanium alloy tube and the surface of the mandrel to strengthen the lubrication of the internal surface of the titanium tube during the cold - rolling process and reduce the probability of cold - rolling defects; the cleanliness of the rolling - mill lubricating oil is maintained by filtration to avoid cold - rolling defects caused by impurities in the oil; the vacuum annealing temperature is determined according to the cold - rolling deformation amount of the titanium alloy tube, and the holding time is determined according to the wall thickness of the titanium alloy tube. The on - site annealing process not only realizes complete recrystallization but also avoids grain growth, ensuring the best plasticity of the titanium tube, thereby minimizing the probability of cold - rolling defects; the observation method for internal and external surface defects of the titanium tube and the combined treatment process for internal and external surface defects completely eliminate the defects that may be generated in the previous cold - rolling pass, avoiding the inheritance of defects to the next pass and continued expansion resulting in the scrapping of the titanium tube; for crack defects with a large opening distance between defects, flowing pickling cannot remove them, and only internal honing and external abrasive - belt polishing methods can be used to remove them. For internal and external surface defects with an opening distance less than 0.02 mm, the acid solution cannot enter the defect interior due to the small opening distance, so the defects can be removed by flowing pickling.

[0022] For the above - mentioned reasons, the present invention can be widely promoted in the fields such as the production of small - diameter thick - wall seamless titanium alloy tubes. Detailed implementation manners

[0023] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0024] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] The present invention provides a production method for small-caliber thick-wall titanium alloy seamless tubes, comprising the following steps:

[0026] Step 1: Obtain a titanium alloy ingot through three times of VAR melting;

[0027] Step 2: Subject the titanium alloy ingot to 5 heating passes of three upsetting and three drawing to form a square billet, 1 heating pass of drawing to form a long bar, and 3 heating passes of rotary forging to form a round bar. The rotary forging temperature is 840°C to 850°C. The round bar meets the AA level of the flaw detection standard of GB / T5193. The round bar is machined into a hollow tube blank with an outer diameter of D and a wall thickness of S through deep hole drilling, internal honing, and external turning. The outer diameter to wall thickness ratio ≤ 5.5; for internal honing, a green silicon carbide oilstone with a W40 grit bonded by a resin binder is used, the working pressure is 1.3 Mpa, the honing speed is 18 - 21 meters per minute, and the roughness of the hollow tube blank after internal honing ≤ 0.4 microns.

[0028] Step 3: Subject the hollow tube blank to three passes of cold rolling to form a finished titanium alloy seamless tube with an outer diameter of D1 and a wall thickness of S1; the wall thickness S of the hollow tube blank is 3 times the wall thickness S1 of the finished titanium alloy seamless tube;

[0029] During the cold rolling process, the deformation rate ε and K value of each pass of cold rolling are smaller than those of the previous pass, and the K value of each pass of cold rolling ≥ 1; when a titanium alloy tube with an outer diameter of Da and a wall thickness of Sa is cold rolled in one pass to form a titanium alloy tube with an outer diameter of Db and a wall thickness of Sb, the calculation formula for the deformation rate ε of this pass of cold rolling is:

[0030] ε = ((Da - Sa) × Sa - (Db - Sb) × Sb) / ((Da - Sa) × Sa);

[0031] The calculation formula for the K value of this pass of cold rolling is: K = (Sa - Sb) × Da / ((Da - Db) × Sa).

[0032] Before each pass of cold rolling, a rolling lubricant prepared by mixing MoS2 with a fineness of 900 meshes, paraffin wax, and No. 32 anti-wear engine oil in a weight ratio of 1:1:8 is applied to the inner surface of the titanium alloy tube and the surface of the mandrel. Before and during each pass of cold rolling, the lubricating oil of the rolling mill is filtered, and the filtration accuracy reaches 3 microns.

[0033] After each cold rolling, the titanium alloy tube is sampled, its crack defects are observed, and the crack defects are removed. The specific method is as follows: after each cold rolling of the titanium alloy tube, a 100 mm long tube section sample is taken, and after the wall thickness of the tube section sample is removed by pickling 0.01 mm, the inner and outer surfaces are cut open to observe, and the distribution, direction, and maximum defect position of the crack defects are confirmed. The longitudinal and transverse metallographic structure samples are taken at the maximum defect position, and the maximum depth of the crack defect is determined to be h and the opening distance of the crack defect is observed, and the crack defects are removed according to the opening distance and the maximum depth h. After removal, a 100 mm long tube section sample is taken, and after confirming that there are no defects on the inner and outer surfaces by using an imager and a stereo microscope, the titanium alloy tube is subjected to intermediate vacuum annealing and the next cold rolling;

[0034] For the inner surface defects with the opening distance of crack defects ≥0.02mm, internal honing is selected to remove the inner surface wall thickness of titanium alloy tube h+0.02mm; internal honing adopts W40 grain green silicon carbide oil stone bonded with resin binder, working pressure 1.3Mpa, honing speed 18-21 meters per minute;

[0035] For the external surface defects with the opening distance of crack defects ≥0.02mm, the outer surface wall thickness of the titanium alloy tube is removed by sanding belt polishing h+0.02mm;

[0036] For the inner and outer surface defects with the opening distance of crack defects less than 0.02mm, the inner and outer surface flow pickling is selected to remove the wall thickness of the titanium alloy tube h+0.02mm. For the inner surface flow pickling alone, the outer surface of the titanium alloy tube is covered with plastic bags, and for the outer surface flow pickling alone, plastic is used to block the two ends of the titanium alloy tube; the pickling liquid is made of HF acid: HNO3 acid: water in a weight ratio of 4:15:81, and flows through the inner and / or outer surface of the titanium alloy tube at a speed greater than or equal to 3 meters / minute.

[0037] After each cold rolling, intermediate vacuum annealing is performed after removing crack defects. The intermediate vacuum annealing process of the titanium alloy tube with an outer diameter of Db and a wall thickness of Sb after cold rolling with a deformation rate of ε is: a heating rate of 2°C / minute, an intermediate annealing temperature of (600+300×ε)°C, a holding time of 55×Sb minutes, and an elongation of the titanium alloy tube after annealing is ≥30%.

[0038] Step 4: vacuum annealing, straightening, pickling, ultra-probing and packaging the titanium alloy finished tube in step 3 to make a small-diameter thick-walled titanium alloy seamless tube with an outer diameter D2 ≤ 10 mm, a wall thickness S2 ≧ 1 mm, and an outer diameter-to-wall thickness ratio ≤ 5.5.

[0039] Example 1

[0040] The production specification is Φ9×1.7mm TA16 titanium alloy seamless pipe, and the outer diameter to wall thickness ratio is 9 / 1.7=5.294.

[0041] The production process flow adopted is as follows: melting a Φ490 round TA16 titanium alloy ingot by three times of vacuum consumable VAR → forging a 210 square billet by free forging with five heating passes of three upsetting and three drawing on a forging machine → drawing and growing into a Φ160 long round bar in one heating pass on a forging machine → sizing into a Φ29 black round bar in three heating passes → machining into a Φ22×5.1 hollow tube blank (outer diameter to wall thickness ratio is 4.3, wall thickness is 1.7×3) by deep hole drilling, internal honing and external turning → cold rolling into a Φ16×3.2 titanium tube (ε is 52%, K value is 1.37) on an LG15 two-high cold rolling tube mill → taking a 100 mm tube section sample and finding that there is a microcrack with a maximum depth of 0.02 mm on the inner surface, the crack opening distance is 0.025 mm, and removing 0.04 mm of the wall thickness of the Φ16×3.2 titanium alloy tube by internal surface honing (using a green silicon carbide oilstone with W40 grit bonded by a resin binder, working pressure is 1.3 Mpa, honing speed is 19 meters per minute) → vacuum annealing and straightening at 756℃ (600 + 300×0.52) for 176 (55×3.2) minutes → cold rolling into a Φ12×2.3 titanium alloy tube (ε is 46%, K value is 1.13) on an LG10 two-high cold rolling tube mill → taking a 100 mm tube section sample and finding that there is a microcrack with a maximum depth of 0.02 mm on the inner surface, the crack opening distance is 0.01 mm, and removing 0.04 mm of the wall thickness of the Φ12×2.3 titanium alloy tube by internal surface flow pickling → vacuum annealing and straightening at 738℃ (600 + 300×0.46) for 126.5 (55×2.3) minutes → cold rolling into a Φ9×1.7 titanium tube (ε is 44%, K value is 1.04) on an LG10 two-high cold rolling tube mill → vacuum annealing and straightening at 732℃ (600 + 300×0.44) for 93.5 (55×1.7) minutes → pickling → ultrasonic testing → packaging.

[0042] The yield strength of the Φ9×1.7 mm specification TA16 titanium alloy seamless tube prepared in this example is 470 Mpa, the tensile strength is 590 Mpa, and the elongation is 28%.

[0043] Example 2:

[0044] Producing a Φ10×1.9 mm TA18 titanium alloy seamless tube, the outer diameter to wall thickness ratio is 10 / 1.9 = 5.263.

[0045] The adopted production process flow is as follows: a Φ490 round TA18 titanium alloy ingot is produced by three times of vacuum consumable melting → a 210 square billet is formed by free forging with 5 forging passes of three upsetting and three drawing on a forging machine → a Φ160 long round bar is formed by drawing on a forging machine in 1 pass → a Φ29 black skin round bar is formed by rotary swaging in 3 passes → a Φ24×5.7 hollow tube blank (outer diameter to wall thickness ratio is 4.21, wall thickness is 1.9×3) is machined by deep hole drilling, internal honing and external turning → a Φ17×3.7 titanium tube is cold rolled on an LG15 two-high cold rolling tube mill (ε is 53%, K value is 1.2) → a 100mm tube section sample is taken and microcracks with a maximum depth of 0.03mm are found on the outer surface, the crack opening distance is 0.02mm, and 0.05mm of the wall thickness of the Φ17×3.7 titanium tube is removed by abrasive belt polishing on the outer surface → vacuum annealing and straightening are carried out at 759°C (600 + 300×0.53) for 203.5 (55×3.7) minutes → a Φ12×2.5 titanium tube is cold rolled on an LG10 two-high cold rolling tube mill (ε is 52%, K value is 1.1) → a 100mm tube section sample is taken and microcracks with a maximum depth of 0.02mm are found on the outer surface, the crack opening distance is 0.01mm, and 0.04mm of the wall thickness of the Φ12×2.5 titanium tube is removed by flowing pickling on the outer surface → vacuum annealing and straightening are carried out at 756°C (600 + 300×0.52) for 137.5 (55×2.5) minutes → a Φ10×1.9 titanium tube is cold rolled on an LG10 two-high cold rolling tube mill (ε is 41%, K value is 1.04) → vacuum annealing and straightening are carried out at 723°C (600 + 300×0.41) for 104.5 (55×1.9) minutes → pickling → ultrasonic inspection → packaging.

[0046] The yield strength of the Φ10×1.9mm specification TA18 titanium alloy seamless tube prepared in this embodiment is 570Mpa, the tensile strength is 680Mpa, and the elongation is 25%.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A production method of a small-diameter thick-wall titanium alloy seamless tube, characterized in that, It includes the following steps: Step 1: Obtain a titanium alloy ingot through three times of VAR melting; Step 2: Open the billet, elongate, and rotary forging the titanium alloy ingot into a round bar. The round bar meets the AA level of flaw detection up to the GB / T5193 standard. The round bar is machined by deep hole drilling, internal honing, and external turning to form a hollow tube blank with an outer diameter of D and a wall thickness of S, and the ratio of outer diameter to wall thickness ≤ 5.5; Step 3: Cold roll the hollow tube blank in three passes to form a finished titanium alloy seamless tube with an outer diameter of D1 and a wall thickness of S1; After each pass of cold rolling, sample the titanium alloy tube, observe its crack defects, and remove the crack defects. After removing the crack defects, perform intermediate vacuum annealing; The wall thickness S of the hollow tube blank is 3 times the wall thickness S1 of the finished titanium alloy seamless tube; Step 4: Vacuum anneal, straighten, pickling, ultrasonic inspection, and package the finished titanium alloy seamless tube in Step 3 to form a small-diameter thick-wall titanium alloy seamless tube with an outer diameter D2 ≤ 10 mm, a wall thickness S2 ≥ 1 mm, and a ratio of outer diameter to wall thickness ≤ 5.5; Among them, in Step 3, after each pass of cold rolling of the titanium alloy tube, take a 100-mm long tube section sample. After pickling to remove 0.01 mm of the wall thickness of the tube section sample, cut it open to observe the inner and outer surfaces, confirm the distribution, trend, and maximum defect position of the crack defects. Take longitudinal and transverse metallographic tissue samples at the maximum defect position to determine the maximum depth h of the crack defects and observe the opening distance of the crack defects. Remove the crack defects according to the opening distance and the maximum depth h. After removal, take a 100-mm long tube section sample. Use an image analyzer and a stereoscopic microscope to observe and confirm that there are no defects on the inner and outer surfaces, and then perform intermediate vacuum annealing and the next pass of cold rolling on the titanium alloy tube; For inner surface defects with an opening distance of the crack defects ≥ 0.02 mm, select internal honing to remove the inner surface wall thickness h + 0.02 mm of the titanium alloy tube; For outer surface defects with an opening distance of the crack defects ≥ 0.02 mm, select belt external polishing to remove the outer surface wall thickness h + 0.02 mm of the titanium alloy tube; For inner and outer surface defects with an opening distance of the crack defects < 0.02 mm, select internal and external surface flow pickling to remove the wall thickness h + 0.02 mm of the titanium alloy tube; In Step 3, the titanium alloy tube with an outer diameter of Da and a wall thickness of Sa is cold rolled in one pass to form a titanium alloy tube with an outer diameter of Db and a wall thickness of Sb. The intermediate vacuum annealing process of the titanium alloy tube with an outer diameter of Db and a wall thickness of Sb after cold rolling with a deformation rate of ε is as follows: heating rate 2 °C / minute, intermediate annealing temperature (600 + 300×ε) °C, holding time 55×Sb minutes, and the elongation rate of the titanium alloy tube after annealing ≥ 30%; 2. The production method of a small-caliber thick-walled titanium alloy seamless tube according to claim 1, characterized in that: In Step 2, the titanium alloy ingot is opened into a square billet through 5 heating times of three upsetting and three drawing operations, elongated into a long bar in 1 heating time, and rotary forged into a round bar in 3 heating times. The rotary forging temperature is 840 °C - 850 °C.

3. The production method of a small-caliber thick-wall titanium alloy seamless tube according to claim 1 or 2, characterized in that: In Step 2, the internal honing uses a green silicon carbide oilstone with a W40 grain size bonded by a resin binder, the working pressure is 1.3 Mpa, the honing speed is 18 - 21 meters per minute, and the roughness of the hollow tube blank after internal honing ≤ 0.4 microns.

4. The production method of a small-diameter thick-wall titanium alloy seamless tube according to claim 1, characterized in that: In Step 3, before each cold rolling pass, a rolling lubricating oil, which is a mixture of MoS2 with a fineness of 900 mesh, paraffin wax, and No. 32 anti-wear oil in a weight ratio of 1:1:8, is applied to the inner surface of the titanium alloy tube and the surface of the mandrel. Before each cold rolling pass and during the rolling process, the lubricating oil of the rolling mill is filtered, and the filtration accuracy reaches 3 microns.

5. The production method of a small-caliber thick-walled titanium alloy seamless tube according to claim 1, characterized in that: In Step 3, for internal honing, a green silicon carbide oilstone with a W40 grit bonded by a resin binder is used, the working pressure is 1.3 Mpa, and the honing speed is 18 - 21 meters per minute; for single internal surface flow pickling, the outer surface of the titanium alloy tube is covered by bundling with a plastic bag, and for single outer surface flow pickling, both ends of the titanium alloy tube are blocked with plastic. The pickling solution is made by mixing HF acid, HNO3 acid, and water in a weight ratio of 4:15:81, and flows through the inner surface and / or outer surface of the titanium alloy tube at a speed of not less than 3 meters per minute.

6. The production method of a small-diameter thick-wall titanium alloy seamless tube according to claim 1, characterized in that: In Step 3, during the cold rolling process, the deformation rate ε and the K value of each cold rolling pass are smaller than those of the previous pass, and the K value of each cold rolling pass is ≥1. A titanium alloy tube with an outer diameter of Da and a wall thickness of Sa is cold rolled in one pass to form a titanium alloy tube with an outer diameter of Db and a wall thickness of Sb. The formula for calculating the deformation rate ε of this cold rolling pass is: ε = ((Da - Sa) × Sa - (Db - Sb) × Sb) / ((Da - Sa) × Sa); The formula for calculating the K value of this cold rolling pass is: K = (Sa - Sb) × Da / ((Da - Db) × Sa).