A niobium alloy precision capillary and a preparation method thereof

Abstract

The present application provides a kind of niobium alloy precision capillary and its preparation method, by increasing inner wall reaming in rolling intermediate pipe blank, two-roll and multi-roll cold rolling process parameter control, core rod drawing instead of all hollow drawing process, prepare φ2.0~3.0*0.2~0.7*L mm Nb521 alloy precision capillary, this kind of niobium alloy precision capillary is a kind of key material for high-speed engine closed cycle system, with high dimensional accuracy, good surface quality, stable mechanical properties and other advantages, can fully meet the demand of high-speed engine closed cycle system to high-temperature heat pipe high quality and high precision.The present application provides the manufacturing method of Nb521 alloy precision capillary, scheme flow is as follows: niobium alloy pipe blank→ skinning, boring→ two-roll rolling→ pickling oil removal→ vacuum annealing→ reaming→ two-roll or multi-roll rolling→ pickling oil removal→ vacuum annealing→ drawing→ pickling→ finished product heat treatment→ finishing→ finished product.

Description

TECHNICAL FIELD

[0001] The application provides a niobium alloy precision capillary and a preparation method thereof, and belongs to the technical field of aerospace. BACKGROUND

[0002] One of the uses of the niobium alloy capillary (a tube material with an outer diameter size of not more than 3 mm is referred to as a capillary) is a heat transfer pipe in a high-temperature environment or a flow guide pipe in a high-temperature corrosion environment, which needs to have high high-temperature mechanical properties, good surface quality and high dimensional precision. The niobium alloy pipe material of the specification produced on the market currently has problems of low control of inner hole size precision, wrinkles and microcracks on the inner surface and the like.

[0003] Nb521 (Nb-5W-2Mo-1Zr) niobium alloy is a medium-strength plastic niobium alloy, which is obtained by adding W, Mo, Zr alloying elements and a small amount of C elements in a niobium matrix to further improve the room temperature and high-temperature mechanical properties of the niobium alloy in a combination of solid solution strengthening and precipitation strengthening. The Nb521 niobium alloy has high melting point, good corrosion resistance, high high-temperature (600-1600 DEG C) specific strength and good cold and hot working performance, can be used to manufacture complex-shaped parts, and is one of important candidate materials for aerospace structural parts. The alloy can be used to manufacture key parts of rocket engines, space-to-ground shuttle, supersonic aircraft, satellites, missiles and nuclear reactors, including protective covers of combustion chambers of high-thrust aerospace engines, combustion chambers, small vector or attitude control nozzles and expansion protective covers of trajectory control engines.

[0004] Nb521 niobium alloy products are mostly supplied in the form of bars, plates and forgings, and the application of pipe materials is less. Usually most of the nozzles are obtained by machining bars, and plates are mostly used for spinning to prepare uniform transition nozzle extension sections. However, with the development of new generation of hypersonic power technology, the adoption of strong precooling technology to alleviate the high-temperature protection problem of the engine body has become one of the key problems to be solved. In order to meet the requirements of "super-strong pressure resistance, super-high heat resistance, super-high precision and super-high reliability" of the heat exchanger, the Nb521 alloy capillary with high temperature and high pressure has become the key material and the most important one for the realization of the closed cycle system of the hypersonic engine.

[0005] Currently, there is no patent and paper related to the Nb521 alloy capillary. Most patents and papers are about the preparation method, structure and performance of niobium alloy ingot, bar, plate and coating, especially in recent years, there are more literatures about the development, mechanical properties, bars and plates of low-density niobium alloy. The niobium alloy capillary currently existing in China has problems of low control of inner hole size precision of the alloy pipe material, wrinkles and microcracks on the inner surface and the like, and is difficult to meet the high quality and high precision requirements of the high-temperature heat transfer pipe of the closed cycle system of the hypersonic engine. Related and similar literatures are as follows:

[0006] Chinese patent CN 113560824 A discloses a preparation method of Nb521 niobium alloy long thin-walled pipe. The invention controls the surface quality of the niobium alloy pipe blank, rolling parameters and complete recrystallization annealing temperature, and obtains a niobium alloy long thin-walled pipe with short processing cycle, good surface quality and good plasticity. The outer diameter of the thin-walled pipe is 10mm-20mm, the wall thickness is 0.5mm-1mm, the length is 3000mm-6000mm, and the surface roughness is not greater than 1.6μm, which meets the market demand for niobium alloy long thin-walled pipe.

[0007] Chinese patent CN 108213109 A discloses a preparation method of large-diameter ultra-long thin-walled NbZr10 niobium alloy pipe. The prepared large-diameter ultra-long thin-walled niobium and niobium alloy pipe has an outer diameter of Φ60-200mm, a wall thickness of 0.5mm-3mm and a length of 3500mm-12000mm. The product has uniform organization, high comprehensive performance and high added value, and has good application prospect, certain economic benefit and social benefit.

[0008] Chinese patents CN 104561575 A and CN 108213109 A disclose preparation methods of niobium-zirconium alloy pipe, which are obtained by powder static pressure forming sintering or extrusion into pipe, respectively. The preparation cycle is relatively long.

[0009] Chinese patent CN 116423167 A discloses a method for improving the plasticity of low-density niobium alloy bar. The processing technology of "sleeve extrusion + forging + water bath cooling" is adopted, so that the grain refinement and homogenization degree of the low-density niobium alloy organization are obviously improved, and the carbide reinforcing phase is more dispersedly distributed, realizing the significant improvement of the room temperature plasticity of the low-density niobium alloy bar, and the tensile strength is also improved, which is beneficial to its application in the field of aerospace.

[0010] Chinese patent CN 115287515 A discloses a lightweight niobium alloy material for cryogenic environment and its preparation method and application. The plastic-brittle transition temperature of the lightweight niobium alloy is greatly reduced by multi-element alloying of tungsten, molybdenum, rhenium, hafnium, titanium, aluminum, vanadium, chromium, zirconium and other elements and suitable proportioning, the high temperature strength of the alloy is improved by solid solution strengthening of the niobium alloy, and the density of the alloy is reduced by adding low-density elements. The alloy can be widely used in deep space exploration, Antarctic and Arctic exploration and other fields.

[0011] Chinese patent CN 114855107 A discloses a preparation method of low-density Nb-Ti-Al-V-Z-C niobium alloy rod, which adopts a process of "twice extrusion + quenching + forging" to prepare the low-density niobium alloy rod. By increasing quenching treatment and twice extrusion process, the carbide strengthening phase TiC is re-precipitated and nucleated and dispersedly distributed in the matrix after re-dissolution, effectively reducing the size of the carbide strengthening phase and improving its dispersity, realizing the improvement of the low-density niobium alloy rod in the elongation after fracture, and making it exhibit high-strength and high-plasticity mechanical properties at room temperature.

[0012] The niobium alloy capillary is generally prepared by repeatedly processing the pipe blank through rolling, pickling, vacuum annealing, rolling and other processes to a small diameter (such as an outer diameter of less than 6 mm), and then through hollow drawing + vacuum annealing to prepare a capillary with a diameter of less than 3 mm. This method has problems such as low control of inner hole size precision, wrinkles and micro-cracks on the inner surface of the niobium alloy capillary, and is difficult to meet the requirements of high-quality and high-precision of the pipe material in high-temperature complex and harsh environments. SUMMARY

[0013] The present application discloses a preparation method of a Nb521 alloy precision capillary, which is a key material for a closed cycle system of a hypersonic engine. The Nb521 alloy precision capillary has the advantages of high size precision (the size deviation of the outer diameter and the inner diameter is less than or equal to ±0.02 mm), good surface quality (the inner and outer surface roughness is less than or equal to 0.8 μm), stable mechanical properties (the tensile strength is greater than or equal to 420 MPa, the specified non-proportional elongation strength is greater than or equal to 280 MPa, and the elongation rate is greater than or equal to 20%), and can fully meet the requirements of high-quality and high-precision of the high-temperature heat transfer pipe for the closed cycle system of the hypersonic engine.

[0014] The present application discloses a preparation method of a Nb521 alloy precision capillary, which is a key material for a closed cycle system of a hypersonic engine. The Nb521 alloy precision capillary has the advantages of high size precision (the size deviation of the outer diameter and the inner diameter is less than or equal to ±0.02 mm), good surface quality (the inner and outer surface roughness is less than or equal to 0.8 μm), stable mechanical properties (the tensile strength is greater than or equal to 420 MPa, the specified non-proportional elongation strength is greater than or equal to 280 MPa, and the elongation rate is greater than or equal to 20%), and can fully meet the requirements of high-quality and high-precision of the high-temperature heat transfer pipe for the closed cycle system of the hypersonic engine.

[0015] The technical scheme of the present application will be described in detail as follows:

[0016] The present application discloses a preparation method of a Nb521 alloy precision capillary, which is a key material for a closed cycle system of a hypersonic engine. The Nb521 alloy precision capillary has the advantages of high size precision (the size deviation of the outer diameter and the inner diameter is less than or equal to ±0.02 mm), good surface quality (the inner and outer surface roughness is less than or equal to 0.8 μm), stable mechanical properties (the tensile strength is greater than or equal to 420 MPa, the specified non-proportional elongation strength is greater than or equal to 280 MPa, and the elongation rate is greater than or equal to 20%), and can fully meet the requirements of high-quality and high-precision of the high-temperature heat transfer pipe for the closed cycle system of the hypersonic engine.

[0017] Step 1: Preparation of pipe blank:

[0018] There are two methods for preparing tube blanks: extrusion tube blank preparation and drilling tube blank preparation. The extrusion tube blank preparation method involves drilling holes in extruded or forged bar blanks to prepare hollow ingots, followed by secondary hot extrusion to produce extruded tube blanks with a diameter-to-thickness ratio (i.e., the ratio of the outer diameter to the wall thickness of the tube) of 6 to 10, resulting in tube blanks with a diameter of 32 to 52 × 3 to 8 × L mm. The drilling tube blank preparation method involves drilling holes in fully recrystallized annealed φ30 to 50 mm bar blanks to prepare hollow tube blanks, with the diameter-to-thickness ratio (i.e., the ratio of the outer diameter to the wall thickness of the tube) controlled at 6 to 10, resulting in tube blanks with a diameter of 30 to 50 × 3 to 8 × L mm.

[0019] Step 2: Surface treatment of tube blank:

[0020] The tube blank prepared in step 1 is surface treated. The inner wall is bored using a boring machine, with a boring amount of 0.3-0.8 mm on one side. The inner wall is then polished with sandpaper to ensure that there are no visible defects. The outer surface is peeled using a peeling machine (if the outer surface of the bar blank has already been machined, it is not necessary to continue peeling the outer surface), with a peeling amount of 0.5-1 mm on one side. If there are still local defects after peeling, they can be thoroughly ground or scraped with a grinding wheel or scraper. The grinding marks left after grinding must be removed with a polishing wheel or flap wheel.

[0021] Step 3: Cold rolling of the tube blank:

[0022] The blanking is carried out using a two-roll cold rolling mill, with a processing rate of ≤45% and a feed rate of 2-4mm.

[0023] Step 4: Pickling and washing of intermediate products:

[0024] First, soak the intermediate pipe material in hot water (some cleaning agent can be added to the hot water or an ultrasonic cleaning device can be added) to remove most of the oil stains. Then, pickle it in pickling solution (H2SO4, HF, HNO3 and water are mixed in a certain proportion). Finally, wash it with water and dry it.

[0025] Step 5: Intermediate annealing:

[0026] Annealing is performed in a vacuum annealing furnace at a temperature of 1300–1450℃ and a holding time of 60–120 min. The vacuum degree of the annealing furnace is not less than 5 × 10⁻⁶. -2 Pa.

[0027] Step 6: Intermediate tube rolling:

[0028] After 3-4 passes of cold rolling on a two-roll mill, with a feed rate of 2-3 mm and a processing rate controlled at 50%-60%, the material is then cold rolled again on a multi-roll mill with a pass processing rate of 28%-36% and a total processing rate of 50%-60%, with a feed rate of 2-3 mm.

[0029] Step 7: reaming of inner wall of intermediate product:

[0030] The inner wall is reamed by a reamer, the single-side cutting amount is 0.2-0.3mm, the inner surface roughness is ≤1.6μm, and the inner wall is ensured to be free of visible defects.

[0031] Step 8: surface oxidation treatment:

[0032] The pipe blank to be drawn is heated in a box-type resistance furnace at a temperature of 650-750℃, and the holding time is 20-40min, and the surface color becomes blue-gray or gray.

[0033] Step 9: hollow and core rod drawing:

[0034] The hollow drawing is first carried out by cold rolling for 2-3 passes, and then the core rod drawing is carried out for 3-5 passes, the pass processing rate is 5%-16%, and the total processing rate is 29%-40%.

[0035] Step 10: pickling, washing and drying of finished pipe:

[0036] The finished pipe can be soaked in kerosene, then cleaned by a cleaning agent, and then pickled (the pickling time is 0.3-0.6 times of the intermediate product pickling time), washed and dried.

[0037] Step 11: surface finishing and treatment of intermediate product and finished pipe:

[0038] The intermediate product and the finished pipe are straightened by a straightening machine after annealing, and the straightness of the pipe after straightening is ≤3mm / m; the pipe is cut and the tail is removed after straightening, the pipe with an outer diameter >10mm can be cut and the tail removed by a pipe cutting machine, and the pipe with an outer diameter ≤10mm can be cut and the tail removed by a wire cutting; the visible defects on the surface of the pipe of each pass can be completely eliminated by a scraper or other means; the inner wall of the pipe before rolling shall not have any hard particles, metal scraps and the like.

[0039] Step 12: annealing of finished product:

[0040] The annealing temperature is 1350-1400℃, the holding time is 60-90min, and the vacuum degree of the annealing furnace is not less than 5×10 - 2 Pa.

[0041] The niobium alloy capillary prepared by the method has high quality and size precision of inner and outer surfaces and stable performance, and fully meets the application of fine pipes in high-temperature complex and severe environments such as high-temperature heat transfer pipes and high-temperature corrosion environment guide pipes.

[0042] Compared with the prior art, the method has the following advantages:

[0043] (1)Small outer diameter, wide range of diameter-thickness ratio: the outer diameter is φ2.0-3.0mm, and the diameter-thickness ratio is 4-15;

[0044] (2)High dimensional accuracy: the dimensional deviation of the outer diameter and the inner diameter is ≤±0.02mm;

[0045] (3)Good inner and outer surface quality: the inner and outer surface roughness is ≤0.8μm;

[0046] (4)Good strong plasticity matching: the tensile strength is ≥420MPa, the specified non-proportional elongation strength is ≥280MPa, and the elongation rate is ≥20%. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a preparation flowchart of the present application. DETAILED DESCRIPTION

[0048] The specific embodiments of the present application are described in detail below in combination with the drawings and examples. It should be understood that the examples are used to illustrate the present application rather than limit the present application. The scope and core content of the present application are determined according to the claims.

[0049] Example 1: Nb521 alloy φ3.0×0.7×L mm precision capillary tube:

[0050] Step 1: Tube blank preparation: φ106mm extruded rod blank of Nb521 alloy is machined to prepare φ97.5×φ35×L mm hollow ingot blank, and then the second hot extrusion is performed to obtain φ52×9.8×L mm extruded tube blank with a diameter-thickness ratio of 6.25.

[0051] Step 2: Tube blank surface treatment: the extruded tube blank is surface treated, the inner wall is bored by a boring machine with a single-side boring amount of 0.8mm, and the inner wall is polished and ground by sandpaper to ensure that the inner wall has no visible defects; the outer surface is peeled by a peeling machine with a single-side peeling amount of 1mm, and the size of the treated tube blank is φ50×8×L mm.

[0052] Step 3: Tube blank breakdown cold rolling: two-roll cold rolling tube machine is used for breakdown, the processing rate is 44%, and the feed amount is 3-4mm; the size of the tube blank after cold rolling breakdown is φ40×5.5×L mm.

[0053] Step 4: Intermediate product pickling, washing:

[0054] First, the intermediate product tube is soaked in hot water (hot water can add some cleaning agent or external ultrasonic cleaning facility), most of the oil stains are removed, then pickling in pickling solution (H2SO4, HF, HNO3 and water are mixed according to a certain proportion), and finally washed, dried.

[0055] Step 5: Intermediate annealing: annealing is performed in a vacuum annealing furnace, the annealing temperature is 1400-1450℃, the holding time is 90-120min, the vacuum degree of the annealing furnace is not less than 5x10 -2 Pa.

[0056] Step 6: Intermediate pipe rolling: after cold rolling 4 passes through a two-roller rolling mill, the feed amount is 2-3mm, the processing rate is controlled at 50%-60%, and the rolling is performed to φ8x1.5xL mm; then, after 3 passes through a multi-roller rolling mill, the pass processing rate is 32%-35%, the total processing rate is 56%, the feed amount is 2-3mm, and the rolling is performed to φ5.4x0.9xL mm.

[0057] Step 7: Intermediate inner wall reaming: the inner wall of the φ12x2xL mm intermediate pipe blank is reamed by a reamer, the single-side cutting amount is 0.25mm, the inner surface roughness is ≤1.6μm, and the inner wall is ensured to have no visible defects.

[0058] Step 8: Surface oxidation treatment: the pipe blank to be drawn is heated in a box-type resistance furnace at a temperature of 750℃, and the holding time is 20-30min, and the surface color becomes gray.

[0059] Step 9: Hollow and core rod drawing: first, 1 pass of hollow drawing + 1 pass of core rod drawing, then 1 pass of core rod drawing + 1 pass of hollow drawing, the pass processing rate is 10%-15%, the total processing rate is 39%, and the drawing is performed to φ3.9x0.8xL mm for acid water washing to remove oil and intermediate annealing; then, 2 passes of core rod drawing + 1 pass of hollow drawing are performed, the pass processing rate is 10%-16%, the total processing rate is 35%, and the drawing is performed to φ3.0x0.7xL mm.

[0060] Step 10: Pickling and washing of the finished pipe:

[0061] The finished pipe can be soaked in kerosene, then cleaned with a cleaning agent, and then pickled (the pickling time is 0.3-0.6 times the intermediate product pickling time), washed with water, and dried.

[0062] Step 11: Surface finishing and treatment of the intermediate and finished pipes:

[0063] After annealing, the intermediate and finished pipes are straightened by a straightening machine, and the straightness of the pipes after straightening is ≤3mm / m; after straightening, the pipes are cut and the tail is removed, pipes with an outer diameter >10mm can be cut and the tail removed by a pipe cutting machine, and pipes with an outer diameter ≤10mm can be cut and the tail removed by a wire cutting machine; the visible defects on the surface of each pass of pipe can be completely eliminated by a scraper or other means; the inner wall of the pipe before rolling must not have any hard particles, metal scraps, etc.

[0064] Step 12: Annealing of finished product: annealing temperature is 1350°C, holding time is 90 min, vacuum degree of annealing furnace is not less than 5x10 -2 Pa.

[0065] The annealed precision capillary pipe φ3.0x0.7xL mm has good tensile strength, 452 MPa, specified non-proportional elongation strength, 301 MPa, elongation, 22.0%, high dimensional accuracy (outer diameter and inner diameter size deviation is less than or equal to ±0.02 mm), and good surface quality (inner and outer surface roughness is less than or equal to 0.8 μm).

[0066] Example 2: Nb521 alloy φ2.0x0.20xL mm precision capillary pipe:

[0067] Step 1: Pipe blank preparation: φ3 mm rod blank of Nb521 alloy completely recrystallized annealed is drilled to prepare φ30x3.3xL mm drilled pipe blank with diameter-thickness ratio of 9.1.

[0068] Step 2: Pipe blank surface treatment: the inner wall of the drilled pipe blank is bored by a boring machine, the single-side boring amount is 0.3 mm, and the inner wall is polished and ground by sandpaper to ensure that the inner wall has no visible defects, and the size of the treated pipe blank is φ30x3.0xL mm.

[0069] Step 3: Pipe blank breakdown cold rolling: two-roll cold rolling pipe machine is used for breakdown, processing rate is 44%, feed amount is 3-4 mm, and the size of the pipe blank after cold rolling breakdown is φ22x2.3xL mm.

[0070] Step 4: Intermediate product pickling, washing:

[0071] First, the intermediate product pipe is soaked in hot water (hot water can add some cleaning agent or external ultrasonic cleaning facility), most of the oil stains are removed, then pickled in acid solution (H2SO4, HF, HNO3 and water are mixed according to a certain proportion), finally washed with water and dried.

[0072] Step 5: Intermediate annealing: vacuum annealing furnace is used for annealing, annealing temperature is 1300-1400°C, holding time is 60-90 min, vacuum degree of annealing furnace is not less than 5x10 -2 Pa.

[0073] Step 6: Intermediate pipe rolling: After cold rolling 3 passes of 2-roller rolling mill, the feed amount is 2-3 mm, the processing rate is controlled at 50%-59%, and the rolling is performed to φ6.5x0.55xL mm; then, after 2 passes of multi-roller rolling mill, the pass processing rate is 33%-35%, the total processing rate is 57%, the feed amount is 2-3 mm, and the rolling is performed to φ4.6x0.33xL mm; after acid water washing and intermediate annealing, the multi-roller rolling is continued to φ3.9x0.26xL mm, and the pass processing rate is 33%.

[0074] Step 7: Intermediate product inner wall reaming: the inner wall of the φ10x1.0xL mm intermediate pipe blank is reamed by a reamer, the single-side cutting amount is 0.2 mm, the inner surface roughness is ≤1.6 μm, and the inner wall is ensured to have no visible defects.

[0075] Step 8: Surface oxidation treatment: the pipe blank to be drawn is heated in a box-type resistance furnace at a temperature of 650-700 ℃, and the holding time is 30-40 min, and the surface color is changed to blue-gray or gray.

[0076] Step 9: Hollow and core rod drawing: first, 1 pass of core rod drawing + 1 pass of hollow drawing is performed, the pass processing rate is 9%-15%, the total processing rate is 48% (including φ4.6x0.33 mm rolling to φ3.9x0.26 mm, the pass processing rate is 33%), the drawing is performed to φ3.3x0.24xL mm, acid water washing and intermediate annealing are performed; then, 2 passes of core rod drawing are continued, the pass processing rate is 15%-16%, the total processing rate is 29%, the drawing is performed to φ2.6x0.22xL mm, acid water washing and intermediate annealing are performed; then, 2 passes of core rod drawing + 1 pass of hollow drawing are continued, the pass processing rate is 5%-16%, the total processing rate is 31%, and the drawing is performed to φ2.0x0.20xL mm.

[0077] Step 10: Pickling and water washing of the finished pipe:

[0078] The finished pipe can be soaked in kerosene, then cleaned by using a cleaning agent, and then pickled (the pickling time is 0.3-0.6 times of the intermediate product pickling time), washed by water, and dried.

[0079] Step 11: Surface finishing and treatment of the intermediate product and the finished pipe:

[0080] After annealing, the intermediate product and the finished pipe are straightened by using a straightening machine, and the straightness of the pipe after straightening is ≤3 mm / m; after straightening, the pipe is cut to remove the head and tail, the pipe with an outer diameter >10 mm can be cut by using a pipe cutting machine, and the pipe with an outer diameter ≤10 mm can be cut by using a wire cutting machine; the visible defects on the surface of the pipe after each pass can be completely eliminated by using a scraper or other means; the inner wall of the pipe before rolling must not have any hard particles, metal scraps, etc.

[0081] Step 12: annealing of finished product: annealing temperature is 1400℃, holding time is 60 min, vacuum degree of annealing furnace is not less than 5x10 -2 Pa.

[0082] The annealed precision capillary pipe φ2.0x0.20xL mm has good tensile strength and plasticity, the tensile strength is 437 MPa, the specified non-proportional elongation strength is 289 MPa, the elongation rate is 23.5%, the size precision is high (the deviation of outer diameter and inner diameter size is ≤±0.015 mm), and the surface quality is good (the inner and outer surface roughness is ≤0.8 μm).

Claims

1. A method for preparing a niobium alloy precision capillary, characterized in that, Includes the following steps: Step 1: Tube blank preparation: The tube blank is prepared by extrusion or drilling. Step 2: Surface treatment of tube blank: The tube blank prepared in step 1 is subjected to surface treatment. The inner wall is bored using a boring machine and polished with sandpaper to ensure that the inner wall is free of defects. The outer surface is peeled using a peeling machine. If there are still local defects after peeling, they are ground or scraped thoroughly using a grinding wheel or scraper. The grinding marks left after grinding must be removed with a polishing wheel or flap wheel. Step 3: Cold rolling of the tube blank: The blank is opened using a two-roll cold rolling mill; Step 4: Pickling and washing of intermediate products: First, the intermediate pipe material is soaked in hot water to remove the oil stains, then pickled in pickling solution, and finally washed with water and dried. Step 5: Intermediate annealing: Annealing is performed in a vacuum annealing furnace at a temperature of 1300–1450℃ and a holding time of 60–120 min. The vacuum degree of the annealing furnace is not less than 5 × 10⁻⁶. -2 Pa; Step 6: Intermediate tube rolling: After 3-4 passes of cold rolling on a two-roll mill, with a feed rate of 2-3 mm and a processing rate controlled at 50%-60%, the product is then cold rolled on a multi-roll mill for 2-3 passes, with a pass processing rate of 28%-36% and a total processing rate of 50%-60%, with a feed rate of 2-3 mm. Step 7: Reaming the inner wall of the intermediate product: The inner wall is reamed using a reamer with a single-sided cutting amount of 0.2–0.3 mm, and the inner surface roughness is ≤1.6 μm to ensure that the inner wall is free of defects. Step 8: Surface oxidation treatment: The tube blank to be drawn is heated in a box-type resistance furnace at a temperature of 650-750℃ and held for 20-40 minutes, and the surface color turns blue-gray or gray. Step 9: Hollow and Core Rod Pulling: First, it undergoes 2-3 passes of cold rolling and hollow drawing, followed by 3-5 passes of drawing with mandrels. The pass processing rate is 5%-16%, and the total processing rate is 29%-40%. Step 10: Pickling and washing of finished pipes: The finished pipes are soaked in kerosene, then cleaned with a cleaning agent, followed by pickling, washing with water and drying. Step 11: Surface finishing and treatment of intermediate and finished pipe products: After annealing, intermediate and finished pipes are straightened using a straightening machine. The straightness of the pipes after straightening is ≤3mm / m. After straightening, the ends of the pipes are cut off. Any defects on the surface of the pipes in each pass are completely removed with a scraper. The inner wall of the pipes before rolling must not have any hard particles or metal shavings. Step 12: Finished product annealing: The annealing temperature is 1350–1400℃, the holding time is 60–90 min, and the vacuum degree of the annealing furnace is not less than 5 × 10⁻⁶. -2 Pa.

2. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 1, the method for preparing the extruded tube blank is to drill holes in the extruded or forged bar blank to prepare a hollow ingot blank, and then perform secondary hot extrusion to obtain an extruded tube blank with a diameter-to-thickness ratio (i.e., the ratio of the outer diameter of the tube to the wall thickness) of 6 to 10, i.e., a tube blank with a diameter of φ32 to 52 × 3 to 8 × L mm.

3. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 1, the method for preparing the drilled tube blank is to drill a φ30~50mm rod blank that has been fully recrystallized and annealed to prepare a hollow tube blank. The diameter-to-thickness ratio of the tube blank, that is, the ratio of the outer diameter of the tube to the wall thickness, is controlled at 6~10, i.e., a tube blank of φ30~50×3~8×L mm.

4. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 2, if the outer surface of the bar billet and the drilled tube billet has already been machined, then it is not necessary to continue peeling the outer surface.

5. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 2, the amount of peeling on one side is 0.5-1mm.

6. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 3, the processing rate is ≤45% and the feed rate is 2-4mm.

7. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 4, a cleaning agent is added to the hot water or an ultrasonic cleaning device is added; the pickling solution is a mixture of H2SO4, HF, HNO3 and water in a certain proportion.

8. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 10, the pickling time is 0.3 to 0.6 times the pickling time in step 4.

9. The method for preparing a niobium alloy precision capillary according to claim 1, characterized in that: In step 11, pipes with an outer diameter > 10 mm are cut off at the beginning and end using a pipe cutter, while pipes with an outer diameter ≤ 10 mm are cut off at the beginning and end using wire cutting.

10. A niobium alloy precision capillary tube, characterized in that: A Nb521 alloy precision capillary tube with a diameter of φ2.0~3.0×0.2~0.7×L mm can be prepared using any one of claims 1-9.

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