A method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-wall pipe by hot and cold rolling

Abstract

The application discloses a preparation method of high-precision molybdenum-rhenium alloy large-diameter thin-wall pipe through hot and cold alternating rolling, and the method comprises the following steps: firstly, after raw material powder is cold isostatic pressed and formed, sintering is carried out; secondly, multiple vacuum electron beam melting is carried out; thirdly, after sawing and processing, high-temperature extrusion is combined with high-temperature forging; fourthly, deep hole drilling, honing and machining treatment are carried out; fifthly, after heating and heat preservation, hot rolling is carried out; sixthly, after cooling, warm and cold transition rolling is carried out; seventhly, after alkaline washing and intermediate heat treatment, controllable cold rolling is carried out; eighthly, the processes in the fifth step to the seventh step are repeated, and the finished product is obtained through inner and outer surface polishing and fixed-length cutting. The alternating rolling process of hot rolling-warm and cold transition rolling-controllable cold rolling is adopted, combined with hydrogen atmosphere protection heating, core rod follow-up support and stress elimination heat treatment between passes, so that the molybdenum-rhenium alloy large-diameter thin-wall pipe with higher dimensional precision and surface quality is obtained, the microstructure is uniform, the mechanical properties are excellent, and the molybdenum-rhenium alloy large-diameter thin-wall pipe is suitable for cladding tubes in nuclear reactors, medical implants and other fields.

Description

Technical Field

[0001] This invention belongs to the field of refractory metal alloy pipe processing technology, specifically relating to a method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled pipes by hot and cold alternating rolling. Background Technology

[0002] Due to its excellent processing performance and superior room temperature and high temperature mechanical properties, molybdenum-rhenium alloy has a wide range of applications as a structural and functional material in fields such as nuclear industry, electronics industry, and medical implants.

[0003] As high-melting-point alloys, especially molybdenum-rhenium alloys with high rhenium content, are typically prepared using powder metallurgy. However, powder-metallurgical alloys suffer from problems such as high impurity content and poor weldability. Furthermore, industries like nuclear power, electronics, and medicine have high purity requirements for materials, making it difficult for high-rhenium-content molybdenum alloys prepared by powder metallurgy to meet the application requirements of these fields. In addition, in these fields, such molybdenum-rhenium alloys are mainly used in the form of tubular materials, such as fuel cladding tubes in nuclear reactors, heat pipes, and cardiovascular stent substrates in the medical field. These tubular materials require extremely high dimensional accuracy and excellent mechanical properties, generally requiring multiple passes of precise high-temperature deformation (forging, rolling, etc.) to achieve this.

[0004] Existing patented technologies struggle to simultaneously meet the requirements of precision and excellent mechanical properties in the fabrication of large-diameter, ultra-thin-walled molybdenum-rhenium alloy pipes. For example, patent CN111036893A uses powder metallurgy to prepare billets, followed by forging and extrusion to obtain molybdenum-rhenium alloy pipes. This technique suffers from low material purity and micro-defects due to the powder metallurgy method, and the extruded pipes also exhibit low dimensional accuracy. Patent CN108213440A similarly uses powder metallurgy to prepare billets, followed by hot isostatic pressing to obtain molybdenum-rhenium alloy pipes. This technique also suffers from low alloy purity, and the lack of pressure processing after hot isostatic pressing results in insufficient material mechanical properties. Although patent CN111014654A employs rolling for multi-pass pressure processing of the molybdenum-rhenium alloy, the powder metallurgy method used for preparing the billet also results in low material purity. Inappropriate matching of outer diameter and wall thickness deformation parameters during pipe rolling leads to pipe cracking, making it difficult to manufacture large-diameter thin-walled pipes. A comparison with existing patents reveals that all of these patents use hot rolling to manufacture pipes. Hot-rolled pipes have poor dimensional accuracy and surface roughness, requiring subsequent processing to obtain pipes that meet dimensional requirements. However, no examples of cold rolling for manufacturing molybdenum-rhenium alloy pipes have been found.

[0005] Meanwhile, existing hot-cold alternating rolling processes exist, but they are all designed for magnesium alloys. Magnesium alloys exhibit good plasticity at medium temperatures and soften easily at high temperatures. Their hot-cold alternating rolling processes use medium-temperature hot rolling at 420-450℃ with fixed-pass deformation and no special atmosphere protection. This process is unsuitable for the low-temperature brittleness and high-temperature oxidation characteristics of molybdenum alloys. Direct application would lead to severe oxidation and cracking of molybdenum alloy tubes, making them unusable for forming. Furthermore, existing magnesium alloy hot-cold alternating rolling processes are mostly for plates, using flat rolls without mandrel support structures. However, tube rolling requires ensuring dimensional accuracy of both inner and outer walls. The material of the mandrel, preheating temperature, and fitting clearance directly affect the rolling effect. The die design for magnesium alloy rolling cannot meet the high-precision rolling requirements of molybdenum alloy tubes. Therefore, there is an urgent need to design a hot-cold alternating rolling process adapted to the characteristics of molybdenum alloys to solve the problems of cracking, oxidation, and low dimensional accuracy in molybdenum alloy tube rolling. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubes by alternating hot and cold rolling, addressing the shortcomings of the prior art. This method employs an alternating rolling process of hot rolling-warm-cold transition rolling-controlled cold rolling to improve the low-temperature plasticity of the tube, ensure continuous tube forming, and achieve efficient and high-precision rolling of molybdenum-rhenium alloy tubes. This results in large-diameter thin-walled molybdenum-rhenium alloy tubes with higher dimensional accuracy and surface quality, solving the technical problems of easy cracking, low dimensional accuracy, and poor low-temperature plasticity in existing molybdenum-rhenium alloy tube rolling processes, while avoiding the process compatibility defects of alternating hot and cold rolling of magnesium alloys.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot and cold alternating rolling, characterized in that the method includes the following steps: Step 1: Weigh the raw material powder according to the nominal composition of the target product, molybdenum-rhenium alloy large-diameter thin-walled pipe, mix it evenly, then put it into a rubber sleeve for cold isostatic pressing, and then place it in a high-temperature hydrogen furnace for sintering to obtain molybdenum-rhenium alloy sintered billet. Step 2: The molybdenum-rhenium alloy sintered billet obtained in Step 1 is subjected to multiple vacuum electron beam melting processes to obtain a smelted ingot; Step 3: After sawing and processing the smelted ingots obtained in Step 2, high-temperature extrusion combined with high-temperature forging is used to obtain molybdenum-rhenium alloy bars; Step 4: The molybdenum-rhenium alloy rod obtained in Step 3 is subjected to deep hole drilling, honing, and machining to obtain a high-precision tube blank; Step 5: Place the high-precision tube blank obtained in Step 4 onto the mandrel, and place them together in a hydrogen atmosphere-protected heating furnace for heating and heat preservation, and then perform hot rolling to obtain a hot-rolled tube blank. Step 6: After the hot-rolled tube blank obtained in Step 5 is naturally cooled in a hydrogen atmosphere, it is subjected to warm-cold transition rolling to obtain a transition tube blank. Step 7: After the inner and outer surfaces of the transition tube blank obtained in Step 6 are washed with alkali, intermediate heat treatment is performed, followed by controlled cold rolling. The inner wall of the tube blank is supported by a sizing mandrel to obtain a cold-rolled tube blank. Step 8: Repeat the processes of heating and holding after hot rolling, natural cooling and then warm-cold transition rolling, and intermediate heat treatment followed by controlled cold rolling in steps 5 to 7. Polish the inner and outer surfaces of the final cold-rolled tube blank and cut it to length to obtain the finished molybdenum-rhenium alloy large-diameter thin-walled tube.

[0008] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot and cold alternating rolling is characterized in that the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled tube, in step one, is Re 47.5% ± 1% by mass percentage, with the remainder being Mo.

[0009] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot-cold alternating rolling is characterized in that the mandrel in step five is an M42 high-speed steel precision-ground mandrel, and is preheated to 300℃~400℃ in advance.

[0010] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot-cold alternating rolling is characterized in that, in step five, the heating and holding temperature is 700℃~900℃, and the holding time is 20min~25min; the hot rolling adopts a double eccentric circular hole die, and the deformation per pass is controlled at 15%~30%, the total hot rolling deformation reaches 60%~70%, the hot rolling speed is 1.5mm / min~2.0mm / min, and the final rolling temperature is not lower than 500℃.

[0011] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot-cold alternating rolling is characterized in that, in step six, the temperature is naturally cooled to 350℃~400℃, the deformation per pass of the hot-cold transition rolling is 10%~20%, the rolling speed is maintained at 1mm / s~1.5mm / s, the total deformation of the hot-cold transition rolling is 15%~30%, and the final rolling temperature is not lower than 200℃.

[0012] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot-cold alternating rolling is characterized in that the intermediate heat treatment temperature in step seven is 1000℃~1100℃ and the holding time is 1h.

[0013] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot-cold alternating rolling is characterized in that the controllable cold rolling pass deformation amount in step seven is 5%~10%, the total cold rolling deformation amount is 20%~25%, and the cold rolling speed is 1.0mm / min~1.5mm / min.

[0014] The above-mentioned method for preparing high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes by hot and cold alternating rolling is characterized in that the outer diameter of the finished molybdenum-rhenium alloy large-diameter thin-walled tube in step eight is 25mm~30mm, the wall thickness is 0.3mm~0.6mm, the dimensional deviation of the tube does not exceed ±0.05mm, Ra<0.5μm, and the straightness does not exceed 0.03mm / 1000mm.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention involves multiple vacuum electron beam melting processes on sintered molybdenum-rhenium alloy billets, resulting in high-purity finished molybdenum-rhenium alloy large-diameter thin-walled tubes with a total impurity content ≤150wppm (testing for more than 60 impurity elements). This meets the high-purity requirements of molybdenum-rhenium alloy materials in the nuclear power and medical fields. Compared to the large number of precipitates present in molybdenum-rhenium alloys prepared by powder metallurgy, the molybdenum-rhenium alloys prepared by vacuum electron beam melting in this invention have a more uniform composition, no precipitates, and better processing performance and elasticity.

[0016] 2. This invention addresses the low-temperature brittleness and high-temperature oxidation characteristics of molybdenum alloys by designing an alternating rolling process of hot rolling, warm-cold transition rolling, and controlled cold rolling. Combined with hydrogen atmosphere-protected heating, mandrel follow-up support, and stress relief heat treatment between passes, this process avoids grain growth in molybdenum-rhenium alloys and improves low-temperature plasticity. At the same time, by precisely controlling the rolling temperature, deformation, and rolling speed at each stage, continuous forming of molybdenum alloy tubes is achieved, resulting in higher dimensional accuracy and surface quality, and producing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubes.

[0017] 3. This invention involves multiple pressure processing steps, such as high-temperature extrusion, high-temperature forging, and hot and cold rolling, to smelt and cast ingots. This results in a large deformation, a more uniform microstructure, and higher strength. The final finished pipe has a room temperature tensile strength of over 900 MPa and an elongation at break of over 20%.

[0018] 4. The high-precision molybdenum-rhenium alloy large-diameter thin-walled tubes prepared by this invention have high purity, high dimensional accuracy, good surface quality, uniform microstructure, and excellent mechanical properties, and are suitable for cladding tubes in nuclear reactors, medical implants, and other fields.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a physical image of the finished molybdenum-rhenium alloy large-diameter thin-walled tube prepared in Example 1 of the present invention. Detailed Implementation

[0021] Example 1 This embodiment includes the following steps: Step 1: Based on the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled pipe, weigh raw material powders Mo and Re with a mass purity greater than 99.5% according to the mass percentage Mo:Re = 56:44, mix them evenly in a V-type mixer, then pack them into a rubber sleeve for cold isostatic pressing, and then sinter them in a high-temperature hydrogen furnace to obtain the molybdenum-rhenium alloy sintered billet; the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled pipe, is as follows (mass percentage): Re 47.5%, the remainder being Mo; Step 2: The molybdenum-rhenium alloy sintered billet obtained in Step 1 is subjected to two vacuum electron beam melting processes to obtain a smelted ingot with a diameter of 90 mm. During both vacuum electron beam melting processes, the vacuum degree in the melting furnace chamber is less than 5 × 10⁻⁶. -3 Pa; Step 3: After sawing and processing the smelted ingot obtained in Step 2, high-temperature extrusion is used to obtain extruded billets. The extruded billets are then subjected to high-temperature forging and polishing to obtain molybdenum-rhenium alloy rods. Step 4: The molybdenum-rhenium alloy rod obtained in Step 3 is subjected to deep hole drilling, honing, and machining to obtain a high-precision tube blank with an outer diameter × wall thickness of φ (40±0.02) mm × (2.5±0.02) mm; Step 5: Place the high-precision tube blank obtained in Step 4 onto the M42 high-speed steel precision grinding mandrel that has been preheated to 300℃, and then place them together in a hydrogen atmosphere protected heating furnace. Heat to 900℃ and hold for 20 minutes. Then, use a double eccentric circular hole die for hot rolling, and control the deformation per pass to 15%, with a total hot rolling deformation of 70%. The hot rolling speed is 1.5 mm / min, and the final rolling temperature is not lower than 500℃ to obtain the hot-rolled tube blank. Step 6: The hot-rolled tube blank obtained in Step 5 is naturally cooled to 350°C in a hydrogen atmosphere without additional heating. Then, it is subjected to warm-cold transition rolling with a deformation of 10% per pass, a rolling speed of 1 mm / s, a total deformation of 30% for the warm-cold transition rolling, and a final rolling temperature of not less than 200°C to obtain the transition tube blank. Step 7: After the inner and outer surfaces of the transition tube blank obtained in Step 6 are washed with alkali, the intermediate heat treatment is carried out at a temperature of 1000℃ and a holding time of 1h. Then, the tube blank is subjected to controlled cold rolling, and the inner wall of the tube blank is supported by a sizing mandrel. The deformation per pass is 5%, the total cold rolling deformation is 20%, and the cold rolling speed is 1.0mm / min to obtain the cold-rolled tube blank. Step 8: Repeat steps 5-7, including hot rolling after heating and holding, warm-cold transition rolling after natural cooling, and controlled cold rolling after intermediate heat treatment. Polish the inner and outer surfaces of the final cold-rolled tube blank, and cut it to length to obtain a finished molybdenum-rhenium alloy large-diameter thin-walled tube with an outer diameter × wall thickness of φ28mm × 0.6mm. Figure 1 As shown.

[0022] Testing revealed that the finished molybdenum-rhenium alloy large-diameter thin-walled tube prepared in this embodiment contained 47.5% Re by mass, with the remainder being Mo. The tube's dimensional deviation was ±0.03 mm, Ra = 0.28 μm, straightness was 0.01 mm / 1000 mm (not exceeding 0.03 mm / 1000 mm), room temperature tensile strength was 1035 MPa, and elongation after fracture was 28%.

[0023] Example 2 This embodiment includes the following steps: Step 1: Based on the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled tube, weigh raw material powders Mo and Re with a mass purity greater than 99.5% according to the mass percentage Mo:Re = 59:41, mix them evenly in a V-type mixer, then pack them into a rubber sleeve for cold isostatic pressing, and then sinter them in a high-temperature hydrogen furnace to obtain the molybdenum-rhenium alloy sintered billet; the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled tube, is as follows (mass percentage): Re 46.5%, the remainder being Mo; Step 2: The molybdenum-rhenium alloy sintered billet obtained in Step 1 is subjected to three vacuum electron beam melting processes to obtain a smelted ingot with a diameter of 65 mm. During the three vacuum electron beam melting processes, the vacuum degree of the melting furnace chamber is less than 3 × 10⁻⁶. -3 Pa; Step 3: After sawing and processing the smelted ingot obtained in Step 2, high-temperature extrusion is used to obtain extruded billets. The extruded billets are then subjected to high-temperature forging and polishing to obtain molybdenum-rhenium alloy rods. Step 4: The molybdenum-rhenium alloy rod obtained in Step 3 is subjected to deep hole drilling, honing, and machining to obtain a high-precision tube blank with an outer diameter × wall thickness of φ (35±0.02) mm × (1.6±0.02) mm; Step 5: Place the high-precision tube blank obtained in Step 4 onto the M42 high-speed steel precision grinding mandrel that has been preheated to 400℃, and then place them together in a hydrogen atmosphere protected heating furnace. Heat to 900℃ and hold for 25 minutes. Then, use a double eccentric circular hole die for hot rolling, and control the deformation per pass to 30%, with a total hot rolling deformation of 60%. The hot rolling speed is 2.0 mm / min, and the final rolling temperature is not lower than 500℃ to obtain the hot-rolled tube blank. Step 6: The hot-rolled tube blank obtained in Step 5 is naturally cooled to 400℃ in a hydrogen atmosphere without additional heating. Then, it is subjected to warm-cold transition rolling with a deformation of 15% per pass, a rolling speed of 1.5 mm / s, a total deformation of 20% for the warm-cold transition rolling, and a final rolling temperature of not less than 200℃ to obtain the transition tube blank. Step 7: After the inner and outer surfaces of the transition tube blank obtained in Step 6 are washed with alkali, the intermediate heat treatment is carried out at a temperature of 1050℃ and a holding time of 1h. Then, the tube blank is subjected to controlled cold rolling, and the inner wall of the tube blank is supported by a sizing mandrel. The deformation per pass is 5%, the total cold rolling deformation is 25%, and the cold rolling speed is 1.5mm / min to obtain the cold-rolled tube blank. Step 8: Repeat the heating and holding process in Steps 5 to 7, followed by hot rolling, natural cooling and warm-cold transition rolling, and intermediate heat treatment followed by controlled cold rolling. Polish the inner and outer surfaces of the final cold-rolled tube blank and cut it to length to obtain a finished molybdenum-rhenium alloy large-diameter thin-walled tube with an outer diameter of φ30mm and a wall thickness of 0.6mm.

[0024] Testing revealed that the finished molybdenum-rhenium alloy large-diameter thin-walled tube prepared in this embodiment contained 46.70% Re by mass, with the remainder being Mo. The tube's dimensional deviation was ±0.04 mm, Ra = 0.16 μm, straightness was 0.03 mm / 1000 mm, room temperature tensile strength was 974 MPa, and elongation after fracture was 36%.

[0025] Example 3 This embodiment includes the following steps: Step 1: Based on the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled pipe, weigh raw material powders Mo and Re with a mass purity greater than 99.5% according to the mass percentage Mo:Re = 55:45, mix them evenly in a V-type mixer, then pack them into a rubber sleeve for cold isostatic pressing, and then sinter them in a high-temperature hydrogen furnace to obtain the molybdenum-rhenium alloy sintered billet; the nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled pipe, is as follows (mass percentage): Re 48.5%, the remainder being Mo; Step 2: The molybdenum-rhenium alloy sintered billet obtained in Step 1 is subjected to four vacuum electron beam melting processes to obtain a smelted ingot with a diameter of 100 mm. During the four vacuum electron beam melting processes, the vacuum degree in the melting furnace chamber is less than 2.0 × 10⁻⁶. -3 Pa; Step 3: After sawing and processing the smelted ingot obtained in Step 2, high-temperature extrusion is used to obtain extruded billets. The extruded billets are then subjected to high-temperature forging and polishing to obtain molybdenum-rhenium alloy rods. Step 4: The molybdenum-rhenium alloy rod obtained in Step 3 is subjected to deep hole drilling, honing, and machining to obtain a high-precision tube blank with an outer diameter × wall thickness of φ (50±0.02) mm × (4±0.02) mm; Step 5: Place the high-precision tube blank obtained in Step 4 onto the M42 high-speed steel precision grinding mandrel that has been preheated to 350℃, and then place them together in a hydrogen atmosphere protected heating furnace. Heat to 850℃ and hold for 20 minutes. Then, use a double eccentric circular hole die for hot rolling, and control the deformation per pass to 25%, with a total hot rolling deformation of 65%. The hot rolling speed is 1.8 mm / min, and the final rolling temperature is not lower than 500℃ to obtain the hot-rolled tube blank. Step 6: The hot-rolled tube blank obtained in Step 5 is naturally cooled to 380℃ in a hydrogen atmosphere without additional heating. Then, it is subjected to warm-cold transition rolling with a deformation of 10% per pass, a rolling speed of 1.2 mm / s, a total deformation of 20% for the warm-cold transition rolling, and a final rolling temperature of not less than 200℃ to obtain the transition tube blank. Step 7: After the inner and outer surfaces of the transition tube blank obtained in Step 6 are washed with alkali, the intermediate heat treatment is carried out at a temperature of 1100℃ and a holding time of 1h. Then, the tube blank is subjected to controlled cold rolling, and the inner wall of the tube blank is supported by a sizing mandrel. The deformation per pass is 10%, the total cold rolling deformation is 25%, and the cold rolling speed is 1.0mm / min to obtain the cold-rolled tube blank. Step 8: Repeat the heating and heat preservation hot rolling, natural cooling and warm-cold transition rolling, and intermediate heat treatment and controlled cold rolling processes from Steps 5 to 7. Polish the inner and outer surfaces of the final cold-rolled tube blank and cut it to length to obtain a finished molybdenum rhenium alloy large-diameter thin-walled tube with an outer diameter of φ25mm and a wall thickness of 0.3mm.

[0026] Testing revealed that the finished molybdenum-rhenium alloy large-diameter thin-walled tube prepared in this embodiment contained 48.36% Re by mass, with the remainder being Mo. The tube's dimensional deviation was ±0.05 mm, Ra = 0.36 μm, straightness was 0.02 mm / 1000 mm, room temperature tensile strength was 950 MPa, and elongation after fracture was 34.5%.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by alternating hot and cold rolling, characterized in that, The method includes the following steps: Step 1: Weigh the raw material powder according to the nominal composition of the target product, molybdenum-rhenium alloy large-diameter thin-walled pipe, mix it evenly, then put it into a rubber sleeve for cold isostatic pressing, and then place it in a high-temperature hydrogen furnace for sintering to obtain molybdenum-rhenium alloy sintered billet. Step 2: The molybdenum-rhenium alloy sintered billet obtained in Step 1 is subjected to multiple vacuum electron beam melting processes to obtain a smelted ingot; Step 3: After sawing and processing the smelted ingots obtained in Step 2, high-temperature extrusion combined with high-temperature forging is used to obtain molybdenum-rhenium alloy bars; Step 4: The molybdenum-rhenium alloy rod obtained in Step 3 is subjected to deep hole drilling, honing, and machining to obtain a high-precision tube blank; Step 5: Place the high-precision tube blank obtained in Step 4 onto the mandrel, and place them together in a hydrogen atmosphere-protected heating furnace for heating and heat preservation, and then perform hot rolling to obtain a hot-rolled tube blank. Step 6: After the hot-rolled tube blank obtained in Step 5 is naturally cooled in a hydrogen atmosphere, it is subjected to warm-cold transition rolling to obtain a transition tube blank. Step 7: After the inner and outer surfaces of the transition tube blank obtained in Step 6 are washed with alkali, intermediate heat treatment is performed, followed by controlled cold rolling. The inner wall of the tube blank is supported by a sizing mandrel to obtain a cold-rolled tube blank. Step 8: Repeat the processes of heating and holding after hot rolling, natural cooling and then warm-cold transition rolling, and intermediate heat treatment followed by controlled cold rolling in steps 5 to 7. Polish the inner and outer surfaces of the final cold-rolled tube blank and cut it to length to obtain the finished molybdenum-rhenium alloy large-diameter thin-walled tube.

2. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, The nominal composition of the target product, the molybdenum-rhenium alloy large-diameter thin-walled pipe, described in step one, is as follows (by mass percentage): Re 47.5% ± 1%, with the remainder being Mo.

3. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, The mandrel mentioned in step five is an M42 high-speed steel precision-ground mandrel, which is preheated to 300℃~400℃.

4. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, The heating and heat preservation temperature in step five is 700℃~900℃, and the heat preservation time is 20min~25min; the hot rolling adopts a double eccentric circular hole mold, and the deformation per pass is controlled at 15%~30%, the total hot rolling deformation reaches 60%~70%, the hot rolling speed is 1.5mm / min~2.0mm / min, and the final rolling temperature is not lower than 500℃.

5. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, In step six, the temperature is naturally cooled to 350℃~400℃. The deformation amount of each pass in the warm-cold transition rolling is 10%~20%, the rolling speed is maintained at 1mm / s~1.5mm / s, the total deformation amount of the warm-cold transition rolling is 15%~30%, and the final rolling temperature is not lower than 200℃.

6. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by alternating hot and cold rolling according to claim 1, characterized in that, The intermediate heat treatment in step seven is performed at a temperature of 1000℃~1100℃ for 1 hour.

7. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, In step seven, the controllable cold rolling pass deformation is 5%~10%, the total cold rolling deformation is 20%~25%, and the cold rolling speed is 1.0mm / min~1.5mm / min.

8. The method for preparing high-precision large-diameter thin-walled molybdenum-rhenium alloy tubing by hot-cold alternating rolling according to claim 1, characterized in that, The finished molybdenum-rhenium alloy large-diameter thin-walled tubes described in step eight have an outer diameter of 25mm~30mm, a wall thickness of 0.3mm~0.6mm, a dimensional deviation of no more than ±0.05mm, Ra<0.5μm, and a straightness of no more than 0.03mm / 1000mm.

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