A method for manufacturing a pure rhenium thin-walled circular tube

Abstract

The present application relates to the technical field of rare refractory metal material processing, and particularly discloses a preparation method of a pure rhenium thin-walled round pipe.The raw material rhenium powder is subjected to screening treatment, and then the screened rhenium powder is subjected to die forming to obtain a rhenium plate compact; the rhenium plate compact is subjected to multi-stage high-temperature sintering under a hydrogen protection atmosphere to obtain a pure rhenium plate blank; the pure rhenium plate blank is subjected to multi-pass cold rolling and intermediate annealing heat treatment by using a rolling mill to obtain a rhenium foil; the rhenium foil is cut and then subjected to punch and round rolling treatment to obtain a pure rhenium sleeve; the longitudinal seam of the pure rhenium sleeve is welded and subjected to stress relief annealing; and finally, polishing and pickling treatment are performed to obtain a pure rhenium thin-walled round pipe product.Compared with the traditional pipe rolling method, the preparation method has the advantages of high product yield, simple process and small investment.

Description

Technical Field

[0001] This invention relates to the field of rare refractory metal material processing technology, and in particular to a method for preparing a pure rhenium thin-walled circular tube. Background Technology

[0002] Rhenium is a rare refractory metal with a melting point as high as 3180℃, second only to tungsten. Rhenium possesses high strength, good plasticity, and excellent mechanical stability, making it suitable for operation in ultra-high temperature and strong thermal shock environments. Furthermore, rhenium exhibits excellent wear resistance and corrosion resistance, maintaining good chemical inertness to most fuel gases except oxygen, and is not corroded by hot hydrogen. Based on these superior properties, rhenium is widely used in aerospace, semiconductor, and electronics industries. Rhenium tubes are used as rocket engine nozzles, satellite orbital control engine tail nozzles, thermocouple protection tubes, and high-temperature structural components in the nuclear industry.

[0003] However, rhenium is a metal with extremely high work hardening, exhibiting a rapid increase in dislocation density and a very high work hardening rate during cold deformation, which severely limits its cold working capabilities. The plastic deformation mechanism of rhenium is mainly based on basal slip and twinning, which easily generates strong anisotropy during rolling, leading to problems such as edge cracking, poor sheet shape, and uneven microstructure. Furthermore, rhenium is extremely sensitive to interstitial impurities at high temperatures; even trace amounts of these impurities can significantly affect rhenium's grain boundary migration and recrystallization behavior, thereby impacting the material's mechanical and processing properties.

[0004] Currently, powder metallurgy combined with rolling deformation is an effective method for preparing high-performance rhenium plates. Regarding forming processes, existing technologies mostly employ cold isostatic pressing, which can obtain compacts with uniform density, but requires significant equipment investment and involves relatively complex procedures. For the preparation of small-to-medium-sized rhenium plate blanks, die pressing using a four-column press with steel molds can also obtain compacts that meet requirements. This method is simpler, easier to operate, and more efficient, making it more suitable for industrial-scale mass production. Multiple hydrogen reduction processes can effectively reduce the impurity content in rhenium powder, and multi-step hydrogen sintering helps remove residual impurities and densify the blank. Using multi-pass cold rolling combined with intermediate annealing can effectively reduce work hardening and lower the risk of edge cracking in the plate.

[0005] However, existing research mainly focuses on the preparation of rhenium plates, and there is a lack of systematic reports on the complete process route of cold-rolling rhenium plates into foils, followed by rolling and welding to form tubes. The process from rhenium plates to thin-walled rhenium tubes involves key steps such as cold-rolling foils, rolling, and longitudinal seam welding. These steps significantly impact the dimensional accuracy, weld quality, and microstructure uniformity of the rhenium tubes. In particular, rhenium foils are prone to cracking, springback, and wrinkling during cold rolling and rolling. Ensuring the dimensional accuracy and surface quality of rhenium tubes is a pressing technical problem that needs to be solved. Traditional tube rolling processes not only have low yields but also involve complex equipment structures, large floor spaces, and high investment costs, while also requiring sophisticated operation and maintenance. Summary of the Invention

[0006] Traditional tube rolling processes not only have low yield rates, but also involve complex equipment structures, large floor space requirements, and high investment costs. Furthermore, they demand high levels of operational and maintenance expertise. The purpose of this invention is to overcome these shortcomings by providing a method for preparing pure rhenium thin-walled circular tubes. This method significantly improves the yield rate, simplifies the overall process, reduces equipment requirements, and substantially lowers investment, making it easier to achieve efficient and stable mass production.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a pure rhenium thin-walled circular tube, comprising the following steps: S1. The raw material rhenium powder is sieved, and then the sieved rhenium powder is molded to obtain a rhenium plate blank; S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a protective atmosphere to obtain a pure rhenium plate blank. S3. The pure rhenium slab obtained in step S2 is subjected to multiple cold rolling passes, and annealing heat treatment is performed during the cold rolling process to obtain rhenium foil. S4. Cut the rhenium foil obtained in step S3, and then roll the cut rhenium foil into a circle to obtain a pure rhenium sleeve. S5. Weld the longitudinal seam of the pure rhenium sleeve obtained in step S4, and then perform stress-relief annealing, polishing, and pickling to obtain a pure rhenium thin-walled round tube. The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is gradually increased to 600-1000℃ at a rate of 3-5℃ / min and held for 2-4 hours to remove impurities from the billet. Then, the temperature is gradually increased to 1100-1500℃ at a rate of 3-5℃ / min and held for 2-4 hours to pre-sinter the billet. Next, the temperature is gradually increased to 1600-2000℃ at a rate of 1-2℃ / min and held for 2-4 hours to densify the intermediate part of the billet. Finally, the temperature is gradually increased to 2250-2350℃ at a rate of 1-2℃ / min and held for 6-10 hours to perform final densification sintering, resulting in a pure rhenium slab billet.

[0008] This invention involves sieving rhenium powder, followed by molding the sieved rhenium powder to obtain rhenium plate blanks. These blanks are then subjected to multi-stage high-temperature sintering under a hydrogen protective atmosphere to produce pure rhenium plate blanks. The pure rhenium plate blanks are then subjected to multi-pass cold rolling and intermediate annealing heat treatment using a rolling mill to obtain rhenium foil sheets. These foil sheets are cut and then stamped and rolled to obtain pure rhenium sleeves. The longitudinal seams of the pure rhenium sleeves are welded and stress-relief annealing is performed. Finally, polishing and pickling are carried out to obtain the finished pure rhenium thin-walled round tube. Compared to the shortcomings of traditional pipe rolling methods, such as low yield, complex equipment, and high investment, the preparation method of this invention has significant advantages such as high yield, simple process, and low investment.

[0009] This invention employs a tube-making process involving multi-stage sintering, multi-pass cold rolling combined with intermediate annealing, and stamping and rolling. Multi-stage sintering achieves a high-density, fine-grained structure through segmented temperature control, reducing internal stress and improving cold-working plasticity from the source. Multi-pass cold rolling combined with intermediate annealing disperses work hardening and eliminates dislocation accumulation through a "small deformation-time recrystallization" approach, effectively avoiding cracking risks. Stamping and rolling utilizes multi-step progressive forming and multi-directional shaping to disperse residual stress and suppress springback, thereby achieving high-precision, low-defect thin-walled round tube production. This process effectively reduces the risk of cracking during processing, eliminates work hardening, and reduces springback after forming. It effectively solves the problems of difficult cold working of pure rhenium and low tube forming accuracy. The resulting pure rhenium thin-walled round tubes have uniform wall thickness, high dimensional accuracy, and good weld quality, making them suitable for the industrial production of thin-walled tubes in aerospace, nuclear industry, and high-temperature equipment fields.

[0010] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, the sieving process in step S1 includes vibratory sieving, with a sieving mesh size of 200-400 mesh.

[0011] In some specific embodiments, the molding conditions include: molding pressure of 400~600MPa and holding time of 3~5min.

[0012] In some specific embodiments, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press in conjunction with the steel mold.

[0013] This invention employs the above-mentioned method to vibrate and sieve rhenium powder, which improves the uniformity and sintering activity of the pressed blank. A four-column press combined with steel molds is used for die forming, resulting in rhenium plate blanks with a relative density of not less than 60%. Compared to cold isostatic pressing, this method requires less equipment investment, is simpler to operate, and has lower mold costs, making it more suitable for the industrial-scale mass production of small and medium-sized rhenium plate blanks.

[0014] In some specific embodiments, the protective atmosphere includes hydrogen.

[0015] Step S2, multi-stage high-temperature sintering, includes the above four stages. Compared with single-stage sintering, multi-stage high-temperature sintering allows internal impurity elements to escape fully and achieves a uniform microstructure and density distribution, thereby improving the purity, microstructure uniformity, and mechanical properties of the final pure rhenium tube. In the temperature range of 600~1000℃, gaseous impurities such as C, O, and S adsorbed in the green blank, as well as some low-melting-point metal impurities such as Fe, Co, and Ni, can be removed. In the temperature range of 1100~1500℃, the powder particles of the green blank can be uniformly coarsened, and through long-term holding, a uniform porous structure is formed. In the temperature range of 1600~2000℃, the density of the green blank is gradually increased, achieving a uniform microstructure and density distribution. In the temperature range of 2250~2350℃, through long-term high-temperature sintering, a pure rhenium slab with relatively uniform grain size and a relative density of not less than 92% is obtained.

[0016] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, in step S3, the total deformation of cold rolling is not less than 90%.

[0017] In some specific embodiments, the deformation of the 3rd to 5th passes of cold rolling is 20% to 25%, the deformation of the 6th to 10th passes is 15% to 20%, and the deformation of the 11th to 20th passes is 10% to 15%.

[0018] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, in step S3, after 1 to 2 passes of cold rolling, an annealing heat treatment is performed.

[0019] In some specific embodiments, the annealing heat treatment temperature is 1600~1800℃, and the annealing heat treatment time is 1~3h.

[0020] The present invention uses the method in step S2 to prepare rhenium foil with a thickness of 0.1~0.5mm.

[0021] This invention improves the microstructure and increases the density through multi-pass rolling, and eliminates work hardening through intermediate annealing, ensuring that the sheet material will not crack during the rolling process.

[0022] Furthermore, the present invention employs a pure rhenium round tube preparation process that combines multi-stage high-temperature sintering, multi-pass cold rolling with intermediate annealing and stamping and rolling, which effectively avoids problems such as material cracking, dimensional deviations and surface damage. The resulting pure rhenium round tubes have a high yield, good dimensional consistency and excellent surface quality, and the process is simple, significantly reducing the required equipment investment and production costs.

[0023] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, the cutting in step S4 includes laser cutting or wire electrical discharge cutting.

[0024] The present invention uses the above-mentioned cutting method to cut rhenium foil sheets of the required size for rolling.

[0025] In some specific embodiments, the welding in step S5 includes laser welding or electron beam spot welding.

[0026] In a preferred embodiment of the method for preparing a pure rhenium thin-walled circular tube according to the present invention, step S4, the rolling process includes: The process involves stamping and rolling the material into round shapes. The stamping temperature is 200~600℃, and the stamping atmosphere is an inert gas.

[0027] The present invention can reduce the deformation resistance of rhenium foil by stamping at 200~600℃ and suppress the oxidation of rhenium foil surface under inert gas protection. This stamping method can disperse residual stress through multi-step progressive forming and multi-directional shaping, thereby suppressing the springback of rhenium foil, improving the roundness accuracy of tubes and reducing the risk of cracking.

[0028] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, the stamping and rolling mold is an upper conical head inner top mold structure, in which the upper conical head pushes the rhenium foil sheet to roll into a circle along the inner wall of the lower mold when it presses downward.

[0029] This invention also incorporates an upper conical head inner top die structure. Under conditions of 200-600℃ and inert gas protection, the rhenium foil is stamped and rolled, effectively reducing its deformation resistance, minimizing springback and cracking tendency, inhibiting surface oxidation, and significantly improving the rolling quality. The upper conical head inner top die structure can disperse residual stress through multi-step progressive forming and multi-directional shaping, thereby suppressing rhenium foil springback, improving tube roundness accuracy, and reducing the risk of cracking.

[0030] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, in step S5, the stress-relief annealing temperature is 1400~1600°C and the stress-relief annealing time is 1~2h.

[0031] The present invention employs stress-relief annealing, which can eliminate residual internal stress generated by cold rolling, reduce work hardening, and restore plastic deformation capacity, thereby reducing the tendency to crack and dimensional distortion during subsequent processing or use.

[0032] In a preferred embodiment of the method for preparing pure rhenium thin-walled circular tubes according to the present invention, in step S5, polishing includes magnetic polishing, with forward and reverse rotation times of 5-10 minutes each and a frequency of 30-60 Hz.

[0033] In some specific embodiments, the pickling solution is a mixture of hydrochloric acid, phosphoric acid and acetic acid, and the pickling time is 10-20 minutes.

[0034] In some specific embodiments, the volume ratio of hydrochloric acid, phosphoric acid, and acetic acid is 1:3:6.

[0035] This invention uses polishing and acid washing to effectively remove the oxide layer and contaminants from the sleeve surface, resulting in a clean surface.

[0036] The preparation method of this invention is applicable to the industrial preparation of pure rhenium thin-walled tubes for use in aerospace, nuclear industry and high-temperature equipment.

[0037] The present invention provides a pure rhenium thin-walled circular tube prepared by the above-mentioned method, wherein the pure rhenium thin-walled circular tube has an inner diameter of 5~50mm, a wall thickness of 0.1~0.5mm, and a length of 50~500mm.

[0038] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing thin-walled circular tubes of pure rhenium. The method employs a tube-making process involving multi-stage sintering, multi-pass cold rolling combined with intermediate annealing, and stamping and rolling. Multi-stage sintering achieves a high-density, fine-grained structure through segmented temperature control, reducing internal stress and improving cold-working plasticity from the source. Multi-pass cold rolling combined with intermediate annealing disperses work hardening and eliminates dislocation accumulation through a "small deformation-time recrystallization" approach, effectively avoiding the risk of cracking. Stamping and rolling utilizes multi-step progressive forming and multi-directional shaping to disperse residual stress and suppress springback, thereby achieving high-precision, low-defect thin-walled circular tube preparation. This process effectively reduces the risk of cracking during processing, eliminates work hardening, and reduces springback after forming, effectively solving the problems of difficult cold working of pure rhenium and low tube forming accuracy. The resulting pure rhenium thin-walled circular tubes have uniform wall thickness, high dimensional accuracy, and good weld quality, making them suitable for the industrial production of thin-walled tubes in aerospace, nuclear industry, and high-temperature equipment fields. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of a method for preparing a pure rhenium thin-walled circular tube according to the present invention; Figure 2 This is a schematic diagram of the inner top mold structure of the upper conical head of the present invention; Figure 3 A scanning electron microscope image of the cross-section of the rhenium foil prepared according to the present invention; Figure 4 This is a macroscopic photograph of the rhenium foil sleeve manufactured using the stamping and rolling process of this invention. Detailed Implementation

[0040] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0041] In the following examples and comparative examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified. Furthermore, the raw materials used in each parallel experiment are the same.

[0042] The method for preparing pure rhenium thin-walled circular tubes provided by this invention is illustrated in the flowchart below. Figure 1 As shown.

[0043] The following is a schematic diagram of the inner ejector mold structure of the upper conical head, as shown below. Figure 2 As shown.

[0044] The upper conical head inner ejector die structure includes an upper conical head and a lower inner ejector die. Its core forming principle is to plastically deform a flat foil into a round tube through the expansion and folding action of a conical punch. The lower end of the upper conical head is a composite structure of a conical guide and a circular arc pressure head: the top end tapers into a conical transition, and the bottom end is a full-circle punch that matches the inner diameter of the finished cylinder. The main body of the lower inner ejector die is a split-type elastic opening and closing mold cavity with a left and right split structure and an elastic support mechanism at the bottom; the inner side of the mold cavity is pre-machined with a semi-circular arc guide groove, the curvature of which perfectly matches the outer diameter of the finished rhenium foil cylinder; elastic limiting supports are provided on both sides. Under normal conditions, the mold cavity opening is open, allowing flat rhenium foil to be laid flat; under pressure, the two sides of the mold can slightly retract outward to adapt to the thickness of the foil roll, and after stamping, it automatically resets and opens due to elasticity, facilitating part removal.

[0045] The specific principle and process are as follows: The cut rhenium foil is placed flat on the positioning support surface of the lower die. The upper end face of the inner core is used as a reference plane to ensure that the center of the foil is automatically aligned with the axis of the upper conical head. The upper part of the upper conical head is connected to the press platform, which drives the upper conical head to descend vertically. The tip of the conical head first contacts the center of the foil. As the pressing depth increases, the conical surface gradually squeezes the foil from the inside to the outside, generating radial tension, which forces the foil material to stretch and slide along the conical surface. When the material slides along the conical surface to the outer edge, it begins to roll upward due to the obstruction of the die wall. At this time, the inner core below restricts the material to accumulate inward and forms a "wedge gap" with the outer wall of the conical head, ensuring that the foil is tightly folded into a cylindrical shape against the outer wall of the conical head, ensuring uniform tube wall thickness and controlling the inner diameter. The upper conical head is pressed down to the set stroke and held for several seconds to eliminate elastic rebound and fix the shape of the rhenium tube.

[0046] Example 1: A method for preparing a pure rhenium thin-walled circular tube This embodiment provides a method for preparing a pure rhenium thin-walled circular tube, including the following steps: S1. Using high-purity rhenium powder with a purity of 99.99%, the raw rhenium powder is first subjected to vibratory sieving with a screen size of 200 mesh. Then, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press with a molding pressure of 500 MPa and a holding time of 5 min to obtain a rhenium powder compact with a thickness of 4 mm.

[0047] S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a hydrogen protective atmosphere. After sintering, it is cooled with the furnace to obtain a pure rhenium plate blank with a thickness of 3 mm (oxygen content <20ppm, density of 93%).

[0048] S3. The pure rhenium slab obtained in step S2 is subjected to 14 passes of cold rolling, with annealing heat treatment during the cold rolling process, to obtain a rhenium foil with a thickness of 0.2 mm (cross-sectional scanning electron microscope image as shown). Figure 3 As shown, the remaining embodiments have similar effects to Embodiment 1.

[0049] S4. The rhenium foil obtained in step S3 is cut using a laser cutting machine to obtain rhenium foil sheets with a width of 63mm and a length of 300mm. The cut rhenium foil sheets are then placed in a stamping machine and stamped and rolled into a circle using an upper conical head inner top die structure. The stamping temperature is 600℃ and the stamping atmosphere is argon atmosphere, to obtain a pure rhenium sleeve (macroscopic photograph as shown). Figure 4 As shown, the remaining embodiments have similar effects to Embodiment 1.

[0050] S5. The longitudinal seam of the pure rhenium sleeve obtained in step S4 is welded using laser spot welding. After welding, it is stress-relieved annealed at 1600°C for 2 hours. Subsequently, the inner and outer surfaces of the annealed sleeve are magnetically polished with a forward and reverse rotation time of 10 minutes and a frequency of 60Hz. After polishing, pickling is performed using a mixed acid solution of hydrochloric acid, phosphoric acid, and acetic acid in a volume ratio of hydrochloric acid:phosphoric acid:acetic acid = 1:3:6 for 15 minutes. After pickling, it is cleaned with alcohol to obtain a finished pure rhenium thin-walled round tube with an inner diameter of approximately 20 mm, a wall thickness of 0.2 mm, and a length of 300 mm. Testing shows that the tube wall thickness is 0.2 ± 0.05 mm, the inner diameter is 20 ± 1 mm, and the weld surface is free of defects such as porosity and cracks.

[0051] The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is increased to 800℃ at a rate of 5℃ / min and held for 4 hours. Then, the temperature is increased to 1000℃ at a rate of 5℃ / min and held for 4 hours to remove impurities from the billet. Next, the temperature is increased to 1200℃ at a rate of 3℃ / min and held for 4 hours. Then, the temperature is increased to 1400℃ at a rate of 3℃ / min and held for 4 hours to pre-sinter the billet. Then, the temperature is increased to 1600℃ at a rate of 2℃ / min and held for 4 hours. Then, the temperature is increased to 2000℃ at a rate of 2℃ / min and held for 4 hours to densify the intermediate part of the billet. Finally, the temperature is increased to 2350℃ at a rate of 2℃ / min and held for 6 hours to perform final densification sintering, obtaining a pure rhenium slab billet.

[0052] In step S3, the thickness of the cold-rolled material changes as follows: 3mm → 2.30mm → 1.8mm → 1.4mm → 1.1mm → 0.9mm → 0.75mm → 0.6mm → 0.52mm → 0.42mm → 0.36mm → 0.31mm → 0.27mm → 0.23mm → 0.2mm.

[0053] After each cold rolling pass, an annealing heat treatment is performed; the annealing heat treatment temperature is 1700℃ and the annealing heat treatment time is 1 hour.

[0054] Example 2: A method for preparing a pure rhenium thin-walled circular tube This embodiment provides a method for preparing a pure rhenium thin-walled circular tube, including the following steps: S1. Using high-purity rhenium powder with a purity of 99.99%, the raw rhenium powder is first subjected to vibratory sieving with a screen size of 300 mesh. Then, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press with a molding pressure of 500 MPa and a holding time of 5 min to obtain a rhenium powder compact with a thickness of 3 mm.

[0055] S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a hydrogen protective atmosphere. After sintering, it is cooled with the furnace to obtain a pure rhenium plate blank with a thickness of 2.6 mm.

[0056] S3. The pure rhenium slab obtained in step S2 is subjected to 16 passes of cold rolling, and annealing heat treatment is performed during the cold rolling process to obtain a rhenium foil with a thickness of 0.15 mm.

[0057] S4. The rhenium foil obtained in step S3 is cut using a laser cutting machine to obtain a rhenium foil with a width of 63mm and a length of 300mm. The cut rhenium foil is then placed in a stamping machine and stamped and rolled into a circle using an upper conical head inner top die structure. The stamping temperature is 400℃ and the stamping atmosphere is argon atmosphere to obtain a pure rhenium sleeve.

[0058] S5. The longitudinal seam of the pure rhenium sleeve obtained in step S4 is welded using laser spot welding. After welding, it is stress-relieved annealed at 1600°C for 1 hour. Subsequently, the inner and outer surfaces of the annealed sleeve are magnetically polished with a forward and reverse rotation time of 10 minutes and a frequency of 60Hz. After polishing, pickling is performed using a mixed acid solution of hydrochloric acid, phosphoric acid, and acetic acid in a volume ratio of hydrochloric acid:phosphoric acid:acetic acid = 1:3:6 for 15 minutes. After pickling, it is cleaned with alcohol to obtain a finished pure rhenium thin-walled round tube with an inner diameter of approximately 20 mm, a wall thickness of 0.15 mm, and a length of 150 mm. Testing shows that the tube wall thickness is 0.15±0.03 mm, the inner diameter is 20±1 mm, and the weld is free of defects such as porosity and cracks.

[0059] The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is increased to 800℃ at a rate of 5℃ / min and held for 4 hours. Then, the temperature is increased to 1000℃ at a rate of 5℃ / min and held for 4 hours to remove impurities from the billet. Next, the temperature is increased to 1200℃ at a rate of 3℃ / min and held for 4 hours. Then, the temperature is increased to 1400℃ at a rate of 3℃ / min and held for 4 hours to pre-sinter the billet. Then, the temperature is increased to 1600℃ at a rate of 2℃ / min and held for 4 hours. Then, the temperature is increased to 2000℃ at a rate of 2℃ / min and held for 4 hours to densify the intermediate part of the billet. Finally, the temperature is increased to 2350℃ at a rate of 2℃ / min and held for 6 hours to perform final densification sintering, obtaining a pure rhenium slab billet.

[0060] In step S3, the thickness of the cold-rolled material changes as follows: 3mm → 2.30mm → 1.8mm → 1.4mm → 1.1mm → 0.9mm → 0.75mm → 0.6mm → 0.52mm → 0.42mm → 0.36mm → 0.31mm → 0.27mm → 0.23mm → 0.2mm → 0.17mm → 0.15mm.

[0061] After each cold rolling pass, an annealing heat treatment is performed; the annealing heat treatment temperature is 1700℃ and the annealing heat treatment time is 1 hour.

[0062] Example 3: A method for preparing a pure rhenium thin-walled circular tube This embodiment provides a method for preparing a pure rhenium thin-walled circular tube, including the following steps: S1. Using high-purity rhenium powder with a purity of 99.99%, the raw rhenium powder is first subjected to vibratory sieving with a screen size of 400 mesh. Then, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press with a molding pressure of 400 MPa and a holding time of 3 minutes to obtain a rhenium powder compact with a thickness of 3 mm.

[0063] S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a hydrogen protective atmosphere. After sintering, it is cooled with the furnace to obtain a pure rhenium plate blank with a thickness of 2.6 mm.

[0064] S3. The pure rhenium slab obtained in step S2 is subjected to 16 passes of cold rolling, and annealing heat treatment is performed during the cold rolling process to obtain a rhenium foil with a thickness of 0.15 mm.

[0065] S4. The rhenium foil obtained in step S3 is cut using a laser cutting machine to obtain a rhenium foil with a width of 63mm and a length of 300mm. The cut rhenium foil is then placed in a stamping machine and stamped and rolled into a circle using an upper conical head inner top die structure. The stamping temperature is 400℃ and the stamping atmosphere is argon atmosphere to obtain a pure rhenium sleeve.

[0066] S5. The longitudinal seam of the pure rhenium sleeve obtained in step S4 is welded using laser spot welding. After welding, it is stress-relieved annealed at 1400°C for 1 hour. Subsequently, the inner and outer surfaces of the annealed sleeve are magnetically polished with a forward and reverse rotation time of 10 minutes and a frequency of 60 Hz. After polishing, pickling is performed using a mixed acid solution of hydrochloric acid, phosphoric acid, and acetic acid in a volume ratio of hydrochloric acid:phosphoric acid:acetic acid = 1:3:6 for 15 minutes. After pickling, it is cleaned with alcohol to obtain a finished pure rhenium thin-walled round tube with an inner diameter of approximately 20 mm, a wall thickness of 0.15 mm, and a length of 150 mm. Testing shows that the tube wall thickness is 0.15 ± 0.03 mm, the inner diameter is 20 ± 1 mm, and the weld is free of defects such as porosity and cracks.

[0067] The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is increased to 600℃ at a rate of 3℃ / min and held for 2 hours. Then, the temperature is increased to 1000℃ at a rate of 3℃ / min and held for 2 hours to remove impurities from the billet. Next, the temperature is increased to 1100℃ at a rate of 3℃ / min and held for 2 hours. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 2 hours to pre-sinter the billet. Then, the temperature is increased to 1600℃ at a rate of 1℃ / min and held for 2 hours. Then, the temperature is increased to 2000℃ at a rate of 1℃ / min and held for 2 hours to densify the intermediate part of the billet. Finally, the temperature is increased to 2250℃ at a rate of 1℃ / min and held for 6 hours to perform final densification sintering, resulting in a pure rhenium slab billet.

[0068] In step S3, the thickness of the cold-rolled material changes as follows: 3mm → 2.30mm → 1.8mm → 1.4mm → 1.1mm → 0.9mm → 0.75mm → 0.6mm → 0.52mm → 0.42mm → 0.36mm → 0.31mm → 0.27mm → 0.23mm → 0.2mm → 0.17mm → 0.15mm.

[0069] After each cold rolling pass, an annealing heat treatment is performed; the annealing heat treatment temperature is 1600℃ and the annealing heat treatment time is 2 hours.

[0070] Example 4: A method for preparing a pure rhenium thin-walled circular tube This embodiment provides a method for preparing a pure rhenium thin-walled circular tube, including the following steps: S1. Using high-purity rhenium powder with a purity of 99.99%, the raw rhenium powder is first subjected to vibratory sieving with a screen size of 400 mesh. Then, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press with a molding pressure of 600 MPa and a holding time of 5 minutes to obtain a rhenium powder compact with a thickness of 3 mm.

[0071] S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a hydrogen protective atmosphere. After sintering, it is cooled with the furnace to obtain a pure rhenium plate blank with a thickness of 2.6 mm.

[0072] S3. The pure rhenium slab obtained in step S2 is subjected to 16 passes of cold rolling, and annealing heat treatment is performed during the cold rolling process to obtain a rhenium foil with a thickness of 0.15 mm.

[0073] S4. The rhenium foil obtained in step S3 is cut using a laser cutting machine to obtain a rhenium foil with a width of 63mm and a length of 300mm. The cut rhenium foil is then placed in a stamping machine and stamped and rolled into a circle using an upper conical head inner top die structure. The stamping temperature is 600℃ and the stamping atmosphere is argon atmosphere to obtain a pure rhenium sleeve.

[0074] S5. Laser spot welding is used to weld the longitudinal seam of the pure rhenium sleeve obtained in step S4. After welding, stress-relief annealing is performed at 1600°C for 2 hours. Subsequently, the inner and outer surfaces of the annealed sleeve are magnetically polished with a forward and reverse rotation time of 10 minutes and a frequency of 60Hz. After polishing, pickling is performed using a mixed acid solution of hydrochloric acid, phosphoric acid, and acetic acid in a volume ratio of hydrochloric acid:phosphoric acid:acetic acid = 1:3:6 for 15 minutes. After pickling, alcohol cleaning is performed to obtain a finished pure rhenium thin-walled round tube with an inner diameter of approximately 20 mm, a wall thickness of 0.15 mm, and a length of 150 mm. Testing shows that the tube wall thickness is 0.15 ± 0.03 mm, the inner diameter is 20 ± 1 mm, and the weld is free of defects such as porosity and cracks.

[0075] The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is increased to 600℃ at a rate of 5℃ / min and held for 4 hours. Then, the temperature is increased to 1000℃ at a rate of 5℃ / min and held for 4 hours to remove impurities from the billet. Next, the temperature is increased to 1100℃ at a rate of 5℃ / min and held for 4 hours. Then, the temperature is increased to 1500℃ at a rate of 5℃ / min and held for 4 hours to pre-sinter the billet. Then, the temperature is increased to 1600℃ at a rate of 2℃ / min and held for 4 hours. Then, the temperature is increased to 2000℃ at a rate of 2℃ / min and held for 4 hours to densify the intermediate part of the billet. Finally, the temperature is increased to 2350℃ at a rate of 2℃ / min and held for 10 hours to perform final densification sintering, resulting in a pure rhenium slab billet.

[0076] In step S3, the thickness of the cold-rolled material changes as follows: 2.6mm → 2.0mm → 1.6mm → 1.3mm → 1.1mm → 0.1mm → 0.75mm → 0.6mm → 0.52mm → 0.42mm → 0.36mm → 0.31mm → 0.27mm → 0.23mm → 0.2mm → 0.17mm → 0.15mm.

[0077] After each cold rolling pass, an annealing heat treatment is performed; the annealing heat treatment temperature is 1800℃ and the annealing heat treatment time is 1 hour.

[0078] Comparative Example 1 Compared with Example 1, Comparative Example 1 does not use multi-stage high-temperature sintering in step S2. The rhenium plate blank obtained in step S1 is sintered at a temperature of 2350°C for 6 hours. The remaining steps are the same as in Example 1.

[0079] Without a multi-stage hydrogen sintering process, impurities inside the pure rhenium slab cannot escape sufficiently, resulting in uneven microstructure and density distribution. After sintering, the oxygen content of the slab reaches 100 ppm, and the density is only 85%. This makes it difficult to control the slab shape during rolling, leading to cracking and curling.

[0080] Comparative Example 2 Compared with Example 1, the high-temperature sintering step S2 of Comparative Example 2 is simplified. The specific high-temperature sintering steps are as follows: The temperature was increased to 800℃ at a heating rate of 5° / min and held for 4 hours. Without further gradient treatment, the temperature was directly increased to 1600℃ and held for 3 hours. Finally, the temperature was directly increased to 2350℃ and sintered for 6 hours.

[0081] The remaining steps are the same as in Example 1.

[0082] Simplifying the multi-stage hydrogen sintering process makes it difficult for impurity elements inside the pure rhenium slab to escape sufficiently, resulting in uneven microstructure and density distribution. After sintering, the oxygen content of the slab reaches 50 ppm, and the density is only 88%. The slab shape is difficult to control during rolling; when rolled to 0.2 mm, the thickness tolerance is ±0.1 mm.

[0083] Comparative Example 3 Compared with Example 1, Comparative Example 3 does not use the multi-pass small deformation cold rolling and intermediate annealing heat treatment method of step S3 in the cold rolling process. Instead, it directly performs single-pass large deformation rolling of 30%, which will cause the work hardening degree of the material to increase sharply, the deformation resistance and internal stress to increase continuously, the plasticity of the material to decrease rapidly, and the rhenium plate to crack after rolling 2 passes.

[0084] Comparative Example 4 Compared with Example 1, Comparative Example 4 does not use the 600°C stamping and rolling process in step S4, but instead uses room temperature stamping and rolling. Due to the poor room temperature plasticity and work hardening sensitivity of pure rhenium, the sheet metal is very easy to crack or even break. In addition, room temperature rolling has a large springback and the surface is prone to scratches and pressure marks, making it difficult to obtain qualified pure rhenium round tubes.

[0085] Comparative Example 5 Compared with Example 1, Comparative Example 5 does not use the stamping and rolling process at 600°C in step S4, but instead uses stamping and rolling at 1000°C. Due to the excessively high stamping temperature, the rhenium foil softens more and its strength decreases, resulting in surface wrinkles and curls during rolling, making it difficult to obtain qualified pure rhenium round tubes.

[0086] Comparative Example 6 Compared with Example 1, Comparative Example 6 does not use the stamping and rolling process in step S4, but instead uses an ordinary rolling machine to prepare pure rhenium round tubes. Because pure rhenium does not have a precision mold to limit it, the roundness and dimensional consistency of the round tubes will be poor, resulting in ellipticity or taper, making it difficult to obtain qualified pure rhenium round tubes.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a pure rhenium thin-walled circular tube, characterized in that, Includes the following steps: S1. The raw material rhenium powder is sieved, and then the sieved rhenium powder is molded to obtain a rhenium plate blank; S2. The rhenium plate blank obtained in step S1 is subjected to multi-stage high-temperature sintering under a protective atmosphere to obtain a pure rhenium plate blank. S3. The pure rhenium slab obtained in step S2 is subjected to 10 to 20 cold rolling passes, and annealing heat treatment is performed during the cold rolling process to obtain rhenium foil. S4. Cut the rhenium foil obtained in step S3, and then roll the cut rhenium foil into a circle to obtain a pure rhenium sleeve. S5. Weld the longitudinal seam of the pure rhenium sleeve obtained in step S4, and then perform stress-relief annealing, polishing, and pickling to obtain a pure rhenium thin-walled round tube. The multi-stage high-temperature sintering in step S2 includes the following four stages: First, the temperature is gradually increased to 600-1000℃ at a rate of 3-5℃ / min and held for 2-4 hours to remove impurities from the billet. Then, the temperature is gradually increased to 1100-1500℃ at a rate of 3-5℃ / min and held for 2-4 hours to pre-sinter the billet. Next, the temperature is gradually increased to 1600-2000℃ at a rate of 1-2℃ / min and held for 2-4 hours to densify the intermediate part of the billet. Finally, the temperature is gradually increased to 2250-2350℃ at a rate of 1-2℃ / min and held for 6-10 hours to perform final densification sintering, resulting in a pure rhenium slab billet.

2. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S1, the screening process includes vibratory screening, and the mesh size of the screening is 200~400 mesh. And / or, the conditions for compression molding include: compression pressure of 400~600MPa and holding time of 3~5min; And / or, the sieved rhenium powder is loaded into a steel mold and molded using a four-column press in conjunction with the steel mold.

3. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S3, the total deformation of cold rolling shall not be less than 90%; And / or, the deformation of the 3rd to 5th passes of cold rolling is 20% to 25%, the deformation of the 6th to 10th passes is 15% to 20%, and the deformation of the 11th to 20th passes is 10% to 15%.

4. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S3, after 1 to 2 passes of cold rolling, an annealing heat treatment is performed. And / or, the annealing heat treatment temperature is 1600~1800℃, and the annealing heat treatment time is 1~3h.

5. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S4, the cutting includes laser cutting or wire electrical discharge cutting. And / or, in step S5, the welding includes laser welding or electron beam spot welding.

6. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S4, the rolling process includes: The process involves stamping and rolling the material into round shapes. The stamping temperature is 200~600℃, and the stamping atmosphere is an inert gas.

7. The method for preparing a pure rhenium thin-walled circular tube as described in claim 6, characterized in that, The stamping and rolling die is an upper conical head inner top die structure. When the upper conical head presses downward, it pushes the rhenium foil sheet to roll into a circle along the inner wall of the lower die.

8. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S5, the stress-relief annealing temperature is 1400~1600°C, and the stress-relief annealing time is 1~2 hours.

9. The method for preparing a pure rhenium thin-walled circular tube as described in claim 1, characterized in that, In step S5, polishing includes magnetic polishing, with forward and reverse rotation times set to 5-10 minutes each and a frequency of 30-60 Hz. And / or, the pickling solution is a mixture of hydrochloric acid, phosphoric acid and acetic acid, and the pickling time is 10~20 min.

10. The pure rhenium thin-walled circular tube prepared by the method for preparing pure rhenium thin-walled circular tubes according to any one of claims 1 to 9, characterized in that, The inner diameter of a pure rhenium thin-walled circular tube is 5~50mm, the wall thickness is 0.1~0.5mm, and the length is 50~500mm.

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