Aluminum alloy seamless gas cylinder and manufacturing method thereof

Abstract

The present application belongs to the technical field of plastic processing of thin-walled aluminum alloy products, and relates to an aluminum alloy seamless gas cylinder and a manufacturing method thereof. The gas cylinder is formed by a cylinder mouth side half cylinder and a cylinder bottom side half cylinder through seamless inertia friction welding. The cylinder mouth side half cylinder and the cylinder bottom side half cylinder are both prepared by performing severe plastic deformation on an aluminum alloy cylinder body at room temperature through a low-temperature high-pressure torsion device. The shoulder and / or bottom curve surface of the cylinder is formed by layer-by-layer crystallization refinement of metal under high pressure, and a uniform nano-scale or sub-micron ultra-fine grain structure is formed in the material. The present application solves the problems of wrinkle, stacking and high scrap rate caused by difficult temperature control in the traditional hot closing process by performing layer-by-layer severe plastic deformation on the aluminum alloy cylinder body at room temperature through a low-temperature high-pressure torsion process, thereby greatly improving the forming quality and mechanical reliability of the gas cylinder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic working of thin-walled aluminum alloy products, and particularly relates to an aluminum alloy seamless gas cylinder and a manufacturing method thereof. BACKGROUND

[0002] With the development of industry, especially the electronic industry, the demand for various standard gases, standard mixed gases and ultra-pure gases is increasing, which leads to a large demand for containers for containing the gases, i.e., aluminum alloy seamless gas cylinders. In the production process of the aluminum alloy gas cylinders, a necking process is a key link, that is, after the aluminum cylinder is formed into a barrel, the barrel is smoothly necked to a required size so as to install a required valve or plug. The necking process of the British Lunfer aluminum cylinder company, which is the largest aluminum cylinder production company in the world, is to heat the opening end of the barrel and then press the opening end into a mold similar to the neck of the barrel at one time, so that m=1 / d>032. This process is a British patent, and the price is 2000 dollars in 1987. Disadvantages of the process are as follows:

[0003] 1) The high heat conduction performance of aluminum is changed from an advantage to a disadvantage. After the end is heated, the heat is quickly transmitted to the barrel, which reduces the strength of the barrel and causes the necking process to easily accumulate to cause waste.

[0004] 2) After necking, the inner surface wrinkles are increased, and even overlapping occurs. The temperature is difficult to control, and the operation is difficult, so that the equipment requirement is high, and the manufacturing cost is increased.

[0005] The inner liner of the large high-pressure storage and transportation gas cylinder and the manufacturing method thereof disclosed in the publication CN109578799B adopt a heating necking spinning machine to spin and form a head and a bottle mouth at the opening of the aluminum alloy inner liner, to obtain a spinning formed piece. However, the scheme adopts the heating necking spinning machine, utilizes the high heat conduction performance of aluminum, and after the end is heated, the heat is quickly transmitted to the barrel, which reduces the strength of the barrel and causes the necking process to easily accumulate to cause waste.

[0006] Therefore, it is urgent to design an aluminum alloy seamless gas cylinder and a manufacturing method thereof to solve the problems of low yield, poor performance, inconvenient operation and high cost in the prior art. SUMMARY

[0007] Therefore, the present application aims to provide an aluminum alloy seamless gas cylinder and a manufacturing method thereof to solve the problems of low yield, poor performance, inconvenient operation and high cost in the prior art.

[0008] The application adopts low-temperature high-pressure torsion severe plastic deformation technology at room temperature to perform isothermal closing, and the whole forming process is completed at room temperature, and the external heating link is completely abandoned. Therefore, the high thermal conductivity of aluminum is no longer a disadvantage, but avoids the problem of overall softening caused by heat conduction, fundamentally eliminates the waste caused by material stacking. Since it is room temperature processing, the dependence on a complex temperature control system is completely eliminated, the process is more stable, and the operation is simpler. Through the way of "layer-by-layer crystallization refinement forming", the metal is compacted and refined layer by layer under ultra-high pressure, the deformation process is more controllable and uniform, and the problems of large-area wrinkles and material overlap on the inner surface caused by traditional one-time pressing are effectively avoided. The seamless inertia friction welding technology is adopted, atomic level bonding is realized through friction heating and top forging pressure, the welding quality is high and flat, and the use requirements can be met without subsequent mechanical processing, greatly simplifying the process, reducing the cost, and ensuring the smoothness of the gas cylinder. Therefore, the application provides an isothermal closing process for an aluminum alloy seamless gas cylinder which can be closed at one time, has high product yield and simple operation.

[0009] To achieve the above-mentioned purpose, the technical scheme of the application is as follows:

[0010] An object of the application is to disclose an aluminum alloy seamless gas cylinder, which is formed by a gas cylinder mouth side half cylinder and a gas cylinder bottom side half cylinder through seamless inertia friction welding.

[0011] The gas cylinder mouth side half cylinder and the gas cylinder bottom side half cylinder are both prepared by severe plastic deformation of an aluminum alloy cylinder body at room temperature through a low-temperature high-pressure torsion device, the shoulder and / or bottom curve surface of the cylinder is formed by layer-by-layer crystallization refinement forming of metal under high pressure, and uniform nanoscale or submicron ultrafine crystal organization is formed in the material.

[0012] Further, the tensile strength of the gas cylinder is not less than 400 MPa, the yield strength is not less than 370 MPa, and the total elongation is not less than 8%.

[0013] Further, the gas cylinder is subjected to aging treatment, the aging temperature is 150-190 DEG C, and the aging time is 45-70 min.

[0014] Another object of the application is to disclose a manufacturing method of an aluminum alloy seamless gas cylinder, which is based on any of the above-mentioned aluminum alloy seamless gas cylinders and comprises the following specific steps.

[0015] S1: using a low-temperature high-pressure torsion device to perform plastic processing on an aluminum alloy cylinder body at room temperature, layer-by-layer crystallization refinement of metal is realized through high-pressure torsion process to form nanoscale or submicron ultrafine crystal organization, and a gas cylinder mouth side half cylinder with layer-by-layer crystallization refinement forming shoulder is prepared.

[0016] S2: using another low-temperature high-pressure torsion device to perform plastic processing on the aluminum alloy cylinder at room temperature, and through high-pressure torsion process, the metal is layer-by-layer crystallized and refined to form a nanometer or sub-micron ultra-fine crystal organization, and a gas bottle bottom side half bottle with a layer-by-layer crystallized and refined bottle bottom is prepared;

[0017] S3: welding the gas bottle mouth side half bottle and the gas bottle bottom side half bottle into a complete gas bottle through seamless inertia friction welding;

[0018] S4: performing aging treatment on the complete gas bottle after welding to obtain a final product.

[0019] Further, in steps S1 and S2, the low-temperature high-pressure torsion device is a 250 t level device, including a rotating head, the rotating head of the low-temperature high-pressure torsion device has the servo motion function of axis rotation and axial lifting, the working pressure of the device is 5-7 GPa, the rotating speed of the rotating head is 1-30 r / min, and the processing temperature is room temperature 20-24℃.

[0020] Further, in step S3, an inside support structure and an outside ring structure are used in the welding process to maintain the welding centering and temperature control.

[0021] Further, in steps S1 and S2, an extrusion ring is further included, and the extrusion ring has a lifting motion function to realize a back pressure process.

[0022] Further, in steps S1 and S2, the lower end of the aluminum alloy cylinder is pre-processed by turning to form an initial shape of the gas bottle shoulder.

[0023] Further, in step S3, the seamless inertia friction welding process uses an inside disc and an outside ring as auxiliary tooling, and the materials of the inside disc and the outside ring are high-purity silicon dioxide with a temperature resistance upper limit of 1650℃.

[0024] Further, in step S3, after the welding is completed, the inside disc is broken by ultrasonic vibration and removed from the inside of the gas bottle.

[0025] Compared with the prior art, the aluminum alloy seamless gas cylinder and the manufacturing method thereof have the following advantages:

[0026] 1. The low-temperature high-pressure torsion process is adopted to perform layer-by-layer severe plastic deformation on the aluminum alloy cylinder at room temperature, which effectively refines the grain structure of the material, forms a uniform nanometer or sub-micron ultra-fine crystal organization, significantly improves the strength, toughness and fatigue resistance of the gas cylinder, solves the problems of wrinkle, stacking and high scrap rate caused by difficult temperature control in the traditional hot closing process, and greatly improves the forming quality and mechanical reliability of the gas cylinder.

[0027] 2. This invention combines low-temperature high-pressure torsion forming and seamless inertial friction welding, and uses inner and outer rings made of high-purity silica as welding auxiliary tooling. This not only effectively constrains the metal flow during the welding process and prevents oxidation, but also utilizes its high-temperature stability and brittleness to facilitate subsequent cleaning, thereby enhancing the metallurgical bonding quality and continuity of the weld interface and significantly improving the integrity and pressure resistance of the overall structure.

[0028] 3. This invention provides an efficient and systematic method for manufacturing gas cylinders. Through a semi-cylinder forming process that can be produced in parallel and a reusable tooling design, it not only simplifies the production process and improves manufacturing efficiency, but also helps to reduce dependence on special equipment and overall production costs. At the same time, it reduces subsequent maintenance needs and has good prospects for industrial application. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 This is a cross-sectional schematic diagram of the shaft at the beginning stage of the low-temperature high-pressure torsion device of the present invention;

[0031] Figure 2 For the present invention Figure 1 Enlarged view of part A;

[0032] Figure 3 This is a cross-sectional view of the shaft running at one step in the low-temperature high-pressure torsion device of the present invention;

[0033] Figure 4 For the present invention Figure 3 A magnified view of part B;

[0034] Figure 5 This is a cross-sectional schematic diagram of the shaft termination stage of the low-temperature high-pressure torsion device of the present invention;

[0035] Figure 6 This is a schematic diagram of the processing of the half-bottle mouth of the gas cylinder according to the present invention;

[0036] Figure 7 This is a schematic diagram of the seamless inertial friction welding of the present invention;

[0037] Figure 8 For the present invention Figure 7 A magnified view of a portion of C;

[0038] Figure 9 For the present invention Figure 7 A magnified view of a portion of the image.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1, cylinder mouth side half bottle; 101, cylinder mouth; 102, port part; 103, aluminum column; 104, bottle mouth; 105, sealing thread; 106, transition round corner; 2, cylinder bottom side half bottle; 3, inertia rotation side clamp; 4, stationary clamp; 5, outer side ring; 6, support rod; 7, inner side disc; 8, lower mold; 9, rotation head; 10, ejector rod; 11, extrusion ring; 12, cylinder blank. DETAILED DESCRIPTION

[0041] In order to make the technical means and purposes of the present application easy to understand, the embodiments of the present application are described in detail below in combination with specific drawings.

[0042] It should be noted that all the terms for indicating direction and position in the present application, such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "inner", "outer", "top", "low", "transverse", "longitudinal", "center", etc., are only used to explain the relative position relationship, connection condition, etc. between components in a certain specific state, and are only for the convenience of describing the present application, and thus cannot be understood as a limitation on the present application that the present application must be constructed and operated in a specific orientation. In addition, the description of "first", "second", etc. in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features.

[0043] In the description of the present application, unless otherwise explicitly specified and limited, the terms "mount", "connect", "connection" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection; can be directly connected, or indirectly connected through an intermediate medium; can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0045] Severe plastic deformation is a kind of plastic processing method, which can introduce strain greater than 1 in the deformation process, so as to effectively refine the metal grains to sub-micron or nanometer level, and prepare complete large size structure. Through microstructure control, this technology can realize the synergistic improvement of high strength and large plasticity of the material. The low temperature high pressure torsion device is one of the typical designs in the plastic processing method.

[0046] As shown in Figures 1-9 The present application provides an aluminum alloy seamless cylinder, which is formed by a cylinder mouth side half cylinder 1 and a cylinder bottom side half cylinder 2 through seamless inertia friction welding;

[0047] The cylinder mouth side half cylinder 1 and the cylinder bottom side half cylinder 2 are both prepared by severe plastic deformation of an industrial extruded 6201 aluminum alloy cylinder at room temperature through a low temperature high pressure torsion device, and the shoulder or bottom curve of the cylinder is formed by layer-by-layer crystallization refinement of the metal under high pressure, and a uniform nanometer or sub-micron ultra-fine grain structure is formed in the material.

[0048] Through the combined process of severe plastic deformation and seamless inertia friction welding, an aluminum alloy seamless cylinder with high strength, high toughness and excellent corrosion resistance is manufactured, which meets the strict requirements of the electronic industry and high-purity gas fields for containers, and completely overcomes the technical problems such as "overall softening of the cylinder, scrap of the necking, and wrinkles on the inner surface" caused by the fast heat conduction of aluminum in the traditional heating and necking process, avoids defects such as pores and cracks that may be caused by fusion welding, and ensures the safety and long service life of the cylinder as a pressure container.

[0049] Through the severe plastic deformation of low temperature high pressure torsion, the grains are refined to nanometer or sub-micron level, the strength of the material is significantly improved, the tensile strength can reach 410 MPa, the yield strength can reach 375 MPa, which is much higher than that of traditional coarse-grained aluminum alloy, and the total elongation can reach 10%, which maintains good plasticity at high strength, avoids brittle fracture of the material, ensures the uniformity of grain refinement of the shoulder and bottom curve of the cylinder, avoids the organization defects caused by uneven temperature in the traditional process, makes the product performance more stable and reliable, the seamless inertia friction welding is completed in solid state, the metal fibers in the welding area are continuous, there is no fusion line, no need for complex machining after welding, simplifies the process flow, reduces the cost, avoids the generation of heat affected zone, reduces the waste caused by improper temperature control, and significantly improves the product yield.

[0050] The present application provides a manufacturing method of an aluminum alloy seamless cylinder, which comprises the following steps:

[0051] S1: preparing a cylinder mouth side half cylinder 1;

[0052] The industrial extruded 6201 aluminum alloy seamless aluminum pipe is selected, the seamless aluminum pipe is cut by mechanical processing, and then an initial conical shape of a local ring of a cylinder shoulder part is formed at one end of the pipe by turning processing, and a cylindrical blank, i.e., a cylinder blank 12, is prepared. The preforming treatment is beneficial to reducing the deformation amount and energy consumption of the subsequent high-pressure torsion process, and improving the material utilization rate and forming efficiency.

[0053] Preferably, the wall thickness is not less than 4 mm, and can be 6 mm, 8 mm, 10 mm, 12 mm, etc.

[0054] The obtained cylinder blank 12 is clamped in a 250-ton low-temperature high-pressure torsion device, which comprises a lower die 8, a rotating head 9, a top rod 10 and an extrusion ring 11. The cylinder blank 12 is arranged on the lower die 8, an axial pressure is applied by the rotating head 9, and the extrusion ring 11 synchronously applies a back pressure to form a three-way pressure stress state, and the top rod 10 is flush with the concave surface of the lower die 8 during processing, and is used to push out the cylinder port side half cylinder 1 after processing. The stress state can effectively inhibit the generation of cracks in the material during plastic deformation, and significantly improve the forming limit.

[0055] The device process parameters are set as follows: working pressure 5-7 GPa, rotating head 9 rotating speed 1-30 r / min, and processing temperature 22±2℃. The rotating head 9 simultaneously implements rotation and axial feeding motion under servo control, and applies severe shear deformation to the port part 102 of the cylinder blank 12. The room-temperature high-pressure torsion process avoids the problems of reduced cylinder strength and wrinkle stacking caused by high thermal conductivity of the aluminum alloy in the traditional hot closing, and the large shear strain is the key to realize grain refinement.

[0056] Preferably, the device process parameters are set as follows: working pressure 6 GPa, rotating head 9 rotating speed 10 r / min.

[0057] In the low-temperature high-pressure torsion device of the application, the rotating head 9 is the core power and execution component for realizing severe plastic deformation. It is not a general simple pressure head, but a composite motion device integrating rotation driving and precise axial feeding functions.

[0058] Specifically, the rotating head 9 has two independent servo motion control functions:

[0059] Axial rotation motion: driven by a servo motor or a hydraulic motor, the rotating head 9 can be controlled to rotate around the central axis at a rotating speed ranging from 1 r / min to 30 r / min. The rotation motion provides necessary shear deformation for the metal material in the mold channel, and is the key to realize grain refinement.

[0060] Axial lifting movement: Driven by servo hydraulic cylinder or precision screw mechanism, the rotating head 9 can realize accurate feeding in vertical direction. This function enables the rotating head 9 to advance layer by layer from bottom to top according to preset step, so as to drive the metal of the port part 102 of the aluminum alloy cylinder blank 12 to flow and crystallize under high pressure layer by layer, and finally form the required bottle shoulder curve.

[0061] The rotating head 9 is usually made of high-strength alloy steel or tool steel to withstand ultra-high working pressure of 5-7 GPa. Its lower end surface matches the mold cavity to ensure uniform pressure transmission. During work, the rotating head 9 cooperates with the extrusion ring 11 to realize step-by-step forming through axial feeding while applying main pressure, and cooperates with the back pressure process of the extrusion ring 11 to effectively control the metal flow direction and prevent material folding or defect generation.

[0062] Back pressure process refers to a key technology for controlling metal flow, improving deformation uniformity and improving product quality by applying an auxiliary pressure opposite to or lateral to the main forming pressure direction through the extrusion ring 11 during the low-temperature high-pressure torsion (ECAP) process.

[0063] In summary, the rotating head 9 is a special actuator with double servo motion functions of "rotation + axial feeding", and its design aims to realize layer-by-layer, isothermal and fine plastic forming of the aluminum alloy cylinder shoulder, which is the core hardware guarantee for realizing the "isothermal closing" process of the present application.

[0064] The rotating head 9 of the low-temperature high-pressure torsion device performs intermittent feeding movement in the axial direction, and the feeding direction is from bottom to top.

[0065] Specifically, the rotating head 9 first applies initial pressure to the 6201 aluminum alloy cylinder blank 12 placed in the mold and starts rotating, drives the metal material to flow violently in the mold cavity under the condition of working pressure of 5-7 GPa and rotating speed of 1-30 r / min. Then, the rotating head 9 performs first axial feeding upward, and after the feeding is completed, the pressure and rotating state are maintained, so that the metal of the port part 102 of the cylinder blank 12 is deformed plastically and realizes crystallization refinement of the first layer under the action of high pressure.

[0066] After the deformation of the layer is stable, the rotating head 9 feeds upward to the next position again to extrude and refine the metal of the second layer. The process is repeated, and the continuous and uniform forming of the bottle shoulder curve is realized through multiple layer-by-layer feeding.

[0067] Wherein, the step length of each feeding, i.e. the feeding amount, is set according to the wall thickness of the aluminum alloy cylinder blank 12, material properties such as flow stress, and the dimensional accuracy and microstructure performance requirements of the final product. In typical embodiments, the entire necking process can be completed in 3 or 5 feedings; for cases requiring higher forming accuracy or more uniform microstructure, more feeding strategies can also be used to achieve more fine-grained layer-by-layer crystallization refinement control.

[0068] The necking process is divided into several times, which can be calibrated according to process tests. For example, if the cylinder wall thickness is 5mm, such as three times of necking, through cylinder breaking and crystal phase analysis, it is found that the refined layer is 1mm thick, uniform and fine, and the two crystalline uniform and fine refined layers are not uniform and have more coarse and fragmented crystals. Further, the subsequent process file specifies that the necking process of this type of cylinder is divided into 5 times.

[0069] The feeding amount is usually less than or equal to the wall thickness of the cylinder, to ensure that the deformation of each step is effectively transmitted and uniform refinement is achieved. For example, if the cylinder wall thickness is 5mm, the feeding amount can be set to 1-2mm / step. The plastic flow ability of 6201 aluminum alloy at room temperature under high pressure determines the maximum safe amount of single feeding. Too large feeding amount may cause local stress concentration or cracking. Smaller feeding amount usually can obtain more uniform microstructure and better surface quality, but will reduce production efficiency. Larger feeding amount is on the contrary.

[0070] Through the above step-by-step, layer-by-layer press forming method, the uniform refinement of the metal microstructure in the bottle shoulder area is effectively ensured, and the material accumulation and surface wrinkles caused by traditional one-time necking are avoided, which significantly improves the product forming quality and yield.

[0071] After the above processing, the port portion 102 of the cylinder blank 12 undergoes layer-by-layer crystallization refinement, and after the grain recombination, a uniform equiaxed ultra-fine grain microstructure with an average grain size of about 100 nanometers is formed, and finally a bottle shoulder curve with a specified contour is formed. Figures 1 to 5 This layer-by-layer refinement method ensures the uniformity and density of the microstructure of the bottle shoulder part, eliminates internal defects, and the nanocrystalline microstructure is the fundamental reason for the ultra-high strength of the gas cylinder of the present application.

[0072] The port portion 102 of the half bottle 1 on the side of the gas cylinder is connected to an aluminum column 103 by seamless inertia friction welding to realize solid-phase connection.

[0073] In the specific welding process, the cylinder blank 12 and the aluminum column 103 are coaxially arranged under the positioning of the welding fixture, to ensure uniform stress and consistency of metal flow at the welding interface. After welding, a weld and a small amount of flash are formed at the connection area between the aluminum column 103 and the port portion 102.

[0074] Then, the aluminum column 103 is milled to process the end into the shape of the bottle mouth 104 according to the design requirements. Next, the flash produced on the outside of the aluminum column 103 and the port portion 102 due to inertial friction welding is turned by using a lathe, and a smooth transition fillet 106 is formed.

[0075] Preferably, the radius of the transition fillet 106 is 5 mm, which is designed to meet the structural strength requirements and facilitate uniform stress distribution to avoid stress concentration.

[0076] Finally, the inner wall of the bottle mouth 104 is turned to prepare a sealing thread 105 for mounting a valve or a plug, and the entire machining process of the gas bottle mouth 101 is completed.

[0077] Through the above process, the high-precision and high-strength integrated manufacturing of the bottle mouth structure is realized, and the sealing and safety of the gas cylinder in a high-pressure use environment are ensured.

[0078] Finally, the bottle mouth 104 is obtained, which meets the standard size, has a smooth shoulder surface, and has an ultra-fine grain structure.

[0079] Compared with the existing extrusion, the low-temperature high-pressure twisting device has a three-way stress state at room temperature, which effectively avoids the problems that the high thermal conductivity of aluminum is turned into a disadvantage, the strength of the cylinder is reduced after the end is heated, and the cylinder is easily stacked to cause waste during closing. 2 After closing, the inner surface wrinkles increase, and even overlap occurs, the temperature is difficult to control, and the operation is difficult, so the equipment requirements are high, which increases the manufacturing cost.

[0080] Compared with the low-temperature high-pressure twisting device of the prior art, the low-temperature high-pressure twisting device has a bottle shoulder or bottle bottom surface, and the thickness direction is realized layer by layer, so that the crystal is refined and uniform, and the aluminum gas bottle shoulder surface has the advantages of nanocrystalline uniformity. Other existing technologies are used in the processing process, which will not be described in detail here.

[0081] S2: Preparation of gas bottle bottom half bottle 2

[0082] Another low-temperature high-pressure twisting device with the same structure and process parameters is used, and an industrial extruded 6201 aluminum alloy cylinder blank 12 with the same material is used as the raw material, and a gas bottle bottom half bottle 2 with a layer-by-layer refined bottle bottom surface is prepared according to the S1 process. The symmetrical process ensures that the two half bottles are consistent in material, microstructure and mechanical properties, provides a basis for subsequent high-quality welding, and avoids performance mismatch in the joint area. The concave-convex of the rotating head 9 and the lower die 8 is opposite to the gas bottle mouth half bottle 1, and other technical means are prior art means.

[0083] Many cups need to be processed by extrusion die in industrial production. At present, the process of reverse extrusion and drawing is generally used for aluminum alloy seamless gas cylinder. The cup processed by conventional reverse extrusion die has a protrusion at the center of the bottom during the drawing process, and the height of the protrusion often exceeds the original base surface by 5-8 mm, which seriously affects the standing of the cup. In order to eliminate the protrusion at the bottom, the method of bottom pressing is generally adopted, that is, the protruding center of the bottom is pressed flat on the hydraulic machine, and then it is directly machined. Since the machining position is far away from the clamping position, tool chatter is easy to occur, affecting the machining efficiency and the machining precision, and more importantly, an additional processing procedure is added, which inevitably increases the occupation of equipment and human resources and the manufacturing cost. Other existing technologies are used in the processing process, which will not be described in detail here.

[0084] S3: seamless inertia friction welding

[0085] As shown in Figure 7 , the obtained two half cylinders are spliced into a whole cylinder by seamless inertia friction welding. Specifically, the side half cylinder 1 at the mouth of the cylinder is clamped by a stationary clamp 4, and the side half cylinder 2 at the bottom of the cylinder is clamped by an inertia rotating side clamp 3 and driven to rotate at a high speed. Before closing the mold, an inner disc 7 and an outer ring 5 are arranged at the butt joint interface, wherein the inner disc 7 is positioned by a support rod 6 and gap-fitted with the inner walls of the two half cylinders. The inner disc 7 and the outer ring 5 are made of high-purity silicon dioxide SiO2 material, and the upper limit of their temperature resistance is 1650°C. The quartz tooling has excellent high-temperature shape stability, can effectively constrain the metal flow in the welding zone, ensure uniform flash forming, and isolate air to prevent oxidation inclusions; the "gap-fitted" structure is not only convenient for assembly but also helps to center and position during the early stage of welding.

[0086] After preparation, the inertia rotating side clamp 3 is started to drive the side half cylinder 2 at the bottom of the cylinder to rotate, and at the same time, the side half cylinder 1 at the mouth of the cylinder is pushed forward to perform upset forging. The friction heat makes the metal at the contact surface reach a hot plastic state, and the upset forging force realizes metallurgical bonding. This solid-phase connection method avoids defects such as pores and cracks commonly seen in fusion welding, the grains are broken and rearranged along the flow lines during the welding process, forming continuous fiber organization, so that the strength of the welding zone reaches more than 90% of the base material, realizing the maximization of joint strength.

[0087] After welding, the inner disc 7 is excited by an ultrasonic steel rod, and the quartz vibration brittleness is broken into fragments, which are taken out through the cylinder mouth 104. This method realizes the efficient removal of the internal auxiliary tooling, and solves the industry common problem of difficult processing and cleaning of the sealed internal cavity of the cylinder.

[0088] Finally, the external flash is machined, and the cylinder mouth thread is precisely machined, to obtain a cylinder product with accurate size and complete appearance.

[0089] Compared with the existing welding technology, the seamless inertia friction welding does not need post-welding processing, and solves the problem of difficult processing of the middle part of the gas cylinder. The outside ring 5 and the inside disc 7 add temperature control structures such as glass fibers, which can effectively ensure that the seamless inertia friction welding of the aluminum alloy seamless gas cylinder combined with the surface metal forging fibers of the joint between the gas cylinder mouth side half cylinder 1 and the gas cylinder bottom side half cylinder 2 is continuous. During the top forging process of the seamless inertia friction welding, the aluminum alloy grains are broken and rearranged along the metal flow direction to form continuous fiber flow lines. This organizational structure makes the tensile strength of the material in the flow direction 30%-50% higher than the transverse direction, and the impact toughness is improved by about 20%-30%. For example, the yield strength and tensile strength of the forged 6061 aluminum alloy is usually 15%-30% higher than that of the cast state, and the fatigue strength is also significantly enhanced. Other existing technologies are used in the processing process, which will not be described in detail here.

[0090] S4: aging heat treatment

[0091] The complete gas cylinder after welding and machining is placed in an aging furnace for heat treatment, the aging temperature is 150-190℃, and the aging time is 45-70min. This treatment can promote the uniform precipitation of ultra-fine grain internal strengthening phases such as Mg2Si, further improve the strength, hardness and organizational stability of the gas cylinder, and optimize the comprehensive mechanical properties.

[0092] The process system is: 175℃ for 55 minutes, and air cooling after taking out of the furnace.

[0093] Performance test:

[0094] The following tests are carried out on the sample of the batch-produced gas cylinder:

[0095] Metallographic analysis: using transmission electron microscope TEM observation, the grain size of the bottle shoulder and the bottle bottom part is uniform, and is nanoscale;

[0096] Preferably, G2 F20 S-TWIN type transmission electron microscope is selected, for each sample, 15 TEM photos are taken, and the area method is used to estimate the grain size.

[0097] Mechanical properties: using digital Vickers hardness tester and universal testing machine for testing, the tensile strength is 410 MPa, the yield strength is 375 MPa, and the total elongation is 10%, which meets the requirements of high-pressure gas cylinder on strength and toughness;

[0098] Preferably, HVS-1000 type digital Vickers microhardness tester is selected to measure the microhardness.

[0099] Strain hardening capacity: showing a higher strain hardening index after yielding, continuously resisting deformation during the stretching process.

[0100] Corrosion resistance: after standard salt spray test, it shows excellent resistance to seawater corrosion, and no stress corrosion cracking tendency.

[0101] Chemical medium resistance: good resistance to alkaline medium, medium resistance to acidic medium. Other prior art is used in the process, which is not described in detail here.

[0102] In summary, the present application successfully prepares high-performance and high-yield aluminum alloy seamless gas cylinders by the innovative combination of low-temperature high-pressure torsion forming and seamless inertia friction welding, supplemented by special quartz tooling, effectively overcoming the shortcomings of the prior art. The tensile strength of the gas cylinder is not less than 400 MPa, the yield strength is not less than 370 MPa, and the total elongation is not less than 8%.

[0103] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A seamless aluminum alloy gas cylinder, characterized in that, The gas cylinder is formed by seamless inertial friction welding of the gas cylinder mouth half (1) and the gas cylinder bottom half (2); Among them, the gas cylinder mouth half-bottle (1) and the gas cylinder bottom half-bottle (2) are both made by subjecting the aluminum alloy cylinder to severe plastic deformation at room temperature using a low-temperature high-pressure torsion device. The bottle shoulder and / or the bottom curved surface are formed by the metal being crystallized and refined layer by layer under high pressure, and a uniform nano- or submicron-level ultrafine crystalline structure is formed inside the material. The specific processing steps are as follows: axial pressure is applied by the rotating head (9) of the low-temperature high-pressure torsion device, and back pressure is applied simultaneously by the extrusion ring (11) of the low-temperature high-pressure torsion device to form a triaxial compressive stress state. The rotating head (9) performs intermittent feeding motion along the axial direction, and its feeding direction is from bottom to top.

2. The seamless aluminum alloy gas cylinder according to claim 1, characterized in that, The gas cylinder has a tensile strength of not less than 400 MPa, a yield strength of not less than 370 MPa, and a total elongation of not less than 8%.

3. The seamless aluminum alloy gas cylinder according to claim 2, characterized in that, The gas cylinder undergoes aging treatment at a temperature of 150–190°C for 45–70 minutes.

4. A method for manufacturing a seamless aluminum alloy gas cylinder, characterized in that, The seamless aluminum alloy gas cylinder according to any one of claims 1-3 includes the following specific steps: S1: The aluminum alloy cylinder is plastically processed at room temperature using a low-temperature high-pressure torsion device. The metal is crystallized and refined layer by layer through the high-pressure torsion process to form a nano- or submicron-level ultrafine crystal structure, and a gas cylinder mouth side half bottle with a layer-by-layer crystallization and refined bottle shoulder is prepared (1). S2: Another low-temperature high-pressure torsion device is used to perform room temperature plastic processing on the aluminum alloy cylinder. The metal is crystallized and refined layer by layer through the high-pressure torsion process to form a nano- or submicron-level ultrafine crystal structure, and a gas cylinder bottom half bottle with a bottom formed by layer-by-layer crystallization is prepared (2). S3: The gas cylinder mouth half (1) and the gas cylinder bottom half (2) are welded into a complete gas cylinder by seamless inertial friction welding; S4: Aging treatment is performed on the welded complete gas cylinder to obtain the final product.

5. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 4, characterized in that, In steps S1 and S2, the low-temperature high-pressure torsion device is a 250-ton-class device, including a rotating head (9). The rotating head (9) of the low-temperature high-pressure torsion device has servo motion functions of axial rotation and axial lifting. The working pressure of the device is 5-7 GPa, the rotation speed of the rotating head (9) is 1-30 r / min, and the processing temperature is room temperature 20-24℃.

6. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 4, characterized in that, In step S3, an inner support structure and an outer ring structure are used during the welding process to maintain welding alignment and temperature control.

7. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 5, characterized in that, In steps S1 and S2, a compression ring (11) is also included, which has a lifting and lowering function to realize the back pressure process.

8. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 4, characterized in that, In steps S1 and S2, the lower end of the aluminum alloy cylinder is pre-machined to form the initial shape of the gas cylinder shoulder.

9. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 4, characterized in that, In step S3, the seamless inertial friction welding process uses an inner disk (7) and an outer ring (5) as auxiliary tooling. The inner disk (7) and the outer ring (5) are made of high-purity silicon dioxide (SiO2) with a maximum temperature resistance of 1650℃.

10. The method for manufacturing a seamless aluminum alloy gas cylinder according to claim 9, characterized in that, In step S3, after welding is completed, the inner disc (7) is broken by ultrasonic vibration and removed from the inside of the gas cylinder.

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