Titanium alloy seamless gas cylinder and manufacturing method thereof

Abstract

The present application belongs to the field of thin-walled titanium alloy product forging processing technology, and relates to a titanium alloy seamless gas cylinder and a manufacturing method thereof. The gas cylinder is formed by seamless inertia friction welding of an upper half gas cylinder and a lower half gas cylinder. The upper half gas cylinder and the lower half gas cylinder are both prepared by local and progressive two-way compression deformation of a TC4 titanium alloy cylinder blank through a step forging process. The bottle shoulder and the bottle opening curved surface are formed by layer-by-layer plastic flow of metal under two-way compression stress. The internal material structure is dense and free of daisy skin and wrinkle defects, and an equal wall thickness structure is realized from the bottle body to the bottle opening. The present application solves the problems of daisy skin, wrinkle and uneven wall thickness caused by the absence of internal support in the traditional spinning process by using the step forging process to perform overall plastic forming on the titanium alloy cylinder blank. At the same time, the destruction of the alpha + beta dual-phase structure of TC4 titanium alloy by high-temperature hot spinning is avoided, thereby greatly improving the forming precision, uniformity of the structure and comprehensive mechanical properties of the gas cylinder.

Description

TECHNICAL FIELD

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

[0002] In recent years, gas cylinders are widely used in the fields of aviation, aerospace, navigation and the like, and higher requirements are put forward for the weight, strength, toughness and the like of the gas cylinders. Titanium alloy becomes a new type of gas cylinder material due to the advantages of high strength, high elastic modulus, low density, high temperature resistance and the like. The manufacturing process of the existing titanium alloy gas cylinder is generally to respectively manufacture a cylinder body and a head through rough machining, to perform precise machining on the cylinder body and the head, and finally to manufacture the cylinder by adopting the method of electron beam assembly butt welding. The process method has the following disadvantages: the machining difficulty is large, the blank utilization rate is low, the production cycle is long, the manufacturing cost is high, there are multiple welds, defects are prone to occur at the welds, the quality control difficulty is large, and generally small-diameter titanium alloy gas cylinders are manufactured. The traditional spinning method is applied to the forming of the titanium alloy gas cylinder, and the head is prone to produce the phenomenon of chrysanthemum skin and wrinkles, thereby bringing safety hazards.

[0003] Titanium alloy is a high-quality high-strength structural steel. In the case of the same material yield strength, the same volume and the same pressure, the titanium alloy gas cylinder has only about 50% of the weight of the steel gas cylinder; the titanium alloy gas cylinder has good heat resistance and corrosion resistance, almost no corrosion occurs in the high-salt and hot-humid environment such as the ocean, the service life is long, and the maintenance cost is low; the titanium alloy gas cylinder has no magnetism, thereby reducing the magnetic field effect of the equipment and increasing the concealment of the ship equipment.

[0004] The α+β type titanium alloy contains a large amount of α phase stabilizing elements and β phase stabilizing elements, has α+β two-phase structures, and can obtain high strength and different metallographic forms and quantities through heat treatment. The titanium alloy includes TC4, TC6, TC11 and the like, and the TC4 is most widely applied and accounts for more than 50% of the number of titanium alloy applications.

[0005] However, the traditional TC4 titanium alloy high-pressure gas cylinder is formed by welding the head and the cylinder, has the defects of low weld strength and the like, affects the service life of the gas cylinder, and has a long processing cycle and a high processing cost. In order to ensure good fusion of the bottom, the traditional steel cylinder hot spinning bottom closing technology has a heating temperature of more than 1100 DEG C and performs oxygen-acetylene flame perforation on the center of the bottom. For the TC4 titanium alloy high-pressure gas cylinder, the material is prone to oxidation, the pipe material forming bottom closing is adopted, and oxidation defects are prone to occur at the center of the bottom, and the fusion quality is poor.

[0006] In order to ensure low forming resistance, the traditional steel cylinder hot spinning closing technology has a heating temperature of more than 1100 DEG C. For the TC4 titanium alloy high-pressure gas cylinder, the high-temperature spinning causes the transformation of the material organization, generates the β phase organization which cannot be reversed by heat treatment, and cannot guarantee the metallographic organization and performance of the α+β type titanium alloy.

[0007] Publication No.: CN108145000B A kind of titanium alloy thick-walled spherical shell isostatic pressing wall thickness homogenization method, by the friction coefficient of punch, the partition design of the plate to be formed, the temperature gradient is formed by respectively heating punch and pull ring, guarantee the wall thickness homogenization of titanium alloy thick-walled spherical shell, the ball bottom thinning rate is reduced from the conventional forming 50% to below 15%, the overall wall thickness fluctuation of shell body does not exceed 30% of blank wall thickness, and size is stable.But the scheme is used for using sheet metal to process spherical shell, it is not applicable to cylinder blank processing gas cylinder, cannot solve the problem that the surface wrinkle increases after closing, even overlapping when cylinder structure is forged.

[0008] Therefore, it is urgent to design a titanium alloy seamless gas cylinder and its manufacturing method to solve the problems of multiple welds, low strength, easy defects, high cost, low efficiency and poor surface quality of the existing titanium alloy gas cylinder. SUMMARY

[0009] Therefore, the present application aims to provide a titanium alloy seamless gas cylinder and its manufacturing method to solve the problems of multiple welds, low strength, easy defects, high cost, low efficiency and poor surface quality of the existing titanium alloy gas cylinder.

[0010] The spinning feature of the prior art is that the wall thickness gradually increases from the outer wall of the titanium pipe to the root of the bottle mouth, which is a spinning feature. Compared with the existing steel and titanium gas cylinder processing, the present application can achieve equal wall thickness. The existing spinning technology cannot achieve equal wall thickness because there is no support on the inside of the gas cylinder shoulder. The unique structure design of the present application, the stepping forging equipment of the present application compared with the existing spinning, the present application realizes the step-by-step integration and gradual change from one-way forging stress state, two-way forging stress state and two-way forging stress state, thus effectively avoiding the disadvantage of high thermal conductivity of titanium alloy. After heating the end, the heat is quickly transferred to the body, reducing the strength of the body and causing waste during closing. At the same time, the inner surface wrinkle after closing is avoided, even overlapping, the temperature is difficult to control, and the operation is difficult, thus the equipment requirements are high, which increases the manufacturing cost.

[0011] 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 and the inside disc are provided with temperature control structures such as glass fibers, which can effectively ensure the continuity of the surface metal forging fibers at the top forging joint in the seamless inertia friction welding. During the top forging process of the seamless inertia friction welding, the titanium alloy grains are broken and rearranged along the metal flow direction, forming continuous fiber flow lines. This organizational structure makes the tensile strength of the material in the flow direction (longitudinal direction) higher than that in the transverse direction, while the impact toughness is improved, and the fatigue strength is also significantly enhanced.

[0012] The seamless titanium alloy cylinder head produced by the step-forging equipment of this invention features a smooth, rounded transition, reducing stress concentration in the transition section and enhancing safety. The head is seamlessly connected to the cylinder body, overcoming the defects of seamed cylinders. Simultaneously, it ensures excellent forming of the titanium alloy cylinder head, preventing chrysanthemum skin and wrinkles from forming on the surface. This invention boasts a high degree of automation, stable process, and a near 100% yield, ensuring complete utilization of the raw material without waste. The cylinder shoulder and neck have clean, defect-free inner and outer surfaces.

[0013] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0014] One objective of this invention is to disclose a seamless titanium alloy gas cylinder, wherein the gas cylinder is formed by seamless inertial friction welding of an upper half and a lower half, both of which are integrally formed by step forging, and the gas cylinder as a whole has no fusion weld seams.

[0015] Furthermore, the upper half of the gas cylinder and / or the lower half of the gas cylinder is made of TC4 titanium alloy.

[0016] Furthermore, after the connection between the upper and lower half of the gas cylinder is seamlessly inertial friction welded, its metal flow lines continuously run through the entire gas cylinder body.

[0017] Furthermore, the wall thickness of the gas cylinder remains consistent from the cylinder body to the cylinder opening.

[0018] Another object of the present invention discloses a method for manufacturing a seamless titanium alloy gas cylinder, based on any of the aforementioned seamless titanium alloy gas cylinders, comprising the following specific steps:

[0019] S1: The upper half and lower half of the gas cylinder are manufactured separately using a step forging process;

[0020] S2: The upper half and lower half of the gas cylinder obtained in step S1 are seamlessly inertial friction welded to form a complete seamless titanium alloy gas cylinder.

[0021] Furthermore, in step S1, the step forging process specifically includes:

[0022] S11: Place the TC4 titanium alloy cylindrical blank in a device that includes a lower die, a core die, and a stepper shaft;

[0023] S12: Controls the cylindrical blank to have a temperature gradient that decreases from bottom to top;

[0024] S13: Through the coordinated action of the lower die, core die and stepper shaft, biaxial compressive stress is applied to a specific annular area at the lower end of the cylindrical blank to perform local plastic deformation;

[0025] S14: Gradually move the deformation area upwards until the overall forming of half of the gas cylinder is completed.

[0026] Furthermore, in step S2, seamless inertial friction welding specifically includes:

[0027] S21: Fix the lower half of the gas cylinder to the stationary clamp, and fix the upper half of the gas cylinder to the inertial rotation side clamp;

[0028] S22: Place an inner plate made of alumina ceramic between the mouths of the two half-bottles as an inner support;

[0029] S23: Start the inertial rotation side clamp to drive the upper half of the gas cylinder to rotate at high speed;

[0030] S24: The mouths of the two halves of the bottle come into contact and rub against each other under the upsetting pressure to generate heat until they reach a thermoplastic state;

[0031] S25: Stop rotating and continue applying forging force to solidify the two halves of the bottle together under high temperature and high pressure;

[0032] S26: Break and remove the inner disc.

[0033] Furthermore, the inner disc is removed by ultrasonic vibration.

[0034] Furthermore, a temperature control structure is provided in the inner disc and / or outer ring.

[0035] Furthermore, the forging temperature in the step forging process is 800℃~960℃.

[0036] Compared with the prior art, the seamless titanium alloy gas cylinder and its manufacturing method of the present invention have the following advantages:

[0037] 1. This invention employs a step forging process to perform localized, progressive biaxial compression deformation on TC4 titanium alloy cylindrical blanks within a temperature range of 800℃ to 960℃. This effectively achieves the integrated forming of the bottle body, bottle shoulder, and bottle mouth, significantly avoiding the problems of chrysanthemum skin, wrinkles, and uneven wall thickness caused by the lack of internal support in traditional spinning processes. At the same time, it ensures the stability of the α+β dual-phase structure of the material, thereby greatly improving the forming accuracy and structural reliability of the gas cylinder head.

[0038] 2. This invention combines step forging integral forming with seamless inertial friction welding technology, and uses an inner plate made of alumina ceramic material as a temporary internal support tooling during the welding process. This not only accurately maintains the geometric dimensions of the bottle mouth docking area and guides the continuous transition of metal flow lines, but also utilizes the high-temperature stability and vibration fragility of ceramic materials to achieve non-destructive cleaning after welding, significantly enhancing the metallurgical bonding quality of the welded joint and the mechanical integrity of the overall structure.

[0039] 3. This invention provides a high-precision, high-yield titanium alloy gas cylinder manufacturing method. By symmetrical design and independent forming of half cylinders, parallel production of key components is achieved. Combined with the servo control of special forging equipment and the reusable characteristics of tooling, it not only significantly shortens the production cycle, improves the degree of automation and material utilization, but also effectively reduces the processing scrap rate and overall manufacturing cost, and has outstanding industrialization promotion value. Attached Figure Description

[0040] 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:

[0041] Figure 1 This is an isometric view of the starting position of the step forging process in this invention.

[0042] Figure 2 This is an isometric view of the first step of forging before the start position of the step forging process in this invention.

[0043] Figure 3 For the present invention Figure 2 A magnified view of part A;

[0044] Figure 4 This is an isometric view of the first forging step at the starting position of the step forging process of the present invention.

[0045] Figure 5 This is an isometric view of the second forging step before the start of the step forging process in this invention.

[0046] Figure 6 For the present invention Figure 5 A magnified view of part B;

[0047] Figure 7 This is an isometric view of the second forging step after the starting position of the step forging process of the present invention.

[0048] Figure 8 This is an isometric view of the final forging step after the start position of the step forging process of the present invention.

[0049] Figure 9 This is a schematic diagram of the gas cylinder part of the present invention;

[0050] Figure 10 This is a schematic diagram of the seamless inertial friction welding of the present invention;

[0051] Figure 11 For the present invention Figure 10 A magnified view of a portion of C;

[0052] Figure 12 This is a schematic diagram of the gas cylinder opening structure of the present invention;

[0053] Figure 13 For the present invention Figure 12 A magnified view of a portion of the image.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1. Lower half of the gas cylinder; 101. Cylinder body; 102. Cylinder shoulder; 103. Cylinder mouth; 104. Cylinder; 105. Sealing groove; 106. Sealing thread; 107. Circumferential weld; 2. Upper half of the gas cylinder; 3. Inertial rotation side clamp; 4. Stationary clamp; 5. Outer ring; 6. Support rod; 7. Inner disc; 8. Cylindrical blank; 9. Lower mold; 10. Heater; 11. Core mold; 12. Stepping shaft; 13. First cutting ring; 14. Second cutting ring; 15. Third cutting ring. Detailed Implementation

[0056] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0057] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0058] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] like Figures 1-13 As shown, the present invention provides a seamless titanium alloy gas cylinder, which is formed by seamless inertial friction welding of an upper half gas cylinder 2 and a lower half gas cylinder 1.

[0061] The upper half of the gas cylinder 2 and the lower half of the gas cylinder 1 are both made by locally and progressively compressing and deforming the TC4 titanium alloy cylindrical blank 8 through a step forging process. The curved surfaces of the cylinder shoulder 102 and the cylinder mouth 103 are formed by the layer-by-layer plastic flow of metal under biaxial compressive stress. The internal structure of the material is dense and free of defects such as chrysanthemum skin and wrinkles, thus achieving a uniform wall thickness structure from the cylinder body 101 to the cylinder mouth 103.

[0062] By combining step forging integral forming with seamless inertial friction welding, a seamless titanium alloy gas cylinder with high strength, high toughness, and excellent fatigue resistance is manufactured. This meets the stringent requirements of aerospace, deep-sea exploration and other fields for lightweight high-pressure vessels. It completely overcomes the technical problems of "chrysanthemum skin, wrinkles, and uneven wall thickness" caused by the lack of internal support in the traditional spinning process and "α+β structure destruction" caused by hot spinning. It also avoids defects such as porosity and cracks that may be generated by electron beam fusion welding, ensuring the safety and long service life of the gas cylinder as a pressure vessel.

[0063] This setup, through biaxial stress forming via step forging, effectively suppresses the material's cracking tendency and significantly improves the forming limit of TC4 titanium alloy. It enables the integral plastic forming of complex shapes within a controllable temperature range of 800℃ to 960℃, ensuring good plasticity while avoiding irreversible β-phase transformation caused by high temperatures (>1000℃), thus maintaining the material's original excellent metallographic structure and comprehensive mechanical properties. Seamless inertial friction welding is completed in the solid state, with the metal fibers in the welding zone continuously running through the entire bottle body. There are no fusion lines or heat-affected zones, eliminating the need for complex post-weld machining, simplifying the process, reducing costs, avoiding scrap due to improper temperature control, and significantly improving product yield.

[0064] This invention provides a method for manufacturing a seamless titanium alloy gas cylinder, comprising the following steps:

[0065] S1: Prepare the lower half of gas cylinder 1;

[0066] TC4 titanium alloy seamless steel pipe is selected and machined into cylindrical blanks 8, which are then vertically clamped in a dedicated walking beam forging machine. This machine includes a lower die 9, a heater 10, a core die 11, and a walking beam 12. The blank 8 is placed on the lower die 9, and its upper end is clamped by the walking beam 12. The walking beam 12 has one servo motion for axial lifting, and the core die 11 also has one servo motion for axial lifting. The lower die 9 has the external shape of the gas cylinder shoulder, and the core die 11 has the internal shape of the gas cylinder shoulder.

[0067] A temperature control structure is provided between the heater 10 and the mandrel 11. When the heater 10 is activated, the billet 8 is heated, and its temperature field is controlled to exhibit a decreasing temperature gradient distribution from bottom to top, with a decreasing temperature gradient characteristic from large deformation to small deformation. This ensures that the forging temperature is stable between 800℃ and 960℃. This temperature range ensures that the TC4 titanium alloy has sufficient plasticity for large deformation while preventing irreversible microstructural degradation.

[0068] like Figures 1 to 8 As shown, the step forging process is carried out in steps:

[0069] Phase 1 ( Figures 2-4 The transition point between the core mold 11 and the bottle shoulder 102 is defined as the first cutting ring 13. The lower end of the cylindrical blank 8 undergoes localized deformation from the first cutting ring 13 downwards in a localized ring shape, and from the first cutting ring 13 upwards, the localized cylindrical blank 8 mates with the outer cylindrical part of the core mold 11. At this time, only the localized annular region below the first cutting ring 13 participates in deformation. Under the synergistic action of the lower mold 9, the core mold 11, and the stepping shaft 12, biaxial compressive stress is applied to this region, achieving localized plastic deformation and gradually conforming it to the surfaces of the lower mold 9 and the core mold 11.

[0070] Phase Two and Subsequent ( Figures 5-7 The deformation area is moved upwards, and the inner cylindrical surface and shoulder surface of the gas cylinder in the core mold 11 switch to the second tangential ring 14, while the outer cylindrical surface and shoulder surface of the gas cylinder in the lower mold 9 switch to the third tangential ring 15. The above biaxial pressing process is repeated to plastically deform the new local annular region.

[0071] The lower end of the cylindrical blank 8 only undergoes local deformation from the second cutting ring 14 downwards, and is divided into a cylindrical section and a section where the first deformation is completed. The lower end of the cylindrical blank 8 only experiences local deformation from the second cutting ring 14 downwards, and shows a trend of increasing forging strain and deformation from top to bottom. The lower end of the cylindrical blank 8, from the second cutting ring 14 upwards, partially mates with the outer cylindrical part of the mandrel 11.

[0072] The lower end of the cylindrical blank 8 is partially suspended only from the third cutting ring 15 downwards. The lower end of the cylindrical blank 8 exhibits localized deformation from the third cutting ring 15 downwards, with a tendency for forging strain and deformation to increase from top to bottom. The lower end of the cylindrical blank 8 partially mates with the outer cylindrical part of the lower die 9 from the third cutting ring 15 upwards. The cylindrical blank 8 also undergoes localized deformation from the third cutting ring 15 upwards, with a tendency for forging strain and deformation to increase from top to bottom.

[0073] like Figure 7 The diagram shows an isometric view of the second forging step after the start of the step forging process. The lower end of the billet 8 is only partially formed downwards from the second cutting ring 14, and is gradually completed upwards from the outer side of the lower end of the billet 8.

[0074] Final stage ( Figure 8 The deformation area is gradually moved upwards until the entire shoulder 102 and neck 103 are formed. Ultimately, the shoulder of the cylindrical blank 8 is partially forged into the lower half of the gas cylinder 1, which includes the body 101, shoulder 102, and neck 103, with uniform wall thickness and a smooth, defect-free surface. Other existing technologies were used in the processing, which will not be described in detail here.

[0075] S2: Prepare the upper half of gas cylinder 2;

[0076] like Figure 9 As shown, another walking beam forging machine with the same structure was used, and TC4 titanium alloy cylindrical blanks of the same material were used as raw materials to prepare the upper half of the gas cylinder 2 according to the process described in S1. This symmetrical process ensures that the two half-cylinders are highly consistent in terms of material, microstructure, and mechanical properties, providing a foundation for subsequent high-quality welding and avoiding performance mismatch in the joint area. Other existing technologies were used in the processing, which will not be described in detail here.

[0077] S3: Seamless inertial friction welding;

[0078] like Figure 10 and Figure 11 As shown, the two halves of the cylinder are joined together as a single gas cylinder using seamless inertial friction welding. Specifically, the process includes: holding the lower half of the gas cylinder 1 with a stationary clamp 4, and holding the upper half of the gas cylinder 2 with an inertial rotating side clamp 3 and driving it to rotate at high speed. Before mold closing, an inner disc 7 and an outer ring 5 are installed at the mating interface. The inner disc 7 is positioned by a support rod 6 and has a clearance fit with the inner walls of the two half-cylinders. Both the inner disc 7 and the outer ring 5 are made of high-purity alumina ceramic Al2O3, with a maximum temperature resistance of over 1800℃. This ceramic tooling exhibits excellent high-temperature morphological stability, effectively constraining metal flow in the welding area, ensuring uniform flash formation, and isolating air to prevent oxidation inclusions. The "clearance fit" structure facilitates assembly and aids in initial alignment during welding.

[0079] Once ready, the inertial rotating side clamp 3 is activated, causing the upper half of the gas cylinder 2 to rotate while simultaneously advancing towards the stationary lower half of the gas cylinder 1 to perform upsetting. Frictional heat brings the metal at the contact surface to a thermoplastic state, and under the action of upsetting force, metallurgical bonding is achieved. This solid-state joining method avoids defects such as porosity and cracks common in fusion welding. During the welding process, the grains break down and rearrange along the flow lines, forming continuous metal fiber flow lines, making the strength of the weld zone superior to that of the base material, thus maximizing the joint strength.

[0080] After welding, the inner disc 7 is excited by ultrasonic waves, which utilizes the vibrational brittleness of the alumina ceramic to break it into fragments, which are then removed through the bottle opening 103. This method achieves efficient and non-destructive removal of internal auxiliary tooling, solving the common industry problem of difficult processing and cleaning of the sealed inner cavity of gas cylinders.

[0081] Finally, the external flash is machined and the 103 thread on the bottle neck is precision machined to obtain a gas cylinder with accurate dimensions and a complete appearance.

[0082] like Figures 12-13 As shown, after steps S2 and S3, the final processing and assembly of the bottle neck 103 is added. A cylinder 104 of suitable size is selected, with its outer diameter slightly larger than the inner diameter of the bottle neck 103 to achieve an interference fit. The cylinder 104 is pressed into the bottle neck 103, ensuring that the end face of the cylinder 104 is higher than the end face of the bottle neck 103, forming a raised structure to facilitate the connection between the cylinder 104 and the bottle neck 103. Argon arc welding is used to weld the cylinder 104 and the bottle neck 103 to form a circumferential weld 107. During the argon arc welding process, high-purity argon gas is used as the protective gas to avoid oxidation in the welding area and ensure weld quality. After welding, the quality of the circumferential weld 107 is checked to ensure there are no defects such as porosity or cracks, and to guarantee welding strength and sealing performance. A milling machine is used to finish the end face of the welded bottle neck 103, removing excess weld material and smoothing the surface. A tight groove 105 is machined on the end face of the cylinder 104. This groove 105 enhances the sealing effect and is typically designed to be circular or square; the specific shape and size can be adjusted according to actual needs. A hole is drilled at the center of the cylinder 104, and a sealing thread 106 is machined into the inner wall of the hole. This thread is used to connect external equipment or interfaces, ensuring the sealing and stability of the connection. When machining the sealing thread 106, the thread precision must be strictly controlled according to the design drawings to ensure a tight fit with the mating components and prevent leakage.

[0083] Through the above steps, the final processing and assembly of bottle neck 103 were completed. The specific steps are as follows:

[0084] Step 1: Prepare a cylinder 104, whose outer diameter is slightly larger than the inner diameter of the bottle mouth 103 to achieve an interference fit. Press the cylinder 104 into the bottle mouth 103, ensuring that the end face of the cylinder 104 is higher than the end face of the bottle mouth 103, forming a raised structure.

[0085] Step 2: Use argon arc welding to weld the cylinder 104 to the bottle neck 103 to form a circumferential weld 107. High-purity argon gas is used for protection during the welding process to ensure that the weld is free of oxidation and defects such as porosity and cracks.

[0086] Step 3: Use a milling machine to finish the end face of the welded bottle mouth 103, removing excess weld material and smoothing the surface. Then, machine a tight groove 105 on the end face of the cylinder 104 to enhance the sealing effect.

[0087] Step 4: Drill a hole at the center of cylinder 104 and machine a sealing thread 106 on the inner wall of the hole. Ensure that the thread accuracy meets the design requirements to guarantee the sealing and stability of the connection.

[0088] Through the above steps, a highly efficient seal and reliable connection are achieved at the bottle neck 103, meeting the stringent requirements for seamless titanium alloy gas cylinders used in high-pressure environments. This design not only improves the overall sealing performance of the gas cylinder but also simplifies subsequent installation and maintenance, demonstrating significant technical advantages and practical value.

[0089] S4: Heat treatment and performance testing;

[0090] The welded and machined complete gas cylinder is placed in a vacuum furnace for stress-relief annealing at a temperature of 650±10℃ for 2 hours, followed by furnace cooling. This treatment eliminates residual stress, stabilizes the microstructure, and improves the dimensional stability and long-term service reliability of the gas cylinder.

[0091] Other existing technologies were used in the processing, which will not be described in detail here.

[0092] Performance testing:

[0093] The following inspections are performed on samples of mass-produced gas cylinders:

[0094] Metallographic analysis: Observation with optical microscope and scanning electron microscope showed that the microstructure of the bottle shoulder 102, bottle mouth 103 and welding area were all uniform equiaxed α+β dual phase microstructure, without coarse grains or abnormal phases.

[0095] Mechanical properties: Tested using a universal testing machine, the yield strength was ≥930 MPa, the tensile strength was ≥1000 MPa, and the elongation was ≥10%, meeting the requirements for ultra-high strength pressure vessels;

[0096] Non-destructive testing: 100% ultrasonic and X-ray testing are performed to confirm that there are no internal defects in the bottle body and welding areas;

[0097] Hydrostatic test: A hydrostatic burst test was conducted according to standards. The burst pressure was far higher than the design pressure, and the rupture location was not in the welded area, verifying the overall safety and reliability of the gas cylinder. Other existing technologies were used in the manufacturing process, which will not be described in detail here.

[0098] In summary, this invention, through the innovative combination of two core processes—step forging integral forming and seamless inertial friction welding—and supplemented by specially designed ceramic internal support tooling, successfully produces high-performance, high-yield seamless titanium alloy gas cylinders, effectively overcoming the shortcomings of existing technologies. The gas cylinders have a yield strength of not less than 930 MPa, a tensile strength of not less than 1000 MPa, and an elongation of not less than 10%.

[0099] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A titanium alloy seamless gas cylinder, characterized by, The gas cylinder is formed by seamless inertia friction welding of the upper half gas cylinder (2) and the lower half gas cylinder (1), the upper half gas cylinder (2) and the lower half gas cylinder (1) are integrally formed by step forging process, and the gas cylinder as a whole has no fusion welding seam. The step forging process specifically comprises: S11: placing the TC4 titanium alloy cylinder blank (8) in an equipment comprising a lower die (9), a core die (11) and a step shaft (12); S12: controlling the cylinder blank (8) to have a temperature gradient decreasing from bottom to top; S13: through the synergistic effect of the lower die (9), the core die (11) and the step shaft (12), a biaxial compressive stress is applied to a specific annular area at the lower end of the cylinder blank (8) to perform local plastic deformation; S14: the step shaft clamps and controls the cylinder blank to gradually move downward, so that the deformation area of the cylinder blank gradually moves upward until the shoulder forming of the half gas cylinder is completed.

2. The titanium alloy seamless gas cylinder of claim 1, wherein, The material of the upper half gas cylinder (2) and / or the lower half gas cylinder (1) is TC4 titanium alloy.

3. The titanium alloy seamless gas cylinder of claim 2, wherein, After the connection between the upper half gas cylinder (2) and the lower half gas cylinder (1) is welded by seamless inertia friction welding, the metal flow line is continuous throughout the gas cylinder body.

4. The titanium alloy seamless gas cylinder of claim 2, wherein, The wall thickness of the gas cylinder remains consistent from the body (101) to the mouth (103).

5. A method of manufacturing a seamless titanium alloy gas cylinder, characterized by, The titanium alloy seamless gas cylinder according to any one of claims 1-4 comprises the following specific steps: S1: preparing the upper half gas cylinder (2) and the lower half gas cylinder (1) by step forging process respectively; S2: performing seamless inertia friction welding on the upper half gas cylinder (2) and the lower half gas cylinder (1) obtained in step S1 to form a complete titanium alloy seamless gas cylinder.

6. The method of manufacturing a titanium alloy seamless gas cylinder according to claim 5, characterized by, In step S2, the seamless inertia friction welding specifically comprises: S21: fixing the lower half gas cylinder (1) to a stationary clamp (4) and fixing the upper half gas cylinder (2) to an inertia rotating side clamp (3); S22: placing an inner side disc (7) made of alumina ceramic as an inner support between the mouths (103) of the two half cylinders; S23: starting the inertia rotating side clamp (3) to drive the upper half gas cylinder (2) to rotate at high speed; S24: making the mouths (103) of the two half cylinders contact and frictionally generate heat to a hot plastic state under the application of a top forging force pressure and high speed rotation; S25: stopping the rotation and continuing to apply the top forging force to make the two half cylinders combine in a solid phase under high temperature and high pressure; S26: breaking and removing the inner side disc (7).

7. The method of manufacturing a titanium alloy seamless gas cylinder according to claim 6, characterized by, The inner side disc (7) is removed after being broken by ultrasonic waves.

8. The method of manufacturing a titanium alloy seamless gas cylinder according to claim 7, characterized by, The inner side disc (7) and / or the outer side ring (5) are provided with a temperature control structure.

9. The method of manufacturing a titanium alloy seamless gas cylinder according to claim 5, characterized by, The forging temperature in the step forging process is 800-960℃.

Images