TA15 titanium alloy pressure-resistant shell and preparation method thereof

Abstract

The application discloses a TA15 titanium alloy pressure-resistant shell and a preparation method thereof, and belongs to the technical field of manufacturing. The technical scheme of the application comprises the processing of a head forging and a cylinder forging, and steps such as assembly welding. The application adopts TA15 titanium alloy, and compared with common titanium alloy materials such as industrial pure titanium and TC4, the TA15 titanium alloy has higher strength, thermal stability, high-temperature performance, welding performance and corrosion resistance. Through steps such as die forging, machining and heat treatment, the internal organization of the forging is uniform, the grain is refined, the overall performance is improved, the welding defects caused by the welding of the curled high-strength plate are avoided, the process flow is simple, the operation difficulty is low, the production flow is short, the material yield is high, the strength of the prepared pressure-resistant shell can reach more than 970 MPa, which is better than 930 MPa of the raw material, the shell thickness is reduced while the high strength is maintained, and the pressure-resistant strength is excellent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of titanium alloy machining, and particularly relates to a TA15 titanium alloy pressure-resistant shell and a preparation method thereof, and mainly applies to the machining of pressure-resistant shells. BACKGROUND

[0002] Titanium alloy is widely used in the fields of aviation, aerospace, navigation, petroleum, chemical industry, medical treatment and the like due to its high specific strength, low density, corrosion resistance and high temperature resistance. In the past, high-pressure cylinders and some pressure-resistant shells in the fields of aerospace and navigation were made of steel. With the increasing requirements for product life and service stability, weight reduction and improvement of corrosion resistance have become the development direction of the cylinders and pressure-resistant shells, and titanium alloy with high specific strength and excellent corrosion resistance has become the first choice of materials.

[0003] At present, the titanium alloy cylinder needs to be welded due to its special structure, and the main titanium alloy materials used at present are industrial pure titanium or TC4. However, the strength of these two materials is low, and the thickness of the shell needs to be increased to increase the carrying capacity in the design. Increasing the thickness of the shell will increase the amount of raw materials, and the clamping and positioning of the thick wall in the machining process are more prone to deviation, and the thick wall welding is more prone to weld defects such as cracks and slag, thereby affecting the strength and sealing performance of the cylinder. The heat conduction and temperature distribution in the thick wall shell are more uneven, and the heat treatment process is complex. At the same time, the increase of the thickness of the shell will lead to the increase of the overall weight of the cylinder, which will affect the fuel efficiency or load capacity of the machine equipment in the fields of aviation, aerospace and automobile, and reduce the flexibility in the use process.

[0004] At the same time, due to the high strength of TA15 titanium alloy, the method of crimping and then axial welding commonly used for industrial pure titanium or TC4 is difficult to be applied to the preparation of pressure-resistant shells, because the weld is prone to internal stress and defects. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a TA15 titanium alloy pressure-resistant shell and a preparation method thereof, which realizes the lightweight of the pressure-resistant shell while still having good overall structural strength.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] The first purpose of the present application is to provide a preparation method of a TA15 titanium alloy pressure-resistant shell, comprising the following steps:

[0008] Head forging processing: After die forging of titanium alloy bar billet, head forging blank is obtained. The head forging blank is then subjected to rough machining, first heat treatment, semi-finishing, second heat treatment and finish machining in sequence to obtain head forging.

[0009] Cylindrical forging processing: The heated titanium alloy bar billet is forward extruded to obtain a cylindrical billet. The cylindrical billet is then subjected to rough machining, third heat treatment, semi-finishing, fourth heat treatment, and finishing to obtain the cylindrical forging.

[0010] Assembly and welding: The two end caps are respectively installed at the openings at both ends of the cylindrical forging and axially tightened to obtain the shell assembly; the shell assembly is circumferentially welded, cleaned, inspected and then heat-treated to obtain the TA15 titanium alloy pressure shell;

[0011] The titanium alloy billet is made of TA15 titanium alloy.

[0012] As one of the inventive points of this invention, the TA15 titanium alloy selected in this invention has higher strength, better thermal stability and high-temperature performance, better weldability and excellent corrosion resistance compared to the industrial pure titanium or TC4 commonly used in the prior art. However, the TA15 titanium alloy itself has higher strength, making it more difficult to machine than the industrial pure titanium or TC4 used in the prior art. In the process of preparing the head forging and the cylinder forging, the present invention, after die forging, rough machining and heat treatment make the internal structure of the forging more uniform, the grains refined, residual stress eliminated, the metal structure and mechanical properties improved, and the overall performance of the forging improved. After semi-finishing, the internal metal structure of the forging is further improved, and then heat treatment is performed to improve the strength of the alloy and improve the pressure resistance of the shell.

[0013] Preferably, in the head forging processing steps, the first heat treatment temperature is 20°C to 30°C below the phase transformation point of the titanium alloy billet, held for 30 min to 60 min, and then air-cooled; the second heat treatment temperature is 700°C to 750°C, held for 30 min to 60 min, and then air-cooled.

[0014] Preferably, in the head forging processing steps, the rough machining leaves a machining allowance of 5mm on one side compared to the finished product, the semi-finishing machining leaves a machining allowance of 2mm on one side compared to the finished product, and the finishing machining involves machining a positioning boss at the welding end of the head forging.

[0015] Preferably, in the cylindrical forging process, the titanium alloy billet is heated to 20°C~30°C below the phase transformation point and then subjected to forward extrusion.

[0016] Preferably, in the cylindrical forging process, the heated titanium alloy billet is subjected to forward extrusion, with a machining allowance of 7mm to 10mm per side compared to the finished product.

[0017] Preferably, in the cylinder forging process, a 5mm machining allowance is reserved on one side during rough machining of the cylinder blank, a 2mm machining allowance is reserved on one side during semi-finishing compared to the finished product, and positioning recesses are machined at both ends of the cylinder during finish machining.

[0018] Preferably, in the assembly and welding step, the welding area between the head forging and the cylinder forging is polished to remove the oxide layer in the welding area.

[0019] Preferably, in the assembly and welding step, electron beam welding is used for circumferential welding, and the welding process parameters are: high voltage 85kV~100kV; focusing 900mA~1000mA; beam current 10mA~20mA; linear velocity 500 mm / min~1200mm / min; vacuum degree ≤1×10 -3 Pa.

[0020] Preferably, in the assembly and welding step, the welded shell assembly is subjected to stress-relief annealing heat treatment. The heat treatment parameters for stress-relief annealing are: holding at 600℃~650℃ for 30 min~60 min, followed by air cooling.

[0021] The second objective of this invention is to disclose the pressure-resistant shell prepared by the above-mentioned method for preparing the TA15 titanium alloy pressure-resistant shell.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses a method for preparing a pressure-resistant shell from TA15 titanium alloy. TA15 titanium alloy is used as the raw material. The head forging is prepared by die forging, and the cylindrical forging is prepared by forward extrusion of titanium alloy. This avoids the problems of internal stress and gaps that easily occur in the weld seams of the pressure-resistant shell when using high-strength TA15 titanium alloy plates for rolling and welding. Furthermore, in the preparation of the head and cylindrical forgings, rough machining after die forging makes the internal structure of the forgings more uniform, refines the grains, eliminates residual stress, improves the metal structure and mechanical properties, and enhances the overall performance of the forgings. Semi-finishing further improves the internal metal structure of the forgings, followed by heat treatment to increase the alloy's strength and pressure resistance. The process proposed in this invention is simple, easy to operate, has a short production cycle, and a high yield. The prepared TA15 titanium alloy pressure-resistant shell has a higher strength than the national standard TA15 titanium alloy billet of 930 MPa, reaching 970 MPa, demonstrating excellent pressure resistance. Attached Figure Description

[0024] Appendix Figure 1 This is a schematic diagram illustrating the fabrication of the shell according to the present invention;

[0025] Figure 2 This is a flowchart of the method of the present invention;

[0026] Among them: 1-1 head forging; 1-2 head forging; 2 cylinder forging; 3-1 weld; 3-2 weld. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] Please see the appendix Figure 1 This is a schematic diagram of the preparation of the shell according to the present invention, which is made from the attached... Figure 2 The illustrated process is prepared by, specifically including the following steps:

[0031] 1. Head forging

[0032] First, the TA15 titanium alloy billet is heated and then placed in a mold to obtain a titanium alloy head pre-forging by die forging.

[0033] Then, rough machining of the head is performed. The TA15 titanium alloy head forging is rough machined with a 5mm machining allowance on one side compared to the finished product.

[0034] Next, heat treatment is performed on the head forgings obtained from rough machining. The heat treatment temperature is 20~30℃ below the phase transformation point, and the temperature is held for 30~60 minutes, followed by air cooling.

[0035] Then, semi-finishing is performed. The rough-machined TA15 titanium alloy part is left with a 2mm machining allowance on one side compared to the finished product, and then semi-finished.

[0036] Next, a second heat treatment is performed on the semi-finished TA15 titanium alloy end caps. The heat treatment temperature is 700~750℃, held for 30~60 minutes, and then air-cooled.

[0037] Finally, the TA15 titanium alloy head is precision machined, and a positioning boss is machined at the welded end.

[0038] 2. Cylinder forging

[0039] First, the cylinder is extruded: After heating, the TA15 titanium alloy billet is placed in the extruder and extruded in the forward direction to obtain the titanium alloy cylinder blank; the temperature of the TA15 titanium alloy billet during extrusion is 20~30℃ below the phase transformation point; the size of the blank after extrusion is 7~10mm machining allowance on one side compared to the finished product.

[0040] Next, rough machining of the cylinder body is carried out, and a 5mm machining allowance is reserved on one side of the TA15 titanium alloy cylinder body blank compared with the finished product.

[0041] Then the rough-machined cylindrical blank is heat-treated;

[0042] Next, the rough-machined TA15 titanium alloy cylinder part is left with a 2mm machining allowance on one side compared to the finished product, and then semi-finished.

[0043] Then, the semi-finished TA15 titanium alloy cylindrical part is heat-treated.

[0044] Finally, the TA15 titanium alloy cylinder is precision machined, and positioning recesses are machined at both ends of the cylinder.

[0045] 3. Fabrication of welding test pieces

[0046] Using the cylindrical blank prepared by the same heat treatment as described above, two 100mm long welding test pieces with the same outer diameter and thickness as the cylindrical blank were machined.

[0047] 4. Shell assembly and welding

[0048] First, use a metal grinding head to polish the surface of the welded end of the end cap and within 20mm of both ends of the cylinder to clean the oxide layer. Then, use acetone to clean the polished area.

[0049] Next, the two head forgings and one cylinder forging are combined, and the three parts are axially tightened using tooling to complete the assembly of the shell forging;

[0050] Then, the assembled shell assembly and the welding test piece were subjected to circumferential welding using electron beam welding: Welding process parameters:

[0051] High voltage: 85KV~100KV

[0052] Focus: 900mA~1000mA

[0053] Beam current: 10~20mA

[0054] Linear velocity: 500~1200 mm / min

[0055] Vacuum degree: ≤1×10 -3 Pa

[0056] After welding is completed, a metal grinding head is used to clean the spatter and weld excess of weld seams 3-1 and 3-2.

[0057] After cleaning, the shell shall be subjected to radiographic inspection, and the welds shall be inspected in accordance with GJB1718A-2005. The welds shall meet the requirements of Class I welds.

[0058] The shell that meets the standard is subjected to stress-relief annealing. The overall components and welded test pieces are subjected to stress-relief annealing in a vacuum heat treatment furnace. The stress-relief annealing regime is: 600~650℃ for 30~60min, followed by air cooling.

[0059] For welding tests, 10mm wide plate-shaped tensile specimens were cut and subjected to tensile tests.

[0060] Pressure testing method: water pressure test.

[0061] The following detailed description is provided in conjunction with specific examples.

[0062] Example 1

[0063] As attached Figure 1 Based on the structure, a TA15 pressure-resistant shell with an outer diameter of φ280mm, a cylindrical body thickness of 1.8mm, and a length of 1200mm was prepared. The specific steps are as follows:

[0064] 1. Head forging

[0065] After heating the TA15 titanium alloy billet, it is placed in a mold and die forged to obtain titanium alloy head forgings 1-1 and 1-2.

[0066] For TA15 titanium alloy head forgings 1-1 and 1-2, leave a 5mm machining allowance on each side compared to the finished product and perform rough machining.

[0067] The head forgings 1-1 and 1-2 obtained by rough machining were subjected to heat treatment with the following parameters: heat treatment at 20℃ below the phase transformation point for 30 min, followed by air cooling.

[0068] For the rough-machined TA15 titanium alloy head forgings 1-1 and 1-2, leave a 2mm machining allowance on each side compared to the finished product and perform semi-finishing.

[0069] The semi-finished TA15 titanium alloy end cap forgings 1-1 and 1-2 were subjected to heat treatment. The heat treatment regime was 700℃ for 30 min followed by air cooling.

[0070] The semi-finished TA15 titanium alloy end cap forgings 1-1 and 1-2 are precision machined, and a positioning boss is machined at the welding end.

[0071] 2. Cylinder forging

[0072] First, the TA15 titanium alloy billet is heated and then placed into an extruder. The titanium alloy cylindrical blank is obtained by forward extrusion using the extruder. The extrusion temperature is 20°C below the phase transformation point. The dimensions of the extruded blank are φ300×φ260×L.

[0073] Leave a 5mm machining allowance on one side of the TA15 titanium alloy cylinder blank compared to the finished product, and perform rough machining;

[0074] The rough-machined cylindrical blank is then heat-treated.

[0075] Leave a 2mm machining allowance on one side of the rough-machined TA15 titanium alloy cylinder compared to the finished product, perform semi-finishing, and then continue heat treatment.

[0076] Heat treatment is performed on the semi-finished TA15 titanium alloy cylindrical part.

[0077] The TA15 titanium alloy cylinder is precision machined, and positioning recesses are machined at both ends of the cylinder to obtain cylinder forging 3.

[0078] 3. Fabrication of welding test pieces

[0079] Using cylindrical blanks subjected to the same heat treatment process, two 100mm long welded test pieces with the same outer diameter and thickness as the cylindrical blanks were machined.

[0080] 4. Shell assembly and welding

[0081] The surface of the end cap forgings 1-1 and 1-2 and the two ends of the cylinder 3 within 20mm is polished with a metal grinding head to clean the oxide layer. The polished area is then cleaned with acetone.

[0082] After assembling the head forging 1-1, the head forging 1-2 and the cylinder 3, tooling is used to tighten them axially.

[0083] Then, the assembled shell assembly and the welding test piece were subjected to circumferential welding using electron beam welding: Welding process parameters:

[0084] High voltage: 85KV

[0085] Focus: 900 mA

[0086] Beam current: 10mA

[0087] Linear velocity: 500 mm / min

[0088] Vacuum degree: 5×10 -3 Pa

[0089] The spatter and weld reinforcement of welds 3-1 and 3-2 after welding were cleaned using a metal grinding head; the welds were inspected in accordance with GJB1718A-2005 and the welds met the requirements of Class I welds.

[0090] The overall components and welded test pieces were subjected to stress-relief annealing in a vacuum heat treatment furnace. The stress-relief annealing regime was: 600℃ for 30 minutes, followed by air cooling.

[0091] 5. Testing

[0092] Two 10mm wide plate-shaped tensile specimens were cut from the welded test piece and subjected to tensile tests. The test results are shown in the table below.

[0093]

[0094] The prepared pressure-resistant shell was subjected to a hydrostatic test. The shell showed no leakage at 9 MPa, which is the medium pressure in a pressure vessel.

[0095] Example 2

[0096] As attached Figure 1 The following are the specific steps for fabricating a TA15 pressure-resistant shell with an outer diameter of φ340mm, a cylindrical body thickness of 2.5mm, and a length of 1350mm:

[0097] 1. Head forging

[0098] After heating the TA15 titanium alloy billet, it is placed in a mold and die forged to obtain titanium alloy head forgings 1-1 and 1-2.

[0099] For TA15 titanium alloy head forgings 1-1 and 1-2, leave a 5mm machining allowance on each side compared to the finished product and perform rough machining.

[0100] The head forgings 1-1 and 1-2 obtained by rough machining were subjected to heat treatment. The heat treatment regime was to hold at 30℃ below the phase transformation point for 45 minutes and then air cool.

[0101] For the rough-machined TA15 titanium alloy head forgings 1-1 and 1-2, leave a 2mm machining allowance on each side compared to the finished product and perform semi-finishing.

[0102] The semi-finished TA15 titanium alloy end cap forgings 1-1 and 1-2 were subjected to heat treatment again. The heat treatment process was 700℃ for 30 minutes followed by air cooling.

[0103] The TA15 titanium alloy forgings 1-1 and 1-2, which have undergone reheat treatment, are then precision machined using TA15 titanium alloy. A positioning boss is machined at the welding end to complete the machining process.

[0104] 2. Cylinder forging

[0105] First, the TA15 titanium alloy billet is heated and then placed into an extruder. The titanium alloy cylindrical billet is obtained by forward extrusion using the extruder. The extrusion temperature is 20°C below the phase transformation point, and the extruded tube blank size is φ356×φ320×L.

[0106] Leave a 5mm machining allowance on one side of the TA15 titanium alloy cylinder blank compared to the finished product, and perform rough machining;

[0107] After heat treatment of the cylindrical blank obtained from rough machining, a 2mm machining allowance is reserved on one side of the finished product for semi-finishing.

[0108] Next, the semi-finished TA15 titanium alloy cylinder is heat-treated, and then the TA15 titanium alloy cylinder is precision-machined. Positioning recesses are machined at both ends of the cylinder, and the cylinder machining is completed.

[0109] 3. Fabrication of welding test pieces

[0110] Using cylindrical blanks subjected to the same heat treatment process, two 100mm long welded test pieces with the same outer diameter and thickness as the cylindrical blanks were machined.

[0111] 4. Shell assembly and welding

[0112] The surface of the end cap forgings 1-1 and 1-2 and the two ends of the cylinder 3 within 20mm is polished with a metal grinding head to clean the oxide layer. The polished area is then cleaned with acetone.

[0113] After assembling the head forging 1-1, the head forging 1-2 and the cylinder 3, tooling is used to tighten them axially.

[0114] Then, the assembled shell assembly and the welding test piece were subjected to circumferential welding using electron beam welding: Welding process parameters:

[0115] High voltage: 95KV

[0116] Focus: 950 mA

[0117] Beam current: 15mA

[0118] Linear velocity: 750 mm / min

[0119] Vacuum degree: 5×10 -3 Pa

[0120] The spatter and weld reinforcement of welds 3-1 and 3-2 after welding were cleaned using a metal grinding head; the welds were inspected in accordance with GJB1718A-2005 and the welds met the requirements of Class I welds.

[0121] The overall components and welded test pieces were subjected to stress-relief annealing in a vacuum heat treatment furnace. The stress-relief annealing regime was: 600℃ for 30 minutes, followed by air cooling.

[0122] 5. Testing

[0123] Two 10mm wide plate-shaped tensile specimens were cut for the welding test and tensile tests were conducted. The test results are shown in the table below.

[0124]

[0125] The prepared pressure-resistant shell was subjected to a hydrostatic test, and the shell showed no leakage at 11 MPa, which is the high pressure level for pressure vessels.

[0126] Example 3

[0127] As attached Figure 1 Based on the structure, a TA15 pressure-resistant shell with an outer diameter of φ390mm, a cylindrical body thickness of 4mm, and a length of 800mm was prepared. The specific steps are as follows:

[0128] 1. Head forging

[0129] After heating the TA15 titanium alloy billet, it is placed in a mold and die forged to obtain titanium alloy head forgings 1-1 and 1-2.

[0130] For TA15 titanium alloy head forgings 1-1 and 1-2, leave a 5mm machining allowance on each side compared to the finished product and perform rough machining.

[0131] The head forgings 1-1 and 1-2 obtained by rough machining were subjected to heat treatment with the following parameters: heat treatment at 30℃ below the phase transformation point for 45 minutes, followed by air cooling.

[0132] Leave a 2mm machining allowance on one side for the rough-machined TA15 titanium alloy end forgings 1-1 and 1-2, and perform semi-finishing.

[0133] The semi-finished TA15 titanium alloy end cap forgings 1-1 and 1-2 were subjected to heat treatment with the following parameters: 700℃ for 30 min and air cooling.

[0134] The semi-finished TA15 titanium alloy end cap forgings 1-1 and 1-2 are precision machined, and a positioning boss is machined at the welding end to complete the machining.

[0135] 2. Cylinder forging

[0136] First, the TA15 titanium alloy billet is heated and then placed into an extruder. The titanium alloy cylindrical billet is obtained by forward extrusion using the extruder. The extrusion temperature is 20°C below the phase transformation point, and the extruded tube blank size is φ400×φ382×L.

[0137] Leave a 5mm machining allowance on one side of the TA15 titanium alloy cylinder blank compared to the finished product, and perform rough machining;

[0138] The rough-machined cylindrical blank is then heat-treated.

[0139] Leave a 2mm machining allowance on one side of the rough-machined TA15 titanium alloy cylinder compared to the finished product, perform semi-finishing, and then continue heat treatment.

[0140] The TA15 titanium alloy cylinder is precision machined, and positioning recesses are machined at both ends of the cylinder to obtain cylinder forging 3.

[0141] 3. Fabrication of welding test pieces

[0142] Using the same heat treatment process as in this embodiment, two 100mm long welding test pieces with the same outer diameter and thickness as the cylinder blank were machined.

[0143] 4. Shell assembly and welding

[0144] The surface of the end cap forgings 1-1 and 1-2 and the two ends of the cylinder 3 within 20mm is polished with a metal grinding head to clean the oxide layer. The polished area is then cleaned with acetone.

[0145] After assembling the head forging 1-1, the head forging 1-2 and the cylinder 3, tooling is used to tighten them axially.

[0146] Then, the assembled shell assembly and the welding test piece were subjected to circumferential welding using electron beam welding: Welding process parameters:

[0147] High voltage: 100KV

[0148] Focus: 1000 mA

[0149] Beam current: 20mA

[0150] Linear velocity: 1000 mm / min

[0151] Vacuum degree: 5×10 -3 Pa

[0152] The spatter and weld reinforcement of welds 3-1 and 3-2 after welding were cleaned using a metal grinding head; the welds were inspected in accordance with GJB1718A-2005 and the welds met the requirements of Class I welds.

[0153] The overall components and welded test pieces were subjected to stress-relief annealing in a vacuum heat treatment furnace. The stress-relief annealing regime was: 650℃ for 60 minutes, followed by air cooling.

[0154] 5. Testing

[0155] Two 10mm wide plate-shaped tensile specimens were cut for the welding test and tensile tests were conducted. The test results are shown in the table below.

[0156]

[0157] The prepared pressure-resistant shell was subjected to a hydrostatic test. The shell showed no leakage at 13 MPa, which is the high pressure in a pressure vessel.

[0158] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a TA15 titanium alloy pressure-resistant shell, characterized in that, Includes the following steps: Head forging processing: After die forging of titanium alloy billet, head forging blank is obtained. The head forging blank is then subjected to rough machining, first heat treatment, semi-finishing, second heat treatment, and finish machining in sequence to obtain head forging. The first heat treatment temperature is 20℃~30℃ below the phase transformation point of the titanium alloy billet, held for 30 min~60 min, and then air-cooled. The second heat treatment temperature is 700℃~750℃, held for 30 min~60 min, and then air-cooled. Cylindrical forging processing: The heated titanium alloy bar billet is forward extruded to obtain a cylindrical billet. The cylindrical billet is then subjected to rough machining, third heat treatment, semi-finishing, fourth heat treatment, and finish machining to obtain the cylindrical forging. Assembly and Welding: Two end cap forgings are respectively installed at the openings at both ends of the cylindrical forging and axially tightened to obtain the shell assembly; the shell assembly is then subjected to circumferential welding, cleaned, inspected, and heat-treated to obtain the TA15 titanium alloy pressure-resistant shell; wherein, electron beam welding is used for circumferential welding, and the welding process parameters are: high voltage 85kV~100kV; focusing 900mA~1000mA; beam current 10 mA~20mA; linear velocity 500 mm / min ~1200mm / min; vacuum degree ≤1×10 -3 Pa; The titanium alloy billet is made of TA15 titanium alloy.

2. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the head forging processing steps, the rough machining leaves a 5mm machining allowance on one side compared to the finished product, the semi-finish machining leaves a 2mm machining allowance on one side compared to the finished product, and the finishing machining involves machining a positioning boss at the welding end of the head forging.

3. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the process of forging the cylindrical body, the titanium alloy billet is heated to 20°C~30°C below its phase transformation point and then subjected to forward extrusion.

4. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the process of forging the cylindrical body, the heated titanium alloy billet is subjected to forward extrusion, with a machining allowance of 7mm to 10mm on each side of the finished product.

5. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the machining steps of the cylindrical forging, a machining allowance of 5mm is reserved on one side during rough machining of the cylindrical blank, a machining allowance of 2mm is reserved on one side during semi-finishing compared to the finished product, and positioning recesses are machined at both ends of the cylindrical blank during finish machining.

6. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the assembly and welding step, the welding area between the head forging and the cylinder forging is polished to remove the oxide layer in the welding area.

7. The method for preparing the TA15 titanium alloy pressure-resistant shell according to claim 1, characterized in that, In the assembly and welding step, the welded shell assembly is subjected to stress-relief annealing heat treatment. The heat treatment parameters for stress-relief annealing are: 600℃~650℃, holding for 30min~60min, followed by air cooling.

8. The pressure-resistant shell prepared by the method of preparing the TA15 titanium alloy pressure-resistant shell according to any one of claims 1 to 7.

Images