35CrNi3MoV high-strength and high-pressure standard cylinder for gas cylinder water pressure external measurement method and manufacturing method of 35CrNi3MoV high-strength and high-pressure standard cylinder

Abstract

The invention relates to the technical field of gas cylinder detection, and particularly discloses a 35CrNi3MoV high-strength and high-pressure standard cylinder for a gas cylinder water pressure external measurement method and a manufacturing method of the 35CrNi3MoV high-strength and high-pressure standard cylinder, aiming at the problem that a thick-wall high-strength and high-pressure standard cylinder which is intact in cylinder body, stable in performance and long in service life is difficult to manufacture by an existing manufacturing process of a standard cylinder for gas cylinder detection. Comprising the following steps that S1, 35CrNi3MoV alloy steel is taken, and a 35CrNi3MoV seamless tube base material is prepared through perforation and continuous rolling; and S2, a 35CrNi3MoV seamless tube base material is taken, plate type spinning is conducted firstly, then a spinning mold is switched, roller spinning is conducted, and the 35CrNi3MoV high-strength and high-pressure standard bottle for the gas cylinder water pressure external measurement method is obtained. A composite spinning forming process technology combining plate type spinning and roller spinning is adopted, material selection, process conditions and the like of a bottle body base material are improved, the surface quality and fusion quality of hot spinning forming of a thick-wall high-strength steel material are improved, and actual production of the standard bottle for the gas cylinder water pressure external measurement method with the thick bottle wall and high strength and pressure is achieved.

Description

Technical Field

[0001] This invention relates to the field of gas cylinder testing technology, and more specifically, to a 35CrNi3MoV high-strength and high-pressure standard cylinder for external water pressure testing of gas cylinders and its manufacturing method. Background Technology

[0003] Gas cylinders are sealed, bottle-shaped metal or non-metal containers used for storing and transporting permanent gases, liquefied gases, dissolved gases, or adsorbed gases. They are mobile, reusable pressure vessels. Due to the high pressure, alternating loads, and corrosive media conditions they operate in, gas cylinders may experience strength reduction due to material fatigue and localized damage after prolonged use, posing a risk of explosion or leakage. Therefore, according to mandatory requirements such as the "Gas Cylinder Safety Technical Regulations," safety inspections of gas cylinders are essential during production and use. Among these inspections, the hydrostatic test is a core component in assessing the structural integrity of gas cylinders. It is used to detect the deformation characteristics of the cylinder under rated pressure, especially the residual deformation rate, to determine whether it still possesses safe service capability.

[0004] In hydrostatic testing, the "external measurement method" involves placing the test bottle into a specially designed water jacket, applying pressure, and observing the amount of water overflowing from the jacket and the amount of water remaining after depressurization. This method measures the total volumetric deformation, elastic volumetric deformation, and residual volumetric deformation of the test bottle. It is widely used due to its ease of operation and high precision. However, the accuracy of the external measurement method is highly dependent on the precision of the testing apparatus. Systematic errors in the apparatus can directly lead to distorted deformation measurements and misjudgments of the cylinder's suitability. When using the external measurement method for hydrostatic testing, a standard bottle must be used as a reference instrument to periodically calibrate the testing apparatus. This involves simulating the test bottle with a standard bottle whose residual deformation characteristics are known, verifying the accuracy of the measurement results, and ensuring the reliability of the test data.

[0005] With the development of industry, the pressure requirements for gas cylinders are increasing. In some special fields, the pressure requirements for gas cylinders have reached over 40 MPa, and the pressure of gas cylinders used for hydrogen storage has even reached 70 MPa. Correspondingly, the pressure of standard cylinders used for testing needs to reach 105 MPa or even higher. Such high pressures have brought great challenges to the manufacturing process of standard cylinders.

[0006] Currently, the standard cylinders used for external hydrostatic testing of gas cylinders are mainly manufactured using methods including stamping and welding, plate spinning, and roller spinning. In stamping and welding, the end caps are stamped from steel plates and then welded to the cylinder body, resulting in a welded structure with low pressure resistance and poor fatigue performance. Plate spinning involves heating seamless steel pipes and then spinning them using plate molds, resulting in a seamless cylinder structure. However, this method suffers from high forming force, leading to surface roughness and defects. Furthermore, for thick-walled materials, rapid demolding results in poor fusion and fusion cracks. Roller spinning involves heating seamless steel pipes and then spinning them multiple times using roller molds, also resulting in a seamless cylinder structure. However, the molds can only withstand a relatively small forming force, requiring multiple passes with small deformations. For thick-walled materials, the forming efficiency of the end caps is low, and the forming process is difficult.

[0007] In summary, standard cylinders used for testing high-pressure gas cylinders require thicker cylinder wall materials to meet the demands of ultra-high pressure environments. However, based on the existing manufacturing processes, it is difficult to produce standard cylinders for external water pressure testing of high-pressure gas cylinders that are intact, have stable performance, and have a long service life. Summary of the Invention

[0009] The purpose of this invention is to solve the problem that the existing manufacturing process for standard gas cylinder testing makes it difficult to produce thick-walled, high-strength, and high-pressure standard cylinders with intact bodies, stable performance, and long service life.

[0010] This invention is achieved through the following technical solution: This invention provides a method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for external pressure measurement of gas cylinders, comprising the following steps: S1 is made from 35CrNi3MoV alloy steel, which is pierced and continuously rolled to produce 35CrNi3MoV seamless tube base material. S2 Take a 35CrNi3MoV seamless tube substrate, first perform plate spinning to complete the initial forming of the end cap, then switch the spinning die and perform roller spinning to improve the surface of the end cap, and at the same time complete the forming of the nozzle fusion zone, to obtain the 35CrNi3MoV high-strength and high-pressure standard bottle for the external water pressure measurement method of the gas cylinder.

[0011] Preferably, in step S2, the plate spinning process includes: First, the end section of the 35CrNi3MoV seamless tube substrate is locally heated at a temperature of 1100℃±50℃ and held for 10min±2min to obtain the tube material to be spun. Next, place the tube to be spun into a spinning machine and use a plate forming die for plate spinning. During this process, control the tube to rotate at a speed of 25 rad / s-29 rad / s and the plate forming die to rotate at a speed of 0.0015 rad / s-0.0035 rad / s until the plate forming die rotates 70°-80° around the axis, thus completing the plate spinning process.

[0012] Preferably, in step S2, the roller spinning process includes: After the plate spinning is completed, the process is switched to roller forming mold. The roller forming mold rotates around the axis at a speed of 0.0010rad / s-0.0030rad / s. While the roller forming mold is rotating, the mold base of the spinning machine moves forward at a constant speed along the axis of the tube. A total of 6-8 roller spinning processes are performed, and the single-pass moving distance is 10mm-15mm. Then, the mold is pushed back. During the pushing back process, the roller forming mold rotates in the opposite direction around the axis at a speed of 0.0010rad / s-0.0030rad / s, and the mold seat moves backward at a constant speed along the axis of the tube.

[0013] Preferably, during the plate spinning process and the switching of the roller forming mold, a welding torch is used to reheat the closing section of the pipe material to maintain the forming temperature at 1100℃-1200℃, and the oxygen pressure of the welding torch is 0.65MPa-0.7MPa.

[0014] Preferably, in step S2, before sheet spinning, the 35CrNi3MoV seamless tube substrate is pretreated. The pretreatment process is as follows: Take a 35CrNi3MoV seamless tube substrate, place it in an annealing furnace, heat it to 550℃-650℃, hold it for 2h-4h for annealing heat treatment, then cool it with the furnace to below 300℃, take it out of the furnace, and then cool it to room temperature at a cooling rate of 50℃ / h-100℃ / h.

[0015] Preferably, in step S1, during the perforation process, the perforation temperature is controlled at 1050℃-1150℃, the head reduction rate is 40%-50%, and the perforation speed is 0.5m / s-1.0m / s.

[0016] Preferably, in step S1, during continuous rolling, the rolling temperature is controlled at 950℃-1050℃, the rolling speed at 2m / s-3.5m / s, the mandrel speed at 0.5m / s-1.5m / s, and the sizing temperature at 850℃-950℃.

[0017] Preferably, in step S1, before performing the piercing process, the 35CrNi3MoV alloy steel is pretreated. The pretreatment process is as follows: Take 35CrNi3MoV alloy steel, heat it to 1050℃-1150℃ at a heating rate of ≤150℃ / h, and hold it for heat treatment; Then, use a 10%-20% sulfuric acid solution to pickle and soak the steel at a temperature of 50℃-70℃. After that, apply tallow and lime to the surface of the 35CrNi3MoV alloy steel and dry it at 200℃-300℃ for 2-3 hours to lubricate it, thus obtaining the 35CrNi3MoV alloy steel to be perforated.

[0018] The high-strength, high-pressure standard cylinder of 35CrNi3MoV, prepared by the above manufacturing method, has a wall thickness of ≥30mm and a pressure of 105MPa and above.

[0019] The technical solution of the present invention has the following beneficial effects: This invention selects 35CrNi3MoV material as the main material. First, a seamless tube rolling process is used to prepare the bottle body substrate. Then, a composite spinning forming process combining plate spinning and roller spinning is adopted. At the same time, improvements are made to the selection of bottle body substrate materials and processing conditions to improve the surface quality and fusion quality of hot spinning forming of thick-walled high-strength steel materials. This enables the actual production of standard bottles for external water pressure testing of gas cylinders with thick walls and high strength and pressure. The invention successfully manufactures standard bottles for external water pressure testing of gas cylinders with a wall thickness of 30mm or more and a pressure of 105MPa or more. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the manufacturing method of the 35CrNi3MoV high-strength and high-pressure standard bottle in this invention. Figure 2 This is a schematic diagram of the mold rotation in the plate spinning process of this invention. Figure 3 This is a schematic diagram of the mold rotation and movement in the roller spinning process of the present invention. Figure 4 This is a schematic diagram of the mold reverse-engineering process for the roller spinning process in this invention.

[0022] In the figure, 1. 35CrNi3MoV seamless tube; 2. Mold base; 3. Plate forming mold; 4. Roller forming mold; 5. Clamping claw.

[0023] Specific implementation details To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents, or raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0024] This invention provides a method for manufacturing a 35CrNi3MoV high-strength and high-pressure standard cylinder for external pressure measurement of gas cylinders. 35CrNi3MoV material is selected as the main material, and a seamless tube rolling process is adopted. A composite spinning forming method combining plate spinning and roller spinning is used to improve the surface quality and fusion quality of the hot spinning forming of thick-walled high-strength steel material, thereby manufacturing an ultra-high-pressure standard cylinder capable of meeting pressures of 105MPa or even higher.

[0025] Specifically, the steps include the following: (1) Part 1: Manufacturing the bottle body substrate 1.1 Billet Pretreatment The cylinder body is made of 35CrNi3MoV alloy steel, with a tensile strength of 1100-1250MPa and a yield strength ≥960MPa. It possesses excellent toughness and fatigue resistance, meeting the requirements of ultra-high strength gas cylinders. Currently, most existing 35CrNi3MoV alloys are forging materials, and the process of rolling them into seamless tubes faces significant technical challenges, mainly due to strict control of heating temperature and sensitivity to deformation rate. In other words, existing processes are almost impossible to successfully roll 35CrNi3MoV alloy into seamless tubes.

[0026] Based on the above, this invention proposes a manufacturing process capable of successfully rolling 35CrNi3MoV seamless tubes, the specific process of which is as follows: Take 35CrNi3MoV billet and heat it to 1050℃-1150℃ at a heating rate of ≤150℃ / h, hold it at that temperature, and perform pretreatment. A significantly higher heating temperature is used to reduce deformation resistance, and the heating rate is controlled to prevent excessive temperature differences between the inside and outside of the thick-walled billet, which could generate thermal stress. The holding time is calculated based on the diameter of the 35CrNi3MoV billet. Those skilled in the art can calculate it at a ratio of approximately 1h-1.5h for every 50mm of diameter, ensuring uniform heating throughout the billet and avoiding localized overheating.

[0027] The heat-treated blank is then surface-treated by immersing it in a 10%-20% sulfuric acid solution at 50℃-70℃ for 60-100 minutes to remove surface oxides. Then, a mixture of calcium-based grease and lime in a mass ratio of 1:2-4 is applied to the inner and outer surfaces and dried at 200℃-300℃ for 2-3 hours to enhance the lubrication effect.

[0028] This invention uses 35CrNi3MoV alloy steel to manufacture a 105MPa ultra-high pressure standard bottle. Under the same pressure, the required thickness is reduced by more than 30% compared to materials such as 35CrMo and 34CrMo4, which reduces the difficulty of molding, increases the hardenability of the product during heat treatment, and reduces costs.

[0029] 1.2 Perforation Treatment The pretreated billet is pierced to obtain a capillary tube. The piercing temperature is controlled at 1050℃-1150℃, under which the material has the best plasticity and the deformation resistance can be reduced by about 30%. During the piercing process, the mandrel reduction rate is controlled at 40%-50% to control the uniformity of the capillary tube wall thickness, and the piercing speed is 0.5m / s-1.0m / s to maintain a good surface morphology of the capillary tube.

[0030] 1.3 Continuous Rolling Tube Processing The tube is rolled at a temperature of 950℃-1050℃, below the piercing temperature, to control grain refinement. The rolling speed is 2m / s-3.5m / s, and the mandrel speed is 0.5m / s-1.5m / s to ensure uniform metal flow. The roll gap accuracy is controlled to ±0.05mm. The mandrel is lubricated with 15%-20% high-temperature graphite emulsion at a pressure of 0.8MPa-1.2MPa to reduce the coefficient of friction to below 0.08. The sizing temperature is 850℃-950℃ to avoid low-temperature work hardening.

[0031] (2) Part Two: Molding and Manufacturing A composite spinning forming method combining plate spinning and roller spinning is employed. First, plate spinning is used to initially form the end cap, creating its overall outline. Then, roller spinning is used to improve the surface of the end cap and form the fusion zone around the nozzle. The specific process is as follows: 2.1 Substrate Pretreatment Take the 35CrNi3MoV seamless tube substrate obtained from the first part, place it in an annealing furnace, heat it to 550-650℃, hold it for 2-4 hours, and perform annealing heat treatment to eliminate stress and avoid molding cracks. Then, cool it with the furnace to below 300℃, take it out of the furnace, and then cool it to room temperature at a cooling rate of 50℃ / h-100℃ / h.

[0032] 35CrNi3MoV seamless tubes, used as the base material for the bottle body, still exhibit certain structural and performance defects after pretreatment. Therefore, considering the material properties, to reduce the difficulty of end-cap forming, the tube base material undergoes annealing heat treatment before spin forming. In this pretreatment, the critical transformation temperature Ac1 of the base material is approximately 730-760℃. Using an annealing temperature lower than Ac1 can avoid austenitization. Furthermore, under a design pressure of 105MPa, the wall thickness of the bottle body base material is approximately 30mm. The corresponding heating and holding time for a 30mm wall thickness is 2-4 hours. Those skilled in the art can extend the holding time as the wall thickness increases, approximately by 1 hour for every 25mm increase in wall thickness.

[0033] 2.2 Plate spinning Existing CNC spinning forming machines and plate forming dies are used for plate spinning processing. The dies are made of cobalt-based alloys or the dies are surfaced with cobalt-based welding rods to increase wear resistance and prevent severe wear of the mold due to high spinning pressure.

[0034] First, heat the empty furnace to 1100℃±50℃. Then, place the pre-treated pipe section inside the furnace and heat it locally at 1100℃±50℃ for 10min±2min. This ensures that the inner and outer sides of the pipe section are heated evenly. The heating length L of the pipe section and the outer diameter φ of the pipe are controlled within the range of L=φ+(100-150)mm. After heating and holding, discharge the material.

[0035] The end of the heat-treated tube away from the closing section is fixed on the spindle of the spinning machine. The spindle jaws 5 clamp the tube end, and the time between the tube exiting the heating furnace and being clamped is controlled to not exceed 45 seconds. Then, the tube is rotated at a speed of 25 rad / s-29 rad / s. The working surface of the plate forming die 3 of the spinning machine is brought close to the closing section end face of the tube. The distance between the axis of rotation of the plate forming die 3 and the axis of the spindle of the spinning machine is controlled to be 40 mm ± 5 mm. While the tube is rotating, the plate forming die 3 rotates slowly around its axis at a speed of 0.0015 rad / s-0.0035 rad / s, that is, the tube is plate spun. During the spinning process, the closing section of the tube is reheated using a welding torch to maintain the forming temperature at 1100℃-1200℃, and the oxygen pressure of the welding torch is 0.65 MPa-0.7 MPa.

[0036] like Figure 2 As shown, when the plate forming mold rotates about 70°-80° around its axis, just before the end cap is about to fuse, the plate spinning process is completed. Then the plate forming mold is removed, and the roller forming mold is switched to the standby position through the switching mechanism to prepare for roller spinning.

[0037] 2.3 Roller spinning Using the aforementioned CNC spinning forming machine, switch to roller forming mold for roller spinning processing.

[0038] After the plate spinning is completed, the roller forming mold is quickly switched to the standby position to prepare for demolding. During the switching process, the welding torch continues to heat up, maintaining the forming temperature at 1100℃-1200℃, and the oxygen pressure of the welding torch is 0.65MPa-0.7MPa. Then, the gap between the tube and the roller is adjusted to be less than 10mm, and the roller oil pressure is 18-21MPa.

[0039] The roller forming die rotates slowly around its axis at a speed of 0.0010 rad / s to 0.0030 rad / s, while simultaneously... Figure 3As shown, the mold base 2 moves forward at a uniform speed along the axis of the tube material via the track, with a single-pass movement distance of 10mm-15mm. Depending on the tube material specifications, a total of 6-8 passes of roller spinning are performed to spin the tube material. The first pass completes the bottom sealing of the end cap based on plate forming. The second and subsequent passes are for nozzle forming. After completing one forming pass, the roller forming mold 4 is fed 10mm-15mm along the track via the mold base 2 based on the previous pass, and then the current pass is performed for demolding. This stage completes the nozzle forming. After the nozzle forming is completed, the final pass involves mold reversal, as shown... Figure 4 As shown, its purpose is to compensate for the thinning of the end cap during the molding process. The mold starts at the transition zone between the nozzle and the end cap, and ends at the transition zone between the end cap and the cylinder. During the reverse process, the roller forming mold rotates slowly in the opposite direction around its axis at a speed of 0.0010-0.0030 rad / s. At the same time, the mold base moves backward at a constant speed along the axis of the tube material via the track, with a moving distance of 10±2 mm. This stage completes the compensation and thickening of the end cap to compensate for the thinning.

[0040] The standard bottle manufactured by this invention through the above-described process steps meets the requirements of high strength, thick wall material, and calibration of high-pressure vessel external hydrostatic testing equipment. Specifically, it adopts a composite spinning forming technology combining plate spinning and roller spinning. Plate spinning is used to form the main body of the end cap, meeting the requirements of large deformation, large spinning force, and rapid forming. Roller spinning completes the surface improvement and refinement of the end cap, sealing and fusion, and nozzle forming, with small deformation and multiple passes, which is conducive to fusion and prevents cracking. Furthermore, a roller reverse push process is used to compensate for the thinning of the end cap, making its surface smoother.

[0041] Example 1 Step 1: Select 35CrNi3MoV alloy steel as raw material, heat it to 1100℃ at a heating rate of 145℃ / h, and hold it at that temperature for 1.2h; then soak it in a 15% sulfuric acid solution at 60℃ for 80min; finally, coat the inner and outer surfaces with a mixture of calcium-based grease and lime in a mass ratio of 1:3, and dry it at 250℃ for 2.5h to obtain 35CrNi3MoV billet.

[0042] Step 2: First, pierce the 35CrNi3MoV billet, controlling the piercing temperature at 1100℃, the mandrel reduction rate at approximately 45%, and the piercing speed at 0.8m / s; then, perform continuous rolling, controlling the rolling temperature at 1000℃, the rolling speed at 2.8m / s, the mandrel speed at 1.0m / s, and the roll gap accuracy at ±0.05mm. The sizing temperature is 900℃. Finally, use 20% high-temperature graphite emulsion to spray lubricate the mandrel at a spraying pressure of 0.8-1.2MPa to reduce the friction coefficient to below 0.08, thus obtaining the 35CrNi3MoV seamless tube 1.

[0043] Step 3: Take 35CrNi3MoV seamless tube substrate, place it in an annealing furnace, heat it to 600℃, hold it for 3 hours for annealing heat treatment, then cool it with the furnace to below 300℃, take it out of the furnace, and then cool it to room temperature at a cooling rate of 75℃ / h to obtain the pre-treated tube material.

[0044] Step 4: First, heat the empty furnace to 1100℃±20℃. Then, place the pre-treated pipe section inside the furnace and heat it locally at 1100℃±20℃ for 10 minutes. The heating length L of the pipe section and the outer diameter φ of the pipe should be controlled to be L=φ+(100-150)mm. The tube material is then placed in a CNC spinning machine equipped with a plate forming die, and the end of the tube material away from the end of the tube is fixed on the spindle of the spinning machine. The spindle jaws clamp the end of the tube material, and the time between the tube material exiting the heating furnace and being clamped is controlled to not exceed 45 seconds. The tube material is then rotated at a speed of 27 rad / s, and the working surface of the plate forming die of the spinning machine is brought close to the end face of the end of the tube material. The distance between the axis of rotation of the plate forming die and the axis of rotation of the spindle of the spinning machine is controlled to be 40 mm. While the tube material is rotating, the plate forming die rotates slowly around its axis at a speed of 0.0025 rad / s to perform plate spinning. During the spinning process, the end of the tube material is heated by a welding torch to maintain the forming temperature at 1150℃, and the oxygen pressure of the welding torch is 0.68 MPa.

[0045] Step 5: After plate spinning is completed, quickly switch the roller forming mold to the standby position to prepare for mold removal. During the switching process, the welding torch continues to provide heat, maintaining the forming temperature at 1150℃ and the oxygen pressure of the welding torch at 0.68MPa. Then adjust the gap between the pipe and the roller to less than 10mm, and the roller oil pressure to 20MPa. Control the roller forming mold to rotate slowly around its axis at a speed of 0.0020rad / s; at the same time, the mold base moves forward at a uniform speed along the axis of the pipe via the track, with a single pass moving a distance of 12mm. Depending on the pipe specifications, a total of 8 passes of roller spinning are performed to spin the pipe.

[0046] The process involves several stages. The first pass completes the bottom sealing of the end cap based on the plate forming process. Passes 2-8 are for nozzle forming. After each forming pass, the roller forming mold advances 12mm along the track from the previous pass before the current pass begins its demolding process, completing the nozzle formation. After nozzle formation, the final pass involves mold reversal. During reversal, the roller forming mold slowly rotates in the opposite direction around its axis at 0.0020 rad / s. Simultaneously, the mold base moves backward at a constant speed of 10mm along the pipe axis via the track to compensate for the thinning of the end cap, resulting in a 35CrNi3MoV high-strength, high-pressure standard bottle for external hydrostatic testing of gas cylinders.

[0047] Table 1 shows the mechanical property test results of the 35CrNi3MoV high-strength and high-pressure standard bottle manufactured in this embodiment; Table 2 shows the water pressure test results of the 35CrNi3MoV high-strength and high-pressure standard bottle manufactured in this embodiment. The test conditions are as follows: Test equipment name: QPNC80-5.5 gas cylinder internal test system, test equipment number: JC029, test temperature: 5-9℃, test medium: tap water, sensor number / accuracy / range: CGY-A2 / 0.5 / 0-250Mpa, pressure gauge number / accuracy / range: CGY-A1 / 0.4 / 0-250Mpa.

[0048] Table 1 Table 2 The test results show that the yield strength of this 35CrNi3MoV high-strength and high-pressure standard bottle can reach 1033MPa, the tensile strength can reach 1127MPa, and the elongation after fracture can reach 18.8%, demonstrating good mechanical properties and high-pressure performance.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that only plate spinning is used for manufacturing until a standard bottle with the same shape and profile is formed, i.e., roller spinning and reverse pushing are not included. The 35CrNi3MoV high-strength and high-pressure standard bottle manufactured in Example 1 is used as the test group, and the standard bottle prepared in Comparative Example 1 is used as the control group.

[0050] The 35CrNi3MoV high-strength, high-pressure standard bottle in Example 1 was manufactured using the technical solution of this invention. Its bottle surface is smoother and flatter than the standard bottle in Comparative Example 1, exhibiting excellent fusion and virtually no cracks. Furthermore, Comparative Example 1 did not perform reverse-pushing compensation for thickening, resulting in less internal deformation than external deformation of the end cap. This means that while the external material was pushed away by the mold, there was little or no internal deformation to compensate. As the number of passes increased, this deformation difference accumulated, leading to severe wall thinning in the transition zone. In contrast, the 35CrNi3MoV high-strength, high-pressure standard bottle manufactured using the solution of this invention in Example 1 effectively solves this problem, enabling the material in the bottleneck area to be pushed back to the transition section for wall thickness compensation.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for external pressure measurement of gas cylinders, characterized in that, Includes the following steps: S1 is made from 35CrNi3MoV alloy steel, which is pierced and continuously rolled to produce 35CrNi3MoV seamless tube base material. S2 The 35CrNi3MoV seamless tube substrate is first spun into a plate to complete the initial forming of the end cap, and then the spun die is switched to perform roller spun to improve the surface of the end cap, while the forming of the nozzle fusion zone is completed at the same time, to obtain the 35CrNi3MoV high-strength and high-pressure standard bottle for the external water pressure measurement method of the gas cylinder.

2. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 1, characterized in that, In step S2, the plate spinning process includes: First, the end section of the 35CrNi3MoV seamless tube substrate is locally heated at a temperature of 1100℃±50℃ and held for 10min±2min to obtain the tube material to be spun. Next, place the tube to be spun into a spinning machine and use a plate forming die for plate spinning. During this process, control the tube to rotate at a speed of 25 rad / s-29 rad / s and the plate forming die to rotate at a speed of 0.0015 rad / s-0.0035 rad / s until the plate forming die rotates 70°-80° around the axis, thus completing the plate spinning process.

3. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 2, characterized in that, In step S2, the roller spinning process includes: After the plate spinning is completed, the process is switched to roller forming mold. The roller forming mold rotates around its axis at a speed of 0.0010rad / s-0.0030rad / s. While the roller forming mold is rotating, the mold base of the spinning machine moves forward at a constant speed along the axis of the tube. A total of 6-8 roller spinning processes are performed, and the single-pass moving distance is 10mm-15mm. Then, the mold is pushed back. During the pushing back process, the roller forming mold rotates in the opposite direction around its axis at a speed of 0.0010rad / s-0.0030rad / s, and the mold seat moves backward at a constant speed along the axis of the tube.

4. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 3, characterized in that, During the plate spinning process and the switching of roller forming molds, a welding torch is used to reheat the end section of the tube material, maintaining the forming temperature at 1100℃-1200℃, and the oxygen pressure of the welding torch is 0.65MPa-0.7MPa.

5. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 1 or 2, characterized in that, In step S2, before sheet spinning, the 35CrNi3MoV seamless tube substrate is pretreated. The pretreatment process is as follows: Take a 35CrNi3MoV seamless tube substrate, place it in an annealing furnace, heat it to 550℃-650℃, hold it for 2h-4h for annealing heat treatment, then cool it with the furnace to below 300℃, take it out of the furnace, and then cool it to room temperature at a cooling rate of 50℃ / h-100℃ / h.

6. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 1, characterized in that, In step S1, during the perforation process, the perforation temperature is controlled at 1050℃-1150℃, the head reduction rate is 40%-50%, and the perforation speed is 0.5m / s-1.0m / s.

7. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 1, characterized in that, In step S1, during continuous rolling, the rolling temperature is controlled at 950℃-1050℃, the rolling speed is 2m / s-3.5m / s, the mandrel speed (the role of the mandrel in the rolling process needs to be explained) is 0.5m / s-1.5m / s, and the sizing temperature is 850℃-950℃.

8. The method for manufacturing a 35CrNi3MoV high-strength, high-pressure standard cylinder for the external pressure measurement method of gas cylinders according to claim 1, characterized in that, In step S1, before the piercing process, the 35CrNi3MoV alloy steel is pretreated. The pretreatment process is as follows: Take 35CrNi3MoV alloy steel, heat it to 1050℃-1150℃ at a heating rate of ≤150℃ / h, and hold it for heat treatment; Then, use a 10%-20% sulfuric acid solution to pickle and soak the steel at a temperature of 50℃-70℃. After that, apply tallow and lime to the surface of the 35CrNi3MoV alloy steel and dry it at 200℃-300℃ for 2-3 hours to lubricate it, thus obtaining the 35CrNi3MoV alloy steel to be perforated.

9. A method for externally measuring the water pressure of a gas cylinder using a 35CrNi3MoV high-strength, high-pressure standard cylinder, characterized in that... The 35CrNi3MoV high-strength and high-pressure standard bottle, manufactured using any one of claims 1 to 8, has a wall thickness ≥ 30 mm and a pressure ≥ 105 MPa.

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