A method of manufacturing a pressure vessel with mass center control requirements

Abstract

A kind of pressure vessel manufacturing method with mass centroid control requirement, by making the connecting place of counterweight ring and cylinder segment into butt joint stop, using outer package form, it is convenient for operation in butt joint and control of butt joint precision, avoid the risk of product length index out of tolerance caused by welding shrinkage, accurately control the position of mass centroid control ring, process and design requirement consistency is high.Using spinning forming process, improve the weight and centroid deviation problem caused by wall thickness of cylinder segment;Through stress relief after welding, ensure the machining quality of pressure vessel with mass centroid control requirement is stable and reliable.The present application designs the piece before welding, spinning, machining, welding, heat treatment and various process method combination process design, so that the pressure vessel with mass centroid control requirement in manufacturing process is consistent in quality, centroid forming, high quality, stable and reliable, meet the design requirements.

Description

Technical Field

[0001] This invention relates to the field of machining, specifically a method for manufacturing a pressure vessel with requirements for mass center control. Background Technology

[0002] This type of pressure vessel is primarily used for engineering simulation training to verify the compatibility of its interfaces with the overall system. Based on functional requirements, its external interface dimensions, mass, center of gravity, and other characteristics must be consistent with those of a production pressure vessel. Typical pressure vessel forming processes mainly involve welding, heat treatment, machining, and other technologies.

[0003] In the original technical solution, the control of the center of mass was mainly constrained by the following points:

[0004] Controlling the weight of the cylindrical section is challenging. During the forming process of this type of pressure vessel, the cylindrical section significantly contributes to the product's weight, requiring precise control. Cylindrical sections are generally manufactured using a process of rolling and welding cylindrical sections or steel pipe blanks. The disadvantages of rolling and welding cylindrical sections are: annealing and straightening processes are required for dimensional adjustment during the rolling and welding process, resulting in a complex manufacturing flow and poor precision in the formed product, affecting accurate weight control. The disadvantages of using steel pipe blanks are: hot-rolled steel pipes are generally used, with a wall thickness tolerance typically of ±0.3mm. The wall thickness error of hot-rolled steel pipes has a significant impact on subsequent weight indicators.

[0005] Controlling the center of mass is challenging. In this type of pressure vessel, the center of mass is primarily adjusted using a mass center of mass control ring. The precision of the fit between the mass center of mass control ring and the cylinder section is crucial for achieving the design specifications. In the manufacturing process of large-diameter pressure vessels requiring mass center of mass control, the mass center of mass control ring must be manually welded internally. Given the limited internal space, controlling the axial position of the mass center of mass control ring and the fit precision between its outer circle and the inner hole of the cylinder section is difficult. This leads to deviations in product weight and center of mass control, preventing compliance with design specifications.

[0006] If the mass of the cylinder and the position of the counterweight ring deviate from the design specifications, the cylinder section and the counterweight ring cannot be accurately welded and positioned due to the outer diameter error. This will cause the mass and center of gravity of the product to deviate from the design requirements after subsequent molding, requiring multiple counterweights to meet the design requirements.

[0007] In summary, while the existing technical methods for machining the front and rear machine port dimensions are mature, their quality and center of gravity control are challenging. This is particularly true for pressure vessels with large length-to-diameter ratios, large dimensions, and heavy weights. Due to factors such as the structure used for quality and center of gravity control being located inside the vessel and the limited operating space within, precise control of quality and center of gravity is impossible. After development, multiple adjustments to the quality and center of gravity based on test results are required, resulting in poor quality stability and compromising product quality assurance. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies where the center of mass is difficult to control precisely and requires multiple adjustments to meet requirements, this invention proposes a pressure vessel manufacturing method with requirements for center of mass control.

[0009] The specific process of this invention is as follows:

[0010] Step 1: Determine the technical condition of the raw materials:

[0011] The raw material is 30CrMnSiA steel forgings, and the heat treatment process is annealed.

[0012] Step 2: Preparation of Pre-welding Components:

[0013] The preparation of pre-welding parts includes machining of pre-welding parts for the front and rear machine ports, machining of the counterweight ring for the center of mass, and spinning and turning of the cylindrical section.

[0014] The machining of parts for welding the front and rear ends of a machine tool includes three stages: roughing, heat treatment, and finishing.

[0015] The inner diameter, outer diameter, and end face of each front and rear machine tool are rough machined by turning.

[0016] Heat treatment is performed using a quenching and tempering method. After heat treatment, hardness is tested using an end-face hardness test method, and the hardness value meets HRC33-38.

[0017] During finishing, allowances are left for machining the butt joint surfaces of the front and rear machine ports, with 3mm allowances for the inner diameter, outer diameter, and end face. Other dimensions are machined to the final dimensions according to the drawings. A bevel is machined at the welding points to the cylindrical section.

[0018] When machining the counterweight ring, 10mm long assembly joint sections are machined onto the outer circumferential surfaces at both ends of the counterweight ring to meet the requirements for subsequent docking with the cylindrical section. These assembly joint sections are used for the insertion of the counterweight ring into the cylindrical section. The mating surfaces of these assembly joint sections have welding bevels.

[0019] The outer contour of the counterweight ring with the center of mass is completed by machining.

[0020] The spinning process of a cylinder is as follows:

[0021] The annealed 30CrMnSiA raw material was used as the blank for the spinning blank. The initial wall thickness of the spinning blank was 13 mm.

[0022] Spin forming of a cylinder. The obtained spun blank is formed by three consecutive spinning passes. After final spinning, the wall thickness of the spun cylinder formed from the spun blank is 4±0.1mm.

[0023] Spinning requirements and process parameters: Install the spinning mandrel, ensuring mandrel runout ≤ 0.05mm. Install the spinning wheel, ensuring spinning wheel runout ≤ 0.05mm. Spindle speed S = 90±15r / min; feed rate F = 67±20mm / min.

[0024] Machining of the cylindrical section; the cylinder obtained by spinning is cut into three cylindrical sections, namely the first cylindrical section, the second cylindrical section, and the third cylindrical section; the outer diameter and wall thickness of each cylindrical section are the same; the length of each cylinder is determined according to the drawing requirements.

[0025] Step 3: Welding

[0026] The welding process includes assembly, tack welding, automatic TIG welding, and flaw detection. The specific process is as follows:

[0027] Assembly: Assemble the components according to the welding requirements, and clean the surfaces of each component within 50mm of the welding position. Assemble the components according to the design requirements, ensuring that the misalignment is ≤0.3mm. This yields the assembly of the pressure vessel to be welded.

[0028] The assembly includes a front weldment component, three counterweight rings, a first cylindrical section, a second cylindrical section, a third cylindrical section, and a rear weldment component.

[0029] Tack welding: The areas of the assembly to be welded are heated to 80±30℃ and welded, and the tack welding of the assembly is completed sequentially. The welding speed is 7~9mm / min, and the welding current is 120~180A. The tack welding is symmetrical 4-point tack welding, and the weld length is 4~5mm.

[0030] Automatic TIG welding: Clamp and align the tack welded assembly with the circumferential welder. Heat each part of the assembly to be welded to 80±30℃ and weld. After welding, heat the weld to 250±30℃ and hold for 10-20 minutes, then allow it to cool naturally.

[0031] Flaw detection: Radiographic testing was performed on the weld. The test results were satisfactory.

[0032] If the flaw detection results of each weld show local defects, repair the local defects until the flaw detection results are qualified.

[0033] Welded structural components of the pressure vessel are obtained.

[0034] Step 4: Heat treatment:

[0035] The heat treatment is a low-temperature aging treatment. The obtained welded structural parts are heated in a furnace to 300±10℃ and held for 100±20 minutes for aging treatment. After the aging treatment, the outer surface of each weld is subjected to magnetic particle testing. If the test results are qualified, a semi-finished pressure vessel is obtained.

[0036] If the magnetic particle test results show local defects, the local defects should be repaired. During the repair, the weld of the defective part should be ground off, and the tack welding process should be repeated until the test results are qualified.

[0037] Step 5: Machining

[0038] The pressure vessel semi-finished product is precision machined to the required length using a milling and turning machining process, according to design requirements.

[0039] Using milling and turning combined machining, the front and rear machine port dimensions of the pressure vessel semi-finished product are precision machined according to the design requirements.

[0040] A pressure vessel was obtained.

[0041] This invention combines pre-welding component design with a process design that integrates multiple techniques such as spinning, machining, welding, and heat treatment. This results in high consistency and stable, reliable quality in the manufacturing process of pressure vessels with quality and centroid control requirements, thus meeting design requirements.

[0042] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0043] 1. This invention, by processing the connection between the counterweight ring and the cylindrical section into a butt joint, changes the internal assembly form of the prior art to an external assembly form. This facilitates the operation during the butt joint and the control of the butt joint accuracy. On the one hand, it avoids the risk of product length deviation caused by welding shrinkage; on the other hand, it precisely controls the position of the centroid control ring, ensuring high consistency between the process and design requirements. The use of a spinning forming process improves the weight and centroid deviation issues caused by the wall thickness of the cylindrical section. Stress relief through post-weld heat treatment ensures stable and reliable machining quality for pressure vessels requiring centroid control. Through the design of the above process route, a new method for manufacturing pressure vessels with centroid control requirements is formed.

[0044] 2. The pressure vessels manufactured using this invention, which require quality and center of gravity control, exhibit high consistency between the manufacturing process and design specifications for their components. This ensures strong feasibility in achieving quality and center of gravity control, and guarantees stable and controlled quality. A total of 26 pressure vessels of two types with quality and center of gravity control requirements were actually manufactured. These include 12 pressure vessels with a diameter of φ1350mm and a length of 7000mm, and 14 pressure vessels with a diameter of φ350mm and a length of 3700mm. Subsequent testing confirmed that the weight and center of gravity control indicators were 100% qualified, meeting the requirements of the design documents.

[0045] This invention optimizes the manufacturing process and designs the pre-weld component insertion structure to avoid welding shrinkage and precisely control the position of the centroid control ring; it improves the wall thickness accuracy of the cylindrical section through spinning forming technology; and it ensures stable and reliable machining quality of pressure vessels with centroid control requirements through stress relief heat treatment after welding. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of the present invention.

[0047] Figure 2 This is a schematic diagram of the front port mechanism.

[0048] Figure 3 This is a schematic diagram of a ring structure with requirements for mass centroid control.

[0049] Figure 4 This is a schematic diagram of the rear port structure.

[0050] Figure 5 This is a structural schematic diagram of a pressure vessel cylinder section.

[0051] Figure 6 This is a flowchart of the present invention.

[0052] In the diagram: 1. Front inlet; 2. Ring with quality center of mass control requirements; 3. First cylindrical section; 4. Second cylindrical section; 5. Third cylindrical section; 6. Rear inlet. Detailed Implementation

[0053] This embodiment describes a pressure vessel with a typical structure and mass center of gravity control requirements, made from 30CrMnSiA high-strength steel. The pressure vessel has an outer diameter of φ350mm, a wall thickness of 4mm, and a total diameter of 3700mm. From front to back, the pressure vessel consists of a front inlet, a mass center of gravity counterweight ring, a first cylindrical section, another mass center of gravity counterweight ring, a second cylindrical section, a mass center of gravity control ring, a third cylindrical section, and a rear inlet.

[0054] The front and rear machine ports are machined from 30CrMnSiA steel forgings. They are first rough-machined, then heat-treated, and finally machined to the pre-welding state. The joint dimensions of the front and rear machine ports need to be guaranteed by the final machining. The inner hole and outer circle allowance is 3mm on each side, and the end face allowance is 5mm. The mass center counterweight ring is machined from forgings to the pre-welding state. The first, second, and third cylindrical sections are machined from forgings into spinning blanks, which are then shaped by multiple spinning passes and cut according to length dimensions.

[0055] After all the pre-welding parts are complete, argon arc welding is used to perform tack welding and automatic argon arc welding on the pre-welding parts from front to back. After the weld is formed, it passes magnetic particle inspection. Welding stress is removed by low-temperature aging. After aging, it passes magnetic particle inspection. Then, the front and rear machine port dimensions are machined. After the machining is completed, the relevant dimensional indicators are tested to ensure they meet the design requirements.

[0056] The specific manufacturing process is as follows:

[0057] Step 1: Determine the technical condition of the raw materials:

[0058] The raw materials are 30CrMnSiA steel forgings, conforming to standards QJ500B-2014 or GB / T3077-2015, and require ultrasonic testing according to HB20159-2014 Class A. The heat treatment regime for the supplied raw materials is annealed.

[0059] Step 2: Preparation of Pre-welding Components:

[0060] The preparation of pre-welding parts includes machining of pre-welding parts for the front and rear machine ports, machining of the counterweight ring for the center of mass, and spinning and turning of the cylindrical section.

[0061] I. Machining of parts for welding the front and rear machine ports.

[0062] The machining of both the front and rear machine tool welded parts is divided into three stages: rough machining, heat treatment, and finish machining.

[0063] The inner diameter, outer diameter, and end face of each front and rear machine tool weldment are rough machined by turning, with a machining allowance of 4mm.

[0064] The heat treatment was performed using conventional methods, specifically quenching and tempering. After heat treatment, the hardness was tested using an end-face hardness test, and the measured hardness value met HRC 33-38.

[0065] During finishing, allowances are left for machining the butt joint surfaces of the components before welding at the front and rear machine ports. These allowances are 3mm for the inner diameter, outer diameter, and end face. Other dimensions are machined to the final dimensions according to the drawings. A weld bevel is machined at the welding points to the cylindrical section; the blunt edge of this weld bevel is 1mm, and the angle is 35°.

[0066] II. Machining of the counterweight ring with center of mass

[0067] A 10mm long assembly joint section is machined onto the outer circumferential surface at both ends of the counterweight ring to meet the requirements for subsequent docking with the cylindrical section. This assembly joint section is used for the insertion of the counterweight ring into the cylindrical section. The mating surface of this assembly joint section has a welding bevel, with a blunt edge of 1mm and an angle of 35°.

[0068] The machining of the counterweight ring is divided into two stages: roughing and finishing. During roughing, a 3mm machining allowance is left for the inner diameter, outer diameter, and end face. During finishing, the machining is carried out according to the design drawings.

[0069] The outer contour of the counterweight ring with the center of mass is completed by machining using conventional methods.

[0070] III. Spinning and Turning of Cylinders

[0071] The cylinder is produced by spinning. Specifically:

[0072] Machining the spinning blank. Annealed 30CrMnSiA raw material is used as the blank material for the spinning blank. The spinning blank is machined to the designed dimensions to obtain a spinning blank with an initial wall thickness of 13mm.

[0073] Spin forming of a cylinder. The obtained spun blank is formed by three consecutive spinning passes. After final spinning, the wall thickness of the spun cylinder formed from the spun blank is 4±0.1mm.

[0074] Spinning requirements and process parameters: Install the spinning mandrel, ensuring mandrel runout ≤ 0.05mm. Install the spinning wheel, ensuring spinning wheel runout ≤ 0.05mm. Spindle speed S = 90±15r / min; feed rate F = 67±20mm / min.

[0075] Formed cylindrical sections; the spun cylinder is divided into three sections: the first section, the second section, and the third section; each section has the same outer diameter and wall thickness; the length of each cylinder is determined according to the drawing requirements. Specifically:

[0076] After three spinning passes, an internal support fixture is used to round and align the cylinder using conventional methods; the internal support fixture is existing technology. After alignment, the four points on the outer circumference of both ends of the cylinder are symmetrical with a diameter of <0.1mm.

[0077] The aligned cylinder is then cut into three sections: the first section, the second section, and the third section. The cutting length is determined according to design requirements. During cutting, weld bevels with a 1mm blunt edge and a 35° angle are machined on the outer edges of the two end faces of the resulting first, second, and third cylinder sections.

[0078] Step 3: Welding

[0079] The welding process includes assembly, tack welding, automatic TIG welding, and flaw detection. The specific process is as follows:

[0080] Assembly: Assemble the components according to the welding requirements. The assembly includes the pre-welding components for the front end, three counterweight rings, the first cylindrical section, the second cylindrical section, the third cylindrical section, and the pre-welding components for the rear end. Sand the area within 50mm of the welding position of each assembly to remove oil, rust, and debris; sand the weld bevels. Assemble the components according to the design requirements, ensuring a misalignment ≤ 0.3mm. This yields the assembly of the pressure vessel to be welded.

[0081] Tack welding: The tack welding is performed using argon arc welding in accordance with the QJ175-1993 Class II standard. Specifically, the areas to be welded on the assembly are heated to 80±30℃ and welded sequentially to complete the tack welding of the assembly. The welding speed is 7~9mm / min, and the welding current is 120~180A. In this embodiment, the welding speed is 8mm / min, and the welding current is 150A.

[0082] The argon arc welding tack weld is a symmetrical four-point tack weld, with a weld length of 4-5 mm. In this embodiment, the weld length is 5 mm.

[0083] Automatic TIG welding: The assembly, after tack welding, is clamped and aligned with the circumferential welder. Each part of the assembly to be welded is heated to 80±30℃ and welded. After welding, the weld is heated to 250±30℃ and held for 10–20 minutes, then allowed to cool naturally. In this embodiment, the holding time is 15 minutes.

[0084] Flaw detection: Radiographic testing is performed on the welds, and the weld quality is evaluated according to the requirements of QJ175-1993 Class II standard. Surface inspection of the welds is performed according to QJ1842A-2011. If the flaw detection results of any weld show local defects, the local defects are repaired; during repair, the defective weld area is ground away, and the aforementioned tack welding process is repeated for repair until the flaw detection results are acceptable.

[0085] Welded structural components of the pressure vessel are obtained.

[0086] Step 4: Heat treatment:

[0087] The heat treatment is a low-temperature aging treatment. The obtained welded structural parts are heated in a furnace to 300±10℃ and held for 100±20 min for aging treatment. After the aging treatment, magnetic particle testing is performed on the outer surface of each weld in accordance with HB20158-2014.

[0088] If the magnetic particle test results show local defects, the local defects should be repaired. During the repair, the weld of the defective part should be ground off, and the tack welding process should be repeated until the test results are qualified.

[0089] A semi-finished pressure vessel is obtained.

[0090] Step 5: Machining

[0091] Before machining, the outer circle of the semi-finished pressure vessel needs to be aligned, and the runout of the outer circumference at both ends should be <0.1mm.

[0092] The pressure vessel semi-finished product is precision machined to the required length using a milling and turning machining process, according to design requirements.

[0093] Using a milling and turning machining process, the front and rear machine ports of the pressure vessel semi-finished product are precision machined according to design requirements to obtain the pressure vessel.

[0094] To verify the effectiveness of this embodiment, a full-size inspection was conducted according to the design drawings to test and record the product quality and center of gravity. The test results showed that the pressure vessel weighed 351 kg and the center of gravity was 2312 mm from the front end face of the machine, which meets the design requirements of 350 ± 5 kg and 2310 ± 8 mm from the front end face of the machine inlet.

Claims

1. A method of manufacturing a pressure vessel having a mass center control requirement, characterized by, The specific process is: Step one: determine the technical state of raw materials: The raw material is 30CrMnSiA steel forgings, and the heat treatment system is annealing state; Step two: preparation before welding: The preparation before welding includes machining of the front and rear machine port welding pieces, machining of the mass center weight ring, spinning of the cylinder, and turning of the cylinder segment; When machining the mass center weight ring, a 10mm long assembly butt joint is machined on the outer circumferential surface at both ends of the mass center weight ring to meet the subsequent butt joint requirements of the cylinder segment; the assembly butt joint is used for the insertion of the mass center weight ring and the cylinder segment; there is a welding groove on the butt joint surface of the assembly butt joint; The shape contour of the mass center weight ring is completed by turning; The spinning process of the cylinder is: 30CrMnSiA annealed raw material is used as the blank of the spinning blank; the initial wall thickness of the spinning blank is 13mm; the obtained spinning blank is formed by three passes of continuous spinning; after the final spinning, the wall thickness of the spinning cylinder formed by the spinning blank is 4±0.1mm; Spinning requirements and process parameters: install the spinning core mold, requiring the spinning core mold runout to be ≤0.05mm; install the spinning wheel, requiring the spinning wheel runout to be ≤0.05; the spindle speed S=90±15r / min; the feed speed F=67±20mm / min; Turning the cylinder segment: the cylinder obtained by spinning is cut into three cylinder segments, namely the first cylinder segment, the second cylinder segment, and the third cylinder segment; the outer diameter and wall thickness of each cylinder segment are the same; the length of each cylinder is determined according to the drawing requirements; Step three: welding: The welding process includes assembly, positioning welding, automatic argon arc welding, and flaw detection, and the specific process is: Assembly: the assembly includes the front machine port welding piece, the three mass center weight rings, the first cylinder segment, the second cylinder segment, the third cylinder segment, and the rear machine port welding piece; assemble according to the group welding requirements, clean the surface within 50mm of each assembly welding position; assemble according to the design requirements, and the misalignment amount is ≤0.3mm; obtain the assembly of the pressure vessel to be welded; Positioning welding: heat the welding position of the assembly to 80±30℃ and weld, sequentially complete the positioning welding of the assembly; the welding speed is 7-9mm / min, and the welding current is 120-180A; Automatic argon arc welding: clamp and align the assembly with the circumferential welder after positioning welding; heat each welding position of the assembly to 80±30℃ and weld; after welding, heat the weld to 250±30℃ for 10-20min and then naturally cool; Flaw detection: perform radiographic flaw detection on the weld, and the detection result is qualified, Obtain the welded structure of the pressure vessel; Step four: heat treatment: The heat treatment is low-temperature aging treatment; heat the obtained welded structure to 300±10℃ in the furnace for 100±20min for aging treatment; after the aging treatment is completed, perform magnetic powder detection on the outer surface of each weld; the detection result is qualified, and the semi-finished product of the pressure vessel is obtained; Step five: machining Use turning and milling combined machining to finish machining the length of the pressure vessel semi-finished product according to the design requirements; The front machine mouth welding pre-piece and the rear machine mouth welding pre-piece are machined, and the machining includes three stages of rough machining, heat treatment and finish machining. The pressure container is obtained.

2. The method of claim 1, wherein the mass centroid control requirement is met by providing a plurality of reinforcing members in the pressure vessel. The front machine mouth welding pre-piece and the rear machine mouth welding pre-piece are machined, and the machining includes three stages of rough machining, heat treatment and finish machining. The inner diameter, the outer diameter and the end face of each front machine mouth welding pre-piece and rear machine mouth welding pre-piece are rough machined by turning; The heat treatment is performed by quenching and tempering; after the heat treatment, the hardness is detected by detecting the hardness of the end face, and the hardness detection value satisfies HRC33-38; In the finish machining, the front machine mouth welding pre-piece butt joint size surface and the rear machine mouth welding pre-piece butt joint size surface are left with subsequent machining allowance, and the machining allowance is 3mm for the inner diameter, the outer diameter and the end face; the size of other parts is machined to the final size according to the drawing; and the welding bevel is machined at the welding position of the cylinder segment.

3. The method of claim 1, wherein the mass centroid control requirement is met by providing a plurality of reinforcing members in the pressure vessel. The positioning welding is symmetrical 4-point positioning, and the welding spot length is 4-5mm.

4. The method of claim 1, wherein the mass centroid control requirement is met by providing a plurality of reinforcing members in the pressure vessel. If the welding seam flaw detection result shows that there is a local defect, the local defect is repaired until the flaw detection result is qualified.

5. The method of claim 1, wherein the mass control requirement is a mass centroid control requirement. If the magnetic powder detection result shows that there is a local defect, the local defect is repaired; in the repair, the welding seam of the defective position is polished, the repair is repeated by the process of the positioning welding until the detection result is qualified.

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