A precision manufacturing method for integrally forming the bottom of a 5m diameter variable curvature tank

Abstract

The present application relates to the field of integrated manufacturing of large aerospace tanks, and specifically discloses a method for manufacturing a tank bottom, including: cutting, including cutting a first semicircular plate and a second semicircular plate of the same shape and size from a plate material; welding the straight edge of the first semicircular plate and the straight edge of the second semicircular plate together to obtain a welded part; annealing the welded part; pre-forming the annealed welded part by drum pressing to obtain a tank bottom preform; annealing the tank bottom preform; spinning the annealed tank bottom preform to obtain a tank bottom part; heat treating the tank bottom part, and trimming the tank bottom part by machining to obtain a tank bottom part. Thus, an overall manufacturing process system is established, which solves the blank of overall precision manufacturing of ultra-large diameter tank bottoms in China and significantly improves the launch reliability of models.

Description

Technical Field

[0001] The present application relates to the technical field of integrated manufacturing of large aerospace tanks, and in particular to a precision manufacturing method for integrally forming the bottom of a 5m diameter variable curvature tank. Background Art

[0002] The tank is the core component of the launch vehicle body structure, accounting for about 2 / 3 of the entire rocket. The tank is both a structural component and a functional component. The working environment is harsh and the manufacturing quality requirements are very strict. Especially for the cryogenic tank, the temperature of the tank shell material changes sharply during filling with liquid hydrogen and liquid oxygen at extremely low temperatures. In the future, there will be a need for long-term storage of propellants. Therefore, the reliability requirements of the propellant tank shell are extremely high. Every technology that increases the reliability of the tank structure will receive great attention and arouse positive response.

[0003] At present, the domestic 2.25-meter and 3.35-meter box bottoms have gradually realized integrated manufacturing processes through whole-plate forming. However, the 5-meter ultra-large diameter box bottoms are restricted by domestic high-end manufacturing equipment dedicated to military industry, making it difficult to achieve integrated manufacturing. The products have many welds and poor consistency, lagging behind domestic development. Summary of the invention

[0004] The present application provides a method for precision manufacturing of the one-piece forming of the bottom of a 5m diameter variable curvature tank, with the aim of forming a full-process process method from raw material supply to precision manufacturing of the overall tank body, establishing an overall manufacturing process system, solving the domestic gap in precision manufacturing of the overall bottom of an ultra-large diameter tank, and significantly improving the launch reliability of the model.

[0005] In a first aspect, a method for manufacturing a tank bottom is provided, comprising:

[0006] Cutting includes cutting a first semicircular plate and a second semicircular plate of the same shape and size from a plate stock;

[0007] Welding the straight edge of the first semicircular plate and the straight edge of the second semicircular plate together to obtain a welded part;

[0008] Annealing the tailor-welded component;

[0009] Performing drum preforming on the annealed tailor-welded formed part to obtain a tank bottom preformed part;

[0010] Annealing the tank bottom preform;

[0011] The annealed tank bottom preform is subjected to spin forming to obtain a tank bottom formed part;

[0012] The tank bottom formed piece is subjected to heat treatment and is machined and trimmed to obtain a tank bottom component.

[0013] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0014] Aiming at the integrated manufacturing of large-scale aerospace tanks, the present invention proposes a precision manufacturing method for the integral forming of the bottom of a 5m-diameter variable-curvature tank, realizing a full-process process method for precision manufacturing of the overall tank body. By combining existing resources and fully considering the applicability of the process, a full high-end precision manufacturing process is formulated, key points of process control are extracted, process control points are formed, and the multi-process coupling state of the manufacturing process is ensured to meet the high-precision requirements of the product and significantly improve the launch reliability of the model.

[0015] In combination with the first aspect, in certain implementations of the first aspect, the first semicircular sheet material and the second semicircular sheet material satisfy: π{D*[1+(5% to 8%)]} 2 =S1+S2+S3,

[0016] Wherein, D is the diameter of the sheet after the first semicircular sheet and the second semicircular sheet are assembled together, S1 corresponds to the area of ​​the top cover area of ​​the tank bottom, S2 corresponds to the area of ​​the circular ring area of ​​the tank bottom, and S3 corresponds to the area of ​​the fork ring area of ​​the tank bottom.

[0017] Since the sheet metal will go through pre-forming, spinning and other processes, the sheet metal can be thinned due to material extension. Based on the calculation based on the principle of equal surface area, the forming process is fully considered to determine the theoretical sheet metal diameter, and by designing the appropriate blanking size, a huge waste of sheet metal customization can be avoided.

[0018] In combination with the first aspect, in certain implementations of the first aspect, the thickness H of the sheet material satisfies:

[0019] H=(δ+5+d*3‰) / 0.7, wherein δ is the maximum wall thickness of the tank bottom, and d is the diameter of the open end of the tank bottom.

[0020] The thickness of the sheet material is determined based on the maximum wall thickness of the product structure (especially the fork ring area), the wall thickness variation law of drum preforming, shear and spinning, heat treatment deformation estimation and machining allowance, which is conducive to the selection of appropriate sheet material.

[0021] In combination with the first aspect, in certain implementations of the first aspect, the staggered spacing of the tailored welding process is less than or equal to 1.5 mm.

[0022] This avoids stress concentration due to tension on the outer surface during subsequent preforming.

[0023] In combination with the first aspect, in certain implementations of the first aspect, the pressure drum preform is punched by an upper die and a lower die, and a weld leak side of the tailor-welded part is in contact with the lower die.

[0024] The weld leak layer with higher elongation (elongation is 3% higher than the other side) is selected as the outer surface to bear the tensile stress. At the same time, the outer surface of the weld leak will subsequently undergo material flow with the spinning forming.

[0025] In combination with the first aspect, in certain implementations of the first aspect, the tank bottom preform includes a first spherical portion and a second spherical portion that are smoothly transitionally connected, the first spherical portion corresponds to the top cover portion of the tank bottom, the second spherical portion surrounds the outer circumference of the first spherical portion, the spherical diameter of the first spherical portion is 2800 to 3200 mm, and the spherical diameter of the second spherical portion is 3500 to 4500 mm.

[0026] The forming process adopts a double-spherical blank design, high-precision matching and pre-forming rigid constraints before spinning to achieve efficient material flow and ensure reliable quality.

[0027] In combination with the first aspect, in certain implementations of the first aspect, the spinning is a shear-spinning process, the number of spinning passes is 16-18, and the spinning process uses oxygen-propane heating at a heating temperature of 170-230°C.

[0028] This reduces the material's resistance to deformation, is beneficial to the stable operation of the equipment, is beneficial to the smooth completion of the spinning process, relatively increases the equipment capacity, reduces equipment concessions, is beneficial to ensuring the profile, and is conducive to comprehensive control of temperature accuracy.

[0029] In conjunction with the first aspect, in certain implementations of the first aspect, the annealing process satisfies:

[0030] Holding temperature: 400℃±10℃; Holding time: 3h; Cooling method: Cool in the furnace at a cooling rate of less than or equal to 30℃ per hour to below 260℃ and then air cool out of the furnace.

[0031] In conjunction with the first aspect, in certain implementations of the first aspect, the heat treatment process satisfies:

[0032] Insulation temperature: 535℃±5℃; Insulation time: 150min-200min; Cooling method: water cooling; Aging method: loading the furnace when it reaches temperature / heating up with the furnace; Aging insulation temperature: 165℃±5℃; Aging insulation time: 20h; Aging cooling method: air cooling.

[0033] In combination with the first aspect, in some implementations of the first aspect, the method further includes:

[0034] Weld detection is performed on a transport vehicle, wherein the transport vehicle includes a hexagonal load-bearing platform, the load-bearing platform has a notch, and the weld detection specifically includes:

[0035] The weld is aligned with the notch, and the weld is inspected by the weld inspection and the notch.

[0036] The detection process utilizes the intermediate gap during the splicing process of the frame and places the weld at the gap of the frame. The X-ray source is located inside the frame to avoid obstruction, achieving full coverage of weld detection and full monitoring of quality defects.

[0037] In combination with the first aspect, in certain implementations of the first aspect, the transport vehicle further includes four support blocks, each of which is arranged at the edge of the carrying platform for carrying the welded parts or the tank bottom preforms or the tank bottom formed parts.

[0038] The notch design is adopted at the connecting diagonal part, and the supporting blocks are flexibly arranged to adapt to products with welds in different states and sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of the bottom of a 5-meter diameter module box.

[0040] Figure 2 A precision manufacturing method for integrally forming a 5m diameter variable curvature tank bottom is provided in an embodiment of the present application.

[0041] Figure 3 Schematic diagram of the surface area composition of the sphere base.

[0042] Figure 4 This is a schematic diagram of welding.

[0043] Figure 5 This is a schematic diagram of the staggered spacing.

[0044] Figure 6 Schematic diagram of pre-forming.

[0045] Figure 7 It is a schematic diagram of the preform of the tank bottom.

[0046] Figure 8 Schematic diagram of a spin-formed part.

[0047] Fig. 9 Driving diagram for transportation.

[0048] Fig.10 This is a schematic diagram of the transport driving parts. DETAILED DESCRIPTION

[0049] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] like Figure 1 As shown, the 5-meter diameter module box bottom is an important component of the current launch vehicle. It is composed of a top cover, a circular ring and a fork ring. It is tangent to three line segments: R2776.8mm, R552.5 and a straight end. The raw material is usually 2219 aluminum alloy. It involves the mutual assembly relationship of the box bottom bracket and wall panel welding. The accuracy requirement is 2mm for the welding area and +6mm for the surface accuracy.

[0051] The welded tank bottoms of current and new generation launch vehicles are made of a top cover, 6 to 8 melon segments and a fork ring (or 2 half rings) which are formed separately and then welded together. Due to the large number of parts and the complex manufacturing process of each part, with the development of aerospace technology, competition in the international market and the urgent need for high-density launches of models, many problems and inadaptability have been exposed in the current tank bottom manufacturing process. The production cycle of manufacturing and welding a single 5-meter tank is about 100 days, and the weld of a single tank bottom is nearly 43 meters long. The production cost and cycle of the tank account for more than 50% of the rocket cost and manufacturing cycle, which makes it difficult to meet the current and future models. High efficiency, high reliability, and low-cost manufacturing requirements. The main problems are as follows:

[0052] (1) The bottom of the box is heavy, and the structural efficiency and carrying capacity are low

[0053] The smaller the structural weight of a launch vehicle, the larger the payload it can carry and launch under the same conditions. Therefore, under the same conditions, minimizing the structural mass has become a key indicator to measure the advancement of launch vehicles and has become the goal pursued by the world's mainstream launch vehicles.

[0054] However, due to the welding process used in the tank bottom, affected by the welding heat input, the strength coefficient of the welded joint after welding can only reach 50-60% of the parent material. Therefore, the tank bottom structure needs to strengthen the weld area structure and increase the wall thickness of the welding area to ensure the balanced bearing capacity of the entire tank bottom. Generally, the thickness of the welding area is about twice the thickness of the non-welding area.

[0055] (2) There are many welds on the bottom of the box, and the product reliability is low

[0056] Since the tank bottom is formed by welding multiple parts, there are many weak links that threaten the safety and reliability of the tank. At present, the TIG welding process is generally used for the bottom of a 5-meter-diameter tank. Because the 2219 aluminum alloy is in an aging-strengthened state, affected by the welding heat input, the strength coefficient of the welded joint after welding can only reach 50% of the parent material. The length of a 5-meter-diameter tank bottom weld is about 43m. The fusion welding of 2219 aluminum alloy is extremely sensitive to porosity defects. In actual production, it is very easy to have welding defects due to the influence of environmental and assembly conditions.

[0057] In addition, the tank bottom of the welded structure is easily affected by the mismatch of the rigidity of the welded products, and stress concentration is very likely to occur in the welding area, which is the weakest link in the entire structure.

[0058] (3) There are many processing steps, long process, low efficiency and high manufacturing cost.

[0059] The melon slices and top cover of the box bottom are first hydraulically drawn using a mold with a rib. The process involves about 23 steps, and annealing and manual grinding are required in between. The process is long, labor-intensive, and has low manufacturing efficiency and high costs. Due to the low manufacturing precision and lack of interchangeability of components, in order to meet the box bottom welding requirements, the melon slices generally require a lot of manual repair. Usually, a melon slice needs to go through 3-4 mold tests before the weld gap can be trimmed to meet the automatic welding assembly requirements. It usually takes 2 days to complete the bottom test and assembly, which greatly affects the production progress and efficiency.

[0060] In order to solve the above problems, the embodiment of the present application provides a precision manufacturing method for integrally forming the bottom of a 5m diameter variable curvature tank. By combining existing resources, fully considering the process applicability, formulating the entire process of high-end precision manufacturing, extracting key elements, forming process control points, ensuring the multi-process coupling state of the manufacturing process, and meeting the high-precision requirements of the product.

[0061] like Figure 2 As shown, the embodiment of the present application provides a precision manufacturing method for integrally forming a bottom of a 5m diameter variable curvature tank, which may include:

[0062] Step 1, cutting, includes cutting a first semicircular sheet and a second semicircular sheet of the same shape and size from a sheet original material.

[0063] Step 2, welding the straight edge of the first semicircular sheet and the straight edge of the second semicircular sheet together to obtain a welded part.

[0064] Step 3, annealing the welded parts.

[0065] Step 4, performing drum preforming on the annealed tailor-welded parts to obtain a tank bottom preform.

[0066] Step 5, annealing the tank bottom preform.

[0067] Step 6, spinning the annealed tank bottom preform to obtain a tank bottom formed part.

[0068] Step 7, heat-treating the tank bottom formed piece, and trimming the tank bottom formed piece by machining to obtain the tank bottom parts.

[0069] In some embodiments, weld inspection may be performed after processing steps such as tailor-made welding, preforming, and spin forming to ensure that the overall processing technology does not affect the weld quality.

[0070] The specific technical solution for the precision manufacturing of the bottom of a 5m-class ultra-large diameter variable curvature tank is as follows.

[0071] (1) Cutting

[0072] According to the above steps, since the sheet material will go through pre-forming, spin forming and other processes, the sheet material can be thinned due to material extension. If the blanking size is not appropriate, it is easy to cause great waste in sheet material customization. In some embodiments provided in this application, based on the principle of equal surface area, the forming process is fully considered to determine the theoretical sheet material diameter, and the sheet material diameter D after the first semicircular sheet material and the second semicircular sheet material are assembled together is calculated with a pre-forming thickness thinning rate of 5%-8%. The specific formula is as follows:

[0073] π{D*[1+(5%~8%)]} 2 =S1+S2+S3

[0074] Where D is the diameter of the sheet after the first semicircular sheet and the second semicircular sheet are assembled together, S1 corresponds to the area of ​​the top cover area of ​​the box bottom, S2 corresponds to the area of ​​the circular ring area of ​​the box bottom, and S3 corresponds to the area of ​​the fork ring area of ​​the box bottom. Figure 3 shown.

[0075] The raw material plate thickness H is determined based on the maximum wall thickness δ of the product structure (especially the fork ring area), the wall thickness variation law of the drum preforming, shearing and spinning, heat treatment deformation estimation, and machining allowance. Among them, the spinning forming is calculated according to 30% based on the 2219 material properties, the heat treatment deformation ellipse redundancy is 2.5-3‰ of the box bottom opening end d, and the machining increases 4-5mm on one side on the basis of the ellipse to avoid the surface deviation caused by the flipping process, that is, H = (δ+5+d*3‰) / 0.7, where H is the raw material plate thickness, δ is the maximum wall thickness of the product structure, and d is the diameter of the box bottom opening end.

[0076] (2) Welding

[0077] Figure 4 The schematic diagram of the first semicircular sheet and the second semicircular sheet welded together to obtain a welded part is shown. In order to maintain the strength of the welded part at the bottom of the box, reduce the heat affected zone at the welded part, and improve the product reliability, the vacuum electron beam welding process is selected. The electron beam welding method can form welds of different widths on both sides of the welded part. The side with a relatively smaller width is the weld leak layer of the weld.

[0078] In addition, for the assembly and welding of long, high and thick plates, Figure 5 As shown, the staggered spacing is required to be no greater than 1.5 mm to avoid stress concentration due to tension on the outer surface during subsequent preforming.

[0079] (3) Annealing after welding

[0080] The full annealing process is used to anneal the welded parts, thereby achieving process treatment of the stress in the welding area and the plasticity of the product.

[0081] Temperature control: Insulation temperature: 400℃±10℃

[0082] Insulation time: 3h

[0083] Cooling method: Cool in furnace at a cooling rate of no more than 30℃ per hour to below 260℃ and then air cool out of furnace.

[0084] (4) Preforming

[0085] like Figure 6 As shown, the preforming adopts the drum preforming to punch the upper and lower dies, and gradually changes point by point to obtain the preformed part of the tank bottom. Considering the difference in elongation on both sides of the thick plate, the weld leak layer with higher elongation (elongation is 3% higher than the other side) is selected as the outer surface to bear the tensile stress. At the same time, the outer surface of the weld leak will subsequently flow with the spinning forming. In addition, pore defects are prone to appear on the surface of the weld. The compressive stress generated by the spinning process can achieve pore closure, effectively avoiding defects such as pores caused by the instability of the electron beam.

[0086] In order to achieve efficient material flow and ensure reliable quality, the forming process adopts a double spherical blank design, high-precision matching and pre-forming rigid constraints before spinning. Figure 7 As shown, the tank bottom preform may include a first spherical portion and a second spherical portion that are smoothly transitionally connected, the first spherical portion may correspond to the top cover portion of the tank bottom, and the second spherical portion surrounds the outer periphery of the first spherical portion. The spherical diameter of the first spherical portion is 2800-3200 mm. The spherical diameter of the second spherical portion is 3500-4500 mm.

[0087] (5) Annealing after preforming

[0088] Temperature control: Insulation temperature: 400℃±10℃

[0089] Insulation time: 3h

[0090] Cooling method: Cool in furnace at a cooling rate of no more than 30℃ per hour to below 260℃ and then air cool out of furnace.

[0091] (6) Spinning

[0092] like Figure 8As shown, according to the precision control of the pre-forming tail top area, the shearing and spinning process of the product is determined, the high and low points of the pre-forming process are selected, the deformation amount of the product in each pass is considered, and the spinning passes are evaluated to be 16-18 passes. Oxygen-propane heating is used in the box bottom spinning process to reduce the deformation resistance of the material, which is conducive to the stable operation of the equipment and the smooth completion of the spinning process. It is relatively increased The capacity of the equipment reduces the equipment concessions, which is conducive to ensuring the surface. In order to fully control the temperature accuracy, a K-type thermocouple is used to measure the temperature of the spinning zone, and the distance of the heating gun is controlled at the same time, and the heating temperature is controlled to 170-230℃.

[0093] (7) Heat treatment

[0094] The bottom of the box adopts spray-type integral quenching, the spray flow is controlled according to the product surface, and the quenching deformation tooling is used to carry out product deformation.

[0095] Insulation temperature: 535℃±5℃

[0096] Insulation time: 150min-200min

[0097] Cooling method: water cooling

[0098] Aging - Loading the furnace to temperature / heating up with the furnace

[0099] Insulation temperature: 165℃±5℃

[0100] Insulation time: 20h

[0101] Cooling method: air cooling

[0102] (8) Machining

[0103] According to the data envelope of the spinning product, the turning and milling composite processing mode is adopted, the inner surface is taken as the theoretical basis for product processing, the thickness is calculated, and the outer surface processing is carried out.

[0104] (9) Weld inspection

[0105] Place the semi-finished product on the transport rack. The structure diagram of the transport rack is as follows: Fig. 9 and Fig.10 As shown. The transport frame adopts a hexagonal design, that is, the carrying platform of the transport vehicle has a hexagonal structure. The notch design is adopted at the connecting diagonal, which can adapt to products with welds in different states and sizes. Specifically, the carrying platform can have a notch, and the load-bearing area of ​​the carrying platform can be adjusted by adjusting the width of the notch. Four support blocks can be set on the diagonals of the carrying platform. One end of the support block is fixed to the edge of the carrying platform, and the other end is used to support the bottom forming part of the box. Projected along the direction of gravity, the projection area of ​​the four support blocks can intersect with the projection area of ​​the carrying platform and the projection area of ​​the bottom forming part of the box.

[0106] The detection process utilizes the intermediate gap during the splicing process of the frame and places the weld at the gap of the frame. The X-ray source is located inside the frame to avoid obstruction, achieving full coverage of weld detection and full monitoring of quality defects.

[0107] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A method for manufacturing a tank bottom, characterized in that: include: Cutting includes cutting a first semicircular plate and a second semicircular plate of the same shape and size from a plate stock; Welding the straight edge of the first semicircular plate and the straight edge of the second semicircular plate together to obtain a welded part; Annealing the tailor-welded component; Performing drum preforming on the annealed tailor-welded formed part to obtain a tank bottom preformed part; Annealing the tank bottom preform; The annealed tank bottom preform is subjected to spin forming to obtain a tank bottom formed part; heat-treating the tank bottom formed piece, and trimming the tank bottom formed piece by machining to obtain a tank bottom part; The first semicircular sheet and the second semicircular sheet satisfy: π{D*[1+(5% to 8%)]} 2 =S1+S2+S3, Wherein, D is the diameter of the sheet after the first semicircular sheet and the second semicircular sheet are assembled together, S1 corresponds to the area of ​​the top cover area of ​​the tank bottom, S2 corresponds to the area of ​​the circular ring area of ​​the tank bottom, and S3 corresponds to the area of ​​the fork ring area of ​​the tank bottom; The thickness H of the sheet material satisfies: H = (δ + 5 + d * 3‰) / 0.7, where δ is the maximum wall thickness of the tank bottom, and d is the diameter of the open end of the tank bottom; The staggered spacing of the welding process is less than or equal to 1.5mm; The press drum preform is punched by an upper die and a lower die, and the weld leak side of the tailor-welded formed part contacts the lower die; The tank bottom preform comprises a first spherical portion and a second spherical portion which are smoothly connected, the first spherical portion corresponds to the top cover portion of the tank bottom, the second spherical portion surrounds the outer periphery of the first spherical portion, the spherical diameter of the first spherical portion is 2800-3200 mm, and the spherical diameter of the second spherical portion is 3500-4500 mm; The spinning process is a shear-spin process with 16 to 18 passes. The spinning process is heated by oxygen-propane at a heating temperature of 170 to 230°C.

2. The method according to claim 1, characterized in that Annealing process, meet: Holding temperature: 400℃±10℃; Holding time: 3h; Cooling method: Cool in the furnace at a cooling rate of less than or equal to 30℃ per hour to below 260℃ and then air cool out of the furnace.

3. The method according to claim 1, characterized in that Heat treatment process to meet: Insulation temperature: 535℃±5℃; Insulation time: 150min-200min; Cooling method: water cooling; Aging method: loading the furnace when it reaches temperature / heating up with the furnace; Aging insulation temperature: 165℃±5℃; Aging insulation time: 20h; Aging cooling method: air cooling.

4. The method according to claim 1, characterized in that: The method further comprises: Weld detection is performed on a transport vehicle, wherein the transport vehicle includes a hexagonal load-bearing platform, the load-bearing platform has a notch, and the weld detection specifically includes: The weld is aligned with the notch, and the weld is inspected by the weld inspection and the notch.

5. The method according to claim 4, characterized in that The transport vehicle further comprises four support blocks, each of which is arranged at the edge of the carrying platform and is used for carrying the tailor-welded parts or the tank bottom preformed parts or the tank bottom formed parts.

Images