Technological forming method of large thick-wall special-shaped curved surface carbon steel stainless steel shell

Abstract

The invention relates to a process forming method for a large thick-wall special-shaped curved surface carbon steel stainless steel shell. According to the process forming method, it is ensured that the high-precision molded surface size of the special-shaped curved surface shell is achieved in the forming process through multi-link optimization control. On the basis of allowance amplification optimization of three-dimensional modeling and expansion, by combining numerical control cutting and leveling processes, simulating a cutter pressing line path through software, and performing trial-manufacturing verification by using equal-proportion sample pieces; line-by-line and tool-by-tool pressing and two times of shaping inspection are adopted in the step-by-step pressing process, and the local deformation amount is corrected in real time; in the pre-assembly stage, the goodness of fit of assembly lines is ensured through three-dimensional lofting and scribing and tool positioning, and welding thermal deformation and residual stress are effectively controlled in cooperation with anti-deformation tool welding and aging treatment. Digital simulation, parameter iterative optimization, process error compensation and mechanical stability control are fused in the whole process, so that the profile precision of the shell meets the design requirement in the cold forming stage, and relying on machining correction is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of shell structure design, and in particular to a process forming method for a large-scale thick-walled special-shaped curved surface carbon steel and stainless steel shell. Background Art

[0002] At present, there are large-sized parts with special-shaped curved surfaces in related industries such as shipbuilding, hydropower, aerospace, wind tunnels, water tunnels, etc. For example, ship plates, shells, cylinders, cave bodies and other parts are all thick-walled special-shaped curved surfaces. The product design in related fields is of great development significance to the national defense construction, research and development of aerospace vehicles, and maritime shipping. At present, such products are basically completed through post-machining methods based on rough shape surfaces.

[0003] The current existing molding production methods have the following main defects: First, a large amount of machining allowance is left for rough periphery for unfolding and cutting, resulting in a large waste of material; second, a machining allowance of 10mm or more is left for cutting on the basic profile, and the workload of subsequent machining by large gantry milling machines or boring and milling machines is large; third, the molding size accuracy is poor, and the subsequent machining molding can only ensure the profile accuracy but cannot ensure the uniformity of wall thickness. Summary of the invention

[0004] Based on the above description, the present invention provides a process forming method for a large thick-walled special-shaped curved carbon steel stainless steel shell to solve the above technical problems in the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A process for forming a large thick-walled, special-shaped curved carbon steel stainless steel shell, comprising the following steps: S1. 3D modeling: model and unfold the special-shaped curved shell, generate a 2D blanking drawing, and optimize the excess volume according to the pressing requirements; S2, cutting and leveling, CNC programming cutting and leveling of the cut material’s flatness and dimensions; S3, lay out the cutting line and optimize it, use software to simulate the cutting line and pressing, and convert the drawing; trial-produce proportionally reduced samples of the same material and thickness, and optimize the cutting line clearance of the formal product based on the trial product inspection; S4, prefabricated lifting points, set lifting lugs on the flat pieces; S5. The formal parts are pressed and formed, and the pressing lines and cutters are pressed and produced line by line according to the positions of the pressing lines on the marked steel plates, and the first inspection and shaping after pressing is carried out; S6. Lofting and marking assembly lines. Lofting and marking various assembly lines of parts according to the drawing requirements. Perform the second inspection and shaping after profiling. Check the shape of the single block and the molding shape line according to the line, and cut the shape of the single block. S7. Prefabrication and welding: Piece-by-piece prefabrication is carried out according to the prefabrication line. The prefabricated products are fixed by the tooling plate, and welding is carried out after adding anti-deformation tooling. S8. Aging treatment: Aging treatment is carried out on the welded products, and the anti-deformation tooling is disassembled and final inspection is carried out.

[0006] Compared with the prior art, the technical solution of the present application has the following beneficial technical effects: The process forming method provided by the present application ensures high-precision profile dimensions during the forming process of the special-shaped curved surface shell through multi-link optimization control. First, based on the optimization of the allowance release in three-dimensional modeling and unfolding, combined with numerical control cutting and leveling processes, flatness and dimensional accuracy are guaranteed from the raw material stage; secondly, the pressing tool path is simulated by software and verified by trial production of an equal-proportion sample, and the gap parameters of the pressing forming are accurately corrected to eliminate the cumulative error of the pressing process; during the step-by-step pressing process, line-by-line and knife-by-knife pressing and two-time shaping inspections are adopted to correct the local deformation in real time; during the prefabrication stage, three-dimensional lofting and marking and tooling positioning are used to ensure the coincidence degree of the prefabrication line, and welding and aging treatment are carried out in cooperation with the anti-deformation tooling to effectively control the welding thermal deformation and residual stress. The whole process integrates digital simulation, parameter iterative optimization, process error compensation and mechanical stability control, so that the shell profile accuracy reaches the design requirements in the cold forming stage, avoiding relying on machining correction.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Further, the modeling and unfolding of the special-shaped curved surface shell to generate a two-dimensional cutting drawing includes: S11. Use three-dimensional software for modeling and unfolding, and form a readable two-dimensional cutting drawing for the numerical control cutting machine. S12. Use three-dimensional software to simulate and determine the inspection gauge graph and size of the pressing surface, and transfer them to the two-dimensional cutting drawing.

[0009] Further, the leveling treatment of the flatness and outer dimensions of the cut material includes: S21. Place the cut material on a rigid horizontal platform surface that meets the cutting size. S22. Carry out flatness detection and mark the out-of-tolerance positions. S23. Carry out pressing and leveling according to the marked area positions.

[0010] Further, the software simulation of drawing the pressing tool line includes: S31. Use three-dimensional software for modeling and simulating the pressing process, and transform it into a two-dimensional unfolding drawing of the pressing tool line position. The pressing tool line is set at a predetermined interval. S32. Transfer and transplant the simulated and set pressing tool line onto the steel plate to be processed.

[0011] Further, the trial-produced sample piece with the same material and equal thickness and in an equal-proportion reduced size, and optimizing the die pressing line clearance of the formal product according to the trial-produced product inspection includes: S33. Trial-produce a sample piece with the same material and equal thickness and in an equal-proportion reduced size; S34. Inspect the external dimensions of the sample piece by inspection; S35. Inspect and optimize the die pressing line.

[0012] Further, the various assembly lines for lofting and marking parts according to the drawing requirements include: S61. Loft and mark the maximum external contour line of the whole part according to the drawing requirements; S62. Loft and mark the cross center line of the whole part according to the drawing requirements; S63. Loft and mark the maximum external contour line of a single block of the part according to the drawing requirements; S64. Loft and mark the cross center line of a single block of the part according to the drawing requirements; S65. Fix the lofting line on the transplant identification platform with dimension markings according to the drawing requirements; S66. Loft and mark the +20mm line of the maximum external contour line of the whole part according to the process optimization requirements.

[0013] Further, the formed external contour line is marked according to the maximum external contour line + 3mm on one side, and the external contour of the single block is pressed and cut according to the position of the marked formed external contour line.

[0014] Further, perform piece-by-piece pre-assembly according to the assembly line, fix the assembled product through the tooling plate, and perform welding after adding anti-deformation tooling, including: S71. According to the drawing requirements, perform enlarged pre-assembly at a predetermined position outside the maximum external dimension; wherein, the enlarged pre-assembly is aligned and assembled according to the maximum external contour line and the cross center line of the whole part and the single block of the part; S72. Fix the splicing position with tooling plates made of the same material and equal thickness as the part at every predetermined distance, and use intermittent welding to reinforce the tooling plates; S73. Reinforce and weld the assembled product to the rigid horizontal platform, and then add anti-deformation tooling to the internal surface or the external surface of the assembled product; S74. Weld the assembled product according to the product process requirements.

[0015] Further, the aging treatment of the welded product is to perform stress-relieving annealing treatment on the assembled product after welding.

[0016] Further, the anti-deformation tooling is disassembled by grinding and cold cutting methods, and is disassembled according to the principle of symmetric distribution, and after disassembly, all the welds connected to the part body are completely removed. Brief Description of the Drawings

[0017] Figure 1 It is the first type of structural schematic diagram of a large thick-walled special-shaped curved carbon steel and stainless steel shell related to the embodiment of the present invention; Figure 2 It is the second type of structural schematic diagram of a large thick-walled special-shaped curved carbon steel and stainless steel shell related to the embodiment of the present invention; Figure 3 It is the schematic diagram of modeling and unfolding the special-shaped curved shell in step S1 of the process forming method provided by the embodiment of the present invention; Figure 4 It is the schematic diagram of lofting and pressing the knife line in step S3 of the process forming method provided by the embodiment of the present invention; Figure 5 It is the schematic diagram of inspecting and optimizing the knife line in the process forming method provided by the embodiment of the present invention; Figure 6 It is the schematic diagram of line-by-line and knife-by-knife pressing and subsequent template inspection in step S5 of the process forming method provided by the embodiment of the present invention; Figure 7 It is the schematic diagram of lofting, marking and assembling lines in step S6 of the process forming method provided by the embodiment of the present invention; Figure 8 It is the schematic diagram of cutting the outer shape of a single block in step S6 of the process forming method provided by the embodiment of the present invention; Figure 9 It is the schematic diagram of piece-by-piece pre-assembly according to the assembly line in step S7 of the process forming method provided by the embodiment of the present invention. Detailed Embodiments

[0018] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of the present application in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0020] It will be appreciated that spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. may be used herein to describe the relationship of one element or feature shown in the figures with other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "beneath them" or "under it" will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "beneath" can include both upper and lower orientations. Additionally, the device may also have other orientations (such as being rotated 90° or other orientations), and the spatial descriptors used herein are to be interpreted accordingly.

[0021] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or connected to the other element through an intermediate element. In the following embodiments, "connection", if there is a transfer of electrical signals or data between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0022] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprise / include" or "have", etc. specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0023] As shown in the figure, the embodiment of the present application provides a process forming method for a large-sized thick-walled special-shaped curved carbon steel and stainless steel shell. For the convenience of description, the structure of the large-sized thick-walled special-shaped curved carbon steel and stainless steel shell involved in the embodiment of the present application is composed of 4 blocks divided by a cross center line (as Figure 1 shown) or composed of 8 blocks divided by four corners and four large surfaces (as Figure 2 shown), and they are assembled, combined and welded into a whole. In this embodiment, the structure shown in Figure 1 is taken as an example for description.

[0024] The process forming method includes the following steps: S1. Three-dimensional modeling, modeling and unfolding the special-shaped curved shell to generate a two-dimensional cutting drawing, and optimizing the allowance according to the pressing requirements, as Figure 3 shown.

[0025] Among them, the modeling and unfolding of the special-shaped curved shell to generate a two-dimensional cutting drawing includes: S11. Use 3D software for modeling and unfolding to form a readable 2D cutting layout drawing for a numerical control cutting machine; S12. Use 3D software to simulate and determine the inspection gauge graphics and dimensions of the pressing surface, and transfer them to the 2D cutting layout drawing.

[0026] In this embodiment, for angle pressing, when it needs to change every 3°, a process inspection gauge needs to be prepared, an as-formed inspection gauge needs to be prepared every 300 mm, the thickness of the inspection gauge is not less than 5 mm, the inspection gauge is not less than 2 / 3 of the shape size of the inspected area, and the width of the inspection gauge is not less than 300 mm to ensure the rigidity of the ruler.

[0027] Preferably, in order to fully meet the pressing requirements for process optimization and allowance, in this embodiment, a 5 mm allowance is optimized for compensation of the outer shape according to the pressing accuracy of the pressing equipment; a 5 mm allowance is optimized for reservation according to the plastic deformation characteristics of the material; a 5 mm allowance is optimized for reservation according to the need for shaping adjustment of the pressing size and attitude; a 5 mm allowance is optimized for reservation according to the flatness of the cutting platform.

[0028] S2. Cutting and leveling. Numerically controlled programming for cutting and blanking, and leveling the flatness and outer dimensions of the cut material; Specifically, ensure that the dimensions meet the pressing requirements. After confirming the equipment, platform, and material, perform numerically controlled programming for cutting. When cutting, confirm that the material size is not less than the optimized size according to the optimized outer shape and dimensions. To ensure the effectiveness of the cutting dimensions, pay attention to the following when cutting: Check and confirm that the functions of the numerically controlled cutting machine are normal and the precision deviation is not greater than 3 mm; to ensure the effectiveness of the cutting dimensions, check the levelness of the cutting platform surface; Place the steel plate lifting device on the cutting platform and check that the flatness is not greater than 5 mm; After checking and confirming that the programming, graphic dimensions, equipment, and platform are normal and error-free, cut and unfold the outer shape; Use numerically controlled programming for cutting and blanking to unfold the outer shape, and the cutting tolerance is not greater than 10 mm; Cutting is achieved by plasma or laser; The inspection gauge is also cut by numerically controlled programming laser.

[0029] Among them, the leveling treatment of the flatness and outer dimensions of the cut material includes: S21. Place the cut material on a rigid horizontal platform surface that meets the blanking size; S22. Perform flatness detection and mark the out-of-tolerance positions; Specifically, according to the size, use an inspection gauge or a level of the full-length size to perform flatness detection to a requirement that the overall is not greater than 5 mm and the flatness at any position in the flat area is not greater than 2 mm, and mark the out-of-tolerance positions with marking lines.

[0030] S23. Press and level according to the marked area positions.

[0031] Specifically, according to the position of the marked area, ensure that no obvious indentation is generated during the pressing and leveling process. After laying a backing plate under the pressing knife, use a numerically controlled hydraulic press to accurately press and level. Among them, the backing plate covers the entire length of the leveling pressing knife and its thickness is not less than 10 mm.

[0032] After completing step S2, inspect the shape of the steel plate. Specifically, place the leveled material on a rigid horizontal platform surface that meets the blanking size requirements; use a full-length inspection ruler or a level to detect, and after ensuring that the overall flatness is not greater than 5 mm, the flatness of any position in the flat area after profiling is not greater than 2 mm, and the gap between the inspection ruler and any straight cross-section is not greater than 2 mm, proceed to the next step.

[0033] S3. Loft the pressing knife line and optimize it. Use 3D software to simulate drawing the pressing knife line and profiling, and perform drawing conversion; trial-produce a scaled-down sample of the same material and equal thickness, and optimize the gap of the pressing knife line of the formal product according to the inspection of the trial-produced product, as Figure 4 shown.

[0034] Among them, the simulation of drawing the pressing knife line using 3D software includes: S31. Use 3D software to build a model and simulate the profiling process, and convert it to a 2D development drawing of the pressing knife line position. The pressing knife line is set at a predetermined spacing; in this embodiment, the predetermined spacing is 100 mm.

[0035] S32. Transfer the simulated and set pressing knife line to the steel plate to be processed.

[0036] Specifically, according to the position of the pressing knife line on the drawing, use a laser ink line instrument and a lofting ink line to transfer the pressing knife line to the steel plate.

[0037] After the pressing knife line is lofted and transferred, it needs to be inspected, as Figure 5 shown. Specifically, inspect the position, angle, spacing of the transferred line, and the coincidence degree between the light of the laser ink line instrument and the lofting ink line, and ensure that they are all not greater than 3 mm; then hoist the steel plate onto the press platform, align the pressing knife line with the equal-level laser cursor line according to the position of the pressing knife line on the drawing, and ensure that the deviation is not greater than 3 mm.

[0038] After the inspection of the pressing knife line is completed, enter the trial production verification process. It should be noted that before the trial production, it is necessary to first check the equipment, prepare the pressing knife head and the backing plate; preferably, according to the bending shape accuracy requirements, no obvious visible indentation is generated at the position of the pressing knife line and on the back, and according to the requirements, equip a curved surface or arc pressing knife head, a backing plate with a thickness not less than 10 mm covering the length of the pressing knife, and a support under the curved surface or arc profiling.

[0039] To ensure the effectiveness of cutting dimensions, it is necessary to check and confirm that the functions of the numerically controlled hydraulic press are normal, the deviation of the stroke accuracy of the cylinder ram is not more than 3 mm, and it is also necessary to check and confirm that the parallelism deviation of the flatness of the press platform surface, the flatness of the curved surface or arc pressing tool head, and the flatness of the lower support surface of the curved surface or arc pressing die is not more than 3 mm.

[0040] The trial production and verification process is to trial produce a proportionally reduced sample of the same material and equal thickness. Optimize the clearance of the pressing tool line for the formal product based on the inspection of the trial-produced product. It includes: S33. Trial produce a proportionally reduced sample of the same material and equal thickness; To ensure the minimum error of the equipment, simulation, and process requirements, first trial produce a sample with the same material and equal thickness, reduced to a height, width, and length of approximately 1000 mm and equal, to verify whether the spacing of the pressing tool lines is optimal.

[0041] S34. Inspect the external dimensions of the sample using a checking gauge; first, check and confirm that the external dimensions of the checking gauge from flatness to straightness are not more than 1 mm, and then use the checking gauge to check until the clearance is not more than 1 mm.

[0042] S35. Check and optimize the pressing tool line.

[0043] According to the above inspection results, optimize the pressing tool line of the formal product. Specifically, for the inspection result data of the checking gauge, refine and increase the spacing of the bent pressing tool line to not more than 50 mm; check and increase the refinement of the spacing, angle, and position of the pressing tool line, with a deviation not more than 3 mm. Check the position, angle, spacing of the transplanting line, and the coincidence degree of the light of the laser ink line instrument and the layout ink line, ensuring that all deviations are not more than 3 mm.

[0044] S4. Precast lifting points and set up lifting lugs on the flat plate parts; Since the pressing process of this large steel plate part requires the assistance of a crane, precast lifting points during the lifting process can effectively prevent deformation; the lifting points are preferably in the form of lifting lugs. To facilitate lifting and movement, the following requirements need to be met: the lifting lugs must be prepared according to the principle of the same material and equal thickness as the parts; the lifting lugs need to be set at the edge of the flat plate part; the lifting lugs must be set one every 1000 mm, at least 3 on each side, and one at a distance of 500 mm from each end point of each side to ensure uniform force on the lifting points; the lifting lugs must be welded with a groove and fully penetrated to ensure that they do not break during the lifting process.

[0045] S5. Press the formal parts into shape, press line by line and knife by knife according to the position of the pressing tool line on the already marked steel plate, and conduct the first inspection and shaping after pressing, as Figure 6 shown.

[0046] Among them, in this embodiment, as emphasized before, the pressing process must be carried out using a backing plate for pressing. To ensure the quality of the pressing, the following points should also be noted in actual production: It is prohibited for the pressing tool to directly contact the steel plate body; preferably, the pressing angle each time is not greater than 1°, and the pressing offset each time is not greater than 150 mm; and after each pressing, use a full-length angle, plane, and straight cross-section for inspection until it meets the requirements; if there are any out-of-tolerance areas after each pressing inspection, the dimensions must be leveled, corrected, and shaped to the requirements at any time before proceeding with the pressing of the next pressing tool line. It is prohibited to carry the deviation to the next process for pressing.

[0047] The first inspection after pressing mainly checks the pressing dimensions. Specifically, in the lying state, use a tape measure to inspect the length, width, and height dimensions of each single block, with all dimensions not greater than 3 mm, and mark the positions of the out-of-tolerance areas; use a straight-edge inspection ruler to inspect the angle and surface of the mold until the gap is not greater than 3 mm, and mark the positions of the out-of-tolerance areas; for pressings with different angles, use a special straight-edge inspection ruler prepared for every 3° change to check each position one by one to ensure that the angle deviation is not greater than 0.05°, and mark the positions of the out-of-tolerance areas. Also, it is necessary to use a straight-edge inspection ruler prepared every 300 mm to check each position one by one and mark the positions of the out-of-tolerance areas.

[0048] Because the part size is large and the part is heavy, a single pressing cannot reach the required position directly. For the out-of-tolerance areas, further leveling, correction, and shaping are required, that is, the first shaping after pressing.

[0049] Then the product enters the assembly process. It is necessary to prepare an assembly inspection platform in advance. The assembly inspection platform must be a rigid casting platform; its size must be at least 1000 mm larger than the maximum size of the overall part for easy measurement; the platform must be horizontally fixed on the ground with a levelness not greater than 2 mm; at least 85% of the contact surface between the assembly inspection platform and the ground must be padded solid to ensure firmness and stability. After the assembly inspection platform is set up, it is also necessary to repeatedly check its levelness and stability to ensure the minimum absolute dimensional error in the assembly posture, and then enter the assembly.

[0050] S6. Lofting and marking the assembly lines. According to the requirements of the drawing, loft and mark various assembly lines of the parts, and conduct the second inspection and shaping after pressing. Check the outer shape of each single block and the formed outer shape line according to the lines, and cut the outer shape of each single block, as Figure 7 and Figure 8 shown.

[0051] Among them, the various assembly lines of the parts lofted and marked according to the requirements of the drawing include: S61. Loft and mark the maximum outer shape line of the whole part according to the requirements of the drawing; S62. Loft and mark the cross center line of the whole part according to the requirements of the drawing; S63. Loft and mark the maximum outer shape line of each single block of the part according to the requirements of the drawing; S64. Loft and mark the cross center line according to the requirements of the drawing. S65. Fix the loft line on the transplant identification platform with dimension marks according to the requirements of the drawing. S66. Loft and mark the +20mm line of the overall maximum outer contour line of the part according to the requirements of process optimization.

[0052] All assembly lines need to be inspected. Specifically, the inspection process is as follows: Use a laser ink line instrument, angle gauge, inspection ruler, and tape measure for a comprehensive inspection until the deviation from the loft dimension is no more than 2mm; For the profiled parts with different angles, use the inspection ruler prepared for every 3° change to check each position, and the angle deviation shall not be more than 0.05°. Mark and identify the positions in the out-of-tolerance area. Use the inspection ruler prepared every 300mm to check each position, and mark and identify the positions in the out-of-tolerance area.

[0053] Then, place the single blocks of each part on the assembly inspection platform according to the loft line that has been marked. Conduct a secondary inspection on the single blocks according to the above requirements, mark and identify the positions in the out-of-tolerance area, and level and correct the out-of-tolerance area.

[0054] Among them, the formed outer contour line is marked according to the maximum outer contour line + 3mm on one side, and the outer contour of the cut single block is cut by pressing the line at the position of the formed outer contour line that has been marked.

[0055] Specifically, before cutting, first check that the pipelines, tracks, switches, etc. of the cutting equipment are in good condition; Conduct a trial cut on a test plate with a length of not less than 1000mm to confirm that the cutting machine runs accurately and effectively, and set the equipment in place; Then cut by pressing the line at the position of the formed outer contour line that has been marked.

[0056] S7. Pre-assembly and welding. Conduct block-by-block pre-assembly according to the assembly line, fix the assembled product through the tooling plate, and weld after adding anti-deformation tooling, as Figure 9 shown.

[0057] Among them, conducting block-by-block pre-assembly according to the assembly line, fixing the assembled product through the tooling plate, and welding after adding anti-deformation tooling includes: S71. Conduct enlarged pre-assembly at a predetermined position outside the maximum outer dimension according to the requirements of the drawing; Among them, the enlarged pre-assembly is aligned with the maximum outer contour line and the cross center line of the overall part and the single block of the part for assembly. In this embodiment, form the outer contour line according to the requirements of the drawing and the enlarged amount requirements of process optimization design, and conduct enlarged pre-assembly with an additional 6mm on the basis of the maximum outer dimension; When assembling, it is necessary to align the maximum outer contour line and the cross center line of the overall part and the single block of the part. After corresponding the outer contour line, center line, and attitude of each single block as required, conduct block-by-block assembly.

[0058] S72. Fix the splicing position with a tooling plate made of the same material and equal thickness as the part at a predetermined distance interval, and reinforce the tooling plate by intermittent welding; Specifically, in this embodiment, fix it with a 150mm*300mm tooling plate made of the same material and equal thickness as the part at an interval of 300mm, and reinforce the tooling plate by intermittent welding. The welding requirements are that the weld fillet is 5mm, the length is 30mm, and the spacing is 30mm.

[0059] After assembly, conduct inspections. For example, in this embodiment, at least the following items need to be inspected: Check the deviation of the "cross center line", not greater than 2mm; check the deviation of the "maximum outer contour line" of a single block, not greater than 2mm; check the deviation of the cross center line of a single block, not greater than 2mm; when changing every 3°, a process inspection ruler needs to be prepared, and a forming inspection ruler needs to be prepared every 300mm to check the gap, not greater than 2mm; the weld fillet of the tooling plate is 5mm, the length is 30mm, and the spacing is 30mm, not less than and without cracks, no false welding, and no missed welding; check the deviation of the outer dimension of both ends, not greater than 2mm; check the gap of all splicing edges, not greater than 3mm; check the misalignment of all splicing edges, not greater than 3mm; check the step difference of all splicing surfaces, not greater than 2mm; use a laser scanner to detect the spatial coordinate dimensions of the profile surface and check the profile surface shape. According to the part structure and material characteristics, stick scanning coordinate points to the part profile surface, and the distance between scanning points is not greater than 100mm. Match and convert the three-dimensional model format of the part with the scanning detection software, and set up data analysis benchmarks, reference points, reference planes in advance for the "part three-dimensional model" and the scanning software, and confirm the outer dimensions of the model, etc.; the inspection process must ensure full scanning detection, and the detection process must ensure no dead angles and no blind spots.

[0060] In actual production, it is necessary to analyze the inspection data, and focus on comparing and analyzing the port edges, docking edges, angle areas, etc. to confirm the absolute reference of the aligned scanning data model and the part model.

[0061] Then it can enter the next step S73. Reinforce and weld the assembled product with a rigid horizontal platform, and then add anti-deformation tooling to the inner surface or outer surface of the assembled product; After the profile surface state meets the requirements according to the above process, then form a rigid body for the assembled product by adding anti-deformation tooling to prevent the shrinkage of the splicing weld from being smaller. Among them, the weld shrinkage is generally made by reserving a gap. This method is a relatively mature method in related fields such as ships, aerospace, and wind tunnels, and will not be elaborated and explained here.

[0062] Specifically, first reinforce and weld the parts to the rigid horizontal platform, and perform intermittent full-penetration welding according to the above requirements. Then, for one side inside or outside the parts, add a rigid tooling so that the distance between the support points is no more than 400 mm, each support point requires line contact, and the contact gap is no more than 1 mm. Among them, the rigid tooling meets the principle requirements of a grid shape with a spacing dimension of 200 mm, a cross-sectional dimension of no less than 150 mm, the same material, and a wall thickness of no less than 8 mm.

[0063] Finally, recheck the state of the added support tooling as required. Usually, there is not much change. For the purpose of more precise control, it is recommended to increase the recheck.

[0064] S74. Weld and assemble the product according to the product process requirements.

[0065] In this embodiment, before welding, first perform pre-welding cleaning, then perform pre-welding preheating welding, backing welding, root cleaning, inter-pass and inter-layer cleaning welding, small heat input welding with a small heat input, and finally perform multi-layer and multi-pass filling welding. During welding, it is required to weld according to the requirements of flat welding, horizontal welding, and vertical welding. Overhead welding is not allowed. Observe the shape during the welding process to control the welding position to meet the requirement of uniform and symmetrical distribution of welding spots. Adjust the welding position according to the actual working conditions. Local concentrated welding is prohibited. After welding, grind the weld surface to be flat and smooth, and clean the spatter in the surrounding area to meet the product design requirements.

[0066] After welding, recheck the welded product. Usually, there is not much change. For the purpose of more precise control, it is recommended to increase the recheck.

[0067] Then enter step S8, aging treatment. Perform aging treatment on the welded product, disassemble the anti-deformation tooling, and perform final inspection.

[0068] The aging treatment of the welded product is stress-relieving annealing treatment for the assembled product after welding.

[0069] Specifically, when loading the parts for stress-relieving annealing treatment, the parts must be padded flat and solid. It is prohibited to load the parts with mutual extrusion force. The distance between parts in the same furnace is not less than 200 mm. It is prohibited to place other parts above the parts. During aging treatment, it is necessary to pay attention to carrying out according to the product aging specification (heating rate, holding temperature and duration, cooling rate, furnace cooling, furnace opening and air cooling), and it is not allowed to change the parameters and requirements randomly.

[0070] Among them, the anti-deformation tooling is disassembled by grinding and cold cutting methods, and is disassembled according to the principle of symmetrical distribution. After disassembly, all welds connected to the part body are completely removed.

[0071] When disassembling the anti-deformation tooling, place the parts with the tooling after aging treatment horizontally on the rigid platform, and pad the parts horizontally flat and solid as required.

[0072] The process forming method provided by this application ensures high-precision profile dimensions of the special-shaped curved surface shell during the forming process through multi-link optimization control. First, based on the optimization of the allowance release in 3D modeling and unfolding, combined with numerical control cutting and leveling processes, the flatness and dimensional accuracy are guaranteed from the raw material stage. Secondly, the die pressing path is simulated by software and verified by trial production of an equal-proportion sample part, and the clearance parameters of die pressing forming are accurately corrected to eliminate the cumulative error of the die pressing process. During the step-by-step die pressing process, line-by-line and knife-by-knife pressing and two-time shaping inspections are adopted to correct the local deformation in real time. During the pre-assembly stage, 3D lofting marking and tooling positioning are carried out to ensure the coincidence degree of the assembly line, and combined with anti-deformation tooling welding and aging treatment, the welding thermal deformation and residual stress are effectively controlled. The whole process integrates digital simulation, parameter iterative optimization, process error compensation and mechanical stability control, so that the shell profile accuracy reaches the design requirements at the cold forming stage, avoiding relying on machining correction.

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for forming a large thick-walled, special-shaped curved carbon steel or stainless steel shell, characterized in that: The following steps are involved: S1. 3D modeling: model and unfold the special-shaped curved shell, generate a 2D blanking drawing, and optimize the excess volume according to the pressing requirements; S2, cutting and leveling, CNC programming cutting and leveling of the cut material’s flatness and dimensions; S3, lay out the cutting line and optimize it, use software to simulate the cutting line and pressing, and convert the drawing; trial-produce proportionally reduced samples of the same material and thickness, and optimize the cutting line clearance of the formal product based on the trial product inspection; S4, prefabricated lifting points, set lifting lugs on the flat pieces; S5. The formal parts are pressed and formed, and pressed line by line and cut by cut according to the position of the pressing knife line on the marked steel plate, and the first inspection and shaping after pressing is carried out; S6. Lofting and marking assembly lines. Lofting and marking various assembly lines of parts according to the drawing requirements. Perform the second inspection and shaping after profiling. Check the shape of the single block and the molding shape line according to the line, and cut the shape of the single block. S7, pre-assembly and welding, pre-assemble piece by piece according to the assembly line, fix the assembled products with tooling plates, and add anti-deformation tooling before welding; S8. Aging treatment: carry out aging treatment on the welded products, dismantle the anti-deformation tooling and conduct final inspection.

2. The process molding method according to claim 1, characterized in that: The modeling and unfolding of the special-shaped curved surface shell to generate a two-dimensional blanking drawing includes: S11, using 3D software to carry out modeling and development, and forming a readable 2D cutting drawing for a CNC cutting machine; S12, using three-dimensional software to simulate and determine the ruler pattern and size of the pressed surface, and converting it into the two-dimensional blanking drawing.

3. The process molding method according to claim 1, characterized in that: The leveling process for the flatness and the outer dimensions of the cut material includes: S21, placing the cut material on a rigid horizontal platform surface that meets the size of the cut material; S22, perform flatness detection and mark the out-of-tolerance positions; S23, pressing and leveling according to the position of the marked area.

4. The process molding method according to claim 1, characterized in that: The use of software to simulate the cutting line includes: S31, using 3D software to simulate the pressing process and convert it into a 2D press line position expansion diagram, where the press lines are set according to a predetermined spacing; S32, transforming and transplanting the simulated set cutting line onto the steel plate to be processed.

5. The process molding method according to claim 1, characterized in that: The above-mentioned trial production of proportionally reduced samples of the same material and thickness, and optimization of the press line clearance of the formal product based on the trial product inspection include: S33. Produce proportionally reduced samples of the same material and thickness; S34, check the dimensions of the sample by inspection; S35. Check and optimize the cutting line.

6. The process molding method according to claim 1, characterized in that: The various assembly lines for parts that are marked out according to the drawing requirements include: S61. Loft and mark the maximum outline of the entire part according to the drawing requirements; S62. Loft and mark the cross center line of the whole part according to the drawing requirements; S63. Loft and mark the maximum outline of the single block of the part according to the requirements of the drawing; S64. Loft and mark the cross center line of the single block of the part according to the drawing requirements; S65. According to the requirements of the drawings, solidify the layout line on the transplant identification platform with size identification; S66. According to the process optimization requirements, mark the +20mm line of the overall maximum outline of the part.

7. The process molding method according to claim 1, characterized in that: The molding contour line is marked according to the maximum contour line + 3mm on one side, and the cut single block body contour is pressed and cut according to the position of the marked molding contour line.

8. The process molding method according to claim 7, characterized in that: Pre-assemble each piece according to the assembly line, fix the assembled products with tooling plates, and add anti-deformation tooling and then weld, including: S71, enlarging and pre-assembling at a predetermined position outside the maximum outer dimension according to the drawing requirements; wherein the enlarging and pre-assembling is performed to align the maximum outer shape line and the cross center line of the whole part and the single block of the part; S72. Fix the splicing positions at predetermined intervals with tooling plates of the same material and thickness as the parts, and reinforce the tooling plates by intermittent welding; S73, reinforce and weld the assembled product to the rigid horizontal platform, and then add anti-deformation tooling to the inner or outer surface of the assembled product; S74. Weld and assemble products according to product process requirements.

9. The process molding method according to claim 8, characterized in that: The aging treatment of the welded product is a stress relief annealing treatment of the assembled product after welding.

10. The process molding method according to claim 8, characterized in that: The anti-deformation tooling is removed by grinding and cold cutting and according to the principle of symmetrical distribution. After removal, all welds connected to the part body are completely removed.

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