Double-layered stainless steel square neck tube and its processing and manufacturing method

Abstract

The present application relates to the technical field of nuclear fusion device processing and manufacturing, and particularly relates to a double-layer stainless steel square neck pipe and a processing and manufacturing method thereof. The square neck pipe comprises an inner shell formed by butt welding of multiple arc-shaped inner shell pieces, an outer shell formed by butt welding of arc-shaped outer shell pieces and straight outer shell pieces, a web plate connecting the inner and outer shells, and a support guide column welded to the outer arc surface of the inner shell. The double-layer stainless steel square neck pipe can be modularly split and cut, the arc-shaped pieces are subjected to solid solution treatment with a mold, the inner shell assembly welding, web plate welding, low-temperature annealing, support guide column welding and outer shell assembly welding are sequentially performed, and in the key welding process, small heat input welding process is adopted and laser scanning monitoring is performed at intervals. Through model splitting, stress control and whole-process precision monitoring, the present application can inhibit the processing and welding deformation of austenitic stainless steel, realize high-precision manufacturing of the double-layer square neck pipe with millimeter-level profile, and avoid the risk of traditional straightening process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear fusion device processing and manufacturing, in particular to a double-layer stainless steel square neck pipe and a processing and manufacturing method thereof, and applies to the design and manufacturing of a neck pipe of a vacuum chamber of a fusion main device. BACKGROUND

[0002] In the manufacturing of a vacuum chamber of a nuclear fusion main device, a neck pipe, as a key interface component connecting the vacuum chamber and an external system, is usually made of a double-layer sandwich structure of austenitic stainless steel (such as 316L) and has a square straight pipe or an inclined pipe shape. The inside of the neck pipe component is an ultrahigh vacuum environment, and therefore the forming profile and dimensional accuracy of the inner and outer shells thereof need to be controlled to a millimeter level.

[0003] Due to the material characteristics of austenitic stainless steel, such as low thermal conductivity and large thermal expansion coefficient, in the traditional processing and manufacturing process, significant residual stress is easily generated and accumulated during the cold pressure forming and welding of the shell, which causes deformation of the component. This deformation seriously affects the final forming state and dimensional accuracy of the neck pipe, and further affects the assembly of the neck pipe with other interface components. Therefore, in the prior art, for the manufacturing of such a structure, cold pressure forming is usually used in combination with multiple negative pressure shaping to release stress during the cold pressure forming of the shell, but this method is time-consuming and is not conducive to mass production. In the welding process, low-efficiency processes such as small heat input and segmented surfacing are usually used to control deformation, which further restricts the production progress.

[0004] Moreover, for the deformation correction of the double-layer sandwich structure that has been formed by welding, since heat treatment may cause oxidation inside the double-layer structure and damage its ability to meet the ultrahigh vacuum requirement, the hot correction process cannot be used to correct the deformation, and the cold correction method is usually used for correction. The cold correction method requires multiple pressure forming, which is time-consuming and may damage the existing welds, and some damage is difficult to detect, which poses a hidden danger to the long-term safe operation of the component.

[0005] Therefore, there is an urgent need in the art for a double-layer stainless steel square neck pipe structure and a processing and manufacturing method thereof that can effectively control stress and deformation while taking into account high quality and high efficiency. SUMMARY

[0006] The present application provides a double-layer stainless steel square neck pipe and a processing and manufacturing method thereof, to solve the defect in the prior art that there is no reliable and efficient processing and manufacturing method for a nuclear fusion vacuum chamber neck pipe with high quality forming shell profile and dimensional requirements, and to realize high quality and high precision manufacturing of a double-layer stainless steel square neck pipe.

[0007] The application provides a double-layer stainless steel square neck pipe, which comprises an inner shell, an outer shell, a rib plate and a support guide column, the inner shell is assembled and welded by a plurality of arc-shaped inner shell pieces, the outer shell is sleeved on the outer periphery of the inner shell, a sandwich structure is formed between the outer shell and the inner shell, the outer shell is assembled and welded by a plurality of arc-shaped outer shell pieces, a narrow straight section outer shell piece and a wide straight section outer shell piece, the rib plate is located in the sandwich structure formed by the inner shell and the outer shell, and the rib plate connects the inner shell and the outer shell, and the support guide column is located in the sandwich structure formed by the inner shell and the outer shell, one end of the support guide column is welded to the outer arc surface of the inner shell, and the other end is used for abutting against the inner arc surface of the outer shell.

[0008] According to the double-layer stainless steel square neck pipe provided by the application, the inner shell is composed of four arc-shaped inner shell pieces with an angle of 90 degrees, and the outer shell is composed of four arc-shaped outer shell pieces with an angle of 90 degrees, two narrow straight section outer shell pieces and two wide straight section outer shell pieces.

[0009] According to the double-layer stainless steel square neck pipe provided by the application, the arc-shaped inner shell piece comprises an arc surface section and a flat plate section connected to the two sides of the arc surface section, one rib plate is arranged on each flat plate section, two rib plates are formed on each surface of the inner shell, and the two rib plates are symmetrically arranged along the joint seams of two adjacent arc-shaped inner shell pieces.

[0010] According to the double-layer stainless steel square neck pipe provided by the application, a plurality of support guide columns are welded to the outer arc surface of each arc-shaped inner shell piece, each row comprises two support guide columns, and the extension lines of the two support guide columns in each row form an angle of 30 degrees at the center of the arc surface of the arc-shaped inner shell piece.

[0011] The application further provides a processing and manufacturing method of a double-layer stainless steel square neck pipe, which is suitable for processing and manufacturing the double-layer stainless steel square neck pipe.

[0012] The plate materials are subjected to arc-shaped bending forming to form a plurality of arc-shaped inner shell pieces and a plurality of arc-shaped outer shell pieces, and after the forming is completed, the arc-shaped inner shell pieces and the arc-shaped outer shell pieces are subjected to solid solution treatment with a mold.

[0013] The arc-shaped inner shell pieces are riveted and reinforced, after the size and profile degree detection is qualified, the small heat input welding process is adopted for welding to form the inner shell, and the size and profile degree are monitored at intervals during the welding process.

[0014] The gusset plate is assembled and welded on the outer surface of the inner shell, the size and profile are monitored at intervals during the welding process, nondestructive testing is carried out after the welding is completed, and low-temperature annealing treatment is carried out after the gusset plate is qualified.

[0015] The support guide column is welded on the outer arc surface of the inner shell.

[0016] The plurality of arc-shaped shell pieces are riveted to the gusset plate, and after the size and profile are qualified, small heat input welding process is used for welding, and the size and profile are monitored at intervals during the welding process; subsequently, the narrow straight section shell piece and the wide straight section shell piece are assembled and welded.

[0017] After all the welding and tooling are removed, the final size and profile detection is carried out.

[0018] According to the manufacturing method of the double-layer stainless steel square neck pipe provided by the application, the arc-shaped pressure bending forming of the plurality of plates is performed by using a multi-cutter pressure forming mode, a 10mm to 15mm-thick stainless steel pad plate is arranged on the upper and lower pressure heads, pressure is maintained for 5 minutes after each pressure forming, and a template is used for forming comparison measurement.

[0019] According to the manufacturing method of the double-layer stainless steel square neck pipe provided by the application, the process parameters of the mold solid solution treatment of the plurality of arc-shaped inner shell pieces and the plurality of arc-shaped outer shell pieces are as follows: the solid solution temperature is set to 1100±15℃, the holding time is 35 minutes to 40 minutes, then water cooling is adopted, and at least one laser scanning is performed after the solid solution treatment to detect the size and profile.

[0020] According to the manufacturing method of the double-layer stainless steel square neck pipe provided by the application, the small heat input welding process includes: symmetric and uniform welding is performed by using manual TIG welding, the welding current is 100~180A, the heat input is controlled to be below 1.8kJ / mm, and the interlayer temperature is controlled to be below 100℃.

[0021] According to the manufacturing method of the double-layer stainless steel square neck pipe provided by the application, the size and profile are detected by using a laser scanner every 1 hour.

[0022] According to the manufacturing method of the double-layer stainless steel square neck pipe provided by the application, the process parameters of the low-temperature annealing treatment are as follows: the annealing temperature is set to 400±15℃, the holding time is 4 hours, then the furnace is cooled to room temperature, the low-temperature annealing treatment is performed after the first nondestructive testing of the gusset plate after welding is qualified, and the second nondestructive testing is performed after the annealing.

[0023] The double-layered stainless steel square neck pipe provided by the application comprises an inner shell formed by splicing a plurality of arc-shaped inner shell pieces, an outer shell formed by splicing an arc-shaped outer shell piece and a straight section outer shell piece, a web plate connecting the inner shell and the outer shell, and a support guide column welded to the outer arc surface of the inner shell. Through model splitting, systematic stress control and precision monitoring in the whole manufacturing process, the processing and welding deformation of the austenitic stainless steel is effectively inhibited, the high-precision manufacturing of the double-layered square neck pipe with millimeter-level profile is realized, the risk of the traditional straightening process is avoided, and the strict requirements of the vacuum chamber of the nuclear fusion device on the ultra-high vacuum interface component are met. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 FIG. 1 is a structural schematic diagram of the double-layered stainless steel square neck pipe provided by the application.

[0026] Figure 2 FIG. 2 is a top view schematic diagram of the double-layered stainless steel square neck pipe provided by the application.

[0027] Figure 3 FIG. 3 is an exploded structural schematic diagram of the inner shell provided by the application.

[0028] Figure 4 FIG. 4 is an exploded structural schematic diagram of the outer shell provided by the application.

[0029] Figure 5 FIG. 5 is a flow schematic diagram of the processing and manufacturing method of the double-layered stainless steel square neck pipe provided by the application.

[0030] FIG. 1 is a structural schematic diagram of the double-layered stainless steel square neck pipe provided by the application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the application more clear, the technical solutions in the application will be described clearly and completely below in combination with the drawings in the application. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0032] The following will be described in combination with Figures 1 to 5This invention describes the double-layer stainless steel square neck tube and its processing and manufacturing method.

[0033] One embodiment of the present invention provides a double-layer stainless steel square neck tube, combined with Figure 1 and Figure 2 As shown, the double-layer stainless steel square neck tube includes an inner shell 1, an outer shell 2, a stiffening plate 3, and a supporting guide post 4. The inner shell 1 is assembled and welded from multiple arc-shaped inner shell parts 11. The outer shell 2 is fitted around the outer periphery of the inner shell 1, forming a sandwich structure between the outer shell 2 and the inner shell 1. The outer shell 2 is assembled and welded from multiple arc-shaped outer shell parts 21, narrow straight outer shell parts 22, and wide straight outer shell parts 23. The stiffening plate 3 is located within the sandwich structure formed by the inner shell 1 and the outer shell 2, and the stiffening plate 3 connects the inner shell 1 and the outer shell 2. The supporting guide post 4 is located within the sandwich structure formed by the inner shell 1 and the outer shell 2. One end of the supporting guide post 4 is welded to the outer arc surface of the inner shell 1, and the other end is used to abut against the inner arc surface of the outer shell 2.

[0034] It is understood that the double-layer stainless steel square neck tube of this embodiment adopts a modular sandwich design, including an inner shell 1 made of multiple arc-shaped inner shell parts 11 welded together, and an outer shell 2 fitted around the outer periphery of the inner shell 1, which is made of multiple arc-shaped outer shell parts 21, narrow straight outer shell parts 22 and wide straight outer shell parts 23 welded together. Together, they form a stable sandwich structure. Within the sandwich structure, stiffening plates 3 and supporting guide posts 4 are provided. The stiffening plates 3 are welded between the inner and outer shells, playing the main role of structural support and force transmission. One end of the supporting guide post 4 is welded to the outer arc surface of the inner shell 1, and the other free end is used to accurately abut against the inner arc surface of the outer shell 2 after assembly, together forming an internal support network that effectively resists external pressure and suppresses shell deformation.

[0035] The manufacturing process of the double-layered stainless steel square neck tube strictly follows the principles of block forming, sequential assembly, and whole-process monitoring. First, the inner and outer shells are split into multiple arc-shaped pieces and straight pieces for blanking and profiling. Then, the inner shell 1 is assembled and welded first, and the welding ribs 3 and support guide columns 4 are welded during this process. Finally, the components of the outer shell 2 are assembled onto the formed inner core structure and the final welding is completed. This embodiment reduces the forming and welding process frequency by splitting the model, reduces the stress caused by the forming and welding process during manufacturing, and avoids the possibility of size and profile deviation caused by deformation. Moreover, a rigid internal skeleton composed of ribs 3 and support guide columns 4 is constructed on the inner core structure before welding the outer shell. The composite support system formed by the ribs 3 and support guide columns 4 significantly enhances the overall stiffness of the sandwich structure, effectively disperses and offsets the welding stress and operating stress generated during manufacturing and subsequent service. The double-layered stainless steel square neck tube of this embodiment can be blanked, formed, machined, and welded by block and slice, which fundamentally suppresses the instability deformation of the shell, not only ensures the millimeter-level profile and size accuracy of the neck tube, but also meets the stringent requirements of the ultra-high vacuum interface, avoids the possible damage to the weld and safety hazards caused by traditional cold straightening, and realizes the unity of high quality and high reliability.

[0036] In some embodiments of the double-layered stainless steel square neck tube of the present application, the inner shell 1 is composed of four 90° arc-shaped arc-shaped inner shell pieces 11; the outer shell 2 is composed of four 90° arc-shaped arc-shaped outer shell pieces 21, two narrow straight outer shell pieces 22 and two wide straight outer shell pieces 23.

[0037] It can be understood that, as shown in Figure 3 , the inner shell 1 of the double-layered stainless steel square neck tube is composed of four identical 90° arc-shaped arc-shaped inner shell pieces 11, which form a regular square tubular base body. Correspondingly, as shown in Figure 4 , the outer shell 2 adopts a more complex combined structure: four 90° arc-shaped outer shell pieces 21 as the main body, and at the four butt joint positions between adjacent arc-shaped outer shell pieces 21, two narrow straight outer shell pieces 22 and two wide straight outer shell pieces 23 are embedded and welded in an alternating and symmetrical manner, thereby forming a complete and closed square outer tube. This embodiment decomposes the complex integral square tube into standardized arc-shaped pieces and functional straight pieces, laying a foundation for subsequent high-precision manufacturing.

[0038] In manufacturing, first, four arc-shaped inner shell pieces 11 are assembled and welded to form a complete inner shell 1. Then, in the outer shell 2 assembly stage, two narrow straight section outer shell pieces 22 and two wide straight section outer shell pieces 23 are positioned on the corresponding gusset plates 3 of the inner shell 1 as connecting bridges, and then four arc-shaped outer shell pieces 21 are filled in between and all seam welds are completed. This embodiment decomposes the large-area and large-curvature deformation difficult to control in traditional integral forming into local forming of multiple small arc-shaped pieces and straight section pieces, greatly reducing the difficulty of single processing and residual stress. Moreover, the introduction of the straight section pieces not only facilitates the docking with the external system interface, but also makes it easier to design and install clamping fixtures during welding, thereby effectively restraining the welding deformation, and finally ensuring the millimeter-level high precision of the overall neck pipe contour and size.

[0039] In some specific examples of the double-layered stainless steel square neck pipe of the present application, referring again to Figure 3 As shown, the arc-shaped inner shell piece 11 includes an arc section and flat plate sections connected to both sides of the arc section, and one gusset plate 3 is arranged on each flat plate section to form two gusset plates 3 on each face of the inner shell 1, and the two gusset plates 3 are symmetrically arranged along the joint of two adjacent arc-shaped inner shell pieces 11.

[0040] It can be understood that each arc-shaped inner shell piece in the present example is a composite structure integrating the middle arc section and the flat plate sections on both sides, and the welding interface of the gusset plate 3 is transferred from the unstable arc surface to the rigid flat plate section. When one gusset plate 3 is welded on each flat plate section of each arc-shaped inner shell piece 11, two gusset plates 3 are naturally formed on each square outer surface of the complete inner shell 1 formed by the four arc-shaped inner shell pieces 11, and the two gusset plates 3 are symmetrically distributed about the joint between the two arc-shaped inner shell pieces 11.

[0041] It needs to be understood that the gusset plate 3 is welded on the flat flat plate section in the present example, which can obtain a larger and more stable welding contact area compared to welding on a curved surface, greatly enhancing the connection strength and avoiding welding defects caused by poor curved surface fitting. Secondly, the symmetrically arranged gusset plates 3 form a force couple type support structure on both sides of the joint, which can effectively resist the tendency of the joint to open when the outer shell 2 is under load or there is welding stress, and evenly disperse the stress to the arc-shaped inner shell pieces 11 on both sides. The structural distribution of the inner shell 1 of the present example fundamentally strengthens the structural integrity of the inner shell 1 itself and provides a solid guarantee for the subsequent stable foundation of the welded outer shell 2.

[0042] In some specific examples of the double-layered stainless steel square neck pipe of the present application, continuing to refer to Figure 3As shown, a plurality of support guide columns 4 are welded on the outer arc surface of each arc-shaped inner shell piece 11, each row including two support guide columns 4, and the extension lines of the two support guide columns 4 in each row forming a 30° angle at the center of the arc surface of the arc-shaped inner shell piece 11.

[0043] It can be understood that the support guide columns 4 in the embodiment are designed as a three-dimensional support network regularly distributed on the outer arc surface of the arc-shaped inner shell piece 11. On the outer surface of each arc-shaped inner shell piece 11, the support guide columns 4 are arranged in multiple rows along the axial direction (i.e. the length direction of the neck pipe), each row including two support guide columns 4, and the theoretical center extension lines of the two support guide columns 4 intersecting at the center of the arc surface of the arc-shaped inner shell piece and forming an accurate 30° angle. This arrangement means that the support guide columns are obliquely extended from the center area of the arc surface to both sides, thereby constructing a stable "V"-shaped support unit in the inner part of the arc-shaped shell, and multiple such units are combined to form a complete internal framework.

[0044] The implementation process of the support guide columns 4 is performed after the inner shell 1 is completed and before the outer shell 2 is assembled. During operation, a special tool is used to ensure that the welding position and angle of the support guide columns 4 meet the design requirement of the 30° angle. The external load (such as vacuum negative pressure) originally perpendicular to the shell can be effectively decomposed into an axial force along the direction of the guide column, thereby greatly improving the ability of the shell to resist deformation. Moreover, after the outer shell 2 is finally welded and abuts against the free end of the support guide column 4, the guide column group distributed at a 30° angle collectively forms an efficient force transmission path, which can uniformly transmit the stress borne by the outer shell 2 to the entire inner shell 1, thereby avoiding stress concentration and significantly enhancing the overall rigidity and stability of the double-layer structure, so as to ensure the persistent accuracy of the neck pipe contour in harsh working conditions.

[0045] The present application also provides a processing and manufacturing method of a double-layer stainless steel square neck pipe, which is suitable for processing and manufacturing the double-layer stainless steel square neck pipe of any one of the above embodiments. Figure 5 As shown, in some embodiments, the processing and manufacturing method of the double-layer stainless steel square neck pipe includes the following steps S1-S6.

[0046] Before processing and manufacturing the double-layer stainless steel square neck pipe, the square neck pipe is first split into the inner shell 1, the outer shell 2, the rib plate 3 and the support guide column 4 according to the design model of the double-layer stainless steel square neck pipe, the inner shell 1 is split into a plurality of arc-shaped inner shell pieces 11, and the outer shell 2 is split into a plurality of arc-shaped outer shell pieces 21, a narrow straight section outer shell piece 22 and a wide straight section outer shell piece 23, and the plate material is cut.

[0047] S1, the multiple pieces of cut plate material are subjected to arc-shaped bending forming to form the multiple arc-shaped inner shell pieces 11 and the multiple arc-shaped outer shell pieces 21, and after the forming, the multiple arc-shaped inner shell pieces 11 and the multiple arc-shaped outer shell pieces 21 are subjected to solid solution treatment with a mold.

[0048] S2, riveting and reinforcing the plurality of arc-shaped inner shell pieces 11, after passing the size and profile detection, using small heat input welding process to weld, forming the inner shell 1, and monitoring the size and profile at intervals during the welding process.

[0049] S3, assembling and welding the rib plate 3 on the outer surface of the inner shell 1, monitoring the size and profile at intervals during the welding process, after the welding is completed, carrying out non-destructive testing, and after passing the test, carrying out low temperature annealing treatment.

[0050] S4, welding the support guide column 4 on the outer arc surface of the inner shell 1.

[0051] S5, riveting the plurality of arc-shaped outer shell pieces 21 to the rib plate 3, after passing the size and profile detection, using small heat input welding process to weld, and monitoring the size and profile at intervals during the welding process; then assembling and welding the narrow straight section outer shell piece 22 and the wide straight section outer shell piece 23.

[0052] S6, after all the welding and tooling are removed, carrying out the final size and profile detection.

[0053] The processing and manufacturing method of the double-layer stainless steel square neck pipe of the embodiment adopts the processes of block forming, sequential assembly and active shape control. First, the whole neck pipe is divided into modular components such as the inner shell 1, the outer shell 2, the rib plate 3 and the support guide column 4, wherein the inner and outer shells are further divided into a plurality of arc-shaped pieces and straight section pieces for separate blanking. Then, the arc-shaped plates are bent and formed, and a mold solid solution treatment process is adopted to eliminate the stress at high temperature, and the mold is used to constrain the formed piece to ensure its size stability. On this basis, the assembly and welding are carried out in strict sequence: the splicing and welding of the inner shell 1 are completed first, then the rib plate 3 is welded, then the key low temperature annealing treatment is carried out to release the welding stress, then the support guide column 4 is installed, and finally the outer shell components are assembled and welded in stages. The whole welding process adopts small heat input process, and laser scanning monitoring is carried out at intervals to realize real-time feedback and control of deformation.

[0054] It can be understood that the modularization and sequential welding decompose the concentrated and complex heat input into dispersed and controllable processes, reducing the cumulative stress and overall deformation from the source. The mold solid solution and the stage low temperature annealing actively eliminate the main internal stress in the forming and welding process, avoiding the damage to the weld and the safety hazard caused by traditional cold straightening, and avoiding the risk of internal oxidation caused by hot straightening. The whole process laser monitoring constitutes a closed-loop quality control system, ensuring the manufacturing precision of each stage, thereby finally ensuring that the double-layer stainless steel square neck pipe can meet the stringent requirements of millimeter-level profile high precision and ultra-high vacuum environment reliability.

[0055] In some embodiments of the method for manufacturing the double-layer stainless steel square neck pipe, the arc bending forming of the multiple plates after cutting in step S1 is performed by using a multi-cutter pressing type, and a 10-15mm-thick stainless steel pad is used as the gasket between the upper and lower pressing heads. After each pressing, the pressure is maintained for 5 minutes, and a template is used for comparison and measurement.

[0056] It can be understood that the arc bending forming in the embodiment is performed by using the principles of gradual force application, flexible contact and real-time verification. The core of the hardware configuration is the combination of a multi-cutter pressing device and a special flexible gasket. A 10-15mm-thick stainless steel pad is used as the gasket between the upper and lower pressing heads and the stainless steel thick plate to be formed (40mm thick). First, the plate is gradually bent to the target arc by using a multi-cutter and a step-by-step method. After each pressing, a strict pressure maintaining program is performed to maintain the pressure for 5 minutes to allow the material stress to fully relax and redistribute. Then, the pressure is immediately removed, and a high-precision template is used to compare and measure the workpiece to confirm the deviation between the actual profile and the theoretical profile of this pressing, and to guide the amplitude and position of the next pressing accordingly.

[0057] It should be understood that the multi-cutter pressing combined with pressure maintaining effectively avoids the sudden increase of internal stress and the generation of micro-cracks caused by one-time large deformation processing, significantly reducing the initial stress level of the formed parts. The use of stainless steel pads forms a flexible buffer layer, which not only protects the surface of the expensive pressing head mold, but more importantly, prevents the generation of surface defects such as indentations and scratches in ultra-high vacuum components. The step-by-step template comparison ensures that the forming process is always under control, allowing for timely detection and correction of profile deviations, thereby ensuring the forming accuracy of each arc-shaped part at the source and laying a solid foundation for subsequent welding and assembly to achieve millimeter-level assembly profile.

[0058] In some embodiments of the method for manufacturing the double-layered stainless steel square neck pipe, the process parameters for the solution treatment of the belt die of the plurality of arc-shaped inner shell pieces 11 and the plurality of arc-shaped outer shell pieces 21 in step S1 are as follows: the solution treatment temperature is set to 1100±15℃, the holding time is 35 to 40 minutes, and then water cooling is adopted. After the solution treatment, at least one laser scanning is performed to detect the size and the profile. In this embodiment, the solution treatment process forms a rapid quenching in a constrained state. First, in terms of process implementation, the arc-shaped inner shell pieces and the outer shell pieces after the press bending forming are sent into a heat treatment furnace together with their forming dies, the material inside the carbonates is fully dissolved and the austenite structure is homogenized at a solution treatment temperature of 1100±15℃ for 35 to 40 minutes, and then it is rapidly water cooled to room temperature. Second, in terms of quality monitoring, this process is set as a necessary detection node, that is, after the solution treatment is completed and the die is removed, at least one comprehensive size and profile detection is immediately performed on the workpiece using a laser scanner to obtain the initial precision data after the heat treatment.

[0059] It can be understood that the combination of belt die solution treatment and rapid water cooling aims to maximize the elimination of residual stress accumulated in the previous press bending process and refine the grains, so as to obtain an austenite structure with uniform composition and stable performance. The constraint effect of the die is crucial, which can effectively prevent the springback or distortion of the workpiece at high temperature due to stress release, and ensure that the forming precision is maintained. Secondly, the subsequent laser scanning detection plays a quality control role, which not only can accurately evaluate the actual influence of the solution treatment on the size stability of the workpiece and verify the effect of the previous process, but also can provide high-precision initial reference data for the subsequent welding and assembly process, and ensure the controllability and traceability of the entire manufacturing process.

[0060] In some embodiments of the method for manufacturing the double-layered stainless steel square neck pipe, the small heat input welding process in steps S2 and S5 includes: adopting manual TIG welding to perform symmetrical and uniform welding, the welding current is 100 to 180 A, the heat input is controlled to be less than 1.8 kJ / mm, and the interlayer temperature is controlled to be less than 100℃.

[0061] It can be understood that the small heat input welding process with a heat input lower than 2.0 kJ / mm can strictly control the total energy input per unit length of the weld in the welding process, and then realize the relatively low temperature state of the welding area, thereby reducing the heat affected zone of the austenitic stainless steel. In the embodiment, the small heat input welding process is specifically selected as the manual TIG welding with stable arc and concentrated heat. In the operation, the welder is required to use the symmetrical and uniform welding sequence to avoid local heat accumulation. In the parameter, the welding current is accurately limited in the lower interval of 100-180 A, and the heat input per unit length is strictly suppressed below 1.8 kJ / mm by controlling the welding speed. Meanwhile, when welding multiple layers of welds, a temperature detector must be used to monitor the weld area to ensure that the interlayer temperature of the previous weld has cooled to below 100℃ when the next weld starts. The combination of low current and low heat input greatly reduces the total heat input into the base material, and fundamentally limits the width of the welding heat affected zone and the degree of grain coarsening. The strategy of strict interlayer temperature control and symmetrical welding ensures that the welding heat can be quickly and uniformly dissipated, effectively avoiding the formation of large non-uniform thermal stress in the structure. Through the combination of low current and low heat input and the strategy of strict interlayer temperature control and symmetrical welding, the deformation tendency in the welding process is maximally inhibited, and the dimensional stability and contour accuracy of the assembled parts after welding are ensured.

[0062] In some embodiments of the manufacturing method of the double-layer stainless steel square neck pipe, the size and profile are monitored every 1 hour in steps S2, S3 and S5.

[0063] It can be understood that, in the three process stages of key inner shell welding (step S2), rib plate welding (step S3) and outer shell assembly welding (step S5) which are the most concentrated and most likely to cause deformation stress introduction, whether the current welding operation is completed or not, the welding operation is suspended every 1 hour as a fixed cycle, and a high-precision laser scanner is used to perform a comprehensive three-dimensional scanning of the workpiece to quickly obtain the overall size and profile data, forming a mandatory interruption and evaluation link in the manufacturing process. First, near-real-time monitoring and quantitative management of welding deformation can be realized, and traditional post-event and result control can be changed to in-process and process control. Through hourly data collection, the small deformation trend of the workpiece under the action of welding stress can be accurately captured, rather than waiting until the deformation accumulates to an irreversible degree. Secondly, data-driven decision-making basis can be provided for operators. Once it is found that the detection data deviates from the expected value or approaches the tolerance limit, the current process can be immediately suspended, the reasons can be analyzed and intervention measures (such as adjusting the welding sequence and optimizing the parameters) can be taken, so as to dynamically correct the manufacturing path and ensure that the deformation is always within the controllable range, thereby fundamentally guaranteeing the realization of millimeter-level precision of the final product.

[0064] In some embodiments of the method for manufacturing the double-layered stainless steel square neck pipe, the process parameters of the low-temperature annealing treatment in step S3 are as follows: the annealing temperature is set to 400±15°C, the holding time is 4 hours, and the furnace is then cooled to room temperature. The low-temperature annealing treatment is performed after the first non-destructive testing of the gusset plate 3 after welding, and the second non-destructive testing is performed after annealing. It can be understood that, first, the entire assembly is sent into the heat treatment furnace only after the gusset plate 3 is welded and the first non-destructive testing (NDT) confirms that the weld quality is qualified; then, the holding time of 4 hours at 400±15°C, which is a critical temperature sufficient to promote the recovery of the metal material and effectively reduce the residual stress, but far below the sensitization temperature and will not affect the corrosion resistance, so that the stress is fully relaxed; finally, the most gentle cooling method of furnace cooling is adopted to room temperature to avoid introducing new thermal stress.

[0065] The low-temperature annealing precisely removes most of the internal stress accumulated during the welding of the gusset plate 3, greatly reducing the risk of serious deformation of the overall structure due to stress superposition when welding a larger area of the outer shell in the subsequent process. The two non-destructive tests frame the annealing treatment within a safe range: the first test ensures that only qualified welds are annealed, avoiding the deterioration of defective welds during heat treatment; the second test verifies that the annealing process itself has no adverse effects on existing welds (such as generating reheat cracks), thereby ensuring the integrity and reliability of the core framework structure before entering the final assembly stage.

[0066] The method for manufacturing the double-layered stainless steel square neck pipe of the present application will be described below in conjunction with specific examples.

[0067] In some specific examples of the method for manufacturing the double-layered stainless steel square neck pipe of the present application, the specific manufacturing process includes the following steps S100-S600.

[0068] First, the raw material plates of the square neck pipe assembly module are disassembled according to the model, and the plates are cut according to the designed size. As shown in FIGS. 1 and 2, the square neck pipe is divided into the inner shell 1 (four arc-shaped inner shell pieces 11), the outer shell 2 (four arc-shaped outer shell pieces 21, two narrow straight section outer shell pieces 22, and two wide straight section outer shell pieces 23), the gusset plate 3, and the support guide column 4, and the plate cutting is performed based on the corresponding disassembled components. Figure 1 Figure 2

[0069] ​​S100. Prepare the sheet metal for four arc-shaped inner shell parts 11 and four arc-shaped outer shell parts 21: The sheet metal shell thickness is 40mm. It is formed by multi-blade pressing using a large bending machine. The forming inner pressure radius R of the arc-shaped inner shell part 11 is 400mm, and the forming inner pressure radius R of the arc-shaped outer shell part 21 is 520mm. The lower pressing die is an arc-shaped die. The upper and lower pressing head pads are made of 10~15mm stainless steel pads to reduce die scratches. The pressing is done in multiple pressings, and the pressure is held for 5 minutes each time. After each pressing, the forming is compared and measured using a template.

[0070] After the S200, arc-shaped inner shell 11, and arc-shaped outer shell 21 are formed, they are placed in a heat treatment furnace along with the molding die for solution treatment at 1100±15℃ for 37 minutes. Water cooling is used for cooling. After solution treatment, the dimensions and contours are scanned for the first time. After removing the tooling, the dimensions and contours are scanned for the second time. If qualified, the surface is ground, excess material is removed by machining, and bevels are machined. UT ultrasonic testing is then performed.

[0071] S300, the four formed arc-shaped inner shell parts 11 are arranged according to... Figure 3 As shown, the riveting process is carried out. After reinforcement with internal welding fixtures and external support plates, the overall shell dimensions and contours are scanned using a laser. If the dimensions and contours are qualified, welding is performed. If they are not qualified, adjustments are made until they are qualified. Manual TIG welding is used, with low heat input, symmetrical and uniform welding, welding current of 100~180A, heat input controlled at 1.8kJ / mm, and interpass temperature less than 100℃. During the welding of the inner shell 1, the dimensions and contours are scanned with a laser every hour to ensure the controllability of welding deformation. After welding is completed, non-destructive testing of the inner shell is performed.

[0072] S400: Two sets of stiffening plates 3 are welded to each side of the inner shell 1, using a symmetrical, distributed welding method. Before welding, the dimensions and contours are measured using a laser scanner. The welding specifications and control requirements during welding are consistent with the welding process of the inner shell 1. During the welding of the stiffening plates 3, the dimensions and contours are scanned with a laser every hour. After welding, a non-destructive test is performed. After passing the test, a low-temperature annealing process is carried out at 400℃±15℃ for 4 hours, followed by furnace cooling to room temperature. After the annealing, a second non-destructive test is performed to re-measure all welds. Each of the four arc-shaped inner shell parts 11 is equipped with eight support guide pillars 4 for deformation prevention, connected at an included angle of 30° at the center of the arc surface, and evenly distributed. After welding, the dimensions and contours are confirmed by a laser scan. After the stiffening plates 3 and support guide pillars 4 are welded, the inner and outer surfaces of the inner shell 1, as well as the stiffening plates 3 and support guide pillars 4, are manually ground using an angle grinder to ensure that the surface roughness meets the requirements.

[0073] S500, rivet four arc-shaped shell parts 21 to the rib plate 3 of the inner shell 1 respectively, ensure that the gap is controlled between 3-5mm, use the annular clamping tool to rivet the arc-shaped shell part 21 on the rib plate 3, use laser scanning to check the size and profile once every 1 hour during the welding process. After the arc-shaped shell part 21 is welded, the overall size and profile are scanned. Rivet the narrow straight section shell part 22 and the wide straight section shell part 23 on the rib plate 3, each of which has two, respectively assembled in symmetrical positions, and laser scanning is used to check the size and profile once every 1 hour during the welding process. After the welding is completed, non-destructive testing and overall size and profile scanning are performed.

[0074] S600, after 24h, laser scanning is performed once for size and profile, and then laser scanning is performed once for size and profile after the external and internal cavity welding tool is removed, to ensure the final welding forming size and profile.

[0075] Based on the above implementation process, first, solid solution treatment with a mold is adopted, which effectively suppresses the distortion of the workpiece at high temperature while eliminating the bending forming stress, so that the profile error of the arc single piece is stably controlled within ±0.8mm, which is better than the conventional treatment of ±2.0mm, and provides a size-stable prefabricated piece for subsequent processing. Secondly, during the welding process, the "small heat input process" is strictly implemented and combined with "laser scanning monitoring every hour", which realizes real-time and quantitative management of the welding heat input and deformation trend, can timely intervene and adjust, and successfully limits the maximum deformation amount in the inner shell welding process to less than 1.5mm. Finally, after the rib plate is welded, "stage low temperature annealing" is introduced, which actively eliminates the internal stress accumulated in the main welding process, avoiding the stress amplification in the subsequent welding. These measures work together to ensure that the final profile of the finished product neck pipe can stably reach the millimeter-level design requirement of ≤2.0mm, and the flatness error of the key interface flange is <0.5mm.

[0076] Due to the maximum prevention and elimination of deformation in the manufacturing process, the product does not need to be corrected by cold or hot straightening after finishing, which is 100%. This completely avoids the microscopic damage of the weld caused by cold straightening, so that the first pass rate of post-weld non-destructive testing (RT / UT) is improved from about 90% of the traditional to more than 99.5%; At the same time, it also eliminates the internal oxidation problem of the double-layer structure caused by hot straightening, and the cleanliness inside the interlayer meets the highest level requirement of GJB1184A (in engineering practice, products that can pass the most stringent PIND test in GJB 1184A are considered to have reached the highest internal cleanliness level requirement. The cleanliness that meets the highest level requirement of GJB 1184A means that the product has almost no free particles that can be detected inside). The method integrates the whole process of quality verification to ensure the quality of the weld and the integrity of the internal structure, so as to meet the extreme reliability requirements of the nuclear fusion device vacuum chamber for the interface components in the ultra-high vacuum environment.

[0077] Compared with the traditional "trial and error" processing and time-consuming "negative pressure shaping" stress relief method relying on operator experience, in the standardized and data-based process flow of the example, the modularization of the splitting strategy reduces the difficulty of single molding, and digital detection means such as laser scanning provides objective and unified evaluation criteria. This not only significantly improves the efficiency, shortens the total manufacturing cycle of single products by about 35%~40%, but more importantly, it ensures the consistency of high quality and high precision among different products. Through the digital detection feedback of laser scanning, the standard deviation of the key dimensions (such as diagonal length, pipe opening size) of different batches of products is reduced by 60%, which lays a solid technical foundation for stable batch production of such high-performance and complex structure components.

[0078] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A double-walled stainless steel square neck finish characterized in that, The utility model relates to a double-layer stainless steel square neck pipe, which comprises the following parts: an inner shell (1) composed of multiple arc-shaped inner shell pieces (11) assembled and welded together; an outer shell (2) sleeved on the outer periphery of the inner shell (1), wherein a sandwich structure is formed between the outer shell (2) and the inner shell (1), and the outer shell (2) is composed of multiple arc-shaped outer shell pieces (21), multiple narrow straight outer shell pieces (22) and multiple wide straight outer shell pieces (23) assembled and welded together; a rib plate (3) located in the sandwich structure formed by the inner shell (1) and the outer shell (2), wherein the rib plate (3) connects the inner shell (1) and the outer shell (2); a support guide column (4) located in the sandwich structure formed by the inner shell (1) and the outer shell (2), wherein one end of the support guide column (4) is welded to the outer arc surface of the inner shell (1), and the other end of the support guide column (4) is used for abutting against the inner arc surface of the outer shell (2).

2. The double-walled stainless steel square neck of claim 1, wherein, The inner shell (1) is composed of four arc-shaped inner shell pieces (11) with an angle of 90 degrees, and the outer shell (2) is composed of four arc-shaped outer shell pieces (21) with an angle of 90 degrees, two narrow straight outer shell pieces (22) and two wide straight outer shell pieces (23) alternately assembled together.

3. The double-walled stainless steel square neck of claim 2, wherein, The arc-shaped inner shell piece (11) comprises an arc surface section and two flat plate sections connected to the two sides of the arc surface section, one rib plate (3) is arranged on each flat plate section, two rib plates (3) are formed on each surface of the inner shell (1), and the two rib plates (3) are symmetrically arranged along the joint of two adjacent arc-shaped inner shell pieces (11).

4. Double-layered stainless steel square neck tube according to claim 2 or 3, characterized in that Multiple support guide columns (4) are welded to the outer arc surface of each arc-shaped inner shell piece (11), each row of support guide columns (4) comprises two support guide columns (4), and the extension lines of the two support guide columns (4) in each row form an angle of 30 degrees at the center of the arc surface of the arc-shaped inner shell piece (11).

5. A method of manufacturing a double-layered stainless steel square neck tube, characterized by, The method for manufacturing the double-layer stainless steel square neck pipe is suitable for manufacturing the double-layer stainless steel square neck pipe according to any one of claims 1 to 4, and the method comprises the following steps: arc-shaped bending forming is performed on multiple plates to form multiple arc-shaped inner shell pieces (11) and multiple arc-shaped outer shell pieces (21), and after the bending forming is completed, solid solution treatment is performed on the multiple arc-shaped inner shell pieces (11) and the multiple arc-shaped outer shell pieces (21) with a mold; the multiple arc-shaped inner shell pieces (11) are riveted and reinforced, after the size and profile degree are detected to be qualified, small heat input welding is performed to form an inner shell (1), and the size and profile degree are monitored at intervals during the welding process; a rib plate (3) is assembled and welded to the outer surface of the inner shell (1), the size and profile degree are monitored at intervals during the welding process, nondestructive testing is performed after the welding is completed, and low-temperature annealing treatment is performed after the nondestructive testing is qualified; support guide columns (4) are welded to the outer arc surface of the inner shell (1); the multiple arc-shaped outer shell pieces (21) are riveted to the rib plate (3), after the size and profile degree are detected to be qualified, small heat input welding is performed, and the size and profile degree are monitored at intervals during the welding process; subsequently, a narrow straight outer shell piece (22) and a wide straight outer shell piece (23) are assembled and welded together; After all welding and tooling is removed, the final size and profile inspection is performed.

6. The method of claim 5, wherein the method further comprises: The arc-shaped bending forming of the plurality of plates is performed by using a multi-cutter pressing type, and a 10mm to 15mm-thick stainless steel pad plate is arranged on the upper and lower pressing head cushions, the pressure is maintained for 5 minutes after each pressing, and a template is used for forming comparison measurement.

7. The method of claim 5, wherein the method further comprises: The process parameters of the solid solution treatment of the plurality of arc-shaped inner shell pieces (11) and the plurality of arc-shaped outer shell pieces (21) with the mold are that the solid solution temperature is set to 1100±15℃, the holding time is 35 minutes to 40 minutes, then water cooling is adopted, and at least one laser scanning is performed after the solid solution treatment to detect the size and profile.

8. The method of manufacturing a double-layered stainless steel square neck tube according to claim 5, wherein The small heat input welding process comprises: symmetrically and uniformly performing welding by using manual TIG welding, the welding current is 100-180A, the heat input is controlled to be below 1.8kJ / mm, and the interlayer temperature is controlled to be below 100℃.

9. The method of manufacturing a double-layered stainless steel square neck tube according to claim 5, wherein The interval predetermined time monitoring of the size and profile is that the size and profile are detected by using a laser scanner every 1 hour.

10. The method of claim 5, wherein the method further comprises: The process parameters of the low-temperature annealing treatment are that the annealing temperature is set to 400±15℃, the holding time is 4 hours, then the furnace is cooled to room temperature, the low-temperature annealing treatment is performed after the first nondestructive testing of the rib plate (3) after welding is qualified, and the second nondestructive testing is performed after the annealing.

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