Method for controlling roundness of a 5m diameter large thickness shell segment

Abstract

The application provides a 5m diameter large-thickness shell segment roundness control method, which comprises the following steps: S1, fixing the shell segment wall plate through a back support backing plate and a pressing mechanism; S2, adopting twice positioning welding to firstly weld the weld seam of the wall plate, and then welding the sealing weld seam; and S3, for the shell segment with the roundness or generatrix straightness of the shell segment weld seam and the circumferential welding area being out of tolerance, bending correction is performed. The 5m diameter large-thickness shell segment roundness control method innovatively designs a convex welding backing plate for the outer surface front weld seam welding of the double-sided welding of the φ5000mm diameter large-thickness shell segment and a concave welding backing plate for the inner surface root weld seam welding, and the problem of the flat weld seam caused by the existing flat welding backing plate is solved.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing technology for thick shell sections, and in particular relates to a method for controlling the roundness of a 5m diameter thick shell section. Background Technology

[0002] The new generation of manned lunar launch vehicles undertakes major aerospace engineering missions such as my country's manned lunar exploration, space station project, and Mars exploration. Its propellant tank diameter is 5000mm, consistent with the Long March 5. The propellant tank, as the fuel carrier, is the core of the launch vehicle, welded together from components such as the front and rear tank bottoms, front and rear short shells, and several intermediate cylindrical sections. The short shells and cylindrical sections are collectively referred to as the shell sections, which are important components of the propellant tank. Given the 5000mm diameter, the thickness of the welded areas in the shell sections is mostly between 15-22mm. To meet the requirements of circumferential seam assembly welding, the roundness of the welded areas in the shell sections must be controlled. However, the following problems exist: One challenge is that welding wall panels thicker than 15mm exceeds the maximum thickness that current equipment can weld, making it difficult to achieve full penetration in one weld. Another challenge is the shell section thickness, which imposes stricter requirements on misalignment during assembly. It is difficult to eliminate misalignment during circumferential seam welding using the internal support of the welding pad. The third challenge is the lack of internal support fixtures for the short shell-bottom circumferential seam assembly. After the short shell is fitted into the fork-shaped ring, the interference fit is used to ensure the short shell is rounded, requiring strict control of the interference fit between 3-5mm. To solve the above problems, it is urgent to develop a method for controlling the roundness of thick shell sections. Summary of the Invention

[0003] In view of this, the present invention aims to propose a method for controlling the roundness of a 5m diameter, thick shell segment, in order to solve the problem of final assembly accuracy of the shell segment.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] A method for controlling the roundness of a 5m diameter, thick shell section includes the following steps: S1, fixing the shell section wall panel by means of a back support pad and a clamping mechanism;

[0006] S2. Two-stage positioning welding is used to first weld the wall panel seams, and then weld the sealing seams.

[0007] S3. For shell sections with excessive roundness or straightness of the weld seam and circumferential weld area, bend and straighten them.

[0008] Furthermore, the back support pad includes a convex welding pad and a concave welding pad that are independently provided. The convex welding pad is used to support the welding front weld inside the weld, and the concave welding pad is used to support the welding root weld outside the weld.

[0009] Furthermore, both the convex welding pad and the concave welding pad are arc-shaped plates.

[0010] Furthermore, the specific method for welding the wall panels first by positioning welding on both sides and then welding the sealing weld in step S2 is as follows: Before welding, mark the welding sequence number at the edge to be welded on each wall panel, such as ①-①, ②-②, ③-③ and ④-④. Perform the assembly welding of the wall panels on the welding fixture. First, weld two sets of one-to-one wall panels to complete the welding of welds ① and ③. Then, weld two sets of two-to-two wall panel assemblies to complete the welding of weld ②. At this time, the four wall panels have been welded together. Measure the arc length of the four wall panel assemblies. If the arc length is too large, the excess can be milled on both sides of the wall panel corresponding to weld ④. Then, complete the welding of the sealing weld ④.

[0011] Furthermore, after the front weld is completed, the shell section is hoisted from the welding fixture to the side of the main unit's vertical column, and at the same time, the welding fixture with the concave pad is rotated to the welding position, and the root weld is welded using a stirring needle.

[0012] Furthermore, the tool used for bending and straightening in step S3 is a straightening trolley, which includes a trolley body, a support arm, and a support frame. The trolley body and the support arm are movably connected, allowing the support arm to be raised at a certain angle relative to the trolley body. A pressure head is fixedly installed below the support arm. A first support frame is installed in the middle of the top of the trolley body, and second support frames are fixedly installed on both sides. The height of the second support frame is greater than that of the first support frame. Several inner rollers are evenly distributed above the first support frame. The inner rollers are movably connected to the first support frame and can move in a circumferential and yaw direction. Several outer rollers are evenly distributed on the second support frame.

[0013] Furthermore, the specific method for bending and correcting shell sections with excessive roundness or straightness of the circumferential weld seam or circumferential weld area in step S3 is as follows: During correction, the support arm is raised to a set angle, and the shell section is placed on the two rows of outer rollers on the correction frame. The outer surface of the shell section to be corrected is supported by the inner rollers. The pressure head presses and feeds the wall panel on the inner surface of the shell section in a single-point progressive manner. Through three-point bending correction, the deformation is gradually achieved point by point to realize the accurate correction of circumferential and yaw curvature and straightness.

[0014] Compared with existing technologies, the roundness control method for a 5m diameter, large-thickness shell section described in this invention has the following advantages:

[0015] (1) The roundness control method of the 5m diameter thick shell section described in this invention innovatively designs a convex welding pad for welding the front weld of the outer surface of the double-sided welding of the φ5000mm diameter thick shell section and a concave welding pad for welding the root weld of the inner surface, which alleviates the problem of straight weld caused by the existing flat welding pad.

[0016] (2) The roundness control method for a 5m diameter, thick shell section described in this invention innovatively proposes a double-sided friction stir welding scheme for the shell section. Based on the difference in heat input between the front and back sides of the friction stir welding, a secondary friction stir welding is performed at the root of the weld. The reverse deformation is used to eliminate or reduce the weld depression caused by the front welding. On the one hand, this solves the problem that shell sections with a thickness of more than 15mm cannot be fully welded in one go, and also reduces the upsetting pressure during the welding process, which is conducive to ensuring the accuracy and stability of the equipment. On the other hand, it can effectively utilize the difference in heat input between the front and back sides of the friction stir welding to achieve reverse deformation of the front weld through root friction stir welding.

[0017] (3) The roundness control method for a 5m diameter and thick shell section described in this invention has a set of straightening frame car, which can conveniently and quickly straighten the entire shell section and the local longitudinal seams after the machine side, and can also accurately straighten the front and rear circumferential welding areas of the shell section, effectively ensuring the final assembly accuracy requirements of the shell section. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 This is a flowchart illustrating the production process of the thick shell segment according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the shell section longitudinal seam friction stir welding equipment according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the concave front weld seam according to an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the weld seam on the front side of the convex welding pad as described in an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the weld root of the concave welding pad according to an embodiment of the present invention;

[0024] Figure 6 This is a flowchart illustrating the shell section wall panel welding process according to an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the root welding of the shell segment reverse assembly according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the welding assembly of the front weld seam of the shell section according to an embodiment of the present invention;

[0027] Figure 9 This is a side view of the shell section straightening frame vehicle according to an embodiment of the present invention;

[0028] Figure 10 This is a front view of the shell section straightening frame vehicle described in an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Friction stir welding equipment; 11-Horizontal base; 12-Vertical column; 13-Piano key pressure plate; 14-Welding host; 15-Welding fixture; 2-Back support pad; 21-Convex welding pad; 22-Concave welding pad; 3-Shell section; 4-Straightening frame; 41-Car body; 42-Outrigger; 43-Pressure head; 44-Support frame 1; 45-Support frame 2; 46-Inner roller; 47-Outer roller; 5-Weld seam. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] A method for controlling the roundness of a 5m diameter, thick shell section, such as... Figures 1 to 10 As shown, it includes the following steps:

[0036] S1. The shell section wall panel is fixed by the back support pad 2 and the clamping mechanism;

[0037] S2. First, weld the two-to-two assembly seams of the wall panel, and then weld the sealing seams.

[0038] S3. For shell sections with excessive roundness or generatrix straightness in the weld seam and circumferential weld area, bending correction is performed. This invention uses convex and concave welding pads designed to fit the inner and outer surfaces of the shell section wall to constrain the weld seam curvature, thus improving the straightness of the weld area caused by the previous use of flat pads for welding shell sections.

[0039] First, it should be noted that the device used for friction stir welding of the longitudinal seam of shell section 3 is a multi-axis linkage friction stir welding machine 1, model GS4-10000, which can be used for precision milling and friction stir welding of the shell section panels of launch vehicles. This equipment utilizes the welding pad and support of the welding fixture to achieve friction stir welding of the longitudinal seam. For ease of understanding and description, the GS4-10000 equipment is briefly described as follows: This equipment mainly consists of a horizontal base 11, a vertical column 12, a key-plate 13, a welding host 14, and a φ5000mm diameter welding fixture 15, etc. Figure 2 As shown. The welding fixture is mounted on a horizontal base, enabling 360° rotation and horizontal movement. The welding host is mounted on a vertical column, enabling movement in the X, Y, and Z directions, and can drive the stirring head to rotate. Simultaneously, the stirring head mounted on the welding host can tilt at + / -5° in the Y direction. This equipment utilizes the welding host to clamp the stirring head, achieving longitudinal friction stir welding through X, Y, and Z-axis linkage and rotation, and employs the welding pad and support of the welding fixture.

[0040] This article uses the 22mm shell section of the core stage propellant tank of a new-generation manned launch vehicle as a typical example. The shell section consists of four wall panels welded together using friction stir welding. The main production process is as follows: the wall panels are subjected to frontal friction stir welding using welding fixtures, and the shell section is fitted onto the main launch vehicle base and then subjected to back-side friction stir welding. The specific process flow is as follows: Figure 1As shown: Wall panel outbound inspection → Determine the shell section assembly position. If the assembly position is in the middle cylindrical section, calculate the theoretical perimeter of the cylindrical section and then calculate the wall panel arc length. If the assembly position is at the bottom, measure the perimeter of the transition shell section at the bottom of the box and then calculate the wall panel arc length. → Wall panel milling allowance → Grinding of oxide film in the welding area → Measuring the thickness of the welding area → Grinding the formal welding stirring head → Numbering welds ①, ②, ③, and ④ → Installing the wall panel corresponding to weld ① on the welding fixture → Tack welding of weld ① → Formal welding of weld ① → Removal of weld ① assembly → Installing the wall panel corresponding to weld ② on the welding fixture → Tack welding of weld ② → Formal welding of weld ② → Adjusting the weld ② Positioning of weld seam ① assembly → Weld seam ③ tack welding → Weld seam ③ formal welding → Adjust weld seam ④ to welding backing plate → Measure the arc length of the assembly. If the arc length does not meet the standard, mill the edge of the wall panel corresponding to weld seam ④ and then perform tack welding of weld seam ④. If the arc length meets the standard, then directly perform tack welding of weld seam ④; → Weld seam ④ formal welding → Shell section removal → Shell section mounting on the main equipment → Sequential back-side formal welding of the four weld seams of the shell section → Shell section removal and flash grinding → Weld seam phased array inspection. If it is unqualified, then the shell section is re-welded after being put back on the frame, and then the shell section is removed from the frame and flash grinding is performed again. If it is qualified, then directly perform weld seam X-ray inspection → circumference measurement.

[0041] During friction stir welding of shell section 3, the wall panel is mainly fixed by the back support pad and the front key clamping mechanism, and the back support pad 2 has a direct impact on the weld curvature. Because the curvature of the wall panel itself deviates significantly from the theoretical curvature during roll forming, and the two sides are relatively straight, coupled with uneven welding deformation caused by uneven heat input during thick plate welding, this invention designs two types of curvature pads with the same inner and outer diameters as the φ5000mm diameter shell section: a convex welding pad 21 and a concave welding pad 22. These two welding pads are installed at different positions on the welding fixture. The convex welding pad is used to support the welding of the front weld 5 inside the weld, and the concave welding pad is used to support the welding of the root weld 5 outside the weld. Figure 4 and Figure 5 As shown.

[0042] Before welding, mark the welding sequence number at the edge to be welded on each panel, such as ①-①, ②-②, ③-③, and ④-④. Assemble and weld the panels on the welding fixture. First, weld two sets of one-to-one panels to complete welds ① and ③. Then, weld two sets of two-to-two panel assemblies to complete weld ②. At this point, the four panels are welded together. Measure the arc length of the four panel assemblies. If the arc length is too large, mill the excess material on both sides of the panel corresponding to weld ④. Then, complete the sealing weld ④. The panel welding process is as follows: Figure 6As shown. The current welding method for the φ5000mm diameter shell section wall panel uses a 2mm long stirring pin for tack welding, followed by a 10mm stirring head for final welding. However, for the welding of a 22mm thick wall panel, due to the increased spindle upsetting pressure during welding, there is a risk that the 2mm stirring pin tack weld will be stretched open by the large stirring head during the final welding. This invention uses a 2mm + 8mm secondary tack welding. Because the stirring pin is conical, the heat input of the plastic material wrapped around the upper surface (i.e., the shoulder of the stirring pin) is greater than that at the root during welding. Uneven heat input in the thickness direction can cause the weld to be concave, such as... Figure 3 As shown. To reduce the degree of concavity, a 17mm thick stirring head was selected for the front-side formal friction stir welding. At this point, approximately 5mm of the 22mm thick shell section wall panel root was still not fully penetrated. This invention innovatively proposes a double-sided friction stir welding scheme. On the one hand, it solves the problem of shell sections thicker than 15mm not being fully penetrated in one pass, and also reduces the upsetting pressure during the welding process, which is beneficial to ensuring equipment accuracy and stability. On the other hand, it can effectively utilize the difference in heat input between the front and back sides of friction stir welding, achieving reverse deformation of the front-side weld through root friction stir welding.

[0043] like Figure 7 and 8 As shown, after the front weld seam is completed, the cylinder section is hoisted from the welding fixture to the side of the main unit's vertical column. Simultaneously, the welding fixture with the concave backing plate is rotated to the welding position. A 6mm long stirring pin, or a longer stirring pin depending on the degree of weld concavity, is used to weld the root weld. During welding, the shoulder is placed at the weld root. The relatively large heat input at the root offsets the weld concavity caused by the front weld seam, further controlling the roundness of the longitudinal weld zone of the shell section. Because the heat input at the beginning of friction stir welding is low, the weld performance is poor. After the stirring pin is withdrawn at the end of welding, a keyhole is left. Therefore, the shell section wall panel needs to have a certain length of allowance at both the front and rear ends based on the theoretical length. After welding, the allowance at both ends is removed by machining. After machining, the roundness of the front and rear weld seams and the circumferential weld zone will change due to the release of welding stress and processing stress such as wall panel rolling. Simultaneously, the roundness of the shell section itself will also exceed tolerances.

[0044] For shell sections with excessive roundness or generatrix straightness in the weld seams and circumferential weld areas, this invention designs as follows: Figure 9 and Figure 10The calibration frame 4 shown includes a body 41, a support arm 42, and a support frame. One end of the body 41 is movably connected to the support arm via a hydraulic cylinder or motor, allowing the support arm to be raised at a certain angle relative to the body. A pressure head 43 is fixedly installed below the support arm. A first support frame 44 is installed in the middle of the upper part of the body, and a second support frame 45 is fixedly installed on each side. Several rollers are evenly distributed on each support frame, and the shell section is placed above the rollers. The height of the second support frame is greater than that of the first support frame. Several inner rollers 46 are evenly distributed above the first support frame, and the inner rollers are movably sleeved with the first support frame and are equipped with buckles (which can conventionally achieve the connection between the rod and the support frame). (The buckles between the rods can be used). Several outer rollers 47 are evenly distributed on the second support frame. During the calibration, the calibration support arm is raised to a set angle, and the shell section is placed on the two rows of outer rollers on the calibration frame. The outer surface of the shell section to be calibrated is supported by inner rollers with adjustable spacing. The inner rollers are spherical and can move in the circumferential and yaw directions. In one embodiment, the support arm is connected to the pressure head through a hydraulic cylinder. The inner surface of the shell section is pressed and fed by the single-point progressive pressure head through hydraulic drive. Through three-point bending calibration, the deformation is gradually achieved point by point to realize the precise calibration of the circumferential and yaw curvature and straightness, meeting the product accuracy requirements. The invention and design of the straightening device can straighten the entire longitudinal weld seam or the local weld seam and the front and rear circumferential welding areas. Most importantly, it can achieve precise rolling straightening of the circumferential and yaw curvature and straightness of shell sections that cannot be straightened by welding after the end allowance has been machined, thus ensuring the final assembly shape and size of the shell section and achieving the requirements of high-precision assembly.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the roundness of a 5m diameter, thick shell segment, characterized in that: The steps include: S1, fixing the shell section wall panel by means of the back support pad and the clamping mechanism. The back support pad includes a convex welding pad and a concave welding pad that are set independently. The convex welding pad is used to support the welding front weld inside the weld, and the concave welding pad is used to support the welding root weld outside the weld. S2. Two-stage positioning welding is used to first weld the wall panel seams, and then weld the sealing seams. S3. For shell sections with excessive roundness or straightness of the circumferential weld seam or circumferential weld area, bend and straighten them. The tool used for bending and straightening in step S3 is a straightening frame vehicle. The straightening frame vehicle includes a vehicle body, a support arm, and a support frame. The vehicle body and the support arm are movably connected, so that the support arm can be raised at a certain angle relative to the vehicle body. A pressure head is fixedly installed below the support arm. A first support frame is installed in the middle of the upper part of the vehicle body, and second support frames are fixedly installed on both sides. The height of the second support frame is greater than that of the first support frame. Several inner rollers are evenly distributed above the first support frame. The inner rollers are movably connected to the first support frame and can move in a circumferential and yaw direction. Several outer rollers are evenly distributed on the second support frame. The specific method for bending and correcting shell sections with excessive roundness or straightness of the circumferential weld seam and circumferential weld area in step S3 is as follows: During correction, the support arm is raised to a set angle, and the shell section is placed on the two rows of outer rollers on the correction frame. The outer surface of the shell section to be corrected is supported by the inner rollers. The pressure head presses and feeds the wall panel on the inner surface of the shell section in a single-point progressive manner. Through three-point bending correction, the deformation is gradually achieved point by point to realize the accurate correction of circumferential and yaw curvature and straightness.

2. The method for controlling the roundness of a 5m diameter, thick shell segment according to claim 1, characterized in that: Both the convex and concave welding pads are curved plates.

3. The method for controlling the roundness of a 5m diameter, thick shell segment according to claim 1, characterized in that: In step S2, the specific method of first welding the wall panels with side positioning welding and then welding the sealing weld is as follows: Before welding, mark the welding sequence number at the edge to be welded on each wall panel, assemble and weld the wall panels on the welding fixture, first weld two sets of one-to-one wall panels to complete the welding of welds ① and ③, then assemble and weld two sets of two-to-two wall panel assemblies to complete the welding of weld ②. At this time, the four wall panels have been welded together. Measure the arc length of the four wall panel assemblies. If the arc length is too large, the allowance can be milled on both sides of the wall panel corresponding to weld ④, and then the welding of sealing weld ④ is completed.

4. The method for controlling the roundness of a 5m diameter, thick shell segment according to claim 1, characterized in that: After the front weld is completed, the shell section is hoisted from the welding fixture to the side of the main unit's vertical column. At the same time, the welding fixture with the concave backing plate is rotated to the welding position, and the root weld is welded using a stirring needle.

Images