Friction stir welding assembly and defect control method for sealing circular seam of storage box with diameter of 5m

Abstract

The invention provides a 5m-diameter storage box sealing circular seam friction stir welding assembly and defect control method. The method comprises the following steps that the diameter of the inner surface of a box bottom welding zone is calculated; measuring the connecting surface assembly clearance between the storage tank and the support ring; the auxiliary operation platform is assembled under the frame and is hoisted into the box bottom; a detachable inner support mechanism is assembled below the rack; after the detachable inner supporting mechanism and the mandrel are assembled, the detachable inner supporting mechanism and the mandrel are integrally hoisted to the box bottom feeding mechanism and are positioned and assembled; the box bottom feeding mechanism pushes the box bottom and inner supporting mechanism into the ring embracing mechanism to enter a welding position; a milling smooth method is adopted to control a welding seam butt joint gap; aligning the detachable inner support mechanism with the center of the welding seam by adopting a scribed line marking method; supporting the supporting block until the diameter of the inner surface of the storage box is enlarged; and tire sticking gaps and welding seam assembly misalignment between the welding base plate and a product are eliminated. The friction stir welding assembly and defect control method for the box sealing circular seam of the storage box with the diameter of 5m has the beneficial effect that the assembly precision and the welding quality are improved.

Description

Technical Field

[0001] The invention belongs to the field of aerospace, and in particular relates to a flexible assembly and defect control method of friction stir welding of sealing ring seams of a 5m-diameter tank in a vertical mode. Background Art

[0002] The new generation of launch vehicles has the characteristics of super-long, large thickness and new structure. The tank has a diameter of 5m, the welding thickness is large, and the tank adopts a double-cavity common bottom structure. For the 5m diameter tank, the current stage adopts the traditional horizontal assembly method combined with the TIG fusion welding process to manufacture the tank sealing ring seam. However, when assembling the sealing inner support in the horizontal state, the inner support core shaft will be affected by gravity and will produce flexural deformation. The overall coordination and linkage between the inner support fasteners are poor, which affects the assembly accuracy before the sealing welding. In addition, the traditional fusion welding process will inevitably have a certain degree of welding defects (such as pores, slag inclusions, microcracks, etc.) and welding residual stress. The mechanical properties of the weld are greatly reduced, the welding deformation of the product is large, and the shape and size of the tank are difficult to guarantee. It can be seen that the production of 5m diameter tanks still has a lot of room for optimization in welding assembly and welding technology. For this type of new structure 5m diameter tank, a research and development production model of vertical assembly combined with stir friction welding technology is proposed at this stage. In the vertical stir friction welding production and manufacturing of the tank, the difficulty of box sealing ring seam assembly and the greatest welding risk. After the sealing ring seam welding is completed, the tank becomes a closed box, and the internal support needs to be disassembled into parts. Affected by the confined space, the sealing inner support is designed to be detachable, and the overall interlocking and linkage performance between the inner support blocks is weak, resulting in low assembly accuracy. In theory, relying on the internal support mechanism to provide sufficient support force can ensure that the product fits the rigid support pad, but in actual engineering applications, affected by the comprehensive factors such as the upstream process barrel section profile and assembly conditions, it is inevitable that there will be assembly misalignment and the product does not fit the rigid support pad, which seriously affects the weld quality. Summary of the invention

[0003] In view of this, the present invention aims to provide a flexible assembly method for friction stir welding of a 5m diameter tank sealing ring seam, so as to solve the problem of low assembly precision of the existing tank sealing ring seam.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows: A flexible assembly method for friction stir welding of a 5m diameter tank sealing ring seam comprises the following steps: S1. Calculate the inner surface diameter of the welding area at the bottom of the box; S2. Lift the convex spherical surface of the bottom assembly downward to the bottom loading mechanism, and measure the assembly clearance between the connection surface of the storage tank and the support ring; S3, assemble the auxiliary operation platform under the frame and hoist it into the bottom of the box; S4, assembling a detachable inner support mechanism under the frame, and making its inner and outer support blocks both in a retracted state; S5. After the detachable inner support mechanism and the mandrel are assembled under the frame, they are hoisted to the feeding mechanism at the bottom of the box as a whole and positioned and assembled; S6. Use an umbrella-shaped support leveling method to keep the inner and outer support blocks of the detachable inner support mechanism level as a whole; S7, the box bottom feeding mechanism pushes the box bottom and the inner support mechanism into the ring mechanism to enter the welding position; S8. Use milling and smoothing method to control the gap of weld joint; S9. Use the engraved marking method to align the removable inner support mechanism with the center of the weld; S10, propping out the support block until the inner surface diameter of the storage tank is enlarged by 2 mm; S11. Eliminate the gap between the welding pad and the product tire and the misalignment of the weld assembly.

[0005] Furthermore, the method for calculating the inner surface diameter of the bottom welding area in S1 is: respectively measuring the outer surface circumference L1 of the bottom welding area and the outer surface circumference L2 of the barrel section welding area, and the thickness δ of the bottom welding area. In the process of welding the barrel section, by controlling the wall panel cutting size, L2 is made 3~5mm smaller than L1. Therefore, when assembling and welding the vertical sealing ring seam, the size data of the bottom welding area is used as the support assembly reference to calculate the inner surface diameter D1 of the bottom welding area, that is, D1=L1 / π-2δ.

[0006] Furthermore, the auxiliary operation platform in S3 includes several profile frames and several foldable aluminum cover plates, and the two are staggered and connected to form a circular ring structure. A support rod is installed in the middle of the bottom of each profile frame, and a support plate is installed at the other end of the support rod. Several support plates form a ring structure; a foot for adjusting the height is installed at the bottom of each profile frame, and the contact part between the foot and the inner surface of the bottom of the box is made of rubber material, and the surface of the foot is a contoured arc surface to ensure surface contact with the bottom of the box.

[0007] Furthermore, the detachable inner support mechanism in S4 includes an inner support core shaft and a support block, the first end of the inner support core shaft is circumferentially evenly hinged to 24 support square beams, a leveling support rod is movably installed under each support square beam, the other ends of the plurality of leveling support rods are circumferentially evenly hinged to the second end of the inner support core shaft, a scale is provided above each support square beam to measure the support amount of the scale support block; a horizontal tensioner is installed between two adjacent support square beams, a support block is fixedly installed at the end of each support square beam, and the outer side of each support block The edges are all provided with welded pads, and the support blocks are respectively inner support blocks and outer support blocks, and the inner support blocks and the outer support blocks are arranged alternately; a guide plate is arranged under each support block, and a spiral force push rod is installed above the supporting square beam connected to the inner support block, and the spiral force push rod is fixedly connected to the inner support block; a number of tightening bolts are also installed on each inner support block, and the force application position of the tightening bolts is on the load-bearing boss of the outer support block; the outer support block and the inner support core shaft are also connected by the outer support block support rod, and the 12 outer support block support rods are evenly hinged to the circumference of the inner support core shaft.

[0008] Furthermore, the specific method of controlling the weld joint gap by the milling and smoothing method in S8 is as follows: before the barrel section and the box bottom are aligned, the end faces of the barrel section welding area and the box bottom welding area are respectively milled and smoothed by the milling axis of the equipment. After milling, the end faces of the barrel section and the box bottom welding area are respectively 25 to 30 mm away from the upper and lower clamping ring mechanism pressure plates, the aluminum chips are cleaned, and the oxide film of the welding area is polished.

[0009] Furthermore, the method of using the engraved line marking method to align the detachable inner support mechanism with the center of the weld in S9 is as follows: taking the end face of the barrel section welding area as a reference, a full circle of assembly position line is drawn on the inner surface of the welding area 45 mm away from the end face, the upper ring mechanism and the barrel section are synchronously lowered to align the butt joint surfaces of the barrel section and the bottom of the box, and the butt joint gap is measured. The butt joint gap can be controlled within 0.3 mm, and the axial height of the detachable inner support mechanism is adjusted by controlling the elevator of the core shaft of the box bottom feeding mechanism to align the upper end face of the welding pad with the assembly position line of the inner surface of the barrel section welding area, thereby achieving alignment between the center of the welding pad and the center of the weld.

[0010] Furthermore, the method for extending the support blocks in S10 until the inner surface diameter of the tank is enlarged by 2 mm is as follows: adjust the length of the support rod of the outer support block to symmetrically extend the outer support blocks, and use a ruler to ensure that the extension amount of each outer support block is consistent. At this time, the extension diameter D of the outer support block is equal to the inner surface diameter D1 of the welding area at the bottom of the tank; use the spiral force push rod to also symmetrically extend the inner support blocks, and use a ruler to ensure that the extension amount of each inner support block is consistent. At this time, the extension diameter D of the inner support block is also equal to the inner surface diameter D1 of the welding area at the bottom of the tank; push out the tightening bolts on both sides of the inner support block evenly, and the outer support block continues to move outward along the slideway between the support blocks to tighten, and synchronously adjust the spiral force push rod of the inner support block to make the inner support block move outward synchronously until the inner surface diameter of the tank is enlarged by 2 mm. After extension, the extension diameters of the inner and outer support blocks are D=D1+2, and the gap between the support block pad and the inner surface of the tank is controlled within 0.2 mm.

[0011] Furthermore, in said S11, the method for eliminating the gap between the backing plate of the inner support block and the tank and the misalignment of the weld assembly is: synchronously reducing the clamping diameters of the upper and lower clamping ring clamping mechanisms by 0.5 mm.

[0012] Compared with the prior art, the flexible assembly method of the 5m diameter tank sealing annular seam friction stir welding of the present invention has the following advantages: (1) The flexible assembly method of friction stir welding of the sealing ring seam of a 5m diameter tank described in the present invention achieves a breakthrough from scratch in the precise assembly and control process of the detachable interlocking structure inner support of the sealing ring seam of the tank body in the vertical mode of the 5m diameter ultra-long and thick common bottom tank of the launch vehicle, and provides an effective solution for realizing the efficient and high-quality friction stir welding production of the sealing ring seam of the 5m diameter tank, thereby improving the assembly accuracy.

[0013] (2) The flexible assembly method of friction stir welding of the sealing ring seam of a 5m diameter tank described in the present invention realizes the strong rigid assembly and tightening of the sealing ring seam. After assembly, the welding area of ​​the tank can be radially enlarged by 2mm, the assembly roundness is ≤±0.8mm, the butt clearance is ≤0.3mm, the assembly misalignment is ≤0.5mm, and the tire clearance is ≤0.2mm. The assembly qualification rate is increased to 100%.

[0014] Another object of the present invention is to propose a defect control method for stir friction welding of a 5m diameter tank sealing ring seam, so as to solve the problem that when welding the tank ring seam by the traditional fusion welding process, there are certain welding defects and welding residual stress, the mechanical strength loss of the weld is large, and the welding deformation of the product is large.

[0015] To achieve the above object, the technical solution of the present invention is achieved as follows: A method for controlling defects in friction stir welding of a 5m diameter tank sealing ring seam comprises the following steps: T1. Perform segmented positioning welding first, then perform full circle positioning welding to preliminarily fix the assembly state of the full circle circumferential seam; T2, perform deep positioning welding to further fix the assembly state; T3. Perform pre-welding to make the weld between the stirring head and the backing plate form a complete closed extrusion die and achieve penetration to a certain extent; T4. Retractable welding uses a retractable stirring head. At the end of welding, the stirring needle is retracted at a uniform speed to eliminate the keyhole defect.

[0016] Furthermore, in T1, the specific method of first performing segmented positioning welding and then performing full-circle positioning welding is as follows: first perform segmented positioning welding, use a positioning stirring head with a needle length of 2~3mm, perform segmented positioning welding of 8~12 sections, and each section weld length is 300~400mm. Focus on positioning the parts with assembly misalignment, fix the state of the positions with poor assembly quality, and then perform full-circle positioning welding. The stirring head is the same as the segmented positioning welding, the welding angle is 358°, and 2° is reserved for non-welding, which is used for seam positioning during retractable stirring friction welding with near-zero thinning, and preliminarily fixes the assembly state of the entire circle of annular seams.

[0017] Compared with the prior art, the 5m diameter tank sealing annular seam friction stir welding defect control method of the present invention has the following advantages: (1) The defect control method for the friction stir welding of the 5m diameter tank sealing ring seam of the present invention reduces the generation of internal defects in the weld and increases the weld qualification rate to 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 It is a flow chart of the flexible assembly method of friction stir welding of the sealing annular seam of a 5m diameter tank according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the existing 5m diameter common bottom tank vertical box annular seam friction stir welding system; Figure 3 A schematic diagram of an auxiliary operation platform according to an embodiment of the present invention; Figure 4 A schematic diagram of a detachable inner support mechanism according to an embodiment of the present invention; Figure 5 for Figure 4 Enlarged view of part A in the middle; Figure 6 A state diagram of the inner support block and the outer support block according to an embodiment of the present invention; Figure 7This is a schematic diagram of the assembly state of the detachable inner support mechanism according to an embodiment of the present invention on a frame; Figure 8 It is a schematic diagram of the axial height adjustment of the detachable inner support mechanism and the synchronous clamping of the upper and lower clamping mechanisms according to the embodiment of the present invention; Fig. 9 It is a flow chart of the method for controlling defects of friction stir welding of the sealing annular seam of a 5m-diameter tank according to an embodiment of the present invention; Fig.10 This is a schematic diagram of a single positioning welding according to an embodiment of the present invention; Fig.11 A schematic diagram of deep positioning welding according to an embodiment of the present invention; Fig.12 This is a schematic diagram of pre-welding according to an embodiment of the present invention; Fig.13 This is a schematic diagram of the retractable stirring welding described in an embodiment of the present invention.

[0019] Description of reference numerals: 1- auxiliary operation platform; 11- profile frame; 12- foldable aluminum cover; 13- foot; 14- support rod; 2- removable inner support mechanism; 21- inner support mandrel; 22- support square beam; 23- spiral booster push rod; 24- ruler; 25- outer support block support rod; 26- leveling support rod; 27- inner support block; 28- outer support block; 281- outer support block load-bearing boss; 29- horizontal tensioner; 210- welding pad; 211- tightening bolt; 3- box bottom assembly; 4- elevator; 5- equipment mandrel; 6- barrel section; B- barrel section full circle assembly position line. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0022] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0023] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0024] The assembly of the sealing ring seam of the tank body of a 5m diameter launch vehicle in the vertical mode is carried out on the tank body ring seam vertical stirring friction welding system. The 5m diameter common bottom tank vertical tank ring seam stirring friction welding system is mainly composed of a jig body, an equipment base, a box bottom feeding mechanism, a barrel section feeding mechanism, an upper holding ring mechanism, a lower holding ring mechanism, a lifting mechanism, a hoisting mechanism, etc. The 5m diameter common bottom tank vertical box ring seam stirring friction welding system is an existing technology. In order to facilitate the understanding of the scheme, the position relationship of the system is briefly described. The barrel section feeding mechanism and the box bottom feeding mechanism are symmetrically installed above the equipment base, and the jig body is installed in the middle. The jig body is sequentially installed with a lifting mechanism, a hoisting mechanism, an upper reporting ring mechanism and a lower holding ring mechanism from top to bottom.

[0025] The box body sealing annular seam is the last annular weld of the storage tank. Before assembly welding, the welded box body part is moved upwards driven by the lifting mechanism, and the barrel section 6 part to be connected is moved into the upper holding ring mechanism. Then the box bottom to be welded is hoisted onto the box bottom feeding mechanism, and the assembled auxiliary operation platform and the detachable inner support mechanism are hoisted into the box bottom feeding mechanism. The box bottom feeding mechanism lifts the box bottom and the detachable inner support mechanism into the lower holding ring mechanism to match, assemble and weld the box body sealing annular seam.

[0026] Flexible assembly method of friction stir welding of 5m diameter tank sealing ring seam, such as Figures 1 to 8 As shown, the following steps are included: S1. Measure the outer surface circumference L1 of the box bottom welding area and the outer surface circumference L2 of the cylinder section welding area, and the thickness δ of the box bottom welding area. During the welding production process of cylinder section 6, the wall panel cutting size is controlled to make L2 3~5mm smaller than L1. Therefore, during the vertical sealing ring seam assembly and welding, the box bottom welding area size data is used as the support assembly reference to calculate the inner surface diameter D1 of the box bottom welding area, that is, D1=L1 / π-2δ.

[0027] S2. Lift the bottom assembly 3 with the convex spherical surface downward to the support ring of the bottom loading mechanism, connect and fix, and measure the assembly clearance between the bottom assembly 3 and the connection surface of the support ring. The clearance should be less than 0.2mm, and not more than 0.5mm in some parts; the bottom assembly 3 is an existing structure. The support ring of the bottom loading mechanism is annular, and a number of weight-reducing holes are evenly distributed on it.

[0028] S3, the auxiliary operation platform 1 is assembled under the frame, and the auxiliary operation platform 1 is hoisted as a whole into the bottom of the box, and the other end of the support rod 14 is screwed and fixed on the core shaft of the feeding mechanism at the bottom of the box.

[0029] The auxiliary operation platform 1 can enable the operator to install and debug the detachable inner support mechanism in the box in the vertical mode, thereby improving the convenience of the operator's operation in the box in the vertical mode. The auxiliary operation platform is assembled under the frame 1, and is hoisted to the working position as a whole after assembly. After the welding operation is completed, it is disassembled into parts in the tank and transported out of the tank through the tank manhole flange. The auxiliary operation platform 1 includes a plurality of profile frames 11 and a plurality of foldable aluminum cover plates 12, and the two are staggered and connected to form a circular ring structure. A support rod 14 is installed in the middle of the bottom of each profile frame 11, and a support plate is installed at the other end of the support rod 14. A plurality of support plates form a ring structure; a foot 13 for adjusting the height is installed at the bottom of each profile frame 11. The contact part of the foot 13 with the inner surface of the bottom of the box is made of rubber material to avoid scratching the tank. The profile of the foot 13 is a contoured arc surface to ensure surface contact with the bottom of the box.

[0030] S4, assemble the detachable inner support mechanism 2 under the frame, and make the inner and outer support blocks both in the contracted state, and use the ruler to ensure that the contraction amount of all outer support blocks is consistent. In order to ensure that the inner and outer support blocks are uniformly extended during the subsequent assembly, and to prevent some inner support blocks from being unable to extend in place due to being squeezed by the adjacent outer support blocks, the sides of the inner support blocks and the outer support blocks should be ensured to fit.

[0031] The detachable inner support mechanism 2 includes an inner support mandrel 21, a support square beam 22, a spiral force push rod 23, a ruler 24, an outer support block support rod 25, a leveling support rod 26, an inner support block 27, an outer support block 28, a horizontal tensioner 29, a welding pad 210 and a tightening bolt 211. The first end of the inner support mandrel 21 is evenly hinged to 24 support square beams 22 in the circumferential direction. A leveling support rod 26 is movably installed under each support square beam 22. The other end of 26 is circumferentially evenly hinged to the second end of the inner support core shaft 21. A scale 24 is provided above each supporting square beam 22, and the scale 24 is used to measure the supporting amount of the inner support block 27 and the outer support block 28. A horizontal tensioner 29 is installed between two adjacent supporting square beams 22. By adjusting the length of the horizontal tensioner 29, the circumferential position of the square beam where the inner support block is located is adjusted to eliminate the gap between the inner and outer support blocks, so that the inner and outer support blocks are in a state of close fit with each other. A support block is fixedly installed at the end of each supporting square beam 22, and a welded pad 210 is provided at the outer edge of each support block. The support blocks are respectively an inner support block 27 and an outer support block 28, and the inner support block 27 and the outer support block 28 are arranged alternately; a guide plate is arranged under each support block, which limits the circumferential freedom of the support block while ensuring sliding along the radial direction of the supporting square beam 22; a spiral force push rod 23 is installed above the supporting square beam 22 connected to the inner support block 27, and the spiral force push rod 23 is fixedly connected to the inner support block 27; in order to achieve strong rigid support of the detachable inner support mechanism 2 and prevent the support block from retreating under the action of the top forging force during stir friction welding, the detachable inner support mechanism 2 further enhances the interlocking rigidity of the inner support block 27 and the outer support block 28 after being supported. A number of tightening bolts 211 are also installed on each inner support block 27, and the force application position of the tightening bolts 211 is on the outer support block bearing boss 281; preferably, a number of 4 tightening bolts 211 and 2 disassembly auxiliary bolts are also installed on each inner support block 27; the outer support block 28 and the inner support core shaft 1 are also connected by the outer support block support rod 25, and the 12 outer support block support rods 25 are evenly hinged to the circumference of the inner support core shaft 1. Before the support operation of the inner support block 27 and the outer support block 28, the horizontality is adjusted by the leveling support rod 26 to ensure radial support. The inner support block 27 and the outer support block 28 are lifted by the support square beam 22, and can slide radially on the support square beam 22. When the support block is extended, the extension diameter is determined by the ruler 24. The outer support block 28 provides the support force during pre-tensioning through the outer support block support rod 25, and the inner support block 27 provides the support force through the spiral force push rod 23. After the inner and outer support blocks are stretched out, the support force is provided by the jacking bolt 211 to achieve strong rigidity tensioning. The welding pad 210 is 90mm wide, and the shape of the welding pad is divided into upper and lower parts with the center as the boundary. The upper part is a straight structure, and the lower part is an arc structure consistent with the inner surface of the welding area on the bottom side of the box. When assembling the support, it can be tightly fitted with the welding area on the side of the barrel section 6 and the welding area on the bottom side of the box.The detachable inner support mechanism 2 adopts a self-locking design concept. After being tightened, the 12 inner support blocks 27 and the 12 outer support blocks 28 can fit together to form a rigid whole to withstand the upsetting force of the welding spindle.

[0032] S5, after the detachable inner support mechanism 2 and the equipment mandrel 5 are assembled under the frame, they are hoisted onto the mandrel of the feeding mechanism at the bottom of the box in an integral form, and the detachable inner support mechanism 2 is quickly positioned and assembled through the guide device on the mandrel, and the detachable inner support mechanism 2 and the equipment mandrel are reliably fixed by bolt connection; S6. To ensure that after the detachable inner support mechanism 2 is tightened and stressed, the welding pad 210 is in surface contact with the inner profile of the tank welding area, and to avoid the detachable inner support mechanism 2 from being tilted, an umbrella-shaped support leveling method is adopted: since one end of the leveling support rod 26 is connected to the square beam 22, and the other end is connected to the inner support mandrel 21, by adjusting the leveling support rod 26 and using a level meter, the inner and outer support blocks are kept level as a whole, and the support blocks are prevented from lowering or raising their heads; S7, the box bottom feeding mechanism pushes the box bottom and the detachable inner support mechanism 2 into the holding ring mechanism and enters the welding position, so that the axial distance between the end face of the box to be welded at the bottom of the box and the pressing plate of the lower holding ring clamping mechanism is 25~30mm, and the lower holding ring clamping mechanism is pre-tightened to ensure that the pressing plate and the box are closely fitted, and the local fitting gap is not greater than 0.2mm; S8. Use the milling and smoothing method to control the weld joint gap. Before the barrel section 6 and the box bottom are aligned, the equipment milling axis is used to mill and smooth the end faces of the barrel section 6 welding area and the box bottom welding area. After milling, the end faces of the barrel section 6 and the box bottom welding area are 25 to 30 mm away from the upper and lower clamping ring mechanism pressure plates, respectively. Clean the aluminum chips and grind the oxide film in the welding area.

[0033] S9. Use the engraved marking method to align the detachable inner support mechanism 2 with the center of the weld. Take the end face of the welding area of ​​the cylinder section as the reference and draw a full circle of assembly position lines on the inner surface of the welding area at a distance of 45 mm from the end face. Figure 8 The upper ring mechanism and the barrel section are lowered synchronously to align the barrel section with the bottom of the box, and the butt gap is measured. The butt gap can be controlled within 0.3mm. By controlling the elevator of the mandrel of the box bottom feeding mechanism, the axial height of the detachable inner support mechanism 2 is adjusted to align the assembly position line of the upper end surface of the welding pad with the inner surface of the barrel section welding area, so as to align the center of the welding pad with the center of the weld.

[0034] S10, adjust the length of the outer support block support rod 25, support the outer support block 28 in a symmetrical manner, and ensure that the extension amount of each outer support block 28 is consistent through the ruler 24. At this time, the extension diameter D of the outer support block 28 is the inner surface diameter D1 of the bottom welding area of ​​the box. When the inner support block 27 is extended, it will be squeezed and blocked by the outer support block 28 before reaching the target support position. Therefore, it is necessary to increase the supporting force to ensure that it is extended in place. The inner support block 27 is also supported in a symmetrical manner through the spiral force push rod 23, and the extension amount of each inner support block 27 is consistent through the ruler 24. At this time, the extension diameter D of the inner support block 27 is also the inner surface diameter D1 of the bottom welding area of ​​the box. The tightening bolts 211 on both sides of the inner support block 27 are pushed out evenly, and the outer support block 28 continues to move outward along the slideway between the support blocks to tighten, and the spiral force push rod 23 of the inner support block is adjusted synchronously to make the inner support block 27 move outward synchronously until the diameter of the inner surface of the tank is expanded by 2mm. After expansion, the diameter of the inner and outer support blocks is D=D1+2, and the gap between the support block pad 210 and the inner surface of the tank can be controlled within 0.2mm.

[0035] S12, synchronously reduce the clamping diameter of the upper and lower clamping rings by 0.5mm, and the clamping direction is Figure 8 The arrow direction at C in the middle further eliminates the gap between the welding pad 210 and the tank and the misalignment of the weld assembly. After assembly by this assembly method, the roundness of the tank welding area can be controlled within ±0.8mm, the misalignment can be controlled within 0.5mm, and the gap between the welding pad 210 and the inner surface of the tank can be controlled within 0.1mm as a whole, and no more than 0.2mm locally.

[0036] The 5m diameter and large thickness sealing ring seam precision assembly technology in vertical mode realizes the strong rigidity assembly and tightening of the sealing ring seam. After assembly, the welding area of ​​the tank can be radially expanded by 2mm, the assembly roundness is ≤±0.8mm, the butt clearance is ≤0.3mm, the assembly misalignment is ≤0.5mm, and the tire clearance is ≤0.2mm, and the assembly qualification rate is increased to 100%.

[0037] For the circumferential seam of a tank with a diameter of 5m and a thickness of 20mm in the welding area, due to structural factors such as the large diameter and thickness of the tank, once defects occur in the weld, the difficulty of excavating and repairing the defects is greater than that of existing tanks. Therefore, the qualified rate of circumferential seam welding should be increased as much as possible to ensure that the weld is qualified in one time. To solve the above problems, this plan proposes a defect control idea of ​​stir friction welding with one-time positioning welding + deep positioning welding + pre-welding + retractable welding to reduce the generation of internal defects in the weld and achieve the goal of qualified welding in one time.

[0038] Defect control method of friction stir welding of 5m diameter tank sealing ring seam, such as Figures 9 to 13 As shown, the following steps are included: T1. One-time positioning welding includes segmented positioning welding and full-circle positioning welding. First, segmented positioning welding is performed. A positioning stirring head with a needle length of 2~3mm is used. 8~12 segments are segmented and the length of each weld is 300~400mm. The parts with assembly misalignment are focused on positioning, and the positions with poor assembly quality are fixed in state to prevent the state from deteriorating during subsequent welding. After that, full-circle positioning welding is performed. The stirring head is the same as the segmented positioning welding. The welding angle is 358°, and 2° is reserved for non-welding. It is used for seam positioning during the stirring needle retractable near-zero-thinning stir friction welding, and the assembly state of the full-circle circumferential seam is initially fixed; T2. Perform deep positioning welding and use a positioning stirring head with a needle length of 8~10mm to further fix the assembly state, enhance the strength of the weld joint, improve the weld's resistance to strong top forging force, and prevent the weld from expanding during the pre-welding process.

[0039] T3. Pre-welding is performed. The Archimedean spiral is used as the structural curve of the stirring head shoulder, which can improve the convergence of the shoulder structure on the plastic metal and the stability of the welding process, thereby reducing the adverse effects of assembly gaps and misalignment on the quality of the weld. The needle length of the stirring head is 0.3~0.5mm less than the actual thickness of the welding area. During the welding process, the weld can fit tightly with the back rigid support under the action of the spindle forging force, eliminating the non-sticking phenomenon between the two, so that the weld between the stirring head and the pad forms a complete closed extrusion die, and achieves penetration to a certain extent. Affected by the assembly state, this process may produce welding defects inside the weld; T4, retractable welding uses a retractable stirring head. At the end of welding, the stirring needle is retracted at a uniform speed to eliminate the keyhole defect. The shoulder diameter of the retractable stirring head is 1~2mm larger than the pre-welding stirring head. The flash generated in the pre-welding can be stirred into the weld again to reduce the loss of the parent metal. In the retractable welding stage, the weld and the rigid support plate have been closely fitted, and the assembly state is better than the assembly state during pre-welding. Therefore, the internal defects of the weld generated during the pre-welding process can be eliminated in the retractable stirring welding stage, and a complete and nearly defect-free weld can be obtained, so that the weld can be qualified in one welding.

[0040] The friction stir welding defect control technology for 5m diameter and thick sealing ring seam in vertical mode proposes a friction stir welding defect control idea of ​​one-time positioning welding + deep positioning welding + pre-welding + retractable welding, which reduces the generation of internal defects in the weld and increases the weld qualification rate to 100%.

[0041] This patent has achieved a breakthrough from scratch in the precise assembly and control process of the detachable interlocking structure inner support of the box body sealing ring seam in the vertical mode of the 5m diameter, ultra-long and thick common bottom tank of my country's new generation of launch vehicles, and provided an effective solution for the efficient and high-quality stir friction welding production of the 5m diameter tank sealing ring seam.

[0042] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

A flexible assembly method for friction stir welding of a 1.5m diameter tank sealing ring seam, characterized in that: The steps include: S1. Calculate the inner surface diameter of the welding area at the bottom of the box; S2. Lift the convex spherical surface of the bottom assembly downward to the bottom loading mechanism, and measure the assembly clearance between the connection surface of the storage tank and the support ring; S3, assemble the auxiliary operation platform under the frame and hoist it into the bottom of the box; S4, assembling a detachable inner support mechanism under the frame, and making its inner and outer support blocks both in a retracted state; S5. After the detachable inner support mechanism and the mandrel are assembled under the frame, they are hoisted to the feeding mechanism at the bottom of the box as a whole and positioned and assembled; S6. Use an umbrella-shaped support leveling method to keep the inner and outer support blocks of the detachable inner support mechanism level as a whole; S7, the box bottom feeding mechanism pushes the box bottom and the inner support mechanism into the ring mechanism to enter the welding position; S8. Use milling and smoothing method to control the gap of weld joint; S9. Use the engraved marking method to align the removable inner support mechanism with the center of the weld; S10, propping out the support block until the inner surface diameter of the storage tank is enlarged by 2 mm; S11. Eliminate the gap between the welding pad and the product tire and the misalignment of the weld assembly.

2. The flexible assembly method for friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The method for calculating the inner surface diameter of the bottom welding area in S1 is: respectively measure the outer surface circumference L1 of the bottom welding area and the outer surface circumference L2 of the barrel section welding area, and the thickness δ of the bottom welding area. In the process of welding the barrel section, by controlling the wall panel cutting size, L2 is made 3-5 mm smaller than L1. Therefore, during the vertical sealing ring seam assembly welding, the bottom welding area size data is used as the support assembly reference to calculate the inner surface diameter D1 of the bottom welding area, that is, D1=L1 / π-2δ.

3. The flexible assembly method for friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The auxiliary operation platform in S3 includes a plurality of profile frames and a plurality of foldable aluminum cover plates, and the two are staggered and connected to form a circular ring structure. A support rod is installed in the middle of the bottom of each profile frame, and a support plate is installed at the other end of the support rod. Several support plates form a circular structure; a foot for adjusting the height is installed at the bottom of each profile frame, and the contact part between the foot and the inner surface of the bottom of the box is made of rubber material, and the surface of the foot is a contoured arc surface to ensure surface contact with the bottom of the box.

4. The flexible assembly method for friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The detachable inner support mechanism in S4 includes an inner support mandrel and a support block. The first end of the inner support mandrel is evenly hinged to 24 support square beams. A leveling support rod is movably installed under each support square beam. The other ends of several leveling support rods are evenly hinged to the second end of the inner support mandrel. A ruler is provided on the top of each support square beam to measure the support amount of the ruler support block. A horizontal tensioner is installed between two adjacent support square beams. A support block is fixedly installed at the end of each support square beam. The outer edge of each support block is It is equipped with a welding pad, and the support blocks are respectively an inner support block and an outer support block, and the inner support blocks and the outer support blocks are arranged alternately; a guide plate is arranged under each support block, and a spiral force push rod is installed above the supporting square beam connected to the inner support block, and the spiral force push rod is fixedly connected to the inner support block; a number of tightening bolts are also installed on each inner support block, and the force application position of the tightening bolts is on the load-bearing boss of the outer support block; the outer support block and the inner support core shaft are also connected by an outer support block support rod, and the 12 outer support block support rods are evenly hinged to the circumference of the inner support core shaft.

5. The flexible assembly method of friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The specific method of using the milling and smoothing method to control the weld joint gap in S8 is as follows: before the barrel section and the box bottom are aligned, the end faces of the barrel section welding area and the box bottom welding area are respectively milled and smoothed by the milling axis of the equipment. After milling, the end faces of the barrel section and the box bottom welding area are respectively 25 to 30 mm away from the upper and lower clamping ring mechanism pressure plates, the aluminum chips are cleaned, and the oxide film of the welding area is polished.

6. The flexible assembly method of friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The method of using the engraved line marking method to align the detachable inner support mechanism with the center of the weld in S9 is as follows: taking the end face of the welding area of ​​the barrel section as a reference, a full circle of assembly position lines is drawn on the inner surface of the welding area 45 mm away from the end face, the upper ring mechanism and the barrel section are synchronously lowered to align the butt joints of the barrel section and the bottom of the box, and the butt joint gap is measured. The butt joint gap can be controlled within 0.3 mm, and the axial height of the detachable inner support mechanism is adjusted by controlling the elevator of the core shaft of the box bottom feeding mechanism to align the upper end face of the welding pad with the assembly position line of the inner surface of the welding area of ​​the barrel section, thereby realizing the alignment of the center of the welding pad with the center of the weld.

7. The flexible assembly method for friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: The method for extending the support block in S10 until the inner surface diameter of the storage tank is enlarged by 2 mm is as follows: Adjust the length of the support rod of the outer support block to support the outer support block in a symmetrical manner, and use a ruler to ensure that the extension amount of each outer support block is consistent. At this time, the extension diameter D of the outer support block is the inner surface diameter D1 of the bottom welding area of ​​the box; use the set spiral force push rod to support the inner support block in a symmetrical manner, and use a ruler to ensure that the extension amount of each inner support block is consistent. At this time, the extension diameter D of the inner support block is also the inner surface diameter D1 of the bottom welding area of ​​the box; push out the tightening bolts on both sides of the inner support block evenly, and the outer support block continues to move outward along the slide between the support blocks to tighten, and synchronously adjust the spiral force push rod of the inner support block to make the inner support block move outward synchronously until the inner surface diameter of the tank is increased by 2mm. After extension, the extension diameters of the inner and outer support blocks D=D1+2, and the gap between the support block pad and the inner surface of the tank is controlled within 0.2mm.

8. The flexible assembly method for friction stir welding of the sealing annular seam of a 5m diameter tank according to claim 1 is characterized in that: In the above S11, the method for eliminating the gap between the backing plate of the inner support block and the tank and the misalignment of the weld assembly is: synchronously reducing the clamping diameter of the upper and lower clamping ring clamping mechanisms by 0.5 mm. A method for controlling defects in friction stir welding of a 9.5m diameter tank sealing ring seam, characterized in that: The steps include: T1. Perform segmented positioning welding first, then perform full circle positioning welding to preliminarily fix the assembly state of the full circle circumferential seam; T2, perform deep positioning welding to further fix the assembly state; T3. Perform pre-welding to make the weld between the stirring head and the backing plate form a complete closed extrusion die and achieve penetration to a certain extent; T4. Retractable welding uses a retractable stirring head. At the end of welding, the stirring needle is retracted at a uniform speed to eliminate the keyhole defect.

10. The method for controlling defects of friction stir welding of 5m diameter tank sealing ring seam according to claim 9, characterized in that: In the T1, the specific method of first performing segmented positioning welding and then performing full-circle positioning welding is as follows: first perform segmented positioning welding, use a positioning stirring head with a needle length of 2-3 mm, perform segmented positioning welding of 8-12 sections, and each section weld length is 300-400 mm. Focus on positioning the parts with assembly misalignment, fix the state of the positions with poor assembly quality, and then perform full-circle positioning welding. The stirring head is the same as the segmented positioning welding, the welding angle is 358°, and 2° is reserved for non-welding, which is used for seam positioning during near-zero-thinning stir friction welding with a retractable stirring needle, and preliminarily fixes the assembly state of the full-circle annular seam.

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