A C-type LPG tank section welding method

Abstract

The present application discloses a method for welding a C-type LPG tank barrel section, comprising the following steps: splicing a plurality of low-temperature steel plates, and rolling the spliced ​​sheet body; moving the rolled barrel section so that the inner groove of the H seam is at the 6 o'clock position, wherein the H seam adopts a V-shaped groove design, and the inner groove of the H seam is bottom welded by an arc welding method, and then the filling and covering welding is performed by a submerged arc automatic welding method; calibrating the barrel section; after the barrel section is calibrated, at least one conformal support frame is respectively installed on the inner side of both ends of the barrel section, and the ellipticity of the barrel section is limited and the rigidity of the barrel section is improved by adjusting the relative position of the support rod and the second mounting part; the outer side welding step of the closing weld, after installing the conformal support frame, moving the barrel section so that the H seam is adjusted to the 12 o'clock position, and welding the outer side weld of the H seam by a submerged arc automatic welding method. The present application can reduce the welding angle deformation of the H seam of the barrel section and avoid the risk of cracking of the H seam during the rounding.

Description

Technical Field

[0001] The present application relates to the technical field of tank barrel section welding, and in particular to a C-type LPG tank barrel section welding method. Background Art

[0002] Reference Figure 1 The C-type LPG tank is composed of several cylinder sections spliced ​​together and the heads at both ends. The cylinder section is spliced ​​and rolled by several pieces of low-temperature steel plates. The splicing weld is the P seam. After rolling, the longitudinal seam is welded and closed. The closed weld is the H seam. The cylinder section rolling process is as follows: Figure 2 Specifically, the low-temperature steel plates are spliced ​​and rolled into a cylinder, and a Y-shaped groove is opened on the H-slit after rolling, in which a 6mm blunt edge is left on the Y-shaped groove to avoid welding through, and positioning welding is performed on the inside of the Y-shaped groove; then the H-slit of the cylinder section is adjusted to the 6 o'clock position by a crane, and the inner groove of the H-slit is welded in a flat welding position, and then the cylinder section is hoisted to the welding tooling platform by a crane, and the H-slit is adjusted to the 12 o'clock position, and a carbon arc air gouging is used to remove the blunt edge of the un-welded part of the H-slit on the outside, and the remaining welding is completed on the outside after the outside groove is gouged, and then it is transferred to the plate rolling machine for rounding after completion.

[0003] However, the low-temperature steel plate used for the cylinder section is relatively thin, with a thickness range of 8 to 13.2 mm and a diameter-to-thickness ratio of 750. The overall rigidity of the cylinder section is relatively weak. During horizontal welding of the cylinder section, the elliptical deformation is severe due to the influence of its own weight. The angular deformation of the H-seam will increase after welding, causing an inward angular deformation after the inner groove of the H-seam is welded. If the inward angular deformation is too large, cracks will appear at the toe end of the outer weld of the H-seam after the cylinder section is rounded, affecting the structural safety of the tank body, and the cracked position of the weld needs to be welded and repaired. Summary of the invention

[0004] The present application aims to solve at least one of the above technical problems in the prior art to a certain extent. To this end, the present application provides a C-type LPG tank barrel section welding method, which can reduce the welding angle deformation of the H seam of the barrel section and avoid the risk of cracking of the H seam during rounding.

[0005] According to the C-type LPG tank section welding method of the embodiment of the present application, the following steps are included:

[0006] The steel plate rolling step includes splicing a plurality of low-temperature steel plates to form a spliced ​​sheet body, wherein the spliced ​​weld is defined as a P seam, and after the P seam welding is completed, the spliced ​​sheet body is rolled, and the rolled cylinder section forms a closed weld to be welded, and the closed weld is defined as an H seam;

[0007] In the inner side welding step of the closing weld, the rolled cylinder section is moved so that the inner groove of the H seam is at the 6 o'clock position, wherein the H seam adopts a V-shaped groove design, and the inner groove of the H seam is welded with a welding rod arc welding method, and then the filling and covering welding is performed with a submerged arc automatic welding method;

[0008] The roundness calibration step is to calibrate the cylinder section after the inner groove welding of the H-seam is completed;

[0009] A conformal support frame step is added. After the cylinder segment is rounded, at least one conformal support frame is respectively installed on the inner side of both ends of the cylinder segment. The conformal support frame includes a first mounting portion installed at the P seam position of the cylinder segment inner wall and a second mounting portion installed at the H seam position of the cylinder segment inner wall. The first mounting portion and the second mounting portion are connected by a support rod. One end of the support rod is connected to the first mounting portion, and the other end of the support rod is fixed to the second mounting portion by positioning welding. The relative position of the support rod and the second mounting portion is adjusted to limit the ovality of the cylinder segment and improve the rigidity of the cylinder segment.

[0010] The steps for welding the outer side of the closing weld are: after installing the conformal support frame, move the cylinder section to adjust the H seam to the 12 o'clock position, and use the submerged arc automatic welding method to weld the outer side weld of the H seam.

[0011] In an optional or preferred embodiment, the cylinder section is formed by splicing two low-temperature steel plates, a P seam is provided, the P seam and the H seam are radially opposite, and the first mounting portion and the second mounting portion of the conformal support frame are radially opposite and connected by a support rod.

[0012] In an optional or preferred embodiment, the second mounting portion includes a tacking adjustment plate and a second ear plate, the tacking adjustment plate is fixed to the inner wall of the cylinder segment and installed across the H-seam, the two ends of the tacking adjustment plate are respectively fixed to the low-temperature steel plates on both sides of the H-seam, the second ear plate is fixed to the end of the support rod, the second ear plate and the tacking adjustment plate are fixed by tacking welding, and the relative position of the second ear plate and the tacking adjustment plate is adjusted to limit the ovality of the cylinder segment and improve the rigidity of the cylinder segment.

[0013] In an optional or preferred embodiment, the first mounting portion includes a mounting ear plate, a first ear plate and a first fastener, the mounting ear plate is fixed to the inner wall of the cylinder section near the P seam, the first ear plate is mounted on the end of the support rod, and the first ear plate is connected to the mounting ear plate via the first fastener.

[0014] In an optional or preferred embodiment, the mounting ear plate is installed with a first offset from the P seam, the first offset being greater than 0, so as to avoid the corner seam between the mounting ear plate and the inner wall of the barrel section from intersecting the P seam. The first offset is 30 mm.

[0015] In an optional or preferred embodiment, the axis of the first fastener is parallel to the P-slit to limit the axial rotation of the support rod along the barrel segment.

[0016] In an optional or preferred embodiment, the P seam of the cylinder section adopts a Y-shaped groove design and is welded using a double-sided submerged arc automatic welding method.

[0017] In an optional or preferred embodiment, the welding material in the electrode arc welding method is a welding rod of the model GB / T5117-E5518-N5P, and the welding rod specification is φ3.2 mm. The welding material in the submerged arc automatic welding method is a welding wire and flux combination of the model GB / T5293-S55P5FB-SUN2M, and the welding wire specification is φ3.2 mm.

[0018] Based on the above technical solution, the embodiments of the present application have at least the following beneficial effects:

[0019] 1. The groove of the H seam of the cylinder section is designed to be V-shaped, and the base is welded by arc welding with a small heat input, so that the angular deformation of the H seam after welding becomes smaller, reducing the risk of cracking of the H seam during the rounding process.

[0020] 2. Then, the submerged arc automatic welding method is used in the V-shaped groove on the inner side of the H-seam to complete the welding of most of the thickness of the H-seam. When the submerged arc automatic welding method is used on the outer side later, the full penetration welding of the H-seam can be achieved without the carbon arc air planing root cleaning process. This can not only ensure the necessary rigidity of the H-seam, but also save the root cleaning operation before the H-seam welding, and reduce the secondary deformation during the root cleaning operation and transportation of the cylinder section.

[0021] 3. The cylinder segment is calibrated before the outer seam of the H seam is welded. Combined with the rigid constraint of the support frame, there is no need to calibrate the cylinder segment after the outer seam of the H seam is welded, thus avoiding the weld cracking problem caused by the outer seam of the H seam being calibrated due to welding deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present application is further described below with reference to the accompanying drawings and embodiments;

[0023] Figure 1 It is a structural schematic diagram of a C-type LPG tank in the prior art;

[0024] Figure 2 It is a schematic diagram of the process of tube segment rolling in the prior art;

[0025] Figure 3 Schematic diagram of the groove of the H-seam of the cylinder section in the embodiment of the present application;

[0026] Figure 4 It is a structural schematic diagram of a conformal support frame for mounting a cylinder segment in an embodiment of the present application;

[0027] Figure 5 It is a step flow chart of an embodiment of the present application.

[0028] Reference numerals: cylinder section 100, low temperature steel plate 111, P seam 121, H seam 122, V-shaped groove 132;

[0029] Head 200;

[0030] The conformal support frame 300 , the first mounting portion 310 , the mounting ear plate 311 , the first ear plate 312 , the first fastener 313 , the second mounting portion 320 , the positioning welding adjustment plate 321 , the second ear plate 322 , and the support rod 331 . DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0037] Reference Figure 1 The C-type LPG tank is composed of several cylinder sections 100 spliced ​​together and the heads 200 at both ends. The cylinder section manufacturing method is usually as follows: the cylinder section 200 is spliced ​​and rolled by several low-temperature steel plates 111, and the spliced ​​weld is a P seam 121. After rolling, the longitudinal seam is welded and closed, and the closed weld is an H seam 122. The cylinder section rolling process is as follows: Figure 2 shown.

[0038] In the prior art, the specific manufacturing method of the cylinder section is as follows: the low-temperature steel plate 111 is spliced ​​and rolled into a cylinder, and a Y-shaped groove is opened on the inner side of the H-slit 122 after rolling, wherein the Y-shaped groove also leaves a 6mm blunt edge to avoid welding through, and positioning welding is performed on the inner side of the Y-shaped groove. Then the H-slit 122 of the cylinder section 100 is adjusted to the 6 o'clock position by a crane, and the inner groove of the H-slit 122 is welded in a flat welding position, and then the cylinder section 100 is hoisted to the welding tooling platform by a crane, and the H-slit is adjusted to the 12 o'clock position, and the blunt edge of the un-welded part of the H-slit is first removed on the outside by a carbon arc air planer, and the remaining welding is completed from the outside after the outside groove is planed, and after the H-slit 122 is welded, it is transferred to the plate rolling machine for rounding.

[0039] It should be noted that those skilled in the art will know that the above-mentioned 6 o'clock and 12 o'clock positions correspond to the time of the clock. The 6 o'clock position refers to the lower position, but is not limited to being exactly at the 6 o'clock position. It can also be in the interval position between the 5 o'clock position and the 7 o'clock position, so as to facilitate welding as a reference. Therefore, when understanding the protection scope of this application, the 6 o'clock position should be understood as the interval position between the 5 o'clock position and the 7 o'clock position, and the best position during operation is close to the 6 o'clock position; the 12 o'clock position refers to the upper position. Similarly, when understanding the protection scope of this application, the 12 o'clock position should be understood as the interval position between the 11 o'clock position and the 1 o'clock position, and the best position during operation is close to the 12 o'clock position. The welding position of the H seam can be understood with reference to the above explanation of the position.

[0040] However, the low-temperature steel plate 111 used in the cylinder section is relatively thin, with a thickness range of 8 to 13.2 mm and a diameter-to-thickness ratio of 750. The overall rigidity of the cylinder section is relatively weak. During horizontal welding of the cylinder section, the elliptical deformation is seriously affected by its own weight. The angular deformation of the H seam will increase after welding, causing an inward angular deformation after the inner groove of the H seam is welded. If the inward angular deformation is too large, cracks will appear at the toe end of the outer weld of the H seam after the cylinder section is rounded, affecting the structural safety of the tank body, and the cracked position of the weld needs to be welded and repaired.

[0041] Refer to the following Figures 3 to 5 , and combined with Figure 2 This embodiment describes a C-type LPG tank section welding method, comprising the following steps:

[0042] S1, steel plate rolling steps:

[0043] A plurality of low-temperature steel plates 111 are spliced ​​together to form a spliced ​​sheet body, wherein the spliced ​​weld is defined as a P seam. After the P seam 121 is welded, the spliced ​​sheet body is rolled, and the rolled cylinder section 100 forms a closed weld to be welded, and the closed weld is defined as an H seam. The H seam 122 needs to be welded in subsequent steps.

[0044] In this embodiment, the cylinder section 100 is formed by splicing two low-temperature steel plates 111, and a P seam 121 is provided, and the P seam 121 and the H seam 122 are radially opposite. The splicing and rolling steps of the C-type LPG tank cylinder section assembly welding method in this embodiment are the same as those in the prior art, such as Figure 2 shown.

[0045] The P seam 121 of the cylinder section 100 adopts a Y-shaped groove design and is welded by a conventional double-sided submerged arc automatic welding method.

[0046] S2, inner side welding steps of the closing weld:

[0047] The rolled cylinder section 100 is moved so that the inner groove of the H seam 122 is at the 6 o'clock position, wherein the H seam 122 adopts a V-shaped groove design, referring to Figure 3 , showing the V-shaped groove 132 of the H-seam 122.

[0048] The inner groove of the H seam 122 is primed by arc welding with small heat input. The arc welding method has small heat input, and the initial deformation of the H seam 122 is small, so that the angular deformation of the H seam 122 after welding is reduced, reducing the risk of cracking of the H seam 122 during the rounding process, and also avoiding the phenomenon of welding through the groove.

[0049] Then use the submerged arc automatic welding method to perform filling and cap welding.

[0050] S3, calibration steps:

[0051] After the inner groove welding of the H-slit 122 is completed, the cylinder section 100 is rounded.

[0052] S4, adding conformal support frame steps:

[0053] Reference Figure 4 After the cylinder segment 100 is calibrated, at least one conformal support frame 300 is installed on the inner side of both ends of the cylinder segment 100. The conformal support frame 300 includes a first mounting portion 310 installed at the position of the P seam 121 of the inner wall of the cylinder segment 100 and a second mounting portion 320 installed at the position of the H seam 122 of the inner wall of the cylinder segment 100. The first mounting portion 310 and the second mounting portion 320 are connected by a support rod 331.

[0054] In this embodiment, the P-slit 121 and the H-slit 122 are radially opposite to each other, and the first mounting portion 310 and the second mounting portion 320 of the conformal support frame 300 are radially opposite to each other and connected by a support rod 331 .

[0055] One end of the support rod 331 is connected to the first mounting portion 310 , and the other end of the support rod 331 is fixed to the second mounting portion 320 by positioning welding. The ovality of the barrel segment 100 is limited and the rigidity of the barrel segment 100 is improved by adjusting the relative position of the support rod 331 and the second mounting portion 320 .

[0056] Specifically, the first mounting portion 310 includes a mounting ear plate 311, a first ear plate 312, and a first fastener 313. The mounting ear plate 311 is fixed to a position near the P seam 121 on the inner wall of the barrel segment 100, and the mounting ear plate 311 is installed with a first offset from the P seam 121 to avoid the corner joint between the mounting ear plate 311 and the inner wall of the barrel segment 100 from intersecting the P seam 121. The first offset is 30 mm. The first ear plate 312 is mounted on the end of the support rod 331, and the first ear plate 312 is connected to the mounting ear plate 311 by the first fastener 313. It can be understood that when the support rod 331 rotates relative to the inner wall of the barrel segment 100 about the axis of the first fastener 313, after installation, the position of the other end of the support rod 331 can be adjusted, and after adjusting to the position with the second mounting portion 320, the next step of positioning welding operation can be performed. Moreover, the axis of the first fastener 313 is parallel to the P-slit 121 to limit the support rod 331 from rotating axially along the barrel segment 100. During the rotation of the support rod 331, it will not rotate toward the axial plane of the barrel segment 100, thereby preventing an object impact accident.

[0057] The second mounting portion 320 includes a positioning welding adjustment plate 321 and a second ear plate 322. The positioning welding adjustment plate 321 is fixed to the inner wall of the cylinder section 100 and installed across the H seam 122. The two ends of the positioning welding adjustment plate 321 are respectively welded and fixed to the low-temperature steel plates 111 on both sides of the H seam 122, and are constrained by fillet welds with a length of 50 mm and a height of 5 mm. The second ear plate 322 is fixed to the end of the support rod 331. The second ear plate 322 and the positioning welding adjustment plate 321 are fixed by positioning welding. By adjusting the relative position of the second ear plate 322 and the positioning welding adjustment plate 321, the relative position of the support rod 331 and the positioning welding adjustment plate 321 can be adjusted, and then the relative position of the H seam 122 and the P seam 121 can be adjusted, so as to limit the ovality of the cylinder section 100. At the same time, since the cylinder section 100 is supported and fixed by two conformal support frames 300, the overall rigidity of the cylinder section 100 can be improved.

[0058] Preferably, the support rod is made of a pipe material of φ80×7mm.

[0059] S5, outer side welding steps of closing weld:

[0060] After the conformal support frame 300 is installed, the cylinder section 100 is moved to adjust the H seam 122 to the 12 o'clock position, and the outer weld of the H seam 122 is welded using a submerged arc automatic welding method.

[0061] In this embodiment, the welding material in the electrode arc welding method is a welding rod of model GB / T5117-E5518-N5P, and the welding rod specification is φ3.2mm. The welding material in the submerged arc automatic welding method is a welding wire and flux combination of model GB / T5293-S55P5FB-SUN2M, and the welding wire specification is φ3.2mm, to ensure the toughness of the LPG tank welding joint in a low temperature environment of -50°C.

[0062] In the above-mentioned C-type LPG tank section welding method, the groove of the H seam of the cylinder section is designed to be V-shaped, and the base is welded by arc welding with a small heat input, so that the angular deformation of the H seam after welding becomes smaller, and the risk of cracking of the H seam during the subsequent rounding process is reduced. Among them, the V-shaped groove design can achieve the groove by flame cutting once, while the conventional Y-shaped groove requires two cuts, vertical cutting and bevel cutting, which can simplify the groove cutting process.

[0063] It is understandable that in the prior art, the H seam is directly welded on one side at a time using the submerged arc automatic welding method. Since the submerged arc automatic welding has high welding efficiency, large welding current, and strong penetration during welding, the H seam will use a Y-shaped groove with a blunt edge to avoid burning through. However, in this case, when welding on the outside, it is necessary to first use a carbon arc air planer to remove the blunt edge of the un-welded part of the H seam on the outside, and then weld the outside weld. At this time, the cylinder section has been severely deformed, and it will be subsequently transported to the plate rolling machine for rounding. After rounding, the weld cracking problem will occur. In this embodiment, the welding of the H seam is first performed on the inside by the arc welding method. The heat input of the arc welding method is small, and the welding deformation generated is reduced, so that the initial deformation of the H seam is small, and the phenomenon of welding through the groove can also be avoided. In this way, the angular deformation of the H seam can be controlled; then the submerged arc automatic welding method is used for filling and capping welding. Thus, the welding method of the present application adopts a welding method combining arc welding with submerged arc welding. The deformation is first controlled by the arc welding method, and then the welding efficiency is ensured by the submerged arc automatic welding method.

[0064] The present application reduces the angular deformation of the H seam after the cylinder section is rolled by improving the groove design and controlling the welding sequence. The angular deformation of the H seam is reduced by optimizing the welding process, and the correction amount of the angular deformation is reduced, thereby avoiding the problem of cracking of the H seam due to excessive angle correction. At the same time, the thickness of the inner groove weld of the H seam 122 is increased accordingly. When the outer weld of the H seam is welded after rounding, the penetration of the inner side of the V-shaped groove of the H seam is large. When the submerged arc automatic welding is used on the outer side, the full penetration welding of the H seam can be achieved without the carbon arc air planing root cleaning process. It can not only ensure the necessary rigidity of the H seam, but also save the root cleaning operation before the H seam welding, and reduce the secondary deformation during the cylinder section root cleaning operation and transportation process.

[0065] In addition, in this embodiment, the rounding of the cylinder section is performed before the outer seam of the H seam is welded. Before the outer welding, the conformal support frame 300 is installed inside the cylinder section, and the angular deformation of the H seam is adjusted by the support of the conformal support frame 300, and the restraint force of the H seam during the welding hot operation is increased, thereby avoiding the secondary angular deformation caused by the welding hot operation. It can be understood that, combined with the rigid restraint effect of the conformal support frame 300, there is no need for secondary rounding after the outer side of the H seam is welded, thereby avoiding the weld cracking problem caused by rounding the outer side of the H seam due to welding deformation.

[0066] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A C-type LPG tank section welding method, characterized in that: The following steps are involved: The steel plate rolling step comprises: splicing a plurality of low-temperature steel plates to form a spliced ​​sheet body, wherein the spliced ​​weld is defined as a P seam, and after the P seam welding is completed, the spliced ​​sheet body is rolled, and the rolled cylinder section forms a closed weld to be welded, wherein the closed weld is defined as an H seam, and the cylinder section is formed by splicing two low-temperature steel plates, and one P seam is provided, and the P seam and the H seam are radially opposite; In the inner side welding step of the closing weld, the rolled cylinder section is moved so that the inner groove of the H seam is at the 6 o'clock position, wherein the H seam adopts a V-shaped groove design, and the inner groove of the H seam is welded with a welding rod arc welding method, and then the filling and covering welding is performed with a submerged arc automatic welding method; The roundness calibration step is to calibrate the cylinder section after the inner groove welding of the H-seam is completed; The step of adding a conformal support frame is that after the cylinder segment is calibrated, at least one conformal support frame is respectively installed on the inner sides of the two ends of the cylinder segment, the conformal support frame comprises a first mounting portion installed at the P seam position of the inner wall of the cylinder segment and a second mounting portion installed at the H seam position of the inner wall of the cylinder segment, the first mounting portion and the second mounting portion are connected by a support rod, one end of the support rod is connected to the first mounting portion, and the other end of the support rod is fixed to the second mounting portion by positioning welding. The first mounting portion and the second mounting portion of the conformal support frame are radially opposite to each other and are connected by the support rod and are connected by the support rod. The relative position of the support rod and the second mounting portion is adjusted to limit the ellipticity of the cylinder segment and improve the rigidity of the cylinder segment, the first mounting portion comprises a mounting ear plate, a first ear plate and a first fastener, the mounting ear plate is fixed on the inner wall of the cylinder segment near the P seam, the first ear plate is installed on the end of the support rod, and the first ear plate is connected to the mounting ear plate by the first fastener; The steps for welding the outside of the closing weld are as follows: after installing the conformal support frame, move the cylinder segment to adjust the H seam to the 12 o'clock position, and use the submerged arc automatic welding method to weld the outside weld of the H seam; place the cylinder segment rounding opportunity before welding the outer seam of the H seam, and before external welding, install a conformal support frame inside the cylinder segment, rely on the support of the conformal support frame to adjust the angular deformation of the H seam, and increase the restraint force of the H seam during the welding heat operation.

2. The C-type LPG tank section welding method according to claim 1 is characterized in that: The second mounting portion includes a tacking adjustment plate and a second ear plate. The tacking adjustment plate is fixed to the inner wall of the cylinder segment and installed across the H-slit. Both ends of the tacking adjustment plate are respectively fixed to the low-temperature steel plates on both sides of the H-slit. The second ear plate is fixed to the end of the support rod. The second ear plate and the tacking adjustment plate are fixed by tacking welding. The relative position of the second ear plate and the tacking adjustment plate is adjusted to limit the ovality of the cylinder segment and improve the rigidity of the cylinder segment.

3. The C-type LPG tank section welding method according to claim 1 is characterized in that: The mounting ear plate is installed with a first offset from the P seam, and the first offset is greater than 0, so as to avoid the corner seam between the mounting ear plate and the inner wall of the cylinder section from intersecting the P seam.

4. The C-type LPG tank section welding method according to claim 3 is characterized in that: The first offset is 30 mm.

5. The C-type LPG tank section welding method according to claim 3 is characterized in that: The axis of the first fastener is parallel to the P-slit to limit the support rod from rotating along the axial direction of the barrel segment.

6. The C-type LPG tank section welding method according to any one of claims 1 to 5, characterized in that: The P seam of the cylinder section adopts a Y-shaped groove design and is welded using double-sided submerged arc automatic welding method.

7. The C-type LPG tank section welding method according to claim 6 is characterized in that: The welding material in the electrode arc welding method is the GB / T5117-E5518-N5P electrode with a specification of φ3.2mm.

8. The C-type LPG tank section welding method according to claim 6 is characterized in that: The welding material in the submerged arc automatic welding method is a combination of welding wire and flux of GB / T5293-S55P5FB-SUN2M, and the welding wire specification is φ3.2mm.

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