A welding method for an ultra-large size head

Abstract

This invention provides a welding method for an ultra-large head, comprising: longitudinally decomposing the ultra-large head into multiple segments of the same size; processing the segments according to their design requirements, and then welding the processed segments onto a welding fixture; assembling the welding fixture, welding the longitudinal welds after assembly, leaving two symmetrical longitudinal welds unwelded as mating joints; subjecting the two halves to flaw detection in a separate flaw detection chamber; performing mating welding on the mating joints after passing the flaw detection; and performing flaw detection on the mating joints after the mating welding, thus obtaining the ultra-large head. This invention, through the segment splicing, half-welding, and jointing method, can ensure the circumferential dimensional accuracy of the ultra-large head, reduce welding difficulty, and solve the problem of the difficulty in performing overall radiographic inspection and overall processing of ultra-large heads due to size limitations.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a welding method for an ultra-large head. Background Technology

[0002] Pressure vessels are widely used in chemical, petroleum, machinery, metallurgy, nuclear energy, aviation, and aerospace industries, and are essential core equipment in the production process. With the increasing size of chemical equipment and power plants, pressure vessels are not only getting larger in diameter, but also requiring increasingly precise dimensional tolerances.

[0003] Heads are the main pressure-bearing components in pressure vessels. In traditional manufacturing processes, the production of large-diameter heads is limited by factors such as press tonnage and press gear spacing, making it difficult to press flat plates into shape in one go. Therefore, a manufacturing solution of pressing multiple pieces into a tiered shape and then joining them together with longitudinal seams is usually adopted. However, during the welding of multiple longitudinal seams, the shrinkage deformation of each weld can be inconsistent due to differences in weld gaps, welder techniques, and interpass temperatures. When multiple welds are welded together, without deformation control measures, it is difficult to guarantee the roundness, circumference, weld edge angles, and geometric tolerances of the workpiece. Furthermore, after welding ultra-large direct-cut heads, their large size makes it difficult to transport them as a whole to the radiography room for RT inspection, and machine tool size limitations hinder overall machining. Summary of the Invention

[0004] The problem solved by this invention is how to provide a welding method for ultra-large heads, avoiding the problems of low precision after welding of ultra-large heads and the difficulty in overall radiographic inspection and overall processing due to size limitations.

[0005] To address at least one of the aforementioned problems, the present invention provides a welding method for an ultra-large head, comprising the following steps:

[0006] Step S1: Based on the structure of the oversized head, the width of the raw material, and the pressing capacity of the press, the oversized head is longitudinally decomposed into multiple segments of the same size.

[0007] Step S2: According to the design requirements of the petal, complete the processing of the petal and process the longitudinal weld bevel of the petal. Then, weld the processed petal onto the welding fixture.

[0008] Step S3: Assemble the welding fixture, weld the assembled longitudinal weld, and leave the remaining two symmetrical longitudinal welds unwelded as fitting joints to obtain two split structures.

[0009] Step S4: The two halves of the structure are respectively sent into the flaw detection chamber for flaw detection inspection;

[0010] Step S5: After the flaw detection inspection is qualified, the mating joint is fitted and welded according to the perimeter of the spliced ​​half structure.

[0011] Step S6: Perform a flaw detection inspection on the mating joint after the mating welding. After the flaw detection inspection is qualified, the oversized end cap is obtained.

[0012] Preferably, in step S2, the welding fixture includes a trapezoidal base, a support, and an arc-shaped plate. The support is perpendicular to the trapezoidal base and is positioned near the short side of the trapezoidal base. One end of the arc-shaped plate is connected to the top of the support, and the other end is connected to the long side of the trapezoidal base. The size of the arc-shaped plate matches the size of the flap.

[0013] Preferably, the bracket is provided with reinforcing ribs, and two reinforcing ribs are arranged intersectingly on the bracket.

[0014] Preferably, in step S1, the extra-large head is decomposed longitudinally into 20 segments of the same size according to the structure of the extra-large head, the width of the raw material and the pressing capacity of the press.

[0015] Preferably, in step S2, the petal is hoisted onto the welding fixture, and the petal is welded to the arc-shaped plate in the welding fixture to fix the petal onto the welding fixture.

[0016] Preferably, in step S3, when welding the spliced ​​longitudinal weld seam, a symmetrical welding method is adopted, and the two longitudinal weld seams spaced 180° apart are welded simultaneously.

[0017] Preferably, in step S3, when welding the spliced ​​longitudinal weld, a segmented welding method is adopted, dividing the longitudinal weld into an upper section, a middle section, and a lower section. First, the middle section of the longitudinal weld is welded, then the lower section of the longitudinal weld is welded, and then the upper section of the longitudinal weld is welded.

[0018] Preferably, in step S3, when welding the spliced ​​longitudinal weld, the front bevel of the longitudinal weld is welded first, and when the weld reaches half the thickness, the root is cleaned, and then the back bevel of the longitudinal weld is welded.

[0019] Preferably, in step S5, the perimeter of the two assembled half-structures is compared with the design requirements of the disc length of the oversized head, and the fitting opening is fitted and welded to control the disc length deviation of the oversized head after the fitting and welding is completed within 5mm.

[0020] Preferably, in step S6, a radiation source is used to perform flaw detection on the mating joint after the mating welding. After the flaw detection is qualified, the oversized end cap is obtained.

[0021] This invention comprehensively considers factors such as the structure of the ultra-large head, the width of the raw material plate, and the pressing capacity of the press. It decomposes the ultra-large head into multiple segments of the same size, reducing the manufacturing difficulty of the segments and facilitating their assembly into an ultra-large head. After the segments are processed, their longitudinal weld bevels are processed and welded to a dedicated welding fixture to fix the segments, facilitating welding between them. During welding, the remaining two symmetrical longitudinal welds are not welded but used as fitting ports. These fitting ports are then welded according to the perimeter of the two resulting halves, thereby controlling the overall structure's disc length deviation and improving processing accuracy. Furthermore, by reserving fitting ports, the halves can be individually inspected in the flaw detection chamber, solving the problem of the ultra-large head being too large to fit into the flaw detection chamber. After welding the fitting ports, they are inspected for flaws. Once the inspection is passed, the welding of the ultra-large head is complete. This invention, through a method of splicing petals and welding the ends together, can ensure the circumferential dimensional accuracy of ultra-large heads, reduce welding difficulty, and solve the problem that ultra-large heads are difficult to inspect and process as a whole due to size limitations. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the welding method for an ultra-large head in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the extra-large end cap divided into multiple lobes in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the welding fixture in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure after the welding fixture and the flaps are assembled in an embodiment of the present invention;

[0026] Figure 5 This is a longitudinal section view of the welding fixture support structure in an embodiment of the present invention;

[0027] Figure 6 This is a top view of the welding fixture support structure in an embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the welding fixture support structure and the assembled welding fixture in an embodiment of the present invention.

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

[0030] 11. Trapezoidal base; 12. Bracket; 13. Arc plate; 14. Reinforcing rib; 2. Petal; 31. Bottom disc; 32. Top disc; 321. Positioning rod; 33. Connecting frame. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0032] It should be noted that, where there is no conflict, the features in the embodiments of this invention can be combined with each other. Furthermore, it should be understood that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0033] This invention provides a welding method for ultra-large head, such as... Figure 1 As shown, it includes the following steps:

[0034] Step S1: Based on the structure of the oversized head, the width of the raw material, and the pressing capacity of the press, the oversized head is longitudinally decomposed into multiple segments 2 of the same size.

[0035] Step S2: According to the design requirements of the petal 2, complete the processing of the petal 2, process the longitudinal weld bevel of the petal 2, and then weld the processed petal 2 onto the welding fixture.

[0036] Step S3: Assemble the welding fixture, weld the assembled longitudinal weld, and leave the remaining two symmetrical longitudinal welds unwelded as fitting joints to obtain two half-structures; the half-structure is to symmetrically divide a head into two halves, each half being a half-structure.

[0037] Step S4: The two halves of the structure are respectively sent into the flaw detection chamber for flaw detection inspection;

[0038] Step S5: After the flaw detection inspection is qualified, the mating joint is fitted and welded according to the perimeter of the spliced ​​half structure.

[0039] Step S6: Perform a flaw detection inspection on the mating joint after the mating welding. After the flaw detection inspection is qualified, the oversized end cap is obtained.

[0040] It should be noted that extra-large heads refer to heads with a diameter exceeding 10m.

[0041] In step S1, taking into account factors such as the structure of the ultra-large head, the width of the raw materials used to make the ultra-large head, and the pressing capacity of the press, the structure of the ultra-large head is decomposed and the ultra-large head is decomposed into multiple lobes 2 along the longitudinal direction.

[0042] Before disassembling the structure of the oversized head, we first design it based on its structural characteristics to obtain a design structure that meets the requirements of the oversized head, satisfies the accuracy requirements, and reduces the number of molds to be made.

[0043] For example, such as Figure 2 As shown, taking an ellipsoidal head with a diameter of 14m as an example, based on its structural characteristics, its edge part is made in proportion to an ellipsoidal structure, while the central part is approximated as a spherical structure, so that the theoretical error of the design structure is controlled within 2mm, which can meet the accuracy requirements and reduce the number of molds to be made; based on the structure of the ultra-large head, the width of the raw material plate and the pressing capacity of the press, the ellipsoidal head with a diameter of 14m is decomposed into 20 lobes along the longitudinal direction.

[0044] In step S2, such as Figure 3 As shown, the welding fixture includes a trapezoidal base 11, a bracket 12, and an arc-shaped plate 13. The bracket 12 is perpendicular to the trapezoidal base 11 and is positioned near the short side of the trapezoidal base 11. One end of the arc-shaped plate 13 is connected to the top of the bracket 12, and the other end is connected to the long side of the trapezoidal base 11. The size of the arc-shaped plate 13 matches that of the petal 2.

[0045] Furthermore, to improve the strength of the welding fixture, the support 12 is provided with reinforcing ribs 14, and two reinforcing ribs 14 are arranged intersectingly on the support 12. In addition, reinforcing ribs 14 are also provided between the arc-shaped plate 13 and the trapezoidal base 11 to improve the stability of the arc-shaped plate 13.

[0046] The size and structure of the welding fixture match the petal 2. The petal 2 can be fixed to the welding fixture by welding, so that the welding fixture supports and fixes the petal 2, improving the structural stability during the welding process and ensuring the welding accuracy.

[0047] Specifically, the petal 2 is hoisted onto the welding fixture, and the petal 2 is welded to the arc-shaped plate 13 in the welding fixture, thereby fixing the petal 2 to the welding fixture. In other words, the petal 2 is connected to the arc-shaped plate 13 in the welding fixture by welding, achieving a fixed connection between the petal 2 and the welding fixture. The structure after the petal 2 is fixed to the welding fixture is as follows: Figure 4 As shown.

[0048] In step S3, the welding fixture is spliced ​​and assembled, and the spliced ​​longitudinal weld is welded. The remaining two symmetrical longitudinal welds are not welded and are used as fitting joints to obtain two half-structures.

[0049] In order to meet the accuracy requirements when assembling the welding fixtures, the welding fixtures and their supporting structures are assembled together in a coordinated manner, such as... Figure 5 and 6 As shown, the welding fixture support structure includes a bottom disc 31, a top disc 32, and a connecting frame 33 disposed between the bottom disc 31 and the top disc 32. Both the bottom disc 31 and the top disc 32 include multiple circumferentially distributed positioning rods 321. The distribution of the positioning rods 321 matches the dimensions of the welding fixture. When the welding fixture is assembled with the welding fixture support structure, the positioning rods 321 of the bottom disc 31 can abut against the two sides of the short side of the trapezoidal base 11 of the welding fixture, while the positioning rods 321 of the top disc 32 can abut against the two sides of the top end of the bracket 12 of the welding fixture. The welding fixture support structure ensures the dimensional accuracy when multiple welding fixtures are assembled, meeting the accuracy requirements.

[0050] After multiple welding fixtures are assembled, the petal 2 is welded to form a longitudinal weld between the petals 2. When welding multiple longitudinal welds, a symmetrical welding method is adopted, that is, two longitudinal welds spaced 180° apart are welded simultaneously.

[0051] For example, taking an ellipsoidal head with a diameter of 14m as an example, it is decomposed into 20 segments 2 along the longitudinal direction. After splicing and assembly, 20 longitudinal welds are evenly arranged in the circumferential direction. By simultaneously welding two longitudinal welds spaced 180° apart, the dimensional and positional tolerances after welding can be reduced and the welding accuracy can be improved.

[0052] In one embodiment, when welding the spliced ​​longitudinal weld, a segmented welding method is adopted, dividing the longitudinal weld into an upper section, a middle section, and a lower section. First, the middle section of the longitudinal weld is welded, then the lower section of the longitudinal weld is welded, and then the upper section of the longitudinal weld is welded.

[0053] By dividing the longitudinal weld into upper, middle, and lower sections, and welding the middle, upper, and lower sections sequentially, deformation during the welding process can be reduced.

[0054] For example, taking an ellipsoidal head with a diameter of 14m as an example, its longitudinal weld length is about 2.7m. If it is directly welded, it is easy to cause the petals 2 to deform during the welding process, resulting in low precision after welding. However, adopting the segmented welding method can reduce the deformation during the welding process and improve the precision of the welded workpiece.

[0055] To ensure welding accuracy, the mating parts of each longitudinal weld can be marked with lines using an outer arc template before welding. During the welding process, the outer arc template can be used for inspection and observation to ensure that the unevenness does not exceed 2mm.

[0056] In another embodiment, when welding the spliced ​​longitudinal weld, the front bevel of the longitudinal weld is welded first, and when the weld reaches half the thickness, the root is cleaned, and then the back bevel of the longitudinal weld is welded.

[0057] In other words, welding is performed alternately using the front and back bevels of the longitudinal weld, and root cleaning is performed when the front bevel is welded to half its thickness to improve welding quality and ensure welding precision.

[0058] In one embodiment, argon arc welding is used to weld the petal 2. Argon arc welding provides stable combustion, is easy to operate and observe, and can improve the welding quality.

[0059] In step S4, the two halves of the structure are respectively placed into the flaw detection chamber for flaw detection inspection. The overall size of the oversized end cap is large, making it difficult to place it into the flaw detection chamber for inspection. However, in this embodiment of the invention, by retaining the fitting opening, two halves are formed, allowing them to enter the flaw detection chamber for inspection.

[0060] In step S5, after the flaw detection inspection is qualified, the mating joint is fitted and welded according to the perimeter of the two half-structures after splicing to obtain the overall structure.

[0061] Specifically, the perimeter of the two assembled halves is compared with the design requirements of the disc length of the oversized head, and the fitting opening is welded to ensure that the disc length deviation of the oversized head after the fitting and welding is completed is controlled within 5mm.

[0062] When welding multiple lobes 2, dimensional accuracy deviations can easily occur. Therefore, after welding the two half-structures, two symmetrical longitudinal welds are reserved as fitting joints, allowing for a certain amount of shrinkage. The perimeter of the spliced ​​half-structures is measured and compared with the disc length requirements of the oversized head. By fitting and welding the fitting joints, the final disc length deviation is controlled within 5mm, ensuring the welding accuracy.

[0063] In step S6, a radiation source is used to perform flaw detection on the mating joint after the mating welding. After the flaw detection is qualified, the oversized end cap is obtained.

[0064] After welding the two halves together, a whole structure is formed. Due to the large size of the whole structure, it is difficult to enter the flaw detection room to inspect the welds of the mating joint. Therefore, it is transported to the outdoor flaw detection bunker and the two longitudinal welds of the mating joint are inspected by X-ray source. Once the requirements are met, the ultra-large head can be obtained.

[0065] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method of welding an ultra-large size head, characterized in that, It comprises the following steps: Step S1, according to the structure of the oversize head, the plate width of the raw material and the pressing capacity of the press, the oversize head is divided into a plurality of petals (2) with the same size along the longitudinal direction; Step S2, according to the design requirements of the petals (2), the petals (2) are processed, and the longitudinal weld bevel of the petals (2) is processed, then the petals (2) after processing are welded to a welding tool, the welding tool comprises a trapezoidal base (11), a support (12) and an arc plate (13), the support (12) is perpendicular to the trapezoidal base (11), and the support (12) is arranged at a position close to one end of the short side of the trapezoidal base (11), one end of the arc plate (13) is connected with the top end of the support (12), the other end is connected with a position close to one end of the long side of the trapezoidal base (11), and the size of the arc plate (13) matches the petals (2); Step S3, the welding tool is assembled, the longitudinal weld after assembly is welded, and the remaining two longitudinal welds symmetrical to each other are not welded, serving as a matching opening, so that two half structures are obtained; Step S4, the two half structures are respectively put into a flaw detection room for flaw detection; Step S5, after the flaw detection is qualified, the matching opening is matched and welded according to the circumference of the two half structures after assembly; Step S6, the matching opening after matching and welding is subjected to flaw detection, and the oversize head is obtained after the flaw detection is qualified.

2. The welding method of the oversize head according to claim 1, characterized in that, The support (12) is provided with reinforcing ribs (14), and the two reinforcing ribs (14) are arranged on the support (12) and intersect with each other.

3. The method of welding an ultra-large sized head according to claim 1, wherein, In step S1, according to the structure of the oversize head, the plate width of the raw material and the pressing capacity of the press, the oversize head is divided into 20 petals (2) with the same size along the longitudinal direction.

4. The method of welding an ultra-large sized head according to claim 1, wherein, In step S2, the petals (2) are hoisted to the welding tool, and the petals (2) are welded with the arc plate (13) in the welding tool, so that the petals (2) are fixed to the welding tool.

5. The method of welding an ultra-large sized head as defined in claim 1, wherein, In step S3, when the longitudinal weld after assembly is welded, a symmetrical welding method is adopted to synchronously weld the two longitudinal welds spaced 180° apart.

6. The method of welding an ultra-large sized head as defined in claim 1, wherein, In step S3, when the longitudinal weld after assembly is welded, a segmented welding method is adopted, the longitudinal weld is divided into an upper segment, a middle segment and a lower segment, the middle segment of the longitudinal weld is welded first, then the lower segment of the longitudinal weld is welded, and finally the upper segment of the longitudinal weld is welded.

7. The method of welding an ultra-large sized head as defined in claim 1, wherein, In step S3, when the longitudinal weld after assembly is welded, the front bevel of the longitudinal weld is welded first, and when the welding is half the thickness, the root is cleaned, and then the back bevel of the longitudinal weld is welded.

8. The method of welding an ultra-large sized head as defined in claim 1, wherein, In the step S5, the circumference of the two half-structure after splicing and assembling is compared with the design requirement of the disc length of the super-large size head, and the fitting welding is performed on the fitting mouth, so that the disc length deviation of the super-large size head after the fitting welding is completed is controlled within 5 mm.

9. The welding method of super-sized closures according to any one of claims 1-8, characterized in that, In the step S6, the fitting mouth after the fitting welding is detected by using a ray source, and the super-large size head is obtained after the detection is qualified.

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