A method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation

Abstract

This invention discloses a large tube sheet surfacing welding method based on in-situ control of welding residual stress and deformation. A surfacing layer is formed on the tube sheet surface by welding, and the surfacing layer includes a transition layer and a surface layer. The specific steps are as follows: (1) Surfacing the transition layer: The transition layer includes a middle part and a peripheral part. First, the middle part of the transition layer is surfacing manually, and then the peripheral part of the transition layer is surfacing along a symmetrical double-helical welding path using a strip electrode welding method; (2) Surfacing the surface layer: The surface layer includes a middle part and a peripheral part. First, the middle part of the surface layer is surfacing manually, and then the peripheral part of the surface layer is surfacing along a symmetrical double-helical welding path using a strip electrode welding method. This invention improves the surfacing method, reducing the welding residual stress and deformation of the tube sheet. After welding, the workload of grinding or finishing the tube sheet is reduced, improving the integrity of the tube sheet structure.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation. Background Technology

[0002] With the increasing efficiency of energy utilization, pressure equipment in petrochemical and nuclear power industries is becoming increasingly larger, such as large thick-walled hydrogenation reactors and large nuclear power steam generators. To improve the corrosion resistance of the inner wall layer, a layer of stainless steel or corrosion-resistant alloy is often welded onto the inner wall. For cylindrical inner wall welding, due to structural constraints, minimal residual deformation occurs after welding. However, for tube sheet welding, current technology typically uses a ring-by-ring welding method, resulting in extremely uneven welding temperature distribution and thermal stress. This causes different expansion or contraction amounts between the tube sheet center and periphery, often leading to significant bottom deformation after welding, with the largest deformation at the tube sheet center. This uneven residual deformation, which affects the tube sheet flatness and weld layer thickness, significantly impacts subsequent manufacturing processes and directly affects the normal operation of the equipment. Currently, to address these issues, control of tube sheet welding deformation mainly employs measures such as pre-deformation at the tube sheet center, uniform reinforcement plates along the circumference of the tube sheet, and alternating stacking and welding of tube sheets. While these measures can effectively reduce weld overlay deformation, some residual deformation still occurs. Subsequent processing still requires precision machining and grinding of the tube sheet, which involves relatively large amounts of work, resulting in a heavy workload and affecting the structural integrity of the tube sheet. Therefore, proposing a more effective method for controlling weld overlay deformation in tube sheets is of great significance for the reliable manufacturing of large pressure-bearing equipment. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation. By improving the surfacing method, the residual stress and deformation of the tube sheet are reduced.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation, characterized in that a surfacing layer is formed on the surface of the tube sheet by welding, and the surfacing layer includes a transition layer and a surface layer, wherein the surface layer covers the transition layer.

[0006] The specific steps are as follows:

[0007] (1) Weld overlay transition layer

[0008] The transition layer has a thickness of 2-3 mm and includes a middle part and an outer part. First, the middle part of the transition layer is welded by manual welding, and then the outer part of the transition layer is welded by strip welding along a symmetrical double-helical welding path.

[0009] (2) Weld overlay layer

[0010] The thickness of the surface layer is 3-4 mm, including the middle part and the outer part. First, the middle part of the surface layer is welded by manual welding, and then the outer part of the surface layer is welded by strip welding along a symmetrical double-helical welding path.

[0011] Furthermore, the specific welding operation when manually welding the middle part of the transition layer in step (1) is as follows: welding is performed along a serpentine path in the 250-350mm diameter range of the middle part of the transition layer using manual welding rods.

[0012] The welding process is as follows: welding voltage 20-25V, welding current 160-200A, welding speed 10-20cm / min, and welding wire diameter 2-5mm.

[0013] Furthermore, the specific welding operation when the outer part of the transition layer is welded along the symmetrical double-helical welding path using strip electrode welding in step (1) is as follows: welding is carried out simultaneously from the inside to the outside along the double-helical welding path in the outer part of the transition layer using strip electrode welding to form two helical welds, and the welding process of the two helical welds is the same.

[0014] The welding process is as follows: welding voltage 25-30V, welding current 1000-1300A, welding speed 25-35cm / min, and the width of the strip electrode for electrode surfacing is determined by the tube sheet diameter-to-thickness ratio.

[0015] Furthermore, the specific welding operation when manually welding the middle part of the surface layer in step (2) is as follows: welding is performed along a serpentine path in the 350-450mm diameter range of the middle part of the surface layer using manual welding rods.

[0016] The welding process is as follows: welding voltage 25-30V, welding current 180-220A, welding speed 15-25cm / min, and welding wire diameter 2-5mm.

[0017] Furthermore, the specific welding operation when the outer part of the surface layer is welded along the symmetrical double-helical welding path using strip electrode welding in step (2) is as follows: welding is carried out simultaneously from the outside to the inside along the double-helical welding path on the outer part of the surface layer using strip electrode welding to form two helical welds, and the welding process of the two helical welds is the same.

[0018] The welding process is as follows: welding voltage 28-32V, welding current 1100-1300A, welding speed 25-35cm / min, and the width of the strip electrode for electrode surfacing is determined by the tube sheet diameter-to-thickness ratio.

[0019] Furthermore, the formula for calculating the bandwidth is:

[0020]

[0021] Where W is the strip width in mm, η is the tube sheet diameter-to-thickness ratio, η = D / T, where D is the tube sheet diameter and T is the tube sheet wall thickness.

[0022] Furthermore, the weld overlay layer is provided in at least one layer.

[0023] Furthermore, the weld overlay layer is provided in two or more layers, and the layers are welded alternately with opposite weld overlay paths.

[0024] The beneficial effects of this invention are as follows:

[0025] The present invention provides a large tube sheet surfacing welding method based on in-situ control of welding residual stress and deformation. By improving the surfacing welding method, the residual stress and deformation of the tube sheet are reduced. After welding, the workload of grinding or finishing the tube sheet is reduced, and the integrity of the tube sheet structure is improved. Attached Figure Description

[0026] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the tube sheet overlay welding of the present invention;

[0028] Figure 2 This is a schematic diagram of tube sheet welding using traditional methods.

[0029] Figure 3 This is a schematic diagram showing the deformation of the tube sheet obtained after welding using the conventional method and the method of this invention.

[0030] Figure 4 The images show the weld deformation curves of the tube sheet obtained by the conventional method and the method of the present invention. (a) is the conventional method, and (b) is the method of the present invention.

[0031] Figure 5 The diagram shows the distribution of residual stress along the thickness direction at the center of the tube sheet obtained by conventional welding and the welding method of this invention. Detailed Implementation

[0032] This invention provides a method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] The present invention will now be described in detail with reference to the accompanying drawings.

[0034] Reference Figure 1 This embodiment uses a large tube sheet made of 12Cr1MoV material as an example for surfacing welding. The steps are as follows:

[0035] (1) Weld overlay transition layer

[0036] The transition layer is 2mm thick and made of E309 material, and includes a middle part and an outer part.

[0037] First, the transition layer is welded in a serpentine path within a 300mm diameter range in the middle part using manual welding rods (i.e., the welding direction of manual welding within this range is serpentine, for example, the first weld is from left to right, the second weld is from right to left, the third weld is from left to right, until the welding of this range is completed). The welding process is as follows: welding voltage 24V, welding current 180A, welding speed 16cm / min, and welding wire diameter 4mm.

[0038] Then, using strip welding, the outer portion of the transition layer is simultaneously welded from the inside out along a double-helical welding path, forming two helical weld passes. The welding process for both helical weld passes is the same: welding voltage 28V, welding current 1150A, and welding speed 30cm / min. The strip width for the strip welding is determined by the tube sheet diameter-to-thickness ratio. Additionally, when welding the outer portion of the transition layer, if strip welding is inconvenient at the very edge of the tube sheet, manual electrode welding can be used. The process parameters for manual welding are the same as those for the middle portion of the transition layer.

[0039] (2) Weld overlay layer

[0040] The surface layer is 3mm thick and made of E308 material, including a middle part and an outer part.

[0041] First, the surface layer is welded in a serpentine path along the middle 400mm diameter area using manual welding rods. The welding process is as follows: welding voltage 26V, welding current 190A, welding speed 18cm / min, and welding wire diameter 4mm.

[0042] Then, using strip welding, the outer portion of the surface layer is simultaneously welded from the outside inward along a double-helical welding path, forming two helical weld passes. The welding process for both helical weld passes is the same: welding voltage 30V, welding current 1200A, and welding speed 30cm / min. The strip width for the strip welding is determined by the tube sheet diameter-to-thickness ratio. Additionally, when welding the outer portion of the surface layer, at the very edge of the tube sheet where strip welding is inconvenient, manual electrode welding can be used. The process parameters for manual welding are the same as those for the middle portion of the surface layer.

[0043] When performing strip welding as described above, submerged arc welding with strip welding can be used. The strip width is determined by the tube sheet diameter-to-thickness ratio, and the specific calculation formula is as follows:

[0044]

[0045] Where W is the strip width in mm, η is the tube sheet diameter-to-thickness ratio, η = D / T, where D is the tube sheet diameter and T is the tube sheet wall thickness.

[0046] In addition, during the above-mentioned transition layer and surface layer welding process, the preheating temperature of the transition layer is set to 150°C. After the transition layer welding is completed, the surface layer welding is carried out immediately. The temperature between weld layers is controlled within 100°C, and the overlap between weld layers is 5-7 mm.

[0047] The ABAQUS software was used to simulate the welding of a large tube sheet (12Cr1MoV material) with a diameter of 4000mm and a wall thickness of 50-400mm according to the above welding process parameters. The transition layer and the surface layer of the weld were both one layer. The deformation was compared with that of the traditional method to study the degree of deformation, as shown in Table 1 below.

[0048] The aforementioned traditional method refers to the method of welding ring by ring along a circular path, such as... Figure 2 As shown, when using the traditional method for surfacing welding, it is also divided into a transition layer and a surface layer (both are one layer). The middle part of the transition layer and the surface layer is manually surfacing, and the outer part is surfacing with a submerged arc welding electrode. The welding process parameters of the transition layer and the surface layer in the traditional method are the same as those in this embodiment. The difference is that in the traditional method, the welding path of the middle part of the transition layer and the surface layer is surfacing sequentially in the same direction, and the welding path of the outer part of the transition layer and the surface layer is surfacing circle by circle along a circular path.

[0049] Table 1

[0050]

[0051]

[0052] As can be seen from Table 1 above, compared with traditional methods, the large tube sheet surfacing welding method of the present invention can effectively control the surfacing deformation during the surfacing stage, realize in-situ regulation of residual stress and deformation of large tube sheet surfacing welding, and as the tube sheet diameter-to-thickness ratio increases, the surfacing deformation gradually decreases, with the deformation reduction percentage remaining stable at around 30%. The deformation reduction in Table 1 above represents the difference in maximum deformation in the tube sheet edge region.

[0053] In addition, for a more intuitive comparison, we will compare and analyze the weld deformation diagram and residual stress distribution of a large tube sheet (12Cr1MoV material) with a diameter of 4000mm and a wall thickness of 100mm, obtained by ABAQUS software simulation. Figure 3-5 As shown.

[0054] like Figure 3 The figure shows a schematic diagram of the tube sheet deformation obtained by the conventional method and the method of the present invention. As can be seen from the figure, the axial deformation of the tube sheet obtained by the conventional method is obviously pot-shaped, and the deformation reaches the maximum in the edge area of ​​the tube sheet, which is 56.48 mm. In contrast, the tube sheet deformation obtained by the method of the present invention is relatively small, especially the deformation of the tube sheet edge area is greatly reduced, with a maximum of 40.75 mm.

[0055] like Figure 4 The figure shows the surface deformation curves of the tube sheet obtained by the conventional method and the method of the present invention. It can be seen from the figure that the surface deformation of the tube sheet obtained by the welding method of the present invention is small and the deformation is relatively uniform.

[0056] like Figure 5 The figure shows the residual stress distribution along the thickness direction at the center of the tube sheet obtained by the conventional method and the method of the present invention. It can be seen from the figure that the uniformity of the residual stress distribution in the tube sheet obtained by the method of the present invention is improved, and the residual stress on the surface of the weld overlay and at the interface between the weld overlay and the base material is also significantly reduced. This demonstrates the effectiveness of the method of the present invention in controlling weld deformation and residual stress.

[0057] Example 2

[0058] In this embodiment, three sets of large tube sheets made of 12Cr1MoV material were used for actual surfacing welding. The tube sheet diameter was 4000mm, the wall thickness was 100mm, and the diameter-to-thickness ratio was 40. The welding process of the three sets of tube sheet samples is shown in Table 2 below.

[0059] Table 2

[0060]

[0061]

[0062] In this embodiment, the tube sheet prepared by the above-mentioned welding method has small deformation. Through testing, the amount of tube sheet grinding and finishing is relatively small. The amount of tube sheet grinding and finishing work can be reduced by half compared with the traditional method, which not only improves the integrity of the tube sheet structure, but also improves the work efficiency.

[0063] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0064] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for surfacing large tube sheets based on in-situ control of welding residual stress and deformation, characterized in that, An overlay layer is formed on the surface of the tube sheet by welding, and the overlay layer includes a transition layer and a surface layer; The specific steps are as follows: (1) Weld overlay transition layer The transition layer includes a middle part and an outer part. First, the middle part of the transition layer is welded by manual welding, and then the outer part of the transition layer is welded by strip welding along a symmetrical double-helical welding path. (2) Weld overlay layer The surface layer includes a middle part and an outer part. First, the middle part of the surface layer is welded by manual welding, and then the outer part of the surface layer is welded by strip welding along a symmetrical double-helical welding path. The specific welding operation when manually welding the middle part of the transition layer in step (1) is as follows: welding is performed along a serpentine path in the 250~350mm diameter range of the middle part of the transition layer using manual welding rods. The welding process is as follows: welding voltage 20~25V, welding current 160~200A, welding speed 10~20cm / min, welding wire diameter 2~5mm; The specific welding operation in step (1) when the outer part of the transition layer is welded along the symmetrical double-helical welding path using strip electrode welding is as follows: welding is performed simultaneously from the inside to the outside along the double-helical welding path on the outer part of the transition layer using strip electrode welding to form two helical welds, and the welding process of the two helical welds is the same. The welding process is as follows: welding voltage 25~30V, welding current 1000~1300A, welding speed 25~35cm / min, and the width of the strip electrode for electrode surfacing is determined by the tube sheet diameter-to-thickness ratio. The specific welding operation when manually welding the middle part of the surface layer in step (2) is as follows: welding is performed along a serpentine path in the 350~450mm diameter range of the middle part of the surface layer using manual welding rods. The welding process is as follows: welding voltage 25~30V, welding current 180~220A, welding speed 15~25cm / min, welding wire diameter 2~5mm; The specific welding operation in step (2) when the outer part of the surface layer is welded along the symmetrical double-helical welding path using strip electrode welding is as follows: welding is carried out simultaneously from the outside to the inside along the double-helical welding path on the outer part of the surface layer using strip electrode welding to form two helical welds, and the welding process of the two helical welds is the same. The welding process is as follows: welding voltage 28~32V, welding current 1100~1300A, welding speed 25~35cm / min, and the width of the strip electrode for electrode surfacing is determined by the tube sheet diameter-to-thickness ratio.

2. The method for large tube sheet surfacing welding based on in-situ control of welding residual stress and deformation according to claim 1, characterized in that, The formula for calculating the bandwidth is: ； Where W is the strip width in mm, η is the tube sheet diameter-to-thickness ratio, η=D / T, where D is the tube sheet diameter and T is the tube sheet wall thickness.

3. The method for large tube sheet surfacing based on in-situ control of welding residual stress and deformation according to claim 1, characterized in that, The weld overlay layer is provided in at least one layer.

4. The method for large tube sheet surfacing welding based on in-situ control of welding residual stress and deformation according to claim 3, characterized in that, The weld overlay layer consists of two or more layers, and the layers are welded alternately with opposite weld overlay paths.

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