Special-shaped butt welding structure stress optimization method and structure

Abstract

The embodiment of the invention provides a special-shaped butt welding structure stress optimization method and structure, the special-shaped butt welding structure comprises a welding joint, and a first base metal part and a second base metal part which are connected with each other through the welding joint, and the surface of the first base metal part and the surface of the second base metal part have a height difference. The method comprises the following steps: determining a to-be-surfaced area on the surfaces of the welding joint, the first base metal part and the second base metal part; the to-be-surfaced area continuously covers the welding joint and part of the surfaces of the first base metal part and the second base metal part on the two sides of the welding joint; and a surfacing layer is formed in the to-be-surfaced area, so that the surface of the first base metal part, the surface of the surfacing layer and the surface of the second base metal part are smoothly connected. According to the embodiment of the invention, the appearance linetype of the structure is optimized through surfacing, and the stress concentration level of the structure is reduced, so that the early failure risk of the special-shaped butt welding structure is reduced, and the service safety level of the structure is improved.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of special-shaped butt joint structures, and specifically relate to a stress optimization method and structure of a special-shaped butt joint welding structure. Background Art

[0002] One side is a straight pipe component, and the other side is a valve, tee, elbow, etc., with inconsistent structural dimensions at both ends, especially unequal inner and outer wall dimensions, and significant thickness differences. The components formed by welding are widely used in engineering practice. For the components formed by the special-shaped structural components with inconsistent structural dimensions at both ends of these welded joints, the national standards and industry standards have certain provisions on how to transition them. However, due to the limitations of manufacturing and processing capabilities or actual production, there are a large number of special-shaped welded joints with sudden changes in knot shape and wall thickness in actual engineering. For these welded joints, the stress concentration position at the component structure change usually overlaps or is adjacent to the fusion zone of the welded joint, making the overlapping or adjacent area the weakest link in the entire component structure. In the long-term use process, especially under the action of additional system stress, early failure cracking is prone to occur, thus causing safety risks.

[0003] The existing technology adopts the method of secondary machining of special-shaped structural sections, using a turning tool to turn the surface of the thick end parent material to form a straight section of a certain length, so that its outer diameter is consistent with the thinner pipe section, and a slope of 15°~30° is used to transition to the outer diameter of the thick end to reduce stress and avoid overlapping of structural stress and welding fusion line.

[0004] However, secondary machining of pipe fittings on site requires certain space conditions to be able to install mechanical turning tools. At the same time, some pipe fittings require special fixtures and tools due to structural reasons, which further limits their application on site and makes mechanical turning difficult to achieve. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a stress optimization method and structure for a special-shaped butt-welded structure.

[0006] One aspect of the present disclosure provides a stress optimization method for a special-shaped butt welded structure, wherein the special-shaped butt welded structure comprises a welded joint and a first parent material portion and a second parent material portion connected to each other by the welded joint, wherein the surfaces of the first parent material portion and the second parent material portion have a height difference. The method comprises: Determine a region to be surfacing on the surface of the weld joint, the first parent material portion, and the second parent material portion; the region to be surfacing continuously covers the weld joint and a portion of the surface of the first parent material portion and the second parent material portion on both sides of the weld joint; A surfacing layer is formed in the area to be surfacing, so that the surface of the first parent material portion, the surface of the surfacing layer and the surface of the second parent material portion are smoothly connected.

[0007] Optionally, determining the area to be surfacing includes: Mechanical turning is used to remove the excess height of the welding joint.

[0008] Optionally, the surface of the first parent material part and / or the second parent material part has a slope section, and the bottom end of the slope section is connected to the welding joint; The step of determining the area to be surfacing includes: A smooth transition zone is formed on the surface of the connecting portion between the slope section and the welding joint.

[0009] Optionally, the welding joint is respectively connected to the end of the straight section of the first parent material part and the bottom end of the slope section of the second parent material part; The surface of the first matrix part has a first widened area, and the surface of the second matrix part has a second widened area; The first widened area is a surface of the first mother material portion extending from the end of the straight section to the other end of the first mother material portion with a length of 5 mm to 10 mm; the second widened area is a surface of the second mother material portion extending from the top of the slope section to the other end away from the slope section with a length of 5 mm to 10 mm; The area to be surfacing continuously covers the first widened area, the surface of the weld joint, the surface of the slope section, and the second widened area.

[0010] Optionally, an angle between the surface of the surfacing layer and the surface of the straight section of the first base material portion is 15°~30°.

[0011] Furthermore, the method further comprises: If the angle between the surface of the surfacing layer and the surface of the straight section of the first parent metal portion is greater than 30°, the first widened area is extended so that the angle reaches 15° to 30°.

[0012] Optionally, before forming the surfacing layer in the area to be surfacing, the method further comprises: Manual arc welding is used to perform crack blocking process welding in the area to be clad.

[0013] Optionally, the surfacing layer includes a filling welding layer and a capping welding layer; The forming of a surfacing layer in the to-be-surfacing area comprises: Performing filling welding in the surfacing area to form a filling welding layer; Cap welding is performed on the surface of the filling welding layer.

[0014] Optionally, forming a surfacing layer in the area to be surfacing includes: While welding the end of the arc, the welding current is attenuated. After the arc pit is filled, the welding head is moved to the edge of the groove to close the arc.

[0015] Another aspect of the present disclosure provides a stress optimization structure for a special-shaped butt welded structure, the structure being obtained by the stress optimization method for a special-shaped butt welded structure described above; The structure includes a welding joint and a first parent material portion and a second parent material portion connected to each other by the welding joint, wherein the surfaces of the first parent material portion and the second parent material portion have a height difference; A continuous cladding layer is provided on the surface of the weld joint and a portion of the first parent material part and the second parent material part on both sides of the weld joint, and the surface of the first parent material part, the surface of the cladding layer and the surface of the second parent material part are smoothly connected.

[0016] A stress optimization method and structure for a special-shaped butt-welded structure in an embodiment of the present invention optimizes the appearance line of the structure and reduces the degree of structural mutation by means of surfacing welding, thereby solving the problem of stress superposition and concentration caused by the overlap or proximity of the stress concentration position of the component structure and the fusion zone of the weld joint, and reducing the structural stress concentration level, thereby reducing the risk of early failure of the special-shaped butt-welded structure, improving the service safety level of the structure, and having good promotion and application value for the improvement and transformation of the same type of components. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an existing special-shaped butt welding structure; Figure 2 A schematic diagram of a process for optimizing stress of a special-shaped butt-welded structure according to an embodiment of the present disclosure; Figure 3 It is a structural schematic diagram of a special-shaped butt welding structure of another embodiment of the present disclosure; Figure 4 It is a structural schematic diagram of a stress optimization structure of a special-shaped butt welding structure according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0019] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0020] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0021] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present disclosure. As used in this disclosure, the term "and / or" includes any one of the associated listed items and all combinations of one or more.

[0022] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present disclosure, and therefore cannot be used to limit the protection scope of the present disclosure.

[0023] One embodiment of the present disclosure provides a stress optimization method for a special-shaped butt welded structure. Figure 1 As shown, the special-shaped butt welding structure includes a welding joint 2 and a first parent material part 1 and a second parent material part 3 connected to each other through the welding joint 2. The first parent material part 1 is a straight pipe section, and the second parent material part 3 is a special-shaped pipe section. There is a height difference between the surfaces of the first parent material part 1 and the second parent material part 3. The welding fusion line (area) 21 of the two sections of parent material overlaps with the stress concentration point 31 of the butt welding structure. During long-term use, the welding joint is prone to early failure and cracking, causing safety risks.

[0024] To solve the above problems, Figure 2 As shown in the figure, the stress optimization method of special-shaped butt welded structure includes: Step S21, determining a region to be surfacing on the surfaces of the weld joint, the first parent material portion, and the second parent material portion.

[0025] Specifically, first measure the surface of the weld joint of the special-shaped butt welding structure to understand the groove structure and width of the weld joint, the pipe diameter and thickness of the special-shaped parts on both sides of the weld joint, the inclination angle and length of the slope section, etc. Figure 1 , use mechanical turning methods, such as an annular beveling machine, to completely turn and remove the excess height 22 that may exist on the surface of the weld joint 2 to be welded, or use a manual grinder to grind and remove the excess height 22 of the weld joint 2, so that the surface of the weld joint 2 to be welded remains flat. When the surface of the first parent material part 1 and / or the second parent material part 2 has a slope section 32, and the bottom end of the slope section 32 is connected to the weld joint 2, manual grinding is performed along the slope section 32.

[0026] like Figure 3 In the special-shaped butt welding structure shown, the welding joint 2 is respectively connected to the end of the straight section of the first parent material part 1 and the bottom end of the slope section 32 of the second parent material part 3, and the area to be welded 4 continuously covers the welding joint 2 and a part of the surface of the first parent material part 1 and the second parent material part 3 on both sides of the welding joint. Specifically, the surface of the first parent material part 1 has a first widening area 41, and the surface of the second parent material part 3 has a second widening area 42. The first widening area 41 is a surface of the first parent material part extending from the end of the straight section to the other end of the first parent material part 1 with a length of 5mm~10mm; the second widening area 42 is a surface of the second parent material part 3 extending from the top end of the slope section 32 to the other end away from the slope section 32 with a length of 5mm~10mm. The area to be welded 4 extends from the left straight pipe section to the right slope section 32, continuously covering the first widening area 41, the surface of the welding joint 2, the surface of the slope section 32 and the second widening area 42. The widened areas 41 and 42 can be used as subsequent enlarged cap welding areas.

[0027] The manual grinding range of the base material should also extend 20mm beyond both sides of the surfacing area 4 to remove rust and dirt to reveal the metallic luster. At the same time, a smooth transition area 43, such as R5 angle, is polished on the surface of the connecting part of the welding joint 2 and the slope section 32. The upper edge of the slope can also be polished to a smooth transition to facilitate the subsequent surfacing process.

[0028] Finally, a macroscopic inspection is used to check the surface quality of the base material in the cladding area and within 20mm on both sides. Only after confirming that there are no defects can the cladding welding process be carried out.

[0029] Step S22, forming a surfacing layer in the area to be surfacing, so that the surface of the first parent material portion, the surface of the surfacing layer and the surface of the second parent material portion are smoothly connected.

[0030] Specifically, the 9%Cr~12%Cr martensitic heat-resistant steel material commonly used in high-temperature and high-pressure pipelines in thermal power plants is used as an example to formulate welding and heat treatment processes. Before forming the cladding layer, the material of the weld joint and the material of the parent material on both sides are checked, and the material spectrum is reviewed, and the materials of the above-mentioned components are tested and reviewed. According to the component materials and specifications, the welding process and post-weld heat treatment process are formulated in accordance with relevant regulations. The welding process parameters are shown in Table 1, and the post-weld heat treatment process parameters are shown in Table 2. Metal parts of other materials and component sizes can be implemented as a reference; for some other low-alloy materials, similar effects can be achieved without post-weld heat treatment, and the heat treatment step is not a necessary step.

[0031] Table 1. Welding process parameters

[0032] Table 2. Post-weld heat treatment process parameters

[0033] Manual arc welding (SMAW, Shielded Metal Arc Welding) is used to perform crack blocking process welding on the cladding welding layer. On the one hand, the surface weld and its heat-affected zone are self-tempered by controlling the weld bead welding thermal cycle to reduce the crack initiation tendency in the weak area of ​​the weld and play a crack "blocking" role. On the other hand, the widening area is used to expand the cap welding area to block the expansion channel parallel to the fusion line after the crack initiation, avoiding low plasticity and rapid fracture of the joint. Preheating before welding is carried out in accordance with DL / T 869-2021 and DL / T 819-2019 standards. The preheating temperature before arc welding is 200℃~250℃. After the temperature rises to the preheating temperature, it is kept warm for at least 0.5h, and the interlayer temperature is controlled at 200℃~250℃. Electric heating and thermocouple temperature measurement are used. The heating width on one side is not less than 4 times the pipe wall thickness and not less than 100mm.

[0034] Then, a surfacing process is performed to form a surfacing layer in the surfacing area. Figure 4 As shown, manual arc welding is used to gradually build up the area 4 to be built up from the straight pipe section side of the first parent material part 1 to the special-shaped structure side of the second parent material part 3 to form a build-up layer 5. Specifically, the build-up weld includes filling welding and capping welding. The filler welding is performed on the area 4 to be built up determined in the previous step S21 to form a filler welding layer, and a remaining weld layer thickness of 2mm to 3mm is reserved. Then, capping welding is performed on the surface of the filler welding layer. After capping welding, the overall profile should be slightly higher than the predetermined build-up layer to facilitate subsequent polishing and smoothing.

[0035] In the above welding process, the filling welding and the capping welding should be carried out continuously if the interlayer temperature allows. AWS E9015-B92 is selected as the welding material. The welding process can be performed by two people symmetrically, and the welding heat input is strictly controlled. The interlayer temperature is controlled by a combination of a heat treatment machine and a temperature measuring gun / temperature measuring pen, and the relevant parameters in the welding process are recorded. Multi-layer and multi-pass thin-layer welding is adopted, and the welding heat input, the width of a single-layer weld and the thickness of the weld layer are strictly controlled. The thickness of a single-pass weld layer shall not exceed 3mm, and the width of a single-pass weld shall not exceed 3 times the diameter of the electrode. The ratio of the weld length welded by each complete electrode to the melting length of the electrode should be greater than 50%. During the welding process, attention should also be paid to the distribution of the weld and the arrangement of the arc closing position to prevent local overheating. The joints of each layer of welds should be staggered by 10mm~15mm. At the same time, attention should be paid to making the weld transition as smooth as possible to facilitate slag removal and avoid "dead corners".

[0036] After each weld is completed, the welding slag, spatter and other debris should be completely removed with an angle grinder or wire brush. The welder can only weld the next layer after self-inspection. The defects between the weld joint layers should be removed by grinding with an angle grinder, especially at the weld joint and the edge of the groove. The molten iron transition adopts free transition. When closing the head, pay special attention to attenuating the welding current. After filling the arc pit, move to the edge of the groove to close the arc to prevent the formation of arc pit cracks. The cover welding and the base material should have a smooth transition, the arc pit at the arc closing should be full, and the joint should be well fused.

[0037] After the above welding process, the final product is as follows Figure 4 The stress optimization structure of the special-shaped butt welding structure shown. In order to meet the engineering stress requirements of the present disclosure, the angle 52 between the surface of the cladding layer 5 and the surface of the straight section of the first parent material part 1 should meet 15°~30°. If it does not meet the requirements, and the angle is greater than 30°, when designing the cladding area 4, the widening area distance of the straight pipe groove on the left side of the figure is extended, that is, the first widening area described above is extended until the angle 52 reaches the requirement of 15°~30°.

[0038] After welding is completed, the welding slag and spatter on the weld surface should be cleaned in time, and the appearance defects that exceed the standard should be polished or repaired. The repair welding process is the same as the formal welding process. After the appearance inspection is passed, prepare for post-weld heat treatment.

[0039] According to the post-weld heat treatment process parameter table described in Table 2 above, in order to ensure the reliability of post-weld heat treatment, it is necessary to adopt a zoned precise temperature control method for post-weld heat treatment. The specific process requirements include: the post-weld heat treatment temperature is 750℃-760℃, the constant temperature time is determined to be 2.5 hours according to the height of the component surfacing area, and the heating and cooling speed is not higher than 80℃ / h. If heat treatment cannot be carried out in time, 350℃×2h post-heat treatment is required.

[0040] After welding and heat treatment, Figure 4 The grinding reference line 51 shown is used to shape the surfacing layer 5, further ensuring that the surface of the surfacing layer 5 is smoothly transitionally connected with the surfaces of the parent materials on both sides.

[0041] A stress optimization method for a special-shaped butt-welded structure in an embodiment of the present invention optimizes the appearance line of the structure and reduces the degree of structural mutation by means of surfacing welding, thereby solving the problem of stress superposition and concentration caused by the overlap or proximity of the stress concentration position of the component structure and the fusion zone of the weld joint, and reducing the structural stress concentration level, thereby reducing the risk of early failure of the special-shaped butt-welded structure, improving the service safety level of the structure, and having good promotion and application value for the improvement and transformation of the same type of components.

[0042] Another embodiment of the present disclosure provides a stress optimization structure for a special-shaped butt-welded structure, and the structure is obtained by the stress optimization method for a special-shaped butt-welded structure described in the above embodiment.

[0043] like Figure 4 As shown, the structure includes a welding joint 2 and a first parent material part 1 and a second parent material part 3 connected to each other through the welding joint 2, and the surfaces of the first parent material part 1 and the second parent material part 3 have a height difference. A continuous covering cladding layer 5 is provided on the welding joint 2 and a part of the surfaces of the first parent material part 1 and the second parent material part 3 on both sides of the welding joint 2, and the surface of the first parent material part 1, the surface of the cladding layer 5 and the surface of the second parent material part 3 are smoothly connected.

[0044] The specific preparation process has been described in detail in the previous examples and will not be repeated here.

[0045] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A stress optimization method for a special-shaped butt welding structure, wherein the special-shaped butt welding structure comprises a welding joint and a first parent material part and a second parent material part connected to each other by the welding joint, wherein the surfaces of the first parent material part and the second parent material part have a height difference, characterized in that: The method comprises: Determine a region to be surfacing on the surface of the weld joint, the first parent material portion, and the second parent material portion; the region to be surfacing continuously covers the weld joint and a portion of the surface of the first parent material portion and the second parent material portion on both sides of the weld joint; A surfacing layer is formed in the area to be surfacing, so that the surface of the first parent material portion, the surface of the surfacing layer and the surface of the second parent material portion are smoothly connected.

2. The method according to claim 1, characterized in that The step of determining the area to be surfacing includes: Mechanical turning is used to remove the excess height of the welding joint.

3. The method according to claim 1, characterized in that The surface of the first parent material part and / or the second parent material part has a slope section, and the bottom end of the slope section is connected to the welding joint; The step of determining the area to be surfacing includes: A smooth transition zone is formed on the surface of the connecting portion between the slope section and the welding joint.

4. The method according to claim 1, characterized in that: The welding joints are respectively connected to the end of the straight section of the first parent metal part and the bottom end of the slope section of the second parent metal part; The surface of the first matrix part has a first widened area, and the surface of the second matrix part has a second widened area; The first widened area is a surface of the first mother material portion extending from the end of the straight section to the other end of the first mother material portion with a length of 5 mm to 10 mm; the second widened area is a surface of the second mother material portion extending from the top of the slope section to the other end away from the slope section with a length of 5 mm to 10 mm; The area to be surfacing continuously covers the first widened area, the surface of the weld joint, the surface of the slope section, and the second widened area.

5. The method according to claim 4, characterized in that The angle between the surface of the surfacing layer and the surface of the straight section of the first parent material portion is 15° to 30°.

6. The method according to claim 4 or 5, characterized in that: The method further comprises: If the angle between the surface of the cladding layer and the surface of the straight section of the first parent metal portion is greater than 30°, the first widened area is extended so that the angle reaches 15° to 30°.

7. The method according to claim 1, characterized in that Before forming the surfacing layer in the area to be surfacing, the method further comprises: Manual arc welding is used to perform crack blocking process welding in the area to be clad.

8. The method according to claim 1, characterized in that The surfacing layer includes a filling welding layer and a capping welding layer; The forming of a surfacing layer in the to-be-surfacing area comprises: Performing filling welding in the surfacing area to form a filling welding layer; Cap welding is performed on the surface of the filling welding layer.

9. The method according to claim 1, characterized in that: The forming of a surfacing layer in the to-be-surfacing area comprises: While welding the end of the arc, the welding current is attenuated. After the arc pit is filled, the welding head is moved to the edge of the groove to close the arc.

10. A stress optimization structure of a special-shaped butt welding structure, characterized in that: The structure is obtained by the stress optimization method of the special-shaped butt welding structure according to any one of claims 1 to 9; The structure includes a welding joint and a first parent material portion and a second parent material portion connected to each other by the welding joint, wherein the surfaces of the first parent material portion and the second parent material portion have a height difference; A continuous cladding layer is provided on the surface of the weld joint and a portion of the first parent material part and the second parent material part on both sides of the weld joint, and the surface of the first parent material part, the surface of the cladding layer and the surface of the second parent material part are smoothly connected.

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