An automatic welding repair method for non-penetrating defects of thick-walled parts

Abstract

This invention relates to an automated welding repair method for non-penetrating defects in thick-walled components, comprising a pre-weld preparation process and a welding repair process. The pre-weld preparation process includes: non-destructive testing (NDT), defect removal, further NDT after removal, and machining of the defective area to form a U-shaped bevel. The welding repair process includes: preheating the U-shaped bevel, selecting different automated welding devices according to the width of the U-shaped bevel, performing support welding, filler welding, and leveling welding sequentially until the entire U-shaped bevel is welded, performing martensitic transformation treatment followed by hydrogen removal treatment, cooling to room temperature, performing NDT on the weld, continuing with capping welding, and performing post-weld heat treatment. This invention has a high degree of automation, improves adaptability to different environments, reduces the requirements for operators' welding skills, reduces labor costs, and the weld repaired by automated welding is of better quality than that repaired by manual welding, with higher impact toughness and less susceptibility to re-cracking.

Description

Technical Field

[0001] This invention belongs to the field of welding repair technology, specifically relating to an automatic welding repair method for non-penetrating defects in thick-walled components. Background Technology

[0002] Most critical components of thermal power plants, such as boilers, the four main pipelines, and steam turbines, are thick-walled structures, typically made of alloy steel and cast steel. These thick-walled components are subjected to long-term high-temperature and high-pressure loads, and some are also subject to alternating loads. Therefore, harsh working conditions place higher demands on the safety of these components. For example, components such as main steam valves, regulating valves, and cast tees on boiler headers, due to their large size and significant variations in wall thickness at different locations, may exhibit uneven microstructure due to varying cooling rates during manufacturing. This can lead to cracks and failure in weak points or areas with manufacturing defects during operation.

[0003] In existing technologies, manual welding is commonly used to repair non-penetrating defects in thick-walled components, such as manual arc welding. However, the equipment structures in thermal power plants are complex, and the space around some defective thick-walled components is narrow, making it difficult for operators to enter and perform manual welding. Furthermore, the harsh on-site environment poses certain safety risks, making manual welding repair methods generally difficult to implement. In addition, the weld quality of manual welding repairs is difficult to guarantee, requiring a high level of welding skill from the operators. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic welding repair method for non-penetrating defects with good welding effect and high degree of automation, which is applicable to thick-walled parts with a thickness greater than 20mm made of P92 steel.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An automated welding repair method for non-penetrating defects in thick-walled components includes the following steps:

[0007] S1: Pre-welding preparation procedures, including:

[0008] (1) Perform non-destructive testing on the defective area to determine the location and depth of the defect, and remove the defect according to its location and depth. After removal, perform non-destructive testing again to confirm that there are no residual defects.

[0009] (2) Process the defective area to form a U-shaped bevel;

[0010] S2: Welding repair process, including:

[0011] (1) Preheat the U-shaped bevel to the set preheating temperature.

[0012] (2) Select different automatic welding devices according to the width of the U-shaped bevel for welding. During welding, perform support welding, fill welding, and leveling welding in sequence. Use multi-layer and multi-pass welding. After completing one layer of welding, inspect and clean the surface of the weld. Only after confirming that the welding quality is qualified can the next layer of welding be performed, until the entire U-shaped bevel is welded.

[0013] (3) Perform martensitic transformation treatment at a temperature of 80-120℃ for 1-2 hours, followed by hydrogen removal treatment. After the hydrogen removal treatment is completed, allow the weld to cool to room temperature before performing non-destructive testing to ensure that there are no defects exceeding the standard in the weld.

[0014] (4) Continue to use automatic welding equipment for cover welding.

[0015] (5) Perform post-weld heat treatment.

[0016] Preferably, in S1(1), a beveling machine is used to remove defects, and when the beveling machine is used to remove defects, the area within 2 to 4 mm around the defect is also removed.

[0017] More preferably, when using a beveling machine to remove defects, the area within 3mm around the defect is also removed.

[0018] Preferably, in S2(1), the preheating temperature is set to 150-250°C.

[0019] Preferably, in S2(5), the temperature of the post-weld heat treatment is 730-740°C.

[0020] Preferably, in S2(2), when selecting different automatic welding devices, a round welding torch is selected when the width of the U-shaped groove is greater than or equal to 15mm, and a flat welding torch is selected when the width of the U-shaped groove is less than 15mm.

[0021] More preferably, the flat welding torch includes a welding torch body and a welding torch rod. The thickness of the welding torch body is 6-10 mm. The welding torch body has a through groove penetrating its opposite sides, and the through groove has an opening facing one end of the welding torch body. The welding torch rod is disposed in the through groove, and one end of the welding torch rod extends out of the opening of the through groove. The other end of the welding torch rod extends out of the other end of the welding torch body. One end of the welding torch rod is connected to a tungsten electrode. The top of the welding torch body has a gas pipe connector and a water pipe connector. The gas pipe connector is used to connect a gas pipe, and the water pipe connector is used to connect a water pipe.

[0022] More preferably, the thickness of the welding torch body is 8mm.

[0023] More preferably, the circular welding torch includes a welding torch body, a welding torch rod, and a cylindrical gas shroud. The welding torch body is disposed outside one end of the cylindrical gas shroud, and the welding torch rod is disposed inside the cylindrical gas shroud. The welding torch rod is connected to the inner wall of the cylindrical gas shroud through a connecting part. The two ends of the welding torch rod pass through the two ends of the cylindrical gas shroud, respectively. One end of the welding torch rod is connected to the welding torch body, and the other end of the welding torch rod is provided with a tungsten electrode.

[0024] More preferably, the connecting part is cylindrical, the outer diameter of the connecting part is the same as the inner diameter of the cylindrical air cover, and an annular groove is formed on the outer circumferential surface of the connecting part, and a sealing ring is provided in the annular groove.

[0025] More preferably, the circular welding torch further includes a filter screen, which is disposed inside the cylindrical gas hood, and the filter screen is closer to the other end of the cylindrical gas hood than the connecting portion.

[0026] Preferably, in S2(2), an automatic welding wire with a diameter of 0.8 to 1.2 mm is used for welding.

[0027] More preferably, ER90S-B9 automatic welding wire with a diameter of 1mm is used.

[0028] Preferably, in S2(2), argon is used as the protective gas during welding, and the purity of argon is 99.999%.

[0029] Preferably, in S2(2), the interpass temperature during welding is 150-250°C.

[0030] More preferably, in S2(2), when performing support welding, the gas flow rate of the shielding gas is 65-70 L / min, and secondary gas protection is added; when performing fill welding, the gas flow rate of the shielding gas is 50-65 L / min; and when performing leveling welding, the gas flow rate of the shielding gas is 30-50 L / min.

[0031] Preferably, in S2(2), during filler welding, the tungsten electrode of the automatic welding device oscillates and the welding torch rod of the automatic welding device swings.

[0032] Preferably, in S2(2), when inspecting and cleaning the weld surface, direct visual inspection and / or camera inspection of an automatic welding device are used.

[0033] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0034] This invention employs an automated welding device for welding repair, which has a high degree of automation, improves adaptability to different environments, reduces the requirements for the welding skills of operators, reduces labor costs, and improves safety. Moreover, the weld repaired by automated welding is of better quality than that repaired by manual welding, with higher impact toughness and less susceptibility to cracking. Furthermore, the overall process is simple and easy to implement. Attached Figure Description

[0035] Appendix Figure 1 This is a schematic diagram of the flat welding torch in this embodiment;

[0036] Appendix Figure 2 This is a schematic diagram of the structure of the circular welding torch in this embodiment;

[0037] Appendix Figure 3 This is a metallographic diagram of the heat-affected zone using the automatic welding repair method of this embodiment;

[0038] Appendix Figure 4 This is a metallographic diagram of the weld area using the automatic welding repair method of this embodiment;

[0039] Appendix Figure 5 Metallographic diagram of the heat-affected zone using existing manual welding repair methods;

[0040] Appendix Figure 6 Metallographic diagram of the weld area using existing manual welding repair methods;

[0041] Appendix Figure 7 This is a comparison diagram of the impact toughness of the weld area after using the automatic welding repair method of this embodiment and the manual welding repair method of the prior art.

[0042] In the attached diagrams above:

[0043] 11. Welding torch body; 110. Through groove; 111. Gas pipe connector; 112. Water pipe connector; 12. Welding torch rod; 13. Tungsten electrode;

[0044] 21. Welding torch body; 22. Welding torch rod; 23. Cylindrical gas hood; 24. Connecting part; 240. Annular groove; 241. Sealing ring; 25. Tungsten electrode; 26. Filter screen. Detailed Implementation

[0045] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] An automated welding repair method for non-penetrating defects in thick-walled components includes a pre-weld preparation process and a welding repair process, comprising the following steps:

[0048] S1: First, perform the pre-welding preparation process, which includes:

[0049] (1) Perform non-destructive testing on the defective area to determine the location and depth of the defect. Non-destructive testing can be performed by methods such as ultrasonic testing and magnetic particle testing.

[0050] The defects are removed according to their location and depth. A beveling machine is used for defect removal. When removing defects with a beveling machine, the surrounding base material within 2 to 4 mm is also removed. Preferably, the surrounding base material within 3 mm is removed.

[0051] After cleaning, perform non-destructive testing again to confirm that there are no residual defects and to ensure that the defects are completely removed.

[0052] (2) The defective part is processed to form a U-shaped bevel. For example, an automatic ring cutting machine can be used for processing.

[0053] S2: After completing the pre-welding preparation process, proceed with the welding repair process, which specifically includes:

[0054] (1) Preheat the U-shaped bevel to the set preheating temperature, which is 150 to 250°C. For example, a far-infrared heater can be used for preheating.

[0055] (2) Select different automatic welding devices for welding according to the width of the U-shaped groove. When the width of the U-shaped groove is greater than or equal to 15mm, select a round welding torch. When the width of the U-shaped groove is less than 15mm, select a flat welding torch.

[0056] The specific structures of round and flat welding torches are as follows:

[0057] like Figure 1As shown, the flat welding torch includes a welding torch body 11 and a welding torch rod 12. The welding torch body 11 is generally flat and has a thickness of 6-10 mm, preferably 8 mm. A through groove 110 is provided on the welding torch body 11, penetrating its opposite sides. The through groove 110 has an opening facing one end of the welding torch body 11. The welding torch rod 12 is disposed in the through groove 110, with one end of the welding torch rod 12 extending out of the opening of the through groove 110 and the other end of the welding torch rod 12 extending out of the other end of the welding torch body 11. A tungsten electrode 13 is disposed at one end of the welding torch rod 12. The top of the welding torch body 11 has a gas pipe connector 111 and a water pipe connector 112. The gas pipe connector 111 is used to connect a gas pipe, and the water pipe connector 112 is used to connect a water pipe. There are two gas pipe connectors 111, which are symmetrically arranged. There are two water pipe connectors 112, which are symmetrically arranged.

[0058] like Figure 2 As shown, the circular welding torch includes a welding torch body 21, a welding torch rod 22, and a cylindrical gas shroud 23. The welding torch body 21 is disposed outside one end of the cylindrical gas shroud 23, and the welding torch rod 22 is partially disposed inside the cylindrical gas shroud 23. Both ends of the welding torch rod 22 penetrate both ends of the cylindrical gas shroud 23. One end of the welding torch rod 22 is connected to the welding torch body 21, and the other end of the welding torch rod 22 is provided with a tungsten electrode 25. Specifically, the cylindrical gas shroud 23 is made of transparent material, and the welding torch rod 22 is connected to the inner wall of the cylindrical gas shroud 23 via a connecting part. The connecting parts 24 are connected, and the connecting part 24 is cylindrical. The outer diameter of the connecting part 24 is the same as the inner diameter of the cylindrical air cover 23. The outer peripheral surface of the connecting part 24 is connected to the inner wall of the cylindrical air cover 23. An annular groove 240 is provided on the outer peripheral surface of the connecting part 24. A sealing ring 241 is provided in the annular groove 240. A filter screen 26 is also provided in the cylindrical air cover 23. The filter screen 26 is also cylindrical. The outer peripheral surface of the filter screen 26 is connected to the inner wall of the cylindrical air cover 23. The filter screen 26 is closer to the other end of the cylindrical air cover 23 than the connecting part 24.

[0059] Automatic welding wire with a diameter of 0.8–1.2 mm is used during welding, preferably ER90S-B9 automatic welding wire with a diameter of 1 mm. Argon gas with a purity of 99.999% is used as the shielding gas during welding. The interpass temperature during welding is 150–250℃.

[0060] During welding, support welding, fill welding and leveling welding are performed in sequence. When performing support welding, fill welding and leveling welding, the welding process parameters of the automatic welding device need to be set, as shown in Table 1.

[0061] During support welding, the shielding gas flow rate is 65–70 L / min, and secondary gas protection is added; during filler welding, the shielding gas flow rate is 50–65 L / min, the tungsten electrode of the automatic welding device is oscillating, and the welding torch rod of the automatic welding device is oscillating to avoid incomplete fusion of the sidewalls; during leveling welding, the shielding gas flow rate is 30–50 L / min.

[0062] Multi-layer, multi-pass welding is used during welding. After completing one layer of welding, the surface of the weld seam is inspected and cleaned. This can be done by direct visual inspection and / or by camera inspection of an automatic welding device. After the welding quality is confirmed to be qualified, the next layer of welding is carried out until the entire U-shaped groove is welded.

[0063] In addition, ultrasonic waves can be applied during the welding process to change the crystallization morphology of the weld metal, thereby reducing the coarse structure and stress level of the weld metal.

[0064] Table 1 Welding process parameters for support welding, filler welding, and leveling welding

[0065] (3) In order to ensure that there are no defects exceeding the standard in the weld, after the entire U-shaped groove welding is completed, the weld is subjected to hydrogen removal treatment. Before the hydrogen removal treatment, the weld is subjected to martensitic transformation treatment at a temperature of 80-120℃ for 1-2 hours. After the hydrogen removal treatment is completed, the weld is subjected to non-destructive testing after cooling to room temperature to ensure that there are no defects exceeding the standard in the weld.

[0066] (4) Continue to use the automatic welding device selected in step (2) for cover welding. The welding process parameters of the automatic welding device need to be set as shown in Table 2.

[0067] Table 2 Welding process parameters for cover welding

[0068] (5) Finally, post-weld heat treatment is carried out. The post-weld heat treatment uses a medium-frequency heat treatment heater and the post-weld heat treatment temperature (tempering temperature) is 730-740℃. This can reduce the impact of heat treatment temperature on the base material after long-term service and further avoid the deterioration of the base material.

[0069] like Figures 3 to 6 The figures shown are metallographic images of the heat-affected zone and weld area obtained using the automatic welding repair method of this embodiment, and metallographic images of the heat-affected zone and weld area obtained using the existing manual welding repair method. Specifically:

[0070] from Figure 3 and Figure 4It can be seen that the microstructure of the P92 base material repaired using the automatic welding method is tempered lath martensite with different orientations. The weld is a typical tempered martensite microstructure, showing the original columnar and periclase crystal morphologies, and is composed of martensite lath bundles with different orientations internally. Figure 5 and Figure 6 It can be seen that the manual welding repair method produces a blocky ferrite structure in the weld area, and the grain size in the coarse-grained zone of the heat-affected zone is significantly larger than that of the automatic welding repair method.

[0071] like Figure 7 The figure shows a comparison of the impact toughness of the weld area after using the automatic welding repair method of this embodiment and the manual welding repair method of the prior art. The impact toughness of the upper surface of the weld using the automatic welding repair method can reach 156.3J, which is significantly higher than 77J of the manual welding repair method. The main reason is that the heat input is large when using the manual welding repair method, resulting in a large volume of molten pool, a longer high-temperature residence time of molten pool metal, and a slower cooling rate. After the weld metal cools from the molten state, it obtains a coarse cast structure, which makes its impact toughness significantly lower than that of the automatic welding repair method. Furthermore, compared with the manual welding repair method, the impact toughness of the surface heat-affected zone of the automatic welding repair method can reach 190J, which is significantly higher than that of the surface heat-affected zone of the manual welding repair method.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An automated welding repair method for non-penetrating defects in thick-walled components, characterized in that: Includes the following steps: S1: Pre-welding preparation procedures, including: (1) Perform non-destructive testing on the defective area to determine the location and depth of the defect, and remove the defect according to its location and depth. After the removal is completed, perform non-destructive testing again to confirm that there are no residual defects. (2) The defective area is processed to form a U-shaped bevel; S2: Welding repair process, including: (1) Preheat the U-shaped bevel to the set preheating temperature. (2) Select different automatic welding devices according to the width of the U-shaped groove for welding. During welding, support welding, filling welding and leveling welding are performed in sequence. Multi-layer and multi-pass welding is used. After completing one layer of welding, the weld surface of that layer is inspected and cleaned. After the welding quality is confirmed to be qualified, the next layer is welded until the entire U-shaped groove is welded. When selecting different automatic welding devices, when the width of the U-shaped groove is greater than or equal to 15mm, a round welding torch is selected. When the width of the U-shaped groove is less than 15mm, a flat welding torch is selected. The flat welding torch includes a welding torch body and a welding torch rod. The thickness of the welding torch body is 6-10mm. The welding torch body has a through groove that runs through its two opposite sides, and the through groove has an opening facing one end of the welding torch body. The welding torch rod is disposed in the through groove, and one end of the welding torch rod extends out of the opening of the through groove. The other end of the welding torch rod extends out of the other end of the welding torch body. One end of the welding torch rod is connected to a tungsten electrode. The top of the welding torch body has a gas pipe connector and a water pipe connector. The gas pipe connector is used to connect a gas pipe, and the water pipe connector is used to connect a water pipe. The circular welding torch includes a welding torch body, a welding torch rod, and a cylindrical gas shroud. The welding torch body is disposed outside one end of the cylindrical gas shroud, and the welding torch rod is disposed inside the cylindrical gas shroud. The welding torch rod is connected to the inner wall of the cylindrical gas shroud through a connecting part. The two ends of the welding torch rod pass through the two ends of the cylindrical gas shroud, respectively. One end of the welding torch rod is connected to the welding torch body, and the other end of the welding torch rod is provided with a tungsten electrode. (3) Martensitic transformation treatment is carried out at a temperature of 80~120℃ for 1~2h, followed by hydrogen removal treatment. After the hydrogen removal treatment is completed, the weld is cooled to room temperature before non-destructive testing is performed to ensure that there are no defects exceeding the standard in the weld. (4) Continue to use automatic welding equipment for cover welding. (5) Perform post-weld heat treatment.

2. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 1, characterized in that: In S1(1), a beveling machine is used to remove defects. When removing defects using a beveling machine, the area within 2 to 4 mm around the defect is also removed.

3. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 1, characterized in that: In S2(1), the preheating temperature is set to 150~250℃; in S2(5), the temperature of post-weld heat treatment is 730~740℃.

4. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 1, characterized in that: In S2(2), an automatic welding wire with a diameter of 0.8~1.2mm is used for welding; argon is used as the protective gas during welding; and the interpass temperature is 150~250℃ during welding.

5. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 4, characterized in that: In S2(2), when performing support welding, the gas flow rate of the shielding gas is 65~70L / min, and secondary gas protection is added. When performing fill welding, the gas flow rate of the shielding gas is 50~65L / min. When performing leveling welding, the gas flow rate of the shielding gas is 30~50L / min.

6. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 1, characterized in that: In S2(2), during filler welding, the tungsten electrode of the automatic welding device swings and the welding torch rod of the automatic welding device oscillates.

7. The automatic welding repair method for non-penetrating defects in thick-walled components according to claim 1, characterized in that: In S2(2), when inspecting and cleaning the weld surface, direct visual inspection and / or camera inspection of the automatic welding device are used.

Images