Welding process and welding robot for heat exchanger tubes and tube sheets

Abstract

This invention relates to the field of welding technology, and discloses a welding process and robot for welding heat exchanger tubes and tube sheets. The welding process is as follows: First, multiple mounting holes are machined on the tube sheet, ensuring that the size of the mounting holes is sufficient for the heat exchanger tubes to pass through; then, the heat exchanger tubes are passed through the mounting holes, allowing the ends of the heat exchanger tubes to protrude from the mounting holes, leaving sufficient welding area at the ends of the heat exchanger tubes for subsequent argon arc welding; finally, the welding robot performs argon arc welding on the welding area between the heat exchanger tubes and the tube sheet, enabling a tight connection between the heat exchanger tubes and the tube sheet. Furthermore, during the welding process, three layers of weld beads are formed, with each subsequent weld bead superimposed on the previous one, improving the stability of the connection between the heat exchanger tubes and the tube sheet and solving the technical problems of poor welding effect and long production cycle in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a welding process method and welding robot for heat exchange tubes and tube sheets. Background Technology

[0002] Heat exchanger tubes and tube sheets are key components in the heat transfer process of heat exchanger equipment. The heat exchanger tubes pass through the tube sheet, and their ends are welded to the surface of the tube sheet to form a sealing surface. A heat exchanger typically contains many heat exchanger tubes, and both ends of each tube need to be welded to the left and right ends of the tube sheet. Welding between heat exchanger tubes and tube sheets is usually done manually or mechanically. Manual welding is labor-intensive, and both methods suffer from large workloads and low production efficiency. Furthermore, defects such as undercut and porosity frequently occur during welding, easily leading to rework. Summary of the Invention

[0003] The purpose of this invention is to provide a welding process and welding robot for heat exchange tubes and tube sheets, thereby solving the technical problem of poor welding effect between heat exchange tubes and tube sheets in the prior art.

[0004] To achieve the above objectives, the present invention provides a welding process for heat exchange tubes and tube sheets, the welding process comprising: Multiple mounting holes are machined on the tube sheet; Pass the heat exchange tube through the mounting hole and extend it out of the mounting hole; The heat exchange tubes and tube sheets are argon arc welded using a welding robot, forming a three-layer weld bead.

[0005] In an embodiment of the present invention, the step of performing argon arc welding on the heat exchange tubes and tube sheet using a welding robot further includes: Obtain and store the optimal welding process parameters for the welding robot; Control the welding robot to perform welding work according to the optimal welding process parameters.

[0006] In an embodiment of the present invention, the step of performing argon arc welding on the heat exchange tubes and tube sheet using a welding robot further includes: Clean the welding areas of the heat exchange tubes and tube sheets until the appearance of the welding areas meets the preset requirements.

[0007] In an embodiment of the present invention, the step of obtaining and storing the optimal welding process parameters of the welding robot includes: After welding is completed, the weld bead is cut. The weld beads after cutting are subjected to performance testing; When the performance parameters of the weld bead meet the preset parameters, the process parameters of the current welding robot are stored as the optimal welding process parameters.

[0008] In an embodiment of the present invention, a welding surface is formed on the weld bead, the welding surface extends circumferentially along the outer peripheral wall of the heat exchange tube, and the inclination angle between the welding surface and the tube sheet and the outer peripheral wall of the heat exchange tube is 45°.

[0009] In an embodiment of the present invention, the thickness range between the end face of the tube sheet perpendicular to the heat exchange tube and the welding surface is greater than or equal to 2.5 mm.

[0010] In an embodiment of the present invention, the width of the weld bead along the axial direction of the heat exchange tube is greater than or equal to 2.5 mm.

[0011] In an embodiment of the present invention, the welding robot has a welding speed of 1.3 mm / s and a wire feeding speed of 350 mm / min.

[0012] In an embodiment of the present invention, the welding voltage of the welding robot is 9~16V, the current polarity of the welding robot is DC positive, the pulse base current is 80~85A, and the pulse peak current is 210~220A.

[0013] In an embodiment of the present invention, a welding robot is proposed, which uses the welding process method described above to weld heat exchange tubes and tube sheets.

[0014] Through the above technical solutions, the welding process and welding robot for heat exchange tubes and tube sheets provided by the embodiments of the present invention have the following beneficial effects: The welding process in this embodiment is as follows: First, multiple mounting holes are machined on the tube sheet, ensuring that the size of the mounting holes is sufficient for the heat exchange tubes to pass through. Then, the heat exchange tubes are passed through the mounting holes, allowing the ends of the tubes to protrude from the holes. Sufficient welding area needs to be left at the ends of the heat exchange tubes for subsequent argon arc welding. Finally, a welding robot performs argon arc welding on the welding area between the heat exchange tubes and the tube sheet, ensuring a secure connection between the heat exchange tubes and the tube sheet. Furthermore, during the welding process, three layers of weld beads are formed, with each subsequent layer superimposed on the previous layer. This improves the stability of the connection between the heat exchange tubes and the tube sheet, solving the technical problems of poor welding effect and long production cycle in the prior art.

[0015] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. Those skilled in the art can obtain other drawings based on the structures shown in these drawings without any inventive effort. In the drawings: Figure 1 A flowchart of the welding process method according to the present invention; Figure 2 This is a cross-sectional view taken from a perspective after the heat exchange tubes and tube sheet have been welded together according to the present invention. Figure 3 This is a cross-sectional view from another perspective after the heat exchange tubes and tube sheet have been welded together according to the present invention; Figure 4 This is a cross-sectional view from another perspective after the heat exchange tubes and tube sheet have been welded together according to the present invention. Figure 5 This is a data table for metallographic testing according to the present invention; Figure 6 This is a data table for hardness measurement according to the present invention.

[0017] Explanation of reference numerals in the attached figures Detailed Implementation

[0018] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] The welding process and welding robot for heat exchange tubes and tube sheets according to the present invention are described below with reference to the accompanying drawings.

[0020] like Figure 1 As shown, in this embodiment, a welding process method for heat exchange tube 1 and tube sheet 2 is proposed. The welding process method includes: S10: Multiple mounting holes are machined on tube sheet 2; S20: Pass the heat exchange tube 1 through the mounting hole and extend it out of the mounting hole; S30: The heat exchange tube 1 and tube sheet 2 are argon arc welded by a welding robot to form a three-layer weld bead.

[0021] In summary, the welding process method in this embodiment is as follows: First, multiple mounting holes are machined on the tube sheet 2, ensuring that the size of the mounting holes is sufficient for the heat exchange tube 1 to pass through. Then, the heat exchange tube 1 is passed through the mounting holes, allowing its end to protrude from the holes. Sufficient welding area is required at the end of the heat exchange tube 1 for subsequent argon arc welding. Finally, an argon arc welding process is performed on the welding area between the heat exchange tube 1 and the tube sheet 2 using a welding robot, ensuring a secure connection between the heat exchange tube 1 and the tube sheet 2. Furthermore, during the welding process, three layers of weld beads are formed, with each subsequent layer superimposed on the previous one. This improves the stability of the connection between the heat exchange tube 1 and the tube sheet 2, solving technical problems such as poor welding effect and long production cycle in existing technologies. In this embodiment, the heat exchange tube 1 protrudes 5mm from the mounting hole to reserve sufficient welding area and ensure a good connection between the heat exchange tube 1 and the tube sheet 2.

[0022] During argon arc welding, a shielding gas needs to be blown into the welding area to ensure a good welding effect between the heat exchanger tube 1 and the tube sheet 2. In this embodiment, argon gas can be used as the shielding gas, and the purity of the argon gas needs to be ensured to be greater than 99.99%, with an output flow rate of 12~16 L / min. It should be noted that in this embodiment, the tube sheet 2, which is the object of welding, is made of carbon steel, and the heat exchanger tube 1 can be made of national standard 20 steel pipe. The dimensions of the tube sheet 2 and the heat exchanger tube 1 can be adjusted according to actual needs. The welding process method of this embodiment is mainly for welding between the tube sheet 2 and the heat exchanger tube 1 with a thickness of more than 2.5 mm. It has a good welding effect on the heat exchanger tube 1 and the tube sheet 2 of the above materials, and can effectively avoid defects such as undercut and porosity during the welding process, ensuring the welding quality of the heat exchanger tube 1 and the tube sheet 2. Specifically, in this embodiment, the welding robot adopts the existing technology such as the KUKA-C4 model robot tube sheet welding system, which includes a robot system and a welding system. The robot system consists of the robot body, robot control cabinet and teach pendant; the welding system includes welding power supply, cable and welding torch.

[0023] In this embodiment, the step of performing argon arc welding on the heat exchange tube 1 and tube sheet 2 using a welding robot further includes: Obtain and store the optimal welding process parameters for the welding robot; Control the welding robot to perform welding work according to the optimal welding process parameters.

[0024] The welding robot can be pre-set with an optimal range of welding process parameters. These parameters can then be manually adjusted based on the welding results of heat exchanger tube 1 and tube sheet 2 before subsequent welding operations. This allows the welding robot to perform welding based on the acquired optimal parameters, ensuring a good welding effect between heat exchanger tube 1 and tube sheet 2.

[0025] In this embodiment, the step of performing argon arc welding on the heat exchange tube 1 and tube sheet 2 using a welding robot further includes: Clean the welding area of ​​heat exchange tube 1 and tube sheet 2 until the appearance of the welding area meets the preset requirements.

[0026] Specifically, the preset requirements in this embodiment mainly include that the welding area is free of oxide scale, oil stains, and impurities. Among them, the welding area should have a uniform metallic color without oxidation; the surface should be dry, smooth, and free of particles and stickiness; and no stains should remain after wiping with a white cloth. This confirms that the welding area is free of oxide scale, oil stains, and impurities.

[0027] The preset requirements can be adjusted according to actual needs. This embodiment ensures that the welding area between the heat exchanger tube 1 and tube sheet 2 is free of oxide scale, oil, and impurities before welding by cleaning the welding area before welding. This prevents oxide scale, oil, and impurities from affecting the welding effect between the heat exchanger tube 1 and tube sheet 2, ensuring the stability of the welding. Furthermore, mechanical expansion is performed after the heat exchanger tube 1 and tube sheet 2 are welded, mainly on the inner side of the tube sheet 3 where the heat exchanger tube 1 is located. When the heat exchanger tube 1 is inserted into the tube sheet 2, there is a certain gap between the inner side of the heat exchanger tube 1 and the wall of the mounting hole. Mechanical expansion allows the heat exchanger tube 1 to undergo plastic deformation at this location, making it tightly fit against the wall of the mounting hole, forming a more stable structure. The tight connection between the heat exchanger tube 1 and tube sheet 2 ensures better heat transfer between them, improving the heat exchange efficiency of the heat exchanger tube 1.

[0028] In this embodiment, the step of obtaining and storing the optimal welding process parameters of the welding robot includes: After welding is completed, the weld bead is cut. The weld beads after cutting are subjected to performance testing; When the performance parameters of the weld bead meet the preset parameters, the current welding robot's process parameters are stored as the optimal welding process parameters. If the performance parameters of the weld bead do not meet the preset parameters, the parameters are not stored. Specifically, the process parameters include the welding robot's pulse base current, pulse peak current, welding voltage, welding speed, wire feed speed, and shielding gas output flow rate.

[0029] Taking the argon arc welding performed after the welding robot inputs the optimal welding process parameters in this embodiment as an example, the optimal welding process parameters in this embodiment are as follows: In this embodiment, the welding material used by the welding robot is ER50-6 welding wire with a specification of 0.1mm; the welding robot current polarity is DC positive, the pulse base current is 80~85A, the pulse peak current is 210~220A, and the welding voltage is 9~16V; the welding speed of the welding robot is 1.3mm / s, the wire feeding speed of the welding robot is 350mm / min, the shielding gas used in the welding process is argon, and the purity of argon is ensured to be greater than 99.99%, and the output flow rate of the shielding gas is 12~16L / min.

[0030] Specifically, the performance testing in this embodiment includes the following testing content: 1. Visual inspection: The weld joints of heat exchange tube 1 and tube sheet 2 are visually inspected in accordance with NB / T 47014-2023 Standard for Qualification of Welding Procedures for Pressure Equipment.

[0031] Results: The welds 3 at the more than 2,000 heat exchange tubes 1 welded to the tube sheet 2 were all well formed, without defects such as cracks or pores, and the heat exchange tubes 1 showed no obvious deformation. This indicates that the above-mentioned optimal welding process parameters can effectively ensure a good welding effect between the heat exchange tubes 1 and the tube sheet 2.

[0032] 2. Non-destructive testing: Welds shall be inspected at 3100% PT-I level in accordance with the requirements of NB / T 47013.3-2015 standard for non-destructive testing of pressure equipment.

[0033] Results: No defects such as cracks, incomplete fusion, or excessive porosity were found in any of the more than 2,000 heat exchange tubes 1 welded to tube sheet 2. This indicates that the above-mentioned optimal welding process parameters can effectively ensure a good welding effect between heat exchange tubes 1 and tube sheet 2.

[0034] 3. Metallographic Examination: Evaluation is conducted according to NB / T 47014-2023, the standard for weld procedure qualification of pressure equipment. Specifically, the heat exchanger tube 1 is cut four times radially, each cut yielding two cross-sectional views of the weld bead, thus providing data from two weld observation surfaces. For example... Figure 3 As shown, eight welding observation surfaces can be obtained by cutting four times. The thickness H of each weld 3 outside the tube sheet 2 is measured in sequence to see if it meets the requirement of H≥2mm, the thickness H1 of the weld 3 along the axial direction of the heat exchange tube 1 meets the requirement of H1≥5mm, and the height a of the weld 3 exposed outside the tube sheet 2 after welding and the width b of the weld 3 exposed outside the tube sheet 2 are measured to determine if |ab|≤3mm.

[0035] like Figure 5As shown, when more than 2,000 heat exchange tubes 1 are welded to the tube sheet 2, the thickness values ​​of the weld 3 on the metallographic inspection surface all meet the requirements. The root of the weld 3 on all inspection surfaces has been fully penetrated. There are no cracks or fusion defects in the weld 3 metal and heat-affected zone. This indicates that the above-mentioned optimal welding process parameters can effectively ensure a good welding effect between the heat exchange tube 1 and the tube sheet 2.

[0036] 4. Hardness testing: The hardness shall be assessed according to NB / T 47014-2023, the standard for qualification of welding procedures for pressure equipment. For example... Figure 4 The diagram shows heat exchange tube 1, the heat-affected zone of heat exchange tube 1, weld 3, the heat-affected zone of tube sheet 2, and the base material area of ​​tube sheet 2.

[0037] like Figure 6 As shown, in this embodiment, only three sets of data were collected during the hardness test, namely... Figure 6 The average of the measured values ​​1, 2, and 3 is the sum of the measured values ​​1, 2, and 3. It should be noted that the hardness of the metal at weld 3 generally does not exceed 120% of the hardness of tube sheet 2. Similarly, the hardness of the heat-affected zone near tube sheet 2 should also not exceed 120% of the hardness of tube sheet 2. The hardness of the heat-affected zone near heat exchanger tube 1 should also not exceed 120% of the hardness of heat exchanger tube 1, which is generally 100-120 HB.

[0038] It can be seen that when more than 2,000 heat exchange tubes 1 are welded to tube sheet 2, the hardness values ​​in all test areas meet the requirements. Therefore, it can be concluded that the above-mentioned optimal welding process parameters can effectively ensure a good welding effect between heat exchange tubes 1 and tube sheet 2.

[0039] In summary, the welding robot using optimal welding process parameters in this embodiment can ensure a stable connection between heat exchange tube 1 and tube sheet 2 under the implemented welding process. Furthermore, during the argon arc welding process, the welding robot lays three layers of weld beads in the welding area between heat exchange tube 1 and tube sheet 2. Each of the three layers is filled with welding wire, eliminating a non-self-fusion welding step compared to existing technologies. This effectively shortens the construction period and improves the efficiency of the welding robot's argon arc welding.

[0040] like Figure 2 As shown, in this embodiment, a welding surface is also formed on the weld bead. The welding surface extends circumferentially along the outer peripheral wall of the heat exchange tube 1 and is inclined between the heat exchange tube 1 and the tube sheet 2. The inclination angle between the welding surface and the tube sheet 2 and the outer peripheral wall of the heat exchange tube 1 is 45°, which ensures that the heat exchange tube 1 and the tube sheet 2 can be tightly welded, and improves the stability of the welding between the heat exchange tube 1 and the tube sheet 2.

[0041] like Figure 3As shown, in this embodiment, the thickness between the end face of the tube sheet 2 perpendicular to the heat exchange tube 1 and the welding surface needs to be greater than or equal to 2.5 mm. A thickness greater than or equal to 2.5 mm indicates a good welding effect, effectively ensuring a tight weld between the heat exchange tube 1 and the tube sheet 2. The thickness between the end face of the tube sheet 2 perpendicular to the heat exchange tube 1 and the welding surface is... Figure 3 The thickness at point H in the diagram.

[0042] like Figure 2 As shown, in this embodiment, the width of the weld bead along the axial direction of the heat exchange tube 1 needs to be greater than or equal to 2.5 mm to ensure a tight weld between the heat exchange tube 1 and the tube sheet 2, preventing the heat exchange tube 1 from detaching due to weak welding. The width of the weld bead along the axial direction of the heat exchange tube 1 is... Figure 2 The width at point K is shown in the diagram.

[0043] In this embodiment, the welding robot's welding speed is 1.3 mm / s, and the wire feeding speed is 350 mm / min. During the process of laying three layers of weld beads along the circumference of the heat exchange tube 1, the welding robot needs to fill each layer with welding wire for argon arc welding. In existing technologies, before laying the three layers of weld beads filled with welding wire, the first layer typically uses a self-fusion method, that is, melting the heat exchange tube 1 and the tube sheet 2, and then filling the second layer with welding wire for welding. This method also involves welding three layers of heat exchange tube 1 and the tube sheet 2, one weld per layer, but the first layer of weld beads does not require self-fusion. The phrase "the first layer does not require self-fusion" means that the heat exchange tube 1 and the tube sheet 2 are not melted during the first layer welding process. Instead, the welding wire is first melted and piled up at the connection between the heat exchange tube 1 and the tube sheet 2, ensuring that the welding wire is "laid" on the surface of the heat exchange tube 1. The first layer of non-self-fusion weld acts as a "root" weld, and it avoids the influence of impurities introduced by excessive melting of the heat exchange tube 1 during the welding process on the weld quality, thus ensuring the dimensional accuracy and appearance quality of the entire weld. Therefore, this embodiment eliminates a non-self-fusion welding step compared to existing technologies, effectively shortening the welding period and improving welding efficiency.

[0044] In this embodiment, the welding voltage of the welding robot during the argon arc welding process is 9~16V, the current polarity of the welding robot is DC positive, the pulse base current is 80~85A, and the pulse peak current is 210~220A, to ensure that the heat exchange tube 1 and the tube sheet 2 can be tightly welded.

[0045] In this embodiment, a welding robot is also proposed, which uses the welding process method described above to weld the heat exchange tube 1 and the tube sheet 2. After obtaining the optimal welding process parameters, the argon arc welding operation of the heat exchange tube 1 and the tube sheet 2 can be carried out stably and accurately, thereby improving the welding efficiency.

[0046] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A welding process for heat exchanger tubes and tube sheets, characterized in that, The welding process includes: S10: Multiple mounting holes are machined on the tube sheet (2); S20: Pass the heat exchange tube (1) through the mounting hole and extend it out of the mounting hole; S30: The heat exchange tube (1) and the tube sheet (2) are argon arc welded by a welding robot to form a three-layer weld bead.

2. The heat exchange tube-to-tubesheet welding process of claim 1, wherein, The procedure prior to the step of performing argon arc welding on the heat exchange tube (1) and the tube sheet (2) using a welding robot further includes: Obtain and store the optimal welding process parameters for the welding robot; The welding robot is controlled to perform welding work according to the optimal welding process parameters.

3. The heat exchange tube-to-tubesheet welding process of claim 1, wherein, The procedure prior to the step of performing argon arc welding on the heat exchange tube (1) and the tube sheet (2) using a welding robot further includes: The welding areas of the heat exchange tube (1) and the tube sheet (2) are cleaned until the appearance of the welding areas meets the preset requirements.

4. The heat exchange tube-to-tubesheet welding process of claim 2, wherein, The step of obtaining and storing the optimal welding process parameters of the welding robot includes: After welding is completed, the weld bead is cut. The weld beads after cutting are subjected to performance testing; When the performance parameters of the weld bead meet the preset parameters, the process parameters of the current welding robot are stored as the optimal welding process parameters.

5. The heat exchange tube-to-tubesheet welding process of any one of claims 1 to 4, wherein, A welding surface is formed on the weld bead, and the welding surface extends circumferentially along the outer peripheral wall of the heat exchange tube (1). The inclination angle between the welding surface and the outer peripheral wall of the tube sheet (2) and the heat exchange tube (1) is 45°.

6. The heat exchange tube-to-tubesheet welding process of claim 5, wherein, The thickness of the tube sheet (2) between the end face perpendicular to the heat exchange tube (1) and the welding surface is greater than or equal to 2.5 mm.

7. The heat exchange tube-to-tubesheet welding process of any one of claims 1 to 4, wherein, The width of the weld bead along the axial direction of the heat exchange tube (1) is greater than or equal to 2.5 mm.

8. The heat exchange tube-to-tubesheet welding process of any one of claims 1 to 4, wherein, The welding robot has a welding speed of 1.3 mm / s and a wire feeding speed of 350 mm / min.

9. The heat exchange tube-to-tubesheet welding process of any one of claims 1 to 4, wherein, The welding robot has a welding voltage of 9~16V, a current polarity of DC positive, a pulse base current of 80~85A, and a pulse peak current of 210~220A.

10. A welding robot, characterized in that, The heat exchange tube (1) and the tube sheet (2) are welded using the welding process method according to any one of claims 1 to 9.

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