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Forms of welding deformation in tube sheets: Poor sealing of the tube sheets and tube pull-out are adverse effects resulting from welding deformation； The common forms of welding deformation in tube sheet welding are as follows: 1. Angular deformation after welding the tube sheet to the shell ； 2. Arching deformation of the tube sheet surface ； 3. Wave deformation of the tube sheet. The angular deformation after welding the tube sheet to the shell causes arching deformation and waviness deformation of the tube sheet surface. Reasons for tube sheet welding deformation: The uneven distribution of transverse contraction deformation resulting from the welding of the cylinder and the tube sheet in the thickness direction is the main cause of tube sheet welding deformation ； The welds between the tube sheet and the cylinder body generally feature a single-sided V-groove. During welding, the amount of weld metal deposited on the backside and the front side of the weld is not identical, which leads to a distortion of the component’s plane; thus, this is a deformation that exists objectively. Welding angular deformation consists mainly of two types of deformation: the change in angle between the cylinder and the tube sheet, and the angular deformation of the tube sheet itself. The former corresponds to the angular deformation caused by welding two workpieces together, while the latter results from cladding on the tube sheet ； The magnitude of welding deformation mainly depends on the stiffness of the tube sheet, groove angle, weld cross-sectional shape, welding line energy, amount of deposited metal, and welding procedures. The main reasons are as follows: 1. The welding direction is not carried out in accordance with the specifications ； 2. Unreasonable welding parameters lead to localized overheating ； 3. The sequence of assembly and welding was not carried out in accordance with the specifications ； 4. The auxiliary measures are inappropriate. Based on the causes of tube sheet deformation and its influencing factors, and given that double-sided welding cannot be implemented in tube sheet welding, single-sided welding with double-sided formation is adopted. Excessive welding current can lead to burn-through and damage to the heat exchange tubes; therefore, when welding the tube sheet to the shell, it is necessary to use a low heat input, reduce heat generation, and increase the rigidity of the tube sheet in order to minimize deformation. Control of tube sheet welding deformation: 1. Control the number of welding passes for the tube sheet. During the welding process, angular deformation is closely related to the number of welding passes; the more passes there are, the greater the deformation. Therefore, it is necessary to control the number of welding passes during tube sheet welding, aiming to reduce it as much as possible. At the same time, while ensuring the quality of the tube sheet welding, efforts should be made to minimize the height of the weld angles. 2. During the welding of the tube sheet, it is necessary to control the bevel angle. Under normal circumstances, the shape of the welding surface and the groove angle have a significant impact on the variation in the angle of the welded joint. The lateral contraction amounts at the lower and upper parts of the welded joint increase as the groove angle increases; therefore, it is necessary to minimize the groove angle as much as possible, provided that the quality of the weld is not compromised. 3. Perform the operation in the correct installation order. During assembly, first install the baffle plates, spacing tubes, and tie rods on the tube sheet; then insert the heat exchange tubes, fit the tube bundle into the cylinder, align the tube sheet with the cylinder. Next, align the cylinder and tube sheet at the other end, pull the tubes out of the tube sheet, and adjust the protrusion length to meet the specified dimensional standards. 4. Control the process parameters of welding. During the welding of the tube sheet, in order to prevent deformation caused by excessively high local temperatures, it is necessary to use as small welding parameters as possible. 5. During the welding of the cylinder and tube sheet, a segmented welding method should be used to process the welds in different areas. The various welds should be separated from one another, and welding should be carried out using a cross-welding method from both ends toward the center. The welds should be offset by 180 degrees from each other. 6. Welding sequence of the tube sheet and tubes. When welding the tubes and tube sheets, welding should start from the middle of the tube sheet. The number of tubes to be welded should be more than 1/3 of the total number of welds required. Once half of one end of the tube sheet has been welded, welding can proceed on the other end; after welding is complete, the unfinished section can then be welded as well. 7. When welding the remaining pipe ends, start by welding at the circumferential joint of the cylinder and the tube sheet, and proceed outward layer by layer. During welding, use a cross-welding method to work from both ends toward the center, ensuring symmetry throughout the process. 8. Use auxiliary methods during the welding process. During the welding of the tube sheet, common auxiliary methods include: first, using a part with high rigidity for fixation; second, passing a long bolt through the middle of the tube sheet and securing both ends with nuts. 9. When welding hardened metals, in order to reduce the extent of the welding heat field and prevent deformation caused by uneven heating, forced cooling can be employed in the welding process.