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Application of welding anti-deformation in the welding process of stacked beams Zhao Shurong and Zhang Lei of Baoye Construction Engineering Safety Branch Abstract: A theoretical study was conducted on the deflection deformation problem that occurs during the welding process of asymmetric H-shaped laminated beams. Through welding tests and theoretical calculations, the main factors affecting the welding deformation were analyzed, and the empirical formula for the welding deflection deformation of asymmetric H-shaped beams was determined. The use of anti-deformation before welding effectively solves the problem of welding deflection deformation of asymmetric H-shaped stacked beams. The manufacturing process of large stacked beams has been optimized to ensure welding quality. keywords: Welding anti-deformation Asymmetric stacked beam welding deformation is an inevitable problem in the welding process of steel structures. Welding deformation is roughly divided into: Longitudinal and transverse shrinkage deformation, bending (flexion) deformation, angular deformation, wave deformation, etc. Generally, welding deformation can be controlled through anti-deformation before welding, reasonable welding processes, welding specifications, post-weld mechanical correction, flame correction and other methods. The choice of method to control welding deformation should be adapted to local conditions and from time to time. The method of effectively controlling welding deformation can achieve twice the result with half the effort, thus saving manpower and material resources to the greatest extent, ensuring welding quality, and shortening the steel structure production period. In factory structures and frame structures, H-shaped beams, including crane beams, generally use H-shaped steel structures with symmetrical upper and lower cross-sections. The angular deformation of the flange plate against the web during the welding process (which is easy due to the different thickness of the flange plate) can be corrected mechanically or by flame. The longitudinal shrinkage deformation can be controlled by leaving a shrinkage allowance. Since the H-shaped steel section is symmetrical, its bending deformation (i.e., H-shaped steel deflection deformation) is negligible. The deformation of asymmetric H-shaped laminated beams during the welding process is different from that of symmetrical H-shaped steel beams. Effective measures must be taken through theoretical calculations to optimize the manufacturing process of laminated beams. The following analyzes the deflection deformation problems during the welding process of large-scale asymmetric H-shaped stacked beams in Taicang Power Plant. In power plant boiler frame steel structures, the cross-section height of large plate beams ranges from 3m to 6m depending on the design rated load of large plate beams. When the cross-sectional height is greater than 4.5m, in order to facilitate production and transportation, large plate beams are generally designed in the form of upper and lower stacked beams. High-strength bolts are used to connect the upper and lower stacked beams. After the components are manufactured, the upper and lower stacked beams are required to meet the design camber requirements at the same time. The structural form of the stacked beams in this project is shown in Figure 1, and the specifications and dimensions are shown in Table 1. Figure 1 Schematic table of laminated beam structure 1 Stacked beam specifications Dimensions Serial number Component number Section size mm Length mm Weight 1 MB-1 Upper stacked beam H3000 * 1000/420 * 30 * 100/25 29100 58618 2 Lower stacking beam H2000 * 450/1000 * 30 * 25/100 29100 39078 3 MB-2 superimposed beam H3600 * 1200/420 * 36 * 120/25 29100 77736 4 Lower stacking beam H2400 * 450/1000 * 36 * 25/120 29100 51824 5 MB-3 superimposed beam H3600 * 1000/420 * 30 * 100/25 33340 101969 6 Lower stacking beam H3000 * 1000/420 * 30 * 100/25 33340 67979 According to the design requirements, the welding of the stacked beams has been completed, and the camber is controlled at 12mm±2mm. Based on past experience in making welded crane beams, pre-cambering of 14mm is generally used when cutting web plates. After welding is completed, the camber can be guaranteed to be controlled within the design requirements. According to this, the MB-1 superimposed beam was pre-cambered by 14mm during blanking, and after welding, the camber reached 25mm, which was much greater than the design requirement. Afterwards, flame correction was performed on the upper flange plate side, which took a total of 14 manpower and about 50m3 of gas to barely reach the camber value required by the design. In response to the above problems, technicians conducted careful analysis and research and found that it is precisely due to the asymmetry of the upper and lower sections of the H-shaped steel beam that the thin plate side and the thick plate have different longitudinal contractions during the welding process, resulting in large deflection deformation, and the post-weld flame correction is not suitable for 100mm * The longitudinal shrinkage effect of the 1000mm upper flange plate is too small, making it difficult to correct the flame. Drawing on the bending deformation estimation formula of T-shaped beams, the bending deformation formula of asymmetric H-shaped steel beams is calculated according to the following formula (A): (A) In the formula: f - Deflection caused by bending of asymmetric H-beam (mm), upward is positive, downward is negative fx - Deflection caused by longitudinal contraction of lower flange plate (mm) fs - Deflection caused by longitudinal contraction of upper flange plate (mm) FH - Cross-sectional area of weld (mm2) e - Distance from the centerline of plastic deformation zone Fs of weld to the neutral axis of member (T-shaped beam) section (mm) L - Length of member (mm) I - cross-sectional moment of inertia of the component (mm4) k1 - varies according to different welding methods, manual arc welding k1 = 0.052, CO2 welding k1 = 0.043, submerged arc welding k1 = 0.074 k2 - longitudinal shrinkage coefficient of the weld during multi-layer welding, k2 = 1 + 85σs /E·n According to formula (A), the deflection calculation of asymmetric H-type stacked beams is detailed in "F1" in Table 2. Among them, the calculated deflection of the MB-1 superimposed beam is 5.3mm, which is quite different from the actual deformation of 11mm. After in-depth research, it is not difficult to find: Formula (A) is the deflection calculation formula under ideal conditions. Due to the different thicknesses of the upper and lower flange plates of asymmetric stacked beams, the angular deformation on the thin plate side is large, and flame correction is required after welding. The thicker the steel plate, the smaller the angular deformation, and flame correction on the thin plate side causes greater deflection deformation. Therefore, equation (A) needs to be modified, see equation (B): f=k3•fx-k4•fs (B) where: k3, k4 - The correction coefficient of flame correction for deflection is based on the specifications of the stacked beams of Taicang Power Plant. The correction coefficient is 1.5 for the thinner flange plate side and 1.0 for the thicker plate side. According to formula (B), the deflection calculation of asymmetric H-type stacked beams is detailed in "F2" in Table 2. The calculated deflection of the MB-1 superimposed beam is 9.4mm, which is close to the actual deformation of 11mm. Table 2 List of deflection calculations for asymmetric H-shaped stacked beams Member number name b1 b2 t1 t2 h tm Neutral axis moment of inertia Fh L K1 K2 Deflection f (positive upward) MB-1 stacked beam f1 1000 420 100 25 3000 30 2141.2 21221778 50 29100 0.074 1.402 F1= 5.3 Upper stacked beam f2 2141.2 21221778 50 29100 0.074 1.402 F2= 9.4 Lower stacked beam f1 450 1000 25 100 2000 30 511.8 7793363 50 29100 0.074 1.402 F1= -11.1 Lower beam f2 511.8 7793363 50 29100 0.074 1.402 F2= -18.8 MB-2 Upper beam f1 1200 420 100 25 3600 36 2529.8 39107483 55 29100 0.074 1.402 F1= 3.6 Upper stacking beam f2 2519.8 39107483 55 29100 0.074 1.402 F2= 6.4 Lower stacking beam f1 450 1200 25 100 2400 36 629.7 14076697 55 29100 0.074 1.402 F1= -7.8 Lower stack beam f2 629.7 14076697 55 29100 0.074 1.402 F2= -13.4 MB-3 Upper stack beam f1 1400 420 120 25 3600 36 2683.7 42989016 55 33340 0.074 1.402 F1= 5.2 Upper stacking beam f2 2683.7 42989016 55 33340 0.074 1.402 F2= 8.8 Lower stacking beam f1 450 1400 25 120 2400 36 530.7 15232137 55 33340 0.074 1.402 F1= -11.2 Lower stack beam f2 530.7 15232137 55 33340 0.074 1.402 F2= -18.4 According to the deflection calculation values in Table 2, the web underwent corresponding welding anti-deformation during blanking. After the welding correction was completed, the deflection values met the design requirements. There was no need for futile flame correction, which saved a lot of manpower and material resources. The processing cycle of each stacked beam was shortened by 5 to 7 days. The manufacturing process of large stacked beams was greatly optimized and very satisfactory results were achieved. The reverse deformation values of each stacked beam are detailed in Table 3. Table 3 Member number name Calculated deflection f (upward is positive) Theoretical reverse deformation value (pre-camber value when web blanking) Post-weld deflection remarks MB-1 Upper stack beam F2= 9.4 12-9.4≈2mm 12mm There is no camber during blanking, and the lower stack beam can be corrected after welding F2= -18.8 12-(-18.8)≈31mm 12mm MB-2 Upper stacked beam F2= 6.4 12-6.4≈6mm 12mm Lower stacked beam F2= -13.4 12-(-13.3)≈25mm 12mm MB-3 Upper stacked beam F2= 8.8 12-8.8≈3mm 12mm There is no need for arching when cutting, and it can be corrected after welding. Lower stacked beam F2= -18.4 12-(-18.4)≈30mm 12mm Conclusion 1 Practice shows that it is feasible to calculate the bending deformation of asymmetric H-shaped stacked beams according to formula (B). This laid a solid theoretical foundation for our company's subsequent smooth processing of large plate beams in power plants. 2. Various factors affecting welding deformation should be carefully analyzed based on actual conditions, and the calculation formula for welding deformation should be flexibly used. 3 Scientific and reasonable welding anti-deformation has the effect of getting twice the result with half the effort in optimizing the welding manufacturing process of steel structures. Welding technicians should use it reasonably according to different steel structures. References Tian Xitang et al. Harbin Institute of Technology. Estimation of welding bending deformation. Welded Structure, 1981.8 About the author: Zhao Shurong, male, born in 1974, engineer. Collected in "Modern Welding"