Measures to Control Welding Deformation of Steel Structure

In the construction of steel structure, welding deformation directly affects the installation and use function of steel members and steel structure, and indirectly affects the service performance of steel structure engineering due to the additional bending moment and secondary stress when bearing, so the control of welding deformation is very important.

Reduce the cross-sectional area of the weld: on the premise of getting a good weld without over standard defects, smaller groove size (angle and gap) should be adopted as far as possible. For the steel with yield strength below 345mpa and less hardenability, smaller heat input should be adopted. Preheating should be avoided or appropriately reduced as far as possible, and the welding method with smaller heat input should be preferred.

For example, for CO2 gas shielded welding and thick plate welding, multi-layer welding should be used instead of single-layer welding as far as possible. If the design requirements are met, the interrupted welding method can be used for the welding of longitudinal reinforcing plate and transverse stiffener. When both sides can be welded, the double-sided symmetrical groove should be used. When multi-layer welding, the welding sequence symmetrical to the neutral axis of the component should be used.

When the thickness of T-joint plate is large, the angle butt weld with open slope is adopted, the anti deformation method before welding is used to control the angle deformation after welding, the rigid fixture fixation method is used to control the deformation after welding, the component reserved length method is used to compensate the longitudinal shrinkage deformation of weld, for example, the longitudinal weld of H-beam can be reserved 0.5-0.7mm, the length of each pair of transverse reinforcement can be reserved 0.5mm, and the reserved perimeter method is used to compensate the welding deformation of cylindrical pipe components If the plate thickness is greater than 10 mm, 2.0 mm girth shall be reserved for each longitudinal and circumferential weld.

For the distortion of long members, it is mainly to increase the flatness of the plate and the assembly accuracy of the members, so as to make the groove angle and clearance accurate, and the arc direction or alignment accurate, so as to make the angular deformation of the weld and the longitudinal deformation value of the wing plate and web consistent along the length direction of the members. In the design, the number and size of the weld should be reduced as far as possible, and the weld should be arranged reasonably. In addition to avoiding dense weld, the weld should also be optimized The position of the welding seam should be close to the neutral axis of the component as far as possible, and the arrangement of the welding seam should be symmetrical with the neutral axis of the component. When the component with many welding seams is assembled and welded or the steel structure engineering is installed, the reasonable welding sequence should be adopted.

Control and correction of welding deformation

The number of welds should be reduced as much as possible. In the design of weld structure, redundant welds should be avoided. The section steel and stamping parts should be used to replace the welding parts as much as possible, so as to reduce the number of rib plates and the workload of welding and deformation correction. The shape and size of welds should be reasonably selected. For butt joints with large thickness, x-groove should be selected instead of V-groove, and the total amount of deposited metal should be reduced to reduce welding For T-joints without strength calculation, the technically reasonable minimum weld leg size should be selected, and intermittent weld can reduce deformation more than continuous weld.

When the fillet weld of T-joint is determined according to the design calculation, the continuous weld should be used instead of the intermittent weld with the same strength, and the double-sided continuous weld should be used instead of the single-sided continuous weld with the same strength, so as to reduce the size of the fillet weld. For the T-joint or cross joint with larger stress, under the condition of ensuring the same strength, the open fillet weld should be used, which can be larger than the general fillet weld It can greatly reduce weld metal and weld deformation.

Reasonable design of structural form and weld position, in the design of structure, should consider the minimum welding workload and the minimum welding deformation during the assembly of components, for thin plate structure, should choose the appropriate plate thickness, reduce the skeleton spacing and welding angle size, in order to increase the stability of the structure, reduce wave deformation, in addition, should avoid the design of curved structure as far as possible, because flat structure is used The surface can make the welding equipment in the fixed state relatively simple and easy to control the welding deformation.

As the transverse shrinkage of the weld is usually more significant than the longitudinal shrinkage, the weld should be arranged parallel to the direction of minimum welding deformation as far as possible, and the position of the weld should be as close to the central axis of the section as possible, and as symmetrical as possible with the central axis, so as to reduce the bending deformation of the structure.