Post-weld residual stress and deformation generally exist at the same time, in the welded structure of mild steel, welding deformation on the welded structure is generally greater than the impact of welding stress.
General welding deformation is divided into two types: overall deformation and local deformation. In the actual structure, these two kinds of deformation exist at the same time. Overall deformation is a change in the size or shape of the entire structure, which usually occurs in the form of longitudinal and transverse shrinkage deformation, bending deformation and warping deformation. In the production of welded structures, not only the overall deformation of the structure occurs, but also the angular deformation and wavy deformation of local areas of the structure.
In addition, welding residual deformation can be divided into in-plane deformation and out-of-plane deformation.
1. Transverse shrinkage of welded joints
Along the length of the welded joint, the transverse shrinkage is uniform. However, this is not the case in actual butt joints, especially butt joints with long weld seams. This is because the actual welded structure often has complex transverse shrinkage, making the transverse shrinkage of the joint uneven. There are two reasons for the non-uniform transverse shrinkage; firstly, the butt joint rotates and deforms as the plate is welded from one end to the other, which depends on the effect of the weld line energy and spot weld position. The second is that the transverse shrinkage of the weld and near-seam region is affected by the degree of constraint, generally the greater the constraint, the smaller the deformation, the greater the residual stress.
2. Longitudinal deformation of welded joints
In the welding process, the weld and the plastic deformation zone generated in the vicinity of the main cause of longitudinal deformation, the existence of butt joints plastic deformation zone will inevitably lead to longitudinal bending deformation of the weldment or longitudinal shortening. Longitudinal deformation of the plate depends on the weld cross-sectional area, weld length and volume of plastic deformation zone, and welding method, weld energy and welding process related to
3. Angular deformation
Angular deformation often occurs in the overlays, open bevelled butt joints, lap joints and T-joint welding. Different forms of joints and welds have different characteristics, angular deformation is mainly due to uneven transverse contraction along the thickness direction.
4. Pressure bending deformation
Welded thin plate components to stay away from the residual compressive stress in the weld region, which will cause pressure-bending deformation of the welded plate, you need to determine whether the wave deformation is caused by pressure-bending stress or caused by bending. The cause of bending deformation is not only different from the bending deformation, but also different shapes and sizes.
