In batch welding processing, the welding sequence has a crucial influence on the deformation of weldments. A reasonable welding sequence can effectively control deformation and ensure the quality and dimensional accuracy of weldments.
First, the uneven distribution of heat during welding is the main cause of weldment deformation. When the welding heat source acts on the weldment, the weld and its surrounding area expand due to heat, and the surrounding cooler metal will constrain it. After cooling, residual stress will be generated and deformation will occur. Different welding sequences will change the heat distribution. For example, if sequential welding is adopted, welding from one end of the weldment to the other end in sequence, the heat will gradually accumulate, so that the first welded part will be more affected by heat during the subsequent welding process, and the deformation will increase easily. On the contrary, the symmetrical welding sequence, that is, welding at the symmetrical position of the weldment at the same time or alternately, can make the heat distribution relatively uniform and reduce the deformation caused by thermal asymmetry. For example, when welding a rectangular frame, first weld the corresponding position welds of two opposite sides at the same time, and then weld the other two sides, which can effectively reduce the overall deformation.
Secondly, the welding sequence will also affect the shrinkage direction and size of the weld. A reasonable welding sequence can guide the weld shrinkage to offset each other or reduce the impact on the overall structure. For example, for weldments with multiple welds crossing, the welding sequence that spreads from the middle to the surroundings can make the weld shrinkage force relatively balanced in all directions. When the middle weld is welded first and contracts during cooling, it will produce a pre-stretching effect on the surrounding unwelded parts. When the surrounding welds are subsequently welded and contracted, the previous tensile deformation can be partially offset, thereby reducing the final deformation.
Furthermore, it is also critical to optimize the welding sequence by considering the structural characteristics and rigidity of the weldment. For parts with greater rigidity, welding can be performed first, because they have a strong ability to resist deformation and can provide a stable foundation for subsequent welding. For parts with less rigidity and easy deformation, welding should be arranged at an appropriate time, combined with appropriate welding process parameters and auxiliary support measures. For example, when welding thin plate splices, first weld the edge positioning welds and some welds at the reinforcing rib position, enhance the overall rigidity, and then weld the large-area splicing welds, which can effectively control the warping deformation of the thin plate.
Finally, in batch welding processing, simulation analysis of different welding sequences through simulation software is an important means to optimize the welding sequence. Finite element analysis and other technologies can be used to predict the deformation of weldments under different welding sequences before actual welding, and the best welding sequence can be selected based on the simulation results. At the same time, in the actual production process, it is necessary to continuously adjust and improve the welding sequence based on experience to adapt to the materials, shapes, sizes and various actual conditions of batch production of different weldments, to ensure that the deformation of weldments is controlled within the allowable range while welding efficiently in batches, and to improve product quality and production efficiency.
