In the process of head welding, cracks are the most important welding defect in welded joints. Its harmfulness is also one of the reasons for the catastrophic accidents caused by the sudden damage of multiple welded structures and vessels. Therefore, by selecting appropriate welding materials, formulating reasonable welding processes, selecting parameters, and conducting welding process assessment. It can prevent the occurrence of defects such as weld cracks, and control the quality of tailor-welded heads. Pre-heating, layer temperature control, post-heat hydrogen depletion treatment and heat treatment during welding are important measures to prevent welding cracks.

　　(1) Pre-heating and layer temperature control before welding. The heating range before and during welding is small, which is likely to cause insufficient and uneven preheating temperature;

　　Poor preheating temperature control or effective monitoring of the preheating temperature during welding can easily cause cracks. The cooling rate of the weldment after welding, the temperature difference between the welding area and the weldment, the welding strain rate, and the restraint of the welding structure are all related to the preheating before welding.

　　(2) Post-heat hydrogen elimination treatment. The post-weld and thermal dehydrogenation treatment is beneficial to prevent the occurrence of cold cracks, accelerate the escape of diffusible hydrogen in the weld metal and the deposited metal in the heat affected zone, and effectively reduce the residual stress to a certain extent.

　　Heat treatment after welding. After the plate is stamped and formed, the quality of the formed head and the weld performance are better guaranteed. The appropriate heat treatment process parameters are used to improve the mechanical indexes of the welded joints, which improves the strength and eliminates welding stress At the same time, to achieve a better match of strength, hardness and impact toughness, to obtain better comprehensive performance, so as to avoid the occurrence of cracks.