In the first stage, the softening a

In the first stage, the softening annealing process was used to improve the plasticity and to prevent fracture failure of the component. After annealing process, no microcracks were found. Subsequently, the upper plate was adhered to the down plate by the spot welding process. During the spot welding, the high temperature would affect the microstructure, mechanical properties and stress status near the solder joint on the surface of the component. After the spot welding, the hardness was increased, but the plasticity was decreased. Therefore, in the second stage, the component had to be annealed before the component was bent to form a hook structure.