Weldability of pre-coated steel sheets

The controlling factors in spot weldability are the melting point and the hardness of the plated film. It was also learned that damage to the electrode tip depends on the kind of plated film. As for are weldability, the vaporizing point of plated film is an important factor. The zinc vaporization incited the plated film causes the formation of blowholes in the zinc plated steel sheet. In addition, unstable vibrations in the molten pool due to zinc vaporization causes pit formation. On the other hand, the defects such as blowholes and pits are not formed in the case of aluminum pre-coated steel sheets because the vaporizing point of aluminum is much higher than that of zinc.