（1. Cold- rolling Department， Shougang Jingtang United Iron and Steel Co.， Ltd.， Tangshan 063200， Hebei， China 2. Manufacturing Department， Shougang Jingtang United Iron and Steel Co.， Ltd.， Tangshan 063200， Heibei， China 3. Sheet Metal Research Institute， Shougang Research Institute of Technology， Beijing 100043， China）
Abstract：To solve the problem of pretermission of plating for the high- strength dual- phase steel produced by the hot dip galvanizing line, based on the analysis of macro and micro structure, chemistry and the formation mechanism of plating leakage, it was defined that the main cause of the surface plating leakage cold- rolled high- strength DP780 steel product, the failure of galvanization sometimes happens locally on the surface, leading to the plating leakage. Both macroscopic and microscopic characteristics and the composition of defect regions were examined. It is concluded that such defects result from the selective oxidation of Si and Mn in steel during annealing, which can block the thermite reaction of Fe and liquid zinc. Accordingly, the increasing of dew point and the decrease of hydrogen gas pressure in the annealing atmosphere have been realized to successfully prevent such defect.
2018, Vol. 28 
