镀锌DP780漏镀缺陷的成因分析与预防措施

Reason for failure of hot dip galvanizing on cold rolled DP780 steel and its preventive measures

为了解决热镀锌线生产高强度双相钢产品出现的表面漏镀问题,通过对缺陷的宏观与微观形貌以及成分进行分析,同时对漏镀的形成机理进行分析,确定影响表面漏镀的主要原因是双相钢中含有硅、锰等元素较多,容易发生选择性氧化,氧化物阻碍铁元素和锌液的铝热反应,形成漏镀。根据分析结果,采取提高炉区加热段露点和降低氢气含量的方法对漏镀进行预防。结果表明,同时提高炉区加热段露点和降低氢气含量能有效解决表面漏镀问题,取得了较好的实用效果,为进一步开发拓展更高级别镀锌双相钢提供了技术基础和理论依据。

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.