合金化热镀锌C-Mn高强钢漏镀缺陷原因分析及其对策

针对合金化热镀锌C-Mn高强钢漏镀缺陷问题,利用扫描电镜(SEM)、能谱(EDS)分析了漏镀缺陷原因,阐述了缺陷形成的机理。结果表明:退火炉加热区的氧分压过低,引起Mn、Si等合金元素在基体表面的外氧化显著,降低了钢基体的浸润性;带钢入锌锅温度较高,加快了镀层的合金化反应进程,加剧了Fe-Zn之间的相互扩散,且由于氧化物覆盖不均匀,氧化物密度高的地方容易产生漏镀点。在实际生产中,通过降低退火炉加热区的氢气含量和带钢的入锅温度、提高锌锅自由Al含量等措施,C-Mn高强钢的合金化镀层表面漏镀缺陷得到了有效改善,质量合格率由原来的75%左右提高到了91%以上。

Cause analysis of plating leakage defects on the surface of galvannealed C-Mn high strength steel strip and its countermeasures

Aiming at the problem of plating leakage defects on the surface of galvannealed C-Mn high strength steel strip, SEM and EDS were used to analyze the causes of the plating leakage defects, and the mechanism of defect formation was discussed. The results show that partial pressure of oxygen in annealing heating section is too low, which causes significant external oxidation of alloy elements such as Mn and Si in steel, reducing the wettability of the steel substrate. The temperature of strip into zinc pot is relatively high, which accelerates the galvannealing degree of the coating and intensifies the mutual diffusion between Fe-Zn. Due to the uneven coverage of oxides, the places with high oxide density are prone to plating leakage spots. During practical production, technological measures were adopted such as decreasing hydrogen content of annealing heating section and the temperature of strip into pot, and increasing the free aluminum content of zinc pot, and the plating leakage defect on the surface of C-Mn high-strength steel strip was effectively controlled. The qualified rate increased from about 75% to over 91%.