热镀锌合金化产品白斑缺陷原因分析及控制

Cause analysis and control of white spots defect on the surface of galvannealed products

针对实际生产过程中热镀锌合金化钢板表面易出现白斑色差条纹缺陷的问题,通过对正常部位和白斑缺陷部位的形貌、成分进行对比分析,揭示了白斑缺陷的形成机理,并提出了工艺改进措施。结果表明:带钢灰色镀层表面沿长度方向分布的白斑缺陷具体表现为边部呈正常的深灰色,中部出现显著的白色条状斑迹;白斑缺陷实际为欠合金化缺陷,带钢中部欠合金化主要是由于出锌锅后的带钢头部板形不良出现C翘,导致带钢上表面中部的镀层厚度大于下表面,使得上表面Fe元素含量偏低导致白斑缺陷。通过优化热轧层流冷却、严格控制热轧平整机辊径、增加冷却段张力和减少调整锌锅纠正辊的压靠量等措施,有效改善了带钢C翘缺陷,取得良好效果。

In order to solve the problem that the surface of galvannealed steel sheet is easy to appear the white spot color difference stripe defect in the actual production process,the morphology and composition of the normal part and the white spot defect part were compared and analyzed,the formation mechanism of white spot defect was revealed and the improvement measures were put forward.The results show that the white spot on the surface of the gray coating is normal dark gray on the edge and obvious white strip in the middle,and the white spot is actually an underalloying defect,the underalloying in the middle of strip is mainly caused by C-warpping in the head of strip,which results in the coating thickness on the upper and middle of strip being larger than that on the lower surface,and the Fe content on the upper surface is lower.By optimizing laminar cooling,strictly controlling the roll diameter of temper mill,increasing the tension of cooling section and reducing the pressure of correcting roll of zinc pot,the C-warping defect of strip was effectively improved,achieving good results.