780 MPa级双相钢条状色差缺陷成因及改善措施

 针对780 MPa级双相钢表面存在严重的条状色差缺陷，从微观特征方面进行系统研究。采用SEM及EPMA分析手段研究缺陷表面情况，结果表明，缺陷处微观形貌呈粗糙破碎状，破碎的密集程度和缺陷的严重程度正相关；能谱和电子探针证明，破碎处只存在轻微氧化。应用辉光手段分析表层富集情况，色差严重程度与硅、锰等元素富集峰值距表层深度密切相关，结合热轧截面分析富集现象在热轧以橄榄石相的形式存在，宏观表现为条状红铁皮，该铁皮经过酸洗后难以除尽，在后续冷轧时不同区域表层元素富集深度及破碎密集程度存在差异，表现为连退板表面的条状色差缺陷。在此研究基础上优化热轧和冷轧生产控制方案，最终有效降低或消除了连退板表面条状色差缺陷。

Origin analysis and improvement measures for striped color defects of 780 MPa grade dualphase steel

The microscopic characteristics of serious color defects on the surface of 780 MPa grade dual-phase steel strip were systematically investigated.The surface condition of defects were studied through SEM and EPMA analysis methods.The results show that the area with color defect was rough and the surface shows the broken topography and there was a positive correlation between the broken intensity and the severity of the color defects.EDS and EPMA proved the existence of slightly oxidization at the broken area.The surface enrichment of the defects was analyzed through GDOES analysis,and the severity of striped color defect was closely related to the depth of enrichment(mainly Si and Mn) peak from the surface.Combined with hot-rolled section analysis,the enrichment has already existed in the form of olivine and its macroscopic state was the red scale defect.The red scale defect was difficult to be wiped off after pickling,the broken intensity and the enrichment depth showed many differences on the surface in different areas after cold-rolling,which finally formed the striped color defects on the surface of annealing plate.Based on the origin analysis,the measurements for hot and cold rolling production have been proposed,which ultimately reduced or eliminated the formation of striped color defects.