原板夹杂物诱发镀锡板点腐蚀缺陷分析

Analysis of Tinplate Rust Defects Induced by Al_2O_3 Inclusion of Black Plate

原板高强减薄和锡量降低是镀锡板发展的重要趋势,直接对原板夹杂物和镀锡板表面缺陷控制提出了更为严格的技术要求。通过对夹杂物含量异常的钢坯进行全流程加工得到的1.1/1.1 g/m2规格镀锡成品卷的研究,发现经过10 d在库测试,镀锡板表面产生点腐蚀缺陷。利用光学显微镜、扫描电镜和电子能谱等方法就镀锡板点腐蚀缺陷进行了深入分析,结果发现黄褐色腐蚀产物元素成分为O、Fe,源于基体腐蚀,并伴有原板夹杂物存在。通过金相切片确认典型点腐蚀缺陷样品夹杂物尺寸为96.82μm×50.00μm×8.86μm,属于原板表面嵌入型夹杂,其成分特征为主要含Al、O元素。夹杂物的存在改变了局部区域的原板轧制纹理和镀层形貌,产生近似椭圆白点缺陷,锡层沉积量由缺陷中心外延逐步增加,整体在11.02%～28.08%范围内波动。根据夹杂物伴随点腐蚀缺陷特征,其诱发镀锡板腐蚀行为与夹杂物形成的原板晶体结构缺陷、锡层差异沉积与夹杂物导电性和硬度直接相关。通过研究,清晰地描述了原板表面夹杂物对后续镀锡板成品的表面质量影响关系,为更好控制原板夹杂物提升镀锡板产品表面质量提供了实际数据支撑。

Thickness reduction of black plate and weight reduction of tin coating have been the important development trends of tinplate,which needs more stringent technical requirements for inclusion control of steel-making and surface qualities of tinplate. In this work,the cast steel billet with abnormal content of inclusion( high aluminum burned) was used to obtain 1.1/1.1 g/m^2 tinplate. The whole process was studied and after the storage test of about 10 days the rust spots were found on the surface. The corrosion defects were analyzed using optical microscopy,scanning electron microscopy( SEM) and electron dispersion spectroscopy( EDS). Results indicated that the yellow-brown corrosion product was composed of O,Fe from the corrosion of the substrate with the inclusions of black plate. Through metallographic section analysis,the typical rust spot sample was 96.82 μm×50.00 μm×8.86 μm in size,and the results confirmed that the inclusion element composition contained Al and O. The inclusion embedded on the surface changed the morphology of black plate and the coating appearance,forming an elliptical-like white spot visually. The Sn content of the typical sample was gradually increased from the epitaxial of the inclusion center to the outside and fluctuated in the range of 11.02%-28.08%. According to the characteristics of the corrosion defects,it was found that the corrosion behavior of the rust spot was relevant to the specific crystal structure defects of black plate,the differential electrodeposition of tin layer,and the conductivity and hardness of the inclusions. This work clearly revealed the influences of inclusions on the surface quality of the subsequent tinplate,and provided the actual data to control the inclusion of black plate and improve the surface qualities of tinplate.