论文部分内容阅读
采用不同轧制及热处理工艺制备了化学成分相同而晶粒尺寸不同的3种超低碳IF钢试样.采用浸泡腐蚀、周浸腐蚀、原子力显微镜(AFM)及扫描电镜(SEM)微观分析、电化学阻抗测试等手段对晶粒尺寸与IF钢耐大气腐蚀性能之间的规律进行了研究.AFM及SEM微观分析结果表明,随着晶粒尺寸从15μm增加到220μm,超低碳IF钢浸泡腐蚀后晶界处的局部腐蚀更加严重,腐蚀裂纹处的深度加深,裂纹宽度变宽.超低碳IF钢晶粒尺寸从15μm增加到46μm,周浸腐蚀实验后锈层中空洞和裂纹增多,锈层电阻下降,耐候性下降;晶粒尺寸进一步增大到220μm后,锈层整体致密性得到增加,锈层电阻上升,耐候性得到增加.对晶粒尺寸影响耐大气腐蚀性能的机理进行了讨论.晶粒尺寸增大后晶界能的减少使得腐蚀表面的宏观总体缺陷数量有所减少,耐候性有所提高;但是晶粒尺寸增大后晶界处因局部腐蚀电流密度增大将会在局部造成更深的腐蚀坑槽并降低耐候性;晶粒尺寸的变化对钢铁材料耐大气腐蚀性能的影响不仅要考虑其对晶界局部腐蚀电流密度的影响,而且还必须考虑对基体整体晶界能所造成的影响.
Three kinds of ultra-low carbon IF steel samples with the same chemical composition and different grain sizes were prepared by different rolling and heat treatment processes. The microstructure of the samples was studied by immersion corrosion, Electrochemical impedance test and other means on the grain size and IF steel corrosion resistance between the atmospheric behavior.AFM and SEM microanalyses showed that as the grain size from 15μm to 220μm, ultra-low carbon IF steel immersion After the corrosion, the local corrosion at the grain boundary is more serious, the depth of the corrosion crack is deepened and the crack width is widened.The grain size of the ultra-low carbon IF steel increases from 15μm to 46μm, the cavities and cracks in the rust layer increase after the immersion corrosion test, The resistance of the rust layer decreased and the weatherability decreased. When the grain size was further increased to 220 μm, the overall compactness of the rust layer increased, the rust resistance increased, and the weatherability was increased. The mechanism of grain size affecting the atmospheric corrosion resistance was investigated The decrease of the grain boundary energy after the grain size increases makes the number of the macro-total defects on the corrosion surface decrease and the weatherability increases. However, when the grain size increases, the local corrosion current density Increasing the degree will cause deeper corrosion pits locally and reduce weatherability; the influence of the grain size changes on the atmospheric corrosion resistance of the steel material not only has to consider its influence on the local corrosion current density at grain boundaries, but also must consider The effect of the grain boundary energy of the entire substrate.