不锈钢中夹杂物三维形貌及其热力学计算

Three-dimensional morphology and thermodynamic calculation of inclusions in stainless steel

采用无水电解法提取不锈钢中存在的典型夹杂物,通过扫描电子显微镜观察夹杂物三维形貌,并根据元素组成对夹杂物进行分类和形貌分析,对具有相同化学成分但不同三维形貌的夹杂物进行了表征和归纳.利用FactSage 7.0热力学软件,对不同夹杂物的平衡状态进行了计算,研究了温度和钢液成分对于夹杂物平衡的影响,并得到相应的平衡相图.结果表明,无水电解可以有效地将不锈钢中夹杂物完整地提取出来,避免了金相法带来的误差,可以更加清晰的观测夹杂物的三维形貌;经扫描电子显微镜观察和测量,较大的氧化铝夹杂物表面较为容易出现钛元素的富集区域,且大部分夹杂物形貌主要为球状和表面较为光滑的多面体状,直径一般不大于5μm.通过热力学计算得到,钢中夹杂物的生成与钢中元素质量分数密切相关,在1873 K时,Mg、Ti、Si元素质量分数的不同会导致生成不同的夹杂物.

The typical inclusions in stainless steels were extracted by the anhydrous electrolysis method,the three-dimensional morphology of the inclusions was observed by scanning electron microscopy(SEM),the inclusions were classified and analyzed according to the element composition,and the inclusions with the same chemical composition but different three-dimensional morphology were characterized and summarized.The equilibrium states of the different inclusions were calculated by the thermodynamic software FactSage 7.0,the effects of temperature and molten steel composition on the equilibrium states of inclusions were studied,and the corresponding equilibrium phase diagrams were obtained.In the results,the inclusions in stainless steels can be extracted effectively by the anhydrous electrolysis method,avoiding the error caused by the metallographic method,and the threedimensional morphology of inclusions can be observed more clearly;according to the SEM observation and measurement,the enrichment area of titanium is likely present at the larger alumina inclusion surface,and most of inclusions are spherical and polyhedral with smooth surface,whose diameters are generally no more than 5μm.According to the thermodynamic calculation,the inclusions in steels are closely related to the mass fraction of elements in steels;the different mass fractions of Mg,Ti,and Si elements may lead to the different inclusions at 1873 K.