Graphite degeneration is the most prominent microstructural defect in the casting skin of ductile iron. Induced by either sulfur or oxygen contained in the molding material, its occurrence can be observed in a large range of iron castings, having substantial negative influences on the mechanical properties, especially fatigue resistance. Previous investigations predominately focused on the influence of the degenerated graphite layer, while accompanying changes of the iron matrix were neglected. The superposition of these effects hinders the evaluation of casting skin defects in state-of-the-art design of ductile iron components. The presented solution utilizes an experimental procedure, which enables the production of specimens with specific, individual microstructural configurations in the casting skin. This approach is based on the application of a modified sand core coating. By adding sulfurizing additives to the coating and adjusting its binder content and viscosity, a predominately homogeneous degenerated layer of 0.5 mm thickness was obtained. Using specific heat treatment steps assured a fully ferritic or pearlitic iron matrix, isolating the degenerated layer as the main microstructural defect. Fatigue testing of these specimens will further enable the numerical evaluation of the fatigue resistance in dependence of the casting skin microstructure.

石墨变性是球墨铸铁皮中最突出的显微组织缺陷。由成型材料中所含的硫或氧引起的这种现象可在大范围的铸铁中观察到，对机械性能（尤其是抗疲劳性）具有实质性的负面影响。先前的研究主要集中在退化的石墨层的影响上，而忽略了铁基体的伴随变化。这些影响的叠加阻碍了球墨铸铁组件最新设计中铸件表皮缺陷的评估。提出的解决方案利用了一个实验程序，该程序能够在铸皮中生产具有特定的，个别的微观结构的试样。该方法基于改性砂芯涂层的应用。通过将硫化添加剂添加到涂层中并调节其粘合剂含量和粘度，获得了厚度为0.5mm的主要均匀的变性层。使用特定的热处理步骤可确保完全铁素体或珠光体铁基体，将退化层隔离为主要的微观结构缺陷。这些样品的疲劳测试将进一步使疲劳强度的数值评估取决于铸件蒙皮的微观结构。分离退化层为主要的微观结构缺陷。这些样品的疲劳测试将进一步使疲劳强度的数值评估取决于铸件蒙皮的微观结构。分离退化层为主要的微观结构缺陷。这些样品的疲劳测试将进一步使疲劳强度的数值评估取决于铸件蒙皮的微观结构。