Detection of Chunky Graphite in Iron Casting using Ultrasonic Scattering

The increasing number of requirements placed on the mechanical properties of cast components leads to an increasingly detailed specification of strengths. The mechanical properties of cast iron materials are not only determined by its matrix. The basic structure, but also type, shape and distribution of the embedded graphite influence its properties as well. In this context, chunky graphite represents a degeneration of the graphite spheres. Its occurrence mainly influences the ductility of the material. At present, there is no nondestructive testing method that can be used to inspect components with respect to chunky graphite. Therefore, Fraunhofer IZFP is developing a method to characterize the nodularity of graphite spheres. In a first step, it is to be shown that the occurrence of chunky graphite can be detected in different microstructures. As it is already known that differences in the matrix and different graphite shapes and sizes influence the scattering behavior of ultrasound, ultrasonic scattering will be used for the investigations. Two different types of cast iron, one ferritic and one pearlitic, will be investigated for chunky graphite and different effects will be compared