LOOKING AT GRAPHITE SPHEROIDS

摘要

Professor Carl Loper, Jr. has been fundamental in the development of cast iron. He has taught numerous metalcasters and scientists the fundamentals of cast iron solidification and the mechanisms involved in the formation of spheroidal graphite. From the liquid state to the finished part, cast iron undergoes numerous transformations. Usually, during failure analysis of a cast iron part, one looks at the final process for answers but examination of the different solidification stages can often help to solve the problem. Areas to consider examining include: the use of conditioners before nodularizing treatment, the type of inoculants and the solid-state transformation can be elucidated using powerful tools such as Optical (OM) and Scanning Electron microscopes (SEM) and Energy Dispersive Spectroscopy (EDS) analysis. A careful observation of rapidly solidified samples, fracture samples and Charpy specimens helps to establish the nucleation mechanisms, the initial spheroid formation in the liquid and the subsequent growth in the liquid and solid state and help to confirm possible theories and to reject other theories about the nuclei for graphite formation. The complete history of a ductile iron part can be studied by looking at the spheroids.