Microstructure and Mechanical Properties of SG-Iron in the Carbon Equivalent Range 3.78 to 5.24

The influence of the variation of percent carbon equivalent (%CE) of spheroidal graphite (SG) cast iron on the microstructure, hardness, tensile properties, and absorbed energy during impact testing has been investigated. The matrix- phases of the sand and metal mould ingots are ferrite and/or pearlite and/or iron-carbide in the range of %CE used. The ratios of these constituent phases depend on the %CE. The curves of the variation of the tensile properties (strength and ductility) and the impact-energy showed a remarkable increase with increasing %CE from 3.78 up to 4.61 and, thereafter, decreased again with increasing %CE until a value of 5.24. The form of the curve of the variation of hardness with %CE showed inconsistency with the tensile strength curve. This point needs further investigation. The present research presents some mechanisms to explain the form of curves obtained for the variation of properties with %CE.