MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF SG-IRON IN THE CARBON EQUIVALENT RANGE 3.78 TO 5.24-PERCENT

The influence of the variation of percent carbon equivalent (%CE) of s pheroidal graphite (SG) cast iron on the microstructure, hardness, ten sile properties, and absorbed energy during impact testing has been in vestigated. The matrix-phases of the sand and metal mould ingots are f errite and/or pearlite and/or iron-carbide in the range of %CE used. T he 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 fro m 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 hard ness with %CE showed inconsistency with the tensile strength curve. Th is point needs further investigation. The present research presents so me mechanisms to explain the form of curves obtained for the variation of properties with %CE.