Improvement of Nodularity Value of Graphite in Ductile Iron and Its Effect on Mechanical Properties

Abstract

AbstractDuctile iron is becoming popular in many industrial applications due to its comparatively high strength and a considerable amount of ductility, which is because of the presence of spheroidal graphite in the microstructure. An effort has been made to improve the nodularity value of graphite in ductile iron by varying the fineness of inoculant, that is, ferro‐silicon (Fe‐Si) and section thickness of the casting. Further, the effects on mechanical properties are also studied. The spheroidal graphite iron specimens for different inoculant treatments, such as without any inoculation, in‐mold inoculation with coarse, and fine Fe‐Si, are prepared. The results have shown that the nodularity increased with in‐mold inoculation with Fe‐Si, and for the same amount of inoculated Fe‐Si, the nodularity is higher for fine Fe‐Si. Ultimate tensile strength is also found to increase with the increase in nodularity, and maximum strength of ≈460 MPa is recorded for a specimen having in‐mold inoculation with fine Fe‐Si. Stepped bar specimens of different thicknesses are also prepared by casting with the same composition for studying the effect of section thickness, and nodularity value is found to be higher for the thinnest section and is about ≈48%.