Influence of magnesium on nodule evolution and solidification behavior of ductile iron

Ductile iron is a well-known engineering material for making engineering components due to its greater ductility and strength than Grey iron. Because of these properties, it has been extensively utilized in wide range of industrial applications, such as pipe, wheels, automotive components, pump housings and gear box. Ductile iron popularly well-known as Nodular iron or S.G Iron contains spheroidal graphite. Understanding shrinkage phenomena of this iron is little difficult since it has longer freezing zone. This material is more sensitive to shrinkage which leads to stringent process control requirement and difficulties in designing the gating and risering system. Magnesium treatment is used primarily in the foundries to convert gray iron to ductile iron. Addition of the magnesium tends to alter the physical properties of cast iron such as viscosity, surface tension, thermal conductivity, fluidity etc, which has the adverse effect on shrinkage tendency of the material. Therefore, this research predominantly focus towards studying the effect of magnesium addition in the solidification behavior of the material. Since the magnesium gets continuously vaporized after nodularization treatment at the rate of 0.001 % to 0.002% per minute, the properties of the ductile iron during the process of solidification gets changed continuously. Microstructural examination, holding studies and spiral tests were carried out in order to study magnesium effect on solidification behavior of the ductile iron.