Rare Earth Helps Improve The Properties
As for the study on high-strength and low-aloyed ductile cast iron, related considerations are involved are not only in the study on Cu and Mo, but also in the one on Ni, Nb and other compositions. Considering of utilizing vanadium titanium iron to create vanadium and titanium-alloy ductile cast iron, some domestic entities have had plenty of systematic work. Though medium manganese ductile cast iron has some unstable properties, they have brought remarkable economic results through systematic researches and practices in many years. In addition, for ductile cast irons with heat resistance property and acid resistance one, they have been developed rapidly as well.
Rare earth material is able to spherize graphite. Since an Englishman-H. Morrogh firstly created ductile cast iron by utilizing Ce, there’re many many people all over the world have studied spheroidization behaviors of all kinds of rare earth elements. Thus it’s concluded that Ce element is the most effective one for spherizing substances, and other elements all have different levels in spheroidizing abilities.
According to its actual conditions, we have had a great deal of researches and studies on spheroidizing ability of rare earth element, and found it’s hard to create a completely uniform distribution of globular graphite structure, compared with magnesium ductile cast iron by adopting rare earth. But if its high-carbon hypereutectic overeutectic composition is up to >4.0wt% and its rare earth residual quantity keeps 0.12～0.15wt%, perfect globular graphite effect can be achieved by utilizing rare earth.