Determination of Microshrinkage Risk Index in Ductile Cast Iron Production

One recurrent problem in the foundry industry producing ductile iron castings for automotive industry is the presence of defects of secondary contraction. The fight against this problem causes extremely high costs for the foundry due to associated low pattern yields, additional final controls and rejections after machining operations. Many foundries drive their processes without controlling this important behaviour related to the specific graphite growth during the whole liquid – solid transition. In this paper a new concept to control the balance between contraction and expansion and subsequent presence of microshrinkage is presented. 

Thermal analysis technique has been used to calculates the energy balance due to solid phase formation during the solidification process and nucleation phenomena, providing a continuous monitoring of the formed austenite and graphite.

The influence of different treatments on the liquid iron is measured showing the importance of both base iron and ulterior procedures before pouring. This technique allows to have under control the metallurgy during the process and to reduce the manufacturing and non-quality costs.