Abstract: It is rather reasonable to use the nodular cast iron possessing in good combination properties as the material for the guide disc of the seamless steel pipe piercing mill and rolling mill.However, when producing the said guide disc with the chrome-nickel-molybdenum alloy nodular cast iron, defects resulting from the casting process are frequently found, including abnormal or declined nodularization, shrinkage porosity, inclusion and subsurface porosity, etc.Analyzed are the characteristics of these defects and the influential elements thereof.Accordingly, countermeasures and preventative actions against the defects are proposed taking consideration of the actual production circumstances into consideration.