Material and technique of S i-Mo heatresistant vermicular iron exhaust manifold

Si-Mo vermicular iron is an ideal material for exhaust manifold that works in high temperature and therm alcycle conditions because its properties oftherm alfatigue resistance and thermal distortion resistance are significantly better than that of gray cast iron and nodular iron. This paper explains that the verm icularity of Si-Mo verm icular iron is better to be controlled approxim ately to 50% for the applications of exhaust manifold castings, and generalizes the successful experience ofverm icularizing technique thatuses sandwich(pourover)process combining with cored-wire injection in trough process together,and uses rare earths-magnesium-silicon as verm icularizing alloy in Disa high speed molding line and autom atic plug rod airpressure pouring furnace. In addition, this paper also describes the method to solve the shrinkage hole and porosity defects in the exhaustm anifold production.