Rare Earth Helps Improve The Properties
So it’s very necessary to add rare earth element according to the actual situation that Chinese ductile iron foundry are generally poor iron quality, high sulfur content (cupola melting) and low tapping temperature. Though Mg Element is a dominant one among one nodulizer for producing ductile iron foundry, rare earth can not only promote spheroidization process among graphite, but also overcome the effect of Su and other impurity elements for ensuring its spheroidization. Rare earth element can prevent interference elements from hampering spheroidization. Research shows that if the total content of Pb, Bi, Sb, Te and Ti interference elements reaches 0.05wt% among ductile iron foundry, adding rare earth material of 0.01wt% (residue vol) can neutralize its interference completely for further blocking the metamorphosis. Most of pig iron castings contain Ti in our country, even the Ti contents in some ones reaches 0.2～0.3wt% as high.
Though, a kind combinations of magnesium and rare earths can be added into ductile iron foundry for helping the rare earth content (residue vol) reaching 0.02～0.03wt%, so they can well ensure spheroidization of graphite. In the event of adding Bi (0.02～0.03wt%) into ductile iron foundry, it would be a scrap. However, in case of adding Ce (0.01～0.05wt%), graphite element among it will restore the original state. The reason behind lies in forming a kind stable complex from the help of Bi and Ce.