Irons containing sulfur from 0.004 to 0.15% were melted in a high frequency induction furnace and nodularization treated at 1,530°C by adding 1.6wt% of Fe-Si-Mg alloy together with various amounts of mishmetal. Different amounts of RE were also added before nodularization treatment to determine the effect of RE addition time on nodule count. The melt was post-inoculated with 0.4% Fe-Si and was cast in CO₂ molds 3, 6 and 9mm in mold cavity thickness and in knock off-type shell molds of 30mm diameter and 150mm length. The chilled structure and nodule count were image analyzed. The nodule count is enhanced by adding RE in the stoichiometric amount to the sulfur content of base iron. The difference of nodule count between the irons containing and not containing RE extends with the cooling rate. The high sulfur iron to which RE has been added before nodularization treatment has lower nodule count, less sulfur and less cerium than the RE added iron.

抄録全体を表示