Effect of Calcium on Iron and Steel Making : Non-Metallic Inclusion and Austenite Grain Size of Plain Carbon Steel
Steels containing 0.3 to 0.5% C were melted in alumina-1ined graphite crucible 3 kg in capacity by a high frequency induction furnace. These steels were prepared from electrolytic iron and pig iron. The melt was deoxidized with electrolytic manganese, metallic silicon and different amounts of aluminium ranging from 0.02 to 0.16%, and cast into metal molds, but to a part of the melt was added the iron-calcium base alloy before casting. After forging, non-metallic inclusions in the steels and grain coarsening temperatures were examined. The results are as follows : While the addition of the iron-calcium base alloy to the molten steel deoxidized only with manganese and silicon is effective in reducing the amount of inclusions belonging to type A consisting of deformed sulphide and silicate and at the same time in raising the grain coarsening temperature, its addition to the molten steel deoxidized with manganese, silicon and aluminium considerably decreases the amount of oxides, especially, of alumina, and increases the amount of aluminium nitride as compared with the case without addition of the iron-calcium base alloy. The addition of this alloy contributes also to the reduction of the grain size, which improves the properties of steel. It is assumed that this reduction of the grain size may be attributed partly to the increase of the amount of aluminium nitride caused by addition of aluminium and the above alloy. The grain size of aluminium- or calcium-killed steels is rapidly coarsened above 1000°?1050℃, while that of rimmed steels is progressively coarsened with the rise of temperature above 700℃.
- Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy 17/18 326-339, 1965