Non-Metallic Inclusions in Calcium-Aluminum Complex Deoxidized Steel

Abstract

In order to reveal the relationship between composition of non-metallic inclusion and condition of deoxidizing by calcium and aluminum, several middle carbon steels (S 45 C) were prepared and sampled from furnace, mold, ingot and forged bar.
Non-metallic inclusions in these samples were investigated on micrographical appearances, cleanliness and the compositions.Compositions of representative inclusions changes from quantitative electron probe microanalysis.It is found that composition of inclusion is not changed during solidification and forging, and the composition of oKide inclusions changes from Mn-Si-O to Al₂O₃ through Ca-Al-Si-O, Ca-Al-O with the increasing amount of aluminum deoxidizer. In case of using rich aluminum deoxidizer, calcium forms CaS or (Ca, Mn) S instead of oxide.
From results of the present experiments, the order of the tendency of reaction between elements is molt-fn steels are as follows;
Tendency to oxygen: Al>Ca>Si>Mn,
sulfur: Ca>Mn>Al,
calcium: 0>S,
manganese: S>0.
These tendencies are also explained from thermochemical standpoint.