下注および上注鋼塊に現われたスカムおよび酸化物系介在物の鉱物組成および顕微鏡的組織について

抄録

In order to investigate the source of oxide inclusions in steel by mineralo-chemical method, mineral composition and microscopic structure of ingot scums and oxide inclusions, appeared in some bottom-and top-teeming ingots produced in our plant, were investigated.
The results were summarized as follows.
1. In bottom-teeming ingot scums, many kinds of constituent mineral, mainly composed of FeO-MnO-Al₂O₃-SiO₂ system with a small quantity of slag mineral, were found. It is characteristic that a large quantity of α-quartz as silica mineral were observed.
2. Oxide inclusions in the bottom-teeming ingot were rich in Al₂O₃ compared with ingot scums, and consist of aluminate minerals (CaO·6Al₂O₃, MgO·Al₂O₃) with a small quantity of silicate matrix.
3. In top-teeming ingot scums, many kinds of constituent mineral, originated from slag, refractories, deoxidation products etc. were found. It is characteristic that a large quantity of α-cristobalite were observed instead of α-quartz as silica mineral.
4. Mineral composition and microscopic structure of oxide inclusions in the top-teeming ingot were similar to that in the bottom-teeming ingot. However, in macroscopic inclusions, three typical forms, -(1) multi-component silicate (spinel, corundum and α-cristobalite with a fine crystal matrix mainly composed of CaO-Al₂O₃-SiO₂ system), (2) silicious silicate, (3) special type (chrome spinel) were observed.
5. Spinel (MgO·Al₂O₃), a main constituent mineral of oxide inclusions, was observed regardless of Aldeoxidation in the ladle. Moreover, in the top-teeming ingot, crystal growth of it was observed comparatively remarkable, coagulating with matrix minerals mainly composed of CaO-Al₂O₃-SiO₂ system.
6. On the basis of these investigation, the source of oxide inclusions was discussed.