キルド鋼の非金属介在物に関する研究(I)

抄録

The microscopic and macroscopic non-metallic inclusions concerning the practical killed steel-ingot of 5 tons were investigated. The results obtained were as follows.
(1) Microscopic inclusions
(i) The microscopic non-metallic inclusions in the practical ingots changed their apperances corresponding to the positions in them (so-called, top or bottom). The cleanness and thickness of inclusions observed in the practical billets were different from those in the 2kg sample-ingot taken under the ladle.
(ii) The conditions of the inclusions were not influenced extremely by the change of pouring method (top-poured or bottom-poured) and Al-amount added in the ladle.
(iii) By observation of the maximum sizes of A-type (elongated) and B-type (not elongated) inclusions about both samples, taken under the ladle and from the practical billets, A-type inclusions showed a large difference between both samples, but B-type were nearly the same.
(2) Macroscopic inclusions (streak seams)
(i) When 430g/t Al was added in the ladle, at top pouring the Al₂O₃ type seams were found at the ingot-bottom and within the end of columnar crystals. These seams decreased, when 220g/t Al was added in the ladle.
(ii) The tendency of distribution of these seams in the bottom poured ingot was not so clear as the top poured ingot.
(iii) The rate of occurrence of these seams between the ingots of the same charge was influenced by the teeming velocity and other conditions of the ingot-making.
(iv) The rate of occurrence of the seams increased, when the molten steel was viscous by the effect of low temperature or other causes.