Abstract
An examination was made of the correlation between the condition of subsurface blowholes ascertained by corner-samples taken from 4-ton semi-killed steel ingots with varied degree of deoxidation and the condition of the seams of the blooms rolled from those ingots and experiments performed further of the change of sub-surface blow-holes accompanying the scaling of the skin of ingots in the soaking pit.
As the result, the relation between the size and the distribution of subsurface blow-holes and the depth of seams was clarified and it seems that in ordinary case the sub-surface blow-holes should be within 2mm from the skin or else the thickness of solid-skim should be made more than 5mm to prevent the forming of the seams.
