In order to understand the mechanism of the accumulation of large non-etallic inclusions under the upper surface of the continuously cast slabs by the bow type machine, slabs, casted by two kinds of submerged nozzles designed to make a different penetration depth of casting stream, were investigated in regard to the distribution and content of large non-metallic inclusions. The resultsobtained are as follows.
1) By use of the nozzle with the shallower penetration depth of the casting stream, the position of maximum amount of large non-metallic inclusions in the accumulated zone and the end point of the accumulated zone shift toward the upper surface and also, their accumulated amount decreases.
2) Total large non-etallic inclusion content in the accumulated zone increases in proportion to the area of “entrapping zone” corresponding to the liquid core between the perpendicular circumscribed with the solidification front at the upper side and the position of the penetration depth of the casting stream in the longitudinal section of the strand during casting.
