Source of Exogeneous Inclusions and Reduction of Their Amount in Continuous Casting Process

Abstract

Investigations to produce clean steel for draw and ironing cans in continuous casting process were carried out.
Results obtained are as follows:
(1) Inclusions which cause flange cracks in manufacturing draw and ironing cans are 50150 μm in size and CaO-Al₂O₃ in compositions, which can be fairly well detected by the magna-flux method.
(2) CaO-Al₂O₃ inclusions are originated from slag which is deoxidized by Al in molten steel, the content being about 0.005% or above.
(3) Main source of the above-mentioned inclusions is tundish-slag, which is spattered into molten steel by the stream of the next ladle in continuous casting.
(4) Good clean steel for draw and ironing cans can be produced by means of either large tundish with dams or reladling method (LLTM process)
(5) The theoretical model to explain the effect appointed out in (4) was proposed.