An Experiment on the Mechanism of the Formation of Oxide Inclusions Originated from Casting-Pit Refractories

Abstract

In order to reduce the oxide inclusions originated from casting-pit refractories, the properties giving the influence on the wear by molten steel and slag were studied for commercial grade casting-pit refractories by laboratory test. The form and the quantity of these bricks entrapped into molten iron were also investigated.
The results were summarized as follows.
(1) It was recognized that semi-zircon brick (Zro₂ 40%) had excellent resistance to chemical attack by molten iron and slag, and high alumina brick and high silica brick (Sio₂ 81.5%) having a stable texture with moderate grain size distribution had good resistance to mechanical wear.
(2) Discussion was made on the slagging mechanism of the bricks by the observation of change in quality of the bricks after slagging test.
(3) The mineral composition of oxide inclusions entrapped into molten iron in the crucibles made of each tested brick were as follows.-wustite-fayalite (FeO-2FeO·SiO₂) for Zro₂-containing brick, silicate glass for high alumina brick, corundum crystallizing silicate glass for pyrophyllite and high silica brick, FeO-containing silicate glass for SiC-added pyrophyllite brick. The fine grains of each brick were also detected in molten iron.
(4) Taking the experimental results on some properties of the bricks after slagging test into account, the tendency of entrapping bricks was considered.
(5) It was considered that conventional pyrophyllite and high silica brick, having good texture with moderate grain size distribution, exhibited a relatively small tendency of entrapping, however these slagging products suspended in molten steel were possible to be a source of aluminate inclusions.