EFFECT OF REACTION SITES ON DECARBURIZATI ON RATE IN THE RANGE OF ULTRA-LOW CARBON CONCENTRATION UNDER REDUCED PRESSURE

Theoretical and experimental studies were carried out to quantitativel y understand the effect of reaction sites on the decarburization rate of ultra low carbon steel. The decarburization rate was studied in a 3 0kg vacuum induction furnace by varying the areas of three reaction si tes such as bath surface, steel melt-crucible interface and inner part of molten steel. With the oxygen content of 400ppm, the ratio of the decarburization rate at the bath surface to the overall one is largest for [C] less-than-or-equal-to 27ppm, whereas the largest is that of t he inner part of molten steel for [C] greater-than-or-equal-to 27ppm. The fluiddynamic calculation of the flow pattern of CO bubbles nucleat ed inside the molten steel of RH vacuum vessel made clear that a part of CO bubbles near the down-leg was sucked into the ladle and dissolve d into the steel melt without decarburization. The effect of each reac tion site on decarburization rate in RH was calculated to be the same tendency as that in the 30kg induction furnace.