The Annals of “Dunarea de Jos” University of Galati. Fascicle IX, Metallurgy and Materials Science (May 2007)
Values of Solutal Marangoni Number in Very Dilute Fe-C-O Solutions at 1873K
Abstract
Low carbon, aluminum killed steels are well represented by the adequate part of the Fe-C-O system, where are available useful experimental data, regarding the surface tension and viscosity. The reference dynamic characteristic scale, of about 1-2 μm at which local chemical inhomogeneities where experimentally observed in some particular conditions is possible to be extended at around 10 μm and even more, according to basic relations. A characteristic concentration of 0.0001%mass oxygen was taken into account at 1873K. At oxygen contents up to 0.0020%mass and at low contents of carbon (0.05-0.15%mass), the values of the Marangoni solutal number (Mas) always were found to be higher than the critical values (Masc = 50) especially due to the reduction of the viscosity with the oxygen content. When the dynamic characteristic length is 6 μm, Mas = 379 and the parameter ε = 6.58, permitting the development of hybrid convection roll cells. Even at such high dilutions, in Fe-C-O solutions at 1873K, the convection due to the solutal effect is present.At a concentration of 0.0017%massO(soluble) takes place a change of the relations between viscosities and between the value of Marangoni numbers. It is sugegested that the finally induced dynamics in liquid steels are responsible for some decreasing of the steel cleaness.
