Effect of Some Technological Factors on the Castability of Aluminum-Killed Steel in a Continuous Billet Caster
Abstract
The oxide inclusions quantities and reoxidation level of liquid steel during secondary treatment and continuous billet casting at EAF plant OAO Severstal are tested. The influence of different technologies on the effectiveness of calcium modification of inclusions and on castability of Al-killed steel 10KB and 20G2R is investigated. It was found that inclusions pollution level in liquid metal during secondary treatment and continuously billet casting at EAF plant OAO Severstal is low. The purity of the melt in ladle-furnace and tundish is provided by prior vacuum-carbon deoxidation and reliable reoxidation protection. Reoxidation-type inclusions and slag-type inclusions were mainly found in samples, taken during initial period of treatment in ladle-furnace. Inclusions of these types were rare in the samples taken at the final stage of treatment and casting if technological requirements concerning reoxidation restriction were executed. It is experimentally found and theoretically explained that the combination of such conditions as high slag basicity, aluminum killing of metal and slag, and intense stirring during vacuum treatment provides the beginnings of liquid calcium aluminates. It is favorable for castability improvement.
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