Effect of Some Technological Factors on the Castability of an Aluminum-Killed Steel in a Continuous Billet Caster

摘要

The number of nonmetallic inclusions during out-of-furnace treatment and continuous casting of 10KB and 20G2R steels in a continuous billet caster in the EAF plant of OAO Severstal' is small. The metal purity is ensured by preliminary vacuum-carbon deoxidation and reliable protection from reoxidation. A combination of a high slag basicity, aluminum metal and slag deoxidation, and active mixing during vacuum treatment leads to a favorable type of inclusions, namely, liquid calcium aluminates, which promotes satisfactory metal castability. Upon reoxidation, slag-induced inclusions and non-metallic inclusions were primarily determined in the samples that were taken at the initial stage of treatment in the ladle-furnace unit. Inclusions of this type are rarely found if the technical requirements regarding the restriction of reoxidation after the introduction of an aluminum wire rod especially in the course of pouring, are satisfied. These results were taken into account in the design of the process of production of 20G2R steel such that a series of eight heats are cast and the billets have the required macrostructure.