Modern technologies for the out-of-furnace treatment of steel in converter shops

The reconstruction of the steel works at the Nizhniy Tagil combine, which produces more than one million tpy of steel for rail transport, through the building of a new ladle furnace, an RH-type vacuum degassing unit, and four-strand continuous caster by Voest-Alpine Industrieanlagenbau (VOI) has significantly reduced nonmetallic inclusions and hydrogen content in the steel. Efficient operation of the complex of equipment for out-of-furnace treatment of steel together with the continuous caster requires that standard auxiliary operations be performed in steelmaking. These include desulfurization of the pig iron, intercepting the converter slag when the steel is tapped from the furnace, and covering the steel in the pouring ladle with specially prepared natural slag mixtures. The RH vacuum degassing units in the converter shop have reduced hydrogen content of rail and wheel steel from 4.0-5.0 to 1.5 ppm when established vacuum degassing procedures are observed in the treatment of a 155 ton ladle over 15-20 min. To avoid hydrogen pickup during casting, the molten steel stream is protected by argon.