Development of the cleanness of different steels for flat and round products

Objective. Huttenwerke Krupp Mannesmann (HKM) produces steel material on co ntinuous slab and round casters to meet the highest demands. In the followi ng, the measures required to improve the cleanness at both casters are pres ented, and the results are discussed. Separation in the tundish was to be i mproved and the formation of coarse inclusions in the nozzles prevented. Summary. Important factors which influence cleanness are strongly varying c asting rates in the instances of slab and round material, and different cas tability. The goal of good cleanness has been achieved for continuously cas t round steel. The most effective measures have been the use of baffles to improve the inner strands, and the optimisation of the submerged entry nozz le geometry. A satisfactory solution for slabs continuously cast under conv entional conditions has not yet been achieved because the ladle pouring rat e is twice as high and the rate of flow into the submerged entry nozzles si x times as high. The submerged entry nozzles on the slab casters are oversi zed in order to counter any clogging. Argon injection into the tundish has been tried out and has brought about a certain improvement. But argon shrou ding of the submerged entry nozzles can lead to a deterioration of the Mida s test results. The argon rates in the tundish and submerged entry nozzle r equire careful monitoring and have to be kept within maximum limits.