Definition of a ladle change strategy to avoid slag entrapment and to control inclusion population

This project involving Arcelor Research, MEFOS, BFI, SIDMAR and Cockerill Sambre focused on ladle changeover strategy to avoid slag entrapment and to control the inclusion population. Activities were driven in agreement with the project planning. Several specific models have been used together with industrial trials to understand what happens to the inclusion population during the end of ladle teeming, the tundish emptying and its refilling. The inclusion population present in the liquid steel and in the product during this period of casting is different than from steady state casting. They are not only de-oxidation inclusions but also ladle and tundish slaggy inclusions, having a size up to some hundred of µm. Some industrial actuators could be defined such as the design of the ladle bottom and tapping hole, the immersed ladle opening, tundish baffles... The inclusion pollution starts before the metal mixing and can continue after the end of grade mixing. Pollutions due to ladle slag and tundish slag can occur at the same moment (or the same location in the strand) or can be separated (first ladle slag and then tundish slag). The concentration of inclusions and its spreading can vary a lot. We propose rules and knowledge to build a quality rating model in terms of position of the pollution, its spreading and intensity and the total inclusion pollution for ladle and tundish slags. We can also use it to react in case of customer's claim to understand the origin of a problem and define suitable countermeasures.