Fine steel alloying during continuous casting : final report

The project aimed to investigate new possibilities of alloy additions during continuous casting of long and flat products. Three solutions for the addition were especially studied : the addition of alloying elements in the tundish, the injection of cored wire or lumpy agents through a special SEN, and the injection of powder directly into the heart of the liquid stream via the hollow jet nozzle (HJN). Mathematical and physical modelling as well as pilot and industrial trials were performed in order to assess completely the alloying addition from a theoretical and practical point of view. It can be concluded that the injection in the tundish has to take place on both sides of he ladle shroud to guarantee a good distribution of the elements in the tundish. Moreover, there exists an optimum location between the ladle shroud and the stopper rod to reduce the transition length and a time-dependent particle injection rate leads to a reduction of the transition length. For the injection through the SEN, an open bottom nozzle configuration has to be used to make wire injection feasible through the stopper rod with an even distribution of the alloying agents. For the injection through the HJN, particles between 100 and 200 μm have to be used in order to obtain a stable and regular injection. For most of the alloying elements, a very good distribution of these elements is observed all over the section of the as-cast products. The parameters identified to reduce the dissolution time are the melt superheat, the homogeneity of the ferro alloy itself, the use of alloys with a reduced melting temperature and the addition of calcium carbonate or silicon.