TREATMENT OF NON-ULTRALOW-DECARBURISED SHEET GRADES IN A HALT FACILITY

Objective. At Thyssen Krupp Stahl AG in Dortmund, the HALT (Heated Arb ed Ladle Treatment) facility is used for alloying applications and, wh en necessary, for the chemical reheating of steel heats. Because of th e low aluminium burn-off occurring in the alloying process. preference is given to treating non-ultralow-decarbulised. surface-critical shee t grades. Summary. A procedure optimised within the scope of this inve stigation has led to the achievement of a higher level of cleanness du ring alloying treatment in the HALT facility than at the conventional stirring stations. Steels chemically reheated in the HALT facility can be used only for grades that entail less stringent surface requiremen ts, because of the high amount of alumina formed in the process. Durin g reheating, there is an unavoidable burn-off of incidental elements f rom the molten steel. the extent of which has to be taken into conside ration in the thermal balance of the reheating process. The burn-off i s high particularly if the refractory-clad bell is not very deeply imm ersed and the aluminium added for reheating purposes is washed out of the reaction chamber beneath the bell. (E 29903).