DETERMINING PROCESS CONDITIONS DURING EAF REFINING TO ENHANCE END POINT CONTROL

Due to the high heating power of the electric arc furnace (EAF), precise end point control of the EAF refining process is essential for efficient melt processing. The evolution of the steel bath temperature was measured during the EAF refining phase using a novel fibre optical measurement system based on BFI’s DynTemp® technique. This measurement system was applied at the high productivity furnace of Ferriere Nord producing construction steels and the furnace of Saarschmiede Freiformschmiede producing high quality forging steel grades. The continuous liquid steel temperature measurements were also used to optimize the performance of dynamic EAF process models. The model validation by conventional thermocouple measurements proved that the liquid steel temperature can be predicted with a modelling error standard deviation of about 11 K for the Ferriere Nord furnace and of about 20 K for Saarschmiede furnace. In addition, to interpret the measurement results, the processes of both steel shops were simulated using computational fluid dynamics (CFD) calculations. Fluid flow and steel bath temperature distribution were modelled to determine optimal measurement time, minimum measurement duration, and influence of the measurement position. Based on the analysis of the liquid steel temperature evolution, more reliable set points for energy input and temperature control are determined. Thus, the combined use of offline CFD calculations, online dynamic process modelling, and fibre optical inline measurement leads to enhanced EAF end point control.