SeAH Besteel, the largest special steel producer in Korea, contracted Danieli to increase the process efficiency for EAF #3 at the Gunsan meltshop. The steel quality targets indicated for this 100-ton electric furnace require the use of low-residual scrap, which results in very dense charge mixes. The need to avoid over-oxidation—thus to maximize process repeatability and steel quality—together with the target of maximizing arc stability and active power in the presence of high-density scrap, were the major reasons for selecting the Q-MELT technological package.

The installed Q-MELT consists of:

• Q-REG electrode control regulator;
• LINDARC real-time gas analysis, laser based, with closed-loop control of soft-blown oxygen during scrap melting; and,
• MELTMODEL for dynamic adaptation of oxygen flowrate setpoints during refining, according to bath oxidation levels.

The results can be summarized as a 2% increase in average active power, a 2% reduction of electrical energy consumption, and a 15% standard-deviation decrease of oxygen content in the steel before tapping.

The achieved results and the strong collaboration established between SeAH Besteel and Danieli technological and research teams paved the way for further improvement in dynamic control logics for the refining stage, which was developed recently due to the unique features of the EAF #3 process. Early oxygen utilization to melt scrap, together with late carbon injection during flat bath operation, make the last refining phase much like a slag reduction stage. For this purpose additional controls on dynamic carbon-injection flowrates, as well as electrical power and oxygen turn-off timing, were implemented.