Effect of hot metal on decarburization in the eaf and dissolved sulfur, phosphorous, and nitrogen content in the steel

Abstract

The effect of hot metal additions on the decarburization and dissolved sulfur, phosphorous, and nitrogen content in the steel of a DC EAF was investigated. The addition of hot metal of maximum 36% provided heat into the EAF allowing faster melting and reduced power on times of the furnace. The increased melting rate lowered the FeO in the slag and seems to allow faster kinetics for CaO dissolution into the slag. Hot metal utilization into the slag resulted in higher phosphorous distribution ratios compared to hot metal free heats achieving comparable phosphorous levels at the ladle metallurgical furnace even though the initial input phosphorous was much higher than hot metal free heats. The effect of hot metal on the desulfurization was not pronounced and no apparent difference could be ascertained compared with the 100% scrap charge. With the addition of carbon saturated iron units in the EAF, the evolution of CO and foaming was promoted, which inhibited the infiltration of nitrogen and lowered the overall partial pressure of nitrogen resulting in lower nitrogen levels in the steel. In addition, the dilution effect of the tramp elements Cu and Sn with hot metal ensured the critical defect index to be less than 10% resulting in a 50% reduction of the quality defect index.