Desulphurization of the high-alloy and middle-alloy steels under the conditions of an eaf by means of synthetic slag based on CaO-Al2O3

Abstract

The article deals with the results of the experimental heats performed in the electric steel plant of TŘINECKÉ ŽELEZÁRNY, a. s. (TŽ, a. s.). The aim was to verify the possibility of deep desulphurization of steel in the basic 10-t electric arc furnace. Experimental procedures making use of the industrially produced synthetic slag were applied in the production of the high-alloy chrome steels and the middle-alloy tool steels, where the desulphurization, in terms of thermodynamics, is a more demanding process than the chrome-nickel steel desulphurization. With the use of the technological processes it is possible to achieve low contents of sulphur in steel, below mass fraction 0.003 %. Achieving these contents depends on a suitable slag basicity, and, in particular, on the ratio of CaO/Al2O3. Based on the analysis of the results, a critical factor significantly affecting the final content of the sulphur and thus the efficiency of the desulphurization of steel, the content of FeO in the reduction slag, is carefully considered. A higher MgO content in slag (up to w = 25 %) had no significant influence on the results of the steel desulphurization.