Deoxidation and desulfurization equilibria of liquid iron by calcium

Abstract

It is important to reduce the oxygen potential in steel in order to lower the sulfur content, and the addition of the strong deoxidizing agent, such as calcium, is considered to be most effective. The deoxidation and the desulfurization equilibria of liquid iron by calcium have been investigated at 1873 K. The following thermodynamic values on the calcium desulfurization have been derived from the experimental results in the present study and in the previous studies by others. CaS(s)+Ca(mass%, in Fe)+S(mass%, in Fe) log K=-6.23(±0.56) eSCa=-22.4(±6.4), eCaS=-28.0(±8.0) (at 1 873 K) Using the thermodynamic data derived in the present study, the deoxidation and the desulfurization equilibria of liquid iron by calcium are proposed in the Fe-Ca-O-S system. The deoxidation and the desulfurization limits of liquid iron by calcium are calculated to be 1.6 mass ppm O (at 15 mass ppm Ca) and 3.5 mass ppm S (at 40 mass ppm Ca) under the condition of aCaO=aCaS=1 at 1873 K.