Refining of steel melts using alkaline earth metals

In secondary refining of steel melts, the use of alkaline earth metals as a slag phase can be of great significance to remove tramp elements of the main groups IV and V. Fundamental data on corresponding refining equilibria and on the solubilities of the alkaline earth metals Mg, Ca, Sr and Ba in iron and iron alloys have been determined by equilibrating the two metal phases, contained in CaO crucibles, under excess argon pressure at 1600°C. The experimental results indicate that tramp elements such as Sn, N, and P are largely transferred from the iron to the alkaline earth metal phase using Ca, Sr or Ba. Equilibrium alkaline earth metal contents are found to be 0.03 % Ca, 0.004 % Sr and 0.0005 % Ba. Solubilities of Ca, Sr and Ba in iron are increased in the presence of Ni and decreased by additions of Cr. In the potential industrial application, reducing conditions must be provided and excessive vaporization must be avoided by adequate techniques of addition of the alkaline earth metals.