Removal of tramp elements from molten iron for recycling ferrous scraps

The possibilities of removing impurities from molten iron by oxidation and evaporation, which are usual methods in metal refining, are firstly investigated. Of all the elements which are dissolved in molten iron, Cu, Sn Ni, Co, Mo and W are found to be difficult to be removed by such usual methods as oxidation and evaporation. The elements which are difficult to be removed in steelmaking when they are once dissolved into molten iron are called “tramp elements”. In recycling ferrous scraps, to begin with, it is important to keep iron from being mixed with tramp elements. But, it is necessary to develop a method to remove tramp elements, because it is impossible to avoid the contamination of these elements completely. In this work, several prospective methods to remove such tramp elements are discussed. Copper, which is one of the key tramp elements in iron, can be removed by evaporation or by sulfurization, although it is not enough to apply them in practical use. As other methods, in this work, the possibilities to remove copper from molten iron by oxidation and by the use of calcium are proposed. It is found that copper and tin in iron can be decreased at the content of 0.2 to 0.4mass% and under 0.001mass%, respectively by oxidation. If pure calcium is equilibrated with iron directly at 1823K, the high distribution ratios, L_Sn(mass) (=(mass%Sn)_{in Ca-Pb/}[mass%Sn]_{in Fe}) = 3400 and L_Cu(mass) (=(mass%Cu)_{in Ca-Pb/}[mass%Cu]_{in Fe}) = 200 are expected.