RELEASE OF FLUORINE-COMPOUNDS FROM CASTIN G SLAGS

Modern casting powders have to fulfill a number of functions, The righ t properties for problem-free casting must be created by optimum selec tion of the raw materials and of the chemical composition. To attain s everal important properties it is necessary to use fluorine in the for m of fluor-spar and other fluorine-bearing agents. The use of fluorine in siliceous melts can, as experience in other areas and from precedi ng research on this topic has shown, lead to the formation of volatile , water-soluble fluorine compounds, in this respect primarily SiF4. In continuous casting machines, fluorine can accumulate in the secondary cooling water, accompanied by a reduction of the pH-value. In such a medium, plant and equipment components are then susceptible to wear. T o counteract this release of fluorine compounds, it has been possible to show in laboratory experiments not only that there is the ability t o reduce the initial fluorine concentrations. but also that elevated s oda concentrations and an increase of the basicity can reduce the rele ase of fluorine.