Abstract: Steels, free from hard inclusions which will not deform during hot working, are obtained by introducing into a molten steel under calcium free conditions a silica based slag powder having fluxing components such as manganese oxide which gives a slag of melting point and of density not higher than that of the steel. The slag powder melts and rises through the molten steel interacting with inclusion components, most of which rise to the surface of the melt, so that when the steel solidifies any inclusions remaining are free from calcium and will deform at hot forming temperatures.