Structure and properties of slags used in the continuous casting of steel: Part 2 specialist mould powders

Abstract

In Part 1, the thermo-physical properties of conventional mould slags used in the continuous casting of steel were reviewed. In Part 2, the properties of mould slags used in specialised continuous casting are collated and examined. The following types of slag have been studied (i) Fluoride-free (ii) Carbon-free (iii) non- Newtonian slags used to cast (iv) high Al steels (v) Ti-stabilised stainless steels (vi) thin-slabs at high speeds and (vii) round billets. The casting problems encountered with each type of slag are outlined and the characteristics of the developed slags described. The empirical rules developed for conventional casting apply to these specialised continuous casting covered here. So values of the viscosity, break temperature and fraction crystalline phase are determined by the mould dimensions, casting conditions and steel grade. Consequently, much of these data were produced in "New powder versus Conventional powder" and tend to have similar property values. However, some systematic studies have been carried out but there are no published values of the density, surface tension and thermal conductivity. The use of non- Newtonian slags provides a new method of improving steel cleanliness and many of the casting problems encountered in the casting of high Al steels have been reduced using calcium aluminate -based slags; however, some further developments are still needed in both cases.