The measurement of thermophysical properties of molten slags and fluxes

Methods for measuring the thermal diffusivity, thermal conductivity, densit y and viscosity of molten slags and fluxes have been critically reviewed. The most common method for determining the viscosity of slags is the concen tric cylinder method and in particular the rotating bob variant. There is n ow a well established reference material suitable for high temperatures and two standards for the most common materials investigated i.e. glass and mo uld powders. For low viscosities (of the order of 5mPa.s) the oscillating v essel method is suitable. The oscillating plate method has been investigate d extensively for the measurement of mould fluxes by Japanese workers. A ma jor problem is the containment of the slags to prevent unwanted reactions a nd the choice of materials used by a selection of workers is reviewed. Fewer density than viscosity measurements have been made. The most popular methods of determining densities are the maximum bubble pressure (also suit able for determining surface tension); Archimedean and sessile drop methods . There is no corresponding infra structure for density measurements of sla gs as for their viscosities. For the thermal diffusivity/conductivity, the most common methods are the l aser flash and the transient hot wire techniques. The treatment of the expe rimental results is complicated, such as including the effects of radiation for translucent materials. It is clear, if the information is industrially important, there are substantial opportunities for further method developm ent including standardisation and understanding the physical processes of h eat transfer in these materials.