Physical properties of casting powders: Part 1. Scheme to represent chemical compositions of powders

A model is presented which allows the chemical compositions of casting powders to be represented by a pseudoternary system of (i) network formers (denoted 'SiO2'), (ii) network breakers (denoted 'CaO'), and (iii) fluorides (denoted 'NaF'). Using this model, liquidus temperatures and viscosities can be read directly from the isoproperty contours of these pseudoternary diagrams; however, in the rare cases where %Na2O>1.63(%F) it is necessary to make adjustments for the 'excess Na2O' present in the slag. The pseudoternary diagrams have been used to present data for the erosion of submerged entry nozzles (SENs). It is shown that the increased erosion observed with decreasing slag viscosity is a consequence of the factors defining the Marangoni number which, in turn, determines the velocity of the Marangoni flow at the SEN/slag/metal interface.