Calculation of Physical Properties for Use in Models of Continuous Casting Process-Part 1: Mould Slags

Abstract

Physical properties of both steels and mould slags are needed as input data for the mathematical modelling of the continuous casting process. Routines for calculating the properties of mould slags and for estimating steel properties have been developed and are described in Parts 1 and 2, respectively. Many mould powders, with differing compositions, are used in casting practice and their properties vary significantly. Reliable models have been developed to calculate these property values as a function of temperature from their chemical composition since this is available on a routine basis. Models have been developed to calculate the following properties: heat capacities, enthalpies, thermal expansion coefficient, density, viscosity, thermal conductivity and surface tension. Solid mould slags can exist as glassy or crystalline phases or as mixtures of the two (i.e. slag films) and the properties for the various phases can vary considerably; methods have been developed to calculate property values for these various states. The software used to calculate the properties is available via the link (i) http://www.mxif.manchester.ac.uk/ resources/software (ii) https://sites.google.com/site/shyamkaragadde/software/thermophysical-properties.KEY WORDS: mould slags; continuous casting; thermophysical properties; steels.carbonates decompose to form CO 2 (g) (ii) Carbon particles in the powder start to oxidise (iii) the oxide components sinter and (iv) then melt when the carbon is consumed, and molten globules mix to form a molten slag pool. Slag from the molten pool then infiltrates into the channel between the steel shell and the mould to form a slag film (Fig. 1); this consists of (i) a liquid layer (ca. 0.1 mm thick) and (ii) a solid layer (ca. 1-2 mm thick). The heat flux between shell and mould is determined, principally, by the thickness of this solid layer (and the amount of crystalline phase present) and the lubrication supplied to the shell is determined by the thickness of the liquid layer. Lubrication involves the following properties: viscosity (η), density (ρ) surface tension (γ) and break (or solidification) temperature (T br ). The heat flux involves the following properties of the mould slag: thermal conductivity (k), T br , the fraction of crystalline phase formed in the slag film (f crys ) and the optical properties of the mould slag.The objective of this study was to develop routines to provide reliable values of the thermo-physical properties of mould slags from their chemical compositions, for input into the model of the continuous casting process. The other aim was to make these routines available as Excel software; open access is provided at (i) http://www.mxif.manchester. ac.uk/resources/software (ii) https://sites.google.com/site/ shyamkaragadde/software/thermophysical-properties. Effect of Structure on Slag PropertiesThe properties of slags are principally determined by the structure of the slag. In silicate slags the basic building ISIJ International, Vol. 56 (2016)block is the Si-O tetrahedron, i...

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