Prediction of Properties of Metals Relevant to Process Simulation

摘要

Industrial metal processes, such as casting, primary production and welding are frequently simulated using physical models which require alloy properties including liquidus and solidus temperatures and fraction solid; properties associated with heat flow: enthalpy, heat capacity and thermal conductivity and properties associated with fluid flow: density, surface tension and viscosity. These properties are required both as a function of temperature and composition. In recent years, significant developments in the experimental methods for measuring these properties have occurred, but their measurement still remains difficult and expensive. These constraints have driven the development of methods for the prediction of the properties based upon the chemical composition of the alloy. The paper describes a software program to predict properties of alloys based upon their chemical composition. The properties included are enthalpy, enthalpy of fusion, heat capacity, density, volume, fraction solid during solidification, solidification range, thermal conductivity, phases formed during solidification and viscosity. Most of the underlying models are based upon thermodynamic calculations using MTDATA, a software tool for the calculation of thermodynamics and phase equilibria developed at NPL. Transport properties such as thermal conductivity and viscosity are difficult to model and for example, thermal conductivity is estimated using empirical relationships. The program has been deliberately designed for the engineer who is not expert in thermophysical properties. The predictions will be compared with measurements for selected alloys.