Measuring Heat Transfer during Twin Roll Casting of Metals

Abstract

Accurate knowledge of the heat transfer coefficient during casting (between a molten and/or semi-solid material and the mold) is critical to be able to develop representative mathematical models for casting process such as Twin Roll Casting (TRC). In this project, an experimental apparatus was developed to enable to measurement of the interfacial heat transfer coefficient (HTC) at the interface between a liquid metal as it solidifies against a chill surface. The experimental apparatus consists of a cylinder and piston surrounded by a heater to melt the metal samples. Pressure can be applied at the top of the piston so that the pressure of the liquid metal at the interface can be varied. The apparatus was instrumented with a number of sensors so that the temperature in both the molten metal and chill surface could be monitored as well as a force sensor so that the interfacial pressure and how it varies during solidification is known. Using the measured temperature time history, the interfacial heat transfer was calculated by using an inverse heat conduction method in conjunction with the known thermo-physical properties of the chill and solidifying metal. The apparatus was tested successfully by using Sn- 7.5%Sb-3.5%Cu alloy as the casting metal solidifying against H13 tool steel chill block. In addition, the effect of different values of chill roughness and test metal superheat were investigated on the heat transfer coefficient.