Heat transfer behavior of molten iron and nickel during the first 0.2 seconds of solidification

Abstract

This study aims at developing a fundamental understanding of the factors controlling strip casting. Heat transfer behavior of molten iron and nickel during the first 0.2 s of solidification has been clarified experimentally. The transient phenomena during solidification were successfully observed using a photo-sensor to measure cast surface temperatures and one wire thermocouple technique to measure the copper plate temperatures. T-type thermocouples were employed as one wire thermocouple method. The following results were obtained by this study. The molten metal ejected from a silica tube was kept as liquid state during the first 0.02 s along with undercooling after which recallescence took place. In addition, fluctuations in temperatures of the cast surface and inside the copper plate, that were co-related each other, were observed during recallescence. The copper plate temperature could catch up with the cast surface temperatures at the plate side thanks to one wire thermocouple technique where one constantan wire was set inside the copper plate. The peak values of heat fluxes were found to be higher with higher superheat of the molten metal. Almost constant values of 10000 (kW/m2) were obtained over 55°C while 3 500 (kW/m2) at 40°C in superheat. According to the results comparing the temperatures of the cast surface and the copper plate, the peak point of the heat flux physically implies how long molten metal state is kept as for solidification of metal.