Numerical investigation of influence of overheating of molten aluminum and heat transfer in continuous combined casting and pressing

Abstract

The results of a numerical investigation into the temperature–temporal dependences in continuous combined casting and pressing of the AK12 experimental aluminum alloy at a different overheating temperature from startup to the instant the steady-state thermal conditions are reached by the installation are reported. Calculations are performed based on a three-dimensional computer model of a complex heat exchange in an installation of a new design equipped by a horizontal rotary crystallizer. Theoretical investigations into the effect of overheating of the poured aluminum melt on the temperature-dependent heat exchange processes are performed. The influence of the character of the heat exchange in the transient thermal mode on the temperature field of the solidified melt for its different remoteness from the pouring point is determined. It is shown that the asymmetry of the temperature field in the control metal cross section near the pressing tool with the maximal temperature to the contacting crystallizer surface increases during crystallizer heating in the transient process. It is established that the duration of the transient process during the installation startup from the cold state until the steady-state thermal mode is attained depends on the temperature of the melt being poured. The maximal limit of overheating of the poured metal is determined, above which, when implementing the continuous combined casting–pressing technology, the aluminum melt does not solidify in the crystallizer and forced cooling of installation elements should be organized. The influence of melt overheating on the character of the temperature field along the crystallizer cross section is evaluated for the entire period of the transient thermal process. The design measures ensuring the rational temperature working conditions of bearings during the installation operation are given.