Numerical Investigation into the Influence of Overheating of Aluminum Melt on the Heat Exchange in the 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.

Numerical Analysis of the Non-Stationary Thermal State of the Tool in the Combined Casting and Extrusion of Non-Ferrous Metals 

“…The supply of liquid metal into the groove, its solidification and extrusion proceed in a continuous mode [27]. 1die stopper; 2press product; 3stationary arcuate segment; 4solidified ingot; 5metal melt; 6dispenser; 7crystallizer wheel; 8annular groove A necessary condition for combining continuous casting and extrusion of metal is the observance of such thermal conditions in the "metal-crystallizer-environment" system, which ensures the solidification of the melt and stabilization of its temperature in the section in front of the container [28][29][30]. An analysis of the thermal regimes of continuous casting before extrusion of aluminum alloys carried out on the basis of the method proposed in [31,32] that confirmed this statement.…”

“…At the same time on the basis of computer simulation it was found that the degree and rate of heating of the crystallizer in the initial period of operation of the installation have the main effect on the nature of unsteady heat transfer and changes in the enthalpy of the melt [33,34]. As a result, operational and design solutions were proposed that ensure rational temperature-time conditions for the installation at a fixed design rotational speed of the mold (the productivity of the installation in terms of the mass flow rate of the melt poured in) in a long-term stable period of its operation [29,30].…”

Numerical analysis of the non-stationary thermal state of the tool in the combined casting and extrusion of aluminum alloy

“…The supply of liquid metal into the groove, its solidification and extrusion proceed in a continuous mode [27]. A necessary condition for combining continuous casting and extrusion of metal is the observance of such thermal conditions in the "metal-crystallizer-environment" system, which ensures the solidification of the melt and stabilization of its temperature in the section in front of the container [28][29][30]. An analysis of the thermal regimes of continuous casting before extrusion of aluminum alloys carried out on the basis of the method proposed in [31,32] that confirmed this statement.…”

“…At the same time on the basis of computer simulation it was found that the degree and rate of heating of the crystallizer in the initial period of operation of the installation have the main effect on the nature of unsteady heat transfer and changes in the enthalpy of the melt [33,34]. As a result, operational and design solutions were proposed that ensure rational temperature-time conditions for the installation at a fixed design rotational speed of the mold (the productivity of the installation in terms of the mass flow rate of the melt poured in) in a long-term stable period of its operation [29,30].…”