An investigation of the influence of heat transfer on crystallisation processes during electron beam melting and casting of metals

The heat transfer is an important parameter for production of thick metal i ngots with given orientation and grain size. Control of the complex hydrody namics, physics and heat processes will be possible in metal casting if the dependences, concerning the interaction between the liquid pool and the cr ystallisation front, are known. This paper presents some results of our inv estigations on the influence of the beam power and the casting velocity on the crystallisation rate and on the values of the temperature gradient in t he crystallisation front during formation of Al, Ti, Cu blocks with 60mm di ameter in a vertical water-cooled crucible. The influence of the heat conta ct at the ingot wall on the kind of crystallisation front and on the condit ions concerning the orientation of the crystals along the ingot axis is tak en into account. It is shown that the heat contact changes its height and i ts position during the casting process. These changes of the heat contact d epend on the thermo-physical characteristics of the heated metal. Electron beam casting conditions for the metals investigated and conditions for prod uction of ingots with desired structure and smooth surface are optimised. ( C) 2001 Elsevier Science Ltd. All rights reserved.