A mould with new gas film definition for aluminum alloy in continuous casting was designed

in which the gas film was formed between mould and initial solidified shell

which can decrease the transverse heat transfer in the mould to form approximately single direction heat transfer condition in the billets and to decrease the liquid front depth and to shorten the length of initial solidified shell to eliminate the inner defects in aluminum alloy ingot and to improve the quality of the ingot.The numerical simulation of heat transfer in new mould and conventional mould has been conducted

showing that the remarkable change of temperature field can be observed in the new mould.The continuous casting 7075 aluminum alloy billets with smooth surface can be produced with new mould in the condition of stability and balance of gas film.The relationship of drawing velocity and gas flux with gas pressure as well as their effects on the billet quality have been described.The stability of gas film can be controlled by gas flux in the condition of a constant liquid surface height.