Study On Air Knife Direct Chill Casting Of High Strength Aluminum Alloys

Effective water flow and utilization rate of second cooling water was studied in this paper, and the effects of process parameters of air knife on blowing second cooling water are investigated, which can determine the optimize process parameters of air knife blowing second cooling water. the melt flow, heat transfer, stress and strain fields of ingot with section of550mm×1600mm under semi-continuous casting with air knife are studied by means of numerical simulation method.The influence of distribution mode of the melt, cooling mode of second cooling water and parameters of air knife on semi-continuous casting process with air knife are discussed in detail. Through analysis the results of simulation and experimental, the conclusions obtained as flows:(1) The utilization rate of second cooling water decreases with the increase of water flow and spray angle; the utilization rate of second cooling water improved with uneven surface state; the appropriate flow of small-angle cooling water can increase the utilization rate of large-angle cooling water;(2) Simulation result shows that:the near-wall maximum pressure decrease with increase of the distance from the wall; Near-wall maximum pressure increases first and then decreases with the increase of the air knife angle, near-wall maximum pressure appears with air knife angle of30°.(3) Critical blowing air pressure increases with the increase of the distance between air knife and wall; meanwhile it decreases first and then increases with the increase of spray angle, the best spray angle is30°.(4) The usage of square distributor with filter can well-distribute flow of melt in the molten pool and decrease sump depth; different water flow in big face and small face benefits to temperature uniformity in ingot, and the reduction of side crack,; the sump depth increase with the reduction of amount of cooling water; the ingot surface temperature rise in the present of air knife, thereby the temperature gradient within the ingot reduced; the sump depth and the recovery temperature of surface increase when the position of air knife moves upward; the Mises plastic stress and strain decrease in the present of air knife in the ingot.(5) Experimental studies shown that:the occurrence of cracks reduced observably with air knife, but the grain size increased in the semi-continuous casting process.The results in this paper show that DC casting with air knife is a new, simple, high efficient, economical method for producing the super-strength aluminum alloys ingots without any cracks. With this method, the difficult problem of producing ingots of high strength aluminum alloy with high alloy elements, which restrains the development of the domestic aluminum industry, is solved effectively.