Effect Of Oscillation On Flow Field And Temperature Field During The Twin-roll Strip Casting Process

Twin-roll casting is a proven technology for economical production of thin stripdirectly from the melt. The advantages of this casting technique are numerous—reducedcapital costs, energy consumption, operating costs and scrap rate compared with aconventional casting route. In recent years, many researchers and companies have paidgreat attention to the thin-roll strip casting. Despite its large potential, twin-roll stripcasting is difficult to control; in all the cases, the high productivity regimes lead to theformation of microdefects (nonuniform texture, coarse grain size, high columnar crystaland center segregation) as well as poor mechanical property. Based on theabove-mentioned defects, our team have designed and manufactured the oscillatingtwin-roll strip caster. The operating principle of this machine is to change flow field of themolten pool by roller oscillating, and then to make some influence on the stripsolidification process. Finally the oscillation has achieved the purpose of improving thequality of the strip.According to the numerical model of conventional twin-roll strip casting and thecharacteristic of the oscillating twin-roll strip caster in the lab, a numerical model coupledwith heat transfer, fluid flow, solidification and oscillation has been developed by usingthe multiphase flow technology. At the same time, a thermal boundary condition which isadapted to the oscillating twin-roll strip casting has been developed. Further more, basedon the modeling of conventional twin-roll strip casting, a transient algorithm has beenused for simulating the oscillating twin-roll AlSi9Cu3aluminum alloy strip castingprocess.In this study, the main innovations are as follows:The effect of oscillating parameters on flow field during the twin-roll casting,especially the velocity distribution of center line in the molten pool has been explored.During the research, it has been found that the scale and intensity of center line’s velocityin the molten pool increase as well as the amplitude or frequency increase. Meanwhile,comparing with the grain size which are made of conventional twin-roll strip casting andoscillating twin-roll strip casting, the point that oscillation is of great advantages to decrease grain size and homogeneous distribution of strip impurity has been validated.Based on oscillation, the distribution of center line’s velocity in the pool as well asthe distribution of turbulence energy in the free liquid surface has been explored when theangle of submerged entry nozzle and the thickness of rolling gap are changed.Based on oscillation, the temperature distribution of strip outlet and the position ofkissing point have been studied when the oscillating parameters are changed.