CAJ | 학술논문

利用CFD商用软件FLUENT建立了7050铝合金超声半连铸圆坯结晶器的有限体积模型,运用动网格模型对超声作用下的结晶器流场进行分析,重点研究了超声声流现象对结晶器流场的影响.结果表明,在由于粘滞衰减产生声压梯度而形成的超声辐射力的作用下,熔体形成大规模的Eckart声流现象.由于声流速度幅值相比结晶器流场速度幅值和规模很小,因此其对结晶器流场无明显影响.在超声半连铸试验中,浇口流场所形成的涡流把超声工具杆端面下空化作用形成的等轴晶和有效形核质点转移到液穴的其他区域,并且把液穴内远离空化区的熔体带入工具杆空化区域形成新的形核质点,如此往复,在整个铸锭截面内都形成了等轴晶组织.声流场对于超声细晶区域的扩大作用很小,因此可以忽略不计.
이용CFD상용연건FLUENT건립료7050려합금초성반련주원배결정기적유한체적모형,운용동망격모형대초성작용하적결정기류장진행분석,중점연구료초성성류현상대결정기류장적영향.결과표명,재유우점체쇠감산생성압제도이형성적초성복사력적작용하,용체형성대규모적Eckart성류현상.유우성류속도폭치상비결정기류장속도폭치화규모흔소,인차기대결정기류장무명현영향.재초성반련주시험중,요구류장소형성적와류파초성공구간단면하공화작용형성적등축정화유효형핵질점전이도액혈적기타구역,병차파액혈내원리공화구적용체대입공구간공화구역형성신적형핵질점,여차왕복,재정개주정절면내도형성료등축정조직.성류장대우초성세정구역적확대작용흔소,인차가이홀략불계.
The FEM model of the mould for 7050 aluminum semi-continuous casting round billets was built up by CFD software Fluent, and flow filed of the aluminum alloy melts sonicated in the mould was analyzed, focusing on effects of acoustic streaming on the flow field. The results reveal that large-scale Echart acoustic streaming was formed in the liquid phase zone, driven by the radiation force which was formed as a result of the acoustic pressure gradient resulting from the viscous attenuation. As the amplitude and the scale of the Eckart acoustic streaming were much smaller than those of the flow field in the mould, effects of acoustic streaming on the flow filed can be neglected. The vortices from the flow field in nozzle transfer the effective nuclei and equiaxed grains formed in the cavitation area to the other area of the liquid pool and brings the other melt to the cavitation area in turn, forcing the others to be equiaxed grains and effective nuclei, finally, the structures of the ingot are all equiaxed grains. Effects of acoustic streaming on enlarging the refinement area can be negligible in the semi-continuous casting experiment.