【摘要】 采用摄影法和电触点法对薄壁镁合金零件的充型特征进行了系统研究.实验结果表明,在低真空度条件下,镁合金呈拱形层状推进,其充型速度随充气流量的变化而变化.过小的充气流量会造成金属液充型速度较小,产生浇不足缺陷,而充气流量过大则会使金属液流动前沿不平稳,产生气孔缺陷.真空度有利于砂型紧实和热解产物的传输,但过高的真空度使金属液呈凹槽形推进,不利于热解产物的溢出,在铸件末端产生集中性气孔缺陷.因此,镁合金真空低压消失模铸造最佳的充气流量范围为3~4 m3/h,真空度低于0.02 MPa.更多还原

【Abstract】 The metal filing process and the effect of inserting gas flux on the filling rate in the expendable pattern casting(EPC) process with low pressure were investigated.The results show that the molten magnesium alloy filled the mould with a convex front laminar flow and the metal filling rate increased significantly with the incensement of gas flux when inserting gas flux was lower than 3m~3/h under condition of vacuum level of 0.02MPa,but once the gas flux exceeded 3m~3/h,the filling rate would increase slightly.Meanwhile,slower melt filling rate would lead to misrun defects,while higher filling rate resulted in folds,blisters and porosity.The experimental results showed also that too higher vacuum level would cause concave filling profiles in lowpressure EPC casting process,which would increased the risk of pore defects in the castings.The optimum inserting gas flux is 3～4m~3/h and lower than 0.02MPa of vacuum level in the low-pressure EPC casting process.更多还原