Real-time Observation Of Shock Absorption Tower Filling Process And The Analysis Of Gas Entrainment In HPDC

Air entrainment defects make that the mechanical property of die-castings cannot be improved by heat treatment during die casting filling process,which limits the application of die castings in high performance components.Numerical simulation can predict die casting filling process and air entrainment defects.However,the complicate flow pattern of the filling process and the difficulties in experimental verification,especially in the thin-walled complex die-castings,result in the differences between the actual filling process and the numerical simulation.So in this paper,shock absorption tower is the research object,and pure aluminum and A380 aluminum alloy is the research material.The filling process is observed in real time at different fast shot velocities.Meanwhile,the differences in flow pattern between the actual filling process and the numerical simulation are compared.Combined with porosity measurement,the location and size of air entrainment defects are analyzed and predicted.The following conclusions are gained:(1)In the slow injection stage of liquid pure aluminum,the numerical simulation agrees with the flow pattern observed in real time.With the advance of die filling,when the liquid aluminum appears fragment or atomization,the real-time observation results are different from the flow pattern simulated by numerical simulation.(2)By observing the filling process of pure aluminum in real time and measuring porosity,it is found that the junction of the two streams of liquid metal would create larger porosity.When the injection velocity is changed,the position of the two streams of liquid metal meeting is obviously changed.In addition,when liquid aluminum flow around two staggered cylinder,the region submerged in the wake of circular cylinder would produce greater porosity,and the injection velocity has a significant impact on the size and location of the wake region.(3)By the real-time observation of A380 aluminum alloy filling process and the measurement of porosity,it is found that the final filling position of liquid aluminum is different under different injection velocities,and the porosity is larger at this position.At the same injection velocity,the porosity at the center of the recirculation zone is greater than that at the last filling position.In addition,it is found the air entrainment defects are generated in the wake region of the cylinder,and the location of air entrainment defect migrates obviously as the filling process goes on.(4)By comparing the filling process of pure aluminum with that of A380 aluminum alloy,it is found that breakup degree of pure aluminum is larger during the filling process,resulting in that the porosity of pure aluminum is greater than that of A380 aluminum alloy at each observation position.