Effect Of Injection Speed On Filling State And Porosity Of Aluminum Alloys

The flow behavior of molten metal in the process of die-casting molding affects the quality of die-castings.It is of great significance to study the flow behavior of molten metal in the cavity under different process conditions for achieving smooth filling and obtaining high-quality castings.At present,the main research methods of flow behavior in die casting process include computer numerical simulation,water simulation and X ray method.Usually,the numerical simulation of the computer can not fully meet the actual working conditions.The water simulation can not reflect the high temperature flow characteristics of the aluminum alloy liquid.The X ray has a low scanning efficiency and the limitation of the penetration ability.Therefore,it is necessary to study the real-time flow process of die casting.This subject takes the A356 aluminum alloy high-speed filling process as the research object to study the effects of different injection velocities on the filling flow state and porosity of aluminum alloys in combination with numerical simulation,through high-speed dynamic real-time detection and analysis of aluminum alloy filling flow process.There are main conclusions of the paper :(1)The time difference between the time point of sudden change in the flow state of the aluminum liquid filling process and the time point of the transition from the slow shot to the fast shot of the injection punch speed curve is 20 ms,9 ms,and-1 ms.With the increase of injection speed,the viscosity of high-temperature aluminum liquid increases slowly,and the time node of the video tends to be consistent with the velocity curve node.The time difference between the contact sensors in the runner is 40 ms,38ms,and 37 ms,and the flow of the molten aluminum in the runner is stable.(2)After the molten metal enters the cavity,it fills the cavity in sequence.Before the rapid injection starts,the metal liquid is filled smoothly,and after the rapid injection starts,the molten metal is sprayed and filled from the position of the inner gate.The metal liquid appeared discontinuous flow,and then atomized to form a thin shell layer.In the later stage of filling,the metal liquid gas curling phenomenon intensified and turbulence appeared.(3)Comparing the video and simulation process analysis,the position of the final filling of the molten metal in the video and simulation is consistent.There is an error between the theoretical model of numerical simulation and the actual model during the injection-type filling process.The aluminum liquid is in a continuous state and there is no atomization phenomenon in the numerical simulation.(4)In the study of gas entrainment in the vortex area,the porosity in the vortex area was 20.79%,9.91%,and 11.14%,respectively,as the injection rate increased from 0.88m/s and 1.59m/s to 2.34m/s.The trend of decreasing first and then increasing.The average grain size of the largest pores was 1488 um,823.6um,and 1179.75 um,decreasing first and then increasing.