Research On Heat Transfer And Deformation Of Injection Mechanism Of Die Casting Machine Under Fluid-Thermal-Solid Coupling

Die casting machine is an important platform to realize the integration of material preparation and parts forming.The injection mechanism is one of the core components of die casting machine,which mainly includes plunger tip and shoot sleeve.The injection mechanism services for long-term under the condition of high temperature,high pressure and high speed.It bears mechanical load and alternating thermal load,and is prone to thermal deformation and thermal fit failure.In this paper,a method for temperature control by applying cooling water to the plunger tip is adopted.It can improve the temperature distribution and thermal deformation failure of the injection mechanism and provide guidance for design and application of the injection mechanism.In this paper,the heat transfer and deformation laws of the injection mechanism were studied by a combination of numerical simulation and experiment under fluid-thermal-solid multi-field coupling.Also,the reasonable cooling water parameters were selected.The major research contents and conclusions are as follows:(1)Based on Fluent,using VOF multiphase flow and dynamic mesh technology,the flow and heat transfer model of molten metal and the cooling model of plunger tip were established.The free surface evolution,phase and velocity distribution,and three-dimensional temperature field of molten metal were obtained.The results show that the molten metal has thermal impact on the shoot sleeve.Axial motion is accompanied by backflow.The temperature of molten metal is distributed in a gradient along the axial direction,and residence time is required after pouring.During injection phase,molten metal surface presents a wavy shape,and the core temperature maintains well.As the turbulent cooling water velocity increases,the heat exchange time between the cooling water and the wall is relatively shortened,but the heat transfer coefficient increases,the exchange efficient improves,and the outlet temperature decreases.(2)Based on Workbench,one-way fluid-thermal-solid coupling calculation was realized,and the distribution laws of the temperature field,stress field and deformation were obtained.The results show that the axial temperature at the top of the shoot sleeve is distributed in a "U" shape.The inner temperature is much higher than the outer,and the circumferential temperature gradient decreases along the axial direction.The inner equivalent stress is greater than the outer,and the stress is gradient distribution along the radial direction.The cross section of the deformed shoot sleeve changes from circle to ellipse.The equivalent stress of the plunger tip decreases with the increase of the radial length,and the temperature and deformation are uniformly distributed in a gradient along the axis direction.The deformed cross section remains approximately circle,and the deformation direction is the normal direction of respective nodes.(3)Through APDL to realize time history post-processing,the deformation and dynamic thermal fit laws of injection mechanism under different cooling water velocity were obtained.The results show that the cooling water effectively improves the temperature and deformation amplitude of the plunger tip.With the increase of cooling water velocity,the temperature rise and deformation reduction of the plunger tip decrease,the thermal fit clearance tends to be stable,and the cooling water velocity is close to the thermal saturation zone.Considering factors of energy loss and cost,the optimal cooling water velocity parameter is determined.(4)Based on the simulation results,K-type thermocouple and blind hole method were selected to build a real-time temperature measurement platform of the injection mechanism.Node deformation was calculated based on the measured temperature.The results show that the change rules of the simulated temperature value are consistent with the experimental values',and the error between the calculated value of the node deformation and the simulated value is within a reasonable range.The cooling water has no obvious effect on the amplitude change of thermocouple A and B.The temperature rise of thermocouple P1 decreases significantly,the response time to peak temperature is shortened,and the node deformation of the plunger tip is reduced.All verify the reliability of the numerical mode of heat transfer and deformation of injection mechanism,the effectiveness of the temperature control method and the rationality of the cooling water velocity selection.