Simulation Study On Semi-continuous Casting Of 2219 Aluminum Alloy Hollow Ingots

With the rapid development of China’s military equipment and aerospace exploration and other fields,the performance and size requirements for large aluminum alloy ring and barrel-shaped structural parts are getting higher and higher.The larger the size of solid ingot,the more difficult it is to transfer heat and mass to the core,which will lead to long liquid cavity depth,high stress,serious uneven temperature and flow field,and coarse eutectic organization and agglomeration in the core,which will seriously limit the breakthrough in size and performance of the toroidal structure.The forming process of aluminum alloy hollow ingot is the simultaneous solidification inside and outside,which can fundamentally solve the above problems,and also reduce the subsequent preparation process,improve the metal utilization rate and save resources.Therefore,it is significant to explore the semi-continuous casting of hollow ingots.However,there are not many studies on the semi-continuous casting process of hollow ingots in China,and even fewer studies on the semicontinuous casting process of large-size aluminum alloy hollow ingots.Therefore,in this paper,we use the FLUENT module of ANSYS to analyze the effect of different casting processes on the temperature field,flow field and liquid cavity of the hollow ingot of aluminum alloy in the semicontinuous casting process,taking the hollow ingot of large size 2219 aluminum alloy of Ф800/Ф420 mm as the object of study.This paper provides theoretical guidance for the subsequent experimental studies.The main work and conclusions of this paper are as follows.(1)For the semi-continuous casting process of large-size 2219 aluminum alloy hollow ingots,the corresponding mathematical model is established,the basic assumptions of the simulation are proposed,and the boundary conditions of the simulation are set.The solidification process of the hollow ingot is derived,and the conclusion that the theoretical position of the center of the bottom of the liquid cavity is closer to the inner surface side of the ingot is obtained.The applicable core taper range was calculated to be taken between 1.5° and 3°.(2)By numerical simulation and comparison between the traditional semi-continuous casting melt inflow method with single and double flow channels and the melt inflow method with multiple manifold ports,it is found that the presence of manifold ports minimizes the heat loss before the melt enters the hot top and the difference in circumferential temperature field is basically negligible.The centerline position of the liquid cavity is basically the same for the three flow supply methods,and all of them are biased toward the inner wall side of the ingot,and the offset distance is basically the same,and the offset rate is 8.2% compared with the center position of the wall thickness.The maximum depth change of liquid cavity is 10.5%,22.08% and 2.17% respectively.The setting of multiple flow ports makes the temperature distribution of the ingot more uniform in the circumferential direction,avoiding the formation of local "hot spots" and reducing the circumferential temperature gradient.The circumferential liquid cavity depth variation is minimized.It increases the uniformity of melt flow,makes the melt flow rate in the hot top more evenly distributed,and reduces the impact of the melt on the hot top and the inner crystallizer.(3)Simulation of different casting process parameters.The casting process parameters include casting temperature,casting speed,and cooling intensity.For casting temperature and casting speed,five different temperature values and five different casting speeds were selected for the investigation.The cooling intensity was divided into three groups of variables for the first cooling zone and external cooling intensity,and the second cooling zone and external cooling intensity,respectively.The temperature field and the shape of the liquid cavity under different process parameters were explored,and the corresponding reasonable selection range of casting parameters was proposed according to the results of simulation analysis.(4)Based on the existing experimental results of semi-continuous casting of 2A14 Ф730/Ф330mm aluminum alloy hollow ingots,simulations were carried out for the same specifications of 2A14 hollow ingots.The experimental results are compared with the simulation results and mathematical model to verify the reliability and accuracy of the simulation results of 2219 aluminum alloy hollow casting ingots of Ф800/Ф420 mm size.