以直径20 mm,包覆比50%的银包铝细棒为研究对象,通过有限元数值模拟以及相应的实验验证,得出了银包铝复合材料立式连铸复合成形工艺的边界条件.采用ProCAST软件模拟了立式连铸成形过程,得出各工艺参数对连铸结果的影响规律,给出了可行的连铸工艺参数范围及工艺调控策略,以模拟结果为指导,制备出表面质量高、复合界面效果良好的银包铝复合棒材.实验结果表明,芯管长度、连铸速度对结果的影响最大,芯管长度影响了芯管出口处双金属的接触温度、接触时间,并直接改变了铝芯固液界面的相对位置.当芯管长度过短时,银铝界面反应较强烈,当芯管长度过长时,芯棒冷却强度大,芯部铝产生明显的冷隔.随着连铸速度的增大,银的固液界面到芯管出口距离逐渐减小,铝的固液界面距出口距离逐渐增大;铝液铸造温度升高,冷却水减少也会带来相似的作用.结果显示,芯管长度30 mm,速度37~67 mm·min-1,银的铸造温度1225~1325℃,铝的铸造温度800℃,冷却水流量约300 L·h-1是可行的银包铝连铸工艺.
Silver clad aluminum composite wire, which combines the high electrical conductivity of silver-coated metal, good welding performance, and low density, has wide application prospects in aerospace and other fields. The preparation of silver clad aluminum bars with high surface quality and good combination of interfaces is an important step in the preparation of silver clad aluminum wire with excellent performance. Continuous casting composite forming is a short, high-efficiency material-forming process, which provides methods for the preparation of silver clad aluminum. The boundary conditions of the vertical continuous casting process of silver clad aluminum composite rod that has a diameter of 20 mm and cladding ratio of 50% were established through finite element numerical simulation using the ProCAST software and corresponding experiments. The effect of each process parameter on continuous composite casting was analyzed, based on which the optimized control method was obtained. A silver clad aluminum composite rod with high surface quality and excellent bonding interface was prepared on the basis of the simulation results. The length of the core tube and the speed of continuous casting are considered to be the most important factors affecting the formation process. The length of the core tube is assumed to affect the contact temperature and time of the aluminum liquid and silver tube at the end of the core tube, and result in the variation of the relative position of the solid-liquid interface of the aluminum. The interface reaction is severe when the core tube is too short. Conversely, significant cold separation occurs in aluminum because of the high cooling intensity when length of the core tube is too large. The actual casting temperature increases with the high continuous casting speed, which can be attributed to the reduction in the distance between solid-liquid interface and the outlet of the core tube for silver and the increase for aluminum. The increase in aluminum casting temperature and reduction in the flow rate of cooling water are found to have a similar effect to that of the increase in continuous casting speed. A series of optimized casting parameters was obtained in this study, i.e., length of the core tube 30 mm, the casting speed is 37-67 mm·min-1, the casting temperature of silver is in the range between 1225℃ and 1325℃, casting temperature of aluminum is 800℃, and the flow rate of cooling water is 300 L·h-1.