Numerical Simulation on the Effect of Conveyor Velocity of the Roller Table on Stress Distribution and Evolution in Large Aluminum Alloy Thick Plates

Abstract

Solution heat treatment combined with a rapid quenching operation, which can effectively suppress the decomposition of the supersaturated solid solution in the matrix, is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties. However, large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates. The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates. The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature. Thus, in the present work, finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process. Four different velocities were utilized in the simulations. The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities. Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.

摘要

固溶-淬火热处理可有效抑制合金基体中过饱和固溶体的分解，是生产具有理想性能的大规格沉淀强化型铝合金厚板的重要工艺步骤。然而厚板淬火过程中，因冷却速度不均匀而产生的巨大温度梯度通常会导致厚板中内部形成严重不均匀分布的残余应力。辊底式淬火炉的出现确保了大规格铝合金厚板连续、整体的固溶-淬火处理。大规格铝合金厚板固溶-淬火处理过程中，淬火炉内部辊道的传送速度是影响厚板内部残余应力分布的一个关键工艺参数，但其在以往的文献中较少涉及。因此，本研究通过考虑辊道的传送速度并采用热力耦合有限元模拟的方法开展了大规格铝合金厚板淬火过程中的温度变化和残余应力分布预测。模拟过程中选用了四种不同的辊道传送速度。结果表明，大规格铝合金厚板淬火处理过程中内部温度演变及其所诱发的残余应力分布受辊道传送速度的影响。较慢的辊道传送速度有助于获得残余应力分布相对均匀的大规格厚板。