结合数值模拟与工业试验,研究了脉冲磁致振荡(pulsed magneto-oscillation,PMO)对180 mm × 180 mm的20CrMnTi钢连铸方坯凝固组织和元素偏析的影响.采用COMSOL软件建立连铸坯三维数值模型,计算了 PMO对铸坯流场和温度场的影响.结果表明:PMO作用于铸坯液芯产生双环流,促进了铸坯表面和心部的热交换.在设定的PMO线圈安装位置和生产工艺下,下环流液相过热度消失,有利于游离晶的增殖和长大,从而细化凝固组织并改善元素偏析.试验结果与模拟结果吻合较好,经PMO处理的铸坯中心缩孔数量和尺寸均显著降低,铸坯心部碳偏析指数从1.38降至1.07,Si、Cr、Mn元素偏析基本消除.
Improvements in Solidification Structure and Segregation of 20CrMnTi Steel by PMO
Effect of pulse magneto-oscillation(PMO)on the solidification structure and segregation of elements in continuously cast billet of 20CrMnTi steel measuring 180 mm by 180 mm was studied by using a combination of numerical simulation and industrial test.A three-dimensional numerical model of the continuously cast billet was established by COMSOL software to calculate the effect of PMO on the flow field and temperature field in the billet.The results indicated that PMO acted on the liquid-core of billet to generate a double circulation,promoting heat exchange between the surface and core of the billet.Under the set installation position of PMO coil and casting process,the degree of superheat of the liquid in the lower circulation disappeared,which was beneficial to the proliferation and growth of floating crystals,thus refining the solidification structure and improving elements segregation.The experimental results were in good agreement with the simulation results,and the amount and size of central shrinkage cavities in the billet subjected to PMO treatment were significantly reduced,the carbon segregation index at the center of the billet decreased from 1.38 to 1.07,and the segregation of Si,Cr,and Mn elements was basically eliminated.
pulsed magneto-oscillation20CrMnTi steelnumerical simulationsolidification structuresegregation of element
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