USS122G钢锭真空电弧重熔工艺的数值模拟

 超高强度不锈钢以其超高强度和良好的韧性以及优异的耐腐蚀性能而广泛地应用在航空、航天等领域。真空自耗重熔(VAR)作为生产超高强度不锈钢铸锭的主要生产技术,具有去除钢中有害杂质、改善钢中元素偏析的功能。为了研究新型Cr-Co-Ni-Mo合金体系超高强度不锈钢USS122G的真空电弧重熔过程,通过工艺仿真优化软件(Melf-Flow-VAR),对VAR过程的宏观传热、传质和流动现象进行模拟,建立USS122G合金VAR过程的二维轴对称数学模型,预测了不同冷却速度下的温度场和熔池形貌,并着重分析了特定熔速下的温度场、流场的演变,有无氦气冷却的元素宏观偏析情况,最后以模拟工艺制备了USS122G合金660 mm铸锭进行验证。结果表明,熔速增加,熔池深度加深,熔池形貌由低熔速扁平状圆弧状高熔速深“U”变化,熔炼速率为4.5 kg/min的熔池形貌具有较窄的糊状区,在此熔速下,熔池形貌呈现圆弧状,且真空自耗炉的输入功率较低,流场模拟结果显示流体的流动方向沿边部向下,中部向上,在铸锭右侧呈现顺时针运动规律;模拟熔池在达到稳态后深度为132 mm,此时模拟熔池深度与实测结果基本一致;在熔炼过程中Cr和C元素均发生正向偏析,采用氦气冷却的铸锭中元素偏析程度较小,在距钢锭1/2R处到边部Cr和C元素分布规律与模拟结果吻合较好。本项研究成果为钢的工业化稳定生产提供了可靠的数据支撑。

Numerical simulation of vacuum arc remelting process of USS122G ingot

Ultra high strength stainless steel with its ultra high strength and good toughness and excellent corrosion resistance is widely used in aviation,aerospace and other fields. Vacuum arc remelting(VAR) is the main production technology of ultra-high strength stainless steel ingot,which can remove harmful impurities and improve element segregation in steel. In this paper,the vacuum arc remelting process of a high strength stainless steel USS122G was studied. Through the process simulation optimization software (Melf-Flow),the macroscopic heat transfer,mass transfer and flow phenomena of the VAR process were simulated,and the two-dimensional axisymmetric mathematical model of the VAR process of USS122G alloy was established.The temperature field and morphology of molten pool under different cooling rates are predicted. The evolution of magnetic field,temperature field and flow field under specific cooling rates and the macrosegregation of elements with or without helium cooling are emphatically analyzed. In order to validate the agreement between the model and experiment results,a full-scale USS122G ingot has been prepared. The results show that with the increase of melting rate,the morphology of molten pool changes from flat to semi-circular,and finally to deep U-shape,the molten pool depth becomes deeper gradually. The melting rate of 4.5 kg/min is determined as the actual melting rate,molten pool morphology has a narrow mushy zone,under the melting speed,molten pool morphology presents the arc shape,and the input power of the vacuum self-consuming furnace is low. The flow field simulation results show that the flow direction of the fluid is downward along the edge and upward in the middle,and it moves clockwise on the right side of the ingot. The simulated pool depth is 132 mm after reaching steady state,which is consistent with the measured results. The Cr and C elements have positive segregation,and the segregation degree of the elements in the ingot cooled by helium is small. From 1/2R away from the ingot axis to the edge,the measured element distribution is in good agreement with the simulation results. The research results provide reliable data support for the steady industrial production of steel.