摘要
通过对PMO处理的连铸GCr15轴承钢固/液界面枝晶形貌和微观偏析的观测,探究了施加PMO对铸坯固/液界面前沿枝晶生长的影响。结果表明:PMO作用于固/液界面处,使枝晶间碳富集程度降低,初生相的面积占比增大,一次枝晶间距减小,二次枝晶臂间距增大,且二次臂细长致密,局部枝晶非对称生长。结合PMO的电磁热力效应分析认为,枝晶生长前沿的温度场和溶质场在PMO作用下出现扰动,固/液界面前沿溶质富集减轻,成分过冷度增大,促进枝晶臂生长,导致初生相占比增大;强制对流使液相温度分布均匀,固/液界面处温度梯度增大,故一次枝晶间距减小;由于垂直于拉坯方向的液相温度梯度减小及微区的磁致振荡效应,柱状枝晶的生长方向发生改变,干扰了枝晶间富集溶质的扩散,进而造成了枝晶的非对称生长。
Influence of PMO on the dendrite growth behavior at solid-liquid interface of GCr15 bearing steel during continuous casting was investigated by observing dendrite morphology and micro-segregation.The results showed that when PMO acted on the solid-liquid interface,the carbon concentration among dendrites decreased,the area fraction of primary phase increased,the primary dendrite spacing decreased,the secondary dendrite arm spacing increased,whose arm was slender and dense,and the local dendrites grew asymmetrically.Combined with the analysis of the electromagnetic thermodynamic effect of PMO,it was considered that the temperature field and solute field in the front of dendrite growth were disturbed by PMO treatment,resulting in the decrease in solute concentration in the front of solid/liquid interface,and increase in compositional undercooling degree,which promoted the growth of dendrite arm,thus resulting in the increase in the area fraction of primary phase.Due to the decrease of temperature gradient in liquid phase perpendicular to the drawing direction and the magneto-induced oscillation effect in micro-region,the growth direction of columnar dendrites changed,which interfered with the diffusion of solute enriched among dendrites,thus resulting in the asymmetric growth of dendrites.
作者
张伶玲
石昊
徐衡
仲红刚
翟启杰
ZHANG Lingling;SHI Hao;XU Heng;ZHONG Honggang;ZHAI Qijie(School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China)
出处
《上海金属》
CAS
北大核心
2019年第5期73-80,共8页
Shanghai Metals
基金
国家自然科学基金(No.U1760204)
关键词
脉冲磁致振荡
连铸
枝晶
碳偏析
pulsed magneto-oscillation(PMO)
continuous casting
dendrite
carbon segregation
