摘要
利用Thermo-Calc热力学软件、金相显微镜(OM)、扫描电子显微镜(SEM)研究了超级奥氏体不锈钢654SMO铸锭的枝晶形貌、元素偏析、析出相等偏析和析出特征,根据合金相图和均匀化扩散动力学曲线提出了超级奥氏体不锈钢654SMO的均匀化处理制度。通过对不同制度均匀化处理后试样的枝晶形貌、残余偏析指数和析出相的分析并结合锻造试验验证,确定了超级奥氏体不锈钢654SMO的合理均匀化工艺。结果表明,超级奥氏体不锈钢654SMO在凝固过程中钼元素偏析最严重,铸锭中心偏析程度大于边缘;钼主要偏聚于枝晶间并促进σ相析出。经1 280℃均匀化处理16 h后,元素偏析基本消除,枝晶充分消融,析出相充分回溶,热塑性得到了显著提升。
The dendritic crystal morphology,element segregation and precipitation behaviors of super austenitic stainless steel 654 SMO ingot were investigated by means of Thermo-Calc calculation,optical microscope(OM)and scanning electron microscope(SEM). Based on the alloy phase diagram and kinetic homogenizing curves,the homogenization treatments of 654 SMO were proposed. Through the analysis of dendritic crystal morphology,residual segregation index and precipitates after different homogenization treatments,combined with forging experiments,the reasonable homogenization treatment of 654 SMO has been determined. The results show that the segregation of Mo was the most serious during the solidification of 654 SMO,and the degree of segregation in the center of ingot was greater than that of the edge. Mo mainly segregated at the dendrite core and promoted the precipitation of σ phase. After homogenizing at1 280 ℃ for 16 h,the segregation of elements was basically eliminated,the dendrite was fully melted,the precipitates were fully dissolved,and the hot ductility of the ingot has been greatly improved.
引文
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