低碳Fe--Mn--Si--Al系TWIP钢的显微偏析行为

利用电子探针对实验室以及工厂冶炼的低碳Fe-25Mn-3Si-3Al TWIP钢的显微偏析进行系统性检测.结果表明：该TWIP钢的实验室铸锭和工厂AOD电极锭具有明显的枝晶偏析,其中AOD电极锭的偏析程度更高,Mn和Al的最大偏析量分别高达6．8%和2．4%；AOD电极锭经电渣重熔后晶界偏析显著,偏析程度并没有得到明显减轻；最后经工厂高温锻造成型后的锭坯中晶界偏析得到改善.合金成分高和结晶温度间隔宽是产生较大显微偏析的主要原因.该TWIP钢的所有试样均呈相同的偏析规律,Mn为负偏析,Al和Si呈正偏析,且Al的偏析程度最高.通过Thermo-Calc对该TWIP钢的溶质分配系数进行计算,发现Mn和Al理论预测的显微偏析规律与实验所得的规律完全相反.通过实验验证,得出Si含量是影响Mn和Al偏析规律的决定性因素.

Microsegregation in low carbon Fe--Mn--Si--Al TWIP steel

Microsegregation in low carbon Fe-25Mn-3Si-3Al TWIP steel produced in the laboratory and steel plant were system-atically investigated by electron microprobe analysis. The results show that the dendritic segregation is serious in both the laboratorial ingot and mold casting after AOD steelmaking at the industrial plant. Additionally, microsegregation in the AOD ingot is higher, and the greatest amounts of segregation of Mn and Al are measured to be 6. 8% and 2. 4%, respectively. After electroslag remelting in the steel plant, the grain boundary segregation is serious, and it completely improves after a forging process. A higher alloy composition and a wider crystallization temperature interval are the main reasons for the serious microsegregation. All specimens of the TWIP steel have the same law. Mn shows obvious negative segregation, Al and Si exhibit positive segregation, and Al has the highest degree of segregation. The elements’ solute distribution coefficient K of the TWIP steel was calculated using the Thermo- Calc software. It is found that the microsegregation laws of Mn and Al in theory are opposite to those in the experiment, and the main reason is silicon con-tent.