高温加热制度对380CL连铸板坯枝晶偏析及轧材带状组织的影响

通过设计6种热处理工艺和4种热轧工艺分别完成气氛保护热处理试验和热轧试验,借助电子探针面分析和定量分析手段检测板坯热处理前后Mn元素枝晶偏析程度的变化,并比较不同加热制度下板材显微组织的差异,从而分析了高温加热制度对380CL板坯枝晶偏析以及轧材带状组织的影响程度。结果发现:加热温度从1 140 ℃逐步升高到1 300 ℃,热处理前后偏析比变化量从1.65%逐渐增大到3.52%,1 200 ℃时保温时间从0.5 h、1.0 h延长到2.0 h,偏析比变化量从1.79%、2.12%增大到3.59%,即加热温度每升高50 ℃左右,或保温时间延长0.5~1.0 h,枝晶偏析减轻0.1%~1.5%;热轧工艺时加热温度从1 140 ℃升高到1 200 ℃,板材带状组织可减轻1级,带状偏析程度可改善20%左右。

Influence of high temperature heating schedule on the dendritic segregation and rolling banded microstructure of 380CL continuous cast slab

The heating treatment under protective atmosphere and hot rolling tests were conducted by designing six heat treatment processes and four hot rolling processes. The change of dendritic segregation degree of Mn in cast slab before and after heat treatment was measured by electronic probe mapping analysis and quantitative analysis approaches. The microstructure difference of plate samples under different heating schedules was compared. The influence degree of high temperature heating schedule on the dendritic segregation of 380CL slab and rolling banded microstructure was analyzed. It was found that the thange degree of segregation ratio gradually increased from 1.65% to 3.52% after heat treatment when the temperature increased from 1 140 ℃ to 1 300 ℃. If the temperature holding time at 1 200 ℃ varied from 0.5 h and 1.0 h to 2.0 h, the thange degree of segregation ratio would increase from 1.79 %, 2.12 % to 3.59%. In other words, when the heating temperature increased by about 50 ℃, or the temperature holding time prolonged by 0.5-1.0 h, the dendritic segregation would decrease by 0.1%-1.5%. When the heating temperature in hot rolling increased from 1 140 ℃ to 1 200 ℃, the banded structure of plate sample could reduce by one level, and the banded segregation degree could improved about 20%.