轻压下条件下管线钢铸坯凝固组织与中心偏析的关系

 为研究在动态轻压下条件下等轴晶和柱状晶组织与管线钢板坯中心偏析的关系，试验通过改变中包钢水过热度来获得铸坯中心不同凝固组织，并分析不同凝固组织内的中心偏析情况。试验铸坯分别采用热酸腐蚀、化学分析的方法，定性、定量分析过热度在11~32℃之间，铸坯厚度方向上元素含量分布和不同凝固组织中的偏析形貌。结果显示：过热度在14℃以下的坯样中心为等轴晶组织，过热度在20℃以上的坯样中心完全为柱状晶组织；在现有轻压下条件下，中心为等轴晶和过热度为32℃时中心柱状晶组织的坯样中心偏析度均较低，但因铸坯中心整个等轴晶区内会分布着偏析点，因而较之中心柱状晶组织，中心为等轴晶组织中点状偏析分布范围较宽；当中心为柱状晶组织时，适当提高过热度、优化压下量，可降低中心偏析度，提高中心偏析评级。

Relationship Between Solidification Microstructure and Centerline Segregation in Pipeline Steel Slabs With Soft-Reduction Condition

As to study the relationship between the solidification structure and centerline segregation in pipeline steel slabs using dynamic soft-reduction, superheat was varied to obtain different center solidification microstructure, and centerline segregation was analyzed at different solidification microstructure of slabs by chemical analysis and hot acid etching respectively. Element content distribution at slab thickness direction and segregation morphology in the different solidification microstructure were analyzed quantitatively and qualitatively at samples with superheat ranging from 11℃ to 32℃. The results show that center solidification structure with superheat below 14℃ is equiaxed while that with superheat over 20℃ is entirely columnar; at present soft-reduction conditions, samples with equiaxed structure have low center segregation degree as well as columnar ones with superheat of 32℃, but because the segregation points will distribution in the whole range of the equiaxed, so the former has a wide range of segregation points while the later has a narrow one. When the solidification structure is columnar, increasing the superheat and reduction amount properly can reduce the centerline segregation degree and improve the centerline segregation degree.