49MnVS3非调质钢连铸方坯中心裂纹分析

采用金相、扫描电镜及能谱分析了连铸方坯中心位置的宏观和微观特征.发现偏析是导致中心裂纹产生的主要原因,裂纹发生在柱状晶末端和粗大等轴晶区,沿一次枝晶晶界展开;开裂方式为沿晶开裂,开裂时期处于液相.存在两种晶界偏析,一种为析出的MnS夹杂物,另一种为聚集的浓化钢液.中心位置析出物未达到非调质钢质量要求. 

Analysis on central cracks in a continuous casting bloom of non-quenched and tempered steel 49MnVS3

Macro- and micro-characteristics at the center of a continuous casting bloom of non-quenched and tempered steel 49MnVS3 were investigated by optical microscopy, scanning electron microscopy and energy dispersive spectrometry. It is found that serious segregation induces a central crack. The crack occurs at the end of columnar grains and the zone of coarse equiaxed grains, and propagates along the boundaries of primary dendrites. The clacking mode is intergranular cracking, which happens in the liquid phase. There are two kinds of grain boundary segregations, one is the precipitation of MnS inclusions, and the other is the concentration of liquid steel. The precipitated inclusions at the central position do not meet the requirements of the non-quenched and tempered steel.