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应用B ridgm an区域熔炼定向凝固设备制备出不同抽拉速度下的定向凝固易切削钢9SMn28。利用光学显微镜、扫描电镜及电子探针显微分析仪对所得试样中的夹杂物及树枝晶进行了观察,并通过凝固理论对其进行了计算和分析。研究发现,9SMn28钢中的夹杂物主要以MnS的形式存在,普遍聚集在树枝晶间隙之中,其形态以球形为主,在二次枝晶臂周围也存在少量纺锤状和条状的夹杂物,其尺寸随抽拉速度的增大而减小。二次枝晶臂间距的计算结果与测量结果比较吻合,同样随抽拉速度的增大而减小。
The directional solidification free-cutting steel 9SMn28 with different drawing speeds was prepared by Briminal’s zone smelting directional solidification equipment. The inclusions and dendrites in the obtained samples were observed by optical microscopy, scanning electron microscopy and electron probe microanalysis, and were calculated and analyzed by solidification theory. It is found that the inclusions in 9SMn28 steel mainly exist in the form of MnS and generally gather in the interdendritic interstices. The morphology of the inclusions is dominated by spheres. There are also a few spindle-shaped inclusions around the secondary dendrite arm , Its size decreases with the increase of drawing speed. The calculation results of the secondary dendrite arm spacing are in good agreement with the measurement results, and also decrease with the increase of the drawing speed.