加热过程中硫系易切削钢中Mns夹杂物行为的动态原位观察

IN SITU OBSERVATION OF MnS INCLUSION BEHAVIOR IN RESULFURIZED FREE-CUTTING STEEL DURING HEATING

以高硫易切削钢轧材中大尺寸、长条状MnS为例,利用高温激光共聚焦扫描显微镜观察了加热过程中MnS夹杂物的演变过程,并分析了升温速率对MnS形态演变的影响.研究表明,在加热过程中,经轧制伸长的大尺寸MnS发生了径向收缩、轴向分裂,使其长度减小、形态趋近纺锤形.当升温速率在0.5—2℃/s时,随着升温速率的增加大尺寸细长MnS的分裂程度逐渐降低;当升温速率增加至6—10℃/s后MnS基本不再发生分裂.

MnS is a common type of non-metallic inclusions in steel,which is of good deformability during rolling.As elongated MnS inclusions in rolling direction often cause poor mechanical property of steel.However,MnS is indispensable in resulfurized free-cutting steel.In order to improve mechanical property,especially cutting property of free-cutting steel,the good control of shape and size of MnS is important.In this study,confocal scanning laser microscope was used firstly to observe the morphology evolution of large-sized slender MnS during heating.The effect of heating rate was also considered.The results indicated that for morphology evolution of MnS,the shrink occurred in longitudinal direction,whereas expansion and contraction happened in radial direction,which finally caused the split of slender MnS.When samples were heated at the rate between 0.5-2℃/s,the split degree of MnS decreased with the increase of heating rate.When the heating rate was in the range of 6-10℃/s,the splitting behavior of MnS could not occur.