定向凝固研究易切削钢中硫化物的生成行为

Study on the formation behavior of sulfides in free-cutting steel by unidirectional solidification

通过定向凝固实验研究了易切削钢中硫化物的生成过程,并建立了枝晶臂间距、硫化物的平均直径与凝固条件之间的关系.实验结果表明:随着温度梯度和拉速的增大,MnS的平均直径减小,数量增多;定向凝固过程中硫化物的完全析出温度大约在固相线温度下100℃左右,MnS形态的改变,主要受其组成元素的活度影响,即MnS形态的改变受其界面自由能的影响;对定向凝固实验中钢的枝晶臂间距、硫化物的平均直径与凝固条件的关系进行了拟合,拟合结果与前人研究结果相吻合.

The formation behavior of sulfides in free-cutting steel was investigated under unidirectional solidification.The relations of the dendrite arm spacing and sulfides＇ average diameter to solidification conditions were established.Experimental results show that the average diameter of MnS inclusions decreases with increasing temperature gradient around the solid/liquid zone and casting speed,but the number of MnS inclusions increases.The complete precipitation temperature of MnS is about 100 ℃ lower than the solidus temperature.The morphological changes of MnS are mainly effected by the activities of constituent elements,in other words,they are mainly influenced by interfacial energy.The relations of the dendrite arm spacing and sulfides＇ average diameter to solidification conditions were regressed,and the regression results are basically in agreement with the ones of previous researchers.