高硫易切削钢的硫负偏析现象及其机制

Negative Segregation of Sulfur in High Sulfur Free Cutting Steel and Its Mechanism

钢中硫是正偏析元素,在铸坯凝固过程中,从柱状晶析出的硫元素排到尚未凝固的中心部位会形成连铸坯的中心偏析。通过对某厂生产的X1215易切削钢连铸坯进行碳、硫元素含量检测,发现连铸坯中心处硫元素出现了负偏析现象。基于Scheil方程和[Mn]-[S]反应平衡方程,建立钢液在凝固过程中硫化锰夹杂物析出的计算模型,并以此模型计算X1215钢凝固过程中硫化锰的析出时期。计算发现,X1215钢中硫化锰在凝固分率为0.45~0.50时开始析出,到达凝固末期时析出完成,进而导致铸坯中心处的硫元素产生负偏析。

be discharged from columnar crystal to the liquid center of solidification,causing the central segregation of sulfur in continuous casting slab.Through detecting the content of carbon and sulfur in X1215free cutting steel continuous casting billet produced by a factory,it was found that the sulfur segregation in the center of the billet was negative.The precipitation model of manganese sulfide inclusions during solidification process of liquid steel was established based on the Scheil equation and[Mn]-S]reaction balance equation.And then the precipitation period of manganese sulfide during the solidification process of X1215steel was calculated.It was found that the manganese sulfide in X1215steel began to precipitate at the rate of solidification of0.45~0.50,and completed at the end of solidification,which resulted in negative segregation of sulfur at the center of slab.