Experimental Study on Inclusions Control of Resulfurized Free Cutting Steel

In this paper,the effects of calcium treatment and magnesium treatment on characters of inclusions in resulfurized free cutting steels were studied by high temperature experiments. The results show that the main types of inclusions after calcium treatment are Ca-Al-O + （Ca,Mn）S complex inclusions, （Ca,Mn） S and MnS. Meanwhile,the main types of inclusions after magnesium treatment are MgAl₂O₄⁺ （Mg,Mn） S,Al₂O₃+ MnS complex inclusions, （Mg,Mn）S and MnS. The proportions of complex inclusions after calcium treatment and magnesium treatment are 0.67% and 3.57%,respectively. The amounts of type II MnS inclusions in the steel are obviously reduced after Mg treatment,and 91.7% of the inclusions are smaller than 3 μm in size. Furthermore,the ratio of spindle inclusions reached 72.5%. Therefore,the effect of controlling inclusions by magnesium treatment is superior to calcium treatment.