Effect of Bismuth and Telluride on the Inclusions of Sulfur Free-Cutting Steel

The development of free-cutting steel is inseparable from the environmentally friendly alloy elements and control inclusions shape. Alloying can affect composition, morphology, size, distribution inclusion, which are main factors affecting machinability steel. This study selected sulfur with different chemical compositions as research object to examine effects bismuth tellurium on sulfur-containing through electrolytic corrosion experiments, metallographic microscopy, scanning electron energy spectrum, backscattering analyzer. results showed that microstructures free-cutting-steel containing sulfur, bismuth, composed ferrite, pearlite, inclusions. in chain, cluster, a few dotted MnS. sulfur-bismuth point After addition Te, number reduced, while chain cluster increased. Most bismuth-containing flake inclusions, class II MnS change into III MnS, beneficial for improving property reduce anisotropy. With other shapes, such heart, water drop, butterfly, etc. length–width ratio less than 4 also appeared MnTe complex fusiform manganese sulfide accounted most Both Bi Te had modification