Effect of tellurium and bismuth on inclusions in 430F free cutting steel

In order to investigate the impact of different Te and Bi contents on the size and distribution of sulfides in 430F freecutting steel, the inclusions were observed and counted by Zeiss metallographic microscope, and the morphology and composition of the inclusions in the samples were compared by scanning electron microscope. The results show that the equivalent diameter of the inclusions in 430F steel is 6.07 μm. With the increase of Te content, the size of sulfides in the steel increases, and the uniformity of sulfide distribution is significantly improved. The inclusions in the steel are mainly MnS and MnS-MnTe, and MnS-MnTe is spindle-shaped or spherical. With the increase of Bi content, the size of sulfides in the steel decreases. The inclusions in the steel are mainly MnS, Bi-MnS and Bi distributed alone. The existence forms of Bi-MnS in steel can be divided into three types: Bi is distributed on the surface of MnS; Bi is wrapped around MnS; Bi completely wraps MnS.