Effect of Electropulsing Treatment on the Formation of MnS Inclusions in SUS303

Electropulsing treatment was imposed on SUS303 free-cutting steels to analyze the evolution of MnS inclusions. SUS303 steels were treated in argon atmosphere under various conditions: before the formation of MnS inclusions (1773 K), at the beginning of the formation of MnS inclusions (1678 K), and after the formation and growth of MnS inclusions (1583 K). The results show that the sizes of globular MnS inclusions decrease with an increase of current density when the electropulsing treatment is treated in the melting stage. Meanwhile, electropulsing treatment restrains the growth of inclusions due to the different conductivities between the molten steel and MnS inclusions when electropulsing treatment is treated in the solidification process. However, the number of fine rodlike MnS inclusions increases with the increase of current density in the samples treated in the inclusion nucleation stage and solidification stage because the reduction in chemical potential produced by electropulsing treatment will require less undercooling. Experimental data demonstrate that the application of electropulsing treatment is a fantastic new method to control the morphology and size of MnS inclusions in the melting stage.