Control of Bismuth and Manganese Sulfide Inclusions in Free-Cutting Steels of Different Classes

The paper investigates the behavior of bismuth and sulfur in modern free-cutting steels. It is shown that today there are no mutually consistent thermodynamic data for calculating the solubility of bismuth in a multi-component steel system. Based on the processing of data from separate works, mutually consistent dependences of the solubility of bismuth in pure iron, as well as Wagner interaction parameters for calculation for steels, were obtained. An attempt was made to model the formation of bismuth simultaneously with manganese sulfides during solidification based on the Ohnaka segregation model. Comparison with experimental data shows acceptable convergence of calculations and experiments.