The present paper analyzes the effect of low aluminum additions and the hot forging process on the microstructure and non-metallic inclusions of high manganese steels. Four high-manganese steels (HMnS) were obtained by adding low aluminum contents of 1.1 and 1.5 wt. % in four medium carbon austenitic steels (0.3 - 0.4 wt% C) with manganese contents of 17 and 22 wt. Samples of the as-cast steels were hot forged to 1100 ?C to obtain a whole reduction of 70 %. The microstructural evolution was studied by microscopy techniques (OM, and SEM-EDS) and X-Ray diffraction measurements for the as-cast and hot forged steels. A typical grain columnar zone obtained during solidification of an ingot casting was obtained in the as-cast condition where the microstructure was constituted by non-metallic inclusions in a fully austenitic matrix. The non-metallic inclusions were identified as Al2O3 and MnS particles. The thermomechanical treatment allows the formation of an austenitic microstructure characterized by twins in high manganese steels while a duplex austenitic-martensitic microstructure was obtained for HMnS which contained the lowest manganese contents. The highest tensile properties were obtained for the steel 17Mn-1Al which showed the lowest grain size and higher non-metallic inclusions content. The hardness values were similar to those obtained in the as-cast condition.

Application of cast steels instead of hot forged or rolled ones will significantly decrease manufacturing costs and the final product price. However, low levels of mechanical properties in cast steels, especially ductility, can slow down the substitution of forged and rolled steels with the cast. In the present work, the authors study the effect of 0.01-0.12 wt% vanadium additions on the microstructure and mechanical properties of 0.25 wt% C cast steels. The yield stress, ultimate tensile strength, and elongation to failure in the studied cast steels are 730-750 MPa, 955-1002 MPa, and 12.3-21.5%, respectively, which correspond to those in hot forged and rolled steels with similar compositions. So, high property values in the 0.25 wt% C cast steels are shown here for the first time. The simultaneous increase in strength and ductility with an increase in V content follow a decrease in pearlite fraction, interlamellar spacing, and average pearlite area size; an increase in amount of degenerated pearlite; an increase in V-rich particle volume fraction and number density in ferrite and pearlite; the occurrence of interphase precipitation (in 0.12 wt% V steel), and an increase in dislocation density in ferrite and pearlite.