Effect of Carbon and Manganese on the Quenching and Partitioning Response of CMnSi Steels

CMnSi steel grades with carbon contents ranging from 0.2 to 0.3 wt% and manganese contents of 3 and 5 wt% were Quenched and Partitioned (Q&P). Tensile properties were assessed and retained austenite fractions measured. Intercritically annealed and fully austenitized conditions were studied. The best combinations of tensile strength and total elongation obtained in the 0.2C-3Mn-1.6Si grade after intercritical annealing were associated with strength levels in the 1 000-1 200 MPa range and total elongations ranging from 14 to 20%. Optimum properties were obtained in the 0.3C-3Mn-1.6Si steel after full austenitization with tensile strength levels ranging from 1 450 to 1 700 MPa and total elongations ranging from 11 to 18%. The 0.2C-3Mn-1.6Si fully austenitized samples also exhibited remarkable strength/ductility combinations albeit at lower strength levels of 1 200-1 450 MPa UTS with 9-15% total elongation indicating the effectiveness of the manganese addition to develop novel property combinations.