Formation of M23C6 type carbides in heat-treated extra low carbon Mn-Si and Mn-Si-Nb high strength low alloy “mar” steels

Structural investigations in extra low carbon mar steels with nominal compositions A1 (4 Mn-1.0 Si), A2 (4 Mn-1.0 Si – 0.042 Nb), A3 (～ 5 Mn-1.5 Si), A4 (2.6 Mn-1.0 Si) and A5 (～ 5 Mn-2.5 Si) in the heat treated condition by X-ray diffraction technique (Debye-Scherrer method) for identifying strengthening mechanisms. Results on the formation of M₂₃C₆ type carbide either singly (in most cases) or in combination with austenite. Discussion pertaining to 1. identification of factors promoting the structural changes and, 2. their likely effect on mechanical properties.