Microstructure Evolution in Medium Carbon Bainitic Steel

A 0.38C steel with 1.97Mn, 1.34Si, 0.8Cr and 0.29Mo (wt. %) bainitic steel melted in a lab scale induction furnace was hot forged and subjected to annealing, austenitizing above Ac3 temperature and in the inter critical temperature range were normalized or austempered in the temperature between 350 to 500 oC to get a versatile range of microstructure with bainite as a major phase. In the annealed condition the steel showed acicular ferrite with pearlite and in the normalized condition from above Ac3 temperature, bainitic ferrite with 7% retained austenite. When the steel is continuously cooled post intercritical austenitization treatment, the microstructure showed ferrite, bainite and pearlite. Austenitization above Ac3, followed by austempering at different temperatures resulted in carbide free bainitic microstructure consisting of bainitic ferrite and austenite between 7 and 16%. Austenitization in the inter critical temperature followed by austempering at different temperatures showed ferrite, banitic carbide and pearlite.