Microstructure Evolution in Medium Carbon Bainitic Steel

Abstract

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 Ac_3, 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.