Development of Cast Austempered Fe-Si-Mn-ME (Microalloying Elements) Steels

Abstract

The present investigation is carried out to examine the influence of austempering temperature on the microstructure and mechanical properties of a low carbon, high silicon ((C-0.13%, Si-1.3%, Mn-1%, V-0.08%) cast steels. The Induction melted casting block is homogenized at 1000oC for 6 hrs. Specimens are prepared from the cast steel block according to ASTM standard for metallographic and tensile properties study. Three different austempering heat treatment temperatures are chosen for micro-structural evaluation of the specimens by means of optical, scanning electron microscopy and transmission electron microscopy. Austempering treatment is carried out by austenitizing the specimen at 9000C for 30 min followed by rapid quenching in a salt bath at three different temperatures of 3500C, 4000C and 4500C for 10 mins and successive air cooling. The austempered microstructure shows the presence of bainitic ferrite and retained austenite, which are identified by X-ray diffraction and confirmed by TEM analysis. With increasing austempering temperature the morphology of bainitic ferrite is observed to be changed from lower to upper bainite. However, the variation in retained austenite observed to be insignificant.