Design and development of cold rolled carbide free bainitic steel through microstructural engineering

Abstract

A cold rolled carbide-free bainitic steel primarily containing C, Mn, Si, Cr and Fe-balance has been developed. It was decided to have a fully pearlitic microstructure after casting and hot rolling to facilitate the subsequent cold rolling operation and finally the cold rolled strip would be transformed to carbide-free bainitic structure by suitable heat treatment. The composition was tailored through performing several virtual experiments in order to develop the desired microstructure. The developed steel achieved good combination of strength (900–1050 MPa YS, ∼1400–1650 MPa UTS) and elongation (∼13% uniform and ∼18% total elongation) in the final condition. Nano-structured bainitic plates (140–180 nm thick) and high dislocation density are the primary contributors to the strength whereas the carbon enriched retained austenite in optimum extent provided good elongation.