Nanostructured bainitic steels with carbide precipitations - a new steel class

Abstract

European Congress and Exhibition on Avanced Materials and ProcessRecent work [1] on the tempering behaviour of nanostructured bainite has demonstrated the particularly interesting tempering resistance of this microstructure. Tempering of high Si nanostructured bainite at an adequate temperature will not destroy it´s unique nanostructure on the contrary supersaturated and metastable phase will tend to equilibrium und therefore reduce internal stresses. Taking these in to account tempering offers a new perspective in the ability to tailor the mechanical properties. The present work is about combining the increasingly well-known performances of nanostructured bainitic steels with a secondary precipitation mechanism. These are based on a previously investigated material (0.65C-1.25Mn-1.5Si-0.75Cr wt%) modified with additions of Mo and V. Mo and V addition does not influence nanostructured bainite formation but changes secondary hardening behavior strongly. Mechanical behavior esp. at elevated temperatures is enhanced due to addition of Mo and V. Steel and process design as well as mechanical properties up to 250°C of 5 different nanostructured bainitic steels grade with different Mo and V addition will be discussed. Results will be compared to conditions without secondary carbide formers and martensitic conditions. Conclusions: We will present the main achievements so far obtained under the auspices of a Research Fund for Coal and Steel (RFCS) project, STEELSECO