Design of a new nanostructured, high-Si bainitic steel with lower cost production

Highlights: → A bainitic steel with a new chemical composition has been designed using a thermodynamic model. → Good combinations of mechanical properties have been achieved with a lower production cost. → This is because of fine sizes of bainitic ferrite plates and presence of tough filmy austenite. → The results show that such steel can be designed without trial and error. -- Abstract: To reduce cost production, a bainitic steel with a new chemical composition was designed using MUCG83 thermodynamic model. The steel was cast as cylinder bar using a high frequency induction furnace under argon gas atmosphere. The cast cylinder was electro-slag remelted (ESR) for obtaining clean steel. Hot rolling was carried out after ESR to reduce the thickness and to change the cast structure to a wrought structure. To obtain a bainitic structure the austenitized samples were transformed isothermally at the temperature range of 200-300 oC for different times and finally were quenched into water. The microstructures were characterized by X-ray diffraction, scanning electron and transmission electron microscopes. The tensile and Charpy impact tests were carried out to evaluate the mechanical properties. The results show a good combination of high tensile strength and impact toughness which is ideal for high performance applications. The prominent mechanical properties are due to the unique microstructural characteristics which are evolved during isothermal transformation.