Hot-rolled and continuously cooled bainitic steel with good strength–elongation combination

Abstract

The current work demonstrates the microstructural evolution and mechanical property evaluation of a newly designed steel composition after hot rolling in laboratory-scale rolling mill, followed by continuous cooling. The steel thus developed has typically about 80% carbide-free bainite; about 20% retained austenite and can deliver ∼1400 MPa ultimate tensile strength along with more than 20% total elongation. The presence of ultra-fine bainite plates (∼100–130 nm thick) with high dislocation density was thought to be responsible for ultra-high strength. Excellent ductility at such strength level could be due to the presence of sufficient amount of retained austenite (∼20%) thermally stable at room temperature but starts transforming to martensite during deformation exhibiting transformation-induced plasticity effect.

Keywords:

• Ultra-high strength steel
• Excellent ductility
• Nano-structured bainite
• Retained austenite

Acknowledgements

The authors express their sincere thanks to Prof H. K. D. H. Bhadeshia for lots of discussion over different technical aspects of this work. The authors also thank the management of Tata Steel Limited, India as well as Tata Steel Research and Technology, Netherlands for allowing us to publish the work.

ORCID

S. Das http://orcid.org/0000-0002-9416-7180

S. Sinha http://orcid.org/0000-0002-0321-1888