The invention is of a low carbon, carbide-free, nanostructured bainitic steel with a yield strength exceeding 1.2 GPa. This was achieved through a two-stage isothermal transformation process, resulting in 0.87 volume fraction of bainitic ferrite, with nearly 50% of bainitic laths measuring below 100 nm. The transformation time is under 8 hours, making it viable for industrial applications. The issue of coarse microstructure was addressed, specifically the coalescence of bainitic plates that typically degrade strength in low carbon steels transformed at low temperatures, without compromising the steel's strength. The material achieved a yield strength of over 1.2 GPa, an ultimate tensile strength exceeding 1.5 GPa, and ductility greater than 18%. Additionally, the plain strain fracture toughness reached 82 MPa√m, and the impact energy was recorded at 31 J, surpassing previous developments in low carbon bainitic steel. This low carbon, carbide-free, nanostructured bainitic steel also offers improved weldability compared to existing high carbon bainitic steels.
Type of IP
Faculty
Category of Patent
Department
Railway industry, Automobile industry, Aerospace industry, Military industry, Heavy Machinery and Equipment industry
- Produces low carbon, carbide-free nanostructured bainitic steel with a strength exceeding 1.2 GPa through a multistep transformation process.
- Achieves reasonable transformation time (within 8 hours), making the process suitable for industrial applications.
- Addresses the issue of bainitic plate coalescence, which can degrade the strength of low carbon steels transformed at low temperatures.
- Demonstrates an exceptional combination of mechanical properties, including strength, ductility, impact toughness, and fracture toughness.
- Offers improved weldability compared to existing high carbon bainitic steels.
5
The invention is currently at the stage of early Prototype development and/or validation in relevant environment.
A composite microstructure of the steel with high strength, ductility and toughness makes it suitable for following applications: Pipe line alloys, railway lines, railway wheels, bearings, automobile bodies, wind turbine gear box etc. It is relevant for many industries such as Railway industry, Automobile industry, Aerospace industry, Military industry, Heavy Machinery and Equipment industry and so on.