Bainitic Steels: Strength and Toughness From a Complex Transformation

Bainite is an acicular ferrite-plus-carbide aggregate formed by the diffusion-controlled (upper bainite) or displacive (lower bainite) transformation between the pearlite and martensite ranges. Bhadeshia and Edmonds (1980) explained the celebrated "silicon effect": Si suppresses cementite, leaving carbide-free bainite with retained austenite that boosts toughness. Bhadeshia (1992) systematised bainite in steels as a design tool.

Low-temperature (nanoscale) bainite, developed by Caballero and Bhadeshia (2002), reaches more than 2 GPa with useful ductility by isothermal transformation at about 200 C for days, giving an ultra-fine ferrite/retained-austenite mixture - a route to stronger, lighter components than tempered martensite at the same carbon level.

For buyers, bainitic grades (for example EN 14NiCrMo, 30CrNiMo8, and the new nano-bainitic steels) suit rails, wheels, linepipe and armour where toughness at high strength matters. JLHSteel can source bainitic and carbide-free-bainitic plate and forgings with specified impact properties.

References
1. Bhadeshia, H.K.D.H., Edmonds, D.V. (1980). The bainite transformation in a silicon steel. Metallurgical Science 14(2): 41-49. https://doi.org/10.1179/03063458079042630
2. Bhadeshia, H.K.D.H. (1992). Bainite in Steels. The Institute of Materials, London.
3. Caballero, F.G., Bhadeshia, H.K.D.H., Mawella, K.J.A., Jones, D.G., Brown, P. (2002). Very strong low temperature bainite. Materials Science and Technology 18(3): 279-284.