Effect of preroll quenching and post-roll quenching on production and properties of ultrafine ferrite in steel

The production of ultrafine (1-2 μm) ferrite grains by single pass rolling of steel has led to the development of two modified rolling processes. The preroll quenching technique aims to produce a homogeneous distribution of ultrafine ferrite grains through the strip thickness, while at the same time relaxing some of the processing constraints associated with the production of these types of microstructure. By quenching the strip directly before rolling, the technique successfully produced a uniform distribution of ultrafine grains in a low carbon microalloyed grade. The post-roll quenching technique involved quenching the strip directly after rolling to control the microstructure of the centre of the strip and produce layered composite structures in both plain and microalloyed low carbon grades. These microstructures displayed novel combinations of very high strength and good ductility. These techniques present further opportunities for microstructural manipulation and the production of strip steels with high performance mechanical behaviour.