Industrial implementation of a next generation advanced high strength steel

This study describes a suitable process for manufacture of a cold rolled and continuous annealed advanced high strength steel with a carbide-free bainitic ferrite or quenching and partitioning microstructure in an existing annealing production line. The effect of variations of the main processing parameters on the phase transformation responses and mechanical properties of potential candidate steels was investigated with particular focus on the effect of the overaging temperatures. The relationship between the microstructure and the tensile properties and the hole expansion capacity was scrutinized. In addition to the second phases such as fresh martensite and retained austenite, the non-relaxed strain gradient in the microstructures might be an important parameter to influence the hole expansion capacity.