Physical metallurgy and modelling of thermomechanically processed microalloyed steels

The effect of thermo-mechanical controlled processes (TMC) followed by accelerated cooling (ACC) or direct quenching (DQ) and their parameters are discussed in relation to the microstructure (development) and mechanical properties of high strength steels, microalloyed with Ti, V, (Mo) and/or Nb. Computer models for calculation of microstructure evolution (grain size, grain growth, precipitation and flow stress) during heavy plate, strip and long product hot rolling are invaluable for design of TMCP-rolling schedules combining a maximum degree of microstructure refinement with acceptably low rolling loads. Intelligent design of deformation/temperature schedules aims to generate an optimal austenite microstructure and subsequently a fine ferrite/bainite conferring both toughness and strength. A comparison is made of the results of laboratory simulations with full scale industrial plate, strip and long product processing using TMCP practices obtained at various (high and low) finish rolling temperatures with and without application of accelerated cooling/direct quenching. (author)