New thermomechanical strategy for production of high strength low alloyed multiphase steel showing transformation induced plasticity effect

In the past few years a lot of research was carried out on the development of transformation induced plasticity (TRIP) assisted multiphase steels. Two principal ways were proposed: (i) controlled cooling during the hot rollin g process to obtain hot rolled TRIP assisted multiphase steels and (ii) the combination of intercritical annealing and isothermal holding at bainite f ormation temperatures during continuous annealing resulting in cold rolled TRIP assisted steel products. Unfortunately, both thermomechanical methods proposed require a high silicon level to inhibit cementite precipitation to avoid a loss of stability for the metastable retained austenite. In additi on, due to high silicon levels, red scale surface defects appear and only m oderate hot dip galvanisability is possible. In this paper a new thermomech anical strategy for the production of high strength low alloyed TRIP assist ed multiphase steels with good hot dip galvanisability and without red scal e defects will be presented.