Influence of Grain Size on Recrystallisation During hot Working of Austenitic Stainless Steels

During the hot rolling of austenitic stainless steels, complete static recrystallisation is expected between passes unless finishing temperatures are low. Typically progressive refinement takes place to grain sizes in the range 20–50μm. However, most experimental studies of the effect of strain, strain rate, temperature and initial grain size on recrystallisation kinetics and recrystallised grain size under hot working conditions have been carried out on initial grain sizes greater than 50μm. Empirical relationships from these data and from more limited results of CMn steels have been extrapolated to smaller grain sizes for use in models of microstructural evolution during rolling.Recent development of a physically based model for the effects of initial grain size, assuming that site saturated nucleation occurs at grain corners, grain edges, grain faces and at intragranular sites leads to interdependence of the effects of strain and grain sizeon nucleation density and hence on recrystallised grain size and recrystallisation rate. Experimental evidence available in the literature and some new results on finer grained Type 316 stainless steel are reviewed and compared with the expectations from the model.