The aim of this research work is to develop computer code based on extensive testing for predicting the progress of phase transformation for use within thermomechanical codes of hot rolling and heat treatment of flat or shaped (mainly round) products. Quantitative metallurgical modelling minimises the need for expensive plant trials to develop new products and modify compositions and rolling schedules. This project extends the phase transformation work in hot rolled steels carried out under previous research work to low alloy (<5% by wt. total) and higher carbon (0.2% - 1%) steels, including the influence of boron and vanadium associated with austenite decomposition, and issues of perlite morphology.