The role of computer modelling in deformation processing

Over the last two decades the application of computer models to all aspects of deformation processing has grown rapidly to become an essential contribution to meeting customer demands for products of enhanced geometric tolerance, surface finish and consistency of properties. Quantification of the evolution of microstructure during industrial processing schedules and modelling its sensitivity to process variables has played a central role for the steel industry and is increasingly recognised as essential by other metal producers. This paper briefly examines the development of modelling for rolling and considers the success and limitations of current microstructural models in relation to their application in conjunction with finite element models to predict the variations in local microstructures. In particular the need to understand the consequences of transient strain rate and thermal histories and of the different strain paths that arise in different elements will be emphasised. This is proposed as a major challenge for physical metallurgy if the full predictive capabilities of finite element models are to be realised in future. The different types of model applied to thermomechanical processing are considered in relation to hot rolling. The need for overall process modelling to account for the interactions of temperature, stress, mocrostucture and material flow is discussed, and the current limitations in making full use of finite element model outputs in predicting local microstructure are highlighted. The development of expert systems by using a combined modelling approach is outlined.