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The recrystallisation of AISI430 ferritic stainless steel during hot working is considered crucial for developing suitable product properties for sheet metal forming. Attention has focused on the ability to accurately reproduce the process route conditions of hot Steckel mill rolling at the laboratory scale. The variability was considered through five complex simulations on the IMMPETUS thermomechanical compression (TMC) test machine. This paper presents the methods employed to translate the industrial practice into laboratory based experiments, and the development of the simulation to a satisfactory level. This paper includes a discussion of the quality of the simulation, particularly with regard to its use as a tool for analysing metallurgical changes.

The restoration mechanisms of AISI430 ferritic stainless steel under industrial rolling conditions (strain 0.6, strain rate 16 s Ϫ1 ) were studied experimentally. Dynamic recovery followed by static recrystallisation and concurrent static recovery were observed in the ferrite phase at the hot rolling temperature (960°C). Complete recrystallisation (Ͼ70 %) was hindered by the impingement of the new grains on the widespread g phase and the extensive recovery. At lower strain rates, typical of nominal laboratory experiments, restoration through a more continuous process was observed, where recovery mechanisms were promoted by the longer deformation time. An explanation of the microstructural evolution of this material under hot rolling conditions and the interaction of these mechanisms is presented.

Plate steel S460 is intercritically rolled during the final stages of industrial processing. A series of experiments to represent the preliminary stages of an intercritical simulation were completed and the isothermal austenite to ferrite transformation kinetics investigated. The growth of the ferrite grains was interpreted using the classic JMAK model and the effect of processing history also examined. A double austenite deformation at 1323 K, to a true strain of 0.2, led to the most acceptable starting microstructure for the extended simulation. The role of niobium in this preliminary simulation is also considered.

Integrated model based control systems are an essential part of modern plant operations. The production requirements have evolved from achieving geometric tolerances to becoming a large, flexible, but accurate metallurgical instrument. Within the steel industry, on-line process and microstructure monitoring systems have been realised for many years on hot strip mills. At recent conferences (including ReX&GG IV), Siemens has described the successful implementation of these models in steel plate production; in applications where there is increased complexity in through thickness microstructure and the final products have safety critical applications. Even with advanced on-line systems and tailored production routes there is a relatively comfortable process window in modern steel manufacture. For the plant builder, light structural metals titanium and magnesium, and harder nickel based high temperature alloys represent another level of complexity and process control requirements. This paper examines the potential of microstructure modelling with respect to the process design for manufacturing wrought products in alternative alloy systems. Metallurgical aspects will be considered and their practical implications discussed. The continued expansion of these materials into markets where high strength/weight ratios, corrosion resistance or high temperature properties are desirable (e.g. automotive, offshore, chemical, aerospace) make this worthwhile from an industrial perspective.