In-line characterisation of microstructure and mechanical properties in the manufacturing of steel strip for the purpose of product uniformity control
Résumé
The uniformity of the microstructure of steel strip over the entire coil length and between different coils of the same grade is key to stable and consistent material behaviour in steel manufacturers’ proprietary processes, like rolling and levelling, and customers’ processes, like pressing and deep-drawing. In particular for high-strength steels, like dual phase and complex phase steels, the microstructure is very sensitive to processing variations resulting in a potentially larger spread in the mechanical properties of the product. In July 2013, a large European consortium consisting of 15 institutes started an RFCS (1) –funded project called “Product Uniformity Control” (PUC) with the primary objective to achieve enhanced and sustained product uniformity of steel strip by improved interpretation of data from inline measurement methods that aim for real-time and non-destructive characterisation of microstructure and techno-mechanical parameters. Commonly, these techniques are based on electromagnetic (EM) or ultrasonic (US) measurement principles, which are favoured because of their non-destructive and potentially contact-free nature. To improve the techniques for in-line materials characterisation, the PUC consortium takes a systematic approach to investigate the interrelations between mechanical properties -- microstructural parameters -- EM & US properties -- inline measurement thereof. The studies involve dedicated laboratory experiments, modelling of the EM and US properties of steel, modelling of inline measurement setups and statistical analysis of data from inline measurement systems. The synthesis of these activities should result in improved, model-based, calibrations and finally in a broader deployment and integration of the inline material characterisation techniques in steel manufacturing, adding value to the product and enhancing the process efficiency throughout the production chain from hot-rolling to finishing. This paper outlines the project approach, highlights interconnecting modelling and experimental research work, and demonstrates first results. Various contributions being presented at this WCNDT conference originate from the collaborative activities of this PUC project. (1). (European) Research Fund for Coal and Steel