Monitoring Metallurgical Properties of Strips inside Annealing Furnace with Laser Ultrasonics

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Final mechanical properties of micro-alloyed (HSLA) and high strength (AHSS) steel strips are highly dependent on metallurgical features before the rapid cooling in the thermal cycle of continuous annealing and galvanising lines. In particular, recrystallisation rate is essential for HSLA, while the ferrite/austenite ratio is of major importance fr AHSS. Laser Ultrasonics (LUS) is expected to be able to assess such metallurgical features, but has not undergone in-line investigations on HSLA and AHSS steel strips at high temperature (~800°C) in the continuous annealing furnace. This pilot and demonstration project aims project aims at verifying the ability of LUS to monitor the metallurgical features in such conditions. The project will rely on laboratory investigations conducted on an exhaustive collection of steel grades determined by ArcelorMittal Belgium (Ghent plant), with an experimental set-up associating an annealing simulator to a laser ultrasonic system owned by ArcelorMittal Maizières Research. In parallel, the consortium will carry out significant efforts on the modelling of the generation and propagation of ultrasonic waves, to allow confirming the scientific background of measurements and identify advanced signal processing techniques to derive quantitative assessments of the metallurgical features of interest. The consortium will undertake the adaptation of a LUS system to run feasibility trials in the context of the Sidgal 3.5 continuous annealing and galvanizing line, at the exit of either the soaking or the slow cooling section. Recorded signals will be analysed off-line for first evaluation, before creating real-time signal analysis.