Realtime monitoring of microstructures during hot rolling

Purpose and goal

Accurate and industrially applicable methods have been developed to gather and interpret ultrasonic signals in relation to the microstructure aiming for quantification of the austenite during and post hot rolling considering (i) grain size, (ii) condition i.e. deformed or recrystallized and (iii) transformation to ferrite in the final product. Steel from industrial production have been investigated statically in laboratory and during thermo-mechanical treatment in Gleeble simulation.

Results and expected effects

The project demonstrated that laser-ultrasonics has potential to monitor microstructure parameters during hot rolling. Requirement specifications have been formulated regarding hardware for industrial use in the hot rolling mill with measurements at high temperatures on oxidized surfaces. An application for a continued implementation project has been submitted to Vinnova and the strategic innovation program for metallic materials - where the aim is pilot trials in the steel industry. Swerea KIMAB has approved an investment in mobile pilot equipment for industry trials.

Approach and implementation

The project was carried out in close dialogue with the representatives from the steel industry, who shared their expectations and requirements regarding industrial use of the LUS technology. The industry partners also contributed with relevant materials for the LUS measurements. The dynamic Gleeble trials brought experimentally complexity to an extent that was not foreseen initially why the project requested an extension which resulted in that planned activities could be performed successfully.