Real-time monitoring of microstructures for efficient development and manufacturing of high performance steel

Purpose and goal

The project aim was to evaluate the capability of laser ultrasonics (LUS) for characterisation of microstructures during hot rolling. A mobile LUS demonstrator was developed and tested in pilot trials at SMT and during industrial full scale trials at SSAB. The trials showed that it is possible to acquire robust and reliable signals in the demanding environment with high temperatures and vibrations. Algorithms that relate LUS signals to the microstructure were successfully developed for quantification of grain size in ferrite and austenite at temperatures up to 1400C.

Expected results and effects

Successful industrial measurements showed that it is possible to acquire relevant microstructure information in-situ during hot rolling using the LUS technology as sensor. Future development of procedures for control of the hot rolling process using information from the LUS sensor will open up new possibilities to achieve more uniform properties and increased product quality. A continuation project is planned with the aim to evaluate the technology during a more permanent installation and at the same time assess possibilities for improved hot rolling process control strategies.

Planned approach and implementation

The project was carried out in 3 phases. The first part aimed to develop LUS hardware and software in lab environment using thermomechanical Gleeble simulations. The methodology developed will be valuable also for future material and process development. The second phase included pilot trials that provided valuable insight how the LUS technology performs during industrial conditions. The last phase focused on the execution of industrial full-scale trials. The project set-up was successful and worked out as intended with gradually increased complexity for each consecutive phase.