Work rolls in the roughing mills : Roll grade and process optimisation to save energy and roll cost of use (WINROLLS) : final report

On-line and off-line tools have been developed to characterise the roll surface evolution (WP1). We focused on oxide thickness measurement, surface characterisation (degradation), sub surface characterisation and slab speed measurement. It allowed us to build a complete database (WP2). We analysed it in order to understand the degradation mechanisms, and specifically the oxidation phenomenon all along the roll life, and also to compare work roll grades (HSS, 1/2HSS and HiCr). A system measuring the heat transfer coefficient in the roll stand has been designed (WP3). Unfortunately, trials couldn’t be performed, but procedure and numerical simulations are done in order to perform the trial under the best conditions. Comparison of classic cooling and HTRC cooling led to the conclusion HTRC was more efficient (WP4) in terms of heat removed. Also the optimal position and pressure have been defined on roll cooling simulator. The optimisation of starting conditions (WP5) revealed that the higher the initial roughness, the quicker the oxidation. Pre-heating of roll also leads to a better oxidation. Trials on the twin disk showed that the pre-oxidation layer on roll was not able to give additional protection (not adhesive enough). A new work roll grade has been developed by Åkers (WP6) based on the analysis and correlation of data gathered in on-line trials, and on laboratory trials performed on existing grades. The new work roll grade (WP7) showed improved oxidation kinetics at the beginning of the campaign. Moreover the depth of thermal cracks is uniform, which limits the risk of pitting