Hot strip flatness optimisation by means of edge masking in the ROT cooling system

This research project had the aim to demonstrate the proper operation of the advanced edge-masking technologies in the Hot Strip Mills (HSM) to improve flatness in strip edges. In order to control the lower temperature in the edges of the strip in the Run-out Table (ROT), edge masking devices were redesigned to be adapted to this kind of facility, implemented and put in operation in the HSM of Arcelor España in Avilés. Now they are working in a robust, continuous and efficient way, proving to have a positive effect on wavy edges reduction. The ROT was monitored with the installation of a new thermographic sensor and a flatness gauge at the entry coiler, so the effects of the edge-masking device (EMD) can be measured by comparison with Finishing Mill Exit Measurements (temperature and flatness). All the variables involved, including those related to the cooling process, were acquired and analysed in the different trials developed, considering several cooling and EMD set-ups, material characteristics, process variables. The initial approach of a direct relation between temperature and flatness has been demonstrated not to be so direct, because there are more factors involved (as phase transformation location, for example) although there is a high correlation. Finally a good predictor on flatness has been developed, not based on physical approach, but on databased, considering and proving the effect of the edge masking system.