Infrared video imaging for in-line evaluation of oxide descaler performance on steel strips

In-line assessment of descaler functionality was conducted through use of high-speed infrared (IR) video imaging of moving steel strips following laminar cooling. IR temperature measurements were obtained for fifteen (15) steel strips at a mill location between laminar cooling and coiling. Anomalous temperature values were observed in the IR images and were attributed to the presence of surface oxides. The location and spacing of these oxides were quantified using an outlier detection method consisting of a Gaussian process and Gaussian mixture model. Validation of the outlier detection method was done through comparison of both the morphology and emissivity of oxide regions to those reported in literature. The oxides were predominately located at the mid-width of the strip, while their transverse spacing correlated well with the descaler nozzle spray patterns. The transverse spacing and location of these oxides indicates that the reheat furnace and/or rough-rolling entry descaler was operating with reduced functionality. Total fraction of surface oxides was also shown to be correlated with the amount of silicon in each strip and the total roll reduction.