Research on a new detection method of slab surface crack in mould during continuous casting

Abstract

Based on the mould temperature measured by thermocouples during slab continuous casting, a new thermograph with difference of temperature change is developed to detect slab cracks. This thermograph allows the characteristics of longitudinal crack during formation and propagation process to be captured and extracted by means of computer image processing algorithms, such as the maximum difference of temperature change, the mean difference of temperature change, height and width, aspect ratio and moving velocity. These characteristics are also compared to the normal and abnormal cold regions. The results show that the maximum and mean differences of temperature change are very large. The moving velocity is almost close to casting speed. The cold region is almost parallel to casting direction. The aspect ratio of cold region caused by longitudinal crack is very large, which is different to other abnormalities. These characteristics of abnormal regions can be used to judge longitudinal crack, normal continuous casting and other abnormalities. This method presents some visual characteristics of cold regions caused by longitudinal crack to operators clearly. Meanwhile, it also has a positive meaning to the intelligence and visualization of mould monitoring during slab continuous casting.