12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet - GALVATECH 2021

With ever increasing targets on productivity, unpredictable down times caused by a weld break can become an important problem. Lately, partly because of drivers like the rise of multiple high strength steel grades and the retirement of highly experienced operators, we have seen CGL lines experience an increase in weld break events. Technologies like pressure sensors, current sensors, cameras and pyrometers are used to help characterize the weld quality. Nonetheless, these instruments cannot be trusted for an automatic rejection or acceptance of the weld. Recently, a new approach was proposed using laser-ultrasonics to characterise the weld in-line with the welding process. It uses ultrasounds through the weld itself, an approach broadly accepted in the world of non-destructive testing. The topic of this paper is about the industrial implementation of a laser-ultrasonic instrument optimized for weld inspection. Results on a long term trial in a North American plant are presented. The impact of steel alloy, weld preparation and surface conditions on the acceptance threshold are discussed.