Infrared sensing techniques for penetration depth control of the submerged arc welding process

Abstract This paper presents an investigation into the development of a rugged, low cost, point infrared sensor to monitor and control the welding process in harsh fabrication environments. Perturbations occurring during the welding process create changes in the temperature distributions of the plates being welded. By monitoring the changes in these temperature distributions, action can be implemented to eliminate or mitigate defects that may form due to the process perturbations. Heat transfer analyses were performed to study the effects of disturbances to the welding process on the surface temperature of the plates being welded. A point sensor was used to monitor changes in the plate surface temperatures occurring during the welding process. The objective was to demonstrate that weld bead penetration depth could be monitored and controlled during both gas tungsten arc welding (GTAW) and submerged arc welding (SAW) processes to eliminate or reduce weld defects. The infrared energy exchange between a defined area on the topside plate surface and the sensor was monitored during the welding process and compared to predictions of the heat transfer analyses. Changes in the plate geometry (gap size, plate thickness, and cooling sinks representing stiffeners) were introduced during the experiments to perturb the welding process. Using the infrared sensor, constant depth of penetration was maintained in the presence of these perturbations by feedback control of the welding process parameters.