Characterization of “Humping” in the GTA welding process using infrared images

•A novel defects identification technique based on the isotherms geometry.•The use of infrared thermography can help to understand the weld bead defect phenomena.•Novel correlations techniques between changes in temperature fields observed by thermography and the occurrence of defects in welds running by the TIG process.•Proposes a real-time monitoring methodology based on the analysis of temperature gradients observed by a thermographic camera.•Digital image processing was used to measure model responses in empirical modelling.

A real-time methodology is proposed for monitoring the occurrence of defects such as “humping” in GTA welding based on temperature gradient analysis, as observed by a thermographic camera. A technique based on the isotherm geometry for identifying defects that can be observed in a region around the arc and weld pool is provided. Isotherms between 1200 and 1400 °C were analyzed. The temperature field near both of these values varied during seamless weld bead deposition and induced a weld bead with “humping”. Abrupt changes in the temperature distribution are identified as being indicative of this type of defect in an on-line monitoring system. The use of thermographic techniques for monitoring the presence of weld defects is a promising tool that can be used for the on-line detection and control of welding process discontinuities.