Tommy Robertson, Kjell-Arne Persson

Abstract

Investigation of the plasma arc by using optical spectrometry has been performed in TIG and MAG welding. Two different spectrometer setups were tested.

The aim was to detect defects such as porosity (gas flow variations), bad penetration, burn through defects and undercuts etc. by using spectrometry. Important factors for the setup and measurement procedure are investigated; also problems with the methods and proposal for improvements and future work are discussed.

Specific material lines were identified and compared to results from other independent institutes, attempts to calculate the plasma temperature were made as well as calculation methods based on the intensity balance between UV, Visible and IR ranges. Some correlation between poor gas flow and information in the plasma arc could be established. Burn through could also be detected by calculating the plasma temperature. Current and voltage variations could also be detected.

More research is necessary to conclude on best setup and the full monitoring possibilities..