On-line monitor of hydrogen porosity based on arc spectral information in Al–Mg alloy pulsed gas tungsten arc welding

• Arc spectral information presents close correlations with hydrogen content.
• Elimination of background spectra will enhance the correlations between them.
• Intensity ratio signal can distinguish hydrogen factor from non-hydrogen factors.
• Peak component of intensity ratio will avoid pulse interference from pulse current.
• A prediction model for porosity was established based on statistical analysis.

An on-line approach based on arc spectral information was proposed to monitor the hydrogen porosity in Al–Mg alloy pulsed gas tungsten arc welding. For this purpose, spectral lines of the hydrogen and argon components of the arc atmosphere were analyzed when porosities occurred, and that interference of the continuous spectra involved in these lines was eliminated. The peak component of the intensity ratio of the H I line at 656.28 nm to the Ar I line at 641.63 nm was extracted as the characteristic signal to avoid the pulse interference and the non-hydrogen disturbances. Based on the statistical analysis of the extracted characteristic signal under different welding conditions, a predicting model for weld porosity detection was established and successfully used to identify the most probable position of the native porosity as well as the exact position of the artificial porosity.