Parameters Involved in the Spectroscopic Monitoring of Atmospheric Contaminants in the Tungsten—Inert Gas Arc Process

Abstract

The parameters involved in the spectral monitoring of atmospheric contaminants in the tungsten–helium arc process were studied under welding conditions. An internal standard was necessary because small variations in arc length, current, condition of metal surface, alloy, the portion of the arc in the aperture, etc. resulted in relatively large variations in spectral response, proportionally much greater than for those same parameters in conventional low current–graphite electrode spectroscopy. Only the argon line internal standard was satisfactory. Warping of the work metal caused the arc to change in space, so a side arm mount for the torch was designed to carry the entrance optics. The high and varying background that resulted from electrode reflections, glowing oxide particulate, focus on hot metal, and possible radiation from the electrode tip required the use of a rotating circular wedge to oscillate the emission lines across the exit slits. Alternating current electronics amplified the difference in signal levels.