Helium TIG arc plasma (left: without metal vapor, right: with metal vapor)
Tungsten Inert Gas (TIG) welding is an arc welding process that is widely used in manufacturing fields. An inert gas flow is used as ashielding gas to prevent oxidation of the weld pool and the tungsten electrode. Upper figure shows the photographs of helium TIG arc plasma. TIG arc plasma using pure helium gas emits a red light on the water-cooled copper (left photograph). On the other hand, the arc plasma shows a blue bowl shape on the stainless steel (right photograph). A weld pool is formed on the stainless steel, and the blue region indicates the presence of metal vapor. In tIG welding, the main source of metal vapor is the weld pool because high-melting point tungsten is used as the electrode. The metal vapor generated from the weld pool surface is transported into the arc plasma and to the tungsten electrode against a shielding gas flow. When the metal vapor is transported, it affects the plasma physical properties such as the electrical conductivity and the net emission coefficient, and the amoount of consumption of electrode. However, the transport mechanism of metal vapor during TIG welding has not been elucidated. I am studing on the elucidation of the transport phenomena of metal vapor using "imaging spectroscopy" that captures only the spectrum of specific particles from various spectra in welding arc plasma as two-dimensional image.