Argon is approximately one and one third times as heavy as air and ten times heavier than helium. Argon, after leaving the torch nozzle, forms a blanket over the weld area. ,Welding grade argon is refined to a minimum purity of 99.95 %. This isacceptable for TIG welding of most metals except for the reactive and refractory metals, for which a minimum purity of 99.997 % is required.
Advantages of argon.