Chemical element, rare gas with the chemical symbol Ar.
The word argon is derived from the Greek word “αργος” meaning “inactive”.
Argon is used as filling gas for fluorescent tubes, as shielding gas for welding (Argonarc welding and TIG process) and for specific melt treatment applications (e.g. bath cover for melting of reactive metals like titanium, hydrogen degassing of aluminum alloys - see Rotary degassing, etc.) and as inert gas for heat treatment.
Argon is also used in steel production in the AOD process. The relative proportion of argon in the earth atmosphere is 0.93 % per volume. This makes argon the third most element in the earth atmosphere even before carbon dioxide. Large-scale production is mainly realized by fractional distillation in industrial air separation plants (see Argon production). The most important physical properties are listed in Table 1.
Other rare gases: