ORIGINAL: yb2normal
Sorry for the OT question, but what is helium used for in welding?
It's used to displace air in some types of arc-welding. Arc welding with many metals will cause the metal to boil and pop if it's exposed to air during the weld, due to rapid oxidation of the metal. The He2 displaces the oxygen away from the arc. In typical steel arc welding CO2 is used for this, I think helium is primarily used in aluminum welding (though why the different gasses, I don't know.)