This special ceramic is for narrow gap TIG welding, having its use in pressure vessel welding in the nuclear industry.
The TIG nozzle guides the flow of inert gas to provide an inert atmosphere for the weldpool. These are mainly manufactured from a ceramic or quartz material to handle the heat of the welding process. The shielding gas is also necessary to prevent air from coming in contact with the tungsten electrode as it would burn out immediately. Gas flow is critical as a too low flow entraps air before it reaches the weldpool causing porosity and too much can have the same effect when the speed of the gas is too high and ?mechanically? mixes the air into the gas stream causing the porosity.