1 - Inert atmospheres play a protective role similar to that of fluxes. In gas-shielded metal-arc [gas-shielded arc welding] and gas-shielded tungsten-arc welding [TIG welding] an inert gas--usually argon--flows from an annulus surrounding the torch in a continuous stream, displacing the air from around the arc [electric arc]. The gas does not chemically react with the metal but simply protects it from contact with the oxygen in the air.
2 -The oxy-acetylene welding torch is used to mix oxygen and acetylene in definite proportions. It also controls the volume of these gases burning at the welding tip, which produces the required type of flame. The torch consists of a handle or body which contains the hose connections for the oxygen and the fuel gas. The torch also has two needle valves, one for adjusting the flow of oxygen and one for acetylene, and a mixing head.