Arc welding operations are performed by conductingthe welding current through consumable electrodes,which take the form of a wire or rod, or nonconsum-able electrodes, consisting of carbon or tungsten rods.Metal arc processes utilize consumable electrodes thatcombine electrode filler metal with the molten basemetal to create the weld. They may also produce a slagcovering to protect the molten metal from oxidation.The nonconsumable arc processes can generate a weldby melting the base metal only, resulting in what istermed an autogenous weld. If filler metal is required ina nonconsumable process, it may be fed either manuallyor mechanically into the molten weld pool. In this case,the nonconsumable electrode serves only to sustain thearc