Types of Weldings

Table 1. Weld Characteristics/Parameter/Criteria for Three Types of Welding

CHARACTERISTIC OR PARAMETER	RECOMMEND OR STANDARD PRACTICES
	GAS TUNGSTEN ARC WELDING (2219 Al)	VARIABLE POLARITY PLASMA ARC WELDING (2219 Al)	ELECTRON BEAM WELDING (INCONEL 718)
Preferred Position	Flat	Vertical	Flat
Shield Gas	Helium (99.999% Purity)	Helium (99.999% Purity)	Vacuum
Plasma Gas	N/A	Argon (99.999% Purity)	N/A
Backing Required	No	No	In Some Instances (1)
Preferred Electrode	2% Thoriated Tungsten	2% Thoriated Tungsten	(Tungsten Filament)
Appropriate for Repair	Yes	Not Usually (2)	Yes
Cleaning Requirements	Mechanical Removal of Oxide, Free of Hydrocarbons	Mechanical Cleaning Not Required, Degrease Only	Special Cleaning for Vacuum Requirements
Used for Tack Welding	Yes	No	Yes
Computer Control	Desirable	Essential	Desirable
Most Prominent Potential Defects	Oxide and Tungsten Porosity, Lack of Penetration or Fusion	Undercut, Lack of Fusion	Improper Seam Tracking, Microfissuring