Shielding gas

About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.

Automatic pipe welding apparatus and method

Abstract: A TIG pipe welding method which employs two sets of machine guide surfaces on the pipe ends. First radially inner guide surfaces cooperate with a sensor coupled to the welding torch to continuously monitor the arc gap between the welding electrode and the weld puddle as the welding electrode moves around the circumference of the pipe. The second set of radially outer surfaces cooperate with a welding carriage to guide the carriage and welding modules around the pipe joint. The carriage is constructed to provide a sealed welding chamber surrounding the electrode. An additional flow of shielding gas is provided around the torch electrode of a TIG or hot wire TIG welding module to augment the normal gas shield. The augmented shield provides a gas flow in opposition to pressurized air flowing through the welding chamber to prevent exposure of the weld nugget to the pressurized air flow being maintained in the welding chamber while permitting the pressure forces to be transmitted through this shield to the weld nugget, creating a "puddle pushing" effect. The transfer of forces through the gas shield, while preventing contaminating air from entering the weld zone itself, provides a positive force for pushing the molten weld puddle through the joint to the interior surfaces of the joined pipe ends. The pressurized air further flows outwardly between the seals of the welding carriage and the pipe surfaces to create an air cushion between the pipes and the carriage. An internal weld backup and pipe alignment ring is also provided.

The effect of shielding gas types on CO2 laser tailored blank weldability of low carbon automotive galvanized steel

Abstract: This study deals with the effects of shielding gas types on CO 2 laser weldability of low carbon automotive galvanized steel. The types of shielding gas evaluated are helium, carbon dioxide, argon, nitrogen and 50% argon+50% nitrogen. The weld penetration, strength and formability (Erichsen test) of laser welds are found to be strongly dependent upon the types of shielding gas used. Further, the maximum travel speed and flow rate to form a keyhole weld are also dependent upon types of shielding gas. The ability of shielding gas in removing plasma plume, and thus increasing weld penetration, is believed to be closely related to ionization/dissociation potentials, which determine the period of plasma formation and disappearance. Further, thermal conductivity and reactivity of the gas with the molten pool also have a strong effect on penetration and porosity formation which in turn affect formability and strength.