A new method of supplying shielding gases in an alternating manner has been developed to enhance the efficiency of conventional Gas Metal Arc Welding (GMAW). However, the available literature on this advanced joining process is very sparse and no cost evaluation has been reported to date. In simple terms, the new method involves discretely supplying two different shielding gases to the weld pool at pre-determined frequencies which creates a dynamic action within the liquid pool. In order to assess the potential benefits of this new method from a technical and cost perspective, a comparison has been drawn between the standard shielding gas composition of Ar/20%CO2, which is commonly used in UK and European shipbuilding industries for carbon steels, and a range of four different frequencies alternating between Ar/20%CO2 and helium. The beneficial effects of supplying the weld shielding gases in an alternating manner were found to provide attractive benefits for the manufacturing community. For example, the present study showed that compared with conventional GMAW, a 17% reduction in total welding cost was achieved in the case of the alternating gas method and savings associated with a reduction in the extent of post weld straightening following plate distortion were also identified. Also, the mechanical properties of the alternating case highlighted some marginal improvements in strength and Charpy impact toughness which were attributed to a more refined weld microstructure

Studies have been carried out to determine the effects of implementing alternating shielding gases for 6082T6 aluminium alloy welding. Alternating shielding gases is a newly developed method of supplying shielding gases to the weld area to enhance the efficiency of the standard gas metal arc welding process.Alternating shielding gases involves discretely supplying two different shielding gases to the weld zone at a predetermined frequency that creates a dynamic action in the weld pool. Several benefits have been identified in relation to supplying shielding gases in this manner, including reduced porosity, marginal improvements in mechanical properties, increased travel speed, and as a result of the lower heat input, reduced distortion. This method of shielding gas delivery therefore presents attractive benefits to the manufacturing community; namely the increased productivity and quality, in addition to a reduction in the amount of post-weld straightening required.However, the literature available on this advanced joining process is very limited, especially so for aluminium alloys. For this reason, an evaluation has been carried out on the application of alternating shielding gases for the gas metal arc welding process on 6082T6 aluminium alloys.

A new method of supplying shielding gases in an alternating manner has been developed to enhance the efficiency of conventional gas metal arc welding (GMAW). However, the available literature on this advanced joining process is very sparse and no cost evaluation has been reported to date. In simple terms, the new method involves discretely supplying two different shielding gases to the weld pool at predetermined frequencies which creates a dynamic action within the liquid pool. In order to assess the potential benefits of this new method from a technical and cost perspective, a comparison has been drawn between the standard shielding gas composition of Ar/20%CO2, which is commonly used in UK and European shipbuilding industries for carbon steels, and a range of four different frequencies alternating between Ar/20%CO2 and helium. The beneficial effects of supplying the weld shielding gases in an alternating manner were found to provide attractive benefits for the manufacturing community. For example, the present study showed that compared with conventional GMAW, a 17 per cent reduction in total welding cost was achieved in the case of the alternating gas method and savings associated with a reduction in the extent of post-weld straightening following plate distortion were also identified. Also, the mechanical properties of the alternating case highlighted some marginal improvements in strength and Charpy impact toughness which were attributed to a more refined weld microstructure

Extensive experimental trials were conducted, emulating the conditions modelled, in order to validate the computational fluid dynamic results. Final results demonstrated that a more constricted nozzle was more effective at creating a stable gas column when subjected to side draughts. Higher shielding gas flow rates further reduce the gas column's vulnerability to side draughts and thus create a more stable coverage. The results have highlighted potential economic benefits for draught free environments, in which, the shielding gas flow rate can effectively be reduced

As part of an ongoing process to fully evaluate the effects of an alternating shielding gas supply on gas shielded welding processes, a comparison between the arc pressures generated using argon, helium, alternating shielding gases and pulsed gas tungsten arc welding (GTAW) has been conducted. Arc pressure variation and peaking are two of the fundamental phenomena produced during the alternating shielding gas process and are said to help create a stirring action within the liquid weld metal. However, there are no published data on arc pressure measurements during an alternating shielding gas supply, and consequently, these phenomena are based solely on theoretical assumptions. The experimental measurements made have shown that alternating shielding gases produce considerably higher arc pressures than argon, helium and pulsed GTAW due to a surge at weld initiation. The transient arc pressure measurements made when using alternating shielding gases are also considerably different from the theoretical assumptions previously reported. List of symbolsF arc arc force, N I welding current, A J current density, A m 22 P arc arc pressure (stagnation pressure at anode), N m 22 r distance in the radial direction, m R radius of arc, m V velocity (m s 21 ) r g density of the shielding gas, kg m 23