Techno-economic evaluation on the effects of alternating shielding gases for advanced joining processes

Abstract

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

Visualisation of alternating shielding gas flow in GTAW

“…The pulsed gas delivery method has been used in both gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) of aluminium alloys [2][3][4], as well as of carbon [5][6][7] and stainless [8,9] steels. Several benefits were reported, such as improved distortion control and re-work reduction [7,10] or refinement of weld structure and thus better mechanical the mechanical properties of the weld [2,8]. The pulsing frequency was shown to influence the dynamics of the melt pool [9] and final geometry of the solidified weld [8,10].…”

“…Several benefits were reported, such as improved distortion control and re-work reduction [7,10] or refinement of weld structure and thus better mechanical the mechanical properties of the weld [2,8]. The pulsing frequency was shown to influence the dynamics of the melt pool [9] and final geometry of the solidified weld [8,10].…”

Artificial neural network prediction of weld distortion rectification using a travelling induction coil

“…It is known that the magnitude of distortion is affected by a number of factors including the shielding gas flow rate, weld geometry, plate thickness and welding speed [8][9][10][11]. In particular welding speed has been shown to have a significant impact on distortion as it is one of the primary parameters of controlling heat input during welding [9].…”

GMAW Gas Shielding - Economic Savings Without Detriment to Quality

“…Initial trails [3] of alternating shielding gases have been performed on 8mm thick DH36 steel plate, which was being welded in a butt configuration. The base case was the normal 80% argon / 20% carbon dioxide shielding gas mixture and welded according to an industry standard.…”

“…The alternating shielding gas process [2][3][4][5] is a relatively new method of delivering the shielding gas to the weld area. It involves discretely supplying two different shielding gases, at a preset frequency, in order to take advantage of the beneficial properties of each gas.…”