Shielding gas

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

Method and apparatus for gmaw welding

Abstract: A method and apparatus of welding along a pass line on a steel workpiece, which method and apparatus comprises simultaneously feeding two welding wires in generally parallel relationship toward a workpiece with extended welding wires generally intersecting the workpiece at individual points spaced from each other a distance in the range about 3/16 inch to about 3/8 inch; then creating a separate arc between each of the wires and the workpiece; passing a single protective envelope of shielding gas axially along two welding wires simultaneously and around said two separate arcs extending between welding wires and the workpiece; and, causing relative movement between the two gas shielded welding wires and the workpiece in the direction corresponding to the desired pass line on the workpiece.

Arc welding system and docking assembly therefor

Abstract: In a MIG arc welding system, a docking body having utilities passages therethrough is mountable at the welding station. Means are provided at one end of the body for accepting incoming utilities such as consumable wire electrode, shielding gas, welding potential and cooling water. Different types of welding gun or torch assemblies are interchangeably manually mountable and demountable at the other end of the welding body without disturbing the docking body or the utilities coupled thereto. Plug-type water fittings on the welding gun or torch assembly are receivable in receptacles in the docking body which communicate with the water passages, actuator tips on the fittings actuating normally-closed, spring-biased check valves in the passages to prevent leakage of water from the docking body when the welding gun or torch assembly is demounted. The gun or torch assembly is held in place by a coupling nut which is threadedly engaged with the docking body. There are provided a fixed-mount embodiment, wherein all utilities but the welding wire enter the docking body radially, and a remote or movable mount embodiment, suitable for mounting on a movable mechanized or robotic support, wherein all utilities enter the docking body axially. A positioning ring on the latter embodiment accurately positions the docking body on the movable support.

Study on the periodic oscillation of plasma/vapour induced during high power fibre laser penetration welding

Abstract: High power fibre lasers have recently received much attention because of their inherent advantages such as high output power, high beam quality, compact size, and flexible fibre delivery. Studies on the mechanism behind fibre laser welding systems may further promote their practical application. In this paper, high speed video observations were used to study the characteristics of the plasma/vapour induced during the bead-on-plate welding of ZL114 using a high power CW fibre laser. We also analysed the cause of the periodic oscillation of the plasma/vapour. The results revealed that plasma/vapour induced from high power lasers oscillate periodically at 450–600 μs cycles above the weld pool surface. The use of a shielding gas has little effect on the oscillation cycle. The plasma/vapour absorption is not the main reason for the periodical oscillation of plasma/vapour induced during fibre laser welding. The periodic oscillation of the plasma/vapour can be attributed to the oscillation of the keyhole.

Welding and Joining of Magnesium Alloys

Abstract: Welding and joining of magnesium alloys exert a profound effect on magnesium application expansion, especially in ground and air transportations where large-size, complex components are required. This applies to joints between different grades of cast and wrought magnesium alloys and to dissimilar joints with other materials, most frequently with aluminum and steel. Due to specific physical properties of magnesium, its welding requires low and well controlled power input. Moreover, very high affinity of magnesium alloys to oxygen requires shielding gases which protect the liquid weld from an environment. To magnify complexity, also solid state reaction with oxygen, which forms a thermodynamically stable natural oxide layer on magnesium surface, is an inherent deficiency of joining (Czerwinski, 2008). Both the conventional and novel welding techniques were adapted to satisfy these requirements, including arc welding, resistance spot welding, electromagnetic welding, friction stir welding, electron beam and laser welding. Since fusion welding has a tendency to generate porosities and part distortion, many alternative joining practices were implemented. These include soldering, brazing, adhesive bonding and mechanical fastening. However, also the latter techniques have disadvantages associated, for example, with stress induced by drilling holes during mechanical fastening, preheating during clinching or extensive surface preparation in adhesive bonding. Hence, experiments are in progress with completely novel ideas of magnesium joining. An application of magnesium is often in multi-material structures, requiring dissimilar joints, involving magnesium alloys as one side where on another end there are alloys with drastically different properties. How to weld dissimilar materials is one of the most difficult problems in welding. A difference in physicochemical properties of dissimilar joint components creates challenges for mechanically bolted assemblies as well. Due to its very low electronegative potential, magnesium is susceptible to galvanic corrosion thus affecting performance of mechanical joints in conductive environments. This chapter covers key aspects of magnesium welding and joining along with engineering applications, challenges and still existing limitations. For each technique, the typical joint characteristics and possible defects are outlined with particular attention paid to weld metallurgy and its relationship with weld strength, ductility and corrosion resistance. Although fundamentals for each technique are provided, the primary focus is on recent global activities.

Effect of magnetic field on plasma control during CO2 laser welding

Abstract: During high power CO 2 laser beam welding, the plasma above the keyhole has a shielding effect that it not only absorbs part of the laser energy but also defocuses the laser beam. As a result, the welding efficiency and the aspect ratio of the welds are influenced. In order to reduce the effect of plasma, helium as a plasma control gas has been used successfully and effectively. However, the cost of helium in Southeast Asia is extremely high and therefore the production cost is significantly increased when helium is used as a continuous bleeding plasma control gas. To search for an alternative plasma control technique, feasibility in using magnetic effect as a control tool is explored in this paper. The influences of the magnetic field strength, laser power, welding speed, field direction and shielding gas (e.g. helium and argon) on the penetration depth and the width of bead were also investigated. Experimental results indicated that the magnetic field can influence the shielding effect of the plasma without using plasma control gas. It was found that at a suitable magnetic field strength the penetration depth was increased by about 7%, but no significant difference on the width of bead was found. Moreover, it was shown that the plasma control effect can be achieved at low magnetic field strength and the penetration depth can be increased significantly under argon atmosphere.