Shielding gas

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

Keyhole stability in disc laser welding of AZ31B and AZ61A magnesium alloys and weld metal properties

Abstract: To confirm the process potential and limitations of laser welding of magnesium alloys, a newly developed disc laser of 16 kW in maximum power was used to weld thin plates of AZ31B and AZ61A alloys. Melting characteristics and weld metal properties were studied under different process parameters. The very high power density of the applied beam caused the keyhole and the molten pool to be unstable. Underfill was the main welding defect limiting the process window and its formation was closely related to the keyhole instability. A process diagram indicating areas of sound and defected welds could be constructed. Sound welded joints could be obtained for AZ31B alloy with similar mechanical properties as that of the base material. The brittle intermetallics network present along the grain boundaries in AZ61A weld metals required a higher energy input to alleviate its detrimental effect on the mechanical properties of the welded joints.

Assessing metal transfer stability and spatter severity in flux cored arc welding

Abstract: Five experimental basic type flux cored arc welding consumable wire electrodes were manufactured from the same base formulation. The composition of these electrodes was adjusted in an attempt to improve the operating performance. This involved additions of various ratios of alkali oxides, namely, lithium, magnesium, sodium, and potassium containing ingredients, in the flux formulations. The operating behaviours of these experimental electrodes and two reference products (i.e. one commercial basic T–5 and one commercial rutile T–1 electrode) were thoroughly investigated by recording welding arc signals using a high speed data acquisition system. By comparing these electrodes among themselves, the experimental electrodes were reported to exhibit extremely stable arcs, some showing electrical arc signals even smoother than those for the reference rutile grade electrode. Despite their improved metal transfer consistency, however, basic electrodes were characterised by somewhat higher spatter levels.

Fatigue Performance of Gas Tungsten Arc, Electron Beam, and Laser Beam Welded Ti-6Al-4V Alloy Joints

Abstract: Titanium alloys have been successfully applied for aerospace, ship, and chemical industries because they possess many good characteristics such as high strength to weight ratio, superior corrosion resistance, and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. The evaluation and prediction of fatigue life are very important for the welded joints to avoid catastrophic failure particularly in titanium alloys. This article compares the fatigue performance of Ti-6Al-4V alloy fabricated by gas tungsten arc welding, laser beam welding, and electron beam welding processes. The resultant fatigue properties of the welded joints are correlated with the tensile properties and microstructural characteristics. Of the three processes considered the joint welded by laser beam welding exhibits higher fatigue limit when compared with the other two processes due to the presence of fine lamellar microstructure in the weld metal region.