Shielding gas

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

Welding Stability System and Method

Abstract: A weld stability system for an arc welding apparatus and method of operation is disclosed. The weld stability system may comprise a shielding gas supply and a control assembly. The shielding gas supply may include a first source of gas, a second source of gas, a mixing chamber, a first valve selectively connecting the first source of gas to the mixing chamber, a second valve selectively connecting the second source of gas to the mixing chamber, and a shielding gas supply line configured to direct gas from the mixing chamber to a weld gun. The control assembly may include a controller operatively engaging the first and second valves, and at least one sensor configured to monitor a parameter of an arc welding process and communicate with the controller.

Study of hybrid additive manufacturing based on pulse laser wire depositing and milling

Abstract: The hybrid additive manufacturing which involves direct metal deposition and high-speed milling has been considered as an effective process to make high performance products with well surface finish. Research that have been reported indicate that continuous energy sources can lead to intolerable residual stress and distortion even after the parts are processed by machine tools. Therefore, a hybrid additive manufacturing machine tool based on pulse laser wire depositing is established taking advantage of its intensive exposure. The designed work area of the hybrid AM machine tool is 50 mm × 50 mm × 100 mm. On this basis, a set of preliminary experiments are carried out to study the performance of the proposed hybrid AM process. Both the substrate and the wire are stainless steel (SUS304), and the wire diameter is 0.6 mm. Depositing trails were kept by oxide film since shield gas is not used during the deposition. Results show that stabilization of the process has a strong impact on both the surface finish and the microstructure. Moreover, experiment results indicate that wire feeding performance is the critical factor influencing the product performance due to the small weld pool size and the rapid melting and solidifying. Typical macrodefects of the fused welding and the exclusive flaw of additive manufacturing are detected. Microstructures show that column grains less than 1 μm dominate the deposition zone, where the column grains grew in the direction of depositing on the middle layers and along the curvature direction on the top surface. A thin wall about 0.5 mm wide is milled, and the result shows that the surface of the bead is greatly improved and no defects are detected after the thin wall is cut. However, the trapezoid cross section indicates that a further study on cutting is still demanded.

Keyhole-induced porosity in laser-arc hybrid welded aluminum

Abstract: Keyhole-induced macro-porosity, which results from the collapse of the keyhole that formed by the reaction forces of metal vapors, is a major problem limiting laser and laser-arc hybrid weldability of age-hardenable aluminum alloys, such as AA2024-T3 The mechanism of porosity suggests that the weld metal solidifies more rapidly than the possible rise velocity of the gas bubbles that formed during keyhole collapse, resulting in severe porosity The porosity behavior of AA2024-T3 during laser-arc hybrid welding was studied using microscopy and X-ray radiography techniques Porosity-free welding of the alloy is attainable in the conduction mode welding, whereas porosity increased significantly with increased laser intensity during keyhole mode welding Porosity was mostly severe when the beam was focused at the surface of the workpiece The laser beam and the arc decouple from each other with increased laser-wire distance, affecting keyhole depth and porosity In order to control porosity during laser-arc hybrid welding of aluminum alloys, the role of various welding parameters on the material’s response should be balanced with the required weld geometry