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Arc Welding Processes
Published in G. Ravichandran, Finite Element Analysis of Weld Thermal Cycles Using ANSYS, 2020
The gas tungsten arc welding process employs a non-consumable electrode made of tungsten, and the arc is struck between the tungsten electrode and the base metal. The heat which is liberated near the non-consumable electrode has to be removed so that the electrode does not get overheated during the process. This is done by external gas cooling or water cooling of the welding torch which houses the electrode. The protection for the arc zone from the atmosphere is provided by an inert gas such as argon or helium which is made to flow around the arc uniformly. Welding may be performed with or without the additional filler metal in the form of rod or wire. The welding process may be either manual or automatic. When the welding is performed manually, the welder will have the welding torch in one hand and the filler metal in the other hand. The arc is moved slowly along the weld line, and the filler metal is added to the molten metal pool as and when required. Figure 2.6 shows the schematic diagram of the gas tungsten arc welding process.
Welding of High Entropy Alloys—
Published in T.S. Srivatsan, Manoj Gupta, High Entropy Alloys, 2020
R. Sokkalingam, K. Sivaprasad, V. Muthupandi
When the electrode is moved close to the workpiece or touched and withdrawn from the workpiece, the available gas in between them ionizes and establishes the electric discharge, resulting in the formation of a high-temperature (~6,000°C) arc. This concentrated high temperature melts the base metal and the filler, and some electric and/magnetic fluxes produced in the circuit lead to intermixing in the molten pool, which on solidification provides the joint with a metallurgical bond. The introduction of the shielding gases provides perfect shielding for the solidifying weld metal from the external atmosphere. Thus, GTAW can provide a clean and quality weld, ensuring the weld quality even for welding reactive metals. However, GTAW can only effectively weld thin plates (~3 mm) due to its lower heat input and power density. Sometimes, the fluxes like SiO2, TiO2, and Cr2O3 are applied on the surface of the base plate to increase the depth of penetration (~5 mm) [57]. However, welding thicker plates can be completed by introducing multiple passes [58].
Weld Design and Joining
Published in Zainul Huda, Manufacturing, 2018
Gas Tungsten Arc Welding: GTAW is an AW process that uses a nonconsumable tungsten electrode to weld a metal that is protected by an inert gas. In general, a filler wire is added to the weld pool separately.
Effect of Welding Speed and Postweld Heat Treatment on Microstructural Characterization and Mechanical Properties of Gas Tungsten Arc Welded Ti-15V-3Al-3Cr-3Sn Joints
Published in Fusion Science and Technology, 2023
K. Vamsi Krishna, Sriharitha Rowthu, Vijay N. Nadakuduru, Ganesh Pilla, N. Kishore Babu
In the GTAW process, welding can be performed with or without filler metal. Welds are referred to as autogenous welds when they are made without the use of filler material. The GTAW process produces sound and smooth welds with less spatter and can be used in all welding positions.2 However, high-energy beam processes like laser beam welding (LBW) and electron beam welding can produce high-quality welds, but the operational costs of these processes are high as compared to GTAW. A few variations in GTAW are narrow gap, flux-cored filler wire, pulsed GTAW, immersed arc, keyhole mode GTAW, and active flux tungsten inert gas welding.3 In addition to this, the welding parameters that can influence weld performance are filler modification, nucleating agents, welding speed, current, etc. However, welding speed is a crucial welding parameter that influences the cooling rate (the product of thermal gradient G and growth rate R) and heat input.4,5 These advancements in this process may lead to metallurgical advantages, which include control of segregation in the weld zone, reduced width of the heat-affected zone (HAZ), fine grain structure in the fusion zone (FZ), etc., which all together can improve the mechanical properties of welds.4
Investigating the effect of GTAW parameters on the porosity formation of C70600 copper-nickel alloy
Published in Canadian Metallurgical Quarterly, 2023
Hossein Bayat Tork, Mehdi Malekan
The GTAW process was used for welding the prepared specimens as it is the standard technique for welding pipes. Direct current and straight polarity were used. Most GTAW welds employ direct current on electrode negative (DCEN) because it produces higher weld penetration depth and higher travel speed than on electrode positive (DCEP) [20,29]. Argon is the most used GTAW shielding gas. It has low ionisation potential and is heavier than air, providing an excellent shielding of the molten weld pool. Furthermore, it is less expensive than helium, the other inert shielding gas used in the process [17,20]. Therefore, the standard Argon, according to DIN EN 439, was used as shielding gas. To control welding conditions, the test coupon was rotated by a hand-made rotating machine with a controlled rotational speed. The pipe is fixed in the horizontally position and can be rotated along the horizontal (X) axis. The welder's position and welding torch remained stationary. Welding is performed on the top of the pipe. This is the most basic welding position that can be achieved. So, the welding position of the flat is selected since it is the most convenient welding position. It is tried to control the parameters that can be examined more accurately by choosing the most specific position. The schematic illustration of this apparatus is shown in Figure 1(b).
Investigating the heat distribution on welded parts from a TIG welding operation in a railcar manufacturing environment
Published in Cogent Engineering, 2022
Walter Thabo Seloane, Khumbulani Mpofu, Boitumelo Ramatsetse, Dithoto Modungwa
TIG welding or GTAW (Gas Tungsten Arc Welding) uses a non-consumable tungsten electrode protected by an inert gas. The electrode is either made of pure tungsten or tungsten mixed with small amounts of oxides (thoriumoxide, zirconiumoxide) to improve the stability of the arc and to make it easier to strike. Since the process uses a non-consumable electrode, extra filler material is usually added (Ericsson, 2003; Avadheshkumar & Patel, 2017). The TIG welding process has been widely used in high-tech industry applications, such as, the nuclear industry, aircraft, the food industry, maintenance and repair work, as well as some manufacturing areas (Larry, 2002, 2012). The process itself can be manual, partly mechanized, fully mechanized or automated (Kazi, 2015). The welding power source delivers direct or alternating current. Helium and argon gases are the most suitable for shielding, as they are not chemically reactive (Joshi, 2014).