Gas Tungsten Arc Welding
Gas tungsten arc welding (GTAW) utilises an intense electric arc formed between a non-consumable tungsten electrode and the workpiece to generate controlled melting within the weld joint. Essentially, the arc can be used as if it was an extraordinarily ho
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Gas Tungsten Arc Welding Manabu Tanaka
Abstract Gas tungsten arc welding (GTAW) utilises an intense electric arc formed between a non-consumable tungsten electrode and the workpiece to generate controlled melting within the weld joint. Essentially, the arc can be used as if it was an extraordinarily hot flame. The stability of the tungsten electrode and the option to use totally inert gas mixtures if desired means that the process can be very clean and easy to implement. It is also a process with the potential to deliver relatively high-power densities to the workpiece, and so can be used on even the most refractory metals and alloys. In this chapter, principles of GTAW including energy transport, momentum transport and weld pool behaviour which are required to understand and control heat source properties of GTAW are reviewed in detail. Furthermore, future trends of applications of GTAW are also described. Keywords Arc welding
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Tungsten Arc plasma Heat source properties
Introduction
Gas tungsten arc welding (GTAW) first made its appearance in the USA in the late 1930s, where it was employed for welding aluminium airframes. It was an extension of the carbon arc process, with tungsten replacing the carbon electrode. The new tungsten electrode, together with an inert helium shielding gas atmosphere, reduced weld metal contamination to the extent that highly reactive metals such as aluminium and magnesium could be welded successfully. For a time, the process was known as ‘heliarc’ in the USA. Other countries substituted the less expensive argon for helium and referred to the process as ‘argon arc’. Later, these distinctions were dropped and the process became known as tungsten inert gas (or TIG)
M. Tanaka (&) Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 576-0047, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2019 Y. Setsuhara et al. (eds.), Novel Structured Metallic and Inorganic Materials, https://doi.org/10.1007/978-981-13-7611-5_9
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welding. More recently, the term gas tungsten arc (GTA) has been introduced to signify that the shielding gas may not necessarily be inert. GTAW is known for its versatility and high joint quality. It can be used with a wide variety of materials, including highly reactive or refractory metals. It may be operated manually at lower currents (e.g. 50–200 A) for single-pass joining of relatively thin sections, or multi-pass welding of thicker sections that have appropriate V- X- or similar-type edge preparations. During the 1960s, the process was extended to much higher current range, allowing the arc forces to play a significant role in increasing weld penetration. At currents above about 250 A, the arc tends to deform the weld pool surface, with the effect increasing as the current is increased further. This mode of operation is generally automated, and in its early manifestations gave rise to terms such as high current, buried arc, and subsurface arc TIG (or GTAW). Plasma arc weld
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