Thermomechanical Analysis of Tungsten Inert Gas Welding Process for Predicting Temperature Distribution and Angular Distortion

Austenitic Type 316L stainless steel plates of very large thicknesses are considered for use in vacuum vessel fabrication in advanced fusion reactors. The possible options for welding of higher-thickness plates are multipass tungsten inert gas (TIG) welding, narrow gap–TIG welding, and electron beam welding (EBW). The manufacture of double-wall vacuum vessel inner components like keys, shells, and ribs are planned to be fabricated using EBW, and some components like field joints are to be fabricated using TIG welding processes. The present paper reports the fabrication of 60-mm-thick Type 316L stainless steel welded samples with multipass TIG welding and EBW processes and sample property characterization studies. The fabricated weld samples have been tested for weld defects with nondestructive tests using X-ray radiography and ultrasonic scan tests. The welded samples have been characterized for mechanical properties such as tensile, bend, Vickers hardness, and Charpy V-notch impact tests. Microstructure analysis has been carried out for both welded samples for the base metal, heat-affected zone, and weld zone. Impact-tested sample fracture analysis has been done by scanning electron microscopy.

A review on TIG welding technology variants and its effect on weld geometry

Tungsten inert gas (TIG) welding has an inherent difficulty in achieving deep penetration. To improve the penetration in TIG welding process, many researchers are continuously working in this field. In this paper, weld penetration of bead on plate TIG welding was compared with flux-bounded TIG (FBTIG) welding which was carried out on 6-mm-thick P91 plates. In the present FBTIG welding, a ceramic flux consisting of alumina was used instead of silica. Sodium silicate was used instead of acetone in the experiments to bind the flux on to the plates. In this paper, bead on plate FBTIG welding was carried out to investigate whether weld penetration could be improved. It was observed that with FBTIG welding, using ceramic flux, the weld penetration increased 2–3 times the penetration obtained during TIG welding. The weld width in all the cases decreased compared with conventional TIG welding. The effect of flux gap on hardness and grain size at the heat-affected zone were also investigated. Compared with TIG welds, FBTIG-welded samples had larger grain size and lower hardness values in the welded and heat-affected zone.

Stainless steel is a widely used material in various industries such as aerospace, chemical processing and transportation. Tungsten Inert Gas (TIG) or Gas Tungsten Arc Welding (GTAW) process is extensively used for joining thin sections of stainless steel. However, it is not useful in joining thick sections in a single pass. Activated TIG (A-TIG) significantly increases weld penetration up to 1.5– 4 times in a single pass. Because of its deep penetration ability, A-TIG is the focus of research amongst the researchers. This article reports the mechanisms associated with A-TIG, effects of various weld parameters on weld bead geometry and optimization techniques to optimize the process variable of the A-TIG welding process. The present work also analyzes the consequence of activated fluxes on microstructure and mechanical properties of A-TIG weld metal. Along with this, recent developments in the TIG welding process have been discussed. The study concludes that the A-TIG welding process enhances the weld penetration to a great extent, but a high amount of slug gets deposited on the weld surface. This drawback can be overcome by novel variants of the A-TIG welding process such as Flux Bounded TIG (FB-TIG) and Flux Zone TIG (FZ-TIG) welding processes which enhance the future scope of research.

Austenitic stainless steel (ASS) plays an important role in fabrication and manufacturing of products due to its good mechanical properties and easy weldability mostly for all types of welding. In fabrication, there are numerous welding techniques available for ASS such as gas metal arc welding, tungsten inert gas (TIG) welding, electroslag welding, submerge arc welding, electron beam, thermite welding. TIG welding is the most common operation use for joining of two similar or dissimilar metals with heating or applying the pressure by using the filler material. TIG welding technique is used in several industries like automobile, aerospace, marine, etc. due to its quick and precise process. This paper systematically reviewed the TIG and A-TIG welding processes of ASS which included several recent experimental activities. In TIG welding, the inputs such as voltage, current, filler materials and shielding gasses, the type of flux and passes ultimately affect its output weld quality. In addition, a comparison has been provided for parameters of TIG and A-TIG welding process and their weld outcomes such as microstructure, mechanical, penetration depth, and weld bead quality. A-TIG has better hardness and mechanical properties than TIG welding.

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively.

Optimization of Process Parameters in TIG Welded Joints of AISI 304L -Austenitic Stainless Steel using Taguchi’s Experimental Design Method

A new variant of activating flux tungsten inert gas (TIG) welding process called flux zoned TIG (FZ-TIG) welding is proposed to weld aluminium alloys based on the mechanism of activating flux constricting welding arc. This process can not only increase weld penetration but also obtain perfect weld surface appearance simultaneously. An alternative current FZ-TIG welding is made using SiO2 as the side region material and flux FZ108 developed by the authors with uniform design method as the central region coat material. The weld penetration can reach above three times that of the conventional alternative current TIG welding. All the weld shape, weld microstructure and weld mechanical properties are fine. Except for argon shielding gas flowrate, other welding parameters, including welding current, welding speed, central coat width, central coat content and solvent, have great effect on the weld penetration of alternative current FZ-TIG welding for aluminium alloys.

Grain fragmentation in ultrasonic-assisted TIG weld of pure aluminum

Effect of fluxes on weld penetration during TIG welding – A review

Austenitic stainless steel (ASS) is widely fabricated by tungsten inert gas (TIG) welding for aesthetic look and superior mechanical properties while compared to other arc welding process. Hitherto, the limitation of this process is low depth of penetration and less productivity. To overcome this problem activated tungsten inert gas (A-TIG) welding process is employed as an alternative. In this investigation the welding performance of conventional TIG welding is compared with A-TIG process using TiO2 and SiO2 flux with respect to weld bead geometry. The experimental investigation on A-TIG welding of ASS-201 grade shows TiO2 flux helps in achieve higher penetration as compared to SiO2 flux. While welding with SiO2 the hardness in HAZ and weld region higher than that of TIG welding process.

PurposePresently, the materials used in light combat aircraft structures are aluminium alloys and composites. These structures are joined together through riveted joints. The weight of these rivets for the entire aircraft is nearly one ton. In addition to weight, the riveted connection requires a lot of tools, equipments, fixtures and manpower, which makes it an expensive and time-consuming process. Moreover, Al alloy is also welded using tungsten inert gas (TIG) welding process by proper control of process parameters. This process has limitations such as porosity, alloy segregation and hot cracking. To overcome the above limitations, an alternative technology is required. One such technology is friction stir welding (FSW), which can be successfully applied for welding of aluminium alloy in LCA structures. Therefore, this paper aims to compare the load carrying capabilities of FSW joints with TIG welded and riveted joints.Design/methodology/approachFSW joints and TIG welded joints were fabricated using optimized process parameters, followed by riveted joints using standard shop floor practice in the butt and lap joint configurations.FindingsThe load-carrying capabilities of FSW joints are superior than those of other joints. FSW joints exhibited 75 per cent higher load-carrying capability compared to the riveted joints and TIG-welded joints.Practical implicationsFrom this investigation, it is inferred that the FSW joint is suitable for the replacement of riveted joints in LCA and TIG-welded joints.Originality/valueFriction stir butt joints exhibited 75 per cent higher load-carrying capability than riveted butt joints. Friction stir welded lap joints showed 70 per cent higher load-carrying capability than the riveted lap joints. Friction stir butt joints yielded 41 per cent higher breaking load capabilities than the TIG-welded butt joints. Moreover, Friction stir lap weld joints have 57 per cent more load-carrying capabilities than the TIG-welded lap joints.

The high efficiency tungsten inert gas (TIG) welding process has been developed, including active flux welding process, mixed shielded welding process and double shielded welding pro- cess, to increase the weld depth/width ratio (D/W ) of conventional TIG welding method. Compared to the active flux method, mixed shielding method can make penetration deeper and the industrializa- tion can be realized easily due to the simplification in operation. Double shielded method can avoid the oxidation of tungsten electrode. The results of experiment and simulation show that the change of the Marangoni convection direction which arises from the adjustment of the oxygen content in the weld pool is one of the main factors contributing to the increase in TIG weld penetration, and the large D/W ratio can be obtained by adjusting the active element content in the liquid pool. High efficiency TIG welding process is not sensitive to welding parameters (welding speed, welding current and electrode gap) and therefore is suitable to be applied in industry easily.

In the present study, forward and reverse mapping problems of the tungsten inert gas (TIG) welding process have been solved using radial basis function neural networks (RBFNNs), which is required to automate the welding process. The performance of an RBFNN depends on its structure and parameters. Here, a few approaches are proposed to optimize its structure and parameters simultaneously. A binary-coded genetic algorithm (GA) has been used for the said purpose. The GA strings carrying information of the networks might have varied lengths, and consequently, it becomes difficult to implement the conventional crossover operator. To overcome this difficulty, a new scheme has been adopted here. The performances of the developed approaches are tested to conduct both forward and reverse mappings of a TIG welding process. Cluster-based approaches are found to perform better than the non-cluster-based ones.

Investigation of heat transfer and fluid flow in activating TIG welding by numerical modeling