Conventional TIG Welding Research Articles

Flux-bound TIG welding on UNS S32760 super duplex stainless steel using activating fluxes

In this article, the effect of activating flux powders viz., Silicon Dioxide (SiO2), Chromic Oxide (Cr2O3), Titanium Dioxide (TiO2) and Vanadium Pentoxide (V2O5) on Flux-Bound TIG (FB-TIG) welding of UNS S32760 Super Duplex Stainless Steel (SDSS) is investigated. Also, conventional TIG welding is done for a comparative study with the FB-TIG welds. The macrographs of the welds are obtained to analyze the depth, width and aspect ratio. The depths obtained with all the fluxes are found to be superior relative to the conventional TIG welds. The highest penetration of 6 mm is obtained for V2O5 welds. Then the microstructure and composition of the welds are analyzed using Optical Microscopy and Area-Mapping analysis. The authors observed the presence of three forms of austenite viz., Grain Boundary Austenite, Intragranular Austenite and Widmanstatten Austenite in the weldment zones. The micro-hardness profiles of the welds are also analyzed, and the profiles obtained with all the FB-TIG welds are found to be relatively smoother without any abrupt variations. Through this investigation, it is delineated that FB-TIG welding can increase the overall productivity in the welding of SDSS, as the penetration obtained is up to thrice relative to the conventional TIG welding.

Elimination of pores and microstructural characterization in Ti-6Al-4V alloy welds using fast-frequency double pulse TIG welding

This study utilizes a fast-frequency double pulse tungsten inert gas (FFDP TIG) process to weld 2 mm thick Ti-6Al-4V alloy, with the objective of investigating the influence of a large fast-frequency current amplitude on porosity, microstructure, and tensile properties of the weld joint. Unlike conventional TIG welding, the FFDP TIG welding process led to a reduction and elimination of porosity, and refined the prior β grain and α phase by 34.3 % and 33.3 %, respectively, while also refining the martensitic α′ structure. Stirring of the molten pool resulted in improved uniformity of grain orientation distribution, accompanied by decreased variant selection of the α phase and reduced texture strength of the α phases. Moreover, three-variant clusters of α/α′ phases with triangular morphology and micro- and nanoscale recrystallized α grains appear in the FFDP TIG weld. Concurrently, the FFDP TIG process significantly enhanced the tensile strength and ductility by 14.5 % and 114 %, respectively, compared to the conventional TIG process.

Development of TIG MIG Hybrid Welding Process: A Brief Review

The purpose of this article is to review the TIG MIG hybrid welding process, which benefits from the advantages of conventional MIG welding and TIG welding. The review focuses more on the studies related to the concepts of each welding process, its advantages and disadvantages, and some applications in the industry. The TIG MIG hybrid welding is a new method that is less popular than the conventional welding process. Thus, fewer experimental studies have been conducted on the process. Since the TIG MIG hybrid welding is promising a better welding process and is potent to improve the welding process with a combination of advantages of both conventional MIG and TIG welding, hence more work needs to be done on the TIG MIG hybrid welding research study to provide more valuable information that is lacking so that it could be applied to the industry.

Improving the Formation and Quality of Weld Joints on Aluminium Alloys during TIG Welding Using Flux Backing Tape

This work aimed to compare the quality and properties of the welded joints of AMg6 aluminium alloy produced via conventional TIG welding with the properties of those produced with flux backing tape. This study focussed on the relative length of oxide inclusions (Δoi) and the amount of the excess root penetration (hroot) of the AMg6 alloy weld beads. The results show the influence of the thickness of the flux layer of the backing tape on the formation and quality on the AMg6 alloy welds, along with the effect of flux backing tape and edge preparation on the mechanical properties of the 6 and 8 mm thick welded plates. In accordance with the results obtained, the joints produced by means of TIG welding with flux back backing tape and without edge preparation have higher mechanical properties. Moreover, the TIG welding of AMg6 alloy using flux backing tape reduces the total welding time by 55%, reduces filler wire consumption by 35%, reduces shielding gas consumption by 43% and electricity consumption by 60% per 1 linear meter of the weld line.

Penetration depth, phase balance and corrosion behaviour in activated TIG welding of UNS S32205

The aim of this research is to investigate the impact of a flux containing 80% TiO2 and 20% CeO2, under protective atmosphere (100% Ar, 98% Ar-2% N2, and 95% Ar + 5% N2) on penetration depth, phase equilibrium, and corrosion behaviour of autogenous A-TIG welds generated at constant current density. The reason for choosing cerium in the flux composition and nitrogen in the shielding gas is their effect on the phase balance of austenite and ferrite in this alloy. Metallography, ferritoscopy, and potentiometry were employed in the examination of the welds. The use of a two-component flux increased the penetration depth in TIG welding by up to 87%. Adding 2% and 5% nitrogen gas to the shielding gas in active TIG welding further increased the penetration depth to 117% and 130%, respectively. The results of ferritoscopic analysis reported the amount of austenite in the base metal and conventional TIG weld as 48% and 32%, respectively. However, the use of two-component flux increased the amount of austenite in the weld metal to 39%. Additionally, the addition of 2% and 5% nitrogen to the shielding gas in active TIG welding increased the amount of austenite in the weld metals to 60% and 76.6%, respectively. According to cyclic potentiodynamic polarization studies, active TIG welding with different nitrogen gas concentrations showed improved general and pitting corrosion properties in weld metals compared to conventional TIG welding. Consequently, weld metal resulting from active TIG welding with 2% nitrogen gas exhibited corrosion properties almost identical to that of the base metal.

The effect of thermomechanical welding on the microstructure and mechanical properties of S700MC steel welds

Grain refinement by plastic deformation during conventional TIG welding can help to compensate for the loss of mechanical properties of welded joints. The thermomechanical welding (TMW) tests were performed on S700MC steel with different combinations of TIG arc energy and high frequency hammering over three target cooling times (t8/5 = 5s, 15s, and 25s). Additionally, the effect of initial microstructures on the weld joint quality was analysed by testing three materials conditions: hot-rolled (as-received) and cold-rolled with 10% and 30% thickness reductions, respectively. The effects of plastic deformation and the mechanical vibration on the grain refinement were studied separately. Optical microscopy, electron backscattered diffraction, and Vickers hardness were used to characterise the weld microstructure heterogeneity. The weld width and depth and the mean grain size were correlated as the function of cooling time t8/5. The results show that the weld dimensions increase with increasing the t8/5. The weld microstructures transformed from the mixed martensite and bainite into mixed ferrite and bainite with increasing the t8/5 time, and the related mean grain size increased gradually. The TMW welds exhibit smaller grains compared to TIG welds due to the coupled effects of mechanical vibration and plastic deformation. The mechanical vibration contributes to weld metal homogenisation, accelerating TiN precipitation in the fusion zone. The proposed TMW process can refine the weld microstructure of S700MC steel, enhancing its mechanical properties.

Effect of Conventional and Pulsed TIG Welding on Microstructural and Mechanical Characteristics of AA 6082-T6 Repair Welds

Effect of Conventional and Pulsed TIG Welding on Microstructural and Mechanical Characteristics of AA 6082-T6 Repair Welds

Evaluation of welding-induced residual stress and distortion in A-TIG welding of duplex stainless steel

Applying non-uniform heat in welding causes residual stress and distortion, which affects the life of components. In the present study, the residual stress and distortion of Duplex 2205 stainless steel in A-TIG welding were investigated numerically and experimentally. The optimal welding parameters for highest penetration depth in welded samples were obtained experimentally. Uncoupled thermal-mechanical analysis using ABAQUS 2017 software has been done. Goldak's parameters were measured by empirical tests. The results include simulation diagrams of four samples consisting of the optimal sample without flux powder and three samples with the highest penetration depth. The simulation results show that the sample without flux has a higher maximum temperature and lower welding-induced distortions. The efficiency used in this research changes using and not using powder; it is concluded that, in similar conditions in A-TIG welding, fewer values of parameters are needed to achieve the appropriate result comparing conventional TIG. The efficiency of workpieces with flux should be considered about 20% lower to have similar results to the conventional TIG. The numerical modeling results showed a good agreement with experimental data both for temperature distribution and welding-induced residual stress and distortion. The distortion in the pieces with conventional TIG welding has increased to 11% at the farthest point from the welding line. The error obtained from comparing the results in residual stress is between 12 and 34%.

Comparative study on autogenous diode laser, CO2 laser-MIG hybrid and multi-pass TIG welding of 10-mm thick Inconel 617 superalloy

The present study investigated comparative welding performance of single-pass autogenous diode-laser (DLW) and CO2+ MIG laser-hybrid welding (LHW) processes with multi-pass conventional TIG welding in 10-mm thick Inconel 617 with comprehensive correlation of bead profile, microstructure with mechanical performance of weldments employing FESEM, XRD, high-speed Nano Indentation, uniaxial tensile and impact testing. Results indicated that welds produced by LHW and DLW constituted ‘wine-cup’ and ‘Y” shaped profiles respectively with reduced fusion zone (FZ) and heat-affected-zone (HAZ), high depth-to-width aspect ratio and low distortion as compared to that of ‘bath-tub’ shaped TIG weld on account of low heat input and high-coupling efficiency of laser. Indeed, inhomogeneous microstructures were observed in both LHW and TIG welds due to dual heat sources in LHW (laser + MIG) and multiple passes in TIG as compared to that of DLW, wherein, refined microstructure with fine secondary-dendritic arm spacing and low levels of micro-segregation in interdendritic regions of FZ. XRD confirms presence of higher amounts of M23C6 and M6C carbides in TIG FZ as compared to that of LHW and DLW counterparts and attributed to enhanced micro-segregation due to reduced cooling rate and repetitive thermal cycling effect of multiple passes. Micro and Nano-Indentation hardness profiling indicated that the hardness of FZ of TIG welds is comparatively lower to that of DLW and LHW on account of enhanced segregation and grain coarsening effect. Weld joint efficiency obtained in DLW and LHW are slightly higher than TIG weldments with highest elongation observed in DLW. Overall, joint efficiency of LHW and DLW was found adequate with vast reduction in distortion and improved adoptability for applications in thermal power plant.

Refined weld microstructure and enhanced joint mechanical property of 1460 Al-Li alloys via double-pulsed variable polarity TIG arc welding

In this work, 1460 Al-Li alloy plates (thickness 2 mm) were butt-welded by using conventional variable polarity TIG welding (VPTIG), low-frequency pulsed (2 Hz) variable polarity TIG welding (P-VPTIG), and double-frequency (low-frequency (2 Hz) + ultrasonic-frequency (20 kHz)) pulsed variable polarity TIG welding (DP-VPTIG). The influences of the three current modes on the weld microstructure and mechanical properties were investigated contrastively. Weld microstructure was characterized by a metallographic optical microscope, scanning electron microscope, and electron backscattering diffraction technology. The mechanical properties of those 1460 Al-Li alloy-based joints were measured by microhardness and room-temperature uniaxial tensile test. Obtained results indicated that modulating pulsed current on the conventional VPTIG current can effectively eliminate the coarse columnar structures, resulting in whole refined equiaxed grains in the weld zone (WZ) and fusion zone (FZ). By comparison, DP-VPTIG current exhibited the most prominent effect of homogenization and refinement on the weld microstructure. In addition, it significantly increased the quantity and width of the fine strip-like equiaxed grain zone. The eutectic phase particles distributed in the grain boundaries were refined prominently by the modulation of pulsed current. Compared with the VPTIG process, both P-VPTIG and DP-VPTIG processes effectively enhanced the strength and elongation of 1460 Al-Li alloy-based joints, with an increase of 6.2 % and 10.9 % in tensile strength and 16 % and 128.6 % improvement in elongation, respectively.

Study of microstructure & mechanical properties of TIG welded aluminized 9Cr-1Mo steel

Aluminide coating on 9Cr steel is candidate coating for blanket module applications of fusion reactors. The welding fabrication processes associated with coated steels are still an issue as the presence of Al in weld metal has several detrimental outcomes. To address this, the authors have attempted a study on conventional TIG welding with V-groove to mitigate the effect of coating on weld metallurgy. This work emphasizes the comparison of mechanical properties and microstructures of aluminide coated and uncoated/bare 9Cr-1Mo steel. Microstructural observations indicated presence of un-dissolved alumina inclusions at the weld fusion line. Despite such inclusions, the observed tensile strength of the weld joint for coated steel is 648 MPa±16 MPa which is in line with the weld joint of un-coated steel (667±14 MPa) and substrate (643 MPa±18 MPa). Impact toughness tests carried out at 0 °C,-25 °C and room temperature also indicate that there is no drastic effect of coating on weld joint and the observed toughness values are acceptable as per the reported data (45 J).

Optimization of CA-TIG welding parameters to predict and maximize tensile properties of super alloy 718 sheets for gas turbine applications

PurposeThe primary objective of this investigation is to optimize the constricted arc tungsten inert gas (CA-TIG) welding parameters specifically welding current (WC), arc constriction current (ACC), ACC frequency (ACCF) and CA traverse speed to maximize the tensile properties of thin Inconel 718 sheets (2 mm thick) using a statistical technique of response surface methodology and desirability function for gas turbine engine applications.Design/methodology/approachThe four factor – five level central composite design (4 × 5 – CCD) matrix pertaining to the minimum number of experiments was chosen in this investigation for designing the experimental matrix. The techniques of numerical and graphical optimization were used to find the optimal conditions of CA-TIG welding parameters.FindingsThe thin sheets of Inconel 718 (2 mm thick) can be welded successfully using CA-TIG welding process without any defects. The joints welded using optimized conditions of CA-TIG welding parameters showed maximum of 99.20%, 94.45% and 73.5% of base metal tensile strength, yield strength and elongation.Originality/valueThe joints made using optimized CA-TIG welding parameters disclosed 99.20% joint efficiency which is comparatively 20%–30% superior than conventional TIG welding process and comparable to costly electron beam welding and laser beam welding processes. The parametric mathematical equations were designed to predict the tensile properties of Inconel 718 joints accurately with a confidence level of 95% and less than 4.5% error. The mathematical relationships were also developed to predict the tensile properties of joints from the grain size (secondary dendritic arm spacing-SDAS) of fusion zone microstructure.

Variants of TIG welding process for improvement of weld penetration depth - A review

This article deals with the various process modifications that occurred in the tungsten inert gas welding process over a decked of time. The conventional TIG welding process usually offers a shallow weld penetration (up to 5 mm). Due to this limited depth of penetration, the industrial applications of this process are very limited and used only for sheet metal working. This article focuses on the various modification that has been made in the conventional TIG welding process to improve the process capabilities. Mainly flux assisted TIG welding, pulse current TIG welding, keyhole TIG welding, multi-electrode TIG welding, TIP-TIG welding process, and their hypothesis responsible to improve the weld penetration were discussed. The effect of various process parameters of these process variants on weld penetration was also discussed. So, this article will help in strengthening the future research trend in TIG welding for enhancement of its industrial application and capability of the process.

Characterisation of Cu–Al alloy lap joint using TIG Welding

It is difficult to join dissimilar material which has different thermal and mechanical properties using conventional arc welding, which is prone to the formation of intermetallic compounds (IMCs). In the present work pure copper (Cu) and aluminium (Al) alloy (Al-6061) is lap joined by conventional TIG Welding. At optimal operating condition, a successful weld is achieved as observed from mechanical testing. The metallurgical properties of joints are investigated by Back Scattered Electron (BSE) image, spot Energy Dispersive X-ray Spectroscopy (EDS) and line EDS. IMCs layers formed for joints varied from 9 μm to 80 μm thickness obtained at different welding parameters. Two different layers of IMCs are formed at the interface and the failure occurred near the copper side of the joint. The mechanical property is investigated by tensile shear test, and the average maximum load-carrying capacity found 1876 N, which is comparable to other non-conventional welding processes.

Analysis of Mechanical, Microstructural Properties and Weld Morphology of A-TIG Welded AH-36 Marine-Grade Steels with Oxide and Duplex Flux Coating

The current study investigates the metallurgical, mechanical properties and weld morphology of AH36 marine grade steel (with a thickness of 8 mm) by activated-tungsten inert gas (A-TIG) butt joints, with the application of different fluxes (MoO3, V2O5, and duplex of MoO3 and V2O5) at various process parameters. The welding speed was kept constant at 120 mm/min, and current varied from 160 A to 220 A uniformly to optimise process parameters to achieve desired mechanical properties, weld morphology, and lowest possible heat input. The study also focused on comparing tensile strength, impact strength, and microhardness, heat input during welding, weld bead depth and width between conventional TIG welding and activated flux TIG welding processes at various operation parameters. Tensile results reported that fracture occurs at the base region in ordinary TIG welding and the activated tungsten inert gas welding process. It was noticed that a higher depth to width ratio attained MoO3 and V2O5 duplex flux coated weldments. There is evidence that the depth of weld joints is enhanced because of stable arc, Marangoni effect, and arc constriction. Microhardness results reported that the fusion zone has a higher microhardness in the activated tungsten inert gas welding than the ordinary TIG welding. It was concluded that out of all fluxes, MoO3 and V2O5 duplex flux coating produce better butt welds of AH36 steel.

Productivity improvement in butt joining of thick stainless steel plates through the usage of activated TIG welding

Activated tungsten inert gas (A-TIG) welding is one variant of conventional TIG welding where a thin layer of suitable activating flux is deposited on the parent components prior to constituting the arc in order to harness enhanced penetration. Despite several benefits, industries are still reluctant in overwhelmingly using this new variant. This article attempts to highlight the productivity benefits in employing A-TIG welding either together with or superseding TIG welding during butt joining of 10-mm-thick AISI-316L austenitic stainless steel components. Initially, three single-component fluxes (Cr2O3, Fe2O3, and SiO2) are tested in forehand welding technique under varying currents but with straight polarity. Filler rod having similar metallurgical composition is also delivered during homogeneous welding. The extent of capability of each of the three fluxes is analysed by comparing the weld bead geometrical parameters (penetration, puddle width, and reinforcement) with the same obtained in conventional TIG welding under similar set of parameters. While Fe2O3 and SiO2 fluxes are found capable in enhancing penetration and reducing puddle width and heat affected zone, Cr2O3 flux failed to exhibit better performance. The article further demonstrates the time saving that can be obtained by adopting flux-assisted TIG for joining 10-mm-thick plates. When joining from both the faces is allowed, about 70% less time is desired if a combination of A-TIG and TIG is employed rather than using only TIG welding. If joining from only one face is allowed, then also usage of flux can reduce welding time by 33%.

A-TIG (activated flux tungsten inert gas) welding: – A review

Abstract TIG welding faces low weld penetration as the major challenge which ultimately limits the productivity of the process. To mitigate this challenge and utilize the peerless benefits of TIG welding, a technique known as Activated flux tungsten inert gas (A-TIG) welding has been developed and is being widely researched upon. In this process, a layer of flux is applied over the surface of workpiece prior to welding. A-TIG is very well capable of increasing the weld penetration depth by almost three times or even more and aspect ratio around 200%, in comparison to conventional TIG welding. This feature of A-TIG pushes its potential to be of more practical use in manufacturing industries requiring high productivity and fine weld quality. Such high depth of penetration is explained with the help of several mechanisms stated by various researchers. The inclusion of different fluxes and the amount of oxygen present in the molten pool zone also plays a major role in A-TIG. A significant change in the mechanical properties and microstructure of weld bead is observed by the effect of enmeshed oxides. Apart from having notable proficiency, this process did not receive enough attention and appreciation which sets up the motion for writing this review paper, discussing A-TIG welding for different metals, welding flux with its chemical composition and various process parameters in detail. The resulting effects of different activated fluxes on mechanical properties and metallurgical aspects like weld pool attributes, weld chemistry and HAZ microstructure, material dilution, slag reactions and mainly weld penetration has been clarified in the study.

Optimization of A-TIG Welding Process Using Simulated Annealing Algorithm

Flux-assisted tungsten inert gas welding process, also known as activated tungsten inert gas (A-TIG) welding, is extensively used in order to improve the performance of the conventional TIG welding process. In this study, the orthogonal array Taguchi (OA-Taguchi) method, regression modeling, analysis of variance (ANOVA) and simulated annealing (SA) algorithm have been used to model and optimize the process responses in A-TIG welding process. Welding current (I), welding speed (S) and welding gap (G) have been considered as process input variables for fabricating AISI316L austenitic stainless steel specimens. Depth of penetration (DOP) and weld bead width (WBW) have been taken into account as the process responses. In this study, SiO2, nano-particle has been considered as an activating flux. To gather required data for modeling, statistical analysis and optimization purposes, OA-Taguchi based on the design of experiments (DOE) has been employed. Then the process responses have been measured and their corresponding signal-to-noise (S/N) ratio values have been calculated. Different regression equations have been applied to model the responses. Based on the ANOVA results, the most fitted models have been selected as an authentic representative of the process responses. Furthermore, the welding current has been determined as the most important variable affecting DOP and WBW with 68% and 88% contributions, respectively. Next, the SA algorithm has been used to optimize the developed models in such a way that WBW is minimized and DOP is maximized. Finally, experimental performance evaluation tests have been carried out, based on which it can be concluded that the proposed procedure is quite efficient (with less than 4% error) in modeling and optimization of the A-TIG welding process.

High-frequency pulse-modulated square wave AC TIG welding of AA6061-T6 aluminum alloy

Bead-on-plate welding of 6-mm thick AA6061-T6 aluminum alloy is used to characterize the high-frequency (HF) pulse-modulated square wave AC TIG (HFPM AC TIG) welding. The modulation HF pulse reduces the reignition voltage of negative half-wave arc. However, its effectiveness on increasing weld penetration is not evident until the penetration rate (penetration-to-workpiece thickness ratio) exceeds 45%. Above this value, the weld penetration increases significantly with increasing peak current of the HF pulse, and first increased and then decreased with increasing pulse frequency from 10 to 40 kHz. Maximum penetration achieved at optimal welding condition increases by 120% compared with that of conventional AC TIG welding. The grain size and width of partially melted zone are visibly reduced. The average equiaxed grain size, pore number density, and average pore size in HFPM AC TIG weld metal decrease with increasing pulse frequency.

Microstructural Characteristics of Wire Arc Additive Manufacturing with Inconel 625 by Super-TIG Welding

Nowadays, the implementation of additive manufacturing (AM) is rapidly growing in various sectors. Many manufacturing industries are demanding an increase in the size of the AM parts. Wire arc additive manufacturing (WAAM) offers a high deposition rate and quality products without size limits. The welding process of gas tungsten arc welding is widely used for WAAM. This paper introduces the WAAM process using Super-TIG welding by Inconel 625. Super-TIG welding is a kind of TIG welding process using C-Filler. The high deposition rate of WAAM can be obtained using Super-TIG welding to build large-scale components. The productivity of Super-TIG welding is higher than in conventional TIG welding. The layering strategies have been developed to refine the microstructure of the WAAM parts. The deposits of the single-pass beads with oscillation have resulted in the formation of larger grains with epitaxial grain growth. However, the multi-pass beads with stringer and zig-zag layering sequences have refined the microstructure with the presence of smaller grains. The influence of heat input on the WAAM properties along with layering strategies has also been observed.