Activated Flux Tungsten Inert Gas Research Articles

Improvement in Depth of Weld Penetration During TIG, Activated-TIG, and Pulsed TIG Welding

Joining of dissimilar materials has gained a lot of interest in the recent years due to the increased demand of high strength and light weight designs. Fusion welding plays a vital role in repairing and manufacturing industries like automobile, construction, ship building, and energy sector. Tungsten inert gas (TIG) welding is more advantageous over other welding processes as it produces high precision welds with aesthetic appearance. The limitation of the process is shallow penetration, distorted and weaker joint formation, and low productivity. In the present work, a critical review and analysis has been done on weld penetration and its enhancement during TIG, activated flux TIG, and pulsed current TIG welding of steels. The purpose of this review is to raise an insight about using the variants of TIG, minimising the energy consumption and heat affected zone while increasing the weld penetration and productivity. Proper selection of welding parameters along with welding speed, electrode diameter, shielding gas, electrode tip angle, arc gap, and flux greatly increase the weld penetration.

Effect of activated flux tungsten inert gas (A-TIG) welding on the mechanical properties and the metallurgical and corrosion assessment of Inconel 625

This article makes an attempt to investigate the outcome of activated flux and filler wire in addition to A-TIG welding and TIG welding of Inconel 625 respectively. Ni-Cr-Mo enriched filler namely ERNiCrMo-3 was used to join 6.5-mm-thick plates. Microstructure characterization, mechanical properties evaluation and secondary dendritic arm spacing measurements were carried out to find the cause of the perceived differences. Tensile test failures were observed at the weld zone in both welding processes. Charpy impact studies showed that weldment using A-TIG revealed a low toughness value compared to the TIG weldment. Root bend test showed no discontinuity in both fusion zones and hence, the weldment was produced without defect. The deleterious laves phase was reduced when activated flux and fillers were used. Corrosion performance was undertaken in a 3.5 wt% NaCl solution, to illustrate the outstanding corrosion resistance in Inconel 625’s fusion zone using A-TIG and TIG welding processes.

Dissimilar Metal Welds used in AUSC Power Plant, Fabrication and Structural Integrity Issues

ABSTRACTIn the current era, the Advanced Ultra Super-Critical (AUSC) plants have been used to substantially increased efficiency with environmental protection. AUSC components boiler header, re-heater and super-heater tube etc. are fabricated by using advanced materials to join by the welding process. Any failure of the power plant can lead to grave consequences, not only of substantial financial losses but additionally immensely treasured and irreparable human life loss. In this review, the dissimilar metal welds (DMWs) have many issues such as metallurgical issue, cracking, carbon migration, welding electrode selection, creep properties, suitable welding process and structure integrity issues which enhanced the failure of weldments. The results of our review showed that DMWs of AUSC power plant are joined by activated flux Tungsten Inert Gas (A-TIG) and Pulse A-TIG process to increase the productivity and cut the significant fraction of cost. However, A-TIG process with Post Weld Heat Treatment (PWHT) improved the mechanical properties and high-temperature creep resistance properties of DMWs. This state of the art is encouraged the researchers about the enormous future scope.

Activated flux TIG welding of dissimilar SS202 and SS304 alloys: Effect of oxide and chloride fluxes on microstructure and mechanical properties of joints

Low depth of penetration limits the use of favored tungsten inert gas (TIG) welding process for joining of ferrous and non-ferrous metals, demanding weld bead profile of high quality. This article aims to study the effect of chloride and oxide fluxes viz. calcium chloride (CaCl2) and ferric oxide (Fe2O3) on micro-structural and mechanical properties of TIG welded joints of dissimilar SS304 and SS202 steels. Results reflected that use of oxide and chloride fluxes significantly affects the weld bead geometry, bead dimensions and penetration. The use of oxide flux resulted in complete penetration and approximately linear root of weld with good fusion of both the base metals. Fusion zone showed columnar dendritic cast grain structure while coarse grain structure was obtained in heat-affected zone. Fusion zone hardness was higher than SS304 base metal and an opposite trend observed for SS202 irrespective of welding condition. Fine grained heat affected zone hardness was higher than coarse rain for all welding conditions.

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.

Effect of Activating Flux (Metal Oxide) on the Weld Bead Nomenclature of Tungsten Inert Gas Welding Process – A Review

Welding is inevitable process in the industry. So, many developments are being carried out in existing welding methods and new welding techniques have been developed. Likewise, Tungsten Inert Gas (TIG) welding process is broadly used in manufacturing firms owing to its capability to produce high quality welds at an affordable cost. The Study of recent advancement in TIG welding is necessary to the welding community. Hence, this review paper dealt the recent evolution in the TIG welding which is Activated flux TIG (ATIG).

Activated flux TIG welding of austenitic stainless steels

The tungsten (W) inert gas (TIG) welding process that is applied with an active flux deposited on the workpiece surface just before welding is called activated flux TIG (A-TIG) welding. Layer deposition can be achieved by brushing or spraying over the surface, and welding is carried out after the surface dries out. This process has shown that it is possible to increase weld penetration and productivity up to three times higher or more compared with the TIG process in steels. In this review paper, A-TIG welding applications of steels were examined. The chemical composition and thickness of the flux and welding parameters (welding current, welding speed, arc length and shielding gas composition and its flow rate) affect the weld geometry. The activated flux welding mechanisms, effects of flux and welding parameters on weld geometry and microstructure and properties of A-TIG welds were explained.

Electrochemical studies and corrosion resistance of activated Tungsten inert gas AISI SS316L weldments

Welding is the most convenient fabrication process with tremendous development in past few decades. The noteworthy technique is Activated flux TIG welding method (also known as A-TIG welding) that was well-equipped a little while back, which enhances productivity and quality of weld joints by better depth of penetration. In this research work, the electrochemical studies are performed to investigate the corrosion resistance of excellent depth of penetration A-TIG welded 316L stainless steel (SS316L) sample at room temperature. At dilute aqueous ambience, Potentiodynamic studies reveal that the SS316L welding joints have an apathetic attitude with certain range. Electrochemical Impedance calculations illustrate the breakdown occurs due to corrosion in alkaline circumstances.

Improving the strength-ductility synergy and impact toughness of dissimilar martensitic-austenitic steel joints by A-TIG welding with wire feed

Activated flux-tungsten inert gas (A-TIG) weld joint of dissimilar martensitic-austenitic steel possesses low strength-ductility synergy and poor impact toughness due to the formation of hard and brittle martensitic structure in the weld zone (WZ). In the present work, a pathway is proposed to improve the strength-ductility synergy and impact toughness of such dissimilar weld joints by feeding the ErNiCrMo-3 wire into the weld pool during welding. ‘A-TIG welding with wire feed’ (patent pending*) successfully modified the WZ chemical composition (Creq: 15.01 and Nieq: 28.16), which altered its microstructure from hard and brittle martensite to Fe-Ni-Cr rich soft austenite. As a result, a superior strength-ductility synergy (ultimate tensile strength: 684.9 MPa and elongation: 45.8%) and unprecedented impact toughness (89 ± 2.4 J) was achieved.

Microstructure and properties of nano-SiO2 activated flux TIG (A-TIG) welding of Incoloy 925 joints

• Improved depth of penetration with the use of activated, nano-oxide flux welding for Incoloy 925. • The yield and tensile strengths of the weld joints were considerably increased when subjected to direct ageing. • The occurrence of γ′, M 7 C 3 , η, and σ phases were noticed along the grain boundaries in the direct aged condition. • High angle grain boundaries (HAGBs) were dominated in the jointed regions after subjecting to ageing. Precipitation strengthened Ni based alloy, Incoloy 925 is widely used in the H 2 S-containing hot sour environments because of its excellent properties. Metallurgical properties, which is known to affect the performace of this alloy greatly depends on the welding technique adopted, ageing condition, formation of inter-metallic phases and hardness. Hence, in this research work, the joints of Incoloy 925 are accomplished in a single pass with the use of nano-SiO 2 activtated flux tungsten inert gas (A-TIG) welding process. Further, the A-TIG welded joints were subjected to direct ageing for 4 h and 8 h at 732 °C and air-cooled. Recrystallized grains were observed in the fusion region in the as-welded (AW) condition. The grain boundaries of the weld seams were precipitated with M 7 C 3 carbides, discrete amounts of η (Eta) and σ (Sigma) phases after subjecting to DA. The tensile strength of the weld seams was increased to ∼ 41 % and 31 % after having exposed to DA for 4 and 8 h respectively. The failures due to tension occurred in the fusion zone of Incoloy 925 irrespective of the DA conditions. The formation of η phase and high angle grain boundaries (HAGBs) resulted in a lower percentage of elongation and impact toughness when aged for 8 h.

“Effects of using oxide fluxes as activating flux on Activated flux Tungsten Inert Gas welding” – A review

Tungsten Inert Gas welding (TIG) is preferred in the Aerospace Industry where thin sections have to be welded with quality and precision. But, when thick sections are to be welded, conventional TIG welding is not usually preferred due to low penetration depth necessitating more passes. Activated flux Tungsten Inert Gas (A-TIG) welding was invented to improve productivity when welding thick sections. This study reviews the effects of using oxide fluxes in the A-TIG welding.

Influence of activating flux tungsten inert gas welding on mechanical and metallurgical properties of the mild steel

Mild steels have versatile application in various structural design like in steel frame buildings, pipelines, railway wagons etc. Tungsten inert gas (TIG) welding is common to use this kind of materials. However, less depth of penetration in single weld pass make it time consuming and less productive during fabrication of thick sections (usually >3 mm). Activating flux tungsten inert gas (A-TIG) welding is growing as solution for less penetration. Successful implementation of the A-TIG welding process on mild steel could reduce the fabrication cost drastically. Therefore, in the current work, efforts are made to develop the weld joint using suitable processes/approaches. In view of above, weld joints of mild steel were developed using conventional TIG welding process and activating flux tungsten inert gas welding process. The weld joints were characterized in respect of weld bead geometry, angular distortion, microstructure, hardness distribution, tensile properties, and the impact toughness. Results have been discussed in light of microstructure study and mechanical behaviour of the weld joints.

Optimization of weldment in bead on plate welding of nickel based superalloy using Activated flux tungsten inert gas welding (A-TIG)

The main objective of this research article is to identify the optimized welding process parameters for a 6.5 mm thick Inconel 625 nickel based superalloy by Activated flux tungsten inert gas welding (A-TIG). The bead on trial experiments was carried out on a L25 orthogonal array with preferable input responses like current, torch speed and arc gap. Output responses considered were welding heat input and heat affected zone width (HAZ). Multi criteria decision making optimization tool, Grey relational analysis (GRA) was used to find the optimum condition. Analysis of variance (ANOVA) was employed to determine the consequence of each individual input’s response. From various experimental trials 300 Amps current, 75 mm/min torch speed and 1 mm arc gap with a heat input of 4.212 kJ/mm were found to be optimal input responses. The optimized sample was examined by Optical microscopy for a detailed study of the interdendritic region of the HAZ and weld zone.

Activated flux TIG welding of stainless steel pipes

In this work, the presence of TiO2 nanoparticle-based activated flux combined with orbital welding of seamless thick-walled pipes of stainless steel and lowcycle pulse current was done, representing a novel combination of welding processes parameters. Control specimens were welded without flux and consumable material, and without flux with the consumable material. Experimental welding with different welding parameters was done. Special attention was given to characterize the flux by zetasizer method, representing a new approach, versus the conventional approach where the nominal oxide particle size is reported. The obtained welds were visually tested, macroanalyzed, their microstructures examined, and their tensile and bending properties determined. The results show that the flux influences a significant increase in penetration depth, up to full penetration, which has a positive effect on the increase in the tensile and bending properties of the weld metal. Material behavior model was developed, based on microstructural features of the near weld-line. Without the flux, grain enlargement occurred near the surface, while with flux, it occurred under the weld, which can be attributed to recrystallization and a reversed Marangoni convection.

Activated flux TIG welding of Inconel 718 super alloy in presence of tri-component flux

ABSTRACTIn this study, we have explored the influence of newly developed tri-component oxide flux (Cr2O3, FeO, and MoO3) on weldability, bead geometry, weld pool temperature variation, and mechanical strength of Inconel 718 welded joints. Moreover, the influence of used flux on weld pool, the surface morphology of electrode and penetration capability of tungsten inert gas (TIG) welding on Inconel 718 plates have been well elucidated. Results indicate that the flux mixture significantly increases the penetration depth as well as aspect ratio almost 200% as compared to conventional TIG welding. The arc constriction caused by newly developed oxide flux upsurges the heat density and the weld pool temperature of joints. The alloying effect caused by entrapped oxide particles greatly improves the hardness as well as the tensile strength of joints. The reported reinforcement in the welding performance may increase potential utility of the developed methods for real-world applications.

Fatigue response evaluation of stainless steel SS 304 L(N) and SS 316 L(N) through cyclic ball indentation studies

This paper presents the results of an experimental investigation of fatigue response of stainless steel SS 304 L(N) and SS 316 L(N) using cyclic ball indentation test method. A Tungsten Carbide (WC) spherical ball of 1.57 mm diameter is used for applying compression-compression fatigue cycling on the test specimen having a nominal thickness of 5 mm; the displacement response is monitored as a function of every cycle of loading. The study focused on cases where the stainless steel specimens were welded by two different welding processes – Activated flux TIG welding and conventional multi-pass TIG welding. Fatigue response was monitored at locations of weld zone, heat affected zone (HAZ) and base metal to identify the effect of microstructure variation on fatigue response. It is observed that there is a steady increase in depth of penetration of the spherical indenter due to fatigue cycling; however, after a number of cycles, there is a sudden increase in depth of penetration which indicates the failure of the material beneath the indenter. The specimens after cyclic ball indentation were examined using a scanning electron microscope and one could observe the presence of secondary cracking in the penetrated region of the specimen.

Studies on the weldability, mechanical properties and microstructural characterization of activated flux TIG welding of AISI 321 austenitic stainless steel

The presence of titanium in AISI 321 austenitic stainless steel, mitigates the corrosion when deployed in specific applications such as boiler shells, aircraft exhaust manifolds and process equipment. Using Commercial flux purchased from Edison Welding Institute (EWI), studies were conducted to note the effect of Activated Tungsten Inert gas (A-TIG) welding on the surface morphology of type 321 austenitic stainless steel welds and compared with conventional TIG welding. A thin flux layer was applied to the surface of the 6 mm thick plate, followed by a conventional TIG welding process. The bead on trial results shows that compared with the TIG welding process, the flux causes the weld depth to increase, weld bead width to decrease and weld area to increase. This incredible depth of penetration (DOP) has been accomplished by the mechanisms of reversal of Marangoni flow and Arc constriction. From various experimental trials, arc length of 3 mm, welding current of 220 Amps and welding speed of 120 mm min−1 were found to be optimal and subsequently used as input parameters to produce a good quality A-TIG welded butt joint. The welded joint is subjected to transverse and longitudinal tensile and bend tests, charpy impact toughness tests, microhardness, optical microscope, x-ray diffraction analysis, ferrite number measurement and Scanned electron fractography. The welded joint exhibited improved tensile strength, bend and charpy impact toughness and hardness. The weld metal microstructure was observed to be austenite, delta-ferrite and TiC intermetallic compounds (Titanium carbides). The XRD pattern indicates that austenite and ferrite phases are present in both base and weld metal. The results of Fischer Feritscope FMP30 (ferrite measurement) show that the content of delta-ferrite in the weld metal (5.9 FN) is much higher than the parent metal (1.2 FN) and shows excellent mechanical properties in the A-TIG welded joint. Scanned electron fractography indicates that the failure of weld metal and base metal occurs in the ductile mode of fracture.

Study of mechanism, microstructure and mechanical properties of activated flux TIG welded P91 Steel-P22 steel dissimilar metal joint

The current work investigates activated flux TIG welding of dissimilar steel combination of 8 mm thick plates of Modified 9Cr-1Mo (P91) steel and 2.25Cr-1Mo (P22) steel. The effect of different fluxes namely- SiO2, TiO2, Cr2O3, MoO3 and CuO on the weld bead geometry was investigated. The possible mechanism for the increase in depth of penetration has been discussed. The integrity of the weld joint made with MoO3 flux was investigated by evaluating metallurgical and mechanical characteristics in as-welded and post weld heat treated (750 °C/2 h) conditions. The occurrence of carbon migration was confirmed by optical microscopy and elemental redistribution through EPMA analysis. The precipitation of carbides of M23C6 type in the carbon enriched zone was confirmed through TEM analysis. The beneficial effect of A-TIG welding in reducing the widths of carbon enriched/depleted regions at the P22 steel-weld interface after post weld heat treatment has been discussed with the help of DICTRA simulations. The weld joints failed from P22 steel base metal in both as-welded and post weld heat treated conditions during a tensile test. The impact toughness was found to be improved after post weld heat treatment.

Microstructure Evolution and Charpy Toughness Relationship of A-TIG Weld Fusion Zone for Varying Tempering Time

In the present research work, activating flux tungsten inert gas (A-TIG) weld joints of AISI 409 ferritic stainless steel was subjected to post weld heat treatment at 750 °C followed by the air cooling. To study the effect of tempering time on the microstructural and mechanical properties of the weld fusion zone, tempering time was varied from 2 to 10 h. The current study also demonstrated the comprehensive microstructure–mechanical property relationships using the collective techniques of optical and electron microscopy, electron dispersive X-ray analysis techniques, and X-ray diffraction analysis. The results indicated that the Charpy toughness of the fusion zone improved after 2 and 4 h of tempering, but the further stretch in tempering time resulted in a drastic drop in Charpy toughness. The shape of the sulphide inclusions was found to be an important factor in deciding the Charpy toughness of the A-TIG weld fusion zone. Maximum impact energy of 116 ± 9 J was observed by the sample tempered for 4 h.

A comparative study on creep behavior of AISI 409 ferritic stainless steel in as-received and as-welded condition (A-TIG and M-TIG)

Activating flux tungsten inert gas (A-TIG) welding process is an evolving welding process to increase the productivity of the conventional or multi-pass tungsten inert gas (M-TIG) welding process. The current work presents the characterization of the microstructure evolution during the creep exposure of Base metal, A-TIG and M-TIG weldments of AISI 409 ferritic stainless steel (FSS). The creep tests were performed at temperature of 600 °C and a stress of 50 MPa. Energy dispersive X-ray spectroscope (EDS) assisted field-emission scanning electron microscopy (FESEM), optical microscopy and microhardness testing were used to evaluate the samples after creep exposure. Creep tests were performed on round creep specimens. The M-TIG and A-TIG creep samples were get ruptured from the heat affected zone during creep test. The rupture time was found nearly equal for A-TIG and M-TIG weldments and maximum for base metal sample.