Gas Tungsten Research Articles

Prevention of weld decay in TIG-welded AISI 304 steel pipes

Weld decay occurs due to chromium carbide precipitation at grain boundaries in the heat-affected zone (HAZ) during tungsten inert gas (TIG) welding of austenitic stainless steels. This issue is particularly significant concerning the welding of AISI 304 steels, commonly used in the food industry. Although this problem can be overcome with different methods, there are some restrictions. A novel technique for welding AISI 304 steel pipes is introduced to reduce weld decay and improve their mechanical properties. The use of this technique, which includes faster cooling after welding, significantly minimizes the time of precipitation of chromium carbide. Temperature measurements and microstructural analyses monitored precipitation, and the impact of the technique on the mechanical characteristics of AISI 304 steel pipes was assessed through hardness and hoop tensile tests. There was a 6% increase in hardness values observed in the HAZ region, as well as a 16.7% increase in maximum load and a 127.4% increase in elongation. The reduction in chromium carbide precipitation observed in the microstructural analysis was confirmed through the double-loop electropotentiokinetic reactivation test, specifically for assessing intergranular corrosion. With the novel method, there were a 25% increase in corrosion resistance in the HAZ and a 40% increase in the weld zone.

Structure–property relationship assessment of dissimilar gas tungsten arc welded joint of pipeline steel and super duplex stainless steel for marine applications

Structure–property relationship assessment of dissimilar gas tungsten arc welded joint of pipeline steel and super duplex stainless steel for marine applications

Combined Gas Tungsten Arc Welding and Shielded Metal Arc Welding Processes for Joining Tube to Tubesheet in Shell and Tube Heat Exchangers

Abstract Flawless tube and tubesheet joints are necessary for shell and tube heat exchanger with high leakproof ability and durability. The consequence of mixing of transfer fluids due to the defective welded or expanded tube-to-tubesheet joint results in complete malfunctioning of the heat exchange process. In this case, there is a high demand for quality assessment of the fabricated tube-to-tubesheet joints (TTS) based on the international standards. Additionally, the literature on assessing the mechanical and metallurgical characteristics of tube-to-tubesheet joints using any one welding technique is available; however, articles dealing with the use of multiple welding techniques are scanty. In the current work, the quality assessment of strength welded and light expanded (3%) tube-to-tubesheet joints followed by light expansion was performed whereas for welding, combined gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) as root pass and cap pass were adopted in the fabrication stage. Quality and sound tube-to-tubesheet joints were produced using welding and tube expansion process. Linear and circular indications representing the cracks were absent on the developer in the liquid penetration test. The minimum leak path (MLP) was greater than the two-third of tube wall thickness. The results strongly qualify the use of combined gas tungsten inert gas and shielded metal arc welding process for manufacturing of tube-to-tubesheet joints. The methodology and results in the current article are beneficial for researchers and industrialists working close to shell and tube heat exchangers and boilers.

ARM Cortex Simulation Design for Trajectory Curves Evaluation of Collaborative Robots’ Tungsten Inert Gas Welding

ARM Cortex Simulation Design for Trajectory Curves Evaluation of Collaborative Robots’ Tungsten Inert Gas Welding

Regulating the microstructure and strength of the advancing side interface zone in AZ31 friction stir welded joint via localized selective remelting

Friction stir welding (FSW) is a solid-state welding technique widely used for various series of magnesium (Mg) alloys. However, in the process of transverse loading for FSW joints in Mg alloys, the ultimate fracture often occurs near the advancing side (AS) interface zone. To enhance the AS interface strength and overall joint strength, this research employed tungsten inert gas welding (TIG) arc to locally remelt the AS interface zone in the FSW-AZ31 joint. The microstructure characterization after remelting showed that two TIG melting zones were formed in the interface area between the AS and nugget zone (NZ). Within these zones, the grains exhibited significant coarsening and the texture intensity noticeably decreased. Conversely, the interface between the retreating side (RS) and NZ, being far from the TIG melting zone, experienced minimal changes in texture and grain size. Mechanical testing conducted at room temperature indicated that the joint ultimately fractured at the RS, resulting in an interface strength difference of ∼16 MPa between the AS and RS. The enhanced strength of the AS interface was attributed to the low Schmid factor of basal slip, reduced dislocation density, and pronounced twinning behavior.

Study of the impact of TIG welding parameters and post-weld heat treatment on the bending properties of AISI 1020 steel welded joints

Tungsten Inert Gas (TIG) is a welding technique that stands out due to its high precision, controlled heat input, and equipment’s cost-effectiveness. TIG welding is utilized to join various grades of steel. Presently, numerous research studies are actively seeking to improve the quality of welded joints, focusing on aspects such as strength, ductility, formability, appearance, and corrosion resistance. These improvements are achieved through the modification of welding methods and/or welding parameters. In this investigation, welding current and gas flow rate were selected as input parameters. Additionally, PWHT at 700 °C for 1.5h was applied to relieve the residual stresses occurring during the welding operation. The objective of this investigation is to examine how the welding current, gas flow rate, and post-weld heat treatment (PWHT) affect the bending properties of welded joints. The bending test was conducted to assess both the bending resistance and bending strain of the joints. The bending resistance increases to attend a maximal value of 790 N and the bending strain decreases to 7.1%, with the welding current and the gas flow rate due to the high heat input and cooling rate. The applied PWHT decreases the bending resistance by 11% and increases the bending strain by 18%, due to the decrease of the joint’s hardness.

Flange joining using friction stir welding and tungsten inert gas welding of AA6082: A comparison based on joint performance

Expanding the use of 6xx aluminum alloy series in various industries is challenging due to the need for cost-effective welding processes and optimal settings to ensure high-quality joints. The present research focused on the comparison of joint performance of the pipes and plates using tungsten inert gas (TIG) and friction stir welding (FSW) The AA6082 alloy material is used for pipes and plates used in the study. Various techniques were utilized, including hardness and tensile tests, and microstructural examinations. Using a scanning electron microscope (SEM), the surface fracture of the specimens that failed under tensile tension was also examined. The present research also included the economic impact on the welding processes used. Results demonstrated that the weld obtained using FSW was defects free whereas, internal flaws were seen in TIG welded samples. The hardness value increased over the base material (BM) for the FSW and TIG by 31–35% and 46-40%, respectively. The FSW joint was welded at a maximum UTS of 3 mm/min and a rotational speed of 3000 rpm. FSW can create the AA60682 flange joints more efficiently and effectively than fusion welding procedures like TIG processes in pipeline applications. For AA6082 flange joints, overall total cost comparisons between FSW and TIG were also made.

Vision-based algorithm for online TIG welding deviation detection of stainless steel welded pipes

Tungsten inert gas (TIG) welding is the main welding process in the production of stainless steel welded pipe. According to the morphological characteristics of the welding molten pool image during the TIG welding process of stainless steel welded pipes, the exact position of the tungsten needle tip is calculated using image moments. Extract the weld region in the contour of the molten pool, interpolate the contour curve based on the cubic B-spline curve interpolation method, utilize the characteristics of the S-G filter, remove the interference coordinates in the contour curve through the detrending of the contour curve, extract the weld feature points, and realize the accurate identification of weld seams. The experimental results show that the method can accurately calculate the welding deviation in the welding process.

Joint Characteristics of Cu-Ni Alloy Fabricated by GTAW and MPAW Processes: A Comparative Study

The current work presents a comparative analysis of the joint behavior of Cu-Ni alloy weldments fabricated by Micro-Plasma Arc Welding (MPAW) and Gas Tungsten Arc Welding (GTAW) processes. The Cu-Ni alloy thin sheets are fabricated at different values of heat input (~40-135 J/mm) by MPAW and GTAW processes, respectively. Further, to evaluate their characteristics, joints are subjected to metallurgical, mechanical, and electrochemical testing. The joints fabricated with a higher magnitude of heat input resulted in deteriorated surface quality with a value of Ra~ 6.13 μm. The increased surface roughness value of the joints resulted in a higher corrosion rate (1.273 mm/year). A finer microstructural morphology is achieved for lower heat input condition. Accordingly, the weldment exhibited higher joint efficiency of ~91%.The prominent reason for achieving higher joint strength is related to the presence of lower secondary dendritic arm spacing (SDAS), which enhances the joint strength and ductility for the joints as compared to higher SDAS value. Further, the micro-fractography analysis reveals the presence of micro/macro-voids for high heat input, whereas the existence of numerous dimples of varying size and depth is observed for low heat input condition, implying the role of heat input of utmost importance.

Artificial Neural Networks Based Prediction of Penetration in Activated Tungsten Inert Gas Welding

Using GTAW, or tungsten inert gas (TIG) welding, weld penetration is usually lesser than the other arc welding processes. ATIG (Activated-flux TIG) welding can be a good alternative to provide deep penetration, and hence, improved productivity. In this work, 304L SS plate of 8 mm thickness was used as base plate, and a flux with a mixture of SiO2, MnO2 and MoO3 was used as a ternary flux in the ratio of 1:1:2. A 2-factor 3-level response surface methodology of central composite design was considered for designing experimental runs. Back Propagation (BP) type Artificial Neural Networks (ANN) model was developed to assess penetration in ATIG welding by using heat input and pulse frequency as the two process parameters. The ANN chosen has 2-10-1 network structure. Results show that the predicted values through ANN are conforming quite well to the experimentally obtained penetration, and hence, the applicability of ANN.

Comparative Study of the Mechanical Property of AISI630 Stainless Steel Gas Tungsten Arc Welds with Different Filler Wires under Room and Cryogenic Temperature

Comparative Study of the Mechanical Property of AISI630 Stainless Steel Gas Tungsten Arc Welds with Different Filler Wires under Room and Cryogenic Temperature

Weld interface metallurgy of dissimilar alloys welded by TIG technique

Abstract TIG welding is an important joining technique for fabricating quality structural components with industrial capability. Dissimilar alloy plates were combined using double-sided tungsten inert gas (TIG) welding. Microstructure evaluation of joints were anayzed by using scanning electron microscopy, optical microscope, energy dispersion spectrometry, elemental mapping, electron back scatter diffraction. DSAW technique increased joint penetration and reduced distortion of joints. In the weld metal zone, austenite, delta ferrite and lath martensite were dominant. The weld pool had high density of Cr7C3 and Fe3C phases and low density of CrFe7C0.45, FeNi, martensite, and Fe3Ni2 phases.

A new approach based on a concurrent cooling method during GTAW and DC-LSND welding to mitigate residual stresses in Al 6061-T6

Welding often induces residual stresses and undesired distortion in components. The negative impacts of these detrimental residual stresses have prompted researchers to explore methods for preventing or mitigating these stresses. Altering the temperature history can influence residual stress, and employing cold or heating techniques during welding has the potential to reduce harmful residual stress. In this study, the dynamically controlled low-stress no-distortion (DC-LSND) method with TIG welding was utilized to reduce the residual stresses in Al alloy 6061-T6. The methodology was simulated using Abaqus software, and the simulation results were validated with experimental data. The Al alloy served as the base metal, alloy (ER-4043) as the filler, and dry ice as the coolant. In the finite element analysis, the longitudinal residual stress at the center of the weld line in TIG welding was calculated to be 77 MPa. In the DC-LSND welding method, this value approached zero. Experimental measurements revealed residual stresses in the center of the welding line to be 183 MPa in conventional welding and 130 MPa in DC-LSND welding. According to the DC-LSND results, a 100% reduction in residual stresses was achieved in the finite element method. In the experimental test, a reduction of approximately 30% in residual stress was observed. The method developed in this research is recommended for application in welding metals and alloys where phase changes do not occur.

Fabrication and Characterization of Nickel‐Aluminide Cladding by Dual‐Wire Arc Additive Manufacturing

Nickel aluminide is a widely utilized intermetallic compound, prized for its high strength, low density, and resistance to both corrosion and creep. This study investigates the impact of heat input during the fabrication of nickel‐aluminide intermetallic compounds using the dual‐wire gas tungsten arc welding process. The results indicate that an increase in clad layer dilution from 28.9% to 33.4% reduces the amount of aluminum in the molten pool from 32.46 to 21.96 wt% while increasing the presence of the Ni3Al phase. Additionally, the NiAl phase decreases when moving from the upper side of the coating to the fusion line. When the arc current is increased from 110 to 150 A, a coarse dendritic structure forms, and the dendritic arms increase from 2.6 ± 0.4 to 5.5 ± 0.3 μm. This increase in current also results in yield strength and tensile strength values of 500.21 ± 14.56 and 752.32 ± 25.12 MPa, respectively, representing decreases of 15.2% and 5.1%. Furthermore, as the arc current increases from 110 to 150 A, both the friction coefficient and the wear rate increase to 0.43 and 0.29 ± 0.02 μg m−1, respectively. However, corrosion resistance improves by 66.3%.

An In-Depth Investigation of the Effects of Tungsten Inert Gas Welding Process Parameters on Hardness and Corrosion Resistance of 2205 DSS Weldments: New Design of Experiment Parametric Studies and Optimization

The aim of this work is to examine and analyze, using response surface methodology, how the TIG welding process parameters of welding current (WC), welding speed (WS), and N2 with argon as shielding gas affect the hardness and corrosion resistance of 2205 DSS weldments. Due to the equal amounts of ferrite and austenite phases and alloying elements, duplex stainless steel DSS offers good mechanical properties and corrosion resistance. The mechanical characteristics and resistance to corrosion of the weld zone, as well as the heat-affected zone of the DSS, are, however, disturbed as a result of the welding process since it changes the distribution of these two phases and also the alloy is thermally disturbed. Therefore, in this work, an in-depth investigation of the effects of the above-mentioned parameters on the DSS quality has been performed. Results showed that increasing welding current while decreasing welding speed, which corresponds to the highest heat input, led to lower critical pitting potential and weld zone hardness but higher heat-affected zone hardness. The same results were obtained for decreasing welding current while increasing welding speed, which correspond to the lowest heat input. However, the addition of a small percent (%) of N2 to argon shielding gas resulted in increasing the critical pitting potential and decreasing the hardness in welds and heat-affected zones. Numerically, the RSM planned experimental results showed that an optimum welding current of 175A, welding speed of 170 mm/min, and 10% N2 with argon as shielding gas maximized the critical pitting potential up to 318 mV and optimized the hardness of the weld and heat-affected zone to about base metal hardness of 288 and 286 HV, respectively.

Development of parametric window and optimization of process parameters to predict bead profile in magnetically controlled gas tungsten arc welding

A novel methodology has been proposed to tame the arc shape by adopting an external magnetic field, resulting weld profile as required. The co-axial magnetic field developed by specially designed electromagnets is superimposed on the welding arc. It was found that 0-0-S-N configuration provided more penetration than conventional gas tungsten arc welding. A parametric window has been developed for the selected configuration to obtain the desired bead geometry. The experiments were performed using process parameters as suggested by the design matrix, developed using response surface method technique. Mathematical models were evolved from experimental data for penetration and bead width. The evolved model for penetration is adequate up to 99.72% confidence level and for bead width is 99.98% confidence level. The effects of process parameters have been presented in a graphical manner for better understanding. The penetration achieved with the magnetically controlled GTAW process is 3.92 mm, which is 30% more than that achieved with conventional GTAW. The bead width increases initially, up to a certain limit, and then reduces with an increase in excitation current. Further, the experiments have been conducted on the optimized parameters for the validation of models. The refined grains were obtained due to magnetic stirring of the molten pool, which is desirable for improvement in mechanical properties of welds. The average grain size was reduced from 42.55 to 31.03 µm. The improved microstructure containing more amount of acicular ferrite was obtained with magnetically controlled arc.

Structural Analysis of Thermal Diffusion and Non-Uniform Temperature Distribution along the Sidewall Thickness of STS316L during Gas Tungsten Arc Butt Welding

This study investigated how welding affects the thermal deformation of square cells produced for casks, which are dry storage containers for spent nuclear fuel. We aimed to minimize structural deformation by utilizing STS316L as the material for the square cells. We explored a method of subdividing the square cells and joining them through butt welding. Keeping the upper plate thickness constant, GTA butt welding was conducted while varying the column’s wall thickness, followed by measurement with a laser vision sensor. The heat conduction and thermal strain were then calculated using a finite element analysis (FEM). Both experimental and analytical results confirmed that there was significant thermal deformation in the cases of thick-walled columns due to variations in heat conduction distribution, with the resulting deformation patterns depending on thickness.

Weld Morphology and Corrosion Characteristics of Flux-Assisted Gas Tungsten Arc-Welded Super Duplex Stainless Steel

Weld Morphology and Corrosion Characteristics of Flux-Assisted Gas Tungsten Arc-Welded Super Duplex Stainless Steel

An Investigation into the Microstructures and Mechanical Properties of a TIG Welding Joint in Ti-4Al-2V Titanium Alloy

The Ti-4Al-2V (wt. %) titanium alloy has garnered widespread applications across diverse fields due to its exceptional strength-to-weight ratio, high toughness, specific strength, and corrosion resistance. The welding of Ti-4Al-2V titanium alloy components is often necessary in manufacturing processes, where the reliability of a welded joint critically influences the overall service life of these components. Consequently, a comprehensive understanding of the welded joint’s microstructure and mechanical properties is imperative. In this study, Ti-4Al-2V titanium alloy was welded using multi-layer and multi-pass TIG welding techniques, and a detailed examination was conducted to analyze the microstructure and grain morphology of each microzone of the welded joint. The results revealed the presence of an initial α phase and a secondary lamellar α phase in the heat affected zone (HAZ). Meanwhile, the fusion zone (FZ) primarily comprised a coarse secondary α phase and a small amount of an acicular martensitic α’ phase. Both the recrystallization zone and the superheated zone exhibited a distinct preferred orientation, with grains smaller than 10 μm accounting for 65.9% and 55.1%, respectively. To assess the mechanical properties of the various microzones and the typical microstructure within the welded joint, nanoindentation tests were performed. The results indicated that the recrystallization zone possessed a higher nanohardness (3.753 GPa) than the incomplete recrystallization zone (3.563 GPa) and the superheated zone (3.48 GPa). Among all the microzones, the FZ exhibited the lowest average nanohardness (3.058 GPa). Notably, the basket-weave microstructure demonstrated the highest average nanohardness, reaching 3.93 GPa. This was followed by the fine-grain microstructure, which possessed a slightly lower nanohardness. The Widmanstätten microstructure, on the other hand, exhibited the lowest nanohardness among the three microstructures within the HAZ. Therefore, the basket-weave microstructure stands out as the most desirable microstructure to achieve in the welded joint. In summary, this study provides a comprehensive characterization and analysis of the microstructure and properties of Ti-4Al-2V titanium alloy TIG welds, aiming to contribute to the optimization of the TIG welding process for Ti-4Al-2V titanium alloy.

Role of buttering layer composition on microstructural heterogeneity and mechanical properties of Alloy 617 and P92 steel dissimilar welded joints for future Indian AUSC program

Restrictive operating conditions (even exceeding 700 °C) of materials in advanced ultra super critical (AUSC) power plants and the need to minimize manufacturing and maintenance costs require the production of dissimilar metal welded joints (DMW). Significant differences in the physical and chemical properties of welded materials lead to phenomena that reduce the weldability of the metals used and force the search for solutions that limit unfavorable phenomena, e.g., the use of buttering layers. The study presents a comparison of two types of joints with Alloy 617 (UNS N06617) and ferritic P92 (UNS K92460) steel made using Inconel 82 (ENiCrFe-3) and Inconel 617 (ERNiCrCoMo-1) alloys buttering layer and the corresponding chemical composition of filler metals. All areas of the joints made with the gas tungsten arc welding process were subjected to structural investigations (optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) and mechanical tests (microhardness, room and high temperature tensile, and toughness testing). Despite the more complicated welding procedure, sound welded joints were obtained with favorable properties resulting, inter alia, from the reduced thickness of the martensite layer in HAZ of P92 steel and the limited diffusion of alloy components compared to welded joints without the buttering layer. This also resulted in a reduction of the maximum hardness (especially in the case of Inconel 82 buttering—by 15–30 HV0.5 in comparison with Inconel 617 buttering) and an increase in strength while limiting the decrease in plasticity (even 663 MPa tensile strength and 21% of elongation for Inconel 617 buttered joint). Moreover, improved high-temperature performance (approximately 70–100 MPa) of the welded joint following the application of the buttering layer was confirmed. The presented results allow for drawing general conclusions that both proposed welding procedures can be recommended for use in the working conditions occurring at AUSC.