Tungsten Inert Gas Process Research Articles

Numerical Study of the Effects of Residual Stress in Welded Pipe Joints

In general, welding processes can be understood as the establishment of the union of parts, generally metallic, using a heat source to promote the fusion of materials, with or without the presence of pressure efforts. Studies related to the distributions and levels of residual resistance arising from the thermal cycles involved in welding processes are of vital importance for evaluating and guaranteeing the integrity of welded pipes. This work proposes the implementation of a routine in PYTHON language to automate the production of thermomechanical coupling welding models using the ABAQUS® CAE finite element tool, considering the heat distribution model of the welding source according to Goldak et al. (1984), better known as the double ellipsoid model. The studies are produced considering an ambient temperature of 20 °C and another with preheating of the tubes to 300 °C. The results achieved by this study are related solely to analyzes of the residual stress fields in a thin walled tube joint manufactured in AISI 304 stainless steel, welded using TIG (Tungsten Inert Gas) processes in a single pass. Thus, this study seeks to analyze the hoop and axial residual stress distributions on the internal or external walls of post-welded tubes in angular positions 0°, 90°, 180° and 270°, whether or not there is uniform preheating of the pre-welding pipes. The results show that, in general, residual stresses differ slightly with the angular position, being relatively high when compared to the yield stress of the steel, and therefore have a considerable impact on reducing the mechanical strength of the welded joint. It should also be noted that when considering the preheating of the pipes there is a significant decrease in the peak temperatures reached in the transfer process, in the cooling rates and in the residual stress levels of the joints, especially in the most critical regions, located in the proximity from the center of the weld beads.

Comparative Study Between Friction Stir Welding and Tungsten Inert Gas Welding Processes

This study compares the properties of the aluminium alloy welded joints prepared by friction stir welding (FSW) to that of tungsten inert gas (TIG). It concentrated on the microstructure, hardness, corrosion resistance, and wear resistance. It has been found that the joints prepared by FSW have fine microstructure while coarse grains microstructure was obtained for joints produced by TIG welding. Also, the lowest Rockwell hardness measured at the centre of the welding line is 52 for joints prepared by FSW and 46 for ones produced by TIG welding. For corrosion resistance the reslt of tests indicated that the welded joints of the TIG process had higher corrosion resistance, the mass loss after 72 hours is 0.2519 grams from TIG joints and it is about double in the case of FSW joints (0.5263 grams). However, TIG joints have lower wear resistance compared to joints produced by the FSW process. It seems that the grain size of the welded joints, in these two considered welding processes, has a great effect on the investigated properties.

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.

Comparative analysis of filler metals on microstructure and mechanical performance of TIG-welded AISI 201 austenitic stainless steel joints

In this study, 4-mm thick AISI 201 austenitic stainless steel butt joints were fabricated using the tungsten inert gas (TIG) process with ER309L, ER316L and ER2209 filler rods. TIG welding was performed using a current of 100 A, voltage of 14 V, with pure argon as the shielding gas at a flow rate of 10 L/min, and filler rod diameters of 2.4 mm. The microstructural and mechanical properties were analysed. ER2209 and ER316L promote an austenitic structure in the fusion zone. ER316L filler produced the finest grain structure (9.39 μm) and the lowest δ-ferrite content (25.85%) in the weld zone. Welds made of ER316L exhibited the highest hardness (314 HV), ultimate tensile strength (857 MPa) and yield strength (448 MPa). ER316L welds also demonstrated superior strain-hardening capacity (0.91) and impact toughness (19.8 GPa). Fracture analysis revealed finer dimples in the ER316L welds, indicating improved ductility and strength compared to other welded joints.

Comparison between Mechanical Properties and Joint Performance of AA 2024-T351 Aluminum Alloy Welded by Friction Stir Welding, Metal Inert Gas and Tungsten Inert Gas Processes.

The aim of this work is to study joining Al 2024-T3 alloy plates with different welding procedures. Aluminum alloy AA 2024-T351 is especially used in the aerospace industry. Aluminum plates are welded by the TIG and MIG fusion welding process, as well as by the solid-state welding process, friction stir welding (FSW), which has recently become very important in aluminum and alloy welding. For welding AA2024-T35 with MIG and TIG fusion processes, the filler material ER 4043-AlSi5 was chosen because of reduced cracking. Different methods were used to evaluate the quality of the produced joints, including macro- and microstructure evaluation, in addition to hardness and tensile tests. The ultimate tensile strength (UTS) of the FSW sample was found to be 80% higher than that of MIG and TIG samples. The average hardness value of the weld zone of metal for the MIG- and TIG-produced AA2024-T3511 butt joints showed a significant decrease compared to the hardness of the base metal AA2024-T351 by 50%, while for FSW joints, in the nugget zone, the hardness is about 10% lower relative to the base metal AA2024-T3511.

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.

Metallurgical and mechanical properties evaluation of the activated flux tungsten inert gas weldments

The activated flux tungsten inert gas welding process is an attractive joining technique to increase the depth of penetration in a single pass. In the last two decades, the research on activated flux tungsten inert gas welding increased drastically. Despite enhanced weld penetration, activated flux tungsten inert gas is not frequently implemented in industries because of a lack of information about the process. However, research on activated flux tungsten inert gas welding has significantly increased in the last decade due to the widespread information related to the advancements in weld penetration and mechanical properties of the activated flux tungsten inert gas process. The activated flux tungsten inert gas welding process provides a high single pass depth of penetration along with good mechanical properties compared to the tungsten inert gas welding process. The current work offers an in-depth analysis of the activated flux tungsten inert gas welding process mechanism, advancement in activated flux tungsten inert gas methodology to improve weld bead geometry, and mechanical and corrosion behaviour of the weldments. The current work also highlights recent progress made in the field of dissimilar metal joining using the activated flux tungsten inert gas welding process.

Immersion and electrochemical corrosion properties and combined corrosion mechanism of TC4 alloy by keyhole TIG welding

In this study, the effect of heat input on the microstructure and its correlation with the immersion corrosion properties of TC4 welded joints by Keyhole tungsten inert gas (TIG) process was researched. The combined corrosion mechanism between immersion corrosion and electrochemical corrosion was established. The results showed that immersion corrosion formed a passivation film on the surface of the welded joint and formed a minimal number of pitting pits. After immersion, electrochemical corrosion testing was carried out. Due to the existence of the passivation film, the self-corrosion potential increased from-0.6 V ∼ −0.2 V–0.1 V–0.6 V, and the self-corrosion current density decreased and the fitting impedance of the film increased. These all showed that the corrosion resistance of the joint was enhanced after immersion. However, due to the combined effect of immersion corrosion and electrochemical corrosion, the potential difference between the surface passivation film and the internal metal was sufficiently large to induce pitting corrosion on the surface. After the breakdown of the passivation film, spot corrosion pits formed. Microcracks propagated along the primary β grain boundary and the α′ phase interface, and continuous corrosion for a long time may even lead to cracking failure of the welded joints. With the increase of heat input, the self-corrosion potential and the self-corrosion current density of immersion corrosion increased firstly and then decreased. The fitting film resistance value of the impedance decreased firstly and then increased. The aforementioned findings indicated that as the heat input increased, the corrosion properties of the joints firstly deteriorated and then improved.

A Comparative Study on the Microstructural Evolution and Mechanical Behavior of 316LN Stainless Steel Welds Made Using Hot-Wire Tungsten Inert Gas and Activated Tungsten Inert Gas Process

A Comparative Study on the Microstructural Evolution and Mechanical Behavior of 316LN Stainless Steel Welds Made Using Hot-Wire Tungsten Inert Gas and Activated Tungsten Inert Gas Process

Effects of heat input on microstructure evolution, mechanical and corrosion properties of TC4 alloy by keyhole TIG welding

In this study, Keyhole tungsten inert gas (TIG) process, a new variation of traditional TIG process, was performed to weld TC4 titanium alloy with a thickness of 6 mm. The effect of heat input on microstructure and their correlation with mechanical properties and corrosion behavior was studied. The results showed that the microstructure of fusion zone and heat-affected zone changed obviously due to the change of heat input. The microstructure in the joints was transformed from equiaxed primary α and α+β lamellae to complete primary β grains, and then α′ phases were precipitated in the primary β grain. With the increase of heat input, the content and length of the acicular α′ phase grains were increased, resulting in a decrease in the number of high angel grain boundaries (HAGBs). Due to the phase strengthening effect of α′ phases, the microhardness of the joints increased, and the tensile strength increased, reaching a maximum value of 1030.1 MPa when the heat input was 1118 J/mm. The impact toughness of the joints increased firstly and then decreased. The corrosion behavior of the joints was worse than that of the base metal (BM). The best corrosion resistance was obtained when the heat input was 1046 J/mm. It concluded that the excellent comprehensive properties can be obtained when the heat input was in the range of 1046–1118 J/mm.

Effect of cobalt addition on wear behaviour of TiB2 coating produced by TIG cladding process

In this paper, the mechanical and tribological characteristics of TiB2 ceramic coating with and without cobalt (Co) addition developed using tungsten inert gas (TIG) cladding process on AISI 304 stainless steel (SS) were investigated. The effect of TIG process conditions as well as cobalt (Co) content on the microstructure, microhardness and resistance to wear were investigated systematically. The phase identification, microstructure, and elemental distribution map of the clad layer formed on the surface of an AISI 304SS substrate were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), respectively. Vickers microhardness testing apparatus and a pin-on-disc tribometer were used to evaluate the microhardness, resistance to wear, and coefficient of friction (COF), respectively. The result demonstrates that a dense and defect-free composite coating with a strong metallurgical bond to the substrate is possible. The average microhardness of the TiB2 ceramic coating without Co addition was 1704 HV, and the average wear rate was 15.1576 × 10−9 g N−1-m−1. In contrast, the TiB2 ceramic coating with Co addition exhibited an improved average microhardness of 1860 HV and a reduced average wear rate of 22.7364 × 10−9 g N−1-m−1, while the AISI 304SS substrate had an average microhardness of 216 HV and an average wear rate of 200.45×10−9 g N−1-m−1. The conclusion is that the TiB2 ceramic coating with Co addition exhibited superior mechanical and tribological characteristics, demonstrating its suitability for use in wear-resistant components. The higher microhardness of the TiB2 ceramic with Co-added coating indicates enhanced hardness and potential resistance to deformation, while the lower wear rate suggests improved durability and the ability to withstand frictional forces. Therefore, the TiB2 ceramic coating with Co addition shows promise for applications where wear resistance is crucial.

Effect of solubilization heat treatment on microstructure and corrosion resistance of joints welded with the autogenous TIG process duplex stainless steel

Duplex stainless steels (DSSs), are used commonly under severe working conditions, subject to high stresses associated with corrosion. A typical DSS is composed of the combination involving two types of microstructures, ferritic and austenitic, which characterizes it as a material with corrosion resistance in aggressive media, due to its ability to passivate. The use of DSS has been increasingly exploited in the oil industry, and its use has occurred in numerous areas, standing out in the production of flexible pipelines, which in most applications, is associated with a welding process. They require special care when welded by the tungsten inert gas (TIG) welding process. Temperature variations in this process, along with heat treatment, promote the formation of precipitates in the matrix and change the phase balance. This significantly influences the mechanical and corrosion properties of DSSs. The objective of this work is to study the influence of two different parameters of solubilization heat treatment after welding on the microstructure and corrosion resistance of a DSSs welded joints. After the autogenous TIG welding process, the welds were subjected to thermal solubilization treatments for 10 and 25 s at 1050 °C. The conditions subjected to the solubilization heat treatment were compared with the as TIG welded control condition. The microstructure was analyzed by confocal microscopy and the corrosion resistance was evaluated by the "A" method of the ASTM G48 standard.

Analysis of mechanical properties and optimization of tungsten inert gas welding parameters on dissimilar AA6061-T6 and AA7075-T6 by a response surface methodology-based desirability function approach

This study explores the influence of welding current, travel speed and gas flow rate on response parameters including ultimate tensile strength (UTS), percentage elongation (PE), microhardness (MH) and residual stress (RS) using face-centred central composite design (FCCCD). Dissimilar AA6061-T6 and AA7075-T6 plates were welded using an automated tungsten inert gas (TIG) process. Mathematical models were developed to predict the mechanical properties. High welding current or low travel speed enhanced the joint quality but raised residual stresses. At a welding current of 145 A, travel speed of 1.28 mm/s and gas flow rate of 18 l/min, the optimized UTS, PE, MH and RS were predicted to be 167.28 MPa, 10.25%, 69.61 HV and 65.49 MPa, respectively. Confirmation experiments were conducted to verify the model’s practicality. The results indicate that travel speed has the greatest influence on the responses, followed by welding current, while the gas flow rate has the least effect.

Development of a Virtual Reality-Based System for Simulating Welding Processes

Arc welding processes, such as shielded metal arc welding (SMAW), metal inert gas (MIG), and tungsten inert gas (TIG), play an important role in industrial applications. To improve the efficiency of the exploitation of traditional welding systems, new technologies have been used. Virtual reality technology is one of them. The virtual reality (VR)-based welding system enables to increase the frequency of practice to help learners obtain welding experience to avoid errors that occur during actual welding processes. This paper presents a VR-based system for simulating three welding processes: SMAW, MIG, and TIG. The developed system includes hardware components and VR software installed on a computer. The change in the physical devices, such as moving the welding torch and the distance from the welding torch to the plates to generate the weld bead, will update in real time and appear on the virtual environment. The functionality of the developed system for simulating the welding processes, such as in the real welding environment, was tested successfully. For implementing the system, welding speed and the distance from the welding torch to the plates are important process parameters, which determine the weld size or the weld formation. In this research, the ranges of the welding speed are 70 ÷ 120 mm/min; 240 ÷ 460 mm/min; and 250 ÷ 450 mm/min for the SMAW, TIG, and MIG processes, respectively. These values were tested experimentally. The distance from the welding torch to the plates to display the weld joint is 1.5 ÷ 5 mm. Outside of this range, no weld joint is formed. The welding widths are 4.4 ÷ 12.9 mm, 7.1 ÷ 12.4 mm, and 7.4 ÷ 11.3 mm for the SMAW, TIG, and MIG processes, respectively.

Experimental investigation for GTAW optimization using genetic algorithm on S-1 tool steel

Industries are using various welding processes for fabrication purposes. Tungsten Inert Gas (TIG) is a very popular technique for welding different parts of articles. Argon gas is necessary for welding metals to enhance the toughness of weld metal and to diminish spatters. Tool steels are hard to weld through conventional type welding in comparison to low-carbon steels. An experiment was conducted on the welding of S-1 tool steel material by using the TIG process. Some samples were prepared to conduct the test in which one sample is parent metal and other samples were welded at different welding currents and various gas flow rates using ER308L 2 mm diameter filler rod and its effect on welding. Thereafter five samples were machined for the Charpy impact test according to ASTM A370. Further, Genetic Algorithm (GA) is using current as 80A − 100A and gas flow rate as 9.1 lpm – 10.5 lpm to determine optimal welding parameters. Analysis of Variance (ANOVA) was used to find the utmost significant factor that influences the response parameters. The result shows the R2 (Determination coefficient) was more than 0.75 and optimum parameter for welding current is 80A and the argon gas flow rate is 10.5 L/min.

Analytical and Neural Network Analysis on Flux-Coated Aluminium Alloy by Activated TIG Welding with Synthesized Nanocomposites

This research focused to synthesize the material by the tungsten inert gas (TIG) welding process with support of appropriate flux coating material. Therefore the required amount of flux coating material was utilized to enhance the mechanical properties of the specified localized welded regions. Hence, this study concentrated to select the nano-SiO2 flux particles that were employed for TIG process. This activated TIG welding composes the flux-coated welding on the base metal of AA5083-H111, as this material was highly reactive with SiO2 by the presence of magnesium precipitates and well synthesized after the welding. The post- and preheat treatment process was achieved before and after welding. The selection of activated TIG process parameters composed of strengthened weld specimens along with constant parameters like electrode tip angle and flow rate, respectively. Initially, the process parameters were designed by the statistical analysis of Box Behnken method with support of regression formulation to determine the optimal solution. The maximum tensile strength was attained at the welding process parameters of welding speed (100 mm/min), voltage (13 V), and current (125 amps). The higher hardness was achieved at the process parameters of welding speed (80 mm/min), voltage (12 V), and current (125 amps), respectively. Finally, the neural network approach was utilized to verify the predicted responses of tensile and microhardness properties. The interaction plots, mean plots, and 3D scatter plots were influenced to enhance the process parameters. In this research, mechanical properties were enhanced by the flux-coated SiO2 and the analytical method also advances the optimal parameters.

Numerical Prediction for the Effects of Welding Interpass Temperature on the Thermal History and Microstructure of Duplex Stainless Steels

Numerical simulation was used to predict the thermal behavior and the resulting microstructure at the heat-affected zone (HAZ) of a 170 mm diameter and 3.5 mm thickness super duplex stainless steel (SDSS) UNS S32750 tube. In order to evaluate the thermal response from the model, a usual welding situation involving interpass temperature (IT) and its influence on the HAZ microstructure was exploited. Thus, two superimposed autogenous welding passes were simulated, the first clockwise with the tube in the room temperature and the second, counterclockwise, with the tube at the temperature of 250oC. Even subjected to successive thermal cycles and high interpass temperature, the proportion and morphology of the phases at the HAZ and Fusion Zone (FZ) did not present significant differences when comparing the two welding passes. Meanwhile, nitrogen losses should be avoided during welding in order to obtain a balanced microstructure in DSS welds, contributing to guarantee satisfactory toughness in addition to resistance to pitting corrosion. The predictions from the simulation were validated by using experimental results obtained from the autogenous TIG (Tungsten Inert Gas) process.

Calorimetric Method for the Testing of Thermal Coefficients of the TIG Process.

This paper presents an original design of a test apparatus for calorimetric measurements of arc efficiency η and melting efficiency ηm in welding processes. The construction and principle of operation of a new flow calorimeter are described, as well as the method for determining the η and ηm values in the process of the surface melting of aluminium–silicon alloy casting surfaces with a concentrated heat flux generated by the TIG (Tungsten Inert Gas) method. The results obtained indicate the advisability of using calorimetric testing to assess the arc efficiency of welding processes. It was demonstrated that changing the welding current and arc scanning speed, as well as changing the chemical composition of the silumin, has an effect on the arc efficiency value η. This has the effect of introducing a different amount of heat into the area of the heated material. The consequence of this is a change in the value of the melting efficiency ηm, which results in a change in the width and depth of the surface melting areas, through this, the cooling conditions of the material. As is well known, this will affect the microstructure of the welds and the width and microstructure of the heat-affected zone, and thus the performance of the welded joints.

Effect of welding current on properties of activated gas tungsten arc super duplex stainless steel welds

Abstract A comparative evaluation of the influence of welding current on Tungsten Inert Gas (TIG) welding and Activated Tungsten Inert Gas (ATIG) welding on the depth of penetration and microstructure properties was performed. Various super duplex stainless steel (SDSS) beads on plate weld joints were studied. Visual observation showed that lower welding current resulted in partial weld penetration in the case of both TIG and ATIG weldments. Weld joints obtained by the ATIG process have a higher depth of penetration and depth/width ratios than weld joints obtained in the conventional TIG process at comparatively lower welding currents. Further, microstructural characterizations were performed using optical microscopy. The weld zone microstructure consists of grain boundary austenite (GBA), widmanstätten austenite (WA) and intragranular austenite (IGA). Ferrite percentage in bulk material and each weldment was measured using ferrite scope. The TIG-welded heat affected zone (HAZ) joints showed higher ferrite content than activated flux TIG-welded HAZ joints for various welding current conditions. Ferrite content measured in the weld-zone, HAZ and base material was within the ranges of the standard values. The TIG weld zone showed higher hardness than that of the ATIG weld zone.

Effect of Various Fluxes on Different Metals and Alloys in A-TIG Process: A Review

Welding is the process of coalescence of two metals/alloys for creating a seamless joint, is a quintessential fabrication process utilised in almost every manufacturing sector. There is a range of welding processes that are used according to their features and the requirement of the fabricator. The tungsten inert gas (TIG) welding process is an extensively used welding process owing to its inherent characteristics like high weld quality, surface cleanliness, and autogenous welding mode. Unfortunately, the TIG process suffers some drawbacks, the most pronounced one is the shallow weld bead and low depth of penetration (DOP). This renders the process unusable for welding thicker sections in a single pass and consequently requires multiple passes which adds to the expenditure. A modification to this process is the A-TIG welding where A stands for Activated, the method utilises activating flux material to augment the penetration depth and depth to width ratio (DWR) of the weld bead. The current work is comprehensive and focuses mainly on the basics of the A-TIG process, understanding of weld pool dynamics that are governing the depth of penetration, analysis of various flux materials for their effects on different metals/alloys and finally the outcomes fetched from using A-TIG process on different commercially important alloys.