Tungsten Inert Gas Welding Process Research Articles

Tungsten inert gas-assisted surface modification of 1045 steel with SiC particles

AISI 1045 steel is a medium-carbon steel with good strength, hardness, machinability, and weldability. However, it has poor wear and corrosion resistance. This study is an attempt to investigate the feasibility of creating a hard and wear-resistant composite layer on the surface of AISI 1045 steel using SiC particles through the tungsten inert gas (TIG) welding. The SiC powder was mixed with sodium silicate glue and polyvinyl alcohol and then applied to the samples using the TIG welding process. The welding voltage was kept constant at 15 V, and the welding current and welding speed were varied from 85 to 95 A and ∼ 0.5 to 1.8 mm/s, respectively. The powder percentage varied between 10 and 30 wt. %. The microstructural evolutions were studied using an optical microscope, a field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectroscope (EDS), and X-ray diffraction (XRD). It was observed that the microstructure of the surface-modified samples consisted of a dendritic Fe–Si matrix with carbon masses remaining from the partial dissolution of SiC particles. The effect of heat input on the microstructure was also investigated. The hardness of the surface-modified samples increased by about eight times compared to the base metal, and their wear resistance was notably improved. The results of the electrochemical corrosion tests showed an overall improvement in the corrosion resistance of the coated samples compared to the base metal.

Effects of Weld Heat Input on Mechanical Characteristics of Low Carbon Sheet Steels

This study focuses on examining the variation in mechanical characteristics of low-carbon sheet steels when they are subjected to heat input from Tungsten Inert Gas (TIG) welding. The weld heat input parameters, such as welding speed and current, were controlled through the TIG welding process. A finite element analysis was performed to evaluate the couple field thermomechanical effects of the weld heat line, using the Gauss heat flux approach for thermal heat variation across the weld heat-affected zone. The numerical study yielded results for weld heat-affected deflection, residual stress, and modal analysis through the finite element model. It was found that the ductility decreased and hardness increased in the fusion zone, as a function of weld current and speed. The residual stresses and their zone of influence, as determined by weld line parameters, were found to be key factors affecting deflection and natural frequencies in structural aspects of low carbon sheet steels.

Corrosion Resistance and Mechanical Properties of Cr-Rich 316 Stainless Steel Coatings Fabricated by the TIG Process Using Flux-Cored Wires.

Arc welded 316 stainless steel coatings with flux-cored wires are very promising for marine service environments due to their low cost, high efficiency, and satisfactory performance, while they suffers from Cr dilution during the preparation process. Herein, based on the consideration of increasing the Cr content and ensuring the same value of the Cr/Ni equivalence ratio (Creq/Nieq), 316-modified flux-cored wires, 316F (19Cr-12Ni-3Mo) and 316G (22Cr-14Ni-3Mo), were designed under the guidance of a Schaeffler diagram for the improvement of the electrochemical and mechanical properties of 316 stainless steel coatings. The designed flux-cored wires were welded into a three-layer cladding by the tungsten inert gas welding (TIG) process, and the microstructure, corrosion resistance, and mechanical properties of the claddings were investigated. The results showed that 316F and 316G consist of γ-Fe (austenite) and a small portion of δ-Fe (ferrite) as the Creq/Nieq is approximately 1.5. However, due to the higher value of the equivalent Cr content (ECC), 316G has an additional intermetallic phase (σ), which precipitates as a strengthening phase at grain boundaries, significantly increasing the tensile and yield strength of 316G but reducing its plasticity. In addition, the corrosion current density (icorr) and pitting potential (Eb) for 316G are 0.20447 μA·cm-2 and 0.634 V, respectively, while the values for 316F are 0.32117 μA·cm-2 and 0.603 V, respectively, indicating that 316G has better anti-corrosion performance.

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.

Residual Stress Prediction during TIG and MIG Welding Process of Steel - A Review

In this study, a forensic review of residual stress predictions and its impact on welded joints especially the steel pipes during the Tungsten inert gas welding and metal inert gas welding processes were reviewed. It was established that in the case of MIG welding, the effect of residual stress can be reduced after treatment. In the case of TIG welding process, increase in current will lead to deformation and residual stresses. Estimating the residual stress is a challenging task. It is common to predict residual stress using a notch stress intensity factor, a numerical simulation approach coupled with a thermal-mechanical finite element model. Thus, adequate design in welding parameters will help in the optimization of the process to achieve a safe and reliable welded joint during TIG and MIG welding process.

Electromagnetic–Computational Fluid Dynamics Couplings in Tungsten Inert Gas Welding Processes—Development of a New Linearization Procedure for the Joule Production Term

The finite volume method (FVM) was used to model a tungsten inert gas (TIG) arc welding process. A two-dimensional axisymmetric model of arc plasma integrating fluid–solid coupling was developed by solving electromagnetic and thermal equations in both the gas domain and the solid cathode. In addition, two additional coupling equations were considered in the gaseous domain where the arc is generated. This model also included the actual geometry of torch components such as the gas diffuser, the nozzle, and the electrode. The model was assessed using numerous numerical examples related to the prediction of the argon plasma mass fraction, temperature distribution, velocity fields, pressure, and electric potential in the plasma. A new linearization method was developed for the source term in the energy conservation equation, allowing for the prediction of Joule effects without artificial conductibility. This new method enhances the efficiency of the classical approach used in the literature.

Tungsten Inert Gas Welding of 6061-T6 Aluminum Alloy Frame: Finite Element Simulation and Experiment.

In order to address the irregularity of the welding path in aluminum alloy frame joints, this study conducted a numerical simulation of free-path welding. It focuses on the application of the TIG (tungsten inert gas) welding process in aluminum alloy welding, specifically at the intersecting line nodes of welded bicycle frames. The welding simulation was performed on a 6061-T6 aluminum alloy frame. Using a custom heat source subroutine written in Fortran language and integrated into the ABAQUS environment, a detailed numerical simulation study was conducted. The distribution of key fields during the welding process, such as temperature, equivalent stress, and post-weld deformation, were carefully analyzed. Building upon this analysis, the thin-walled TIG welding process was optimized using the response surface method, resulting in the identification of the best welding parameters: a welding current of 240 A, a welding voltage of 20 V, and a welding speed of 11 mm/s. These optimal parameters were successfully implemented in actual welding production, yielding excellent welding results in terms of forming quality. Through experimentation, it was confirmed that the welded parts were completely formed under the optimized process parameters and met the required product standards. Consequently, this research provides valuable theoretical and technical guidance for aluminum alloy bicycle frame welding.

The effect of heat input on weld-bead geometry, mechanical, phase transformation temperature, and corrosion properties of autogenous double pulse TIG welded nitinol sheets

This research aims to analyze the welding of 1 mm thick NiTinol sheets using an autogenous double pulse tungsten inert gas (DPTIG) welding process. The effect of heat input (HI) on bead geometry, microstructure, hardness, tensile strength, phase transformation temperature (PTT), and corrosion behavior was studied. The lower (111.25 J/mm), and higher (120.14 J/mm) HI produced an average grain size of 26 μm and 36 μm, respectively. The microstructure of the fusion zone (FZ) had coarser columnar grains with intermetallic phases such as Ni3Ti, and TiO2. The grain size in the FZ increased with the increase in HI. Sample P (111.25 J/mm) showed a higher hardness of 280.54 HV and tensile strength of 566 MPa due to a higher proportion of austenite phase (99.4%), the smaller grain size of 26 µm, a larger fraction of high angle grain boundary (HAGB) of 75.8%, and higher kernel average misorientation (KAM) value of 4.93. Compared to base metal (BM), sample P (111.25 J/mm), and sample S (120.14 J/mm) exhibited a reduction in tensile strength of 19.14% and 32.29%, respectively. The decline in hardness and tensile strength was attributed to the formation of intermetallic phases, a decrease in the Ti/Ni ratio, coarser grain formation, and a decrease in HAGB fraction and KAM values. The fractured tensile samples showed a mixed mode of fracture with dimples and cleavage facets. Compared to BM, Sample Q (118.05 J/mm) exhibited lesser variation in temperature hysteresis values for austenite and martensite temperatures, with a deviation of 0.4°C and 3.1°C, respectively. All the welded samples had better corrosion behavior than the BM due to a higher Ti/Ni ratio.

Real-Time Recognition of Molten Pools Based on Improved DeepLabV3+ in Keyhole Tungsten Inert Gas Welding Applications

During the Keyhole Tungsten Inert Gas (K-TIG) welding process, a significant amount of information related to the weld quality can be obtained from the weld pool and the keyhole of the topside molten pool image, which provides a vital basis for the control of welding quality. However, the topside molten pool image has the unstable characteristic of strong arc light, which leads to difficulty in contour extraction. The existing image segmentation algorithms cannot satisfy the requirements for accuracy, timing, and robustness. Aiming at these problems, a real-time recognition method, based on improved DeepLabV3+, for identifying the molten pool more accurately and effectively was proposed in this paper. First, MobileNetV2 was selected as the feature extraction network with which to improve detection efficiency. Then, the atrous rates of atrous convolution layers were optimized to reduce the receptive field and balance the sensitivity of the model to molten pools of different scales. Finally, the convolutional block attention module (CBAM) was introduced to improve the segmentation accuracy of the model. The experimental results verified that the proposed model had a fast segmentation speed and higher segmentation accuracy, with an average intersection ratio of 89.89% and an inference speed of 103 frames per second. Furthermore, the trained model was deployed in a real-time system and achieved a real-time performance of up to 28 frames per second, thus meeting the real-time and accuracy requirements of the K-TIG molten pool monitoring system.

Prediction of Hardness of Mild Steel Welded Joints in a Tungsten Inert Gas Welding Process using Artificial Neural Network

The Hardness of a material is used to quantify its toughness and how reliable it is to withstand load with little or no deformation. High structural integrity in terms of hardness can be predicted if combinations of process parameters and their response pattern can be studied. Hence, the objective of this work is to predict the hardness of mild steel welded joints in a tungsten inert gas welding process using Artificial Neural Network (ANN). The central composite design matrix was applied to train the network, while the box-beckhen design matrix were employed to predict the unknown responses. 200 pieces of mild steel coupons measuring 27.5x10x10mm were prepared and used for the experiment, the experiment was performed 20 times, using 5 specimens for each run, after which the hardness was measured and results analyzed respectively. The outcomes obtained indicates ANN capability in predicting the hardness of mild steel welded joints with a p-value less than 0.05, and an R2 of 87.44 with an allowable system noise of 7.14242.

Process parameters based machine learning model for bead profile prediction in activated TIG Welding using random forest machine learning

The bead profile in the activated tungsten inert gas welding process depends on process parameters and flux composition. Using a conventional statistical-based model, the correlation of these input parameters with the bead shape geometry is complex. Therefore, machine learning-based techniques were implemented to predict the bead shape geometry, that is, penetration (D), width (w), and D/w ratio in the A-TIG welding process of austenitic stainless steel. Random forest regression and classification models were implemented to predict bead shape geometry in the A-TIG welding process. Based on the results, classification-based modeling was appropriate for predicting the bead profile. In addition, the correlation of the process parameters and flux composition with the bead profile was established.

Microstructure and mechanical properties of T-joints in mid-thick Q345 steel plates welded using deep penetration tungsten inert gas welding

The deep penetration tungsten inert gas welding process was first used to realize efficient manufacturing of T-joints. The macroscopic morphology, microstructure, microhardness, and mechanical properties of T-joints were investigated. The welding parameters are a welding current of 465 A, a welding speed of 4 mm/s, and the distance between the tungsten electrode tip and the web plate and flange plate is 2 mm. The one-side welding both sides formation of T-joint was realized under these welding parameters. The Widmanstätten austenite in the web plate's overheated zone hinders the crack’s propagation. The failure crack in the flange plate first propagates in the brittle fusion zone and then propagates in the weld metal. The fracture mode of DP-TIG joints of Q345 steel is mainly brittle fracture. The maximum tensile strength of the joint welded using DP-TIG is 302.15 MPa.

Effects of welding parameters on mechanical properties and microstructure of TIG welded joints of AA4043

Welding technology has played a vital role in the manufacture of complicated structures in automobile, petrochemical, aerospace, power plant, and ship industries. Tungsten Inert Gas welding process is superior technique and produces high quality weld economically. Aluminum alloy 4043 is currently preferred material in automobile, kitchen utensils and aviation industry sector due to its lightweight properties. The effective TIG welding process for AA4043 material is not studied yet with regard to micro-hardness, impact strength properties in correlation with the microstructure. Hence, consequence of welding parameters, namely welding current, voltage, and weld speed on micro-hardness, impact strength is studied based on Taguchi method. As per the developed experimental matrix, the TIG welded samples of AA4043 plates are produced using the tungsten electrode and filler wire of AA4043 in pure argon as shielding gas. Micro-hardness, impact tests are performed on welded samples and microstructures of different zones of weld are evaluated. Weld zone has highest micro hardness compared to heat affected zone (HAZ) and base metal due to presence of small grain structure. As current increases, large amount of solute enrichment in weld zone and HAZ, whereas severe grain structure change is predominantly observed in transition zone. The optimal parameters are obtained as welding current of 180 A, the voltage of 45 V and welding speed of 3.5 mm/sec for maximum micro-hardness of weld zone and impact strength of weld joint.

Certification of welder for tungsten inert gas welding in unmanned aerial vehicle systems

Aluminum and its alloys is one of the extensively used non-ferrous metal in aerospace engineering applications due to its excellent properties like higher strength to weight ratio, non-magnetic property, high thermal conductivity, good machinability, recyclability, and excellent formability. However, welding of aluminum and its alloys has always been a challenge due to drastic reduction in strength near heat affected zone (HAZ). Due to softness, ductility, lower melting point of aluminum and its alloys impose additional challenges to weld aluminum alloy components. Due to this, the quality and quantum of skill set needed to weld aluminum alloy joints for flight critical components is much more than that of welding of ferrous materials. The qualification and certification of welder is one of the prime requirements in welding applications especially in aerospace industry. This paper mainly discusses the various aspects involved in qualifying and certifying a welder for tungsten inert gas (TIG) welding process of aluminum alloys, which is treated as one of the special processes. The welder certification is a written verification that weld joints produced by welder meets the prescribed standard of welder performance. It is to verify the ability of an individual to execute a qualified welding procedure specification to produce a sound weld. Aluminum alloy 6xxx series is considered for base metal for sample preparation and weld joint assessment studies, as it is one of the prevalently used aluminum alloy material in unmanned aerial vehicle (UAV) applications. Weld samples are prepared as per internationally practiced standards and welding procedure specification (WPS) is recorded. Various mechanical tests carried out on weld samples during certification process are discussed in the paper. Weld joints are subjected to tensile testing, bending test and macro test. The certifying agencies are involved at every stage to ensure consistency of welder performance.

Dissimilar autogenous TIG joint of Alloy 617 and AISI 304H steel for AUSC application

To reduce costs and improve high-temperature performance in Advanced Ultra Super Critical (AUSC) boilers, it is necessary to weld austenitic steel to Inconel alloy. In this study, the autogenous tungsten inert gas (TIG) welding process was used to join Alloy 617 and an austenitic AISI 304H steel plate of thickness 5 mm. Microstructural analysis showed that the microstructure formation was uneven along the weldments, with columnar and cellular dendrites near the interface while the central area of the weld exhibited a combination of columnar, cellular, and equiaxed dendrites. The use of energy dispersive spectroscopy and electron probe micro-analysis unveiled the presence of an unmixed layer at the interface between the weld and AISI 304H steel. Furthermore, a notable variation in the concentration of alloying elements such as Fe, Cr, Ni, Co, and Mo was observed. Within the weld metal, inter-dendritic areas showed the presence of precipitates rich in Cr, Ti, and Mo. Meanwhile, the heat-affected zone (HAZ) of Alloy 617 exhibited the presence of phases like Cr and Mo-rich M23C6 as well as Mo-rich M6C. Hardness tests showed non-uniform hardness along the weldments, with a hardness of 199 ± 6 HV in the weld metal and 225 ± 4 HV in Alloy 617 HAZ, and 207 ± 7 HV in AISI 304H HAZ. The Mo and Cr segregation in the inter-dendritic spaces led to a decline in the tensile properties of the welded parts and resulted in failure from the region of the weld metal.

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.

Numerical Investigation of the Iron and Oxygen Transport in Arc Plasma During an Activated Tungsten Inert Gas Welding Process

Numerical Investigation of the Iron and Oxygen Transport in Arc Plasma During an Activated Tungsten Inert Gas Welding Process

Study of the TIG Welding Process of Thin-Walled Components Made of 17-4 PH Steel in the Aspect of Weld Distortion Distribution.

This article presents the results of a study on the distribution of weld distortion in thin-walled components made of 17-4 PH steel, resulting from TIG (Tungsten Inert Gas) welding. Both manual and automatic welding processes were examined. Physical simulation of the automated welding process was conducted on a custom-built welding fixture. Analysis of weld distortion in thin-walled components made of 17-4 PH steel was based on the results of measurements of transverse shrinkage and displacement angle values. These measurements were taken on thin-walled parts before and after the welding process using a coordinate measuring machine (CMM). To determine the effect of manual and automated welding processes on the microstructure of the welded joint area, metallographic tests and hardness measurements were performed. The microstructure was analyzed using a scanning electron microscope (SEM). An analysis of the chemical composition of selected welded joint zones was also conducted. These tests were performed using an optical emission spectrometer (OES). According to the results, the use of automated welding and special fixtures for manufacturing thin-walled aircraft engine components made of 17-4 PH steel reduces the propensity of these components for distortion due to the effects of the thermal cycle of the welding process. This conclusion is supported by the results of the observation of the microstructure and analysis of the chemical composition of the various zones of the welded joint area.

Microscopic and Mechanical Characterization of Co-Cr Dental Alloys Joined by the TIG Welding Process.

Due to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas welding (TIG) produces a high-quality weld with a composition very close to that of the base material. Therefore, in this work, six commercially available Co-Cr dental alloys were joined by TIG welding, and their mechanical properties were evaluated to determine the quality of the TIG process as a technology for joining metallic dental materials and the suitability of the Co-Cr alloys used for TIG welding. Microscopic observations were made for this purpose. Microhardness was measured using the Vickers method. The flexural strength was determined on a mechanical testing machine. The dynamic tests were carried out on a universal testing machine. The mechanical properties were determined for welded and non-welded specimens, and the results were statistically evaluated. The results show the correlation between the investigated mechanical properties and the process TIG. Indeed, characteristics of the welds have an effect on the measured properties. Considering all the results obtained, the TIG-welded I-BOND NF and Wisil M alloys showed the cleanest and most uniform weld and, accordingly, satisfactory mechanical properties, highlighting that they withstood the maximum number of cycles under dynamic load.

Process parameter optimization of hot-wire TIG welding of 10 mm thick type 316LN stainless steel plates

This study aims to reduce the number of weld passes and total heat input to 316LN stainless steel during hot-wire tungsten inert gas (HW-TIG) welding process by optimizing process parameters. Therefore, the response surface methodology (RSM) of design of experiments (DOE) approach has been adopted to optimize HW-TIG welding parameters and study the interaction between the parameters and responses. In order to minimize the total number of experimental runs, a design matrix was generated with 30 sets of process parameters. The bead-on plate welding experiments were carried out based on the above generated process parameters. Using the RSM, a quadratic model was developed based on a central composite design to establish the regression equations between input variables (welding current, wire feed current, welding speed, and wire feed rate) and responses (bead width, depth of penetration, and weld cross sectional area). The input process parameters and their responses were correlated with the regression model. Further, parameter values were optimized using the desirability approach and the optimized solutions were generated. Using the optimized process parameters, 316LN stainless steel weld joints were fabricated. Tensile testing and metallography samples were extracted from the fabricated weld joints. The results reveal that the optimization of process parameters by RSM based approach reduced the number of weld passes and improved the weld quality with lower heat input to 316LN stainless steel. In addition, the fabricated weld joint of 316LN stainless steel using the optimized process parameters exhibited better microstructure and strength properties.