Tungsten Inert Gas Arc Welding Research Articles

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.

Improving Welding Penetration and Mechanical Properties via Activated-Flux Smearing by Tungsten Inert Gas Arc Welding

For the welding process of thick-walled structural components in liquid rocket engines, the activated-flux TIG method can effectively address issues such as the formation of intermetallic phases in the weld seams, thereby enhancing mechanical performance. The present study investigates the activated-flux TIG welding technique on 10mm thick 1Cr21Ni5Ti duplex stainless steel plates. Various activated-flux, including -SiO2, TiO2, V2O5, NiO, MnO2, CaO, AlCl3, CaF2, B2O3 Cr2O3, and Al2O3, were examined to understand their impact on the weld-bead geometry. The aim was to determine the optimal activator ratio for the effective welding of 1Cr21Ni5Ti duplex stainless steel. The weld-shift experiment confirmed that the deep penetration observed in flux-assisted welding is attributed to Marangoni convection in the molten pool. Comprehensive evaluations and analyses were performed on the microstructure and mechanical properties of the normal welded joint and the A-TIG welded joint. Finally, the study delves into a discussion on the factors influencing changes in the weld penetration, microstructure, and mechanical properties of the weld.

Grain refinement of 5A06 aluminum alloy welds caused by tungsten inert gas welding arc characteristics under Ar–He alternating gas supply conditions: a coupled method of water-cooled copper plate test/numerical simulation

Grain refinement of 5A06 aluminum alloy welds caused by tungsten inert gas welding arc characteristics under Ar–He alternating gas supply conditions: a coupled method of water-cooled copper plate test/numerical simulation

The simulation of terahertz waves transmission in the arc plasma

The diagnostic of high-density hot plasma is a challenging task due to its high temperature and electron density. Arc plasma is one of the typical hot density plasmas, and its diagnosis is the key to develop its new applications. In this paper, the temperature and density distributions of welding plasmas with different discharge currents are numerically simulated based on a Tungsten Inert Gas Arc Welding model, and the electron density distributions are calculated. Then propagation properties of broadband terahertz (THz) waves in the modeling arc jets are calculated by the finite difference time domain method. These results not only provide a preliminary theoretical guidance for in-depth understanding the problems of blackout in re-entry communication, but also develop a new idea for the terahertz diagnostic of plasma with high density.

Understanding the factors critical to the TIG welding of Cu components in bar wound electric motors

Developing robust manufacturing processes for electric traction motors is essential to support GM's electrification roadmap. When assembling an electric motor, many copper components in the form of wires, bars, and bus rings are joined together. The joints must be highly conductive to achieve high efficiency as well as mechanically strong to survive the harsh service environment. A potential joining method that could meet the above-mentioned requirements is tungsten inert gas arc welding (TIG). TIG welding offers the highest energy density compared with other arc welding processes and requires far less capital investment compared with laser and electron beam welding. In this report, we will four factors critical to the welding process, namely: the type of shielding gas, weld current, electrode to workpiece distance, and weld time; and how each factor influences the weld quality.

Mechanism of δ-ferrite decomposition in high Si-bearing austenitic stainless steel weld metal during aging at 550°C

The 15Cr-9Ni-Nb austenitic stainless steel weld metal with 3.5 wt% Si content was designed and prepared via tungsten inert-gas arc welding and then stabilized heat treatment (SHT) at 900 °C for 3 h. The mechanism of δ-ferrite decomposition during the aging process at 550 °C was investigated for both the as-welded (AW) and the SHT weld metals via scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and high-resolution transmission electron microscopy (HRTEM), and its impact toughness effect was also discussed. The original δ-ferrite for both the AW and SHT weld metals decomposed to the σ-phase, A16Mn6Si7-type G-phase, and more stable δ-ferrite during aging. The coarse σ-phases were distributed at the δ/γ interface and the relatively fine G-phases (A16Mn6Si7) were at the δ/γ interface or inside the δ-ferrite. Si promoted the formation of the G-phases and σ-phases during aging, consumed a large amount of Cr, Ni, Si, and Mn from the δ-ferrite, and stabilized the remaining δ-ferrite. The impact toughness of the AW weld metal sharply dropped during aging due to the coarse σ-phases promoting the formation and propagation of intergranular cracks. The SHT reduced the δ-ferrite in the weld metal, thus avoiding the formation of a large number of σ-phases during aging and therefore improving the impact toughness.

Control of various Zn-based weld seam/steel interface structures in AA5083/FH36 steel welded joint

Replacing steel with aluminum alloy is appealing to realize the lightweight of ship structure, so it is inevitable to weld these two materials in products. When joining AA5083 aluminum alloy to FH36 steel with the thickness of 6 mm by tungsten inert gas (TIG) arc welding process, the liquid Zn-based filler metal reacted with steel matrix to form Fe-Zn intermetallic compounds (IMCs) and Fe-Al IMCs. A novel interface structure composed of spinous Г-Fe3Zn10, thinner η-Fe2Al5Zn0.4 and a small number of dispersed δ-FeZn10 with a relatively high bonding strength can be obtained at the weld seam/steel interface by optimizing the backing welding current. When the backing welding current was 120 A, the maximum tensile strength of joint could reach 98 MPa. Simulation indicated that a large stress concentration developed at the weld seam/steel interface, within crack active temperature range of Fe-Zn and Fe-Al IMCs, during the backing welding process. The lattice misfit of δ-FeZn10/η-Fe2Al5Zn0.4 and Г-Fe3Zn10/η-Fe2Al5Zn0.4 interfaces were 19.9% and 9.4%, which revealed that dislocations were more likely to accumulate around δ-FeZn10, providing the location of crack initiation in aluminum alloy/steel welded joints.

Galvanic corrosion of AA5052/304SS welded joint with Zn-based filler metal in marine engineering

Galvanic corrosion and localized corrosion behavior of AA5052/weld seam/304SS tri-metallic couples were examined by EIS, ZRE, SKP and SVET tests after tungsten inert gas (TIG) arc welding. The results showed that the weld seam had a relatively high corrosion susceptibility. The asymmetric corrosion of weld seam was attributed to the macro-galvanic effect between the weld seam/AA and the weld seam/SS. Localized corrosion of Zn in δ-FeZn10 induced the corrosion trenches and channels initiation. The deep corrosion propagation at the weld seam/SS interface was brought on by local acidity and micro-galvanic effect.

Offset impacting of a liquid aluminum droplet train on a molten pool on a horizontally moving substrate during TIG-assisted droplet deposition manufacturing

Internal metallurgical defects and poor mechanical properties and surface quality of the formed parts are the most important challenges of metal micro-droplets deposition manufacturing technology. Lack of strong coalescence between neighboring droplets and the blocking effects of periodic ripples on the fusion process are major sources of abovementioned problems. To address this issue, a tungsten inert gas (TIG) welding arc was introduced to pre-melt the material below the droplet impacting location, thus, one droplet train will be deposited on a curved molten pool surface to fabricate deposited layers in an additive approach. In the present work, a numerical model based on the computational fluid dynamics (CFD) method was developed to investigate the dynamic behaviors of successive droplets’ impact and coalescence on the molten pool created by a tilted TIG welding arc, and focuses on the effect of the offset distance between the impacting point of droplet and the longitudinal plane of molten pool on the deposition morphology and the impact-induced molten pool behaviors. The simulated tracks exhibit regular scaly shapes at different offset distances, which is validated against the corresponding experiments. The results indicated that as the lateral offset distance increases, the symmetric spreading and recoiling of the subsequent droplets on the pre-existing bead will be broken due to the inclined and curved solidification front morphologies, the inclined front morphologies are caused by the increased growth rate of the solidification front at the impact zone. With an increased lateral offset distance, the volume of the molten pool decreases, the width of the rear molten pool increases slightly. The calculated solidification parameters are found to be dependent of the offset distance, and vary significantly at the onset of solidification at different portions of the molten pool. The scientific findings provide useful insights for further researches of TIG-assisted DDM.

Influence of laser and tungsten inert gas arc welding on magnetic properties of AISI M‐43, and M‐47 grade cold‐rolled non‐oriented electrical steel

AbstractThe magnetic properties and core losses of cold‐rolled non‐oriented electrical steel are influenced by gas tungsten arc, and laser welding. Investigations are carried out on the toroidal core sample welded on six sides around the outer periphery for estimating the variation in magnetic properties by increasing magnetic flux density and grain size. The percentage increase of power loss density in gas tungsten arc for M‐43 grade (M‐43‐TIG) and laser‐welded core samples for M‐43 grade (M‐43‐LB) were 24.7 % and 11.86 %, whereas 18.43 % (M‐47‐TIG), and 4.9 % (M‐47‐LB), respectively. A significant decrease in permeability of about 55.39 % and 53.57 % was experienced in M‐43‐TIG and M‐43‐LB, respectively. However, in M‐47 grade, the decrease was more for M‐47‐TIG (52.58 %) than the M‐47‐LB (39.52 %) welded sample when tested at 1.5 T. All the parameters investigated are compared with sticking, non‐welded core sample.

A Study on Welding Characteristics, Mechanical Properties, and Penetration Depth of T-Joint Thin-Walled Parts for Different TIG Welding Currents: FE Simulation and Experimental Analysis

Considering the effect of heat input of tungsten inert gas (TIG) arc welding for T-joint welding of thin-walled parts of aluminum alloy 6061-T6, here, the welding characteristics are analyzed via the finite element method. The experiments are carried out using scanning electron microscope (SEM), optical microscope (OM), and tensile test of specimens to investigate the microstructure variation of the weld zone (WZ), heat-affected zone (HAZ), and base metal (BM), and the mechanical properties of the T-welded joint. The mechanical properties of the T-welded joint are explored and assessed combined with the tensile test in terms of yield strength, tensile strength, and Vickers hardness. Furthermore, the effects of different welding currents on welding penetration variation under welding deformation are thoroughly investigated, and the appearance of porosity and incomplete fusion defects of T-welded joints are clearly illustrated. The results show that the yield and tensile strength of T-welded joints, respectively, account for less than 37% and 74% of the base metal (BM) strength. Moreover, the welding penetration depth and microstructure of T-welded joints are deeply affected by the welding current. The maximum penetration depth is achieved at about 2.18 mm under the maximum welding current, and partial welding defects emerged, affecting and reducing the mechanical properties of the welded joint. It is expected that these results will provide an analysis foundation for optimization of the welding process, suppression of welding defects, and promotion of mechanical properties for thin-walled parts in the future.

Study on the weld formation, microstructure and mechanical properties of AZ31B Mg alloy in AC/DC mixed gas tungsten arc welding process

In this work, a new welding electrical signal waveform of the AC/DC mixed waveform is purposed to improve the welding quality of magnesium alloy TIG. The method is named as AC/DC mixed tungsten inert gas arc (MIX-TIG) welding. The AZ31B Mg alloy welded joints were obtained by AC-TIG and MIX-TIG. Through investigation of the weld formation, microstructure and mechanical properties of welded joints, the results showed that when the welding current of 90A∼110 A, the completely penetration of welded joints could be obtained. There was no obvious difference for the geometrical parameters of the weld cross-section between the AC-TIG and MIX-TIG. The microstrcuture of fusion zone consisted of α-Mg matric and β-Mg17Al12 phase. At the same welding conditions, the average grain size and β phase number in the MIX-TIG were less than that of the AC-TIG. The microhardness of the AC-TIG fusion zone was slightly larger than that of the MIX-TIG owing to the increase of β phase number. The strain of the AC-TIG welded joint was reduced by approximately 24% compared with that of the MIX-TIG welded joint.

A numerical study of the effects of cathode geometry on tungsten inert gas type electric arcs

In this paper we address the question of the influence of cathode tip geometry on the physical quantities relevant to Tungsten Inert Gas (TIG) arc welding. Although cathode geometry is known to influence arc-plasmas, a thorough quantification of the Lorentz phenomenon, which is the dominant source of momentum in the fluid flow of TIG arcs has not been strongly investigated. Therefore, we have performed a numerical parametric study at a constant inlet electric current and arc height, for different cathode sizes and shapes (pointed, chamfered and rounded tips), parameterised by the truncation angle and tip radius. To this end, we developed a coupled steady-state magneto-hydrodynamic finite element model in a 2D axi-symmetric configuration, implemented in the [Display omitted] toolbox. The paper characterises, quantifies and analyses the influence of tip geometry on TIG arcs and the workpiece. The model reveals that tip size and truncation angle similarly influence the magnitude of the transported quantities of the arcs. We find that the imparted momentum and transferred heat flux to the workpiece vary about 4 and 2-fold between the bluntest and sharpest cathodes, respectively. This signifies the importance of the choice of cathode tips in numerical TIG welding simulations. Agreement between the literature and the current work is analysed and discussed and the importance of coupling the cathode and arc domains is highlighted.

Fe2O3 Nanowire Flux Enabling Tungsten Inert Gas Welding of High-Manganese Steel Thick Plates with Improved Mechanical Properties

Economic welding of thick steel plates is an emerging challenge for various engineering applications. However, tungsten inert gas (TIG) arc welding, as an economic and widely used method, is not regarded as a suitable tool to weld thick steel plates due to the shallow penetration in a single-pass operation. In this technical progress, the joining of austenitic high manganese steel of 8 mm thickness was successfully performed using nanowire flux activated TIG welding with a full penetration and a narrow bead geometry. Fe2O3 nanowire was used as flux and compared with microscale Fe2O3 flux. Experimental results showed that with nanowire fluxes, the welding yielded the maximum of more than 8 mm thick penetration (full penetration and melt over the plate) with proper operating parameters in a single pass. In sharp contrast, the penetration is only less than 4 mm for a single pass welding without Fe2O3 flux with the similar parameters. Arc voltage—time variation during welding process was analyzed and the angular distortion was measured after welding to understand the activating effect of optimized flux mixture. Compared to welding joint without flux and with microscale Fe2O3 flux, nanoscale Fe2O3 flux has a larger arc voltage and higher energy efficiency, higher joint strength and less angular distortion. The developed joint with nanowire flux qualified the tensile test with tensile strength of 700.7 MPa (82.38% of base material strength) and 34.1% elongation. This work may pave a way for nanotechnology-enabling welding innovation for engineering application.

The Effect of Post Weld Heat Treatment (PWHT) on the Microstructure, Microhardness and Sulphide Stress Corrosion Cracking (SSCC) of Ni-Base Superalloy IN625 Hot Wire TIG Cladding on AISI 4130 Steel

This study aims to investigate the effect of post-weld heat treatment (PWHT) on the microstructure, microhardness, and sulfide stress corrosion cracking (SSCC) of IN625 weld overlay on AISI 4130. In this paper, cladding was conducted by TIG (tungsten inert gas arc welding) technique, then PWHT was carried out at 650, 750, and 850°C temperatures with the constant time of 1 h. Also, the SSCC test was performed for 720 h. According to the results, columnar dendrites with MC carbide in g solid solution matrix comprise the microstructure. Furthermore, there was not any crack in the Weld Overlay (WO), tempered martensite, bainite in the base metal (BM), coarse tempered martensite, and ferrite in the heat-affected zone (HAZ). The results demonstrate that as the temperature of PWHT rises, the hardness of BM and HAZ reduces while hardness in the WO increases; it can be seen that at 750°C γ'' phase rapidly emerged and changed to stable δ at 850°C by the shearing mechanism. Furthermore, the results of the magnetic test showed stress crack in samples that heat-treated at 850°C. SEM images reveal that stress cracks in BM continued along grain boundaries and reached the WO.

Phase and chemical structure characterization in double sided TIG arc welding of HARDOX 450 and AISI 430 steel

In this study, HARDOX 450 and AISI 430 grades are combined using double-sided tungsten inert gas (TIG) welding process. Microstructural properties of weld zone were evaluated with optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), electron back scatter diffraction (EBSD), elemental mapping analysis. After tensile testing, fracture surface morphology was evaluated using SEM. The width and depth of the weld seam increased with the increase in current. Carbon and chrome diffusion gradients were formed on the HARDOX 450 steel side by FSS in welded joints. The crystallographic plane was dominated by blue and, concentrated in the direction of {101}, {001}, {111}.

The behavior of TIG welding arc in a high-frequency axial magnetic field

The effect of high-frequency axial magnetic field (HFAMF) on the shape of the welding arc and welding formation of tungsten inert gas (TIG) welding is analyzed theoretically and experimentally. The 316L stainless steel plate was welded with HFAMF produced by the excitation coil installed on the welding torch. The influence of the HFAMF on the welding process is studied by changing the magnetic frequency from 0 to 2000 Hz. The experimental results show that when the magnetic field frequency reaches 1500 Hz, the arc rotation radius is decreased to the minimum; the arc shape changes from cone to compressed cylinder; and the arc temperature, the arc pressure, and the depth-width ratio of the weld beam reached the maximum. Otherwise, the effect of applied HFAMF on the stress of arc and weld pool is discussed, and the mechanism of arc contraction is analyzed.

Investigation of fatigue and fracture characteristics for low-temperature metals considering the effects of various alloying components

In the past few decades, low-temperature metals such as SUS304L, nickel alloys, and high-manganese steels have been widely used for liquefied natural gas (LNG) storage tanks to satisfy the structural integrity requirements at low temperature. Many researchers have conducted studies to characterize the fatigue and fracture performance of low-temperature metals. However, only a limited number of studies have considered the effects of various welding processes and consumables. This study addresses the fatigue and fracture performance of low-temperature metals while considering the effects of various alloying components. Moreover, we investigated the fatigue and fracture performance of various welding processes. Flux core arc welding (FCAW) was employed for both SUS304L and 9 wt.% nickel alloy steel, while tungsten inert gas (TIG) and shield metal arc welding (SMAW) were applied to SUS304L and 9 wt.% nickel alloy steel, respectively. Submerged arc welding (SAW) was employed for high-manganese steel. Fatigue and fracture tests were conducted according to ASTM E647 and BS 7448. The mechanical properties of the weld metals were systematically analyzed. SUS304L with FCAW exhibited excellent crack tip opening displacement (CTOD) and fatigue crack growth rate (FCGR). We also observed the microstructure of weld metals and discuss the mechanisms related to the fatigue and fracture performance in the parent and weld metals.

Microstructure and mechanical properties of stainless steel clad plate welding joints by different welding processes

This work aims to study the microstructure and mechanical properties of stainless steel/carbon steel clad plate joints with three welding types: welding without transition layer, welding with transition layer using tungsten inert gas arc welding and shielded metal arc welding, respectively. Both of transition layer-weld metals contain ferrite + austenite phases obtained by different solidification modes. The brittle martensite zone is formed in the stainless steel weld metal without the transition layer because of the excessive diffusion of Cr, Ni elements. The clad plate joints with transition layer welded by shielded metal arc welding achieved the best welding quality without excessive alloy element dilution or formation of brittle phase, which reveals a perfect welding joint without obvious hardness gradient and obtains outstanding mechanical properties.

Fundamental research and numerical simulation of new hot stamping tool manufactured by surfacing technology

A novel manufacturing method of hot stamping tool is proposed in this study. The four preselected materials were welded on the specimens by using tungsten inert gas arc welding. High-temperature compressive yield strength, heat conductivity, thermal expansion coefficient, and microstructures of welding materials were experimentally investigated. CuCrZr and Fe-based alloy were selected as the intermediate layer (IL) and surface layer (SL) of new hot stamping tool respectively. Moreover, the simulation results indicated that the dwell time of new tool (NT) can be saved by 25% in comparison to traditional tool (TT); the temperature of traditional and new tool would reach dynamic thermal equilibrium after 4 and 5 stamping circles respectively; the temperature and stress of new tool were always lower than traditional tool; the maximum stress of new tool in each area was always less than the yield strength of the corresponding welding materials, which demonstrated that new tool manufactured by surfacing technology could satisfy the strength requirement and deserve further research in the future.