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The paper presents a detailed theoretical analysis of the electromagnetic forces in the arc plasma and the weld pool metal in Tungsten Inert Gas (TIG) welding at direct current (DC) and high-frequency pulse current (HFPC) modulation with a frequency of 10 kHz. The electromagnetic (Lorentz) force, acting on arc plasma and metal is presented via potential (magnetic pressure) and rotational (equivalent electromagnetic force) force components. This approach allows us to substantially simplify the analysis of the Lorentz force effect on the arc plasma and weld pool metal under different arc burning modes. It was shown that in HFPC TIG welding with a given frequency, the effect of modulated current on the arc plasma is inherently non-stationary, whereas the effect on the weld pool metal is determined by the time-averaged magnitude of electromagnetic force throughout the period of current modulation. The proposed approach serves as a basis for numerical analysis of the electromagnetic forces in arc plasma and weld pool metal during DC and HFPC modes of the welding process. We established that the application of HFPC modulation promotes a greater intensity of both the gas-dynamic processes in the welding arc, thereby significantly increasing the pressure on the weld pool surface, and convective heat transfer from the most heated central region near the weld pool surface towards the weld pool bottom. Both these factors lead to an increase of the arc penetrability in the case of the HFPC mode compared with the DC mode, all other conditions being equal. • Only rotational part of the Lorentz force initiates vortical flow. • Square-wave pulse is used as a welding current wave form. • Non-stationary magnetic field diffusion equation is solved numerically. • In-house Wolfram Language code is used for FEM-analysis. • HFPC modulation increases the effective driving force in the weld pool. [ABSTRACT FROM AUTHOR]

Products of thin-sheet copper are widely used in radio electronics, instrumentation, power engineering, etc. This article considers micro-plasma and TIG welding of copper with a thickness of 0.2 mm in argon and helium. As a result of the conducted research, it was established that in case of using helium as a shielding gas, the welding speed increases by more than 2 times compared to the microplasma process and by almost 5 times compared to TIG welding in argon. At the same time, the width of the weld and heat-affected zone (HAZ) decreases to 1.4…1.6 mm and 1.0…1.5 mm, respectively. Metallographic examinations of the welds did not reveal defects such as pores, cracks or lack of fusion. The weld microstructure consists of a set of equiaxed crystallites with a grain size of 4…8 μm without clearly expressed crystallization direction and with a smooth transition of the fusion line. The mechanical properties of the welded joints such as temporary resistance and microhardness were determined. Ref. 8, Fig. 7, Tab. 2 [ABSTRACT FROM AUTHOR]

In this article, transient transport phenomena in the arc and weld pool for different ambient pressures during tungsten inert gas welding were reported. Arc plasma and weld pool behaviour vary with ambient pressure because of changes in arc thermophysical properties. The maximum arc temperature decreases with decreasing ambient pressure because of reduced plasma electrical conductivity. Decreased arc mass density results in a lower maximum weld pool surface temperature and a decrease in maximum metal vapour content as ambient pressure decreases. Arc pressure decreases with decrease in ambient pressure, resulting in shallower penetration. Calculated arc temperature distribution and weld cross-section are compared with experiments to validate the modeling method for simulating heat and mass transfer phenomena in low ambient pressure welding. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work aimed to compare the quality and properties of the welded joints of AMg6 aluminium alloy produced via conventional TIG welding with the properties of those produced with flux backing tape. This study focussed on the relative length of oxide inclusions (Δoi) and the amount of the excess root penetration (hroot) of the AMg6 alloy weld beads. The results show the influence of the thickness of the flux layer of the backing tape on the formation and quality on the AMg6 alloy welds, along with the effect of flux backing tape and edge preparation on the mechanical properties of the 6 and 8 mm thick welded plates. In accordance with the results obtained, the joints produced by means of TIG welding with flux back backing tape and without edge preparation have higher mechanical properties. Moreover, the TIG welding of AMg6 alloy using flux backing tape reduces the total welding time by 55%, reduces filler wire consumption by 35%, reduces shielding gas consumption by 43% and electricity consumption by 60% per 1 linear meter of the weld line. [ABSTRACT FROM AUTHOR]

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.

The attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. However, welding as a fabrication process has a detrimental effect on this alloy’s properties which affects its mechanical performance. In this work, to compensate for the loss in mechanical properties caused by welding, proper heat treatment operations are adopted. To this end, 1.5 mm AA7075 sheets were first preheated and butt welded using the gas tungsten arc welding process. The welded sample was solution heat treated, quenched, and then artificially aged. Microhardness tests showed an increase of hardness in all zones of the aged specimen compared to those of the original welded blank before heat treatment. A maximum microhardness value of 180 HV was recorded in the heat-affected zone of the aged specimen. In addition, elongation at break, and strength (yield, tensile, and fracture) of the original welded blank increased by about 50% after the artificial aging operation.

Nd: YAG Laser and Tungsten Inert Gas (TIG) welding processes are the most promising joining techniques used for stainless steel (SS) alloys due to their significant weld characteristics. In this study, the effect of two process parameters (weld power and travel speed) on the mechanical properties (ultimate tensile strength and microhardness) of the weldment is investigated. Two different machine learning techniques, namely Adaptive Neuro-Fuzzy Inference System (ANFIS) and Unified Convolutional Neural Network (UCNN) are also evaluated for prediction of mechanical properties and defect detection through the image processing technique, respectively. A correlation has been performed between these two machine learning approaches with the experimental values. The training data sets are developed for the machine learning techniques, and the obtained results of (ANFIS) and (UCNN) models are related to the actual experimental values. The output of both developed models (ANFIS & UCNN) showed a good agreement with the actual experimental test results. The predicted tensile and microhardness values from the (ANFIS) model were found to greatly agree with the Peak Signal-to-Noise Ratio (PSNR) values from the (UCNN) model. However, owing to the increase in the applications of welding processes in industries, the utilization of machine learning techniques would be more efficient when compared with the other traditional methods that are being adopted.

The 7075-T6 aluminum (Al) alloy is a high-strength material with great application potential. However, the tensile strength and elongation of its arc-welded joints are severely reduced compared to the base metal (BM), with only 57.3% and 14.4% of the BM values, respectively. To improve both strength and plasticity simultaneously, a novel post-weld composite treatment process combining solution treatment, partial rolling, and natural aging treatment (SRA) was proposed. The SRA process enhanced the strength and elongation of welded joints to 84.5% and 83.1% of the BM, respectively. In different regions of the joints, the SRA process involved different strengthening mechanisms, including stronger work hardening in Region I, η′ phase precipitation and weaker work hardening in Region II, and refinement of the η’ and η phase in Region III. The SRA process also improved the formability of the welded joints from 62.5% to 87.5% of the BM. In addition, the SRA process increased the median fatigue life of welded joints by a factor of approximately 2–6. This was achieved by increasing the strength and microhardness of the fusion zone, which, in turn, reduced the number of fatigue crack sources and shifted crack sources from the surface to subsurface regions.

The non-consumable tungsten electrode plays a key-role in the tungsten inert gas (TIG) welding process, governing the behavior of the electrical arc that is essential for generating the necessary heat in welding. This study is focused on varying of electric parameters in the purpose to identify the appropriate conditions that promote electrode integrity. The post weld cathode analysis revealed that both the input current intensity and its frequency affect the overall morphology and microstructural and mechanical performance of the refractory electrode. Noticeable physical alterations occur with increased current, leading to larger grains and a reduction in microhardness values. In addition, it causes apparent defects such as perforation and superficial deformation. However, applying higher frequencies mitigates these defects significantly. Based on these findings, it seems crucial to take into consideration the interactive effect of current applied and its frequency to ensure better electrode conservation, thereby enhancing the efficiency of the welding process. [ABSTRACT FROM AUTHOR]

Cathode erosion is a serious problem in long hours of Tungsten Inert Gas (TIG) welding. The evolution of electrode end shape and corresponding arc behaviour was studied at different welding currents and cathode parameters. The results illustrate that slow erosion, shedding, and expansion are three typical erosion modes. Slow erosion is an inevitable mode, causing the arc root width (Ra) and arc diameter (Rb) to slowly increase by 2.1% and 2.6%, respectively. With the increasing welding current or the decreasing cone angle and diameter, Ra and Rb are increased in shedding mode by 6.3% and 1.0%, respectively. Expansion appears when the electrode end has a truncated cone shape, causing gradual decrease of 5.7% and 2.3% in Ra and Rb, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The main direction of improving the operational characteristics of titanium alloys is creation of heat-resistant and high-temperature titanium alloys. The high specific strength and corrosion resistance of this type of alloys at temperatures up to 500-600 °C, enables making them the main structural material for aircraft and rocket engineering. However, their widespread use is associated with the problem of precipitation of brittle phases during welding, which requires additional technological operations, such as local heat treatment or preheating. In this paper, the finite element modeling method was applied to study the influence of the TIG welding thermal cycle of high-temperature titanium alloy of Ti-6.5Al-5.3Zr-2.2Sn-0.6Mo-0.5Nb-0.75Si system with and without the use of preheating and to plot the cooling rate diagrams of the produced welded joints. [ABSTRACT FROM AUTHOR]

The present research work focuses on the investigation of hot cracking susceptibility of TIG-welded AA5052 aluminum alloy with two filler materials ER4043 and ER5356, respectively. Welded samples were undergone Houldcroft testing to estimate the solidification cracking susceptibility in the weldment. Microstructural characterization, microhardness testing, X-ray diffraction analysis and scanning electron microscope examination were performed on the weldments. The solidification cracking is not identified while using ER4043 since it has relatively narrow freezing range. High crack sensitivity of 29% is found when welding was performed using ER5356. Hardness for the specimens welded with ER4043 filler material showed 106 ± 3 HV and 116 ± 2 HV in heat affected zone (HAZ) and fusion zone (FZ), respectively, but the specimens welded with ER5356 filler material showed higher hardness of 160 ± 2 HV and 150 ± 4 HV in HAZ and FZ, respectively. The specimens welded by ER4043 and ER5356 showed the formation of Mg2Si at FZ. [ABSTRACT FROM AUTHOR]

Welding of two dissimilar metals is a very difficult process. However, in today's industry, it has become very important to use different metals in the same structure and therefore combine them in order to reduce the weight of parts and structures. In this study, (6061-T6) aluminum alloy and (St-37) low carbon steel were joined by TIG and brazing welding methods, and their mechanical and microstructural properties were examined. Welding applications were carried out with samples with thicknesses of 2 mm, 5 mm and 10 mm. Hardness tests and tensile tests were applied to determine the characteristics of the weld areas of the samples we obtained and to examine their strength. In addition, changes in the microstructure were observed by SEM image analysis. According to the results, it was found appropriate to join 2 mm and 5 mm sheets by brazing, and to join 10 mm and thicker materials by TIG welding. [ABSTRACT FROM AUTHOR]

There is an increasing demand for welding of steel pipes meant for pressure purposes. P355NH (1.0473) steel became an important construction material used for structuring and restructuring of a medium-pressure gas pipeline due to its properties, such as significant tensile strength at the level of 600 MPa and increased yield point. These properties ensure appropriate service life of the principal pipeline structures. When welding P355NH steel, processes that enable high-quality welds without significant changes in the chemical composition of the base material, are applied. It is recommended to use the TIG welding process to produce joints, although P355NH steel joints are considered as difficult to weld. During welding, various welding defects might appear, which mainly include sticking and lack of fusion. Creation of joints with the desired properties, including those used in the construction of medium pressure gas pipelines, with the required class B quality, requires selection of appropriate parameters and compliance with the welding process practice. This is very important for the service life of the structure. Therefore, the article aims to select the most appropriate parameters and thermodynamic conditions for welding P355NH steel in order to obtain the best mechanical properties. The most important of the tested welding parameters of P355NH steel is welding speed, welding current, preheating temperature, interpass temperature and, above all, the role of various shielding gases. (Three different shielding gases containing argon and helium additives were tested.) The obtained joints were tested by: non-destructive tests, such as VT—visual examination; MT—magnetic particle testing, PT—penetration tests, UT—ultrasonic testing and by the destructive methods, such as tensile strength, impact toughness, bending test, light microscopy and scanning electron microscopy. The cause-and-effect relationships between the obtained joint structure and its mechanical properties were determined. The considerations were supported by the nucleation model and the mechanisms of formation of the acicular ferrite phase in the joint material. The chosen parameters of TIG process allow to obtain joint with adequate strength for the production of the gases pipeline, without welding defects. The results have a practical implication, the developed production technology for the obtaining the joints. The presented solution gives the possibility of producing correct welded joints, which can be used in the responsible steel construction. The originality of manuscript is the presentation the newly, uncomplicated solution of obtaining joint with good mechanical properties included the thin-walled tubular structure with a thickness of 3.6 mm. A novelty in the article is a clear indication of the importance of detailed thermodynamic welding conditions and obtained weld structure on the mechanical properties of the P355NH steel joint, which lead to the formation of various non-metallic titanium inclusions, which have a decisive impact on the mechanical properties of the joint, especially its strength and impact strength. [ABSTRACT FROM AUTHOR]

This work is based on a comparative study of the weldments fabricated by Activated Flux Tungsten Inert Gas (A-TIG) welding and autogenous Tungsten Inert Gas (TIG) welding of 10 mm thick Inconel 617 plates. Flux powders used for A-TIG welding were Titanium dioxide (TiO2) and Silicon dioxide (SiO2). Macrostructure and microstructure analyses and characterization of mechanical properties of both A-TIG and TIG weldments were investigated. The microstructure of Inconel 617 was made up of several secondary phases and fine austenitic grains. Mechanical testing carried out in this study included Bend Test, Tensile Test, Vicker's Micro-Hardness Test and Charpy Impact Test at room temperature (RT) and a sub-zero temperature (SZT) of −50 ∘ C. The Bend test was found satisfactory for both A-TIG and TIG weldments. TIG weldments' tensile strength and microhardness were determined to be 782 MPa and 265.44 HV, respectively. However, it was determined that the base metal had a tensile strength of 756 MPa and that the tensile strength and microhardness of the A-TIG weldment were 707 MPa and 252.73 HV, respectively. The TIG weldment was proved to have the highest tensile strength and microhardness due to the availability of strengthening elements like Molybdenum (Mo) and Chromium (Cr), as carbides in the fusion zone. Impact toughness of the A-TIG weldment was higher than that of the TIG weldment both at room and sub-zero temperatures due to the application of TiO2 as flux and the high heat input during A-TIG welding. The ductile mode of fracture was observed in all weldments. [ABSTRACT FROM AUTHOR]

In the present day, the joining of dissimilar metals used in the same industry applications is of great interest. MIG and TIG welding processes are among the most common methods used to join dissimilar metals with high strength and reliability. Due to the different mechanical properties of dissimilar metals to be joined by these welding methods and welding parameters, they must be carefully selected. In this study, the effects of Total Accumulated Weld Volumes (TAWV) and different groove angles (45°, 60°, 75° and 90°) on the mechanical properties of AISI 1040 and AISI 8620 cylindrical steel joints were investigated experimentally. In addition, the fracture surfaces of the samples were examined by scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX). In the process with MIG and TIG welding, only current and voltage changes were made in order to measure the effects of parameters on the mechanical properties of the joints more clearly. As a result of the studies, the highest average Ultimate Tensile Strength (UTS) was 579.611 MPa and the lowest average UTS value was 424.611 MPa. Based on TAWVs, the highest average UTS value was obtained in TIG welded joints, and the lowest average UTS value was obtained in MIG welded joints. It was observed that the UTS values of the joints were positively affected by the increase in TAWV. The UTS value of the 90° groove angled joint was found to be 40.25% higher than the UTS value of the 45° groove angled joint. [ABSTRACT FROM AUTHOR]

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Aluminum alloys such as AA2124 and AA7075 are widely used in aeroplane construction. Certain applications of aircraft manufacturing need dissimilar joint of the aforementioned aluminum alloys. The investigation involves predicting residual stresses in multiple directions (X, Y, and Z) along the transverse direction of welding in butt-welds using ANSYS APDL. Simulated stresses which are tensile along weld bead are well concurrent with the XRD experimental findings (Gas Turbine Research Establishment). During TIG welding of these plates different currents were used to form dissimilar joints and all of them form visible cracks along the weld bead. This formation of cracks is well accord with both simulated and experimental tensile residual stresses. The simulated stresses are compared to the numerical values i.e., experimental findings, and the discrepancy of less than 10% has been noticed. Thus, simulated model can be used as tool for prediction of cracks for joining dissimilar aluminum alloys of above said. [ABSTRACT FROM AUTHOR]

Dissimilar welding joints of Inconel 718 (IN718) nickel superalloy with low-carbon AISI 304L austenitic steel (SS304L) were conducted using the Tungsten Inert Gas (TIG) welding process. The present investigation focuses on the effect of different welding currents on the produced dissimilar joints' microstructure and mechanical properties. The microstructure study was carried out by light optical (LOM) and scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS) analysis. The nanoscale investigation was performed via a high-resolution transmission electron microscope (TEM). The mechanical behavior of the TIG joints was investigated via Vickers hardness testing. In all cases, the morphology and the microstructure of the fusion zone (FZ) and the corresponding heat-affected zones (HAZ) of the TIG-welded IN718 and SS304L verified the absence of porosity or other metallurgical defects. Except for carbides and carbonitrides, hard and brittle Laves phases ((FeNiCr)2(NbMoTiSi)) were also identified, which were dispersed in the interdendritic spaces in the form of elongated islands. Prolonged exposure to high temperatures and a slower cooling rate due to higher initial heat input led to the precipitates' coarsening both in FZ and HAZ and, thus, to the consequent gradual embrittle of the dissimilar joints. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents the method of preparing the tube sheet of a heat exchanger made of B265 Grade 1 titaniumclad steel with B338 grade 2 titanium tubes allowing for the qualification of the TIG (Tungsten Inert Gas) orbital welding technology. A test plate was made of A516M Grade 485 unalloyed steel clad with B265 Grade 1 titanium using the explosive method. The 300 x 300 mm plate consisted of a layer of 60 mm thick non alloy steel and 5 mm titanium clad. It had 20 holes drilled in a triangular arrangement, into tubes with a diameter of 34.93 mm made of B338 Grade 2 titanium with a thickness of 0.7 mm were welded. In order to obtain mechanical restraint inside the holes in the test plates, the titanium tubes were rolled out. For rolling, a five-roller was used, equipped with a retaining collar which allows the tube to move freely during rolling. The tests carried out showed that the proposed technology for preparing tube -- sieve bottom elements allow for the preparation of a test plate for the qualification of welding technology. The test plate made in accordance with the technological assumptions met all the requirements necessary to qualify the technology for welding tubes with tube plates. Both in the case of non-destructive testing and macrographic testing, there were no problems with compliance with the PN-EN ISO 15614-8:2005 standard. [ABSTRACT FROM AUTHOR]

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This paper explores the optimization of Tungsten-Inert-Gas (TIG) welding process parameters for creating a hybrid structure of Aluminium 6061 and Stainless Steel 304 using a copper filler rod (ER-Cu). The Welding of these two materials has industrial relevance owing to its weight reduction capabilities and environmental benefits. However, Aluminium and Stainless-Steel have different melting points and thermal properties. Aluminium has twice coefficient of thermal expansion and six times coefficient of thermal conductance as compared to Stainless-Steel. This difference often results in residual stresses and brittle intermetallic compounds in the weld region. We have chosen the Welding Current, Welding Speed, and Gas Flow Rate as input parameters, and Ultimate Tensile Strength (UTS) and Micro-hardness as response parameters. We have employed the Response Surface Methodology (RSM) using a Box-Behnken design to evaluate the influence of input parameters on UTS and Micro-hardness. Furthermore, an Analysis of Variance (ANOVA) is conducted to determine the input parameters' significance on the response parameters. Our surface plots demonstrate that UTS improves with increased Welding Current and reduced Welding Speed. Simultaneously, Micro-hardness increases with elevated Welding Speed and decreased current, up to a specific limit. The peak value of UTS (79 MPa) was observed with a Current range of 85-90 A, Speed range of 95-100 mm/min, and Gas Flow Rate of 14.5-15 l/min. On the other hand, maximum Micro-hardness (260HV) was obtained with a Current range of 80-85 A, Speed range of 105-110 mm/min, and Gas Flow Rate of 14.5-15 l/min. This research contributes to improving the manufacturing process of hybrid structures, specifically by optimizing the advantages of both Aluminium and Stainless Steel while addressing the challenges that arise during their combination. The study's conclusions have major consequences for sectors looking to take advantage on the mutually beneficial characteristics of different metals in welding applications. [ABSTRACT FROM AUTHOR]

The main direction of improving the operational characteristics of titanium alloys is the creation of heat resistant and high temperature titanium alloys. The high specific strength and corrosion resistance of this type of alloys, at temperatures up to 500…600 °С, enables making them the main structural material for aircraft and rocket engineering. However, their widespread use is associated with the problem of precipitation of brittle phases during welding, which requires the use of additional technological operations, such as local heat treatment or pre-heating. In this paper, the finite element modeling method was applied to study the influence of the TIG welding thermal cycle of the high temperature titanium alloy of Ti‒6.5Al‒5.3Zr‒2.2Sn‒0.6Mo‒0.5Nb‒0.75Si system with and without the use of pre-heating and to plot the cooling rates diagrams of the produced welded joints. Ref. 10, Tabl. 2, Fig. 12. [ABSTRACT FROM AUTHOR]

The attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. However, welding as a fabrication process has a detrimental effect on this alloy's properties which affects its mechanical performance. In this work, to compensate for the loss in mechanical properties caused by welding, proper heat treatment operations are adopted. To this end, 1.5 mm AA7075 sheets were first preheated and butt welded using the gas tungsten arc welding process. The welded sample was solution heat treated, quenched, and then artificially aged. Microhardness tests showed an increase of hardness in all zones of the aged specimen compared to those of the original welded blank before heat treatment. A maximum microhardness value of 180 HV was recorded in the heat-affected zone of the aged specimen. In addition, elongation at break, and strength (yield, tensile, and fracture) of the original welded blank increased by about 50% after the artificial aging operation. [ABSTRACT FROM AUTHOR]

Al/Cu dissimilar welding is a key technology for weight reduction in fabricating high-functional products, however, conventional tungsten inert gas (TIG) welding is difficult to be applied due to a large fusion area. The constricted nozzle equipped inside the conventional TIG torch has been developed and can improve the position accuracy of tungsten electrode and arc plasma characteristics, moreover increase the heat input density. In this study, 0.5 mm-thick Al and Cu dissimilar sheets were butt welded using pulsed TIG welding with the constricted nozzle under two welding speed-current combinations of 50 mm/s-85 A and 100 mm/s-105 A. The 50 mm/s-85 A joint exhibited that Al and Cu mixed each other in the entire weld metal, containing two intermetallic compounds (IMC) of Al2Cu and Al4Cu9 mainly in the Al side. In contrast, both elements hardly mixed each other in the 100 mm/s-105 A weld metal and the interface exhibited hook-like shape at a nearly constant pitch, depending on the welding speed and pulse frequency. Consequently, the formation of IMC layers was limited. Based on the three-dimensional images reconstructed using a serial sectioning technique, the hook-shaped Al/Cu interface was also formed inside the weld metal. The mixed-zone volume per unit weld length of the 100 mm/s-105 A joint was estimated to be about 0.12 mm3/mm, and is much smaller than that of the 50 mm/s-85 A joint (0.97 mm3/mm). The average tensile strength of the 100 mm/s-105 A joint were higher than those of the 50 mm/s-85 A joint, suggesting that the hook-shaped Al/Cu interface together with the reduced mixed zone seems to increase the joint strength. [ABSTRACT FROM AUTHOR]

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In batch operation, most industries require engineers to maintain low hardness on the welded parts, particularly for low carbon steel. This article focuses on tungsten inert gas (TIG) welding performed on 0.90 mm of a C67 grade sheet by varying different welding parameters such as current, velocity, and temperature. Samples were collected from the tool side, mid-wall, and operator side for metallographic and micro-hardness examinations considering various parameters. Without post welding heat treatment (PWHT), the welded parts were quenched at room temperature, while with PWHT the welded parts were kept at 710 ℃ for 99 s after welding, and subsequently, the samples were cooled slowly by air at ambient temperature. An increase in hardness was registered in either the fusion zone or melted zone, with decrements in the heat affected zone (HAZ) for both procedures. When the the welding was performed without PWHT, a martensitic and bainitic microstructure was noticed in the melting zone (MZ) and HAZ, respectively. In contrast, a bainitic microstructure was observed in either the melting or heat affected zone in the welding with PWHT. Metallographic images revealed crack propagation when welding was performed without PWHT. A larger HAZ was noted in the welding sample with PWHT, and hardness was also relatively lower compared the samples without PWHT. There was no significant difference in hardness among the samples taken from tool side, mid-wall, and operator side for both procedures. Finally, the lowest microhardness (265 HV) was found in the MZ when the welding was carried out with PWHT employing a 90 A current and 10 mm/s velocity.

Thin-walled tubes of austenitic stainless steel TP321 preferred for nuclear steam generator applications were used to fabricate butt joint using Tungsten inert gas (TIG) welding process. Optimal TIG welding parameters were identified to achieve complete penetration: welding current of 100 A and a welding rotation speed of 450 mm/min at an arcing space of 2 mm. Scanning electron microscopy (SEM) images revealed the presence of austenite, delta-ferrite, and TiC precipitates. Energy-dispersive x-ray spectroscopy (EDS) analysis of the weld zone indicated the uniform dispersion of elements and a slight increase in Fe was confirmed. The EDS line scan highlighted the existence of TiC in WM region. The Ferrite number (FN) measured using Feritscope for the base metal (BM) and welded tube recorded 1.4 and 4.8 FN, respectively, indicating the minor increase in delta ferrite after welding. The average hardness of the WM was 210 ± 3.5 HV exhibiting good strength in comparison to the BM (180 ± 2.5 HV). The flattening test outcomes revealed good compression strength and ductility of welded TP321 tubes without any surface irregularities or cracks. The tensile strength (UTS) and Elongation of the TP321 butt joint were 619 MPa and 57.50%, higher than that of BM (UTS-501 MPa and Elongation-68.50%). The welded joint subjected to the pull-out test revealed maximum strength of 577 MPa and 56.4% elongation. SEM fracture surface examination of the BM and WM specimens subjected to tensile test and pull-out test indicated the ductile nature of failure. [ABSTRACT FROM AUTHOR]

An experimental investigation of the mechanical properties of copper B370 and stainless steel 434 dissimilar welded joints is presented in this paper. In this study the TIG welding of dissimilar copper B370 & stainless steel 434 welded joint were made of 100 × 50mm plates with silicon bronze as filler then investigated under orthogonal array of L9 experiments. From the experimental study it is concluded that maximum Vickers hardness of 110 and tensile strength of 238.21MPa can be achieved with a process parameters combination of 130 amps of welding current, 60 IPM of feed rate and 15V of voltage for the welding joint. By using the regression equation, this sample has shown the greatest strength of 233.35 MPa with an error percentage of 2.04% compared with experimental result. Microstructure examination revealed that the base of copper B370 and base of stainless steel 434 has twin alpha grain and twin austenite grain respectively. Heat affected zone of copper B370 and stainless steel revealed that both has complete fusion between the weld and base metal. Welding zone reveals Cu-Fe-Mn eutectic particles in the matrix of Cu solid solution. [ABSTRACT FROM AUTHOR]

In this work, Al3Zr/A356 particle-reinforced aluminum matrix composites with 3% particle content were successfully prepared by in situ reaction. The effects of different welding parameters on the microstructure, microhardness and corrosion performance have been contrasted by controlled variables. The result shows when the pulse frequency is 15 kHz and the pulse peak current is 200 A, the welded seam is well-formed and the reinforcements are uniformly dispersed, which makes the hardness of the weld increase by 35% compared with the base metal. The electrochemical test combined with soak corrosion test exhibiting the corrosion mechanism is mainly pitting corrosion, supplemented by the comprehensive effect of stress corrosion and electrochemical corrosion. In addition, the corrosion mechanism of the welded joint of the composite was modeled according to the experimental results. [ABSTRACT FROM AUTHOR]

In modern digitization, safety industries demand flaw-free and high-integrity welds, due to part localization on high uncertainty makes automation a challenging task. Integrating robotic welding with high-value manufacturing sector makes volume rise through pre-programmed repetitive performance on desired welding space. Further, the establishment of fully automated robotic-based welding operations with different configurations on controlled localization is the least available due to unviable cost. Hence, the proposed work concentrates on internet of things (IoT)-driven robotic tungsten inert gas (TIG) welding on stainless steel (SS) 304 by incorporating online programming (OP) with visual control schemes to classify the nature of weld quality using an artificial neural network. Continuous sensory-guided techniques with IoT high-level operator interface affords automated welding planning by using feature matching strategies. Area scan-based complementary metal oxide semiconductor (CMOS) cameras have been used to capture passive vision real-time images of the weld species for defect classification. In real-time, discrete reference workpiece and image feature extraction processes seem to be complicated in an unstructured welding environment. Hence, the present idea will enhance the efficiency of high product variance, but the accuracy of the automation relies on the weld image database. The proposed method (a) adaptively regulates its welding parameter variation on the welding trajectory path, (b) adapts and produces precise good weld workpieces with a 92% production rate with flaw-free welds and (c) initiates the automatic tuning of robot kinematics through IoT closed-loop online external control strategy. The proposed research experimental results confirm that fully automated IoT-driven robotic TIG welding affords good welding with an 88% improved quality rate through online passive vision-based image feature analysis. [ABSTRACT FROM AUTHOR]

Large residual stress of 2219 aluminum alloy induced by Tungsten Inert Gas (TIG) welding decreases its service performances. Shot peening was adopted to decrease the residual stress of TIG welding. Numerical models of TIG welding and shot peening were established using the combined discrete and finite element methods (DEM–FEM). The results show that TIG welding induces tensile residual stress due to the heat exchange effect and the longitudinal stress is larger than that in the transverse direction. The maximum tensile stress occurs at a depth of 0.1 mm. The surface tensile stress changes to compressive stress after shot peening as the severe deformation induced by the shots changes the stress state of the plate. The maximum value of compressive stress (σm) and the peened depth with compressive stress (Z0) are adopted to describe the peening effect. The absolute value of σm increases with the increased peening speed and nozzle height. Mixed shots with a diameter of 0.8 mm and 1.2 mm induce larger value of σm than those with only a diameter of 1.2 mm. The value of Z0 increases with the ascending shots diameter and nozzle height, while it varies nonmonotonically with the peening speed. The effect of shot peening on the residual stress in TIG welding is discussed. [ABSTRACT FROM AUTHOR]

Welding is an important manufacturing process for joining complex parts. Despite their widespread use, there exist some drawbacks in the existing liquid-state (e.g., formation of undesirable heat-affected zones around weld area) and solid-state (e.g., high equipment and tooling costs, low production rates, and difficulty in joining intricate geometries) methods. These limitations continually spur the search for new joining processes to improve existing welding methods or develop new ones that circumvent these limitations. To provide a “greener” and low-cost alternative to the traditional welding processes that often produce “soft” heat affected zones (HAZs), we develop and evaluate the expansion of cold spray process—a solid-state high-velocity particle deposition process—to solid-state welding, a process we term cold spray welding (CSW). Using well-defined processing parameters, we cold spray welded (CSWed) AA 6061-T651 plate and compared the results with Tungsten inert gas (TIG) welded counterpart. Although TIG-welded samples exhibit higher tensile properties than CSWed samples (at least based on the CS processing parameters used in this study), our findings show that CSW indeed circumvents major drawbacks in traditional welding processes, including negligible microstructural alterations and the inhibition of deleterious phase transformation and suppression of deleterious HAZ. The examination of CSWed parts reveals low yield strength is connected to ubiquitous microvoids that are formed due to lack of metallurgical bonding; these microvoids act as microcrack initiation sites. We proceed to establish a failure mechanism in the CSWed part to provide direction for future optimization.

Results of mathematical modeling of an argon arc with refractory cathode in case of a deformed surface of the weld pool (arc anode) are described. It is assumed that there is a depression (crater) on the anode surface, the shape and size of which are preset; arc plasma has axial symmetry, and it is in a stationary state; metal evaporation from the anode surface is ignored. A mathematical model of the processes of energy, momentum, mass and charge transfer in the arc column and anode region is briefly described. A numerical study was conducted of thermal, electromagnetic and gas-dynamic processes in the arc column with a curved surface of the anode, as well as conditions of electric, thermal and force interaction of the arc with the anode surface, depending on the crater depth. Results of computational experiments are illustrated by the fields of isotherms, isobars and current lines in an arc with a curved surface of the anode, which are compared with similar fields in the case of an anode with a plane surface. A procedure for calculation of normal components of the vectors of electric current density and specific heat flux into the anode with a curved surface is described, and results of calculation of radial distributions of these characteristics, depending on the depth of the crater on the anode surface, are given. These results are complemented by numerical studies of the influence of the crater depth on arc pressure distribution over the anode surface. A conclusion was made that sagging of the weld pool surface in TIG welding can significantly change the conditions of electric and thermal interaction of the arc with the metal being welded, namely it can influence the thermal and hydrodynamic processes in the liquid metal, which determine the penetrability of the arc with the refractory cathode. [ABSTRACT FROM AUTHOR]

Acoustic emission signals (AE) were used to determine the quality of welding parameters with the Global Best Modified Artificial Bee Colony (GBMABC) algorithm. The RSM-Box–Behnken design was used to experiment. The effect of tungsten inert gas welding process parameters on microstructure, hardness and tensile properties of 5086 Al alloy was studied. Moreover, the input parameters were optimized to achieve better mechanical properties. The online monitoring AE method exhibited energy, hits and counts showing significant variations in their rate concerning the failure region. The GBMABC algorithm is one of the more promising biologically inspired metaheuristic approach to finding the optimal solutions. The higher tensile strength of 296.32 MPa and the hardness of 84.69 Hv achieved at 191 A, 26 V and 3.33 Hz were computed through the GBMABC algorithm. The validation test was conducted at the optimal condition, showing that predicted and experimental responses were much closer. [ABSTRACT FROM AUTHOR]

Results of mathematical modeling of an argon arc with refractory cathode in case of a deformed surface of the weld pool (arc anode) are described. It is assumed that there is a depression (crater) on the anode surface, the shape and size of which are preset; arc plasma has axial symmetry, and it is in a stationary state; metal evaporation from the anode surface is ignored. A mathematical model of the processes of energy, momentum, mass and charge transfer in the arc column and anode region is briefly described. A numerical study was conducted of thermal, electromagnetic and gas-dynamic processes in the arc column with a curved surface of the anode, as well as conditions of electric, thermal and force interaction of the arc with the anode surface, depending on the crater depth. Results of computational experiments are illustrated by the fields of isotherms, isobars and current lines in an arc with a curved surface of the anode, which are compared with similar fields in the case of an anode with a plane surface. A procedure for calculation of normal components of the vectors of electric current density and specific heat flux into the anode with a curved surface is described, and results of calculation of radial distributions of these characteristics, depending on the depth of the crater on the anode surface, are given. These results are complemented by numerical studies of the influence of the crater depth on arc pressure distribution over the anode surface. A conclusion was made that sagging of the weld pool surface in TIG welding can significantly change the conditions of electric and thermal interaction of the arc with the metal being welded, namely it can influence the thermal and hydrodynamic processes in the liquid metal, which determine the penetrability of the arc with the refractory cathode. [ABSTRACT FROM AUTHOR]