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In this research, the effect of current intensity on the corrosion resistance of Ti-6Al-4V alloy welded by Tungsten-inert Gas (TIG) method was investigated. For this purpose, 3 × 50 × 40 mm specimens were prepared and after preparing the surfaces, in a way but joint two-way single pass in vacuum chamber with inert argon with a flow rate of 70, 80 and 90 A were welded. Microstructural studies of base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) were performed using optical microscopy and scanning electron microscopy (SEM). Then, in order to investigate the corrosion resistance of Ti-6Al-4V welded cross sections, the roots of the welded specimens were examined by potentiostatic polarization in seawater and 3.5% NaCl. The results showed that by increasing the welding current intensity from 70 to 80A, the grain size in the weld area as well as the corrosion rate of the weld area in Ti-6Al-4V alloy increased. By varying the flow intensity from 80 to 90A, the corrosion rate and grain size of the weld zone did not change significantly. The corrosion rate of Ti-6Al-4V alloy in 3.5% NaCl solution compared to seawater revealed that the corrosion rate of alloy in 3.5% NaCl solution is higher than its corrosion rate in seawater.

In this work, a new welding method, AC-DC hybrid TIG welding, is used to weld 304 stainless steel. Research on the formation, microstructure, and properties of 304 stainless-steel welded joints are studied by using optical microscope and microhardness. The results show that the weld with AC/DC hybrid welding is a fish-scale pattern, and the density of the fish-scale pattern increases with the increase of AC proportion. Both the weld penetration and the ratio of weld penetration to weld width are the highest when AC accounts for 30%. At this point, the weld penetration is 0.83 mm larger than DC mode, an increase of 93.26%, and the ratio of weld penetration to weld width is 1.6, which is 76.19% higher than DC mode. When the proportion of AC is increased, the microstructure of the weld is equiaxed or columnar, and the microstructure of the heat-affected zone is ferrite in the form of lath. The hardness of the weld is greater than that of the base metal, and the hardness of the heat-affected zone is the lowest. The microhardness distribution of the weld with AC 50% is the most uniform. When AC accounts for 20% and 30%, the average weld hardness is the highest, which are 196.7 HV and 198.1 HV, respectively.

[Display omitted] • A machine learning model was proposed to predict the tensile properties of 2219-T8 Al alloy TIG welded joint. • Relationship between tensile strength of joint and weld geometry, weak zone properties was developed. • The collaborative regulation mechanism of geometry and property was discussed. • The machine learning model could be used to optimize and guide welding process. The tensile properties of 2219-T8 aluminum alloy TIG welding joint were significantly affected by the microstructure, local mechanical properties and weld geometry. This paper proposed a machine learning model to predict and optimize the tensile properties of 2219-T8 aluminum alloy TIG welding joint. The relationship between tensile strength of joint and weld geometry, weld zone and partially melted zone (PMZ) properties was developed by Kriging model combining whale optimization algorithm (WOA). This surrogate model demonstrated a high precision, with R2 = 0.952 and RMSE=3.77 MPa. The surrogate model, which also served as a welding process guide, was utilized to determine the ideal weld geometry corresponding to various weak zone properties. By applying the optimization process based on the surrogate model, the optimized joint strength coefficient reached 70 %, and elongation exceeded 4 %. The collaborative regulation mechanism of geometry and property was also discussed. [ABSTRACT FROM AUTHOR]

In this paper, high-temperature impact fatigue (HTIF) was carried out on a Co-based surface layer cladded by TIG welding, and cracks emerged at 400-cycle condition. The reasons for cracking were investigated from three aspects: microstructure, stress distribution, and crystal orientation. Crack generation was induced by high stress distribution in eutectic carbides at grain boundaries and the great disparity in orientations between grains on two sides of the crack path. The microstructural advantage for cracking behavior played a key role in emergence of cracks, which was verified by the investigation and comparison of three distances from the weld interface. Moreover, the interface microstructure of Co-based layer and FB2 substrate was characterized by transmission electron microscopy, and the phase composition of the weld interface comprised Fe Co and M 23 C 6. The results presented that the addition of Ni-based transition layer caused the acquisition of the crack-free surface layer after HTIF. Finally, microhardness test was conducted on samples with and without a transition layer. The hardness of Co-based surface layer without the transition layer was mainly affected by the transformation of carbides, dilution of Fe, and work hardening during HTIF. The hardness of Co-based surface layer with the transition layer showed minimal change during HTIF, and this finding was attributed to the slight variation in the microstructure. • The microstructural evolution of Stellite 6 layer was revealed. • Mechanisms of cracks generation during HTIF were illustrated. • Crack problem was solved by the addition of Inconel 625 transition layer. • The phase composition of interfacial layer was determined. • Reasons for hardness variation during HTIF was explained. [ABSTRACT FROM AUTHOR]

Welded connection technique in welding must have strong strength. TIG (Tungsten Inert Gas) welding has different welding parameters depending on the welding material, one of the welding parameters is the welding current because it will affect the value of the heat input that will come out. Heat input will affect the mechanical characteristics of the weld area, this study aims to see the value of the tensile strength with different welding current in the AISI 316 stainless steel material formed according to the ASTM E8 tensile test specimen, and the filler of the welding material is AISI 316, and the shielding gas used is argon. The current variations that will be used are 3 variations, namely 110 A, 130 A, and 150 A. Tensile testing uses a universal material testing machine to find the maximum load value that can be resisted by the weld area with static loading. The highest strength of the welded joint is obtained by a welding current of 130 A with a tensile stress of 476.4978 MPa. [ABSTRACT FROM AUTHOR]

An attempt is made to investigate mechanical-microstructural-magnetic properties on the welded Cold Rolled Non-Oriented Electrical steel (CRNGO) sheets. Single 0.5 mm thin sheets susceptible to Tungsten Inert gas (TIG) welding current are stacked and edge welded using a range of welding current from 30 A to 110 A. The influence of weld with varying current is analyzed through various testing for joint performance, micro-hardness, Residual stress, weld seam characterization, Grain size variation and Magnetic property evaluation of post-welded samples. The results showed the variations of micro-hardness varies by 33 HV and 42 HV at the Heat affected zone (HAZ) and Fusion zone (FZ), respectively. The relative residual stress ranged from 26.85 MPa to 127.6 MPa, weld strength ratio is about 42.9%, depth to width ratio varies from 0.446 to 0.527. The ferritic and largest fine grains size of 79.7 μm is transformed to coarse 282 μm in HAZ. The changes of magnetic properties showed a significant increase in core loss and magnetic field strength with decrease in the relative permeability. The study is useful for electric motor industries to generate varieties during stacked welding of transformer core as per the need of the application. [ABSTRACT FROM AUTHOR]

Industrial applications often require welded joints of dissimilar metals to perform reliably under adverse working conditions. Such conditions demand high resistance to failure modes, such as fatigue, corrosion, and creep. In applications involving intense vibrational and cyclic loading conditions, high strength-to-weight ratio metals, including aluminum, are more vulnerable to fatigue failure. This study investigates the fatigue strength of base metals and tungsten inert gas welded joints of the two most widely used aluminum alloys, AA7075 and AA2024, under four-point rotating bending. For the comparative study, these dissimilar alloys were joined together by using two different filler rods, AA4047 and AA4043, under similar welding conditions. SN curves for all the samples were generated through the experimental iterations. A comparison of different results shows that welded samples have better fatigue strength than the base metals, while, as a filler, AA4047 has better resistance to fatigue fracture than AA4043. [ABSTRACT FROM AUTHOR]

Traditional evaluation of weld joint mechanical properties by destructive testing shows the limitations of these methods, including equipment limitations, high materials/testing cost, and challenging repeatability. This work presents an experimental approach for utilizing passive infrared thermography and tensile testing to evaluate the correlation between thermal and localized TIG-welded Inconel 625 joints' mechanical properties. The results show that different areas of interest deform differently during the tensile test. The dog-bone shaped TIG-welded samples were divided into five regions of interest on both sides of the weldment, of which two are repetitive on both sides of the sample representing Inconel 625 base metal alloy, heat-affected zones, and weld beads. The temperature change rate in these three regions varied from 0.17 to 0.67°C per minute as the tensile test progresses. The fractography analysis showed that the failure occurred within the weld beads, even though the highest temperature was observed in the heat-affected zones, suggesting higher strength in the heat-affected zones. The improvement mechanism introduced in this work utilizes thermography visualization to predict weld failure as nonlinear elongations are observed across different stages during the tensile tests. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum 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 welding of aluminium alloys especially in dissimilar combination is challenging owing to numerous problems. The present study focuses to optimize processes parameters for dissimilar welding of 6 mm thick dissimilar Al-6061 and Al-5083, using Tungsten Inert Gas welding as well as to investigate the influence of the process parameters on tensile properties and microstructure of developed welds. A single V-butt joint configuration (bevel angle 60 ° and root gap 2 mm) of plates was used for welding. Three levels of input parameters viz. voltage, current and welding speed were selected for performing experiments as per L9 orthogonal array. The hardness and tensile strength were taken as output parameters or performance characteristic in the study. The optimum parameter settings for highest heat affected zone hardness and ultimate tensile strength of dissimilar welds have been suggested by using S/N ratio. The result predicted by optimization has an error of 2-3%. Finally, the effects of voltage, current and welding speed on m icro structure, hardness and tensile strength of welds have been investigated. Welding speed and current were the most influencing process parameter for controlling the hardness of HAZ and tensile strength of the welds. [ABSTRACT FROM AUTHOR]

Aluminium alloys are widely used in the fields of electric module packaging, electronic technology, automotive body structure, wind and solar energy management, due to the advantages of high specific strength, high processability, predominantly anti-erosion, increased conductivity, eco-friendly nature and recoverability. The objective of the study is to review the previous papers on aluminium usages, application, and workability parameters. The methodology adopted for the study is to use the structure literature review technique, and the time period selected for the study is 2008–2019 from the Scopus database. The findings of the study concluded that there are various types of aluminium alloys has been used by the previous researchers, and only 6061 is least explored aluminium alloy among all of them. The future scope of the study is to investigate using distinct activating fluxes for raising penetration & to understand consequences on mechanical components & rust behaviour of TIG-welded aluminium metal welds.

High strength rebars are generally developed by increasing carbon and manganese contents depending on the size and strength capacity requirement. These elements in steel beyond certain level adversely affect weldability and impact toughness which are very critical for structural steels. In this study, an attempt has been made to analyse and optimize the welding parameters on higher carbon equivalent (0.60) of 36-mm-diameter structural rebar by Arc and TIG welding process to arrive at exact preheating temperature for obtaining desired weld properties at minimum possible cost. The basic aim of this work is to establish the welding process parameters on structural steel to use as an earthquake-resistant steel without compromising the properties such as yield strength, tensile strength, tensile strength to yield strength ratio, and minimum uniform elongation. Before and after the welding, changes in the microstructure and mechanical properties in the fusion zone and heat affected zone (HAZ) of the welds were investigated. From the results, it was observed that 150 °C is the optimum preheating temperature to obtain good welds. The microstructural studies revealed that martensite is not present in the HAZ of the 150 °C preheated sample and the same was substantiated from resultant mechanical properties also. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of TIG welding on the mechanical properties of Inconel 600 alloy. Inconel 600 alloy was welded using TIG welding. Accordingly, the samples were prepared for characterization and testing. Samples were prepared for X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), microhardness testing and tensile testing. XRD analysis of the welded joint revealed the formation of different intermetallic compounds at the welded joints. These intermetallic joints improved the mechanical properties of the welded joints. Next, optical microscopy and SEM of the welded joints revealed minimal porosity at the welded joints. The lower porosity at the welded joints improved the mechanical properties of the welded joints. Microhardness analysis revealed that the hardness of the weld joint was higher than that of the heat-affected zone (HAZ) and was lower to the base Inconel 600 alloy. Further, the yield strength (YS), ultimate tensile strength (UTS), and % elongation of the TIG welded Inconel 600 joints was higher than the base Inconel 600 alloy. The YS, UTS, and % elongation of TIG welded Inconel joint was 9%, 15% and 22% higher than the base Inconel 600 alloy respectively. Fracture analysis of the joints revealed a dimple type of structure indicating a ductile type of failure. [ABSTRACT FROM AUTHOR]

This study focuses on experimental study of mechanical characterisation for the carbon steel material SA516GR70, steel alloy welds through tungsten inert gas (TIG) welding process used for the applications of pressure vessel and heat exchanger. Current work describes the preparation of test coupons which is used for sample preparation of tensile, bending and hardness test. Welding process parameters optimization is carried out using Taguchi method for the carbon steel weld material to improve the properties. Using the orthogonal array, experiments are setup and weld joint obtained is used for mechanical testing. Graphs are obtained from the full factorial design using the Mini tab software which is helpful in studying the effects of the parameters on properties. Interpretation of the statistic for various parameters is analysed and the coefficients are determined. Main effects plot, interaction plot and residual plots are plotted which reveal that model fits the data with the average acceptance level of 91.85%. [ABSTRACT FROM AUTHOR]

This current research focuses on optimizing the welding process parameters and penetration of 5052 alloys using a TIG welding process based on the Taguchi methods. Process parameters such as current, voltage, and speed with three different levels were taken to form the L27 orthogonal array using the design of experiments. Analysis of variance, signal-to-noise ratio analysis, and regression analysis were performed. The regression analysis indicated that the developed model has greater adequacy in predicting the reinforcement form factor (RFF), penetration shape factor (PSF) and hardness of the weld specimens. In addition, the optimized parametric condition for the welded specimen was found to be current, voltage, and speed of 140 A, 18 V, and 300 mm/min, respectively. [ABSTRACT FROM AUTHOR]

A self-consisted mathematical model is presented, describing nonstationary processes of energy, momentum, mass and charge transfer in plasma column and anode boundary layer of an electric arc burning in atmospheric pressure inert gas at pulsed modulation of current. A numerical study of distributed and integrated characteristics of 2 mm long argon arc was performed in the case of current modulation by rectangular pulses at 10 kHz frequency and different values of the duty cycle (0.3; 0.5; 0.7) under the condition that the average current value remains unchanged and equal to 140 A. Calculated time dependencies of plasma temperature, velocity and current density in the arc column centre, as well as axial values of plasma temperature and pressure near the anode surface, anode current density and heat flux into the anode are given for the selected values of duty cycle. Radial distributions of averaged over the current modulation period heat flux, introduced by the arc into the anode, pressure and force of friction of arc plasma flow on its surface were calculated, which are the determinant ones for simulation of thermal and hydrodynamic processes in the metal being welded in TIG welding with high-frequency pulsed current (HFPC) modulation. Results of simulation of nonstationary arc characteristics are compared with the respective results for a direct current (DC) arc, at current equal to average value of modulated current. Analysis of the obtained results leads to the conclusion that in the case of HFPC TIG welding at 10 kHz frequency decrease of duty cycle (increase of pulse current) at constant value of average current leads to greater force impact of such an arc on weld pool metal and to increase of its penetrability, respectively. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V is a material that is extensively used in the gas turbine application. The fabrication of the assemblies of the gas turbine made up of Ti-6Al-4V involves Tungsten Inert Gas (TIG) welding. It is preferred to have a minimal bead width for minimal distortion with full penetration welds meeting the required weld quality as per aerospace weld standards. The primary purging gas which is usually employed during TIG welding is inert argon gas. In this present study argon and helium gas mixture was adopted as shielding gas. Taguchi design of experiment has been employed involving L9 orthogonal array with 3 parameters and 3 levels. The aim of the study was to understand the effect of the weld parameters and Ar-He gas mix ratio on the bead width of the welds. The obtained results were analyzed using ANOVA and found the welding current having significant effect on bead width followed by welding speed and Ar-He gas mix. A linear regression mathematical model is generated of the response variable. In order to ascertain the optimized parameters confirmation tests are conducted and obtained results are correlated. Macroscopic images do not show any crack or porosity and thereby confirm that defect free welds can be produced within the range of process parameters. [ABSTRACT FROM AUTHOR]

The quality and integrity of welded joints is highly influenced by the optimal combination of the welding input parameters. Due to the rapidly changing scenario in the manufacturing industry, optimization of process parameters is essential for a manufacturing unit to respond effectively to the severe competitiveness and increasing demand for quality products in the market. An attempt is made to study the effect of heat input parameters properties of Tungsten Inert Gas (TIG) welding process. The application of the surface plot in the investigation of the combined effect of input parameters on heat input and heat affected zone was pursued in this study. The central composite design matrix was used to obtain data from sets of experiments. Mild steel coupons measuring 60mm x 40mm x 10mm were welded with tungsten inert gas welding process. This study developed a model using expert systems, such as Response Surface Methodology and Artificial Neural Network to optimize and predict weld heat input and heat affected zone from input parameter such as current, voltage and welding speed. With the data collected from twenty experimental runs in this study, the result from one Response Surface Methodology analysis shows that a current of 130.00Amps, voltage of 20.94V, speed of 0.48m/min will produce heat input of 0.64277Kj/mm and heat affected zone of 5.42078mm with a desirability of 0.962. [ABSTRACT FROM AUTHOR]

Austenitic 316L Stainless Steel are TIG (Tungsten Inert Gas) welded and are water jet peened by varying two main parameters - pressure and stand-off distance. This induces compressive residual stresses by local plastic deformation. The residual stresses of samples before and after water jet peening are measured using XRD. TIG welded samples show residual tensile stress and peened samples show compressive stress. Compressive stresses in the range of 111MPa to 118MPa are induced by water jet peening, of which the samples peened with 50mm Stand-Off Distance (SOD) has more compressive residual stress. Samples peened with SOD of 50mm shows good corrosion resistance, micro hardness and good surface finish when compared to samples peened with SOD of 75mm. It has been observed that only SOD plays an important role in enhancing the properties after peening. The microstructure of the peened region in the weldment consists of fine grains due to impact of high pressure water jet. [ABSTRACT FROM AUTHOR]

In arc welding, a groove is often used between metal pieces being welded. In tungsten inert gas welding of high-manganese stainless steels with arc voltage control (AVC), the penetration depth was found to increase with groove wall height. The purpose of this study is to understand the influence of the groove on the penetration depth, mainly through numerical simulation. Spectroscopic measurements were also conducted to validate the simulation. The simulation results showed that when no groove is present, several eddies are formed around the arc column and electrode tip, leading to a recirculating flow pattern. When using a groove, shielding gas introduced from the nozzle flows directly into the arc without forming eddies. In the former case, the metal vapour was transported upwards by the recirculating flow into the arc column and the electrode regions. In contrast, in the latter case, the metal vapour was pushed downward to form a dense metal vapour region over the weld pool and was then swept away horizontally. The arc voltage without a groove is about 1 V lower than that with a groove because the metal vapour around the electrode tip increases the arc electrical conductivity. This affects the arc length control when AVC is used. When the arc voltage increases, the AVC shortens the arc length to keep the voltage constant, leading to the deeper penetration by concentrating the heat input and arc pressure. These mechanisms cause the change of penetration depth when the height of the groove wall is changed. [ABSTRACT FROM AUTHOR]

Among the stainless steels, the most widely used group is austenitic stainless steels. The prominent reason why austenitic stainless steels are preferred in welded stainless steel fabrications is their good weldability. AISI/SAE 304L austenitic stainless steels exhibit adequate corrosion resistance in oxidizing environments. AISI/SAE 304L austenitic stainless steels are also used in filling interfaces of runners between the Tri-Nitro-Toluen filling vessel and ammunitions in defense industry. For the manufacture of the runners, the stainless steel plates and the stainless steel pipes are mainly joined by fusion welding. These runners are cleaned with hot tapping water at 70°C after each filling of ammunutions by TNT so that cleaning operation can deteriorate the corrosion properties of runners especially weld zones. Austenitic stainless steel weldments include basically delta-ferrite and austenite phases on weld regions. Delta ferrite phase exhibits resistance to chloride bearing medias while austenite phase is more resistive to high temperature oxidizing ambients. In this study; 3 mm thick 304L austenitic stainless steel plates and rings are welded to each other with two different filler weld wires of ER316L and ER2209 by Tungsten Inert Gas welding method under pure argon shielding gas. Weld metals and heat-affected zones of welded joints were examined using optical metallurgical microscope. It has been determined that the additional filler weld wires have changed the weld metal and the heat affected zone microstructures and phase distributions dominantly. Microstructures of all welded joints have been compared. Besides, phase distributions of weld metals and heat effected zones are made by image analysis software and Schaefflers diagram. ER 2209 welding filler metal increased the phase fraction of delta-ferrite in weld metals while it decreased the austenite phase fraction as compared to ER316L filler metal. [ABSTRACT FROM AUTHOR]

Transporting substances with high radioactivity used in nuclear medicine is strategic. Lean duplex stainless steel UNS S32304 is a candidate for external construction of a cask for transporting radioactive material. Thin sheet lean duplex stainless steel specimens were welded by autogenous TIG processing (tungsten inert gas) in order to avoid neutron activation of the filler metal. Post-welding heat treatments were studied considering a possible scenario of fire or crash during transportation. The metallographic analysis indicated that post-welding heat treatments promoted a change in austenitic phase content in the fusion zone. An analysis of the stress-strain curves using work hardening models revealed that only the Voce and Hockett–Sherby models presented goodness-of-fit to the experimental data. It was demonstrated that the parameters of both models are correlated to the volumetric austenitic phase content present in the fusion zone, being equivalent to the quantification of the bulk phase. This work proposes a new direct evaluation methodology for volumetrically quantifying phases using both mathematical work hardening models fitted to the experimental data from stress-strain curves. [ABSTRACT FROM AUTHOR]

TIG welding method is generally used for welding stainless steel and aluminum alloys. It is preferred for the welding of thin sheets due to its low heat input. The fact that the TIG torch does not deviate from the surface to be welded and the arc stability are extremely important factors for welding quality. For this reason, the use of fixtures is an important equipment for TIG welding work. In this study, a multivariable portable and fixed fixture is designed. There are suggestions for fixing the samples to be combined, minimizing the vibration problem and solutions based on heat input. The designed fixture has an adaptable for at least two-axis machines. Sheets of different lengths and widths can be easily welded with this technique without being exposed to distortion. However, copper planch and aluminum cooling fin are used in the method to reduce heat input. Semi-automatically welded 304L austenitic stainless steel sheet materials were compared with manually welded stainless steels and the results were evaluated.

This article presents a fuzzy system-based modeling approach to estimate the weld bead geometry (WBG) from the welding process variables (WPVs) and to achieve a specific weld bead shape. The bacterial memetic algorithm (BMA) is applied to solve these problems in two different roles, as a supervised trainer, and as an optimizer. As a supervised trainer, the BMA is applied to tune two different WBG models. The bead geometry properties (BGP) model follows a traditional approach providing the WBG properties as outputs. The direct profile measurement (DPM) model describes the bead profiles points by a non-linear function realized in the form of fuzzy rules. As an optimizer, the BMA utilizes the developed fuzzy systems to find the solution sets of WPVs to acquire the desired WBG. The best performance is achieved by applying six rules in the BGP model and eleven rules in the DPM model. The results indicate that the normalized root means square error for the validation data set lies in the range of 0.40 - 1.56% for the BGP model and 4.49 - 7.52% for the DPM model. The comparative analysis suggests that the BGP model estimates the BWG in a superior manner when several WPVs are altered. The developed fuzzy systems provide a tool for interpreting the effects of the WPVs. The developed optimizer provides multiple valid set of WPVs to produce the desired WBG, thus supporting the selection of those process variables in applications.

The effect of sensitization on the intergranular corrosion (IGC) of TIG welded AlMg6Mn was investigated by means of scanning electron microscopy (SEM) and corrosion NAMLT tests. The as-received hot rolled AlMg6Mn alloy plates with a thickness of 8 mm were welded by TIG welding with S-AlMg5 as a filler material. Specimens were sensitized at 100°C for 7 days. It was found that welded specimens are sensitive to IGC. The. mass loss in NAML test was 106.7 mg/cm². The welding increases the susceptibility to IGC, since the mass loss of the base metal at the same test was 70.7 mg/cm². The increase of susceptibility to IGC is attributed to significant continually precipitated Mg-rich phase along the grain boundaries during the sensitization treatment.

Automated and intelligent classification of defects can improve productivity, quality, and safety of various welded components used in industries. This study presents a transfer learning approach for accurate classification of tungsten inert gas (TIG) welding defects while joining stainless steel parts. In this approach, eight pre-trained deep learning models (VGG16, VGG19, ResNet50, InceptionV3, InceptionResNetV2, Xception, MobileNetV2, and DenseNet169) were explored to classify welding images into two-class (good weld/bad weld) and multi-class (good weld/burn through/contamination/lack of fusion/lack of shielding gas/high travel speed) classifications. Moreover, four optimizers (SGD, Adam, Adagrad, and Rmsprop) were applied separately to each of the deep learning models to maximize prediction accuracies. All models were evaluated based on testing accuracy, precision, recall, F1 scores, training/validation losses, and accuracies over successive training epochs. Primary results show that the VGG19-SGD and DenseNet169-SGD architectures attained the best testing accuracies for two-class (99.69%) and multi-class (97.28%) defects classifications, respectively. For “burn through,” “contamination,” and “high travel speed” defects, most deep learning models ensured productivity over quality assurance of TIG welded joints. On the other hand, the weld quality was promoted over productivity during classification of “lack of fusion” and “lack of shielding gas” defects. Thus, transfer learning methodology can help boost productivity and quality of welded joints by accurate classification of good and bad welds.

Many applications in industry require a material-to-material joining process of Duplex Stainless Steels (DSS). Therefore, it is essential to investigate the material's properties during a welding process to control the weld quality. With the help of Laser-Induced Breakdown Spectroscopy (LIBS), the chemical composition during the Tungsten Inert Gas (TIG) welding process of DSS could be monitored in situ. The chemical composition could be quantitatively measured using pre-established calibration curves. Although the surface temperature and the welding plasma have a high influence on the spectral intensities, reliable composition measurements were possible. The concentration of alloying elements could be mapped during the TIG welding process.

Wire Cut EDM technique is widely used to make small and precision cuts. Generally, a material with fragile geometry and hard structure is cut using a wire cut EDM. The main advantage of this method is that, it is a non-conventional machining process therefore it does not have a contact between the tool (wire) and the workpiece. This advantage gives it an edge over other machining techniques and it makes the process capable of machining even the weak structured and delicate materials. In the present experimental work, by using various machining parameters (Pulse on Time, Pulse off Time, and Wire Speed) were optimized using Taguchi’s L9 orthogonal array. Welding is most the important industrial processes, therefore lots of techniques have been developed to get an efficient and low-cost welding process for different types of materials. In this we will discuss about the welding characteristics of the of tig welding joints produced using different currents. That is, by changing the voltages for the number of passes to improve and strengthen the welded joint The research work aims to optimize the wire cut EDM process parameters for AISI 308 steel and analyze the welding characteristics of Tungsten Inert Gas (TIG) welded joints of the same material. The study intends to find the optimum combination of process parameters that would lead to the highest material removal rate, lowest wear rate, and best tensile properties of the material.

7075 aluminum alloy butt welding was carried out by TIG welding with self-made 7075 wire. The effects of different currents on the microstructure and mechanical properties of the joint before and after heat treatment were studied. Before heat treatment, the strength and elongation of the joint are 274.84 MPa and 6.3%, which are determined by the presence of a large number of second phase precipitates with different shapes. After heat treatment, the tensile strength and elongation are increased to 511.75 MPa and 13.76%. Since most of the second phase has been dissolved, the grain size becomes the decisive factor. The fine grain size and more sufficient recrystallization degree make the mechanical properties of the low-current joint better.

Inconel 718 alloy is widely used in applications that require advanced strength properties especially at high temperature conditions. Combust room walls, exhaust parts, jet tribune blades and gas tribune equipment are the most known using areas. This alloy can be welded with various fusion welding methods, but TIG (Tungsten Inert Gas) welding is preferred since, it provides simply application, mobility and low cost. This study was aimed to clarify that how adjusting the welding parameters and welding automatically can help to achieve promising mechanical properties before heat treatments. The welding experiments were conducted on three different welding current values and attention was paid to provide full penetration for each condition. The results showed that the highest welding current value which did not cause welding defects lead to decrease heat input due to the high transverse speed usage. Moreover, by automatically welding, the heat input was decreased to a minimum level that provided excellent tensile strength and elongation properties. Dendrites turned to cellular from colon. Hazardous zones, such as HAZ and PMZ, narrowed down. The Laves phase ratio and grain size also decreased. Microhardness results confirmed these microstructure observations. The crack observations after tensile tests showed that failures were near HAZ in high-heat input conditions. However, failures were observed in FZ for low-heat input conditions. Additionally, ductile fracture and fracture similar to cleavage mechanisms were observed together due to adjusting the parameters and automatization. [ABSTRACT FROM AUTHOR]

Tungsten Inert Gas (TIG) welding has been learnt to be the most widely used technique among the fusion welding techniques. Welding of different components of boilers is preferably accomplished by TIG welding, due to the process capabilities of the technique to produce sound joints, even in case of Dissimilar Metal Joints (DMJ). DMJs owing to the techno-economic advantages, find vast area of application especially in boiler fabrication industry. It has been learnt that the quality of welded joints is signified by mechanical properties of the joint. The present paper is focused on the behavioural aspects of similar and dissimilar metal joints of ASME SA 213 GR. T11 and BS 3059:1987 PT 1 ERW 320, the boiler steam tube materials, prepared by TIG welding under torsional loading. It has been observed that the dissimilar metal joint has performed better than the individual similar metal joints under torsional loading by achieving 85% of the torsion strength of one of the parent metal, whereas in the case of individual similar metal joints of ASME SA213 Gr. T11 and BS3059:1987 PT1 ERW320, 78% and 68% of the torsion strength of respective parent metals has been observed. ANOVA statistics have validated the existence of significant impact of input process variables on the output quality measure of the welded joint at 95% level of confidence. The predictive models for optimum torsional strength have been proposed by regression analysis. [ABSTRACT FROM AUTHOR]

Poor penetration in TIG welding was overcome by using backing plates. This study reports improved weld penetration, in 6.0 mm thick P91 plates, during TIG welding using backing plates of cast iron, copper, and mild steel. Bead-on-plate (BOP) TIG welding was carried out at the maximum heat input parameters based on earlier studies. In this study, the cast-iron backing plate gave the maximum penetration. It has been noticed that as the weld penetration increases, the grains in the heat-affected zone, get coarser and the average hardness decreases. [ABSTRACT FROM AUTHOR]

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A device was designed that allows inserting a tungsten dart probe into the plasma of arc column during TIG welding. The operation of the device envisaged that a metal string with a diameter in the range of (0.25…0.4) · 10–3 m was elastically deformed (twisted) under the action of torque. During the movement of the arc column plasma, the probe was subjected to a pressure force, the string was elastically deformed and this allowed establishing the velocity of the arc column plasma rotating around its axis during TIG welding under a constant longitudinal magnetic field. The arc burned between the tungsten electrode and a copper plate with a thickness of 6,0 · 10–3 m on the direct polarity without mixing the electrode (vw = 0). The length of the arc was 4.0 · 10–3 m. It was found that at a welding current of 200 A, an increase in the induction of the magnetic field from 18 to 45 mT leads to an increase in the azimuthal velocity of the arc column plasma at a distance within (3…4) · 10 -3m from its axis in the range from 17 to 20 m/h, and the angular speed of rotation is in the range from 750 to 940 rps. The plasma probings of the arc column were performed with a double probe during TIG welding with the effect of a constant longitudinal magnetic field. In capacity of probes, tungsten darts with a diameter of 0.3 ∙ 10–3 m served. According to the results of measuring voltage drop, between the probes the values of longitudinal and azimuthal current densities at a set point during TIG welding were established. It was found that at the level of magnetic field induction within 18…45 mT and arc current of 200 A, the values of the azimuthal component of current density in the arc column are approximately the same as the values of the longitudinal component of current density in the arc column. 14 Ref., 6 Fig. [ABSTRACT FROM AUTHOR]

It is difficult to join dissimilar material which has different thermal and mechanical properties using conventional arc welding, which is prone to the formation of intermetallic compounds (IMCs). In the present work pure copper (Cu) and aluminium (Al) alloy (Al-6061) is lap joined by conventional TIG Welding. At optimal operating condition, a successful weld is achieved as observed from mechanical testing. The metallurgical properties of joints are investigated by Back Scattered Electron (BSE) image, spot Energy Dispersive X-ray Spectroscopy (EDS) and line EDS. IMCs layers formed for joints varied from 9 μm to 80 μm thickness obtained at different welding parameters. Two different layers of IMCs are formed at the interface and the failure occurred near the copper side of the joint. The mechanical property is investigated by tensile shear test, and the average maximum load-carrying capacity found 1876 N, which is comparable to other non-conventional welding processes. [ABSTRACT FROM AUTHOR]