Search Results (230)

Nickel is used in aerospace, military, energy, and chemical sectors. Commercially pure (CP) Ni, and its alloys, including solid-solution strengthened (SSS), precipitation strengthened (PS), and specialty alloys (SA), are widely utilized, typically at elevated temperatures, in corrosive settings and in cryogenic milieu. Ni or Ni-based alloys frequently require welding realized, inter alia, via methods using electric arc and beam power. Tungsten inert gas (TIG) and Electron-beam welding (EBW) have been utilized most often. Friction stir welding (FSW) is the most promising solid-state welding technique for connecting Ni and its alloys. The primary weldability issues related to Ni and its alloys are porosity, as well as hot and warm cracking. CP Ni exhibits superior weldability. It is vulnerable to porosity and cracking during the solidification of the weld metal. Typically, SSS alloys demonstrate superior weldability when compared to PS Ni alloys; however, both types may experience weld metal solidification cracking, liquation cracking in the partially melted and heat-affected zones, as well as ductility-dip cracking (DDC). Furthermore, PS alloys are prone to strain-age cracking (SAC). The weldability of specialty Ni alloys is limited, and brazing might provide a solution. Employing appropriate filler metal, welding settings, and minimal restraint can reduce or avert cracking. Full article

Stainless steel, due to its exceptional comprehensive properties, has been widely adopted as the primary material for liquid cargo tank containment systems and pipelines in liquefied natural gas (LNG) carriers. However, challenges such as hot cracking, excessive deformation, and the deterioration of welded joint performance during stainless steel welding significantly constrain the construction quality and safety of LNG carriers. While conventional tungsten inert gas (TIG) welding can produce high-integrity welds, it is inherently limited by shallow penetration depth and low efficiency. Magnetic field-assisted TIG welding technology addresses these limitations by introducing an external magnetic field, which effectively modifies arc morphology, refines grain structure, enhances penetration depth, and improves corrosion resistance. In this study, TIG bead-on-plate welding was performed on 304 stainless steel plates, with a systematic investigation into the dynamic arc behavior during welding, as well as the microstructure and anti-corrosion properties of the deposited metal. The experimental results demonstrate that, in the absence of a magnetic field, the welding arc remains stable without deflection. As the intensity of the alternating magnetic field intensity increases, the arc exhibits pronounced periodic oscillations. At an applied magnetic field intensity of 30 mT, the maximum arc deflection angle reaches 76°. With increasing alternating magnetic field intensity, the weld penetration depth gradually decreases, while the weld width progressively expands. Specifically, at 30 mT, the penetration depth reaches a minimum value of 1.8 mm, representing a 44% reduction compared to the non-magnetic condition, whereas the weld width peaks at 9.3 mm, corresponding to a 9.4% increase. Furthermore, the ferrite grains in the weld metal are significantly refined at higher alternating magnetic field intensities. The weld metal subjected to a 30 mT alternating magnetic field exhibits the highest breakdown potential, the lowest corrosion rate, and the most protective passive film, indicating superior corrosion resistance compared to other tested conditions. Full article

This paper delves incto the tungsten inert gas (TIG) welding process, renowned for its efficacy in creating robust metal joints and widely employed in diverse industries for fusing similar or dissimilar materials. The focus of this study is the welding of mild steel with stainless steel, showcasing the method’s ability to amalgamate exceptionally sturdy metals and alloys. The resultant welded joints exhibit a meticulously refined microstructure and an impressive strength-to-weight ratio. The primary aim is to scrutinize TIG-welded joints, specifically those connecting mild steel with stainless steel, to elucidate their metallurgical and mechanical attributes. Notably, joints formed between distinct materials, such as mild steel and stainless steel, manifest commendable mechanical and metallurgical properties. This paper extensively investigates the metallurgical microstructures and tensile characteristics of both comparable and dissimilar metal junctions, contributing valuable insights to the field. Full article

This study presents numerical analyses of the thermal, metallurgical, and mechanical processes involved in welding. The temperature fields were computed by solving the transient heat transfer equation using the ABAQUS/Standard 2024 finite element solver. Two types of moving heat sources were applied: a surface Gaussian distribution and a volumetric model, both implemented via DFLUX subroutines to simulate welding on butt-jointed plates. The simulation accounted for key welding parameters, including current, voltage, welding speed, and plate dimensions. The thermophysical properties of the INC 738 LC nickel superalloy were used in the model. Solidification characteristics, such as dendritic arm spacing, were estimated based on cooling rates around the weld pool. The model also calculated transverse residual stresses and applied a hot cracking criterion to identify regions vulnerable to cracking. The peak transverse stress, recorded in the heat-affected zone (HAZ), reached 1.1 GPa under Goldak’s heat input model. Additionally, distortions in the welded plates were evaluated for both heat source configurations. Full article

This investigation explores the application of supervised machine learning regression approaches to predict various responses, including penetration, bead width, bead height, hardness, ultimate tensile strength, and percentage elongation in autogenous TIG-, A-TIG-, and TIG-welded joints of SS304H, which is considered as an advanced high-temperature resistant material. The machine learning (ML) models were constructed based on the data gathered from 50 experimental runs, considering eight key input variables: gas flow rate, torch angle, filler material, welding pass, flux application, root gap, arc gap, and heat input. A total of 80% of the collected dataset was used for training the models, while the remaining 20% was reserved for testing their performance. Six ML algorithms—Artificial Neural Network (ANN), K-Nearest Neighbors (KNN), Support Vector Regression (SVR), Random Forest (RF), Gradient Boosting Regression (GBR), and Extreme Gradient Boosting (XGBoost)—were implemented to assess their predictive accuracy. Among these, the XGBoost model has demonstrated the highest predictive capability, achieving R² scores of 0.886 for penetration, 0.926 for width, 0.915 for weld bead height, 0.868 for hardness, 0.906 for ultimate tensile strength, and 0.926 for percentage elongation, along with the lowest values of RMSE, MAE, and MSE across all responses. The outcomes establish that machine learning models, particularly XGBoost, can accurately predict welding characteristics, marking a significant advancement in the optimization of TIG welding parameters. Consequently, integrating such predictive models can substantially enhance the precision, reliability, and overall efficiency of welding processes. Full article

Automated and robotic welding have become standard practices in manufacturing, requiring precise control to maintain weld quality without relying on skilled welders. In Tungsten Inert Gas (TIG) welding, monitoring the weld pool is crucial for ensuring the necessary weld penetration, which is vital for maintaining weld integrity. Real-time observation is essential to prevent defects and improve weld quality. Various sensing technologies have been developed to address this need, with vision-based systems showing particular effectiveness in enhancing welding quality and productivity within the framework of Industry 4.0. This review looks at the latest technologies for monitoring weld pools and bead shapes. It covers methods like using Complementary Metal-Oxide Semiconductors (CMOS) to take clear images of the melt pool for better process identification, Active Appearance Model (AAM) to capture 3D images of the weld pool for accurate penetration measurement, and Charge-Coupled Devices (CCD) and Laser-Induced Breakdown Spectroscopy (LIBS) to analyze plasma spectra and create material composition graphs. Full article

Tungsten Inert Gas (TIG) welding is a widespread welding process used in the industry for high-quality joints. However, this welding process suffers from lower productivity. Activated Tungsten Inert Gas (ATIG) is a variant of the TIG that aims to increase the depth penetration capability of conventional TIG welding. This is achieved by applying a thin coating of activating flux material onto the workpiece surface before welding. This work investigates the effect of the thermophysical properties of individual metallic oxide fluxes on 316L stainless steel weld morphology. Four levels of current intensity (120, 150, 180, 200 A) are considered. The weld speed up to 15 cm/min and arc length of 2 mm are maintained constant. Thirteen oxides were tested under various levels of current intensity in addition to multiple thermophysical properties combinations, and the depth penetration (D) and the aspect ratio (R) were recorded. This process has provided 52 combinations (13 oxides * 4 currents). Based on the numerical observations, linear and nonlinear models for describing the effect of the thermophysical parameters on the weld characteristics were tuned using a particle swarm optimization algorithm. While the linear model provided good prediction accuracy, the nonlinear exponential model outperformed the linear one for the depth yielding a mean absolute percentage error of 17%, a coefficient of determination of 0.8266, and a root mean square error of 0.9665 mm. The inverse optimization process, where the depth penetration ranged from 1.5 mm to 12 mm, thus covering a large spectrum of industries, the automotive, power plants, and construction industries, was solved to determine the envelopes’ lower and upper limits of optimal oxide thermophysical properties. The results that allowed the design of the fluxes to be used in advance were promising since they provided the oxide designer with the numerical ranges of the oxide components to achieve the targeted depths. Future directions of this work can be built around investigating additional nonlinear models, including saturation and dead-zone, to efficiently estimate the effect of the thermophysical properties on the welding process of other materials. Full article

Inconel 600 alloy has gained consideration as a favourable material for heat and power applications, particularly in turbine blades, due to its superior mechanical behaviour encompassing strength, toughness, oxidation resistance, and ductility. Tungsten Inert Gas (TIG) welding is one of the preferred techniques for joining these alloys. Therefore, the investigation of the mechanical behaviour after the welding process is crucial for selecting the appropriate technique for joining Inconel 600 sheets. This research focuses on investigating the microstructure and mechanical behaviour of TIG-welded Inconel 600 through a series of tests, such as tensile, fatigue, creep, and hardness evaluations. In addition, microstructural analysis is combined with these mechanical evaluations to simulate the operating conditions experienced by turbine blades. Key parameters such as yield strength, tensile strength, and elongation have been evaluated through these analyses. The Ramberg–Osgood relationship has been investigated using the engineering and true stress–strain curves obtained from the welded specimens. The results of the fatigue test illustrate the relationship between strain amplitude and the number of cycles to failure for single and double-edge notched specimens. The test was performed at two different loads including 400 MPa and 250 MPa at a constant temperature of 650 °C, and the corresponding strain-time curves were recorded. The results showed rapid creep failure at 650 °C, suggesting that TIG welding may need to be optimized for high temperature applications. Full article

A power factor correction circuit for a single-phase arc welding power source using digital soft switching technology is proposed. The overall hardware structure of the system, the topology principle of the selected soft switch boost circuit, and the software design approach are discussed. The power factor correction results of the soft switch are verified under two conditions: electronic load and TIG arc welding. By using the electrical signals of the resonating capacitor and switching tube, it is confirmed that the circuit successfully achieved zero current conduction and zero voltage turn off. Through testing the power factor and efficiency of electronic loads at different powers, it was confirmed that the power factor can reach 0.985 or above, and the overall efficiency has been improved. Through TIG arc welding experiments under different welding currents, the corrected electrical signals are analyzed to verify the effectiveness of power factor correction for single-phase arc welding power. Full article

Adding hydrogen (H₂) to shielding gas in Tungsten Inert Gas (TIG) welding has garnered attention for its potential to enhance weld quality. This study explores the effects of H₂ and helium (He) content on AISI 316L stainless steel welding, focusing on their influence on weld bead geometry, microstructural properties, and mechanical properties. The H₂ (1.5%, 3%, 4.5%) and He (10%, 20%, 30%) concentrations were evaluated in a shielding gas primarily composed of argon (Ar). The study underscores the need for precise gas blend control to balance enhanced performance with material safety. These findings offer insights into optimizing welding parameters for AISI 316L, with implications for broader applications in industries demanding high quality. The result shows that H₂ (1.5–3.0%) improves penetration, geometry, and surface finish, while He (10–20%) enhances arc stability and smoothness; however, excessive levels of H₂ (>4.5%) cause defects. Optimal mechanical properties (UTS: 714.54 MPa, YS: 449.03 MPa, hardness: 93.34 HRB, impact toughness: 34.45 J) are achieved with 3% H₂, 30% He, and 150 A arc current. Full article

The paper presents the results of oxidation tests on the alloy based on the intermetallic phase, Fe40Al5Cr0.2TiB, in the air at 700–1000 °C temperature. The kinetics of corrosion processes were determined, the surface condition after oxidation was assessed, and the type and morphology of the oxides formed were determined. In addition, the paper presents the possibility of applying the technology of surfacing Fe40Al5Cr0.2TiB alloy on the surface of steel grade S235JR as a protective coating that is resistant to high temperatures. The process was carried out using the TIG method by direct current (DC). After the surfacing, the structure of the surfacing weld made of the tested material on the base of structural steel grade S235JR was determined. It was found that a protective Al₂O₃ oxide layer is formed on the surface of the oxidized alloy based on the intermetallic phase from the FeAl system, and the oxidation kinetics have a parabolic course. Moreover, it was found that the morphology of the oxides formed on the surface varies depending on the oxidation temperature, which clearly indicates a different mechanism of oxide layer formation. The formation of a stable α-Al₂O₃ oxide variety on the surface of the Fe40Al5Cr0.2TiB alloy protects the material from further corrosion, which favors the application of this alloy on structures and fittings operating at elevated temperatures. The aim of the research was to use the Fe40Al5Cr0.2TiB alloy with very good oxidation resistance as a layer overlay on ordinary quality S235JR steel. In this way, conditions were created that fundamentally changed the surface condition (structure and physicochemical properties) of the system: steel as a substrate—intermetallic phase Fe40Al5Cr0.2TiB as a surfacing layer, in order to increase resistance to high-temperature corrosion and erosion (in the environment of gases and solid impurities in gases) often occurring in corrosive environments, especially in the power industry (boilers, pipes, installation elbows) and the chemical industry (fittings). At the same time, the surfacing method used is one of the cheapest methods of changing the surface properties of the material and regenerating or repairing the native material with a material with better properties, especially for applications in high-temperature corrosion conditions. Full article

The Invar steel molten pool is characterized by low fluidity of the molten pool due to high tension, which hinders the escape of gases and exacerbates the formation of porosity defects. In this study, the influences of different welding process parameters, material properties, and U-groove on the flow behavior of the molten pool of laser–tungsten inert gas (TIG) hybrid welding of Invar steel are investigated by numerical simulation and high-speed photography. This research proposes effective measures to suppress porosity defects, such as optimizing process parameters and extending the existence time of the molten pool. In conclusion, this study systematically investigates the dynamic mechanism of the formation of welding defects in 4J36 Invar steel and provides important theoretical support for the optimization of the welding process of 4J36 Invar steel. The results indicate that controlling the laser power at 4–6 kW, welding speed at 0.5–1.0 m/min, and welding current at 150–170 A can stabilize the molten pool flow and keyhole and promote the molten pool flow and gas escape. Full article

This research investigates the application of activated tungsten inert gas (A-TIG) welding on boiler grade SA516 Grade 70 carbon steel using nano titanium dioxide (TiO₂) nano flux to enhance weld penetration depth, microstructure, and mechanical properties. A unique flux application technique was devised and experiments were carried out. Response Surface Methodology (RSM) was utilized to optimize weld parameters, namely arc length, welding current, and travel speed.The selection between A-TIG and TIG welding significantly influences penetration depth, as A-TIG benefits from arc constriction and elevated current density. The welding speed is crucial for controlling heat input, whereas current and arc length enhance penetration by influencing arc force and energy distribution. Optimizing all three parameters guarantees optimal penetration and weld quality. Microstructural research revealed enhanced mechanical properties in A-TIG weldments, distinguished by acicular ferrite in the fusion zone, which augmented toughness and tensile strength (520 MPa) compared to TIG weldments (470 MPa) and the base metal (480 MPa). Although A-TIG welds exhibited reduced impact toughness (68 J) relative to the base metal (128 J), A-TIG joints had superior ductility. The findings of this research clearly demonstrate the A-TIG welding process improved the depth of penetration and mechanical strength of the weld joints. Full article

Ti-6Al-4V (Ti64) alloy is widely utilized in the aerospace industry due to its high strength, fatigue resistance, corrosion resistance, and cryogenic properties. However, its high raw material costs and machining difficulties necessitate the development of efficient manufacturing processes. This study evaluates the mechanical reliability and microstructure of Ti64 components fabricated using wire laser additive manufacturing (WLAM) and subsequently joined via tungsten inert gas (TIG) welding. The WLAM process produces refined microstructures with superior mechanical properties by minimizing defects; however, insufficient process optimization may result in a lack of fusion (LOF) and porosity. Microstructural analysis revealed that the WLAM deposits exhibited a fine basket-weave α structure with an average α-lath width of 1.27 ± 0.69 μm, while the TIG-welded region exhibited a coarsened α-lath, reaching 3.02 ± 2.06 μm, which led to a reduction in ductility. Tensile testing demonstrated that the WLAM deposits exhibited superior mechanical properties, with a yield strength of 910 MPa, ultimate tensile strength of 1015 MPa, and elongation of 12.8%, outperforming conventional wrought Ti64 alloys. Conversely, the TIG-welded joints exhibited reduced mechanical properties, with a yield strength of 812 MPa, ultimate tensile strength of 917 MPa, and elongation of 7.5%, primarily attributed to microstructural coarsening in the weld region. The findings of this study confirm that WLAM enhances the mechanical properties of Ti64, whereas TIG welding may introduce structural weaknesses. This research provides insight into the microstructural evolution and mechanical behavior of WLAM-fabricated Ti64 components, with valuable implications for their application in aerospace structures. Full article

Orbital TIG welding is widely applied to weld pipes to pipes in many fields, such as food, chemicals, oil, gas, and transportation. Optimizing welding parameters such as voltage, current, and travel speed is critical to achieve a good-quality weld. This study investigated the impacts of orbital welding parameters and filler wire diameters on the tensile strength of 304 stainless steel pipes. The 304 stainless steel pipe has an outer diameter of 76 mm and a thickness of 2 mm. Filler wire is used with the workpiece, and is available in three diameters of 0.8 mm, 1 mm, and 1.2 mm, wire feed speed from 3.8 mm/s to 5.6 mm/s, current from 90 A to 110 A, and travel speed fixed at 5.5 mm/s. The highest tensile strength of 562 MPa was achieved with heat input of 0.32 kJ/mm and wire feed speed of 3.8 mm/s. In addition, the best parameters via the Taguchi method were found. The parameters’ influence trends on the weld quality were also revealed. Full article