Shielding Gas Research Articles

Optimal Tungsten Inert Gas Welding Parameters of Dissimilar Aluminum Alloys Al 7075 and Al 6061 Using Ultrasonic Vibration and Nanocomposite Filler (Al 5356/ZrB2) to Alleviate Hot Cracking Phenomenon

Abstract In this study, the welding of dissimilar aluminum alloys, Al 7075 and Al 6061, was investigated using Al 5356 filler rods reinforced with ZrB2 particles. The welding process was conducted using tungsten inert gas (TIG) welding, with and without ultrasonic vibration, to enhance weld quality and reduce hot cracking. Optimization of process parameters for dissimilar TIG welding was performed through Response Surface Methodology (RSM), which generated a design matrix to analyze the influence of process parameters on response variables. Numerical and graphical optimization was applied to minimize hot cracking sensitivity and maximize microhardness. The RSM-based models suggested an optimal welding current of 93 A, the use of Al 5356/ZrB2 nanocomposite filler, and the application of ultrasonic vibrations. Experimental validation of the identified solution demonstrated improvements in weld quality, including increased yield strength and ductility. The combination of nano-reinforced fillers and ultrasonic vibrations was found to enhance weldability and mitigate hot cracking in dissimilar aluminum joints. The mechanism of hot cracking reduction involved grain refinement, degassing, and homogenization due to ultrasonic vibrations, as well as the modification of weld pool chemistry and control of dilution by the nanocomposite filler, which collectively minimized solidification shrinkage and stress. Under these optimized conditions, no hot cracking was observed experimentally.

Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue.This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Variation of Surface Tension of Liquid Metal with Fluorides in Tungsten Inert Gas Welding

Real-time measuring and obtaining surface tension of liquid metal during the arc welding process is critical for studying the behavior of the weld pool, such as Marangoni flow and flow velocity. The dynamic variation of surface tension of weld pool during tungsten inert gas welding process with and without fluoride flux was measured by weld pool oscillation sensing system, and the effect of fluoride flux on surface tension and pool behavior was analyzed. The results show that the surface tension gradient of liquid metal can convert from a negative to a positive value in a critical arc time. The flow velocity of liquid metal and critical arc time significantly increased and decreased, respectively, with fluoride flux. The variation of surface tension, flow velocity, and critical arc time with fluoride flux was induced by arc temperature increasing.

Enhancement of Additive Manufacturing Processes for Thin-Walled Part Production Using Gas Metal Arc Welding (GMAW) with Wavelet Transform

Additive manufacturing encompasses technologies that produce three-dimensional computer-aided design (CAD) models through a layer-by-layer production process. Compared to traditional manufacturing methods, additive manufacturing technologies offer significant advantages in producing intricate components with minimal energy consumption, reduced raw material waste, and shortened production timelines. AM methods based on shielded gas welding have recently piqued the interest of researchers due to their high efficiency and cost-effectiveness in manufacturing critical components. However, one of the most formidable challenges in additive manufacturing methods based on shielded gas welding lies in the irregularity of weld bead height at different points, compromising the precision of components produced using these techniques. In this current research, we aimed to achieve uniform weld heights along the welding path by considering the most influential parameters on weld bead geometry and conducting experimental tests. Input parameters of the process, including nozzle angle, welding speed, wire speed, and voltage, were considered. Simultaneously, image processing and wavelet transform were employed to assess the uniformity of weld bead height. These parameters were applied to produce intricate parts after identifying optimal parameters that yielded the smoothest weld lines. According to the results, the appropriate bead for manufacturing the part was extracted. The results show that the smoothest bead line is achieved in 27 V as the highest level of voltage, at a 90° nozzle position and the maximum wire feed rate. Parts manufactured using this method across different layers exhibited no distortions, and the repeatability of production substantiated the high reliability of this approach for component manufacturing.

Influence of Silicon Carbide Incorporation on Thermal and Ablation Properties of Carbon Fabric-Phenolic Resin Composites

To shield re-entry spacecraft from the extreme heat experienced during hypersonic flight through a planet's or the earth's atmosphere, thermal protection systems (TPS) were developed. This work involved the fabrication of composites using a polyacrylonitrile (PAN) based carbon fabric (Cf)-phenolic resin matrix (PR) modified with different weight percentages (wt.%) of silicon carbide (SiC), namely 0 wt.% (Cf/PR), 1wt.%, 3wt.%, and 5wt.%. The composites were prepared using the hydraulic hot press method. The manufactured composites were analyzed for their thermal conductivity and resistance to ablation using an oxyacetylene torch test. Furthermore, the ablated composites underwent X-ray diffraction (XRD), revealing a SiO2 compound layer on the ablated composite surface. The experimental results demonstrated that the Cf/PR composites modified with 3wt.% of SiC exhibited superior characteristics. The composites consist of 3wt.% Cf/PR-SiC exhibited a thermal conductivity value of 0.57 W/m K. Additionally, these composites showed a noticeable decrease in the mass ablation rate (MAR) at 0.0052 mm/sec and linear ablation rates (LAR) at 0.025061 gm/sec. This study proposed an effective way to improve the thermal and ablation characteristics of TPS materials.

Thermal stability and anti-ablation performance of plasma spray coated-YSZ on Al2TiO5 modified novel ablative carbon-phenolic composites

Abstract Despite ongoing challenges, ablative thermal protection systems are among the most promising methods for safeguarding spacecraft during re-entry thermal protection systems (TPS). A novel aluminium titanate (Al2TiO5/AT) and a highly efficient thermal barrier of coating (TB/TBCs) made from yttria-stabilized zirconia (YSZ), powder, but deposited using the plasma spray technique on polyacrylonitrile (PAN)-based carbon fiber fabric(C)-reinforced with resorcinol phenol formaldehyde resin (RF) composites (C-RF)) would be a potential candidate for TPS applications. This study investigates the composites with varying wt.% of AT that were developed, namely 0 wt.% (YSZ-C-RF), 1 wt.%, 3 wt.%, and 5 wt.% (YSZ-AT-C-RF) by utilizing a hot press moulding machine. Thermal stability and ablation performance of unmodified C-RF with modified YSZ-C-RF and YSZ-AT-C-RF composites are examined through thermogravimetric analysis (TGA) and oxyacetylene torch test/OAT (4.0 MW/m2 for 60 sec). Also, the phase composition and microstructure of the ablated surface are determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The TBC of YSZ has an obvious influence on the residual weight ratios at high temperatures in C-RF and also plays a positive role in increasing thermal stability under nitrogen atmosphere for enhancing ablation resistance concerning YSZ-C-RF. The mass and linear ablation rates (MAR and LAR) of the composites after modifying the surface by YSZ-coated particles are reduced by 82.98% and 15.65%, respectively. Similarly, the introduction of AT particles and TBC of YSZ results in evidence of improving the thermal stability and the ablation resistance in varying wt.% of YSZ-AT-C-RF composites. The primary optimum AT weight loading for enhancing ablation resistance in YSZ-C-RF composites is 1wt.%. The modification of 1wt.% AT particles and YSZ-Coated particles reduce MAR and LAR by 54.79% and 61.94%, respectively. This work offers a meaningful method to remarkably enhance the ablation performance of the modified C-RF and YSZ-AT-C-RF composites.

Effect of water quenching into strength, hardness and microstructure of the welded AA 6061 plates

Purpose The purpose of this study is to find the effect of heat treatment on the mechanical proeprties of aluminum. Aluminum exhibits a good response to heat treatment, especially quenching, according to the mechanical property improvement. The presence and orientation of secondary phases (Al-Fe-Mn-Si) are greatly affected by the quenching process. Design/methodology/approach The present work deals with the effect of water quenching on the mechanical properties of welded AA 6061 plates which were joined by using metal inert gas (MIG) welding, tungsten inert gas welding and friction stir welding (FSW). Three tests like tensile, bending and hardness were considered. The microstructural variation was analyzed by optical microscopy and elemental mapping through field emission scanning electron microscope. Findings A significant enhancement in the tensile strength and hardness was achieved on postquenched specimens. This improvement in mechanical properties is caused by the distribution of fine alloying elements throughout the metal solution rather than precipitation at the grain boundaries. In comparison to the “untreated specimens,” an improvement of 76.7%, 25.32% and 56.81% in the tensile strength of quenched TIGW, MIGW and FSW specimens, respectively, was observed. Originality/value The quenching process has increased the strength of the MIG welded joint over the base metal. The MIG welded joint has a larger flexural modulus than the other two welded plates, according to the results of the bending test. Furthermore, a uniform distribution of hardness was observed in postquenched welded specimens. It was found that welded zone was harder than heat-affected zone. Out of all the specimens, the base metal zone has the lowest hardness.

ИССЛЕДОВАНИЕ ВОЗНИКНОВЕНИЯ ПОЖАРА ОТ ВОСПЛАМЕНЕНИЯ И ВЗРЫВА ПАРОВОЗДУШНОЙ СМЕСИ ПРИ ПРОВЕДЕНИИ ГАЗОСВАРОЧНЫХ РАБОТ

Using the example of a real fire that occurred as a result of violations of fire safety requirements during gas welding operations, it is demonstrated how the combined use of instrumental and computational methods makes it possible to determine the cause of the fire. The nature of combustible substances has been determined by fluorescence spectroscopy, gas-liquid chromatography and infrared spectroscopy. Using mathematical calculations, the amount of combustible substances necessary for the formation of an explosive mixture was determined. It is demonstrated how a combination of physical-chemical research methods and computational methods, allows for the determining the causal relationship between gas welding operations and the aforementioned explosion.

Effects of Oxide Powders as Activating Flux on AMIG 304L Welds

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a filler metal. Five oxides (SiO2, TiO2, Fe2O3, Mn2O3, and Cr2O3) have been investigated without edge preparation. The welded joints were evaluated for weld morphology, microstructure, mechanical properties, and corrosion, and the findings were compared. The depth of the AMIG weld was determined to be greater than that of the MIG weld. The microstructure is composed of austenitic and retained delta ferrite with 3.3% for MIG and up to 8% for AMIG weld carried out with Cr2O3 oxide flux, the tensile strength is up to 604 MPa when using Cr2O3 oxide against MIG weld (532 MPa), and the resistance to sudden load in AMIG welds (189 J/cm2) is higher than that of MIG weld (149 J/cm2). The corrosion resistance of the weld made with Fe2O3 oxide flux is greater than that of the other AMIG and MIG welds, as well as the parent metal. The AMIG welding technique variant enhances productivity and decreases the cost and energy consumption of the welding material compared to the traditional MIG process. This allows for joining the same thickness without affecting mechanical properties and corrosion resistance, meeting the industry’s requirements.

Microstructural and Mechanical Characterization of the Laser Beam Welded SAF 2507 Super-Duplex Stainless Steel

The influence of laser beam welding parameters (power, welding rate, focusing, head oscillation, shielding gas) on the microstructure, mechanical properties and corrosion resistance of the super-duplex stainless steel SAF 2507 was studied in this paper. The presented results clearly report the effects of welding parameter changes on the character of the steel’s microstructure. The presence of secondary phase M2N in weld metals has an important influence on their mechanical properties. Optimal mechanical properties, an acceptable ferrite/austenite ratio, and the minimum content of M2N nitride required in the weld metal were acquired in the case the following application: 1100 W power, welding speed of 10 mm/s, focusing of 4 mm, and pure nitrogen shielding gas (20 L/min).

Influence of the Pulse Mode of Manual Metal Arc Welding on Weldment Distortions.

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder.

Analyzing the Influence of Titanium Content in 5087 Aluminum Filler Wires on Metal Inert Gas Welding Joints of AA5083 Alloy

As the demand for lightweight structures in the transportation industry continues to rise, AA5083 aluminum alloy has become increasingly prominent due to its superior corrosion resistance and weldability. To facilitate the production of high-quality, intricate AA5083 components, 5087 aluminum filler wire is commonly utilized in metal inert gas (MIG) welding processes for industrial applications. The optimization of filler wire composition is critical to enhancing the mechanical properties of AA5083 MIG-welded joints. This study investigates the effects of modifying 5087 aluminum filler wires with different titanium (Ti) contents on the microstructure and weldability of AA5083 alloy plates using MIG welding. The influence of Ti contents was systematically analyzed through comprehensive characterization techniques. The findings reveal that the constitutional supercooling induced by the Ti element and the formation of Al3Ti facilitate the heterogeneous nucleation of α(Al), thereby promoting grain refinement. When the Ti content of 5087 filler wire is 0.1 wt.%, the grain size of the weld center was 78.48 μm. This microstructural enhancement results in the improved ductility of the AA5083 MIG-welded joints, with a maximum elongation of 16.64% achieved at 0.1 wt.% Ti addition. The hardness of the joints was the lowest in the weld center zone. This study provides critical insights into the role of Ti content in MIG welding and contributes to the advancement of high-performance filler wire formulations.

Improvement of the Microstructure and Mechanical Properties of Welded Joint of Wire Arc Additive Manufacturing-AZ31B Magnesium Alloy by Using AC/DC Mixed Current Waveform in Tungsten Inert Gas Welding

Improvement of the Microstructure and Mechanical Properties of Welded Joint of Wire Arc Additive Manufacturing-AZ31B Magnesium Alloy by Using AC/DC Mixed Current Waveform in Tungsten Inert Gas Welding

Texture and surface morphology influence of A106 carbon steel pipe on mechanical properties and corrosion resistance after welding process

The surface morphology influenced the corrosion resistance, which depended on the welding process and its parameters. In this study, we investigated the relevance of the welding process that produces excellent mechanical properties and corrosion resistance, which gives the best working performance for carbon steel pipes that transfer refined oil products in an Iraq oil refinery. AISI 1020-A106 carbon steel pipes are welded using shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW). Electrochemical corrosion tests were performed in 3.5% NaCl and immersion tests in heavy Naphtha at 50, 75, and 100 °C. The results show that retained austenite, ferrite, pearlite, and martensite phases are produced after the SMAW process. In contrast, ferrite, pearlite, and a small amount of martensite are produced after GTAW. The ultimate tensile strength of the SMAW samples was higher than those of the GTAW samples, but the GTAW samples had higher fracture elongation, and all samples had no cracks in the welding area during the bending test. The electrochemical and immersion corrosion rates of the samples welded with SMAW are higher than those welded with GTAW. The corrosion rate increases when the naphtha temperature increases and has a higher and unacceptable value at 100 °C.

Effect of welding gas mixtures on weld material and bead geometry

Abstract Shielding gas is an essential parameter in welding processes, serves to shield the molten material from the atmosphere and external contaminations while providing a stable electric-arc pathway during the process, thus influencing the quality of the weld bead and several other aspects of the process. Therefore, any welding-based process, such as wire-arc additive manufacturing, could benefit from shielding gas mixture optimisation to selectively improve the processing and possibly the final mechanical properties of the welded material. In this study welding of EN AW 5183 aluminium (single weld bead and wire-arc additive manufacturing build-up) was conducted using several gas mixtures and their influence on final geometry defects, and microstructure measured. The gas mixtures used were a combination of varying amounts of carbon dioxide, nitrogen, and oxygen. These were added to commercially available argon gas. It was observed that: CO2 additions led to an unfavourable bonding defect and increased mean grain size; nitrogen additions caused a decrease in mean grain size, decreased pore count while maintaining a similar pore volume fraction to the reference argon mixture samples; oxygen additions showed slight reduction of mean grain size, decreased pore count and decreased pore volume fraction. These results further showcase that varying shielding gas mixtures influence the final material properties and should be considered as an additional improvement route for conventional welding and additive manufacturing.

Improved semantic segmentation method for weld penetration prediction of TIG welding with dual ellipsoid heat source

TIG welding is a manufacturing process that uses argon as a shielding gas and tungsten as an electrode to join metals at high temperatures. The weld penetration is the key to determining the quality of the weld. However, the lack of sensing technology makes weld penetration difficult to predict, which imposes a major challenge to process stability and weld quality. To address this challenge, a semantic segmentation-based approach for calibrating the weld penetration prediction model under dual ellipsoidal heat source is proposed to improve the prediction accuracy. To realize this, a semantic segmentation model Self-Attention-Structural-Reparameterization-BiSeNet (SASR-BiSeNet) is built for molten pool parameter extraction. The model introduces a self-attention mechanism as an enhancement to the convolution module. Meanwhile, the RepVGG-style structural reparameterization design decouples the training-time and inference-time architectures. Further, a mask feature extraction method is designed to obtain the calibration parameters of the molten pool and to correct the prediction model. The accuracy of the calibrated prediction model is verified by welding experiments using 304L steel materials on a robotic welding system. The results show that the maximum Mean Intersection over Union (mIoU) of the SASR-BiSeNet is 92.51 %, which is a 13.87 % improvement compared to the BiSeNet, and the maximum depth of molten pool error decreasing from 16.59 % to 9.84 %. This method can improve the precision of welding penetration control and plays an important role in promoting welding intelligence.

Optimization of Joining Parameters in Pulsed Tungsten Inert Gas Weld Brazing of Aluminum and Stainless Steel Based on Response Surface Methodology

Combining aluminum and steel offers a promising solution for reducing structural weight and fuel consumption across various industries. Pulse in tungsten inert gas (TIG) weld brazing effectively suppresses interfacial brittle intermetallics and enhances joint strength by influencing pool stirring and heat input during aluminum-to-steel joining. However, optimizing the pulsed TIG weld brazing process is challenging due to its numerous welding parameters. This study established statistical models for Al/steel joint strength without reinforcement using response surface methodology (RSM) based on central composite design (CCD). The models’ adequacy and significance were verified through analysis of variance (ANOVA). The four welding parameters influence weld strength in the following descending order: pulse on time > base current > pulse current > pulse frequency. Additionally, interactions between pulse current and pulse frequency, and between pulse on time and base current, were observed. Numerical optimization using RSM determined the optimal pulsed GTA weld brazing parameters for aluminum and stainless steel. With these optimized parameters, the joint strength reached 155.73 MPa, and the intermetallic compound (IMC) thickness was reduced to 3.4 μm.

Dissimilar MIG Welding Optimization of C20 and SUS201 by Taguchi Method

This study looks at how welding intensity, speed, voltage, and stick-out affect the structural and mechanical characteristics of metal inert gas (MIG) welding on SUS 201 stainless steel and C20 steel. The Taguchi method is used to optimize the study’s experiment findings. The results show that the welding current has a more significant effect on the tensile test than the welding voltage, stick-out, and welding speed. Welding voltage has the lowest influence. In addition to the base metals’ ferrite, pearlite, and austenite phases, the weld bead area contains martensite and bainite microstructures. The optimal parameters for the ultimate tensile strength (UTS), yield strength, and elongation values are a 110 amp welding current, 15 V of voltage, a 500 mm.min−1 welding speed, and a 10 mm stick-out. The confirmed UTS, yield strength, and elongation values are 452.78 MPa, 374.65 MPa, and 38.55%, respectively, comparable with the expected value derived using the Taguchi method. In the flexural test, the welding current is the most critical element affecting flexural strength. A welding current of 110 amp, an arc voltage of 15 V, a welding speed of 500 mm.min−1, and a stick-out of 12 mm are the ideal values for flexural strength. The flexural strength, confirmed at 1756.78 MPa, is more than that of the other samples. The study’s conclusions can offer more details regarding the dissimilar welding industry.

The Dynamics Stability Judging Method for a Gantry-type Welding Robot

In order to improve the dynamic performance of gantry-type welding robot, this paper introduces the structural dynamics model and Lyapunov stability criterion of the gantry-type welding robot frame with nine degrees of freedom. The dynamic equations of the welding robot satisfy the Euler–Lagrange form, and the calculation index of welding robot Lyapunov stability is judged by matrix eigenvalues. Combining with the specific design parameters of an industrial welding robot, the motion stability of the gantry-type welding robot frame and the displacement response of the welding torch are analyzed. The influence of the change of the frame design structure on the stability of the welding torch for end effector of welding robot is discussed, furthermore, the improvement direction of vibration damping and anti-interference of welding robot system is pointed out. Finally, the dynamics simulation of the optimized gantry-type welding robot end effector is carried out by using ADAMS software, and the torque variation curve of the end effector is obtained, which provides a strong basis for the selection of motor models and the design of control system.

Microstructural characteristics and mechanical properties of dissimilar AA5052-H32 and AA5083-H111 alloy joints made using tungsten inert gas welding and ER5356/scandium composite cast filler rod

In this research, casted filler rod with combination of ER5356 and scandium (Sc) composites are subjected to conduct the Tungsten Inert Gas (TIG) welding on AA5052-H32 and AA5083-H111 was investigated. The mechanical properties and microstructure of the TIG welded dissimilar joints were analysed. The responses like tensile and microhardness were improved on TIG welded joints with appropriated process parameters and fusion zone enhanced with defect free joints through the microstructure.The composed filler rod is newer technique to achieve the good quality welding which was more dependable and very flexible in different sectors of engineering applications. The following parameters like ER5356, ER5356 with 0.25% and 0.50% scandium filler rods are used to conduct the TIG welding with specified parameters of current at 150 A and gas flow rate at 12 L/min. The tensile strength of dissimilar TIG welded joints were increased 60.6%–86.7% of the Al–Mg alloy base metal. The enhanced mechanical strength was attained to the creation of scandium made ER 5356 filler rods dispersed that successfully restrict the grain growth in boundary regions and recrystallization of the fusion zone. The microhardness of the Tig welded joint made with ER 5356 with 0.255 and 0.50% improves the hardness (88 and 110 Hv) than the no scandium added TIG welded joint hardness (68 Hv). This enhancement in mechanical properties is associated with modifications in microstructure and the progression of strengthening phases precipitation.