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Real-time quality monitoring through molten pool images is a critical focus in researching high-quality, intelligent automated welding. However, challenges such as the dynamic nature of the molten pool, changes in camera perspective, and variations in pool shape make defect detection using single-frame images difficult. We propose a multi-scale fusion method for defect monitoring based on molten pool videos to address these issues. This method analyzes the temporal changes in light spots on the molten pool surface, transferring features between frames to capture dynamic behavior. Our approach employs multi-scale feature fusion using row and column convolutions along with a gated fusion module to accommodate variations in pool size and position, enabling the detection of light spot changes of different sizes and directions from coarse to fine. Additionally, incorporating mixed attention with row and column features enables the model to capture the characteristics of the molten pool more efficiently. Our method achieves an accuracy of 97.416% on a molten pool video dataset, with a processing time of 16 ms per sample. Experimental results on the UCF101-24 and JHMDB datasets also demonstrate the method's generalization capability. [ABSTRACT FROM AUTHOR]

In the present work, the Q345B low-alloy steel with different contents and ER309L stainless steel were melted together to obtain new alloys. The aim was to design the composition of weld metal (Q345B low-alloy steel as the base material and ER309L welding wire as the filler material) and improve the corrosion resistance of the weld metal. During the welding process, the composition of the weld metal was controlled to match the new alloys by changing the welding heat input. A relationship curve between fusion ration and welding heat input was obtained. The research focused on analyzing the effect of mixed-smelting ratio between Q345B and ER309L and welding heat input on the microscopic structure and corrosion performance of the prepared samples. The results show that the melted alloys containing 20% to 30% Q345B consist of a ferrite (δ) phase and austenite (A) phase, the samples containing 45% to 50% Q345B consist of a martensite (M) phase and austenite (A) phase, and the sample containing 40% Q345B consists of a martensite (M) phase, ferrite (δ) phase, and austenite (A) phase. As the mixed-smelting ratio of Q345B/ER309L increased, the corrosion resistance of samples decreased gradually. For the weld metal, the fusion ration between Q345B base material and ER309L welding wire increases with the welding heat input. When the heat input changed from 0.645 kJ/mm to 2.860 kJ/mm, the composition of the weld metal was consistent with the melted alloys containing 20–45% Q345B. The microstructure and corrosion resistance of the weld metal could be designed by the melting means, which has important guiding significance for engineering applications. [ABSTRACT FROM AUTHOR]

The rapid spread of the use of high-density polyethylene (HDPE) pipes is due to the wide variety of methods for connecting them. This study keeps pace with the developments of butt fusion welding of HDPE pipes by exploring the relationship between the performance of the weld joints by studying ultimate tensile strength and exploring the joint welding profiles by studying the shape of the joint at the outer surface of the pipe (height and width of the joint cap) and the shape of the joint at the internal surface (height and width of the joint root). Welding pressure, heater temperature, stocking time, and cooling time were the parameters for the welding process. Regression was analyzed using ANOVA, and an ANN was used to analyze the experimental results and predict the outputs. Two optimization techniques (pattern search and genetic algorithm) were applied to obtain the ideal operating conditions and compare their performance. The results showed that pattern search and genetic algorithms can determine the optimal output results and corresponding welding parameters. In comparison between the two methods, pattern search has a limited relative advantage. The optimal values for the obtained outputs revolved around a tensile strength of 35 MPa (3.45 and 4.5 mm for the cap and root heights, and 8 and 6.98 mm for the cap and root widths, respectively). When comparing the effects of welding parameters on the results, welding pressure had the best effect on tensile strength, and plate surface temperature had the most significant effect on the welding profile geometries. [ABSTRACT FROM AUTHOR]

In the present study, considering the features and advantages of solid-state welding methods as compared with fusion welding methods such as arc welding, laser welding induction welding, and solid-state welding, they are used to connect CK45 steel to AISIS 304L steel to achieve the desired mechanical and metallurgical properties through experimental and practical tests, by trial and error, suitable parameters of distance, depth, and advance are obtained for welding, and finally a healthy and desirable weld is obtained. The purpose of the present study is to evaluate the weldability of CK45 steel to AISIS 304L steel by friction stir welding method. The distance, advance, and penetration depth parameters were experimentally determined as 950 rpm, 24 mm/min, and 0.35 mm, respectively, to obtain a healthy weld in terms of appearance. Then, through mechanical and metallurgical tests, the effect of the input parameters on the friction stir welding process was determined. The mechanical and metallurgical properties were also evaluated. The results show that the structure of the onion rings in the welding area is caused by the friction stir welding process, which is caused by the massive plastic deformation and the heat generated during the process. The scanning electron microscope image of the welded section of the steel sample shows the formation of a pearlite structure. Considering the severe plastic deformation and dynamic recrystallization in the friction stir welding process, the results obtained from the welding of dissimilar CK5 and AISI304 L show better mechanical properties and acceptable strength. [ABSTRACT FROM AUTHOR]

In this study, 316L austenitic stainless-steel (ASS) plates fabricated using an additive manufacturing (AM) process were joined using tungsten inert gas (TIG) and laser welding techniques. The 316L ASS plates were manufactured using a laser powder bed fusion (LPBF) technique, with building orientations (BOs) of 0° and 90°, designated as BO-0 and BO-90, respectively. The study examined the relationship between indentation resistance and microstructure evolution within the fusion zone (FZ) of the welded joints considering the effects of different BOs. Microstructural analysis of the weldments was conducted using optical and laser confocal scanning microscopes, while hardness measurements were obtained using a micro-indentation hardness (HIT) technique via the Berkovich approach. The welded joints produced with the TIG technique exhibited FZs with a greater width than those created by laser welding. The microstructure of the FZs in TIG-welded joints was characterized by dendritic austenite and 1–4 wt.% δ-ferrite phases, while the corresponding microstructure in laser-welded joints consisted of a single austenite phase with cellular structures. Additionally, the grain size values of FZs produced using the laser welding technique were lower than those produced using the TIG technique. Therefore, TIG-welded joints showcased hardness values lower than those welded by laser welding. Furthermore, welded joints with the BO-90 orientation displayed the greatest cooling rates following welding processing, leading to FZs with hardness values greater than BO-0. For instance, the FZs of TIG-welded joints with BO-0 and BO-90 had HIT values of 1.75 ± 0.22 and 2.1 ± 0.09 GPa, whereas the corresponding FZs produced by laser welding had values of 1.9 ± 0.16 and 2.35 ± 0.11 GPa, respectively. The results have practical implications for the design and production of high-performance welded components, providing insights that can be applied to improve the efficiency and quality of additive manufacturing and welding processes. [ABSTRACT FROM AUTHOR]

Carbon and low-alloy steel plates clad with stainless steel or other metals are a good choice to meet the demand for cost-effective materials to be used in many corrosive environments. Numerous technical solutions are developed for the production of clad steel plates, as well as for their joining by fusion welding. For thick plates, a careful strategy is required in carrying out the multiple passes and in choosing the most suitable filler metals, having to take into account the composition of the base metal and the cladding layer. The specificity of the different processes and materials involved requires an adequate approach in the study of the metallurgical characteristics of clad steel, thus arousing the interest of researchers. Focusing mainly on ferritic steel plates clad with austenitic steel, this article aims to review the scientific literature of recent years which deals with both the production and the fusion welding processes. The metallurgical issues concerning the interfaces and the effects of microstructural characteristics on mechanical behaviour and corrosion resistance will be addressed; in particular, the effects on the fusion and thermally affected zones that form during the fusion welding and weld overlay processes will be analysed and discussed. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue on advanced and unconventional manufacturing processes. It includes research articles on topics such as friction welding, laser direct joining, tool wear, and surface quality evolution. The articles cover a range of processes and techniques aimed at improving the efficiency, sustainability, and quality of manufacturing. The authors come from various research groups around the world, highlighting the global expertise in the field. The special issue provides valuable insights and knowledge for researchers and practitioners in the manufacturing sector. [Extracted from the article]

Welding defects have a significant influence on welding quality and structural strength, and the rapid and accurate detection of welding defects is required. In order to achieve this goal, it is imperative to create corresponding high-quality datasets. However, capturing image information through a single sensor presents certain limitations. In this study, a magneto-optical imaging device and an infrared thermal imaging device were combined to collect images of resistance spot welding samples. The imaging principles of magneto-optical imaging device and the infrared thermal imaging device are discussed, and the possible factors affecting the imaging modes are analyzed. By synthesizing the 3D gray image, the gray histogram, and inherent image features, the imaging rules of magneto-optical image and the infrared image of resistance spot welding samples have been summarized. Under the guidance of these two image types and imaging modes, image enhancement technology has been utilized to optimize the quality of sample images. The Peak Signal to Noise Ratio (PSNR), Structural Similarity Index (SSIM), and Universal Image Quality Index (UIQI) indicators were used to evaluate the optimization quality of the enhanced images. Compared with Histogram Equalization (HE), the Gamma transform, Brightness Preserving Bi-Histogram Equalization (BPBHE), and the Digital Detail Enhancement (DDE) method, the scores of the enhanced infrared images showed improvement across all indicators. The magneto-optical image yielded the best results in the PSNR index, while the other two indices showed only moderate performance. The image dataset, enhanced with appropriate image enhancement techniques, can be utilized for further research into magneto-optical and infrared image information fusion and welding defect identification. [ABSTRACT FROM AUTHOR]

Owing to their unique high-temperature mechanical properties and outstanding high-temperature oxidation resistance, superalloys have become key materials in aviation, aerospace, petrochemical, metallurgy, electric power, automotive, and other industrial fields. Due to the structural complexity and high manufacturing cost of the hot sections of aeroengines, vessel engines, and gas turbines, the development and practicality of superalloy welding technology are critical to satisfying the design and maintenance requirements of hot sections. In this work, the research progress of superalloy fusion welding is described. Its advantages and application scope, such as arc welding, electron beam welding, and laser welding, are elaborated. Common types of welding cracks are introduced, and the mechanisms and influencing factors of solidification cracks, liquation cracks, strain-age cracks, and ductility-dip cracks are summarized. The primary techniques to enhance the weldability of fusion welding are also examined in terms of heat input, material composition, microstructure, and welding residual stress. The requirements for the temperature-bearing level of superalloys in industrial development are constantly increasing; thus, the types of superalloys are also being iteratively updated. They have evolved from deformed superalloys to ordinary cast polycrystalline superalloys to novel superalloy materials such as directional solidification and single-crystal superalloys. Thus, continuously conducting welding research on emerging superalloys, traditional nonweldable superalloys, and dissimilar materials that are extremely incompatible with metallurgy is necessary. Because the composition and microstructure of the base material have an important bearing on weldability, it is necessary to strengthen the composition design of emerging superalloys and conventional nonweldable superalloys in future works. Moreover, it is critical to pay attention to the improvement of welding process technology and pre- and post-weld treatment methods. In particular, research on detection and elimination measures of welding residual stress should be strengthened, which is one of the most effective approaches for lowering the weld crack-sensitivity of superalloys. This is of great importance for synergistically enhancing the welding performance of superalloys. Moreover, monitoring and simulation techniques for the welding process can be used to perform in-depth research on scientific issues such as molten pool flow and welding heat and mass transfer during the fusion welding process. This is of great scientific value for promoting the development of fusion welding technology. Based on the foundation of enhancing welding processes, future work on automation and intelligence of welding processes should also gradually deepen, which is one of the important directions to improve welding stability and reliability and promote the widespread application of superalloy fusion welding.

High strength low alloy steels which are having excellent corrosion-resistant properties are called corten steels. In the present investigation, 3 mm thick ASTM A242 Corten steel sheets were welded together using the cold metal transfer (CMT) method based on two welding controllable parameters like welding current and welding speed. The controllable input parameters like welding current and welding speed have been altered to produce joints that have no flaws and a complete depth of weld penetration. The evaluation of the microstructure and weld geometry was performed for the cold metal transfer welded ASTM A242 sheets using ER70S6 filler wire. The experimental design of welding parameters was developed using an orthogonal array of full factorial design. The dominance of acicular ferrite microstructure is visible in the fusion zone. Results from Energy Dispersive x-Ray Analysis (EDAX) show that manganese content is higher and nickel concentration is lower in the weld fusion region. The fusion zone of the CMT welded specimen has the greatest hardness, which was measured at 270.2 HV. Due to the formation of acicular and bainite microstructure in the welding seam, the tensile properties at room temperature (RT) were found to be 589.79 and 405.63 MPa, accordingly. Bend tests additionally confirmed the satisfactory ductility of the welded joint. [ABSTRACT FROM AUTHOR]

High-strength dissimilar aluminum alloys are difficult to connect by fusion welding, while they can be successfully joined by friction stir welding (FSW). However, the asymmetrical deformation and heat input that occur during FSW result in the formation of a heterogeneous microstructure in their welded zone. In this work, the grain structure and texture evolution in the bottom zones of dissimilar FSW AA2024-T351 and AA7075-T651 joints at different welding speeds (feeding speeds) were quantitatively investigated. The results indicated that dynamic recrystallization occurs in the bottom zones of dissimilar FSW joints, and equiaxed grains with low grain sizes are formed at the welding speed of 60–240 mm/min. A high fraction of the recrystallized grains were generated in the bottom zones of the joints at a low welding speed, while a high fraction of the substructured grains are produced at a high welding speed. Different types of shear textures are produced in the bottom zones of the joints; the number fraction of shear texture types depends on different welding speeds. This study helps to understand the mechanism of microstructure homogenization in dissimilar FSW joints and provides a basis for further improving the microstructure of the welded zone for engineering applications. [ABSTRACT FROM AUTHOR]

The results of experimental studies in the manufacture of components of the supporting structure of the first wall panel, carried out as part of the manufacture of a model of the International Thermonuclear Experimental Reactor (ITER) using laser welding technology, are presented. The influence of laser welding modes on the quality of formation, microstructure characteristics, and mechanical properties of a welded joint made of 10 mm thick 316L steel was studied. A coaxial nozzle was designed and manufactured to protect the weld pool with a curved trajectory. The mechanical properties of the welded joint are 98–100% that of the base metal, and the microhardness of the welded joint and base metal is in the range of 180–230 HV. It was established that the lower part of the weld metal on the fusion line has transcrystalline grains and differs in δ-ferrite content; due to a high welding speed, the ratio of the depth to the width of the welding seam is 14 times. The width of the rectilinear part of the seam is 15–20% larger than its curved part. [ABSTRACT FROM AUTHOR]

The laser direct fusion welding of SiO 2 ceramics was a global challenge in the manufacture of radome. The paper explored the laser direct fusion welding of SiO 2 ceramics, investigated the influence of filling powder addition and welding material composition on the formation of weld. The findings revealed that the addition of welding material effectively addressed the issue of weld formation in laser direct fusion welding SiO 2 ceramic. However, the abundance of internal bubbles within the weld emerged as a significant impediment to further enhancing weld strength. The addition of SiO 2 /Al 2 O 3 mixed powder not only significantly reduced the quantity and size of internal bubbles within the weld but also generated the strengthening phase Al 2 SiO 5 , leading to a substantial increase in weld shear strength, reaching a maximum of 106 % of the base material. The research results provided a new solution for direct melting welding of ceramics. [ABSTRACT FROM AUTHOR]

Weight reduction strategies are essential for the transportation sector to reduce greenhouse gas emissions or extend the range of electric vehicles. In the field of lightweight assembly strategies, multi-material design offers great potential. Joining materials typically used in the automotive sector, such as aluminum and steel, brings challenges as conventional processes such as fusion welding are unsuitable. Therefore, new technologies can extend the design options. In previous studies, a mechanical interlocking between cold-rolled surface structures with undercuts on a steel sheet and die-cast aluminum was presented. This method has now been extended to double-sided structures for more complex applications with a joint on both sheet surfaces. Numerical simulations and validation experiments were performed to investigate the manufacturing of the double-sided structures. Furthermore, the influence of the alignment of the upper and lower structures in relation to each other on the resulting structural geometry and the rolling forces were analyzed. More advantageous geometric parameters, e.g., 24% larger undercuts, and approx. 24.1% lower forming forces at 20% height reduction were observed for a shifted alignment. However, significantly higher wear of the structured rollers occurred in the corresponding experiments. [ABSTRACT FROM AUTHOR]

High‐density polyethylene (HDPE) is one of the most used thermoplastic materials for piping applications, due to its significant advantages. The butt‐fusion process is the most used joining processes for HDPE welding. During the process, the behavior of the material changes. This behavioral change depends on the applied welding process and on the used parameters. Thermal analysis can be used as a tool to reveal and evaluate the modifications of the physical and mechanical properties. In this study, an experimental program was applied to HDPE to assess the effects of different parameters on the welding process including heating temperature, heating duration and the applied strength. Tests are performed according to a full factorial design of experiment (DOE). Mathematical models derived from experimental data are used to establish relationships between the input parameters, such as force and heating duration and the corresponding outputs such as temperature distribution during the different welding phases and the thickness of the molten polymer. The empirical models can be used to implement a control strategy for the temperature and hence quantify the thickness of the molten zone to improve the quality of the weld joint by selecting the appropriate welding conditions for the molten zone. Highlights: High‐density polyethylene piping butt‐fusion joint examination using Infrared imaging.Spatial–temporal distribution of temperature for different phases of the welding process.Mathematical Regression techniques are performed.Thickness of molten polymer is assessed.Results are useful for saving material and improvement of the process. [ABSTRACT FROM AUTHOR]

The aim of this work is to study joining Al 2024-T3 alloy plates with different welding procedures. Aluminum alloy AA 2024-T351 is especially used in the aerospace industry. Aluminum plates are welded by the TIG and MIG fusion welding process, as well as by the solid-state welding process, friction stir welding (FSW), which has recently become very important in aluminum and alloy welding. For welding AA2024-T35 with MIG and TIG fusion processes, the filler material ER 4043—AlSi5 was chosen because of reduced cracking. Different methods were used to evaluate the quality of the produced joints, including macro- and microstructure evaluation, in addition to hardness and tensile tests. The ultimate tensile strength (UTS) of the FSW sample was found to be 80% higher than that of MIG and TIG samples. The average hardness value of the weld zone of metal for the MIG- and TIG-produced AA2024-T3511 butt joints showed a significant decrease compared to the hardness of the base metal AA2024-T351 by 50%, while for FSW joints, in the nugget zone, the hardness is about 10% lower relative to the base metal AA2024-T3511. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) of galvanized steel offers unique advantages as it can avoid the extensive metallurgical problems associated with fusion welding. However, conventional FSW still leads to a higher temperature in the stir zone, which deteriorates the microstructure. To obtain a satisfactory weld, the welded joints of galvanized steel were created by FSW with different cooling rates employing a W–Re rotary tool with a large-diameter needle. The correlation between the microstructure evolution and mechanical behavior of joints at different cooling rates was systematically studied. The results demonstrate that the rapid cooling rate favors the refinement of ferrite and diffuse distribution of Fe3C. In addition, weakening of the texture and dispersion of dislocations were also observed after fast cooling FSW. It can be concluded that the microstructural evolution mechanism of the stirring zone (SZ) is continuous dynamic recrystallization at a slow cooling rate, while the microstructure has discontinuous dynamic recrystallization as the primary evolution mechanism at a fast cooling rate. Based on these advantages, the tensile specimens with fast cooling FSW obtained a synergistic improvement in strength-ductility, even surpassing the base material. This work provides new ideas for welding galvanized steel. [ABSTRACT FROM AUTHOR]

Narrow gap welding of 316L stainless steel thick plate was carried out using the cold metal transition pulsed wire-arc swing method. The effects of heat input, arc swing, and shielding mode on weld shaping and lack of fusion were investigated, and microstructure and tensile properties of welded joints were analyzed and characterized. The results indicate that arc swing amplitude was the primary factor affecting sidewall fusion. The tendency of undercut and incomplete fusion at the weld toe increased with the increase of wire feeding speed. Narrow gap weld with built-in shielding was easy to produce pores. The microstructure of welded joints was mostly represented by twin crystals in HAZ and columnar dendrites in the weld. Solidification sub-boundaries were produced between dendritic crystal clusters in the middle of the weld under high heat input, resulting in severe regional segregation and crystalline cracks that extended along subgrain boundaries. The microhardness of the weld and HAZ was greater than that of the base material. The tensile strength of welded joints was comparable to that of base material with good mechanical properties. [ABSTRACT FROM AUTHOR]

Dissimilar welds between ferritic and austenitic steels represent a good solution for exploiting the best performance of stainless steels at high and low temperatures and in aggressive environments, while minimizing costs. Therefore, they are widely used in nuclear and petrochemical plants; however, due to the different properties of the steels involved, the welding process can be challenging. Fusion welding can be specifically applied to connect low-carbon or low-alloy steels with high-alloy steels, which have similar melting points. The welding of thick plates can be performed with an electric arc in multiple passes or in a single pass by means of laser beam equipment. Since the microstructure and, consequently, the mechanical properties of the weld are closely related to the composition, the choice of the filler metal and processing parameters, which in turn affect the dilution rate, plays a fundamental role. Numerous technical solutions have been proposed for welding dissimilar steels and much research has developed on welding metallurgy; therefore, this article is aimed at a review of the most recent scientific literature on issues relating to the fusion welding of ferritic/austenitic steels. Two specific sections are dedicated, respectively, to electric arc and laser beam welding; finally, metallurgical issues, related to dilution and thermal field are debated in the discussion section. [ABSTRACT FROM AUTHOR]

Joining high strength 2xxx series aluminum is known to be complex and difficult; these alloys are traditionally considered non-weldable for fusion welding. This paper describes details on welding AA2029-T8 for skin-stiffened structures using refill friction stir spot welding (RFSSW). RFSSW is a solid-state process invented in the early 2000s that produces spot welds that are strong, lightweight, flush, and hermetic. Cycle times between 1 and 3 s are discussed, and process forces within a range of 8 to 14 kN are demonstrated. Furthermore, lap-shear quasi-static tensile strengths are shown to be between 10 kN and 12 kN in 9 mm diameter spots. A comparison of the performance of RFSSW welds made with various tool materials—which include H13 tool steel, tungsten carbide, and MP159—is detailed. Comparisons of parameters, weld consolidation, and heat-affected zones are presented with discussion related to heat generation specific to each tool material. [ABSTRACT FROM AUTHOR]

In this study, the welding performance of three filler wires, ER4043, ER5356, and the newly developed FMg0.6, were systematically investigated in the gas metal arc welding of high-strength AA6011-T6 plates. An extensive analysis of the microstructural evolution, mechanical properties, fatigue resistance, and corrosion behavior of different weldments was conducted. The ER4043 and FMg0.6 joints exhibited finer grain sizes in the fusion zone (FZ) than the ER5356 joint. The as-welded ER5356 and FMg0.6 joints exhibited higher hardness and tensile strength values than the ER4043 joint. The FMg0.6 joint demonstrated the highest mechanical strength among all of the joints with superior fatigue resistance under both the as-welded and post-weld heat treatment (PWHT) conditions. In the as-welded state, the ER5356 joint exhibited the lowest corrosion resistance, attributed to the precipitation of β-Al2Mg3 at the grain boundaries. The FMg0.6 joint, characterized by a high-volume fraction of eutectic Mg2Si in the as-welded state, exhibited a higher corrosion rate than that of the ER4043 joint. However, the PWHT effectively improved the corrosion resistance of the FMg0.6 joint. Given its excellent tensile properties, superior fatigue properties, and satisfactory corrosion resistance, particularly with PWHT, the newly developed FMg0.6 filler has emerged as a promising candidate for welding high-strength 6xxx alloys. [ABSTRACT FROM AUTHOR]

Flow-accelerated corrosion (FAC) preferentially attacks the downstream heat-affected zone of the root-pass weld in steam pipe systems. A detailed characterization identifies the fusion boundary as the initiation location for the attack. Alloying elements are found depleted along the weld fusion boundary, and multiple welding thermal cycles and repetitive austenite-to-ferrite phase transformations result in an increased proportion of grains with Goss {110}<001> texture along the fusion boundary. The synergistic effects of chemical segregation and the Schmid factor may contribute to the preferential initiation of FAC cracks along the root weld fusion boundary, making it the weakest link for FAC attack in steam pipe girth welds. [ABSTRACT FROM AUTHOR]

There are a lot of problems with the conventional fusion welding process, so ultrasonic welding has been used for about 20 years and has helped a lot of manufacturing industries, including aviation, medicine, and microelectronics. Ultrasonic welding takes less than one second, making it suitable for mass production. Poor weld quality and joint strength are common issues that industries encounter as a result of this process. Actually, the success and quality of the welding are determined by its control parameters. This research examines the impacts of weld time, vibrational amplitude, and weld pressure on the welding of 0.6 mm thick sheets of two different metals, specifically copper and aluminum (AA2024). Responses, including tensile shear stress, weld area, and T-peel stress, are acquired through experiments that follow a full factorial design including four replicas. The highest recorded tensile shear stress was 4.34 MPa, the maximum weld area measured was 63.6 mm2, and the peak T-peel stress reached 1.22 MPa. A second-order non-linear regression model was constructed using all of these data points, which related the responses to the predictors. Due to the importance of quality in the production sector, the process parameters were determined by the combination of genetic algorithm (GA) and fuzzy logic (FL) approaches. The impact of the weld zone temperature on various quality characteristics has been investigated through experiments. It has been noted from the confirmatory test that FL produces superior output outcomes compared to the genetic algorithm, with FL achieving a fuzzy multi-performance index of 0.94 compared to 0.61 for GA. By conducting microstructural analysis, weld quality levels, including "under-weld," "good weld," and "over-weld," were established. [ABSTRACT FROM AUTHOR]

The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties. [ABSTRACT FROM AUTHOR]

An investigation into the evolution of temperature and stress fields, as well as the phase transformation in marine steel EH36 during multi-pass welding, and their subsequent effects on Charpy impact toughness, remains in great lack. In this study, submerged arc welding (SAW) was employed to carry out multi-pass welding on EH36 steel plates, followed by the low-temperature toughness test of weldments. Comsol software version 6.2 and finite element analysis are utilized to simulate the evolution of the microstructure, temperature, and residual stress fields throughout the multi-pass welding process. As welding progressed, the heat absorption along the vertical direction was enhanced; in contrast, a decrease is observed in the horizontal direction away from the heat source. This complicated temperature history favors the bainite transformation in the vicinity to the heat source, whereas areas more remote from the weld zone exhibit a higher prevalence of acicular ferrite due to the reduced cooling rate. The concentration of residual stress is predicted to occur at the boundary of the melt pool and at the interface between the weld and the heat-affected zone, with the greatest deformation observed near the fusion line at the top surface of the model. Furthermore, multi-pass welding may alleviate the residual stress, especially when coupled with the formation of acicular ferrite upon cooling, leading to improved low-temperature impact toughness in regions remote from the heat source. These findings offer valuable insights for the design and optimization of multi-pass welding in future applications. [ABSTRACT FROM AUTHOR]

Crack defects in ceramic welding are a significant challenge in electronic packaging that requires urgent resolution. In this study, fiber laser-based welding was employed to join 1 mm thick Al 2 O 3 ceramic plates. The investigation focused on weld surface formation, crack defects, and performance attributes across varying heat input and preheating temperatures. The findings indicate a propensity for crack initiation at the weld center or within the base material during Al 2 O 3 ceramic laser welding. Nonetheless, the susceptibility to cracking in Al 2 O 3 welded joints can be mitigated, and joint flexural strength enhanced by adjusting heat input or by introducing a preheating treatment. The flexural strength peaked at a preheating temperature of 100 °C, exhibiting a 112 % increase compared to non-preheated welded joints. In addition, the best matching relationship between heat input and the preheating temperature was obtained through numerical calculations. The relationship between heat input and preheating temperature determines the cracking tendency region, and based on their interrelation, the cracking tendency region is partitioned into three distinctive regions. Subsequently, the three regions were experimentally validated, with results exhibiting a high degree of congruence, thereby offering significant guidance in the selection of laser welding parameters for Al 2 O 3 ceramics. [ABSTRACT FROM AUTHOR]

The confinement boundaries of spent nuclear fuel (SNF) canisters are typically fusion welded. Welded microstructures, strain hardening, and residual stresses combined with a chemically aggressive, chloride-rich environment led to concerns that the welded canister may be susceptible to chloride-induced stress corrosion cracking (CISCC). A comprehensive understanding of the modification of stainless steel (SS) metallurgical and mechanical properties by fusion welding could accelerate the predictive analysis of CISCC susceptibility. This paper describes a submerged arc welding (SAW) procedure that was developed and qualified on 12.7 mm (0.5 in.) thick AISI 304/304L SS to produce joints in a way similar to actual SNF canister manufacturing. This procedure has the potential to reduce the production cost and weld CISCC susceptibility by using fewer welding passes and lower heat input than current industrial applications. Global and local mechanical behaviors and properties, as well as residual stress distributions on the welded joint, were studied. The results indicate that hardness values in the fusion zone (FZ) and heat-affected zone (HAZ) are slightly higher than that of the base metal. Strain localization was presented in the HAZ before the tensile stress reached its maximum value, and then it shifted to the FZ. The specimen finally broke in the FZ. High tensile residual stresses exhibited in the FZ and the nearby HAZ suggest the highest CISCC-susceptible spots. The maximum tensile residual stresses were along the welding direction, indicating that if cracks occur, they would be perpendicular to the welding direction. This study involved developing and qualifying a SAW procedure for SNF canister production. The new procedure yielded cost savings (SAW working efficiency increased by about 80%), improved mechanical properties, and presented moderate residual stresses. Analysis revealed that the welded joint's low-stress and high-stress damage assessments may be affected by shifts in the strain localization spot under loading. [ABSTRACT FROM AUTHOR]

Pipes are subjected to axial pulling forces that lead to shear stresses at the soil–pipe interface and axial strain distributions from various circumstances, including pulled-in-place pipe installation and permanent ground deformations. This study investigates the axial pullout response of fusible polyvinyl chloride pipes in dense sand. Three tests were conducted using a large-scale soil chamber to assess the development of axial resistance and the impact of non-continuous pulling and fusion weld joints. The measured maximum load response was significantly underpredicted by guidelines typically used in practice. Additionally, non-continuous pulling and changes to the pull rate had negligible impacts on the load–displacement response. Pipes were instrumented with distributed fibre optic sensors (DFOS) to capture the nonlinear development of strains along these flexible pipes and the mobilization of soil friction along the soil–pipe interface. Measurements have provided insight into the propagation of axial strains along the pipe, the additional longitudinal restraint provided by fusion weld joints, and their impact on the axial force distribution along pipes. The "locked-in" strains due to residual soil–pipe friction remaining after the axial pulling force is removed have also been measured using DFOS. [ABSTRACT FROM AUTHOR]

Conventional fusion welding of high-nitrogen stainless steel (HNSS) can lead to a number of potential defects, such as nitrogen porosity, weld metal subjected to solidification cracking, heat-affected zones (HAZ) subjected to liquation cracking, lowering of dissolved nitrogen content, and formation of nitride precipitates in the HAZ. Among these, solidification cracking in the weld zone and liquation cracking in the HAZ are the most serious ones. Susceptibility of materials to hot cracking is an important factor to be considered while combining the materials, particularly in HAZ. Thermo-mechanical history of the weld can be simulated by applying a strain to induce cracking and measuring the material's response to cracking. To assess the hot strength and ductility of the material and its susceptibility to hot cracking, a series of hot tensile tests were conducted at temperatures below the solidus temperature using Gleeble thermo-mechanical simulator. Based on the results obtained from the series of tensile tests, it was noticed that for temperatures above 1250 °C, liquid film formation was more pronounced. During heating, nil ductility was observed above 1357 °C. On the other hand, during cooling a significant recovery in ductility (45%) and a ratio of ductility recovery of 53.85% during the thermal cycle were observed. Thus, it can be concluded that the hot cracking tendency in the heat-affected zone of HNSS is very low. [ABSTRACT FROM AUTHOR]

Strain gradient plasticity phenomenon in the parent material (PM), heat affected zone (HAZ) and fusion zone (FZ) of butt and lap joint of shielded metal arc welded AISI A36 steel is studied. The deformation mechanisms of the weldment were explained using mechanistic and phenomenological plasticity and dislocation models. The hardness of the FZ and HAZ of the lap weldment were 1.83 GPa and 1.56 GPa, which were slightly higher than the 1.63 GPa and 1.49 GPa of the FZ and HAZ of the butt. Tensile strengths of the butt joint was ∼384 MPa and that of lap was ∼361 MPa, which were higher than the parent material of ∼290 MPa. The difference in strength between the butt and lap joint were due to the weld configuration and the limited fusion of the single build of the lap joint. The material length scale parameters varied due to microstructural transition from the PM to the FZ as a function of temperature. Length scales of ∼34.37 μm and 22.75 μm were observed for the fusion zones of the lap and butt joints, whereas the lowest of 14.76 μm was for the as-received A36 steel. The geometrically necessary and statistically stored dislocations densities were higher in the lap weldment than for the butt. The average shear strain estimations were used to elucidate the underlying dislocation structures and densities. Grain refinement and localised stress and strain states at the HAZ and FZ led to variations in the mechanical properties. The implications of the results for robust design of welds for structural applications are discussed.

In recent years, the welding industry has witnessed the integration of numerous automation and intelligent technologies, driven by the challenging working conditions inherent in the welding process. Despite these advancements, particularly in specialized environments such as high-altitude and underwater welding, or in the production of low-volume, high-quality products, reliance solely on automation and smart technologies remains insufficient. The quality of welding is profoundly impacted by the skill and expertise of the personnel involved in the operation. Addressing this pivotal issue, our paper introduces a novel approach aimed at enhancing welding quality assessment in such demanding environments. Central to our proposal is the introduction of a quality scoring module integrated into a comprehensive welded box quality scoring system. This innovative system combines BiAGAN’s advanced quality inference model with operation result scoring, providing a robust framework for evaluating welding quality. To validate the efficacy of our approach, extensive offline comparisons were conducted, demonstrating remarkable results with an accuracy rate of 95% and a recall rate of 92%. Moreover, to ensure the reliability and applicability of our findings in real-world scenarios, we conducted online tests involving multiple operators, thereby further corroborating the effectiveness of our proposed methodology. Our study represents a significant advancement in welding quality assessment practices, offering a practical solution tailored to the challenges posed by diverse and demanding environments. By harnessing the capabilities of BiAGAN-based methodologies alongside operation result scoring, our approach holds promise for revolutionizing welding quality assessment, ultimately leading to improved productivity and product quality.

The high entropy alloys (HEAs) are relatively a new class of materials that have attracted significant attention of engineering sector in recent years due to their extensive mechanical properties, high strength to weight ratio, thermal stability and resistance to corrosion and oxidation. HEAs are characterized by their unique composition that is typically composed of five or more elements in equal or somewhat substantial proportions. This leads to the evolution of highly complex microstructure that makes it challenging to weld. To fulfil the key requirements of the design and manufacturing, these HEAs must be capable of being welded in a satisfactory manner. The joining of similar and dissimilar combinations of HEAs and other engineering materials system have been proved to be feasible which further expands their structural applications in aerospace, nuclear and defence sector. Additionally, the fillers of HEAs disclosed greater potential in suppressing the evolution of detrimental intermetallics and enhancing the mechanical properties of joints. So, in this study, a comprehensive review on the current state of research in fusion welding of HEAs particularly AlxCoCrFeNi and CoCrFeMnNi is provided to address the weldability of HEAs under the diversity of composition, initial working condition, welding processes, operating parameters, configuration of joint and operating conditions. The latest challenges, progress and future perspectives in fusion welding of HEAs are reviewed critically with a particular focus on microstructure and mechanical properties of joints. The effect of fusion welding processes such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), electron beam welding (EBW) and laser beam welding (LBW) on microstructural characteristics, mechanical properties and corrosion behaviour of HEAs joints is reviewed and discussed. The effect of post weld heat treatment and HEAs fillers on the mechanical properties and microstructural evolution of welded joints is also discussed. Further, an insight into the potential application of HEAs in advanced engineering applications is provided. The current review article aims to provide an overview of challenges, opportunities, current state of research and main directions in fusion welding of AlxCoCrFeNi and CoCrFeMnNi HEAs and to highlight their potential as high-performance material in a range of applications.

The 2000 series aluminium alloys are qualified for widespread use in lightweight structures, but solidification cracking during fusion welding has been a long-standing issue. Here, we create a zirconium (Zr)-core-aluminium (Al)-shell wire (ZCASW) and employ the oscillating laser-arc hybrid welding technique to control solidification during welding, and ultimately achieve reliable and crack-free welding of 2024 aluminium alloy. We select Zr wires with an ideal lattice match to Al based on crystallographic information and wind them by the Al wires with similar chemical components to the parent material. Crack-free, equiaxed (where the length, width and height of the grains are roughly equal), fine-grained microstructures are acquired, thereby considerably increasing the tensile strength over that of conventional fusion welding joints, and even comparable to that of friction stir welding joints. This work has important engineering application value in welding of high-strength aluminum alloys. Solidification cracking during fusion welding of high-strength aluminum alloys has been a long-standing issue. Here, the authors achieve reliable and crack-free welding of 2024 aluminum alloy using a Zr-core-Al-shell wire and the oscillating laser-arc hybrid welding technique. [ABSTRACT FROM AUTHOR]

In this work, tungsten–copper (W–Cu) alloy with multi-scale tungsten phase was prepared by cold isostatic pressing, vacuum sintering and hot extrusion processes. The microstructure of W-70Cu alloy was examined by scanning electron microscopy and transmission electron microscopy. The arc erosion resistance of W-70Cu alloy was studied in the JF04C electrical contact testing system. The erosion morphology of the contact surface was characterized. The action mechanism of tungsten particles in arc erosion process was discussed in detail. The arc erosion property and mechanism of W-70Cu alloy were analyzed. The results show that the material transfer occurs from the cathode to the anode. With enhancing the current and voltage, the arcing time and arcing energy increase while the contact resistance falls slightly. In the arc erosion process, tungsten particles increase the work function of W–Cu alloy and make the arc disperse better. The large tungsten particles in W–Cu contact can help to maintain the shape of the contact and delay the occurrence of fusion welding. Tungsten nano-particles enhance the viscosity of the molten pool, reduce metal splashing, and hinder the crack initiation and propagation. Under the action of multi-scale tungsten particles, W–Cu alloy has the better resistance to arc erosion. [ABSTRACT FROM AUTHOR]

Digital twins are employed to monitor, analyze, and predict the behavior of a manufacturing system. In literature, the concept of digital twin is mainly associated with simulation models, and only a few works addressed the integration between physics-based and data driven models. This work extends this definition and describes how different kinds of knowledge can be integrated in a hybrid knowledge based system supporting digital twin. Following the Industry 5.0 paradigm, the hybrid system can improve the human-centricity, sustainability, and resilience of a manufacturing system. The hybrid digital twin is structured as an enterprise information system, which can be connected to the other information systems of the company, such as ERP, MES, and PLM, as well as other platforms of total quality management and total productive maintenance. A discussion on the application of the proposed approach in fusion welding, as an example of a very complex process, is also presented. [ABSTRACT FROM AUTHOR]

The SA516 Gr.70 steel possessing excellent toughness and plasticity has been widely used in the cryogenic field. However, the appearance of coarse bainite in the heat affected zone (HAZ) of the fusion welded joint deteriorates the toughness and ductility. In this work, 4.5 mm thick SA516 Gr.70 steel was joined using shielded metal arc welding (SMAW) and friction stir welding (FSW), respectively, and the microstructure and mechanical properties of joints were investigated in detail. The Charpy energy in the HAZ in the FSW joint was 80 J/cm2, which was higher than that of the HAZ in the SMAW joint (60 J/cm2) and due to microstructure refinement. In addition, the total elongation (TE) of the SMAW joint was 17.5%, which was higher than that of the FSW joint (12.1%) and caused by a wider nugget zone with high hardness. The post-welding annealing was used to improve the toughness and ductility of the SMAW and FSW joints, and the microstructure and mechanical properties of the joints after annealing were analyzed. The toughness in the HAZ of the SMAW and FSW joints were 80 and 103 J/cm2, and the TE of the SMAW and FSW joints were 18.6% and 25.2%, respectively. Finally, the as-annealed FSW joints exhibited excellent toughness and ductility. The abovementioned excellent mechanical properties were primarily attributed to the appearance of tempering martensite, decrease in dislocation density, and fine grain. [ABSTRACT FROM AUTHOR]

The high entropy alloys (HEAs) are relatively a new class of materials that have attracted significant attention of engineering sector in recent years due to their extensive mechanical properties, high strength to weight ratio, thermal stability and resistance to corrosion and oxidation. HEAs are characterized by their unique composition that is typically composed of five or more elements in equal or somewhat substantial proportions. This leads to the evolution of highly complex microstructure that makes it challenging to weld. To fulfil the key requirements of the design and manufacturing, these HEAs must be capable of being welded in a satisfactory manner. The joining of similar and dissimilar combinations of HEAs and other engineering materials system have been proved to be feasible which further expands their structural applications in aerospace, nuclear and defence sector. Additionally, the fillers of HEAs disclosed greater potential in suppressing the evolution of detrimental intermetallics and enhancing the mechanical properties of joints. So, in this study, a comprehensive review on the current state of research in fusion welding of HEAs particularly AlxCoCrFeNi and CoCrFeMnNi is provided to address the weldability of HEAs under the diversity of composition, initial working condition, welding processes, operating parameters, configuration of joint and operating conditions. The latest challenges, progress and future perspectives in fusion welding of HEAs are reviewed critically with a particular focus on microstructure and mechanical properties of joints. The effect of fusion welding processes such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), electron beam welding (EBW) and laser beam welding (LBW) on microstructural characteristics, mechanical properties and corrosion behaviour of HEAs joints is reviewed and discussed. The effect of post weld heat treatment and HEAs fillers on the mechanical properties and microstructural evolution of welded joints is also discussed. Further, an insight into the potential application of HEAs in advanced engineering applications is provided. The current review article aims to provide an overview of challenges, opportunities, current state of research and main directions in fusion welding of AlxCoCrFeNi and CoCrFeMnNi HEAs and to highlight their potential as high-performance material in a range of applications. [ABSTRACT FROM AUTHOR]

Fusion welding causes joint deterioration when joining aluminum alloys, which limits the use of aluminum alloy components in high-end equipment. This paper focuses on an overview of how to achieve high-strength aluminum alloy welded joints using welding/plastic deformation composite forming technology. The current technology is summarized into two categories: plastic deformation welding and plastic deformation strengthening. Plastic deformation welding includes friction stir welding, friction welding, diffusion welding, superplastic solid-state welding, explosive welding, and electromagnetic pulse welding. Plastic deformation strengthening refers to the application of plastic deformation to the weld seam or heat-affected zone, or even the whole joint, after welding or during welding, including physical surface modification and large-scale plastic deformation technology. Important processing parameters of plastic deformation welding and their effects on weld quality are discussed, and the microstructure is described. The effect of plastic deformation strengthening technology on the microstructure and performance evolution, including the hardness, tensile strength, fatigue property, residual stress, and hot cracking of aluminum alloy welded joints, and its evolution mechanism are systematically analyzed. Finally, this paper discusses the future development of plastic deformation strengthening technology and anticipates growing interest in this research area. [ABSTRACT FROM AUTHOR]

The arc welding with weaving has been used widely to obtain better weld quality by avoiding lack of side wall fusion and improve the weld efficiency by obtaining the wide weld. But the effect of weaving process parameter on the weld is not clear. The aim of this work is to study the effect of process parameters on arc behavior and weld formation in Weaving-Gas Tungsten Arc Welding (W-GTAW), those parameters include welding current, tungsten electrode height from the electrode tip to upper surface of workpiece, weave angle, weave speed, and weave stop time on the left and right sides. The instantaneous arc shape and electrical signal data were collected by high-speed camera and electrical signal acquisition system, respectively. Furthermore, the weld morphology was also systematically analyzed. This result shows that the bottom surface radius of the arc changed with weaving in the W-GTAW. When the weave speed increased to 0.40 × 10−1 rad/s, the change of the radius was the least, with only 0.10 mm drift, and the difference between the arc forces in the middle and the two sides of the molten pool was smallest in all experiments. Compared with the welding stability of each process, decreasing the tungsten electrode height, weave angle and speed could significantly enhance the welding stability. The forming coefficient of weld with a weave angle of 1.9° was 3.11. It shows that increasing reasonably the weave angle and speed can increase the weld penetration and might help reduce stress concentration and hot crack tendency of the weld. When the welding current is reduced to 130 A for W-GTAW welding, the hardness transition from base metal (BM) zone to weld zone (WZ) is more gentle. Furthermore, the W-GTAW technology shows great application potential in weld forming control by adjusting process parameters. [ABSTRACT FROM AUTHOR]

Friction taper stitch welding (FTSW) is a novel technique that uses multiple inserts to conceal surface crack in a given substrate. The inserts are rotated and forced to fill the crack as plasticized material, and forge with the substrate in solid-state. The process is well suited for alloys such as duplex stainless steel, which suffers degradation of properties during fusion welding. A detailed experimental and theoretical investigation is presented here on FTSW of a duplex stainless steel (DSS). The experimental results show the presence of a ferrite-rich phase along the interface. The results computed by the numerical process model reveal a direct influence of thermal cycle in the amount of ferrite along the joint interface. The welded joint shows near homogeneous structure and properties similar to those of the substrate. [ABSTRACT FROM AUTHOR]

Unlike the conventional fusion welding process, friction stir welding (FSW) relies on solid-state bonding (SSB) to join metal surfaces. In this study, a straightforward computational methodology is proposed for predicting the material bonding defects during FSW using quantitative evaluation of the in-process thermal-mechanical condition. Several key modeling methods are integrated for predicting the material bonding defects. FSW of AA2024 is taken as an example to demonstrate the performance of the computational analysis. The dynamic sticking (DS) model is shown to be able to predict the geometry of the rotating flow zone near the welding tool. Butting interface tracking (BIT) analysis shows a significant orientation change occurring to the original butting interface, owing to the material flow in FSW, which has a major impact on the bonding pressure at the butting interface. The evolution of the interfacial temperature and the interfacial pressure at the butting interface was obtained to analyze their roles in the formation of material bonding. Four bonding-quality indexes for quantifying the thermal-mechanical condition are tested to show their performance in characterizing the bonding quality during FSW. When the BQI is below a critical value, a bonding defect will be generated. The paper indicates that the simulation-based prediction of a material bonding defect is highly feasible if the developed methodology is extended to quantitatively determine the critical value of the bonding quality index for successful SSB for various alloys. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is a solid-state welding method for the welding of aluminum alloys and has been used in aerospace, railway, automotive, and marine applications. Solid-state welding processes solve several problems that occur during fusion welding of Al-alloys like HAZ liquation cracking, porosity, and segregation. Aluminum alloys of two different series AA5052 and AA6061 thickness of 6 mm are FS welded using process parameters like tool rotational speed (900, 1100, 1400) rpm, transverse speed (40, 50, 60) mm/min, and pin profiles (cylindrical, conical, and square). This article aims to optimize the mechanical and metallurgical properties of the above dissimilar combination to evaluate the performance and characteristics of the welded joints. The combined Taguchi and Grey relation analysis experimental method was chosen to construct the number of welding experiments. The plates are successfully welded, and the welded plates are tested at room temperature to examine their tensile strength and hardness. The findings indicate that the maximum tensile strength of 183.04 MPa, which is 79.58% with AA5052-H32 and 59.05% with AA6061-T6 individually of the base material strength and the square pin profile, the rotational speed of 1400 rpm, and the transverse speed of 40 mm/min are the optimum parameters for joining these dissimilar joints. Tool pin profile has the most prominent FSW process parameters, with a 54.15% contribution. [ABSTRACT FROM AUTHOR]

One of the primary candidate materials used in 650°C ultra-supercritical (USC) thermal power plant units is a novel thick grade of heat-resistant steel, 08Cr9W3Co3VNbCuBN (G115), for which China has complete intellectual property rights. In this study, G115 steel with a 115 mm thick wall was successfully welded using gas tungsten arc welding (GTAW) + shielded metal arc welding (SWAM), which was a significant step toward achieving its application in large-diameter boiler tubes. The influence of the welding process on the microstructure and mechanical properties of the G115 welded joint after post-weld heat treatment (PWHT) at 770°C for 11 h was investigated. The findings demonstrate that the weld zone (WZ) after PWHT was composed of martensite and ferrite, and M23C6 was the precipitate. The average hardness of WZ was 273.1 HV, and the average impact toughness was above 39J, which was sufficient for actual production applications. It offered the necessary theoretical foundation for the practical development of thick-walled G115 heat-resistant alloy steel during welding. [ABSTRACT FROM AUTHOR]

In fusion welding processes, the components to be joined are subjected to a thermal cycle which influences their microstructure and thus the resulting mechanical properties and the behavior of the resulting welded construction in exploitation. The paper presents the possibilities of monitoring the temperature of the welding thermal cycle for fusion welding of S890QL type steel using the Gas Metal Arc Welding robotic process. For the measurement of the temperature values related to the thermal cycle in welding, contact (contact thermometer and thermocouples) and noncontact measurement methods (infrared thermography) were used. [ABSTRACT FROM AUTHOR]

The most common gas-shielded arc welding method is tungsten inert gas welding, which uses shielding gas to isolate the welded area. Such technique is mostly used in the industrial domain, including steel framework fabrication and installation, plumbing systems, and other building jobs. The welding method and the implementation of a suitable welding joint based on some factors that contribute to the fusion process were studied in the present research. The research investigated the specifications and efficiency of the area to be welded in terms of the thermal effect on the welding joint shape and some significant mechanical property-related factors which that were determined during the welding process. In this paper, aluminum alloy sheets, AA 6061-T6, with a thickness of 3 mm, were used with a 60mm width and 80mm length. These sheets were prepared to be welded using welding currents of 90A, 95A, and 100A, welding speeds of 60mm/min, 80 mm/min, and100 mm/min, and gas flow rates of 8 l/min, 9 l/min, and 10 l/min. The experiments were designed at three distinct levels. These levels were selected to create the L9 orthogonal array. Regression analysis, signal-to-noise ratio evaluation, and analysis of variance were carried out. The created model has enhanced accuracy by predicting the reinforced hardness found in the weld specimens, according to the regression study, which showed R2= 90.09%. In addition, it was discovered that the ideal welding parameters for a welded specimen were 100 A for welding current, 80 mm/min for welding speed, and 9 l/min for gas flow. The present research examined the shape of the thermal distribution of welded parts using the engineering computer program ANSYS. The experimental results clarified the proposed approach, as they showed that the welding current is the most influential factor in the hardness of the weld using the fusion process of 90.95%, followed by the welding speed of 7.48%, while the gas flow rate of 1.52% has the least effect. The authors recommend using qualified welders to ensure optimal performance. It is anticipated that these findings will serve as a foundation for analysis to optimize welding processes and reduce welding defects.

Titanium and its alloys have significant uses in the biomedical, chemical, and aerospace industries. In this article, the current and gas flow rates were varied using Taguchi’s experiment design. The mechanical properties of the welded joint made using tungsten inert gas (TIG) welding and Ti6Al4V ELI as filler metal was characterized using the microstructure, microhardness, and tensile strength. The joint was classified into three regions, namely, fusion zone (FZ), heat affected zone (HAZ), and base metal (BM). Results show martensitic microstructure within the fusion zone (FZ) and the heat affected zone (HAZ), which resulted in an increased hardness within the fusion and heat affected zone.

Two austenitic stainless steel (ASS) plates, 304L and 316L, were cold-rolled (304R and 316R) with a 10% reduction in thickness and then subjected to laser welding. Cold rolling caused slight surface hardening and introduced residual tensile stress into the ASS plates. The susceptibility to stress corrosion cracking (SCC) of the welds (304RW and 316RW) was determined using the U-bend test pieces in a salt spray. To highlight the stress concentration at the weld's fusion boundary (FB), the top weld reinforcement was not ground off before bending. Moreover, micro-shot peening (MSP) was performed to mitigate the SCC of the welds by imposing high residual compressive stress and forming a fine-grained structure. Cold rolling increased the susceptibility of the 304R specimen to pitting corrosion and intergranular (IG) microcracking. Moreover, pitting corrosion and SCC were found more often at the FBs of the 304RW. The corrosion pits of the peened 304RW (304RWSP) were finer but greater in amount than the those of the un-peened one. The results also indicated that the 316L ASS welds with MSP were resistant to the incidence of pitting corrosion and SCC in a salt spray. The better reliability and longer service life of dry storage canisters could be achieved by using 316L ASS for the construction and application of MSP on it. [ABSTRACT FROM AUTHOR]

A few components used in the aerospace and petrochemical industries serve in corrosive environments at high temperatures. Corrosion-resistant metals or unique processes, such as coating and fusion welding, are required to improve the performance of the parts. We have used laser powder bed fusion (LPBF) technology to deposit a 5 mm thick corrosion-resistant CoCrMo layer on a high-strength IN625 substrate to improve the corrosion resistance of the core parts of a valve. This study found that when the laser volumetric energy density (EV) ≤ 20, the tensile strength increases linearly with the increase in EV, and the slope of the curve is approximately 85°. The larger the slope, the greater the impact of EV on the intensity. When EV > 20, the sample strength reaches the maximum tensile strength. When the EV increases from 0 to 20, the fracture position of the sample shifts from CoCrMo to IN625. When EV ≤ 38, the strain increases linearly with the increase in EV, and the slope of the curve is approximately 67.5°. The sample strain rate reaches the maximum when EV > 38. Therefore, for an optimal sample strength and strain, EV should be greater than 38. This study provides theoretical and technical support for the manufacturing of corrosion-resistant dissimilar metal parts using LPBF technology. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) processes are playing a significant role in several industrial sectors such as construction and machine building industries, involving a wide variety of metallic materials. Among these, the AM of aluminium alloys has developed significantly over the last decade, mainly through Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) processes. Despite the many advantages of AM technology, some large or complex products cannot be produced entirely without the use of conventional manufacturing and joining processes, generally for financial or operational reasons. In this way, the ability to join conventionally and additively manufactured components or parts represents a crucial step towards their future use and the consolidation of conventional and additive manufacturing technologies. Despite the growing interest in AM technologies, there is still a significant lack of information on the joining of conventionally and additively manufactured components. The present work proposes a first review of the literature evaluating the weldability of AM aluminium alloys. The focus is on the use of fusion and solid-state welding processes and analysing the achieved microstructural evolution and mechanical properties. A clear relationship is observed between the AM technology used to produce the part, and the physical principles of the joining process. In addition, the gaps in the literature are highlighted to enable focused future work. [ABSTRACT FROM AUTHOR]