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In this study, fiber laser butt welding was performed on a 6 mm thick Ti-6Al-3Nb-2Zr-1Mo alloy and 10CrNi3MoV steel using two interlayer configurations, with the innovative introduction of an external alternating magnetic field. The microstructure, element distribution, and mechanical properties of the welded joint were investigated through various methods including scanning electron microscopy, energy-dispersive X-ray spectrometer, and X-ray diffraction. Results showed that joints with two interlayer configurations were present in an interfacial layer with non-uniform thickness and poor mechanical properties, due to the heterogeneous heat distribution in the thickness direction and the mixing of elements during the laser welding process. Applying an alternating magnetic field facilitated convection of the molten pool from center to sides, which accelerated forced convection in both vertical and horizontal directions leading to more uniform heat distribution as well as element distribution resulting in a significant reduction or disappearance of unmelted Cu for different interlayers, while also reducing the thickness of the interfacial layer at the upper part of the joint and significantly improving tensile strength by 5.9% and 8.3%, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT 6016‐T4 aluminum (Al) alloy plate was butt welded to the cold‐rolled steel plate by a friction stir welding (FSW) technique, and the fatigue properties of Al/steel dissimilar welds were investigated. Some dissimilar welds were die‐press formed to the hat shape, and specimens were sampled from the corners of the hat shape, where severe plastic deformation occurred by the die‐press forming. The die‐press‐formed samples had better tensile strengths and hardness than the as‐welded ones because of the work hardening. It indicates that the die‐press forming is applicable for the Al/steel dissimilar welds. However, large voids were formed around the steel fragments dispersed into Al matrix by die‐press forming. Those voids acted as the fatigue crack nucleation sites, thus reducing the fatigue lives of the die‐press‐formed specimens. When the bottom side of the welds experienced tension plastic deformation, the fatigue strength was the lowest. [ABSTRACT FROM AUTHOR]

To repair a pipeline system, an automatic welding process is used to carry out the sleeve welding. In this study, the repair performance of the sleeve was studied, and the research results will help improve the repair quality of pipeline systems in the future. The results show that the tensile strength of the fillet weld was lower than the minimum nominal tensile strength of X65 steel. There were small cracks at the root of the fillet weld. The fracture surfaces of the side bend test of the butt weld and the notching hammer break test of the fillet weld indicated defects to different degrees. The tensile tests of butt welds indicated breaks in the base metal, and the average tensile strength was 587 MPa. The ductile-brittle transition temperature of the butt weld and the fusion line ware both lower than −60°C , and the average crack tip opening displacement (CTOD) values of −10°C fracture toughness tests of the butt weld and heat affected zone were 0.181 and 0.510 mm, respectively. [ABSTRACT FROM AUTHOR]

The fatigue crack growth properties of G20Mn5QT cast steel and corresponding butt welds, using compact tension specimens, were monitored and investigated via acoustic emission (AE) techniques. Fatigue crack growth is a combination of cyclic plastic deformations before the crack tip, tensile crack fractures, and shear crack fractures. The cyclic plastic deformations release the maximum amount of energy, which accounts for half of the total energy, and the second-largest number of AE signals, which are of the continuous-wave type. The tensile crack fractures release the second-largest amount of energy and the largest number of AE signals, which are of the burst-wave type. The shear crack fractures release the least amount of energy and the lowest number of AE signals, which are similar to the burst type, albeit with a relatively longer rise time and duration. Crack tip advancement can be regarded as a discontinuous process. The critical area before the crack tip brittlely ruptures when the fatigue damage caused by cyclic plastic deformations reaches critical status. The ruptures produce a large number of tensile crack fractures and rare shear crack fractures. Through fractography observation, the shear crack fractures occur probabilistically around defects caused by casting or welding, which lead to stress and strain in the local complex. [ABSTRACT FROM AUTHOR]

AbstractThe key goal of this research was to study the effect of the traverse speed of a tool on microstructural changes, mechanical properties and fracture morphology of pure copper butted weld joint by friction stir welding technique. In this study, other parameters like tool rotational speed (1000 rpm), axial force (4.2 kN), tilt angle (0˚) and tool offset (0 mm) were fixed. A cylindrical tool with a non-threaded tapered pin was used to fabricate the weld joints. All the weld joints produced by varying the traverse speeds (11, 20 and 24 mm min−1) were defect-free. It was noticed that the grains in the stir zone were tiny, well distributed and homogeneous at 24 mm min−1 owing to the adequate heat generation and complete intermixing of material in the stir zone. The utmost tensile strength of 187 MPa was achieved by the welded joint attained at 24 mm min−1. It was observed that a densely populated dimple structure enhances the joint ductility in the case of 24 mm min−1. [ABSTRACT FROM AUTHOR]

In this investigation, two distinct composites were produced using the liquid metallurgy vortex-route method with an aluminum AA6013 matrix and 0.5% and 1% nano-Al2O3 reinforcement by weight. The effects of nano-Al2O3 ceramic particles added into the AA6013 alloy to increase the hardness and strength of the composite were investigated. Samples for welding were prepared from cast composite materials with dimensions of 250 × 110 × 60 mm. The obtained specimens were joined via butt welding at 110-A and 120-A current intensities, and at a constant speed of 400 mm/min by cold metal transfer (CMT) and pulse multi-control (PMC) welding methods. Using the use of micro- and macrostructural evaluations, hardness measurements, and tensile testing, the impacts of each welding parameter on the mechanical characteristics and weld structure of the cast composites were examined. The composite material with 0.5% nano-Al2O3 reinforcement that was joined at 120 A utilizing the CMT process achieved the highest tensile strength value at 96.6 MPa. At 110-A and 120-A welding current values, 0.5% reinforced composite demonstrated the maximum strength in both welding techniques. [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]

The 45 mm thick plate of 9% Ni steel was successfully butt welded with NiCrMo-4 filler metal adopting the submerged arc welding (SAW) via a multi-layer and multi-pass process. After welding, the weld joints were tested in cryogenic and room temperature, respectively, to reveal the influence of microstructure evolution on fracture toughness. The microstructure of the heat-affected zone (HAZ) was characterized by reversed austenite and tempered martensite like the base metal (BM) after post-weld heat treatment, and the weld metal (WM) was presented by austenite in the form of layered columnar grain region (CGR) and fine equiaxed grain region (FGR). With the decrease in temperature, most of the reversed austenite in 9%Ni steel transformed into martensite, resulting in the plastic deformation ability of 9%Ni steel decreased significantly. Moreover, many microvoids formed in WM during the cryogenic fracture process due to the strength mismatch between precipitates and austenite. Compared to FGR, larger and more densely distributed microvoids in CGR were more likely to aggregate into macrocracks, making CGR the weak region in WM at cryogenic temperature. [ABSTRACT FROM AUTHOR]

The effects of laser beam welding (LBW) process parameters on the characteristics of Nd:YAG laser butt welding 1.5 mm thick 2205 duplex stainless steel. Specifically, the study focuses on the depth of penetration, bead width, ultimate tensile strength (UTS) and elongation. To achieve this, a parametric study is conducted using a central composite design (CCD) with response surface methodology (RSM) to establish mathematical regression equations that identify the key process parameters and their effects on the responses. The investigations showed that the size of the meltpool at the fusion zone (FZ) increases as the laser power increases. This leads to the formation of wider and deeper weld beads, ultimately leading to stronger and more flexible joints. Similarly, pulse width and scanning speed have a significant impact on the weld bead geometry, UTS, and elongation. It is observed that the FZ is free of any visible cracks, voids, or porosity. The LBW process parameters have been optimized to reduce operating costs by lowering the line energy, without compromising the welding quality. The optimal UTS value for the welded joint is around 865 MPa, which is almost equivalent to 99% of the UTS of the 2205 duplex stainless steel base material (BM). To obtain high-quality welded joints, it is recommended to use a laser power ranging from 423 to 425 W, scanning speed of 5.3 mm/s and pulse width of 5.4 ms. [ABSTRACT FROM AUTHOR]

Fatigue poses significant challenges for the structural integrity of monopiles, the most common type of foundation for offshore wind turbines. These structures are usually manufactured by rolling and welding together large steel plates. Offshore wind turbines are typically designed to operate for 20 years or longer, thus the number of cycles to failure ( N f ) that these structures are required to withstand lies in the so called ultrahigh-cycle fatigue (UHCF) regime ( N f > 10 8 ). Moreover, because, in the past few years, there has been a continuous increase in the size of monopiles, the fatigue life reduction caused by the utilization of thicker steel plates plays an important role (i.e., thickness or size effect). Different regions worldwide apply distinct codes to ensure that offshore structures can withstand fatigue damages, but most of them are tailored for the high-cycle fatigue (HCF) regime. This paper seeks to compare a selection of these codes, highlighting both differences and similarities, while also questioning their suitability in the UHCF regime and for much thicker structures (compared to the reference thickness values reported in the standards). By doing so, it aims to contribute to the ongoing efforts to optimize the efficiency of the fatigue life assessment of offshore wind infrastructures. The focus of this study is on double-V transverse butt welds and their S-N curves in air and seawater (with and without cathodic protection), while the analyzed standards are those provided by the Det Norske Veritas (DNV-RP-C203-2021), the British Standards Institution (BS 7608, including the amendments of 2015), and the European Union (EN 1993-1-9, updated in 2005). The results have been discussed in terms of the level of conservatism that each of these standards offers and in identifying the areas for further research to enable extended lives in the current and future offshore wind monopile foundations. [ABSTRACT FROM AUTHOR]

There is a growing number of welded steel bridges in the world that are reaching the end of their design life. Repair of fatigue damage (cracks) or replacement with new modern designs is becoming an increasing issue. Fatigue damage is now one of the main design and construction risks associated with the construction of new dynamically stressed steel structures. Fatigue damage is now one of the main design and engineering risks associated with the construction of new dynamically stressed steel structures. Increasing fatigue life can be achieved by HFMI treatment that can be applied to new weld as well as existing welded joints. This paper presents the results of experiments focused on HFMI treatment to new and repaired butt welds of higher thicknesses. [ABSTRACT FROM AUTHOR]

Most premature failures of double-pass weldments are associated with limited knowledge of the mechanical and microstructural evolution following the welding process. Thus, this study aims to investigate the effect of double-pass tungsten inert gas welding on the mechanical and microstructural properties of type AISI 1008 mild steel joints. Double-pass TIG welding in butt joint configuration was adopted to weld the plates maintaining a 2.5 mm root gap in between plates. The double-pass tungsten inert gas welded AISI 1008 joints showed improved ultimate tensile strengths in contrast to the unwelded counterpart, with the least joint efficiency of 82.67 % (weld W3). An increase in the heat input led to a corresponding increase in the weld metal hardness, whereas the hardness of the heat-affected zones increased first and then decreased. The internal geometry of the welds reveals an increase in the bead width, height of reinforcement, width of the heat-affected zone, and weld metal area as the heat input increases. Lastly, the microstructural evolutions of the weld metal zones were primarily dominated by widmanstatten ferrite, acicular ferrite, and pearlite structures, accounting for the enhanced tensile strength and hardness of the joints. Meanwhile, the heat-affected zones were characterised by coarse columnar dendrite structures resulting in lower hardness values. This study gives an insight into the mechanical and microstructural properties of the industry's most frequently used steel grade, which has not been given much attention in past studies. The research finding enriches the welding theory of A1SI 1008 steel for industrial and academic benefits. [ABSTRACT FROM AUTHOR]

Welding buckling deformation is one of the foremost failure modes of thin plate welded structures. It is important to estimate welding buckling for structural design and process optimization. Inherent strain-based welding buckling evaluation methods have been proved to be valid, but the existing methods have low efficiency due to requiring multiple inherent forces. In this study, a novel welding buckling evaluation method based on longitudinal shrinkage force was established. The effectiveness of the proposed method was validated using a butt welded joint. In addition, this method was applied in a large-scale thin plate structure for evaluating the structural stability, the effects of heat input, welding manner, and external constraints on welding deformation and buckling were also discussed. The results reveal that the proposed inherent strain-based welding buckling evaluation method can be used to judge whether welded structures are buckled. The reduction of welding heat input and the use of single-sided welding can mitigate welding deformation. Increasing external constraints can not only reduce the welding deformation, but also improve the welding critical buckling load for preventing welding buckling. [ABSTRACT FROM AUTHOR]

Tungsten argon arc welding (TIG), cold metal transfer (CMT) welding and flash butt welding (FBW) are used to join M390 and 304. The mechanical properties of M390 and 304 welded joints with different welding methods were compared by tensile and microhardness experiments. The microstructure evolution and phase changes of TIG, CMT and FBW welded joints were compared and analyzed by scanning electron microscope (SEM) and x-ray diffraction. The grain size of weld metal (WM) and M390 heat-affected zone of three types of welded joints were measured by Image J software. Corrosion resistance of three types of weld joints was characterized by electrochemical corrosion tests, and the microstructure of post-corrosion test specimens was characterized by SEM and EDS. The results show that three types of welded joints without cracks and voids can be obtained between dissimilar metals M390 and 304. The microstructure of TIG weld metal is composed of martensite and the carbides M7C3 and M23C6 due to higher heat input during TIG welding processes. Because extensive C, Cr and Ni element diffusion occurs during FBW welding due to low heat input, the microstructure of the weld metal is composed of martensite and austenite matrix and carbides of M7C3 and M23C6. The filling of nickel-based alloys during CMT welding processes make the microstructure include austenite and (Al, Ni, Ti) carbide. The tensile strength and elongation of CMT welded joint can reach 501 MPa and 21.8%, the corrosion current density is 4 mA cm−2, and the corrosion voltage is − 21 mV, which is the best mechanical properties among the three types of welded joints. The welded joints with the three welding methods are all fractured at WM position. [ABSTRACT FROM AUTHOR]

In this study, finite element (FE) simulation by the software Abaqus was relied on to investigate the roll forming process of a wheel rim made of an innovative dual-phase steel, i.e., DP590, after flash butt welding (FBW). In the simulation, an FE model was generated, including the design of the dies for flaring, three-roll forming, and expansion, and detailed key processing parameters based on practical production of the selected DP590. Combined with the microstructures and properties of the weld zone (WZ) and heat-affected zones (HAZs) after FBW, the distribution of stress/strain and the change in thickness of the base metal (BM), WZ and HAZs were analyzed, and compared in the important stages of roll forming. Theoretically, the variation in the microstructure and the corresponding stress–strain behaviors of the BM, WZ, and HAZs after FBW have led to the thickness reduction of DP590 that originated from softening behaviors occurring at the region of subcritical HAZs (SCHAZs), and a small amount of tempered martensite has evidently reduced the hardness and strength of the SCHAZ. Meanwhile, the distribution of stress/strain has been influenced to some extent. Further, the study includes the influence of the friction coefficient on the forming quality of the wheel rim to guarantee the simulation accuracy in practical applications. In sum, the dual-phase steel has to be carefully applied to the wheel rim, which needs to experience the processes of FBW and roll forming, focusing on the performance of SCHAZs. [ABSTRACT FROM AUTHOR]

High-speed railway vehicle bogies are the main load-bearing components, which are welded together from steel plates and tubes. Butt joint and T-joint are the main types and the joint thickness is between 8–20mm. The stability of laser-arc hybrid welding (LAHW) process correlated strongly with keyhole behaviour. In this paper, the common quality defects in full penetration root pass by LAHW were analysed. Controlling the root gap is adopted to stabilize the keyhole, to improve the stability of weld quality. A novel type of butt joint with micro structure based on Y-shaped grooves has been designed, to meet both the requirement of controlling root gap and industrial large-scale batch production. Two new structure parameters, 2 mm of the remaining blunt edge thickness and 0.3 mm of the half width of root opening, were proved by the flat plates welding test. Finally, the joint with micro structure and the root pass welding parameters were transferred to the welding process of tube crossbeam components. The LAHW process verification was completed, and the test results showed the process meets the requirements of ISO 15614. [ABSTRACT FROM AUTHOR]

The work presented in this paper focuses on modeling the welding process to develop a numerical model able to perform a good prediction of welding distortions. The model is developed for a butt welded joint using S235 steel as the base metal and an electrode (AWS E6013) as the filler metal. To assess accuracy, numerical and experimental results are compared. The present work makes it possible to identify the main factors influencing the accuracy of the numerical model, which must be taken into account to obtain satisfactory results. To carry out this analysis, the effect of the mechanical properties of deposited metal and the effect of the deposition process were taken into account. The effect of the variation of the mechanical properties of the filler metal on the distortions is illustrated. The model was developed by using APDL language, and the birth and death technique is used to model the deposition process. Distortion results obtained by numerical models approach properly the experimental measurement. Further analysis of the numerical data reveals considerable fluctuation of the obtained results by modifying the models used to describe the plastic behavior and the work hardening process. Regarding this strong correlation, numerical modeling of the welding process needs a vigilant identification of the work hardening mode appropriate for the used materials. [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 magnetic pulse welding method using a uniform pressure electromagnetic actuator can effectively weld dissimilar metal plates. However, the existing uniform pressure welding method leads to serious thinning of the plate at the chamfer, lack of welding at the center, and bulging of the welded sample, which seriously affects the quality of the welded joint. To solve these problems and improve the quality of welded joints, a new uniform pressure welding method of dissimilar metal plates based on pre-deformation was developed in this work. In this study, using the welding of an AA1060 aluminum plate and an SS304 steel plate with a thickness of 1 mm as an example, it was confirmed through numerical simulation and experimental research that the pre-deformation of the flyer plate controlled the impact angle of the central area of the plate, and it effectively suppressed central non-welding and serious bulge issues. Further, the welding method also reduced the height of the cushion blocks on both sides, thus mitigating aluminum plate thinning at the chamfer, ultimately improving the tensile strength of the joint. Additionally, a microscopic observation showed that the welding interface formed a wavy composite interface, and the connection strength was good. This welding method can also be extended to welding other dissimilar metal plates. [ABSTRACT FROM AUTHOR]

In the shipbuilding industry, welding automation using welding robots often relies on arc-sensing techniques due to spatial limitations. However, the reliability of the feedback current value, core sensing data, is reduced when welding target workpieces have significant curvature or gaps between curved workpieces due to the control of short-circuit transition, leading to seam tracking failure and subsequent damage to the workpieces. To address these problems, this study proposes a new algorithm, MBSC (median-based spatial clustering), based on the DBSCAN (density-based spatial clustering of applications with noise) clustering algorithm. By performing clustering based on the median value of data in each weaving area and considering the characteristics of the feedback current data, the proposed technique utilizes detected outliers to enhance seam tracking accuracy and responsiveness in unstructured and challenging welding environments. The effectiveness of the proposed technique was verified through actual welding experiments in a yard environment. [ABSTRACT FROM AUTHOR]

The detection of keyhole-induced pore positions is a critical procedure for assessing laser welding quality. Considering the detection error due to pore migration and noise interference, this research proposes a regional prediction model based on the time–frequency-domain features of the laser plume. The original plume signal was separated into several signal segments to construct the morphological sequences. To suppress the mode mixing caused by environmental noise, variational modal decomposition (VMD) was utilized to process the signals. The time–frequency features extracted from the decomposed signals were acquired as the input of a backpropagation (BP) neural network to predict the pore locations. To reduce the prediction error caused by pore migration, the effect of the length of the signal segments on the prediction accuracy was investigated. The results show that the optimal signal segment length was 0.4 mm, with an accuracy of 97.77%. The 0.2 mm signal segments failed to eliminate the negative effects of pore migration. The signal segments over 0.4 mm resulted in prediction errors of small and dense pores. This work provides more guidance for optimizing the feature extraction of welding signals to improve the accuracy of welding defect identification. [ABSTRACT FROM AUTHOR]

Load‐bearing and fatigue behaviour of butt welds in plates of different thicknesses The cross‐section of long‐span steel structures is usually adapted to the bending moment distribution. For this purpose, a thickness transition is applied in the area of butt‐welded joints in flanges of I‐shaped beam members. The fatigue behaviour of these constructional details is complex and differs from a butt‐welded joint in steel plates of the same thickness. This paper presents the results of 30 notch detail tests and compares the behaviour of butt‐welded joints in plates with a thickness transition with those of the same thickness. The statistical analysis of the experimental studies shows a higher fatigue resistance for butt‐welded joints with a thickness transition compared to butt welds of plates of the same thickness. The classification of the latter constructional detail in detail category 90 acc. to FprEN1993‐1‐9:2024 can be confirmed. The prognosis of the notch detail tests with the Two‐Stage‐Model confirms its applicability for the analytical‐numerical prediction of the service life of complex welded constructional details. In addition, the application of the model proves the influence of the thickness ratio and stress ratio on the service life of butt‐welded joints with thickness transition. [ABSTRACT FROM AUTHOR]

Laser beam welding (LBW) is a highly demanded process for premium-quality joints in aeronautic, energy, or industrial sectors, where flexibility and low-heat-affected zones are required. One of the main applications of LBW in the near future is expected to be the welding of new turbine engine components, which are typically made of Nickel-based superalloys. However, parameter setup is time- and resource-consuming, where experiment-based methods are typically employed. Therefore, the process development is far from an efficient resource utilization. In the present work, an LBW numerical model is developed and experimentally validated through a machine-integrated monitoring system. The LBW model is based on solving the heat transfer problem produced by the laser and provides the resulting temperature field, as well as the weld bead dimensions. The model includes a variable heat source that automatically adapts to the welding regime, conduction, or keyhole. For the model validation, two Inconel 718 sheets of different thicknesses are butt-welded and an error of around 10% is obtained, which ensures the validity of the model. [ABSTRACT FROM AUTHOR]

The International Maritime Organization (IMO) is currently rolling out more restrictive regulations in order to achieve net-zero GHG emissions by 2050. In response, the shipping industry is planning to pivot to green energy sources such as hydrogen fuel. However, since hydrogen has an extremely low boiling point (−253 °C), materials for storing liquid hydrogen must be highly resistant to low-temperature brittleness and hydrogen embrittlement. A 316L stainless steel is a typical material that meets these requirements, and various welds have been studied. In this study, 3 pass butt welding was performed by applying the FCAW (flux cored arc welding) process to 10 mm thick ASTM-A240M-316L stainless steel, with the size of the fusion zone and HAZ investigated by mechanical testing and heat transfer FE analysis according to process variables, such as heat input, welding speed, and the number of passes. In all cases, the yield and tensile strengths were about 10% and 3% higher than the base metal, respectively. Furthermore, heat transfer FE analysis showed an average error rate of 1.3% for penetration and 10.5% for width and confirmed the size of the HAZ, which experienced temperatures between 500 °C and 800 °C. [ABSTRACT FROM AUTHOR]

The coil is used for electrical connection and energy conversion in the electromagnetic pulse welding (EMPW) process, so its structure affects the welding effect. In this work, for the dual H-shaped (DH) coil, the influence of the symmetry coefficient on the Cu-Al sheets EMPW was studied through the simulation and experiment. When the voltage was 7 kV and the symmetry coefficient g was 0.75, 1, and 1.33, the Vc-β trajectory curve contained by the simulation combined with the welding window curve (WWC) to analyze the dynamic process and welding effect. The relative impact speed was the fastest and the corresponding weld seam length was the longest when g was 1.33. The welding experiment results were consisted with the simulation results, it was beneficial to weld the Cu-Al sheets when g was 133. The symmetry coefficient could change the impact speed and angle to affect the welding effect. This work is of great significance for DH coil design. [ABSTRACT FROM AUTHOR]

In this paper, finite element calculations are used to simulate the melting flow pattern within a titanium/steel dissimilar welded joint with Cu as the transition layer under an oscillating laser welding process, and these calculations are used as a guide for bias oscillating laser welding experiments. When using 304SS side bias oscillating laser welding, welded joints with a tensile strength of 395 MPa were obtained. Compared to the linear bias welding process, it was found that the bias oscillation laser welding process can, on the one hand, generate a stirring effect on the melting pool during the welding process, forming Fe-rich structures encapsulated by Cu layers, which in turn strengthen the Cu layers, and on the other hand, effectively reduce the content of Fe-Ti brittle intermetallic compounds in the weld and obtain a Cu-Ti IMC layer with a thickness of only 10 μm, thus significantly improving the tensile strength of the weld joint and reducing the possibility of incidental fracture. [ABSTRACT FROM AUTHOR]

The paper proposes a method for determining diagrams of the limiting cycle amplitudes of welded joints with steady-state residual tensile stresses based on the test results of small-sized specimens and presents the corresponding calculation dependencies. This technique is an express method for estimating the fatigue resistance characteristics of welded joints if full-scale tests are not feasible. The analysis of literature data for various types of welded joints shows a good fit of the experimental and calculated values of the endurance limits of welded joints of low-carbon steels with low-alloy, low-strength steels. It is shown that the inclined section of the diagram with steady-state residual stresses is shifted in parallel relative to the diagram of cycle amplitudes of welded specimens without residual stresses. It has been established that the diagrams of the limiting cycle amplitudes of welded joints with different values of the steady-state residual stresses end on a line where each point at different average cycle stresses corresponds to the minimum limiting cycle amplitude of the welded joint with its particular value of the ultimate steady-state residual stress, which ensures the realization of the ultimate stress cycle. With the same value of the steady-state residual stress, the endurance limit of welded joints decreases with an increase in the yield strength. It is shown that low values of steady- state residual stresses result in nearly the same endurance limit reduction of butt welded joints of steels of different strengths. In contrast, their higher values aggravate the endurance limit deterioration of steels with higher mechanical characteristics. [ABSTRACT FROM AUTHOR]

The direct welding of alumina ceramic and titanium using ultrashort pulse laser was successfully achieved for the first time. Benefitting from the extremely high peak power of ultrashort pulse laser, ceramics can be melted at a very low laser power. The emerging welding method was conducted at room-temperature without the need for preheating. Within the joint, a combination of Ti and Al elements was observed. A newly formed TiO 2 phase was identified at the Al 2 O 3 /welding seam interface. Under the optimal welding parameters (welding speed: 0.8 mm/s, laser power: 19.52 W), the joint achieved a maximum four-point bending strength of approximately 134.9 MPa. This study proposed a new methodology for butt welding of ceramics and metals and shows a much higher efficiency than the commonly used ceramic-metal joining approaches such as brazing and diffusion bonding. [ABSTRACT FROM AUTHOR]

Vibration-assisted welding has evolved as a high-quality weld-production technology. Researchers have recently adopted medium and high frequency assisted welding to improve mechanical qualities. The primary goal of this research is to investigate and optimize process parameters while employing low frequency vibration-assisted welding. The impact strength of 5 mm thick butt-welded MS plates is investigated in this study, employing a novel vibratory approach to impart vibration to the workpiece at frequencies ranging from 150 to 250 Hz during shielded metal arc welding. The Taguchi approach has been used to optimize the process parameters viz. Current, vibration time, and vibration frequency on the impact strength of welded specimens. SEM analysis was also used to examine the microstructure of welded MS plates. The results showed that a low heat input of 81 Amp, a frequency of vibration of 171.97 Hz, and a period of vibration of 110.45 s provided the most effective performance in terms of welded MS plate impact strength. The frequency of vibration has been discovered to be the most crucial characteristic affecting the toughness of the welded joint. For LFVW welded butt joints, a fine grain structure is seen, suggesting enhanced impact strength values owing to weld pool excitation. [ABSTRACT FROM AUTHOR]

This study investigated how welding affects the thermal deformation of square cells produced for casks, which are dry storage containers for spent nuclear fuel. We aimed to minimize structural deformation by utilizing STS316L as the material for the square cells. We explored a method of subdividing the square cells and joining them through butt welding. Keeping the upper plate thickness constant, GTA butt welding was conducted while varying the column's wall thickness, followed by measurement with a laser vision sensor. The heat conduction and thermal strain were then calculated using a finite element analysis (FEM). Both experimental and analytical results confirmed that there was significant thermal deformation in the cases of thick-walled columns due to variations in heat conduction distribution, with the resulting deformation patterns depending on thickness. [ABSTRACT FROM AUTHOR]

The azimuth track is an important component of the radio telescope wheel–rail system. During operation, the azimuth track is inevitably subject to phenomena such as track wear, track fatigue cracks, and impact damage to welded joints, which can affect observation accuracy. The 110 m QiTai radio telescope (QTT) studied in this paper is the world's largest fully steerable radio telescope at present, and its track will bear the largest load ever. Since the welded joint of an azimuth track is the weakest part, an innovative welding method (multi-layer and multi-pass weld) is adopted for the thick welding section. Therefore, it is necessary to study the contact mechanical properties between the wheel and the azimuth track in this welded joint. In this study, tensile tests based on digital image correlation technology (DIC) and Vickers hardness tests are carried out in the metal zone (BM), heat-affected zone (HAZ), modified layer, and weld zone (WZ) of the welded joint, and the measured data are used to fit the elastic–plastic constitutive model for the different zones of the welded joint in the azimuth track. Based on the constitutive model established, a nonlinear finite element model is built and used to simulate the rolling mechanical performance between the wheel and azimuth track. Through the analysis of simulated data, we obtained the stress distribution of the track under different pre-designed loads and identified the locations most susceptible to damage during ordinary working conditions, braking conditions, and start-up conditions. The result can provide a significant theoretical basis for future research and for the monitoring of large track damage. [ABSTRACT FROM AUTHOR]

This paper studied the effect of the longitudinal magnetic field (LMF) on the microstructure evolution and mechanical properties of AZ40 argon tungsten arc welding joints. Magnetic field-assisted argon tungsten arc welding technology was used to achieve butt welding of an AZ40 Mg alloy sheet with a thickness of 1.5 mm. The microstructure of the Mg alloy weld was studied by using metallographic microscopy and scanning electron microscopy. Mechanical performance of the Mg alloy weld was evaluated by using a hardness tester and universal tensile machine. The experimental results revealed that the average crystallite dimension of the weld zone of the Mg alloy joint reached 43 μm without an LMF. By introducing LMF-assisted technology, the weld structure was significantly refined and the average crystallite dimension of the weld seam was reduced by 39.5% to 26 μm with a coil current of 1.2 A. For the joint without magnetic field assistance, the optimum tensile strength of the AZ40 weldment was 225 MPa under a welding current of 80 A, and fracture occurred in the center of joint welding seam. Under an LMF coil current of 1.2 A, the joint strength increased from the initial 225 MPa to 254 MPa, and fracture occurred at the weld edge with obvious plastic fracture characteristics. It can be confirmed that the LMF-assisted welding process effectively improved the microstructure characteristics of the weld seam and strengthened the microhardness and mechanical performance of the AZ40 joint. [ABSTRACT FROM AUTHOR]

Nickel-free high nitrogen stainless steel (HNS) is having great demand in cryogenic industries, biomedical instruments and various medical implants and stents. This is also being used in electronic industries and defense like armored battlefield vehicles. In this paper, efforts have been put to prepare butt welded 5 mm thickness HNS by spattering free highly efficient cold metal transfer (CMT) process using multi-pass welding to study the material characterization, microstructural evolution, ferrite content and furthermore residual stresses. The addition of nitrogen is found to be economical with better mechanical results. Results show that nitrogen plays a significant role in enhancing mechanical properties. Low heat input welding effectively welds HNS with substantial tensile strength. Due to the development of martensite, the higher heat input welded sample (710.40 J/mm) has the maximum tensile strength, microhardness, joint efficiency, and compressive residual stress with the lowest ductility. Due to heat accumulation between multiple passes and high ferrite concentration at the center of the weld bead, the microhardness value of the weld bead is decreased. Grain size is 36.49 µm at the junction of weld bead (WB) and heat-affected zone (HAZ), 31.87 µm at HAZ, 23.74 µm at junction of HAZ and base metal (BM), and 15.61 m at BM, with microhardness of 317.76, 336.72, 347.28, and 362.05 HV, respectively. Grain size evolution from base metal to weld bead shows a significant impact on the mechanical properties. [ABSTRACT FROM AUTHOR]

The mobility sector is considered a major contributor to global greenhouse gas emissions and air pollution. As a result, many countries have initiated the transition from fossil fuel-powered to electrified powertrains. This transformation of the powertrain concept will lead to a rapid increase in the production of electric vehicles and, therefore, to a high demand for so-called traction batteries. As a production step of the traction batteries, a connection between the cell connector and the terminal of the battery cell has to be manufactured. For this purpose, laser beam welding is a reliable and efficient joining technique. In order to ensure continuous quality of the welding process during production and to detect defects in real time, reliable process monitoring is required. In this study, spectral and acoustic emissions during laser beam welding were recorded using a laser welding monitor and an optical microphone. For determining possible correlations between the signals and weld defects, various failure cases were generated by the systematic placement of disturbance elements. These elements included a contaminated surface, a gap between the cell connector and the battery cell, and a misalignment of the cell connector. Based on the recorded signals, statistical metrics were calculated. Finally, weld seams with and without defects were compared to assess the capability of both sensor systems for detecting the weld defects. [ABSTRACT FROM AUTHOR]

The prerequisite of the weld bead finishing is intricately linked to the quality of the welded joint. It constitutes the final, yet pivotal, stage in its formation, significantly influencing the reliability of structural components and machines. This article delineates an innovative post-weld surface finishing method, distinguished by the movement of a specialized cutting tool along a butt weld. This method stands out due to its singular approach to machining allowance, wherein the weld bead height is considered and eradicated in a single pass of the cutting tool. Test samples were made of AISI 304L, AISI 316L stainless steels and EN AW-5058 H321, EN AW-7075 T651 aluminum alloys butt-welded with TIG methods. Following the welding process, the weld bead was finished in accordance with the innovative method to flush the bead and the base metal's surface. For the quality control of welded joints before and after the weld finishing, two non-destructive testing methods were chosen: Penetrant Testing (PT) and Radiographic Testing (RT). This article provides results from the examination of 2D profile parameters and 3D stereometric characteristics of surface roughness using the optical method. Additionally, metallographic results are presented to assess changes in the microstructure, the microhardness, and the degree of hardening within the surface layer induced by the application of the innovative post-weld finishing method. [ABSTRACT FROM AUTHOR]

The welding process plays a central role in the welding industry, where the joint zone undergoing the welding process experiences structural and mechanical property changes. This research evaluates the comparison of current strength and parameters in the directional welding joint model, a critical aspect of addressing common weaknesses in welded joints. The research objects include four current levels (100, 120, 140, 160 A) and three types of welding directions (longitudinal, transversal, and combination). The aim of this study is to detect the optimal combination in welded joints that can produce a maximum tensile strength ratio. The research method involves tensile testing on various specimen models of joint types at specific current strength levels. The research results indicate that at the current strength level of 120 A, the combined directional welding joint model (longitudinal+transverse) provides a maximum tensile strength reaching 335.370 MPa. This finding stands out significantly, surpassing the tensile strength values at other current levels and welding model types, such as at 100 A (331.574 MPa), 140 A (332.315 MPa), and 160 A (332.685 MPa). This discovery highlights that the combined joint model yields a substantial improvement in joint strength, making it an optimal solution for various current strength levels and joint models. The key feature of this research involves specific recommendations for the welding industry, including guidelines on selecting optimal parameters to enhance the tensile strength of joints. The directional welding joint models can be a reference in designing welding procedure specifications to incorporate construction elements using ST 42 material. This research contributes both theoretically and practically, offering opportunities for improving efficiency and structural safety in the welding process, thus positively impacting the quality of joints in construction and manufacturing applications [ABSTRACT FROM AUTHOR]

The accuracy of the defect assessment methods strongly depends on the accuracy of limit load solutions. Usually, many parameters classify welded structures. Therefore, parametric analysis of such structures may be time-consuming. The upper bound theorem supplies an efficient method for reducing lengthy calculations. The mathematical features of this theorem allow for accurate estimations of the limit load to be found using rather simple kinematically admissible velocity fields. In the case of highly undermatched welded joints, the known singular velocity behavior near the bi-material interface can be taken into account to choose a kinematically admissible velocity field satisfying some features of the real velocity field. The present article provides such a solution for V-bevel butt welds containing a crack of quite an arbitrary shape. The welded joint is subject to tension. The solution consists of two steps. The first step determines the limit load of the specimen with no crack. This step requires the numerical minimization of a function of one variable. The second step accounts for the crack, assuming that the solution for the uncracked specimen is known. This step is purely analytical. The accuracy of the solution is confirmed by comparison with a solution for a particular geometry of the weld found using Riemann's method. The effect of the weld geometry on the limit load is revealed. [ABSTRACT FROM AUTHOR]

Crack-like indications were identified in a gas transmission pipeline during a routine integrity assessment. Visual examination and CT scanning confirmed the presence of cracks on the pipe internal diameter and throughout the wall thickness near the weld seam. Fractographic and metallographic analysis indicated that the cracking occurred in numerous repair welds that were made prior to the final pipe seam weld. The presence of copper on crack faces and within internal cracks, as well as the intergranular path of those cracks, indicated the cracking occurred by copper contamination cracking associated with repair welding. [ABSTRACT FROM AUTHOR]

The objective of this work is to improve the mechanical properties of friction stir welded square butt joints of AA6061 and pure copper employing activated flux of B4C micro powder. Rotational speed, transverse feed and tool penetration depth were optimized using Taguchi method to produce joints devoid of defects. Rotational speed was found to be the most influential process parameter in achieving the higher ultimate tensile strength and has 49% contribution followed by feed and penetration depth. Model predictions for the optimal strength were validated and found to have 5 % variation. Highest ultimate tensile strength and micro Vickers hardness of 259.57 MPa and 98.58 HV respectively were obtained for joints made with speed, feed and penetration depth of 1250 rpm, 20 mm/min and 0.1 mm respectively. The microstructural analysis revealed that B4C particles were distributed uniformly in the stir zone which could be the reason for improved mechanical properties. [ABSTRACT FROM AUTHOR]

A cryogenic hose is used to transport liquefied natural gas at sea, where flexible fittings are sealed by corrugated lining and end flange welding. However, the extreme cryogenic temperatures of the conveyed fluid introduce substantial challenges to the integrity of the fitting seals' structure during the LNG transfer process. In order to study the sealing performance of the fitting under LNG conveying conditions, this paper was based on the general finite element software ABAQUS 6.11 to carry out a thermo-mechanical coupling analysis of the end sealing stress. This paper also established a sealing performance analysis model of the corrugated fitting welding area under the fitting action of LNG load and internal pressure load. A sensitivity analysis was conducted on the influence of weld clearance, blunt edge size, and weld residual height on the weld stress of a fitting ring. The results show that, under the combined action of the medium internal pressure and cryogenic load, the size design of the weld area significantly affects the sealing performance of the fitting, among which the equivalent force of the weld clearance butt sealing area has the greatest impact. Moreover, it was found that a pressure of 5 MPa was 2 mm when the weld clearance was 2 mm, and the average stress at the weld was 53.68 MPa. Further, considering the synergistic influence of the blunt edge size, the weld clearance was 3 mm, the stress was minimal when the blunt side size was 4 mm, and the average stress was 17.42 MPa. These research results can serve as a reference for the design and analysis of the sealing structure of non-adhesive inner corrugated cryogenic hose fittings. [ABSTRACT FROM AUTHOR]

Laser welding of the near α-phase titanium alloy Ti-4Al-2V, used for complex components in the nuclear industry, has been rarely reported. In this study, butt weld joints made of Ti-4Al-2V alloy plates under different parameters, including the laser power, the welding speed, and the defocus distance, were manufactured and analyzed. The results showed that adjusting the combination of 4.2 kW of laser power, a 20 mm/s welding speed, and a −2 mm defocus distance could achieve a penetration depth exceeding 6 mm. Porosity defects were prone to forming in the middle and bottom parts of the fusion zone, due to rapid cooling. The microstructure of the fusion zone was mainly needle-like α martensite, which precipitated in the form of specific clusters. The interior of a cluster was composed of three types of variants with <11−20>/60° phase interfaces to achieve the lower boundary's energy. Affected by the microstructure and welding defects, the strength of the weld joint was basically similar under different welding conditions, namely about 720 MPa, slightly higher than that of the base metal, while the rupture elongation at breaking decreased by more than 50%. The micro-Vickers hardness of the weld joints was about 50–60 HV higher than that of the base metal, while the impact toughness was about 40 KJ, almost half that of the base metal. This research lays a solid foundation for the engineering application of laser welding of Ti-4Al-2V alloys. [ABSTRACT FROM AUTHOR]

The welding process itself is a non-linear, multivariable, coupled physical metallurgical process that is easily perturbed. Improper welding parameter selection and welding process conditions will interfere with the welding process and affect the final welding quality. This study aims to identify and locate two types of welding interference, insufficient shielding gas and unremoved oxidation film on the base metal surface, during the Pulse Multi-Control Gas Metal Arc Welding (PMC GMAW) process of aluminum alloy. The Characteristic Intrinsic Mode Function (IMF), which is closely related to the short circuit transition process, was obtained by applying the Complementary Ensemble Empirical Mode Decomposition (CEEMD) method to the welding current signal measured during the welding process. Time and frequency domain analysis of the acquired characteristic IMF was then performed. The experimental results demonstrated that for a stable welding process, the frequency of the characteristic IMF is concentrated within a narrow range. The frequency spectrum of the characteristic IMF exhibits distinct variations under different types of welding interference. Based on this, the chronological arrangement of characteristic IMF components' frequency spectrum allows for locating welding interferences by analyzing their abnormal signals within the reconstructed signal sequence. [ABSTRACT FROM AUTHOR]

The weldability of a CoCrFeMnNi high-entropy alloy (HEA) and 304 stainless steel (304 SS) was investigated to determine their potential for application in the nuclear and aerospace fields. Autogenous dissimilar butt welding was performed using gas tungsten arc welding, and the resulting joint was complete with no defects. SEM/XRD analysis showed that the fusion zone microstructure consisted of a single fcc phase without the formation of intermetallic compounds. However, there is an unmixed zone near the 304 SS side, which can be attributed to subcooling of the composition caused by the lower liquidus temperature of the bulk weld metal than that of the base metal. Furthermore, a small increase in the hardness of the fusion zone compared with that of the CoCrFeMnNi HEA was observed. These results can be attributed to the grain refinement of the weld and the strengthening effect owing to the incorporation of carbon. The joints exhibited a tensile strength of ~ 465 MPa and ductility of 38%, where the strength was comparable to that of the CoCrFeMnNi HEA, and a joint fracture was found at the side of the CoCrFeMnNi HEA. This indicates that the weldments are suitable for room temperature structural applications. [ABSTRACT FROM AUTHOR]

Residual stresses are inevitably generated during the welding process of steel structures, which can have a negative impact on the structure's normal use and fatigue performance. With the continuous advancements in intelligent manufacturing technology and modular construction of steel structures, there is a growing need for accurate prediction of residual stresses. This paper presents a visualization procedure using Python language and ABAQUS commercial software to predict the full-field residual stress of butt welds in cast steel nodes. The procedure takes into account the geometry and welding parameters of the girth butt weld as input data and provides the post-weld residual stress field as output. Instead of using the traditional thermodynamic coupling finite element calculation method, this procedure develops a parameter function form that uniformly describes the residual stress field. A radial basis function network, trained by a genetic algorithm, is employed to establish a nonlinear relationship between the input and output data. The dataset is generated through finite element simulation, and a visualization interface is created within the ABAQUS software. Experimental results validate the speed and accuracy of the proposed method. This procedure can serve as a valuable reference for quickly determining residual stress fields and optimizing welding parameters during the construction process of steel structures. [ABSTRACT FROM AUTHOR]

Mathematical simulation of stress states arising in butt weld joints of AMg61 aluminum alloy plates (δ = 2, 4, and 8 mm) induced by electrodynamic treatment (EDT) at different temperatures was performed. The vertical velocity V0 of the indenter electrode (EDT tool), determined by the energy characteristics of EDT equipment, was taken to be V0 = 5 m/s. The T values were set to represent the EDT conditions after welding (20°C) and during fusion welding (150 and 300°C). The three-dimensional problem was solved by the finite element method using an ANSYS software package. The conditions for the stresses arising in the EDT plates after and during welding were defined by the mechanical characteristics of an AMg61 alloy at 20, 150, and 300°C, which were described by the kinematically-hardened material model. The computational results for kinetics and residual stress states in weld joints are presented. EDT at 150°C (during welding) was established to be more effective than that at 20°C (after weld cooling). EDT of weld joints (δ = 2–4 mm) was found to result in residual compression stresses across the whole width of the plate, with their values being close to the yield strength of an AMg61 alloy. EDT of weld joints (δ = 8 mm) generates residual compression stresses on the outer plate surface and the tensile ones on its back surface. Thus, for optimum residual stress states of weld joints with δ = 2–4 mm, one-sided EDT (at given V0) is sufficient, while for δ = 8 mm, two-sided EDT would be required. [ABSTRACT FROM AUTHOR]

This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective gas used in TIG closed butt welding. The effect of the shielding-gas flow rate on the properties of CP grade 1 titanium butt-welded joints made using the tungsten inert gas (TIG)-welding method. Butt-welded joints were made for different values of the shielding-gas flow from the side of the root of the weld. Argon 5.0 was used as the shielding gas in the welding process. As part of the research, the welded joints obtained were analysed using optical and scanning electron microscopy. The microstructural characteristics of the joints were examined using an optical microscope, and the mechanical properties were determined using hardness and tensile tests. It was observed that as the flow of the shielding gas decreases, the hardness of the weld material increases and its brittleness also increases. A similar trend related to the amount of gas flow was also noticeable for the tensile strength of the joints. The increase in the hardness of the weld and the heat-affected zone compared to the base metal is mainly related to the increase in the amount of acicular structure (α′ phase). The optimal gas flow rates from the side of the root of weld were found at the values of 12 dm3/min. [ABSTRACT FROM AUTHOR]

Temperature variation during the welding will cause different solid-state phase transformations in the welding area and result in a heat-affected zone (HAZ) between the weld metal (WM) and the base metal (BM). Depth-sensing indentation (DSI) is a doable technique to characterize mechanical properties of materials in the HAZ, which is usually not big enough for the fabrication of coupons for traditional tension tests. The basic idea of DSI technique is to push a hard tip into the surface of the material and then reveal its mechanical properties based on the response of the material. In this study, mechanical properties of butt welds of Q355D steel were investigated with DSI tests and reverse analytical approach. Different welding zones, including BM, subcritical HAZ, fine-grain HAZ, coarse-grain HAZ, top pass of WM and middle pass of WM, were distinguished by microstructures observed by scanning electron microscope (SEM). DSI tests were conducted on these welding zones. Mechanical properties were characterized based on load-penetration depth (P-h) curves obtained by DSI tests. These mechanical properties were adopted in finite-element (FE) simulation of DSI tests. P-h curves obtained by FE simulation agree well with results of DSI tests for all welding zones, especially for the loading curves. The agreement validates the applicability of DSI technique in characterizing mechanical properties of materials. Tension coupon tests were conducted on the BM and the middle pass of WM to verify the accuracy of the DSI technique. Variation of mechanical properties across the welding area were discussed in accordance with microstructures of materials in different welding zones. [ABSTRACT FROM AUTHOR]

The article presents the results of studying the choice of temperature-time and energy-force parameters in flash butt welding (FBW) of the railway crosspiece core (110G13L steel) with rail (K76F steel) through an intermediate chrome-nickel austenitic insert (08Kh18N10T steel). Using an algorithm of numerical solution of the three-dimensional heat conduction equation under the initial and boundary conditions corresponding to the real conditions of welding of the specimens, thermal cycles in fBw of k76f steel with austenitic 08khl8n10t steel and 110g13l steel with austenitic 08khl8n10t steel and temperature distribution in welded joints (in the heat-affected zone for both steels) were obtained. Ranges of varying the main technological parameters of the FBW process have been determined, in which during flashing of rails from K76F, 110G13L and 08Khl8N10T steels, their uniform heating across the cross-section and length is provided, sufficient for achieving deformation to the specified extent during upsetting. [ABSTRACT FROM AUTHOR]

The quality of wheel rims has a strong impact to vehicle safety and reliability during steering. The objective of this work is to reveal the fatigue failure mechanism of the radial fatigue fracture in the flash butt welded joint of 590CL HSLA steel. Morphology and fractography were performed to analyze the microstructure and fatigue crack surface of the wheel rim. The results show that the fatigue crack is located near the region of rim-well radius where the thickness variation and stress level are relatively high. By means of microstructure comparative analysis of the flash butt welded joint on both failed rim and qualified rim, the cause of the fracture is mainly attributed to heat input of the flash butt welding process. [ABSTRACT FROM AUTHOR]

Twin tungsten electrode-wire electrode indirect arc welding (TTW-IAW) is a new welding method, in which the twin tungsten electrodes are connected to the power source together with the welding wire, while the base metal is not connected to the power source, so that the indirect arc is formed between the twin tungsten electrodes and the welding wire. Currently, only the arc characteristics and the droplet transition behavior have been studied, which limits the application of this process in practical welding. In this paper, the thin-plate butt welding process is applied for the first time in TTW-IAW, and the effects of process parameters on weld formation, microstructure, and its hardness are investigated. Additionally, the formation mechanisms of burn-through and hump defects are revealed by the static model and hydraulic jump model of the molten pool, respectively. The results show that TTW-IAW achieves stable weld formation at a maximum welding speed of 600 mm/min, a fourfold increase compared to conventional cold-wire single-TIG welding (conventional cold-wire STW), which reflects its advantages of large deposition rate and high welding efficiency. The degree of influence of the welding current on the penetration of base metal is greater than the welding speed, and the increase in welding current is conducive to the increase in the base metal penetration and the heat-affected zone (HAZ) width, while the increase in welding speed can reduce the convex height of the weld. However, excessive welding currents cause the downward component of arc force and droplet impact to be increased and the upward component of surface tension to be decreased, which results in destabilization of the molten pool, leading to the formation of burn-through defects. Excessive welding speed causes the flow rate of the liquid in the molten pool to be increased and the critical value for the occurrence of a hydraulic jump is exceeded, leading to the formation of a hump. [ABSTRACT FROM AUTHOR]