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Arc welding is a widely applied process in the fabrication of stainless steel structures. Various difficulties may arise in joining of these steels, particularly if high heat input is used. The main aim of this study is to evaluate the influence of heat input on microstructure of the joint region and thus on the mechanical behavior of gas metal arc welded AISI 304 L austenitic plates. To this end, AISI 304 L plates with a thickness of 5 mm were butt-welded by employing two different heat input values. Detailed microstructural and mechanical characterization were carried out. In addition, the influence of heat input on the microstructure and joint performance values was also determined. The higher heat input resulted in a complete recrystallization at the heat affected zone whereas the base metal microstructure was maintained in the lower heat input joint. Both joints displayed strength matching within the weld region, thus exhibited slightly higher tensile strength than that of the base plate (102 %).

Dissimilar SAE 213 T11 and SAE 213 T91 boiler graded steel tubes are welded using magnetically impelled arc butt welding (MIAB) process, a hybrid welding process that combines the advantage of solid state and pressure welding technique. In this research, dissimilar tubes with an outer diameter of 44.5 mm and thickness of 4 mm with a length of 250 mm were joined by using the MIAB welding process. The microstructural behavior and changes of MIAB welded T11 and T91 tubes were analyzed at different zones of the butt-welded tubes using the metallurgical microscope and scanning electron microscope. Micro-Vickers hardness and potentiodynamic polarization test and radiographic testing were conducted. The hardness was taken at different zones along the transverse direction of the join. In the weld interface, the formation of a 2-3 µm martensitic structure leads to the hardness value of 281HV1, and at the base metal of T11 is 217HV1, T91 is 254HV1. The bead width at the welded region is approximately 10-12 µm with the narrow heat-affected zone. The metallurgical bonding between the T11 and T91 dissimilar tubes shows sound joint, which is confirmed with the radiography test.

Determined that with increasing length of contact butt welding of the waveguide linearly increases the speed and performance of seam welding. The use of low-power piezoelectric transducers for ultr...

Submerged arc welding (SAW) is widely used for butt welding of thick plates in large steel structures because of its high deposition rate and high weld quality. With a thickness of 150 mm or more, ...

Introduction. Magnetically impelled arc butt welding (MIAB) method differs from the existing arc methods by high productivity, stable quality of welded joints, high degree of mechanization and automation of the technological process and so on. Welding is performed automatically, which significantly reduces the influence of theoperator-welder on the quality of welded joints. The optimal values of the magnetic field induction components for thin-walled tubular parts with a diameter of 212 mm are determined. The basic technological parameters on welding of tubular details in stationary conditions are defined, it is: qualitative preparation of end faces of pipes;optimal distribution of induction of the control magnetic field (CMF); arc voltage; the magnitude and order of programming the welding current; the rate of closure of the arc gap in the process of upset. The influence of liquid metal melt in the arc gap during upset on the formation of welded joints of pipes is determined. Metallographicstudies showed no defects in the weld line and a relatively small area of thermal impact. Mechanical properties of welded joints at the level of mechanical properties of the base metal. Studies have been conducted to determine theparameters that affect the stable movement of the arc along the thin-walled edges of tubular parts and the influence of liquid metal melt in the arc gap during heating on the formation of welded joints.Problem Statement. Pipes of small diameters (up to 220 mm) are used in various industrial enterprises and construction of pipelines. The work requires high-performance automatic welding methods that allow obtaining stable and reliable welded joints.Purpose. The purpose is to raise labor productivity and to save materials by using equipment and technology for press welding of magnetically controlled arc of thin-walled tubular parts.Materials and Methods. Steel thin-walled tubular parts with a diameter of 42mm and 212 mm, with a wall thickness of 2.5… 3 mm were used for research on press welding. To create a control magnetic field, magnetic systems for tubular parts with a diameter of 212 mm were developed. Experimental welding was performed andsamples of welded joints of pipes with a diameter of 212 mm with a wall thickness of 3 mm were investigated. In the course of the research, the main parameters are recorded and the welding process is controlled by computer. Results. The main technological parameters: preparation of pipe ends; magnitude and distribution of control magnetic field induction; the arc voltage; the magnitude and order of programming the welding current; the rateof closure of the arc gap during upset, which affects the formation of welds have been determined. The experimental industrial technology for welding of thin-walled tubular details with a diameter up to 212 mm for thepurpose of its industrial use and the concept of the welding equipment has been developed, patents for the invention have been received.Conclusions. The mechanical and metallographic tests have shown that the properties of welded joints are at the level of the properties of the base metal. The use of press welding technology for tubular parts increases productivity and automates the welding process. The influence of the bandwidth of the liquid molten metal in the arc gap, while heating, on the formation of welded joints of pipes has been experimentally established. The main technological parameters and their influence on the quality of welded joints in the process of heating, the ends, and the upset of thin-walled tubular parts have been determined. Experimental industrial technology for press welding of thin-walled tubular parts has been developed and industrial tests have been conducted, in accordance with the customer's requirements.

The effect of process temperatures on joint quality in friction stir butt welding of bimodal high density polyethylene (HDPE) was investigated. Process temperatures were manipulated by varying the rotation speed and welding speed. Further control of the process temperatures was achieved by heating the bottom side of the welded plates using a film heater. Temperatures on the top and bottom surfaces of the welded plates were measured by infrared thermography and thermocouples, respectively. Material flow patterns were also visualized by implementing a novel welding technique where two different colors of HDPE were placed on the advancing and retreating sides, respectively, and the cross section of the welding zone was inspected after welding. It was found that proper welding of this bimodal HDPE takes place when the material is maintained at high enough temperatures in the viscous state throughout its thickness. Under these conditions, proper interphase mixing and fusion of the material takes place. Weld efficiencies in excess of 100% and large elongations in the order of 60% were also obtained at the optimum range of welding temperatures.

In this study, a series of butt welding tests with oscillating fiber laser beams were performed on zinc-coated thin sheets of 0.8 and 1.2 mm thicknesses. The optimized welding parameters were used to produce robust welds with no perforations or pores. The weld formation process, microstructure, and mechanical properties of welded joints with the butt surfaces processed via laser and shear cutting techniques were systematically investigated. Besides, the corrosion resistance of the laser oscillating welded joint was analyzed in detail. The welded joint with the butt surface processed by laser cutting shows less undercutting degree with a more favorable weld appearance. The two welded joints had similar microstructures containing different forms of ferrites. The heat-affected zone was almost identical to the base metal in microstructure but had larger grains. Widmanstatten ferrites’ content in the large-grained weld metal of welded joints with surface processed via laser cutting exceeded that of shear cutting-processed ones. The former had lower tensile strength than the latter, but their overall mechanical performance was better than base metal. After salt spray corrosion and electrochemical corrosion tests, the laser oscillating welded joint was only slightly corroded and exhibited no obvious deterioration in corrosion resistance.

Nb-1%Zr-0.1%C alloy is mostly used in high-temperature reactor (HTR) as a structural material, due to its high-temperature strength, resistance to irradiation and nuclear environment. In the present study, the issues related to control and optimization of laser welding parameters are dealt in order to obtain the welded joints with satisfactory strength and ductility. Laser butt welding of 0.5 mm thin sheets is conducted in continuous wave mode to analyze the significance and influence of process parameters, i.e., beam diameter, welding speed and laser power on the mechanical and metallurgical properties of the joints. Welding speed is found to be the most significant process parameter, which controls the changes in the mechanical and metallurgical properties. Bead profile, hardness, tensile strength, microstructural and phase variations in these joints are evaluated to study their dependence on the welding speed varied in the three levels of 1000 mm/min, 1250 mm/min and 1500 mm/min. Welding speed alters the cooling rate; cooling rate regulates the grain refinement, phase change and ultimately alters the hardness, and tensile strength of the fusion zone (FZ). The increment in hardness value in the FZ and loss of ductility as compared to base metal can be attributed to some hard and brittle phases (Nb6C5 and NbC) formed due to increased welding speed. The failure of the welded joints after the tension tests is observed to be located in both FZ and the base metal, that indicates both the brittle and ductile modes of failure in the FZ of the samples having hardness value (VHN)>410 and base metal, respectively.

The Electron Beam welding (EBW) process was employed to fabricate 18 mm thick fully penetrated butt welds of AISI 321 stainless steel. Nail shaped weld wide at the top and narrow at the bottom was obtained. Characterization of the weld joint was carried out using optical microscopy, scan electron microscopy, X-ray diffraction, microhardness, impact toughness test and tensile strength test. The microstructure of the weld metal was found to be free from defects like cracks porosity etc. The weld metal consisted of the primarily austenitic matrix with skeletal and vermicular morphology of δ-ferrite by the side of the grain boundaries. Carbides of Cr and Ti were found in the weld metal after the thermal aging treatment of 750°C for 24 hours as reveled by the XRD analysis. The tensile strength study revealed a maximum strength of 575 MPa at the root of the weld joint in the as-welded state. The maximum impact toughness of 129.3 J was obtained in the top section of the weld in the as-welded condition. The results in terms of structure-property correlaterelationship. This study recommends the effectiveness of EBW for joining 18 mm thick AISI 321.

Ultrasonic vibration-assisted plasma arc welding with controlled pulse current waveform was developed to weld the 8 mm thick stainless steel plates. Both bead-on-plate and butt welding experiments were carried out with open-loop and closed-loop control strategies under different welding conditions. The signals of welding current and efflux plasma voltage and the images of keyhole exit were sensed to monitor the keyhole status during the welding process. It was found that the ultrasonic vibration-assisted plasma arc can completely penetrate the stainless steel plates with the thickness of 8 mm in a single pass with higher welding speed or lower peak welding current in controlled pulse keyhole mode. By continuous real-time adjustment of welding current waveform in closed-loop strategy, the “one-pulse-one-open keyhole” mode was achieved successfully with lower welding heat input. Due to the reduction of heat input and further constriction of plasma arc under the action of ultrasonic vibration, the weld was narrowed and the depth-width ratio was raised.

Narrow gap TIG welding is a high efficiency and low-cost welding technique for heavy structures building. Due to the narrow groove’s constriction, the TIG arc characteristics are different from butt welding. Understanding the unique arc characteristics of narrow gap TIG welding is the foundation for investigating the heat and mass transfer, metallurgic process, as well as process design. This research conducted numerical simulation on the TIG arc plasma in the narrow groove. The effects of welding current and arc length on the arc characteristics are investigated. Results show that, with the welding current increasing, the global velocity magnitude of plasma rises. The evolution of axial velocity and radial velocity has different responses to the current changes. The arc pressure increases drastically, and the global temperature of arc plasma also goes up. With the arc length increasing, global axial velocity rises, but the axial velocity and its gradients decrease near the anode surface. Centripetal radial velocity near the cathode increases, while centrifugal radial velocity rises at the outside of arc plasma and drops near the central axis. The maximum arc pressure on the anode surface decreases. At the lower part of the arc, arc temperature decreases near the central axis and increases at the outside of the arc.

The joining of plastics is required because component geometries are severely restricted in conventional manufacturing processes such as injection molding or extrusion. In addition to established processes such as hot plate welding, infrared welding, or vibration welding, hot gas butt welding is becoming more and more important industrially due to its advantages. The main benefits are the contactless heating process, the suitability for glass fiber reinforced, and high-temperature plastics as well as complex component geometries. However, various degradation phenomena can occur during the heating process used for economic reasons, due to the presence of oxygen in the air and to the high gas temperatures. In addition, the current patent situation suggests that welding with an oxidizing gas is not permissible depending on the material. On the other hand, however, there is experience from extrusion welding, with which long-term resistant weld seams can be produced using air. Investigations have shown that the same weld seam properties can be achieved with polypropylene using either air or nitrogen as the process gas. Experimental investigations have now been carried out on the suitability of different gases with regard to the weld seam quality when welding polyamides, which are generally regarded as more prone to oxidation. The results show that weld strengths are higher when nitrogen is used as process gas. However, equal weld strengths can be achieved with air and nitrogen when the material contains heat stabilizers.

Box-type steel structure has been widely applied in the field of buildings and bridges because of its unique advantages. However, there are still many problems in field welding that need to be solved. In order to improve the level of automation and intellectualization in field welding of box girder, a new type of on-site all-position welding robot system is developed and designed in this paper. The convenience of on-site installation and debugging of the robot is realized by the scheme of permanent magnet adsorption and straight-arc combined track. The motion matching scheme of bilateral wheel-axle clamping makes the circumferential movement of the robot much smoother and more stable which makes the system with better overall force characteristics and load-carrying capacity. Then, a novel visual sensor based on combined laser structured lights is proposed and designed, which can realize several functions such as groove parameters detection, welding joint tracking and torch posture detection in field welding based on single detection image, so as to effectively improve the flexibility and intelligence of field welding robot. After that, based on the designed visual sensor and welding robot system, a visual servo-control system based on Visual Studio platform is established. Through the effective integration of detection image reading, image processing and calculation, image feature parameters transmission, motion control board call and feedback control signal output, the adjustment and control of welding torch's position and posture based on visual servo-control are realized. Furthermore, based on the kinematics calculation and the welding process requirements of the box girder, the welding process design is planned for the all-position welding of the box steel girder, which solved the technical problem of the rectangular fillet welding in the box steel butt welding (the welding torch position and posture transition control in right-angled corner of girth butt joint). Finally, all-position welding experiments of box steel girder were carried out. The results show that the welding robot based on visual servo-control can realize better control of weld formation in all-position welding of box steel girder.

The consideration of residual stresses in fatigue-loaded welds is currently done only qualitatively without reliable knowledge about their real distribution, amount and prefix. Therefore, the tools which enable a more or less unsafe consideration in design concepts are mainly based on unsafe experiences and doubtful assumptions. Since the use of explicitly determined residual stresses outside the welding community is state of the art, the target of the presented paper is to show a practicable way for an enhanced consideration of residual stresses in the current design tools. This is not only limited on residual stresses induced by welding, but also on post-weld treatment processes like HFMI or shot peening. Results of extended experiments with longitudinal fillet welds and butt welds of low and high strength steels evidently show that an improved use of residual stresses in fatigue strength approximation enables a better evaluation of peening processes as well as of material adjusted welding procedures or post-weld stress relief treatments. The concept shows that it is generally possible to overcome the existing extremely conservative but although unsafe rules and regulations and may also enable the improved use of high strength steels.

Heat input for gas tungsten arc welding process was varied at three different levels to fabricate three AISI 304L stainless steel welds to examine the influence of variable arc energy input on their sensitization and pitting performance. Welds were subjected to post-weld thermal aging treatments comprising of low-temperature sensitization of 500 °C for 1, 5, and 11 days and classical sensitization of 650 °C for 1, 12, and 24 h. Different morphologies of ferrite present in the fusion zone and the degree of the coarsening of grains in the heat-affected zone (HAZ) of the weldments under different aging conditions influenced their tendencies for carbide formation, which consequentially affected their sensitization and pitting corrosion behavior significantly. Lower heat input welds having lathy morphology of δ-ferrite in the fusion zone along with less coarsened HAZ exhibited a lesser degree of carbide precipitation. They hence showed a lower degree of sensitization (DOS), which accounted for higher pitting potential (Epitt). However higher heat input welds having vermicular morphology of δ-ferrite in the fusion zone and relatively higher grain coarsened HAZ promoted a higher degree of carbide precipitation, and thus accounted for the higher value of DOS and lower pitting potential (Epitt).

In the process of K-TIG deep penetration welding, the workpiece does not need to be bevelled; therefore, the welding method is butt welding, and the gap to be welded is very narrow (0.2~1 mm). Because of the large welding current, the welding arc light intensity is very strong. These factors cause difficulties in the K-TIG weld seam tracking process. To realize weld seam tracking in the K-TIG welding process, it is necessary to extract the keyhole entrance centre and weld centreline accurately. To reduce the interference of strong arc light in the process of K-TIG welding, the information of keyhole entrance and weld seam in the process of K-TIG welding is obtained by using a high-dynamic-range camera. An image processing algorithm based on Mask-RCNN is proposed to extract the centre of the keyhole entrance accurately. An image processing algorithm based on Hough line fitting is used to accurately identify the weld centreline in the welding image and extract the welding deviation. In welding experiments, it is verified that the welding deviation extracted by the method proposed in this paper fluctuates within ± 0.133 mm, which meets the requirements of actual K-TIG welding seam tracking.

Small-opening slots have been used to simulate cracks in butt welds. The influence of the orientation of the slot ribs on their detectability with pulse echo and diffraction methods of ultrasonic testing has been studied. It is shown that the processes occurring during the scattering of elastic waves on cracks should be modeled by a three-dimensional problem. However, theoretical analytical and numerical studies in this area most often concern two-dimensional problems of diffraction of elastic waves, where the target edge under study is located on the acoustic axis of the ultrasound source and/or receiver and is oriented perpendicular to the incident beam. The article presents experimental results illustrating the influence of the orientation of the edge (rib) in three-dimensional problems on the received signals both when using diffraction schemes of the TOFD type, and in classical ultrasonic testing by the pulse echo method according to the “tandem” scheme and with the transducers turned according to the “duet” scheme.

Experimental testing of flash-butt welded premium rail steel samples was undertaken to quantify the variation in strength through the cross-section of the weld, with results showing a general correlation between the width of the heat-affected-zone and the ultimate tensile strength. Microstructural examination and fractography revealed the presence of defects in some samples. Large defects can be identified by non-destructive testing methods as part of routine structural integrity assessment; however, small defects may escape detection but could propagate under cyclic loading in service leading to catastrophic failures. This work demonstrates the requirement for stringent control of heat input to prevent the development of defects in premium rail steels with high alloying content.

Double-sided synchronous TIP TIG arc butt welding (DSSTTABW) is firstly carried out to join 5-mm SAF 2205 duplex stainless steel (DSS) plates without grooving. The microstructure and mechanical properties of DSSTTABW joints, including microhardness, transverse tension, and bend properties, are evaluated systematically. Results show that sound DSS joint, with excellent appearance and properties, can be obtained through the DSSTTABW process. In DSSTTABW joints, a deal of second austenite (γ2) appears in the weld metal, resulting in a slight increment of austenite volume fraction of the weld zone. Meanwhile sigma (σ) phase precipitates at the grain boundaries of delta ferrite (δ-Fe) and austenite of the weld zone. Mechanical property tests show that the DSSTTABW weldment exhibits higher tensile strength and microhardness but lower ductility compared to 2205 DSS base metal due to the existing Widmanstten-type austenite (WA) and σ phase. All weldments fracture at the weld zones in the mode of ductile. After bending tests, no surface cracks are observed on the DSSTTABW joint.

For welding path determination, the use of vision sensors is more effective compared with complex offline programming and teaching in small to medium volume production. However, interference factors such as scratches and stains on the surface of the workpiece may affect the extraction of weld information. In the obtained weld image, the weld seams have two distinct features related to the workpiece, which are continuous in a single process and separated from the workpiece’s gray value. In this paper, a novel method is proposed to identify the welding path based on the region of interest (ROI) operation, which is concentrated around the weld seam to reduce the interference of external noise. To complete the identification of the entire welding path, a novel algorithm is used to adaptively generate a dynamic ROI (DROI) and perform iterative operations. The identification accuracy of this algorithm is improved by setting the boundary conditions within the ROI. Moreover, the experimental results confirm that the coefficient factor used for determining the ROI size is a pivotal influencing factor for the robustness of the algorithm and for obtaining an optimal solution. With this algorithm, the welding path identification accuracy is within 2 pixels for three common butt weld types.

Flash butt weld process parameters determine the weld quality. The presence of weld defects due to inappropriate process parameters leads to entrapment of oxides in the weld causes premature failure. It was also observed that the flash butt process parameter is dependent on the chemistry of the steel that is processed. The high weight percentage of Mn and Si leads to a higher weight fraction of the oxides during welding. Altering the flashing length and upset length leads to the elimination of weld defects achieving full joint strength. Thermodynamic calculations predict the oxides to be primarily FeO, Fe2O3 (hematite), and SiO2 (cristobalite) along with the presence of MnO, Mn2O3, and Cr2O3. The presence of Mn, Al, and Ti in the oxides at the fractured surface is correlated with the chemical potential of these elements in the liquid steel. It can be inferred from the modeling and experimental results that with an increase in temperature, a more liquid slag phase is formed as compared to solid oxides. Slag is less viscous and can be easily extruded during the upsetting stage as opposed to solid inclusion which can be trapped during the welding operation.

The framework for a fatigue assessment of welded joints under service loading conditions of crane structures from the low cycle to the high cycle fatigue regime includes the consideration of elastic-plastic material behavior, variable amplitude loading, and acceptable calculation times. Therefore, an integral treatment of butt joints has been developed for fatigue life estimation. The butt weld is considered in its entirety, so that it can be described by its cyclic behavior. The evaluation of the cyclic stress-strain behavior and tri-linear strain-life curves of butt joints for different high-strength, fine-grained structural steels, derived by strain-controlled fatigue tests, is the basis for this description. This procedure is not limited to conventionally applied gas metal arc welding only, but also the fatigue assessment of laser beam welding is possible, for example. Cyclic transient effects have been analyzed and a distinctive cyclic softening is described by linearization of Ramberg-Osgood parameters, depending on the damage content of each cycle derived from constant amplitude, strain-controlled tests. On the basis of the cyclic behavior in combination with memory and Masing behavior, a simulation of the stress-strain paths of investigated butt welds, under constant and variable amplitude loading, has been performed. Damage parameters are used to accumulate the damage cycle by cycle in order to derive the fatigue lifetime. Finally, calculated fatigue lives were compared with experimentally determined lives, showing the impact of this procedure.

Residual tensile stresses generated during butt welding of plates using arc welding process lead to deformation and deterioration of fatigue strength of welded parts. This research implemented particle swarm optimization (PSO) algorithm to present optimum welding parameters to minimize the tensile residual stresses of butt-welded 304 stainless-steel plates with 4–15 mm thicknesses. A set of 32 experiments was designed using Taguchi method and simulated using ABAQUS commercial software based on element birth-and-death finite element technique. An artificial neural network and PSO were utilized to discover the optimum welding settings. To ensure the accuracy of simulation results, slitting method was implemented to measure residual stresses utilizing digital image correlation technique beside the strain gauges.

Electron beam butt welding of zircaloy-4 plates of dissimilar thickness (with different thickness ratio, defined as the thickness of one side plate with variable thickness to that of another reference plate of fixed thickness) was performed in order to investigate the effect of plate thickness on the evolution of cooling rate, microstructure and its correlation to mechanical properties. Faster cooling rate on thicker plate results in lower peak temperature, finer grain size both in fusion zone and heat-affected zone with more but uniform porosity distribution than those in the thinner plate. The size of HAZ was higher on thinner plate compared with that of thicker plate. Although the width of fusion zone remained unaffected, the depth of penetration decreased with increase in thickness ratio at same heat input rate. Fusion zone consisted of columnar grains with lamellar widmanstatten features, while HAZ consisted of equiaxed grain with randomly oriented small acicular α-Zr phase in β-Zr phase. A small amount of fine second-phase particles of Zr(Fe,Cr)2 was identified in the fusion zone, which affected the tensile properties marginally. Weld failed in the base metal during tensile test, and YS and UTS are found to be comparable to that of base metal. However, the ductility and notch toughness of the joint was found to be inferior to those of base metal, which deteriorated with increase in thickness ratio. At constant heat input, porosity was found to be higher in dissimilar joint than its similar counterpart, which might be one of the reasons for inferior ductility and notch impact strength in addition to unfavourable microstructural features.

The present investigation focused on parametric optimization for improving joint efficiency of friction stir welded nylon-6 sheets using particle swarm optimization algorithm using a response surface method-based regression model. Initially, parametric effects on weld quality characteristics such as weld bead profile, bead shape and its microstructure along with micro-hardness variation and stress–elongation behavior of the butt weld have been studied considering cylindrical, square and triangular pin contours. The thermal cycles along advancing and retreating side of tool rotation have also been acquired during welding which was further used in the response surface models for the improvement in weld quality prediction capability. The joint efficiency was found to be maximum (49.68%) at intermediate value of each parameter using square pin. The material scooping action and undercut defects along with non-uniform grain morphology with micro-cavities were primary reasons for weld failure at weld interface. The response surface-based regression model of joint strength of the weld was significant, whereas weld hardness and percent elongation were found to be insignificant. However, weld peak temperature with associated cooling rate-based regression models was found to be highly adequate as per substantial improvement for the prediction of each weld quality-based features. Finally, response surface-based regression model of joint strength was further used for parametric optimization using response surface method as well as evolutionary particle swarm optimization tools. The particle swarm optimization was found to be more precise with better optimization capability than response surface methodology.

The present investigation is concerned with high‐cycle axial fatigue testing of a 2‐mm AA6060‐T6 hybrid metal extrusion & bonding (HYB) butt weld produced in the solid state using AA6082 filler metal addition. The results complement the three‐point bend testing and the tensile testing done in two previous studies. In this study, optical microscope and scanning electron microscope examinations have been carried out to reveal the joint macro/microstructure and document possible surface and root defects deemed to affect fatigue life. In the as‐welded condition, the HYB weld suffers from surface irregularities at the weld face and ‘kissing’ bond formation in the root region. Despite of this, the subsequent testing shows that the fatigue properties exceed those reported for comparable AA6082‐T6 gas metal arc butt welds and matching those reported for corresponding high‐strength laser beam and friction stir weldments. © 2020 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

We survey various state-of-the-art methods for welding magnesium alloys and steels using different joint configurations. Microstructural characterizations indicate that four microstructures may form at the Mg/steel interface after welding: unwelded gap, metal oxides, solid solutions, or intermetallic compounds. Reaction products at the Mg/steel interface vary with different welding methods, alloying elements in base materials, interlayers or coatings applied, and preparations of base material before welding. Mechanical property characterizations, (a) lap tensile shear testing for lap-welded and spot-welded joints, (b) tensile testing for butt-welded joints and (c) fatigue properties of lap-welded and spot-welded joints are summarized and compared, separately. Reaction products at the Mg/steel interface are correlated with mechanical properties. Finally, ways to enhance Mg/steel joint strength, such as introducing interlocking features during friction stir lap and butt welding, are discussed.

Laser cleaning technology for pre-weld and post-weld treatments is a promising market due to its high efficiency and consistency, easy operation, and eco-friendly features. The weld quality influence of laser cleaning pre-treatment for the succeeding laser welding of the widely used industrial HSLA steel plates has been investigated in this work. The experimental results show that the laser cleaning pre-treatment can effectively remove the rusting and grease from the workpiece surface, create a corrugated micro-groove texture which could increase the absorption rate of the laser beam energy, help avoid the occurrence of pores and cracks in the weld, and significantly increase the mechanical properties of laser butt welding joints (30% for the tensile strength, 200% for the elongation). These experimental results should be helpful for developing hybrid laser cleaning & welding technologies for the emerging high-performance weld applications in practices.

We analyze the influence of numerous factors, such as an NS4 model soil medium, the load ratio (R = 0.1 and 0.9), and the potential of cathodic protection (–0.98 V) on the cyclic crack-growth resistance of the base metal and the metal of circular butt weld of 17G1S pipe steel in the intact state and after 30 years of the operation in a gas main. It is shown that the long-term operation of steel maximizes the negative influence of the soil medium on its cyclic crack-growth resistance under the combined action of the high load ratio and high potential of cathodic protection.

Full-penetration butt welds are often specified to connect the beam flanges to the column flange in welded moment resisting connections. Partial-penetration butt welds are cheaper than full-penetration butt welds and also more cost effective when compared to large fillet welds. EN 1993-1-8 standard includes a definition of an “effective full penetration of T-butt welds” implying that it can be used to replace butt welds leading to cost savings. This study evaluates the seismic performance of welded beam-to-column connections using effective full penetration of T-butt welds. Three full-scale T-shaped specimens were tested under cyclic loading. The results demonstrate that the effective full-penetration butt welds work very well under seismic loading, forcing the failure mode into the beam and enabling considerable energy to be dissipated within the beam plastic hinge, with no failure in the beam to column welds. Mock-up specimens were fabricated under real workshop conditions to examine the feasibility of reliably fabricating the weld penetration profiles required by EN 1993-1-8. This paper makes recommendations to the use of “equivalent strength” partial-penetration butt welds that can be used by the designer and/or fabricator to replace full-penetration butt welds.

The effect of metal transfer modes on mechanical properties of welded 3CR12 stainless steel was investigated. This was achieved by butt welding 10 mm thick plates of 3CR12. The effect of the metal transfer modes on the microstructure and the mechanical properties of the 3CR12 steel was then investigated as it was hypothesized that the change in welding positions will affect the transfer modes partly because of gravity. The microscopic examination revealed that the substrate was characterized by dual phase microstructure. Using the spectroscopic examination results, the ferritic factor calculation had shown that the microstructure was expected to be ferritic–martensitic during air cooling process. The tensile strength and Charpy impact energy were measured to be 498 MPa and 102 J, respectively. The heat input in the material was observed to be greater than 1 kJ/mm, which is the limiting factor for grain growth. Grain growths were observed in the heat affected zone of the welded materials. Ferritic–martensitic microstructure was observed in the microstructure. The grain growth altered the mechanical properties of the test material. Globular down hand had higher mechanical properties than spray down hand. Globular vertical up had better mechanical properties than globular vertical down.

The fracture mechanics-based IBESS approach is applied to the determination of FAT classes of butt welds with crack initiation along the weld toe. The aim is an investigation of the effect of the geometrical parameters toe radius, flank angle, reinforcement and secondary notches such as roughness or undercuts. The influence of these parameters is discussed both individually and in combination; however, excluding statistical distributions of them and the material data. The results, when compared with conventional FAT classes for butt welds, are encouraging with respect to a potential contribution of IBESS to the discussion of more advanced quality criteria for welds. To that purpose, demands for further research are proposed.

In this task, a numerical study is utilized to determine the residual stress of the flash butt joint in the UIC60 rail. To accurately predict critical locations of tensile residual stress, the infl...

Corrosion fatigue behavior of Alloy 52/52M dissimilar metal weld (DMW) was investigated in borated and lithiated high-temperature water. The fatigue life of Alloy 52/52M DMW in high-temperature water decreased in comparison with that in air. The fatigue cracks initiated at Alloy 52M butt weld or at the interface of Alloy 52 buttering and Alloy 52M butt weld. The welding residual strain and ductility dip cracking in Alloy 52M butt weld promoted the initiation and propagation of fatigue cracks. The environmentally assisted fatigue damage in high-temperature water is discussed by taking account of microstructure defects.

Electron beam welding (EBW) is widely used to connect thin-walled high-temperature alloy structures in aeroengines. However, the residual stress and deformation caused by the high-temperature gradients generated during welding would affect the rigidity, dimensional stability, and fatigue resistance of the welded structures. The study reported here used a model combining ellipsoidal and Gaussian rotating body heat sources to undertake a numerical simulation of the temperature and residual stress generated during the EBW process. The model was systematically refined by observing and measuring the molten pool morphology. The error rates for key dimensions determining the molten pool shape were less than 6%. With a microscope-based examination, the energy distribution characteristics were detected by the microstructure analysis of grain type and size in different regions to verify the viability of the heat source model. The residual stress of a butt welding was simulated by the proposed heat source model based on the full consideration of a full-loop thin-walled combustor casing structure and material properties. It was found that the average errors for longitudinal and transverse residual stresses of welded joints and their adjacent areas were 10% and 12%, respectively, by comparing with the experimental results. Simultaneously, the low cycle fatigue life of the welded combustor casing would be decreased by 32% considering the influence of welding residual stress. These conclusions can be used as a basis for studying the integrity of thin-walled welded structures in aeroengines.

In this research, the effect of pulse currents on the weld geometry and angular distortion in pulsed GTAW (PGTAW) process in 3 mm thick SS-304 autogenous butt weld joint was investigated. Welding method uses pulse current and continuous current. The mean current and welding speed were kept constant with the peak current and base current were varied. During pulsed GTAW process, the arc condition was captured directly using a charge-coupled device (CCD) camera. Weld geometry was carried out using a digital microscope. Distortion was measured using Coordinate Measuring Machine (CMM). The results show that the peak current and base current have an influence on weld geometry and angular distortion. The weld geometry on pulsed GTAW was produced wider of weld bead width than continuous GTAW. However, angular distortion on continuous GTAW was higher than pulsed GTAW. Pulsed GTAW can widen the weld bead by 0.57% - 25.09%, but can reduce distortion by 15.15%-88.17%. As compared with weld geometry to the continuous GTAW, the widest result occurs at peak current 212A and base current 40A. The smallest of distortion on pulsed GTAW was achieved at peak current 138A and base current 80A.

High strength low alloy steels subjected to the thermomechanical control process present excellent strength–toughness combination, high strength/weight ratio, and weldability. Therefore, they are widely used in structural components, such as pressure vessels, oil/gas transportation pipes, lifting equipment, vehicles, shipbuilding and offshore industries, and in the automotive industry where low thickness (0.8–3 mm thickness) is of great importance. Usually, these steels are welded by conventional gas metal arc welding, which creates wide heat-affected zones, large residual stresses, and distortion in the welded parts. Laser welding is nowadays an alternative process to weld high strength low alloy steel parts due to its advantages. The aim of this work is to understand the effect of process parameters on defects, weld bead geometry, microstructure, and mechanical properties, namely hardness and tensile strength. We identify the main laser welding parameters and their influence on the weld bead geometry and defects, for a 3 mm thick high strength low alloy steel welded under a maximum power of 2 kW. A cross section of the weld seam was optimized achieving a good geometry without porosity. The threshold value of the heat input to achieve complete penetration was determined for different focus diameters. The microstructure, size, and hardness of the heat-affected zone and of the fusion zone are strongly influenced by the heat input. The values of the tensile strength achieved in butt welds were close to the base metal by an appropriate selection of the laser welding parameters and the heat input.

This paper describes the experimental study of strength characteristics and the microstructure of a permanent joint of dissimilar materials (VT20 titanium alloy and V-1461 aluminum alloy), obtained by laser butt welding. Optical and electron microscopy, X-ray spectral and phase analysis, and the transmission diffraction method with the help of synchrotron radiation are all used to investigate the properties of a weld. It is shown that the laser radiation offset relative to the contact surface of dissimilar materials significantly changes the microstructure and phase composition of the intermetallic interlayer formed between the materials welded, thereby affecting the strength of dissimilar welded joints.

Dissimilar metal welding leads to the development of brittleness in the welded joints due to incompatibility in mechanical and physical properties of the metals to be joined. To overcome such brittleness, suppressing the formation of intermetallic compound is the key factor for attaining reliable welded joints. The present study attempts to find the possibility of obtaining joints of crack-free surface in laser butt welding of Ti6Al4V with AISI 304 stainless steel sheets using intermetallic layer through electroplating process. Laser welding on Ti6Al4V titanium alloy with AISI 304 stainless steel sheets of 5 mm thickness has been performed providing copper as an intermetallic layer using electroplating process. Electroplating of the welding edges of two different materials was carried out with and without adding sulphuric acid in the electrolyte solution. The electroplating results indicate that addition of sulphuric acid in the solution increases the thickness of the coating. Presence of copper at the welding edges provides compatibility between Ti6Al4V and AISI 304 during the laser welding process and reduces brittleness. Laser welding was conducted using 3.5-kW CO2 laser with 3-m/min welding speed. The quality of weldment was characterized by macrostructure analysis by scanning electron microscope (SEM), analysis of composition of weldment by energy dispersive spectroscopy (EDS), phase analysis by X-ray diffraction (XRD), microhardness across the weldment by Vickers hardness tester and estimation of welding strength by dynamic mechanical analyser. Welding strength of around 34 MPa has been obtained and it is quite acceptable.

Most Japanese shipyards that build general merchant ships use arc welding, but they always have the problem that the accuracy of the hull construction is poor as a result of the thermal deformation caused by arc welding. As one method to overcome this problem, it is expected to adopt laser arc hybrid welding that can suppress the total heat input as a result of heat input concentration, but the initial introduction cost is high and this welding method has a poorer gap tolerance than conventional arc welding. In addition, few experiences to apply laser arc hybrid welding for constructing the joints at the plate thickness level used for hull members of general merchant ships. An improved procedure to fabricate a butt joint with a plate with a thickness of 15 to 20 mm, which is widely applied as a hull member of general merchant ships, is proposed in this study. Proposed procedure is that the Λ-shaped groove with a very small angle and one-pass welding by laser arc hybrid welding with CO_2 gas shielded arc welding to satisfy the weld reinforcement on the front side weld bead. The joint quality manufactured by using our proposed procedure was confirmed according to the Guidelines for Laser Arc Hybrid Welding by a classification society Nippon Kaiji Kyokai (ClassNK). It is expected to be introduced as an alternative method of plate joint welding for hull members, especially submerged arc welding with large heat input.

Recently, pipe welding has been widely applied in the pipe fitting operations. There are many types of pipe welding facilities available. In this research work, experimental investigations related to Electro fusion and Butt fusion welding of HDPE pipe and optimization of different welding process parameters are performed. In electro-fusion welding a fitting device is used for joining of two pipes namely called ‘fusion coupler’. Fusion coupler has a copper coil which is wounded in inner surface of coupler. Two pipes are fitted in the coupler and the current is applied in the coil with the help of kitrik pin which has provided in the coupler to generate heat and finally to create the weld. In butt-fusion welding for joining of two pipes, the welded joint is produced with the help of heated plate. After performing the welding, the joints are tested for tensile strength using universal testing machine. Two performance parameters viz. temperature and tensile strength and three process parameters viz. Starting Welding voltage, Specific fusion time and Cooling time for Electro fusion welding and Heating plate temperature, Drag pressure, Welding pressure for Butt fusion welding of HDPE pipes (82 mm inner diameter and 8 mm wall thickness) are optimized using Grey relational analysis optimization technique. The optimized parameters for electro fusion welding of these pipes are welding voltage, specific fusion time, cooling time and optimized parameters for Butt welding are heating plate temperature, drag pressure, welding pressure.

The present investigation is concerned with the high-cycle axial fatigue behaviour of a third generation Al-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB). In this particular weld, metallurgical bonding is achieved by a combination of microscale mechanical interlocking and intermetallic compound (IMC) formation, where the IMC layer is in the sub-micrometre range (

The demand for dissimilar joining of steel grades, namely austenitic stainless steels to low-alloy steels, may increase in near future owing to the fact that the storing of LNG is currently becoming a necessity, particularly in Europe, due to the shortage of supply or interruptions in the supply. Therefore, successful dissimilar joining of steel grades using traditional fusion welding techniques in such applications is required. In this study, butt-welded joints of AISI 316L austenitic steel and low-alloy steel plates (containing 9% Ni) of 10 mm thickness were fabricated by gas tungsten arc welding employing a Ni-based filler wire. The microstructure and mechanical properties of the weldment were examined by detailed optical microscopy, extensive micro-hardness measurements, and tensile tests. Further, fracture toughness of the joint at cryogenic temperatures (- 196 degrees C) was also determined by Charpy impact test. The dissimilar joint exhibited a high tensile strength of 633 MPa, which is higher than that of the lower-strength AISI 316L base plate (about 600 MPa), while its elongation (21%) was much lower due to confined plasticity. The lowest impact energy was displayed by HAZ-F notched specimens, namely about 62.6 J (0.83 J/mm(2)). However, it is still reasonably above the minimum impact energy specified for the LNG storage tanks, i.e., 0.75 J/mm(2).

Reduced-pressure electron beam (EB) plate butt welds were manufactured in two low-alloy pressure-vessel steels, SA508 Gr 3 Cl 1 and SA508 Gr 2, at two thicknesses in both steels, 30 mm and 130 mm. Transient temperatures during welding were recorded using thermocouple arrays. Residual stresses in the as-welded condition and after post-weld heat treatment were measured using diverse methods: neutron diffraction and the contour method at 30 mm thickness; and deep hole drilling and the contour method at 130 mm. Incremental centre hole drilling measurements were performed at 130 mm thickness to better understand near-surface stresses. Weld and heat-affected zone microstructures and microconstituents were evaluated using a combination of hardness mapping, optical microscopy and electron microscopy. The as-welded residual stresses exhibit the characteristic M-shaped distribution for hardenable steels, reaching 500–600 MPa in tension in both steels at both thicknesses. However, the modest changes to the chemical composition and the change in plate thickness both significantly influenced microstructures, mechanical properties and residual stress distributions. These sensitivities underline the need for physically faithful models. This extensive characterisation study enables the development and validation of models that predict the development of microstructures and residual stresses in EB welds in low alloy pressure vessel steels.

As complete elimination of porosity from the weld is very difficult, the next option available is to minimize this weld porosity, which is crucial for the safe performance of the welded components. However, this investigation through experiments alone is very tedious and time consuming. Additionally, very limited models are available in the literature for accurate prediction of different porosity attributes. The present study, thus, addressees both the experimental as well as modelling aspect on the study of micro-porosity during Electron Beam Welding (EBW) of SS304 plates. Welding parameters are reported to have significant influence on the micro-porosity. Hence, the influences of these parameters on micro-porosity attributes, namely pores number, average diameter, and sphericity are extensively studied experimentally employing optical microscopy (OM), scanning electron microscopy (SEM), X-ray computed tomography (XCT), and Raman spectroscopy. This is followed by an elaborate modelling through seven popular and well-recognized Machine Learning Algorithms (MLAs) namely, Multi-Layer Perceptron (MLP), Support Vector Regression (SVR), M5P model trees regression, Reduced Error Pruning Tree (REPTree), Random Forest (RF), Instance-based k-nearest neighbor algorithm (IBk) and Locally Weighted Learning (LWL). These different techniques enhance the chance of obtaining the better predictions of the said micro-porosity attributes by overcoming the effect of data-dependence and other limitations of individual MLAs. The different model-predicted micro-porosity data are also validated through experimental data. Statistical tests and Monte-Carlo reliability analysis are additionally utilized to evaluate the performances of the employed algorithms. IBk and MLP are overall found to perform well.

The main objective of this paper was focused on a numerical study related to a proper evaluation of the temperature field during the laser-welding process. The investigated material used for the experiments was Fe3Al, given its properties and promising application potential. The original experiment was based on a 3D model of a butt weld. However, to reduce the computational complexity, a planar variant of the heat-transfer equation with suitable choices of surface and volumetric heat sources, given by modified Gaussian pulses, is used to model the temperature distribution in the fixed cross cut during the laser welding. Subsequently, the numerical scheme based on the discontinuous Galerkin method was employed to evaluate the temperature field more properly and to identify the main characteristics of the molten zone. Finally, the numerical study was performed for various combinations of the welding parameters, such as laser-beam power and welding speed. The obtained results were in good agreement with the expected behavior, and thus illustrate the optimization potential of the proposed numerical scheme in the similar issues of a laser-welding processes.

Intelligent welding parameter control is fast becoming a key instrument for attaining quality consistency in automated welding. Recent scientific breakthroughs in intelligent systems have turned the focus of adaptive welding control to artificial intelligence-based welding parameter control. The aim of this study is to combine artificial neural network (ANN) decision-making software and a machine vision system to develop an adaptive artificial intelligence (AI)-based gas metal arc welding (GMAW) parameter control system. The machine vision system uses a laser sensor to scan the upcoming seam and gather seam profile data. Based on further processing of the seam profile data, welding parameters are optimized by the decision-making system. In this work, the developed system is tested in a multivariable welding condition environment and its performance is evaluated. The quality of the welds was consistent and surpassed the required quality level. Additionally, the heat-affected zone (HAZ) was evaluated by microscopy, X-ray, and scanning electron microscope (SEM) imaging. It is concluded that the developed ANN system is suitable for implementation in automated applications, can improve quality consistency and cost efficiency, and reduce required workpiece preparation and handling.

A discussion is provided on demands that must be met in order to apply fracture mechanics to the determination of overall fatigue lifetime and strength, i.e., S-N curves and fatigue limits. These comprise the determination of the cyclic crack driving force for all stages of fatigue crack propagation, in particular for the short crack stage where the crack driving force has to be determined for elastic-plastic deformation and the gradual build-up of the crack closure phenomenon. Special emphasis is put on a fatigue damage relevant specification of the initial crack size. Different approaches in the literature are discussed. Another important aspect is the adequate treatment of multiple crack propagation. Finally, the discussion is illustrated by an example of a butt weld made of a medium strength steel.