Search Results (90)

The inferior electrical conductivity and elevated hardness of AgSnO₂ electrical contact materials have impeded their development. To investigate the effects of Co, Bi, and La doping on the stability and electrical properties of AgSnO₂, this study established interfacial models of doped AgSnO₂ based on first-principles calculations initiated from the atomic structures of constituent materials, subsequently computing electronic structure parameters. The results indicate that doping effectively enhances the interfacial stability and bonding strength of AgSnO₂ and thereby predicted improved electrical contact performance. Doped SnO₂ powders were prepared experimentally using the sol–gel method, and AgSnO₂ contacts were fabricated using high-energy ball milling and powder metallurgy. Testing of wettability and electrical contact properties revealed reductions in arc energy, arcing time, contact resistance, and welding force post-doping. Three-dimensional profilometry and scanning electron microscopy (SEM) were employed to characterize electrical contact surfaces, elucidating the arc erosion mechanism of AgSnO₂ contact materials. Among the doped variants, La-doped electrical contact materials exhibited optimal performance (the lowest interfacial energy was 1.383 eV/Ų and wetting angle was 75.6°). The mutual validation of experiments and simulations confirms the feasibility of the theoretical calculation method. This study provides a novel theoretical method for enhancing the performance of AgSnO₂ electrical contact materials. Full article

The microstructure and mechanical properties of welded joints of API 5L X-52 steel plates cladded with AISI 316L-Si austenitic stainless steel were evaluated. The gas metal arc welding process with pulsed arc (GMAW-P) and controlled arc oscillation were used to join the bimetallic plates. After the root welding pass, buttering with an ERNiCrMo-3 filler wire was performed and multi-pass welding followed using an ER70S-6 electrode. The results obtained by optical and scanning electron microscopy indicated that the shielding atmosphere, welding parameters, and electric arc oscillation enabled good arc stability and proper molten metal transfer from the filler wire to the sidewalls of the joint during welding. Vickers microhardness (HV) and tensile tests were performed for correlating microstructural and mechanical properties. The mixture of ERNiCrMo-3 and ER70S-6 filler materials presented fine interlocked grains with a honeycomb network shape of the Ni–Fe mixture with Ni-rich grain boundaries and a cellular-dendritic and equiaxed solidification. Variation of microhardness at the weld metal (WM) in the middle zone of the bimetallic welded joints (BWJ) is associated with the manipulation of the welding parameters, promoting precipitation of carbides in the austenitic matrix and formation of martensite during solidification of the weld pool and cooling of the WM. The BWJ exhibited a mechanical strength of 380 and 520 MPa for the yield stress and ultimate tensile strength, respectively. These values are close to those of the as-received API 5L X-52 steel. Full article

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

Over the past 20 years, laser beam–electric arc hybrid welding has gained popularity, enabling high quality and efficiency standards needed for steel welds in structures subjected to severe working conditions. This process enables single-pass welding of thick components, overcoming issues concerning the individual use of traditional processes based on an electric arc or laser beam. Therefore, thorough knowledge of both processes is necessary to combine them optimally in terms of efficiency, reduced presence of defects, corrosion resistance, and mechanical and metallurgical features of the welds. This article aims to review the technical and metallurgical aspects of hybrid welding reported in the scientific literature mainly of the last decade, outlining possible choices for system configuration, the inter-distance between the two heat sources, as well as the key process parameters, considering their effects on the weld characteristics and also taking into account the consequences for solidification modes and weld composition. Finally, a specific section has been reserved for hybrid welding of clad steel plates. Full article

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

The combined use of laser beam and electric arc for welding thick clad steel plates in a single pass has been developed to solve the issues concerning the individual applications of the heat sources, such as the low filling efficiency of conventional electric arc methods and the drawbacks concerning laser beam defects due to rapid cooling and solidification. This work was addressed to the weldability assessment of ferritic steel plates, clad with austenitic stainless steel, under the laser-leading configuration, testing the effects of two different values of the inter-distance between the laser beam and the electric arc. Specimens of the welded zone were investigated by metallographic observations and EDS measurements; mechanical properties were characterized by the Vickers microhardness test and by the FIMEC instrumented indentation test to obtain the local values of the yield strength. Welding simulations by theoretical modelling were also carried out to outline the differences in the thermal fields generated by the two heat sources, their interaction, and their effect on the configurations of the weld pool and the thermal profiles to which the materials are subjected. The welding setup with higher inter-distance was more suitable for joining clad steel plates, since the action of the deep keyhole mode is substantially separated from that of the shallower electric arc. In this way, the addition of alloying elements, performed by melting the filler wire, concentrated in the cladding layer, helping maintain the austenitic microstructure, while the laser beam acts in depth along the thickness, autogenously welding the base steel. Full article

To address anisotropy challenges in electric arc-based additive manufacturing of Inconel 718 alloy, this study develops a novel wire feeding oscillated double-pulsed gas tungsten arc welding additive manufacturing method (DP-GTA-AM) enabling precise thermal-mass transfer control. Series of crack-free thin-walled Inconel 718 alloy parts were successfully obtained by this proposed approach, and the microstructure and mechanical properties of the parts were thoroughly studied. The results indicate that the microstructure changes from dendrites and cellular crystals in the bottom to equiaxed grains in the midsection and entirely equiaxed crystals in the top, resulting in notable grain refinement. With an average grain size of 61.76 μm and an average length of 83.31 μm of large angle grain boundaries, the density of the <001> direction reaches 19.45. The difference in tensile strength and ductility between the horizontal and the vertical directions decreases to 6.3 MPa and 0.38%, which significantly diminishes anisotropy. Fractographic analysis confirms quasi-cleavage failure with homogeneous dimple distribution, demonstrating effective anisotropy mitigation through controlled solidification dynamics. Full article

This study investigates the machining parameters that affect the surface roughness of additively manufactured specimens employing wire arc additive manufacturing (WAAM) using electric arc welding as a heat source. The specimens were prepared using E6013 and E7018 filler rods for layered deposition on a mild steel base plate. For the machining operation, two variable parameters, cutting speed and depth of cut, were selected and coded as high (480 RPM, 0.5 mm depth) and low (310 RPM, 0.25 mm depth) while keeping the feed rate constant. The study employed a 2^k factorial design of experiment (DOE) using Minitab software to assess the impact of parameters and their levels on the output response of surface roughness. Analysis of variance (ANOVA) results show that cutting parameters like cutting speed and their interaction with the depth of cut significantly affect surface quality. The experimental data were also used to develop polynomial model response equations for predicting surface roughness. This study firmly demonstrates the critical role of machining parameters in enhancing the surface quality of low-cost additively manufactured components using an electric arc welding heat source. Full article

Effective thermal management is essential in welding processes to maintain structural integrity and material quality, especially in high-precision industrial applications. This study examines the thermal behavior of an AISI 1080 steel plate containing 100 blind holes filled using robotic electric arc welding. Temperature measurements, recorded with eight strategically positioned thermocouples, monitored the thermal evolution throughout the robotic welding process. The experimental results validated a computational heat transfer model developed with ANSYS Fluent software to simulate and predict temperature distribution achieving a mean absolute percentage error (MAPE) below 4.53%. A feedforward neural network was trained with simulation-generated data to optimize welding sequences. The optimization focuses on minimizing the area under the thermal history curves, reducing temperature gradients, and mitigating overheating risks. Integrating CFD simulations and neural networks introduces a hybrid methodology combining precise numerical modeling with advanced predictive capabilities. The hybrid CFD-FNN results reached a determination coefficient ($R^2$) of 0.93 and an MAPE of 3.5% highlighting the potential of this approach to predict the thermal behavior in multipoint welding processes. This model generated optimized welding trajectories improving the uniformity of the temperature field, reducing thermal gradients and minimizing temperature peaks, thus aiding in preventing overheating. This framework represents a significant advancement in welding technologies, demonstrating the effective application of deep learning techniques in optimizing complex industrial processes. Full article

The main aim of this research is to investigate the possibilities and challenges involved in the electric arc welding of solid-state-recycled EN AW 6082 aluminum alloy. Lately, solid-state recycling has gained increased attention as a more sustainable and efficient aluminum recycling method, whereby only about 30% of the energy of conventional recycling is used. This method is based on the deformation of small-sized metal waste into solid recycled specimens without a remelting step. For the welding of solid-state-recycled specimens, both metal inert gas welding and tungsten inert gas welding methods are used. To evaluate the weldability of solid-state-recycled material, welded specimens are compared with welded, commercially produced EN AW 6082 aluminum alloy sheets. The welding is performed using the same processes, parameters, and conditions. To evaluate the welding potential of solid-state-recycled alloy, tensile tests, microhardness tests, optical metallography, and scanning electron microscopy, accompanied by energy-dispersive spectroscopy analysis, are performed. Full article

Arc quenching has many advantages, including generating large amounts of heat in a short time, a self-quenching ability, and simple equipment. The electric arc energy from a TIG welding machine was used to modify the surface properties of S45C Carbon Steel Cylinders. The study focuses on the impact of arc length, current intensity, travel speed, gas flow rate, heating angle, and pulse on surface hardness after arc quenching an S45C steel tube with a cylinder surface. The study found that the hardness reduces from 45.1 HRC to 41.2 HRC as the current intensity increases from 125 A to 140 A. According to Taguchi’s results, the ranking of factors which have the greatest impact on surface hardness are pulse time, travel speed, intensity, gas flow rate, arc length, and heating angle. The pulse time has the highest impact because it directly influences the heating input, followed by the travel speed. Arc length and heating angle, on the other hand, have the least effect. The base metal, heat-affected area, and hardened area are the three distinct areas that make up the microstructure structure. After the arc quenching process, the case hardening depth is represented by the heat-affected zone at 1536 μm. A highly colored residual austenite and a needle-shaped martensite phase make up the hardened region. The hardened region is 1200 μm thick and has a hardness of more than 300 HV0.3. The study’s findings may improve the application and understanding of the arc quenching treatment procedure in the industrial sector. Full article

The ignition of combustible materials by electric welding spatters represents a significant cause of fires in welding operations, and the current intensity is a sensitive factor that affects the ignition capacity of welding spatters. In this work, the influence of different current intensities on the physical properties and ignition capacity of welding spatters on common combustible materials was investigated, and the ignition mechanism of electric welding spatter was also explained by means of the hot-spot theory. The results indicated that the splash range, the total generated quantity, the maximum diameter, and the temperature of electric welding spatters increased with the enhancement in current intensity. Furthermore, a higher current intensity was associated with a greater likelihood of producing irregular spatter particles. The probability of ignition of electrode welding spatters was found to be sensitive to their physical properties, exhibiting a non-linear increase with increasing current intensity. At a current intensity of 360 A, a surge in both the physical properties and ignition capacity of the spatters was observed, which is attributed to the coupling of a reduction in the critical hot-spot radius and an unstable pulsation in the arc. Full article

The nitrogen bubble bursting phenomenon during the welding process of high nitrogen steel (HNS) can lead to unstable droplet transfer and welding process, reducing the quality of weld formation. In this study, a novel approach, ultrasonic-assisted gas metal arc welding (U-GMAW), is proposed to suppress the escape of nitrogen gas during droplet transfer. This study investigates the influence of ultrasound on the metal transfer process during two distinct metal transfer modes: short-circuiting and droplet transfer. Ultrasound has a significant effect on the welding process; as ultrasonic power increases, both the arc length and droplet size decrease, while the droplet transfer frequency increases and the electrical signal stabilizes. Under the experimental conditions of this study, ultrasound has the most effective improvement on the metal transfer behavior when the ultrasonic power reaches 2 kW. Ultrasound enhances the stability of the droplet transfer process, making U-GMAW an effective and novel approach for controlling the droplet transfer behavior of high nitrogen steel. Full article

The effective development of modern welding technologies and the improvement of equipment and materials inevitably require deep theoretical knowledge about the physical phenomena occurring in the electric arc column and in the near-electrode region. However, there is still no convincing theoretical description of an arc discharge. This article demonstrates, through the generalization of known experimental facts and studies using a high-speed camera, that the conductive channel of an electric arc has a discrete structure, consisting of a set of thin channels through which the main discharge current passes. The cathode spot of an arc discharge is a highly heated and brightly glowing area on the cathode’s surface. Electron emission occurs from this region, which supports the discharge as well as the removal of the cathode material. We propose a new technique to study the reverse side of the cathode spot, revealing a structure consisting of individual cells or fragments of the cathode spot. For the first time, we present the anode spots captured by a high-speed camera. We carry out an analysis of the spots’ structure. We determine the parameters affecting the mobility of cathode and anode spots. We propose a hypothesis based on the obtained experimental facts about the heterogeneous structure of cathode and anode spots in an arc discharge and the existence of current filaments that affect the mobility of spots during arc combustion. Full article

Wire Arc Additive Manufacturing (WAAM) technology, known for its low equipment and material costs, high material utilization, and high production efficiency, has found extensive applications in the fabrication of key components for the aerospace and aviation industries. The stability of the arc is crucial for the WAAM process as it directly affects the forming of the parts. In this study, the monitoring data of electrical signals and arc morphology during the WAAM process of 2319 aluminum alloy were investigated using a high-speed camera system and current/voltage acquisition system. By analyzing the current and voltage signals, as well as the arc imaging results, the influence of arc stability on the forming of the cladding layer was studied. The experimental results indicated that when both current and voltage exhibit regular periodic fluctuations, this manifests as a stable short-circuit droplet transition form, while sudden changes in these signals represent abnormal droplet transition forms. The adaptability of the process directly influenced the arc shape, thereby affecting the forming of the cladding layer. Under the process parameters of welding speed of 240 cm/min and wire feeding speed of 6.5 m/min, it was observed that the current signal exhibited a tight state and the variance of the arc width was minimized. This indicated that at a higher wire feeding speed, the droplet transfer frequency was increased. Under these process parameters, the arc output was more stable, resulting in a uniform metal coating. Full article