High Welding Research Articles

Process Parameters of High Frequency Welding.

High frequency (HF) welding of polymer materials is increasingly used in modern manufacturing processes. The literature on HF welding process parameters was reviewed and it was found that 3-5 basic welding parameters were considered, which is insufficient for the scientific study of HF welding of polymeric materials. This article presents the mathematical expressions for the evaluation combining 17 influential parameters. For the first time, the specific and latent heat of the welded polymer material were used. The breaking forces of welds made by RF welding are investigated by varying the anode current, the coupling capacitor, and the exposure time of the HF electromagnetic fields. It was found that the amount of HF energy supplied depends on the breaking forces of the weld. A characteristic inflection point was also observed in the graph of the dependence of the breaking forces on the percentage of the coupling capacitor and the anode current. During elongation, it was observed that the weld is separated by peeling before the inflection point and breaks after the inflection point by tearing at the extruded edges of the weld. If the HF energy is applied to the weld for too long, there will be excessive melting of the material in the weld, thinning of the weld, unfavourable appearance of the extruded edges and electrical breakdown, and a drastic drop in the breaking force.

Temporal power modulation in high power laser beam welding of round bars

Temporal power modulation bears an enormous potential for high power laser beam welding of round bars since all its specific challenges are faced. They can be summarised as deviating welding conditions towards the round bar‘s centre. Accordingly, a tailored amount of energy would be provided to that area. The investigations are conducted on 30 mm diameter bars of 1.4301 stainless steel with the use of a 16 kW disk laser. The modulation parameters comprise 6/12/50/100/200 Hz modulation frequency and 0.30/0.47/0.73 modulation depth or power modulation ratio. Post analysis focuses on metallographic longitudinal sections and calculations. The modulation‘s outstanding capability is creating deeper and narrower weld seams due to higher peak power and more intense evaporation of protrusions along the keyhole front wall. Therefore, more laser power is provided to the weld root and despite applying lower average power, the same weld depth is achieved. Finally, more ecological and economical welding as well as welding of more temperature sensitive materials is enabled.

Development of High Efficient Welding Technology in Offshore Wind

Development of High Efficient Welding Technology in Offshore Wind

Advancements in energy-efficient welding production techniques: Innovative models and methods for combined workpiece fabrication

This article highlights notable advances in energy-efficient welding manufacturing techniques, with particular emphasis on new models and methodologies for combined welding machines. High energy density welding processes such as laser beam and electron beam welding are being investigated for their potential to optimize energy use in various industrial applications. Furthermore, the examination extends to energy- efficient high-density welding procedures, notably encompassing electric arc, gas welding, and autogenous welding, while also taking into account factors tied to corrosion processing. Technological advances in machining, cutting techniques, and specialized connectors are also explored in detail, and their contribution to reducing energy consumption and improving overall equipment efficiency is examined. This thorough investigation would not be complete without considering the implications for the energy sector, where the use of energy-efficient welding techniques is critical in reducing costs and refining manufacturing processes.

Improving the weld seam quality in laser welding processes by means of Bayesian optimization

The determination of appropriate process parameters is crucial for the development of laser welding processes. This usually requires extensive and time-consuming experimentation combined with expert knowledge. To reduce the number of experiments required to determine appropriate process parameters, Bayesian optimization was used in this work. Bead on plate laser welding of AA5754 samples was performed while optimizing the laser power, the welding speed, the focus position and the power distribution in the core-ring fiber laser system with the objective of achieving welds with a specific weld depth and low number of defects at high welding speeds. The welds were evaluated using X-ray imaging and height measurements. A cost function was developed to quantify the overall weld quality based on the weld properties. It is demonstrated that the Bayesian optimizer can determine appropriate process parameters for the given objective, based on a cost function, within a comparatively small number of 29 experiments.

Effect of concentric intensity distributions on spatter formation in full penetration welding of high-alloy steels

Welding of high-alloy steels results in spatter formation addressing high welding speeds above 8 m/min, i.e., the seam quality is significantly reduced due to material losses and adhering spatter. A reduction of spatter can be addressed by using concentric intensity distributions consisting of core and ring, by affecting melt and metal vapor flow. In this paper, the understanding of spatter formation on sheet top and bottom side is significantly enhanced for full penetration welds of AISI 304. Therefore, different concentric intensities and tophat distributions were systematically studied and compared. Fundamental interactions between concentric intensity distributions and spatter formation during full penetration welding were determined and summarized in model concepts. In particular, spatter formation can be reduced on both sheet sides using a concentric intensity distribution due to a smaller keyhole geometry with a smaller angle of inclination of the keyhole front.

Predict the machining performance of FSW of dissimilar material of AI5052 and AZ31 using Multi-Objective Dragonfly Algorithm

In this study, two dissimilar materials (Al 5052 and AZ31) have been welded using the Friction stir process (FSW). Taguchi’s philosophy has been used to design the experiment using four input parameters (Tool types (TP), Tool traverse speed (TTS), Tool tilt angle (TTA), and Tool rotation Speed (TRS)). The machining performances have been identified using ultimate tensile strength (UTS) and Vickers hardness (HV). The models are evaluated for sufficiency, and then the most significant parameters are determined using analysis of variance (ANOVA). The ANOVA results revealed that TTS has a maximum contribution of 50.2% and 46.5% towards obtaining the high UTS and HV, respectively. The mathematical model using the non-linear model for UTS and HV has been created to predict the mechanical properties of FSWed joints. The prediction welding accuracy of a multi-objective optimization has been performed using the Multi-Objective Dragonfly Algorithm (MODA). The adopted strategy shows a high welding accuracy with minimum computational time.

Three-dimensional transient heat transfer analysis of micro-plasma arc welding process using volumetric heat source models

Abstract The micro plasma arc welding process is associated with different physical phenomena simultaneously. This results in complexities to comprehend the actual mechanism involved during the process. Therefore, a robust numerical model that can compute the weld pool shape, temperature distribution, and thermal history needs to be addressed. Unlike, other arc welding processes, the micro plasma arc welding process utilizes thin sheets of thickness between 0.5 and 2 mm. However, joining thin sheets using a high-density arc welding process quickens the welding defects such as burn-through, thermal stresses, and welding-induced distortions. The incorporation of a surface heat source model for computational modeling of the high energy density welding process impedes heat transfer analysis. In that respect, researchers have developed numerous volumetric heat source models to examine the welding process holistically. Although, selecting volumetric heat source models for miniature welding is a significant task. The present work emphasis developing a rigorous yet efficient model to evaluate weld pool shape, temperature distribution, and thermal history of plasma arc welded Ti6Al4V sheets. The computational modeling is performed using a commercially available COMSOL Multiphysics 5.4 package with a finite element approach. Two different prominent thermal models, namely, Parabolic Gaussian and Conical power energy distribution models are used. A comparative analysis is carried out to determine the most suitable heat source model for evaluating temperature distribution, peak temperature, and thermal history. The analysis is done by juxtaposing the simulated half-cross-section weld macrographs with the published experimental results from independent literature. The numerical results showed that the proximity of top bead width magnitude was obtained using the Parabolic Gaussian heat source model for low heat input magnitude of 47.52 and high heat input magnitude of 65.47 J·mm−1, respectively. In terms of percentage error, the maximum top bead width percentage error for the Parabolic heat source model is 13.26%. However, the maximum top bead width percentage error for the Conical heat source model is 18.36%. Likewise, the maximum bottom bead width percentage error for the Parabolic heat source model and the Conical heat source model is 12.3 and 25.8%, respectively. Overall, it was observed that the Parabolic heat source model produces the least deviating outcomes when compared with the Conical distribution. It was assessed that the Parabolic Gaussian heat source model can be a viable heat source model for numerically evaluating micro-plasma arc welded Ti6Al4V alloy of thin sheets.

Parameter Optimization in Orbital TIG Welding of SUS 304 Stainless Steel Pipe

The influence of welding angle, welding current, travel speed, pulse time, and torch height on the geometry, macrostructure, and mechanical properties of Tungsten Inert Gas (TIG) orbital welding on an SUS 304 stainless steel pipe is investigated in this study. The results show that an electrode angle of 45° produces better weld joints than angles of 30°, 60°, 90°, and 120°. Furthermore, the electrode angle of 30° results in an acceptable weld width but a low depth of penetration (DOP) value. Welding current and weld speed have a significant impact on heat dispersion during TIG welding of an SUS 304 stainless steel pipe. The high welding current may result in blow-hole flaws, particularly near the conclusion of the welding process when heat is accumulated. A long torch height of 2 mm causes unevenness in the weld joints because the arc may be distorted when compared to shorter torch height cases. The pulse time of 0.2 s is too lengthy for a low-welding current situation because it will generate a small weld pool. As a result, the weld pool solidification process speeds up, and porosity emerges in the weld bead. A pulse time of 0.1 s results in a better weld joint. To avoid blow-hole creation, the welding current should be gradually reduced during the process. In addition, the Taguchi results demonstrate that the welding current has the greatest effect on the ultimate tensile strength (UTS) value, followed by welding speed, pulse time, electrode angle, and torch height. Furthermore, the ideal parameters for the UTS value are an electrode angle of 45°, a torch height of 2.0 mm, a welding current of 174 A, a welding speed of 72 mm/min, and a pulse time of 0.3 s.

Study on the mechanism of Ni-26W-6Cr alloy solidification cracking: Effect of laser welding heat input

The segregation of P, S, Al, Si and Mo at solidification grain boundary (SGB) results in the formation of the low-melting-point liquid film. As heat input (HI) increases from 76.9 to 214.3 J/mm, upper weld seam width increases by 63 % and lower seam width decreases by 29.3 %. High welding HI generates lower temperature gradient, which could reduce thermal stress. The average hardness of weld metal (WM) drops from 273 to 235 HV and there is a 90 % reduction in the total length of welding solidification crack (WSC). The lower hardness under high HI facilitates the release of thermal stress, which permits the WM to accommodate the tensile stress generated during the solidification phase. Reduced thermal stress decreases the driving force of the formation of WSC.

Laser welding of additively manufactured parts - A review

Additive manufacturing (AM) is a process in which parts are built up layer by layer, introducing novel approaches to how parts can be manufactured with less material waste, shorter lead times and lower costs than traditional manufacturing. One of the key advantages of AM over conventional manufacturing is its design flexibility, which enables for manufacturing of parts with highly detailed geometries in one go, leaving out the need for molding, casting, etc. However, due to the chamber size of the machines, the size of AM parts is limited. To overcome this limitation, joining AM parts together or to wrought or cast material has been proposed. Among the various welding technologies, laser welding is considered a suitable candidate for joining AM parts because of its low heat input, resulting in low deformation, high welding speed, and full automation capability. This study will provide a fundamental understanding of laser welding of AM parts by reviewing current research in the field. The possibility of joining most commonly used AM parts such as AlSi10Mg, AISI 316L, Ti6Al4V and Nickel alloy 718 by laser welding are investigated. Furthermore, the effect of laser welding parameters on mechanical and microstructural properties of joined AM parts are discussed.

Process advantages of laser hybrid welding compared to conventional arc-based welding processes for joining thick steel structures of wind tower

The most common welding processes when joining thick-walled steels in the industry are arc-based welding processes such as GMAW or SAW. For this purpose, the sheets are joined in multi-layer technique, which can lead to productivity losses due to high welding times. The process-specific challenges in welding thick steels using multi-layer technique relate to the high heat input from the process. Therefore, alternative welding processes are being actively sought. A suitable alternative is provided by beam-based welding processes such as the laser hybrid welding processes, which are characterized by deep penetration welds and lower heat input. With implementation of the laser hybrid welding process in the heavy industry, such as the wind tower industry, economic benefits can be reached such as the increase in productivity by reducing the layer number, and the lower consumption of filler material and energy. When comparing SAW welded 25 mm thick steels in five to six layers and single-pass laser hybrid welding, the welding time can be reduced more than 80 % and the costs of filler material, flux and energy can be saved up to 90 %. However, the industrial use of the laser hybrid welding process is still limited to applications, where the material thickness does not exceed 15 mm due to some process-specific challenges such as the sagging, sensitivity to manufacturing tolerances such as gaps and misalignment, limited filler wire mixing, and deteriorated mechanical properties resulting from high cooling rates. To overcome these challenges, a contactless electromagnetic backing based on an externally applied AC magnetic field was used. Eddy currents are induced due to the oscillating magnetic field, and an upward-oriented Lorentz force is generated to counteract the droplets formed due to gravitational forces. It allows to weld up to 30 mm thick structural steels in a single-pass with a 20-kW fiber laser system. Additionally, the gap bridgeability and the misalignment of edges were increased to 2 mm when welding 20 mm thick steels. With the aid of the AC magnetic field, a vortex was formed in the weld root, which had a positive effect on the filler wire mixing. A further significant advantage of the EM backing was the possibility to expand the process parameter window to maintain desired cooling times and mechanical properties, without suffering adverse effects concerning the root quality of the weld.

High Energy Density Welding of IN792 Ds Superalloy

Ni base superalloys are commonly employed in the industrial fields of aerospace, automotive and energy production due to their excellent mechanical properties and corrosion resistance at high temperature. Superficial defects and cracks may occur during both manufacturing process of components and their service life. High energy density welding techniques, electron beam (EBW) and laser beam (LBW) welding, can be used to create efficient repairs. Joints, obtained by EBW and LBW of IN792 directionally solidified (DS) superalloy, have been investigated to determine the presence of defects, and evaluate the mechanical properties related to specific microstructural features. The results showed that a pre-heating temperature (PHT) higher than 200 °C is always necessary to prevent the formation of hot cracks in the molten zone (MZ) and heat affected zone (HAZ). The process parameters have been optimized to get a good quality of the seams (lack of macro-defects, a good penetration depth and width). Some preliminary test of post-welding heat treatments (PWHTs) have been investigated to homogenize as far as possible the microstructure and the mechanical properties across the seams. The results obtained by the two techniques, EBW and LBW, have been compared and discussed.

High-Speed Laser Beam Welding of Magnesium Alloy AZ31 for Enhancing the Mechanical Properties

Laser beam welding is still the focus of research all over the world since new laser sources with more brilliance, higher power, or higher efficiency are being developed. High brilliance leads to thinner fibers when solid-state lasers are used. For welding applications, a thin beam, respective a small focus spot is recommended for low heat input resulting in less deformation. The edge preparation of the welding pieces must be as accurate as possible, and a zero gap is recommended. In earlier research, it was shown, that the gap bridging capacity could be enhanced by the wobbling of small focus spots, as well as refining the grain size in the weld zone by decreasing the focus diameter. Inventions in the optics, like the beam splitting into a core and a ring part, avoid the use of a scanner and can lead to better gap bridging. Nevertheless, the use of a brilliant beam, resulting in a small focus in combination with high power can result in very high welding velocities, just limited by the used machinery. In the present study, a disk laser with 4 kW maximum power and 100 μm focus spot was used to weld 2 mm thick magnesium AZ31 sheets at speeds up to 20 m/min. As expected, the seam width becomes smaller with raising velocity, and some underfill and access material occurred on the surface and the root of the welded sheets. Surprisingly, the texture of the weld seam changed from random at low velocity to a more pronounced texture at high speed with respect to the basal texture of the plate base material. This influences the mechanical behavior, namely the strain to fracture, of the welded joints positively. The high-speed weldments are compared to state-of-the-art weldments of magnesium AZ31, in terms of mechanical strength and elongation to fracture, based on the texture analysis.

Recent Advances in W–Cu Composites: A Review on the Fabrication, Application, Property, Densification, and Strengthening Mechanism

Tungsten–copper (W–Cu) composite is a pseudoalloy prepared by powder metallurgy method with tungsten and copper as the main components, which are widely used in electrical contacts, electrical discharge machining electrodes, electronic packaging, aerospace, and military fields due to its good conductivity, thermal conductivity, high melting point, high electrical breakdown strength, low contact resistance, high welding resistance, and high heat resistance. Herein, the recent advances of W–Cu composites are reviewed systematically. First, the preparative techniques of W–Cu composites are introduced in detail, and their advantages and disadvantages are evaluated objectively. Second, an introduction of the main application fields and corresponding characteristics advantages for W–Cu composites are provided. Subsequently, the densification techniques and strengthening mechanisms and their effects on microstructure, mechanical properties, and physical properties of W–Cu composites are mainly discussed. Finally, based on a comprehensive review of W–Cu composites, its future development trends and potential research challenges are summarized and prospected.

Achieving novel copper–steel joints with a combination of high strength and ductility reinforced by in-situ Fe-rich particles

Strength and ductility are typically mutually exclusive in traditional copper–steel joints. This work proposes a strategy to overcome the inherent trade-off between strength and ductility through high speed electron beam welding with a preferred deflection to facilitate the in-situ formation of Fe-rich particles in the Cu matrix. The Fe-rich particles with an average diameter of 178.5 nm feature a 3D spatial network distribution across practically the entire joint. The obtained joint reinforced with such Fe-rich particles achieves ultimate high tensile strength (413 MPa) while maintaining excellent ductility (22%). The improved strength of the copper–steel joint is derived from the combined effects of dislocation strengthening and grain refinement strengthening, while the increase in room-temperature ductility is mainly due to the high Schmid factor up to 0.454, which promotes the primary slip system to initiate easily during tensile deformation. This work provides a novel perspective on creating copper–steel joints in terms of achieving microstructural refinement and outstanding strength-ductility synergy.

Fe‐Based Filler Material Forming Austenite‐Covered Packet Lath Martensite for Gas Tungsten Arc Welding of 9% Ni Steel

Fe‐based filler material with a composition of Fe–20Ni–5Co–2.5Mn–0.2C is developed for welding 9% Ni steel. To ensure high weldability through compositional similarity, the composition of the Fe‐based filler material is designed based on that of 9% Ni steel. The filler material has elements such as Ni, Mn, Co, and C to enhance its compatibility with the 9% Ni steel. The Fe‐based filler material is designed to control the martensite formation temperature, resulting in the appearance of the martensite–austenite dual phase during rapid cooling. The weld joint shows a distinct microstructure characterized by the presence of austenite‐covered packet lath martensite. The mechanical properties of the weld joint are investigated via Vickers harness and tensile tests at 25 and −163 °C. In comparison to 9% Ni steel, the weld joint prepared using the Fe‐based filler material exhibits yield and tensile strengths that are ≈5.5% higher. Additionally, the tensile fracture of the specimen occurs exclusively within the base metal, without any involvement of the weld metal or heat‐affected zone. Further, the fracture surface is observed. In the findings of this study, the applicability of the Fe‐based filler material for welding 9% Ni steel is demonstrated.

An improved simulation of temperature field in PMHW of Ti-6Al-4V alloy

This article describes a coaxial plasma–MIG hybrid welding (PMHW) method to improve the welding quality of titanium alloy plates. Aiming at the temperature field analysis of a Ti-6Al-4V alloy plate in the PMHW process, an improved hybrid heat source model capable of accurately characterising the heat input of a hybrid arc on workpieces and the arc deflection phenomenon, is proposed. Experiments were conducted on 4-mm Ti-6Al-4V plates in PMHW surfacing, and a corresponding simulation analysis was performed. To calculate the weld geometry, a weld pool shape was used in accordance with the experimental results. The results showed that, as plasma current increased from 60 to 80 A, the weld reinforcement and offset decreased, and the size of the weld pool increased. Plasma arc power had a greater effect on the length than on the width of the molten pool. Hybrid arcs had a stronger penetrating ability; hence, achieving deep penetration welding and high welding efficiency in the PMHW of the Ti-6Al-4V alloy was easier. Microstructure analysis showed that the Ti-6Al-4V alloy base metal zone was organised by α- and β-phase transformations; β grains in the weld zone were internally formed by a mixture of Weischer tissue and net basket tissue; and the size of β grains in the heat-affected zone decreased with the increase in the distance from the weld.

Effect of process parameters on the mechanical behavior of additively manufactured and FSW joined PLA wood sheets

AbstractFriction stir welding (FSW), a solid‐state joining method, is an innovative technique widely employed in the welding of thermoplastics, with broad application areas such as the automotive and aerospace industries. Due to its inherent advantages, including ease of processing, biodegradability, and printability, polylactic acid (PLA) and its derivatives are notably the most commonly used polymers in 3D printing. The limited print area of 3D printers necessitates post‐production joining processes. In this study, the weldability of plates obtained using PLA Wood filament through the FSW is evaluated. For this purpose, different pin geometries (triangle, square, and screw), feed rates (20, 40, and 60 mm/min), and tool rotation speeds (1250, 1750, and 2250 rpm) are employed. Visual inspections are conducted to determine the effects of process parameters on weld quality and to identify defects in the weld region. Temperature values are measured to investigate the influence of heat generated during the FSW process. Furthermore, after determining the highest weld strengths achieved for each pin geometry, the weldability of PLA Wood material with PLA‐CF and PLA Plus materials is investigated using these parameters. The results indicate that the highest weld quality for joining PLA Wood plates is achieved using the square pin geometry, 20 mm/min feed rate, and 1750 rpm with an efficiency of 74.5%. When welding PLA Wood with PLA‐CF and PLA Plus, high weld strengths are obtained using the same process parameters (square pin, 20 mm/min, and 1750 rpm).Highlights Friction stir welding process of 3D printed PLA Wood material. Friction stir welding process of dissimilar materials pairs. Effect of welding parameters on weld strength and hardness. Identifying the fracture surface images occurring in parts after friction stir welding. Examination of temperature generation during friction stir welding.

Assessing the viability of high-frequency spot melting for super duplex stainless steel 2507 via electron beam powder bed fusion

This study investigates the use of Electron Beam Powder Bed Fusion (PBF-EB) spot melting on SDSS 2507, a material known for its high tensile strength, corrosion resistance, and welding properties. Spot melting, a localized melting technique, utilize a stationary beam to create melt pools before rapidly repositioning to form new ones, offering precise control over material properties in additive manufacturing. We conducted a design of experiments with 32 samples and analysed them using SEM, XRD, EBSD, optical microscopy, nanoindentation and statistical modelling.Elevated PBF-EB processing temperatures significantly influence microstructure and phase composition. XRD analysis identified the presence of the detrimental sigma phase. EBSD analysis revealed a composition primarily consisting of austenite (63 %) and sigma phase (33.5 %), with residual ferrite (3.5 %). Statistical modelling demonstrated that a combination of spot-time, spot distance, focus offset, and layer thickness was the most reliable predictor for density while area energy proved to be the most accurate predictor for hardness, with R2adj values of 0.766 and 0.802, respectively.Our study confirms that PBF-EB is capable of processing SDSS 2507 through spot melting, resulting in high-density samples at high productivity rates. The presence of sigma phase shows a need for post build heat treatment to achieve the desired phase distribution. This research enhances the understanding of the process and also holds promise for industrial applications.