Further development of manufacturing methods and metallic alloys is crucial for creating next-generation energy production systems with enhanced strength, toughness, creep resistance, and/or corrosion resistance. For wire-based additive manufacturing (AM), wire materials are often cheaper than powdered metal, impurity contents are easier to control, deposition rates are substantially higher than those of powder-based AM, and wire arc AM is backed by decades of experience in multipass welding, cladding, and build-up repairs. To further expand the capabilities of wire arc additive manufacturing, a multiwire gas tungsten arc welding AM system was developed to independently introduce two commercially available nickel-based alloys, Alloy 617 and Alloy 740H, as weld wires into a single weld pool, thereby introducing chemical composition gradients with the intent of altering local material properties. This research analyzed weld metal dilutions and evaluated the composition profiles at different proportions of nickel alloy filler wires. The work demonstrated that multiwire gas tungsten arc-directed energy deposition can deposit graded compositions predictably via a simple mathematical analysis based on mass balance.
The use of scrap for steel making has increased worldwide and is expected to continue as steelmakers and users pursue sustainability efforts. Advances in steelmaking practices have enabled greater scrap recyclability and energy savings, but have come at the cost of reduced control over residual elements such as copper. This work studies the effect of increased copper content, up to 0.26 wt-%, on the base-metal microstructure and resistance spot-welding behavior of a low-carbon automotive sheet steel. Alloys were subcritically annealed prior to spot welding, tensile-shear testing, electrical resistivity measurements, and microstructural analysis. The higher-copper alloys showed increased base-metal strength, likely due to copper solid-solution strengthening. The higher-copper content alloys also exhibited higher electrical resistivity, resulting in a greater incidence of expulsion during resistance spot welding. Despite increased expulsion at high welding currents, resistance spot welds of the higher copper content alloys showed higher strength and lower ductility in tensile-shear testing. This work shows that elevated residual copper content can be accommodated in welded automotive steel sheets, provided base metal processing and welding parameters are adjusted to account for its influence.
Droplet temperatures in metal-cored arc welding (MCAW) were measured for the first time using a solid-state calorimeter and a water-cooled cathode, with a commercial metal-cored wire and pure argon shielding gas, and a current range of 210 to 290 A. In MCAW, droplet temperatures ranged from 1900°C to 2145°C with an average uncertainty of ± 35.5°C. Compared to gas metal arc welding (GMAW) at the same current range, droplet temperatures in MCAW were consistently lower than those in GMAW, with an average difference of approximately 260°C. High-speed video revealed that the metal core, consisting mostly of iron powder in the MCAW, remained in a near-solid state until immediately before detachment, contributing to lower droplet temperatures. A mass and energy balance analysis indicated that the sheath was hotter than droplet temperature by approximately 150°C and 90°C at the assumed core temperatures of 1200°C and 1500°C, respectively. The molten sheath temperature was predicted to be comparable to that of solid wire in GMAW under similar conditions. In MCAW, the metal transfer mode remained globular, while the transfer morphology shifted from symmetrical to biased droplet formations with rising current. MCAW also exhibited higher overall anode fall voltages (7.9-10.0 V) compared to GMAW (6.8 V), which was attributed to either the Thomson effect near the electrode or changes in metal transfer morphology. The presence of a colder powder core suggests a reduction in manganese evaporation, which could significantly lower manganese fume emissions, an important consideration for occupational health and environmental safety.
This paper is the second of a three-part series covering the field of high-speed videography in welding. This second part provides a comprehensive discussion of two of the most common techniques of high-speed imaging of welding: backlighting and frontlighting, including broad and narrow-spectrum lighting (lasers in the case of backlighting) with both techniques. In all cases, building on the foundations laid out in Part 1, detailed descriptions of appropriate setups are provided together with examples of published practical implementations. The welding processes addressed include laser beam welding, gas tungsten arc welding, gas metal arc welding (GMAW), flux cored arc welding, and submerged arc welding. The advantages and disadvantages of front- and backlighting are explored in detail. Frontlighting is especially useful for processes with high dynamic range, such as short-circuit metal transfer in GMAW. Backlighting is less used with modern digital cameras; however, small amounts of backlighting can highlight features such as the electrode extension when using natural radiation lighting. Narrow-spectrum sources such as lasers are especially useful in combination with narrow bandpass filters to eliminate unwanted radiation sources. The implementations of front- and backlighting reviewed in this paper, together with those for natural radiation lighting in Part 3 and the fundamental concepts and resulting quantitative guidelines provided in Part 1, provide welding researchers with a previously inexistent compilation of criteria to select proper equipment, accessories, and parameters for high-speed imaging of a vast variety of phenomena in welding, laser welding, and associated processes such as additive manufacturing or cutting.
Increasing amounts of residual copper in the steel scrap stream can lead to enrichment in recycled steel products. While copper is often controlled to avoid issues during thermomechanical processing, its downstream effects on microstructure and properties after welding are less known. This work explores the effect of increased copper content, up to 0.83 wt-%, on microstructure and Charpy impact behavior of hot-rolled low-carbon steel plates welded with gas metal arc welding (GMAW). Microstructural characterization of the hot-rolled base metal and GMAW heat-affected zone (HAZ) was conducted. It was found that austenite stabilization and an increase in hardenability from copper led to a higher fraction of more brittle non-ferritic microstructural constituents in the base metal, resulting in a higher 20 ft center dot lb ductile-brittle transition temperature (DBTT). However, the GMAW HAZ of all the alloys primarily consisted of tempered martensite, resulting in an overall lower DBTT than that of the base metals, with little effect from copper content. This work shows that copper's effects on microstructural evolution must be considered during thermomechanical processing and welding to ensure high toughness in low-carbon steel plate.
Our previous work noted that thinning the coating significantly improves the weldability of Al-Si-coated press-hardened steel (PHS). However, an Al enrichment formed at the weld toe of the thin (similar to 16 mu m) coating PHS during laser welding at a high welding speed of 7 m/min, originating from the coating outside the weld. In this work, a surface pre-alloying (SPA) technique was applied to the thin Al-Si coating near the weld toe before laser welding. After conducting the SPA process, the fraction of intermetallic compounds (IMCs) in the coating increased significantly, and the IMCs consisted of Fe2SiAl7 (tau 5), Fe2Al5 (eta), and Fe3Al2Si3 (tau 1). When the energy input to SPA exceeded 0.48 kJ/cm, the fraction of IMCs in the coating exceeded 60%. This significantly increased the coating's liquidus temperature near the weld toe due to the altered chemical composition, reducing the molten amount of the coating and preventing it from entering the weld through the weld toe. In this case, the Al enrichment at the weld toe disappeared after high-speed welding, and the tensile joints failed at the base metal. Eventually, the thin Al-Si coating PHS was stably welded at a high welding speed because of the application of SPA.
Further development of manufacturing methods and metallic alloys is crucial for creating next-generation energy production systems with enhanced strength, toughness, creep resistance, and/or corrosion resistance. For wire-based additive manufacturing (AM), wire materials are often cheaper than powdered metal, impurity contents are easier to control, deposition rates are substantially higher than those of powder-based AM, and wire arc AM is backed by decades of experience in multipass welding, cladding, and build-up repairs. To further expand the capabilities of wire arc additive manufacturing, a multiwire gas tungsten arc welding AM system was developed to independently introduce two commercially available nickel-based alloys, Alloy 617 and Alloy 740H, as weld wires into a single weld pool, thereby introducing chemical composition gradients with the intent of altering local material properties. This research analyzed weld metal dilutions and evaluated the composition profiles at different proportions of nickel alloy filler wires. The work demonstrated that multiwire gas tungsten arc-directed energy deposition can deposit graded compositions predictably via a simple mathematical analysis based on mass balance.
Continuous ultrasonic welding is an efficient and precise technology widely used for joining composite materials. However, compared to ultrasonic single-point welding, continuous ultrasonic welding exhibits lower joint quality, posing significant challenges for quality control. This study focuses on the joint quality of continuous ultrasonic welding. Based on the acoustic wave transmission principle, the acoustic behavior during continuous ultrasonic welding is simulated, and a model is proposed for predicting welding quality. Welding pressure, welding speed, and the radiation radius of welding energy are key factors influencing weld quality. The heating process of continuous ultrasonic welding is simulated using the finite element method, and the energy attenuation characteristics and heat distribution during welding are analyzed to validate the quality prediction model. Experimental verification further confirms the model's accuracy. The results demonstrate that under stable welding conditions, the model reliably predicts welding quality, offering an effective solution for quality assessment in continuous ultrasonic welding of thermoplastic composites.
This paper presents a modified Goldak heat source (GHS) model applied to duplex stainless steel (DSS) wall-of-weld (WoW) and AA5356 aluminum in wire arc additive manufacturing (WAAM) using gas metal arc welding. Although prior modifications to the GHS exist, none have addressed the actual arc origin following arc initiation. Consequently, maintaining realistic parameter ranges in the standard GHS often results in artificially high temperatures, inconsistent interlayer boundaries, or large relative errors compared to experimental data. In this study, an arc origin offset (as a new Goldak parameter, Z(0)) is introduced in the double ellipsoidal heat source equations, reflecting the actual location of peak heat input. As a result, Z(0) improves the prediction of solid-liquid phase transitions of the melt pool crosssectional geometry validated by the macrographs. A thermal study optimizing this parameter, alongside a parametric study of this Modified GHS (MGHS), is first implemented on DSS-WoW and subsequently on the AA5356-WoW. The standard GHS and the MGHS are compared in each case and validated against experimental results and DSS macrographs. The results demonstrate how Z(0) enhances standard GHS and, more importantly, adjusts it to WAAM beyond a single weld bead. Additionally, an experiment conducted by the authors on an AA1100 Tube-to-Weld using a moving pyrometer (MIKRON-ME-PI 140) accurately confirmed the MGHS model. To estimate the Z(0) value in a more generalized way, a novel dimensionless number was developed to empirically relate Z(0) to five alloys and process parameters. This enables researchers and engineers to select the desired Z(0) value.
In this work, a novel ultrasonic-assisted soldering (UAS) process was demonstrated for joining large stacks (64 films) of aluminum metallized polymer current collectors (MPCCs) to a tab for lithium-ion batteries (LIBs). When integrated into cells, MPCCs can act as a passive safety mechanism for thermal runaway and increase the gravimetric energy density. Joining MPCCs is difficult due to their composite nature, and traditional processes may be insufficient to enable integration of MPCCs in LIBs at scale. This experimental study investigated the impact of three key process parameters of through-hole UAS (welder cylinder pressure, ultrasonic vibration time, and vibration amplitude) on the electrical resistance and mechanical strength of the resulting joints. Varying the cylinder pressure had an insignificant effect on joint quality, except that at high cylinder pressures, film damage occurred at the joint area. Inconsistent joint quality was observed with short ultrasonic vibration times. For long ultrasonic vibration times, over-soldering occurred where the solder penetrated through the tab. The amplitude of vibration significantly impacted the mechanical strength and electrical resistance of the joints. The best performing joints were prepared within the low-to-middle range of vibrational amplitude tested (7.8-14.4 & micro;m). A more thorough layer-by-layer resistance analysis was also performed on joints produced with near-optimum conditions. These joints had an average layer resistance of 0.0045 ohms. Optical microscopy and SEM imaging revealed that joints made with near-optimum conditions had deeper solder penetration between MPCC films, compared to joints made with a lower amplitude.
This work focused on profiling the caustic and measuring the power of a handheld laser beam welding (HLBW) system. A Primes (R) FocusMonitor FM+ and PowerMonitor CPM-F-10 were used to characterize a Miller OptXTM 2 kW HLBW system. Spot size and power density are key process variables for laser beam welding. For HLBW, these variables are constantly subject to variations since they depend on the welder's experience and the ability to maintain a steady torch position. In this context, accurate characterization of the laser beam becomes essential to HLBW procedures. Laser beam profiling routines were performed using four different beam powers, while the power was measured in the entire adjustable range. The beam exhibited a waist diameter of approximately 40 mu m, a Rayleigh length of 1.1 mm, and a divergence angle of 40.3 mrad. The average beam parameter product and M2 were 0.44 mm mrad and 1.3, respectively. The measured power output was consistently 4% above the nominal value across the entire power range. The results confirmed that beam geometry is sensitive to torch positioning due to the small spot size and short Rayleigh length. The proposed methodology yielded consistent results for beam characteristics and power output in HLBW systems.
This paper is the third of a three-part series covering the field of high-speed videography in welding in depth. This third part provides a comprehensive discussion of natural radiation lighting. The effect of optical filters is discussed in detail, with the beneficial use of long-wavelength edge filters around the near-infrared range. Building on Part 1, detailed descriptions of appropriate setups are provided with examples of published practical implementations. Welding processes addressed include gas metal arc welding, gas tungsten arc welding, flux-cored arc welding, submerged arc welding, electroslag welding, and laser cladding. Advantages and disadvantages are explored thoroughly. Natural radiation lighting is especially useful because of the simplicity of the equipment involved, information about the morphology and temperature of the surface of the molten metal, and information about the arc, such as the presence of metal vapors. Modern digital cameras typically have the necessary high dynamic range that enables the use of this technique. The implementations of natural radiation lighting reviewed in this paper, together with those for front and back lighting in Part 2, and the fundamental concepts and resulting quantitative guidelines in Part 1 provide welding researchers with a previously inexistent compilation of criteria to select proper equipment, accessories, and parameters for high-speed imaging of a vast variety of phenomena in welding, laser welding, and associated processes such as additive manufacturing or cutting.
Due to the shielding effect of fluxes, investigations into element transfer during submerged arc welding are often restricted by and/or limited to compositional analysis of the weld metal (WM). Therefore, meaningful discussions about specific locations where responsible reactions occur, such as the arc-containing droplet zone and arc-free slag-metal zone, are often nebulous. To counter such challenges, designed droplet collection trials were conducted over a water-cooling system. By examining the contribution of droplets to element transfer in the WM, the locations and possible pathways facilitating salient element transfer behaviors were elucidated. The results indicated that the transfer levels of Si, Mn, and Ti from the flux into the droplet were, on average, 0.016 wt-%, 0.079 wt-%, and 0.004 wt-% higher, respectively, than levels into the WM, suggesting that element transfer occurred primarily in the droplet zone. The transfer level of O from fluxes into droplets was, on average, 0.022 wt-% lower than that to the WM, indicating that beyond the droplet zone, alternative sources contributed to the increase in O content within the WM. The findings provide a theoretical foundation for precisely manipulating WM compositions and potentially optimizing the entire welding process to a new level.
This paper is the second of a three-part series covering the field of high-speed videography in welding. This second part provides a comprehensive discussion of two of the most common techniques of high-speed imaging of welding: backlighting and frontlighting, including broad and narrow-spectrum lighting (lasers in the case of backlighting) with both techniques. In all cases, building on the foundations laid out in Part 1, detailed descriptions of appropriate setups are provided together with examples of published practical implementations. The welding processes addressed include laser beam welding, gas tungsten arc welding, gas metal arc welding (GMAW), flux cored arc welding, and submerged arc welding. The advantages and disadvantages of front-and backlighting are explored in detail. Frontlighting is especially useful for processes with high dynamic range, such as short-circuit metal transfer in GMAW. Backlighting is less used with modern digital cameras; however, small amounts of backlighting can highlight features such as the electrode extension when using natural radiation lighting. Narrow-spectrum sources such as lasers are especially useful in combination with narrow bandpass filters to eliminate unwanted radiation sources. The implementations of front-and backlighting reviewed in this paper, together with those for natural radiation lighting in Part 3 and the fundamental concepts and resulting quantitative guidelines provided in Part 1, provide welding researchers with a previously inexistent compilation of criteria to select proper equipment, accessories, and parameters for high-speed imaging of a vast variety of phenomena in welding, laser welding, and associated processes such as additive manufacturing or cutting.
All-position welding is essential for pipeline installation, yet dynamic variations in butt gaps, groove mismatches, and welding positions challenge weld quality. To address these issues, this study developed an innovative adaptive control system for all-position root pass welding. The system integrated an innovative laser-GMAW hybrid all-position welding with copper liner coordinated control, offering robust process stability and a wide process window. It enables high-quality welding under dynamic fluctuations in work conditions while providing parameter adjustment margins for adaptive control. Furthermore, a particle swarm optimization-back propagation (PSO-BP) neural network was employed to establish an adaptive process database. Additionally, an improved gray centroid method was proposed for U-groove, achieving accuracies of 0.10 mm (0.00394 in.) for butt gaps and 0.07 mm (0.00276 in.) for groove mismatches. Validated on Phi 800 x 12 mm (31.5 x 0.472 in.) pipelines, the system produced welds with 3 similar to 4 mm (0.118 similar to 0.157 in.) backside reinforcement width and 0.50 similar to 0.80 mm (0.0197 similar to 0.0315 in.) height. This research provides theoretical and technical foundations for pipeline welding from double-sided to single-sided processes. Future work will focus on weld seam tracking and path planning to develop a comprehensive, all-position adaptive welding control system that integrates root, filler, and capping passes.
This paper is the first of a three-part series comprehensively covering the field of high-speed videography in welding. This first part provides the fundamental concepts and resulting quantitative guidelines provided for minimum frame rates for several welding phenomena for maximum possible image resolution and the ability to capture thermal radiation from the welding process. Welding phenomena discussed include metal transfer, arc, and weld pool evolution with examples for gas metal arc welding (GMAW) and shielded metal arc welding (SMAW). The maximum possible image resolution for a given system is established based on the amount of time recorded, the buffer memory, the sensor resolution, the bit depth of the sensor, and the frame rate used. The application of Planck's radiation law indicates that emission at low temperatures can be undetectable. Quantitative guidelines are also provided for filter type and critical wavelengths associated with light emitted by plasmas of different welding processes and thermal emission from the hot metal. Digital sensors, lenses, optical filters, and digital formats for processing and distribution are treated in detail. The fundamentals reviewed in this paper, together with the practical implementations for front and back lighting (Part 2) and natural radiation lighting (Part 3), will provide welding researchers with a previously inexistent compilation of criteria to select proper equipment, accessories and parameters for high-speed imaging of a vast variety of phenomena in welding, laser welding, and associated processes, such as additive manufacturing or cutting.
Production of three-dimensional metallic parts through integration of an articulated robot and gas metal arc welding, also known as wire arc additive manufacturing (WAAM), can produce large-scale components with moderate geometrical complexity. This technology is particularly appealing due to its high deposition rates, scalability, and cost-effective feedstock compared to other AM processes. Despite its advantages, WAAM adoption is hindered by challenges in ensuring geometric conformity without extensive distortion, defect-free structures, and consistent mechanical properties. Finite element analysis (FEA) is often used to address the challenge of geometrical conformity. As the size of parts increases, the best practices for mesh size and temporal resolution known in the literature become computationally unviable. This research examined the effects of mesh and time-step resolutions during transient FEA of a large-scale (248 layers) metallic part. The impact of computational parameters on the thermal history, displacement, and residual stress distributions were evaluated. The results showed that predicted distortion was consistent across resolutions, while time-step length significantly affected predicted thermal history, and mesh size influenced residual stress distributions. To investigate this relationship further, directionally biased meshes were considered and analyzed. The results indicated that increasing mesh resolution perpendicular to the welding path yielded stress predictions that aligned closely with higher-resolution models while offering substantial computational savings. The significances of this research are related to verification and validation of WAAM models for widespread industrial adoption and pragmatic guidelines for optimizing computation parameters for balancing computational efficiency and predictive accuracy of residual stress and distortion.
There is a clear need for sustainable material production to reduce waste and improve efficiency. Incorporating recycled scrap into aluminum production can improve sustainability. However, with each successive recycling iteration, the aluminum scrap accumulates elements such as Si, Fe, and Cu that degrade recyclability. This paper explores using an end-of-life aluminum scrap stream, called twitch, to make a wire feedstock for welding and additive manufacturing. A composition was selected from the twitch composition space based on predictions of solidification cracking susceptibility and potential age-hardening response. Cu and Si contents were predicted to have the largest influence on cracking, and susceptibility was predicted to be reduced at contents greater than 2.5 wt-% Cu and 0 wt-% Si. Powder core tubular wire was produced based on the target composition and used to make gas tungsten arc directed energy deposition builds. Secondary phases predicted by the thermodynamic simulations were generally observed experimentally, namely α-Al15(Fe, Mn)3Si2, Q-Al5Cu2Mg8Si6, θ-Al2Cu, and Si. The alloy exhibited an age-hardening response when heat-treated at 190°C, resulting in a peak hardness between 110 and 120 HV, comparable to 6061. This work shows great potential for designing new welding and additive
Advanced process monitoring and model validation are essential for improving weld quality in both welding and welding-based additive manufacturing processes. Specifically, temperature is a key quantity of interest for understanding defect formation and microstructural evolution, which significantly impact mechanical properties. However, achieving accurate in-situ temperature imaging is challenging due to emissivity variations across the dynamic melt pool. To address this, we implemented a two-color imaging technique using a single commercial color camera to reduce temperature readings’ sensitivity to emissivity variations. High dynamic range images during melting were captured at various exposure times, and spatial and temporal filters were applied to minimize interference from the plasma arc emissions. The resulting temperature fields within the melt pool were then utilized to estimate cooling rates, which were further correlated to ex-situ hardness measurements. The strong correlation observed between cooling rates ranging from 20 to 600 K/s and hardness ranging between 250 to 400 HV demonstrated the potential of our easy-to-use two-color thermal imaging setup for preliminary evaluation of mechanical properties in a non-destructive manner. Beyond its significance for predicting mechanical properties, this technique provides a validated temperature measurement approach that can enhance the accuracy of physics-based models, such as those used to predict defect formation mechanisms, like porosity.
