Weld Bead Research Articles

Numerical simulation of a laser beam welding process: From a thermomechanical model to the experimental inspection and validation

In laser beam welding (LBW) complex physical phenomena occur during laser-material interaction, which prolong the parameterisation of the process due to the extended trial and error tests. Therefore, predicting the process behaviour leads to a more productive and cost-reduced process experimental tuning. Besides, as LBW is a thermal process, part distortion plays a relevant role in the final result, and hence, thermal and mechanical analysis are both required. In view of this, in the present research, a novel multiscale numerical model, capable of predicting the thermomechanical behaviour of the LBW process has been developed. The significance of the model is its capability of forecasting the part distortion and thermal field employing two fully coupled modules, where the laser heat source automatically adapts to the welding regime without the need to consider the melt pool dynamics and at a low computational cost. The local model determines the melt pool dimensions and thermal field. Besides, the second module, the global model, figures out the part distortion based on the thermal results. Finally, the presented numerical simulations are experimentally validated with the corresponding temperature monitoring during the welding process, the posterior metallography inspection, and the part deformation measurement. The results present a high accuracy, with a maximum error below 10 % at the temperature measurements, an average dimensional deviation of 0.14 mm and 0.18 mm respectively for the weld bead depth and width, and a vertical deformation average error of 0.15 mm.

Location-Dependent Phase Transformation Kinetics During Laser Wire Deposition Additive Manufacturing of Ti–6Al–4V

This work models the microstructural evolution as a function of position in laser-wire deposited Ti–6Al–4V parts using a classical multi-component JMAK nucleation and growth model with additive isothermal time-steps. Model predictions are compared to experimental observations. The model can be used to interpret nucleation and growth kinetics of various characteristic features of the microstructure that are inaccessible by experiments. It explains the presence of “layer bands” at specific locations unrelated to the weld bead structure. The last re-heating (of multiple thermal cycles) of a solidified layer, and where it peaks, plays a key role in increasing the nucleation density at specific locations, resulting in full α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}-colony microstructures constituting the “layer bands,” while the rest of the build is predominantly basketweave. Additionally, changes in the basketweave α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}-lath thickness as a function of the distance from the substrate are studied and compared with an Arrhenius-type function, with results highlighting a more complex relationship than an Arrhenius-type function would suggest.

Microstructure and corrosion characteristics of AA5083 alloy weld beads produced by GTAW and SpinArc-GMAW

In this study, bead-on-plate welding was performed on a sheet of AA5083 alloy using two distinct welding techniques: gas tungsten arc welding (GTAW) and SpinArc-gas metal arc welding (SA-GMAW). This study compares the microstructural, mechanical, and corrosion characteristics of processed weld beads. The microstructural features of the weld beads were characterized using optical microscope (OM), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HR-TEM). The corrosion characteristics of weld beads were determined by potentiodynamic polarization method, and the corrosion morphology of the specimens were observed under SEM. In addition, a microhardness study was performed on the weld beads across the base metal (BM), heat affected zone (HAZ), and fusion zone (FZ). The findings indicate that the weld bead produced by GTAW exhibited superior corrosion resistance compared to the weld bead processed by SA-GMAW. The presence of porosities in the latter facilitated the corrosive medium to penetrate and break the passive layer easily that developed deeper corrosive pits. The presence of Fe and Mn rich intermetallics in FZ of GTAW processed weld bead assisted in better rate of corrosion observed at 0.1259 mm/yr. The hardness observed in the FZ of the SA-GMAW bead was found to be lower compared to the GTAW weld bead due to the presence of porosities and coarser grains.

Impact Analysis of Welding Sequence to Reduce Weld Deformation in Aluminum Hulls

Aluminum hulls, which are preferred in the marine industry due to their durability, corrosion resistance, and lightweight properties, face serious challenges due to thermal deformation during welding. This study aims to predict and minimize transverse deformations due to welding sequences for a transverse model in the lower part of an aluminum hull. To predict deformations, heat source dimensions obtained from actual weld beads were used as simulation conditions, and various welding sequence conditions were simulated through the developed finite element method (FEM). The simulation results were compared with actual deformation measurements to verify their reliability, and the optimal welding sequence which minimized deformation was derived. The simulation results show that by changing the welding sequence conditions, the maximum displacement can be reduced from a maximum of 52.1% to a minimum of 39.1%, and the effective plastic strain can be reduced from a maximum of 19.6% to a minimum of 4.8%. These results show that adjusting the welding sequence conditions can significantly improve structural integrity by minimizing deformation. The results of this study suggest that the control of the welding sequence can be used to reduce the deformation of aluminum hulls and promote a more sustainable marine industry with improved quality.

Optimization of gas metal arc welding parameters for dissimilar steel welds: A case study on duplex stainless steel 2205 and stainless steel 316L

The significance of welded connections in steel structures necessitates precise structural designs and processing adaptations to ensure robust mechanical strength and durability. Gas metal arc welding (GMAW) employing controlled curves presents advantages over conventional methods, offering enhanced weld bead properties, improved aesthetics, and reduced thermal inputs. This research investigates the impact of GMAW parameters using controlled curves on the microstructure and geometry of welds between dissimilar structural steels—duplex stainless steel 2205 and stainless steel 316L grade 50—commonly employed in construction. The aim is to optimize the GMAW welding process with controlled curves and surface tension transfer between these dissimilar steels. Through a 23-factorial experimental design encompassing feed speed (Va), arc focus (FC), and peak-to-base amplitude (APB), the study examines welding energy, geometry, deposition efficiency, microstructure, microhardness, tensile strength, and corrosion properties. Optimal welding energy fosters refined microstructures and uniform hardness, aiding in predicting weld throat area. Higher energy levels expand the heat-affected zone and coarse grains, while lower energies escalate variability. Predictive models facilitate fine-tuning welding energy and throat area for desirable properties and penetration while minimizing disruptions. This process optimization can be achieved by employing derived equations that limit welding energy and curve parameters, striking a desired balance between cost, structural integrity, and reliability.

Experimental Investigations on the Fabrication of Low Alloy Steels Using Wire Arc Additive Method

Wire arc additive manufacturing (WAAM) has emerged as a transformational technology with the capacity to redefine the landscape of alloy steel component production. This method utilizes an electric arc to selectively fuse a continuous wire feed, progressively constructing intricate metal structures layer by layer. GMAW-based WAAM adaptability enables the creation of complex geometries and customized part designs, making it applicable across diverse industrial sectors. This paper investigates WAAM-specific applications in alloy steel fabrication, focusing on key process variables such as voltage, travel speed, and Gas mixture ratio. The experimental parameters for a single layer are examined with voltage ranging from 20 to 22, travel speed from 23, 25, and 27 mm/min, and Gas mixture ratio 1,5,9 mm/min. It utilizes materials like TM B9, a 1.2- diameter flux-cored wire. Additionally, the study considers the nominal composition (wt-%) of 9 Chromium, and 1 Molybdenum, with small additions of nitrogen and niobium to improve the creep resistance. Furthermore, the final findings of the study suggest that the optimal combination of process variables for achieving highquality weld beads in WAAM of alloy steel components can be determined through Response Surface Methodology (RSM). RSM is a statistical method for analysing and modeling the relationship between the response of interest and some independent variables. In this case, the response variable would be the quality of the weld bead, which encompasses factors such as bead geometry, integrity, and absence of defects.

TIG welding of in-situ produced syntactic metal foam-filled tubes

Abstract Aluminium matrix double composites were produced via an in-situ pressure infiltration method. AlSi12 alloy matrix with densely packed lightweight expanded clay aggregate particle-filled foam was produced in-situ within AlMgSi0.5 alloy tubes. The attainable size of such double composites is limited; therefore, joining them is required to create larger parts. For the joining of these double composites, the applicability of tungsten inert gas (TIG) welding was tested. TIG welding was found to be applicable to join such composites. Metallurgically sound welded joints were produced. Nevertheless, the TIG welding of metal foam-filled tubes is very challenging and needs experienced welding personnel, and the weld bead was a bulk material, not a foam anymore.

Effect of laser welding parameters on the microstructure and tensile properties of low-alloy high-strength steel

Abstract The studying employed orthogonal experimental approach to optimize the laser welding process parameters for HC420LA low-alloy high-strength steel. Through metallographic analysis, microhardness testing, and tensile testing, the study assessed and contrasted the properties of laser-welded and arc-welded joints. The findings revealed that the most optimal laser welding conditions were 1.8 kW laser power, 2.5 m min−1 welding speed, and a focus distance of 1.5 mm, resulting in a well-formed ‘X’ shaped weld bead. Comparative analysis demonstrated that the laser-welded joint exhibited a finer microstructure, primarily composed of bainite and ferrite, whereas the arc-welded joint consisted of ferrite and martensite. Notably, the laser-welded joint exhibited superior mechanical properties, including increased microhardness and tensile strength, underscoring the distinct advantage of laser welding technology in high-strength steel welding, particularly in enhancing the weld joint’s quality and performance.

The influence of Cu on the microstructure and properties of TC4/Q345 high-entropy joints by laser welding

FeCoNiCrCu high-entropy alloy (HEA) and Cu foils were utilized as the intermediate layer to conduct laser welding of TC4 titanium alloy and Q345 steel. Welding is performed by adding single HEA and Cu/HEA double foils as interlayer respectively. We conducted in-depth studies on the microstructure and mechanical properties of the joint by stereomicroscopy, metallographic microscope, scanning electron microscope (SEM), micro-area X-ray diffraction (XRD), nanoindentation, electron backscatter diffraction (EBSD), and tensile testing. The results indicate that the position of the copper foil significantly affects the microstructure and performance of the joint. When the copper foil is on the TC4 side, its lower melting point causes a deeper keyhole, resulting in a narrower weld bead and then reduced content of Fe and Ti in the weld. Simultaneously, the increased proportion of Cu in the weld significantly enhances the content of Cu-rich phases. In the weld zone, we observed freely distributed Cu-rich phases and Ti-rich phases generated along the interface. Under tensile loads, cracks primarily initiate and propagate along the Cu-rich phases, leading to typical delamination on the fracture surface. With the copper foil on the TC4 side, due to the increased copper content in the microstructure, the hardness of the interface between the titanium alloy and the weld decreases, while the joint exhibits the highest tensile strength, reaching a maximum of 417 MPa.

Digital bead modeling for wire-arc directed energy deposition

Prediction of 2D cross-section and full 3D geometry for stacked weld beads is critical for the outcome of wire-arc directed energy deposition (DED) parts; however, most additive path planning software packages model beads as extrusions of a rectangle. Weld beads are not rectangular, and the resulting shape is dependent upon physics effects at the moment of deposition. Physics phenomena such as the geometry of the underlying surface, the heat input of the welding mode, and the direction of gravity contribute to bead shape. This paper presents a novel implicit modeling method that discretizes a 2D area or 3D volume of space into pixels or voxels and constructs fields based on these physics phenomena. The fields are combined using a weighting scheme trained on 3D scan measurements of welds and wire-arc DED prints. Pixels or voxels are added until the known amount of deposited volume has been achieved. Thereby, a strong conservation of mass principle is applied to the process. Utilizing machine learning techniques, the present model can be trained on a database of scans allowing for the representation of a wide variety of prints. Results show that this method can produce predictions with realistic bead morphology and sub-millimeter form error.

FSW of AA2024: effects of tool wear on energy consumption

ABSTRACT This study shows that the progressive adhesion of weld material to the tool in friction stir welding AA 2024-T3, up to tool saturation, brings about a decrease in power consumption until a plateau is reached. The cause of this behavior is the hindering of the stirring action of the tool due to the material accumulated on it. The built-up material changes the nature of the tool/material interaction and then the friction condition at their interface. The direct consequence is a decrease in the shearing strain and therefore in the heat generated by friction. Bits of this adhering material break off from the tool at intervals. Macro and micro detachments are identified. Micro-detachments happen continuously at small periodic intervals and produce vibrations. The amplitude of these vibrations increases in all their characteristic spectral components up to tool saturation. Macro-detachments generate oscillations in power consumption and leave galling on the weld bead.

A new method for joining Incoloy825/X65 composite plate by laser and CMT welding

Incoloy825/X65 composite plate had good application in the submarine transporting pipelines due to combination of the high resistance to Cl− corrosion and preferred mechanical properties. But the enrollment of Fe into Ni layer deteriorated the corrosion resistance in welding the transition layer of composite plate. In view of this, the paper respectively adopted the laser welding on the Ni layer without filler metal and then the swing arc CMT welding with steel filler metal as a transition in order to inhibit the Fe into Ni layer. The results showed the laser welding bead on Ni layer with uniform and fine γ microstructure ensured the better corrosion resistance. The CMT welding controlled the dilution rate under 6 % through optimizing the welding speed and swing frequency of arc. Finally, the tensile strength of transition weld was up to 500 MPa surpassing the base metal of 490 MPa. The clad bead with charge transfer resistance of 756 kΩ·cm2 satisfied general submarine pipeline anti-corrosion requirement.

Flux Filling Rate Effect on Weld Bead Deposition of Recycled Titanium Chip Tubular Wire

Flux Filling Rate Effect on Weld Bead Deposition of Recycled Titanium Chip Tubular Wire

A study on the performance of super duplex stainless steel cladding over mild steel using a CMT welding

Low carbon steels can be cladded with super-duplex stainless steels to enhance the surface’s mechanical and wear properties. The current study examines the impact of process parameters on weld bead geometry and dilution % during cold metal transfer (CMT) cladding of super duplex stainless steel 2507 over low carbon steel. Response Surface Methodology (RSM) with a Central Composite Design matrix was used to optimize the process parameters (welding current, welding speed, and nozzle to workpiece distance (NTD)). The adequacy of the model was checked using an ANOVA analysis. The optimal bead width, height, penetration, and dilution values were 8.05 mm, 4.52 mm, 1.56 mm and 14.64%, respectively. The ideal input parameters were 200 A of welding current, 4.64 mm/s of welding speed, and 14 mm of NTD. The welding speed is the most dominant parameter, followed by the welding current and NTD. The cladding samples were prepared from the optimal parameters. The CMT-clad layer’s microstructure, microhardness, and wear properties were also evaluated. The results indicate a dense crack-free and non-porous clad surface was obtained under optimal conditions.

Analyzing weld bead geometry and microstructure in ultrasonic-assisted activated flux TIG welding of ST37 steel

Analyzing weld bead geometry and microstructure in ultrasonic-assisted activated flux TIG welding of ST37 steel

Fatigue assessment of structural components through the Effective Critical Plane factor

The integrity assessment of structural components under complex loading conditions relies on the evaluation of the fatigue damage typically arising from stress concentrations, such as geometric irregularities, notches, weld beads, grooves etc.. Various methodologies, including the Notch Stress Approach (NSA), the Theory of Critical Distances (TCD), the Strain Energy Density (SED), and the Critical Plane (CP) concept, have been pivotal in assessing fatigue strength for notched and welded components. Recent works combine some of the above mentioned methodologies, while other works propose to vary the embedded parameters accounting for the loading type or the fatigue lives, trying to improve the accuracy of the fatigue assessment process. This paper introduces a novel approach, the Effective Critical Plane (ECP), which is founded on the critical plane concept. The CP factor is, however, calculated starting from an averaged, over a small volume, stress–strain field. The size of the averaging volume is assumed to be a material parameter and is determined by a best fitting procedure over different experimental data sets. The novel approach is illustrated by means of the Fatemi-Socie and the Smith-Watson-Topper CP damage factors. Its potential application to other CP formulations is straightforward, as well. Literature experimental data for low carbon steel specimens possessing different notches and loading conditions are used to validate the method’s capability in accurately determining the fatigue life and to set the radius of the averaging volume for the given material and CP parameter. A spherical volume or circular area are used in case of fully 3D or 2D numerical models, respectively. Results are compared to those of some of already existing methods, namely SED, TCD and the Modified Wöhler Curve Method.

Evaluating edge joint preparation impact on penetration depth in laser-arc hybrid welding

Nowadays, conventional welding technologies such as submerged arc welding (SAW) are still used in most heavy-steel industries. This type of traditional technology means that welding takes up a large part of the productive time. As a solution to this problem, there are welding methods, such as Laser-Arc Hybrid Welding (LAHW), that have the potential to reduce the cost of manufacturing large steel structures. This is possible due to the reduced number of weld passes required to join thicker steel sections, as large thicknesses can be welded in one or a few passes.A problem with LAHW is achieving satisfactory quality. For this reason, it is essential to study the starting conditions, e.g. edge joint preparation. The target of this research work is to find out the relationship between the penetration value of the weld bead obtained and the edge joint preparation. The evolution of the molten pool and the behavior of the molten material in the joint is discussed for the different edge joint preparation configurations. The effect of the roughness is that it affects the wetting of the molten material in the joint, which would affect the penetration result, together with the gap and air volume gap used in the joint. Cut-wire is also used in the research, in samples that presented a larger air volume gap. The behavior of the molten metal inside the joint in this case is also discussed. In addition, the quality of the weld beads has also been determined by making macrographs, microstructural analysis, X-ray, microhardness profiles, tensile test and Charpy test. Some pores and cracks have been found, although destructive tests show adequate behavior of the weld bead. It is possible to elucidate from the findings that as the roughness, gap and/or air volume gap of the edge joint increases, the penetration value obtained increases. Cut-wire samples obtained full penetration.

Crucial effects of plasma gas on the weld and microstructural characteristics of plasma arc welded aero engine Ti6Al4V alloy joints

This study explores the influence of plasma gas flow rate (PGFR) on the defects, microstructure evolution and mechanical properties during plasma arc welding of Ti6Al4V titanium alloy thin sheets using microscopic analysis, spectroscopic analysis, tensile and microhardness tests. The variation in PGFR affects the welding arc in terms of its stability, pressure and constriction which results in transformation of arc from conduction mode to keyhole mode and changes in microstructure as well. All the other welding process parameters were kept constant except for PGFR which was varied to investigate its significance. Excess weld metal was observed under the weld bead is an attribute of keyhole formation. Macrographs exhibits increments in weld geometry measurements whereas weld defects such as lack of penetration and porosity decreased with increased PGFR. The microstructural examination showed a variety of phase formations that includes majorly with acicular α and Widmanstätten α morphologies. Tensile strength and hardness at the weld region of the welded joints increases with increase in PGFR. An oxygen rich brittle subsurface layer called α-case morphology was observed at the weld region of 1 L/min joint causes significant reduction in ductility.

Investigations on corrosion rate, mechanical properties and structural homogeneity of interpulse TIG dissimilar weldments

This manuscript aims to investigate the welding characteristics, bead profile, structural integrity and corrosion behavior of low-carbon steel and Monel grade 400 dissimilar joints. The structures were developed using advanced welding technique, gas tungsten constricted arc welding, with Mo-based filler wire. Dissimilar metals after welding have been tested for internal inspection using X-ray radiography and confirmed to be free from all welding defects. Corrosion tests were carried out at various zones of weldment and characterized in a 3.5 wt% NaCl solution at 10 mV/s scan rate. The welding characteristics have been studied by conducting various tests including Vickers hardness, tensile and impact test. To reveal the structural integrity and perform chemical composition analysis of constricted arc weldment, OM/SEM techniques were used. Corrosion rate at steel interface is lower than that at the Monel 400 interface by 9.7% due to the less accumulation of heat. Uniform grain distribution and structural homogeneity were also observed along the weld zone due to constricted arc and controlled heat input.

Role of Activating Flux in Weld Bead Symmetricity during Dissimilar Metal Joining

Ferritic/martensitic steels and austenitic stainless steels are high‐strength steels, and highly recommended in high‐temperature and high‐pressure application. In general, multimetallics with different Inconel alloys are used for joining. This is quite a complex and time‐consuming procedure. The current work demonstrates the efforts made to weld 8 mm‐thick P91 steel and 316L SS plates in a single pass using activating flux tungsten inert gas (A‐TIG) welding process without any interlayers. The main challenge is to get the symmetric weld bead profile. Flux coating is optimized in terms of flux composition, coating density, and coating pattern to get the full penetration with symmetric appearance. The current work discusses the possible cause and their solution of asymmetricity during dissimilar welding. Differential flux coating density is found to be very effective in controlling the arc column shape, fluid flow, and consequently the bead geometry. High coating density is used in the P91 side compared to 316L side. Symmetric weld profile with full penetration is achieved by applying multicomponent flux (33–38% TiO2, 38–43% SiO2, 13–17% NiO, and 8–10% CuO) during A‐TIG welding.