Weld Bead Surface Research Articles

Numerical evaluation of interwire angle influence on molten pool fluid dynamics and weld defects in tandem NG-GMAW of 5083 aluminum alloy

The impact of interwire angle on the fluid dynamics and weld defects in tandem NG-GMAW of 5083 AlMg alloy was investigated through experimental and simulation methods. The rotating coordinate system was employed to model the inclined arc and arc interaction, while a pulsed Gaussian distribution arc model was adopted to consider factors such as arc heat, arc pressure and drag force. Experimental results demonstrate that different interwire angles lead to different weld formation and varying levels of porosity and pore distribution. A sound weld bead with no formation defect and low porosity was achieved when the interwire angle was set at 10°. Simulation results illustrate the relationship between weld formation, bubble escape and molten pool fluid dynamics under diverse interwire angles. As the interwire angle increases, the weld surface becomes concave. At the interwire angle of 0°, the weld bead surface appears leveled and porosity tends to occur near the sidewalls due to roundabout flows in that region. At an interwire angle of 14°, roundabout flows converge at the central longitudinal section, resulting in significant porosity in this area. However, when the interwire angle is set at 10°, backward flows driven by two arcs suppresses roundabout flow throughout the entire molten pool, leading to a lower percentage of porosity area.

A comprehensive survey on the cold metal transfer process in welding similar and dissimilar materials and for cladding

The growing use of aluminum in a variety of industries is driving technologists to create practical and effective techniques and processes for joining aluminum alloys. The main aim of this artifact is to critically review and examine the maturity of welding for comparable and differing materials and also for cladding using Cold Metal Transfer. CMT, which stands for Cold Metal Transfer in the acronym, is a modified MIG welding technique. The CMT and its modes are used in similar and dissimilar welding of Al as well as its alloys of 2xxx, 5xxx, 6xxx, and 7xxx series, and with other materials is discussed in detail and compared with other joining methods. The recent advancements in this field with enhanced mechanical properties of Al alloys, as well as high-performance welding techniques, are discussed in this article. The mechanical and microstructural properties of weld like weld strength, microhardness, corrosion behavior, surface morphology, ductility, and fracture mechanism were used to assess the efficiency of the weld. The following aspects of weld bead surface consistency are investigated in terms of bead uniformity along the welding path, bead surface smoothness, and spattering strength. The effort is made to conclude the welding system which is free from all welding flaws, like gas porosity, spattering, and intermetallic formation, resulting in welded joints with the highest mechanical properties. CMT as an advanced welding approach has gained a significant attraction from researchers in investigating it for the cladding process. The geometric and microstructural properties of a clad-like microhardness assessment, and corrosion resistance analyses were used to evaluate the applicability of CMT in the cladding process.

Prediction of electron beam weld quality from weld bead surface using clustering and support vector regression

Destructive manual experiments are primarily used for quality assessment of electron beam welded components, which consume the resources and time significantly. Vision-based and other NDT-based quality monitoring in EBW is rarely reported, and consequently, more investigation is required. An inexpensive quality evaluation technique for the welded joints has been proposed using the weld bead surface attributes. These attributes have a good correlation with quality indicators like aspect ratio and mechanical properties of the joint. Here, electron beam welding of CuCrZr alloy was conducted to get varying weld profiles, and the surface weld attributes were measured. The model correlating top and bottom bead widths with the process variables was established using support vector regression. The predicted unlabelled weld attributes were employed as inputs for the unsupervised clustering algorithms, namely fuzzy C-mean clustering and density-based clustering. The clustering algorithms provided different clusters of the joints, namely poor, fair and good. FCM was found to be more precise for the clustering of welding data. Poor category of the joints was represented by that with partial penetration and lower aspect ratio, and the corresponding process variables’ combination could be avoided in the next iteration through the feedback. The fair category represented the joints with a high aspect ratio and keyhole-based profiles with moderate strength and ductility. The good category signified the weld joints having the maximum joint strength and ductility, and an acceptable aspect ratio with the conduction mode of welding. Keyhole-based weld profile could be obtained using high beam power (5.5 kW to 6.3 kW) with high welding speed (1000 mm/min and above). A combination of 0.1 mm oscillation amplitude and 900 Hz oscillation frequency was found to be the most favourable one, in this study.

In Situ Modification of CaF2-SiO2-Al2O3-MgO Flux Applied in the Aluminium-Assisted Transfer of Titanium in the Submerged Arc Welding of Carbon Steel: Process Mineralogy and Thermochemical Analysis

Flux formulations are specified to target chemical and physico-chemical parameters. Chemical parameters set flux element transfer behaviours and weld metal oxygen contents. Physico-chemical parameters such as slag viscosity, surface tension and melting range are targeted to ensure an acceptable weld bead profile and surface appearance. Slag detachability is an important physico-chemical property required to ensure high welding productivity, smooth weld bead surface and no slag entrapment. Here, bead-on-plate welding tests were made with and without metal powder additions, including aluminium powder as a de-oxidiser. Difficult slag detachability was observed in weld runs made with metal powder additions. Mineralogy of the post-weld slags, and thermochemical calculations, show that the flux was modified due to the aluminothermic reduction of MnO and SiO2 from the slag to form alumina. Increased quantities of spinel phase were identified in the post-weld slag samples, at the weld pool–slag interface. The combined effect of increased slag viscosity, from increased spinel in the slag, and lowered weld pool solidus temperature, resulted in the formation of a rough bead surface morphology, which, in turn, caused mechanical fixation of the slag to the weld bead. Flux modification to higher CaF2 content should ensure that higher quantities of spinel phase can be tolerated in the slag.

A comprehensive analysis of ultrasonic pulse current reducing hot cracking in Inconel 718 welds

A novel self-induced ultrasonic tungsten inert gas (U-TIG) welding has been successfully applied to weld the Inconel 718 sheet with thickness of 2 mm to reduce hot cracking. The welding arc, weld formation, microstructure and micro-hardness distribution between TIG and U-TIG welding were analyzed systematically. The relationship between micro-hardness and characteristics of grain size, grain orientation, grain boundary, segregation and recrystallization proportion in transition zone (from weld metal zone to heat affected zone) was investigated. The characteristics of sizes, disorientations and boundaries of adjacent grains, as well as the micro-strain distributions in weld metal zones of TIG and U-TIG welds were analyzed contrastively. The results indicate that the welding arc with symmetrical shrinkage induced by ultrasonic pulse current greatly intensifies the central depression of the weld bead surface, which benefits the release of welding thermal stress. With the promoted transformation of coarse columnar dendrites to fine equiaxed dendrites with similar orientation in U-TIG welds, the segregation in grain boundaries is greatly reduced, which reduces potential of the hot cracking initiation and propagation. In addition, the improvement of micro-hardness distribution is contributed by grain refinement and segregation dispersion in U-TIG welds.

Augmentation in depth of penetration of hastelloy C-22 by FATIG welding

Flux assisted tungsten inert gas welding (FATIG) welding is a modified version of tungsten inert gas (TIG) welding to achieve a higher depth of penetration. In the present work, nanoparticles SiO2, Al2O3, Fe2O3, and CuO mix with acetone and coated on the joint before welding. Bead on plate welding using different variants of FATIG welding performed on Hastelloy C-22. A comparative study of these variants called Activated tungsten inert gas (ATIG) and Flux bound tungsten inert gas (FBTIG) welding was conducted to find out their effects on depth of penetration, depth to width (D//W) ratio, surface appearance, and slag detachability. In addition, the influence of acidic and basic nature of flux on weld bead geometry and surface appearance are analyzed. Acidic fluxes produce a smoother weld surface than basic oxide fluxes; additionally, acidic flux slag is less sticky than basic flux slag. activated TIG (ATIG) welding with SiO2 flux increases penetration and D/W ratio by 125% and 190%, respectively compared to normal TIG welding.

Influence of the laser position in laser-assisted WAAM process on weld bead shape and surface properties

The lateral use of the laser in laser-assisted WAAM processes, resulting in a directional dependence, can influence the bead shape and the bead surface. The influence of the laser position on the weld bead is investigated. Beads with different laser positions are applied and the height and width as well as the waviness of the beads are evaluated. In addition, claddings are welded and the waviness is measured. The waviness along the beads ranges from 8.77 to 34.66 µm, and no significant correlation with the welding direction could be determined. For the bead shape, the differences in height range from 3.54 to 3.90 mm and in width from 8.20 to 8.89 mm. Based on the results, a dependence on the laser position for surface properties and weld bead shape becomes clear.

Effect of process parameters on stress and strain of hybrid deposition and micro-rolling

PurposeThis paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the shaping strain and residual stress. And the rolling parameters combination was further optimized to guide the actual production.Design/methodology/approachThis paper proposed a three-dimensional coupled thermo-mechanical model of the HDMR process. The validated model is used to investigate the influences of rolling parameters on stress and plastic strain (the distance between the energy source and roller [De–r], the rolling compression [cr] and the friction coefficient [fr]). The orthogonal optimization of three factors and three levels was carried out. The influence of rolling parameters on the plastic strain and residual stress is analyzed.FindingsThe simulation results show that HDMR technology can effectively increase the shaping strain of the weld bead and reduce the residual tensile stress on the weld bead surface. Furthermore, the influence of rolling parameters on stress and strain is obtained by orthogonal analysis, and the corresponding optimal combination is proposed. Also, the rolling temperature significantly affects the residual stress, and the rolling reduction has a substantial effect on the plastic deformation.Research limitations/implicationsOwing to the choice of research methods, this paper failed to study microstructure evolution.Originality/valueThis paper provides a reference principle for the optimal selection of rolling parameters in HDMR.

Investigation of tool forces, weld bead micro-hardness and surface roughness during friction stir welding of Aluminium 6063 alloy

ABSTRACT From last decade, Friction Stir Welding (FSW) process finds increasing applications in industry as the process is environment-friendly and offers inherent advantages in mechanical and metallurgical properties of welded joints. FSW employs a non-consumable rotating tool, which generates frictional heat and plastic deformation at the welding location while the material is in solid state. In this paper, mechanical behaviour of Aluminium 6063 alloy (AA6063) FSW joints in terms of tool forces, weld bead micro-hardness and surface roughness was investigated varying the welding parameters, namely the welding speed and feed which were varied in the range of 385–960 rpm and 18–45 mm/min, respectively. It has been observed that tool forces and hence, the surface roughness decreases with increase in welding speed and feed. Lower tool forces at higher values of welding speed and feed can be attributed to increase in temperature at weld bead resulted in softening of the material at higher welding parameters. Micro-hardness of the weld bead has been observed little affected within the domain of the weld parameters selected in the present study.

Weld Bead Surface Defects Formation and Its Implications – A Review

Weld Bead Surface Defects Formation and Its Implications – A Review

Effects of Helium Addition to Ar-Based Shielding Gas on the Lap-Joint Performance of 5052 Aluminum Alloy to Galvanized Steel Sheet during the MIG Weld-Brazing Process

In the metal inert gas (MIG) weld-brazing process, the lap-joint welds between 5052 aluminum alloy and automotive galvanized steel sheet were achieved employing an automatic MIG welding machine. The different percentage of helium (He) gas addition to pure argon (Ar) shielding gas was selected to investigate the performance of lap-joint welds such as appearance of weld bead surface, weld bead geometry, microstructure, tensile strength, fracture surface of welds and thickness of intermetallic compounds (IMCs) layer between the dissimilar materials in the brazing zone. The results showed that the lap-joint welds produced by adding 5% and 10% He gas to Ar shielding gas were provided with better performance of specimens. The average tensile strength of lap-joint welds between 5052 aluminum alloy and automotive galvanized steel sheet is 206.23 MPa. In additions, the amount of porosity in the fusion zone that specimens produced by using 10% He addition to Ar-based shielding gas is less than others. It can be found that the thickness of IMCs layer between the weld bead and automotive galvanized steel sheet from 3.30 μm to 4.90 μm.

Detection of irregularities on weld bead from the L-Statistic analysis of the acquired sound during pulse mode laser welding process

Since several past decades, many studies prove that the statistical or signal features extracted from the sound acquired from laser welding process was significantly giving information on the weld condition. However, a considerable amount of studies were only emphasizing on the use of common statistical features in which it is restricted to some limitation when dealing with non-stationary random sound signal. In this particular work, the main aim was set to detect the irregularities along the weld bead by way of implementing the L-Statistic analysis on the acquired sound during pulse mode laser welding process. To achieve the goal, pulse mode laser welding have been done onto 22MnB5 boron steel plate in butt joined configuration. During the process, sound signal was acquired using microphone and further analyzed by extracting L-statistic features from it. According to the findings, among all the L-statistic features analyze in this study, L-Cv (scale) was found giving a significant indicator of the weld bead surface condition. Larger value of L-Cv was recorded at the point where the large underfill occurred. On the other hand, it was also found that the L-kurtosis values could give remarkable information on the existence of the irregularities on bead width and depth. Hence, it could be drawn into conclusion that the irregularities on the weld bead during the pulse mode laser welding could be detected from the appropriate L-statistic features of the acquired sound signal. The finding in this work was believed to be essential in enhancing the capability of acoustic sound method to be developed as online monitoring system for pulse mode laser welding process.

Numerical and experimental investigation on weld formation during laser+MIG hybrid fillet welding of aluminum alloy in horizontal position

A three-dimensional transient model is proposed to investigate the weld formation during laser + metal inert gas (MIG) hybrid welding of aluminum alloy for horizontal fillet joint, which considers the coupling of keyhole, droplet, and liquid metal pool as well as the influence of joint geometry feature and welding position. An asymmetrical double-elliptic heat source is utilized to model the arc heat input and a conic heat source with increased peak heat density is used to describe the laser energy. The coordinate rotation is used to take into account the inclination of heat source and the related forces. According to the experimental and simulated results, weld formation mechanism of horizontal fillet joint is studied. At a lower laser power, the fluid flow pattern in hybrid welding is similar to that in MIG welding and a strong downward flow caused by both gravity and arc pressure occurs at the liquid metal zone of the vertical plate, leading to the accumulation of molten metal at the horizontal plate and the resultant weld asymmetry. At high laser power, a clockwise vortex appears above the keyhole. In this case, the sagging of liquid metal near weld pool surface due to effect of gravity is an important factor responsible for the asymmetry of fillet weld. Besides, with increasing laser power, the tendency of weld pool free surface sagging is enhanced to some extent and weld bead surface becomes concave.

Effects of laser energy allocation on weld formation of 9%Ni steel made by narrow gap laser welding filled with nickel based alloy

The allocation of laser power was a complicated process for narrow gap laser welding with filler wire. The narrow gap laser welding of a 16 mm thick 9%Ni steel plate was performed with nickel based alloy as filler wire. The effects of laser power, defocusing amount, and the distance between laser and filler wire were investigated through orthogonal experiments. The allocation paths of laser energy on molten pool, keyhole, metallic vapor, and filler wire were presented. The influencing mechanism and optimization strategies of sidewall fusion ratio, coarse grain region width, and weld bead surface evenness were investigated.

Molten pool behaviors and their influences on welding defects in narrow gap GMAW of 5083 Al-alloy

The welding defects such as porosity and lack-of-fusion is more likely to occur in the narrow gap gas metal arc welding (NG-GMAW) of aluminum alloy. In this study, a three-dimensional transient numerical simulation was carried out to investigate the molten pool behaviors as well as their influences on welding defects. A pulsed arc welding mode was employed, which is accompanied with elliptically symmetric arc models. Three different weld bead surface shapes i.e. the convex, flat and concave surface were achieved both by experiment and simulation with varied welding current. The flow pattern varied significantly due to the different thermal and force conditions. The formation process of lack-of-fusion defect was analyzed and the effect of flow pattern on porosity in all cases were discussed. The results indicate that the upward fluid flow near the sidewall border of molten pool facilitates the formation of lack-of-fusion defect and the downward and backward fluid flow near the sidewalls may induce the porosity.

Study of weld formation in swing arc narrow gap vertical GMA welding by numerical modeling and experiment

A three-dimensional unified model is proposed to simulate the weld pool dynamic behavior in swing arc narrow gap vertical GMA welding with allowing for swing feature of arc heat source and joint configuration. Both the moving direction of arc and its inclination are considered by transformation of coordinate system. The model can simulate the weld pool sagging process reasonably. Based on the calculated and experimental results, the mechanism of weld formation in swing arc vertical-up welding is studied. The weld pool size and the peak temperature of liquid metal are reduced largely in the case of swing arc, which leads to the faster solidification of weld pool and is the major factor responsible for suppression of weld pool sagging. Meanwhile, upward component of arc force and the enhanced support force from solidified metal bulge benefits the weakness of downward flow of liquid metal. With increasing the swing frequency, weld cross section geometry tends to be symmetrical and weld bead surface becomes smoother. When the swing frequency is higher than 0.6 Hz, the satisfied weld formation can be obtained.

Study on influence of concave geometry shoulder tool in Friction Stir Welding (FSW) by using Image Processing and Acoustic Emission Techniques

In the present study, the influence of concave geometry shoulder tool of FSW on weld quality was analysed by using Acoustic Emission and Image processing techniques has been done. The interaction of tool shoulder with base material in the arrangement of friction stir weld is studied by contemplated the banded texture of weld bead surface using image processing techniques. Experiments are carried out by capturing the images of weld bead surface of friction stir welded specimens produced using different process parameters. The images are digitally processed and analysed by characterizing locale of interest along good and defect weld region based on X-Ray radiography and AE results of friction stir welded specimens to determine first order and second order measurable statistical textural parameters of weld bead surface using MATLAB

Effects of ultrasonic peening treatment on surface quality of CMT-welds of Al alloys

The porosity number and porosity area percentage of weld beads close to the weld surface reduce after ultrasonic peening treatment. The grains are refined significantly in severe deformation layer and transition layer. The refined grain size is approximately 200nm on the surface of weld bead after ultrasonic peening treatment. The loads on severe deformation layer and transition layer are larger than those on weld beads without ultrasonic peening treatment with the same indentation displacement in nano-indentation tests. After ultrasonic peening treatment, the elastic modulus of the weld bead surface increases slightly due to the decrease of porosity fraction. The hardness values of severe deformation layer and transition layer increase, which leads to the enhancement of wear resistance of welded joints.

Effect of Activating Flux on Penetration in ATIG Welding of 316 Stainless Steel

Tungsten inert gas welding is popular in some industries due to the possibility of obtaining good weld bead surface and high-quality joint without any weld defect. However, compared to many welding processes, shallow penetration of TIG welding hinders its applicability to weld thick components in one pass, thus the productivity is relatively low. An increased depth of penetration can be achieved by Activated TIG (ATIG) welding leading to overall reduction in number of welding passes, and thus increasing productivity. In the present work, attempts were made to find out the optimum flux mixture of SiO and TiO from various ratio of mixtures by carrying out 2 2 bead-on-plate welding on AISI 316 Stainless Steel specimens. From the obtained experimental data, suitable flux ratio was tried to find out giving the highest depth of penetration.

Effect of Activating Flux on Penetration in ATIG Welding of 316 Stainless Steel

Tungsten inert gas welding is popular in some industries due to the possibility of obtaining good weld bead surface and high-quality joint without any weld defect. However, compared to many welding processes, shallow penetration of TIG welding hinders its applicability to weld thick components in one pass, thus the productivity is relatively low. An increased depth of penetration can be achieved by Activated TIG (ATIG) welding leading to overall reduction in number of welding passes, and thus increasing productivity. In the present work, attempts were made to find out the optimum flux mixture of SiO and TiO from various ratio of mixtures by carrying out 2 2 bead-on-plate welding on AISI 316 Stainless Steel specimens. From the obtained experimental data, suitable flux ratio was tried to find out giving the highest depth of penetration.