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In wire arc additive manufacturing (AM), as in arc welding, arc heat thermally deforms substrates and articles. For industrial applications, deformation characteristics of various materials must be understood and appropriate materials and methods of reducing deformation must be devised. Therefore, angular distortions of different materials were investigated through bead-on-plate welding and finite element analysis. A model that simplifies temperature-dependent properties was developed to establish relationships between thermomechanical properties and angular distortion. A simplified model of temperature-dependent properties was used, and angular distortion characteristics were extensively investigated for different material properties and heat inputs. Coefficient of thermal expansion, density, and specific heat all notably affected angular distortion depending on heat input conditions. Results showed that during wire arc AM, flatness of both substrates and articles could vary depending on material properties, heat input, substrate thickness, and bead accumulation. Study findings can provide insight into deformation characteristics of new materials and how to mitigate thermal distortions.

The objective of the present experimental work is to obtain an appropriate welding parameter on pulsed current gas tungsten arc welding (GTAW) ferritic stainless steel AISI 409L with a thickness of 4.5 mm. Frequency affected penetration, and the ratio of bead width to penetration (aspect ratio) is the main objective of the research. A Taguchi L9 orthogonal array with three level four factors was chosen to execute the bead on plate welding. It leads to optimize the input process parameters on main effect plot via analysis of variance, and it has imposed to determine their contribution level of each parameter with respect to responses. Taguchi optimized conditions for butts weld with the pulsed TIG and its surface morphology, and mechanical characteristics of AISI 409L weld was investigated. A full penetration with an optimal aspect ratio was accomplished using high-frequency pulsing, according to the findings. The mechanical properties were characterized using Vickers microhardness and tensile tests on the base material and weld metals. Microstructural study revealed that these variables have a greater impact on the bead profile. Pulsed TIG showed maximum UTS of 445 MPa and a minimum of 385 MPa, with an average of three samples of 415 MPa. The weld metal in all of the zones had influenced superior tensile strength (UTS) as compared to base metal, according to the findings. The obtained strain percentage for both butt and TIG welds, however, was smaller than that of the parent metal. The formation of martensitic was attributed for the higher tensile strength with minimized ductility of the pulsed TIG welds. Furthermore, results on the hardness are in concurrence with the tensile experiments, as the zone for fusion has a higher hardness than the base metal. Corrosion behavior of the parent metal and welded specimen was analyzed using a potentio-dynamic polarization technique. The electrochemical behavior of base material and weld samples confirmed that the overall corrosion resistance is better in parent material than the other zones.

Some studies have been developed to demonstrate that welded plates have their natural frequencies reduced when comparing them to non-welded similar plates, which is caused by welding residual stress. This phenomenon can be used to develop a new welding residual stress detection method. This new method, analyzing the plate vibrational responses, would have the advantage of being nondestructive, when comparing to hole drilling, and simpler and cheaper than X-ray diffraction, ultrasound and neutron diffraction methods. Therefore, in the search of this new technique, more research is being developed and more progress is still required. Some experimental work in the field has used bead-on-plate weldments for data analysis. However, this work demonstrates that bead-on-plate weldments do not present the same vibrational responses due to welding residual stress than butt-welded plates. This experimental work compares the vibrational responses of two identical plates welded by two different manners: bead-on-plate and butt-welded. Two stainless steel AISI 316L plates, with 302 × 150.5 × 6.30 mm, were tested. First, the entire plates had their natural frequencies measured, using a laser vibrometer. Then, one plate was Gas Tungsten Arc welded bead-on-plate on its center. The other plate was wire Electrical Discharge Machining cut in its center and then butt-welded. There was no material addition, in order to avoid additional mass interference in the natural frequencies values. Finally, the natural frequencies were measured again and the variations were calculated for the first six vibrational modes. Even though it was employed the same heat inputs and welding parameters in both welds, it is shown that the butt weld had higher modal variations than the bead-on-plate. The higher modal variations in the butt-welded plate indicate that butt weld induced higher welding residual stresses in the plates than bead-on-plate. Therefore, this work demonstrates that researchers willing to advance in the studies about the new welding residual stress method using vibrational responses should be attentive to this disparity.

The extended use of laser welding in the industry requires a less sensitive process in terms of geometrical tolerances of the joint edges. As the industrial availability of laser systems increases, the demand to use laser welding technology possibly with parts coming from less precise production steps is increasing. Gap formation is often caused by the edge quality of the parts coming from previous manufacturing steps such as sheet forming. Al alloy sheets deformed to box-shaped 3D forms often require welded joints on the edges in lap, but, and corner joint configurations. These joints are hard to carry out by laser welding due to the large gap formation caused by the tolerances of the deformation processes involved. Laser welding of Al alloys is already challenging in the absence of gap formation, while these joint configurations have been not feasible with a stationary beam due to incomplete fusion and defect formation. Laser welding with beam oscillation and wire feeding can improve the weldability of these joints. The oscillating motion of the high-intensity beam can achieve a deep weld together with a wider seam. Combined with wire feeding, the process can close gaps in the butt, lap, and corner joint configurations. On the other hand, the added oscillation and wire-related parameters require extending the experimental space, which requires a methodological study to identify feasible conditions. Accordingly, this work proposes a methodological approach to identify and set laser welding process parameters with beam oscillation and wire feeding for an EN AW 5083. Process parameters were initially studied using a simple analytical model that depicts the beam trajectory. Bead-on-plate tests were conducted to assess beam size, power, and weld speed ranges. Lap, butt, and corner joint conditions with a 0.5-mm gap were welded with high quality by manipulating the laser power, oscillation amplitude, and wire feed rate. The results show that welding speeds could be maintained as high as 55 mm/s with complete filling of gaps of up to 0.5 mm, eliminating the surface undercuts and achieving weld widths in the order of 2.5 mm. Moreover the results show the possibility control the depth of the welds from 3 mm to full-penetration conditions.

Hairpin winding technology is a crucial part of the contemporary electric drives used for traction applications. The contacting of the hairpin couples requires a fast process with high quality and cleanliness in the processing environment. High-brilliance NIR sources provide industrially accepted solutions with high productivity, while spatter, porosity, and material burst defects remain open issues to be resolved. The use of conduction mode welding may provide a more stable process in the absence of keyhole fluctuations. The blue wavelength at high power can provide the means for a conduction mode weld with high absorptivity despite low irradiance, sufficiently deep and wide as required by the hairpin welding applications. This work investigates the use of a 3 kW blue diode laser with 720 µm spot size for the welding of pure Cu hairpin couples. The work systematically investigates the melting capacity of the blue laser beam from bead-on-plate experiments to the hairpin welds with elliptical trajectories and an increasing number of scans. The results show that the blue laser is capable of producing the weld beads with sufficient size using scan speeds between 50 and 150 mm/s and a number of rotations between 2 and 7, characterized by low porosity and reduced material ejection. The process was observed to be relatively slower compared to keyhole welding but proved to be favorable for reducing spatter generation. The conduction-based welding is also provided to correlate more easily the external dimensions of the weld bead to weld strength and electrical resistance. Such features are highly appealing for an easier process of quality assessment.

This study presents a basic investigation on angular strain behaviour of substrate using experiment and three different numerical computations based on elastic and elastic–plastic FEM methods. In simulation, a 3D simplified rectangular weld bead geometry was modelled and computed using general purposed numerical software MSC Marc/Mentat. While elastic FEM with well-known inherent strain method-user defined (ISM-UD) and new ISM weld-kinematics (ISM-WK) were applied in which the inherent strain values were empirically estimated with regard to process parameters, physical properties, and effective area on heat affected zone, the most popular elastic–plastic or thermo-mechanical method (TMM) considers temperature-dependent isotropic hardening rule and heat source model. For verification purpose, experimental analysis was conducted as bead-on-plate process with austenitic stainless steel material SS316L using GMAW robotic welding. It can be concluded that TMM can predict the total experimental angular strain with mean percentage error up to ca. 7% compared to ISM with 19% for weld kinematics and 29% for user defined. In terms of computational time, ISM gave higher potential to be implemented with only 10% of TMM.

The underwater welding process used to repair offshore engineering structures involves a large number of processing parameters that must be selected and strictly controlled to achieve the required metallurgical and mechanical characteristics. Internal and surface porosity is a very common serious problem in underwater welding directly dependent on the process parameters. In this research work, a novel modeling and optimization study applying support vector regression (SVR) model and sequential quadratic programming (SQP) algorithm in order to predict and optimize the main process parameters of underwater flux cored arc welding (FCAW) on surface porosity in bead-on-plate welds of ASTM A36 steel is investigated. For this purpose, the experimental underwater wet FCAW process was carried out in an open tank with a 30-cm fresh water column. A composed central design was used to obtain the experimental matrix of 17 underwater welding tests with several combinations of parameters and variation levels: voltage ( V , 22–26 V), welding speed ( v , 3–10 mm/s), and wire feed speed ( WFS , 6350–11,430 mm/min) and the surface porosity was counted to each weld bead. In general, the results showed that this new computational approach using SVR satisfactorily approximates the level of surface porosity according to the operational variables. The model was validated with experimental results obtained from optimization with sequential quadratic programming algorithm. Using both mathematical methods, it was possible to obtain adequate parameters ( V = 24V, WFS = 8890 mm/min, and v = 3.4 mm/s) to experimentally produce underwater welds with minimal surface porosity (fewer than 10 pores in a bead length of 30 cm).

In order to obtain results from simulations that are close to reality, it is necessary to correctly set the parameters of the welding process. One of them is the efficiency of the welding process. Currently, new modifications of MIG/MAG methods are being created, which are characterized by lower heat introduced into the material (smaller efficiency coefficient). The efficiency coefficient determined by the European standard EN 1011–1 is no longer accurate enough for simulations. Therefore, it is necessary to accurately determine the efficiency coefficient of the method even for the mentioned modified welding processes. An experiment of calorimetric measurement of the efficiency of the CMT process (cold metal transfer—modification of the MIG/MAG method) was proposed. The specific heat capacity of the base material was accurately measured. Furthermore, a calorimetric measurement of the efficiency of the welding process was carried out on a flat sample (bead-on-plate method) and on a sample with a V-groove to simulate the treatment of welding surfaces. Accurate method efficiency values were determined for different welding current settings and different V-groove depths. The geometric characteristics of the fusion faces in butt welds have a greater influence on the efficiency coefficient than the size of the welding current.

The need to manufacture components out of copper is significantly increasing, particularly in the solar technology, semiconductor, and electric vehicle sectors. In the past few decades, infrared laser (IR) and green laser (GL) have been the primary technologies used to address this demand, especially for small or thin components. However, with the increased demand for energy saving, alternative joint techniques such as blue diode laser (BDL) are being actively explored. In this paper, bead-on-plate welding experiments on 0.2 mm thick pure copper samples employing a BDL are presented. Two sets of parameters were carefully selected in this investigation, namely Cu-1: Power (P) = 200 W; Speed (s) = 1 mm/s; and angle = 0°, and Cu-2: P = 200 W; s = 5 mm/s; and angle = 10°. The results from both sets of parameters produced defect-free full penetration welds. Hardness test results indicated relatively softer weld zones compared with the base metal. Tensile test samples fractured in the weld zones. Overall, the samples welded with Cu-1 parameters showed better mechanical properties, such as strength and elongation, than those welded with the Cu-2 parameters. The tensile strength and elongation obtained from Cu-1 were marginally lower than those of the unwelded pure copper. The outcomes from this research provide an alternative welding technique that is able to produce reliable, strong, and precise joints, particularly for small and thin components, which can be very challenging to produce.

Abstract In order to improve welding efficiency of conventional TIG welding process, a new activating TIG (A-TIG) welding process, named activating arc two-TIG (AT-TIG) welding, was developed by using two-TIG arc activated via mixing minor oxygen into the shielding gas of the front welding torch. The effect of the oxygen flow rate, welding current carried by two tungsten electrodes, and welding speed on the weld formation were investigated for the bead-on-plate welding of SUS304 stainless steel. It was found that, compared to conventional TIG welding, this method can successfully obtain a markedly deepened weld penetration, even at a relatively higher welding speed. Mixing of O2 into the argon shielding gas do not have a significant effect on the microstructure of the weld metal. The dramatically improved weld depth can be achieved at a lower oxygen flow rate and the corresponding impact toughness energy of the weld reaches as much as 92.3% of the workpiece. In addition, the modulation of the current proportions for each welding torch plays a prominent role in the weld formation, which was accounted by a numerical model that the current apportionment for each electrode results in the change of the arc plasma flow and thus the oxygen transfer process from the arc plasma to the weld pool. The predominant effect of the oxygen on the formation of the weld pool shape and the weld formation was demonstrated by a weld-bead-shift experiment. Therefore, the oxygen transfer process from the arc plasma to the weld pool and the mechanisms for enhancing the weld penetration in this welding process were clarified.