Search Results (18)

The Gas Metal Arc Welding (GMAW) process is widely utilized in industrial production, requiring careful selection of appropriate procedures to ensure the highest quality. A key area of study closely related to GMAW quality is the control of process stability. This research presents a methodology for analyzing welding data to identify instability, thus enabling the development of a stability indicator. Our approach focuses on sensory fusion by integrating multiple sources of information, including sound signals, images, and current signals captured during the welding process. This work explores various configurations of variables to analyze the three primary transfer modes. Additionally, a comprehensive statistical analysis of the results obtained is conducted. Image processing techniques, sound analysis, and artificial intelligence methodologies are employed to enhance the analysis process. Full article

The microstructure and mechanical properties of welded joints of API 5L X-52 steel plates cladded with AISI 316L-Si austenitic stainless steel were evaluated. The gas metal arc welding process with pulsed arc (GMAW-P) and controlled arc oscillation were used to join the bimetallic plates. After the root welding pass, buttering with an ERNiCrMo-3 filler wire was performed and multi-pass welding followed using an ER70S-6 electrode. The results obtained by optical and scanning electron microscopy indicated that the shielding atmosphere, welding parameters, and electric arc oscillation enabled good arc stability and proper molten metal transfer from the filler wire to the sidewalls of the joint during welding. Vickers microhardness (HV) and tensile tests were performed for correlating microstructural and mechanical properties. The mixture of ERNiCrMo-3 and ER70S-6 filler materials presented fine interlocked grains with a honeycomb network shape of the Ni–Fe mixture with Ni-rich grain boundaries and a cellular-dendritic and equiaxed solidification. Variation of microhardness at the weld metal (WM) in the middle zone of the bimetallic welded joints (BWJ) is associated with the manipulation of the welding parameters, promoting precipitation of carbides in the austenitic matrix and formation of martensite during solidification of the weld pool and cooling of the WM. The BWJ exhibited a mechanical strength of 380 and 520 MPa for the yield stress and ultimate tensile strength, respectively. These values are close to those of the as-received API 5L X-52 steel. Full article

One of the prospective methods of robotic welding with a consumable electrode in shield gas metal arc welding is the GMAW Rapid HF process (GRHF, HF-high frequency), in which welded joints with deep penetration welds are obtained thanks to the specially programmed welding characteristics of the arc. A pulsed frequency equalized to 5000 Hz was used to achieve consumable electrode arc stabilization and improve penetration. This work consists of two main sections, including the research and analysis of wire electrode melting and weld pool formation in the innovative GRHF process and its influences on joint strength and the economic advantages of welding. As a result of our research and strength tests, as well as an image analysis of phenomena occurring in the welding arc and weld pool, assumptions were developed about the use of the GRHF process, which is characterized by deep penetration welds without welding imperfections that reduce the quality of the welded joints and their strength. Welding conditions and parameters leading to welded joints characterized by high relative strength related to the weight of the used filler material were proposed. As a result of our research, it was found that the use of welding processes with deep penetration leads to material savings related to the reduced consumption of filler materials while maintaining the required high strength of welded joints. Savings of filler materials reaching 80% were achieved compared with hitherto used methods. At the same time, the maximum load-carrying capacity of welding joints was maintained. Full article

Gas metal arc welding (GMAW) is widely used in various industries, such as automotive and heavy equipment manufacturing, because of its high productivity and speed, with solid wires being selected based on the mechanical properties required for welded joints. GMAW consists of various components, among which consumables such as the contact tip and continuously fed solid wire have a significant impact on the weld quality. In particular, the copper-plating method can affect the conductivity and arc stability of the solid wire, causing differences in the continuous welding performance. This study evaluated the welding performance during 60 min continuous GMAW using an AWS A5.18 ER70S-3 solid wire, which was copper-plated using chemical plating (C-wire) and electroplating (E-wire). The homogeneity and adhesion of the copper-plated surface of the E-wire were superior to those of the C-wire. The E-wire exhibited better performance in terms of arc stability. The wear rate of the contact tip was approximately 45% higher when using the E-wire for 60 min of welding compared with the C-wire, which was attributed to the larger variation rate in the cast and helix in the E-wire. Additionally, the amount of spatter adhered to the nozzle during 60 min, with the E-wire averaging 5.9 g, approximately half that of the C-wire at 12.9 g. The E-wire exhibits superior arc stability compared with the C-wire based on the spatter amount adhered to the nozzle. This study provides an important reference for understanding the impact of copper plating methods and wire morphology on the replacement cycles of consumable welding parts in automated welding processes such as continuous welding and wire-arc additive manufacturing. Full article

The nitrogen bubble bursting phenomenon during the welding process of high nitrogen steel (HNS) can lead to unstable droplet transfer and welding process, reducing the quality of weld formation. In this study, a novel approach, ultrasonic-assisted gas metal arc welding (U-GMAW), is proposed to suppress the escape of nitrogen gas during droplet transfer. This study investigates the influence of ultrasound on the metal transfer process during two distinct metal transfer modes: short-circuiting and droplet transfer. Ultrasound has a significant effect on the welding process; as ultrasonic power increases, both the arc length and droplet size decrease, while the droplet transfer frequency increases and the electrical signal stabilizes. Under the experimental conditions of this study, ultrasound has the most effective improvement on the metal transfer behavior when the ultrasonic power reaches 2 kW. Ultrasound enhances the stability of the droplet transfer process, making U-GMAW an effective and novel approach for controlling the droplet transfer behavior of high nitrogen steel. Full article

In the welding process of thick plate narrow gap pulse gas metal arc welding (P-GMAW) overhead welding station, the arc characteristics and droplet transfer behavior that become more complex due to the combined effects of narrow gap groove, gravity, and welding torch oscillation. The welding stability is more difficult to control. High-speed imaging and electrical signal acquisition systems were established to observe and record the arc behavior and droplet transfer during the welding process at different oscillation widths, further revealing the formation mechanism of welding seam in narrow gap P-GMAW overhead welding station. Research has found that with an increased oscillation width, the arc deflects towards the sidewall from a trumpet-shaped symmetrically distributed around the center of the groove at an increasing deflection angle, and the droplet transfer changes from one droplet per pulse to multiple droplets per pulse, resulting in defects such as lack of sidewall fusion and undercutting of the weld seam. Based on the welding process discussed in this study, it is recommended to use an oscillation width of 2.6 mm. Full article

In fields, such as oil and gas pipelines and nuclear power, narrow-gap welding has often been used for the connection of thick and medium-thick plates. During the welding process, a lack of fusion was prone to occur due to groove size limitations, seriously affecting the service safety of large structures. The vertical oscillation arc pulsed gas metal arc welding (P-GMAW) method was adopted for narrow-gap welding in this study. The influence of the oscillation width on arc morphology, droplet transfer behavior and weld formation during narrow-gap welding was studied. Oscillation widths from 0 to 4 mm were used to weld narrow-gap grooves with a bottom width of 6 mm. The results show that, in non-oscillation arc welding, the arc always presented a bell cover shape, and the droplet transfer was in the form of one droplet per pulse, while the sidewall penetration of the weld was relatively small, making it prone to a lack of fusion. With an increase in the oscillation width, the arc gradually shifted to the sidewall. The droplet transfer mode was a mixed transfer of large and small droplets, and the sidewall penetration continued to increase, which was conducive to the fusion of the sidewall. However, when the oscillation width was wider than 3 mm, it led to the phenomenon of the arc climbing to the sidewall, and the weld was prone to porosity, undercutting and other welding defects. The oscillation width has a major impact on the stability of the welding process in vertical oscillation arc narrow-gap welding. Full article

Pulsed gas metal arc weld (GMAW) was widely used for the advantages of controllable heat input, all-position welding, and no spatter. In order to obtain an ideal welding process, the stability of the arc length was studied in many researches, but the influence of arc length on the properties of weld metal was ignored. In this paper, the effect of arc length on oxygen content and mechanical properties of weld metal during pulsed GMAW was studied. Q690 high strength steel was selected as the base metal, and ER69-G solid wire, with a diameter of 1.2 mm, was used as the electrode wire. Additionally, the shielding gas and the wire feed rate were 82% Ar + 18% CO₂ and 4 m/min, respectively. The results showed that as the arc length raised from 2.9 mm to 9.2 mm, the oxidation reacted more completely in the droplet transfer zone, and the oxygen content of the weld metal increased significantly. The tensile strength of the weld metal reduced but the −40 °C impact energy heightened. Due to the longer arc, the proportion of acicular ferrite (AF) in the microstructure decreased, but the proportion of lath bainite (LB) and granular bainite (GB) decreased. The higher oxygen content of weld metal was useful for the formation of inclusions, which promoted the nucleation of acicular ferrite and dimples, contributing to the growth of plasticity and toughness of weld metal. Full article

One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a computational model to describe the melt-pool behaviour in root-pass gas metal arc welding (GMAW). Three-dimensional numerical simulations have been performed using an enhanced physics-based computational model to unravel the effect of groove shape on complex unsteady heat and fluid flow in GMAW. The influence of surface deformations on the magnitude and distribution of the heat input and the forces applied to the molten material were taken into account. Utilising this model, the complex thermal and fluid flow fields in melt pools were visualised and described for different groove shapes. Additionally, experiments were performed to validate the numerical predictions and the robustness of the present computational model is demonstrated. The model can be used to explore the physical effects of governing fluid flow and melt-pool stability during gas metal arc root welding. Full article

In this paper, we present the results of a study on droplet transferring with arc space short circuits during wire-arc additive manufacturing (WAAM GMAW). Experiments were conducted on cladding of single beads with variable welding current and voltage parameters. The obtained oscillograms and video recordings were analyzed in order to compare the time parameters of short circuit and arc burning, the average process peak current, as well as the droplets size. Following the experiments conducted, 2.5D objects were built-up to determine the influence of electrode stickout and welding torch travel speed to identify the droplet transferring and formation features. Moreover, the current–voltage characteristics of the arc were investigated with varying WAAM parameters. Process parameters have been determined that make it possible to increase the stability of the formation of the built-up walls, without the use of specialized equipment for forced droplet transfer. In the course of the research, the following conclusions were established: the most stable drop transfer occurs at an arc length of 1.1–1.2 mm, reverse polarity provides the best drop formation result, the stickout of the electrode wire affects the drop transfer process and the quality of the deposited layers. The dependence of the formation of beads on the number of short circuits per unit length is noted. Full article

In wire arc additive manufacturing of Ti-alloy parts (Ti-WAAM) gas metal arc welding (GMAW) can be applied for complex parts printing. However, due to the specific properties of Ti, GMAW of Ti-alloys is complicated. In this work, three different types of metal transfer modes during Ti-WAAM were investigated: Cold Metal Transfer, controlled short circuiting metal transfer, and self-regulated metal transfer at a direct current with a negative electrode. Metal transfer modes were studied using captured waveform and high-speed video analysis. Using these modes, three walls were manufactured; the geometry preservation stability was estimated and compared using effective wall width calculation, the microstructure was analyzed using optical microscopy. Transfer process data showed that arc wandering depends not only on cathode spot instabilities, but also on anode processing properties. Microstructure analysis showed that each produced wall consists of phases and structures inherent for Ti-WAAM. α-basketweave in the center of and α-colony on the grain boundary of epitaxially grown β-grains were found with heat affected zone bands along the height of the walls, so that the microstructure did not depend on metal transfer dramatically. However, the geometry preservation stability was higher in the wall, produced with controlled short circuiting metal transfer. Full article

In this study, GMAW and CMT welding technologies were evaluated in terms of their technological lifecycles based on their patent datasets together with the S-curve concept, and the joints were evaluated in terms of their welding characteristics. To predict the future trends for both technologies, different models based on the time-series and growth-curve methods were tested. From a process point of view, the results showed better performance and stability for the CMT process based on the heat input to the base material and the frequency of the short circuits. The temperature distribution in the sample revealed that the GMAW process delivers higher values and, consequently, greater heat transfer. Regarding the technological lifecycle, the analyses revealed that the CMT welding process, despite being recent, is already in its mature phase. Moreover, the GMAW welding process is positioned in the growth phase on the S-curve, indicating a possibility of advancement. The main findings indicated that through mathematical modelling, it is possible to predict, in a precise way, the inflection points and the maturity phases of each technology and chart their trends with expert opinions. The new perspectives for analysing maturity levels and welding characteristics presented herein will be essential for a broaden decision-making market process. Full article

Weld bead geometry features (WBGFs) such as the bead width, height, area, and center of gravity are the common factors for weighing welding quality control. The effective modeling of these WBGFs contributes to implementing timely decision making of welding process parameters to improve welding quality and enhance automatic levels. In this work, a dynamic modeling method of WBGFs is presented based on machine vision and learning in multipass gas metal arc welding (GMAW) with typical joints. A laser vision sensing system is used to detect weld seam profiles (WSPs) during the GMAW process. A novel WSP extraction method is proposed using scale-invariant feature transform and machine learning. The feature points of the extracted WSP, namely the boundary points of the weld beads, are identified with slope mutation detection and number supervision. In order to stabilize the modeling process, a fault detection and diagnosis method is implemented with cubic exponential smoothing, and the diagnostic accuracy is within 1.50 pixels. A linear interpolation method is presented to implement sub pixel discrimination of the weld bead before modeling WBGFs. With the effective feature points and the extracted WSP, a scheme of modeling the area, center of gravity, and all-position width and height of the weld bead is presented. Experimental results show that the proposed method in this work adapts to the variable features of the weld beads in thick plate GMAW with T-joints and butt/lap joints. This work can provide more evidence to control the weld formation in a thick plate GMAW in real time. Full article

Gas metal arc welding (GMAW)-based additive manufacturing has the advantages of a high deposition rate, low cost, the production of a compact and dense microstructure in the cladding layer, and good mechanical properties, but the forming process is unstable. The shape of the welding bead critically affects the layer height and dimensional accuracy of the parts manufactured, and it is difficult to control. A series of experiments were designed and the results indicated that when the value of the predefined layer height is set in a certain range and other parameters are held constant, the height of the thin wall produced by GMAW-based additive manufacturing is almost equal to the predefined layer height multiplied by the number of layers. This research work shows that during the GMAW process, the changes in the distance between the torch and the top surface of the part cause a variety of dry extensions of the electrode; furthermore, the changes lead to a variety in the heat input into the molten pool. Therefore, the dry extension of the electrode is the key factor influencing the geometry of the welding bead, especially the layer height, and it has a compensating effect that makes the actual layer height close to the predefined value. A three-dimensional numerical model was established to study the influence of the predefined layer height to the fluid flow and heat transfer behaviors during the weld-deposition process. Full article

Droplet transfer plays a crucial role in welding stability and quality of pulsed gas metal arc weld (GMAW), referring to the process of heat and mass transition. In this work, the appearance, microstructure, microhardness, tensile properties, and impact toughness with three typical modes of droplet transfer in pulsed GMAW (ODMP: one drop per multiple pulses; ODPP: one drop per pulse; MDPP: multiple drops per pulse) were studied and compared. The results showed that the better welding appearance, the deeper penetration, and the less fume covered on the steel plate could be found during the ODPP welding process. At the same wire feeding speed and arc length, the average current was similar in ODPP and MDPP conditions. However, the average current in the ODMP condition was about 15 A larger than the other two, contributing to the higher heat input. Compared with MDPP and ODMP, the longest elongation and impact energy of the welded joint were found in the ODPP condition. Furthermore, the decrease of elongation and impact toughness in the ODMP condition might result from the higher heat input and the coarsen microstructure, like the proeutectoid ferrite and ferrite side plate. Full article