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54 pages, 14354 KiB

Open AccessFeature PaperReview

The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review

by Kai Treutler and Volker Wesling

Appl. Sci. 2021, 11(18), 8619; https://doi.org/10.3390/app11188619 - 16 Sep 2021

Cited by 177 | Viewed by 25253

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review. Full article

(This article belongs to the Special Issue Metal Additive Manufacturing and its Applications: From the Material to Components Service Life)

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11 pages, 6118 KiB

Open AccessArticle

A Unified Adjustment Model for Gaussian Pulse Welding on Aluminum Alloys

by Qiang Zhu, Ping Yao, Xiaoyan Yu, Bin Xie, Jiaxiang Xue and Haibiao Hu

Metals 2021, 11(4), 671; https://doi.org/10.3390/met11040671 - 20 Apr 2021

Viewed by 2320

Abstract

To solve the challenge of welding aluminum alloys, a unified adjustment model for Gaussian pulse welding is established. This model can achieve improved welding performance by adjusting the base current of the weak pulse group within a specific range of average welding current inputs. The flat overlaying welding is carried out on the base material: 6061 aluminum alloys with thicknesses of 2 mm, 3 mm, and 5 mm. A stable welding process, indicated by reduced spatter, is produced, with a soft arc sound and good repeatability in the waveforms of the real-time current and voltage. The weld has a shiny surface and regular fish scale ripples. Metallographic analysis shows that the fusion line is clear, and there are no visible defects, while the weld zone has fine dendritic structures. The tensile test results indicate that fractures occur in the heat-affected zone, and that the tensile strength reaches about 68% of that of the base metal. Full article

(This article belongs to the Special Issue Advanced Welding Technology in Metals II)

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15 pages, 3534 KiB

Open AccessArticle

Numerical Analysis of the Heating Characteristics of Magnetic Oscillation Arc and the Fluid Flow in Molten Pool in Narrow Gap Gas Tungsten Arc Welding

by Xiaoxia Jian, Xing Yang, Jingqian Li, Weihua Wang and Hebao Wu

Materials 2020, 13(24), 5799; https://doi.org/10.3390/ma13245799 - 18 Dec 2020

Cited by 3 | Viewed by 2490

Abstract

Magnetic oscillation arc (MOA) technology was developed to avoid insufficient fusion defects appearing at the sidewalls in narrow gap gas tungsten arc welding (NG-GTAW). In this work, a unified model was developed to simulate the process of MOA assisted NG-GTAW. The model included the MOA, welding pool, workpiece and the coupling interaction between them. The heating characteristic of the MOA and the flow of liquid metal were simulated, and the mechanism of forming a uniform welding bead under MOA was investigated. It was found that if the magnetic flux density increased to 9 mT, the MOA could point to the sidewall directly; the maximum heat flux at the bottom declined by almost half and at the side, it increased by more than ten times. Additionally, the heat flux was no longer concentrated but dispersed along the narrow groove face. Under the effect of MOA, there were mainly two flow vortexes in the molten pool, which could further increase the heat distribution between the bottom, sidewall and corner, and was beneficial for the formation of a good-shape weld. The model was validated by experimental data. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 7303 KiB

Open AccessArticle

3D Numerical Study of External Axial Magnetic Field-Controlled High-Current GMAW Metal Transfer Behavior

by Lei Xiao, Ding Fan, Jiankang Huang, Shinichi Tashiro and Manabu Tanaka

Materials 2020, 13(24), 5792; https://doi.org/10.3390/ma13245792 - 18 Dec 2020

Cited by 15 | Viewed by 2670

Abstract

For gas metal arc welding (GMAW), increasing the welding current is the most effective way to improve welding efficiency. However, much higher current decreases the welding quality as a result of metal rotating-spray transfer phenomena in the high-current GMAW process. In this work, the external axial magnetic field (EAMF) was applied to the high-current GMAW process to control the metal transfer and decrease the welding spatters. A unified arc-droplet coupled model for high-current GMAW using EAMFs was built to investigate the metal rotating-spray transfer behavior. The temperature fields, flow fields in the arc, and droplet were revealed. Considering all the heat transferred to the molten metal, the Joule heat was found to be the dominant factor affecting the droplet temperature rise, followed by the anode heat. The conductive heat from the arc contributed less than half the value of the other two. Considering the EAMFs of different alternating frequencies, the arc constricting effects and controlled metal transfer behaviors are discussed. The calculated results agree well with the experimental high-speed camera observations. Full article

(This article belongs to the Collection Welding and Joining Processes of Materials)

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17 pages, 6857 KiB

Open AccessArticle

A Convenient Unified Model to Display the Mobile Keyhole-Mode Arc Welding Process

by Yan Li, Chen Su, Ling Wang and Chuansong Wu

Appl. Sci. 2020, 10(22), 7955; https://doi.org/10.3390/app10227955 - 10 Nov 2020

Cited by 2 | Viewed by 4446

Abstract

Keyhole-mode plasma arc welding (PAW) has a good prospect in the manufacturing industry. Unified models of plasma arc and workpiece help to reveal the physical mechanism in PAW for a better application. Previous unified models either deal with a constant keyhole situation or take too much computational time to display the dynamic keyhole process with a two-phase flow method. In view of the convenience for industrial application as well as good accuracy, a convenient unified model was developed to describe the mobile keyhole-mode PAW. With a simplified technique, the multiphase heat and force effect between plasma arc and workpiece was turned into a single-phase problem at each individual domain. Thus, it takes less computational time than previous unified models. The temperature field and weld pool during the mobile keyhole-mode PAW process were revealed, the arc flow and pool flow were displayed and the electric potential was predicted. The experiment was conducted on a stainless-steel plate, and the weld pool image and the measured arc pressure agree well with the calculated result. The calculated electric potential drop also coincides with the experiment. The model provides a convenient and accurate method to display the mobile keyhole-mode arc welding process. Full article

(This article belongs to the Special Issue Recent Advances in Joining and Welding Technology Coping with New Material Combination)

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15 pages, 4841 KiB

Open AccessArticle

Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

by Xiaoxia Jian and Hebao Wu

Metals 2020, 10(10), 1351; https://doi.org/10.3390/met10101351 - 9 Oct 2020

Cited by 19 | Viewed by 3060

Abstract

The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%. Full article

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