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In this paper, ER50-6 steel was fabricated by wire arc additive manufacturing (WAAM) with an A-W GTAW system. The microstructure, mechanical properties, and corrosion behaviors of ER50-6 steel by WAAM were studied. The results showed that, with the GMAW current increased, from the bottom to the top of the sample, the microstructure was fine ferrite and granular pearlite, ferrite equiaxed grains with fine grains at grain boundaries, and columnar ferrite, respectively. The average hardness in the vertical direction of samples 1# and 2# was 146 and 153 HV, respectively. The hardness of sample 2# increased because of the refinement of grain. The pores in the sample increased as the bypass current increased. The higher bypass current also has a deterioration effect on the corrosion behavior of ER50-6 steel. [ABSTRACT FROM AUTHOR]

A three-dimensional numerical model of arc in gas metal arc welding (GMAW) with single cable-typed wire was established based on the theory of arc physics. The influences of different shielding gas flow rates on the features of temperature field, velocity field and pressure field were investigated. The results showed that the maximum velocity of arc plasma along radial direction and the arc pressure on the surface of workpieces were increased obviously with the increase of the shielding gas flow rate, while the arc temperature was changed little. This phenomenon was mainly attributed to the increasing collisions between arc plasmas and the self-rotation action of cable-typed wires. The arc temperature at the tip of the cable-typed wire reached the maximum. The maximum flow velocity of arc plasma was located at the tip of wire (2–8 mm). The arc pressures in the central axis reached the maximum pressure. The simulation results were in agreement with the experimental results. [ABSTRACT FROM AUTHOR]

A three-dimensional numerical model of double-arc in tandem gas metal arc welding (GMAW) was established based on the theory of arc physics, momentum equation, energy equation, continuous equation and Maxwell equations. The effects of different welding current on temperature field, velocity field and pressure field on the surface of workpieces were investigated. The results showed that the maximum values of arc temperature, arc plasma velocity and arc pressure on workpieces surface were increased with the increasing welding current. These maximum values occurred at the tip of double-wire. The current density and axial deflection angle of coupling arc were increased following the increasing welding current. [ABSTRACT FROM AUTHOR]

The high manganese steel surfacing layer was deposited on Q235 steel by flux-cored wire gas shielded welding. The as-welded surfacing layer was heated at 1050 ∘ C and quenched in the water, then was tempered at 300 ∘ C. The microstructure, hardness and wear resistance of as-welded surfacing layer and that after heat treatment were comparatively analyzed. The results showed that compared with the as-welded surfacing layer, a large number of fine carbides dispersed in the austenite matrix for the surfacing layer after heat treatment. Meanwhile, the hardness and wear resistance of surfacing layer were slightly improved. The furrow in the abrasive wear for surfacing layer was shallower. Under the action of work hardening, the hardness of high manganese steel surfacing layer gradually increased while the loss weight decreased with the wear time less than 30 min. The hardness of surfacing layer reached the maximum and the loss weight of wear remained unchanged when the wear time was 30–60 min. [ABSTRACT FROM AUTHOR]

The stirring effect of a rotating laser on a molten pool can expand the range of the laser heat source and effectively inhibit defects such as pores and improve the quality of the weld joint. Due to laser rotation, the physical characteristics of the heat source and the dynamic behavior of the keyhole and molten pool are more complicated than those of conventional laser welding. This paper adopts a numerical simulation method. A three-dimensional model is developed, which takes into account the coupling of the keyhole, recoil pressure, and molten pool. The model can describe the dynamic behavior characteristics of keyholes and fluid flow and the formation process and mechanism of keyhole-induced pores in welds during rotating laser welding. It can be concluded that in conventional laser welding, the keyhole is deep, narrow, and unstable, which usually results in the formation of bubbles. If the bubbles in the molten pool fail to overflow in time, pores are formed. With an increase in laser rotation frequency, the keyhole becomes shallow and wide, and the dynamic behavior of the keyhole tends to be stable, which can effectively inhibit the formation of pores. When the rotating frequency is increased up to 150 Hz, the formation of pores can be completely suppressed. [ABSTRACT FROM AUTHOR]

• A numerical analysis model is developed for the arc of hybrid welding with T-joint. • The interaction behavior between arc and laser-induced metal vapor during welding process can be simulated. • Laser-induced metal vapor has a cooling effect on the arc. • The influence of laser rotation frequency on arc and laser-induced metal vapor is discussed. • The influence of laser rotation radius on arc and laser-induced metal vapor is discussed. In order to improve the reliability and stability of complex joints hybrid welding, this paper establishes an arc numerical analysis model, studies the T-joint high-frequency rotating laser-GMAW hybrid welding arc physical characteristics, and expounds the effects of laser rotation frequency along with rotation radius on arc plasma temperature, velocity, and metal vapor concentration field distribution. The research results show: the arc is more likely to start on the bottom plate and vertical plate surfaces, and the current density at the angle between the plates decreases significantly; temperature drops at the hybrid welding arc tail, the current effective distribution radius was reduced, and current density was more concentrated; the laser beam rotation frequency increases, the eruption speed of the metal vapor ejected from the keyhole decreases, while the meeting height of arc plasma and laser-induced metal vapor decreases; and, with an increase in rotation radius, the laser rotation speed increases accordingly. At the same rotation frequency, the injected metal vapor kinetic energy and rising height are reduced. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A cable-type welding wire (CWW) gas metal arc welding (GMAW) method was proposed as a novel approach, using CWW for the consumable electrode. Droplet transfer influences the welding process, and the forces on the droplet were analyzed to elucidate the metal transfer phenomenon observed during the welding process. The effects of the arc pressure, rotating force, and welding parameters were analyzed to understand the metal transfer. The special structure of the CWW affected the arc characteristics and forces during metal transfer as part of the welding process. The droplet formed by droplets from each thin wire, the arc, and electromagnetic forces on droplet formation and the coupling process were analyzed. The arc pressure and rotating forces are beneficial to metal transfer and increase the droplet transfer frequency. The droplet size decreases with increasing welding parameters. [ABSTRACT FROM AUTHOR]

The present study aims to develop a unified three dimensional numerical model for fiber laser+GMAW hybrid welding, which is used to study the fluid flow phenomena in hybrid welding of aluminum alloy and the influence of laser power on weld pool dynamic behavior. This model takes into account the coupling of gas, liquid and metal phases. Laser heat input is described using a cone heat source model with changing peak power density, its height being determined based on the keyhole size. Arc heat input is modeled as a double ellipsoid heat source. The arc plasma flow and droplet transfer are simulated through the two simplified models. The temperature and velocity fields for different laser powers are calculated. The computed results are in general agreement with the experimental data. Both the peak and average values of fluid flow velocity during hybrid welding are much higher than those of GMAW. At a low level of laser power, both the arc force and droplet impingement force play a relatively large role on fluid flow in the hybrid welding. Keyhole depth always oscillates within a range. With an increase in laser power, the weld pool behavior becomes more complex. An anti-clockwise vortex is generated and the stability of keyhole depth is improved. Besides, the effects of laser power on different driving forces of fluid flow in weld pool are also discussed. [ABSTRACT FROM AUTHOR]

Arc shape, droplet transfer, weld pool behavior and temperature fields were studied to investigate the influence of low current auxiliary TIG arc on weld formation and microstructure in TIG-MIG hybrid welding and compared with conventional MIG welding. Results indicated that the MIG arc is stabilized by a leading TIG arc while it is destabilized by a trailing TIG arc. Regardless of the TIG arc leading or trailing, it decentralized the MIG arc force and reduced the impingement of droplet. The backward fluid flow in the hybrid welding was decelerated relative to the conventional MIG welding. The slower backward fluid flow in hybrid welding impeded the accumulation of high temperature filler metal in the tail of weld pool and provided the molten metal more time to fill the weld toe which resulted in suppression of the undercut defect. The top surface temperature gradient at the middle and tail of the hybrid weld pool was lower than that in the MIG weld pool, albeit the welding heat input was increased. Microstructure analysis showed evidence of prominent dendrite formation at higher welding speeds with no obvious grain coarsening in the weld zone of TIG-MIG hybrid weld joint while its HAZ became narrower. [ABSTRACT FROM AUTHOR]

Considering the coupling of a droplet, keyhole, and molten pool, a three-dimensional transient model for the full penetration laser + metal inert gas (MIG) hybrid welding of thin copper alloy plate was established, which is able to simulate the temperature and velocity fields, keyhole behavior, and generation of the welding defect. Based on the experimental and simulation results, the weld formation mechanism for the hybrid butt welding of a 2 mm-thick copper alloy plate was comparatively studied in terms of the fluid dynamic feature of the melt pool. For single laser welding, the dynamic behavior of liquid metal near the rear keyhole wall is complex, and the keyhole has a relatively drastic fluctuation. An obvious spattering phenomenon occurs at the workpiece backside. Meanwhile, the underfill (or undercut) defect is formed at both the top and bottom surfaces of the final weld bead, and the recoil pressure is identified as the main factor. In hybrid welding, a downward fluid flow is strengthened on the rear keyhole wall, and the stability of the keyhole root is enhanced greatly. There are large and small clockwise vortexes emerging in the upper and lower parts of the molten pool, respectively. A relatively stable metal bulge can be produced at the weld pool backside. The formation defects are suppressed effectively, increasing the reliability of full penetration butt welding of the thin copper alloy plate. [ABSTRACT FROM AUTHOR]

• A unified model is developed for hybrid welding with horizontal fillet joint. • Formation process of bubble and porosity can be simulated directly. • Forward flow resulting from clockwise vortex is weakened in hybrid welding. • Keyhole collapses at its middle part easily, raising the possibility of generating large bubble. • The effect of welding current on keyhole behavior and weld porosity is discussed. The keyhole induced porosity in laser-MIG hybrid fillet welding of aluminum alloy in the horizontal position was investigated with simulation and experimental methods. A three dimensional model is developed, which takes into account geometric feature of horizontal filled joint and the coupling of keyhole, droplet and molten pool. Meanwhile, the major forces are also incorporated in the model. The inclination of heat source is dealt with through rotation of coordinate system. This model is able to calculate the keyhole dynamic behavior and the formation process of gas bubble as well as keyhole induced porosity directly. Also, it can describe the merging and disappearing of bubbles. The weld porosity was examined by the X-ray non-destructive testing. Large weld pool size provides more time for bubble to escape from the molten pool, which is the major factor responsible for the reduction in hybrid welding. Besides, the forward flow caused by the clockwise vortex is weakened, which also plays a positive role in improving the stability of back keyhole wall. The keyhole collapses at the middle part easily in horizontal fillet welding, raising the possibility of forming large pore. Bubble is easy to be captured by the upper weld pool boundary when floating up. With enhancing the welding current, the stability of keyhole is enhanced to some extent and the keyhole induced porosity is reduced. [ABSTRACT FROM AUTHOR]

A three-dimensional numerical model is used to simulate heat transfer and fluid flow phenomena in fiber laser + gas metal arc welding (GMAW) hybrid welding of an aluminum alloy, which incorporates three-phase coupling and is able to depict the keyhole dynamic behavior and formation process of the keyhole-induced porosity. The temperature profiles and fluid flow fields for different arc powers are calculated and the percent porosities of weld beads were also examined under different conditions by X-ray non-destructive testing (NDT). The results showed that the computed results were in agreement with the experimental data. For hybrid welding, with raising arc power, the keyhole-induced porosity was reduced. Besides the solidification rate of the molten pool, the melt flow was also closely related to weld porosity. A relatively steady anti-clockwise vortex caused by arc forces tended to force the bubble to float upwards at the high temperature region close to the welding heat source, which benefits the escape of the gas bubble from the melt pool. When increasing the arc power, the anti-clockwise region was strengthened and the risk of the gas bubble for capture by the liquid/solid interface underneath the keyhole tip was diminished, which resulted in the lower weld percent porosity. [ABSTRACT FROM AUTHOR]