Hybrid Welding Of Aluminum Alloy Research Articles

The influences of Ar-He shielding gas mixture on welding characteristics of fiber laser-MIG hybrid welding of aluminum alloy

During laser or laser-arc hybrid welding process of aluminum alloy, laser power waste and keyhole fluctuation are drastic due to the shielding effect of dense plasma. Consequently, small weld penetration depth and numerous weld porosity defects are produced. In the present work, Ar-He shielding gas mixture was used to improve the weld quality of fiber laser-metal inert gas (MIG) hybrid welded aluminum alloy. The influences of Ar-He shielding gas mixtures with various He volume ratios on plasma temperature, electron density, weld penetration depth and porosity defect were investigated, respectively. The He volume ratio enough for improving the weld penetration depth and suppressing the porosity defect was 50%. The effective laser power density increased with the increasing He volume ratio, which contributed to the increase of weld penetration depth. The weld porosity defects were suppressed efficiently, since the stability of the keyhole was improved while using Ar-He shielding gas mixture.

The influence of hybrid arc coupling mechanism on GMAW arc in VPPA-GMAW hybrid welding of aluminum alloys

In this study, the hybrid arc shape, thermal cycling curve, voltage-current characteristics, and weld formation of 7A52 high-strength armor aluminum alloys welded by a variable polarity plasma arc (VPPA) combined with gas metal arc welding (GMAW) (VPPA-GMAW) were investigated and compared with those of 7A52 aluminum alloys welded by GMAW. The influence of the hybrid arc coupling mechanism on the GMAW arc was studied. The results show that the electromagnetic coupling of the VPPA-GMAW hybrid arc has a dynamic compression effect on the GMAW arc. The GMAW arc is compressed parallel to the axis of the welding direction during the VPPA direct current electrode negative (DCEN) period. In addition to the ampere force of the hybrid arc magnetic field, the GMAW arc is also subjected to the hot extrusion of the hybrid arc’s coupling zone, and the arc shrinkage is greater during the direct current electrode positive (DCEP) period. With increasing VPPA current, the compression effect of the GMAW arc is enhanced. An 11-mm-thick 7A52 aluminum alloy is one-sided welded by cooperative control of the hybrid arc welding parameters.

Modelling of fluid flow phenomenon in laser+GMAW hybrid welding of aluminum alloy considering three phase coupling and arc plasma shear stress

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.

Elements loss analysis based on spectral diagnosis in laser-arc hybrid welding of aluminum alloy

Aluminum alloy has been widely used in automobiles, high-speed trains, aerospace and many other fields. The loss of elements during welding process causes welding defects and affects the microstructure and properties of the joints. This paper discusses the correlation between welding process, spectral intensity and loss of elements in laser-arc hybrid welding of Al alloys. The results show that laser power and arc current have a significant impact on the spectral intensity and loss of elements. Compared with the base metal, the contents of alloying elements in the weld area are lower. The burning losses of alloy elements increase with the welding heat input.

Investigation on droplet momentum in VPPA-GMAW hybrid welding of aluminum alloys

Variable polarity plasma arc-gas metal arc welding (VPPA-GMAW) is a superior technology for welding thick plates of high-strength aluminum alloys. It integrates the advantages of energy focusing and high penetration depth in VPPA welding, and those of high welding efficiency and wide range of technological parameters in GMAW process. In this work, we investigated the droplet momentum in paraxial VPPA-GMAW hybrid welding of 7A52 aluminum alloys, and the technological parameters of welding process was also optimized. The images of droplet transfer were captured by high-speed camera, while the droplet speeds and sizes were statistically analyzed by t tests of independent samples. The results showed that the speeds of droplet arriving at the weld pool were significantly between GMAW and VPPA-GMAW processes, and the droplet speed increases with increasing plasma currents within a certain range. Meanwhile, the droplet momentum in VPPA-GMAW process is larger than that in conventional GMAW process. We also found that as the droplet momentum increased, the depression of weld pool grew more obvious and greatly facilitated the deep-penetration welding. In VPPA-GMAW process, it became more and more easier for the droplet to fall off the wire when the electromagnetic force gradually increased during pulse period. Droplet movement through the arc zone was further accelerated since the central pressure of arc column increased during base period. This research can provide some theoretical support for thick plate welding of high-strength aluminum alloys and help for deeper understanding of the hybrid arc coupling mechanism.

Improving the efficiency of hybrid welding of aluminum alloys

Improving the efficiency of hybrid welding of aluminum alloys

Comparison on welding mode characteristics of arc heat source for heat input control in hybrid welding of aluminum alloy

Presently in shipbuilding, transportation and aerospace industries, the potential to apply welding using laser and laser-arc hybrid heat sources is widely under research. This study has the purpose of comparing the weldability depending on the arc mode by varying the welding modes of arc heat sources in applying laser-arc hybrid welding to aluminum alloy and of implementing efficient hybrid welding while controlling heat input. In the experimental study, we found that hybrid welding using CMT mode produced deeper penetration and sounder bead surface than those characteristics produced during only laser welding, with less heat input compared to that required in pulsed arc mode.

Keyhole-induced porosity in laser-arc hybrid welded aluminum

Keyhole-induced macro-porosity, which results from the collapse of the keyhole that formed by the reaction forces of metal vapors, is a major problem limiting laser and laser-arc hybrid weldability of age-hardenable aluminum alloys, such as AA2024-T3. The mechanism of porosity suggests that the weld metal solidifies more rapidly than the possible rise velocity of the gas bubbles that formed during keyhole collapse, resulting in severe porosity. The porosity behavior of AA2024-T3 during laser-arc hybrid welding was studied using microscopy and X-ray radiography techniques. Porosity-free welding of the alloy is attainable in the conduction mode welding, whereas porosity increased significantly with increased laser intensity during keyhole mode welding. Porosity was mostly severe when the beam was focused at the surface of the workpiece. The laser beam and the arc decouple from each other with increased laser-wire distance, affecting keyhole depth and porosity. In order to control porosity during laser-arc hybrid welding of aluminum alloys, the role of various welding parameters on the material’s response should be balanced with the required weld geometry.

アルミニウム合金のフィラー・レーザ・ＭＩＧアークハイブリッド溶接（ＦＬＡ溶接法）のビード形成およびギャップ裕度に関する検討

アルミニウム合金のフィラー・レーザ・ＭＩＧアークハイブリッド溶接（ＦＬＡ溶接法）のビード形成およびギャップ裕度に関する検討

Understanding of Laser and Hybrid Welding Phenomena

This paper describes laser and hybrid welding phenomena for the production of a sound and deep weld. The penetration of laser weld beads depended upon the power and power density at low and high welding speeds, respectively. It was reveled that the weld fusion zone geometry was formed by keyhole behavior and melt flows. It was also understood that the production of sound welds without porosity was attributed to no bubble formation in TIG-YAG hybrid welding of stainless steel and the disappearance of bubbles from the molten pool surface in YAG-MIG hybrid welding of aluminum alloy.

アルミニウム合金のフィラー・レーザ・アークハイブリッド溶接（ＦＬＡ溶接法）に関する検討

アルミニウム合金のフィラー・レーザ・アークハイブリッド溶接（ＦＬＡ溶接法）に関する検討

Study of Improvement of Gap Tolerance in Laser-MIG Arc Hybrid Welding of Aluminum Alloy

Study of Improvement of Gap Tolerance in Laser-MIG Arc Hybrid Welding of Aluminum Alloy

Laser-Arc Hybrid Welding

Hybrid welding of stainless steels or aluminum alloys was performed using the heat sources of YAG laser and TIG, or YAG laser and MIG, respectively. The effects of welding conditions and melt flows on penetration depth, weld bead geometry and bubble/porosity formation were investigated with X-ray transmission real-time observation method. A great effect of melt flows on penetration depth and weld geometry was consequently confirmed. Concerning porosity suppression in YAG-TIG hybrid welding of stainless steel, no bubble generation was attributed to no porosity formation. On the other hand, it was revealed that the disappearance of bubbles from the concave molten pool surface played an important role of no porosity in YAG laser-MIG hybrid welding of aluminum alloys.