Arc Hybrid Welding Research Articles

Analysis-effective induction efficiency of laser in pulse laser-GTA welding of titanium alloy

This study aims to explain the effective induction efficiency of laser in the laser-gas tungsten arc (GTA) hybrid welding process by arc plasma characteristics and keyhole behaviors analysis during the process experiment, the real-time monitoring, and the theoretical analysis. The emission spectrum of the arc plasma was acquired by a spectrometer, and the dynamic keyhole behaviors were synchronously observed using a high-speed camera. The electron temperature and the ratio of resistivity of the arc plasma were calculated. Results indicate that defocusing distance greatly affects the effective induction efficiency of the laser in hybrid welding, and an appropriate defocusing distance can maximize the effective induction efficiency of the laser. The main reason is that the defocusing distance influences arc plasma characteristics and keyhole behaviors, and these determine the coupling discharge of laser-induced plasma and GTA plasma. Finally, by comparing the effective induction efficiency of the laser at different defocusing distances, it was found that when the laser focuses inside the keyhole, the induction efficiency is more effective.

Status analysis of keyhole bottom in laser-MAG hybrid welding process.

The keyhole status is a determining factor of weld quality in laser-metal active gas arc (MAG) hybrid welding process. For a better evaluation of the hybrid welding process, three different penetration welding experiments: partial penetration, normal penetration (or full penetration), and excessive penetration were conducted in this work. The instantaneous visual phenomena including metallic vapor, spatters and keyhole of bottom surface were used to evaluate the keyhole status by a double high-speed camera system. The Fourier transform was applied on the bottom weld pool image for removing the image noise around the keyhole, and then the bottom weld pool image was reconstructed through the inverse Fourier transform. Lastly, the keyhole bottom was extracted from the de-noised bottom weld pool image. By analyzing the visual features of the laser-MAG hybrid welding process, mechanism of the closed and opened keyhole bottom were revealed. The results show that the stable opened or closed status of keyhole bottom is directly affected by the MAG droplet transition in the normal penetration welding process, and the unstable opened or closed status of keyhole bottom would appear in excessive penetration welding and partial penetration welding. The analysis method proposed in this paper could be used to monitor the keyhole stability in laser-MAG hybrid welding process.

TRENDS AND PERSPECTIVES OF HOT METHODS FOR RECONDITIONING OF WEAR DETAILS

The structure, trends and perspectives in development of hot methods as such used for reconditioning of worn details during the new Millennium are presented in the article as well as trends in production of consumables in industrially developing countries. The structure of welding methods is also shown giving priority to its development until 2020. It can be concluded that in the industrially developed countries by 2020 the share of arc welding will be stabilized at levels of 10-15% of the total number of methods used for weld overlaying of worn-out components. These figures will be 45-55 % and 7-9% for gas shielded and submerged arc welding respectively. The welding methods that will be prioritized for the period until 2020 will be gas shielded arc welding, contact, laser beam and hybrid welding.

Weldability of TWIP and DP steel dissimilar joint by laser arc hybrid welding with austenitic filler

In this paper, an innovative 18% Mn austenitic TWIP steel, which exhibits a very good combination of strength and ductility, was joined by laser arc hybrid welding to a conventional DP steel, which consists of ferrite and martensite obtained by an inter-critical heat treatment and fast cooling. An austenitic filler wire was used to improve the weld strength by avoiding the formation of Mn segregations and improper microstructures in the fusion zone by Mn dilution. Metallographic examinations, microhardness and tensile tests were carried out to assess the effects of the laser and materials interaction on the weldability of TWIP-DP dissimilar welds. Hybrid welding and austenitic filler can have a positive effect on the weldability of the DP-TWIP dissimilar joint.

Study on the Characteristics and Mechanics of Droplet Transfer in Laser Arc Hybrid Welding Process

Study on the Characteristics and Mechanics of Droplet Transfer in Laser Arc Hybrid Welding Process

Effect of Laser-arc Hybrid Welding Energy Parameters on Welding Stability

The high-speed camera was used to collect the droplet transfer pattern and arc pattern of the laser-arc hybrid welding process. Using the methods of image processing and mathematical statistics, the effects of different laser and arc power conditions on the welding stability were studied. The results show that the melting width depends on the welding current, the depth of penetration depends on the laser power, the droplet transition pattern, the actual filament spacing and the arc length determine the welding stability of the laser arc hybrid welding.

Effect of Heat Source Positioning on Hybrid TIG-MAG Arc Welding Process

Hybrid TIG-MAG Arc Welding implies the two conventional arc welding processes combine to provide a more improved outcome overcoming their limitations at the individual level. The hybridization demands the favorable interaction of the participating heat sources to produce an effective coalescence. The participating heat sources interact in harmony when positioned optimally to enter each other’s domain of influence in the synergistic manner. This study is an attempt to investigate the effect of positioning of heat sources on the hybrid arc welding process in terms of the achieved weld penetration for the bead on plate welding of mild steel. The study presents special welding torch geometries for easy location and clamping on an indigenous fixture which forms an automated assembly to carry out the devised hybrid arc welding process. The study identifies torch angles, arc lengths and the arc separation as the 5 parameters critical in positioning of the heat sources. Torch angles have been optimized through a 2-stage preset experimentation. The arc lengths and the arc separation have been optimized considering 4th order parameter interactions in a quadratic through a designed experiment by analyzing the generated response surfaces and the parameter interaction profile.

Friction-Stir-WeldingおよびGas-Tungsten- Arc-Weldingのハイブリット法による低炭素鋼の高速接合

Friction-Stir-WeldingおよびGas-Tungsten- Arc-Weldingのハイブリット法による低炭素鋼の高速接合

Effect of leading and trailing torch configuration on mixing and fluid behavior of laser-gas metal arc hybrid welding

The paper introduces the results of mixing and fluid flow studies for full penetration laser-gas metal arc (GMA) hybrid welding with GMA leading and trailing torch configuration. The material used was austenitic stainless steel with the thickness of 10 mm. The joint configuration was butt joint without gap. It was found that the molten pool at the root side is a longer time in the molten state than the pool at the weld surface. Compared to autogeneous laser welding, the addition of GMA makes the upper bead wider. This effect is more prominent in the case of GMA trailing compared to the case of GMA leading. The simulation results also show a similar trend of bead shape change in the case of GMA leading and trailing configuration compared to the experimental ones. Mixing behavior of filler and base metal is also evaluated and compared by both experimental studies and simulations. In GMA leading configuration, the mixing is more pronounced in the upper part of the weld cross section, while in GMA trailing, the mixing is more efficient in the whole cross section compared to GMA leading case. Simulation results support this difference in mixing behavior. Laser is the main source that provides full penetration and forms a molten pool on upper and root surface. The direction of wire feeding affects the mixing behavior. In GMA leading configuration the wire droplets impinge in front of the laser beam and in the front edge of the molten pool, whereas in GMA trailing configuration, the wire droplets impinge behind the laser beam where the molten pool is fully developed. This causes the difference in mixing.

Factors affecting weld root morphology in laser keyhole welding

Welding production efficiency is usually optimised if full penetration can be achieved in a single pass. Techniques such as electron and laser beam welding offer deep high speed keyhole welding, especially since multi-kilowatt lasers became available. However, there are limitations for these techniques when considering weld imperfections such as weld cap undercuts, interior porosity or humps at the root. The thickness of sheets during full penetration welding is practically limited by these root humps. The mechanisms behind root morphology formation are not yet satisfactory understood. In this paper root humping is studied by reviewing previous studies and findings and also by sample examination and process observation by high speed imaging. Different process regimes governing root quality are presented, categorized and explained. Even though this study mainly covers laser beam and laser arc hybrid welding, the presented findings can generally be applied full penetration welding in medium to thick sheets, especially the discussion of surface tension effects. As a final result of this analysis, a map of methods to optimise weld root topology is presented.

Laser–arc hybrid welding of high-strength steel and aluminum alloy joints with brass filler

ABSTRACTThe laser–tungsten inert gas hybrid welding method was adopted to realize the welding process between Q460 high-strength steel and 6061 aluminum alloy. The influence of the dual heat source on the mechanical properties and microstructure of the welded joints are discussed. In addition, the effects of including a copper–zinc interlayer on the microstructure, elemental distribution, and mechanical properties of welded joints are also studied. The results show that the mechanical properties of the welded joints are influenced by the relative heat inputs of the two heat sources and the Cu-Zn interlayer. The braze welded joint fabricated without a Cu-Zn interlayer fractured at an Al-Fe intermetallic compound (IMC) layer formed at the interface, whereas the braze welded joint fabricated with a Cu-Zn interlayer fractured at an Al-Cu IMC layer formed at the interface. Comparisons show that the maximum tensile shear load of the brazed welded joint with the Cu-Zn interlayer was increased by about 20% relative to that formed without the interlayer. The formation of Al-Fe IMC layer in the deep penetration joint was inhibited by the combined effect of the dual heating sources and the Cu-Zn interlayer.

Innovative hybrid welding process for structural steelwork engineering—Laser submerged arc hybrid welding

The welding of thick metal sheets has become increasingly important for structural steelwork engineering applications (e.g., pipe- or crane building). Nowadays, welding tasks are performed using a time-consuming conventional submerged arc welding process. Here, a large number of welding passes are necessary, which leads to a thermally induced distortion. Therefore, there is a high demand for a welding process which allows a cost-effective welding of thick metal sheets. By the development of a laser beam submerged-arc hybrid welding process (LUPuS), a technique is created which combines the high penetration depth of the laser with the high thermal efficiency of the submerged arc process. This leads to synergy effects which predestine LUPuS for the given welding task. Earlier projects have shown a general feasibility of LUPuS. Steel plates with thicknesses of up to 50 mm have been joined without any welding issues using the double-sided single pass technique. However, different results of the notch impact test in the laser beam-dominated and submerged arc-dominated welding areas are noticeable. This contribution will demonstrate the effect on the mechanical-technological properties in the different welding seam areas by changing the flux and the wire of the submerged arc welding process. In order to investigate these properties, impact strength tests have been performed. Moreover, the dynamic behavior of the molten pool was studied. Furthermore, the results of the investigation of the weld metal structure are presented.

Multipass laser hot-wire welding: Morphology and process robustness

There are great prospects for utilizing multipass laser hot-wire welding to join thick steel sheets, especially for techniques commonly performed in single passes, e.g., laser arc hybrid welding, fall short, presenting great opportunities for vehicle industries and offshore applications. Many modern approaches for applying these techniques rely on customized wire feeding nozzles or special scanner optics to ensure proper laser–wire interactions and, in turn, robust process behavior, making them less accessible to many industries. Here, we present a modified adaption of laser hot-wire welding, utilizing more readily available equipment, including an unmodified welding source and a nozzle, presented and evaluated through means of, e.g., high speed imaging and macroscopy. This technique was found to have high process robustness, especially for sealing passes, if wire resistance heating is kept within suitable levels. It is able to both maintain proper laser–wire interaction and produce close to net-shape weld caps. Also, recommended process parameters are presented, together with a description of a potential method for suppressing solidification cracking.

The Effect of Welding Speed on the Weld Seam Profile in MAG and TIG/MAG Hybrid Arc Welding

Abstract The effect of welding speed on the weld seam profile in MAG and TIG/MAG hybrid arc welding was investigated in a low carbon steel. AISI 1020 steel materials having 5 mm thickness were used in the experiments. A fixed MAG and TIG welding currents (90 A and 100 A, respectively) and three different welding speeds (0.14, 0.21 and 0.30 m/min) were selected for welding process for a 100 mm long weld. The welded specimens were cut into several cross-sections; then metallographic tests were performed. The effect of TIG/MAG hybrid arc welding process was compared with the conventional MAG welding. The study showed that welding speed and the selected method have influence on the penetration and that the ratio of penetration depth / weld seam width is increased with increasing welding speed. This increase is more pronounced in TIG/MAG hybrid arc welding compared to conventional MAG welding. The microstructure of the weld metal was also changed relatively by variation of welding speed. With all welding parameters, the weld metal hardness is higher than hardness of the HAZ and the base metal.

Weld characterization of laser arc hybrid welding of pure copper

A series of experiments of high-power fiber laser-arc hybrid welding of pure copper was carried out. It could be seen that the microstructure of weld metal was obviously coarsened, and the columnar grain spacing at fusion zone and the massive grain size at heat-affected zone were both linearly increased with the increase of heat input. The weld conductivity decreased with the increase of heat input because the widening weld increased the microstructure nonuniformity of test samples. The heat input as well as welding parameter has no obvious effect on the ultimate tensile strength (UTS) of cross-weld but has obvious effect on the elongation. The UTS of all the welds was 200 MPa or so. The elongation was bigger than 20% when the heat input was in the optimization range from 250 to 380 J/cm. The decrease of the elongation was attributed to either high porosity at insufficient heat input or coarser grain at excessive heat input.

Numerical simulation of keyhole behaviors and fluid dynamics in laser–gas metal arc hybrid welding of ferrite stainless steel plates

The fluid dynamics in weld pool and keyhole behaviors in laser–gas metal arc hybrid welding play a dominant role in affecting the weld quality of ferrite stainless steel plates. In this study, a transient model is developed for numerical simulation of the keyhole dynamics and heat transfer & fluid flow in hybrid weld pool. The heat, mass and momentum transfer due to droplets as well as the interaction between laser and arc are taken into account. The formation, expansion and sustainment of keyhole in weld pool are numerically simulated, and the transient variation of keyhole is demonstrated in three stages. The weld pool and keyhole shapes and sizes, and the fluid flow and thermal field in hybrid weld pool are quantitatively analyzed. The model is validated by hybrid welding experiments on ferrite stainless steel plates. It lays foundation for optimizing the process parameters in hybrid welding.

Analysis of plasma characteristics and conductive mechanism of laser assisted pulsed arc welding

This study aims to investigate the arc plasma shape and the spectral characteristics during the laser assisted pulsed arc welding process. The arc plasma shape was synchronously observed using a high speed camera, and the emission spectrum of plasma was obtained by spectrometer. The well-known Boltzmann plot method and Stark broadening were used to calculate the electron temperature and density respectively. The conductive mechanism of arc ignition in laser assisted arc hybrid welding was investigated, and it was found that the plasma current moved to the arc anode under the action of electric field. Thus, a significant parabolic channel was formed between the keyhole and the wire tip. This channel became the main method of energy transformation between the arc and the molten pool. The calculation results of plasma resistivity show that the laser plasma has low resistivity as the starting point of conductive channel formation. When the laser pulse duration increases, the intensity of the plasma radiation spectrum and the plasma electron density will increase, and the electron temperature will decrease.

Relationship between pool characteristic and weld porosity in laser arc hybrid welding of AA6082 aluminum alloy

Effects of welding parameters on the porosity of laser arc hybrid welded AA6082 aluminum alloy were investigated. The percent porosity was examined by X-ray non-destructive testing. The pool shapes were characterized by weld transverse and longitudinal profiles, which were observed by optical and scanning electron microscopes with elemental tracer technique, respectively. Under optimized welding parameters, the weld porosity could be reduced to less than 0.5%. It was found that the pool shape characteristics were closely relative to weld porosity. A volume characteristic coefficient, Φ was then proposed by pool profiles to predict the percent porosity of hybrid welds. The higher the Φ, the easier the bubble escaping away the pool, and the lower the weld percent porosity. When the Φ was larger than 0.52, the weld percent porosity was less than 0.5%, which is the criterion of first grade weld.

Influence of laser on the droplet behavior in short-circuiting, globular, and spray modes of hybrid fiber laser-MIG welding

The effects of laser on the droplet behavior in short-circuiting, globular, and spray modes of hybrid fiber laser-MIG welding were studied. Transfer sequence of a droplet, welding current wave and morphology of plasma in the three modes of arc welding and hybrid welding were comparatively investigated. Compared with arc welding, the transfer frequency and landing location of droplet in the three modes of hybrid welding changed. In short-circuiting and globular modes, the droplet transfer was promoted by the laser, while the droplet transfer was hindered by the laser in spray mode. The magnitudes and directions of electromagnetic force and plasma drag force acting on the droplet were the keys to affect the droplet behavior. The magnitudes and directions of electromagnetic force and plasma drag force were converted due to the variation of the current distribution into the droplet, which were caused by the laser induced plasma with low ionization potential.

A study of droplet transfer behavior in ultra-narrow gap laser arc hybrid welding

Laser arc hybrid welding became a useful method to weld thick plates. But a sound weld is not so easy to obtain because of the uncontrollability of droplet transfer state, especially in ultra-narrow gap welding process. In this study, V-like ultra-narrow gap welds were carried out using 80 % Ar + 20 % CO2 blend as shielding gas. A high-speed video system was used to observe the droplet transfer behaviors. The results showed that the transfer mode did not change with the same welding current. The transfer mode changed from the short circuiting transfer to the mixture of the short circuiting and the globular transfer and then to spray transfer as the welding current increased. The relationship between the droplet transfer process and the welded defects was studied to obtain high-quality weld joint with a stable transfer process. The optimal parameter window between welding current and groove size was found. Only when the welding current was 200 to 270 A and groove gap was 2 to 3 mm, can a good welded joint be got. Finally, 30-mm-thick plate with 5.49-mm maximum groove gap was welded well by one pass laser autogenous welding and seven passes laser arc hybrid welding process.