Tungsten Inert Gas Hybrid Welding Research Articles

Characteristic of keyhole, molten pool and microstructure of oscillating laser TIG hybrid welding

In this research, the dynamic change of laser keyhole of vertical oscillating laser keyhole was studied, and it was found that the laser keyhole depth was periodic. The keyhole depth decreased with the increase of oscillation amplitude and frequency, but the stability of the keyhole increased. This was closely related to the energy distribution of oscillating laser. The special energy distribution made the “two molten pools“ phenomenon appear in oscillating laser tungsten inert gas (TIG) hybrid welding, and the grains in the keyhole molten pool were smaller than those in the conduction molten pool. The narrow gap (NG) oscillating laser TIG hybrid welding (OL-T) was carried out, and the microstructure and mechanical properties of OL-T welding were compared with that of TIG welding and general laser TIG hybrid welding (L-T). The grain of the OL-T welding seam was refined because the OL-T welding had a lower line energy, which changed the crystalline morphology of the welding seam. The tensile strength of the weld joint was almost equivalent to that of TIG welding and base metal, reaching 559 MPa. It was observed that there was no lack of sidewall fusion in the welding seam of the NG OL-T welding, and the weld efficiency was much higher than that of TIG welding. The morphology of the molten pool in oscillating laser-TIG hybrid welding and the arc shape in the groove were collected using high-speed cameras. It was observed that the elimination of lack of sidewall fusion in NG welding mainly depended on the direct heating on the sidewall and stirring molten pool by oscillation laser.

Characteristics of droplet transfer, molten pool formation, and weld bead formation of oscillating laser hot-wire tungsten inert gas hybrid welding

Oscillating laser hot-wire tungsten inert gas (TIG) hybrid welding of 10 mm thick 316LN austenitic stainless steel in the vertical position was performed. The characteristics of droplet transfer, molten pool formation, and forming mechanism of different oscillating parameters were investigated by the experimental method. A high-speed camera was employed to observe the arc, droplet transfer, and molten pool formation. Results showed that the larger molten pool area, more intense fluid flow, and better weld bead formation were achieved when the oscillating laser joined to TIG as compared to TIG or normal laser-TIG hybrid welding. Due to the dynamic wire feed, the form of droplet transfer was mainly contact transfer, and the frequency of droplet transfer was equal to the frequency of wire feed and was independent of the parameters of the heat source. The electrical signals in the TIG and oscillating laser-TIG weld processes were collected, respectively, and the results showed that the change of conductivity might be the reason why the laser can compress the arc. The addition of laser increased the arc voltage and active power and improved the efficiency of hybrid welding.

Prediction and fitting of weld morphology of Al alloy-CFRP welding-rivet hybrid bonding joint based on GA-BP neural network

Abstract In the riveting-welding hybrid bonding of aluminum alloy and the Carbon Fiber Reinforced Polymer (CFRP), the welding joint morphology was one of the most important factors for the welding property. In the hybrid bonding process, laser-induced tungsten inert gas hybrid welding technology was used as the welding source, which had a plurality of parameters, such as laser power, arc current, defocused distance and welding speed and etc. The variation of each parameter could directly influence the welding properties. The prediction model of the laser power, welding current, defocused distance and welding speed on the profile of the welding joint morphology was established by using the BP neural network optimized through the genetic algorithm (GA-BP). The contour data of the welding joint was acquired by establishing the polar coordinate system. The geometric morphology of the welding joint was ideally fitted by using the cubic interpolation fitting in MATLAB. The results showed that the fitting line was close to the actual profile of the welding joint, and the prediction accuracy of the GA-BP was favorable. The mean absolute percentage error (MAPE) of each group of data did not exceed 3% while the standard deviation (STD) of that was less than 0.1. The study provided a new method to grope for energy transfer and real-time monitoring of laser induced TIG hybrid welding quality.

Riveting–welding hybrid bonding of high-strength steel and aluminum alloy

ABSTRACTBased on laser-induced tungsten inert gas hybrid welding source, the riveting–welding hybrid joining technology was applied to join Q460 high-strength steel and 6061 Al alloy. The mechanism of the action of hybrid welding source was discussed. The effect of welding penetration of the Al alloy sheet on mechanical properties and element distribution of hybrid joints was investigated. In addition, the formation mechanism of Al-steel interface was also explored. Under the action of laser-induced arc hybrid welding source, three load-bearing areas were generated in the joint, which were, respectively, the steel-steel welding joint, the Al-steel mixing area, and the Al/steel interface formed by the sidewalls of Al alloy plate and steel rivet. When the penetration of Al alloy “H” was between 300 and 400 μm, the tensile shear load of the hybrid joint was evaluated to 5.3 ± 0.2 kN, which was 90% of the strength of Q460 steel. In addition, the properties of joints were improved by the bonding effect of the Al alloy plate and steel rivet.

基于Ni中间层的铝合金与高强钢激光诱导TIG复合焊接

基于Ni中间层的铝合金与高强钢激光诱导TIG复合焊接

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.

Comparative Study of 5A06 Aluminum Alloy Welded Joints Obtained by Different Laser–Tungsten Inert Gas Hybrid Welding

Two different hybrid processes which contain the laser–tungsten inert gas (TIG) double-side welding (LTDSW) and the laser–TIG single-side welding (LTSSW) were applied on 5A06 aluminium alloy sheets. The three-dimensional (3D) finite element models are developed to investigate the thermally induced stress field during the hybrid welding. Based on the thermal history data obtained from these combined heat source models, the residual stress distribution in weld metal, heat affected zone and base metal characteristics have been calculated and found to be in reasonable agreement with the X-ray diffraction (XRD) experimentally measured values. The results show that the longitudinal residual stress in the LTDSW welded joints is less (10–12 %) than that of the LTSSW welded joints. Meanwhile, from the mechanical and metallurgical point of view, it could be confirmed that it makes a good sense to use LTDSW instead of LTSSW for the 5A06 aluminium alloy welding structure.

Microstructures of laser–tungsten inert gas hybrid welding of dissimilar AZ31 Mg alloy and Q235 steel with Ni as interlayer

Microstructures of a laser–tungsten inert gas (TIG) hybrid welding joint of dissimilar Mg alloy and steel with and without Ni interlayer are studied comparatively by SEM. The results show that there are a lot of precipitates of Mg17Al12 with mesh structures in the molten pool of Mg to steel dissimilar joints of laser–TIG hybrid welding without Ni interlayer, leading to the reduction in the mechanical properties of the welded joints. However, the addition of the Ni interlayer improves the microstructures of Mg to steel joints by laser–TIG hybrid welding. The precipitates in the molten pool are mainly composed of Mg2Ni and Mg17Al12 in the form of dispersive particles with the size of <5 μm. The shear strength of Mg to steel joints by laser–TIG hybrid welding with Ni interlayer is higher than that without Ni interlayer.

The influence of laser pulse waveform on laser–TIG hybrid welding of AZ31B magnesium alloy

By dividing laser pulse duration into two parts, three kinds of laser waveforms are designed, including a high power density pulse (HPDP) laser in a short duration set at the beginning of the laser waveform. This paper aims to find out the laser pulse waveform and idiographic critical values of HPDP, which can affect the magnesium penetration in laser–tungsten inert gas (TIG) hybrid welding. Results show that when the laser pulse duration of HPDP is not more than 0.4 ms, the welding penetration values of lasers with HPDP are larger than otherwise. Also, the welding penetration values of laser with HPDP have increased by up to 26.1%. It has been found that with HPDP, the laser can form the keyhole more easily because the interaction between laser and the plate is changed, when the TIG arc preheats the plate. Besides, the laser with high power density and short duration strikes on the plates so heavily that the corresponding background power can penetrate into the bottom of the keyhole and maintain the keyhole open, which facilitates the final welding penetration.

Dissimilar welding of WC–Co cemented carbide to Ni 42Fe 50.9C 0.6Mn 3.5Nb 3 invar alloy by laser–tungsten inert gas hybrid welding

Dissimilar welding between cemented carbide and invar alloy was carried out using CO 2 laser beam and argon arc as heat sources. η Phase was formed near WC–Co/weld interface and precipitations in the fracture were discovered. In order to disclose the microstructure and mechanical property, firstly, η phase’s morphology and composition at interface were investigated using backscattered electron imaging (BEI); and element diffusion across heat affected zone near WC–Co/weld interface was further studied. Secondly, bend strength values of butt joint with different welding parameters were tested by four-point bend strength experiment. Finally, WC migration mechanism was further discussed and the bend strength was measured. The results showed: (1) microstructures consisted of columnar crystals, cellular crystals, eutectic structure and fir-tree crystal and dendritic crystals. The columnar crystals were surrounded by lots of fir-tree crystals. (2) WC migration was driven by stirring effects of welds, high pressure of molten materials and ionized shielding gas, interface reaction and surface tension. (3) η Phases dispersion did not decrease bend strength of butt joint. And the maximum bend strength was 1493.56 MPa, which was attributed to NbC precipitations featured with super-fine fir-tree.

Study on microstructure and mechanical properties of 304 stainless steel joints by TIG, laser and laser -TIG hybrid welding

This paper investigated the microstructure and mechanical properties of 304 stainless steel joints by tungsten inert gas (TIG) welding, laser welding and laser-TIG hybrid welding. The X-ray diffraction was used to analyze the phase composition, while the microscopy was conducted to study the microstructure characters of joints. Finally, tensile tests were performed and the fracture surfaces were analyzed. The results showed that the joint by laser welding had highest tensile strength and smallest dendrite size in all joints, while the joint by TIG welding had lowest tensile strength, biggest dendrite size. Furthermore, transition zone and heat affected zone can be observed in the joint of TIG welding. The fractograph observation showed that the TIG welding joint existed as cup–cone shaped fracture, while the laser welding and hybrid welding joints existed as pure-shear fracture. The laser welding and hybrid welding are suitable for welding 304 stainless steel owing to their high welding speed and excellent mechanical properties.

Microstructure characteristics and mechanical properties of laser–TIG hybrid welding joint of TA15 titanium alloy

The laser–tungsten inert gas (TIG) hybrid welding technique is used to weld TA15 titanium alloys. The microstructure and mechanical properties of the welded joint are then analysed systematically. The results indicate that the laser beam can centralise the energy of TIG arc and increase the penetration of weld seam. There are columnar crystals on the top of the weld seam and equiaxed crystals at the bottom. By the way of element analysis, it is found that the major elements, such as Ti, Al, Mo and V, distribute uniformly in the weld seam. Besides, the tensile strength of hybrid welding joint achieves 98% of that of base metal and the fracture of samples proves to be a gliding fracture. The TA15 titanium alloy is joined successfully by laser–TIG hybrid welding in this experiment.

Laser–tungsten inert gas hybrid welding of dissimilar AZ based magnesium alloys

The microstructure and mechanical properties of dissimilar AZ based magnesium alloys subjected to laser–tungsten inert gas (TIG) hybrid welding have been investigated. The results show that magnesium alloys can be readily welded as dissimilar joints using this process. The microstructure of the dissimilar magnesium alloy joints is composed of primary α phase (Mg) and β phase (Mg17Al12), based on electron probe microanalysis (EPMA) and X-ray diffraction (XRD) data. In addition, the tensile strength of AZ31B–AZ61 and –AZ91 joints is equal to that of AZ31B base metal. It has also been found that the presence of β phase has a severe influence on the tensile strength and mirohardness of dissimilar magnesium alloy joints.