Laser Gas Tungsten Arc Research Articles

Effect of Alloying Elements in Steels on the Interfacial Structure and Mechanical Properties of Mg to Steel by Laser-GTAW Hybrid Direct Lap Welding.

Mg alloy AZ31B was directly bonded to SK7 with a low alloy content, DP980 with a high Mn content, 316L with a high Cr and high Ni content by laser-gas tungsten arc welding (GTAW) and hybrid direct lap welding. The results showed that the tensile loads of AZ31B/SK7 and AZ31B/DP980 joints were 283 N/mm and 285 N/mm respectively, while the tensile load of AZ31B/316L joint was only 115 N/mm. The fracture and interface microstructures were observed using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and identified through X-ray diffractometry (XRD). For AZ31B/SK7 and AZ31B/DP980, the interface of the front reaction area and the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase. However, for AZ31B/316L, the interface of the keyhole reaction area was mainly composed of an Fe-Al phase and an Al-Mn phase, but a multi-layer composite structure consisting of the Mg17Al12 compound layer and eutectic layer was formed in the front reaction area, which led to a deterioration in the joint property. The influencing mechanism of Mn, Cr and Ni elements in steel on the properties and interface structure of the laser-GTAW lap joint between the Mg alloy and the steel was systematically analyzed.

A Composite Joint Based on Two Kinds of Connection Mechanisms for TA2/T2 Bimetallic Sheets by Laser-TIG Hybrid Weldings

The possibility of two pass welding for TA2/T2 bimetallic sheets joint with laser-TIG hybrid weldings was studied. Laser-gas tungsten arc welding (TIG) hybrid welding of TA2/T2 bimetallic sheets has been applied using BCuP-2 wire as filler metal. A new welding process for TA2/T2 butt joint was introduced on the basis of the controlling the formation of Ti-Cu intermetallics in the joint. One process was two pass welding involving creation of a joint with one laser weld and one TIG weld separated by remaining unmelted TA2/T2 interface. When laser beam on the TA2 side junction surface, T2 would not be completely melted in joint. When TIG welding in groove, the filler metal melted occurred at the TA2 and T2 interfaces. Through two pass welding, the the formation of Ti-Cu intermetallics can be completely avoided during welding. In the paper, microstructure and mechanical characterization of Ti/Cu clad plates laser and arc welded joints were carried out. The unmelted part of TA2/T2 explosive interface acted as a diffusion barrier between Ti and Cu. The unmelted TA2/T2 explosive interface was beneficial to relieve and accommodate the thermal stress. The joint fractured mainly at the brazed weld with the maximum tensile strength of 610 MPa.

Bonding of immiscible Mg/steel by butt fusion welding

An appropriate intermetallic compound interface layer that can achieve improved lattice matching for Mg and Fe immiscible welding system is difficult to select and prepare. Lattice matching strengthening by promoting the diffusion of alloy elements in the IMC could be employed when the IMC layer is obtained. Immiscible Mg and Fe were bonded by laser-gas tungsten arc welding with Ni interlayer. Nanoscale (Al, Mg) (Ni, Mn, Fe) intermetallic-based and α-(Fe, Ni) solid solutions were formed at the interface. The interplanar misfit for the (110)(Al, Mg) (Ni, Mn, Fe)||(0002)Mg system was reduced by 42.2% with the diffusion of alloy elements in the Al-Ni interface layer.

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.

Effect of laser-GTAW hybrid welding heat input on the performance of Mg/Steel butt joint

The most common welding method for Mg/steel dissimilar metals is melt-brazing with lap joints; however, the butt fusion welding of Mg/steel joint remains a challenging task. 1.6mm AZ31B Mg alloy was joined with 1.0mm Q235 steel by using laser-gas tungsten arc welding (GTAW) hybrid butt welding with AZ61 filler metal. The influence of welding heat input on the morphology, interface bonding, mechanical properties and fracture modes of welded joints was systematically analyzed. Resultsshow that laser-GTAW hybrid welding with filling wire can be used to combine high-performance joints and Mg/steel dissimilar metals during butt assembly. The maximum average tensile fracture load of the joints can reach up to 3265N (the load equal to that of steel base metal). The tensile load of the joints decreases with the decrease in heat input. A reaction layer is formed on the welding interface enriched with Al and Mn elements. The morphology of Mg/steel joint and the thickness of interface transition layer are the key factors affecting the properties and fracture mechanism of the welded joint. With the decrease in heat input, the Mg/steel butt joints had three fracture modes, including the fracture on the base metal of steel, Mg weld seam, and Mg/steel interface.

Comparative study on interactions between laser and arc plasma during laser-GTA welding and laser-GMA welding

This paper describes an investigation on differences in interactions between laser and arc plasma during laser-gas tungsten arc (LT) welding and laser-gas metal arc (LM) welding. The characteristics of LT heat source and LM heat source, such as plasma behavior, heat penetration ability and spectral information were comparably studied. Based on the plasma discharge theory, the interactions during plasma discharge were modeled and analyzed. Results show that in both LT and LM welding, coupling discharge between the laser keyhole plasma and arc happens, which strongly enhance the arc. But, the enhancing effect in LT welding is much more sensitive than that in LM welding when parameters are adjusted.

Analysis of energy utilisation efficiency in laser–GTA hybrid welding process

The effect of welding parameters on energy utilisation efficiency in laser–gas tungsten arc (GTA) hybrid welding process is investigated. Then, optimum butt joints are made by laser welding, GTA welding and laser–GTA hybrid welding, and the energy consumption in each process is calculated and compared. Both plasma and keyhole behaviours are studied. Results indicate that the parameter Dla greatly affects the energy utilisation efficiency in hybrid welding. The reason is that Dla determines keyhole behaviour and laser induced plasma, and these determine the coupling discharge of laser induced and GTA plasmas. Compared with laser and GTA welding, hybrid welding is more energy efficient.

Hybrid Welding of AA5754-H111 Alloy Using a Fiber Laser

The new generation of high power fiber lasers presents several benefits for industrial application. Nevertheless, due to the small spot size of the laser, the fiber laser has difficulties in some welding applications. These shortcomings can be overcome by laser-arc hybrid welding technique such as laser-gas metal arc welding or laser-gas tungsten arc welding. In this work, a high power fiber laser was coupled to an arc welder and the AA5754-H111 magnesium aluminum alloy was welded. The trials were carried out using laser leading configuration. A new generation of high power fiber laser was used. The experimental trials included process parameters such as laser power, welding speed and arc current. Microstructure, microhardness and weld appearance were analyzed. The experimental results showed that laser leading configuration produces full penetration for some welding parameters. The obtained results worth a larger investigation based on the experimental design technique.