Welding characteristics in different laser-TIG hybrid manners

An experiment for determining the laser-TIG hybrid welding characteristics was carried out in three kinds of hybrid methods: CO_2 laser-TIG coaxial hybrid, CO_2 laser-TIG paraxial hybrid and Nd: YAG laser-TIG paraxial hybrid. The experimental results indicate that hybrid welding has two welding mechanisms in CO_2 laser-TIG hybrid welding: deep penetration welding and heat conduction welding. As the effect of the laser-induced keyhole, the arc root is condensed, the current density and penetration depth increase significantly, the welding characteristic is apt to deep penetration welding. When current increases to some degree, the keyhole induced by laser disappears, which produces a shallow penetration and wide bead. The weld exhibits heat conduction welding characteristics. Furthermore, the arc images and weld bead cross-sections of three kinds of hybrid manners were also compared and analyzed at different welding currents, which established the foundation for understanding the welding characteristics of laser-TIG hybrid welding comprehensively.

Effect of materials on the forming characteristics of laser-MIG hybrid welding process with filler wire for aluminum alloy

In this study,the test subjects included the aluminum alloys 2A14 and 5A06,as well as the welding wires ER2319 and ER5356,single laser welding,laser welding with filler wire,laser metal inert gas(laser-MIG)hybrid welding and laser-MIG hybrid welding with filler wire were carried out respectively to research the influence of aluminum alloy base material and welding wire on weld forming charac-teristics.The results show that:under the same test conditions,the penetration of the base material 5A06 is greater than that of 2A14,the maximum is about 51.3%,and the penetration filling ER5356 is greater than that of ER2319,the maximum is about 32.2%;for 2A14 alu-minum alloy,the penetration is basically unchanged after filling with ER5356,and there is a relatively large decrease after filling ER2319,the maximum is about 21.2%;for 5A06 aluminum alloy,the penetration decreases after filling both kinds of welding wire,the penetration achieved with filler wire ER2319 is lower than that of ER5356.At the same time,through the process of laser absorption in different metal materials,it was found that the differences in material composition led to different laser absorption rates,resulting in different energy utiliza-tion,which is an important reason for the correlation between aluminum alloy materials and laser-MIG hybrid welding with filler wire.

The characteristics of welding currents in a rotating arc leadtandem GMAW process and the weld-seam tracking

Tandem gas metal arc welding （ T-GMAW） process shows a high deposition rate that up to three times o f the single electrode GMAW, so the welding speed could be significantly increased in this process. However, the majority o f this process applications are based on the pre-programmed robotic welding, which does not allow them to track the seam real-time during welding. Rotating arc sensor, sensing the seam position by detecting the changing of welding currents, has been widely adopted in the automatic robot welding process. It is proposed in this paper to integrate the rotating arc sensor with a trailing torch to develop a new approach of rotating arc lead tandem gas metal arc welding （RLT-GMAW） process. The characteristics of the welding currents in the proposed new welding process were firstly studied, and then a self-turning fuzzy control seam tracking strategy was developed for the mobile robot automatic welding. The experimental results showed that the proposed RLT-GMAW process had an excellent seam tracking performance and high welding deposition rate. Even if there were some electromagnetic interactions between the two arcs, the deviation of the welding seam could also be reflected by the fluctuation of the welding currents on the leading arc once the correct welding parameters were selected. Based on the detected deviation, the welding tracking experiments showed that the proposed self-turning fuzzy controller had a good performance for the RLT-GMAW process seam tracking.

Novel hybrid method: pulse CO_2 laser-TIG hybrid welding by coordinated control

In continuous wave CO2 laser-TlG hybrid welding process, the laser energy is not fully utilized because of the absorption and defocusing by plasma in the arc space. Therefore, the optimal welding result can only be achieved in a limited energy range. In order to improve the welding performance further, a novel hybrid welding method--pulse CO2 laser-TIG arc hybrid welding by coordinated control is proposed and investigated. The experimental results indicate that, compared with continuous wave CO2 laser-TIG hybrid welding, the absorption and defocusing of laser energy by plasma are decreased further, and at the same time, the availability ratio of laser and arc energy can be increased when a coordinated frequency is controlled. As a result, the weld appearance is also improved as well as the weld depth is deepened. Furthermore, the effect of frequency and phase of pulse laser and TIG arc on the arc images and welding characteristics is also studied. However, the novel hybrid method has great potentials in the application of industrials from views of techniques and economy.

Weld Characteristics and NC Bending Formability of QSTE340 Welded Tube

The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend.

Effect of Heat Input on Microstructure and Mechanical Properties of Joints Made by Bypass-Current MIG Welding–Brazing of Magnesium Alloy to Galvanized Steel

Experiments were carried out with bypass-current MIG welding–brazing of magnesium alloy to galvanized steel to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. Experimental results indicated that the joint efficiency tended to increase at first and then to reduce with the increase of heat input. The joint efficiency reached its maximum of about 70% when the heat input was 155 J/mm. The metallurgical bonding between magnesium alloy and steel was a thin continuous reaction layer, and the intermetallic compound layer consisted of Mg–Zn and slight Fe–Al phases. It is concluded that bypass-current MIG welding–brazing is a stable welding process, which can be used to achieve defect-free joining of magnesium alloy to steel with good weld appearances.