scholarly journals Numerical Analysis of the Heating Characteristics of Magnetic Oscillation Arc and the Fluid Flow in Molten Pool in Narrow Gap Gas Tungsten Arc Welding

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5799
Author(s):  
Xiaoxia Jian ◽  
Xing Yang ◽  
Jingqian Li ◽  
Weihua Wang ◽  
Hebao Wu
Keyword(s):  
Heat Flux ◽  
Arc Welding ◽  
Molten Pool ◽  
Gas Tungsten Arc Welding ◽  
Magnetic Flux Density ◽  
Narrow Gap ◽  
Maximum Heat ◽  
Gas Tungsten Arc ◽  
Magnetic Oscillation ◽  
Gas Tungsten

Magnetic oscillation arc (MOA) technology was developed to avoid insufficient fusion defects appearing at the sidewalls in narrow gap gas tungsten arc welding (NG-GTAW). In this work, a unified model was developed to simulate the process of MOA assisted NG-GTAW. The model included the MOA, welding pool, workpiece and the coupling interaction between them. The heating characteristic of the MOA and the flow of liquid metal were simulated, and the mechanism of forming a uniform welding bead under MOA was investigated. It was found that if the magnetic flux density increased to 9 mT, the MOA could point to the sidewall directly; the maximum heat flux at the bottom declined by almost half and at the side, it increased by more than ten times. Additionally, the heat flux was no longer concentrated but dispersed along the narrow groove face. Under the effect of MOA, there were mainly two flow vortexes in the molten pool, which could further increase the heat distribution between the bottom, sidewall and corner, and was beneficial for the formation of a good-shape weld. The model was validated by experimental data.

Real-time observation of cathodic cleaning during variable-polarity gas tungsten arc welding of aluminium alloy

2009 ◽  
Vol 223 (9) ◽  
pp. 1143-1157 ◽  
Author(s):  
R Sarrafi ◽  
D Lin ◽  
R Kovacevic
Keyword(s):  
Real Time ◽  
Process Parameters ◽  
Arc Welding ◽  
Molten Pool ◽  
Gas Tungsten Arc Welding ◽  
Process Conditions ◽  
Current Electrode ◽  
Gas Tungsten Arc ◽  
Variable Polarity ◽  
Gas Tungsten

Online observation is expected to provide a better understanding of the cathodic cleaning of oxides from the molten pool during variable-polarity gas tungsten arc welding (VP GTAW) of aluminium alloys. In this paper, a machine-vision system with appropriate illumination and filtering is used to monitor in real time the effect of different process parameters on the cleaning of oxides from the molten pool during VP GTAW of Al 6061. Based on the observations, the process conditions under which a clean molten pool can be achieved are determined. In addition, the control of the welding process to maintain the consistency of cathodic cleaning is discussed. The results showed that in order to have an oxide-free molten pool, the solid surface in front of the molten pool should be cleaned from oxides by the electric arc. The choice of process parameters to satisfy this condition has been discussed. It was found that the percentage of direct current electrode positive (DCEP) polarity in the cycle of current has the highest impact on the cathodic cleaning, with the arc current having less influence, and the welding speed showing the least effect. Furthermore, in order to keep the consistency of oxide cleaning, process parameters should be set or controlled to maintain the cleaned zone larger than the molten pool.

The Welding Deformations of Stainless Steel Pipes With Thick Wall by Narrow Gap Gas Tungsten Arc Welding

2010 ◽  
Author(s):  
Jainxun Zhang ◽  
Chuan Liu ◽  
Jing Niu
Keyword(s):  
Stainless Steel ◽  
Arc Welding ◽  
Welding Process ◽  
Gas Tungsten Arc Welding ◽  
Thick Wall ◽  
Fe Model ◽  
Narrow Gap ◽  
Steel Pipes ◽  
Gas Tungsten Arc ◽  
Gas Tungsten

The austenitic stainless steel pipes with thick wall are widely used in the nuclear power station and are welded by narrow gap gas tungsten arc welding process. The welding deformations of multi-pass butt-welded pipes with 65 and 70mm thickness are investigated experimentally and numerically in the paper. The transient axial deformation and axis shift deformation are measured during welding. An axisymmetric FE model and a thermal mechanical calculating procedure are presented to simulate the welding axial deformations. An effective calculating method by only considering the contraction of each welding pass in the model is proposed. The experimental results show that the axis shift deformation is very small and demonstrates an elastic movement during welding; the axial shrinkage of welded pipes is the mainly deformation, which is very significant during the first several weld pass, and decreases sharply after the weld groove has been filled at the height of 30% wall thickness that makes the stiffness of pipes large enough to resist the welding shrinkage.

scholarly journals Estimation of heat flux parameters during static gas tungsten arc welding spot under argon shielding

2017 ◽  
Vol 114 ◽  
pp. 205-212 ◽  
Author(s):  
Sreedhar Unnikrishnakurup ◽  
Sébastien Rouquette ◽  
Fabien Soulié ◽  
Gilles Fras
Keyword(s):  
Heat Flux ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Gas Tungsten Arc ◽  
Welding Spot ◽  
Gas Tungsten

scholarly journals Modeling of Melt Flow and Heat Transfer in Stationary Gas Tungsten Arc Welding with Vertical and Tilted Torches

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6845
Author(s):  
Shahid Parvez ◽  
Md Irfanul Haque Siddiqui ◽  
Masood Ashraf Ali ◽  
Dan Dobrotă
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Drag Force ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Filler Wire ◽  
Gas Tungsten Arc ◽  
Gas Tungsten ◽  
Steady State Simulation ◽  
Gas Drag

A 3D numerical simulation was conducted to study the transient development of temperature distribution in stationary gas tungsten arc welding with filler wire. Heat transfer to the filler wire and the workpiece was investigated with vertical (90°) and titled (70°) torches. Heat flux, current flux, and gas drag force were calculated from the steady-state simulation of the arc. The temperature in the filler wire was determined at three different time intervals: 0.12 s, 0.24 s, and 0.36 s. The filler wire was assumed not to deform during this short time, and was therefore simulated as solid. The temperature in the workpiece was calculated at the same intervals using heat flux, current flux, gas drag force, Marangoni convection, and buoyancy. It should be noted that heat transfer to the filler wire was faster with the titled torch compared to the vertical torch. Heat flux to the workpiece was asymmetrical with both the vertical and tilted torches when the filler wire was fully inserted into the arc. It was found that the overall trends of temperature contours for both the arc and the workpiece were in good agreement. It was also observed that more heat was transferred to the filler wire with the 70° torch compared with the 90° torch. The melted volume of the filler wire (volume above 1750 °K) was 12 mm3 with the 70° torch, compared to 9.2 mm3 with the 90° torch.

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