GTAW liquid pool convections and the weld shape variations under helium gas shielding

The heat and mass transfer behavior and the morphological evolution of the solidification structures in the weld pool were simulated by the multi-scale model which combines the finite element (FE) and the cellular automata (CA) methods to investigate the columnar to equiaxed transition (CET) process during welding. The grain structure evolution within the entire weld and the competitive dendrite growth at different locations were studied to better understand the CET process. The results indicate that with the decrease of the distance to weld center, the undercooled zone width and the maximum undercooling increase. In this case, more equiaxed dendrites form in the undercooled melt, and the distance between the equiaxed dendrites and the columnar front also becomes lager. There is more space for the equiaxed dendrites to grow up and block the columnar dendrites. Therefore, the equiaxed dendrites become more competitive, and the CET tendency increases.

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“…These conservation equations in three-dimensional Cartesian coordinate system are shown as follows. 20)…”

Section: The Model Descriptionmentioning

confidence: 99%

Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

Han

Dong

et al. 2016

ISIJ Int.

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“…Due to its great welding quality and low equipment cost, this process is extensively applied to stainless steel, titanium alloy, and non-ferrous metals welds [1]. In the GTA welding process, a tungsten electrode is protected by a flow of inert gas; argon is usually employed, as well as helium, nitrogen, hydrogen, or mixtures.…”

Section: Introductionmentioning

confidence: 99%

A GTA Welding Cooling Rate Analysis on Stainless Steel and Aluminum Using Inverse Problems

Magalhães

Silva

2017

Applied Sciences

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Abstract:This work presents an analysis of the thermal influence of the heat transfer by convection and radiation during GTA (gas tungsten arc) welding process. The authors' in-house C++ previously-developed code was modified to calculate the amount of heat transfer by convection and radiation. In this software, an iterative Broydon-Fletcher-Goldfarb-Shanno (BFGS) inverse method was applied to estimate the amount of heat delivered to the plate when the appropriate sensitivity criteria were defined. The methodology was validated by accomplishing lab-controlled experiments on stainless steel AISI 304L and aluminum 6065 T5 plates. Due to some experimental singularities, the forced thermal convection induced by the electromagnetic field and thermal-capillary force were disregarded. Significant examples of these singularities are the relatively small weld bead when compared to the sample size and the reduced time of the welding process. In order to evaluate the local Nusselt number, empirical correlations for flat plates were used. The thermal emission was a dominant cooling effect on the aluminum cooling. However, it did not present the same behavior as the stainless steel samples. The study found that the heat losses by convection and radiation of the weld pool do not affect the cooling process significantly.

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“…The shape and dimension of the weld pool is a key parameter in defining the weld strength [13][14][15]. The heat transfer and fluid flow in the weld pool has a strong effect on formation of the weld pool and then determination of the weld shape [14,16,17,3].…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of heat transfer and fluid flow in hybrid laser–TIG welding of aluminum alloy AA6082

Faraji

Goodarzi

Seyedein

et al. 2014

Int J Adv Manuf Technol

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This paper describes a three-dimensional numerical model based on finite volume method to simulate heat transfer and fluid flow in laser-tungsten inert gas (TIG) hybrid welding process. To simplify the model and reduce the calculation time, keyhole dynamics are not considered; instead, a new modified volumetric heat source model is presented for the laser source to take into account the effect of the keyhole on the heat transfer into the workpiece. Due to the presence of arc current, an appropriate electromagnetic model based on the Maxwell equations are also solved to calculate electromagnetic forces in the weld pool. The results of computer simulation, including temperature, current density, electromagnetic, and melted material velocity field, are presented here. Furthermore, several dimensionless numbers are employed to recognize the importance of fluid flow driving forces in the weld pool. It is deduced that the fluid flow has an important effect on the weld pool shape. It is also founded that among the driving forces, Marangoni force is dominant fluid force in the weld pool. Besides, calculated results of hybrid welding process are compared with those of TIG and laser welding processes. The weld pool depth is relatively the same, but the width of the weld pool is highly larger in hybrid welding than lone laser welding. Eventually, the presented model is validated by comparison between calculated and experimental weld pool shape. It is founded that there is a good agreement as the capability of this model can be proved.

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GTAW liquid pool convections and the weld shape variations under helium gas shielding

Cited by 50 publications

References 31 publications

Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

Multi-scale Simulation for the Columnar to Equiaxed Transition in the Weld Pool

A GTA Welding Cooling Rate Analysis on Stainless Steel and Aluminum Using Inverse Problems

Numerical modeling of heat transfer and fluid flow in hybrid laser–TIG welding of aluminum alloy AA6082

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