Journal of Welding Science

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This paper investigates the effect of boehmite nano-particles surface adsorbed byboric acid (BNBA) along with other input welding parameters such as welding current, arc voltage, welding speed, nozzle-to-plate distance on weld penetration. Weld penetration modeling was carried out using multi-layer perceptron artificial neural network (MPANN) technique. For the sake of training the network, 70% of the obtained data from experimentation using five-level five-factor central composite rotatable design of experiments was used. The performance of the network shows a good agreement between the experimental data and the data obtained from the network. Hence, it is to be concluded that MPANN is highly accurate in predicting the weld penetration in SAW process.

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Welded tubular joints are widely used in various industry structures for high efficiency subjected to pressure, bending and twisting.Welded structures are the main parts of structures, buildings, bridges, gas pipes, pressure vessels and power transmission equipment in the ship building, construction, oil, gas, petrochemical industries and power plants.A sample of pipe-welded joints is a X-tubular joint that has been investigated in this study.The main objective of the present work is to investigate the heat transfer and residual stress caused by the three-stage welding process in X-tubular joint made of St52 using Simufact Welding software.The welding process involves three welding steps using arc welding. The finite element model contains the thermal and mechanical properties of base metal and welding metal as a function of temperature.Also, advanced modeling tools such as mesh adaptation during the process and meshing compatible with the welding site, the birth and death technique of the element and the source of heat transfer have been used.Welding simulation showed that significant residual stresses were created in the joint after welding. Comparison of the results shows that the numerical results and empirical measurements are in good agreement with each other and the existing model can provide a good prediction of temperature distribution and stress control in this welding process.

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The superalloy Inconel 738LC is considered one of the most challenging alloys in welding processes due to its widespread use in gas turbine blades and its high microstructural sensitivity to heat. The most significant limitation in welding this alloy is its high susceptibility to hot cracking in the heat-affected zone (HAZ), which arises from the formation of intergranular liquid films during the welding thermal cycle. In this study, the effect of activated tungsten inert gas (A-GTAW) welding on the behavior of the heat-affected zone, liquid film thickness, and hot cracking susceptibility in Inconel 738LC superalloy was investigated. For this purpose, specimens were welded with various fluxes under approximately constant heat input conditions, and the effect of the active flux on weld geometry, HAZ width, and liquid film thickness was evaluated. The results showed that the use of active flux, by inducing arc constriction and altering the molten metal flow pattern due to the reverse Marangoni effect, leads to more effective heat transfer into the depth of the workpiece and reduces lateral heat dissipation. This resulted in a reduction of HAZ width and a decrease in liquid film thickness in some specimens. It was also found that cracking behavior is a function of the interaction between liquid film thickness and the contraction stress of the weld pool. In the flux-free specimen, despite the formation of a greater number of liquid films, none developed into hot cracks, which was attributed to greater stability of the liquid films and their ability to fill discontinuities. Overall, the results of this study indicate that the A-GTAW process can influence hot cracking susceptibility in Inconel 738LC superalloy by controlling the heat transfer pattern and liquid film formation conditions.

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