Aluminum alloys have many applications in transportation industry because of their abundance, ease of production, and appropriate mechanical and physical properties. One of these alloys is obtained by combining aluminum with silicon and magnesium (Al-Mg-Si alloys). Since the plates of this alloy are rolled up, heat transfer and crystallization in the heat-affected zone is an important point in their welding. In this study, we have attempted to invesTIGate welding-induced recrystallization in this alloy using the finite element method. For this purpose, the physics of the problem was defined and simulated using the ANSYS software. In the next step, the results of theoretical (simulated) and experimental invesTIGations were compared and the effect of current on the size of weld pool and thermal cycle of different samples was assessed. Then, through microscopic examination of different areas of the welded samples, the size of recrystallized area was measured and compared with the results of mathematical calculations. Finally, the hardness of the weld zone and recrystallized area was analyzed. A temperature of 630° C and a holding time of about 0. 3 s will be sufficient for recrystallization of this alloy during welding.

A-TIG welding is a welding method in which TIG welding is conducted by covering a thin layer of activating flux on the weld bead beforehand. The most benefit of this process is the gain in weld penetration depth. A-TIG welds were produced on mild steel plates with TiO2 flux. The emphasis of this paper lies in introducing the effects of various process parameters (welding current, welding speed, powder/acetone ratio of the flux, arc length and electrode angle) in mild steel A-TIG welding. The weld penetration depth was the measured metallographically. An optimum value was determined for each welding parameter.

In the present study, effect of current, welding speed and preheat temperature during FB-TIG welding of AA5083 aluminum alloy was studied. Using the Taguchi method, 9 different tests were designed to invesTIGate the effect of welding parameters on the penetration depth. Consistent with predictions, increasing the current and preheat temperature, and reducing the welding speed led to an increase in penetration depth. The maximum penetration depth of 8. 02 mm was achieved at the current of 220 A, welding speed of 120 mm/min, and the preheat temperature of 100 °C. Taguchi analysis showed that increasing the welding current and preheat temperature had a more significant effect than the welding speed. Microstructural analysis indicated that the weld metal is fine-grained, along with coarse-grain in the HAZ of all samples. Many pores were observed in the samples with high welding speed and high welding current in the fusion zone. The sample with the highest heat input had the highest penetration depth. This sample had the highest elongation, equal to 69% of the base metal. Moreover, microhardness test demonstrated that the hardness of this sample dropped sharply from 70 Vickers to 58 Vickers in the HAZ.

Tungsten inert gas (TIG) welding process is one of the complex production methods. The reason is the drastic changes in the metallurgical structure of welding parts due to the heating and cooling cycle during welding. These changes cause various metallurgical and mechanical defects of the parts and weaken the mechanical properties of the parts. Many parameters in welding have different effects on the quality of welding parts. To create a suitable weld, it is necessary to identify the effect of these parameters and to be able to estimate it and select the appropriate and optimal conditions. Accordingly, In this study, an experimental invesTIGation were conducted on determining the mechanical characteristics of the pieces through variation of three main welding parameters including advance speed, welding amperage and preheating temperature.  Due to the difficulty of changing the rate of advance speed in manual welding, a robotic welding arm was designed for welding 316 stainless steel in the current paper, in which a microcontroller tuned the speed and welding length. By collecting the practical data, the effect of the input data (advance speed, welding amperage and preheating temperature) invesTIGated in durability and strength of the joints. In other words, the tension and durability of the joints for stainless steels are proposed for various welding parameters to enhance the optimal conditions based on the experimental results. In samples with low advance speed, in addition to increase the solidification time, the coarseness of the structure and the burning of the edges of the welded parts due to the low speed and high amps, reduce the tensile strength. Also, the results showed that by increasing the amperage, the strength of welding parts decreases due to the burn defect of the plate edges, which can be minimized by increasing the welding speed and reducing the effect of extreme heat on the edges. Finally, by analyzing the effect of the input parameter on the output, the best conditions of the adjustment parameters in butt-welding were acquired among existed samples for welding 316 stainless steel.

In the TIG-MIG hybrid welding, higher weld efficiency and better weld quality are obtained with respect to each individual TIG and MIG welding methods. Moreover, in this method, the MIG arc is more stable in pure argon shielding gas. Therefore, in this study, the influence of TIG-MIG hybrid welding parameters on the welds appearance quality and welds depth to width ratio of a 316L austenitic stainless steel was invesTIGated using optimum parameters of Taguchi design of experiments (DOE). Microstructure of the heat affected zone (HAZ) obtained from the hybrid welding was compared with those of each individual MIG and TIG welding techniques under equal heat-input condition. The results indicated that the most important parameter in the hybrid method to obtain the best appearance quality and the highest depth to width ratio is the distance between the two arcs. The MIG and TIG currents are the next influencing parameters. The width of HAZ and the size of constituent grains in hybrid welding with optimum parameter, were smaller than those of each individual TIG and MIG processes due to the higher associated cooling rate in the hybrid welding technique.

Hybrid laser-arc welding is a new welding process which has received particular attention in various industries because of its technological and economic advantages. This process combines a laser beam and an electric arc to incorporate the advantages of both laser and arc welding processes. The main goal of this paper is to evaluate the performance and ability of hybrid Nd: YAG laser-TIG welding compared to lone laser welding process for welding of aluminum foam sandwich (AFS) panels of AA6082. To this aim, a set of experiments for both laser and hybrid laser-TIG welding were done to invesTIGate the effects of welding parameters including laser power, arc current and welding speed on weld dimensions.Then, appropriate welding parameters for the laser and hybrid laser-TIG welding of AFS panels were calculated by statistical analysis. The results show that laser power threshold for creating the keyhole was less in hybrid laser-TIG welding than lone laser welding. Moreover, increasing the laser power and decreasing the welding speed result in increasing both the weld depth and width. But, with increasing the arc current, the weld depth remains almost unchanged and only the weld width increases.Comparing the laser and hybrid laser-TIG results show that adding a 100 A arc to a 2000 W laser source can increase the welding speed from 2 to 3 m/min which proves the high ability and efficiency of hybrid laser-TIG welding process.

Gas tungsten arc welding is a popular process in those applications requiring a high degree of quality and accuracy. However, this process has a big disadvantage against the substantially high productivity welding procedures. Hence, many efforts have been made to improve its productivity. One of these efforts is the use of activating flux (A-TIG welding). In this study, the performance of A-TIG welding on 304L austenitic stainless steel plates has been presented. Two oxide fluxes, TiO2 and SiO2 were used to invesTIGate the effect of A-TIG welding process on weld morphology, microstructure and mechanical properties of weldments. The experimental results indicated that A-TIG welding could increase the weld penetration and depth-to-wide ratio. It was also found that A-TIG welding could increase the delta-ferrite content of weld metals and improve the mechanical properties. Moreover, a 2D axial symmetric model was developed to simulate the flow behavior in the melting pool. These results were compared to those experiments carried out on a stainless steel (304L) melted by a stationary heat source.

One of the fastest ways to repair a damaged airfield, is using the matting plates. These plates are manufactured with various size and materials. If there is no way to continuously manufacture the plates, one can produce two separately parts of them and weld to each other. In this paper, the strength of a matting plate namely AM-2 welded by TIG welding process has been analyzed. For determination of the landing loads, Hercules C-130 aircraft has been considered. Various values of subgrade CBR have been studied. The joining plan of plates has been considered in such a way that the strength in the weld region be greater than before. The results showed that by using the matting plate welded by TIG welding process, the value of the subgrade CBR should be at least 15. Simulating test with crane has been carried out in this paper and good agreement was found in the results obtained by experimental tests and that evaluated by numerical analyses.