This paper investigates the dynamic behavior of Gas Metal Arc Welding (GMAW) process for two types of power supplies-inverter and rectifier-for short circuit transfer mode. The large ripples on the rectifier power source are able to perturb the metal transfer mode. In this experimental work some operating points in the short circuit mode have been selected using an automatic pipeline welding system, and the effects of both rectifier and inverter effects (as the power supplies) on the process have been illustrated. For small voltage and currents, the two power supplies effects are similar in the short circuit transfer mode. On the other hand, for larger voltage and current values, the responses will be different as the rectifier power supply produces more perturbations on the metal transfer. However, the process with the inverter has a more regular behavior and a more stable detachment.

Among the Aluminum-Magnesium alloys, 5083 alloy has specific characteristics such as high mechanical features, good weldability, and the most important of all its excellent resistance to corrosion under water. These characteristics caused 5083 alloy to be used widely in the marine industries. One of the welding methods for this alloy, especially suited for thick plates, is GMAW welding method. In welding process of this alloy, in order to eliminate surface moisture and to avoid porosity, lack of fusion and possible distortion, preheat is needed. In this project Al5083-H321 alloy test plates were welded in six different preheat temperatures with GMAW method, using ER5183 filler metal, to investigate the effects of preheat temperature on microstructure. Optical metallugraphy, macrography and scanning electron microscope equipped with EDS, were used to examine the microstructure of this alloy, and also to determinate the effect of changing the preheat temperature on the size of grains, and created precipitations in weld metal and heat affected zone. Finally three kinds of precipitation included precipitations rich in Magnesium (Al-Mg), rich in Iron and Manganese (Al-Fe-Mn) and also precipitations rich in Silicon and Magnesium (Al-Mg-Si) were observed in this alloy. Besides, increasing the preheat temperature caused an increase in the amount of created precipitations and the size of grains and the heat affected zone (HAZ).

Introduction: The present study was carried out to compare contrast sensitivity among three groups of professional welders including (1) those who use gas metal Arc welding (GMAW) (2) those who use shield metal Arc welding (SMAW) and the group that uses resistance welding.Material and Method: In this research, all the welders who use GMAW, SMAW and resistance welding working in an industry who were all male, performed contrast sensitivity test, using Freiburg. The contrast sensitivity test was done at three spatial frequency of 1cpd, 5cpd and 15 cpd under a constant condition. The three selected groups were similar regarding age and work experience. The result of the three groups at each spatial frequency were recorded and compared with other groups.Results: ANOVA test showed that decrease contrast sensitivity in spatial frequency of GMAW group at the spatial frequency 15cpd, significantly decrease comparing to SMAW group (p=0.028) and resistance welding group (p=0.041). The mean (SD) of contrast sensitivity at frequency of 1cpd, 5cpd and 15cpd was respectively 140.69±51.8, 172.7±43.75 and 39.8±25.92 for the GMAW group and 157.8±42.2, 183.21±32.01 and 60.57±54.30 for the SMAW group and 149.10±50.68, 180.60±35.42 and 57.38±39.22 for resistance welding.Conclusion: Although all welders use goggle or other personal protective equipment, loss of contrast sensitivity of GMAW workers can be attributed to the cumulative effects of the radiation.

In this research, the effect of vibration at the resonant range (75 Hz) on the hardness and tensile strength of AA5083-H321 aluminum alloy, were welded by gas metal arc welding (GMAW) investigated. Vibration forces were ranged from 850 N to 2200 N, under identical welding parameters. Tensile strength and hardness testing of welded samples were performed. After mechanical tests, the fracture surfaces of welds were examined using scanning electron microscope (SEM) and discussed. The results showed that with increasing vibration force, the tensile strength and fracture strength of the specimens were welded during vibration, were increased by about 3 and 9 percent, respectively, compared to the non-vibrated weld sample. However, no significant change was observed in the hardness of the welded specimens. Mean grains size and heat affected zone of the sample was welded was welded with conventional GMAW, were about 200 μ m and 1800 μ m, but due to inducing vibration, as vibration force increased from 850 N to N 2200 N, Mean grains size was reduced to about 75 μ m and HAZ was reduced from about 1000 μ m to 700 μ m, that is, about 44 to 61%.

Dissimilar welding of AISI 304L austenitic stainless steel to AISI 409 ferritic stainless steel with GMAW process usingtwo Ar-O2 and Ar-CO2 shielding gas mixtures was studied. ER316LSi and ER309LMo filler metals were chosen by considering 5 and 15% delta ferrite according to the Schaeffler equations and diagram. Based on the observations, both filler metals accompanied by Ar-2%O2 shielding gas resulted in acceptable weldments. Yield strength and UTS of tensile samples were 288 and 424 MPa, respectively. All tensile samples fractured in the ferritic base metal. Microhardness test results demonstrated that the maximum hardness of 190-200 HV was obtained from ER316LSi weld metal. The minimum hardness of 145 HV was found in the HAZ of 409 side mainly due to the grain coarsening. Microstructural examinations revealed needle-like precipitates formed perpendicular to each other in the HAZ of 409 stainless steel. It seemed that the pre-existing TiC precipitates evolved into the needle shape precipitates as a result of rapid heating and cooling rates during the welding process.

In this study, samples of carbon steel St37 was junction with thickness of 4 and 8 mm by two process GMAW and FCAW welding methods. The samples was junction by using solid wires and flux cored for welding GMAW and FCAW respectively, to near the chemical composition connected. Evaluation of microstructure was performed by optical microscopy and scanning electron microscopy (SEM) with EDS analysis. The results showed that, with increasing the thickness of the Ferrite circulators content reduced in the Weld zone and the amount Weidman Ashton ferrite and grain boundary ferrite phases increased. Also in the FCAW process due to potential areas for nucleation sites and the formation of Ferrite circulators than the process GMAW, better mechanical properties was observed. The results of the tensile test showed the highest the amount of tensile properties in the sample thickness of 4 mm and obtained in welded by FCAW method. Hardness test results showed, highest the amount of hardness in welding and heat affected zone related to sample with thickness 4 mm and is welded by FCAW method. SEM images were showed, the amount of inclusions and cavities weld metal was FCAW more of GMAW method.Images SEM showed that the impact test samples with the increase in thickness in both welding methods the fracture surfaces, fracture but also show evidence of brittle behavior as well.

In Wire and arc additive manufacturing (WAAM) based on Gas metal arc welding (GMAW) is one of the methods of manufacturing metal layer by layer. One of this method's basic steps is predicting the welding geometry created in each welding step. In the current research, an experimental study was conducted in this field considering the effective parameters of welding geometry. For this purpose, three parameters of voltage, welding speed, and wire feeding speed were considered as effective parameters on the welding geometry of the process. The width and height of the weld bead was selected as the answer according to the type and application of the research. The least squares support vector machine was used to model the welding geometry in the process. The results obtained from the regression (R2) of train, test, validation, and total were 0. 945, 0. 793, 0. 894, and 0. 881 respectively. The comparison between the experimental data and the model data shows the significance of the proposed model.

Wire-arc additive manufacturing (WAAM) is a prominent technique for producing large metallic components due to its high deposition rate. Utilizing austenitic stainless steels in this process not only reduces production costs but also provides greater design freedom. Among these steels, SS310, known as heat-resistant steel in the industry, offers excellent oxidation resistance and high-temperature performance. However, it is highly susceptible to hot cracking during welding and additive manufacturing processes. In this study, the microstructure and mechanical properties of SS310 fabricated using WAAM with Cold Metal Transfer (CMT) and Gas Metal Arc Welding (GMAW) processes were compared. The results revealed that the CMT process, due to its lower heat input, effectively reduces the susceptibility of SS310 to hot cracking compared to the GMAW process. These findings emphasize the importance of selecting an appropriate process to achieve high-quality components and minimize structural defects.