This paper presents the results of a study on the development of a Metal active gas (MAG) welding technology for an industrial furnace component made of steel S235JRC+N with respect to the ...minimizationof welding deformation. A numerical simulation of the welding process was performed in the first phase of the research. The numerical simulation was carried out with the SYSWELD software. For the numerical simulation of the welding process, the FEM method was used. In the simulation, four variants of restraint of the industrial furnace wall panel elements during the execution of the welding process were investigated. They differed in the number of restraints (model 1-4). It was found that the difference between the maximum mean strain in model 1 and the lowest mean strain in model 4 was only 11%. A physical simulation of the welding process was then performed with a restraint variant according to model 1. The displacement results obtained from the physical simulation of the welding process were compared with the displacement results from the numerical simulation. Discrepancies between numerical and physical simulation displacement values were found. The quality of selected welded joints was also evaluated. Visual testing (VT) and measurements of weld geometries were performed for this purpose. Metallographic tests and hardness measurements were performed to determine of influence of the welding process on the microstructure of the welded joint area, especially the heat affected zone (HAZ). The results obtained confirm the correctness of the assumptions made regarding the technology of manufacturing the furnace wall panels.
In this paper, in order to reduce the time cost of prediction experiments in industry, a new narrow gap oscillation calculation method is developed in ABAQUS thermomechanical coupling analysis to ...study the distribution trend of residual weld stresses in comparison with conventional multi-layer welding processes. The blind hole detection technique and thermocouple measurement method verify the reliability of the prediction experiment. The results show that the experimental and simulation results have a high degree of agreement. In the prediction experiments, the calculation time of the high-energy single-layer welding experiments is 1/4 of the traditional multi-layer welding. Two welding processes of longitudinal residual stress and transverse residual stress distribution trends are the same. The high-energy single-layer welding experiment stress distribution range and transverse residual stress peak are smaller, but the longitudinal residual stress peak is slightly higher, which can be effectively reduced by increasing the preheating temperature of the welded parts. This implies that in the specific case of increasing the initial temperature of the workpiece, the use of high-energy single-layer welding instead of multi-layer welding to study the residual stress distribution trend not only optimizes the weld quality but also reduces the time cost to a large extent.
This paper presents research of the impact toughness and hardness distribution in specific zones of a 'single V'butt multiple-pass welded joints of the high-strength low-alloyed steels. Obtained ...values of the impact toughness are analyzed in correlation with a microstructure in specific zones of the welded joint, together with the micro hardness distribution found in the related zones. Based on the carried out analysis and results obtained in experiments, the applied technology of welding was evaluated. The original conclusions on influence of the selected welding procedure manual metal arc (MMA) for the root passes and metal active gas (MAG) for the filling and covering passes) on impact toughness of the high-strength low-alloyed steels are drawn. The paper also presents discussion on the valid standards and recommendations related to welding of those steels, from the aspect of applications in design of steel welded constructions.
The gas metal arc welding (GMAW) process involves arc plasma, metal transfer, and weld pool phenomena. In addition, metal vapor is formed by evaporation from the high-temperature metal and mixes with ...the arc plasma. These phenomena interact with each other and are very complicated. A numerical approach that includes their interaction is therefore important for clarifying the GMAW phenomena. We have developed a unified model and used the model to investigate the influence of the shielding gas on the metal transfer. When argon shielding gas was used, for an arc current of less than 230 A, globular transfer occurred. For higher currents, spray transfer occurred. On the other hand, when Ar + 18 %CO
2
gas was used, the transition from globular to spray transfer occurred at around 280 A. This difference was caused by changes in the driving force exerted on the molten metal by the arc plasma. The arc pressure that lifts up the molten metal and interferes with its detachment from the wire tip becomes stronger when the gas mixture is used.
The welding with hybrid heat sources combined a high-power disk laser and a metal actives gas (MAG) arc was performed on the I-groove joint of 12 mm thick high-strength steel plates. To investigate ...the effect of laser focal position on joint formation, the combination effect of laser power and focal position on the cross section and the backing bead shape was investigated. The results showed that a good welded joint was obtained at the minimum laser power of 8 kW when focal position is 6 mm below the surface of the base material. At the minimum laser power, it was clarified that the welding penetration depth was deeper at focal position of the below the surface than at focal position of the above the surface.
In an automatic welding system using a visual sensor, it is necessary to clearly observe the weld pool to control the welding phenomenon with a visual sensor. However, since the arc light is too ...strong, it is difficult to take clear weld pool images. It is important to reduce the influence of the arc light. Therefore, the spectral distribution of the weld pool and arc light in plasma arc welding and pulse MAG welding was measured changing the current. Based on the measurement results, the characteristics of the spectral distribution in each welding method were found. Using the results, a filter suitable for the weld pool observation was selected.
Non-Destructive Testing of Dissimilar Welded Joints DIJMĂRESCU, Maria-Cristina
The Annals of "Dunărea de Jos" University of Galaţi. Fascicle IX, Metallurgy and Material Science (Online),
03/2021, Volume:
44, Issue:
1
Journal Article
Peer reviewed
Open access
This paper presents research’s results of non-destructive examination of dissimilar welded samples. The samples were made using sheets of austenitic stainless steel and carbon steel welded through ...the method of MAG welding with tubular wire. The samples were subjected to non-destructive testing in order to analyse the integrity of the welded seam, heat affected zone and the adjacent area of the weld.
The article presents results of an experimental study and simulation of the effect of welding arc energy characteristics on the nature of electrode metal transfer in MIG-MAG welding. Based on the ...research results, a method has been developed for determining the coefficient of welding arc plasma flow pressure. The method makes it possible to take into account the dependence of the electrode metal transfer pattern and plasma flow pressure on geometrical dimensions of a welded joint.
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