Shielded metal arc welding

About: Shielded metal arc welding is a research topic. Over the lifetime, 4462 publications have been published within this topic receiving 40560 citations. The topic is also known as: manual metal arc welding & flux shielded arc welding.

RBF-NN-based model for prediction of weld bead geometry in Shielded Metal Arc Welding (SMAW)

Abstract: Welding processes are considered as an essential component in most of industrial manufacturing and for structural applications. Among the most widely used welding processes is the shielded metal arc welding (SMAW) due to its versatility and simplicity. In fact, the welding process is predominant procedure in the maintenance and repair industry, construction of steel structures and also industrial fabrication. The most important physical characteristics of the weldment are the bead geometry which includes bead height and width and the penetration. Different methods and approaches have been developed to achieve the acceptable values of bead geometry parameters. This study presents artificial intelligence techniques (AIT): For example, radial basis function neural network (RBF-NN) and multilayer perceptron neural network (MLP-NN) models were developed to predict the weld bead geometry. A number of 33 plates of mild steel specimens that have undergone SMAW process are analyzed for their weld bead geometry. The input parameters of the SMAW consist of welding current (A), arc length (mm), welding speed (mm/min), diameter of electrode (mm) and welding gap (mm). The outputs of the AIT models include property parameters, namely penetration, bead width and reinforcement. The results showed outstanding level of accuracy utilizing RBF-NN in simulating the weld geometry and very satisfactorily to predict all parameters in comparison with the MLP-NN model.

Effect of torch position and angle on welding quality and welding process stability in Pulse on Pulse MIG welding–brazing of aluminum alloy to stainless steel

Abstract: In this paper, Pulse on Pulse metal inert gas (MIG) welding–brazing of 6061 aluminum alloy to 304 stainless steel in a lap configuration was developed to investigate the effect of torch position and angle on the welding quality and welding process stability. Images of arc, electrical signals of welding current, and welding voltage were acquired in synchronous modes by a high-speed camera and electrical signal acquisition system, respectively. The obtained results demonstrate that arc shape, macrostructure, microstructure, and mechanical properties are sensitive to torch aiming position when torch travel angle is 20° and work angle is 0°. However, when travel angle is 20° and work angle is 20°, the effect of torch aiming position is insignificant. It is easier to strike arc and maintain it on the surface of aluminum alloy compared to stainless steel. High-strength joints, whose fracture occurred at heat-affected zones of Al alloys at 89 MPa up to 72 % of the tensile strength of Al alloys, have been obtained. Moreover, a comprehensive evaluation method for the welding process stability based on statistical techniques has been proposed. This method can be easily and quickly integrated in real-time control of the welding process, which provides a quantitative guidance in MIG welding–brazing of aluminum alloy to stainless steel.

Digital Control for an Arc Welding Machine Based on Resonant Converters and Synchronous Rectification

Abstract: This paper presents a field-programmable gate array (FPGA)-based generation of optimized drive signals for resonant converters using synchronous rectification (SR) applied to an arc welding machine. The proposed digital implementation makes the most of the FPGAs capabilities by setting in open loop the arc welding current with enough resolution to establish precisely the operation point, according to the welding technique and metal part requirements. It also optimizes other parameters of interest such as the initial and final welding transient. The resulting system is very flexible because is valid for Tungsten inert gas, shielded metal arc welding, and metal inert gas welding techniques. A novel ad-hoc SR control algorithm for current mode operation that eliminates the dead-times of the power MOSFETs' switching period is proposed. Finally, the experimental results are presented including an efficiency comparison between diodes and SR solutions.

The effect of ferro-alloy additions and depth on the quality of underwater wet welds

Abstract: Underwater wet welding offers significant cost savings over other repair techniques for submerged structures, but the weld metal mechanical properties are not equal to those of surface welds. The problems of porosity and oxidation of the weld pool as underwater depths increased were addressed by additions of manganese, titanium, boron, and rare earth metals (REM) to the coating of a rutile-based SMAW electrode. A test matrix of 60 coating formulations was prepared and test welds were made at four depths: 70, 140, 200, and 300 ft (21, 43, 61, 91 m). With the addition of titanium, a strong deoxidant, it was possible to control weld metal chemical composition. Low porosity was associated with electrodes that deposited a slag with a basicity index approaching neutral (1.0). Slag basicity may influence transfer of hydrogen to the weld pool and, thus, influence porosity. Addition of titanium and boron produced a microstructure of 60 to 90 vol-% acicular ferrite. Tensile strength increased with the combined addition of manganese, titanium, and boron. The results of this investigation demonstrated some of the adverse effects of increasing underwater depth on weld metal quality can be mitigated by modifications to the electrode coatings.

Development of a highly efficient hot-wire laser hybrid process for narrow-gap welding—welding phenomena and their adequate conditions

Abstract: The purpose of this work is to develop hot-wire laser welding for narrow-gap joints. Test pieces of ASTM A 304 stainless steel with a gap width of 3 mm were used. With welding by tentative filler rod made of Inconel 600 alloy, melting phenomena of the molten pool and the weld bead formation during welding were investigated by in situ observation using a high-speed camera. Variations in the main welding parameters such as wire current, wire feeding position, laser irradiation angle, and wire feeding angle were investigated to determine appropriate conditions. Experiments showed that under the optimum welding conditions, hot-wire laser welding was able to produce complete weld deposition with very low dilution of the base metal. An experiment on laser beam reflection indicated that the laser beam reflected from the molten pool was a crucial phenomenon to explain the formation of the weld bead, especially in terms of melting the side groove wall of the base metal. Welding parameters as mentioned above significantly affected weld quality. Furthermore, in the case of welding with filler wire ER NiCrCoMo-1, the Vickers hardness distribution along the transverse welding direction was examined to evaluate weld properties and the bonding strength at the fusion interface was examined in a tensile test, and the results showed that there was no great difference in the hardness profile throughout the cross section of the weld plate. Additionally, metallurgical examination of the fracture surface revealed the rupture occurred at the weld metal, probably because the bonding at the fusion interface was stronger than the weld metal. Therefore, the development of laser welding with hot wire can advance the multi-pass weld for an ultra-narrow-gap joint.