Weld Quality Research Articles

Optimizing and Redesigning the Vertical Milling Fixture for Friction Stir Welding of Aluminium Alloy (Al 6061)

Friction stir welding is a kind of solid-state fusion process for welding like or unlike metals. Established and patented by “The Institute of Welding” in the UK in December 1991, it involves using a compressive force applied by a conventional milling machine to make contact with work-pieces. The work-pieces are one or the other revolving or moving proportional to a pin tool, generating the heat necessary for atomic diffusion and thereby uniting the material at the edges. FSW can be functional in a variety of materials, together with stainless steel, aluminium, and various alloys. The process typically takes place on vertical milling machines, requiring a vertical milling fixture to firmly hold the plates being welded. In this paper, vertical milling holding setup and fixture for FSW procedures on vertical milling machines are established. Materials such as aluminium and aluminium alloy (Al 6061) are analyzed for their suitability in FSW operations, to identify the best material for the process. Additionally, there is potential for extending the FSW process to plastics and similar materials. Friction stir welding offers significant advantages in terms of weld quality, strength, and versatility across a range of industries, making it a versatile option for solid-state joining processes.

Welding Procedure Control and Monitoring of Weld Quality

Welding Procedure Control and Monitoring of Weld Quality

Research on intelligent perception and decision system for special welding mechanical arm of float plate in crude oil storage tank

Abstract In the rapid development of the petrochemical industry in the context of the increasing number of large tanks, large tanks in the production and installation process encountered the first problem the pontoon plate welding deformation and weld seam is too large and other defects, through the construction of the ship plate welding special robotic arm of the intelligent perception and decision-making system to solve such defects. Summarize the Structure of crude oil storage tanks and welding process characteristics based on the ultrasonic distance measurement in the distance sensor to obtain the characteristic data set, combined with the distinct data and computer programming language to build the intelligent perception and decision-making system of the unique robotic arm for ship plate welding. They set the relevant parameter values based on simulation experiments on the welding of a particular robot arm perception and decision-making system for the application of example analysis. Compared to the traditional LSTM algorithm, the YOLO-v5 network-driven weld target detection algorithm has a 5.5% higher accuracy and a 9.1% higher success rate in time robustness evaluation. In addition, the welding decision model based on the DDPG algorithm possesses excellent computational accuracy, and the average error of each parameter in the welding decision of the ship plate is controlled within 5%. This study greatly improves the welding quality of the pontoon plate of crude oil storage tanks and provides solid technical support for the successful completion of the project.

Airtight welding technology for aircraft composite mold panel

In this paper, the airtightness problem caused by welding defects in the manufacturing process of composite mold is analyzed. The mechanism analysis of the weld defects of composite mold is conducted. According to the mechanism of weld failure, the welding process monitoring, weld metallographic analysis, weld X-ray inspection, panel airtightness detection, and other methods are used to evaluate the welding quality of different welding forms in the welding process of composite mold panels. The measures to optimize the welding quality of composite mold panels are put forward. Finally, through the actual verification, it is proved that the optimized air-tightness welding method is stable and reliable.

Design and simulation of a multi-functional radiofrequency tissue welding electrode

Purpose: To explore the effect of electrode structure on welding quality by modifying the structure of magnesium alloy electrode. Methods: Two novel electrodes were designed in this study, including one with a circle (C) surface and the other with a square and arched (SA) surface. The designed electrodes were compared to a control electrode with a smooth surface in terms of temperature distribution, thermal damage to tissue, and effective welding area. Finite element analysis was used to analyze the stress and strain of all electrodes and thermal damage to the tissue. Results: Pressure applied to the designed electrodes was within the elastic limit, and the deformation was less than 1%. The highest temperature of SA electrode (99.6 ℃) was similar to that of the control (100 ℃), while that of C electrode (106 ℃) was higher than the control. The mean temperature at the welding site in intestine of the control electrode was significantly higher than that of the other two electrodes. Besides, the mean temperature of C electrode was also slightly higher than that of SA electrode. The tissues welded by the control electrode, C electrode and SA electrode were completely necrotic within an axial distance of 2.546 mm, 2.079 mm, and 1.835 mm from the edge of the welding area, respectively. Conclusion: SA electrode has the lowest thermal damage compared with the other two electrodes due to smaller effective welding area. Therefore, SA electrode is better than the other two electrodes.

Numerical Simulation and Experimental Analysis on Seam Feature Size and Deformation for T-Joint Laser-GMAW Hybrid Welding.

As an innovative technique, laser-GMAW hybrid welding manifests significant superiority in enhancing welding productivity and quality, albeit the optimization of process parameters poses a challenge for practical application. The present manuscript elucidates the influence of process parameters on the dimensional characteristics of the welding seam and the distortion of 8 mm T-joints in the context of laser-GMAW hybrid welding, and channels both simulation and experimentation. The outcomes denote that the dual conical model serves as an efficacious aid for the numerical simulation of T-joint laser-GMAW hybrid welding. Furthermore, the repercussions of process parameters on welding seam dimensional characteristics remain consistently similar in both the simulation and experimental results. From the simulation outcomes, it becomes apparent that the distortion of the base material can be efficiently managed by implementing anti-distortion measures. This inquiry offers both a theoretical and experimental foundation for optimizing process parameters of T-joint laser-GMAW hybrid welding, presenting certain engineering applicability.

Review on Recent Laser Welding Trend in Electric Powered Vehicle Production

In this study, we summarize the state-of-the-art laser welding used for welding copper and aluminum alloys, which are key materials for electrified powertrain components. Extensive research on laser beam modulation, power control, beam control, and process monitoring to improve welding reliability and to solve the challenges of dissimilar welds are reviewed and summarized. Furthermore, various techniques for real-time behavior of the weld pool and weld quality monitoring are presented. Along with various techniques to improve spatter and weld pool instability during welding, we have also included research results on process monitoring using artificial intelligence and deep learning techniques. Moreover, computer simulation helps understand various welding phenomena. The research results on improving the quality of welded products through laser beam dynamic control are also included.

Consideration on the Applicability of Electron Beam Welding for the Manufacture of Small Modular Reactor

The overall technology required for the application of electron beam welding to ultra-thick plate pressure vessel in small modular reactors was considered. Electron beam welding has the advantage of reducing the manufacturing time compared with traditional arc welding, but it requires the construction of complex equipment and the establishment of related process technology. Based on the thickness of 150~250 mm, the electron beam welding equipment for application to SMR pressure vessel requires large-capacity equipment of 120~170 kV, 150 kW or more, which has never been commercially manufactured so far. A stable beam must be maintained for a constant time. Anti-arcing and seam tracking functions are also required. Electron beam welding of low-alloy steel has superior characteristics in terms of strength and toughness compared with arc welding. The welded area can be made into a base material by solution heat treatment. Cleaning and gap control are important for weld quality. Weld area should not be affected by magnetic fields. As circumferential welding overlaps in span at the welding start and end, it requires precise setting of welding parameters. For welding of large pressure vessel, customized cylindrical vacuum chamber or local vacuum chamber are suitable. It must be shielded from X-rays generated during welding.

Investigation of the influence of pulse parameters on the resulting weld seam quality in pulsed electron beam welding of AW 6061

Utilizing pulsed lasers in favor of a continuous wave in laser beam welding is a well-established method to achieve higher process efficiency and reduce heat input into the workpiece, which is especially useful for thin-walled workpieces (Steen, 2005). In addition, pulsed processes have shown to lead to smaller grain sizes due to higher cooling rates, which can lead to a reduction in hot cracks in some aluminum alloys (Beiranvand et al., 2019). Since an electron beam can also be pulsed, a technique industrially utilized in electron beam drilling, the same principles apply (Schultz, 2000). However, pulsed electron beam welding is rarely used in industrial welding applications due to the risk of pores, spiking and sputtering resulting from the pulsed process dynamic, especially in the deep welding regime (Kautz, 1991). This study aims to develop a pulsed electron beam welding process for AW 6061 sheet metal, which is susceptible to hot cracking. The influence of the welding and pulse parameters, as well as the combination of a pulsed beam with high frequency beam oscillation is discussed. Furthermore, suitable welding parameters for pulsed electron beam welding of AW 6061 are developed, and the increased efficiency of pulsed welding is shown by comparison to continuous welds.

Microstructure and mechanical properties of welds at keyhole closures in variable-polarity plasma arc aluminum welding

The variable-polarity plasma arc (VPPA) keyhole welding technology offers an efficient solution for producing defect-free aluminum alloys, but a keyhole is left at the end of the welding process. Traditional manual TIG welding, which involves filling keyholes, often lacks productivity and can result in inconsistent weld quality, hindering the production of high-strength and high-precision parts. In this study, a keyhole self-closing method was proposed, and the microstructure and mechanical properties of keyholes closed by the proposed method were compared to those closed by manual TIG welding. The results showed that the self-closed keyhole had a smaller fusion line wide, and the weld zone had a uniform distribution of equiaxed crystal, with fewer pore defects. While the manual TIG welding-filled keyhole had a higher density of dislocations, which leads to an increase in the microhardness. The presence of pores in the manual TIG welding-filled keyhole reduces its tensile strength and elongation, which were lower than those of the self-closed keyhole by 61.5 MPa and 5.8 %, respectively. The self-closing method can effectively address the keyhole retention issue in VPPA keyhole welding. By using this method, higher-quality welds with better microstructure and mechanical properties can be produced, which can have important implications for various industrial applications, and in applications where mechanical properties are critical.

In situ localised post-weld heat treatment with electron beam welding of S690QL steel

The objective of this research is to assess the influence of in-situ localised electron beam post-weld heat treatment (LEB-PWHT) on the microstructure and mechanical properties of high-strength S690QL steel welded joints utilising highly sophisticated electron beam welding (EBW) technology. Although EBW is well-known for creating high-quality welds, the addition of the novel LEB-PWHT technique may significantly improve the characteristics of the welded joints. To systematically analyse the impacts of PWHT on the welded joints, the study employs microstructural analysis like optical microscopy and mechanical properties like microhardness testing, bending, tensile, and impact tests. Furthermore, tensile fractography analysed by scanning electron microscopy (SEM) to provide detailed insights into the fracture behaviour of the welded joints. The results show that the in-situ PWHT approach improves the microstructure and mechanical characteristics of the welded joints, such as a lower hardness peak in the heat affected zone (HAZ), increased tensile strength (5%), and improved toughness by 7 times. LEB-PWHT fractured surface revealed smaller, more sharply defined dimples and micro-voids. These results suggest that in-situ PWHT is an attractive option for improving the quality and performance of welds in a wide range of applications incorporating S690QL steel.

Frequency-based analysis of active laser thermography for spot weld quality assessment

Frequency-based analysis of active laser thermography for spot weld quality assessment

Mechanical and metallurgical characterization of friction stir welded AA2024 to pure copper using specific variables and positioning

A simple cylindrical pin shaped tool made economically of H13 tool steel was used to butt weld dissimilar metal plates of AA2024 and pure copper with friction stir welding with three different welding arrangements of plate positionings and tool offsets. Plunge depth, tool tilt angle and tool traverse speed remained steady while tool rotation speed varied in every arrangement. Tensile strength testing, microhardness testing, SEM, EDS and fractography were performed to evaluate the impact of plate positioning, tool offset and tool rotational speed on weld quality. The NZ showed swirl and vortex microstructures, and ductile fracture was identified as the cause of rupture in the FSWed samples. The arrangement AA2024 was placed in the advancing side without tool offset at tool rotation speed of 900 rpm demonstrated UTS, YS and microhardness as 198.98 MPa, 153.86 MPa and 251 HV respectively whereas maximum elongation, joint efficiency found 8.39%, 85.54% respectively.

Numerical Study of Laser Welding of 270 μm Thick Silicon–Steel Sheets for Electrical Motors

In this study, the shape of laser welding parts required to develop a welding automation system was analyzed to improve the production process of thin-plate silicon–steel. During laser welding, a welding defect occurs in the welding area, resulting in beads. This can be measured and analyzed through computational fluid dynamics. When welding thin plates with a laser, precise parameter settings are required to reduce bead height and side effects to improve weld quality. Twelve simulation cases with different laser powers and scan speeds were carried out to compare bead heights. We discussed ways to improve the productivity of electrical steel sheets by applying data collected through simulations of a laser welding automation system.

Reinforcement learning as data-driven optimization technique for GMAW process

Welding optimization is a significant task that contributes to enhancing the final welding quality. However, the selection of an optimal combination of various process parameters poses different challenges. The welding geometry and quality are influenced differently by several process parameters, with some exhibiting opposite effects. Consequently, multiple experiments are typically required to obtain an optimal welding procedure specification (WPS), resulting in the waste of material and costs. To address this challenge, we developed a machine learning model that correlates the process parameters with the final bead geometry, utilizing experimental data. Additionally, we employed a reinforcement learning algorithm, namely stochastic policy optimization (SPO), with the aim to solve different optimization tasks. The first task is a setpoint‐based optimization problem that aims to find the process parameters that minimize the amount of deposited material while achieving the desired minimum level of penetration depth. The second task is an optimization problem without setpoint in which the agent aims to maximize the penetration depth and reduce the bead area. The proposed artificial intelligence-based method offers a viable means of reducing the number of experiments necessary to develop a WPS, consequently reducing costs and emissions. Notably, the proposed approach achieves better results with respect to other state-of-art metaheuristic data-driven optimization methods such as genetic algorithm. In particular, the setpoint‐based optimization problem is solved in 8 min and with a final mean percentage absolute error (MPAE) of 2.48% with respect to the 42 min and the final 3.42% of the genetic algorithm. The second optimization problem is also solved in less time, 30 s with respect to 6 min of GA, with a higher final reward of 5.8 from the proposed SPO algorithm with respect to the 3.6 obtained from GA.

Numerical simulation and experimental investigation on thermal characteristics during induction rolling welding of Fe/Al dissimilar metals

In order to realize the effective welding of Fe/Al dissimilar metals, an induction rolling welding (IRW) method was proposed and an electromagnetic-thermal coupling numerical model was established. The results show that the influence range and peak value of the magnetic flux density on the steel side will increase with the increase of feed velocity. When the welding feed velocity is in a low level, resulting in an increase for the heat transfer time and the heat input, and the welding quality will decrease. When the welding feed velocity is in a high level, resulting in a decrease for heat transfer time and the heat input, and the welding quality will also decrease. When the power supply is 35 kW and the welding feed velocity is 1.0 mm/s, the temperature values of each temperature reference point tend to be balanced, and the heat source input is stable. The uniformity of temperature distribution increases first and then decreases with the increase of feed velocity and power supply. The temperature measured and the boundary shape of the aluminum alloy molten pool accord well with the numerical simulation results. The test results of shear properties show that the inductively rolled welding joint has good reliability.

Evaluation of dissimilar TIG welded joints of novel high strength low alloy steel for automotive applications: Experiment and numerical comparative approach

Modern automotive, aerospace, and manufacturing sectors use tungsten inert gas (TIG) welding widely as a critical procedure due to the weld's quality and joint efficiency. In this study, mechanical characterization of TIG-welded joints of high strength low alloy (HSLA) steel with two different grades (S1 and S2) was performed experimentally and mechanical properties were calculated in terms of hardness profile along the weldment and load-displacement curves. True stress-strain curves of base metal, heat-affected zone, and melted zones were used for calibration of the 8-node solid numerical model. The highest hardness value of 386 HV was obtained in the melted zone whereas a softening zone was observed in the heat-affected zone (HAZ) of S2 where the Vicker's microhardness value was 270 HV. During the comparison of simulation results with experimental data, it was found that the overall error was less than 5% which reflects a good accuracy of material models used for numerical modeling. A higher ultimate tensile strength was found in similar S1-S1 steel joints as compared to similar S2-S2 and dissimilar S1-S2 steel joints. Furthermore, the results of simulations revealed that the maximum von Mises stress (1050 MPa) concentrations were found in the HAZ of a similar S1-S1 welded joint, whereas the minimum von Mises stresses (880 MPa) in S2-S2 welded joint, and intermediate von Mises stresses (1010 MPa) on the side of S1 HAZ in S1-S2 dissimilar welded joint. The results of simulations and experimental study of TIG welding joints show good agreement with reasonable accuracy.

Effect of Water Cooling on the Microhardness of Friction Stir Welded High-Density Polyethylene Sheets: Experimental Study

The objective of the current work is to analyze the influence of water cooling of high density polyethylene (HDPE) sheet welding by friction stir process (FSW) on mechanical strength, based on microhardness tests. In the present work, the process using the conventional tool (C-FSW) is presented with the new procedure developed for FSW for HDPE, called water conventional friction stir welding (W-FSW). Test results for water-cooled and non-cooled welded samples were compared. HDPE sheets were initially welded by FSW process, and intensive water cooling was performed to weld after the tool exceeded the initial welding position by 30mm. The tool rotation speed of 1100 rpm and welding speed of 26 mm/min was used. The results were compared and evaluated with the hardness tests. A decrease in the hardness was observed when the sheets were treated by quenching, especially in the weld cores. It was found that the average hardness was much lower than that of untreated welded plates. Additionally, there is a region outside the core that has more or less the same stiffness value. The use of intensive quenching and conventional tooling has proven to be of great importance in improving surface finish, reducing defects, and increasing the mechanical strength of welds. The resulting recrystallization modified the hardness and thus increased the efficiency of the joint. These findings indicate the welding quality of the studied polyethylene.

Research Progress of Aluminum Alloy Welding/Plastic Deformation Composite Forming Technology in Achieving High-Strength Joints.

Fusion welding causes joint deterioration when joining aluminum alloys, which limits the use of aluminum alloy components in high-end equipment. This paper focuses on an overview of how to achieve high-strength aluminum alloy welded joints using welding/plastic deformation composite forming technology. The current technology is summarized into two categories: plastic deformation welding and plastic deformation strengthening. Plastic deformation welding includes friction stir welding, friction welding, diffusion welding, superplastic solid-state welding, explosive welding, and electromagnetic pulse welding. Plastic deformation strengthening refers to the application of plastic deformation to the weld seam or heat-affected zone, or even the whole joint, after welding or during welding, including physical surface modification and large-scale plastic deformation technology. Important processing parameters of plastic deformation welding and their effects on weld quality are discussed, and the microstructure is described. The effect of plastic deformation strengthening technology on the microstructure and performance evolution, including the hardness, tensile strength, fatigue property, residual stress, and hot cracking of aluminum alloy welded joints, and its evolution mechanism are systematically analyzed. Finally, this paper discusses the future development of plastic deformation strengthening technology and anticipates growing interest in this research area.

Submerged Arc Welding of SA 516 Gr70 Material: Parametric Optimization of Mechanical Properties UT-Strength and Hardness

In this study, the Taguchi technique was employed to optimize the process parameters of submerged arc welding (SAW) in terms of mechanical properties such as Ultimate Tensile Strength (UTS) and hardness. The study considered a variety of weld quality factors and provided a detailed explanation of the procedure and results using the Taguchi method, which is a statistical analysis approach that requires fewer trials. The experiment was conducted on SA 516 GR70 material using a L9 orthogonal array and a range of current, voltage, and speed settings. The comparison of anticipated and experimental values with the mathematical model of regression analysis-ANOVA with and without interaction helped in achieving the desired results. Lastly, a verification experiment confirmed that the Taguchi technique is reliable in predicting UTS and hardness performance. Overall, this research provides valuable insights into optimizing the SAW process parameters for mechanical properties and demonstrates the effectiveness of the Taguchi technique in predicting and achieving optimal welding performance.