Arc Welding Research Articles

Influence of CMT welding parameters on microstructural and properties investigation of dissimilar weld joint for aluminum bronze and carbon steel

Cold Metal Transfer (CMT) welding technology has improved the appearance of weld beads and revolutionized the welding of thicker materials and dissimilar metals with precise metal deposition and reduced heat input. Cold Metal Transfer welding is predominantly used in a variety of industry applications, including aerospace, shipbuilding, automotive and marine industries. In this study, aluminum bronzes and carbon steel were joined by using CMT welding, a variant of the Gas Metal Arc Welding process, with ERCuAl-A2 as the filler metal. Optical microscopy was used to examine the microstructure of the CMT weld joint between aluminum bronze and carbon steel. Results have indicated that dissimilar metals such as aluminum bronze, and carbon steel could be successfully joined by CMT under various processing parameters. The tensile and bending strengths of the dissimilar joint were 490 MPa and 822 MPa, respectively. A variety of intermetallic compounds and solid solutions were generated in the weld zone and fusion zone. The micro-hardness in the carbon steel side of the fusion zones increased sharply, which was 164 HV in the welded condition. The dissimilar joint was stronger than the carbon steel, as the ductile fracture occurred on the carbon steel during the transverse tensile test of the welded specimen. The microstructure interpretation of welded dissimilar joints was analyzed by scanning electron microscopy and transmission electron microscopy.

Effects of random meso‐defects on fatigue behavior of welded joints: Damage evolution and lifetime prediction

AbstractRandom meso‐scale defects within welded joints can affect the structural damage process and cause dispersion in the fatigue lifetime of welded joints. In this paper, a meso‐scale stochastic damage approach is used to investigate the effect of random, meso‐scale defects on the fatigue damage lifetime of welded joints under different loads. First, we established an elastic–plastic fatigue damage model considering meso‐defects in the weld metal. Secondly, the fatigue lifetimes for gas tungsten arc welding and gas metal arc welding welded joints were predicted, with most of the predictions within the twofold dispersion factor. Thirdly, the Monte Carlo simulation method was used to investigate the influence of meso‐defect size on the fatigue lifetime dispersion degree, and the fatigue lifetime distribution under different loads was statistically analyzed.

Penetration state recognition for tungsten inert gas welding via an alternating cusp-shaped magnetic field-assisted molten pool-oscillation

To ensure optimal penetration in direct current (DC) argon tungsten arc welding, a method was proposed to recognize the molten pool penetration during molten pool oscillation under alternating cusp-shaped magnetic field (ACSMF). An arc discharge model is established to analyze the oscillation mechanism of the molten pool under ACSMF. The periodic variation of arc shape induces the periodic oscillation to establish a mapping relationship with the fluctuation of arc voltage waveform. At the excitation current of 3 A and frequency of 10 Hz, the arc voltage waveform undergoes abrupt changes at 1.26 V and 1.37 V, corresponding to the critical and the full penetration states, respectively. The errors in identifying moving penetration are 0.8 % and 0.7 %, with a full penetration weld, demonstrating a penetration rate of 100 %, indicating effective penetration recognition. Arc sensing technology for tungsten inert gas (TIG) welding under ACSMF is poised for gradual application in single-side welding and double-side forming of medium and thick plates. It is anticipated to evolve towards real-time identification technology for molten pool penetration monitoring.

Optimizing Elemental Transfer Predictions in Submerged Arc Welding via CALPHAD Technology under Varying Heat Inputs: A Case Study into SiO2-Bearing Flux

With the advancement of the manufacturing industry, performing submerged arc welding subject to varying welding heat inputs has become essential. However, traditional thermodynamic models are insufficient for predicting the effect of welding heat input on elemental transfer behavior. This study aims to develop a model via CALPHAD technology to predict the influence of heat input on essential elements such as O, Si, and Mn when typical SiO2-bearing fluxes are employed. The predicted data demonstrate that the proposed model effectively forecasts changes in elemental transfer behavior induced by varying welding heat inputs. Furthermore, the study discusses the thermodynamic factors affecting elemental transfer behavior under different heat inputs, supported by both measured compositions and thermodynamic data. These insights may provide theoretical and technical support for flux design, welding material matching, and composition prediction under various heat input conditions subject to submerged arc welding processes when SiO2-bearing fluxes are employed.

Experimental investigation on solidification cracking & intergranular corrosion of AISI 321 & AISI 316 L dissimilar weld on pulsed current gas tungsten arc welding (PCGTAW)

Dissimilar metal combinations are frequently employed in the power generation and nuclear industries. Where stainless steel piping systems are connected to pressure vessels made of low-alloy steel, the subsystems of liquid rocket engines also have different, dissimilar material combinations. Dissimilar welding plays a vital role in ensuring the integrity, performance, and reliability of components and structures operating in cryogenic environments, in this study, plates of AISI 316L and AISI 321, each 5 mm thick, were successfully joined using the pulsed current gas tungsten arc welding (PCGTAW) technique with optimized process parameters. These weld joints are mostly present in rocket engines subjected to a cryogenic environment. Due to the low temperature environment, the metallurgical properties of these joints change, which affects their mechanical properties. As it is a structural part, PCGTAW welding is most common method for joining this kind of material.In this work, Microstructural analysis of the weldment revealed a combination of vermicular, lacy, and acicular ferrite morphologies in the fusion zone at the root, mid, and crown locations.Furthermore, no solidification cracking was detected in the weldments based on the optical micrograph and SEM results. Intergranular corrosion (IGC) testing indicated the absence of a ditch structure, suggesting that the heat-affected zone (HAZ) on both sides of the weld joint was not being susceptible to sensitization. However, the HAZ of the AISI 316L side exhibited coarser grains compared to AISI 321. Analysis of tensile properties revealed a significant influence of the testing environment on the tensile strength of the dissimilar welded joints. At room temperature, the average ultimate tensile strength (UTS) was measured as 621 MPa. Remarkably, at cryogenic conditions, the average tensile properties significantly increased to 1319 MPa.Microhardness analysis showed the highest hardness associated with the AISI 321 side. The fusion zone exhibited a large deviation in the hardness profile (205 ± 10 HV), with the highest average hardness observed in the middle part of the weld. However, the hot cracking behavior of the weld was investigated by using a suutula diagram at various locations of the weld. The investigation revealed that the Creq/Nieq ratio exceeded the critical threshold value, effectively diminishing the propensity for hot cracking in the fusion zone. Overall, these findings underscore the effectiveness of the PCGTAW technique in joining dissimilar materials, as well as the importance of microstructural and mechanical property evaluations, especially under extreme operating conditions such as cryogenic temperatures.Paraphrase.

Influence of Submerged Arc Welding Current Intensity on the Mechanical Properties and Microstructure of Pressure Vessel P355N Steel.

This article presents a study on the influence of the intensity of the welding current on the properties of the mechanical strain strength of welded joints made by using submerged arc welding technology. The influence of the welding current on the microstructure of the welded joints was also observed in different regions of the cross-section of the welding seam. Also subject to observation was the mode of influence of the welding current on the geometry and dimensions of the welding seams. The welded samples were obtained using five different welding regimes whose main variable was the intensity of the welding current, which had values between 300 A and 700 A. The criterion used as a reference for comparing the effects produced by the studied welding regimes was a standard welding regime that is used in the industry for welding railway tank wagons, with a welding current intensity of 480 A. The base material used in the experiments was a fine-grained carbon steel specially intended for the manufacture of pressure vessels identified as P355 N; the semi-finished product from which the samples were made consisted of 6 mm thick laminated sheets used in the manufacture of the covers of the vessels that make up the railway tank wagon. The aim of this study was to highlight the differences that may appear through varying the current welding parameter and identify welding regimes that can provide welded joints with superior mechanical properties compared to what is currently employed in the industry. This study focused on the most widespread technology of welding pressure vessels: the submerged electric arc welding method.

Evaluation Method of Magnetic Field Stability for Robotic Arc Welding Based on Sample Entropy and Probability Distribution

In this study, we analyzed the arc magnetic field to assess the stability of the arc welding process, particularly in robotic welding where direct measurement of welding current is challenging, such as under water. The characteristics of the magnetic field were evaluated based on low-frequency fluctuations and the symmetry of the signals. We used double-wire pulsed MIG welding for our experiments, employing Q235 steel with an 8.0 mm thickness as the material. Key parameters included an average voltage of 19.8 V, current of 120 A, and a wire feeding speed of 3.3 m/min. Our spectral analysis revealed significant correlations between welding stability and factors such as the direct current (DC) component and the peak power spectral density (PSD) frequency. To quantify this relationship, we introduced a novel approach using sample entropy and mix sample entropy (MSE) as new evaluation metrics. This method achieved a notable accuracy of 88%, demonstrating its effectiveness in assessing the stability of the robotic welding process.

Ensemble-based deep learning model for welding defect detection and classification

This study introduces an ensemble-based deep learning approach for monitoring and detecting submerged arc weld defects in weld beads and adjacent zones during Non-Destructive Testing (NDT). The methodology utilizes an open-source image dataset to categorize submerged arc weld conditions into three defect types: cracks, lack of penetration and porosity, and ideal welds (no defects). To enhance image analysis, we employ preprocessing and feature extraction in both spatial and frequency domains using segmentation techniques like grey level difference method (GLDM), grey level co-occurrence matrix (GLCM), discrete wavelet transform (DWT), Fast Fourier Transform (FFT), and texture analysis. Following image preparation, the preprocessed data undergoes training and testing in our proposed ensemble-based deep learning model. The model's performance is thoroughly assessed using key metrics such as precision, recall, F1 score, receiver operating characteristics (ROC) curve, and a confusion matrix, resulting in an impressive accuracy rate of 93.12% for detecting and classifying weld faults. In comparing our model to state-of-the-art techniques in existing literature, our ensemble-based deep learning approach consistently demonstrates a high fault detection and classification performance in the face of a simplistic MLP-based core architecture, ratifying the robustness of our feature ensemble approach. The study concludes that this model has significant potential for integration into current inspection systems, offering an efficient and robust solution for real-time condition monitoring of welds along weldment joints.

Online welding status monitoring method of T-joint double-sided double arc welding based on multi-source information fusion

In modern manufacturing, double-sided double arc (DSDA) welding brings advantages in properties and efficiency for T-shaped joints. However, the double-side forming makes it difficult to detect the imperfections and ensure weld joint quality, which few studies have covered. Most existing methods deal with single-arc welding with limited sensing sources. To fill the gap, an online welding status monitoring method for DSDA welding is proposed based on the fusion of welding current, arc voltage, arc sound, and weld pool images. In pre-processing, the automatic weld pool region of interest (ROI) detection method based on the lightweight YOLO-L model and the waveform denoising algorithm are designed. In feature engineering, waveform signals are analyzed in both the time and frequency domain. A weld pool feature extractor based on a convolutional neural network (CNN) is proposed with good effectiveness and interpretability. The output feature combination is refined by Fisher-based selection and evaluation. In model building, an ensemble learning model based on three high-fit basic learners is proposed, with an accuracy of 98.538 %. The proposed model shows significant advantages over the single basic classifier and other ensemble methods. Experiments verify high precision and robustness, laying a foundation for accurate real-time monitoring of DSDA welding production.

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO2. These HfO2 can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.

Vision-Based Online Molten Pool Image Acquisition and Assessment for Quality Monitoring in Gas–Metal Arc Welding

In gas–metal arc welding (GMAW), the welding quality is influenced by various factors, including the welding conditions and external environment. Achieving a high welding quality requires careful observation and control. Welding monitoring is crucial for validating a planned welding process and assessing its quality. This study introduces a vision system for the online acquisition of clear molten pool images. It uses a small camera equipped with a complementary metal-oxide-semiconductor sensor during GMAW, as well as a method for constructing this system. The proposed vision system does not require triggering using devices such as field-programmable gate arrays, facilitating lower costs and online quality monitoring under various welding conditions during mild-steel GMAW. Accurate measurement of radiation from the weld is essential for clear observation of the molten pool during welding, emphasizing the importance of selecting an optical system with appropriate lenses and filters. In addition, appropriate digital camera parameters must be set for monitoring. High-quality images were successfully captured using the proposed method, and the image quality was evaluated using the blind/referenceless image spatial quality evaluator algorithm.

A multi-objective trajectory planning approach for vibration suppression of a series–parallel hybrid flexible welding manipulator

Although the series–parallel hybrid welding manipulator has advantages over the traditional series manipulator, its must run continuously and smoothly according to a specific trajectory at the rated velocity. Considering a flexible manipulator with a complex series–parallel hybrid structure as the research object, this paper proposes a multi-objective approach to indirectly suppress the vibration. In view of the complex flexible mechanism with a multi-kinematic pair arrangement and a multi-motor drive, a system comprehensive elastodynamics model is established, and the effectiveness of the model is verified through the hammer test method. To achieve synchronous and coordinated planning of the end position and attitude, the spatial arc welding trajectory is planned on the basis of the synchronous planning controller and the dual-S velocity profile interpolation function. Then, a multi-objective optimization model considering the travel time, energy consumption and terminal amplitude fluctuations is proposed, the trajectory planning problem is transformed into a parameter optimization problem in the interpolation function, and then the elite non-dominated sorting genetic algorithm (NSGA-II) is employed to determine the optimal trajectory. The optimal trajectory thus obtained effectively suppresses the vibration of the system. Finally, compared with the classic fifth-degree polynomial trajectory planning method, the system vibration suppression effect is significant, which verifies the effectiveness and feasibility of the proposed method and provides a theoretical basis for further realizing real-time control.

Analysis of Gas Metal Arc Welding Process Using Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise

Analysis of Gas Metal Arc Welding Process Using Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise

Multi-response Optimization of GTAW Process Parameters in Terms of Energy Efficiency and Quality

This work optimizes the current (I), voltage (V), flow rate (F), and arc gap (G) of the gas tungsten arc welding (GTAW) of the Ti40A titanium alloy to decrease the heat input (HI) and improve the ultimate tensile strength (TS) and micro-hardness (MH). The radial basis function network (RBFN) was utilized to present performance measures, while weighted principal component analysis (WPCA) and an adaptive non-dominated sorting genetic algorithm II (ANSGA-II) were applied to estimate the weights and generate optimal points. The evaluation via an area-based method of ranking (EAMR) was employed to determine the best solution. The results indicated that the optimal I, V, F, and G are 89 A, 23 V, 20 L/min, and 1.5 mm, respectively. The improvements in the TS and MH were 1.2 % and 19.8 %, respectively, while the HI was saved by 18.4 %. The RBFN models provided acceptable accuracy for prediction purposes. The ANSGA-II provides better optimality than the conventional NSGA-II. The HI, TS, and MH of the practical GTAW Ti40A could be enhanced using optimality. The optimization method could be utilized to deal with optimization problems for not only other GTAW operations but also other machining processes.

Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding + gas tungsten arc welding combination welding

Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding + gas tungsten arc welding combination welding

Coupling effect of post-weld heat treatment and fatigue damage on the hydrogen embrittlement of X80 steel welded joints

The influence of post-weld heat treatment (PWHT) and fatigue damage on the hydrogen embrittlement sensitivity of X80 steel welded joints, obtained using flux-cored arc welding method, was investigated in the study. Compared to the as-welded specimens, the sensitivity of hydrogen embrittlement after PWHT was decreased. However, the coupling effect of PWHT and fatigue damage improved significantly the HE sensitivity. Furthermore, the fracture site of the PWHT + pre-fatigue specimens with hydrogen-charged was transferred to the weld metal, and the fracture was characterized by intergranular fracture, quasi-cleavage (QC) and shallow dimples ductile fracture. The increase of the hydrogen content might be attributed to the evolutions of dislocation and the proportion of high-angle grain boundary caused by fatigue damage. Meanwhile, the size of QC for the hydrogen-charged welded joints was related to the degree of fatigue damage, hydrogen content and microstructure strength.

Innovative rotary friction welding of heat exchanger tube nozzles on high pressure headers

This paper describes an innovative application, driven by an industrial requirement for an alternative welding process to submerged arc welding of header heat exchanger tube nozzles, of an automated friction hydro-pillar processing (FHPP) welding platform (WeldCore©). This was the first successful application of rotary friction welding of heat exchanger tube nozzles to high pressure-headers used in the high-pressure heaters of a boiler on a 609 MW steam turbo-generator unit. The FHPP WeldCore platform allows highly time- and cost-effective welding and repair of high temperature, high pressure power plant using a procedure that was approved in the 2015 ASME Boiler and Pressure Vessel Code, Supplement 3 as Code Case 2832 (WPS qualification for Friction Taper Hydro-Pillar (FTHP) welding). This certification opened the way to using FHPP welding for repair and refurbishment of power generation and high temperature process plant. After completing the welding of 448 nozzles onto each of two HP headers, all welds were found to be defect-free using ultrasonic testing, and test nozzle welds passed the weld qualification procedure required by industry.

SiO2-bearing Fluxes Induced Evolution of γ Columnar Grain Size

Understanding the controlling mechanisms of γ columnar grain size in the weld metal of low-carbon, low-alloy steel is critical for optimizing resultant microstructures and the weld metal’s ensuing properties. Here, we investigate the role of welding flux composition upon the γ columnar grain size by submerged arc welding of EH36 shipbuilding steel with designed CaF2-SiO2 fluxes. We found that the addition of SiO2 from 5 to 40 mass-% increases average columnar grain size by a factor of nearly 2.5, which results from the change of the weld pool solidification mode from peritectic to primary δ solidification. Such a change is directly related to element transfer behaviors between the flux and the weld metal. Furthermore, we offer compelling evidence that alterations in γ columnar grain size are not primarily governed by significantly populated inclusions and/or weld metal macro-morphological changes. Our findings may largely serve as a viable strategy toward designing welding consumables to match base metals to ensure the soundness of the weldment.

Metallurgical and mechanical properties of marine grade AA5356 using wire arc additive manufacturing

In the current work, a Gas metal arc welding (GMAW)-based Wire Arc Additive Manufacturing (WAAM) procedure was used to build a wall construction of measuring Aluminium alloy (AA) AA5356 on an AA5083 base plate. The microstructure and mechanical properties of AA5356 were examined at two places along the wall structure’s horizontal deposition direction and in two deposition orientations (horizontal and vertical). Optical microscopy, SEM, EDAX, and fractographical examinations were used to analyse the microstructure. Tensile and microhardness tests were performed at two wall locations to evaluate mechanical parameters. A microstructure analysis reveals a mixture of columnar grain structure and coarser intermetallics in the remelting zone, with finer granular structure in the central region. The horizontal direction of AA5356 deposition exhibited a highest elongation and tensile strength of 4.4% and 249 MPa than the vertical direction. For the horizontal and vertical orientations, the average microhardness values were determined to be 80 HV and 72 HV, respectively. Fracture analysis of the tensile samples showed that the deposited metal had a ductile mode of failure with a predominance of dimples with tearing shape. This study provides valuable insights into constructing wall structures and analyzing their mechanical properties.

Study on the Effect of Current Pulsing During Gas Tungsten Arc Welding of Ti – 6Al – 4V Alloy

Study on the Effect of Current Pulsing During Gas Tungsten Arc Welding of Ti – 6Al – 4V Alloy