Quality Of Welded Joints Research Articles

Study on the Microstructural and Proficiencies of Heat‐Affected Zone in High‐Slope Mountainous Welded Pipeline Steels

The failure rate of pipelines in mountainous areas is much higher than that in other service areas. To ensure the efficiency and quality of the project, automatic welding has become a development trend. The heat‐affected zone (HAZ) as a weak area, to a large extent, reflects the quality of welded joints. Herein, the microstructure and mechanical properties of HAZ on both sides of welded joints under a 30° large slope are characterized by high‐resolution transmission electron microscopy, electron backscattered diffraction, and Charpy impact. The results show that the properties of HAZ are affected by many strengthening mechanisms such as grain refinement, solid solution, dislocation, and precipitation, among which grain refinement plays a leading role. The slope will affect the NbC phase size and grain size, resulting in differences in HAZ properties on both sides. The grain size of each microzone in the lower side HAZ is coarsened compared to the higher side, and the dislocation density is lower, leading to a decrease in hardness and impact toughness, thus becoming the weakest region in the welded joint. Therefore, for welding under the condition of slope, attention must be paid to the influence of slope on the performance of welded joints.

A body welded joint quality prediction method incorporating reconstruction error

A body welded joint quality prediction method incorporating reconstruction error

Study on the Electron Beam Repair Welding of 5000 Aluminum Alloys

Electron beam welding (EBW) has been attracted due to its high energy density, high depth-to-width ratio, low thermal strain, compared with arc and laser welding. In addition, it ensures high quality weld joint in structural metals in a wide range of thickness from 0.025 mm to 300 mm. Therefore, EBW is widely used in industries such as automotive, aviation, nuclear power plant, etc. Although a lot of studies on EBW for several decades have been presented, EB based repair welding with supplement of filler metal has less reported. In this work, EB repair welding for 5083 aluminum alloys was investigated because the aluminum alloys are becoming more important as a lightweight material in mobility industries. Material characterization and mechanical properties of the repair-welded specimens were evaluated, compared with characteristics of base metal and bead welding without repair. The optimized experimental conditions showed tensile strength of 294 MPa, which is a similar to base metal. Our study indicates that EB repair welding can be considered for the candidate of repair welding of aluminum alloys.

Influence of welding angle in the process of submerged arc welding of pressure vessel steel

Abstract In the industrial production of pressure vessels (PV), a very important role is played by the welding of the elements that make up the vessel. The predominant welding technology in the case of manufacturing PV is the submerged arc welding (SAW) for which different welding regimes are defined depending on the characteristics of the base material. The welding regimes are made up of various parameters easy to manipulate by the operators of the welding machines, one of them is the welding angle. In this article, aspects are discussed regarding the way in which the welding angle of SAW influences the quality of welded joints. Tensile tests were carried out on specimens taken from plates joined by SAW using different values of the electrode tilt. Aspects regarding the geometry and dimensions of the welded joints obtained as a result of the variation of the welding angle are analysed and, in the end, an optimal angle is indicated for the welding process of PV. The basic material used in the experiments is a fine-grained material intended for the manufacture of vessels that work in high pressure and high temperature regimes, named in the technical literature P355 N.

Review and Analysis of Modern Laser Beam Welding Processes.

Laser beam welding is the most modern and promising process for the automatic or robotized welding of structures of the highest Execution Class, EXC3-4, which are made of a variety of weldable structural materials, mainly steel, titanium, and nickel alloys, but also a limited range of aluminum, magnesium, and copper alloys, reactive materials, and even thermoplastics. This paper presents a systematic review and analysis of the author's research results, research articles, industrial catalogs, technical notes, etc., regarding laser beam welding (LBW) and laser hybrid welding (LHW) processes. Examples of industrial applications of the melt-in-mode and keyhole-mode laser welding techniques for low-alloy and high-alloy steel joints are analyzed. The influence of basic LBW and LHW parameters on the quality of welded joints proves that the laser beam power, welding speed, and Gas Metal Arc (GMA) welding current firmly decide the quality of welded joints. A brief review of the artificial intelligence (AI)-supported online quality-monitoring systems for LBW and LHW processes indicates the decisive influence on the quality control of welded joints.

Dynamic behavior regulation of droplet transfer based on arc-bubble control by ultrasound-induced during underwater wet welding

In comparison to welding in air, the periodic formation of unstable arc bubbles is a significant factor contributing to the unstable mass transfer process during underwater wet welding (UWW). Up to now, there is no ideal method to control droplet transfer and improve arc stability. In this study, the ultrasound-induced method (UIM) was used to regulate the droplet transition behavior and improve the process stability. The behavior features and key mechanisms of arc-bubble and droplet transfer induced by ultrasound were revealed with the employment of highspeed camera and X-ray observation, respectively. The incident angle of ultrasound was taken as a variable to reveal its effects and mechanism of action on the behaviors of arc bubble and droplet transfer, weld formation quality, microstructure, and property of weld joint. The results show that ultrasound-induced a new rising mode of arc bubble, which can significantly reduce the repulsive resistance that come from the bubble rising on the droplet transfer process. Compared with underwater wet welding without ultrasound, the average diameter of molten droplets reduces from 3.2 mm to 1.7 mm, and the droplet transfer frequency increases from 7.8 Hz to 13 Hz as the incident angle of ultrasound increases to 60°. In addition, the weld seam without obvious defects could be produced by UWW with UIM, of which the Variation coefficient of weld reinforcement is reduced from 21.3 to 11.6 and 17.4 at an ultrasonic incident angle of 30° and 45°. With increasing of ultrasound incident angle, it showed that the microhardness of the weld joint has a slight increase. In the heat-affected zone, the microhardness for the joint increased from 290 HV to 320 HV while the incident angle increased to 60°. This research shows that an appropriate incident angle of ultrasound can obtain good-quality joints which has a stable metal transfer process in underwater wet welding.

Industrial Radiography Testing & Technique Safety for Human Body

The use of Industrial Radiography for examining the quality of Weld joints is very popular worldwide. In India, many welding activities like construction and laying the huge pipelines for gas and water transportation and distribution as well construction of storage tanks are performed. The objects are working under high pressure and therefore, it is important to produce the weld beads with high quality. Industrial radiography uses ionizing radiation to view objects in a way that cannot be seen otherwise. The method has grown out of engineering, and is a major element of non-destructive testing (NDT) to inspect materials for hidden flaws. The radiation caused by these facilities is very dangerous however, with the use of new technologies and proper protection, risks of injury and death associated with radiation can be greatly reduced. Use or radiation sources are associated with a certain amount of radiation hazard. With proper card, this can be minimized. Radiation hazards may be broadly classified as external hazards an internal hazard. External hazards occur when the source of radiation is outside the body and internal hazards arise when the source for radiation gets into the human system. Hazard evaluation is necessary in order to adopt suitable measures to control radiation exposure. The problem of internal hazard does not arise in the use of X-ray equipment. It is considerably easy to estimate the external radiation hazard and there are a number of devices suitable for this purpose.

A new method of magnetic pulse welding of dissimilar metal plates using a uniform pressure electromagnetic actuator based on pre-deformation

The magnetic pulse welding method using a uniform pressure electromagnetic actuator can effectively weld dissimilar metal plates. However, the existing uniform pressure welding method leads to serious thinning of the plate at the chamfer, lack of welding at the center, and bulging of the welded sample, which seriously affects the quality of the welded joint. To solve these problems and improve the quality of welded joints, a new uniform pressure welding method of dissimilar metal plates based on pre-deformation was developed in this work. In this study, using the welding of an AA1060 aluminum plate and an SS304 steel plate with a thickness of 1 mm as an example, it was confirmed through numerical simulation and experimental research that the pre-deformation of the flyer plate controlled the impact angle of the central area of the plate, and it effectively suppressed central non-welding and serious bulge issues. Further, the welding method also reduced the height of the cushion blocks on both sides, thus mitigating aluminum plate thinning at the chamfer, ultimately improving the tensile strength of the joint. Additionally, a microscopic observation showed that the welding interface formed a wavy composite interface, and the connection strength was good. This welding method can also be extended to welding other dissimilar metal plates.

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.

Design and manufacturing of Welded Vacuum Testing (WVT) tool

To ensure the quality of welded joints in the hull area, welding testing is very important and must be carried out. But unfortunately, currently the quality testing process of welded joints was still limited to penetrant tests and lime tests. The purpose of this study was to obtain a portable welding testing machine that was able to obtain fairly accurate test results on hull welding defects using a vacuum system. The research method is experimental by involving data collection through field experiments, testing is carried out with the resulting weld defect research subjects and the length of testing time on 1G and 3G position welding. The results of the study by compared tests among Welded Vacuum Testing (WVT) machines, Magnetic Particle tests (MP), and Penetrant Tests (PT). The three experiments detected leaking weld defects, spark sparks, pinholes, overlaps, and undercuts. For test results with machines made, welding defects that were successfully detected were leaks in the 1G position welding workpiece and undercut in the 3G position welding workpiece. Air bubbles at a vacuum pressure of 0.2 bar are detected, meaning that there is a defect in the welded joint. This tool can be used in bilge testing.

Fatigue crack growth behavior of laser welded QP980 steel at low temperatures with water-cooling assistance

Cooling assistance holds great promise for enhancing the quality of welded joints. In this paper, the fatigue properties of laser welded quenching and partitioning 980 steel joints are improved using a water-cooling assistance process at low temperatures. This process facilitates the creation of high-quality welded joints characterized by both strength and ductility. Hardness and Charpy impact tests are conducted in conjunction with microstructure observation. Fatigue crack growth tests are performed under different stress ratios (R = 0.1, 0.3 and 0.5) at three temperatures (T = 25 °C, −40 °C and −80 °C). Results indicate that the fatigue life of welded joints increases by factors of 2.0 (at 25 °C), 2.2 (at −40 °C) and 1.5 (at −80 °C) and ductile-to-brittle transition temperature decreases with the use of water-cooling assistance at low temperatures.

Unraveling microstructure evolution induced mechanical responses in coaxial fiber-diode laser hybrid welded Fe–36Ni Invar alloy

Invar alloys, renowned for its ultra-low coefficient of thermal expansion, are qualified for widespread use in aerospace applications. This study explores the utilization of fiber-diode laser hybrid welding in Fe–36Ni Invar alloy, specifically focusing on addressing the undesirable microstructure and properties arising from unstable molten pool and high-temperature gradient encountered during single fiber laser welding. Experimental and simulation analyses were conducted to systematically explore the influence of diode laser power on the microstructure evolution and mechanical responses of fiber-diode hybrid laser welded Invar alloy joints. Results indicate that the addition of diode laser could notably widen the keyhole opening and improve the molten pool stability. An acceleration of dynamic recrystallization is observed in the weld seam, with a significant increase in high-angle grain boundaries, which account for over 90 % of the total. Moreover, with increasing diode laser power, temperature gradient decreases, leading to the formation of numerous equiaxed grains. Electron backscatter diffraction (EBSD) results demonstrate a considerable enhancement in the intensity of the γ texture, particularly the {111}<110> texture. Comparatively, fiber-diode laser hybrid welding exhibits superior plasticity and tensile strength over single fiber laser welding, with a tensile strength reaching 493.1 MPa. The research findings presented here provide essential theoretical foundations and technical guidance for enhancing the quality of Invar alloy weld joints and facilitating the broader application of fiber-diode laser hybrid welding in the future.

Analysis of welding conditions at synchronous operation of resistance welding machines

The paper is devoted to analysis of power losses in a resistance welding machine including supplying system and examination of welding conditions of the welding machine current in a case of synchronous (simultaneous) operation of multiple welding machines, i.e., during the conduction of welding current. Analysis of the most important contributors of power losses generated on the current path between a power source and the welded joint is carried out. The analysis is carried out for a DC (direct current) welding machine with power electronics inverter. AC (alternating current) welding machines are also taken into account. The analysis is divided in two parts. The first one is the analysis of single welding machine operation, while in the second part, coexistence (mutual operation) of two synchronous welding machines is considered. The analysis is based on results of numerical and experimental investigations. The first one is focused on calculation of power losses in the energy path (including a Sankey type power loss distribution diagrams), and the second one is based on experimental tests carried out to determine the diameter of the weld nugget and the strength of the joints, for cases of reducing the welding current. An example of simultaneous operation of welding machines was presented and discussed. The percentage voltage drops and power losses in the entire power supply path of the resistance welder are shown. The analysis carried out is extremely important from this point quality of welded joints.

Study of the impact of TIG welding parameters and post-weld heat treatment on the bending properties of AISI 1020 steel welded joints

Tungsten Inert Gas (TIG) is a welding technique that stands out due to its high precision, controlled heat input, and equipment’s cost-effectiveness. TIG welding is utilized to join various grades of steel. Presently, numerous research studies are actively seeking to improve the quality of welded joints, focusing on aspects such as strength, ductility, formability, appearance, and corrosion resistance. These improvements are achieved through the modification of welding methods and/or welding parameters. In this investigation, welding current and gas flow rate were selected as input parameters. Additionally, PWHT at 700 °C for 1.5h was applied to relieve the residual stresses occurring during the welding operation. The objective of this investigation is to examine how the welding current, gas flow rate, and post-weld heat treatment (PWHT) affect the bending properties of welded joints. The bending test was conducted to assess both the bending resistance and bending strain of the joints. The bending resistance increases to attend a maximal value of 790 N and the bending strain decreases to 7.1%, with the welding current and the gas flow rate due to the high heat input and cooling rate. The applied PWHT decreases the bending resistance by 11% and increases the bending strain by 18%, due to the decrease of the joint’s hardness.

Unravelling the mechanism of columnar-to-equiaxed transition and grain refinement in ultrasonic vibration assisted laser welding of Ti6Al4V titanium alloy

In this study, the microstructural evolution and mechanical properties of Ti6Al4V titanium alloy welded joints subjected to ultrasonic assisted laser welding were scrutinized, while numerical simulations were employed to explicate the grain refinement mechanism. The simulations indicate that the ultrasonic vibration significantly improves the overall fluidity and temperature of the molten pool. Under the identical condition of laser power and welding speed (1500 W, 1.3 m/min), the presence of 0.2A ultrasonic current yields a more uniform refinement of columnar grains, along with a denser arrangement of acicular martensite. The refinement mechanism can be attributed to the small temperature gradient, cavitation effects, and stress induced by ultrasonic vibration. Notably, the welded joint attains a peak tensile strength of 945.2 MPa under the aforementioned 0.2A condition, distinctly demonstrating the characteristics of ductile fracture. This research further reveals the underlying mechanism of grain refinement in Ti6Al4V alloy laser-welded joints induced by ultrasonic vibration, providing valuable references for optimizing process parameters and improving the quality of such welded joints.

Artificial Neural Networks and Experimental Analysis of the Resistance Spot Welding Parameters Effect on the Welded Joint Quality of AISI 304.

The automobile industry relies primarily on spot welding operations, particularly resistance spot welding (RSW). The performance and durability of the resistance spot-welded joints are significantly impacted by the welding quality outputs, such as the shear force, nugget diameter, failure mode, and the hardness of the welded joints. In light of this, the present study sought to determine how the aforementioned welding quality outputs of 0.5 and 1 mm thick austenitic stainless steel AISI 304 were affected by RSW parameters, such as welding current, welding time, pressure, holding time, squeezing time, and pulse welding. In order to guarantee precise evaluation and experimental analysis, it is essential that they are supported by a numerical model using an intelligent model. The primary objective of this research is to develop and enhance an intelligent model employing artificial neural network (ANN) models. This model aims to provide deeper knowledge of how the RSW parameters affect the quality of optimum joint behavior. The proposed neural network (NN) models were executed using different ANN structures with various training and transfer functions based on the feedforward backpropagation approach to find the optimal model. The performance of the ANN models was evaluated in accordance with validation metrics, like the mean squared error (MSE) and correlation coefficient (R2). Assessing the experimental findings revealed the maximum shear force and nugget diameter emerged to be 8.6 kN and 5.4 mm for the case of 1-1 mm, 3.298 kN and 4.1 mm for the case of 0.5-0.5 mm, and 4.031 kN and 4.9 mm for the case of 0.5-1 mm. Based on the results of the Pareto charts generated by the Minitab program, the most important parameter for the 1-1 mm case was the welding current; for the 0.5-0.5 mm case, it was pulse welding; and for the 0.5-1 mm case, it was holding time. When looking at the hardness results, it is clear that the nugget zone is much higher than the heat-affected zone (HZ) and base metal (BM) in all three cases. The ANN models showed that the one-output shear force model gave the best prediction, relating to the highest R and the lowest MSE compared to the one-output nugget diameter model and two-output structure. However, the Levenberg-Marquardt backpropagation (Trainlm) training function with the log sigmoid transfer function recorded the best prediction results of both ANN structures.

A Comparison of CNN-based Image Feature Extractors for Weld Defects Classification

&lt;span lang="EN-US"&gt;Classification of the types of weld defects is one of the stages of evaluating radiographic images, which is an essential step in controlling the quality of welded joints in materials. By automating the weld defects classification based on deep learning and the CNN architecture, it is possible to overcome the limitations of visually or manually evaluating radiographic images. Good accuracy in classification models for weld defects requires the availability of sufficient datasets. In reality, however, the radiographic image dataset accessible to the public is limited and imbalanced between classes. Consequently, simple image cropping and augmentation techniques are implemented during the data preparation stage. To construct a weld defect classification model, we proposed to utilize the transfer learning method by employing a pre-trained CNN architecture as a feature extractor, including DenseNet201, InceptionV3, MobileNetV2, NASNetMobile, ResNet50V2, VGG16, VGG19, and Xception, which are linked to a simple classification model based on multilayer perceptron. The test results indicate that the three best classification models were obtained by using the DenseNet201 feature extractor with a test accuracy value of 100%, followed by ResNet50V2 and InceptionV3 with an accuracy of 99.17%. These outcomes are better compared to state-of-the-art classification models with a maximum of six classes of defects. The research findings may assist radiography experts in evaluating radiographic images more accurately and efficiently.&lt;/span&gt;

Enhanced impact toughness of 316L stainless steel welded joint by ultrasonic impact

316 L welded structures have been widely used in the industrial field, but the weld defects seriously affect the reliability. The ultrasonic impact treatment (UIT) is used to improve the quality of welded joints and the effects of the UIT on the impact toughness, fracture morphology, microhardness and microstructure of the 316 L stainless steel welded joint were studied. Moreover, the coupled finite element model of the 316 L stainless steel welding-UIT was established to study the effects of the UIT on the residual stress. The results showed that the UIT could effectively improve the impact toughness of the 316 L stainless steel welded joint, and the impact toughness could be improved with the increasing of the UIT current. According to the fracture morphology, it was found that the fibrous region increased, and the radical region decreased. In addition, the dimple of the material tends to become deeper and larger, and the increase of dimple was accompanied by the increase of energy absorption. The microhardness of the welded joint was improved, and the grain was refined, which indicated that the 316 L stainless steel welded joint generated obvious plastic deformation. The simulation results show the welded joints can introduce the significant residual compressive stress under the action of the UIT. Based on the comprehensive analysis of the UIT on impact toughness, the generated plastic deformation, the reduced grain size, and the introduced residual compressive stress of the 316 L stainless steel welded joint were the main reasons for the improvement of the impact toughness.

Improving the Formation and Quality of Weld Joints on Aluminium Alloys during TIG Welding Using Flux Backing Tape

This work aimed to compare the quality and properties of the welded joints of AMg6 aluminium alloy produced via conventional TIG welding with the properties of those produced with flux backing tape. This study focussed on the relative length of oxide inclusions (Δoi) and the amount of the excess root penetration (hroot) of the AMg6 alloy weld beads. The results show the influence of the thickness of the flux layer of the backing tape on the formation and quality on the AMg6 alloy welds, along with the effect of flux backing tape and edge preparation on the mechanical properties of the 6 and 8 mm thick welded plates. In accordance with the results obtained, the joints produced by means of TIG welding with flux back backing tape and without edge preparation have higher mechanical properties. Moreover, the TIG welding of AMg6 alloy using flux backing tape reduces the total welding time by 55%, reduces filler wire consumption by 35%, reduces shielding gas consumption by 43% and electricity consumption by 60% per 1 linear meter of the weld line.

Enhancing TIG Welding Parameters For Direct Tensile Load (DT-load) On Various Steel Thicknesses

The car body repair process is integral to vehicle development and structural repair. The primary objective of this study is to enhance the quality of thin material welding utilized in automobile body repair. The impetus for this research stems from the necessity to improve the structural integrity and longevity of thin materials prone to deformation throughout the welding procedure while minimizing distortion. This study aims to identify optimal parameters for the tungsten inert gas welding (TIG welding) process on thin materials, particularly for automobile body rearrangement. The Taguchi method conducted the experimental analysis of variations in welding parameters, including electrode diameter, gas flow rate, and welding current. Adjusting TIG welding parameters to their optimal values significantly improves weld joint direct tensile load (DT-load) and overall structural quality, according to the findings of this study. ANOVA analysis and the S-N ratio indicate that gas flow rate and welding current are significant determinants of the quality of welded joints in thin materials. This research contributes to a better understanding of the optimal parameters for fusing thin materials, particularly in automobile body repair. The automotive industry can use these findings as a guide to enhance the quality and strength of welding processes, which are critical to the structural integrity of vehicles.