Welding in the World最新文献

Dissimilar metal welding between 9Cr18MoV and 3Cr13 offers promising practical applications in the tool manufacturing industry. However, limited previous studies have investigated the effects of post-weld quenching and tempering heat treatment on the performances of dissimilar welded joints of martensitic stainless steels, specifically between 3Cr13 and 9Cr18MoV. This study examined the evolution of microstructure, mechanical properties, and corrosion resistance of the dissimilar welded joints of 3Cr13 and 9Cr18MoV after post-weld quenching and tempering. It was found that the microstructures of the weld metal (WM) were changed, with the disappearance of columnar and dendritic grain morphologies following the generation of tempered martensite after the post-weld heat treatment (PWHT). The grain size in the WM decreased from 67.1 μm to 9.2 μm. After the PWHT, the corrosion resistance of the WM was enhanced based on the results of electrochemical corrosion tests. Additionally, the welded joint exhibited a significant increase in hardness and ultimate tensile strength, with an approximate 18% rise in tensile strength noted. However, the impact toughness of the WM dropped from 7 ± 2.2 J/cm² to 0.87 ± 0.2 J/cm², representing the lowest value among all samples tested.

Internal defects in friction stir welded (FSW) joints can undermine weld integrity, while the release of ultrafine particulates (UFPs) during welding presents significant occupational health concerns. This study evaluates the effectiveness of induction preheating-assisted FSW for marine-grade AA6082 aluminium alloy by comparing preheated (250 °C) and non-preheated conditions, using identical welding parameters (58 mm/min traverse speed; tool rotation speeds of 636, 900, and 1224 rpm). UFP emissions were measured with a scanning mobility particle sizer (SMPS), while internal defects were assessed via phased array ultrasonic non-destructive testing. Additionally, the study also examines the microstructural evolution of the joints using field-emission scanning electron microscopy (FE-SEM) and optical microscopy, alongside comprehensive assessments of mechanical properties through tensile and microhardness testing. The results showed that induction preheating reduced UFP emissions by 41% to 59% across all tool rotation speeds, highlighting its potential to lower health risks for workers. Internal weld defects were successfully mitigated in joints produced with induction preheating. Microstructural analysis showed the formation of finer grains (~ 4–6 μm) in the stir zone of preheated joints. Mechanically, the highest transverse tensile strength of 161.94 MPa, representing 97.06% of the work material’s strength, was achieved in preheated joints, along with notable improvements in hardness compared to conventional FSW joints. These findings demonstrate that induction preheating-assisted FSW offers substantial benefits for both weld quality and environmental safety, providing a promising approach for the fabrication of high-performance aluminium joints.

In this study, original welds of 12 mm thick S355J2G4 steel used for railway vehicles were repaired through Metal Active Gas (MAG) welding to determine influence of repair welding numbers on microstructure and mechanical properties of welded joints. The results indicated that the weld macrostructure did not significantly change with increasing repair welding numbers, the phase composition of the microstructure in the heat affected zone were the same while the grain size slightly increased. The microhardness values on upper weld surface between the repaired and original weld fusion lines gradually reduced as repair welding number increased. Both the average yield and tensile strengths reduced with increasing repair welding numbers, while the average elongations remained nearly constant. The tensile specimens all fractured in base metal. There were no visible cracks appeared on surface of the bending test specimen. The average impact energy and median fatigue strength both presented gradual downward trends as repair welding number increased. The fatigue specimens of the 0R (original), 1R (repaired once), and 2R (repaired twice) welded joints all fractured in weld metal, while the fatigue specimens of the 3R (repaired thrice) welded joints fractured near fusion line, this change was primarily due to the serious joint softening as repair welding number increased. The above results indicated that the microstructure and mechanical properties of the repair-welded joints still could meet the application requirements even the repair welding number reached up to three, which could provide practical guidance for developing repair strategies in industrial applications.

Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed.

In this paper, 6082 aluminum alloy and DP980 dual-phase steel are taken as the research object, and the laser power, welding speed, defocusing amount, frequency, and duty cycle are selected as variables to study the effects of various parameters on the dissimilar alloy 6082-DP980 brazing or welding laser spiral joint, by selecting the best welding parameters to verify the best welding method. The microstructure and mechanical properties of the welded joint, heat-affected zone, and base metal were analyzed. The results showed that the joint strength is the highest and the best welding results were obtained; when using the defocusing amount of 0.75 mm, the duty cycle is 90%, the frequency is 5500 Hz, the power is 560 W, and the speed is 20 mm/s. Under the super depth of field microscope, the best parameter group showed brazing, brittle metal compound (IMC) is weak, and there is no macroscopic crack, while the control group showed fusion welding with an obvious IMC layer, large deformation, and many cracks. SEM observation showed that the IMC thickness of the optimized group was 4 ~ 15 µm, and the control group is much larger and has a wider diffusion of element. In the tensile test, the preferred group showed higher tensile strength and yield strength, and slightly lower plasticity; the strength of the control group is lower but the ductility is better. This study can guide the welding process behavior of the emerging laser spiral spot welding of aluminum-steel dissimilar metals in practical engineering applications.

Laser marking has evolved into a vital tool for industrial identification, ensuring traceability and combating counterfeiting with its precision and efficiency. This study delves into fiber laser marking, offering insights into its advantages, applications, and monitoring mechanisms like advanced control systems. Detailed analysis of laser marking methods aids manufacturers in selecting optimal solutions. Critical factors such as parameters and material choices are highlighted for optimizing practices in industrial applications. Additionally, the study explores laser color marking, enhancing industrial markings aesthetically. Integration of Artificial Neural Networks with RGB image processing represents a significant advancement, showcasing the study’s pioneering spirit. These findings underscore laser marking’s crucial role in industrial operations, driving efficiency and quality while pushing the boundaries of achievable outcomes in marking technology.

The pre-melted electron beam fabrication (PEBF) method is proposed in this paper. Numerical simulation techniques are utilized to calculate the dynamic variations in internal stress and deformation within the component during the PEBF process and its interaction with the fixture. A contact theory is incorporated. Unlike traditional rigid or purely elastic mechanical boundary conditions, our model considers the contact between the workpiece and the fixture, employing Coulomb’s friction law to address the contact issues. The penalty function method is utilized to solve the Coulomb friction problem. The deformation of the deposited material shows minimal reduction throughout the deposition process; each deposition layer contributes to an increase in the deformation at the end of the first layer, although the increment of deformation gradually decreases. During the deposition, the interaction between the fixture and the substrate affects the deformation of the deposited material, with the lateral expansion of the substrate resulting in a reduction in the vertical deformation of the deposited structure. Temperature field analysis indicates that, except for the first layer, the cooling rate variation for subsequent layers does not exceed 15%, suggesting that multiple thermal cycles during additive manufacturing have a minimal impact on the stress and deformation of the existing deposited material.

The surface flatness of traditional large-size weld beads was measured by cutting the weld area of the workpiece, then manually calculating the ratio of weld width to reinforcement height, which was time-consuming and inaccurate. This work combined a machine vision system with deep learning technology to reduce calculation errors and improve adaptability. A new network model, UG-Net, was proposed for analyzing laser stripe images of weld beads in complex backgrounds, achieving 93.69% mean intersection over union (mIoU). The Steger algorithm was used to extract the centerline from the identified laser stripes, which was segmented into feature and baseline sections. The feature section underwent cubic spline curve interpolation, while the baseline section was processed using straight-line fitting based on random sample consensus. The feature curve of the weld bead was derived to obtain extreme points. The 3D coordinates of extreme points and corresponding feature points on the baseline were determined using structured light triangulation. Finally, the difference between the feature points on the baseline and the extreme points was calculated to obtain the maximum and minimum weld bead heights, representing the surface flatness. Testing three sample sets with different welding parameters, the relative errors between the proposed algorithm’s results, and manual measurements following wire-electrode cutting were 1.132, 1.067, and 1.039%, respectively. These results proved the reliability of the proposed algorithm and introduced a new approach for fast and accurate measurement of large-size weld beads’ surface flatness. 

Directed energy deposition-arc with metals (DED-ARC/M) is gaining popularity in aerospace applications due to its cost-reduction potential and shorter lead times. A notable example of expensive products manufactured traditionally is pressure tanks with oval shapes. These parts are roughly machined from bulk material and then reduced to their final thickness. By employing DED-ARC technology, material waste and CNC machining time can be minimized, leading to a significant reduction in overall part costs. This paper focuses on the design of experiments (DoE) for optimizing welding parameters to manufacture a pressure tank for aerospace applications using 17–4 PH stainless steel. To meet the high-quality and lightweight requirements of aerospace applications, it is crucial to set the welding parameters correctly. The presented DoE consists of three stages. Initially, a number of single beads with distinct parameters are deposited for a layer height of 2–3 mm. Through geometric macro inspection, most of the single-bead parameters are eliminated. Using the remaining parameter sets, flat walls are manufactured, and the specimens are taken from these walls to assess their mechanical properties. Finally, the parameter sets that yield the highest mechanical quality are employed in the additive manufacturing of the pressure tank for aerospace applications.

Wire-arc directed energy deposition (WA-DED) is the subject of extensive research in metal additive manufacturing (AM). This study investigates the influence of ultrasonic vibration (UV) on the material properties of deposited ER2209 duplex stainless steel filler wire and evaluates the effects of UV treatment on walls fabricated both with and without weaving. The results demonstrate the effectiveness of a specially developed UV table prototype, showing clear impacts on grain size and ferrite content in the deposited samples. UV treatment reduces the primary ferrite grain width and enhances phase distribution homogeneity, potentially influencing the ferrite-to-austenite transformation during successive reheating cycles. Although the effects on surface morphology and hardness were minimal, significant microstructural changes occurred within the deposited material. UV-induced grain refinement modifies the austenite content, revealing a beneficial interaction between vibration and phase evolution. The UV table design provides a valuable foundation for reproducibility; nevertheless, further optimization of the setup is required to improve performance and support its integration into advanced industrial applications.