Welding in the World最新文献

The relationship between local weld geometry and fatigue life has been extensively studied over the past decades, driven by the need to enhance structural integrity and optimize costs throughout a structure’s service life. While numerous studies have explored the influence of weld geometry on fatigue strength, the comparative effect of different welding methods under comparable weld geometry quality remains largely unexplored. Furthermore, the influence of local geometric variations for each welding method has not been systematically evaluated. This study explores a large dataset of laser-scanned butt welds, analyzing key geometric parameters. The dataset is categorized by welding method (laser-hybrid welding, submerged arc welding, and flux core arc welding), and statistical distributions are examined to assess variations in weld geometry and compliance with ISO 5817 quality groups. The characteristic fatigue life for each quality group is estimated. The correlation between geometric factor and fatigue life is evaluated through the residual analysis of stress-life curve linear fitting. According to the findings, different geometry features dominate depending on the welding method. The fracture location is strongly influenced by angular misalignment, while fatigue strength is better explained by quantile-based analysis of local geometry. These results provide a basis for future predictive modeling and quality assessment in welded structures.

Liquefied hydrogen storage tanks are poised to play a pivotal role in the realization of a carbon–neutral society. While stainless steel is considered the material of choice for the first 50,000-m³ tank, there is a potential for carbon steel to be employed as the inner tank material in the future to increase capacity. The welding materials combined with the carbon steel are expected to be Hastelloy and Inconel alloys, which are currently used in LNG (liquefied natural gas) tank construction. However, since some reports have shown that the effect of Ni on hydrogen embrittlement properties deteriorates significantly on the high-Ni side, we conducted evaluation tests that took into account the operating environment. The SSRT (slow strain rate testing) revealed that the GTAW (gas tungsten arc welding) weld metal exhibited severe hydrogen embrittlement, whereas no significant crack propagation was observed in the constant-load CT (compact tension) tests. We analyzed the discrepancies between the two experimental methods and concluded that the differences are largely related to pre-straining and hydrogen diffusion and accumulation. From a FFS (fitness for service) perspective, the results of the CT tests are considered more representative of real-world conditions, indicating that this material combination is suitable for use in liquid hydrogen storage tanks.

Ceramic phase modification is an effective method to improve the performance of wire arc additive manufacturing (WAAM) aluminum alloy components. In this paper, a preparation method of ceramic aluminum alloy flux-cored wire was developed. An advanced apparatus was developed for the preparation of flux-cored wires. The preparation system comprises three integral units: a wire forming module, a drawing module, and a coiling module. The wire forming module features a configuration of three forming rollers and three closed dies, while the drawing and reduction module incorporates 12 sets of wire drawing dies with varying diameters, with each stage maintaining a controlled compression ratio of 20%. The fluidization properties of the core powder mixture were systematically examined, revealing that optimal powder flow characteristics were achieved when the constituent particles were sized as follows: aluminum particles at 300 μm, copper particles at 250 μm, and silicon particles at 200 μm. The pre-heat treatment parameters for the aluminum strip substrate were optimized, with the process conditions established as follows: heating temperature of 230 °C, soaking duration of 120 min, and air cooling as the cooling method. Through a sequential series of 12 drawing and reduction operations, a 1.2 mm diameter Al-Cu-NiO aluminum alloy flux-cored wire was successfully fabricated. During the WAAM process employing the developed Al-Cu-NiO flux-cored wire, the process exhibited stable arc combustion, consistent droplet transfer, and minimal spatter. The developed flux-cored wire was successfully utilized to fabricate the aircraft skin, demonstrating high formability and suitability for such applications.

To fulfill the requirements for dependable low-temperature soldering of high-temperature lead-free materials and to inhibit the transformation of Cu₆Sn₅ to Cu₃Sn during transient liquid phase diffusion bonding (TLPB) and aging processes, along with minimizing joint porosity, Cu particles were initially coated with a Ni layer through electroless plating, followed by Sn layer deposition via stannous sulfamate electroplating to achieve Cu@Ni@Sn core-shell structured powder. The study explored the oxidation resistance of Cu@Ni@Sn powder and examined the formation rate and activation energy of Cu₃Sn in both Cu@Sn and Cu@Ni@Sn TLPB joints, clarifying the Ni coating’s role in restricting element migration and phase transformation. The Cu@Ni@Sn TLPB joint displayed a three-dimensional network of intermetallic compounds enveloping Cu particles. This joint demonstrated thermal endurance of at least 400 °C, room temperature shear strength exceeding 80 MPa, and shear strength of no less than 28 MPa after aging at 250 °C for 336 h, representing a 20% improvement compared to the Cu@Sn system. Joint porosity was lowered from 10% in the Cu@Sn system to 5% in the Cu@Ni@Sn system, surpassing both high-lead and nano-sintered Ag systems. The findings illustrate that the introduction of a Ni coating successfully restricted Cu diffusion, suppressed Cu₆Sn₅ phase transformation, decreased void formation, and improved the high-temperature oxidation resistance of Cu@Ni@Sn powder. After undergoing reflow at 250 °C, the Cu@Ni@Sn joint exhibited thermal conductivity of 156 W/m·K and electrical resistivity of 4.2 μΩ·cm, surpassing those observed in the Cu@Sn system, Cu₆Sn₅, and Cu₃Sn. These results imply that Cu@Ni@Sn TLPB joints fulfill the criteria for high-performance interconnections, presenting a viable replacement for high-lead and sintered nano-Ag soldering materials, making them a favorable candidate for high-temperature, high-reliability interconnect applications in power modules.

FeNi36 is employed in aerospace, remote sensing, and mapping applications due to its low coefficient of thermal expansion, making it suitable for high-precision micro-parts. Customizing large FeNi36 parts through wire arc additive manufacturing has emerged as a new research direction. However, the high temperature gradient and cooling rate during the wire arc additive manufacturing process result in a coarse and uneven microstructure, leading to significant anisotropy in the mechanical properties and thermal expansion coefficient of FeNi36, which does not meet high-precision performance requirements. This study presents the development of a macro–micro volume fluid phase field model to simulate heat transfer and dendrite growth during wire arc additive manufacturing FeNi36 thin-walled specimens. The simulation results closely match the experimental data. By comparing the simulation results with the experimental data, the microstructure of wire arc additive manufacturing FeNi36 was optimized, and more suitable process parameters were identified. The mechanical property anisotropy of FeNi36 specimens prepared with these parameters is minimal. The tensile strength of specimens in various directions and positions ranges from 545 to 575 MPa, with elongation between 26.8 and 30.2%. Furthermore, the thermal expansion coefficient curves of the samples in different directions are nearly identical, all being below 2.0 × 10⁻⁶ K⁻¹, which satisfies the commercial FeNi36 requirements.

The temperature field of austenitic stainless steel narrow gap girth weld and nickel-based alloy over-layer is carried out respectively. The microstructure solidification, microsegregation, and microhardness are analyzed by SEM, EDS, and OM. The average microhardness of the austenitic stainless steel at RW, FW, and CW is 207 HV, 208 HV, and 207 HV respectively, the average microhardness at the center of RW, FW, and CW is 191 HV, 190 HV, and 194 HV respectively. Austenitic stainless steel, its girth weld CW and nickel-based alloy over-layer 1 (welding speed v: 0.54 mm/s) boundary position FTZ, is prone to ITZ, martensite zone, hot crack, and decarburization layer, and it is easy to form crack source in ITZ tip area. The nickel-based alloy over-layer 1 is mainly composed of the γ phase, and its grain morphology is various. The columnar crystals and equiaxed crystals in different regions are distributed irregularly, crystal cracks, and hot cracks are prone to occur. At the position of over-layer 2 (welding speed v: 0.54 mm/s) in nickel-based alloy over-layer, it is competitive growth of dendritic crystal zone and cellular crystal zone, epitaxial growth of equiaxed crystal zone and cellular crystal zone. Contact growth of cellular crystal zone and cellular crystal zone is occurred.

The primary objectives of this study are to propose a modified approach to monitor the strength of weld joints in the pulsed metal inert gas welding (P-MIG) process and give a novel contribution to available literature on model selection criteria. The focus is on achieving high ultimate tensile strength (UTS) by considering various welding parameters such as pulse voltage, background voltage, pulse duration, pulse frequency, wire feed rate, welding speed, and root mean square values of welding current and voltage. The study also examines the effects of these parameters on UTS by developing a mathematical model using a hybrid approach that combines artificial neural networks and regression, referred to as the multiple nonlinear neuro-regression method. Forty-seven different models, including linear, trigonometric, logarithmic, quadratic, and rational forms, are proposed to mathematically define the UTS behavior of mild steel plate. A stability analysis assessed the model’s ability to account for the welding process parameters during the modeling phase. This approach has not previously been employed as a criterion for model selection in prior modeling studies. Furthermore, the study includes modified versions of different optimization methods; differential evaluation, random search, simulated annealing, and the Nelder-Mead algorithm simultaneously. The results indicated that the different algorithms converged on the same design, which corresponds to the UTS of 499 MPa. This represents a 7% increment compared to the value reported in the referenced study. Besides, four algorithms presented seven distinct alternative designs. The proposed neuro-regression methodology is expected to be highly effective in accurately defining complex engineering phenomena.

This study addresses the residual stresses generated during multi-process chains—including stamping, welding, and aging—in the manufacturing of automotive chassis components. An integrated method for synthesizing and simulating initial stresses is proposed. By developing a coupled simulation workflow and an efficient stress mapping algorithm, the multi-process residual stress fields are systematically synthesized. Bench test validation demonstrates that this method significantly improves the accuracy of fatigue life predictions, revealing that welding-induced residual stress is the dominant factor affecting fatigue damage. The approach provides an effective solution for durability design and process optimization of chassis components.

There is a need in the industry for a highly productive and cost-effective additive manufacturing process that is capable of processing copper-zinc alloys in such a way that acceptable material properties are achieved. To develop technologies that fulfill the requirements, wire and arc-based additive manufacturing with copper-zinc alloys is investigated. As part of the technology development, experiments on tungsten inert gas (TIG) welding with CuZn37 filler wire on CuZn37 substrates are carried out. By varying the arc length, it is shown that with shorter arcs, fewer lack of fusion occur at the seam edges. With further welding experiments, preferred parameters for the manufacturing of higher wall structures are determined. The investigations demonstrate that the reproducible build-up of 20-layer wall structures and cylindrical blanks made of CuZn37 is possible with a TIG process. The cross-sections of selected welds and wall structures are analyzed and measured using an optical microscope. Some samples are scanned using a laser scanner to create height profiles. To investigate the mechanical properties within the additive manufacturing technology, tensile tests are carried out as well.