Welding in the World最新文献

To address the challenges of irregular geometry, significant curvature variations, and disordered normal vector distribution in aviation Invar steel S-type molds, this paper proposes a welding trajectory generation method based on multi-level trajectory fitting and adaptive connection. To address issues such as high trajectory fitting error rates and trajectory gaps caused by irregular geometric shapes and significant curvature variations, the model point cloud is first segmented into regions. Subsequently, trajectory points are extracted using slicing operations and domain searches, and trajectory fitting is performed via Euclidean clustering. After obtaining a simple trajectory, an adaptive connection mechanism is introduced to enhance the algorithm’s practicality, thereby translating the algorithm’s intended outcomes into actual results. The proposed algorithm achieves a fitting accuracy exceeding 90%, with smoothness and average Z-direction values below 0.1, objectively demonstrating the high accuracy and stability of the trajectory fitting method presented herein. This study provides a feasible solution for automated welding of aviation Invar steel molds and offers new insights for the development of robotic welding trajectory planning.

Residual stresses induced during welding can significantly compromise the structural integrity and performance of welded components. Accurate modeling of the welding heat source is crucial for reliable prediction of temperature distributions and residual stresses. This study introduces an efficient computational method for optimizing welding heat source parameters by integrating computer vision techniques with an improved genetic algorithm. A specialized software, WHSO.2025a, was developed within the Unity platform to facilitate real-time visualization of the molten pool and support unified optimization for multi-layer and multi-pass welding processes. The method incorporates a simplified geometric approach to reduce computational time without compromising accuracy. Additionally, three weld activation methods—birth–death element, field variable, and event series—were evaluated, with the field variable method demonstrating superior computational efficiency. The proposed approach was validated through a case study involving a Q355B single-sided V-groove butt-welded plate with 4 layers and 4 passes. Simulation results closely matched experimental data in terms of molten pool geometry and residual stress distributions, confirming the method's effectiveness and potential for practical engineering applications.

Directed energy deposition with wire feeding (L-DED-wire) provides manufacturers with higher production rates and lower initial costs compared to powder bed fusion techniques. However, direct deposition exposes the material to relatively more extreme thermal gradients and a less protective atmosphere. Subsequently, the microstructure and mechanical properties of the processed metal can be more sensitive to manufacturing parameters. Accordingly, this study investigates 316LSi stainless steel processed via L-DED-wire to evaluate the parametric window and properties of the L-DED-wire and the processed metal, respectively. Two wall structures were manufactured using an industrial robotic setup with a continuous wave fiber laser and wire feedstock. Test samples were prepared and analyzed via quasi-static tensile testing (in both parallel and perpendicular orientations), scanning electron microscopy, Vickers hardness measurements, and surface roughness evaluation. The results indicate that due to irregular material accumulations, there is a higher possibility of defects such as lack of fusions, e.g., at the very end of deposited tracks. Also, parallel-oriented tensile specimens exhibited higher yield and ultimate tensile strengths than perpendicular ones, indicating the interlayer boundaries as the main weak points in the L-DED-wire component. The resultant microstructure was austenitic with hierarchical subgrain features and localized ferrite. The diversity in subgrain morphology and size, potentially driven by complex thermal gradients during deposition, was linked to local variations in Vickers hardness across sample cross-sections. The average surface roughness (Ra) of the as-built parts was 25 µm, which was in the range of other components made via direct deposition techniques per the literature.

The purpose of this study is to develop a simulation method to predict leak limit tensile strain from weld flaws in girth-welded high-pressure pipe subjected to uniaxial tension. Tensile tests are conducted using a girth-welded joint of pipe with artificially introduced notches at the weld metal or heat-affected zone. Regardless of the internal pressure level, a notch located in the weld metal on the inner surface of the pipe is the most susceptible to leaks. Material properties of each area are measured by experiments using proposed small-size specimens that could be extracted from narrow areas such as the weld metal and heat-affected zone. Ductile crack growth simulation is conducted using FE models of girth-welded pipe to which the measured material properties are assigned. It is demonstrated that the simulation method is applicable to predict the notch location most susceptible to leaks and the leak limit tensile strain of the girth-welded pipe.

Robot welding is the main form of automatic welding system. Although the application of machine vision, intelligent teaching, offline programming, and other technologies had greatly improved the manufacturing flexibility of the welding system, the existing robot welding was not fully adapted to the manufacture of products with small batch and customized needs, and the manufacturing flexibility needed to be further improved. To solve this problem, a flexible stacking welding manufacturing method known as direct stacking welding manufacturing (DSWM) has been proposed as a cost-effective method for constructing common metal structures. DSWM fabricates metal structures by stacking welding of modular pieces one-by-one bottom-to-top. A multi-robot system with vision guidance has been developed to conduct the DSWM process. This system sequentially combines the operations of cutting, grasping, assembling, and welding the modular pieces. 3D visions were employed to recognize modular pieces and intermediate states of the structure, thereby providing guidance for the grasping, assembling, and welding procedures. The proposed methodology and the developed system were validated through two manufacturing cases. The case studies demonstrated that the designed algorithms were capable of accurately recognizing and localizing the modular pieces. The manufacturing accuracy achieved was found to be compliant with relevant quality standards. In terms of production time, the DSWM process was markedly shorter than that of wire arc additive manufacturing (WAAM). In terms of production cost, it was estimated that the DSWM process incurred approximately one-fourth the cost of WAAM. For a detailed visual demonstration of the project, please refer to the accompanying video available at (https://youtu.be/gN-wKduHa3s?si=0xLW0Nd6sX8sm1r2).

Selective laser melting (SLM) is one of the advanced manufacturing techniques. The purpose of this work is to develop a new reasonable SLM process optimization methodology for improving multiple quality attributes of the SLM parts. The multiple quality attributes are converted into a single comprehensive quality index (CQI) using the multi-attribute decision-making (MADM) method, and the optimization result may differ according to the applied MADM. To address this, this work proposed the final CQI (FCQI) as the priority weighted mean value of the CQIs from the multiple MADMs (it is called the integrated MADM method) and determined the optimal process parameters to maximize the FCQI using the Taguchi method. The methodology was applied to optimize the laser power (P), scan speed (S), and overlap rate (O) for improving tensile strength, hardness, relative density, and surface roughness of the SLM-manufactured AlSi10Mg alloys. The optimal process parameters were P of 320 W, S of 600 mm/s, and O of 35%, respectively. The innovation and superiority of the proposed methodology are as follows: (1) It can evaluate the comprehensive quality of the SLM parts more accurately using the FCQI combined with the multiple MADMs, not only one MADM. (2) It can reflect the priority weights of the multiple MADMs to improve the accuracy and reasonability of the final CQIs. (3) It can clearly understand the effects of the process parameters by introducing the effect scores. The methodology could be applied to the SLM process optimization for not only Al alloys but also various metals/alloys.

This paper establishes a three-dimensional numerical simulation model for the cladding process of Fe60 alloy powder onto a 27SiMn steel substrate, simultaneously coupling the temperature field, flow field, and stress field. The isotherms are densely distributed at the leading edge of the melt pool, and the thermal cycle curves of each clad layer exhibit multiple peaks, indicating remelting between adjacent layers. Within the melt pool, the liquid metal forms vortices flowing from the center outward and from the surface inward, from the bottom to the surface. This flow pattern is primarily caused by the combined effects of surface tension, gravity, and thermal buoyancy on the liquid metal. The stress at the center of the melt pool is the lowest, approaching zero. The thermal stress during the cladding process follows a tensile-compressive-tensile variation pattern, and the substrate exhibits concave deformation after cladding. Based on the central composite design (CCD) response surface method (RSM), the scanning speed was identified as the most influential parameter affecting substrate deformation. Within the given parameter range, scanning speed is negatively correlated with deformation magnitude; laser power is positively correlated with deformation magnitude; when the overlap ratio R < 50%, the overlap ratio is positively correlated with deformation magnitude; when the overlap ratio R > 50%, the overlap ratio is negatively correlated with deformation magnitude. The optimal process parameters were determined to be laser power P = 2000 W, scanning speed V = 25 mm/s, and overlap ratio R = 60%.

IN625 alloy is widely used for pump chambers in high-temperature, high-pressure, and corrosive environments. However, its wear and impact resistance face challenges under extreme conditions involving high abrasion and high-speed impact. The introduction of TiC particles to fabricate IN625-TiC coatings has proven to be an effective strategy to enhance these properties. In this study, IN625-TiC coatings with TiC mass fractions of 0%, 5%, 10%, and 15% were prepared on an IN625 superalloy substrate via plasma cladding. The microstructure was characterized using XRD, SEM, and EBSD, while microhardness, wear behavior, and dynamic compression mechanical properties were systematically investigated to elucidate the influence mechanism of TiC content. Results show that increasing the TiC fraction induces lattice distortion in the γ-phase and refines coating grains. The fraction of γ-phase grains with sizes below 5 μm increased from 73.92% (with 5% TiC) to 95.2% (with 15% TiC). Microhardness increases with TiC addition, reaching 354.4 HV_0.2 for the 15% TiC coating—a 47% improvement over the substrate, while the friction coefficient reached a minimum value of 0.421 at 10% TiC. All coatings exhibited strain-rate strengthening behavior at strain rates from 700 to 2100 s⁻¹, with dynamic yield strength and peak stress increasing with TiC content. Moderate TiC (5–10%) synergistically improves comprehensive properties through solid-solution strengthening, grain-boundary pinning, and hard-phase dispersion. However, excessive TiC (15%) weakens the interfacial bonding between hard phases and the matrix, causing particle detachment and consequent degradation of wear resistance. This study provides a theoretical and technical reference for developing high-performance wear-resistant coatings for pump chambers.

Gray cast iron components in nuclear power plants suffer from surface degradation under harsh conditions. This study investigates the additive repair of defective gray cast iron using double-sided laser cladding, focusing on the effects of laser power and scanning rate on the repair layer’s morphology, microstructure, and mechanical properties. Results indicate that the synergistic effect of these parameters significantly regulates cladding quality. Increasing power or decreasing scanning speed enlarges the cladding dimensions and heat-affected zone (HAZ), while insufficient heat input causes poor bonding. The microstructure exhibits a gradient distribution: the fusion zone (FZ) has fine grains and higher hardness (~ 400 HV) than the substrate (~ 200 HV), while the partial melting zone (PMZ) and HAZ undergo non-equilibrium phase transitions. Under optimal parameters (2400 W, 800 mm/min), the repair layer achieves a smooth surface, narrow HAZ (19 mm), and improved ultimate tensile strength (~ 250 MPa), meeting the FC200 standard. This work provides a process optimization basis for laser cladding repair to extend the service life of critical nuclear components.