Search Results (7)

In pipeline all-position welding processes, laser scanning provides critical geometric data of width-changing bevel morphology for welding torch swing control, yet conventional second-order derivative zero methods often yield pseudo-inflection points in practical applications. To address this, a third-order derivative weighted average threshold algorithm was developed, integrating image denoising, enhancement, and segmentation pre-processing with cubic spline fitting for precise bevel contour reconstruction. Bevel pixel points were captured by the laser sensor as inputs through the extracted second-order derivative eigenvalues to derive third-order derivative features, applying weighted threshold discrimination to accurately identify inflection points. Dual-angle sensors were implemented to synchronize laser-detected bevel geometry with real-time torch swing adjustments. Experimental results demonstrate that the system achieves a steady-state error of only 1.645% at the maximum swing width, a dynamic response time below 50 ms, and torch center trajectory tracking errors strictly constrained within ±0.1 mm. Compared to conventional methods, the proposed algorithm improves dynamic performance by 20.6% and exhibits unique adaptability to narrow-gap V-grooves. The results of these studies confirmed the ability of the method to provide real-time, accurate control for variable-width weld tracking, forming a swing-width adaptive control system. Full article

During the all-position narrow-gap welding process of pipelines, welding defects tend to occur in non-flat welding positions, constraining the quality and efficiency of pipeline construction. This paper addresses the sidewall and interlayer lack of fusion defects that commonly arise in all-position pipeline welding. Based on the research achievements of scholars and engineering technicians at home and abroad in recent years, the paper summarizes the influence laws of droplet transfer characteristics, arc morphology, and molten pool behavior on weld seam formation under different welding positions during gas metal arc welding. Additionally, the paper explores strategies for optimizing weld bead formation, including optimizing welding process parameters, controlling the molten pool flow with an external magnetic field, and using laser–arc hybrid welding. The paper points out the development trends of all-position pipeline welding technology, providing technical guidance and problem-solving ideas for alleviating the flow of the molten pool and optimizing the formation of all-position weld seams in engineering practice. Furthermore, it offers direction for scientific research for relevant researchers. Full article

Vertical oscillation arc welding for narrow gap gas metal arc welding (NG-GMAW) has a relatively simple structure, and it is widely used in all-position pipeline field welding. However, it has some shortcomings, such as incomplete fusion defects on the sidewall and interlayer. Aiming at resolving these shortcomings, a mathematical model is proposed to obtain appropriate welding parameters in different positions. In this model, the response surface methodology (RSM) based on the central composite design (CCD) was developed to study the interactions between welding parameters and the weld bead geometry. Then the analysis of variance (ANOVA) was used to evaluate the accuracy and significance of the proposed model. Finally, experiments were carried out in flat, vertical, and overhead positions to obtain the optimal parameters. The macroscopic metallography of the transversal section of the weld bead under the optimizing welding parameters showed that the weld beads were free of defects in the sidewall and interlayers. Full article

Pulsed gas metal arc weld (GMAW) was widely used for the advantages of controllable heat input, all-position welding, and no spatter. In order to obtain an ideal welding process, the stability of the arc length was studied in many researches, but the influence of arc length on the properties of weld metal was ignored. In this paper, the effect of arc length on oxygen content and mechanical properties of weld metal during pulsed GMAW was studied. Q690 high strength steel was selected as the base metal, and ER69-G solid wire, with a diameter of 1.2 mm, was used as the electrode wire. Additionally, the shielding gas and the wire feed rate were 82% Ar + 18% CO₂ and 4 m/min, respectively. The results showed that as the arc length raised from 2.9 mm to 9.2 mm, the oxidation reacted more completely in the droplet transfer zone, and the oxygen content of the weld metal increased significantly. The tensile strength of the weld metal reduced but the −40 °C impact energy heightened. Due to the longer arc, the proportion of acicular ferrite (AF) in the microstructure decreased, but the proportion of lath bainite (LB) and granular bainite (GB) decreased. The higher oxygen content of weld metal was useful for the formation of inclusions, which promoted the nucleation of acicular ferrite and dimples, contributing to the growth of plasticity and toughness of weld metal. Full article

Weld bead geometry features (WBGFs) such as the bead width, height, area, and center of gravity are the common factors for weighing welding quality control. The effective modeling of these WBGFs contributes to implementing timely decision making of welding process parameters to improve welding quality and enhance automatic levels. In this work, a dynamic modeling method of WBGFs is presented based on machine vision and learning in multipass gas metal arc welding (GMAW) with typical joints. A laser vision sensing system is used to detect weld seam profiles (WSPs) during the GMAW process. A novel WSP extraction method is proposed using scale-invariant feature transform and machine learning. The feature points of the extracted WSP, namely the boundary points of the weld beads, are identified with slope mutation detection and number supervision. In order to stabilize the modeling process, a fault detection and diagnosis method is implemented with cubic exponential smoothing, and the diagnostic accuracy is within 1.50 pixels. A linear interpolation method is presented to implement sub pixel discrimination of the weld bead before modeling WBGFs. With the effective feature points and the extracted WSP, a scheme of modeling the area, center of gravity, and all-position width and height of the weld bead is presented. Experimental results show that the proposed method in this work adapts to the variable features of the weld beads in thick plate GMAW with T-joints and butt/lap joints. This work can provide more evidence to control the weld formation in a thick plate GMAW in real time. Full article

Pulsed gas metal arc welding (GMAW) is widely applied in industrial manufacturing. The use of pulsed GMAW was found superior to the traditional direct-current (DC) welding method with respect to spatter, welding performance, and adaptability of all-position welding. These features are closely related to the special pulsed projected metal transfer process. In this paper, a monitoring system based on a high-speed camera and laser backlight is proposed. High-quality images with clear droplets and a translucent arc can be obtained at the same time. Furthermore, a novel image-processing algorithm is proposed in this paper, which was successfully applied to remove the interference of the arc. As a result, the edge and region of droplets were precisely extracted, which is not possible using only the threshold method. Based on the algorithm, centroid coordinates of undetached and detached droplets can be calculated, and more parameters of the kinematic characteristics of droplets can be derived, such as velocity, acceleration, external force, and momentum. The proposed monitoring system and image-processing algorithm give a simple and feasible way to investigate kinematic characteristics, which can provide a new method for possible applications in studying mathematic descriptions of droplet flight trajectory and developing a precise automatic welding system. Full article

In this study all-position automatic tungsten inert gas (TIG) welding was exploited to enhance quality and efficiency in the welding of copper-nickel alloy pipes. The mathematical models of all-position automatic TIG weld bead shapes were conducted by the response surface method (RSM) on the foundation of central composition design (CCD). The statistical models were verified for their significance and adequacy by analysis of variance (ANOVA). In addition, the influences of welding peak current, welding velocity, welding duty ratio, and welding position on weld bead geometry were investigated. Finally, optimal welding parameters at the welding positions of 0° to 180° were determined by using RSM. Full article