Gas metal arc welding

About: Gas metal arc welding is a research topic. Over the lifetime, 11706 publications have been published within this topic receiving 109555 citations. The topic is also known as: metal active gas welding & GMAW.

Computer vision technology for seam tracking in robotic GTAW and GMAW

Abstract: Due to ever increasing demand in precision in robotic welding automation and its inherent technical difficulties, seam tracking has become the research hotspot. This paper introduces the research in application of computer vision technology for real-time seam tracking in robotic gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). The key aspect in using vision techniques to track welding seams is to acquire clear real-time weld images and to process them accurately. This is directly related to the precision of seam tracking. In order to further improve the accuracy of seam tracking, in this paper, a set of special vision system has been designed firstly, which can acquire clear and steady real-time weld images. By analyzing the features of weld images, a new and improved edge detection algorithm was proposed to detect the edges in weld images, and more accurately extract the seam and pool characteristic parameters. The image processing precision was verified through the experiments. Results showed that the precision of this vision based tracking technology can be controlled to be within ?0.17mm and ?0.3mm in robotic GTAW and GMAW, respectively. Using computer vision technology, we have solved some problems of seam tracking in robotic welding automation.We have designed a set of special vision sensor system for seam tracking and it has worked very well.A new improved Canny edge detection algorithm was proposed to detect the edges of weld image.We have further improved the precision of image processing in seam tracking.This paper systematically studied the application of computer vision technology in robotic GTAW and GMAW.

The humping phenomenon during high speed gas metal arc welding

Abstract: A commonly observed welding defect that characteristically occurs at high welding speeds is the periodic undulation of the weld bead profile, also known as humping. The occurrence of humping limits the range of usable welding speeds in most fusion welding processes and prevents further increases in productivity in a welding operation. At the present time, the physical mechanisms responsible for humping are not well understood. Thus, it is difficult to know how to suppress humping in order to achieve higher welding speeds. The objectives of this study were to identify and experimentally validate the physical mechanisms responsible for the humping phenomenon during high speed gas metal arc (GMA) welding of plain carbon steel. A LaserStrobe video imaging system was used to obtain video images of typical sequences of events during the formation of a hump. Based on these recorded video images, the strong momentum of the backward flow of molten metal in the weld pool that typically occurred during high speed welding was identified as the major factor responsible for the initiation of humping. Experiments with different process variables affecting the backward flow of molten weld metal were used to validate this hypothesis. These process variables included welding speed, welding position and shielding gas composition. The use of downhill welding positions and reactive shielding gases was found to suppress humping and to allow higher welding speeds by reducing the momentum of the backward flow of molten metal in the weld pool. This would suggest that any process variables or welding techniques that can dissipate or reduce the momentum of the backward flow of molten metal in the weld pool will facilitate higher welding speeds and productivity.

Metal vapour causes a central minimum in arc temperature in gas-metal arc welding through increased radiative emission

Abstract: A computational model of the argon arc plasma in gas‐metal arc welding (GMAW) that includes the influence of metal vapour from the electrode is presented. The occurrence of a central minimum in the radial distributions of temperature and current density is demonstrated. This is in agreement with some recent measurements of arc temperatures in GMAW, but contradicts other measurements and also the predictions of previous models, which do not take metal vapour into account. It is shown that the central minimum is a consequence of the strong radiative emission from the metal vapour. Other effects of the metal vapour, such as the flux of relatively cold vapour from the electrode and the increased electrical conductivity, are found to be less significant. The different effects of metal vapour in gas‐tungsten arc welding and GMAW are explained.

Prediction of weld pool and reinforcement dimensions of GMA welds using a finite-element model

Abstract: Mathematical models of the gas metal arc (GMA) welding process may be used to study the influence of various welding parameters on weld dimensions, to assist in the development of welding procedures, and to aid in the generation of process control algorithms for automated applications. In this work, a three-dimensional (3-D), steady-state thermal model of the GMA welding process has been formulated for a moving coordinate framework and solved using the finite-element method. The model includes temperature-dependent material properties, a new finite-element formulation for the inclusion of latent heat of fusion, a Gaussian distribution of heat flux from the arc, plus the effects of mass convection into the weld pool from the melted filler wire. The influence of weld pool convection on the pool shape was approximated using anisotropically enhanced thermal conductivity for the liquid phase. Weld bead width and reinforcement height were predicted using a unique iterative technique developed for this purpose. In this paper, the numerical model is shown to be capable of predicting GMA weld dimensions for individual welds, including those with finger penetration. Also, good agreement is demonstrated between predicted weld dimensions and experimentally derived relations that describe the effects of process variables and their influence on average weld dimensions for bead-onplate GMA welds on steel plate.