A sensing torch for on-line monitoring of the gas tungsten arc welding process of steel pipes

Abstract

Non-intrusive and real-time monitoring techniques are increasingly required by manufacturing industry in order to detect flaws in arc welding processes. In this work the development of an optical inspection system, for monitoring the manual gas tungsten arc welding (GTAW) process of steel pipes, is described. The arc plasma visible emission produced during the process was acquired and spectroscopically analysed. Measuring the intensities of selected argon emission lines allowed real time calculation and recording of the axial electron temperature of the plasma. Experimental results showed that the temperature signal varies greatly in the case of instabilities of the weld pool that cause weld defects. A suitable algorithm, based on a statistical analysis of the signal, was developed in order to real time flag defective joints. It is shown that several weld defects such as porosity, dropout, lack of fusion, solid inclusions and craters were successfully detected in a production environment. The performances of the optical sensor were compared with the results of state-of-the-art post-weld controls such as x-rays and penetrating dyes, showing good agreement and thus demonstrating the validity of this quality monitoring system.

Studies on characteristics of CO2 laser-GTAW hybrid welding of austenitic stainless steel

“…20 Hence, measured electron temperature remained largely unaffected by coupling of arc with laser-generated plasma. Therefore, temperature obtained from FeI provided information about the most peripheral portion of the plasma plume, which is less perturbed by process instabilities.…”

Optical Methods for On-line Quality Assurance of Welding Processes in Nuclear Steam Generators

“…For a welding seam with constant parameters, Te is expected to be within a particular range of values; and any unexpected variation can be attributed to a perturbation of the process, and hence to a potential defect. Several statistical analysis techniques have been proposed to detect in real time any possible defect (Ancona et al, 2004) (Bebiano & Alfaro, 2009). Fig.…”

Arc-Welding Spectroscopic Monitoring based on Feature Selection and Neural Networks

“…Although there are several proposals based on plasma optical spectroscopy [7-8, 15], the interpretation of the resulting temperature profiles is not always easy, and an efficient algorithm allowing defect classification is still to be formulated. Moreover, the identification and selection of the emission lines participating in the analysis could lead to ambiguities, especially if the system is designed to be fully-automated.…”

“…Input optics based on collimators attached to the welding torch have been proposed [8], but these have limited applicability in general terms. In a previous communication we proposed a new sensor arrangement based on the use of an optical fiber embedded within a TIG torch [9].…”