An arc profile-based approach to evaluate gas pollutants in welding.

Abstract

Welding is widely used to make assembly of structural components and it will trigger serious environmental pollution, especially waste gas, i.e., carbon dioxide (CO2), ozone (O3), nitrogen oxide (NOx), and particulate matter (PM). It is hard to accurately measure gas pollutants because of their fluidity and diffusivity. However, the pollutants could be evaluated by exploring its generation procedure, i.e., how these pollutants are produced and how to quantify these pollutants. In this paper, an arc profile-based approach to evaluate the emissions of gas pollutants in welding was proposed. The emission of gas pollutants in welding can be calculated according to the chemical reaction and corresponding reaction condition, i.e., the intensity of discharge that determines the coverage volume of the welding arc. To obtain the coverage volume, the welding arc was observed using a high-speed camera and the arc edge was extracted and reconstructed by a binarization processing based method. A welding experiment was performed for recording the arc shape and measuring the emission of gas pollutants. Results show that the measured concentrations of NOx and O3 are 70% and 79% of the calculated emissions of gas pollutants, respectively. It demonstrates the proposed method is credible and feasible, which can help quantitatively analyze the emission of gas pollutants. Meanwhile, the influence of welding time, welding current, and arc length on the emission of gas pollutants was investigated for lowering emission of gas pollution in welding, in order to support the development of sustainable manufacturing processes.