Modeling of Fume Formation from Shielded Metal Arc Welding Process
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INTRODUCTION
NUMEROUS mathematical models dealing with the metal transfer mechanism and thermal analysis of welding are available in the literature,[1–4] while those relating to fumes are limited. The first attempt to model welding fumes appears to be the work of Hewitt and Hirst.[5] The authors developed and validated a model to predict the fume composition from a flux core arc welding (FCAW) process. During the year 2000 to 2002, Deam et al.,[6] Dennis et al.,[7] and Redding[8] independently developed three semi-empirical models to predict the fume formation rate (FFR) from a gas metal arc welding (GMAW) process. The Deam’s model of fume formation was based on the concepts of physical chemistry of the metal vapor mechanism and depicted that the FFR was controlled by the droplet diameter. The authors concluded that the FFR was proportional to the saturated metal vapor density at the surface of the droplet. The mean free path and molecular speed in the plasma were found to have a direct influence on FFR. Dennis’s model considered the evaporation of metal droplets and the partial vapor pressures of the individual
S.P. SIVAPIRAKASAM is with the Industrial Safety Engineering Lab, Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India. Contact e-mails: [email protected] and [email protected] SREEJITH MOHAN formerly with the Industrial Safety Engineering Lab, Department of Mechanical Engineering, National Institute of Technology, is now with Vimal Jyothi Engineering College, Kannur, Kerala, India. M.C. SANTHOSH KUMAR is with the Advanced Materials Lab, Department of Physics, National Institute of Technology. M. SURIANARAYANAN is with the Cell for Industrial Safety and Risk Analysis, Chemical Engineering Department, Central Leather Research Institute, Adyar, Chennai, India. Manuscript submitted November 4, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
metallic species like Fe and Mn to predict the FFR. The authors validated the model through experiments. The Redding’s model was developed with some minor modifications in the Dennis model in which the Langmuir equation for evaporation was replaced with the calculation of convective mass transfer coefficients’ for Fe and Mn. He also avoided the use of some of the difficult-to-measure welding parameters like arc length for predicting FFR. Recently, Shinichi and Manabu[9] developed a fume formation model for GMAW process consisting of heterogeneous condensation model, homogeneous nucleation model, and coagulation model. They found that the most part of the fume was produced from the evaporation of droplets in the downstream region near the welding arc. All these models were, however, limited to the prediction of FFR from a GMAW process. The first fume prediction model for shielded metal arc welding (SMAW) was proposed by Chan et al.[10] The authors conducted an experimental investigation by collecting respirable fume particulate from two welding electrodes, E 6013 and E316-16. The parameters varied were electrode type, elect
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