Welding fumes were generated from several kinds of low hydrogen type electrodes which changed the atmosphere with use of various gases, such air, Ar, CO2 and N2, and were collected in water with an impinger. These fumes were analyzed by X-ray refractometry and chemical analysis, and pH of their collecting water was measured. Based on these results, this paper discusses the mechanism of scattering K and Na in fumes from low hydrogen welding which are considered to be the sources of respiratory tract irritation.
All sample fumes from low hydrogen welding in several atmospheric conditions contained fluorite (CaF2). The pH of water in which all sample fumes were collected remarkably elevated. Chemical composition ratios of both K2O and Na2O in all sample fumes were larger than those in coating materials. The sample fumes from welding in each of both N2 and CO2 atmosphere showed higher ratios of K2O and Na2O than those in Ar.
The conclusions obtained from the discussion are as follows:
The potential gradient of the arc becomes larger during welding in the atmosphere with use of N2 or CO2 because the dissociation voltage of N2 and CO2 is very low. Furthermore, fluorite (CaF2) makes the slag more fluid. Then, K and Na become easily dispersed from the arc column of low hydrogen welding.