Abstract: It is realized to systematic analysis of the particulate size distributions and shape, composition, crystal structure for grade particles of welding aerosol, for the first time, by means of DMPS (Differential mobility particle sizer) method and ATEM (Analytical transmission electron microscopy) method. The distribution functions of particles of order 10 nm for the E4303 and E5015 electrodes are shown as Dp1E4303 ～ LN(0.042 mm，1.37) and Dp1E5015～LN(0.054 mm，1.42) during welding. The results show that the particles of order 10 nm follow lognormal distribution and relate to metal vaporizing. The G-P conversion (Gas to Particle Conversion) process and nucleation mechanism of 10 nm particles of welding aerosol have been investigated. The crystal structure of particles of order 10 nm is confirmed as Fe3O4. The particles of order 10 nm are generated according to the homogeneous form by way of G-P conversion and its controlling reaction is physical condensation process of Fe(g)→ Fe(l).The model of particulate nucleation zone in welding arc is put forward. It is important to analysis G-P conversion process and nucleation mechanism of welding aerosol particle.

Key words: G-P conversion, Homogeneous nucleation, Model of nucleation zone, Welding aerosol, Welding fume