Multicomponent condensation in the plasma of welding fumes

• The subject of study is the plasma of welding fume, in which the particles are the result of vapor condensation.
• The nucleation and the growth of the nuclei are considered simultaneously with their coalescence.
• The deposition of the multicomponent vapor leads to the change in chemical composition of condensed droplets.
• As a result, the ousting of iron from the nano-sized droplets and replacing it by low-boiling components occur.

The subject of study is the multicomponent condensation in the low-temperature plasma, which forms when shielded metal arc welding is applied. The modeling of heterogeneous ion-induced nucleation and nuclei growth in the strongly ionized environment with account of their coagulation is performed. The formation of the bimodal size distribution of the liquid particles after start of nucleation of the predominant component (iron) is demonstrated. This distribution consists of the nano-sized mode of nuclei and the larger-sized mode of the aggregated droplets. The condensation of the accompanying low-boiling components on these droplets causes the termination of nucleation earlier than conditions for the condensation growth of the equilibrium nuclei arise. Therefore, the growth of the nuclei occurs only by their coalescence. The deposition of the accompanying components on the iron nuclei leads to replacement of the iron by these components in the particles of the nuclei mode.