Normally, non-metallic inclusions are always present in welds made by any fusion welding method. The only exceptions are electron beam and electroslag welding which may provide conditions that allow non-metallic inclusions in the weld metal to be markedly decreased. All the rest of the fusion welding methods are usually characterized by an increased content of non-metallic inclusions in the weld or the deposited metal compared with that of the initial welding consumables used. Composition of non-metallic inclusions, their quantity, size, shape, and distribution in the weld may have a marked effect on the mechanical properties of a welded joint. Therefore, despite the fact that welds are, owing to the small volume of the weld pool, an inconvenient object for investigation of non-metallic inclusions, quite considerable number of papers are dedicated to this issue.