Conclusion
Non-metallic inclusions in steel

The very origin of the inclusions shows that these chemical compounds are an integral part of the structure of steels, in the same way as carbides which, grouped in clusters, or even isolated but elongated as in extra-soft steels, clearly modify the characteristics of the metal; these carbides, moreover, are separated from non-metallic inclusions only by a conventional boundary.

These inclusions are part of the life of steel, from the moment they are born, passing through a period of transformations before reaching maturity for use as mechanical parts. Inclusions are permanent, and their number cannot decrease (except in the rare case of digestion of FeO particles by the steel's carbon), but can increase as a result of surface pollution. They can migrate; internal inclusions can end up on the surface as a result of working (effects of splitting grooves, stamping...