Steel Glossary | Glossary of Terms | Platts
https://www.steelbb.com/steelglossaryThis is an abbreviation of ... This type of steel is produced during ingot casting, with the resulting ingot having a very pure surface layer, or rim. This feature is due to the absence or near absence of a deoxidising agent during steel production, which allows carbon monoxide to be formed from the oxygen and carbon in the melt.