So less gas is. given off in the mould than with rimming steel, but enough bubbles form at the top of the ingot to counteract most of the shrinkage.
In the case of rimming steel, no or some deoxidation is carried out before casting. During the solidification in the mould carbon monoxide is formed and the gas makes the steel boils.
Some CO gas remains in the ingot, and eventually blow holes are formed in the steel. These blow holes counteract the shrinkage which occurs during solidification and no pipe is formed. With small portion to be scrapped rimming steel has a high yield of good steel.
In the case of rimming steel, no or some deoxidation is carried out before casting.
