Cleaning of metals using special metallurgic processes. This should be the task of steel mills and refineries but not that of foundries.

Refining is basically the recycling of scrap metals on the basis of melting-metallurgic processes forming new metals with an appropriate degree of pureness.

Strictly speaking, the conventional processes in foundries applied for decreasing the content of certain additives and gases are cleaning processes and not refining processes.

Additional references:
Refining agents