The degree of oxidation marks the oxygen content in a melt. In this respect, it is distinguished between dissolved and bound oxygen (oxides as slag in the melt). The sum of both is the total oxygen content of the melt which can be analytically determined by hot extraction.
The oxygen content can be reduced by deoxidation. In contrast to this, it is increased by means of oxidation or oxidizing melting.
In gray solidified cast iron alloys, the degree of oxidation is an important quality attribute and is usually determined by thermal analysis. It may be the cause of casting defects and vary within a wide range.
If the tendency for gas blisters and slag formation is increasing, this is often caused by excessively oxidized melts (degree of oxidation > 60 %). Cast iron melts with degrees of oxidation of < 40 % have a high tendency of cavity formation (see Cavities).
If the degree of oxidation is at approx. 50 %, casting without risers is possible. The oxygen content in excessively oxidized melts can be reduced by additionally deoxidizing inoculants (SiC, FeSi).