Reduction of segregation during casting of 100Cr6 bearing steel by cerium inoculation

In order to reduce the segregation of alloying elements during casting of 100Cr6 high carbon chromium bearing steel, cerium was added to form dispersoids that act as inoculants to facilitate the formation not of columnar but of equiaxed grains. The influence of adding cerium alone to 100Cr6 steel on the degree of segregation and the resulting as-cast microstructure have been investigated. By adding cerium, the equiaxed grains became finer and the segregation diminished considerably. As a result, the rolling contact fatigue life of the steel was improved markedly. Among dispersoids, CeO₂ is supposed to play a more important role in refining as-cast structures because the observed number of CeO₂ was much larger than that of CeS and the size of the former was quite similar to that reported to be effective as inoculants. Consequently, the addition of cerium is proposed as the solution to one of the biggest subjects with regard to 100Cr6 steel, the reduction of segregation during casting.