Effect of Mg and Ca Treatment on Behavior and Particle Size of Inclusions in Bearing Steels

The effect of Mg and Ca treatment on the behavior and the particle size of inclusions in bearing steels were studied by industrial experiments and thermodynamic calculations. The results showed that the excess addition of Mg wires is not conducive to control the total oxygen content in bearing steel because of the secondary oxidation. The irregular and clustered Al2O3 inclusions are the dominant in the aluminium killed bearing steels. The different quantity Mg wires were added, which can change the irregular and clustered Al2O3 inclusions into the spherical MgO or MgO center dot Al2O3 inclusions. When the Ca addition is insufficient, the Al2O3 and MgO center dot Al2O3 inclusions could not completely change into the spherical CaO-MgO-Al2O3 system inclusions. By the three-dimensional morphologies analyze, Al2O3 inclusions are easy to gather and the size of clustered Al2O3 inclusions is large. By the Mg or Ca treatment, the size of Al2O3 inclusions can be reduced, but the large size CaO inclusions are brought into steel after the Ca treatment.