Tailoring Nonmetallic Inclusions in 42CrMo4 as a Preparative Tool for Active and Reactive Steel Melt Filtration

This study investigates the effect of different temperatures during deoxidation of 42CrMo4 on nonmetallic inclusions (NMI). Tailoring NMIs by a modified temperature during deoxidation is the last step before a combination of reactive and active steel melt filtration. Extensive investigations of metallographic sections together with electrolytic extraction allow analysis of inclusions' size distributions, chemical compositions, and morphologies. Reducing the temperature during deoxidation from approximately 1630 degrees C to a slightly lower temperature (LT) of approximately 1600 degrees C leads to a shift of inclusion size distribution toward smaller NMIs. Ultrasonic fatigue testing (USFT) reveals the largest particles within the cyclically loaded volume, showing a dendrite (1600 degrees C) instead of plate-like morphology (1630 degrees C) of NMIs due to the LT level. The fatigue limit seems to be almost unaffected by the change in NMIs' morphologies and is evaluated by Murakami's root area parameter model. The LT during oxidation and deoxidation is found to offer promising conditions for the application of a combination of reactive and active steel melt filtration.