Effect of Compositions of Non-metallic Inclusions on CC Nozzle Clogging of a Fe-Cr-Ni-Mo System Stainless Steel

A study was carried out to understand the effect of non-metallic inclusion compositions on nozzle clogging of a Fe-Cr-Ni-Mo system stainless steel, aiming at developing the consecutive continuous casting technology of two ladles. At first, nozzle clogging took place leading to the reduction in casting speed. It was found that the major oxide phase in the accretion observed on the nozzle wall consisted of MgO・Al2O3 spinel oxides. The inclusions observed in the sample taken from the tundish were spinel which was consistent with the accretion composition. The phase stability diagram was calculated with the thermodynamic data to understand how to control the inclusion compositions to prevent nozzle clogging. It was suggested that the inclusion composition should be controlled to MgO with high melting point as a countermeasure. It was confirmed that this control brought the successful casting practices avoiding nozzle clogging. The consistency of the inclusion compositions with the phase stability diagram proved the validity to apply thermodynamic data based on the standard taking infinite dilute solution for the present alloy system.