Thermodynamics and transient behavior of the inclusion in Si deoxidized stainless steel for high-grade plate

Abstract

The experiments were carried out to determine the transient behavior of the inclusion in Si-deoxidized stainless steel for high-grade plate. The samples were taken from three heats of the steel during the whole production process from the AOD to the mold, which were subsequently examined by an automatic scanning electron microscope with field energy dispersive spectrometer (FE-SEM&EDS). It can be summarized that appropriate calcium treatment intensity could modify inclusions into liquid ones. Excessive calcium treatment above ([Ca] = 25 ppm) will increase the melting point of the inclusions, which cannot keep in the liquid region at the solidification temperature. Therefore, the calcium addition in Si-deoxidized stainless steels should be controlled to a relatively lower value ([Ca] = 10 ppm). In addition, the content of aluminum in steel also has an important influence on the control of inclusion. When the content of aluminum ([Al] = 0.012%) is too high, the inclusions in steel are difficult to be controlled within the liquid phase. The chemical evolution of the inclusions in steel at high temperature and during solidification process were comprehensively calculated, considering all types of inclusions such as calcium oxide, aluminum oxide, silicon oxide, calcium aluminate, calcium silicate, mullite, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si-deoxidized stainless steels.