<p>Modeling is an essential tool to provide insights in the evolution of non-metallic inclusions in metallurgical processes. To provide comprehensive depictions of phase developments in laboratory experiments and the associated steel cleanness in high-speed steels, a combination of modeling approaches is employed and compared with analytical data. Macroscopic phase changes are represented using the effective equilibrium reaction zone model. This model, in conjunction with analytical and numerical approaches, also serve to describe steel cleanness modifications. The model described, together with delineated boundary conditions based on literature as well as measured data for the defined system, demonstrated a high degree of agreement with the measurements. Macroscopic changes are characterized by a mean absolute deviation between measured and calculated steel and slag component contents of 0.035 pct points with a standard deviation of 0.093 pct points and 0.92 pct points with a standard deviation of 1.61 pct points, respectively. For steel cleanness modifications, comparative analysis of inclusion compositions, mean ECDs and inclusion number densities were conducted. The mean absolute deviation of the mean ECD showed 0.02&#xa0;<i>μ</i>m with a standard deviation of 0.03 <i>μ</i>m and the inclusion number density 155 inclusions per mm² with a standard deviation of 224 inclusions per mm².</p>