Investigation of Thermo‐Chemical Processes in Commercial MgO‐C Refractory Bricks With and Without MgO‐C Recyclate at Elevated Temperatures

In the present study, the chemical processes occurring during high‐temperature testing are investigated for two commercial MgO‐C brick grades. One grade consists exclusively of virgin raw materials, while the other contains 47.5 wt.% MgO‐C recyclate. High‐temperature testing is conducted under argon atmosphere at ambient pressure using induction heating. To evaluate the effect of MgO‐C recyclate incorporation on thermo‐chemical processes, X‐ray diffraction (XRD), electrothermal vaporization (ETV), differential thermal and thermogravimetric analysis (DTA/TG) coupled with mass spectrometry (MS) are applied. Scanning electron microscopy (SEM) combined with energy‐dispersive X‐ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) provide phase characterization after exposure at 1300°C and above. The results show that mechanisms typically occurring during the service of refractory materials such as the carbothermal reduction of magnesia, the incorporation of impurity phases into the newly formed MgO surface layer, and the deposition of calcium‐rich phases and whisker‐like structures also occur when MgO‐C is exposed to the applied gas atmosphere. This confirms the relevance of the observed thermo‐chemical processes and surface phase formation for real contact with molten steel and slag. Under the present test conditions, however, no significant influence of MgO‐C recyclate incorporation on the thermo‐chemical behavior of the coked MgO‐C materials is detected.