Cathodoluminescence imaging for rapid identification of low-melting CaO–MgO–SiO2 phases in MgO-based refractories involving the steelmaking process

Abstract

For MgO–C refractories used in the steelmaking process, identifying low-melting CaO–MgO–SiO2 phases is crucial because they accelerate the corrosion of the refractories. However, electron probe microanalysis, a conventional method for identifying such phases, is time-consuming. Herein, cathodoluminescence (CL) imaging is proposed for the rapid identification of low-melting CaO–MgO–SiO2 phases at the reaction interface between MgO-based refractory and steelmaking slag. Monticellite, merwinite, and melilite were identified as the low-melting phases, emitting green, red, and violet luminescence, respectively, in the CL images. Other mineral phases emitted luminescence whose colors differed from those of the low-melting phases (3CaO·2SiO2 and 2CaO·SiO2) or no luminescence (magnesiowüstite, MgO·Al2O3, Ca2Fe2O5, 3CaO·SiO2, MnS, and FeS). The CL images (area: 0.5 ×0.3 mm2) were obtained in 30 s. Therefore, CL imaging is effective for the rapid identification of mineral phases, which limit the service life of MgO–C refractories during steelmaking.