Applicability of Time-Gated Raman Spectroscopy in the Characterisation of Calcium-Aluminate Inclusions

Abstract

Calcium aluminate (CaO–Al₂O₃) phases play a critical role in the study of non-metallic inclusions in aluminium killed, and calcium treated steels. In this study, the Raman spectroscopy technique, a versatile and non-destructive approach, was used to characterise binary calcium aluminate phases qualitatively and quantitatively. Calcium aluminate samples with varying CaO/Al₂O₃ ratios were synthesised to produce a binary phase samples mixture of C12A7–C3A and C12A7–CA. Quantitative estimation was based on plotting a linear regression calibration model between the ratio of Raman band intensities and the phase fraction in the samples. With the linear regression, the phase fraction of C12A7–C3A and C12A7–CA was estimated with average absolute errors of 2.97 and 2.55 percentage points. This work demonstrates the potential suitability of using Raman spectroscopy technique for evaluating whether calcium aluminate phases in oxide inclusions fall within the liquidus region at steelmaking temperatures.