Rapid quantitative analysis of fayalite and silica formed during decarburization of electrical steel

Subscales on surfaces are affected by the temperature and oxidation potential during decarburization annealing of electrical steel containing 3 wt% silicon. Knowledge of the structural and chemical properties of the surface oxide layer subscales permits the control of high-temperature oxidation processes in the electrical steel. In the present work, the oxide layers were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry, and glow discharge optical emission spectrometry (GD-OES). The main oxide compounds formed within the subscales during decarburization annealing of the electrical steel were fayalite (Fe2SiO4) and silica (SiO2). The fayalite and silica contents were quantitatively determined by wet analysis via the galvanostatic electrolysis method, and these oxide content measurements were compared with the fayalite content determined by FTIR spectrometry and the silica determined by GD-OES. The results determined by rapid methods and wet analysis showed good agreement. The present findings show that FTIR spectrometry and GD-OES measurements may be used for the rapid quantitative analysis of fayalite and silica in surface oxide layers during the manufacture of electrical steel. Copyright (C) 2011 John Wiley & Sons, Ltd.