Determination of calcium in steels by emission spectrometry with a high energy pre-discharge

Determination of calcium in steels by conventional emission spectrometry is difficult. This is because calcium is present in complex oxides such as CaO·SiO2·Al2O3 or complex sulfide-oxides in which the complex oxides are surrounded by sulfides, (Fe, Mn)S, and during the measurement preferential discharge occurs at these inclusions. Thus, the data obtained by conventional emission spectrometry are always different from those determined by chemical analysis. In the present investigation, (a) short time-high energy discharges or (b) long time-low energy discharges were applied to the sample surface of the steels before the conventional spectroscopic measurements with low energy discharge. Both pretreatments were effective to disperse homogeneously the oxide and sulfide-oxide inclusions in the matrices, thus giving reliable analytical data. It was demonstrated that the spectroscopy with pretreatment of short time-high energy discharge was superior to that with pretreatment long time-low energy discharges in both rapidity and accuracy.