Bulk analysis of steel samples with surface scale layers by enhanced laser ablation and LIBS analysis of C, P, S, Al, Cr, Cu, Mn and Mo

Abstract

To control the steel composition during production in steel works, samples are taken from the melt. After solidification, the samples exhibit scale layers of ∼0.1–1 mm thickness. At present, for analysis of the bulk composition, e.g. by optical emission spectrometry using arc/spark excitation, the scale layer is removed by grinding or milling and afterwards the prepared sample is measured. In this study we use multi-pulse bursts of a Nd∶YAG laser at 1064 nm wavelength to ablate the scale layer of low-alloy steel samples locally in a first step, and the bulk material is analysed in a second step by laser-induced breakdown spectrometry (LIBS). With a LIBS set-up including a Paschen-Runge spectrometer, detection limits below 10 µg g⁻¹ are determined for elements such as C, P, S, Al, Cr, Cu, Mn and Mo. Production control samples with one original scale side and one ground side are analysed on both sides and the analytical results are compared. The values correlate with a coefficient of determination greater than 0.99 averaged over the observed elements.