Rapid in-situ analysis of liquid steel by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) denotes a technique where a pul sed laser beam is used to ablate small amounts of the target material. The characteristic optical emission line intensities of the excited species in the laser-generated plasma allow a quantitative chemical analysis of the ta rget material. LIBS is a fast, non-contact method allowing large working di stances between the sample under investigation and the detection system. Th ese properties make LIBS applicable to process control in metallurgy. We de scribe an apparatus designed for rapid in-situ analysis of solid and molten metals at variable distances of up to 1.5 m. A variable lens system allows compensation for varying positions of the liquid steel surface. The LIBS s ignal is guided by a fiber optic bundle of 12-m length to the spectrometer. Analysis of an element's concentration takes 7 s. Laboratory experiments u sing an induction furnace showed that the addition of admixtures to liquid steel results in rapid response of the system. Results including the in-sit u monitoring of Cr, Cu, Mn and Ni within certain concentration ranges are p resented (Cr: 0.11-13.8 wt.%; Cu: 0.044-0.54 wt.%; Mn: 1.38-2.5 wt.%; Ni: 0 .049-5.92 wt.%). (C) 2001 Elsevier Science BN. All rights reserved.