Analyse multi-elementaire rapide d'une coulee d'acier par spectrometrie d'emission induite par laser
Fast multi-element analysis of steel melts by laser-induced emission spectroscopy
The direct laser-based measurement of the composition of steel melts aims for the improvement of process and quality control in secondary metallurgy. This paper describes a novel approach which significantly enhances the performance of laser-based analysis and its application to ladle metallurgy. Laser-induced emission spectrometry (LIBS) uses the spectrally dispersed light emission of a plasma for the chemical analysis of solid and liquid materials. A collimated high-intensity laser beam, directed onto the material, produces the plasma. The interaction between the laser radiation of a Nd:YAG laser and the substrate (steel or steel melt) can be influenced in a definite manner by controlling the laser power output (laser modulation). Laser modulation enables plasma conditions to be created, which are advantageous in emission spectrometry. A comparison can then be made between the plasma conditions generated using laser modulation and those produced with standard laser parameters, in ord er to demonstrate the benefits of the laser modulation technique. It has been shown for the first time that the use of the laser modulation technique considerably improves the analytical performance of laser-induced emission spectrometry. Calibration curves have been determined for 15 elements. For solid samples, the detection limits range from 6 ppm (boron) to 300 ppm (nickel). Within 30 seconds, a laboratory demonstration was able to produce the results of a multi-element analysis of 15 elements. A lance was designed for the melt access which comprises the optical components for the beam guiding and assures a defined melt position at the measuring location.