Rapid inspection of defects of steel by laser induced breakdown spectroscopy

A rapid and simple technique has been developed for inspection of defects of steel using laser induced breakdown spectroscopy (LIBS). Irradiation from a Q-switched Nd:YAG laser was focused onto the sample surface by a plano-convex lens with a spot diameter of about 1mm to ablate a portion of sample and generate a micro plasma. Emission from the plasma was transmitted by a fiber optics to a Paschen- Runge mounting polychrometer. Each sample was analyzed at two points, normal and defect parts and these two analytical results were compared with each other. Typical elements could be detected at defect part with significantly high intensities for different types of inclusion; Al for alumina, Al, Ca, Mg, Si, Na for mold flux and Al, Ca, Mg for slag. Therefore, type of non-metallic inclusion causing the defect could be attributed by LIBS. An evaluation time was within 30 minutes including sample preparation. The developed method was also applied to elemental mapping of central segregation of slabs.