Inspection of the Defects of Steel by Using Laser Induced Breakdown Spectroscopy

Quick evaluation technique of the defects of steel materials by Laser-Induced Breakdown Spectroscopy (LIBS) was established. A Q-switched Nd-YAG laser with high pulse energy was used for laser breakdown, and the emission from breakdown plasma was transmitted and introduced into a spectrometer via optical fiber. A Paschen-Runge mounting type spectrometer was used for multi elemental analysis. As a result of measurement, LIBS could detect specific elements in defect parts due to alumina inclusions (Al) and contaminations from continuous casting mold flux (Al, Ca, Mg, Si, Na) as well as slag (Al, Ca, Mg), which caused surface defects. The proposed method made it possible to inspect the steel defects within 30 min including the sample preparation at the production site. Elemental mapping (C, Si, S) of central segregation of slabs was also shown. The results demonstrated the possibility of the fast mapping technique for the purpose of screening of the slabs.