Analysis of C and S Trace Elements in Steel Using Orthogonal Preablation Dual-Pulse Laser Induced Breakdown Spectroscopy

The contents of nonmetallic elements such as C, S and P have an important influence on the hardness and strength of steel, so the detection the contents of these nonmetallic elements is critical task for the steel quality evaluation. In this paper, the C, S trace elements in steel are analyzed by using orthogonal preablation dual-pulse Laser induced breakdown spectroscopy (OP-DP-LIBS), and the spectral enhancements of C II 513.328 nm and S I 386.76 nm are observed as compared to SP-LIBS. The spectral intensity of C II 513.328 nm and S I 386.76 nm are increased with inter-pulse delay time and get maximum at delay time of 10 and 20 μs respectively, then decrease with inter-pulse delay time. Based on quantitative analysis of several trace elements in six alloy steel standard samples, correlation coefficient (R²) of C II 513.328 nm and S I 386.76 nm are all more than 0.9 and relative standard deviation (RSD) of two spectrum are all within 6%. The limit of detection (LOD) of C II 513.328 and S I 386.76 nm calculated are 209 and 7.32 ppm, respectively. It is demonstrated that detection precision and reliability can be enhanced by using OP-DP-LIBS, which means that nonmetal trace elements such as C and S in steel is become reality to detect within the range of 200–900 nm in air environment using OP-DP-LIBS technique.