Selection of Spectral Variables in Multivariate Calibration of C, Mn, Si, Cr, Ni, and Cu Concentrations in Low-Alloy Steels by Laser-Induced Breakdown Spectroscopy

摘要

Multivariate models for calibration of C, Mn, Si, Cr, Ni, and Cu concentrations from low-resolution emission spectra (190-440 nm, resolution 0.4 nm, spectral step 0.1 nm) by the least-squares method were developed in sets containing from 31 to 39 reference samples of low-alloy steels. Three methods of selection of spectral variables are considered, namely, method of ranking spectral variables by their correlation coefficient with the sought parameter, a successive projection algorithm, and an original modification of the method of searching combination moving window. The partial least-squares model with selection of spectral variables by searching combination moving window for C is quantitative (root-mean-square deviation 0.004, residual deviation in the test sample 23.4 in the concentration range from 0.13 to 0.43). The concentration calibrations are also quantitative for Mn (0.04 and 5.2 in the range of 0.47-1.15), Si (0.003 and 20.7 in the range of 0.15-0.33), Cr (0.04 and 3.1 in the range of 0.09-0.43), and Ni (0.01 and 4.8 in the range of 0.05-0.25). The calibration for Cu in the concentration range of 0.06-0.26 is qualitative (0.04 and 1.4).