Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

We have realized industrial online monitoring of the molten alloys component by laser-induced breakdown spectroscopy. By this technology, main and trace elements of the molten alloys can be analyzed in realtime. A vacuum induction smelting furnace can smelt for alloy refining, and this is the most popular method for refining alloys.

Analysis of the molten material components during the course of industrial processes can effectively improve the production quality. LIBS has the advantages of fast and long-distance analysis. It is a good method to realize online ingredient analysis for industrial application.

Demonstrating the procedure will be Xin Li and Shenghai Zhao, a PhD student and a technician from my laboratory. To begin this procedure, analyze the standard samples and construct the calibration curve of the quantitative analysis as outlined in the text protocol. Then put the unknown sample into the smelting system.

Next open the laser generator and realize the pulsed laser output using a pulse width of 20 nanoseconds, a frequency of five hertz, and an energy of 90 millijoules for each pulse. Open the spectrometer and the spectrum deposit software, and determine the spectrum using a spectral range of 190 to 600 nanometers, a resolution of 0.06 nanometers at a wavelength of 200 nanometers, and an integration time of 10 milliseconds. After this, adjust the laser focusing position, and optimize it until the strongest spectrum signal is attained.

Determine the laser breakdown spectrum, taking note that each laser pulse generates a frame of the spectrum and that 20 frames of the spectrum are obtained and averaged for the analysis. Intensity of plasma spectral signal is an important factor to get good precision of quantitative analysis. In our experiments, the value of the highest peak should exceed 10, 000.

For spectrum pretreatment, perform background correction, such as deleting the background effect caused by breaking radiation, to perform spectrum fitting. Then perform analysis elemental concentration by the internal standard method from the calibration curve. In this study, 10 nickel-based alloy samples are used to construct internal standard calibration curves.

Nickel is the internal standard element, and the calibration curves for copper, titanium, molybdenum, aluminum, and chromium are shown here. The calibration curves all show a near-linear relationship between the concentration of the element and the peak intensity. All signal peaks are filtered by the signal intensity, the central wavelength, and the Lorentz fitting effect.

The limit of detection for each element is calculated according to the standard of International Union of Pure and Applied Chemistry. Experimental results have shown that this technology can be used on industrial vacuum melting production, and this major components of molten alloys can be quantitatively analyzed.