Oxidation layer measurement by using visible and near infrared reflectance spectrum

High strength steels, which contain alloy elements like Si and Mn, are desired for automotive applications in order to develop lightweight cars with sufficient strength. In this case, oxidation layer monitoring and control on the steel surface is necessary to guarantee high surface wettability of those steels in galvanizing. Oxidation layer measurement using visible and near infrared reflectance spectrum is one of the promising techniques to accomplish the purpose due to high accuracy with sufficient robustness and reliability. This paper describes research results of oxidation layer measurement employing reflectance spectroscopy in visible and near infrared region. The simulation result considering the refractive indexes of FeO and pure iron is obtained. An experimental setup employing a halogen lamp, two delivery fibers, detection probe, and two spectrometers covering ultraviolet (UV) and visible (VIS) to near infrared (NIR) spectral regions is also fabricated in the laboratory. The experimental result shows a good agreement to the calculation. A proto-type system for on-line measurement was fabricated and its performance was tested in the pilot plant.