Present Status of Microstructural Characterization of Steel by Analytical Methods

Abstract

A review on recent microstructural characterization of iron and steel by analytical methods is described. The bulk chemical composition of iron and steel is determined by chemical analytical methods in production lines so as to obtain their target properties or microstructures. These analytical methods enable a reliable and reproducible composition to be rapidly determined. On the other hand, microscopic analyses for a thin layer or small area are also important, since steel products demonstrate a heterogeneous microscopic chemical composition, which affects their properties. For instance, glow discharge optical emission spectrometry (GD-OES), which is a plasma spectrometric and microscopic method, rapidly provides quantitative depth profiles of thin layers such as coatings formed on the surface of iron and steel. In this paper, several examples analyzed by GD-OES are demonstrated together with the advantages of such analyses. Besides GD-OES, other microscopic analytical methods are applied for elucidating the mechanism of microscopic phenomena in steel products. Electron spectroscopy, mass spectrometry, electron microscopy and other methods are microscopic analytical methods, but it takes a long time to prepare and measure samples using these methods. In addition, in spite of the usefulness of these microscopic analytical methods, it may be difficult to quantitatively compare results analyzed by these methods with each other. This is because steel products are generally composed of various microstructures, and therefore the results differ from one analyzed area to another one. The present paper reviews the present status of not only the usefulness of a microscopic analysis such as GD-OES but also the meaning of the microscopically analyzed results.