Short-time oxidation behavior of low-carbon, low-silicon steel in air at 850-1,180 °C -: I:: Oxidation kinetics

In this study, the oxidation kinetics of low-carbon, low-silicon steel in flowing air at 850-1,180 degrees C within 30 or 60 s were examined. The parabolic kinetics were established from the very early stage at 850 degrees and 1,000 degrees C, whereas the oxidation kinetics at 1,100-1,180 degrees C appeared to obey a linear law initially and a more-parabolic one at a later stage. When the oxidation kinetics followed the linear law, "rough"-scale with an undulating, saw-teeth like microstructure developed, whereas when the parabolic law was followed, smooth scale developed. It appeared that a critical scale thickness existed, at which the scale-growth mechanism changed from linear to parabolic. This thickness was less than 7 mu m at 850 degrees C, about 10 mu m at 1,000 degrees C, about 50 mu m at 1,100 degrees C and in the range of 60-80 mu m at 1,180 degrees C under the conditions examined. Blister formation at 900 degrees C prevented clear observation of the linear-to-parabolic transition.