Abstract
The results related to oxidation of Fe and (Fe-C-Cr-Mn-Ni-Si) steels in ambient air at temperatures from 940 to 1100 °C for 180-910 min are reported in this paper. It is possible to describe the course of steel oxidation as well as Fe-oxidation by the use of parabolic law. The coefficients kp of the parabolic law depend in both cases, steels and Fe, on temperature T and, moreover, in the case of steels, on the chemical composition of the steels and on the phase transformations occurring in the steels in the course of oxidation anneal. The coefficients k_p(st) can be expressed by the coefficient k_p(γ Fe), concentrations Ni of the alloying elements in the steels and oxidation parameters α_oⁱ corresponding to the individual alloying elements. The results of the measurements of the growth of relative weight Δ w/w, length Δ L/L and diameter Δφ/φ are added to the results related to the measurements of the thickness l of the scale layers. These additive measurements show that the growth of the quantities which are proportional to the value l can be described by the parabolic law, as well. The rate of high temperature oxidation of steels is proportional to the carbon diffusivity D, which controls the rate of decarburization of steels oxidated at high temperatures in ambient air.

Key words
iron, steels, oxidation, ambient air, initial stage, high temperatures

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