Oxidation of Low-Carbon Steel in 17H2O-N2 at 900 °C

Abstract

The oxidation kinetics of two low-carbon steels in a flowing 17H 2 O-N 2 gas mixture at 900°C and the scale structures developed are examined. Similar linear and parabolic oxidation kinetics are observed for the two steels, although some differences are observed within the first 5 minutes of oxidation and in the linear-to-parabolic transition period. The oxidation behaviors observed in the linear kinetics stage are more consistent with published results, exhibiting typical surfacereaction-controlled patterns. However, the observed parabolic oxidation rates are two orders of magnitude smaller than those of iron and steel oxidation in air and oxygen as well as that predicted using Wagner's parabolic oxidation theory. Similar oxide scale structures are observed on the two steels for the samples oxidized for more than 15 minutes. The surfaces of the scales exhibit pyramidal, faceted grain structures with growth ledges developed on some crystal faces and growth pits at the peaks of the pyramidal grains. In their cross sections, the scales have a columnar structure and appear two layered, with a thin, outer magnetite layer and an inner, growing wustite layer. The wustite grains coarsen with increased oxidation time and develop a growth texture with preferred (111) and (110) orientations in parallel to the sample surface after oxidation for longer than 60 minutes. Conventional oxidation theories cannot provide a satisfactory explanation of the apparently conflicting results observed during the parabolic oxidation stage.

Numerical Simulation of Heat Transfer and Scale Formation in a Reheat Furnace

“…In Si‐containing steels fayalite may form as part of the scale, which is ignored in this study. According to previous experiments, the basic scale formation procedure can be divided into four steps: 1) the oxygen near the slab is initially adsorbed onto slabs, 2) chemical reactions occur at the surface to form a thin scale film with 1–10 μm oxide grains, 3) the thin film of scale continues growing, 4) a porous layer of scale is formed with 10–50 μm oxide grains on the surface.…”

Degradation of Mild Steel in Ethanol Burning Environment: Oxidation Kinetics and Microstructural Aspect

“…Similar discrepancies have been observed by Jha et al [14] during oxidation studies in low alloy steels oxidized in high pressure oxidative environments from 700 to 1000 °C for oxidation times 10−250 hours whereas for steel oxidized in ethanol the scatters was attributed to the breakaway oxidation observed in the second parabolic regime at 800 °C after oxidizing for 4 hours. Furthermore, the activation energy for low carbon steel (Fe-0.04C-0.2Mn-0.02Si) was found to be 274 kJ/mol in 10%CO2-90%N2 at temperature range of 950-1150 °C [8]. Lee et al [15] studied oxidation of low carbon steel (Fe−0.04C−0.015Mn−0.26Si) in 112% air−fuel (CH4) combustion gas at the temperature of 700−1200 °C.…”

A Comparative Study of the Oxidation Behavior of Hot-Rolled Steel established from Medium and Thin Slabs oxidized in 20% H2O-N2 at 600-900°C

“…In a static mode, the hydrogen dissolved in the oxide was formed by assuming that the partial pressures of the gases in the reactor were constant. The thermodynamic information of the oxidation reaction was calculated using the data compiled from [34,35] and the result is shown in Table II. Figure 4 shows the mass gain after being exposed to water vapor at 600-900 °C for 30, 60, and 90 min.…”