Abstract
High temperature oxidation tests of rimmed and killed steels have been carried out in the CO2-CO, air, 3%O2, 300 ppm O2 and CO gas atomospheres in the temperature range from 350 to 530°C under the pressurized condition up to 42 kg/cm2. The oxide scales formed have been analized by mean of a scanning electron microscopy, X-ray diffraction, EPMA and measurements of electric resistance and porosity. The results obtained are summarized as follows:
(1) Oxidation resistance of the killed SS41 steel is superior to the rimmed SS41 steel in the all tested atmospheres.
(2) The above described tendency is remarkable especially in the cases of 3% O2 and CO2-CO atmosphere. It is considered that the former is due to the electro-chemical effect of Si in Fe2O3 and the latter the suppression of Boudouard's reaction (2CO→CO2+C) by Si at the interface of scale/matrix.
(3) It is possible that the excrescences appear in CO or CO2 gas, but the excrescences don't appear in the oxygen only atmosphere.
(4) It is considered from the results of EPMA and electrical resistivity measurement that Si doesn't exist at the scale/matrix interface as a layer of SiO2.
