1997 Volume 46 Issue 12 Pages 789-796
Type 430 stainless steels with 0.09 and 0.9 mass% Mn were heated to 1273 K with heating rates of 5, 33, and 50 Ks-1, and then oxidized in 1.67×104 Pa O2-balanced N2 for up to 300s, in which the total pressure was 1.013×105 Pa and the flow rate of the gas was 200cm3min-1. The effect of the heating-up rate on the oxide thickness, morphology, and crystal structure has been studied. When the temperature reached to 1273 K with 50Ks-1, an iron rich corundum type oxide with a thickness of 40 nm was formed for the steels with 0.09 and 0.9 mass% Mn. Contrary, the oxides with 5 and 33Ks-1 were composed of corundum type one rich in chromium and the thicknesses were two times thicker than that with 50Ks-1. Spinel type oxide was also formed for the steel with 0.9 mass% Mn with 5 and 33Ks-1. As the oxidation proceeds at 1273 K, the thicknesses of the oxides, surface composition, and crystalline structures became similar independent of the heating rates. The surface morphology and the amount of the spinel type oxide were, however, affected by the heating rate at relatively longer oxidation time.
