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Steel Scrap Oxidation Acceleration by Surface Impregnation Techniques.
U S Pat 3 620 715 1971 Nov; :
Steel scrap oxidation is accelerated in a reduction-roast operation in which the scrap is used to convert low-grade iron ore to fe3o4. e.g., steel strips cut from new, unpainted low-carbon, deep drawing steel fender skirts and hoods were immersed for various periods of time in a 10 pct aqueous solution of navo3.H2o. The strips were removed and oxidized at 900 deg. C with a co2-15 pct CO gas mixture. The progress of oxidation was followed with time by recording the weight gain in the oxidizable sample. The degree of oxidation was calculated on the basis of the original scrap weight prior tothe vanadate bath and on the assumption that o2 uptake would continue until the fe content of the sample was transformed to fe3o4. Oxidation data for steel strips pickled in the vanadate solution for periods of 10 s, 6 h, and 72 h were taken. Best results were obtained for shorter pickling times and the degree of oxidation in the 1st 10 min was increased by approximately 8-fold for samples pickled for only 10 s. It is suggested that surface impregnation with an accelerator, during subsequent high-temperature oxidation, forms low-melting eutectics among the oxide scales on the surface which allows rapid atomic or ionic diffusion through the oxide layer for sustenance of the oxidation reaction.
U.S. Pat. 3,620,715; Nov. 16, 1971; Chem. Abstr. 76:48,838A
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division