1623. JOHANSSON, A., AND VON SETH, R., AND ELFSTROM, N. [Investigations on the Surface Decarburization of Steel.] Jernkontorets Ann., vol. 116, 1932, pp. 565-655; Chem. Abs., vol. 27, 1933, p. 3429.

Return to Abstracts of Literature 1500-1749

Literature Abstracts

Equilibrium isotherms have been determined for the systems 3Fe+2CO→Fe₃C+ CO₂ (1) and 3Fe+CH₄→Fe₃C+2H₂ (II) between 680° and 1,100°. The isotherm for (1) at 710° shows a decreasing CO₂ pressure with increasing C content, a result which is inconsistent with the assumption that C is insoluble in ferrite below the Ac₁ point. Above 900°, FeO cannot be reduced to metallic Fe free from C. At 680° the reaction proceeded too slowly for establishing equilibrium, but a mutual solubility of cementite and ferrite was indicated. From 900°-1,100° the activity coefficient of C was found to be nearly unity in cementite and Mn steels. By varying the CO₂:CO ratio in carburetted gas, either carburizing or decarburizing conditions may be established. At 1,250° and 1,320° the solubility of C in molten Fe was 4.4 and 4.56%, respectively. In (II) the rate of reaction was found to be a maximum at 950° but was noticeable at 600°, and falling again above 1,000°. Ni, Mn, W, and Cr steels gave about the same rate as unalloyed steel. No decarburization was found with N₂ and none with air at 750°, 710°, or 650°, probably because a protective oxide layer prevents diffusion of gas to the Fe surface. 26 refs.