167.    BAUKLOH, W., SCHULTE, F., AND FRIEDERICHS, H.   [Decarburizing Annealing of Plain and Alloyed Malleable Cast Iron in Carbon Monoxide-Carbon Dioxide Mixtures.]  Arch. Eisenhüttenw., vol. 16, 1943, pp. 341-354; Chem. Abs., vol. 37, 1943, p. 6619.

                  Effects of wall thickness, duration of annealing, temperature, gas composition, and contents in the casting of Mn, Ni, Cr, V, Mo, and S on decarburization velocity were investigated on white-cast Fe in CO-CO₂ mixtures at 950°-1050°.  The diffusion constant for C in Fe was determined.  The decarburization velocity increases with increasing temperature and decreases with time approximately hyperbolically.  The gasification of C takes place virtually only at the surface of the specimen.  The velocity of diffusion of C from the interior to the edges determines the decarburization velocity.  The quantity of C gasified in unit time does not increase proportionally with the original C content in hypoeutectoid white-cast Fe, as it does in steel.  For short annealing times, the primary cementite inclusions seem to decrease the diffusion velocity and thus, the decarburization velocity, but for longer annealing times this is hardly noticeable.  Low contents of Mn, Ni, Cr, and V have hardly any effect on decarburization velocity.  Mo at 1050° increases decarburization velocity.  S seems to hinder decarburization.  The highest decarburization velocity is obtained, for low-flow velocity, with a gas mixture of about 28% of CO₂ and 72% CO.  CO₂ contents above 28% at 1050° cause scaling of the Fe and decrease of decarburization velocity.  The results obtained with pure CO-CO₂ mixtures can be applied also to the tempering in N₂-containing CO-CO₂ mixtures.