On the Decarburization of Iron and Steel (4th Report). The Relation between Rate of Gas Extraction and Diffusion Constant of Carbon in Iron

Abstract

The rate of gas extraction was measured by, (i) reservoir method and (ii) differential Pirani method. The diffusion constant of carbon was calculated from the rate of gas extraction as the solution of Ficks equation, provided that the boundary conditions of the equation were as follows: (a) the diffusion constant is independent of its concentration, (b) initial concentration is uniform everywhere in iron, and (c) the concentration of surface is always zero at t=0, As the diffusion constant obtained from gas extraction was always much smaller than that of carbon, the rate of reaction on surface was considered in place of the assumption (c), and represented the rate as: \[k=A[C]e^−Q⁄RT\]
The result obtained was satisfactory and the rates of reaction were represented as: 2 & K_α=7.4 ×I_o^27e^-48500/RT[C] &  & molecules/cm^2 ·sec,
& K_γ=7.4 ×I_o^27e^-52400/RT[C] && molecules/cm^2 ·sec.