Enhanced Carburization of Iron by CH₄-containing Gas at 1573 K

摘要

The carburization rate of iron by N_(2)-11 vol% CH_(4) gas was investigated at 1573 K employing an induction furnace in order to minimize the pre-decomposition of methane. Unlike the carburization of iron by CO or CO+H_(2) gases, the carburization rate of iron by CH_(4)-containing gas was controlled not by chemical reaction at the surface, but by diffusion of carbon in the liquid phase of Fe–C. The carburization rate by CH_(4) was about 30 times faster than that by 50 vol% CO. The effects of H_(2) addition and change in CH_(4) concentration supported that the chemical reaction do not control the total carburization rate. The formation of graphite rods confirmed that the surface had a very high carbon concentration and the chemical reaction rate is sufficiently fast. Numerical simulation of the carbon diffusion in the spherical iron estimated the diffusivity of carbon () in liquid iron at 1573 K to be 3 × 10~(–9) m~(2)/s. In addition, the moving mechanism of liquid/solid interface was schematically proposed.