Abstract
A kinetic study of the first stage graphitization in white cast irons containing chromium has been carried out based upon quantitative structural analysis. The results are as follows : (1) The dissolution of cementite is the main reaction in the first stage graphitization. (2) Additional element chromium retards the reaction of cementite dissolution with increasing chromium content in the specimens and prolongs annealing time. (3) The rate constant Kd of cementite dissolution decreases exponentially with the chromium concentration on the surface of dissolving cementite during graphitization. (4) The above results are explained in terms of the structure and bonds of cementite crystal. Namely a chromium atom forms a stronger bond than an iron atom and hence, when present in cementite, it makes cementite more stable.
