EXPERIMENTAL-STUDY OF THE AUSTENITIZATION PROCESS OF HYPEREUTECTOID STEEL ALLOYED WITH SMALL AMOUNTS OF SILICON, MANGANESE AND CHROMIUM, AND WITH AN INITIAL STRUCTURE OF GLOBULAR CEMENTITE IN A FERRITE MATRIX

The austenitization process was examined in steel containing 0.80 wt.% C, 2.02 wt.% Si, 2.06 wt.% Mn and 1.05 wt.% Cr by structure observations in the scanning electron microscope, and microanalytical measurements of structural phases. The initial structure of the material, consisting of globular cementite in a ferrite matrix, was obtained in two different ways, resulting in two types of initial structure. The kinetics of the alpha --> gamma-transformation in this steel is very slow. The kinetics and the morphology of the structure are significantly influenced by the type of initial structure, and in particular by the morphology of the ferrite grains. The origin of these effects is regarded as being the result of the specific influence of silicon on carbon activity in austenite, and of the redistribution of silicon and manganese at the alpha-gamma phase boundary during the alpha --> gamma-transformation.