Effects of Austenitization, Cooling Path, and The Divorced Eutectoid Transformation on Spheroidization of 52100 Steel

摘要

Spheroidizing heat treatments of hypereutectoid steels typically involve a hold in the austenite plus carbide phase field, followed by controlled cooling into the ferrite plus carbide phase field. Specifics of the thermal processing path determine the relative effects of carbide dissolution and particle ripening during both heating and the isothermal hold, and reprecipitation and nucleation of cementite during cooling. To better understand how these factors affect spheroidization, fully-pearlitic 52100 steel samples were annealed at 825 and 860 deg C for 15 minutes followed by a controlled cooling along paths that extended down in temperature through the eutectoid. Variations in cementite shape and size were monitored using SEM The nature of the eutectoid transformation associated with a given spheroidization heat treatment processing path was defined by its resulting cementite morphology and particle number density.