Abstract
Effects of isothermal heating temperature and holding time on carbide precipitations of cold-rolled 13% Mn Hadfield steels, which had three kinds of carbon content 1.2%, 0.9%, and 0.65% were studied by micrography. In addition, effects of the cold-working ratio on carbide precipitations in heating process of both elongated and hammered Hadfield steels were studied by thermal dilatometry.
By cold working, isothermal carbide precipitations of steels were started quickly at all precipitation temperature ranges. When steels were heated isothermally at about 500° firstly the carbide films were formed at a slip plane and on grain boundary in steels, and gradually they were grown up to the shape of platelet carbides. As the holding time increases, pearlitic constituents were nucleated at around the platelet carbide and the grain boundary carbide in steels, and gradually they were grown up to the shape of nodular forms. Recrystallized grains were nucleated in deformed austenite grains at carbide precipitation temperature. Therefore, the recrystallized grains were coexistent with the precipitates in steels. With heavy-worked steels, the precipitation of carbides in heating process were started at a lower temperature than in the case of light-worked or none-worked steels, and the more the working ratio was increased, the more the precipitates was increased. But, the severely worked standard Hadfield steels apparently did not precipitate the carbide at temperature below 350° in continuous heating process.
