The Role of Retained Austenite in the Structure of Carbide-Free Bainite of Construction Steels

The paper discusses the influence of retained austenite formed in a structure after the phase transition in the bainitic temperature range on the properties of structural low-alloy steels. It is shown that the bainite transformation proceeds through two stages. The first stage is characterized by the formation of completely carbide-free bainite containing up to 45% retained austenite, which is stable under deep cooling. The second stage develops with increasing holding time and is accompanied by the release of carbides and a reduction in the amount of retained austenite. The mechanical properties of steels are given in terms of the morphology and chemical composition of the phases forming in the course of isothermal transformation in the bainitic temperature range.