The Effect of Time and Temperature Variations during Isothermal Annealing on the Mechanical Properties of High Carbon Bainitic Steel

Abstract

The industrial development require new materials characterized highest mechanical properties. The conditions of thermo-mechanical treatment proved to highest level of mechanical properties for steels. Another method of making strong materials is to reduce the scale of the microstructure using heat treatment [1]. The paper presents the results of investigation into the effect of time and temperature variations during isothermal annealing on the mechanical properties of high carbon (c.a. 0,8%C) bainitic steel. Chemical composition of that steel (addition Si, Mn, Mo and Cr) obtain high level of tensile strength and good plastic properties. The analyzing of published results of researches of high carbon bainitic steels shown, that transformation of bainite can take between 2 to 60 days within the temperature range 125÷325°C [2,3] Based on results of researches of investigated steel a isothermal annealing in temperature range 200÷300°C were done. The experiments were done for 24, 50 and 100 hours of annealing. After that the mechanical tests were done. A Zwick Z100 testing machine was used for tests. The force and elongation values were recorded. On their basis, the proof stress and tensile strength of the steel tested were determined as a function of annealing temperature. The microstructure were determinated too.