Study On The Formation Conditions And Mode Of Sheave-like Bainite In High-carbon Silicon Steel

The structure characteristics of the products of bainitic transformation under austenitization at different temperatures in the Fe-0.88C-1.45Si-0.37Mn(wt. %) steel have been investigated by X-ray diffraction, optical microscope, transmission electron microscopy(TEM), and the calculation of the vacancy energy. The influence of austenitization temperature on characteristics of bainitic transformation curve has been studied, as well as the formation condition of sheave-like bainite. A kind of formation mode of sheave-like bainite has been put forward by vacancy migration.It was found that the bainitc transformation curve turned to lower left with increasing austenitizing temperature. For the experimental steel, bainite sheaves consists of lath ferrite and retained austenite were formed by bainitic transformation only after austenitization temperature from 880°C~950°C. The morphological characteristics of the sheave-like bainite were affected by the migration of vacancy combination and interstitial carbon atoms. When austenitizing at lower temperature near 880°C, bainite ferrite is likely to nucleate in such area where the solid solubility of carbon is low and develop into ferrite band with small length-diameter ratio. High-concentration vacancies caused by high austenitization temperature near 950°C made the face-centered cubic γ â†' body-centered cubic α embryo nucleus resulted from the migration of di-vacancies combination easily to form. However,The inhibitory effect that the interstitial carbon atoms had on the formation of face-centered cubic γ â†' body-centered cubic α embryo nucleus caused by the migration of di-vacancies combination was enhanced,which limited the bainite ferrite to nucleate in small area and develop into ferrite band with large length-diameter ratio.