This scientific paper presents the research on influence of austenitizing temperature on kinetics and evolution of the spheroidal plain cast

iron during eutectoid reaction in isothermal conditions. The cast iron has been austenitized in temperatures of 900, 960 or 1020°C. There

were two temperature values of isothermal holding taken into consideration: 760 or 820°C. The order of creation of reaction products and

their morphology have been analyzed. The particular attention has been paid to the initial stage of transformation. The qualitative research

has been executed using the transmission electron microscope (TEM), as well as quantitative research (LM). The influence of austenitizing

temperature has also been determined on transformation kinetics and structural composition. It was found that the increase of austenitizing

temperature is conductive to the initial release of structures by metastable system. A reduction of time was observed of the initial stage of

transformation at temperature close to Ar12 with its simultaneous elongation at temperature close to Ar11, with an increase of austenitizing

temperature. The dependences obtained by the metallographic method confirm the prior results of dilatometric research of eutectoid

reaction.