ROŻNIATA Edyta AGH University of Science and Technology

Present work corresponds to the research on the kinetic of phase transformation of undercooled austenite and analysis of the microstructure, hardness of new hypoeutctoid steels with 0.3 % Mo. The kinetic of phase transformation of under cooled austenite of investigated alloy was presented on CCT diagrams (continuous cooling transformation). Also the methodology of a dilatometric samples preparation and the method of the critical points determination were described. The paper presents metallographic research, measurements of the average diameter of austenite grain as well as hardness measurements. The austenitising temperature was defined in a standard way i. e. 30°C ÷ 50°C higher than Ac3 temperature for hypoeutectoid steels. The technology of full annealing was proposed for the iron based alloy. The microstructure of the investigated material was examined by the light microscope Axiovert 200 MAT. The hardness measurements were performed with the Vickers HPO250 type, which imposes a force equal to 10 kG and 30 kG. The dilatometric measurements were performed with the L78R.I.T.A. dilatometer. The CCT diagrams were made on the grounds of dilatograms recorded for samples cooled with various rates.