The degree of non-equilibrium microstructure of hardened steel samples taken during its melting in an electric arc furnace

Austenite to ferrite and pearlite transformation has not been studied enough for low-carbon peritectic steels. Experiments were carried out in the electric arc furnace. Samples of the liquid metal were taken during smelting; three sample at melting, oxidation and reduction as well as one sample from the bucket were taken. The optical binocular microscope Axio Imagez A2m (production of the German company Zeis AG) was used to analyze the samples for the chemical composition of the elements and for the microstructure(ferrite and pearlite amount). It makes it possible to determine ferrite-to-pearlite relation in steel by means of the special program Thixomet Pro. Experimental percentage of ferrite was compared with the equilibrium percentage of ferrite calculated from the carbon content in the sample from the Fe-C phase diagram. It has been found that during charge melting experimental ferrite content is 0,52-1,7 equilibrium ferrite content. During the recovery period the microstructural heterogeneity stabilizes and is equal to 0,91-0,93 equilibrium heterogeneity. This ratio is in good agreement with the data available in literature. The amount of rejected finished metal as function of the tem-perature of the melt at the outlet of the furnace has been determined as well. The amount of rejected steel is minimum if steel is 1,052-1,07 times overheated above the liquidus point which is equal to the temperature of equilibrium microheterogeneity of the molten metal