INFLUENCE OF CHUNKY GRAPHITE ON LATENT HEAT

摘要

The study presents the results of investigations of the thermal effects that take place during the heating and cooling of samples of the spheroidal graphite cast iron with different amounts of chunky graphite (CHG) in the microstructure. In order to obtain a different amount of CHG, cone blocks Phi 300 mm x 350 mm were casted. Two different test melts, EN-GJS-400-18 with 0.7 % of the mass fraction of Ni and EN-GJS-400-15 with 3.5 % of the mass fraction of Si were used. From each block three samples, with different cooling rates, were prepared. For studies of phase transformations, the technique of differential scanning calorimetry (DSC) was used. The microstructure was examined before and after DSC by optical microscopy. The obtained values of the enthalpy of melting and solidification differ and depend on the initial microstructure of the examined samples. The remelting of samples results in magnesium oxidation and significant changes in the eutectic morphology, which, at room temperature, consists of fine and/or coarse undercooled types of graphite with a lamellar morphology.