Latent heats of phase transformations in iron and steels

The latent heat and the temperature of phase transformations in iron and steel have been measured by differential scanning calorimetry (DSC). The samples were provided in the form of cylinders 3 mm in diameter and 3 mm long. The tests on the DSC apparatus were conducted with a heating process to 1000 °C at a constant rate of 5 °C min - 1 and with a cooling process to 300 °C at the same rate. The latent heat of A 3 transformation of iron on heating was 16 kJ kg - 1 and on cooling 19 kJ kg - 1 . The relationship between the temperature of phase transformation and the carbon content of the steel was examined and made clear. For carbon steel, the latent heat on heating and cooling approximately correlated with the carbon content.