Tetragonal Structure of Carbon Steel

IT has been shown by Westgren, Vewer, and many others that the martensite of carbon steel has only the crystal structure of α iron, and sometimes has simultaneous structures of α and γ iron with carbon in the state of solid solution. Recently Fink and Campbell (Transactions of the American Society of Steel Treating, 9, 717; 1926) found the body-centred tetragonal structure with a ratio of axes 1.06 in carbon steel (1.5 per cent. carbon) after quenching in water from 940° C. Our investigations of carbon steel quenching in water show also the body-centred tetragonal structure. The following table gives the carbon content, the temperature of quenching T, the ratio of axes c = a/b, and their dimensions a and b: