Volume 6, Issue 5 (May 2009)
Enhanced Hardenability through Application of Magnetic Fields
Even with the great improvements in new materials, the substitution of steels in most applications is not yet economically justifiable. Steels are the most important alloys utilized as structural materials and will certainly continue to be so in the next decades. The effects of the conventional heat treatments in changing the mechanical properties of steels are well known by now. However, the effects of magnetic fields on phase transformations have recently been considered and new perspectives of study and of applications are now being opened for steels. Magnetic fields lower the Gibbs free energy, and the transformation temperature of steels increases for an applied magnetic field. As a result, different properties and microstructures could be achieved after heat treatments due to magnetic field effect. The main objective of this work is to show a process to enhance the hardenability of steels through modifications in heat treatment. The chemical composition of the material studied is similar to AISI 52100 steel. The procedure consists of applying a magnetic field in the sample throughout or in different steps of the heat treatment. All the samples were heat treated at the same temperature and cooled at the same cooling rate. The results of the magnetic field applied in steel samples were compared to conventional heat treatments. A significant improvement in microhardness of the samples was measured after applying a magnetic field. A considerable rise in the hardenability and a modification in the Fe-C equilibrium diagram were also verified, as shown in the literature.