Micro-alloying of Rare Earths in Heavy Rail Steel

In the present study, heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects of Rare earths (RE) on microstructure and mechanical properties of heavy rail steel were systematically investigated by metallographic microscope, SEM, integrated mechanical testing machine, impact tester and so on. Metallographic analysis shows that, a few of RE can evidently delay the growth of austenite grain and fine pearlite. When the RE content is 0.016%, both annealing and normalizing pearlite laminae distances reach the minimum which is 115 nm (annealing) and 104nm (normalizing), respectively. But when the RE content reaches 0.133%, the annealing and normalizing pearlite laminae distance is respectively increased by 40% and 13%. Mechanical properties tests show that, a few of RE has not notable effect on the strength, but both plasticity and ductility can be improved obviously. When the RE content is 0.016%, both plasticity and ductility reach maximum. The maximum of elongation and reduction of area is 13.3% and 29.0%, respectively. However, when the RE content reaches 0.133%, the strength, plasticity and ductility are decreased. Especially, the low temperature (-40 ℃) and room temperature (20 ℃) ballistic work is respectively decreased by 9% and 24.8%.