The role of microalloying and copper additions on the microstructure and mechanical properties of eutectoid rail steels

The role of microalloying elements and of copper additions on the mechanical properties of two series of experimental eutectoid rail steels have been studies. It is found that microalloying and copper additions can result in significant improvements to the strength levels in the as-rolled and normalized conditions as compared with plain carbon pearlitic rail steel. These steels are fully pearlitic, and the microalloying elements result in microstructural refinement and carbide precipitation in the pearlitic ferrite which contributes to an increased strength level. It has also been discovered recently that the copper can precipitate in both the ferrite and the cementite phases of the pearlite during decomposition of the austenite. These forms of precipitation are significant in steels with high carbon levels because of the large volume fraction of pearlite and pearlitic cementite present in the microstructure. The fine dispersion of copper particles in both lamellar phases of the pearlite can result in strengthening without a corresponding reduction in tensile ductility and toughness values. (author)