Comparability of Railway Rail Steels Low Cycle Fatigue Behaviour

Licentiatavhandling, 2011

Several different kinds of steel are used for railway rails. From simple pearlitic steels for rarely used tracks over premium pearlitic steels for high performance lines to special bainitic, martensitic and austenitic steels for switches and crossings. Most of these steels have been trial and error developed over time in track. The main reasons for replacement of rails are fatigue and wear. For material selection purposes fatigue properties must be taken into account. Simple fatigue testing methods that allow comparison of different steels are scarce in literature. In this thesis results from low cycle fatigue test of four different steels are compiled and a comparison based on strain energy density is presented. The steels are all used for railway rail application. One is near fully pearlitic steel which is mainly employed in common track. The other three are used for different parts in switches and crossings. It is one carbide free bainitic steel, one high manganese austenitic steel and a martensitic steel. Results show the martensitic and bainitic steel as the superior steels at low strain ranges (<0.4%). At high strain ranges the bainitc steel fails to perform due to crack sensitivity and the martensitic and the pearlitic steels are superior. The austenitic steel can not readily be compared to the other steels through low cycle fatigue tests because of its unique hardening property. The comparison of strain energy densities is a viable way to compare standard steels.