THE INFLUENCE OF HEAT TREATMENT ON MICROSTRUCTURE AND TRIBOLOGICAL PROPERTIES OF RESISTANCE BUTT WELDS MADE OF A CAST BAINITIC STEEL

摘要

This work deals with the influence of heat treatment on microstructure and tribological properties of specimen cast assigned as a material used for frogs in railway crossovers. Materials used nowadays in the railway industry for frogs: Hadfield cast steel (GX120Mn13) and forged pearlitic steel (R260) do not fulfil strict conditions of exploitation and speed that should be reached on railway as indicated in the UIC Decision No. 1692/96. One of the possible solutions is using cast steel with bainitic or bainitic-martensitic microstructure, which allows to gain high strength properties (R_m = 1400 MPa, R_(p0,2) = 900 MPa and up to 400 BHN). The test material is an alternative to railway frogs made of Hadfield cast steel. It remains problematic to determine the properties at the weld of the frog with the rail, which can also have bainitic microstructure. To ensure similar wear in both the resistance joint and the base material the resistance butt joint should have almost the same mechanical and tribological properties as the base metal. The main objective of the present work is to study the influence of heat treatment on microstructure and tribological properties of resistance welds made of bainitic cast steel used for frogs in railway crossovers.