Abstract
	The fundamental parameters of rail steel life (wear and contact failure resistance, resistance to low temperature fracture) are related with the basic strength and plasticity-related values (yield strength, tensile strength, elongation and reduction of area). These properties are affected by the pearlite microstructure parameters, including, above all, the pearlite colony size the interlamellar spacing and the volume fraction of cementite. A thermo-plastic finite-element model is applied to the problem of designing strong quench schedules for production of head-hardened pearlitic rail. Computed temperature-time histories are compared with transformation diagram of 900B rail steel, to show how the schedule of cooling must be tailored to the steel’s transformation characteristic, in order to have the possibility of producing fine pearlitic microstructure in a layer near the rail head running surfaces. One of the examined properties is hardness – and its gradient across the head cross section. Considering this parameter, we achieved surprisingly good results. According to the computer simulation, the hardness value found 20 mm below the surface was only 4 HV lower, which still meets the requirements of the standards. The computer simulation revealed a technological problem related to edges of the rail head. These cool markedly faster than the rest of the rail due to heat dissipation to two surfaces. Upon relative comparison, we estimate that the hardness of heat treated rails shall be 320 HV.