Abstract
	This paper is concerned with heat treatment of rails. Increasing axial forces acting on rails have become a fact, to which the rail manufacturers have to adapt.  Fundamental parameters of rail steel life (wear resistance, resistance to contact failures and low-temperature brittle fracture) are related to basic strength and plasticity properties (yield strength, ultimate strength, elongation, reduction of area). These properties are influenced by microstructural parameters of pearlite: namely the pearlite colony size, interlamellar spacing and cementite volume fraction. It is possible to modify these either by changing the chemical composition of the steel or by heat treatment of the rail head. Both the metallurgical and technological aspects of the issue are discussed here. The practically-focused section of the paper provides description of a laboratory experiment involving measurements of cooling curves for two cooling equipment configurations. 11 thermocouples inserted in drilled holes were used for measuring temperatures across the rail cross section. The holes were cut with a water jet. A thermal imaging camera was used for collecting images accompanying the measurements.  The measured cooling curves were incorporated into the CCT diagram. For this superposition to be done, the temperature of the onset of transformation to pearlite (Tps) had to be established for each cooling curve. The criterion for finding the Tps temperature was a deviation of the cooling curve from the expected exponential trend of more than 0.5%. Results of previous experiments were used for estimating the resulting hardness of a rail upon such treatment. Using a tangential fan made it possible to increase the hardness of the rail head by 30 HV at the least. However, this was accompanied by an undesired increase in the hardness of the rail flange.