The authors have made continuous cooling diagrams for the transformation of supercooled austenite used in the rail steel K76V that contains 0,026 and 0,092 % of chromium. They have determined the through-hardening capability of the steel and carried out the thermometering of end-quenched bars. The research has revealed the peculiarities of microstructure and how the cooling rate, temperature of heating and the content of chromium in the steel affect microstructure and hardness. It has established the rates of cooling that enable to obtain homogenous pearlite microstructure and determined the limit hardness of that structure.