Analysis of the influence of the cooling rate on the hardness of steel for railway rails of the pearlite and bainetic classes

Abstract

The process of operating vehicles determines the interaction between the wheel and the rail. Traffic safety and the main technical and economic indicators of track manage-ment and rolling stock largely depend on the parameters of this process. The result is the effect arising from the rolling friction and especially from the friction of the wheel sliding on the rail during braking, relative to these changes there is a significant increase in the intensity of wear of the wheels of the rolling stock, which, in turn, can lead to catastro-phic results for the locomotive industry. Also, in the process of operation of the rail in most cases, defects are formed that have the character of a complicated state: its head is subject to wear, crumpling, cracking and buckling, contact fatigue damage can develop in the metal. In pearlite steels, the wear resistance is provided by the high carbon content and the small distance between the pearlite plates (achieved by the hardening process of the rail head), both of which increase hardness. Based on research in recent years, it is known that the strength of pearlite rail steels has reached its limit. In addition, a further increase in the carbon content will affect the impact strength and weldability of rail ma-terials. Therefore, there is an urgent need for other alternative materials. Bainite steel, which provides both high strength and excellent plasticity, is considered one of the most promising directions. It was established that the structure of the test steel at a cooling rate of 0.2˚С/s to 0.52˚С/s has a bainite structure with a small amount of martensite and residual austenite; with an increased cooling rate from 1.3˚C/s - martensite structure with residual austenite.