Rail steel grades
Materials used in the construction of railroad lines
Due to the strategy adopted for the development of high-speed railroads, the topic of materials used for railroad rails and turnouts is still topical. Steel that exhibits adequate resistance to frictional and fatigue wear is used for the production of rail, block and needle sections, which are a major part of the railroad infrastructure. Properly selected material for these components ensures long service life and safety of rail transportation.
Tracks and turnouts are built from rail, needle and block sections with the appropriate dimensions shown in Table 1. These products must meet the high requirements for the mechanical properties of the steels from which they will be produced, as well as the appropriate shape and continuity of the material structure throughout. These components are exposed to high dynamic and impact loads from the wheels of rail vehicles. In the construction of railroad turnouts, KL49 and Kl60 block sections produced by hot rolling are the most commonly used.
These parts of railroad infrastructure are subject to surface layer destruction, which leads to changes in the dimensions and shape of the contacting rolling surfaces of the rail-wheel system. Due to the requirements for high mechanical properties, rail sections are mainly produced from high-carbon steels, characterized by high strength and hardness, high resistance to abrasion and fracture, and low ductility.
According to the European standard PN-EN 13674, 5 grades of steel in the raw state after rolling (R200, R220, R260, R260Mn and R320Cr) and 2 grades of steel after heat treatment (R350HT and R350LHT) are used for rail construction. The steels differ in chemical composition, which alters the strength and plastic properties, while heat treatment increases tensile strength (>1175MPa) and hardness of about 390HB and provides high wear resistance. Of the aforementioned grades, R260 and R350HT steels are the most commonly used for any type of section.
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