Rails (from the plural English.rails — from lat.regula — direct stick, are invented by ancient Romans, initial width between them made 143,5 cm) — the steel beams of special section stacked on cross ties or other support for formation, as a rule, of double-stranded way on which the rolling stock of railway transport, city railways, specialized structure in mines, pits, the crane equipment moves.
Rails serve for the direction of wheels at their movement, directly perceive and is elastic transfer pressure from wheels to underlying elements of upper structure of way. On sites with electric draft rails serve as conductors of the reverse power current, and on sites with automatic lock-out — conductors of signal current.
Rails for railway transport are made of carbonaceous steel. Quality of rail steel is defined by its chemical composition, microstructure and macrostructure.
Carbon increases the hardness and wear resistance of steel. However the high content of carbon, with other things being equal, does steel brittle, the chemical composition at increase of content of carbon has to be maintained more rigidly, especially concerning harmful impurity. Manganese increases hardness, wear resistance and viscosity became. Silicon increases the hardness and wear resistance. Arsenic increases the hardness and wear resistance of steel, but in large numbers reduces impact strength. Vanadium, titanium, zirconium — the microalloying additives, improve structure and quality of steel.
Phosphorus and sulfur are the harmful impurity giving fragility of steel. The high content of phosphorus does rails hladnolomky, high content of sulfur — hot-brittle (cracks when rolling are formed).
The microstructure of rail steel represents lamellar perlite with ferrite streaks on borders of perlitovy grains. Hardness, resistance to wear and viscosity is reached by giving of steel of homogeneous sorbitny structure by means of heat treatment by surface (on 8 — 10 mm) tempering of head or volume tempering of rail. Objyomnozakalenny rails have the increased wear resistance and durability. The macrostructure of rail steel has to be fine-grained, homogeneous, without emptiness, not uniformity and foreign inclusions.
Classification of railway rails
In Russia production of the railway rails intended for link and jointless way of the railroads and for production of railroad switches is regulated by GOST P 51685-2000.
Rails railway subdivide:
- on types:
- P65K (for outside threads of curve sites of way);
- on categories of quality:
- In — the rails thermostrengthened the superior quality;
- T1, T2 — the rails heat-strenghtened;
- N — the rails which are not heat-strenghtened;
- on availability of bolt openings:
- with openings on both ends;
- without openings;
- on way of smelting became:
- M — from martin steel,
- To — from converter steel;
- E — from Elektrostal;
- by the form initial preparations:
- from ingots;
- from the continuous and cast preparations (CCP);
- on way of protivoflokenny processing:
- from the vacuumized steel;
- passed controlled cooling;
- passed isothermal endurance.