According to GB/T 2585-2021 "Hot-rolled Rails for Railways", the regulations for 60kg/m heavy rails are as follows:
Dimensions and allowable deviations
Height: 176mm, allowable deviation is ±0.8mm.
Bottom width: 150mm, allowable deviation is ±1.0mm.
Head width: 73mm, allowable deviation is ±0.6mm.
Waist thickness: 20mm, allowable deviation is ±0.7mm.
Length and allowable deviation
Standard lengths are 12.5m and 25m, with an allowable deviation of ±20mm. For non-hole rails, the allowable deviation of length is ±10mm.
The fixed length and multiple length are determined by negotiation between the supply and demand parties and are indicated in the contract. The allowable deviation of length is + 40mm.
Appearance
Curvature: The curvature is not greater than 10mm within the full length of the rail, and not greater than 2mm within 1m of the end.
Twist: The rail shall not have obvious twist.
Weight
The theoretical weight is 60.76kg/m. The rails are delivered according to the actual weight or the theoretical weight. When delivered according to the theoretical weight, the nominal size for calculating the weight adopts the middle value of the dimensional tolerance.
Technical requirements
Chemical composition: C (carbon) content is 0.72% - 0.80%, Mn (manganese) content is 1.30% - 1.70%, Si (silicon) content is 0.50% - 0.80%, P (phosphorus) content is not more than 0.035%, S (sulfur) content is not more than 0.035%. Depending on the different steel grades, it may also contain alloy elements such as V (vanadium), Cr (chromium), Re (rare earth).
Mechanical properties: For different steel grades, the mechanical properties requirements are different. For example, the tensile strength of U75V steel grade is not less than 980MPa; the tensile strength of U77MnCr steel grade is not less than 980MPa, etc. Yield strength is not less than 440MPa, elongation is not less than 10%.
Hardness: The centerline hardness of the top surface of the rail head is 260-360HBW; the centerline hardness of the top surface of the heat-treated rail grade H rail head is 320-420HBW.
Surface quality: The surface of the rail should be smooth, without cracks, folds, scars, ears and other defects that affect use. The end surface of the rail should be flat and free of burrs.