According to the latest GB standard GB/T 2585-2021 "Hot-rolled Rails for Railways", the relevant regulations for 75kg/m heavy rails are as follows:
Dimensions: height 192mm (±0.9mm), bottom width 150mm (±1.0mm), head width 75mm (±0.6mm), waist thickness 25mm (±0.7mm).
Length: standard length 12.5m, 25m, allowable deviation ±20mm (±10mm for holeless rail), allowable deviation + 40mm for fixed length and multiple length.
Appearance: full length bending deflection is not more than 10mm, end is not more than 2mm within 1m, no obvious torsion.
Weight: theoretical weight 74.41kg/m, can be delivered according to actual or theoretical weight.
Technical requirements: Chemical composition C is 0.72% - 0.82%, etc.; mechanical properties such as tensile strength of ordinary rails is not less than 980MPa, etc.; rail head hardness is 260 - 360HBW (heat-treated rails 320 - 420HBW); the surface should be smooth and have relevant quality and other performance requirements.