Industry knowledge
Material and performance requirements of national standard heavy rails
National standard heavy rails have high standards in material selection, mainly using high-quality carbon steel or low-alloy steel, and common steel grades are U71Mn, U75V, U78CrV, etc. These steels have good comprehensive mechanical properties and can cope with the continuous impact and wear on the rails caused by high-intensity and high-frequency trains.
Taking U71Mn steel as an example, its tensile strength requirement is not less than 880MPa, and its yield strength is not less than 785MPa. It has good ductility and toughness and is suitable for a variety of heavy-duty transportation environments. Steels such as U75V and U78CrV have added elements such as vanadium and chromium to their composition, which further improves the wear resistance and fatigue life of the rails, and are suitable for high-intensity and high-frequency coal transportation lines or heavy-duty freight lines.
In addition to material properties, national standard heavy rails also require strict control of metallurgical quality and dimensional tolerances during the manufacturing process. For example, the hardness distribution of the rail head must be uniform, and there must be no metallurgical defects such as cracks, shrinkage holes, and bubbles inside. To ensure quality, all heavy rail products must undergo multiple tests such as ultrasonic flaw detection, tensile testing, metallographic analysis, etc. before leaving the factory, in compliance with national standard technical specifications such as GB/T 11264.
At the project application level, the reasonable selection of rail material and model is of great significance for controlling later maintenance costs and extending the service life of the line. High-strength heavy rails combined with welded long rail technology and automated inspection systems have become an important means for modern railways to improve operating efficiency and safety levels.
