Material Differences between National Standard and Foreign Standard Rails
- What are the common materials for national standard rails?
Common materials for national standard rails are U71Mn, U75V, etc. U71Mn has a carbon content of about 0.65%-0.76% and a manganese content of 1.10%-1.50%, with good strength and toughness, widely used in ordinary railways. U75V has a carbon content of 0.70%-0.80% and a vanadium content of 0.04%-0.12%. Through micro-alloying, its strength and wear resistance are improved, suitable for heavy-haul railways and some high-speed railways. Its chemical composition must be strictly controlled, such as phosphorus content ≤0.030% and sulfur content ≤0.030% to ensure stable performance.
- What are the characteristics of typical materials for foreign standard rails?
European standard UIC rails commonly use S355JR material, with a yield strength of ≥355MPa and a carbon content of ≤0.22%, having good weldability, suitable for the European railway network. American standard AREMA rails have materials such as AAR M102 Grade 115, with a tensile strength of ≥790MPa, emphasizing fatigue resistance. By optimizing the alloy ratio, it adapts to the complex railway operating environment in the United States, such as large axle loads and long-distance transportation.
- How do material differences affect the strength of rails?
The tensile strength of national standard U75V rails can reach above 980MPa, higher than 510-680MPa of European standard S355JR, which can better withstand wheel loads and reduce deformation in heavy-haul transportation. American standard AAR M102 Grade 115 rails, due to their high strength characteristics, have a fatigue life 20%-30% higher than national standard U71Mn under long-term cyclic loading, suitable for railway conditions with frequent starts and stops and large loads.
- What are the differences in welding processes for rails of different materials?
National standard U71Mn rails commonly use flash butt welding, with the preheating temperature controlled at 800-900℃ and the upsetting pressure at 100-120MPa to ensure that the strength of the welded joint is equivalent to that of the base metal. European standard S355JR, due to its good weldability, can use the more convenient gas pressure welding, with a welding temperature of 1200-1300℃ and relatively flexible operation. American standard AAR M102 Grade 115 requires special welding materials, such as nickel- and molybdenum-containing electrodes, to ensure the toughness and strength matching of the welded joint.
- How does material selection adapt to different railway operating environments?
In high-temperature areas, such as desert railways, national standard heat-resistant rail materials containing chromium and molybdenum can prevent deformation caused by thermal expansion and contraction, ensuring track stability. In cold regions, foreign standard rail materials with low-temperature toughness containing nickel can avoid cold brittle fracture of rails and improve safety. In coastal areas, due to high humidity and salinity, corrosion-resistant national standard or foreign standard stainless steel rail materials need to be selected to extend service life.