Dimensional Compatibility and Connection Process for National and Foreign Standard Rails
- When connecting domestic standard 60kg/m rail (rail head width 33mm) with foreign standard UIC60 rail (rail head width 34mm), what problems does the rail head size difference cause, and how to solve it with a transition fishplate?
The 1mm difference in rail head width between domestic and foreign standard rails causes a step at the joint, increasing wheel-rail impact and accelerating wear. A transition fishplate with a 150mm+ gradual rail head (33mm to 34mm) is required for smooth wheel-rail transition. Made of Q345 steel (tensile strength ≥470MPa), it matches both rails' strength. Bolt hole spacing on both sides fits domestic (140mm) and foreign (135mm) standards, tightened to 300-350N·m. After installation, check rail surface smoothness with a 1m straightedge, requiring height difference ≤0.3mm.
- When welding foreign standard AREMA136RE rail (web thickness 19.05mm) with domestic 75kg/m rail (web thickness 20mm), how to adjust flash butt welding parameters to prevent defects?
The 0.95mm web thickness difference risks incomplete fusion or slag inclusion. Extend preheating time by 10% (50s to 55s), reduce flash current by 5% (800A to 760A), and increase upset force by 8% (350kN to 378kN). Clean rail ends to remove oxide scale (≤0.1mm) before welding; post-weld temper at 250℃ for 2 hours to reduce stress. Use ultrasonic testing to ensure no cracks or incomplete fusion, with 100% qualification rate.
- After connecting domestic and foreign rails, how to adjust gauge blocks to adapt to rail base width differences (e.g., 150mm for domestic 60kg/m vs. 155mm for UIC60)?
Width differences cause ≥0.5mm gaps between standard gauge blocks and rail bases, reducing lateral stability. Replace with custom blocks-widen foreign rail-side blocks by 5mm (20mm to 25mm) to ensure tight fit. Blocks use high-strength ABS plastic (compressive strength ≥20MPa). Check gaps with a feeler gauge (≤0.2mm) and tighten bolts to 300-350N·m to prevent lateral displacement.
- In ballasted tracks, what special tamping requirements apply to the ballast at domestic-foreign rail joints, and why?
Adopt "enhanced tamping": increase depth by 50mm (300mm to 350mm) and vibration force by 15% (30kN to 34.5kN) to boost ballast stiffness. Joints bear complex stress, leading to 5mm annual settlement (vs. 3mm for regular sections). After tamping, check track alignment (≤1mm/10m) and recheck ballast density every 3 months (void ratio ≤25%) to prevent compaction or looseness.
- Why is the maintenance cycle for domestic-foreign rail joints 20% shorter than single-material joints, and what are key maintenance items?
Stress concentration at mixed joints causes frequent bolt loosening and fishplate wear, shortening the cycle from 3 months to 2.4 months. Key items: ① Check bolt torque (retighten if deviation >±15%); ② Magnetic particle testing for fishplate cracks (>3mm requires replacement); ③ Grind rail surface burrs (Ra ≤6.3μm); ④ Replenish ballast if loss >5%. Test vibration acceleration after maintenance (≤0.3g) for comfort.