Common Materials and Their Trade-Offs
Fishplates made of Q235 steel are relatively low in price and have good processing performance, meeting the basic connection needs of ordinary railways, but their strength is relatively low and they deform easily on heavy-haul railways. Q345 steel fishplates have good strength and toughness, suit railways with medium traffic volume and speed, and bear large loads, but their corrosion resistance is average and anti-corrosion measures must be strengthened in humid environments. Fishplates made of 45# steel have high hardness and wear resistance, often used on lines with frequent starting and braking such as marshalling yards, but their cost is relatively high. Ductile iron fishplates have good shock absorption and reduce train noise, suitable for noise-sensitive areas, but their strength is lower than steel and they are not suitable for heavy-haul lines.
Selection by Line Characteristics
For ordinary railway lines with low train loads and speeds, Q235 steel fishplates can be selected to reduce cost, such as on local branch railways where the strength requirement is not high. For busy trunk railways with large traffic volume and high speed, Q345 steel fishplates should be selected to ensure connection reliability. Heavy-haul railways carrying large-axle-load trains need high-strength fishplates, and 45# steel is more suitable because it bears huge pressure. In urban rail transit and other noise-sensitive areas, ductile iron fishplates are a better choice, meeting connection needs while effectively reducing noise.
Impact on Connection Reliability
Fishplates made of high-strength materials such as Q345 steel and 45# steel provide stronger connecting force, reduce displacement at the rail joint and improve connection reliability. Good toughness prevents brittle fracture under train impact: Q345 steel fishplates are not easy to break when bearing impact. Corrosion-resistant materials ensure performance in harsh environments: in coastal areas, corrosion-resistant alloy steel fishplates prevent the reduction of connection strength due to corrosion. Appropriate hardness reduces wear between the fishplate and the rail, and 45# steel's high hardness reduces wear and prolongs the service life of the connecting parts.
Service Life Differences
Q235 steel fishplates last about 5 to 8 years in ordinary environments, shortened to 3 to 5 years in harsh environments due to limited strength and corrosion resistance. Q345 steel fishplates last 8 to 12 years, with good comprehensive performance and long-term connection stability. Due to their high hardness and wear resistance, 45# steel fishplates can last 10 to 15 years under normal use, especially on heavy-haul and severely worn lines. Ductile iron fishplates last about 6 to 10 years in medium-load environments such as urban rail transit, and their life is greatly shortened if used on heavy-haul lines.
Safety Hazards of Unreliable Connections
Unreliable connections cause large displacement at the rail joint, resulting in strong impact when trains pass, which may break the fishplate and bolts, disconnect the rail and seriously endanger driving safety. Joint displacement changes the gauge, makes wheel-rail contact abnormal and increases the risk of derailment, especially at high speed. Loose connections aggravate the wear of fishplates and rails, cause premature damage at the joint, increase maintenance workload and cost, and affect running smoothness. Long-term unreliable connections also degrade the overall stability of the track structure, causing ballast compaction, sleeper loosening and other track diseases.
FAQ
Q: Which fishplate material suits heavy-haul lines?
A: 45# steel, for its high hardness, wear resistance and ability to bear huge pressure.
Q: Why is toughness important for connection reliability?
A: Tough materials resist brittle fracture under train impact, preventing sudden connection failure.
Q: How long do Q345 fishplates last?
A: About 8 to 12 years, with good comprehensive performance and long-term stability.
Q: What is the advantage of ductile iron fishplates?
A: Good shock absorption that reduces train noise, ideal for urban rail transit and noise-sensitive areas.
Q: What are the consequences of unreliable connections?
A: Joint impact, gauge change, derailment risk, accelerated wear and degradation of track stability.
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