Fishplate and Rail Joint Connection Technology
What are the requirements for the material selection of fishplates?
The material of the fishplate must match the corresponding rail material to ensure that the strength and toughness at the joint are consistent with the rail body. The common materials of fishplates for national standard rails are mostly low-alloy steels matching U71Mn and U75V, with a tensile strength not lower than that of the rail itself. The material of fishplates for foreign standard rails must comply with UIC, AAR and other standards, such as alloy steel fishplates matching S355JR rails. The material should have good weldability and wear resistance, and be able to withstand repeated impacts when trains pass. Matching materials can avoid the joint becoming a weak link in strength and ensure the overall stability of the line.
What are the technical points for the cooperation between fishplates and bolts?
Fishplates and bolts must be selected as a complete set according to the rail specifications, and the bolt diameter and length must be accurately matched with the holes of the fishplate. Bolts should be galvanized on the surface with a zinc layer thickness of ≥85μm to ensure rust and corrosion resistance, and the thread accuracy should meet the requirements of GB/T197. During installation, the bolts should be tightened according to the specified torque, usually in two steps (initial tightening and final tightening) to ensure uniform force bearing. The fitting surface between the fishplate and the rail joint should be flat and free of debris to ensure tight connection and reduce vibration. Matching use and standardized installation can ensure the connection strength at the joint and avoid loosening or fracture.
What are the special requirements for fishplates in heavy-haul railways?
Fishplates for heavy-haul railways must have higher strength and fatigue resistance to withstand huge wheel-rail pressure and cyclic loads. Their material should be high-strength alloy steel with a tensile strength of ≥1200MPa and a yield strength of ≥800MPa, far exceeding the standards for ordinary lines. The structural design of the fishplate needs to be optimized to increase the stress-bearing area, reduce stress concentration, and avoid cracking at the joint. High-strength bolts must be used during installation with higher tightening torque to ensure firm connection. Fishplates on heavy-haul lines need to be regularly inspected, and fatigued or worn components should be replaced in a timely manner to ensure joint safety.
Why are diseases prone to occur at rail joints?
Rail joints are weak links in the track system. When trains pass, large impacts and vibrations are generated, leading to stress concentration. Components such as fishplates and bolts at the joint are subject to alternating loads for a long time, which are prone to fatigue wear, loosening or fracture. The rail gap at the rail joint will expand and contract with temperature changes, aggravating the impact at the joint. If the fishplate is not closely attached to the rail, it will cause uneven force bearing and accelerate the occurrence of diseases. If the diseases at the joint are not handled in a timely manner, it may lead to serious safety accidents such as rail fracture.
How to improve the reliability of fishplate connections?
Firstly, it is necessary to ensure that the materials of fishplates and bolts match the rails, select high-quality products that meet the standards, and eliminate unqualified accessories. Before installation, clean the impurities and rust on the fitting surfaces of the rail joint and fishplate to ensure tight fitting. Tighten the bolts strictly according to the specified torque, using a calibrated torque wrench to ensure consistent tightening force for each bolt. Regularly inspect the fishplates and bolts, focusing on wear, loosening, rust and other conditions, and perform maintenance and replacement in a timely manner. Adopting advanced connection technologies, such as high-strength bolts and anti-loosening devices, can further improve connection reliability.