Fishplate and Rail Joint Connection Technology
What mechanical requirements must the material selection of fishplates meet?
The material of fishplates must match the rail material; high-strength alloy steels such as 40CrMnMo are commonly used to ensure that the tensile strength and yield strength are close to those of rails. The material must have good toughness and fatigue resistance, and can withstand repeated impact loads when trains pass through the joint. Fishplates need to undergo heat treatment to improve surface hardness and wear resistance, extending service life. Their elongation rate must meet certain standards to avoid brittle fracture of the joint under stress. The material must also have corrosion resistance, especially in coastal and alpine environments, and corrosion protection treatment is required to enhance durability.
What are the technical points of fishplate section design?
The section of the fishplate must fit the shape of the rail head, web and base to ensure uniform force after connection and reduce stress concentration. The section size must be precisely controlled-excessively large or small gaps with the rail will affect joint stability, and the gap is usually controlled within 0.5mm. The position and number of bolt holes of the fishplate must be designed according to the rail model to ensure uniform distribution of bolt clamping force. Some fishplates adopt widened and thickened designs to enhance joint stiffness, adapting to the needs of heavy-haul lines. The section design also needs to consider installation convenience, facilitating rapid on-site assembly and maintenance.
What are the requirements for the cooperation between fishplates and bolts?
Fishplates and bolts must be used in conjunction; the bolt specification must be determined according to the fishplate thickness and rail model to ensure sufficient clamping force. When tightening bolts, the specified torque must be applied in sequence to avoid joint loosening due to insufficient torque or bolt fracture due to excessive torque. The bolt holes of the fishplate need to be chamfered to reduce stress concentration during bolt installation. Elastic washers can be installed between bolts and fishplates to enhance anti-loosening performance and cope with vibrations caused by train operation. The fit gap must be strictly controlled to prevent bolt loosening or fishplate deformation, affecting the joint connection effect.
What are the differences in performance requirements for fishplates in different line types?
Fishplates for ordinary railways focus on reliability and economy, needing to meet the impact load requirements of speed ≤160km/h with tensile strength ≥880MPa. High-speed railway lines have higher requirements for the stiffness and smoothness of fishplates; special designs are required to reduce wheel-rail impact at the joint and ensure stable operation at speed ≥300km/h. Fishplates for heavy-haul lines must have higher bearing capacity, mostly made of high-strength alloy steel, and the number of bolts can be appropriately increased to enhance joint tightness. Fishplates for urban rail transit need to balance vibration and noise reduction, and elastic joint designs can be adopted to reduce joint vibration and noise. Fishplates for extreme environment lines must also have weather resistance, adapting to working conditions through anti-corrosion and anti-freezing treatments.
What are the key steps in the installation and maintenance of fishplates?
Before installation, check the flatness of the fishplate and rail joint, remove impurities and rust at the joint to ensure tight fit. Fishplates must be installed symmetrically, and bolts should be tightened in diagonal order, gradually applying the specified torque to avoid uneven force. After installation, check the joint gap to ensure it does not exceed the allowable range, and simultaneously detect whether the gauge meets the standard. In daily maintenance, regularly check whether the fishplate has cracks or deformation, and whether the bolts are loose or rusted. Timely handle problems, replace damaged fishplates and bolts, and avoid safety hazards caused by joint failure.