Fishplate Material Differences and Connection Compatibility
- What are the common materials of fishplates? What are their performance characteristics?
Ordinary carbon steel fishplates (such as Q235) have moderate strength, good plasticity, and low price, but poor wear resistance and corrosion resistance, suitable for low-speed, light-load lines. Low-alloy steel fishplates (such as 16Mn) have higher strength than carbon steel, with a yield strength of more than 345MPa, good toughness and wear resistance, suitable for medium-speed trunk railways. High-strength alloy steel fishplates (such as 40Cr) have a tensile strength of more than 800MPa, excellent wear resistance and fatigue resistance, suitable for high-speed, heavy-haul railways and turnout areas.
- What is the matching principle between fishplate material and rail material?
Follow the "equal strength matching" principle, that is, the tensile strength of the fishplate should not be less than 90% of the connected rail. For example, when connecting 60kg/m high-strength rails (tensile strength 880MPa), the tensile strength of the fishplate should be ≥792MPa. The elastic modulus of the materials should be close to avoid stress concentration due to excessive elastic differences. For example, when the rail is U71Mn, it is advisable to choose fishplates of the same series of alloy materials. For lines with high corrosion resistance requirements, fishplates and rails should use the same or similar anti-corrosion materials, such as galvanized treatment.
- What are the differences in connection reliability between fishplates of different materials?
High-strength alloy steel fishplates have the highest connection reliability. Under repeated impacts of heavy-haul trains, the joint loosening rate is only 1/3 of that of ordinary carbon steel fishplates, and the service life can reach more than 15 years. Low-alloy steel fishplates have moderate connection reliability, suitable for lines with annual traffic volume below 50 million tons, with a joint maintenance cycle of about 3 years. Ordinary carbon steel fishplates have low connection reliability, prone to bolt loosening and plate deformation under high-frequency loads, requiring maintenance every 1-2 years.
- What effects can material mismatch have on fishplate connections?
If the strength of the fishplate material is lower than that of the rail, the fishplate will be deformed prematurely due to insufficient bearing capacity, causing the rail joint to have a step, affecting train smoothness. Excessive difference in elastic modulus between the two will generate additional stress when the train passes, aggravating the wear of the fishplate and rail, and shortening the service life of the joint. Mismatched corrosion resistance of materials, such as stainless steel rails with ordinary carbon steel fishplates, will form electrochemical corrosion, accelerating the rusting speed of fishplates, which need to be replaced in 3-5 years.
- How to select fishplate material according to rail type?
For ordinary rails of 50kg/m and below, Q235 carbon steel fishplates can be used to meet basic connection needs. 60kg/m trunk railway rails need to be matched with 16Mn low-alloy steel fishplates to balance strength and cost. 60N rails used in CRTSⅢ slab ballastless tracks of high-speed railways should be matched with 40Cr high-strength alloy steel fishplates to ensure connection strength and stability. Foreign standard UIC60 rails need to use S355J2 low-alloy steel fishplates conforming to EN standards to ensure material performance matching.