Fishplate Material Matching and Rail Connection Compatibility
- What is the material matching principle between fishplates and rails?
The basic principle is that their strength grades are similar. Low-carbon steel rails should be matched with low-carbon steel fishplates (such as Q235 with Q235), medium-carbon steel rails with medium-carbon steel fishplates (such as 45 steel with 45 steel), and high-strength alloy steel rails must be matched with fishplates of the same grade (such as U75V rails with U75V fishplates). The difference in material strength should not exceed 100MPa to avoid local damage due to uneven stress.
- What connection problems will be caused by mismatched materials?
If the strength of the fishplate is lower than that of the rail, the fishplate will undergo plastic deformation first under load, leading to loose rail connections and increased rail gaps; if the fishplate strength is too high, it will cause stress concentration at the rail joint, and the rail is prone to cracks near the joint. Both situations will shorten the service life of track components and increase maintenance frequency.
- What are the common material combinations of fishplates and rails?
Ordinary lines commonly use Q235 rails with Q235 fishplates, suitable for small and medium traffic volumes; trunk railways mostly use 50Mn rails with 50Mn fishplates, with moderate strength; heavy-haul railways use U71Mn rails with U71Mn fishplates, which can bear large loads; high-speed railways use U75V rails with U75V fishplates to ensure the matching of high strength and high toughness.
- How to test the material matching between fishplates and rails?
Through material testing, analyze the chemical composition of both to ensure that the content difference of main elements (such as carbon, manganese, silicon) is within the allowable range. Conduct hardness tests, and the hardness deviation between the fishplate and the rail should be ≤20HB. In the stress simulation test, measure the strain values of both, and a strain difference of no more than 15% is considered a qualified match.
- How to ensure material matching when replacing fishplates?
Before replacement, check the rail material model and refer to the product manual to determine the corresponding fishplate material; after the new fishplate arrives, check the material certificate and sample for inspection if necessary; conduct a hardness comparison test before installation, and use it only if it meets the deviation requirements. It is strictly forbidden to replace high-strength fishplates with low-strength ones. In special cases, temporary replacement requires reducing the line load and shortening the inspection cycle.