Classification and Application of Fishplates
The main function of a fishplate is to connect the ends of two rails with bolts, forming a continuous track. It must withstand the enormous pressure and impact generated by passing trains, as well as the expansion and contraction of the rails due to temperature changes. Therefore, the design and manufacture of fishplates must meet stringent strength and durability requirements. Based on different railway conditions and application needs, fishplates have been developed into various classification methods.
Classification by Rail Type
Standard Gauge Fishplates
Standard gauge (1435mm) is the most widely used railway gauge in the world, covering major railway networks in North America, most of Europe, and China. Standard gauge fishplates are therefore the most widely produced and used type.
43kg/m rail type fishplates are commonly found on early-constructed railway branch lines or secondary lines. Their design is relatively simple, with moderate load-bearing capacity, suitable for lines with lower speeds and smaller traffic volumes.
50kg/m and 60kg/m rail type fishplates are the mainstream models for Chinese railways, widely used in the upgrading of existing main lines and the construction of new lines. These two types of fishplates have been optimized in terms of bolt hole spacing, plate thickness, and strength design to meet the requirements of increased axle load and higher speed in modern trains.
The 75kg/m rail type fishplate represents the development direction of heavy-haul railways. It employs a thicker cross-section design and higher strength materials, capable of withstanding repeated crushing by heavy-haul trains with axle loads exceeding 30 tons, and is widely used in freight lines and bulk cargo transportation corridors.
Narrow-gauge fishplates
Narrow-gauge railways (with a gauge smaller than standard gauge) still play an irreplaceable role in specific fields.
Mining railways often use 24kg/m and 30kg/m narrow-gauge fishplates. These fishplates are compact in design and lightweight, facilitating underground transportation and installation. Considering the often-exposed water and highly corrosive mineral dust in mining environments, narrow-gauge fishplates often undergo special anti-corrosion treatment.
Narrow-gauge fishplates are also widely used in light railways such as forest railways and sugarcane transport railways. These railways typically feature small curve radii and steep gradients, requiring fishplates with excellent torsional resistance to adapt to complex track conditions. Some narrow-gauge fishplates are also designed with adjustable angles to accommodate changes in track orientation.
Broad-gauge fishplates
India, Finland, and other countries use broad gauge systems such as 1520mm and 1676mm, and their fishplate designs are also unique.
Broad-gauge railways typically bear greater axle loads, therefore broad-gauge fishplates often exceed those of standard-gauge fishplates of the same grade in thickness and strength.
Another characteristic of broad-gauge fishplates is that they are often matched with the rail sections of specific countries to form a complete track system. This systematic design ensures the precision and reliability of the connection.
Classification by Material
Ordinary Carbon Steel Fishplates
Ordinary carbon steel fishplates are mainly manufactured using Q235 and Q345 steel. Through reasonable cross-sectional design and heat treatment processes, their tensile strength typically reaches over 500MPa, sufficient to meet the needs of most conventional speed railways.
The advantages of this type of fishplate are mature technology, relatively low cost, and ease of processing and maintenance. In China, the vast majority of existing railway lines still use carbon steel fishplates, which have been proven reliable through decades of practical experience.
Alloy Steel Fishplates
With the increase in train speed and axle load, alloy steel fishplates have emerged. By adding alloying elements such as chromium, molybdenum, vanadium, and nickel, the overall performance of the material is significantly improved.
High-strength alloy steel fishplates boast a tensile strength exceeding 800 MPa, more than 60% higher than ordinary carbon steel. This allows for thinner and lighter fishplate designs with the same load-bearing capacity, reducing material usage and track weight. High-toughness alloy steel fishplates maintain excellent impact toughness even at low temperatures, avoiding the risk of brittle fracture. This characteristic is particularly important for railways in cold regions.
Weather-resistant alloy steel fishplates, through the addition of elements such as copper and phosphorus, form a dense protective film on the surface, resulting in atmospheric corrosion resistance 2-8 times that of ordinary carbon steel. This makes them particularly suitable for corrosive environments such as coastal areas and industrial zones.
Alloy steel fishplates are widely used in China’s high-speed railways. For example, the fishplates used on the Beijing-Shanghai high-speed railway employ a special alloy formula, capable of withstanding the high-frequency vibrations and impact loads brought by high-speed trains traveling at 350 km/h.
Stainless Steel Fishplates
In highly corrosive environments such as marine areas, saline-alkali land, and near chemical plants, stainless steel fishplates demonstrate irreplaceable advantages.
Austenitic stainless steel fishplates (such as 304 and 316 series) have excellent corrosion resistance and formability, but relatively low strength and hardness. Therefore, engineers often improve their strength through cold working or by adding nitrogen.
Duplex stainless steel fishplates combine the advantages of both austenitic and ferritic materials, offering good corrosion resistance as well as high strength and resistance to stress corrosion. In applications requiring both corrosion resistance and high strength, such as railway connections for cross-sea bridges, duplex stainless steel is an ideal choice.
Multi-dimensional considerations for fishplate selection
In practical engineering, the selection of fishplates requires comprehensive consideration of multiple factors:
- Railway conditions: including track gauge, curve radius, gradient, axle load, transport capacity, speed, etc.;
- Environmental factors: temperature range, humidity, corrosive media, seismic intensity, etc.;
- Economic factors: initial investment, maintenance costs, service life costs;
- Technical factors: ease of installation, maintainability, and compatibility with existing systems.
