Elastic rail clips fasten the steel rail to the baseplate or concrete sleeper. Usually they are made of forged spring steel produced by a hot forging process, and the uniform microstructure of forged clips is considered better than that of clips made by other metal forming processes. This article explains how rail elastic clips are produced, step by step.
Why Forging Is Used for Rail Clips
A rail clip must work as a spring for millions of load cycles, so the material structure inside the clip is critical. Hot forging heats the steel above its recrystallization temperature and presses it into shape, which refines the grain structure, closes internal voids and produces a uniform microstructure. The result is a clip with consistent hardness, strength and fatigue performance across the whole cross-section.
Production Steps at a Glance
The production sequence for an elastic rail clip is: raw material purchasing, shearing, heating to forging temperature, forming, hardening, tempering, surface treatment, inspection and packing. Each step is controlled so that the finished clip meets the hardness, toe load and fatigue requirements of the order.
Heating and Forming
The raw material is a long spring-steel rod. The first operation is to shear the rod into pieces of the required length. The sheared pieces are then charged into a heating furnace, where the temperature is kept at 950 to 1000 degrees Celsius. Once the steel is heated through, the clips are formed in three stages of bending by hot forming equipment, which gradually shapes the wire into the final clip profile without cracking the material.
Hardening and Tempering
After forming, the clips are conveyed into a quenching oil tank, where they are cooled rapidly to form a hard martensitic structure. Quenching alone leaves the steel hard but brittle, so the clips are then tempered at 400 to 500 degrees Celsius to adjust the hardness and restore toughness. After tempering, the elastic rail clips must have a hardness between 40 and 48 HRC, which gives the right balance of clamping force and ductility for service.
Surface Treatment, Inspection and Packing
The heat-treated clips are finally oiled or otherwise surface-treated to protect them from corrosion, and then packed for shipment. Representative models and their wire diameters and weights are listed below.
| Model | Wire diameter | Weight | Material |
|---|---|---|---|
| Type III | 18 mm | 0.80 kg/pc | 60Si2MnA |
| E1609 | 16 mm | 0.43 kg/pc | 60Si2MnA |
| E1809 | 18 mm | 0.61 kg/pc | 60Si2MnA |
| E1813 | 18 mm | 0.62 kg/pc | 60Si2MnA |
| E2009 | 20 mm | 0.80 kg/pc | 60Si2MnA |
Every batch is inspected for dimensions, hardness and surface quality before packing, and the material can be traced back to the original heat through the production records, so that any non-conforming clip is removed before it reaches the track.
Frequently Asked Questions
Why are rail clips made by hot forging? Hot forging produces a uniform microstructure with refined grains, which gives the clip consistent hardness, strength and fatigue life under repeated loading.
What is the forging temperature for rail clips? The sheared spring-steel rod is heated to 950 to 1000 degrees Celsius before forming.
Why is tempering needed after quenching? Quenching makes the steel hard but brittle; tempering at 400 to 500 degrees Celsius restores toughness and sets the final hardness of 40 to 48 HRC.
What hardness should a finished elastic clip have? The finished clips must have a hardness between 40 and 48 HRC after heat treatment.
How is quality controlled during production? Every batch is inspected for dimensions, hardness and surface quality, and the material is traceable to the original heat through production records.
