60Si2CrA Plain Coating SB Rail Clip: Specifications and Use
Oct 16, 2025
The SB rail clip (SB rail clamp) is a spring steel fastening element used with railway sleepers to fasten the rail on both sides of the rail foot. It belongs to the family of forged elastic fasteners associated with Italian railway practice and the UNI 3545 standard, and is used on lines and industrial tracks where a compact, high-clamping-force clip is specified.
Manufacturing Process
SB rail clips are manufactured from spring steel by hot forging. The bar is heated, formed to the clip geometry in a closed die, and then heat treated - oil quenched and tempered - to reach the specified hardness band. Hot forging is preferred over other metal forming processes for rail clips because it produces a uniform microstructure and preserves the grain flow of the steel around the bends of the clip, which is directly related to fatigue life under repeated wheel loading. After heat treatment, each clip is checked for geometry, hardness and surface condition before coating.
Technical Parameters
| Parameter | Value |
|---|---|
| Material | 38Si7, 60Si2CrA |
| Reference standards | UNI 3545, GB/T 1222 |
| Hardness | 42-46 HRC |
| Fatigue testing | not less than 5 million cycles |
| Clamping force | 10.7-10.9 kN |
| Coating | Plain, painting |
Material Notes
Two spring steel grades are offered for the SB clip. 38Si7 is a silicon alloyed spring steel with a balanced carbon content, referenced to EN practice; 60Si2CrA is a chromium-alloyed spring steel with higher hardenability, which gives a deeper and more consistent hardness after quenching and improved wear resistance in demanding service. Both grades are covered by GB/T 1222 for spring steel. The 42-46 HRC hardness band is slightly lower than that of typical E-clips (44-48 HRC), reflecting the SB clip's design philosophy of combining spring flexibility with resistance to permanent set.
Clamping Force and Fatigue Performance
The SB clip develops a clamping force in the 10.7-10.9 kN range at its design deflection. This toe load holds the rail foot firmly on the pad or baseplate while allowing the elastic deflection that damps vibration. Fatigue testing to not less than 5 million cycles verifies that the clip survives the repeated loading of train passage without cracking or loss of clamping force, which is the key requirement for a fastener that is expected to stay in service for the life of the sleeper.
Coating Options
Plain coating means the clip is delivered with the natural oxide surface from heat treatment, sometimes with a light oil film for transport protection. Painted coating adds a protective layer where the project specification requires it, for example for corrosion protection in humid environments or for color coding by size. The coating choice does not change the spring characteristics of the clip.
Application
Fastening rails to concrete sleepers through cast-in or bolted shoulders in fastening systems based on UNI 3545 practice.
Industrial sidings, port and mining tracks where a robust, high-clamping-force clip is required.
Lines maintained under Italian or European rail fastening specifications.
Replacement and re-fastening work where the installed shoulder is designed for the SB clip geometry.
Frequently Asked Questions
1. What does SB stand for in SB rail clip?
SB is the designation of this clip family in the UNI 3545 fastening system. It identifies the clip geometry - a forged spring clamp that seats in the shoulder and presses on the rail foot on both sides.
2. Which standard is UNI 3545?
UNI 3545 is an Italian (UNI) standard that covers rail fastening components including spring clips. The SB clip is also produced to GB/T 1222 for the spring steel grade, and the finished product is verified to the purchaser's specification.
3. What is the difference between 38Si7 and 60Si2CrA for this clip?
38Si7 is a silicon spring steel with good fatigue behaviour and cost efficiency; 60Si2CrA adds chromium for higher hardenability, giving a more consistent hardness through the section and better wear resistance. Either grade meets the 42-46 HRC requirement when correctly heat treated.
4. Why is hot forging preferred for rail clips?
Hot forging produces a uniform, dense microstructure with grain flow following the clip's bends. Compared with cold forming or machining, this improves the clip's resistance to fatigue cracking at the highly stressed bend radii, which is where clips fail in service.
5. What is the clamping force of the SB clip?
The clamping force (toe load) is 10.7-10.9 kN at the design installed deflection. The clip should be installed with the tooling specified for the fastening system so that this force is developed without overstressing the spring.
6. Can the SB clip be supplied with other coatings?
Yes. Plain and painted are standard, and other finishes such as zinc plating or hot-dip galvanizing can be applied where the project environment requires additional corrosion protection.
