What Steel Are Railroad Clips Made Of? Grades and Heat Treatment
Dec 29, 2025
When engineers ask what steel railroad clips are made of, the short answer is heat-treated spring steel. The complete answer depends on which part of the fastening assembly is meant, because the elastic clip that grips the rail foot and the spike that fixes a base plate are made from different steel families and are heat treated for different reasons.
The Two Steel Families in a Rail Fastening
The load-carrying spring element of a railroad clip is a silicon-bearing spring steel. Silicon raises the elastic limit, so the clip can be deflected during installation and still return to shape after millions of load cycles. Fasteners that simply hold components together, such as screw spikes and plain base plates, are made from ordinary carbon steel, where stiffness and thread strength matter more than elastic recovery. Recognising which family a part belongs to is the first step in selecting or verifying a material.
Spring Steel Grades and What They Contain
| Grade | C (%) | Si (%) | Mn (%) | Cr (%) | Role in the assembly |
|---|---|---|---|---|---|
| 60Si2MnA | 0.56-0.64 | 1.60-2.00 | 0.60-0.90 | ≤0.35 | main grade for E-type clips |
| 60Si2CrA | 0.56-0.64 | 1.40-1.80 | 0.40-0.70 | 0.70-1.00 | deep-hardening grade for thick sections |
| 55Si2Mn | 0.52-0.60 | 1.50-2.00 | 0.60-0.90 | ≤0.35 | general-purpose clip profiles |
| 38Si7 | 0.35-0.42 | 1.50-1.80 | 0.50-0.80 | - | lighter, easily formed tension clamps |
Phosphorus and sulphur are held to 0.03 % maximum in all four grades, which keeps notch toughness adequate for a part loaded in bending and torsion.
Why These Particular Steels Are Chosen
Elasticity and strength: the silicon content lifts the elastic limit so the clip sustains its installed deflection without yielding.
Fatigue resistance: tempered martensite with a fine, uniform grain structure resists the repeated loading and unloading applied by passing trains.
Hardenability: chromium in 60Si2CrA allows full hardening through thicker bar sections, which matters as bar diameter increases.
Availability and cost: these are standard spring steel grades covered by DIN 17221, BS 970 and GB/T 1222 rather than special melts.
Coating compatibility: the steels accept hot-dip galvanizing, zinc plating or paint, which controls corrosion life in wet tunnels and coastal cuttings.
Heat Treatment Practice for Railroad Clips
Spring steel rod is sheared to length and heated to 950-1000 degrees C before forming, after which the clip is quenched in oil. Tempering follows at 400-500 degrees C to convert the hard as-quenched structure into tempered martensite. E-type clips finish with a hardness of 44-48 HRC and SKL-type tension clamps at 42-47 HRC, and typical fatigue acceptance is 3 million cycles for an 18 mm section and 5 million cycles for a 20 mm section. Hardness below the specified band lets the clip relax and lose toe load, while hardness above it raises the risk of brittle fracture.
Standard Clip Types, Sizes and Material Pairing
| Model | Diameter | Material | Toe load | Hardness | Weight |
|---|---|---|---|---|---|
| E1609 | 16 mm | 60Si2MnA | ≥950 kg | 44-48 HRC | 0.43 kg/pc |
| E1809 | 20 mm | 60Si2MnA | ≥950 kg | 44-48 HRC | 0.61 kg/pc |
| E1813 | 18 mm | 60Si2MnA | ≥950 kg | 44-48 HRC | 0.62 kg/pc |
| E2001 / E2007 / E2009 | 20 mm | 60Si2MnA | ≥950 kg | 44-48 HRC | 0.80 kg/pc |
| E2039 / E2055 / E2063 | 20 mm | 60Si2MnA | ≥950 kg | 44-48 HRC | 0.80 kg/pc |
| SKL1 / SKL3 / SKL12 / SKL14 | 13 mm | 60Si2CrA, 38Si7, 60Si2MnA | per track design | 42-47 HRC | 0.48-0.53 kg/pc |
Custom geometries are forged from the same grades to the customer drawing, and carbon steel types such as Q235 and 45# remain in use for spikes that do not carry the rail clamping function.
Frequently Asked Questions
Q: What steel are railroad clips made of?
Elastic railroad clips are made of heat-treated silicon spring steel, mainly 60Si2MnA, 60Si2CrA, 55Si2Mn and 38Si7.
Q: Is any part of a rail fastening made of plain carbon steel?
Yes, screw spikes, base plates and similar components use Q235, 35# or 45# carbon steel where stiffness rather than elastic recovery is required.
Q: What hardness should a railroad clip reach?
E-type clips are controlled at 44-48 HRC and SKL-type tension clamps at 42-47 HRC after quenching and tempering.
Q: Why is 60Si2CrA used on heavier clips?
Its chromium content improves hardenability, so thicker bar sections harden through to the core and still meet the fatigue requirement.
Q: What fatigue life is expected of a clip?
Acceptance testing commonly requires 3 million cycles without fracture for an 18 mm section and 5 million cycles for a 20 mm section.
Q: Which standards cover railroad clip steel?
The spring steel grades are specified in DIN 17221, BS 970 and GB/T 1222, while clip geometry follows UIC, AREMA or customer drawings.
