38Si7 Plain Coating D Rail Clip

What is a D-type elastic rail clip?

Rail clips are the working element of a railway fastening system. They clamp the rail foot to the baseplate and sleeper so that the gauge is maintained and the rail cannot move vertically or laterally relative to the sleeper. Among the many clip shapes in service, the D-type elastic rail clip is a hot-pressed spring steel clip with a closed loop profile, widely used on light rail, mining lines and industrial track, and in several markets in South America and elsewhere where this fastening pattern is standard.

The clip works through elastic deformation: when it is driven into position, the spring legs deflect and store energy. That stored energy provides the clamping force and, at the same time, absorbs the vibration and shock of passing trains. Because the clamping force comes from elastic strain rather than from rigid bolting, the clip keeps holding the rail firmly even under repeated dynamic loading.

Materials and chemical composition

The D-type clip is made from hot-pressed spring steel. The standard grades are 38Si7, 60Si2Mn, 60Si2MnA and 60Si2CrA, selected according to the strength required for the rail section and the service environment. Typical compositions are shown below.

Material	Typical chemical composition (%)
60Si2MnA	C 0.56–0.64, Mn 0.60–0.90, Si 1.60–2.00, Cr ≤ 0.35, P ≤ 0.03, S ≤ 0.03
60Si2CrA	C 0.56–0.64, Mn 0.40–0.70, Si 1.40–1.80, Cr 0.70–1.00, P ≤ 0.03, S ≤ 0.03
55Si2Mn	C 0.52–0.60, Mn 0.60–0.90, Si 1.50–2.00, Cr ≤ 0.35, P ≤ 0.03, S ≤ 0.03
38Si7	C 0.35–0.42, Mn 0.50–0.80, Si 1.50–1.80, P ≤ 0.03, S ≤ 0.03

38Si7 is a silicon spring steel with lower carbon than the 60-series grades; it offers very good ductility for cold and hot forming while still providing the spring properties needed for medium-load fastenings. The chromium-bearing 60Si2CrA grade is used where higher strength and better fatigue resistance are required.

Technical parameters

Parameter	Value
Materials	60Si2Cr, 38Si7, 60Si2Mn, 60Si2MnA, 60Si2CrA, 55Si2Mn
Hardness	HRC 44 – 48
Fatigue testing	Fatigue life 3 million cycles
Toe load	≥ 10 kN (as per test assembly)
Coating	Plain, painting

Why plain coating is specified

Plain coating means the clip is supplied without a metallic finish, normally with a light oil film. It provides effective protection against rain, dust and normal atmospheric conditions while keeping the clip surface clean for inspection. Plain-coated clips reduce corrosion during storage and transport, extend component life, and help lower maintenance costs caused by fastener failure, while the elasticity and clamping force of the clip are fully preserved. Where the environment is more aggressive, painted or coated versions can be supplied.

D-type clip dimensions

Wire diameter (mm)	Weight (kg)	Toe load (kgf)
Ø12	0.18	200 – 400
Ø14	0.30	400 – 600
Ø16	0.44	500 – 700
Ø18	0.59	800 – 1000
Ø20	0.76	1100 – 1400
Ø25	0.49 – 0.68	1200 – 1500

The toe load is the force the clip exerts on the rail foot at the design deflection. In the standard dimension range, heavier wire diameters give higher toe loads; the Ø25 clip is produced for heavy toe-load requirements, with the exact weight and toe load defined on the production drawing for the specified rail section. Larger diameters and higher-strength materials can be produced to customer drawings.

Installation and application

D-type clips are installed by pressing or driving the clip over the shoulder of the baseplate or into the fastening assembly with a manual tool. They are commonly paired with a baseplate, rail pad and the corresponding shoulder or dowel for the fastening pattern. Typical applications include light rail, tramways, mining and quarry lines, crane runways, and industrial sidings where a resilient, low-maintenance fastening is required.

Frequently asked questions

What does toe load mean for a rail clip?

Toe load is the clamping force the clip applies to the rail foot at its designed installation deflection. It is the main parameter that holds the rail down against vertical movement and maintains the gauge. Higher toe loads are needed for heavier rail and higher axle loads.

How is the fatigue life of 3 million cycles tested?

The clip is installed on a test assembly at the designed toe load and cyclically deflected at a set frequency until it fails or reaches the specified number of cycles. A fatigue life of 3 million cycles means the clip is expected to survive that many load applications without cracking or losing its clamping force.

Can a D-type clip be used on concrete sleepers?

Yes, when the fastening system provides the correct shoulder or dowel arrangement. On concrete sleepers the clip works with a baseplate or direct fastening components; the fastening pattern must match the clip geometry.

What is the difference between 38Si7 and 60Si2MnA?

38Si7 is a lower-carbon silicon spring steel with better formability, while 60Si2MnA has higher carbon and manganese for greater strength and hardness after heat treatment. The choice depends on the required toe load and the fatigue demand of the line.

Is plain coating suitable for coastal environments?

Plain-coated clips are intended for normal atmospheric conditions. For coastal or chemically aggressive sites, painted or otherwise protected versions are recommended to prevent surface corrosion.

Can clip sizes and materials be customised?

Yes. Special sizes, higher-strength materials and custom coating requirements can be produced to customer drawings, with the toe load and fatigue performance verified by testing.