What are the mechanical properties of Profile S20 rail?
The mechanical properties of the Profile S20 light rail (DIN 5901) depend entirely on the steel grade selected for production. It is primarily manufactured in two distinct steel grades: 55Q (Medium-Carbon) for active rolling wear and Q235B (Low-Carbon) for light-duty or structural tracks.
1. Mechanical Properties Matrix
| Mechanical Property | 55Q Steel Grade (Standard/Wear-Resistant) | Q235B Steel Grade (Cost-Effective/Weldable) |
| Tensile Strength | ≥ 685 MPa | 375 – 460 MPa |
| Yield Strength | ≥ 390 MPa | ≥235 MPa |
| Elongation | ≥14% | ≥ 26% |
| Brinell Hardness (HBW) | 200 – 260 HBW | ~140 HBW |
2. Sectional Structural Performance (Geometric Strengths)
In addition to the raw material limits, the physical shape of the S20 profile provides specific cross-sectional strengths to resist vertical bending and lateral twisting under load:
| Theoretical Weight | 19.8 kg/m (39.91 lb/yd) |
| Cross-sectional Area (A/S) | 25.26 cm² (3.92 in²) |
| Moment of Inertia (Ix) | 346 cm⁴ (8.31 in⁴) |
| Section Modulus (W) – Base/Rail Foot | 66.8 cm³ (4.08 in³) |
| Section Modulus (W) – Rail Head | 66.8 cm³ (4.08 in³) |
3. Engineering Performance
- AnalysisLoad-Bearing Threshold: When rolled with 55Q steel, the S20 profile safely handles wheel loads up to 35 to 45 kN (3.5 to 4.5 metric tons per wheel). The Q235B grade should be restricted to significantly lower, static, or non-critical wheel tracks.
- Fatigue vs. Elasticity: The 55Q grade provides the high tensile strength (≥ 685 MPa) required to prevent micro-crack propagation along the 10 mm web under high-frequency cycling. Q235B offers superior elongation (≥ 26%), which means it provides high ductility and impact cushioning but is susceptible to plastic deformation (mushrooming) under high stress.
How Do the Yield and Tensile Strengths of the S20 Steel Track Rail Prevent Permanent Track Distortion?
The yield and tensile strengths of 55Q steel keep the S20 rail perfectly aligned and prevent permanent track damage through two mechanisms:
- Yield Strength (≥ 390 MPa) prevents sagging and flattening: It allows the narrow 44 mm rail head to act like a spring. When a heavy wheel passes over, the rail flexes micro-fractionally and snaps back into place. Without sufficient yield strength, the rail head permanently flattens out (mushrooms) and sags between supports.
- Tensile Strength (≥ 685 MPa) prevents twisting and cracking: When a crane brakes or turns, the wheel flanges push hard against the side of the rail. High tensile strength stops the thin 10 mm web from twisting sideways or cracking at the base, keeping the track gauge perfectly uniform.
In short: High yield strength stops the rail from bending down, while high tensile strength stops it from twisting out.
FAQ
- What is the exact difference between tensile strength and yield strength for an S20 steel rail?
Tensile strength measures the maximum stress an S20 steel rail can handle before tearing or fracturing completely. Yield strength defines the lower limit where the steel begins to deform permanently. For safe track operation, your maximum calculated wheel loads must always remain well below the yield strength threshold.
- What is the mechanical benefit of using matching joint bars on a DIN rail S20 profile?
Using high-strength joint bars manufactured from compatible steel formulations ensures that the rail joint shares the vertical load evenly between rail lengths. This uniform load sharing prevents localized bending stresses from overloading the rail ends, reducing the risk of bolt-hole cracking across your S20 Railway Steel Rail path.
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GNEE RAIL manufactures premium DIN5901 steel rail and complete light track systems, stocking extensive reserves of 6m and 10m 20kg light steel rail units for immediate dispatch. We provide full customization including precision length sawing and custom web drilling, fully supported by our matching joint bars, base plates, and resilient tracking fasteners.Please contact us today to secure volume pricing and request technical drawings or certified material datasheets.
