What is the hardness of Crane Rail A55?
The hardness of A55 Crane Rail is not a single fixed value; it is determined by the Material Grade specified during procurement. Under the DIN 536-1 standard, the hardness is directly correlated to the minimum tensile strength of the steel.
Here are the hardness values for the two most common grades of A55 rail:
1. Hardness by Material Grade
Hardness is typically measured using the Brinell Scale (HBW).
| Material Grade | Tensile Strength (Rm) | Typical Hardness (HBW) |
| Grade 700 | ≥ 690 MPa | 200 – 240 HBW |
| Grade 900 | ≥ 880 MPa | 260 – 300 HBW |
| Grade 1100 | ≥ 1080 MPa | 320 – 380 HBW |
2. Why Hardness Matters for A55 Rails
The A55 profile has a relatively small head width (55 mm), which means the contact area between the crane wheel and the rail is narrow. This creates high Hertzian contact pressure.
- Wear Resistance: Higher hardness (Grade 900 or 1100) prevents the rail head from "mushrooming"-a type of plastic deformation where the steel flows over the sides of the rail profile due to the weight of the crane.
- Work Hardening: Rail steels like U71Mn (often used for Grade 900) have the ability to "work harden" during the first few months of service. The friction from the crane wheels can actually increase the surface hardness of the rail head by an additional 10–15% over its factory state.
| Property | U71Mn (Standard) | Grade 900 (High Quality) | Grade 1100 (Premium/HH) |
| Standard Reference | GB/T 2585 | DIN 536-1 | DIN 536-1 / EN 13674 |
| Tensile Strength ($R_m$) | ≥ 880 N/mm^2 | ≥ 880 N/mm^2 | ≥1080 N/mm^2 |
| Yield Strength ($R_e$) | ≥ 440 N/mm^2 | ≥ 460 N/mm^2 | ≥640 N/mm^2 |
| Elongation ($A_5$) | ≤10%$ | ≤ 10% | ≤ 9% |
| Hardness (HBW) | 260 - 300 | 260 - 300 | 320 - 380 |
| Carbon (C) | 0.67% - 0.80% | 0.60% - 0.82% | 0.72% - 0.82% |
| Manganese (Mn) | 0.70% - 1.05% | 0.80% - 1.20% | 0.80% - 1.30% |
| Silicon (Si) | 0.15% - 0.35% | 0.20% - 0.50% | 0.20% - 0.60% |
| Phosphorus (P) | ≤ 0.040% | ≤ 0.035% | ≤ 0.025% |
| Sulfur (S) | ≤ 0.040% | ≤ 0.035% | ≤ 0.025% |
U71Mn vs. Grade 900: In most international trade scenarios, U71Mn is considered the functional equivalent to Grade 900. They share nearly identical hardness and tensile profiles, making them the "industry standard" for heavy-duty overhead cranes.
Dimensions of Rail A55
A55 crane rail, designed according to the DIN 536 P1:1991 standard, is a specialized, low-profile track. Its key, standard dimensions include a 65mm total height, 150mm base width, 55mm head width, and 31mm web thickness, with a calculated mass of 31.8 kg/m.
- Height: 65mm
- Base Width: 150mm
- Head Width: 55mm
- Web Thickness: 31mm
- Weight: 31.8 kg/m
- Standard Lengths: 6m–12m (custom lengths, such as 25m, are available upon request)
| Size | Dimension(mm) | Weight | Material | Length | |||
|---|---|---|---|---|---|---|---|
| Head(mm) | Height(mm) | Bottom(mm) | Web(mm) | ||||
| A 55 | 55 | 65 | 150 | 31 | 31.8 | 900A | 10-12 |
| A65 | 65 | 75 | 175 | 38 | 43.1 | 900A | 10-12 |
| A75 | 75 | 85 | 200 | 45 | 56.2 | 900A | 10-12 |
| A100 | 100 | 95 | 200 | 60 | 74.3 | 900A | 10-12 |
| A120 | 120 | 105 | 220 | 72 | 100 | 900A | 10-12 |
FAQ
- What is the standard Brinell hardness for A55 crane rail?
The standard hardness for a Grade 700 A55 rail is typically between 200 HBW and 240 HBW. For high-performance applications, the Grade 900 (S900Q) offers a higher hardness range of 260 HBW to 300 HBW to resist heavy wear.
- Does the hardness affect the welding of A55 rails?
Yes. High-hardness rails like the S900Q A55 rail material require specialized pre-heating and specific welding portions when using Alumothermic Welding kits for Rails. This ensures the weld metal matches the hardness of the rail, preventing "soft-joint" wear.
Why is surface hardness important for the crane wheels?
The hardness of the A55 rail profile must be compatible with the crane wheels. If the rail is significantly softer than the wheels, the 55 mm head will experience rapid metal loss and deformation. A balanced hardness ratio ensures both components wear evenly over time.
- Can you provide custom hardness levels for specific industrial environments?
While we primarily produce to the DIN 536 Standard, our metallurgical control allows us to optimize the chemical material composition of A55 rail to reach specific performance targets for wear resistance in extreme environments, such as high-heat steel mills.
- How does the 31.8 kg/m weight relate to the rail's hardness?
The weight is a function of the A55 rail dimensions, while the hardness is a function of the steel grade. A 31.8 kg/m rail can be produced in either S700 or S900Q grades, offering different hardness levels within the same geometric profile.
Request Latest Price
At GNEE RAILWAY RAILWAY, we provide the technical data and high-strength products needed to build a durable DIN536 A55 Rail System. Our team is available to help you select between S700 and S900Q grades based on your specific wheel load and duty cycle requirements.Please contact us today to receive a complete technical submittal, including hardness profiles and material data sheets for the A55 rail profile. Our global logistics and factory-direct support are ready to provide the professional-grade solutions your project demands.