Rail Steel Is a Special Material, Not Mild Steel
A rail is a hot-rolled steel section that carries the wheel load, guides the train and provides the running surface, and it does this while being subjected to contact pressures of more than a gigapascal under each wheel and to millions of load cycles per year. Ordinary structural steel cannot survive this duty: it is too soft for the wear and too weak in fatigue for the rolling contact stress. Rail steel is therefore a high-carbon steel, generally in the range 0.60 to 0.82 percent carbon, with a pearlitic microstructure of fine alternating ferrite and cementite lamellae. The pearlite gives the combination that matters: high hardness for wear resistance and adequate toughness to stop cracks from propagating. The carbon content places rail steel clearly above construction steels, and the composition is tightly controlled because every 0.1 percent of carbon, manganese or silicon shifts the wear rate, the fatigue strength and the weldability of the rail.
Grade Chemistry Across the Main Standard Systems
Rail grades are defined by the standard system of the purchasing country, and the same nominal rail can exist in several national versions. The table below summarises the widely traded grades with their typical carbon and manganese ranges.
| Grade | Standard system | Carbon percent | Manganese percent | Alloying or treatment | Typical use |
|---|---|---|---|---|---|
| U71Mn | GB/T 2585, TB/T 2344 | 0.65-0.76 | 1.10-1.40 | Manganese | Mainline and crane rails |
| U75V | GB/T 2585, TB/T 2344 | 0.71-0.80 | 0.70-1.05 | Vanadium | High-speed lines, curves |
| U77MnCr | TB/T 2344 | 0.72-0.82 | 0.90-1.30 | Manganese-chromium | Heavy-haul and high-hardness service |
| U78CrV | TB/T 2344 | 0.74-0.82 | 0.90-1.30 | Chromium-vanadium | 75 kg/m heavy-haul rails |
| R260 | EN 13674-1, UIC 860 | 0.62-0.80 | 0.70-1.20 | None | Conventional mainline |
| R350HT | EN 13674-1 | 0.70-0.82 | 0.60-1.25 | Head-hardened | Heavy-haul, sharp curves, high wear zones |
| 900A | UIC 860 | 0.60-0.80 | 0.80-1.30 | None | Freight and mixed-traffic lines |
Two families stand out. The U-series grades are the Chinese rail steels: U71Mn is the workhorse, U75V adds vanadium for higher strength on fast lines, and the chromium and vanadium grades serve heavy-haul and very high hardness demands. The EN 13674-1 family uses the R designation with the hardness or strength in the name: R260 is the standard grade, and the head-hardened grades such as R350HT and R370CrHT push surface hardness into the 350 to 390 HBW range for severe wear conditions.
Heat-Treated and Alloyed Rails
When the wear demand exceeds what a plain pearlitic grade can deliver, the answer is head hardening or alloying, or both. Head hardening is an in-line heat treatment of the rail head after rolling: the head is rapidly cooled so that it forms a fine pearlite with a surface hardness of 350 to 390 HBW for grades such as R350HT, while the web and base keep a tougher, more weldable structure. This concentrates hardness exactly where wear happens and keeps the rest of the rail formable and weldable, which is why head-hardened rails dominate heavy-haul lines and severe curves. Alloying works alongside: vanadium and chromium refine the pearlite and raise strength, and niobium micro-alloying improves toughness. The very high strength grades used on the heaviest lines, such as the chromium-molybdenum and bainitic rails now emerging, push hardness and toughness beyond the pearlitic limit, but they are still specified by the same standards framework and verified by the same tests: tensile strength, surface and core hardness, impact energy and fatigue behaviour.
Light Rails and Crane Rails
Not all rails are mainline rails. Light rails of 8 to 30 kg/m, used for mine haulage, light industrial track and temporary lines, are rolled to GB/T 11264 with softer grades such as 55Q and Q235, because their duty is low speed and low axle load, where wear resistance matters less than economy and machinability. Crane rails, the QU series from QU70 to QU120, are used on gantry and overhead crane tracks; they are rolled to the crane rail specification with a wide, flat head designed for the flat wheels of cranes, and the Chinese QU rails are commonly supplied in U71Mn, with the hardness and straightness requirements set by the crane rail standard rather than by mainline practice. The distinction matters in procurement: a mainline R260 rail cannot simply be substituted into a crane track or a mine tramway, because the profile, the hardness and the fastening system are different.
Selecting the Grade for a Project
Grade selection starts from the project standard, not from a table of names. The governing inputs are axle load, annual tonnage, maximum speed, curve severity and climate. Heavy-haul lines with high annual tonnage and sharp curves choose the highest hardness grades, head-hardened or chromium-alloyed, because wear, not fatigue, sets the rail life. High-speed passenger lines choose grades with high fatigue resistance and consistent hardness, such as U75V in China or R260 in Europe, with surface quality requirements tightened. Conventional mixed-traffic lines are well served by the standard grades, R260 or U71Mn. Cold-region lines add an impact-energy requirement at the minimum service temperature, and corrosive environments may add alloying or coating requirements. In every case the buyer should state the profile, the grade and the governing standard, for example 60 kg/m U75V to GB/T 2585 or 60E1 R260 to EN 13674-1, and request the mill test certificate so the delivered chemistry and mechanical values can be checked against the grade limits.
Frequently Asked Questions
Q1: Is rail steel just high-carbon steel?
It is high-carbon steel, 0.60 to 0.82 percent carbon, but it is also controlled in manganese, silicon and residuals, rolled to a precise profile and tested for hardness, tensile strength and fatigue. The grade and the standard together define the material.
Q2: What is the difference between R260 and R350HT?
R260 is the standard pearlitic grade with a minimum tensile strength of 880 MPa. R350HT is the same family but head-hardened to a surface hardness of 350 to 390 HBW for heavy-haul and high-wear service.
Q3: What does the U in U71Mn mean?
The U prefix is the Chinese designation for rail steel. U71Mn is a manganese rail steel with 0.65 to 0.76 percent carbon and 1.10 to 1.40 percent manganese, per GB/T 2585.
Q4: Why are head-hardened rails used on curves?
Because curves generate the highest wear rates. Head hardening puts 350 to 390 HBW hardness exactly on the running surface, extending rail life several times compared with a standard grade on the same curve.
Q5: Can crane rails be used on railway lines?
No. Crane rails have a different head profile, hardness and fastening system, designed for flat crane wheels and low speeds. Railway lines require the railway profile and grade of the governing standard.
Q6: How is the delivered grade verified?
By the mill test certificate with the heat number, ladle analysis and mechanical tests, and by checking the chemistry against the grade limits of the standard. Hardness can be verified on the rail head with a portable tester at delivery.