Definition and Classification of GB Heavy Rails
Chinese practice classifies rails by nominal mass per metre: light rails up to 30 kg/m are covered by GB/T 11264, and heavy rails of 38 kg/m and above by the GB/T 2585 and TB/T 2344 rail families. Within the heavy rail range, the specifications in common production are 38, 43, 50, 60 and 75 kg/m. The larger the section, the greater the section modulus, the higher the bending and fatigue capacity, and the heavier the traffic the line can carry, at the price of higher material cost and greater demands on fastening and sleeper support. Selecting the specification is therefore a tonnage and axle-load decision, not a preference decision.
Standard Dimensions of the GB Heavy Rail Family
The key dimensions of each section are defined in the standard and controlled by tight rolling tolerances, because rail height, base width and head width determine how the rail sits in the fastening and how the wheel contacts the head.
| Section | Rail height (mm) | Base width (mm) | Head width (mm) | Typical use |
|---|---|---|---|---|
| 38 kg/m | 134 | 114 | 68 | Branch lines, industrial sidings |
| 43 kg/m | 140 | 114 | 70 | Secondary lines, light main lines |
| 50 kg/m | 152 | 132 | 70 | Regional trunk lines, medium traffic |
| 60 kg/m | 176 | 150 | 73 | Passenger and main freight trunk lines |
| 75 kg/m | 192 | 150 | 75 | Heavy-haul coal and ore corridors |
Rails are rolled in standard lengths of 12.5 m and 25 m, and for high-speed and heavy-haul projects they are welded into long continuous rails on site or delivered in long welded strings.
Performance Requirements That All Heavy Rails Must Meet
Every heavy rail section must satisfy four engineering requirements. Strength comes first: the rail must carry the bending moment of the heaviest axle without exceeding its elastic limit, and on heavy-haul lines this pushes material selection toward the 980 MPa class of steels. Impact toughness follows: trains impose dynamic loads from starting, braking, curves and joints, and the steel must absorb that energy without brittle fracture, which is why impact testing is mandatory and why cold-region lines need steels with verified low-temperature toughness. Wear resistance determines life: the rail head wears in proportion to cumulative tonnage and curve severity, so harder head material, either by alloying or heat treatment, extends the interval between rail replacements. Dimensional accuracy ties the rail to the fastening system: height, base width and web thickness must stay within the tolerance band so that the rail seats fully in the clip shoulder and the track geometry is built accurately in one pass.
50 kg/m and 60 kg/m Rails: The Workhorses
The 50 kg/m rail balances strength and toughness for medium traffic. It is common on regional trunk lines, marshalling yards and industrial railways where trains run at moderate speeds with moderate axle loads, and it offers a good cost-to-capacity ratio where 60 kg/m would be over-specification. Inside steel plants and other large industrial sites, 50 kg/m rails carry heavy raw material vehicles with acceptable service life and lower first cost than heavier sections.
The 60 kg/m rail is the standard for the Chinese passenger network and for the busiest mixed-traffic corridors. Its dimensional precision supports high-speed operation, its strength carries 25 t axle freight, and its toughness copes with the repeated starting and braking of busy hubs. Because the network is built overwhelmingly on 60 kg/m, welding procedures, fastening systems, maintenance machines and spare-part inventories are all standardised on this section, which makes life-cycle support simpler than for any other specification.
75 kg/m Rails for Heavy-Haul Service
The 75 kg/m rail exists for one mission: carrying the heaviest freight in the world's most intensive service. On corridors such as the Daqin coal railway, axle loads of 25 to 30 t and trains of 20,000 t class produce annual tonnage in the hundreds of millions of tonnes, and the 75 kg/m section provides the bending stiffness and head volume that keep wear and fatigue within manageable limits. In practice these lines use heat-treated 75 kg/m rails with head hardening, high-hardness steel, and a maintenance strategy of regular grinding, because the rail head is consumed by wear as well as loaded by bending. The same logic applies to large open-pit mine railways and dedicated ore corridors, where 75 kg/m rails are selected despite their higher cost because the cost of rail replacement in lost production is far higher.
Choosing the Right Section for a Project
As a rule of thumb, select the section from the tonnage and axle load, not from speed alone. Light branch and industrial traffic suits 38 or 43 kg/m; regional and secondary trunk lines with moderate traffic suit 50 kg/m; passenger lines, high-speed lines and busy mixed corridors use 60 kg/m; and heavy-haul, mining and port corridors with axle loads above 25 t and high annual tonnage use 75 kg/m. Always check the fastening system and the sleeper spacing together with the rail: a heavier section demands stronger clips, wider tie plates and more robust sleeper support, so the rail, the fastening and the sleeper must be specified as one system.
FAQ
What counts as a heavy rail in Chinese practice?
Rails of 38 kg/m and above are classified as heavy rails; rails below 38 kg/m, down to 8 kg/m, are light rails covered by GB/T 11264 and used for trams, mines and industrial track.
What steel grades are used for GB heavy rails?
The common grades are U71Mn, with a minimum tensile strength of 880 MPa, and U75V, with a minimum tensile strength of 980 MPa; heat-treated versions such as U75VH add head hardening for high-wear service.
Why is 60 kg/m the dominant section in China?
Because the passenger network, the standard fastening systems, the welding fleet and the maintenance machinery are all built around it, which gives the lowest system cost over the life of the line.
How much weight can a 75 kg/m rail carry?
It is designed for heavy-haul service with axle loads up to about 30 t and annual tonnage of several hundred million gross tonnes when combined with heat treatment, grinding and a full heavy-haul maintenance regime.
Are 50 kg/m rails still being produced for new lines?
Yes, for regional, industrial and yard applications where the tonnage does not justify 60 kg/m; the specification remains standard production in the GB rail family.
What length are GB heavy rails delivered in?
Standard delivery lengths are 12.5 m and 25 m, and for high-speed and heavy-haul projects rails are also delivered as long welded strings or welded on site into continuous welded rail.