GB 75KG heavy rails, that is, heavy-duty rails weighing 75 kilograms per meter and produced in strict accordance with Chinese national standards, occupy a pivotal position in the field of railway transportation, especially in heavy-duty railways.
Its birth stems from the development needs of heavy-duty transportation. The frequent operation of large-axle-weight and large-volume trains makes it difficult for ordinary-specification rails to withstand huge pressure and impact. GB 75KG heavy rails came into being and became the key to ensuring the safety and efficiency of heavy-duty transportation. On heavy-duty lines such as the Daqin Railway, which has an annual transportation volume of hundreds of millions of tons, it undertakes heavy transportation tasks.
From the structural point of view, GB75KG heavy rails adopt a special symmetrical cross-section design, with a wide and thick rail head, which can increase the contact area with the wheel, disperse pressure, and reduce wear; the rail waist is thickened to enhance the bending resistance and resist the huge bending moment generated when the train passes; the rail bottom is wide to ensure good fit with the sleeper and improve stability.
| Classification | Height(mm) | Head (mm) | Bottom (mm) | Thick(mm) | Weight (kg/m) | |
| Light Rail | 8 KG/M | 65 | 25 | 54 | 7 | 8.42 |
| 9 KG/M | 63.5 | 32.1 | 63.5 | 5.9 | 8.94 | |
| 12 KG/M | 69.85 | 38.1 | 69.85 | 7.54 | 12.2 | |
| 15 KG/M | 79.37 | 42.86 | 79.37 | 8.33 | 15.2 | |
| 18 KG/M | 80 | 40 | 80 | 10 | 18.06 | |
| 22 KG/M | 93.66 | 50.8 | 93.66 | 10.72 | 22.3 | |
| 24 KG/M | 107 | 51 | 90 | 10.9 | 24.46 | |
| 30 KG/M | 107.95 | 60.33 | 107.95 | 12.3 | 30.1 | |
| Heavy Rail | 38 KG/M | 134 | 68 | 114 | 13 | 38.733 |
| 43 KG/M | 140 | 70 | 114 | 14.5 | 44.653 | |
| 45 KG/M | 145 | 67 | 126 | 14.5 | 45.546 | |
| 50 KG/M | 152 | 70 | 132 | 15.5 | 51.514 | |
| 60 KG/M | 176 | 73 | 150 | 16.5 | 60.64 | |
| Crance Rail | QU 70 | 120 | 70 | 120 | 28 | 52.8 |
| QU 80 | 130 | 80 | 130 | 32 | 63.69 | |
| QU 100 | 150 | 100 | 150 | 38 | 88.96 | |
| QU 120 | 170 | 120 | 170 | 44 | 118.1 | |
In terms of manufacturing technology, it requires multiple complex processes. First, high-quality steel billets are selected, and medium-carbon microalloy steel, such as U75V, is often used. After the molten iron is pretreated to remove impurities, it is smelted in a converter or electric arc furnace, and then refined outside the furnace. The gas and inclusion content in the steel is reduced by vacuum degassing, calcium treatment and other means. Then it is continuously cast, using large square billet continuous casting technology. During the process, electromagnetic stirring, dynamic light pressure and other processes are used to improve the internal quality of the billet. Finally, it undergoes multiple rolling processes in the rolling mill to accurately control the rolling temperature and deformation to ensure that the dimensional accuracy and performance meet the standards.
In terms of performance, the GB75KG heavy rail has extremely high strength, with a yield strength of over 400MPa and a tensile strength of over 700MPa. It can withstand the strong pressure and impact brought by heavy-loaded trains; it has good wear resistance, and the rail surface has been specially heat treated to greatly improve the hardness, effectively reduce the wear rate, and extend the service life; it has excellent fatigue resistance and can withstand the alternating stress generated by millions of round trips of trains.
Due to its excellent performance, GB75KG heavy rails are widely used in heavy-duty railways and special railways for large industrial and mining enterprises. In heavy-duty railways, they ensure the safe and stable operation of 10,000-ton trains; in industrial and mining enterprises, they help to transport raw materials and products efficiently. In the future, as railway transportation develops towards higher volumes and higher speeds, GB75KG heavy rails will continue to be optimized and upgraded to provide solid support for the development of the railway industry.