a key component of railways--Rails
Rail, as the core component of railways, bears the heavy responsibility of direct contact with the wheels of locomotives and vehicles. Its quality has a decisive impact on the safety and stability of driving.
The basic requirements that rails must meet include sufficient strength and wear resistance to cope with the uncertain and highly random forces applied by the wheels. At the same time, the possible impact of climate and other factors on rails must also be considered.
In order to ensure that the rails can continue to work under long-term heavy loads without fatigue damage, and to prevent lateral fractures caused by peeling of the inner side of the rail head, the rails must have excellent fatigue resistance and toughness. In addition, my country's railway system has made detailed classifications of rails to adapt to different operating conditions. Specifically, there are 7 types of rails, including 75kg/m, 60kg/m, 50kg/m, 43kg/m, 38kg/m, 60N and 50N. Among them, rails of 50kg/m and above are defined as heavy rails, while those below 50kg/m are classified as light rails.
High-speed, intercity and passenger-freight Class I railway main lines usually use 60kg/m rails. For passenger-freight Class II railway main lines, either 60kg/m rails or 50kg/m rails can be selected. For heavy-duty railway main lines, rails of 60kg/m and above should be used to ensure the stability of the line. In addition, the main line rails and turnout basic rails mainly use 60N and 75N two profile section rails, which are designed so that the contact point between the wheel and the rail head is basically located at the center of the tread, thereby effectively optimizing the contact relationship between the wheel and the rail.
In terms of length, there are many options for the fixed length of rails in my country, including 12.5m, 25m, 75m and 100m. It is worth mentioning that the fixed length of rails used in high-speed railways is 100m, which not only helps save costs and shorten shipping time, but also speeds up welding progress. Since high-speed railways adopt a seamless line design, the longer the rail length, the fewer welded joints there are, thereby reducing the impact of welded joints on line smoothness.
