Rails are strips of steel used for railway tracks, crane tracks, etc. to carry and guide wheels. They can be divided into different types according to their uses and performance differences: heavy rails are rails with a weight of more than 38 kg per meter, with high strength and good stability. They are often used on railway trunk lines and can withstand the rolling of heavy-loaded trains; light rails weigh no more than 30 kg per meter and are suitable for medium-volume rail transportation in cities, such as some urban light rail lines; QU series crane rails are specially designed for cranes, with a low height, wide head and thick waist, and can withstand the huge wheel pressure and frequent impact when the crane is running. They are commonly used materials for crane rails in ports, workshops and other places.
Rail production is a complex process involving the coordination of multiple processes and the integration of multiple technologies. Starting from the pretreatment of raw materials, through a series of core processes such as refining and vacuum degassing, to the final inspection, sawing and drilling, each process has a decisive influence on the quality of the rails.
Rail production process
Pretreatment
Through physical methods such as shot blasting and sand blasting, the rust, scale and other impurities on the surface of the steel billet are removed forcefully, and the steel billet is strictly inspected, accurately cut and straightened. During shot blasting, high-speed projectiles impact the surface, and sand blasting relies on high-pressure airflow to push sand grains for grinding. This step can effectively improve the surface quality and avoid impurities causing defects in subsequent rolling, laying a solid foundation for the production of high-quality rails.
Refining
This is the core process to improve the intrinsic quality of the rails, by removing harmful impurities in the molten steel, accurately adjusting the alloy element composition and controlling the temperature. For example, adding manganese and silicon to improve strength and wear resistance, adding micro-alloy elements to refine the grains, so that the rails have higher strength, good wear resistance and toughness, and meet the heavy-load and high-speed requirements of railway transportation.
Vacuum degassing
Placing the molten steel in a vacuum environment greatly reduces the solubility of gas in the molten steel, and promotes the rapid escape of gases such as hydrogen and nitrogen. If the gas remains, the rails are prone to problems such as pores and looseness. Vacuum degassing effectively improves the purity of the molten steel and enhances the density and reliability of the rail structure.
Continuous casting
The refined molten steel is continuously cast and solidified into a casting with a specific cross-sectional shape and size specifications, realizing the key transition from liquid to solid. The quality of the continuous casting directly affects the subsequent rolling. Good continuous casting can ensure the stability of the rail forming and reduce rolling defects.
Rolling
The strong pressure of the rolling mill is used to make the continuous casting plastically deformed and gradually rolled into a standard rail shape and size. The rolling process not only gives the rail an outer shape, but also improves the internal structure and enhances the mechanical properties of the rail, making it adaptable to long-term rolling and impact by trains.
Heat treatment
A series of operations such as heating, heat preservation and cooling are performed on the rolled rail to change its internal structure and eliminate residual stress. Through reasonable heat treatment, the strength and hardness of the rail are significantly improved, the fatigue resistance is enhanced, the service life is extended, and the long-term safe operation of the railway is guaranteed.
Straightening
With the help of special straightening equipment, pressure or tension is applied to the rail with bending deformation to make it bend in the opposite direction to offset the original deformation. Whether it is the repeated bending of roller straightening or the axial tension of stretch straightening, it can be precisely controlled to ensure that the straightness and dimensional accuracy of the rails meet the standards and meet the laying requirements.
Inspection (ultrasonic flaw detection)
ultrasonic flaw detection technology is used to emit ultrasonic waves into the inside of the rails, and the reflected signals are used to determine whether there are internal defects such as cracks and pores. This non-destructive detection method can accurately detect hidden dangers that cannot be detected by the naked eye, strictly control the quality of rails, and prevent unqualified products from entering the railway laying process.
Sawing and drilling
According to the actual railway laying requirements, the rails are sawed into appropriate lengths and holes for connection are drilled. Accurate sawing ensures consistent rail lengths, and standardized drilling ensures tight and stable connections between rails, so that the rails are perfectly adapted to the railway lines and ensure smooth operation of trains.