1. Smelting technology
High-clean steel smelting: In the production of GB light rails, high-clean steel smelting is the key starting link. Through the pre-desulfurization treatment of molten iron, the sulfur content in the molten iron can be effectively reduced, the hot brittleness problem caused by sulfur impurities inside the rails can be reduced, and the toughness of the rails can be improved. The subsequent LF refining further removes inclusions in the molten steel, improves the purity of the molten steel, and lays the foundation for the subsequent rolling of high-quality light rails.
Alloy element addition and control: According to the different usage scenarios and performance requirements of GB light rails, it is very important to reasonably add alloy elements. For example, in the production of some rails that need to improve wear resistance, manganese will be added in an appropriate amount. Manganese can enhance the strength and wear resistance of steel, so that the rails can maintain good performance in frequent friction environments. For rails with special corrosion resistance requirements, alloy elements such as chromium and nickel are added to form a dense oxide film, which improves the corrosion resistance of the rails and extends the service life in harsh environments such as humidity and seaside. In addition, advanced testing equipment is used to monitor the content of alloy elements in the molten steel in real time to ensure that the composition is accurate and in line with the standard.
2. Rolling process
Hot rolling process: Hot rolling is the main process for forming GB light rails. The smelted and refined steel billets are heated to a suitable temperature range, generally around 1000℃ - 1200℃, to give them good plasticity. Subsequently, the steel billets are gradually rolled into the required light rail shape and size through multiple passes of rolling on the hot rolling mill. In this process, the rolling force, rolling speed and the amount of reduction in each pass are precisely controlled to ensure the dimensional accuracy of the rails. For example, for rails of different specifications such as 8kg/m and 12kg/m, the cross-sectional size deviation is strictly controlled within the standard range to ensure the interchangeability and installation accuracy of the rails. At the same time, a reasonable hot rolling process can improve the internal organizational structure of the rails, refine their grains, and enhance the comprehensive mechanical properties of the rails.
Semi-continuous rolling process: Some advanced GB light rail production lines adopt semi-continuous rolling process. This process combines the advantages of continuous rolling and intermittent rolling, improving product quality while ensuring production efficiency. In the semi-continuous rolling process, the billet is rough-rolled and then enters the continuous rolling unit for finishing rolling, which reduces the temperature drop during the rolling process and ensures the uniformity of the rail structure.
3. Heat treatment technology
Normalizing treatment: Normalizing is one of the commonly used heat treatment methods for GB light rails. The rolled rails are heated to an appropriate temperature, generally 30℃ - 50℃ above Ac3 (the temperature at which all ferrite is transformed into austenite when hypoeutectoid steel is heated), kept warm for a certain period of time, and then cooled in the air. Through normalizing treatment, the internal stress generated during the rolling process of the rails can be eliminated, the internal structure can be improved, the grains can be refined, and the rails can obtain good comprehensive mechanical properties, such as improving the balance of strength, toughness and hardness, to meet the use requirements under different working conditions.
Quenching-tempering treatment: For GB light rails with higher strength and wear resistance requirements, quenching-tempering treatment will be used. First, the rail is heated to the quenching temperature, and then quickly cooled to obtain the martensitic structure, which greatly improves the hardness and strength of the rail. Then, the tempering treatment is carried out. The tempering temperature and time are adjusted according to the required performance to eliminate the quenching stress, appropriately reduce the hardness, and improve the toughness, so that the rail can achieve a good match of strength, hardness, and toughness.
4. Surface treatment technology
Rust prevention: In order to prevent GB light rails from rusting and corroding during storage, transportation and use, surface rust prevention treatment is very necessary. Common methods include coating anti-rust paint, selecting anti-rust paint with strong adhesion to the surface of the rail and good weather resistance, and spraying it evenly on the surface of the rail to form a dense protective film, isolating oxygen and moisture, and slowing down the corrosion rate of the rail. In addition, the hot-dip galvanizing process can also be used to immerse the rail in molten zinc liquid to form a zinc layer on its surface. The sacrificial anode protection of zinc is used to protect the rail substrate from corrosion, which is especially suitable for rail protection in humid and high humidity environments.
Grinding treatment: Grinding is an important means to improve the surface quality of GB light rails. Professional grinding equipment is used to finely grind the surface of the rails to remove minor surface defects, oxide scale, and unevenness caused by the rolling process. The surface finish of the rails after grinding is improved, which can effectively improve the contact conditions between the wheels and rails, reduce friction resistance during operation, reduce wear, and improve the stability and safety of train operation. In the production of light rails for sightseeing tracks in some scenic spots, grinding not only ensures the performance of the rails, but also improves the overall aesthetics, providing tourists with a better riding experience.