Compatibility of Mixed Use of National Standard and Foreign Standard Rails
- What are the key geometric dimension differences between the domestic standard 60kg/m rail and the foreign standard UIC60 rail, and how to make adaptation adjustments?
The head width of the domestic standard 60kg/m rail is 73mm, the web thickness is 16.5mm, and the base width is 150mm. While for the UIC60 rail, the head width is 70mm, the web thickness is 17mm, and the base width is 155mm. During mixed installation, for the difference in rail head width, a special fastener system can be customized, such as widening the clamping part of the fastener to ensure effective fastening for different rail head widths. For the different web thicknesses, the groove depth of the under-rail pad needs to be adjusted to make the rail fit tightly with the pad. In the face of the change in rail base width, the bolt hole spacing of the sleeper can be replaced or adjustable sleeper fasteners can be used to ensure the stable installation of the rail base.
- From the perspective of material properties, what are the precautions when mixing domestic standard U71Mn rails and foreign standard rails of similar strength grades?
The domestic standard U71Mn rail has a carbon content of 0.65 - 0.76% and a manganese content of 0.70 - 1.20%, with good strength and toughness. Foreign standard rails of similar strength grades may have differences in chemical composition, such as some foreign standard rails adding special alloy elements. Before mixing, a comprehensive chemical composition analysis and mechanical property test of the two types of rails are required to ensure that they are close in key performance indicators such as hardness, tensile strength, and yield strength. Avoid problems such as stress concentration and inconsistent deformation at the rail joints due to excessive performance differences under the action of train loads. At the same time, pay attention to the fatigue resistance and wear resistance of different materials, and strengthen protection and monitoring of weak links.
- In the track circuit system, what impacts will the differences in electrical properties between domestic standard rails and foreign standard rails bring, and how to solve them?
The electrical impedance, magnetic permeability and other electrical properties of domestic standard rails are designed according to the domestic track circuit standards, and foreign standard rails may be different. This will lead to unstable track circuit signal transmission, affecting the accuracy of train operation control and signal display. The solution is to install special electrical compensation devices, such as track circuit adapters, in the area where rails are mixed to compensate and adjust for the differences in electrical properties of different rails, ensuring that the track circuit signals can be transmitted and received normally. At the same time, the parameters of track circuit related equipment need to be recalibrated and optimized according to the actual mixing situation.
- When using a mixture of domestic and foreign standard rails in the curve section, how to consider the differences in their lateral force characteristics?
Rails in the curve section bear large lateral forces, and domestic and foreign standard rails may be different in lateral stiffness, anti-roll ability and other lateral force characteristics. For example, some foreign standard rails are designed for high-speed curve sections and have higher lateral stiffness. When mixing rails, the superelevation setting of the curve section needs to be accurately calculated. According to the differences in the lateral force characteristics of the two types of rails, the superelevation value is reasonably allocated so that when the train passes, both types of rails can share the lateral force evenly. In addition, the lateral restraint of the track structure can be strengthened in the curve section, such as adding rail braces and strengthening the compaction of the ballast bed, to improve the overall lateral stability of the track and meet the force requirements of different rails.
- In the rail welding process, what are the special requirements for the welding process of domestic standard rails and foreign standard rails?
Due to the differences in chemical composition and material properties of the two types of rails, the welding difficulty increases. Before welding, a welding process qualification test must be carried out to determine appropriate welding parameters, such as welding current, voltage, and welding speed. For rails of different materials, different welding materials, such as electrodes and welding wires, may need to be selected to ensure that the strength and toughness of the weld match the base metal. During the welding process, the welding environment must be strictly controlled to prevent defects such as pores and cracks. After welding, a comprehensive non-destructive inspection of the weld, such as ultrasonic flaw detection and magnetic particle flaw detection, is required to ensure that the welding quality meets the requirements of the track project and guarantee the connection reliability of the mixed rails.