Rail clips are commonly used in the railway systems. Its main function is to connect the rails and sleepers, primarily using the stored energy from the elastic deformation of the spring clip to mitigate mechanical vibrations and impact forces. It operates under long-term and cyclical bending, as well as torsional alternating stresses induced by dynamic loads, functioning in extremely harsh working environments.
In the production of spring clips, the primary raw material used is hot-rolled spring steel. The microstructure of the spring clip should consist of uniformly tempered martensite and troostite, with trace amounts of discontinuous ferrite allowed in the core. The decarburization depth on the surface of the spring clip should not exceed 0.3mm. After 5 million fatigue tests, the spring clip should not break, and the residual deformation should not exceed 1mm. The production process for spring clips includes material shearing, medium-frequency induction heating, hot forming, oil quenching, tempering, rust prevention treatment, finished product inspection, and packaging.
The main reason for the failure of spring clips during use is material defects. Stress often occurs on the surface layer of spring steel, so the surface quality of spring steel has a significant impact on fatigue strength. Cracks, defects, and scars caused during the rolling process of spring steel are often one of the reasons for the fatigue fracture of spring clips. Additionally, metallurgical defects such as non-metallic inclusions, bubbles, folding, element segregation, etc., can also lead to the premature formation of fatigue cracks between inclusions and the matrix interface.