Objective In response to the mass fracture problems of rail vehicle axle box steel springs in a certain region of China during application, it is necessary to analyze the spring fracture causes and develop relevant measures to address this issue.

Method  A comprehensive analysis is conducted from the perspectives of spring design, manufacturing, and maintenance application. The static strength and fatigue strength of the springs are evaluated, and parameters such as the chemical composition, mechanical properties, and surface quality of the spring materials are analyzed. Additionally, dynamic stress testing of the line and investigations of vehicle status are carried out.

Result & Conclusion  The main causes of fractures in the steel spring support coils are as follows: excessive grinding duration or excessive grinding volume during the machining of the support coils leads to an overly high surface temperature of the springs, while during the cooling process, surface cracks form due to thermal contraction. Consequently, improper formation of the support coils results in localized contact or eccentric loading, causing abnormal wear and micro-cracks in operation. The main fracture cause of the steel spring transition coils is the poor contact line quality during manufacturing. This leads to the discontinuous line contact or localized point contact, resulting in stress concentration in the contact areas.