Effects of Low Temperature on the Friction and Wear Performance of Q355B High‐Speed Railway Brake Disc Material

In cold climates, ice formation on the brake discs of high‐speed trains results in surface scratches and subsequent abnormal wear during braking. It is imperative to investigate the friction and wear performance of high‐speed train brake discs in low‐temperature environments. A series of pin‐on‐disc tests were performed to study the tribological properties of the brake friction pair under different temperature conditions (20, 0, −10, and −20°C). The wear performance of the brake disc exhibited a strong dependence on temperature. At low temperature (−20°C), the mean coefficient of friction is about 30.12% higher than that at 0°C, exhibiting a maximum wear depth of 24 μm. The analysis indicates that the primary reasons are as follows: under low‐temperature conditions, crack propagation is accelerated, and pitting and spalling pits form on the worn surface, resulting in severe surface damage. Concurrently, microstructural analysis at different temperatures revealed that at low temperatures, in the Q355B brake disc, the ferrite undergoes embrittlement and a loss of plasticity, with dislocation motion being hindered. Meanwhile, the stability of pearlite decreases. The cementite lamellae act as crack initiation sites, thereby accelerating brittle fracture. This paper gives a certain theoretical basis and reference for subsequent research on brake disc wear in extremely cold environments.