抄録
We investigated the microstructure of the brake rotor used in service, and the re-heated specimen in order to clarify the effects of heat process on the micro structural change of brake rotor. 1) The microstructure of brake rotor transforms to austenite crystal forms when heated to the point of AC3 transition temperature. Since the austenite crystal size in steel becomes larger in proportion to heating temperature, heat history of the used brake rotor can be presumed by measuring the crystal grain size of the rotor. 2) When the brake rotor is heated to the transition temperature, the refinement of grain size and the phase transformation occur simultaneously. The crystal size of white layer is smaller than that of re-heated specimen, which seemes to be caused by the dynamic recrystallization due to strain on the white layer. 3) Analysing the surface temperature of the brake rotor using the infrared thermography revealed that the brake rotor temperature rises locally at the hot spot when braking. The analysis also enabled us to estimate the maximum surface temperature of the brake rotor at braking
