Abstract：The chemical composition, macroscopical low magnification observation, high magnification microstructure observation and hardness test of 40Cr steel flywheel were carried out by means of direct reading spectrometer, infrared carbon sulfur analyzer, optical microscope, and hardness tester. Combined with the manufacturing technology of flywheel, the causes of cracking were analyzed. The results showed that the quenching and tempering hardness of flywheel and the quenching hardness of shaft neck could not meet the requirements. The surface quenching hardness of the wide shaft neck of flywheel was not uniform, and local areas were unquenched. There was stress concentration between this unquenched area and the quenching layer. Moreover, some sulfide inclusions with large size and width existed in the flywheel material, which caused the cracking of flywheel.
2021, Vol. 39 
