Official Answer
Answer
Austempering is a heat-treating process that results in a bainitic microstructure rather than the traditional martensitic structure. For SAE 1070 or 1090 carbon steel rings, austempering involves quenching from the austenitizing temperature into a salt bath held above the Martensite Start ($M_s$) temperature. This results in a ring with equivalent hardness but significantly higher impact toughness and ductility. This is especially beneficial for spiral rings that must be expanded significantly during installation, as it reduces the risk of 'snapping' during the assembly of heavy-duty truck drivelines.
