METALS

摘要

Two air-hardening steels said to have strength and hardness equivalent to SAE 52100 and SAE 4140, with less distortion, have been introduced by Ovako Steel, Sweden. Hardenability of steel is limited by the critical cooling rate, defined as the slowest cooling rate possible while still resulting in a martensitic structure. The company says that by slow cooling in air, the surface-to-core temperature gradient is very small when the austenite transforms to martensite. As a result, the transformation is homogeneous, and distortion is significantly reduced.