What is condition e4 in steel?

Condition E4 in steel refers to a specific heat treatment process that involves quenching, followed by tempering. This process typically aims to enhance the mechanical properties of the steel, such as its hardness, strength, and toughness, by optimizing its microstructure. E4 condition is often associated with tool steels and other high-performance applications where a balance between hardness and ductility is crucial. The precise parameters of this treatment can vary depending on the steel grade and intended use.