2. Measurement of the hardenability
2.1. Hardenability of steels
A practical indication of steel hardenability is the critical minimum cooling rate for the formation of a fully martensitic microstructure. Hardenability is measured quanti- tatively, usually by determining the extent or depth of hardened zone of a standard size and shape of test specimen in a standardized quench conditions. The hardness variation with the depth of the Jominy sample is a result of variation in the type and content of martensite, bainite, ferrite and pearlite which arises since the cooling rate decreases with distance from the water quenched end. Hardenability depends on the chemical composition of the steel and also can be affected by prior processing condi- tions, such as the austenitizing temperature which affects the austenite grain size and amount of carbide/nitride forming elements in solid solution.