The hardened layer depth is the measure of harden-ability. A good harden-ability will sense even thicker sections are uniformly hardened. Conversely a poor harden-ability will generate a soft core within the piece of steel. The harden-ability is dependent on the given factors as:

a) The steel composition plays a significant role. The steels along with high carbon content harden to a greater depth than steels along with lower carbon for the former have lower critical cooling rate. Alloying element as like chromium enhance the harden-ability.

b) The quenching intermediate.

c) The section of dimensions.

The standards explain the steel harden-ability by stating the ruling section that is maximum thickness which can be utilized and yet achieve the stated properties via the section. Size of thickness plays a significant role also in terms of distortion that may arise in the material. Variations in the rate of cooling inside the component can lead to various amount of contraction at various points across the section. Such differential contraction will outcome in the component distortion.