scope:

This method covers a procedure for calculating minimum, mean, and maximum ideal critical diameters (D_I) for base chemical composition (D_IB) and for the case chemical composition D_IC of wrought and cast heat treatable steels. The calculated values of D are intended to serve as a guide to the range of hardenability that can be expected for a grade or family of steels. Steels without standard hardenability (H) bands can therefore be compared to those with H bands. The calculated D_I's are not intended to mean that a D_I value for a particular heat of steel will never exceed the stated minimum or maximum, but that most of the time the D_I will fall within the stated D_I range. Calculated D_I's are normally used only for comparative purposes but they may also be used for calculating hardenability bands.