Abstract: The calculation method of the nonlinear equation is used to calculate the hardenability of 20CrMnTiH steel, and it can only be corrected by the actual production data, and can be used to calculate and predict the hardenability accurately. The deviation between the calculated value and the measured value is not more than 2HRC. By chemical composition design and control 20CrMnTiH steel ,it is to ensure △ [C] less than 0.007% ,△ [Si] less than 0. 04% , △ [ Mn ] , △ [Cr] less than 0.02% ,△ [Ti] less than 0. 01% , △ [ Alt] less than 0. 010% , [ Ni] , [ Cu] no more than 0. 05% , [ Mo] , [ W], [V] no more than 0.03% , [ P] , [ S] no more than 0. 020% , [ N] and [ B] no more than 0. 006 0% and 0. 000 5% respectively ,and the control of carbon segregation index is less than 1.035% ,the end quenching can achieve the international advanced level of the permeability of HRC4 bandwidth control.

Key words: 20CrMnTiH, Hardenability Calculation, Narrow Hardenability Band Control