Hollomon-Jaffe parameters

The Hollomon-Jaffe parameter

${\displaystyle H_{p}={\frac {T}{1000}}\cdot (C+\log(t))}$

describes the effect of tempering , a type of heat treatment for steel. It is a function of the tempering duration t and the tempering temperature T. The temperature T in Kelvin and the time t in hours are included in this non- unitary formula . C is a material-dependent constant. Different combinations of duration and temperature of the heat treatment can result in identical Hollomon parameters; the initial effect is then also comparable.

The relationship can be used to save time and energy in hardening shops .

Example: Hardened steel parts made of C45 ( carbon steel without special carbide former) with an initial hardness of 61 HRC achieve the target hardness of 53 HRC after tempering for 4 hours at 190 ° C. To achieve the same hardness value, the tempering time can be reduced to 1.5 hours at a temperature of 210 ° C instead.

literature

• JH Hollomon, LC Jaffe (1945): Time-Temperature Relations in Tempering Steel . Trans. AIME, Iron and Steel Division 162, pp. 223-249.