Hollomon-Jaffe parameter

The Hollomon-Jaffe parameter, or HP, describes the effect of a heat treatment at a temperature for a certain time.^[1]

Effect

The effect of the heat treatment depends on its temperature and its time. The same effect can be achieved with a low temperature and a long holding time, or with a higher temperature and a short holding time.

Formula

In the Hollomon-Jaffe parameter, This exchangeability of time and temperature can be described by the following formula:

$H_p = \frac {(273.15 %2B T)}{1000} \cdot (C %2B \log(t))$

This formula is not consistent concerning the units; the parameters must be entered in a certain manner. T is in degrees Celsius. The argument of the logarithmic function has the unit hours. C is a parameter unique to the material used. The Hollomon parameter itself is unitless and realistic numeric values vary between 15 and 21.

$H_p = T (C %2B \log(t)) \,$

where T is in kilokelvins, t is in hours, and C is the same as above.

References

^ Brooks, Charlie (1996). Principles of the heat treatment of plain carbon and low alloy steels. ASM International. p. 158. ISBN 0871705389. http://books.google.com/books?id=fVIlbCFTodgC&pg=PA158&dq=%22Hollomon-Jaffe+parameter%22&hl=en&ei=MM_STNDEGsOblgeJ4M3vDQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCwQ6AEwAQ#v=onepage&q=%22Hollomon-Jaffe%20parameter%22&f=false.