FLAME METALLURGICAL, INC.
F.E. Harris developed a formula to predict total (not effective) case depth based on the effect of time and temperature for normal carburizing. Normal carburizing means saturated austenite at the steel surface while at temperature. Note also that the temperature is time at carburizing temperature not including 'heat-up' or any subsequent cycle diffusion time :
t = time at temperature in hours.
T = absolute temp in degrees Rankine (F + 460).

Input time in hours:
Input temp deg. F :
Total Case depth (inches) =

For case depths in the 0.040" - 0.070" range, the calculated case depth will correspond to a point on the gradient about 0.07%C higher than the core carbon content.

The case depth will be less than the calculated depth if the surface carbon concentration during processing is less than the saturated austenite level. For a given temperature, the solubility of carbon in austenite for plain carbon steels can be represented by the Acm line on the iron-carbon phase diagram. Most of the common carburizing steel alloying elements move the cementite line to the left (decrease the solubility).