Calculate the Hollomon-Jaffe tempering parameter (P) to predict tempered hardness from temperature and time for carbon and low-alloy steels
Input Parameters
Results
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Hollomon-Jaffe Parameter
×10³
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Estimated Tempered HRC
HRC
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Estimated Hardness
HV
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Tempering Effect
Note: The Hollomon-Jaffe parameter allows comparison of different tempering cycles. The same P value from different temperature/time combinations gives approximately the same hardness. C ≈ 20 for most carbon and low-alloy steels.
Reference
Hollomon-Jaffe Tempering Parameter:
P = T(K) × (C + log10(t))
T = tempering temperature in Kelvin
t = time in hours, C = material constant (~20 for carbon steels)
Higher P = more softening. Equivalent tempering: same P from different T/t combos.