Predicting the mechanical properties of a quenched and temperedsteel thanks to a “tempering parameter”

Abstract

The Hollomon-Jaffe parameter is commonly used to characterize thermal cycles and definetime-temperature equivalences during tempering, but it can only be computed for simplethermal cycles defined by a couple of values [temperature; time]. Its use is not adaptedfor complex thermal cycles. Three tempering parameters which integrate the full thermalcycles were investigated: the Hollomon-Jaffe derivative parameter, and the Tsuchiyama andArrhenius laws. Simple and complex thermal cycles were performed on a water-quenchedcarbon steel (i.e. different heating and cooling rates or two-step cycles, withtemperature varying between 450 °C and 750 °C and times from 30 s to 3 days). All threetempering parameters show good correlation with the tensile properties of the material,even when complex cycles were performed, provided that the material constant is optimized.The sensitivity to the determination of this constant is low for the Tsuchiyama andArrhenius laws: they can be considered as robust and reliable. On the contrary, theHollomon-Jaffe derivative parameter proved unstable.