AbstractThe available data on minimum strain rate (‘secondary creep’) in creep tests and on maximum stress (first peak stress) in hot deformation tests obtained forγiron and forγFe–C alloys have been reviewed and allocated in the form of an equationɛ=4·6×1017(σ/E)3·0exp (α%C) sinh (60·137σ/T) exp (−32 714/T), whereɛis the strain rate (s−1),σis the stress (MN m−2), E is the elastic (Young's) modulus (MN m−2) according to E=230 950−99·04T, %C is the per cent carbon content, and T is the absolute temperature. The range of validity is from approximately Z′=ɛexp (32 714/T) exp (−α%C)=103to 1014s−1(where Z′is a modified Zener–Hollomon parameter), which covers the temperature range from 900 to 1400°C. The factorαdescribing the influence of carbon content is given by the expressionα=2·3−2·1 log (60·137;amp;#x03C3;/T). Hence, the softening of austenite by carbon decreases with increasing stress and decreasing temperature. At very highσ/T ratios, the factor ;amp;#x03B1; may even become negative reversing the effect of carbon to strengthening. A procedure is suggested by which the given equations can be applied also for the description of primary creep.MST/1386