The available data on secondary creep in creep tests and on maximum stress in hot deformation tests obtained forδandαferrite have been reviewed and expressed in the form of the equationϵ= K(σ/E)Pcsinh(Vσ/RT) exp(—Qc/RT) with pc= 2·5, V = 0·0013 m3mol−1, and K = 2·6×1017s−1, E and Qcbeing temperature dependent functions. The approximate range of validity is Z =ϵexp (Qc/RT)≈101—1011s−1. Together with the corresponding equation for austenite the data can be used to predict the viscoplastic behaviour of austenite—ferrite mixtures.MST/1538