The original viscoplastic framework at low homologoustemperature is based on the coupling of the E. Rauch'soriginal approach for mixing athermal and viscous termin the flow stress of ferritic steels, a general viscoplasticpotential and a microstructure based quasi-static behaviorlaw. The formalism gives accurate results in excellentagreement with available experimental results with only twoadjusted parameters, over a wide range of strain rates andtemperatures.