The paper presents a model offering improved implementation of material behaviour in plastomechanical simulations of hot‐forming processes. Microstructural states at any instant during forming are evaluated successively on the basis of semi‐empirical equations determining the state of dynamic recrystallization, and the corresponding flow stress is inferred. Upsetting tests were used to determine the characteristic data for a Cr‐V steel in a spectrum of ט = 830–1150°C, ∊ = 0.05–5 s−1 and dγo = 70–108μm. The developed model is used to simulate upsetting tests, validating its accuracy in terms of structural description and flow‐stress determination.

In metal forming, the workpieces are formed to the desired shapes or profiles. Especially in hot forming, the microstructure of workpiece changes during plastic deformation. Modern forming technologies allow to control the shape and the microstructure of formed product in a wide range and will gain increasing importance in future in the field of metal forming. In order to develop this forming technology which may be called “macroscopic microscopic materials processing”, theoretical predictions of plastic deformation as well as microstructural changes are indispensable. A new mathematical formulation to predict flow stress and microstructural change in hot forming will be presented in this paper. This model is based on an incremental formulation taking the dislocation density as a representative variable.

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