VASILYEV Alexander St.Petersburg State Polytechnical University

Spoluautoři SOKOLOV Dmitry, OGOLTCOV Alexey, SOKOLOV Semen, KOLBASNIKOV Nikolay

Mathematical models of the mechanical properties for steels with a complex microstructure are presented. These models are a component of a recently developed integral hot rolling model for mill 2000 of SEVERSTAL (STAN 2000), along with the models for predicting austenite microstructure evolution under hot rolling and its transformation during subsequent cooling. The models for predicting yield and tensile stresses are based on the rule of mixture according to which the contributions of individual structural components are proportional to their volume fractions. The following structural components are considered: polygonal ferrite, pearlite, bainite of different morphology, and martensite. The ferrite grain size contribution is described using the Hall-Petch equation. Pearlite contribution is calculated taking into account the combined effect of its volume fraction and inter-lamellar distance. Bainite contribution to strength properties is determined taking into account the size of bainite blocks, volume fractions of bainites with different morphology and dislocation density. Martensite contribution is defined with account of its volume fraction. For the micro-alloyed steel grades, additional hardening caused by the Nb(C,N) and V(C,N) precipitates formed at the hot rolling stage is taken into account. The models were calibrated using experimental data base on mechanical properties for a number of steel grades rolled on mill 2000 of SEVERSTAL with chemical compositions covering the following ranges of alloying elements content: С(≤0.65); Mn(≤2.0); Si(≤1.0); Cr(≤0.9); Ni(≤0.6); Cu(≤0.5); Mo(≤0.4); Nb(≤0.05); V(≤0.065); Ti(≤0.06). The predicted mechanical properties are in good agreement with the experimental data.

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