Abstract
Problem Statement (Relevance): To be able to control the structural and mechanical properties of the material going through a hot strip mill, it is necessary to build a mathematical model for the recrystallization kinetics of deformed austenite under the conditions that simulate the strain rates and the temperatures characteristic of a real rolling operation. Objectives: This research aimed to develop a mathematical model for the static recrystallization of austenite in carbon and low-alloy steels under hot rolling conditions. Methods Applied: 3D recrystallization graphs showing the recrystallization of austenite in carbon and low-alloy steels were used for recrystallization model development. The above graphs were built following an experimental study of the austenite structure formed under the conditions that simulate the strain rates and the temperatures found within the finishing mill of a real hot strip mill. The method of multiple regression analysis was applied for obtaining the factors of the recrystallization kinetics equations. Originality: A model of the austenite recrystallization kinetics has been developed that, alongside the strain parameters, considers the chemical composition of steel, as well as the austenite grain size prior to deformation. Findings: With the help of the developed model, the effect of the chemical composition on the recrystallization kinetics in low-alloy steels has been analysed. The article demonstrates that a change in the chemical composition of different low-alloy steel grades may change the recrystallization time of de-formed austenite by more than twenty times. Variations of the chemical composition within a steel grade may also produce a considerable impact on the recrystallization kinetics, which should be taken into account when developing processes for hot rolling of steel. Practical Relevance: The austenite recrystallization model can be used for predicting changes in the austenite structure, as well as for hot strip rolling optimization.
Keywords
Recrystallization, austenite, hot rolling, hot strip mill, modeling, steel, chemical composition.
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