Prediction Models of the final properties of steel rods obtained by thermomechanical rolling process

摘要

The objective of this research project was the setting up of a numerical model able to predict the microstructure of rod rolled products which, taking into account the rolling schedule and cooling, is able to provide the mechanical and microstructural final characteristics. The model was developed starting from the theoretical knowledge proposed by many researchers who have dealt with these issues, and the experience gained in the design of rolling systems by Siemens-VAI. In order to allow the maximum working flexibility to the final user, the prediction model requires to fill in the thermomechanical conditions for rod rolling (preheating temperature, reduction pass, rolling temperatures, interpass time, strain rate and cooling profile); a database of more than 150 steel types was developed, containing CCT curves and the mechanical properties relative to the cooling rates. The tool provides the CCT curves, suitably modified to take into account the microstructure of the rolled, superimposed with the cooling trajectory set up by the operator, as well as mechanical and microstructural data of interest for that particular class of steel. The Model was validated by direct comparison with the properties of rod rolled products under controlled conditions, obtaining an excellent prediction capability.