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Title

GRAIN SIZE PREDICTION BY USING A MESHLESS ROLLING SIMULATION SYSTEM

Authorship

Hanoglu, Umut; Šarler, Božidar

Hanoglu, Umut

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Šarler, Božidar

I am this author

DOI

10.5151/9785-9785-32360

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Abstract

The aim of this research is to be able to predict the grain size of steel during the hot rolling process. A rolling simulation system has been previously developed to calculate the deformation, stress, strain, and temperature fields by using a novel meshless method. Initial size of the billet, bloom or slab and the geometry of the grooves at each rolling stand are completely user defined. This prediction model may be applied to any of the roll pass designs. The information obtained by this rolling simulator has been considered in the one way coupled grain size prediction model. First the critical strain for dynamic recrystallization is being checked. If the calculated strain is higher than that, considering also the time for meta-dynamic recrystallization, dynamic or meta-dynamic grain size calculations are carried out. If the stain is too low then only the static recrystallization is considered together with its required time. Finally, austenite grain size and ferrite grain size are calculated respectively as the steel cools down. A further model of yield stress and ultimate tensile strength predictions, which requires chemical composition of the steel, may also be included as well. The solution procedure of hot rolling is based on cross sectional slices as computational domains which are aligned towards the rolling direction. For each slice position, the exact time and effective strain field are known from the simulation results. These two are the crucial variables of a successful grain size prediction system. The current prediction model is based on collection of empirical relations found in literature. The user is free to choose or create the model he wants with his own parameters. The simulation is capable of simulating up to 12 consecutive rolling stands and results may be visualized for each slice separately. The simulation system has been coded as a user friendly computer application for an industrial use based on C# and .NET framework and runs on regular PCs. The computational time for a rolling simulation is usually less than one hour. Because of this, it can be easily used for the optimization of the rolling mill design.

Keywords

Grain size, rolling simulation, meshless methods, slice model