With the aim of simulating the hot rolling process, single and double hit compression tests were performed in the temperature range 800 to 1200$ sp circ$C at strain rates of 0.2 to 50 s$ sp{-1}$ on selected low carbon steels containing niobium, boron and copper. The stress/strain curves determined at high strain rates were corrected for adiabatic heating and constitutive equations were formulated. When dynamic recovery is the only softening mechanism, these involve a rate equation, consisting of a hyperbolic sine law, and an evolution equation with one internal variable. When dynamic recrystallization takes place, the incorporation of the dynamically recrystallized fraction in the above evolution equation makes it possible to predict the flow stress after the peak. / The kinetics of static recrystallization were characterized in terms of the mean flow stresses, which lead to more accurate results than alternative methods. Appropriate expressions were formulated for the recrystallization kinetics and the mean austenite grain size as a function of predeformation, temperature and particularly strain rate. / Particular attention was paid to prediction of the temperature distribution through the thickness of the rolled plate or strip. The effects taken into account are radiation and convection from the surface when the material is between stands, and conduction to the rolls and the temperature increase due to mechanical work when the material is in the roll gap. An explicit finite difference method was used to calculate the temperature distribution through the thickness of the workpiece during processing. / On the basis of the temperature model and the constitutive and recrystallization kinetics equations, a computer model for the prediction of multi-stage rolling force and microstructural evolution was developed. The predictions of these models are in good agreement with measurements on both experimental and commercial steels. Also, by appropriate control of the thermomechanical parameters, high strength steels with transition temperatures below $-$100$ sp circ$C were developed. These results constitute a step towards the on-line control of plate and hot strip mills, and the development of new tough high strength steels.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74284 |
| Date | January 1990 |
| Creators | Laasraoui, Abdellatif |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001074450, proquestno: AAINN63492, Theses scanned by UMI/ProQuest. |
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