Supervisor: Prof Barbara Shollock

Project:

Processing strip steel products from as-cast reheated slabs with optimum surface quality poses unique challenges especially for the case of electrical steels, where attainment of a defect-free surface combined with excellent magnetic properties is of critical importance. 

The challenges arise from numerous factors, e.g. the feedstock/strip moves several metres per second through the rolling stages and also experiences a range of reheat temperatures and gas environments with varying dew points together with cycles of cooling and deformation. These diverse conditions impact the surface of the steel by influencing the oxides formed and their subsequent behaviour. 

The nature of the oxides formed during reheating is mainly influenced by (i) alloy composition, especially Si and Al in the case of electrical steels and (ii) the heating profile - time (which can be from seconds to hours), temperature, heating rate and atmosphere. The evolution of these oxides during steel processing is also influenced by high-pressure descaling, growth, deformation and transformation during rolling and subsequent cooling. In some steels, external and internal oxidation occurs, and understanding the oxidation processes, the metal/oxide interface and the effect of oxidation on the underlying steel microstructure will help gain insight into the mechanical response of the steel in terms of descalability, oxide scale behaviour under deformation and downstream finishing processes (pickling, annealing and cold rolling).  

This project will study, through a combined approach of experimental and modelling work, the factors influencing the kinetics and development of oxides on steels grades, especially NGO electrical steels (Non Grain Oriented) during primary reheating (1100-1200^oC) in both natural and mixed gas. 

The research provides a basis for understanding the descalability and regrowth of secondary scale of these steels and their decomposition/internal oxidation upon cooling. The PhD will especially focus on interface and internal oxidation issues with the view to develop key descriptors and underlying mechanisms that will feed into alternative and beneficial routes for controlling oxidation of electrical steels.

To understand this, the diffusion of the oxidizing and the oxidizing species through the metal matrix or the oxide scale will be studied to determine the rate controlling process. This will be accomplished using tracer gases and secondary ion mass spectrometry in simulated process conditions. The morphology of the internal and external oxidation will be examined using FIB-FEGSEM microscopy and details of elemental segregation will be determined using chemical analysis in the STEM. Thermo-dynamic predictions of oxide stability will also be carried out to inform internal oxidation/diffusion models developed at Tata Steel UK Swinden Technology Centre. The influence of internal oxidation and formation of intrusions at the scale-metal interface on bendability will be examined using in-situtesting in the SEM with digital image correlation. 

From knowledge developed during reheating , descaling and cooling, guidelines will be developed leading to more robust prediction and control of oxidation which will complement ongoing work carried out at Tata Steel Europe R&D.

Entry Requirements:

Due to funding regulations application is restricted to UK students only.

Applicants should possess a first degree of at least a second class honours standard or the equivalent.

If you are interested in applying please email us at engd<στο>warwick.ac.uk, phone us on 024 765 23837 or fill out our online enquiry form.