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Title: Development of novel ULC/IF strip steels
Author: Ooi, S. W.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2006
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As part of this study, two experimental Ultra Low Carbon (ULC)/Interstitial Free (IF) steel grades were investigated, one based on combined vanadium and titanium additions and the other based on titanium only additions. The overall aim is to explore the potential of vanadium additions for the development of novel ULC/IF strip steel grades for automotive applications. The experimental study employed hardness testing, tensile testing, optical and transmission electron microscopy carried out on both novel steel grades. Light optical microscopy and mechanical testing was performed, using both steel grades in the as received (cold rolled) conditions as well as to numerous batch and continuous annealed cycle designed to result in suitably high formability values, thus optimising the applications potential of both steel grades. Grain size measurements were also carried out in both batch and continuous annealed samples and samples subjected to simple annealing experiments, for studying the evolution of grain size with time and temperature. The volume fraction of precipitated species under equilibrium conditions is also being calculated using solubility product equation and MTDATA thermodynamic modelling software. The primary conclusion drawn from this investigation is that novel Ti-V strip steels have the potential for achieving very high formability values employing lower dwell temperatures during continuous annealing. Precipitate studies of the novel ULC steels helped identify the major role of TiC precipitates in retarding the recrystallisation behaviour as well as the grain growth of {111} texture grains during annealing for both strip steel grades. It has been confirmed that VC precipitation on TiN during coiling plays a key role for stabilising carbon. The processing of Ti-V grades could be tailored producing bake hardening ULC grades, thus increasing the strength of the formed component without any additional costs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available