The development of high strength hot rolled steels is an important area for
improving vehicle fuel efficiency. In collaboration with ArcelorMittal, this project
focussed on developing a hot rolled steel with 980 MPa ultimate tensile strength, 800
MPa yield strength and 50% hole expansion ratio. To achieve the target mechanical
properties, four different chemistries were trialled which varied the carbon, niobium and
vanadium contents. Six combinations of finishing, coiling and intermediate temperatures
were trialled for each chemistry.
The effects of thermomechanical processing parameters and alloying contents on
the mechanical properties were determined through tensile and hole expansion testing.
Microstructural analysis was completed to correlate the mechanical properties to the
microstructural characteristics. Microscopy techniques performed included optical
microscopy, scanning electron microscopy, transmission electron microscopy and atom
probe tomography. The phase transformations which occur during thermomechanical
processing were investigated using dilatometry testing.
Microstructural characterization was used to determine the breakdown of
strengthening contributions from intrinsic, solid solution, grain boundary, precipitation
and dislocation strengthening. Trials varying the processing parameters and steel
chemistry led to an understanding of how thermomechanical processing and alloying
influence the microstructural features and corresponding mechanical properties in hot
rolled microalloyed steels. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24349 |
| Date | January 2019 |
| Creators | Hutten, Esther |
| Contributors | Zurob, Hatem, Materials Science and Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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