Infrared thermography provides an option for characterising surface reactions and their effects on the solidification of steel under different gas atmospheres. In this work, infrared thermography has been used during solidification of Twin Induced Plasticity (TWIP) steel in argon, carbon dioxide and nitrogen atmospheres using a confocal scanning laser microscope (CSLM). It was found that surface reactions resulted in a solid oxide film (in carbon dioxide) and decarburisation, along with surface graphite formation (in nitrogen). In both cases the emissivity and, hence, the cooling rate of the steel was affected in distinct ways. Differences in nucleation conditions (free surface in argon compared to surface oxide/graphite in carbon dioxide/nitrogen) as well as chemical composition changes (decarburisation) affected the liquidus and solidus temperatures, which were detected by thermal imaging from the thermal profile measured.

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Confocal scanning laser microscopy is a growing technique as it offers the unique capability to observe (amongst other things) the solidification of high melting point materials such as steels. Here this technique has been expanded to incorporate an infrared thermographer to gain bulk information about solidification of both pure iron and a low carbon steel. This technique shows a clear indication of the onset and competition of solidification at rates up to 10 °C/s and as such becomes more applicable to the rates expected during steel casting compared to conventional calorimetry.Highlights  An upgrade of the CSLM has been proposed that incorporates thermography. Solidification has been successfully monitored using this technique  Comparisons has been made to conventional DSC techniques. ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T Characterisation of solidification using combined Confocal Scanning Laser Microscopy withInfrared Thermography. ABSTRACTConfocal scanning laser microscopy is a growing technique as it offers the unique capability to observe (amongst other things) the solidification of high melting point materials such as steels. Here this technique has been expanded to incorporate an infrared thermographer to gain bulk information about solidification of both pure iron and a low carbon steel. This technique shows a clear indication of the onset and competition of solidification at rates up to 10 °C/s and as such becomes more applicable to the rates expected during steel casting compared to conventional calorimetry.

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