from the conferences organized by TANGER Ltd.
Next generation casting technologies such as thin slab, belt or strip casting have gained popularity due to the reported energy saving, which can be as high as 1.6GJ/tonne when compared to conventional thick slab casting. However, these casting approaches result in changes in cooling rate during solidification and in thickness reduction to the required product geometry, which could affect the resulting microstructure and elemental segregation. In this work the secondary dendrite arm spacing (SDAS) and micro-segregation levels for the range of cooling rates relevant for different casting technologies (0.8 to 6°C/s) have been assessed using predicted COMSOL modelling coupled with known empirical SDAS and cooling rate relationships. A dual phase DP800 steel has been selected as the material to evaluate its specific role in micro-segregation. SEM-EDX grid maps have been used to characterise micro-segregation levels. To complement the experimental observations, Thermo-Calc simulations were conducted to predict micro-segregation behaviour using both initial cooling rates and post-solidification profiles for validation. The segregation ratios have been mapped for various cooling rates, correlating to the casting relevant techniques enabling quantification of segregation severity. The influence of CR on the SDAS and microsegregation of Mn has been investigated in this study. The SDAS results show for a DP wedge mould, that at lower CR (0.68℃/s) the dendritic structure is coarse with SDAS at 104.01µm (± 4.49µm), where the SDAS was refined at higher CR (5.8℃/s) measured at 40.02µm (± 1.87µm). The SR behaviour showed a difference at the lower CR 0.68℃/s and higher CR 5.8℃/s as well as the mid-section (all of which can be broken down into three distinct regions) and will be discussed.
Keywords: Cooling rate, microsegregation, secondary dendrite arm spacing, solidification, casting© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.