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- Tadesse, Abel, 1983-, et al.
(författare)
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On the Solidification and Structure Formation during Casting of Large Inserts
- 2017
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - 1073-5615 .- 1543-1916.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Graphite nodule count and size distributions for Boiling Water Reactor (BWR) and Pressure Water Reactor (PWR) inserts have been investigated by taking samples from heights of 2160 and 1150 mm, respectively. In each cross-section, two locations were taken into consideration for both the microstructural and solidification modeling. The numerical solidification modeling was performed in a two-dimension model by considering nucleation and cell growth in a eutectic ductile cast iron. The microstructural result reveals that the nodule size and count distribution along the cross-sections are different in each location for both inserts. Finer nodule graphites appear in the thinner sections and close to the mold walls. Coarser structure is distributed mostly in the last solidified location. The simulation result describes the finer nodules are related with higher cooling rate and lower degree of microsegregation, whereas the coarser are related to lower cooling rate and a higher degree of microsegregation. The solidification time interval and the last solidifying locations for BWR and PWR are also different.
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| 2. |
- Tadesse, Abel, 1983-, et al.
(författare)
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On Volume changes during the solidification of peritectic steel
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The volume change during the solidification of an industrial high nickel peritectic steel was studied by using Linear Variable Differential Transformers (LVDT). The effects of the different primary phase precipitation on the volume change were studied by modifying the molten metal with Ti. The addition of Ti varies from 0.13, 0.15 and 0.25 wt-%. The microstructures of the final casting also went through an Optical Microscopy analysis to assess the differences between different samples. The displacement change measurement shows that the peritectic steel expands or contracts during the solidification. The primary austenite (γ) precipitation during the solidification in the metastable region is accompanied by gradual expansion on the casting sides. Primary δ-ferrite precipitation under stable phase diagram complemented by a severe contraction in the solidification region. The microstructural analysis reveals that the only difference between the samples is grain refinement with the Ti addition. Moreover, the severe contraction in the solidification region might be the source for the crack formation, and further theoretical analysis is required in the future to verify the observations.
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| 3. |
- Tadesse, Abel, 1983-, et al.
(författare)
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The Effects of Carbon on the Solidification of Nodular Cast Iron– its Study with the help of Linear Variable Differential Transformer and Microstructural Analysis
- 2017
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Ingår i: International Journal of Cast Metals Research. - 1364-0461 .- 1743-1336.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The effect of carbon on the solidification of ductile cast iron (DCI) was studied using linear variable differential transducers (LVDT) and microstructural analysis. Thermal expansion during the eutectic solidification was investigated by using LVDT and temperature measurements in a sand mould. The eutectic volume change was compared with the theoretical calculation. In addition to that, the primary austenite during the solidification was evaluated by using differential thermal analysis (DTA) and the samples undergo a dilatometer experimentation to assess the effect of cooling rates. It was found that the samples show no expansion in the transversal direction due to higher micro-shrinkages in the centre whereas in the longitudinal direction the samples shows expansion until solidifications completed. The theoretical and measured volume changes agree with each other. The austenite fraction and micro-shrinkage pores decrease with increase in carbon content. The nodule count and distribution changes with carbon content. The thermal contraction of DCI is not influenced by the variation in carbon content at lower cooling rate.
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