On modelling of volume related defect formation in cast irons
2000 (English)In: Proceedings of the Ninth International Conference on Modeling of Casting, Welding and Advanced Solidification Processes / [ed] Peter R. Sahm, 2000, 102-109 p.Conference paper (Refereed)
Formation of defects, e.g. porosity's and expansion penetration in cast irons, are highly related to volume changes during solidification. Prediction of porosity and expansion penetration requires a detailed modelling of structure formation and of the related volume change during solidification.
The phase transformations in cast iron are highly dependent on the kinetics and therefore also strongly influenced by the cooling rate, nucleation and chemical composition. The transformation of liquid to solid, involves formation of phases with a variety of densities. The resulting volume changes often leads to formation of porosity or excess of material. The excess of material helps to give a sound casting but if the geometry is not favourable the metal penetrates into the sand mould. The balance between shrinkage and expansion is important to understand, since it is a fundamental problem to make iron castings without shrinkage or penetration defects. The volume changes of the phases can not be measured by direct methods, but with a combination of modelling and experiments an improved understanding can be obtained.
The volumes of iron and carbon in liquid and austenite have been modelled by using a sublattice molar volume model. The models of volumes and solidification are implemented in a computer program to simulate the kinetics of phase formation and resulting volume changes of the system. Thermal analysis curves are coupled to the phase and volume changes.
The paper discusses the modelling of solidification using kinetic models and the volume change during the cooling and precipitation of the solid phases. Influence of the compositions, solidification mode and nucleation on the volume change will be calculated.
Place, publisher, year, edition, pages
2000. 102-109 p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-87054ISBN: 3826572300ISBN: 9783826572302OAI: oai:DiVA.org:liu-87054DiVA: diva2:584517
The 9th International Conference on Modeling of Casting, Welding and Advanced Solidification Processes held in Aachen, Germany, on August 20 to 25, 2000