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Microstructure and tensile property simulation of grey cast iron components
Department of Mechanical Engineering and Industrial Organisation / Component Technology, Jönköping University, Jönköping.
2004 (English)Report (Other academic)
Abstract [en]

Designers and manufacturers of grey cast iron components have for a long time been interested in predicting microstructures and tensile properties. Accurate predictions are desirable to develop and optimize cast components as well as to reduce manufacturing expenses.

Recent developments in the field of eutectic nucleation, eutectic growth and prediction of tensile strength in grey cast iron have been implemented into commercial, finite difference method based, simulation software. Cylindrical samples with varied cooling conditions and a complex shaped cylinder head have been simulated. The simulation procedure includes kinetic models for microstructure prediction. A new fading law is introduced to calculate the nucleated eutectic and inoculants adapted eutectic growth. The tensile strength is calculated using a model based on the stress intensity in the metallic matrix caused by the presence of graphite flakes.

Cooling curves, microstructure and tensile properties obtained by simulation are compared to measured values.

Place, publisher, year, edition, pages
Jönköping: Ingenjörshögskolan , 2004. , 16 p.
Series
Research Report. School of Engineering., ISSN 1404-0018 ; 2
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-87062OAI: oai:DiVA.org:liu-87062DiVA: diva2:584641
Available from: 2013-01-09 Created: 2013-01-09 Last updated: 2013-01-09
In thesis
1. On microstructure formation and mechanical properties in grey cast iron
Open this publication in new window or tab >>On microstructure formation and mechanical properties in grey cast iron
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A major user of cast components is the automotive industry, where the functionality of the components is related to environmental demands. Internal combustion engines are constantly being improved to emit less pollution. A vital part in this development is to increase the material properties of engine components during their life cycle. In particular, cylinder heads, cylinder blocks and piston rings for diesel engine are produced in grey cast iron. Cast iron is expected to be in use far into the foreseeable future, due to favourable properties and low production costs. This work has been devoted to study microstructure formation, the tensile properties of cast iron and to some extent defect formation.

The microstructure develops during solidification and solid state transformations. An inverse thermal analysis method was developed to study the kinetics of the microstructure formation. The inverse thermal analysis used, the Fourier method, analyses the cooling curves of two thermocouples to study the solidification or transformation. To decrease experimental errors, simulations have been done and the cooling curves were analysed. The best results were obtained when the thermocouples were placed close to each other.

With the help of the thermal analysis a time dependent and fading nucleation law of the eutectic cells was found to fit the experimental results best. The experiments were made by multiple thermal analyses, and six different types of inoculants were investigated. The eutectic growth behaviour during solidification was evaluated with inverse thermal analysis, and it was found that commercial inoculants not only affect the eutectic nucleation but they also control the eutectic growth rate.

Models of densities and volume changes are an integral part of a microstructure simulation of cast irons. These models are important for the inverse thermal analysis and an understanding of the porosity and expansion penetration in cast iron.

The tensile strength of grey cast iron has been discussed by examining the fracture mechanism of the material at failure. The ultimate tensile strength is a result of the intimate collaboration between the graphite flake and the primary phases. Several parameters, including the graphite morphology, carbon content, inoculation and cooling conditions influence the ultimate tensile strength by offseting the equilibrium between the major constituents, the graphite flakes embedded in the primary metallic matrix. A model to predict the ultimate tensile strength is developed based on the interpretation of the stress intensity behaviour in a eutectic cell.

The models developed for nucleation, eutectic growth and prediction of tensile strength were introduced into a casting simulation program. Mould filling, solidificauon, microstructure development and tensile strength of a complex. shaped cylinder head were simulated.

Place, publisher, year, edition, pages
Jönköping: Jönköping, 2004. 25 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 871
Keyword
grey iron, nucleation, primary austenite, eutectic cell, growth rate, inoculation, thermal analysis
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-23153 (URN)2557 (Local ID)91-7373-939-1 (ISBN)2557 (Archive number)2557 (OAI)
Public defence
2004-05-14, Föreläsningssal E 101, Ingenjörshögskolan, Jönköping, 10:00 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-01-09

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