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The Influence of alloying elements on Chill Formation in CGI
Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
2010 (English)In: Science and processing of cast iron IX: selected peer reviewed papers from the Ninth International Symposium on Science and Processing of Cast Iron, Luxor-Egypt, November 10-13, 2010 / [ed] Nofal, A. and Waly, M., Stafa-Zürich: Trans Tech Publications , 2010, p. 126-131Conference paper, Published paper (Refereed)
Abstract [en]

The influence of alloying elements on the chill formation in Compacted Graphite Iron (CGI) is investigated. Chill wedges cast in an industrial foundry were used to investigate the chill formation. A total number of 19 chemical compositions were studied, including three trials of varying nodularity treatment level; four trials of varying copper content; four trials of varying silicon content; four trials of varying tin content and four trials of varying carbide promoter content. Three wedges were cast for each alloy composition, of which one was used for measuring the temperature at three different heights in the wedge.

Contrary to some previous reports, the results indicate that low-nodularity CGI is not more prone to chill formation (columnar white) than high-nodularity CGI. Trends regarding the effect of alloying elements on chill formation are shown to generally be in agreement with previous work on spheroidal graphite iron and lamellar graphite iron. Most of the samples also show carbide formation in centre line areas of the wedge (inverse chill), this occurrence is also discussed in the paper.

 

Place, publisher, year, edition, pages
Stafa-Zürich: Trans Tech Publications , 2010. p. 126-131
Series
Key Engineering Materials, ISSN 1013-9826 ; 457
Keywords [en]
CGI, Chill Formation, Chill Wedges, Microstructure Formation, Simulation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:hj:diva-14225ISBN: 9780878492275 (print)OAI: oai:DiVA.org:hj-14225DiVA, id: diva2:384063
Conference
Science and Processing of Cast Iron IX
Available from: 2011-01-07 Created: 2011-01-07 Last updated: 2017-08-14Bibliographically approved
In thesis
1. Microstructure Formation During Solidification and Solid State Transformation in Compacted Graphite Iron
Open this publication in new window or tab >>Microstructure Formation During Solidification and Solid State Transformation in Compacted Graphite Iron
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Compacted graphite iron (CGI) is rapidly becoming an attractive alternative material for engine components in the automotive industry, replacing lamellar graphite iron (LGI) in applications where high mechanical strength is desired. However, the gain in mechanical strength comes with a cost; thermal conductivity, process control and machining are three areas that are more challenging for CGI. This generates a need for research regarding various aspects concerning CGI. In this thesis the microstructure formation during solidification and solid state transformation will be the focus of interest.

The phase transformations relevant for microstructure formation of importance to properties in CGI were studied. Experiments were performed in an industrial foundry giving this research direct relevance to regular production of CGI castings.

Solidification of the grey (graphite/austenite) eutectic will be discussed, focusing on some relevant aspects influencing the graphite morphology of CGI. The formation of graphite nodules has been investigated by studying colour-etched microstructures. In a material containing mainly CGI cells it was found that nodules form either early during solidification as a consequence of high undercooling or late in the solidification sequence due to a combination of high undercooling and segregation of nodularising elements. Solidification of the white (cementite/austenite) eutectic was studied using chill wedges and the influence of some alloying elements on the amount of carbides was examined. To further enhance the understanding of carbide formation in CGI a commercial casting simulation software was used to correlate real castings to simulations. It was found that the alloying elements investigated influence the carbide formation in a similar way as in other graphitic cast irons and that high nodularity CGI is more prone to chill formation than low nodularity CGI. The solid state transformation was studied and a deterministic model was developed. The model divides a eutectic cell into layers, in order to take into account segregation of alloying elements, which was observed to be influential for the ferrite growth. Moreover, the effect of alloying elements on mechanical properties (tensile properties and hardness) was evaluated. Properties were correlated to microstructural features originating from both solidification and solid state transformations. The trends found generally confirmed previous results regarding properties in graphitic cast irons.

Place, publisher, year, edition, pages
Gothenburg: Chalmers University of Technology, 2011. p. 50
Series
Doktorsavhandlingar vid Chalmers tekniska högskola, ISSN 0346-718X ; 3206
Keywords
Cast Iron, CGI, Microstructure Formation, Mechanical Properties, Modelling, Solidification, Solid State Transformation
Identifiers
urn:nbn:se:hj:diva-15694 (URN)978-91-7385-525-9 (ISBN)
Public defence
2011-05-17, E1405, Gjuterigatan 5, 55111, Jönköping, 10:00 (English)
Opponent
Supervisors
Available from: 2011-08-08 Created: 2011-07-13 Last updated: 2011-12-14Bibliographically approved

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König, MathiasWessén, MagnusSvensson, Ingvar L.

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