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| 3. |
- Belov, Ilja, et al.
(författare)
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A thermal conductivity model for grey iron
- 2024
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193. ; 18:3, s. 2107-2117
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Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity is an important property for many iron cast components, and the lack of widely accepted thermal conductivity model for cast iron, especially grey cast iron, motivates the efforts in this research area. The present study contributes to understanding the effects alloy microstructure has on thermal conductivity. A thermal conductivity model for a pearlitic cast iron has been proposed, based on the as-cast alloy composition and microstructural parameters obtained at different solidification rates. According to the model, available parallel heat transfer paths formed by connected graphite flakes across eutectic cells are determined by the space between dendrite arms. The uncertainties both for model inputs and for validation measurements have been estimated. Sensitivity analysis has been conducted to result in better understanding of the model behaviour. The agreement between modelled and measured thermal conductivities has been achieved within 5% on the average for the investigated samples.
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- Belov, Ilja, et al.
(författare)
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A thermal conductivity model for lamellar and compacted graphite irons
- 2024
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193.
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Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity is an important property for cast components produced from different types of cast iron. Development of a general widely-accepted thermal conductivity model for compacted and lamellar graphite irons poses a research challenge. The present study extends the modeling approach introduced earlier for pearlitic lamellar graphite iron toward compacted graphite iron and ferritic lamellar graphite iron. The proposed thermal conductivity model of the bulk material is based on the alloy microstructure and Si segregation between eutectic cells and non-cell regions, at the main assumption that the heat paths in the eutectic cells are formed by connected graphite phases surrounded by ferrite phases. The overall thermal resistance of these heat paths is determined by the hydraulic diameter of the interdendritic region. The uncertainties both for the modeled and for experimentally derived thermal conductivities have been estimated. The importance of considering the Si segregation in the model has been discussed. For the investigated samples, the agreement between modeled and measured thermal conductivities has been achieved within 4% on the average, at the same value of the single fitting parameter found for pearlitic, pearlitic–ferritic lamellar, and compacted graphite iron alloys. The results contribute to the understanding of the material microstructure effects on the cast iron thermal conductivity.
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| 7. |
- Diaconu, Lucian Vasile, et al.
(författare)
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Influence of molybdenum alloying on thermomechanical fatigue life of compacted graphite irons
- 2012
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 25:5, s. 277-286
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Tidskriftsartikel (refereegranskat)abstract
- In this study four compacted graphite irons (CGIs) and one grey cast iron (FGI) were produced and tested in the laboratory. The molybdenum content of the four CGI grades was varied between 0 and 1·01 wt-%. The purpose of the investigations was to examine the effect of the different molybdenum contents of the CGI on the thermomechanical fatigue (TMF) behaviour. The TMF tests were performed by cycling a constrained specimen between 110 and 600°C. For every material three tests were performed on specimens machined from a Ø20 mm cylinder. Other tests were performed on specimens machined from Ø55 mm and Ø85 mm cylinders respectively. The tests showed that additions of molybdenum improved the fatigue resistance of CGI. It was observed that additions of molybdenum refined the pearlite and that the specimens with a finer metallic matrix had a higher TMF resistance.
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| 8. |
- Diaconu, Lucian Vasile, et al.
(författare)
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Stress relaxation of compacted graphite iron alloyed with molybdenum
- 2013
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Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 26:1, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- In a previous study, the thermomechanical fatigue resistance of four compacted graphite irons (CGIs) and one grey cast iron was investigated. The molybdenum content of the four CGIs varied between 0 and 1.01 wt-%. It was observed that during thermal cycling, the maximum value of the compressive stress continuously decreased while the value of the maximum tensile stress continuously increased. The continuous decrease in compressive stresses showed that stress relaxation occurs at elevated temperatures during thermal cycling. The goal of the present investigation was to investigate the phenomenon of stress relaxation at elevated temperatures. The tests were performed at 350 and 600uC respectively. The results of the stress relaxation tests performed at 600uC showed the same trend observed at thermomechanical fatigue testing. The tests showed that additions of molybdenum improved the fatigue resistance of CGI by lowering the stress relaxation rate.
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| 10. |
- Diószegi, Attila, 1962-, et al.
(författare)
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Austenite Dendrite Morphology in Lamellar Cast Iron
- 2014
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Ingår i: The 10<sup>th</sup> International Symposium on the Science and Processing of Cast Iron, SPCI10, November, Mar del Plata, Argentina, 2014. - : The Institute for Research in Materials Science and Technology (INTEMA).
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Konferensbidrag (refereegranskat)abstract
- Primary austenite has been underestimated in general when the theories of nucleation, solidification, microstructure formation and mechanical properties was established for cast iron and particularly for lamellar cast iron. After extensive use of colour etching during the last two decades it has been found that primary austenite dendrites can be characterized using general morphology parameters like those used for other technical cast alloys with dendritic structure. The present work aims to investigate the primary austenite morphology of as-cast samples of a hypoeutectic lamellar cast iron produced with different cooling rates. Morphological parameters as the area fraction primary austenite, the secondary dendrite arm spacing, the dendrite envelope surface, the coarseness of the primary dendrite expressed as the relation between the volume of the dendrite and its envelope surface and the coarseness of the interdendritic space also known as the hydraulic diameter are measured. Furthermore the role of the size of investigation area is revealed be sequential investigation. A strong relation between all measured morphological parameters and the solidification time have been established excepting the volume fraction of primary austenite which is constant for all cooling conditions.
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