| 1. |
- Diószegi, Attila, 1962-, et al.
(author)
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Defect formation mechanisms in lamellar cast iron related to the casting geometry
- 2015
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In: Advances in the science and engineering of casting solidification. - Hoboken, NJ : John Wiley & Sons. - 9781119082385 - 9781119093367 ; , s. 251-259
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Conference paper (peer-reviewed)abstract
- Although lamellar cast iron has been used in advanced applications for about twenty years, our knowledge about the mechanisms affecting microstructure and defect formation is relatively limited. The present paper summarizes some solidification related phenomena from a series of recently published peer reviewed papers and scientific theses and suggests a mechanism of defect formation which is dependent on the shape of the solidifying casting geometry. When shrinkage porosity or metal expansion penetration occurs evidence of material transport in the intergranular zone of primary equiaxed austenite grains in the casting and in the intergranular regions between the sand grains in the mold material is seen. Material transport occurs across the casting-mold interface where the existence of or the permeability of the primary columnar zone determines if material transport can take place.
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| 2. |
- Svidró, Peter, et al.
(author)
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Characterization of primary dendrite morphology in complex shaped lamellar cast iron castings
- 2014
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In: The 10<sup>th</sup> International Symposium on the Science and Processing of Cast Iron, SPCI10, November, 2014, Mar del Plata, Argentina. - : The Institute for Research in Materials Science and Technology (INTEMA). ; , s. 1-7
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Conference paper (peer-reviewed)abstract
- Shrinkage porosity and metal expansion penetration are two fundamental defects appearing during the production of complex shaped lamellar cast iron components. Simplified test models simulating the thermal and geometrical conditions existing in complex shaped castings have been successfully used to provoke shrinkage porosity and metal expansion penetration. A stereological investigation of the primary dendrite morphology indicates a maximum intra-dendritic space in connection with the casting surface where the porosity and the penetration defects appear. Away from the defect formation area the intra-dendritic space decreases. Comparison of the simulated local solidification times and measured intra-dendritic space indicates a strong relation which can be explained by the dynamic ripening process. The slow local solidification time situated at the boundary between the casting surface and its surrounding is explained to be the reason for the formation of an austenite morphology which can promote mass flow between dendrites, thereby provoking shrinkage porosity or metal expansion penetration.
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| 3. |
- Bagni, T., et al.
(author)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
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In: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 34:5
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Journal article (peer-reviewed)abstract
- A newly designed superconducting magnet of the Canted-Cosine-Theta (CCT) type was developed as a result of a collaboration between Swedish universities (Uppsala and Linneaus) and Swedish industries. This magnet was designed to function as a replacement of the present LHC orbit corrector magnets, which are approaching their end of life due to the radiation load. As a result, the new CCT magnet was developed to be more radiation tolerant and to constitute a one-to-one replacement to the currently installed version, which is a 1 m long 70 mm double aperture dipole magnet. The final magnet, which is currently under construction, will be tested at FREIA laboratory at Uppsala University and generate a magnetic field of 3.3 T and an integrated field of 2.8 Tm at about 85 A. To examine the magnet quench behavior and to identify a suitable quench protection system, the 3D electro-magnetic and thermal behavior of the coil was modeled using the RAT-Raccoon software. Based on the simulation results, a Metrosil varistor was selected to protect the magnet during the test. In this article, we report the results of the numerical analysis. The magnet model is equipped with a spot heater to initialize the quench and the temperature and voltages are monitored during the avalanche effect. The simulated current decay and the hot-spot temperature are analyzed with a focus on the impact of quench-back on the magnet protection.
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| 4. |
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| 5. |
- Diószegi, Attila, et al.
(author)
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Defect formation mechanisms in lamellar graphite iron related to the casting geometry
- 2016
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In: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 29:5, s. 279-285
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Journal article (peer-reviewed)abstract
- Although lamellar cast iron has been used in advanced applications for about 20 years, our knowledge about the mechanisms affecting microstructure and defect formation is relatively limited. The present paper summarises some solidification-related phenomena from a series of recently published peer-reviewed papers and scientific theses and suggests a mechanism of defect formation which is dependent on the shape of the solidifying casting geometry. When shrinkage porosity or metal expansion penetration occurs, evidence of material transport in the intergranular zone of primary equiaxed austenite grains in the casting and in the intergranular regions between the sand grains in the mould material is seen. Material transport occurs across the casting-mould interface, where the existence of or the permeability of the primary columnar zone determines if material transport can take place.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Dugic, Izudin, 1962-, et al.
(author)
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An investigation of the effect of five different inoculants on the metal expansion penetration in grey cast iron
- 1999
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Reports (other academic/artistic)abstract
- The production of quality castings requires the casting surface to be clean and free from defects. In some grey cast iron components which are cast in sand moulds, the metal sometimes penetrates into the mould, producing difficulties in cleaning the components. The defect causes very high costs due to component rejection and increased fettling in the casting industry. Most of the grey iron foundries around the world have problems with metal penetration on applicable components. In this work the problem of metal penetration has been studied using a commercial casting component. Eight castings were mounted on the pattern plate and five different inoculants were investigated. The experiments show that the inoculation of grey cast iron will influence the metal penetration in areas with late solidification times and where the melt is in contact with the sand mould. In all experiments 0.14 % inoculant was added in the pouring ladle. The experiments show that the best results to reduce metal penetration have been obtained when using the inoculant which contained silicon, aluminium and zirconium. Using this inoculant, the average penetration area was only about 20 % of what was found using the worst inoculant. However, this inoculant also gave rise to a large tendency to formation sinks.The experiments also show two main classes of eutectic cell size. One class nucleated at the beginning of the eutectic solidification and one at the end of the solidification. Two other inoculants, both containing Al and Si have about the same base composition. From the measurements of penetration areas, one can draw the conclusion that the inoculant with the smallest grain size gives nuclei with the shortest lifetime. The coarser grains give a longer dissolution time and this promotes the survival of the nuclei. At the end of solidification, a larger amount of graphite will precipitate at higher temperatures if new nuclei can be activated. If the hot spot is located close to the metal surface, the metal will expand into the mould; resulting in metal expansion penetration. The worst cases of metal penetration have been obtained using an inoculant containing titanium. A large number of small eutectic cells and high volume of the small cells were observed, which leads to severe penetration.
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| 10. |
- Dugic, Izudin, 1962-, et al.
(author)
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An investigation of the effect of inoculants on the metal expansion penetration in grey iron
- 1999
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In: International Journal of Cast Metals Research. - 1364-0461 .- 1743-1336. ; 11:5, s. 333-338
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Journal article (peer-reviewed)abstract
- The production of quality castings requires the casting surface to be clean and free fromdefects. In some grey cast iron components which are cast in sand moulds, the metalsometimes penetrates into the mould, producing difficulties in cleaning the components. Thedefect causes very high costs due to component rejection and increased fettling in the castingindustry. Most of the grey iron foundries around the world have problems with metalpenetration on applicable components.In this work the problem of metal penetration has been studied using a commercial castingcomponent. Eight castings were mounted on the pattern plate and five different inoculantswere investigated. The experiments show that the inoculation of grey cast iron will influencethe metal penetration in areas with late solidification times and where the melt is in contactwith the sand mould. In all experiments 0.14 % inoculant was added in the pouring ladle.The experiments show that the best results to reduce metal penetration have been obtainedwhen using the inoculant which contained silicon, aluminium and zirconium. Using thisinoculant, the average penetration area was only about 20 % of what was found using theworst inoculant. However, this inoculant also gave rise to a large tendency to formation sinks.The experiments also show two main classes of eutectic cell size. One class nucleated at thebeginning of the eutectic solidification and one at the end of the solidification.Two other inoculants, both containing Al and Si have about the same base composition. Fromthe measurements of penetration areas, one can draw the conclusion that the inoculant withthe smallest grain size gives nuclei with the shortest lifetime. The coarser grains give a longerdissolution time and this promotes the survival of the nuclei. At the end of solidification, a larger amount of graphite will precipitate at higher temperatures if new nuclei can beactivated. If the hot spot is located close to the metal surface, the metal will expand into themould; resulting in metal expansion penetration.The worst cases of metal penetration have been obtained using an inoculant containingtitanium. A large number of small eutectic cells and high volume of the small cells wereobserved, which leads to severe penetration.
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