One of the most significant challenges in the composite development field is to find a low-cost manufacturing route capable of producing large volumes of material. This thesis develops and characterises a potential avenue for addressing this, an induction furnace-based process. This process produced a composite of A357 matrix and 10% wt Dramix 3D 80/30 SL steel fibres. The method was evaluated by microstructural analysis and optimum casting parameters were approximated. The fibres were introduced to liquid A357 at 700°C and the composite was brought to a measured temperature of 650°C over not more than 120 seconds before being removed from the furnace and cooled. 10% wt was the ideal reinforcement ratio for this process. Characterising the tensile and compressive strength of the composite material, it reached a peak stress 130% higher than A357 produced under the same conditions, though the peak stresses were still 20% of the literature values for T6 tempered A357. This suggests the need for development of a temper which does not degrade the properties of the composite. 3-point bending tests and some tensile specimens also showed post-failure strength. Under dynamic loading, the composite showed a peak stress in excess of 100 MPa without reaching maximum compression under SHPB loading, and comparable performance to SiC-reinforced MMCs under ballistic testing. The linear decrease in work-hardening with increasing distance from the impact site shows shock and pressure-pulse dissipation properties, attributed to the difference in acoustic impedance between the matrix and the reinforcement.

Made available in DSpace on 2014-10-09T12:25:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:06Z (GMT). No. of bitstreams: 1 02233.pdf: 1898081 bytes, checksum: ca8d5eb71d409e24aba2146df83dd874 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

This work involved an investigation into the mechanisms governing the reduction of material in the solids bed of the Ifcon® process. Thermo gravimetric analyses were done to investigate the influence of various operational parameters on the rate of solid state reduction. The experiments were modeled, and model predictions were compared to experimental results. Kinetic data was analised and the reduction rate constants were calculated. The rate constants were used as inputs to a model, which describes the reduction behaviour and temperature profile in a composite solids bed (similar to that in the Ifcon® process). High temperature reduction- and melting tests were done in an 150 kW induction furnace, to simulate final reduction in a solids bed. The temperature profile through the solids bed was measured and results were compared to model predictions. Finally the extent to which solid state reduction occurs in the solids bed was estimated as a function of production rate. / Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted

To stay competitive in the steel industry, steelmakers are utilizing different production methods to reduce production cost without compromising on the quality of their products. In steelmaking, the production process plays a significant role on the steel cleanliness. Recent increasing demands on the cleanliness level therefore require optimization of production process to meet the requirement. Often, the types and distribution of non-metallic inclusions in steel determines the steel cleanliness. In order to optimize the production process, complete assessment of the non-metallic inclusions in the steel is necessary, leading to implementation of measures to control and/or remove non-metallic inclusions in the steel. The present study was performed to investigate the cleanliness level of steel bars produced from a high frequency induction furnace (HF) route at Uddeholms AB. Experimental studies were carried out and characteristics such as number, composition, size distribution and morphology of non-metallic inclusions were investigated. Total oxygen and total nitrogen content were also measured for indirect assessment. Further, the production operations at the HF were observed and evaluated to determine their influence on the inclusion characteristics. The characteristics obtained were compared with characteristics of inclusions in steel bars produced from an electric arc furnace production (EAF) route at Uddeholms AB and a competitor producer sample. The results showed that the level of cleanliness varies from different production routes and is hence dependent on the process at each production route. The number, maximum and mean size of inclusions were found to be higher in the HF route compared to the other routes. More so, there were differences in the types of oxide inclusions observed from each process route. However, sulphide inclusions exhibit similar characteristics from the different process routes. Further, the compositions of oxide inclusions observed from the HF route were found to be closely related to the steel chemistry. More importantly, the types of inclusions formed in the HF route were found to be sensitively affected by the extent of aluminium and calcium contents in the steel. Thus, the oxide inclusion types in the HF samples could be traced to the extent of different additions and operations such as deoxidation and calcium treatment that were carried out during the steelmaking process.

L’allègement des structures, et notamment des câbles électriques, est un enjeu majeur pour les industries aéronautique et ferroviaire, grandes consommatrices en ressources énergétiques. L’utilisation de nanotubes de carbone (NTC) comme renforts dans l’élaboration de matériaux composites à matrice aluminium est une solution prometteuse pour obtenir un matériau à propriétés améliorées. L’élaboration par métallurgie liquide en four à induction d’un matériau Al-NTC fait face à des challenges tels que l’intégration et la dispersion des NTC dans l’aluminium liquide. Une démarche par intégration d’échelles a été mise en œuvre avec des fibres et des nanofibres de fibres de carbone (NFC), et a permis d’identifier que la présence d’une interface cuivrée à la surface des renforts et un brassage mécanique sont les points clés pour favoriser le mouillage et la dispersion des NTC. Un matériau Al-NFC à propriétés mécaniques améliorées a été élaboré et la contribution du cuivre apporté par l’interface a pu être quantifiée. La contribution des NFC sur l’amélioration de la résistance élastique par rapport à l’aluminium de référence est de +44% avec des paramètres d’élaboration optimisés.Le comportement des NTC avec et sans interface cuivre dans l’aluminium liquide a été étudié selon des considérations thermodynamiques et cinétiques. Un modèle de croissance de carbures d’aluminium a ainsi pu être établi théoriquement et calibré expérimentalement avec une méthode de corrélation par intégration d’images. L’influence des NTC sur la germination hétérogène de l’aluminium a également été étudiée et une méthode permettant d’obtenir des éprouvettes à structure équiaxe fine a été déterminée. / The lightening of structures, including electrical cables, is a major issue for aviation and rail industries, major consumers of energy resources. The use of carbon nanotubes (CNTs) as reinforcements in the preparation of composite materials with aluminum matrix is a promising solution to achieve improved properties in the material. The preparation by liquid metallurgy of an Al-CNT material with induction furnace processing is facing challenges such as the integration and dispersion of CNTs in liquid aluminum.A scales integration method has been implemented with fiber and carbon fiber nanofibres (NFC). It has allowed to identify that the presence of a copper interface at the surface of reinforcements and mechanical stirring are the key points to promote wetting and dispersion of CNTs. An Al-NFC composite material with improved mechanical properties was developed and the copper contribution provided by the interface could be quantified. NFC contribution to improving the elastic strength relative to the reference aluminum is + 44% with optimized elaboration parameters.The behavior of CNTs with and without copper interface in liquid aluminum has been studied using thermodynamic and kinetic considerations. An analytic model for aluminum carbide growth has been established theoretically and was experimentally calibrated with an integrate-pictures correlated method. The influence of CNTs on the heterogeneous nucleation of aluminum has also been studied and a method to obtain fine equiaxed structure has been determined.

The subject of this work is to validate the possibility of managing the cast iron strength through residual Mg content and to determine methodically whether it is possible to exploit this technology in a foundry. It is another subject to determine the economics of the exchange of cupola furnace for electric induction furnace and methodically assess the possibilities of melting in the electric induction furnace.

Die Existenz der nichtmetallischen Einschlüsse in der Metallschmelze führt zur Verschlechterung der physikalischen Eigenschaften des gegossenen Stahls. Die im Rahmen des SFB 920 entstandene Arbeit beschäftigt sich hauptsächlich mit der Untersuchung der reaktiven Reinigung und aktiven Filtration der Metallschmelze im Induktionsofen mithilfe der numerischen Strömungsmechanik. Dazu werden im Rahmen der Arbeit neue numerische Simulationsmodelle entwickelt. Die Ergebnisse zeigen, dass die reaktive Reinigung einen ausschlaggebenden positiven Einfluss auf die Entfernung der Einschlüsse aus der Metallschmelze hat, wobei der Reinheitsgrad der Metallschmelze innerhalb einer kurzen Eintauchzeit des kohlenstoffgebundenen Filters ansteigt. Der in der reinen aktiven Filtration erzielte Reinheitsgrad ist deutlich niedriger als im Falle der reaktiven Reinigung. Des Weiteren befasst sich die Arbeit mit dem Effekt der Turbulenzmodellierung auf die Beschreibung der Schmelzeströmung und der Verteilung der Einschlüsse. Weiterhin stellt die Arbeit ein experimentelles Wassermodell zur Nachbildung der rezirkulierenden Schmelzeströmung im Induktionsofen vor.:Abstract List of figures List of Tables Nomenclature 1 Introduction 2 State of the Art 3 Numerical Model 4 Results 5 Summary and Conclusion 6 Outlook Bibliography / During the continuous casting, non-metallic inclusions such as deoxidation or reoxidation products may arise in steel melt due to different reactions. These inclusions have to be removed from the melt with the aim of improving the cleanliness of steel products. There are many approaches in continuous casting to enhance inclusion removal from the melt. However, this Phd thesis focuses particularly on inclusion removal by reactive cleaning and active filtration during the melt casting in an induction crucible furnace using ceramic foam filter developed in CRC 920. For this purpose, a numerical model is developed in OpenFOAM in order to simulate the melt flow and reactive cleaning as well as active filtration. Besides the numerical model, an experimental water model are created to validate the capability of the numerical model to predict the recirculating turbulent flow in the induction crucible furnace. The results show that reactive cleaning and the formation of carbon monoxide bubbles, which arise on the inclusions, have a positive impact on the melt cleanliness. Reactive cleaning can improve inclusion removal and enhance the melt cleanliness sufficiently. Based on the results, one can conclude that the rate of inclusion removal in case of reactive cleaning is considerably higher than that in case of active filtration. Furthermore, the results indicate the considerable influence of filter position and filter number on the flow field as well as on the cleaning efficiency in the induction crucible furnace. Moreover, the results shows that turbulence modeling has a considerable impact on the prediction of the melt flow and inclusion dispersion in the induction crucible furnace.:Abstract List of figures List of Tables Nomenclature 1 Introduction 2 State of the Art 3 Numerical Model 4 Results 5 Summary and Conclusion 6 Outlook Bibliography

The aim of this work is optimalisation of induction furnace in foundry for company PROMET FOUNDRY a.s. The company has two induction furnances. There are installed as identical construction. They have 2 modes of operation. First mode is founding and second mode is mode, where is temperature in maintain mode. Only one induction furnance can work in the founding mode at a time though. Inducion furnances are in the single-phase connection and they cause unbalance in the distribution network. Near the foundry there is a small network area whitch it is operated by company Zásobování teplem Vsetín a.s. The consumption of electrical energy in foundry so big, that in the year 2009 was made elaborate for Zásobování teplem Vsetín a.s. It was write at Laboratoře diagnostiky výkonů (Laboratory of performance diagnostics), which is a part of Electrotechnic Department at Technical Univarsity of Ostrava. The ordered study was named “Verification of causes of increased reactive energy consumption during transition from electricity delivery to electricity consumption”. The conclusion of this assignment confirms that in distribution network in the Jiráskova area in Vsetín there is unbalance of electrical energy and there is high part of reactive power. The next conclusion is crucial to find the customer who made the unbalance and to set relevant remedy. The last step will be the identification whether such device can actually be effectively balanced. It was subsequently proved that the Promet Foundry was causing the unbalance and that balanced consumption would be reasonable. Promet Foundry thus addressed Autel a.s. company with an inquiry to make a study of removing the causes of the unbalance which is caused by current induction furnaces operation at a minimum possible cost, least possible influence on the performance and minimum construction changes concerning the building. In this thesis there will be some topics. The result of which will be introducing of used heating technology, introducing of company and of effective plant performance and subsequent suggestions of possible unbalance removal or reactive power decrease. Several ways which are being implemented in the industry in order to balance consumption will be described. A suitable balancing plant will be subsequently chosen and its parameters will be calculated.