This diploma thesis describes the process of production of the cast by the lost-wax casting method. It includes the manufacturing of prototype models by additive technology, creation of ceramic shell molds. The work also includes an experimental part focused on the production of the selected parts by the method of the lost-wax casting and the comparison of this method with other types of production.

O processo de fundição por cera perdida representa, há muitos anos, o principal processo de produção gerador de peças de alta complexidade para atender os mais variados segmentos industriais tais como o automotivo, geração de energia, médico e bélico. A característica principal deste processo é a de obter cascas cerâmicas por meio de banhos de lama cerâmica ancorados por material refratário granulado aplicados sobre a superfície de modelos em cera com o formato da peça final. Estudou-se neste trabalho as propriedades do pó de telhas e também das cascas cerâmicas produzidas com lamas utilizando o próprio pó de telhas como material refratário tanto na lama primária quanto na lama secundária. O pó de telhas apresentou alta dispersão granulométrica #20-#325 mesh e em sua composição foram identificados compostos refratários importantes como a sílica e a alumina. Os ensaios realizados nas cascas cerâmicas confeccionadas com lamas de pó de telhas apresentaram resultados de módulo de ruptura à verde e calcinado (1000 °C) de respectivamente 1,02 MPa e 4,95 MPa e de permeabilidade a quente (1000 °C) 4,2 L/min. Os ensaios nas cascas cerâmicas utilizadas na indústria apresentaram resultados de módulo de ruptura a verde e calcinado respectivamente de 2,48 MPa e 5,7 MPa e permeabilidade de 3,8 L/min. As cascas cerâmicas confeccionadas com pó de telhas apresentaram módulo de ruptura inferior as cascas industriais, porém, com resultado de permeabilidade superior. As cascas cerâmicas com lamas de pó de telhas apresentaram bom comportamento durante o vazamento dos metais líquidos alumínio 356, bronze e ferro fundido cinzento, não foi observado quebras no molde e nem reação com o metal. As peças fundidas com as cascas cerâmicas produzidas com lamas de pó de telhas atenderam as tolerâncias dimensionais exigidas pela norma ABNT NBR 15990. / The lost wax process has for many years been the main production process generating parts of high complexity to meet the most varied industrial segments such as automotive, power generation, medical and military. The main feature of this process is to obtain ceramic shells by means of ceramic slurry baths anchored by granular refractory material applied to the surface of wax models in the shape of the final part. This work evaluated the properties of tile powder and also the ceramic shells produced with slurries using the tile powder itself as a refractory material in both primary and secondary slurries. The powder of tiles presented high particle size dispersion # 20 - # 325 mesh and in its composition important refractory compounds such as silica and alumina were identified. The tests carried out on the ceramic shells made with tile powder slurries showed green and calcined (1000 °C) modulus of 1.02 MPa and 4.95 MPa respectively and a heat permeability of (1000 °C) 4, 2 L / min. The tests in the ceramic shells used in the industry showed green and calcined rupture modulus results of 2.48 MPa and 5.7 MPa and permeability of 3.8 L/min respectively. The ceramic shells made with powder tiles had a lower rupture modulus than the industrial ceramic shell, but with a higher permeability result. The ceramic shells with tile slurries showed good performance during the casting of liquid aluminum 356, bronze and gray cast iron, no mold breaks and no reaction with the metal. The parts cast with the ceramic shells produced with tile powder slurries e met the dimensional tolerances required by ABNT NBR 15990.

The diploma thesis deals with the possibilities of using numerical simulation in investment casting technology. The first chapter of practical part deals with the use of simulations in the design of gating system for the shape-complex casting. At the same time, the practical part verified the accuracy of the simulation by test castings on which the X- ray inspection was performed. The results showed that the occurrence of internal defects predicted by simulation corresponded to the locations in the test casts. Next part of the thesis describes improvement of the use of liquid metal (so called “yield”) by numerical simulations. Two specific castings were chosen to perform simulation of current and newly designed variant of the gating system.

This diploma theses deals with possibilities of using numerical simulation for optimizing production of highly demanding thin-section casting produced by investment casting process. The casting made of aluminium alloy in which the manufacturing process was very problematic (occurrence of macro and micro shrinkages) has been chosen. By numerical simulation the existing technology has been analysed and based on this the possible reasons for defects found. This was later confirmed also by metallographic examinations. Following to this several options for a new technology were proposed and again by simulation checked their suitability. By comparing all above mentioned options two versions have been chosen in the end which was later tested in production with satisfactory results.

This diploma thesis deals with the possibilities of optimization of ceramic shell molds in the method of investment casting. In the first part is mentioned a complete technological process of the method with focusing on production and quality control of the ceramic shell and components, from which it is produced. The experimental part is divided into two parts, in the first are results of laboratory tests, which were tested both the current ceramic shell and shells which have been considered as a possible replacement. In the second section were verified conclusions of the experimental findings and recommendations of the laboratory results in pilot plant conditions.

The purpose of this thesis is to assess the current state of production of ceramic shells in MESIT Foundry, a.s. and optimize it. The shells are evaluated in terms of their bending strength, gas permeability and microstructure. Subsequently, castings produced using the shells are evaluated with regard to number of non-conforming products and presence of defects. The final part seeks to compare different shells and outlines a possible new approach to the development of ceramic shells.

The goal of this thesis is to examine a possible influence of the water soluble cores on the microstructure of commonly used aluminum alloys AlSi7Mg and AlSi10Mg in the lost wax technology. This thesis only deals with the changes of the eutecticum on the contact surface between the metal and the core and its surroundings where interactions can appear between the core based on the alkali salts NaCl and KCl and the alloy modified by sodium or strontium. The experimental part investigates the influence of the alkali salts on the modification additives and the modification of the structure itself.

Dans une démarche pluridisciplinaire, qui emprunte aussi bien aux sciences humaines et sociales (archéologie, histoire des techniques, réexamen des textes anciens) qu’aux sciences chimiques (science des matériaux, métallurgie expérimentale, chimie analytique), cette recherche vise à reconstituer l’évolution des techniques de fonte à la cire perdue, depuis les plus anciens témoignages de son utilisation à Mehrgarh (Pakistan, 5e millénaire av. J.-C.) jusqu’aux premières grandes statues de bronze dans le monde égéen (fin du VIe, début du Ve s. av. J.-C.).L’étude des objets a parfois nécessité des développements analytiques spécifiques pour pallier à leur très forte altération, comme par exemple l’imagerie de photoluminescence synchrotron. Cela a notamment permis de reconstituer en détail la chaîne opératoire de fabrication de la rouelle de Mehrgarh, l’une des plus anciennes fontes à la cire perdue connue à ce jour. Sur la base de ces résultats, il est suggéré que la fonte à la cire perdue pourrait avoir été inventée pour donner la possibilité aux individus non métallurgistes de créer des objets importants en métal tels que ces amulettes, par le biais du façonnage d’un modèle en cire.Nous montrons que la cire perdue a ensuite été mise à profit pour donner naissance à une nouvelle forme de sculpture, la statuaire de métal. Au prix de parois très épaisses et d’assemblages mécaniques, nous mettons en évidence une première période de production de grandes statues en Mésopotamie pendant la deuxième moitié du 3e millénaire av. J.-C. Après un long hiatus, la grande statuaire métallique renaît de façon spectaculaire pendant la première moitié du 1er millénaire av. J. C., à la fois dans les mondes égyptien, sabéen et égéen. Nous identifions deux innovations importantes responsables de cette renaissance : le procédé indirect et l’assemblage soudé.Des essais de coulabilité effectués en faisant varier la composition de l’alliage et le matériau du moule sont présentés dans la dernière partie de notre travail. En moule de plâtre et avec un fort préchauffage, une coulabilité exceptionnelle a été obtenue pour le bronze à fort taux de plomb, donnant pour la première fois une idée des conditions de coulée nécessaires à l’obtention des parois très minces souvent observées sur les grandes statues antiques. / Following a multidisciplinary approach combining social sciences (archaeology, history of techniques, examination of ancient texts) and chemistry (materials science, experimental metallurgy, analytical chemistry), our research aims to reconstruct the evolution of lost-wax casting techniques, from the earliest evidence of its use in Mehrgarh (Pakistan, 5th millennium BC) to the first large bronze statues in the Aegean (end of the 6th, beginning of the 5th century BC).The archaeological artefacts under study have sometimes required specific analytical developments to overcome their very strong alteration, such as synchrotron photoluminescence imaging. This allowed reconstructing in detail the chaîne opératoire of the Mehrgarh wheel-shaped amulet, one of the oldest lost-wax castings known to date. Based on the results thus obtained, it has been suggested that lost-wax casting might have been invented to give non-metalworkers the opportunity to create important metal objects such as amulets by simply shaping a wax model.We show that lost-wax casting was afterwards used to create a new form of sculpture, namely metal statuary. At the cost of very thick metal walls and mechanical assemblies, this led to an early production step of large statues in Mesopotamia during the second half of the 3rd millennium BC. After a long hiatus, large metal statuary reappeared spectacularly during the first half of the 1st millennium BC, both in the Egyptian, the Sabean and the Aegean areas. We were able to identify two important innovations responsible for this renaissance: the indirect process and the flow fusion welding.Castability tests carried out by varying the composition of the alloy and the material of the mould are presented in the last part of our work. An exceptional castability was obtained for highly-leaded bronze in plaster mould and with a high preheating. For the first time some insights are thus drawn on the casting conditions necessary to obtain the very thin walls often observed on large metal statues during the Classical Antiquity.

This diploma thesis deals with the optimization of gating systems of shape-complex aluminum castings produced by investment casting process. Two castings whose massive gating systems make problem with the use of liquid metal (so called yield) were chosen for optimization. Each casting is described in its own chapter. The individual subchapters deal with description of the original and newly designed gating system. Simulation, test castings, X-ray inspection and metallographic examination were performed for each variant. At the end of each chapter there is an evaluation of the results of the optimization of gating system.

The aim of this paper is to compare a bottom filling of a ceramic form made by lost wax process and a top filling conventional method. A computer simulation of filling and casting solidification will contribute to this comparison. The comparison includes evaluation of readings DAS and characteristic readings of porosity with chosen varieties of casting. The results show that the readings DAS did not change much but characteristic readings of porosity were much better at bottom filling. The computer simulation also showed a certain contribution in the field of model smelting technology.