The paper presents measurement results of standing wave ratio to be used as an efficiency indicator of microwave absorption by used moulding and core sands chosen for the microwave utilization process. The absorption measurements were made using a prototype stand of microwave slot line. Examined were five used moulding and core sands. It was demonstrated that the microwave absorption measurements can make grounds for actual microwave utilization of moulding and core sands.
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W artykule przedstawiono wyniki badań dotyczących określenia współczynnika fali stojącej, będącego miarą skuteczności pochłaniania promieniowania elektromagnetycznego przez materiały formierskie. Wstępne badania z wykorzystaniem mikrofalowej linii szczelinowej wykazały, że odlewnicze piaski kwarcowe, chromitowe i magnezytowe odznaczają się małą zdolnością pochłaniania mikrofal. Wykazano, że istotny wpływ na zmianę skuteczności pochłaniania mikrofal mają związki chemiczne wchodzące w skład badanych substratów. Ustalono, że użycie mikrofalowej linii szczelinowej pozwala precyzyjnie wyznaczyć charakterystyczne wartości pochłaniania promieniowania elektromagnetycznego przez różne materiały formierskie. Wartości te są niezbędne do określenia ich przydatności do mikrofalowego suszenia/utwardzania form i rdzeni lub do innych procesów odlewniczych. Stwierdzono, że stosowane w badaniach urządzenie może znaleźć zastosowanie do identyfikacji składników masy, a także do określania np. ziarnistości osnowy za pomocą precyzyjnie wyznaczonych współczynników odbicia |/] i położeń minimum sygnałów.
EN
In the paper, a research on determining the standing wave ratio as a measure of electromagnetic absorbing capacity of moulding materials is presented. Preliminary tests that have been performed using a microwave strip line showed that high-silica, chromite and magnesite moulding sands are characterised by low absorbing capacity of microwaves. It was demonstrated that microwave absorbing capacity is significantly affected by chemical compounds included in the examined substrates. It was found that use of a microwave strip line permits precise determining characteristic microwave radiation absorbing capacities of various moulding materials and thus their suitability for microwave drying/hardening of moulds and cores or for other foundry processes. Such a microwave drier can be applied for identifying mass components and for determining e.g. base granularity by means of precisely determined reflection ratios |/1 and positions of minimum signal values.
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This paper outlines the history of bell founding. The exceptional character of bells, which are products of supracultural importance, was stressed. The complexity of the bell manufacturing process and a unique approach to the technology design were highlighted. Basing on the data obtained from foundry shops currently operating in Poland, known as bell-casting foundries, the main guidelines for the bellcasting process as used nowadays by the Felczyński Foundry with long-standing traditions and Wojdak’s Foundry, both of which are casting bells according to modern technologies, using modern moulding materials and metal alloys, were described.
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The results of dilatometric measurements presented in the paper are a supplement to the investigations concerning broadening the composition of ceramic slurry intended for investment casting technology with ceramic fibre matrix. An applying of fibre material and a change of rheologic characteristics of ceramic slurry have impelled to develop the method of applying the material to the pattern sets. The technology of multi-layer spraying has been found to be the most favourable method. Partial replacing of the grain silica materials with aluminosilicate materials in the fibrous form has affected the magnitude of dimensional changes taking place during the heating process. In order to determine the magnitude of these changes, there have been prepared slurries of various fibre fraction in the matrix and their thermal expansion has been examined within the temperature range of 273-1273 K.
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The presented investigations have been aimed to determine strength properties of shell ceramic moulds produced on the basis of silica sol with the matrix composed of MK75 silica flour and Cerafiber 10 aluminosilicate ceramic fibre, the chemical composition of the latter being 56% SiO2 and 44% Al2O3. The sample material has been obtained by multi-layer spraying of ceramic slurry onto the pattern sets. The achieved results, concerning strength properties revealed during the controlled bending test performed by means of the four-point deflectometer, have been compared with the presented elsewhere results [16-19] for moulding material with grain or grain-fibre matrix, where TC E08 fibre produced by Thermal Ceramics (i.e. Kaowool HP-50-E-08 fibre) has been applied as a matrix component.
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The work presents the results of investigation centred around the selection of a ceramic slurry composition if ceramic fibre is applied as a component of moulding material used for the lost wax technology. Producing a ceramic material of assumed parameters demands for changing the surface properties of the mineral grains. The critical concentration of solid particles or the gel point depends on the size of mineral particles, their shape and ability to aggregate. This ability has been achieved by modifying their surface properties by adding some polymer and the wetting agent (surfactant), which are adsorbed. Using the fibre material has required developing a method of its applying to the pattern set. The technology of multi-layer spraying has been recognised as the most advantageous one. The performed laboratory experiments have allowed for determining both the material composition and the parameters of its applying, such as air pressure, nozzle diameter, and the spraying distance for gravity pneumatic spraying gun.
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